JP2022541570A - Method for preparing silicon dioxide suspension - Google Patents

Abstract

The present invention is a method for producing a silicon dioxide suspension comprising the steps of providing silicon dioxide powder and a liquid, mixing the silicon dioxide powder with the liquid to obtain a slurry, and sonicating the slurry. and passing at least a portion of the precursor suspension through a first multi-stage filter device, the first multi-stage filter device comprising: having at least first, second and third filter stages, each filter stage comprising at least one filter, the second filter stage positioned downstream of the first filter stage, and the third filter stage comprising Located downstream of the second filter step, the first filter step has a filter opening of 5 μm or more, the second filter step has a filter opening in the range of 0.5 to 5 μm, and the third The filter step has a filter opening of 1 μm or less, and at least one of the filter steps selected from the first, second and third filter steps has a separation rate of 99.5% or more. Regarding the method of containing. The invention also relates to the silicon dioxide suspension thus obtained, the granules obtained therefrom and the resulting products. [Selection drawing] Fig. 1

Description

The present invention is a method for producing a silicon dioxide suspension, comprising the steps of preparing a silicon dioxide powder and a liquid, mixing the silicon dioxide powder with the liquid to obtain a slurry, and ultrasonicating the slurry. and passing at least a portion of the precursor suspension through a first multi-stage filter device, the first multi-stage filter device comprising: having at least first, second and third filter stages, each filter stage comprising at least one filter, the second filter stage positioned downstream of the first filter stage, and the third filter stage comprising , arranged downstream of the second filter step, the first filter step has a filter opening of 5 μm or more, the second filter step has a filter opening in the range of 0.5 to 5 μm, 3 filter steps have a filter opening of 1 μm or less, at least one of the filter steps selected from the first, second and third filter steps has a separation rate of 99.5% or more, Separation rates for specified filters are in each case described in accordance with ISO 16889, where the filter opening indicates what is the smallest particle size that the filter will retain. . The present invention also relates to available silicon dioxide suspensions and value chain granules and products that can be made therefrom.

Fused silica, fused silica products, and products containing fused silica are known. Likewise, various processes for preparing quartz glass and quartz glass bodies are already known. Nevertheless, considerable efforts are still being made to identify preparation processes that are capable of preparing even higher purity, ie, impurity-free, quartz glass. Many applications of quartz glass and its processed products make high demands, for example in terms of homogeneity and purity. This applies in particular to quartz glass which is processed into light conductors or light emitters. Impurities can cause absorption in this area. This is a disadvantage as it leads to color changes and attenuation of the emitted light. A further application of high-purity quartz glass is in manufacturing processes in the fabrication of semiconductors. In this field, any impurities in the glass body can lead to defects in the semiconductor, so that rejects can occur during fabrication. The range of high purity fused silica used in these processes, especially the range of high purity synthetic fused silica, is labor intensive to prepare. These are precious.

Furthermore, there is a demand in the market to provide such high-purity silica glass, particularly high-purity synthetic silica glass, and products derived therefrom at low prices. Therefore, it is desired to provide high-purity silica glass at a lower price than before. In this regard, there is a need for both more cost-effective manufacturing methods and cheaper raw material sources.

A known process for preparing quartz glass bodies involves melting silicon dioxide and producing quartz glass bodies from the melt. Irregularities in the glass body, for example due to inclusion of gas in the form of bubbles, can lead to breakage of the glass body under load, especially at high temperatures, or render it unusable for certain purposes. . Impurities in the raw material of quartz glass may cause cracks, bubbles, streaks and discoloration in the quartz glass. When employed in processes for semiconductor preparation and processing, impurities contained in the glass body may be released and migrate to the processed semiconductor component. This is the case, for example, in etching processes, leading to defective semiconductor billets. A common problem associated with the known preparation processes is therefore the insufficient quality of the quartz glass bodies.

A further aspect relates to raw material efficiency. Injecting fused silica and raw materials that are otherwise stored as by-products into preferred industrial processes for fused silica products can reduce the cost of using these by-products as fillers in construction or the like. It seems to be more advantageous than disposing of it as garbage. These by-products are often separated out as fine dust on filters. This fine dust poses additional problems, especially with respect to health, occupational safety and handling.

SUMMARY OF THE INVENTION It is an object of the present invention to at least partially overcome one or more of the shortcomings of the prior art.
It is a further object of the present invention to provide light guides, emitters, moldings and coatings with a long lifetime.
It is a further object of the present invention to provide light guides, luminophores, moldings and coatings made from glass that is bubble-free or has a low bubble content.
It is a further object of the present invention to provide light guides, moldings and coatings made from glass with high transparency.
It is a further object of the present invention to provide light guides, phosphors, moldings and coatings with low opacity.
It is a further object of the present invention to provide a light guide with low attenuation.
It is a further object of the present invention to provide light guides, emitters, moldings and coatings with high contour accuracy. In particular, it is an object of the present invention to provide optical conductors, emitters, moldings and coatings which do not deform even at high temperatures. In particular, it is an object of the present invention to provide light guides, light emitters, moldings and coatings which are shape-stable even when formed in large sizes.
It is a further object of the present invention to provide light guides, emitters, moldings and coatings that are resistant to tearing and breakage.
It is a further object of the present invention to provide light guides, phosphors, moldings and coatings that are efficient to prepare.
It is a further object of the present invention to provide light guides, emitters, moldings and coatings that are cost effective to prepare.
It is a further object of the present invention to provide light guides, luminophores, moldings and coatings which do not require lengthy further processing steps to prepare, such as tempering (strengthening, tempering).
It is a further object of the present invention to provide optical conductors, emitters, moldings and coatings with high thermal shock resistance. It is a particular object of the present invention to provide optical conductors, light emitters, moldings and coatings which exhibit only a small thermal expansion even with large thermal fluctuations.
It is a further object of the present invention to provide light conductors, emitters, moldings and coatings with high hardness.
It is a further object of the present invention to provide optical conductors, phosphors, moldings and coatings with high purity and low foreign atom contamination. The term foreign atom is adopted to mean a constituent that is not intentionally introduced.
It is a further object of the present invention to provide light conductors, emitters, moldings and coatings with a low content of dopant materials.
It is a further object of the present invention to provide light conductors, emitters, moldings and coatings with high homogeneity. Homogeneity of a property or material is a measure of the uniformity of distribution of this property or material in a sample.
It is a particular object of the present invention to provide optical conductors, emitters, moldings and coatings with high material homogeneity. Material homogeneity is a measure of the uniformity of the distribution of elements and compounds, especially OH, chlorine, metals, especially aluminum, alkaline earth metals, refractory metals and dopant materials, contained in a light guide, light emitter or semiconductor device.

Provided is a quartz glass body which is suitable for use in light guides, illuminants and moldings and coatings made from glass and which at least partially solves at least one and preferably some of the above objects. It is a further object of the present invention.
It is a further object of the invention to provide a quartz glass body having a linear morphology. In particular, it is an object to provide a quartz glass body with a high bending radius. In particular, it is a further object to provide a quartz glass body with high fiber curl.
It is a further object to provide a quartz glass body with the lowest possible migration of cations.
It is a further object to provide a quartz glass body with high homogeneity over the entire length of the quartz glass body.
In particular, it is a further object of the invention to provide a quartz glass body having a high refractive index homogeneity over the entire length of the quartz glass body.
In particular, it is a further object of the invention to provide a quartz glass body having a high viscosity homogeneity over the entire length of the quartz glass body.
In particular, it is a further object of the invention to provide a quartz glass body having a high material homogeneity over the entire length of the quartz glass body.
In particular, it is a further object of the present invention to provide a quartz glass body with high optical homogeneity over the entire length of the quartz glass body.

It is a further object of the present invention to provide silicon dioxide powders with high sintering activity.
It is a further object of the present invention to provide silicon dioxide powders with low sintering temperatures.
It is a further object of the present invention to provide a silicon dioxide powder from which stable granules can be obtained.

It is a further object of the present invention to provide silicon dioxide granules with good handleability.
It is a further object of the present invention to provide silicon dioxide granules having a low fine dust content.
It is a further object to provide silicon dioxide granules that can be easily stored, transported and transported.
It is a further object of the present invention to provide silicon dioxide granules capable of forming bubble-free quartz glass bodies. It is a further object of the present invention to provide silicon dioxide granules containing the lowest possible gas volume as bulk material.
It is a further object of the present invention to provide open-pored silicon dioxide granules.

It is a further object of the present invention to provide a process by which a quartz glass body can be prepared in which at least some of the above objects are at least partially solved.
It is a further object of the present invention to provide a process by which quartz glass bodies can be prepared more simply.
It is a further object of the present invention to provide a process by which quartz glass bodies can be prepared continuously.
It is a further object of the present invention to provide a process by which quartz glass bodies can be prepared by a continuous melting and forming process.
It is a further object of the present invention to provide a process capable of forming a quartz glass body at high speed.
It is a further object of the present invention to provide a process by which quartz glass bodies can be prepared with low rejection rates.
It is a further object of the present invention to provide a process capable of preparing an assemblable quartz glass body.
It is the present invention to provide a process for the preparation of quartz glass bodies in which silicon dioxide granules can be processed in a melting furnace without having to undergo a prior deliberate densification step, for example by temperature treatment above 1000°C. is a further object of
It is a particular object of the present invention to provide a process for the preparation of quartz glass bodies in which silicon dioxide granules with a BET of 20 m ² /g or more can be introduced into a melting furnace, melted and processed to obtain quartz glass bodies. is.
It is a further object of the present invention to provide an automated process by which quartz glass bodies can be prepared.

A further object of the present invention is to provide a method for producing a silicon dioxide suspension with as few particles as possible different from silicon dioxide with a particle size of more than 1 μm.
A further object of the present invention is to provide a method for producing a silicon dioxide suspension, the silicon dioxide suspension containing as few impurities as possible.
A further object of the present invention is to provide a method for producing a silicon dioxide suspension, wherein the solid components of the silicon dioxide suspension contain only Si, O, H, Cl and C atoms.
A further object of the present invention is to provide a method for producing a silicon dioxide suspension, wherein the solid components of the silicon dioxide suspension contain as few atoms as possible which are not Si, O, H, Cl or C. is.
A further object of the present invention is to provide a method for producing a silicon dioxide suspension from soot powder which is as homogeneous as possible and stable during storage.
A further object of the invention is to describe a method for producing high purity quartz glass.
A further object of the invention is to describe a method for producing quartz glass which is as bubble-free as possible.
A further object of the invention is to describe a method for producing quartz glass that is free of particles of metallic impurities.

It is the subject matter of the independent claims that contributes to at least partly carrying out at least one of the objects set forth above. The dependent claims are preferred embodiments that at least partly contribute to meeting at least one of the above objectives.

|1| A method for producing a silicon dioxide suspension, comprising:
(i) providing silicon dioxide powder;
(ii) providing a liquid;
(iii) mixing the silicon dioxide powder with the liquid to obtain a slurry;
(iv) sonicating the slurry to obtain a precursor suspension;
(v) passing at least a portion of the precursor suspension through a first multi-stage filter device, comprising:
the first multi-stage filter device having at least first, second and third filter stages;
each filter step includes at least one filter;
a second filter step downstream of the first filter step and a third filter step downstream of the second filter step;
The first filter step has a filter opening of 5 μm or more,
The second filter step has a filter opening in the range of 0.5 to 5 μm,
The third filter step has a filter opening of 1 μm or less,
At least one of the filter steps selected from the first, second and third filter steps has a separation rate of 99.5% or more,
The separation ratios for the filters described are in each case according to ISO 16889,
and said filter opening indicates what the minimum particle size that said filter will hold.

The silicon dioxide suspension of step (v) is preferably obtained after passing through the multi-stage filter device described above.

|2| wherein the first filter device is characterized by:
(a) the first filter step has a separation rate of 90% or less;
(b) the first filter step has a filter opening in the range of 5-15 μm;
(c) the second filter step has a separation rate of 95% or greater;
(d) the second filter step has a filter opening of 0.5 to 2 μm;
(e) The method of embodiment |1|, wherein the third filter step has a separation rate of 99.5% or greater, or a combination of two or more thereof.

|3| Embodiment |1| or The method according to embodiment |2|.

|4| The method of any one of embodiment |1| through embodiment |3| wherein said slurry is treated with ultrasound for at least 10 seconds.

|5| The method of any one of embodiment |1| through embodiment |4| wherein sonicating said slurry is characterized by a power density of up to 600 W/liter.

|6| Any of Embodiment |1| through Embodiment |5| wherein the slurry has less than 5% by weight of additives for stabilizing the slurry, wherein the weight % is based on the total weight of the slurry. or the method of claim 1.

|7| The method of any one of embodiments |1| through embodiment |6|, wherein the silicon dioxide powder is made from a compound selected from the group comprising siloxanes and silicon alkoxides.

|8| The silicon dioxide powder has the following properties:
a. a carbon content of less than 100 ppm;
b. a chlorine content of less than 500 ppm;
c. an aluminum content of less than 200 ppb;
d. Content of atoms other than Si, O, H, C, Cl less than 5 ppm,
e. at least 70% by weight of the powder particles have a primary particle size in the range of 10-100 nm;
f. tamping densities (Stampfdichte) in the range from 0.001 to 0.3 g/cm ³ ,
g. residual moisture less than 5% by weight,
h. a BET surface area of less than 35 g/m ² ;
or at least one of the properties a. ~ h. having a combination of two or more of
The method of any one of embodiment |1| through embodiment |7|, wherein said weight percentages, ppm and ppb are in each case based on the total amount of silicon dioxide powder.

|9| The slurry has the following properties:
a. ) a solids content of at least 20% by weight, based on the dry weight of the slurry;
b. ) as a 4 wt% slurry, the slurry having a pH value in the range of 3 to 8;
c. ) at least 90% by weight of the silicon dioxide particles have a particle size in the range of 1 nm to less than 10 μm;
d. ) a chlorine atom content of 500 ppm or less,
e. ) content of atoms other than Si, O, H, C, and Cl of 5 ppm or less;
f. ) the slurry is rheopexic,
wherein the weight percent and ppm are always based on the total solids content of the slurry. Embodiment |1| through Embodiment |8|.

|10| The silicon dioxide suspension has the following properties:
A. Rheopexic properties at temperatures below 45° C. and solids concentrations in the range of 20-70% by weight, the weight percent being based on total solids in the suspension,
B. at least 90% of the silicon dioxide particles, based on the total weight of all silicon dioxide particles, have a particle size in the range of 1 nm to less than 10 μm;
C. As a 4 wt% suspension, the suspension has a pH value in the range of 3 to 8, this wt% being based on the solids content of the suspension;
D. a chlorine content of less than 500 ppm;
E. an aluminum content of less than 200 ppb;
F. having a content of at least one of atoms other than Si, O, H, C, Cl less than 5 ppm, wherein said ppm and ppb are based on the total amount of silicon dioxide particles Embodiment |1| to Embodiment |9 The method according to any one of |.

|11| any of embodiments |1| through embodiment |10| wherein the service life of the first multi-stage filter device is at least 250 liters, the liters being based on the filtered volume of the precursor suspension filter device or the method of claim 1.

|12| The method of any one of embodiments |1| through embodiment |11|, wherein at least one further filter device is employed downstream of the first multi-stage filter device.

|13| A silicon dioxide suspension obtainable by the process according to any one of embodiments |1| to embodiment |12|.

|14| A method for producing silicon dioxide granules, by the silicon dioxide suspension according to embodiment |13| or by the method according to any one of embodiments |1| to |12| A method in which the resulting silicon dioxide suspension is treated to obtain silicon dioxide granules, the silicon dioxide granules having a larger particle size than the silicon dioxide particles present in the silicon dioxide suspension.

|15| The method of embodiment |14|, wherein the treatment produces granules comprising silicon dioxide granules, the granules having a spherical morphology.

|16| The method of embodiment |14| or embodiment |15| wherein the treatment is spray granulation.

|17| Spray drying has the following properties:
a] spray granulation in a spray tower,
b] Silicon dioxide suspension at the nozzle up to 40 bar, for example in the range from 1.3 to 20 bar, 1.5 to 18 bar, 2 to 15 bar, or 4 to 13 bar, particularly preferably in the range from 5 to 12 bar. , which is stated as an absolute value (relative to p=0 hPa),
c] the temperature of the droplets entering the spray tower is in the range from 10 to 50°C, preferably in the range from 15 to 30°C, particularly preferably in the range from 18 to 25°C,
d) the temperature on the side of the nozzle facing the spray tower is in the range from 100 to 450° C., for example in the range from 250 to 440° C., particularly preferably from 320 to 430° C.
e] The silicon dioxide suspension is in the range from 0.05 to 1 m ³ /h, for example from 0.1 to 0.7 m ³ /h or from 0.2 to 0.5 m ³ /h, particularly preferably from 0.25 to passes through the nozzle in the range of 0.4 m ³ /h,
f] Silicon dioxide is at least 40% by weight, for example in the range from 50 to 80% by weight, or in the range from 55 to 75% by weight, particularly preferably from 60% to having a solids content in the range of 70% by weight;
g] a gas stream entering the spray tower in the range 10-100 kg/min, such as in the range 20-80 kg/min or in the range 30-70 kg/min, particularly preferably in the range 40-60 kg/min;
h] gas entering the spray tower at a temperature in the range from 100 to 450°C, for example in the range from 250 to 440°C, particularly preferably in the range from 320 to 430°C,
i) the temperature of the gas exiting the spray tower is less than 170°C;
j] the gas is selected from the group consisting of air, nitrogen and helium or a combination of two or more thereof, preferably air;
k] when removed from the spray tower, the granules are in each case less than 5 wt. %, or in the range from 0.01 to 0.5% by weight, particularly preferably in the range from 0.1 to 0.3% by weight,
l] at least 50% by weight, based on the total weight of the silicon dioxide granules produced by spray drying, for a time in the range from 1 to 100 seconds, for example from 10 to 80 seconds, particularly preferably from 25 to 70 seconds to complete the flight time,
m] based on the total weight of the silicon dioxide granules produced by spray drying, at least 50% by weight of the fly over, or over 200 m, or in the range of 20-200 m, or 10-150 m, or 20-100 m, particularly preferably in the range of 30-80 m,
n] the spray tower has a cylindrical shape,
o] the height of the spray tower is more than 10 m, such as more than 15 m, or more than 20 m, or more than 25 m, or more than 30 m, or in the range 10-25 m, particularly preferably in the range 15-20 m,
p] filtering out particles with a size of less than 90 μm before removing the granules from the spray tower;
q] After removing the granules from the spray tower, preferably on a vibrating chute, filtering out particles with a size greater than 500 μm,
r] An embodiment characterized in that at least one droplet of the silicon dioxide suspension emerges from the nozzle at an angle of 30-60° to the vertical, particularly preferably at an angle of 45° to the vertical. The method of any one of |14| through embodiment |16|.

|18| The silicon dioxide granules have the following properties:
A) an angle of repose in the range 23-26°;
B) a BET surface area in the range of 20-50 m ² /g;
C) bulk density in the range of 0.5 to 1.2 g/ ^cm3 ;
D) the silicon dioxide granule particles have an average particle size in the range of 50-500 μm;
E) a carbon content of less than 50 ppm;
F) a chlorine content of less than 500 ppm;
G) an aluminum content of less than 200 ppb;
H) content of atoms other than Si, O, H, C less than 5 ppm;
I) the silicon dioxide granule particles have a tamping density in the range of 0.7 to 1.3 g/ ^cm3 ;
J) the silicon dioxide granule particles have a pore volume in the range of 0.1 to 2.5 mL/g;
K) the silicon dioxide granule particles have a particle size distribution (particle size distribution) _D10 in the range from 50 to 150 μm,
L) the silicon dioxide granule particles have a particle size distribution _D50 in the range from 150 to 300 μm,
M) the silicon dioxide granule particles have a particle size distribution D ₉₀ in the range from 250 to 620 μm, and the ppm and ppb are in each case based on the total weight of the silicon dioxide granules The method of any one of embodiment |14| through embodiment |17|.

|19| A method for manufacturing a quartz glass body comprising at least i. ) providing silicon dioxide granules obtainable by the method of any one of Embodiments |14| through |18|;
ii. ) forming a glass melt from the silicon dioxide granules;
iii. ) forming a quartz glass body from at least a portion of the glass melt.

|20| A quartz glass body obtained by the method described in Embodiment |19|.

|21| The following properties:
A] a chlorine content of less than 500 ppm,
B] an aluminum content of less than 200 ppb,
C] content of atoms other than Si, O, H, C less than 5 ppm,
D] 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 ~ log ₁₀ (η (1300 ° C) / dPas) = 12.2, or log ₁₀ (η (1350 ° C) / dPas) = 10.5 to log ₁₀ (η (1350 ° C) / dPas) = 11.5 range of viscosities (p=1013 hPa),
E] refractive index homogeneity of less than 10 ⁻⁴ ,
F] Cylindrical morphology,
G] a tungsten content of less than 5 ppm,
H] at least one molybdenum content of less than 5 ppm, said ppb and ppm being in each case based on the total weight of the quartz glass body |20|.

|22| A method for manufacturing a light guide, comprising:
A/ A quartz glass body according to embodiment |20| or embodiment |21| or obtainable by the method according to embodiment |19| is provided, and the quartz glass body is first processed. , obtaining a hollow body having at least one opening;
B/ inserting one or more core rods into the hollow body from step A/ through at least one opening to obtain a precursor;
C/ drawing this precursor while heating to obtain a light guide having one or more cores and a jacket M1.

|23| A light guide obtainable by the method according to embodiment |22|.

|24| A method for manufacturing a light guide, comprising:
(i) providing a quartz glass body according to embodiment |20| or embodiment |21| or obtainable by the method according to embodiment |19|, which quartz glass body is first processed; to obtain a hollow body having at least one opening;
(ii) attaching electrodes to the hollow body as required;
(iii) filling the hollow body from step (i) with a gas.

|25| A light guide obtainable by the method according to embodiment |24|.

|26| A method for producing a molded body, comprising:
(1) Providing the quartz glass body according to Embodiment |20| or |21| or obtained by the method according to Embodiment |19|;
(2) A method including the step of molding the quartz glass body to obtain a molded body.

|27| A molded article obtained by the method described in Embodiment |26|.

|28| A method of manufacturing a coating on a substrate, comprising:
providing a silicon dioxide suspension and a substrate according to the method of any one of |A|Embodiment|1| through Embodiment |12|;
|B| depositing a coating of the silicon dioxide suspension on a substrate.

General Remarks As used herein, the ranges stated include the values stated as the limits. Therefore, a description of the type “range from x to y” for a variable A means that A can take on the values x, y and between x and y. Thus, a unilaterally restricted range of the type "up to y" for variable A implies values y and less than y.

FIG. 1 schematically shows the process steps for producing a silicon dioxide suspension according to the first aspect. FIG. 2 shows a first filter arrangement with three filter stages, first, second and third filter stages. FIG. 3 shows a further arrangement of filters. FIG. 4 schematically shows a method of manufacturing a quartz glass body. FIG. 5 shows, by way of example, a) the particle size distribution of the slurry, b) the particle size distribution of the precursor suspension after dispersion. FIG. 6 shows three hot quartz glass bodies: a) many bubbles, b) few bubbles, c) very many bubbles (foam glass). FIG. 7 shows that the melt used is a) a vitreous body, which is granules formed from an unfiltered silicon dioxide suspension, and b) the melt used is filtered dioxide as in the present invention. A comparative image with a glass body obtained from granules of silicon suspension is shown.

Contributions to at least partially meeting at least one of the above objectives are made by the independent claims. The dependent claims provide preferred embodiments that contribute to at least partially fulfilling at least one of the objectives.

A first aspect of the present invention is a method for producing a silicon dioxide suspension, comprising:
(i) providing silicon dioxide powder;
(ii) providing a liquid;
(iii) mixing the silicon dioxide powder with the liquid to obtain a slurry;
(iv) sonicating the slurry to obtain a precursor suspension;
(v) passing at least a portion of the precursor suspension through a first multi-stage filter device, comprising:
the first multi-stage filter device having at least first, second and third filter stages;
each filter step includes at least one filter;
a second filter stage located downstream of the first filter stage and a third filter stage located downstream of the second filter stage;
The first filter step has a filter opening (accuracy) of 5 μm or more,
The second filter step has a filter opening in the range of 0.5 to 5 μm,
The third filter step has a filter opening of 1 μm or less,
At least one of the filter steps selected from the first, second and third filter steps has a separation rate of 99.5% or more,
The separation ratios are stated in accordance with ISO 16889, in each case based on the stated filters,
and c. indicating what the minimum particle size the filter will hold.

Silicon Dioxide Powder In the present invention, it is possible in principle to obtain silicon dioxide powder from silicon dioxide that occurs in nature or from synthetically produced silicon dioxide. Preferably, synthetic silicon dioxide powder is used. Particular preference is given to using silicon dioxide powders produced by calcination.

The silicon dioxide powder can be any silicon dioxide powder having at least two particles. The method of manufacture is common to those skilled in the art and can be any method deemed suitable for the present purpose.

According to one embodiment of the invention, silicon dioxide powder is produced as a by-product in the production of quartz glass, in particular in the production of so-called soot bodies. Silicon dioxide from such sources is often also referred to as "soot dust".

A preferred source of said silicon dioxide powder is silicon dioxide particles obtained from the synthetic preparation of a soot body by application of a flame hydrolysis burner. In preparing the soot body, a rotating carrier tube with cylinder jacket surfaces is moved back and forth along the row of burners. The flame hydrolysis burner can be supplied with oxygen and hydrogen as burner gases in addition to the raw materials for producing the silicon dioxide primary particles. The silicon dioxide primary particles preferably have a primary particle size of up to 100 nm. Silicon dioxide primary particles produced by flame hydrolysis agglomerate or agglomerate to form silicon dioxide particles with a particle size of about 9 μm (DIN ISO 13320:2009-1). For silicon dioxide particles, scanning electron microscopy can identify the shape of the silicon dioxide primary particles and measure the primary particle size. A portion of the silicon dioxide particles deposit on the cylinder jacket surface of the carrier tube rotating about its longitudinal axis. In this way, the soot body is built up layer by layer. Another portion of the silicon dioxide particles does not deposit on the cylinder jacket surface of the carrier tube, but rather accumulates, for example, as dust in the filter system. Another portion of the silicon dioxide particles constitutes silicon dioxide powder, often referred to as "soot dust". Based on the total weight of the silicon dioxide particles, generally the portion of the silicon dioxide particles that deposit on the carrier tube is greater than the portion of the silicon dioxide particles that accumulate as soot dust for the preparation of the soot body.

These days, soot dust is generally disposed of as waste at a cost and for a fee, or as a non-value-added filler, for example in road construction, as an additive in the dye industry, for the tile industry and in building foundations. It is used as a raw material for the preparation of hexafluorosilicic acid, which is used in the repair of For the present invention, soot dust is a suitable raw material and can be processed to obtain high quality products.

Silicon dioxide prepared by flame hydrolysis is commonly referred to as calcined silicon dioxide. Calcined silicon dioxide is usually available in the form of amorphous silicon dioxide primary particles or silicon dioxide particles.

According to a preferred embodiment, the silicon dioxide powder can be prepared from mixed gases by flame hydrolysis. In this case, silicon dioxide particles are also produced in the flame hydrolysis and removed before lumps or agglomerates are formed. Here, silicon dioxide powder, referred to above as soot dust, is the major product.

Suitable raw materials for producing silicon dioxide powder are preferably siloxanes, silicon alkoxides and inorganic silicon compounds. Siloxane means linear and cyclic polyalkylsiloxanes. Preferably, the polyalkylsiloxane has the general formula Si _p O _p R _2p
wherein p is an integer of at least 2, preferably 2 to 10, particularly preferably 3 to 5,
R is an alkyl group having 1 to 8 C atoms, preferably 1 to 4 C atoms, particularly preferably a methyl group.

Particularly preferred are siloxanes selected from the group consisting of hexamethyldisiloxane, hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5), or two of these It is a combination of the above. When the siloxane contains D3, D4 and D5, preferably D4 is the major component. Preferably, the main component is at least 70% by weight, preferably at least 80% by weight, such as at least 90% by weight or at least 94% by weight, particularly preferably at least 98% by weight, in each case based on the total amount of silicon dioxide powder. is present in an amount of Preferred silicon alkoxides are tetramethoxysilane and methyltrimethoxysilane. Preferred inorganic silicon compounds as sources of silicon dioxide powder are silicon halides, silicates, silicon carbide and silicon nitride. Silicon tetrachloride and trichlorosilane are particularly preferred inorganic silicon compounds as raw materials for the silicon dioxide powder.

According to a preferred embodiment, the silicon dioxide powder can be prepared from compounds selected from the group consisting of siloxanes, silicon alkoxides and silicon halides.

Preferably, the silicon dioxide powder is hexamethyldisiloxane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane, tetramethoxysilane and methyltrimethoxysilane, silicon tetrachloride and trichlorosilane or two of these. It can be prepared from compounds selected from the group consisting of combinations of two or more, for example from silicon tetrachloride and octamethylcyclotetrasiloxane, particularly preferably from octamethylcyclotetrasiloxane.

Various parameters are important for the production of silicon dioxide from silicon tetrachloride by flame hydrolysis. A preferred composition of a suitable mixed gas includes a flame hydrolysis oxygen content in the range of 25-40% by volume. The hydrogen content can range from 45 to 60% by volume. The content of silicon tetrachloride is preferably 5-30% by volume, all the above volume percentages being based on the total volume of the gas stream. Further preferred are combinations of the above-mentioned volume proportions of oxygen, hydrogen and _SiCl4 . The flame in flame hydrolysis preferably has a temperature in the range from 1500 to 2500°C, for example in the range from 1600 to 2400°C, particularly preferably in the range from 1700 to 2300°C. Preferably, the primary particles of silicon dioxide resulting from flame hydrolysis are removed as silicon dioxide powder before lumps or agglomerates are formed.

The silicon dioxide powder may have at least one, such as at least two or at least three, or at least four, preferably at least five, of the following characteristics.
i. a BET surface area of less than 35 m ² /g, such as 25-35 m ² /g, or in the range of 25-30 m ² /g, and ii. 0.01 to 0.3 g/cm ³ , for example 0.02 to 0.2 g/cm ³ , preferably 0.03 to 0.15 g/cm ³ , more preferably 0.1 to 0.2 g / ^cm3 , or bulk density in the range of 0.05-0.1 g/ ^cm3 ,
iii. a carbon content of less than 100 ppm, such as less than 50 ppm or less than 30 ppm, particularly preferably in the range from 1 ppb to 20 ppm,
iv. a chlorine content of less than 500 ppm, such as less than 300 ppm or less than 150 ppm, particularly preferably in the range from 1 ppb to 80 ppm,
v. an aluminum content of less than 200 ppb, for example in the range from 1 to 100 ppb, particularly preferably in the range from 1 to 80 ppb,
vi. a total content of atoms other than Si, O, H, C, Cl less than 5 ppm, for example less than 2 ppm, particularly preferably in the range from 1 ppb to 1 ppm;
vii. at least 70% by weight of the powder particles have a primary particle size in the range from 10 to 100 nm, such as from 15 to less than 100 nm, particularly preferably from 20 to less than 100 nm,
viii. in the range of 0.001 to 0.3 g/cm ³ , such as in the range of 0.002 to 0.2 g/cm ³ , or in the range of 0.005 to 0.1 g/cm ³ , preferably 0.01 to 0.06 g/cm a tamping density in the range of ³ , preferably in the range of 0.1-0.2 g/cm ³ or in the range of 0.15-0.2 g/cm ³ ;
ix. A residual water content of less than 5% by weight, for example in the range from 0.25 to 3% by weight, particularly preferably in the range from 0.5 to 2% by weight.
The above weight percentages, ppm and ppb are each based on the total weight of the silicon dioxide powder.

The silicon dioxide powder contains silicon dioxide. Preferably, the silicon dioxide powder contains more than 95% by weight, such as more than 98% by weight, or more than 99% by weight, or more than 99.9% by weight of the dioxide Contains silicon. Particularly preferably, the silicon dioxide powder comprises a proportion of silicon dioxide greater than 99.99% by weight, based on the total weight of the silicon dioxide powder.

The silicon dioxide powder preferably has a content of atoms other than Si, O, H, C, Cl of less than 5 ppm, for example less than 2 ppm, particularly preferably less than 1 ppm, in each case based on the total weight of the silicon dioxide powder. but the silicon dioxide powder often has a content of atoms other than Si, O, H, C, Cl in an amount of at least 1 ppb. Atoms other than Si, O, H, C, and Cl may be present, for example, as elements, ions, or as part of molecules, ions, or complexes.

Preferably, at least 70% of the powder particles of said silicon dioxide powder, based on the number of powder particles, have a primary particle size of less than 100 nm, such as in the range from 10 to 100 nm or from 15 to 100 nm, particularly preferably in the range from 20 to 100 nm. . This primary particle size is measured by a dynamic light scattering method according to ISO 13320:2009-10.

Preferably, at least 75% of the powder particles of said silicon dioxide powder, based on the number of powder particles, have a primary particle size of less than 100 nm, such as in the range from 10 to 100 nm or from 15 to 100 nm, particularly preferably in the range from 20 to 100 nm. .

Preferably, based on the number of powder particles, at least 80% of the powder particles of said silicon dioxide powder have a primary particle size of less than 100 nm, such as in the range from 10 to 100 nm or from 15 to 100 nm, particularly preferably in the range from 20 to 100 nm. .

Preferably, at least 85% of the powder particles of said silicon dioxide powder, based on the number of powder particles, have a primary particle size of less than 100 nm, such as in the range from 10 to 100 nm or from 15 to 100 nm, particularly preferably in the range from 20 to 100 nm. have

Preferably, based on the number of powder particles, at least 90% of the powder particles of said silicon dioxide powder have a primary particle size of less than 100 nm, such as in the range from 10 to 100 nm or from 15 to 100 nm, particularly preferably in the range from 20 to 100 nm. .

Preferably, based on the number of powder particles, at least 95% of the powder particles of said silicon dioxide powder have a primary particle size of less than 100 nm, such as in the range from 10 to 100 nm or from 15 to 100 nm, particularly preferably in the range from 20 to 100 nm. have

Preferably, the silicon dioxide powder has a specific surface area (BET surface area) in the range of 20-35 m ² /g, such as 25-35 m ² /g, or 25-30 m ² /g. This BET surface area is determined according to the method of Brunauer, Emmet and Teller (BET) according to DIN 66132, based on gas absorption on the surface to be measured.

Preferably, the silicon dioxide powder has a pH value of less than 7, for example in the range from 3 to 6.5, or from 3.5 to 6, or from 4 to 5.5, particularly preferably in the range from 4.5 to 5. have. This pH value can be measured with a single rod measuring electrode (4% silicon dioxide powder in water).

The silicon dioxide powder preferably has a combination of characteristics a. /b. /c. or a. /b. /f. or a. /b. /g. , more preferably a combination of features a. /b. /c. /f. or a. /b. /c. /g. or a. /b. /f. /g. , particularly preferred combinations of features a. /b. /c. /f. /g. have

The silicon dioxide powder preferably has a combination of characteristics a. /b. /c. with a BET surface area in the range of 20-35 m ² /g, a bulk density in the range of 0.05-0.3 g/mL and a carbon content of less than 40 ppm.

The silicon dioxide powder preferably has a combination of characteristics a. /b. /f. having a BET surface area in the range of 20 to 35 m ² /g, a bulk density in the range of 0.05 to 0.3 g/mL, and a total content of metals other than aluminum in the range of 1 ppb to 1 ppm be.

The silicon dioxide powder preferably has a combination of characteristics a. / b. /g. with a BET surface area in the range of 20-35 m ² /g, a bulk density in the range of 0.05-0.3 g/mL, and at least 70% by weight of the powder particles in the range of 20-100 nm It has a primary particle size.

The silicon dioxide powder preferably has a combination of characteristics a. /b. /c. /f. with a BET surface area in the range of 20-35 m ² /g, a bulk density in the range of 0.05-0.3 g/mL, a carbon content of less than 40 ppm, and the sum of metals other than aluminum The content is in the range of 1 ppb to 1 ppm.

The silicon dioxide powder preferably has a combination of characteristics a. / b. /c. /g. with a BET surface area in the range of 20-35 m ² /g, a bulk density in the range of 0.05-0.3 g/mL, a carbon content of less than 40 ppm, and a powder particle of at least 70 wt. % have a primary particle size in the range from 20 to less than 100 nm.

The silicon dioxide powder preferably has a combination of characteristics a. /b. /f. /g. having a BET surface area in the range of 20 to 35 m ² /g, a bulk density in the range of 0.05 to 0.3 g/mL, and a total content of metals other than aluminum in the range of 1 ppb to 1 ppm and at least 70% by weight of the powder particles have a primary particle size in the range of 20 to less than 100 nm.

The silicon dioxide powder preferably has a combination of characteristics a. /b. /c. /f. /g. with a BET surface area in the range of 20-35 m ² /g, a bulk density in the range of 0.05-0.3 g/mL, a carbon content of less than 40 ppm, and the sum of metals other than aluminum The content is in the range of 1 ppb to 1 ppm and at least 70% by weight of the powder particles have a primary particle size in the range of 20 to less than 100 nm.

Steps (i) to (v) of the first aspect can be read as follows.
(i) providing silicon dioxide powder;
(ii) providing a liquid;
(iii) mixing the silicon dioxide powder with the liquid to obtain a slurry;
(iv) sonicating the slurry to obtain a precursor suspension;
(v) passing at least a portion of the precursor suspension through a first multi-stage filter device, comprising:
the first multi-stage filter device having at least first, second and third filter stages;
each filter step has at least one filter;
a second filter step downstream of the first filter step and a third filter step downstream of the second filter step;
The first filter step has a filter opening of 5 μm or more,
The second filter step has a filter opening in the range of 0.5 to 5 μm,
The third filter step has a filter opening of 1 μm or less,
At least one of the filter steps selected from the first, second and third filter steps has a separation rate of 99.5% or more,
The separation rates are stated in accordance with ISO 16889, in each case based on filters,
The filter opening indicates what the minimum particle size the filter will hold.

Further filter steps may be provided between the filter steps referred to as the first, second and third filter steps.

For the purposes of the present invention, liquid is taken to mean a substance or mixture of substances which is liquid at a pressure of 1013 hPa and a temperature of 20°C.

For the purposes of the present invention, "slurry" means a mixture of at least two substances, the mixture having at least one liquid and at least one solid, given the current conditions. . A slurry and a precursor suspension are formed during the method. The precursor suspension is also a slurry, but it is sonicated as in step (iv). Unless the description below explicitly refers to a "slurry" or a "precursor suspension", i.e. to a "slurry" in general, the description is in principle a slurry or a precursor suspension, or It may be applied to both slurries and precursor suspensions. This is because when processing a slurry to obtain a precursor suspension, not all the properties described below change with the processing, or even if the properties do change, the properties are It can be justified on the grounds that it generally stays within the stated properties.

Suitable liquids are all materials and mixtures of materials known to the person skilled in the art and considered suitable for the present application. Preferably, the liquid is selected from the group consisting of organic liquids and water. Preferably, the solubility of said silicon dioxide powder in liquids is less than 0.5 g/L, preferably less than 0.25 g/L, particularly preferably less than 0.1 g/L, each g/L of liquid 1 It is given as grams of silicon dioxide powder per liter.

Preferred suitable liquids are polar solvents. These can be organic liquids or water. Preferably, the liquid is selected from the group consisting of water, methanol, ethanol, n-propanol, iso-propanol, n-butanol, tert-butanol, and mixtures of two or more thereof. Particularly preferably, said liquid is water. Particularly preferably, the liquid also comprises distilled or deionized water, eg "ultra-pure water". Such water has an electrical conductivity of less than 0.2 μS/cm.

Preferably, the silicon dioxide powder is processed (processed) to obtain a slurry. Silicon dioxide powder is sparingly soluble in liquids at room temperature, but can be introduced into liquids in high weight proportions to obtain slurries.

The silicon dioxide powder and liquid can be mixed in any manner. For example, the silicon dioxide powder can be added to the liquid, or the liquid can be added to the silicon dioxide powder. The mixture can be agitated during or after the addition. Particularly preferably, the mixture is stirred during and after the addition. Examples of agitation are shaking and stirring, or a combination of both. Preferably, the silicon dioxide powder can be added to the liquid under stirring. Further, preferably a portion of the silicon dioxide powder is added to the liquid, the mixture thus obtained is agitated, and then this mixture is mixed with the remaining portion of the silicon dioxide powder. Similarly, a portion of the liquid may be added to the silicon dioxide powder, the mixture thus obtained is agitated, and then this mixture is mixed with the remaining portion of the liquid.

A slurry is obtained by mixing the silicon dioxide powder and the liquid. Preferably, the slurry is a suspension of silicon dioxide powder uniformly distributed in a liquid. "Uniform" means that the density and composition of the slurry at each location does not deviate from the average density and composition by more than 10%, in each case based on the total mass of the slurry. A uniform distribution of silicon dioxide powder in the liquid can be prepared and/or obtained by agitation as described above.

Preferably, the slurry has a weight per liter in the range 1000-2000 g/L, such as in the range 1200-1900 g/L, or in the range 1300-1800 g/L, particularly preferably in the range 1400-1700 g/L. . Weight per liter is determined by weighing a volume-calibrated container.

According to a preferred embodiment, at least one, for example at least two, or at least three, or at least four, particularly preferably at least five, of the following features are applied to the slurry.
a. ) the slurry contains at least 20% by weight, such as in the range 20-70% by weight, or in the range 30-50% by weight, or in the range 55-75% by weight, in each case based on the total weight of the slurry; having a solids content in the range of 60-70% by weight;
b. ) The slurry has a pH value in the range of 3 or more, such as greater than 4, or in the range of 4.5 to 8 or 4.5 to 7, which pH value is based on a 4 wt. It is determined,
c. ) in a 4% by weight slurry, at least 90% of the silicon dioxide particles have a particle size according to DIN ISO 13320-1 in the range from 1 nm to less than 10 μm, such as from 200 to 300 nm,
d. ) content of atoms other than Si, O, H, C and/or Cl of 5 ppm or less;
e. ) the slurry is rheopexic,
f. ) the slurry is conveyed in contact with the plastic surface,
g. ) the slurry is sheared,
h. ) the slurry has a temperature above 0° C., preferably in the range of 5-35° C.
i. ) The slurry has a viscosity according to DIN 53019-1 (5 rpm, 30 wt.

According to another embodiment, the above property a. ) to j. ) also applies to the precursor suspension.

In a 4% by weight aqueous slurry, the silicon dioxide particles preferably have a particle size D10 in the range from 50 to 250 nm, particularly preferably in the range from ₁₀₀ to 150 nm. In a 4% by weight aqueous slurry, the silicon dioxide particles preferably have a particle size D ₅₀ in the range from 100 to 400 nm, particularly preferably from 200 to 250 nm. In a 4% by weight aqueous solution, the silicon dioxide particles preferably have a particle size D ₉₀ in the range from 200 to 600 nm, particularly preferably in the range from 350 to 400 nm. This particle size is determined according to DIN ISO 13320-1. References to particle sizes D ₁₀ , D ₅₀ , D ₉₀ or combinations of two or more thereof may also apply to the precursor suspension.

Particle size is taken to mean the size of the particles coalesced from the primary particles present in the silicon dioxide powder, in the slurry, in the precursor suspension or in the silicon dioxide granules. The average particle size is taken to mean the arithmetic mean of all particle sizes of the substances mentioned. The _D50 value indicates that 50% of the particles, based on total particle number, are smaller than the stated value. A D10 value indicates that ₁₀ % of the particles, based on the total number of particles, are smaller than the stated value. The _D90 value indicates that 90% of the particles, based on total particle number, are smaller than the stated value. Particle size is determined by dynamic image analysis according to ISO 13322-2:2006-11.

"Isoelectric point" is taken to mean the pH value at which the zeta potential takes the value zero. Zeta potential is determined according to ISO 13099-2:2012.

The pH value of the slurry is preferably set to a value in the range mentioned above. To set the pH value of the slurry, a substance such as NaOH or _NH3 may preferably be added to the aqueous slurry solution while stirring the slurry frequently. What has been said about the pH value of the slurry may also apply to the pH value of the precursor suspension.

In the next step (iv), the slurry is sonicated to obtain a precursor suspension. For treatment with ultrasound, any method and any source of ultrasound may in principle be chosen on the basis known to the person skilled in the art and considered suitable for the present application.

In the present context, ultrasound is sound with peak frequencies in the range of 20-100 kHz. This may be a single frequency or bandwidth tone. In the latter case, at least 60% of the ultrasound frequencies used in the treatment range over the peak frequency ±10 Hz.

In further embodiments, the slurry is sonicated for at least 10 seconds, such as at least 20 seconds, at least 40 seconds, or at least 60 seconds, 120 seconds, 180 seconds, or 240 seconds.

In further embodiments, the slurry is sonicated for up to 1000 seconds, such as up to 500 seconds or up to 200 seconds, or up to 100 seconds, 50 seconds or 20 seconds.

In a further embodiment, the slurry is sonicated for a period ranging from 10 seconds to 1800 seconds, such as from 30 seconds to 1000 seconds, or from 30 seconds to 600 seconds, or from 40 seconds to 300 seconds.

The power density used in ultrasound is obtained by dividing the power uptake of the ultrasound source by the volume of the slurry. In a further embodiment, the ultrasonic source used is an ultrasonic generator or an agitator ball mill, or a combination of both.

In further embodiments, the temperature of the slurry during sonication is in the range of 5-45°C, such as 10-40°C, or 15-40°C.

In further embodiments, the power density applied to the slurry by ultrasound is less than 600 W/liter, such as less than 450 W/liter, or about 300 W/liter, the power density being based on the volume of the slurry. Power densities are typically 100 W/liter or more.

In a further embodiment, the ultrasonic power density ranges from 400 to 500 W/liter and the treatment time ranges from 10 to 90 seconds.

In another embodiment, the ultrasonic power density is in the range of 300-400 W/liter and the treatment time is in the range of 90-250 seconds.

In the next step (v), at least a portion of the precursor suspension is passed through a first multi-stage filter device, the silicon dioxide suspension being the filtrate as the precursor suspension passes through the multi-stage filter device. can get. The first multi-stage filter device has at least first, second and third filter stages. The first multi-stage filter device may have further filter steps, for example possibly fourth and fifth and possibly sixth. The filter steps within a multi-stage filter device are arranged in a particular order. They are numbered sequentially downstream. That is, the precursor suspension first flows through a first filter stage, downstream thereof through a second filter stage, and so on. It is also conceivable to arrange several filters in parallel, in which case different amounts of suspension flow through the parallel arranged filters at approximately the same time. Placing multiple filters in parallel within a single filter stage can improve the useful life of the filter stage, or the throughput through the filter stage, or both. Further filter steps may be provided between the first and second filter steps described above, or between the second and third filter steps not further described here. Also, one or more further filter steps independent of each other may be provided between the second and third filter steps not further described here.

Each filter step includes at least one filter. Within one filter step, a single filter may be provided. Also, multiple filters may be provided. These are usually arranged in parallel, in which case the multiple filters are usually filters of the same characteristics. Multiple filters may be arranged in parallel as already described to split the flow within the filter step. This often results in improved service life within the filter process, or throughput through the filter process, or both.

The first filter step has a filter opening of 5 μm or more, such as 5 μm to 15 μm, or about 10 μm or about 15 μm.

The second filter step has a filter opening in the range of 0.5-5 μm, such as in the range of 0.5-2 μm, or about 1 μm or about 2 μm.

The third filter step has a filter opening of 1 μm or less, for example 1 μm or 0.5 μm.

At least one of the filter steps selected from the first, second and third filter steps has a separation rate of 99.5% or greater, such as 99.8% or 99.9%.

Filter opening refers to the smallest particle size that a filter can filter out with a given efficiency. Hereinafter, the filter opening is also referred to as x.

The separation rate ε _x (also called filtration rate) is stated in all cases according to ISO 16889:2008. In this standard, the value of _βx is given as the ratio of _Nx to _Nh , where _Nx = the number of particles upstream of the filter, _Nh = the number of particles downstream of the filter, and x is the filter index. Open. The filter opening is the particle size (μm) for which the separation rate is determined. The separation ratio is also called ε _x and is (β _x −1)/β _x .

As an example, the separation rate ε ₁₀ =75% for a suspension with 400 particles with a particle size of 10 μm or more per unit volume upstream of the filter is equal to It means that there are 100 particles with a particle size of 10 μm or more. In this example, 75% of the particles collected from the suspension had a particle size of 10 μm or greater.

Borrowing the definitions of separation ratio and filter opening for individual filters, corresponding details may be made for filter processes involving one or more individual filters. The above ranges and preferred embodiments apply.

(a) the first filter step has a separation rate of 90% or less, such as 85%, 80% or 75%, or 80 to 99.9%, or 80 to 95%; have
(b) the first filter step has a filter opening of 5 μm or more, 5 to 25 μm, or 5 to 15 μm, for example, 10 μm or 5 μm;
(c) the second filter step has a separation rate of 80% or more, such as 95% or more, such as 98%, 99%, 99.9% or 99.99%, or 80-99.9% or 80-95% with a separation rate in the range of %,
(d) The second filter step has a filter opening of 0.5 μm or more, such as 5 to 10 μm, or in the range of 0.5 to 2 μm, such as 0.5 μm, 1.0 μm, 1.5 μm, or 2.0 μm has a
(e) the third filter step is 80% or more, such as 99.5% or more, such as 99.9% or 99.99%, or in the range of 80-99.9%, or 95-99.9% with a range of separation ratios,
(f) the third filter step has a filter opening in the range of 0.5 μm or more, such as 0.5 to 10 μm, or 0.5 to 3 μm, or 0.5 to 1 μm;
or by a combination of two or more of properties (a) to (e), each combination of example values being particularly preferred. In one embodiment, all combinations of properties (a) to (f) are advantageous, for example example F1.3 in Table 1 below.

In a preferred embodiment, the first filter step has a filter opening of 5 μm or more, eg in the range of 5 μm to 25 μm, and a separation rate in the range of 80% to 99.9%, preferably 80% to 95%.

In a further embodiment, the second filter step has a filter opening of 0.5 μm or more, such as in the range of 0.5 μm to 10 μm, and a filter opening in the range of 80% to 99.9%, preferably 95% to 99.9%. has a separation rate of

In a further embodiment, the third filter step has a filter opening of 0.5 μm or more, such as in the range of 0.5 μm to 10 μm, and a have a separation rate.

According to a further example, the first filter device may be characterized by a combination of the following properties.

In a further embodiment, the first multi-stage filter device comprises at least one depth filter. In the present context a depth filter is taken to mean a filter in which the particles to be separated are retained over a portion within the filter so that normally no filter cake is formed during filter operation. On the other hand, in area filters or surface filters, particles to be separated are separated at the interface of the surface filter, so that filter cake accumulates during filter operation. The first multistage filter may further include multiple depth filters. It is also possible that all filters used in the first multistage filter arrangement are depth filters.

In a further embodiment at least one further, preferably multi-stage filter device is employed downstream of the first multi-stage filter device. Two, three, four, five, and up to ten or more multi-stage filter devices may be provided arranged downstream in sequence.
In a further embodiment, the second multi-stage filter device comprises at least a depth filter.

In a further embodiment, the second filter stage of the first filter device at least comprises a first filter with a separation rate of 90% or less and at least one further filter with a separation rate of 95% or more.

In a further embodiment, the service life of the first multi-stage filter is at least 100 liters, such as 150 liters or more, or 250 liters or more, or 500 liters or more, or 800 liters or more, or 1000 liters or more, wherein the liters are Both cases are based on the volume of precursor suspension filtered by the first multi-stage filter device.

In a further embodiment, the service life of the second optional multi-stage filter device is at least 100 liters, such as 150 liters or more, or 250 liters or more, or 500 liters, which liters in each case is the second Based on volume of precursor suspension filtered by multi-stage filter device.

In the context of filter devices, service life means the amount of suspension that can pass through the filter device before it clogs. Clogging can be recognized by an increase in the pressure upstream of the filter to at least 1.5 times that of a new filter with no change in pump output. If the filter becomes clogged, work must be stopped and the clogged filter cleaned or replaced.

In a further embodiment, the slurry has less than 5 wt%, less than 2 wt%, such as 0 wt% (none) of additives, especially stabilizing additives, wherein this wt% is the total weight of the slurry. based on. Often the slurry has at least 0.1 weight percent additive, such as in the range of 0.1 to 5 weight percent additive, based on the total weight of the slurry. The additive content changes little or not at all during the filtration process. Therefore, the precursor suspension and the silicon dioxide suspension obtained by the method have a stabilizing additive content as described for the slurry.

According to a further embodiment, the silicon dioxide suspension obtained by the method has at least one, for example at least two or at least three or at least four, particularly preferably at least five, of the following properties.
A. The silicon dioxide suspension is rheopexic under the test conditions described.
B. In a 4% by weight slurry, at least 90% of the silicon dioxide particles in the silicon dioxide suspension have a particle size according to DIN ISO 13320-1 in the range from 1 nm to less than 10 μm, such as in the range from 200 to 300 nm,
C. The silicon dioxide suspension has a pH value in the range of 3 or more, such as in the range of greater than 4, or in the range of 4.5 to 8, or 4.5 to 7, which pH value is 4 wt. determined by % slurry,
D. a chlorine content in the solids content of the silicon dioxide suspension of 500 ppm or less, 350 ppm or less, or 200 ppm or less, where ppm is based on the total amount of solids in the silicon dioxide suspension;
E. an aluminum content of 200 ppb or less, for example in the range from 1 to 100 ppb, particularly preferably in the range from 1 to 80 ppb, this ppm being based on the total amount of solids in the silicon dioxide suspension,
F. Containing atoms other than Si, O, H, C, Cl atoms of 5 ppm or less,
G. The silicon dioxide suspension contains at least 20% by weight, such as in the range of 20-70% by weight, or in the range of 30-50% by weight, or in the range of 55-75% by weight, in each case based on the total weight of the slurry. with a solids content in the range, particularly preferably in the range from 60 to 70% by weight,
H. the silicon dioxide suspension has a temperature above 0° C., preferably in the range of 5-35° C.
I. Said silicon dioxide suspension has a viscosity according to DIN 53019-1 (5 rpm, 30 wt.

A second aspect of the invention is a silicon dioxide suspension obtainable by the method according to the first aspect. The embodiments described in this connection are also considered.

A third aspect of the present invention is a method for producing silicon dioxide granules, which comprises the steps (i) to ( A method for obtaining silicon dioxide granules from the silicon dioxide suspension produced by carrying out v).

The silicon dioxide granules have a particle size larger than the silicon dioxide particles present in the silicon dioxide suspension. The embodiments described in relation to the first and second aspects relating to the preparation and properties of the silicon dioxide suspension are also embodiments of the third aspect.

For the production of the silicon dioxide granules in question, in principle all methods known to the person skilled in the art are suitable which achieve an increase in particle size.

The silicon dioxide granules have a larger particle size than the silicon dioxide powder and the silicon dioxide particles contained in the silicon dioxide suspension.

The silicon dioxide granules have a particle size larger than that of the silicon dioxide powder. The particle size of the silicon dioxide granules is preferably in the range of 500 to 50,000 times, for example, 1,000 to 10,000 times, particularly preferably 2,000 to 50,000 times the particle size of the silicon dioxide powder. 8,000 times.

In each case, based on the total weight of the silicon dioxide granules, step i. At least 90% of the silicon dioxide granules produced in ) are preferably produced from silicon dioxide powder produced by calcination, for example at least 95% by weight or at least 98% by weight, particularly preferably at least 99% by weight or more. is produced from silicon dioxide powder produced by calcination.

Preferably, processing forms silicon dioxide granules having granules, the granules having a spherical morphology, more preferably processing comprises spray granulation or roll granulation.

Powder is taken to mean dry solid particles having a primary particle size in the range from 1 to less than 100 nm.

The silicon dioxide granules may be obtained by granulating silicon dioxide powder. Silicon dioxide granules generally have a BET specific surface area of 3 m ² /g or more and a density of less than 1.5 g/cm ³ . Granulation is taken to mean the conversion of powder particles into granules. During granulation, multiple silicon dioxide particles clump together to form large agglomerates called "silicon dioxide granules." These are also often referred to as "silicon dioxide granule particles" or "granule particles". The granules as a whole form granules, for example silicon dioxide forms "silicon dioxide granules". Silicon dioxide granules have a larger particle size than silicon dioxide powder.

The process of granulation, which transforms powder into granules, is described in detail below.

In the present context, silicon dioxide grains are taken to mean silicon dioxide particles obtained by grinding silicon dioxide bodies, in particular quartz glass bodies. Silicon dioxide grains typically have a density greater than 1.2 g/cm ³ , for example in the range of 1.2 to 2.2 g/cm ³ , particularly preferably about 2.2 g/cm ³ . More preferably, the BET surface area of the silicon dioxide granules is typically less than 1 m ² /g, measured according to DIN ISO 9277:2014-01.

All silicon dioxide particles suitable for the person skilled in the art may in principle be considered silicon dioxide particles. Silicon dioxide granules and silicon dioxide granules are preferably selected.

に従って等面積円相当径ｘ_Ａとして求められる粒子の直径を意味すると解釈され、上記式中、Ａ_ｉは画像分析によって調べられた粒子の面積である。適切な決定方法は、例えば、ＩＳＯ １３３２２－１：２０１４又はＩＳＯ １３３２２－２：２００９である。「…よりも大きい粒子サイズ」等の比較記述は、常に基準値が同じ手段で決定されることを意味する。 The particle diameter or particle size is determined by the formula

is taken to mean the diameter of the particle determined as equivalent circle diameter x _A according to the above formula, where A _i is the area of the particle determined by image analysis. Suitable determination methods are for example ISO 13322-1:2014 or ISO 13322-2:2009. A comparative statement such as "particle size larger than" always means that the reference value is determined by the same means.

The granules of silicon dioxide granules preferably have a spherical morphology. Spherical morphology means that the particles are round to elliptical in shape. Granules of silicon dioxide granules preferably have an average sphericity in the range from 0.7 to 1.3 SPHT3, for example an average sphericity in the range from 0.8 to 1.2 SPHT3, particularly preferably from 0.85 to 1.1 has an average sphericity in the range of . The characteristic SPHT3 is described in the test methods.

More preferably, the granules of the silicon dioxide granules have an average symmetry in the range 0.7-1.3 Symm3, such as an average symmetry in the range 0.8-1.2 Symm3, particularly preferably 0.85-1 It has an average symmetry in the range of 0.1 Symm3. The property of mean symmetry Symm3 is described in the test methods.

Granulation The silicon dioxide granules are obtained by granulation from silicon dioxide powder. Granulation means converting powder particles into granules. During granulation, agglomeration of multiple silicon dioxide powder particles forms larger agglomerates (agglomerates) called "silicon dioxide granules." They are also often referred to as "silicon dioxide particles", "silicon dioxide granule particles" or "granule particles". The granules collectively constitute a granule, for example silicon dioxide granules constitute a "silicon dioxide granule".

For the present invention, any granulation process known to the person skilled in the art and which the person skilled in the art considers suitable for granulating the silicon dioxide powder can in principle be chosen. Granulation processes can be classified as agglomeration granulation processes or press granulation processes, and can be further classified as wet granulation processes and dry granulation processes. Known methods are roll granulation on granulation plates, spray granulation, centrifugal granulation, fluidized bed granulation, freeze granulation, granulation processes using granulation mills, densification, roll pressing, briquetting, inner Crushing (Schuelpenherstellung), or extrusion.

Preferably, silicon dioxide granules having a spherical morphology are formed in the above process, which process is more preferably carried out by spray granulation or roll granulation. More preferably, the silicon dioxide granules with granules having a spherical morphology contain up to 50% granules, preferably up to 40% granules, even more preferably up to 20% granules, more preferably from 0 to 50%, or 0-40%, or 0-20%, or 10-50%, 10-40%, or 10-20% of granules that do not have a spherical morphology, and these proportions are in any case is also based on the total number of granules in the granules. Granules with a spherical morphology have SPHT3 values as described herein.

Spray drying According to a preferred embodiment of the third aspect, the silicon dioxide granules are obtained by spray granulation of a silicon dioxide suspension. Spray granulation is also known as spray drying.

Spray drying is preferably carried out in a spray tower. For spray drying, the silicon dioxide suspension is preferably pressurized at elevated temperature. The pressurized silicon dioxide suspension is then depressurized through a nozzle and sprayed into a spray tower. A droplet is then formed that dries instantly to form an initially dry microscopic particle (“nucleus”). The tiny particles form a fluidized bed with the gas stream impinging on them. In this way, the particulate can remain suspended and form a surface for drying additional droplets.

The nozzle through which the silicon dioxide suspension is sprayed into the spray tower preferably forms the entrance to the interior of the spray tower.

The nozzle preferably has a contact surface with the silicon dioxide suspension during atomization. "Contact surface" means the area of the nozzle that contacts the silicon dioxide suspension during atomization. Often, at least part of the nozzle is formed as a tube through which the silicon dioxide suspension is guided during atomization, so that the inside of this hollow tube is in contact with the silicon dioxide suspension. It's becoming

The contact surface preferably comprises glass, plastic or a combination thereof. Preferably, the contact surface comprises glass, particularly preferably quartz glass. Preferably, the contact surface comprises plastic. In principle, all plastics known to those skilled in the art are suitable which are stable at the process temperature and which do not allow foreign atoms to pass through the silicon dioxide suspension. Preferred plastics are polyolefins, for example homopolymers or copolymers comprising at least one olefin, particularly preferably homopolymers or copolymers comprising polypropylene, polyethylene, polybutadiene or combinations of two or more thereof. Preferably, the contact surface is made of glass, plastic or a combination thereof, for example selected from the group consisting of fused silica and polyolefins, particularly preferably fused silica and polypropylene, polyethylene, polybutadiene or their It is selected from the group consisting of homopolymers or copolymers, including combinations of two or more. Preferably, the contact surfaces are metal-free, in particular free of tungsten, titanium, tantalum, chromium, cobalt, nickel, iron, vanadium, zirconium and manganese.

In principle, the contact surface and the further part of the nozzle can be made from the same material or from different materials. Preferably, the further part of the nozzle comprises the same material as the contact surface. Likewise, it is possible for further portions of the nozzle to comprise a different material than the contact surface. For example, the contact surfaces can be coated with a suitable material, eg glass or plastic.

Preferably, the nozzle comprises more than 70% by weight, such as more than 75% by weight, or more than 80% by weight, or more than 85% by weight, or more than 90% by weight, or more than 95% by weight, based on the total weight of the nozzle, Particularly preferably more than 99% by weight are made of elements selected from the group consisting of glass, plastic or a combination of glass and plastic.

Preferably, the nozzle includes a nozzle plate. The nozzle plate is preferably made of glass, plastic, or a combination of glass and plastic. Preferably, the nozzle plate is made of glass, particularly preferably quartz glass. Preferably, the nozzle plate is made of plastic. Preferred plastics are polyolefins, eg homopolymers or copolymers comprising at least one olefin, particularly preferably homopolymers or copolymers comprising polypropylene, polyethylene, polybutadiene or combinations of two or more thereof. Preferably, the nozzle plate is free of metals, in particular free of tungsten, titanium, tantalum, chromium, cobalt, nickel, iron, vanadium, zirconium and manganese.

Preferably, the nozzle includes a helical portion. The helical portion is preferably made of glass, plastic, or a combination of glass and plastic. Preferably, the helical portion is made of glass, particularly preferably quartz glass. Preferably, the helical portion is made of plastic. Preferred plastics are polyolefins, eg homopolymers or copolymers comprising at least one olefin, particularly preferably homopolymers or copolymers comprising polypropylene, polyethylene, polybutadiene or combinations of two or more thereof. Preferably, the helical portion is free of metals, in particular free of tungsten, titanium, tantalum, chromium, cobalt, nickel, iron, vanadium, zirconium and manganese.

Additionally, the nozzle can include additional components. Preferred further components are nozzle bodies, particularly preferably nozzle bodies surrounding said helical portion and nozzle plate, crosspieces and baffles. Preferably, the nozzle comprises one or more, particularly preferably all, of these further components. This further component can, independently of one another, in principle, be made of any material known to the person skilled in the art and suitable for this purpose, for example a material containing metal, glass or plastic. Preferably, the nozzle body is made of glass, particularly preferably quartz glass. Preferably, the further component is made of plastic. Preferred plastics are polyolefins, eg homopolymers or copolymers comprising at least one olefin, particularly preferably homopolymers or copolymers comprising polypropylene, polyethylene, polybutadiene or combinations of two or more thereof. Preferably, the further component is metal-free, in particular free of tungsten, titanium, tantalum, chromium, cobalt, nickel, iron, vanadium, zirconium and manganese.

Preferably, the spray tower includes a gas inlet and a gas outlet. Gas can be introduced into the interior of the spray tower through a gas inlet and discharged through a gas outlet. It is also possible to introduce the gas into the spray tower via a nozzle. Similarly, the gas can be released via the outlet of the spray tower. Furthermore, the gas can preferably be introduced via the nozzle and the gas inlet of the spray tower and discharged via the outlet of the spray tower and the gas outlet of the spray tower.

Preferably, the interior of the spray tower contains air, an inert gas, at least two inert gases or a combination of air and at least one inert gas, preferably air and at least one inert gas. There is an atmosphere selected from a combination, preferably two inert gases. Inert gases are preferably selected from the group consisting of nitrogen, helium, neon, argon, krypton and xenon. For example, air, nitrogen or argon, particularly preferably air, is present inside the spray tower.

More preferably, the atmosphere present in the spray tower is part of the gas stream. This gas stream is preferably introduced into the spray tower via a gas inlet and discharged via a gas outlet. It is also possible to introduce part of the gas stream through the nozzle and part of the gas stream out through the solids outlet. The gas stream can obtain further constituents in the spray tower. These originate from the silicon dioxide suspension during spray drying and can be transferred to the gas stream.

Preferably, a dry gas stream is supplied to the spray tower. A dry gas stream means a gas or gas mixture whose relative humidity is below the condensation point at the temperature set in the spray tower. A relative air humidity of 100% corresponds to a water content of 17.5 g/m ³ at 20°C. The gas is preferably preheated to a temperature in the range 150-450°C, eg 200-420°C, or 300-400°C, particularly preferably 320-400°C.

The interior of the spray tower is preferably temperature controllable. Preferably, the temperature inside the spray tower has a value of up to 550°C, for example 300-500°C, particularly preferably 320-450°C.

Preferably, the gas stream has a temperature at the gas inlet in the range 150-450°C, eg 200-420°C, or 300-400°C, particularly preferably 350-400°C.

The gas stream discharged at the solids outlet, the gas outlet or both preferably has a temperature of less than 170.degree. C., for example from 50 to 150.degree.

Furthermore, the difference between the temperature of the gas stream on introduction and the temperature of the gas stream on discharge is preferably in the range 100-330°C, eg 150-300°C.

The silicon dioxide granules thus obtained are present as agglomerates of individual particles of silicon dioxide powder. Individual particles of silicon dioxide powder are still recognizable within the agglomerates. The average particle size of the particles of this silicon dioxide powder is preferably in the range from 10 to 1000 nm, such as from 20 to 500 nm, from 30 to 250 nm, from 35 to 200 nm, or from 40 to 150 nm, particularly preferably from 50 to 100 nm. . The average particle size of these particles is measured according to DIN ISO 13320-1.
Spray drying can be carried out in the presence of auxiliaries. In principle, all materials known to the person skilled in the art and which appear suitable for the present application can be employed as auxiliaries. As auxiliaries, for example, so-called binders can be considered. Examples of suitable binding materials are metal oxides such as calcium oxide, metal carbonates such as calcium carbonate, and polysaccharides such as cellulose, cellulose ethers, starch and starch derivatives.

Particularly preferably in the context of the present invention the spray-drying is carried out without the use of auxiliaries.

Preferably, a portion of the silicon dioxide granules is separated before, after, or before and after removal from the spray tower. For the separation, all processes known to the person skilled in the art and considered suitable can be considered. Preferably, the separation is done by screening or sieving.

Preferably, before the silicon dioxide granules formed by spray drying are removed from the spray tower, particles having a particle size of less than 50 μm, such as a particle size of less than 70 μm, particularly preferably less than 90 μm are separated by screening. be done. This screening is preferably carried out using a cyclone arrangement arranged in the lower region of the spray tower, particularly preferably above the outlet of the spray tower.

Preferably, after removing the silicon dioxide granules from the spray tower, particles with a particle size of more than 1000 μm, for example a particle size of more than 700 μm, particularly preferably more than 500 μm, are separated by sieving. Sieving of the particles can in principle be carried out according to all processes known to the person skilled in the art and suitable for this purpose. Preferably, this screening is done using a vibrating chute (ramps).

According to one embodiment, the spray-drying of the silicon dioxide suspension in the spray tower through nozzles is characterized by at least one, such as two or three, particularly preferably all, of the following properties: .
a] spray granulation in a spray tower,
b] the pressure of the silicon dioxide suspension at the nozzle does not exceed 40 bar, for example in the range from 1.3 to 20 bar, from 1.5 to 18 bar, from 2 to 15 bar or from 4 to 13 bar or particularly preferably from 5 to 12 bar and this pressure is stated absolutely (relative to p=0 hPa),
c] the temperature of the droplets on entering the spray tower is in the range 10-50°C, preferably in the range 15-30°C, particularly preferably in the range 18-25°C,
d) the temperature on the side of the nozzle facing the spray tower is in the range from 100 to 450° C., for example in the range from 250 to 440° C., particularly preferably in the range from 320 to 430° C.
e] The throughput of the silicon dioxide suspension through the nozzle is in the range of 0.05 to 1 m ³ /h, such as in the range of 0.1 to 0.7 m ³ /h or 0.2 to 0.5 m ³ /h. , particularly preferably in the range from 0.25 to 0.4 m ³ /h,
f] the silicon dioxide suspension contains at least 40 wt. preferably having a solids content in the range of 60-70% by weight,
g] a gas stream entering the spray tower in the range 10-100 kg/min, such as in the range 20-80 kg/min or in the range 30-70 kg/min, particularly preferably in the range 40-60 kg/min;
h] the temperature of the gas stream as it enters the spray tower is in the range from 100 to 450°C, for example in the range from 250 to 440°C, particularly preferably in the range from 320 to 430°C,
i) the temperature of the gas stream as it exits the spray tower is less than 170°C;
j] the gas is selected from the group consisting of air, nitrogen and helium, or a combination of two or more thereof, preferably air;
k] when removed from the spray tower, the granules are in each case less than 5 wt. %, or in the range from 0.01 to 0.5% by weight, particularly preferably in the range from 0.1 to 0.3% by weight,
l] In each case, based on the total weight of the silicon dioxide granules produced by spray drying, at least 50% by weight of the spray granules are preferably over a period of 25-70 seconds to complete the flight time,
m] based on the total weight of the silicon dioxide granules produced by spray drying, at least 50% by weight of the fly over, or over 200 m, or in the range of 20-200 m, or 10-150 m or 20-100 m, particularly preferably in the range of 30-80 m,
n] the spray tower has a cylindrical shape,
o] the height of the spray tower is more than 10 m, such as more than 15 m, or more than 20 m, or more than 25 m, or more than 30 m, or in the range 10-25 m, particularly preferably in the range 15-20 m,
p] filtering out particles with a size of less than 90 μm before removing the granules from the spray tower;
q] After removing the granules from the spray tower, preferably on a vibrating chute, the particles with a size greater than 500 μm are filtered out,
r] The droplets of silicon dioxide suspension emerge from the nozzle at an angle of 30-60° to the vertical, particularly preferably at an angle of 45° to the vertical.

Vertical means the direction of the vector of gravity.

Flight path means the path taken by droplets of the silicon dioxide suspension from exiting a nozzle in the gas chamber of the spray tower to form granules until the flight and drop action is complete. The flight and drop motion is typically terminated by the impact of the granules on the floor of the spray tower or with other granules already rolling on the floor of the spray tower, whichever comes first.

Flight time is the period of time required for the granules to follow the flight path within the spray tower. Preferably, the die granules have a helical flight path within the spray tower.

Preferably, based on the total weight of the silicon dioxide granules produced by spray drying, at least 60 wt. or more than 150 m, or more than 200 m, or in the range from 20 to 200 m, or in the range from 10 to 150 m, or in the range from 20 to 100 m, particularly preferably in the range from 30 to 80 m.

Preferably, based on the total weight of the silicon dioxide granules produced by spray drying, at least 70 wt. or more than 150 m, or more than 200 m, or in the range from 20 to 200 m, or in the range from 10 to 150 m, or in the range from 20 to 100 m, particularly preferably in the range from 30 to 80 m.

Preferably, based on the total weight of the silicon dioxide granules produced by spray drying, at least 80 wt. or more than 150 m, or more than 200 m, or in the range from 20 to 200 m, or in the range from 10 to 150 m, or in the range from 20 to 100 m, particularly preferably in the range from 30 to 80 m.

Preferably, based on the total weight of the silicon dioxide granules produced by spray drying, at least 90 wt. or more than 150 m, or more than 200 m, or in the range from 20 to 200 m, or in the range from 10 to 150 m, or in the range from 20 to 100 m, particularly preferably in the range from 30 to 80 m.

Roll Granulation According to another embodiment of the first aspect, the silicon dioxide granules are obtained by roll granulation of the silicon dioxide suspension.

Roll granulation is carried out by stirring the silicon dioxide suspension in the presence of gas at elevated temperature. Preferably, roll granulation is performed in a stirred vessel equipped with a stirring tool. Preferably, the stirring vessel rotates in the opposite direction to the stirring tool. Preferably, the stirring vessel further comprises an inlet through which the silicon dioxide powder can be introduced into the stirring vessel, an outlet through which the silicon dioxide granules can be removed, a gas inlet and a gas outlet.

A pin-type stirring tool is preferably used for stirring the silicon dioxide suspension. A pin stirrer tool means a stirrer tool with a plurality of elongated pins having a longitudinal axis coaxial with the axis of rotation of the stirrer tool. The trajectories of the pins preferably describe coaxial circles about the axis of rotation.

Preferably, the silicon dioxide suspension is set to a pH value of less than 7, for example a pH value in the range 2-6.5, particularly preferably in the range 4-6. An inorganic acid is preferably used for setting the pH value, for example an acid selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, particularly preferably hydrochloric acid.

Preferably, in the stirred vessel there is an atmosphere selected from air, an inert gas, at least two inert gases or a combination of air and at least one inert gas, preferably two inert gases. exist. Inert gases are preferably selected from the group consisting of nitrogen, helium, neon, argon, krypton and xenon. For example, air, nitrogen or argon, particularly preferably air, is present in the stirred vessel.

Furthermore, preferably the atmosphere present in the stirred vessel is part of the gas stream. A gas stream is preferably introduced into the stirred vessel via the gas inlet and discharged via the gas outlet. The gas stream can obtain further constituents in the stirred vessel. These originate from silicon dioxide suspensions in roll granulation and can be transferred to the gas stream.

Preferably, a dry gas stream is introduced into the stirred vessel. A dry gas stream means a gas or gas mixture whose relative humidity is below the condensation point at the temperature set in the stirred vessel. The gas is preferably preheated to a temperature in the range 50-300°C, for example 80-250°C, particularly preferably 100-200°C.

Preferably, 10 to 150 m ³ of gas per hour, for example 20 to 100 m ³ of gas per hour, particularly preferably 30 to 70 m ³ of gas per hour, are introduced into the stirred vessel per kg of silicon dioxide suspension employed.

During mixing, the silicon dioxide suspension is dried by the gas stream to form silicon dioxide granules. The granules formed are removed from the stirred vessel.

Preferably, the removed granules are further dried. Preferably drying is carried out continuously, for example in a rotary kiln. Preferred temperatures for drying are in the range from 80 to 250°C, for example in the range from 100 to 200°C, particularly preferably in the range from 120 to 180°C.

In the context of the present invention, "continuous" with respect to a process means that the process can operate continuously. This means that the materials involved in the process can be introduced and removed continuously while the process is running. There is no need to interrupt the process for this.

"Continuous" as an attribute of an object means that the object is configured such that the process performed in the object, or the process steps performed in the object, can be performed continuously, e.g. means that

Granules obtained from roll granulation can be sieved. Sieving can be done before or after drying. Preferably, the granules are sieved before drying. Granules with a particle size of less than 50 μm, for example a particle size of less than 80 μm, particularly preferably of less than 100 μm are preferably sieved. Furthermore, preferably granules with a particle size of more than 900 μm, for example a particle size of more than 700 μm, particularly preferably of more than 500 μm, are sieved. The sieving of larger particles can in principle be carried out according to any process known to the person skilled in the art and suitable for this purpose. Preferably, the sieving of large particles is done with a vibrating chute.

According to one embodiment, the roll granulation is characterized by at least one, such as two or three, particularly preferably all, of the following features.
[a] granulation is carried out in a rotating stirred vessel;
[b] granulation is carried out at a gas flow rate of 10 to 150 kg per hour per kg of silicon dioxide suspension;
[c] The gas temperature at the time of introduction is 40 to 200 ° C.
[d] granules with particle sizes less than 100 μm and greater than 500 μm are sieved;
[e] the granules formed have a residual moisture content of 15-30% by weight;
[f] The granules formed are dried at 80-250° C., preferably in a continuous drying tube, particularly preferably to a residual moisture content of less than 1% by weight.

Silicon dioxide granules, preferably obtained by granulation, preferably by spray granulation or roll granulation, are processed after being processed to obtain quartz glass bodies. This pretreatment can serve a variety of purposes, either facilitating the processing to obtain the quartz glass body or influencing the properties of the resulting quartz glass body. For example, the silicon dioxide granules I can be densified, refined, surface-modified or dried.

According to a further embodiment of the first aspect, the silicon dioxide granules have the following properties.
A) an angle of repose in the range 23° to 26°;
B) a BET surface area in the range from 20 m ² /g to 50 m ² /g, and C) in the range from 0.5 to 1.2 g/cm ³ , such as from 0.6 to 1.1 g/cm ³ , particularly preferably bulk density in the range of 0.7 to 1.0 g/ ^cm3 ;
D) an average particle size in the range of 50-500 μm;
E) a carbon content of less than 50 ppm;
F) a chlorine content of less than 500 ppm, such as 350 ppm or less, or 200 ppm or less;
G) an aluminum content of less than 20 ppb;
H) tamping density in the range 0.7-1.2 g/cm ³ ;
I) a pore volume in the range from 0.1 to 2.5 ml/g, for example in the range from 0.15 to 1.5 ml/g, particularly preferably in the range from 0.2 to 0.8 ml/g,
J) an angle of repose in the range of 23-26°;
K) a particle size distribution D ₁₀ in the range from 50 to 150 μm,
L) a particle size distribution D ₅₀ in the range 150-300 μm,
M) a particle size distribution D ₉₀ in the range 250-620 μm,
The above ppm and ppb are in each case based on the total weight of the silicon dioxide granules.

Although the silicon dioxide granules preferably have a metal content of metals other than aluminum of less than 1000 ppb, for example less than 500 ppb, particularly preferably less than 100 ppb, in each case based on the total weight of the silicon dioxide granules. However, the silicon dioxide granules often have a content of metals other than aluminum of at least 1 ppb. The silicon dioxide granules contain less than 1 ppm, preferably in the range of 40 to 900 ppb, for example in the range of 50 to 700 ppb, particularly preferably in the range of 60 to 500 ppb, in each case based on the total weight of the silicon dioxide granules. It often has a metal content of metals other than aluminum. Such metals are, for example, sodium, lithium, potassium, magnesium, calcium, strontium, germanium, copper, molybdenum, titanium, iron and chromium. They may be present, for example, as elements, as ions, or as part of molecules or ions or complexes.

The silicon dioxide granules may contain other constituents, for example in the form of molecules, ions or elements. The silicon dioxide granules preferably contain less than 5 ppm, such as less than 3 ppm, particularly preferably less than 1 ppm of atoms other than Si, O, H, C, Cl, in each case based on the total weight of the silicon dioxide granules. including. Other constituents represented by atomic amounts other than Si, O, H, C, and Cl are contained in an amount of at least 1 ppb. This other constituent may in particular be selected from the group consisting of carbon, fluoride, iodide, bromide, phosphorus or a mixture of at least two of these.

The silicon dioxide granules preferably contain less than 10 ppm, for example less than 8 ppm, or less than 5 ppm, particularly preferably less than 4 ppm, of carbon, in each case based on the total weight of the silicon dioxide granules. Silicon dioxide granules often contain carbon in an amount of at least 1 ppb.

The silicon dioxide granules preferably contain less than 100 ppm, for example less than 80 ppm, particularly preferably less than 70 ppm, of other constituents, in each case based on the total weight of the silicon dioxide granules, although the silicon dioxide Granules often contain other constituents in amounts of at least 1 ppb.

A fourth aspect of the present invention is a method for manufacturing a quartz glass body, comprising at least i. ) providing silicon dioxide granules by the method according to the third aspect or by the method according to one of the embodiments mentioned in this context;
ii. ) forming a glass melt from the silicon dioxide granules;
iii. ) forming a quartz glass body from at least a portion of the glass melt.

step i. ) may be performed in any manner and manner known to those skilled in the art suitable for the method. This may be done, for example, by the methods already described for making silicon dioxide granules according to the third aspect, for example by spray granulation or roll granulation. The silicon dioxide granules so obtained are fed into a furnace, step ii. ) into a glass melt. The silicon dioxide granules may be produced by performing steps (i) to (v) of the first aspect of the present invention and then performing the method of the third aspect of the present invention. Embodiments that are preferred in both ways are also preferred here.

step ii. )
step ii. ), a glass melt is formed from silicon dioxide granules. Generally, silicon dioxide granules are heated until a glass melt is obtained. The heating of the silicon dioxide granules to obtain the glass melt can in principle be carried out by any method known to those skilled in the art for this purpose.

Vertical configuration (V-Zug) for the preparation of glass melts
Formation of a glass melt from silicon dioxide granules, for example by heating, can be carried out in a continuous process. This preferably allows the silicon dioxide granules to be continuously introduced into the furnace or the glass melt to be continuously removed from the furnace, or both. In addition, silicon dioxide granules are continuously introduced into the furnace and glass melt is continuously removed from the furnace.

Furnaces with at least one inlet and at least one outlet are suitable in principle for this purpose. Inlet means an opening through which silicon dioxide and optionally further materials can be introduced into the furnace. Outlet means an opening through which at least part of the silicon dioxide can be removed from the furnace. The furnace can be arranged vertically or horizontally, for example. Preferably, the furnace is arranged vertically (upright). Preferably, at least one inlet is positioned above at least one outlet. "Above" in relation to furnace fixtures and features, particularly in relation to inlets and outlets, means that a fixture or feature that is positioned "above" another is at a height greater than zero absolute height. It means that there is "Vertical" means that the line directly connecting the inlet and the outlet of the furnace deviates from the direction of gravity by 30° or less.

According to one embodiment of the first aspect, the furnace includes a suspended metal sheet crucible. The silicon dioxide granules are introduced into a suspended metal sheet crucible and heated to obtain a glass melt. Metal sheet crucible means a crucible containing at least one rolled metal sheet. Preferably, the metal sheet crucible has a plurality of rolled metal sheets. These sheets are joined by suitable fasteners such as rivets. A suspended sheet metal crucible means a sheet metal crucible as described above which is placed in a suspended position in a furnace.

The suspended metal sheet crucible can in principle be made of all materials suitable for melting silicon dioxide known to those skilled in the art. Preferably, the metal sheet of the suspended metal sheet crucible comprises a so-called sintered material, eg sintered metal. Sintered metal means a metal or alloy obtained by sintering a metal powder. The sintered metal can be reshaped into a metal sheet, for example by rolling. The metal sheet crucible preferably contains two or more or a plurality of metal sheets. These metal sheets can be made from rolled sintered metal.

Preferably, the metal sheet of the metal sheet crucible comprises at least one element selected from the group consisting of refractory metals. By refractory metals is meant Group 4 (Ti, Zr, Hf) metals, Group 5 (V, Nb, Ta) and Group 6 (Cr, Mo, W) metals.

Preferably, the metal sheet of the metal sheet crucible comprises a sintered metal selected from the group consisting of molybdenum, tungsten or combinations thereof. Further preferably, the metal sheet of the metal sheet crucible comprises at least one further refractory metal, particularly preferably rhenium, osmium, iridium, ruthenium or a combination of two or more thereof.

Preferably, the metal sheet of the metal sheet crucible comprises an alloy of molybdenum and a refractory metal or an alloy of tungsten and a refractory metal. Particularly preferred alloying metals are rhenium, osmium, iridium, ruthenium, or combinations of two or more thereof. According to a further example, the metal sheet of the metal sheet crucible is an alloy of molybdenum with tungsten, rhenium, osmium, iridium, ruthenium, or a combination of two or more thereof. For example, the metal sheet of the metal sheet crucible can be an alloy of tungsten with molybdenum, rhenium, osmium, iridium, ruthenium, or a combination of two or more thereof.

Preferably, said metal sheet of the metal sheet crucible can be coated with a refractory metal. According to one example, the metal sheet of the metal sheet crucible is coated with rhenium, osmium, iridium, ruthenium, molybdenum or tungsten, or a combination of two or more thereof.

Preferably, the metal sheet and the coating have different compositions. For example, a molybdenum metal sheet can be coated with one or more coatings of rhenium, osmium, iridium, ruthenium, tungsten, or combinations of two or more thereof. According to another example, a tungsten metal sheet is coated with one or more layers of rhenium, osmium, iridium, ruthenium, molybdenum, or combinations of two or more thereof. According to a further example, the metal sheet of the metal sheet crucible is made of molybdenum alloyed with rhenium or tungsten alloyed with rhenium, and the interior of the crucible is made of rhenium, osmium, iridium, ruthenium, or two of these. It can be coated with one or more layers, including combinations of two or more.

Preferably, the metal sheet of the suspended metal sheet crucible has a density of 95% or greater of theoretical density, such as 95% to 98%, or 96% to 98%. More preferred are higher theoretical densities, especially densities in the range of 98-99.95%. The theoretical density of the base material corresponds to the density of a 100% dense material without pores. A metal sheet density greater than 95% of the theoretical density of the metal sheet crucible is obtained, for example, by sintering the sintered metal and then densifying (compressing) the sintered metal. Particularly preferably, a metal sheet crucible can be obtained by sintering a sintered metal, rolling to obtain a metal sheet, and processing the metal sheet to obtain a crucible.

Preferably, the metal sheet crucible has at least a lid, walls and a bottom plate. Preferably, the suspended metal sheet crucible has at least one, such as at least two, at least three or at least four, particularly preferably at least five or all of the following features.
(a) at least one, for example more than one or at least two or at least three or at least five, particularly preferably three or four, layers of metal sheets,
(b) at least one metal sheet, such as at least 3, or at least 4, or at least 6, or at least 8, or at least 12, or at least 15, or at least 16, or at least 20 metal sheets, particularly preferably 12 or 16 metal sheets,
(c) at least one bond between two sheet metal parts, for example at least two between the same two sheet metal parts of a suspended sheet metal crucible or between a plurality of different sheet metal parts, or at least 5, or at least 10, or at least 18, or at least 24, or at least 36, or at least 48, or at least 60, or at least 72, or at least 48, or at least 96, or at least 120 or at least 160, particularly preferably 36 or 48 bonds,
(d) the sheet metal parts of the suspended sheet metal crucible are riveted, for example by deep drawing at least one joint, for example by a combination of deep drawing and collaring or countersinking of the metal sheet; screwed or welded, particularly preferably riveted, for example by electron beam welding and sintering of the weld points,
(e) the metal sheet of the suspended metal sheet crucible is obtained by a forming process with an increase in physical density, preferably by forming a sintered metal or sintered alloy, and more preferably this Forming is rolling,
(f) a hanger assembly of copper, aluminum, steel, iron, nickel, or a refractory metal such as a crucible material, preferably a water-cooled hanger assembly of copper or steel;
(g) a nozzle, preferably a nozzle permanently fixed to the crucible;
(h) a mandrel, for example a mandrel fixed to the nozzle with a pin, a mandrel fixed to the lid with a support rod, or a mandrel mounted under the crucible with a support rod;
(i) at least one gas inlet, for example in the form of a filling pipe or as a separate inlet;
(j) at least one gas outlet, for example as a separate outlet provided in the lid or wall of the crucible;
(k) a cooling jacket, preferably a water-cooled jacket;
(l) outer insulation, preferably made of zirconium oxide;

The suspended metal sheet crucible can in principle be heated by any method known to and deemed suitable by the skilled person. For example, a suspended metal sheet crucible can be heated by an electrical heating element (resistance) or by induction. In resistive heating, the solid surface of the metal sheet crucible is heated from the outside and energized from there to the inside.

In the case of induction heating, energy is coupled using a coil directly to the sidewall of the melting crucible and transmitted from there to the interior of the crucible. In resistive heating, energy is coupled via radiation, whereby a solid surface is warmed from the outside and energy is transferred from there to the inside. Preferably, the melting crucible is induction heated.

According to one embodiment of the invention, the energy transfer to the melting crucible, in particular for melting bulk material, consists of a flame, such as a burner flame, directed into or above the melting crucible. It is not done by using to warm the melting crucible, or the bulk material present therein, or both. According to a further embodiment, no burners are used to melt the bulk material.

The suspended arrangement allows the suspended metal sheet crucible to move within the furnace. Preferably, the crucible can be moved at least partially into and out of the furnace. If there are different heating zones in the furnace, their temperature profiles are transferred to the crucibles present in the furnace. By changing the position of the crucible within the furnace, multiple heating zones, varying heating zones, or multiple varying heating zones can be created within the crucible.

A metal sheet crucible has a nozzle. The nozzle is made from a nozzle material. Preferably, the nozzle material has a density of more than 95%, for example in the range from 98 to 100%, particularly preferably from 99 to 99.999%, in each case based on the theoretical density of the nozzle material. Includes materials that have been processed. Preferably, the nozzle material comprises a refractory metal such as molybdenum, tungsten or a combination of these with further refractory metals. Molybdenum is a particularly preferred nozzle material. Preferably, nozzles containing molybdenum can have a density of 100% of the theoretical density.

Preferably, the bottom plate included in the sheet metal crucible is thicker than the sides of the sheet metal crucible. Preferably, the bottom plate is made from the same material as the sides of the metal sheet crucible. Preferably, the bottom plate of the metal sheet crucible is not a rolled metal sheet. The bottom plate is, for example, 1.1 to 5000 times thicker, 2 to 1000 times thicker, 4 to 500 times thicker, particularly preferably 5 to 50 times thicker than the wall of the metal sheet crucible. is the thickness of

According to a preferred embodiment of the first aspect of the invention, the furnace comprises a suspended or standing sintering crucible. Silicon dioxide granules are introduced into a suspended or vertical sintering crucible and heated to obtain a glass melt.

Sintered crucible means a crucible made from a sintered material that contains at least one sintered metal and has a density of 96% or less of the theoretical density of the metal. Sintered metal means alloy metal obtained by sintering metal powder. The sintered material and sintered metal in the sintering crucible are not rolled.

Preferably, the sintered material of the sintered crucible has a density of 85% or more of the theoretical density of the sintered material, for example 85% to 95%, or 90% to 94%, particularly preferably 91% to 93%. have a density.

The sintering material can in principle be made from any material known to the person skilled in the art and suitable for melting silicon dioxide. Preferably, the sintered material is made from at least one element selected from the group consisting of refractory metals, graphite, or materials lined with graphite foil.

Preferably, the sintered material comprises a first sintered metal selected from the group consisting of molybdenum, tungsten and combinations thereof. Further preferably, the sintered material is particularly preferably selected from the group consisting of molybdenum, tungsten, rhenium, osmium, iridium, ruthenium, or a combination of two or more thereof, with the first sintered metal It further comprises at least one additional refractory metal that is different.

Preferably, the sintered material comprises an alloy of molybdenum and a refractory metal or an alloy of tungsten and a refractory metal. Particularly preferred alloying metals are rhenium, osmium, iridium, ruthenium, or combinations of two or more thereof. By way of further example, the sintered material includes alloys of molybdenum with tungsten, rhenium, osmium, iridium, ruthenium, or combinations of two or more thereof. For example, the sintered material can include alloys of tungsten with molybdenum, rhenium, osmium, iridium, ruthenium, or combinations of two or more thereof.

According to further embodiments, the sintered material described above may comprise a coating comprising a refractory metal, especially rhenium, osmium, iridium, ruthenium or a combination of two or more thereof. According to one example, the coating includes rhenium, osmium, iridium, ruthenium, molybdenum, tungsten, or a combination of two or more thereof.

Preferably, the sintered material and its coating have different compositions. One example is a sintered material comprising molybdenum coated with one or more layers of rhenium, osmium, iridium, ruthenium, tungsten, or a combination of two or more thereof. According to another example, a sintered material comprising tungsten is coated with one or more layers of rhenium, osmium, iridium, ruthenium, molybdenum, or combinations of two or more thereof. According to another example, the sintered material is made of molybdenum alloyed with rhenium, or tungsten alloyed with rhenium, and the crucible interior contains rhenium, osmium, iridium, ruthenium, or two or more thereof. can be coated with one or more layers comprising combinations of

Preferably, the sintered crucible is made by sintering a sintered material to obtain a mold. A sintered crucible can be molded as a whole. It is also possible to mold individual parts of the sintered crucible and then process them to obtain the sintered crucible. Preferably, the crucible is made from multiple parts, such as for example a bottom plate and one or more side parts. The side pieces are preferably made integrally (in one piece) on the basis of the crucible circumference. Preferably, the sintered crucible can be made with a plurality of side pieces arranged one above the other. Preferably, the side parts of the sintered crucible are sealed by means of screwed or tongue-and-groove connections. Threading is preferably achieved by making the side piece with a thread at the interface. In the case of tongue-and-groove connections, the two side parts to be joined each have a notch at the boundary, into which a tongue is introduced as a third connecting part, perpendicular to the plane of the crucible wall. The shape is such that a closed connection is formed. Particularly preferably, the sintered crucible is made of a plurality of side parts, for example two or more side parts, particularly preferably three or more side parts. Particularly preferably, the parts of the suspended sintering crucible are screwed. Particularly preferably, the parts of the standing sintered crucible are connected by tongue-and-groove connections.

The bottom plate can in principle be connected to the crucible wall by any means known to the person skilled in the art and suitable for this purpose. According to a preferred embodiment, the bottom plate has outwardly directed threads and is connected with the wall of the crucible by being screwed. According to a further embodiment, the bottom plate is connected with the wall of the crucible by means of screws. According to a further embodiment, the bottom plate is suspended within the sintered crucible, for example by placing the bottom plate on an inwardly facing flange of the crucible wall. According to a further embodiment, at least part of the crucible wall and the densified bottom plate are integrally sintered. Particularly preferably, the bottom plate and the crucible wall of the suspended sintering crucible are screwed. Particularly preferably, the bottom plate and the crucible wall of the standing sintered crucible are connected by a tongue and groove connection.

Preferably, the bottom plate contained in the sintered crucible is thicker than the sides, for example 1.1 to 20 times thicker, or 1.2 to 10 times thicker, or 1.5 to 7 times thicker. , particularly preferably 2 to 5 times the thickness. Preferably, the side wall thickness is constant over the circumferential and height directions of the sintered crucible.

A sintering crucible has a nozzle. The nozzle is made from a nozzle material. Preferably, the nozzle material has a density of more than 95%, for example in the range from 98 to 100%, particularly preferably from 99 to 99.999%, in each case based on the theoretical density of the nozzle material. Includes materials that have been processed. Preferably, the nozzle material comprises a refractory metal such as molybdenum, tungsten or a combination thereof with a refractory metal. Molybdenum is a particularly preferred nozzle material. Preferably, nozzles containing molybdenum can have a density of 100% of the theoretical density.

The suspended sintering crucible can be heated by any method known and deemed appropriate by those skilled in the art. A suspended sintering crucible can be, for example, induction heated or resistance heated. In the case of induction heating, the energy is introduced directly through coils on the side walls of the sintered crucible and from there is supplied to the interior of the crucible. In resistive heating, energy is introduced by radiation, which heats a solid surface from the outside and supplies energy from there to the inside. Preferably, the sintered crucible is induction heated. In resistive heating, energy is introduced by radiation, which heats a solid surface from the outside and supplies energy from there to the inside. Preferably, the sintered crucible is induction heated.

According to one embodiment of the present invention, energy transfer to the melting crucible, especially for melting bulk materials, uses a flame, such as a burner flame, directed into or above the melting crucible. It is not done by heating the melting crucible, or the bulk material present therein, or both.

Preferably, the sintering crucible has one or more heating zones, for example 1 or 2 or 3 or more than 3 heating zones, preferably 1 or 2 or 3 heating zones , particularly preferably with one heating zone. Each heating zone of the sintering crucible can be at the same temperature or at different temperatures. For example, all heating zones can be raised to one temperature, or all heating zones can be raised to different temperatures, or two or more heating zones can be raised to one temperature and one or more heating zones can be raised to other temperatures independently of each other. Preferably, all heating zones are raised to different temperatures. For example, the temperature of the heating zone increases in the direction of material transport of the silicon dioxide granules.

A suspended sintering crucible means a sintering crucible as described above which is arranged in a suspended manner in a furnace.

Preferably, the suspended sintering crucible has at least one, such as at least two, at least three or at least four, particularly preferably all, of the following features.
{a} a suspension assembly, preferably a height-adjustable suspension assembly;
{b} at least two rings sealed together as side pieces, preferably at least two rings screwed together as side pieces;
{c} nozzles, preferably permanently attached to the crucible;
{d} A mandrel, e.g. a mandrel fixed to the nozzle with a pin, a mandrel fixed to the lid with a support rod, or a mandrel mounted under the crucible with a support rod;
{e} at least one gas inlet, e.g. in the form of a filling pipe or particularly preferably as a separate inlet in the form of a filling pipe;
{f} at least one gas outlet provided, for example, in the lid or wall of the crucible;
{g} a cooling jacket, particularly preferably a water-cooled jacket,
{h} An insulating layer, preferably made of zirconium oxide, on the outside of the crucible, for example the outside of the cooling jacket.

The suspension assembly is preferably a suspension assembly installed during the construction of the suspended sintered crucible, for example a suspension assembly provided as an integral component of the crucible, particularly preferably the crucible A suspension assembly provided from a sintered material as an integral component of the. Furthermore, preferably the suspension assembly is a suspension assembly that is installed on the sintering crucible and is made of a material different from the sintering material, such as aluminium, steel, iron, nickel or copper, preferably copper. A fabricated suspension assembly, particularly preferably a cooled, e.g. water-cooled, copper suspension assembly that is placed on the sintered crucible.

The suspension assembly allows the suspended sintering crucible to move within the furnace. Preferably, the crucible can be at least partially introduced into and withdrawn from the furnace. If there are different heating zones in the furnace, their temperature profiles are transferred to the crucibles present in the furnace. By changing the position of the crucible within the furnace, multiple heating zones, varying heating zones, or multiple varying heating zones can be created within the crucible.

A standing sintering crucible means a sintering crucible of the type previously described, which is arranged vertically in a furnace.

Preferably, the standing sintered crucible has at least one, such as at least two, at least three or at least four, particularly preferably all, of the following features.
/a/ A region formed as a standing area, preferably a region formed as a standing area on the bottom surface of the crucible, more preferably a region formed as a standing area on the bottom plate of the crucible, particularly preferably the crucible A region formed as a standing area on the outer edge of the bottom surface of the
/b/ at least two rings sealed to each other as side pieces, preferably at least two rings sealed to each other by tongue and groove connections as side pieces;
/c/ Nozzle, preferably permanently attached to the crucible, particularly preferably to a region of the bottom surface of the crucible that is not formed as a standing area,
/d/ mandrel, e.g. a mandrel pinned to the nozzle, a mandrel pinned to the lid, or a mandrel attached from below the crucible with a support rod;
/e/ at least one gas inlet, e.g. in the form of a fill tube or as a separate inlet;
/f/ at least one gas outlet, for example as a separate outlet provided in the lid or crucible wall;
/g/ lid.

A vertical sintering crucible preferably has separate gas compartments in the furnace and in the region below the furnace. The area under the furnace means the area under the nozzle where the withdrawn glass melt resides. Preferably, the gas compartments are separated by the surface on which the crucible stands. Gases present in the gas compartment of the furnace between the inner furnace wall and the outer crucible wall do not leak into the area under the furnace. The removed glass melt does not come into contact with gases from the gas compartment of the furnace. Preferably, the glass melt removed from the furnace in which the sintered crucible is placed vertically and the quartz glass body formed therefrom is the melt removed from the furnace in which the sintered crucible is placed in suspension and the quartz glass body formed therefrom. The surface purity is higher than that of a quartz glass body.

Preferably, the crucible is positioned in the furnace such that the silicon dioxide granules can enter the crucible through the crucible inlet and the furnace inlet, and the glass melt is removed through the crucible outlet and the furnace outlet. Connected with inlet and outlet.

Preferably, the crucible comprises, in addition to at least one inlet, at least one opening, preferably a plurality of openings, through which gas can be introduced and removed. Preferably, the crucible has at least two openings, at least one of which can be used as a gas inlet and at least one which can be used as a gas outlet. Preferably, at least one opening is used as a gas inlet and at least one opening is used as a gas outlet to create a gas flow within the crucible.

The silicon dioxide granules are introduced into the crucible through the crucible inlet and then heated within the crucible. Warming can be carried out in the presence of a gas or in the presence of a mixture of two or more gases. Furthermore, during warming, the water adhering to the silicon dioxide granules can migrate into the gas phase and form additional gas. This gas or a mixture of two or more gases is present in the gas compartment of the crucible. Gas compartment of a crucible means the area not occupied by solid or liquid phases within the crucible. Suitable gases are, for example, hydrogen, inert gases, and two or more thereof. Inert gas means a gas that does not react with the material present in the crucible up to a temperature of 2400°C. Preferred inert gases are nitrogen, helium, neon, argon, krypton and xenon, particularly preferably argon and helium. Preferably, warming is performed in a reducing atmosphere. This is provided by hydrogen or a combination of hydrogen and an inert gas, for example hydrogen and helium, hydrogen and nitrogen or hydrogen and argon, particularly preferably hydrogen and helium. can do.

Preferably, the at least partial gas exchange of air, oxygen and water with hydrogen, at least one inert gas, or a combination of hydrogen and at least one inert gas is performed on the silicon dioxide granules done above. This at least partial gas exchange is performed on the silicon dioxide granules at the time of introduction of the silicon dioxide granules, or prior to warming, or during warming, or during at least two of the above activities. be. Preferably, the silicon dioxide granules are warmed until molten in a gas stream of hydrogen and at least one inert gas such as argon or helium.

Preferably, the furnace has at least one gas outlet, preferably also the melting crucible therein, through which gases introduced into the furnace and formed during operation of the furnace are removed. The furnace can also have at least one dedicated gas inlet. Alternatively or additionally, for example together with the silicon dioxide particles, or before the silicon dioxide particles, or after the silicon dioxide particles, or by a combination of two or more of the above possibilities, the gas through the inlet, also called solid inlet can be introduced.

The furnace and gas stream are preferably characterized by the features described in the context of the first aspect. Preferably, the gas stream is formed by introducing gas into the furnace via an inlet and removing gas from the furnace via an outlet. "Gas replacement rate" means the amount of gas discharged from the furnace through the outlet per unit time. Gas replacement rate is also referred to as gas flow throughput or volumetric throughput.

Preferably, the gas replacement rate of the gas stream is in the range from 200 to 3000 L/h, eg from 200 to 2000 L/h, particularly preferably from 200 to 1000 L/h.

The furnace temperature for melting the silicon dioxide granules is preferably in the range of 1700-2500°C, for example in the range of 1900-2400°C, particularly preferably in the range of 2100-2300°C.

Preferably, the holding time in the furnace ranges from 1 hour to 50 hours, such as from 1 to 30 hours, particularly preferably from 5 to 20 hours. In the context of the present invention, holding time means the time required to remove the melting furnace charge from the melting furnace in which the glass melt was formed in a manner according to the invention when carrying out the process. . The charge is the total mass of silicon dioxide in the melting furnace. In this context, silicon dioxide can be present as a solid and as a glass melt.

Preferably, the furnace temperature increases over the length of the material conveying direction. Preferably, the temperature of the furnace increases by at least 100°C, for example by at least 300°C, by at least 500°C, or by at least 700°C, particularly preferably by at least 1000°C, over its length in the material conveying direction. Preferably, the maximum temperature in the furnace is 1700-2500°C, for example 1900-2400°C, particularly preferably 2100-2300°C. The furnace temperature increase can proceed uniformly or according to a temperature profile.

Preferably, the furnace temperature is lowered before the glass melt is removed from the furnace. Preferably, the furnace temperature is reduced by 50-500° C., for example 100° C. or 400° C., particularly preferably 150-300° C., before the glass melt is removed from the furnace. Preferably, the temperature of the glass melt during removal is from 1750 to 2100°C, for example from 1850 to 2050°C, particularly preferably from 1900 to 2000°C.

Preferably, the furnace temperature increases over the length of the material conveying direction and decreases before the glass melt is removed from the furnace. In this connection, the temperature of the furnace preferably increases by at least 100° C., for example at least 300° C., at least 500° C., or at least 700° C., particularly preferably at least 1000° C., over its length in the material conveying direction. Preferably, the maximum temperature in the furnace is 1700-2500°C, for example 1900-2400°C, particularly preferably 2100-2300°C. Preferably, the furnace temperature is reduced by 50-500° C., for example 100° C. or 400° C., particularly preferably 150-300° C., before the glass melt is removed from the furnace.

Preheating Section Preferably, the furnace comprises at least a first chamber and a further chamber connected to each other by passages, the first and second chambers having different temperatures, the temperature of the first chamber being Lower than the temperature of the further chamber. In one of the further chambers a glass melt is formed from the silicon dioxide granules. This chamber is hereinafter referred to as the melting chamber. Also, a chamber connected to the melting chamber via a duct but located upstream of the melting chamber is called a preheating section. One example is that at least one outlet is directly connected to the inlet of the melting chamber. The above arrangement is also possible with a separate furnace, in which case the melting chamber becomes a melting furnace. However, as used herein, the term "melting furnace" may be interpreted as being identical to the term "melting chamber". Therefore, what is said about the melting furnace may be taken to apply to the melting chamber and vice versa. The term "preheat section" means the same thing in both cases.

Preferably, the silicon dioxide granules have a temperature in the range of 20-1300° C. upon entering the furnace.

According to a first embodiment, the silicon dioxide granules are not preheated (tempered) before entering the melting chamber. The silicon dioxide granules have, for example, a temperature in the range from 20 to 40°C, particularly preferably from 20 to 30°C, on entering the furnace. Silicon dioxide granules II are produced in step i. ), the silicon dioxide granules II preferably have a temperature in the range from 20 to 40° C., particularly preferably in the range from 20 to 30° C., on entering the furnace.

According to another embodiment, the silicon dioxide granules are preheated to a temperature in the range of 40-1300° C. before entering the furnace. Preheating means setting the temperature to a selected value. Preheating can in principle be carried out by any method known to those skilled in the art and known for preheating silicon dioxide granules. For example, preheating can be performed in a furnace located separately from the melting chamber or connected to the melting chamber.

Preferably, preheating is performed in a chamber connected to the melting chamber. Preferably, therefore, the furnace comprises a preheating section with which the silicon dioxide can be preheated. Preferably, the preheating section itself is a feed furnace (continuous furnace, Durchlaufofen), particularly preferably a rotary kiln. Feed furnace means a heated chamber that, in operation, moves silicon dioxide from the feed furnace inlet to the feed furnace outlet. Preferably, the outlet is directly connected to the inlet of the melting furnace. In this way the silicon dioxide granules can reach the melting furnace from the preheating section without further intermediate steps or means.

It is further preferred that the preheating section comprises at least one gas inlet and at least one gas outlet. Gas can reach the gas chamber of the internal, preheating section from the gas inlet, and gas can be removed from the gas outlet. It is also possible to introduce gas into the preheating section via the inlet of the preheating section for the silicon dioxide granules. It is also possible to remove the gas from the exit of the preheating section and then separate it from the silicon dioxide granules. Furthermore, preferably the gas is introduced via the inlet for the silicon dioxide granules and the gas inlet of the preheating section and can be removed via the outlet of the preheating section and the gas outlet of the preheating section. .

Preferably, the gas flow is generated in the preheating section of the melting furnace, in particular the crucible present therein, using gas inlets and gas outlets. Suitable gases are, for example, hydrogen, inert gases, and two or more thereof. Preferred inert gases are nitrogen, helium, neon, argon, krypton and xenon, particularly preferably nitrogen and helium. Preferably, a reducing atmosphere exists in the preheating section. This can be provided in the form of hydrogen or a combination of hydrogen and an inert gas, for example hydrogen and helium or hydrogen and nitrogen, particularly preferably hydrogen and helium. Furthermore, preferably, an oxidizing atmosphere exists in the preheating section. This can preferably be provided in the form of oxygen or a combination of oxygen and one or more further gases, air being particularly preferred. More preferably, the silicon dioxide can be preheated in a preheating section under reduced pressure.

For example, the silicon dioxide granules can have a temperature in the range of 100-1100°C or 300-1000°C or 600-900°C as they enter the furnace.

According to one embodiment, the furnace includes at least two chambers. Preferably, the furnace comprises a first chamber and at least one further chamber. The first chamber and the further chamber are connected to each other by a passageway.

Said at least two chambers can in principle be arranged in any way in the furnace, preferably vertically or horizontally, particularly preferably vertically. Preferably, the chambers are arranged such that, when carrying out the process according to the first aspect, the silicon dioxide granules pass through the first chamber and are then heated in a further chamber to obtain a glass melt. placed in the furnace in a manner. The further chamber preferably has the above-mentioned features of the melting furnace and the crucible arranged therein.

Preferably each chamber includes an inlet and an outlet. Preferably, the inlet of the furnace is connected via a passageway to the inlet of the first chamber. Preferably, the outlet of the furnace is connected via a passageway to the outlet of the further chamber. Preferably, the outlet of the first chamber is connected via a passageway to the inlet of the further chamber.

Preferably, the plurality of chambers are arranged such that the silicon dioxide granules can reach into the first chamber through the inlet of the furnace. Preferably, the chambers are arranged such that the silicon dioxide glass melt can be removed from the further chamber via the outlet of the furnace. Particularly preferably, it is possible that the silicon dioxide granules reach the first chamber through the furnace inlet and the silicon dioxide glass melt is removed from the further chamber through the furnace outlet.

Silicon dioxide in the form of granules or powder can enter the further chamber from the first chamber via the passage in the direction of material transport defined by the process. A reference to chambers connected by passages includes a reference to an arrangement in which a further intermediate element is arranged in the material transport direction between the first chamber and the further chamber. In principle, gases, liquids and solids can pass through the channels. Preferably, the silicon dioxide powder, the suspension of silicon dioxide powder and the silicon dioxide granules can pass through the passageway between the first chamber and the further chamber. All materials introduced into the first chamber while the process according to the invention is being carried out can reach the further chamber via the passageway between the first chamber and the further chamber. Preferably, only silicon dioxide in the form of granules or powder reaches the further chamber via the passageway between the first chamber and the further chamber. Preferably, the passageway between the first chamber and the further chamber is closed by silicon dioxide, such that the gas chambers of the first chamber and the further chamber are separated from each other, preferably for different gases or Mixed gases, different pressures or both can be present in the gas chamber. According to another embodiment, said passageway is formed by a gate, preferably a rotary gate valve.

Preferably, the first chamber of the furnace has at least one gas inlet and at least one gas outlet. The gas inlet can in principle have any form known to the person skilled in the art and suitable for the introduction of gas, for example in the form of a nozzle, vent or tube. The gas outlet can in principle have any form known to the person skilled in the art and suitable for removing gas, for example in the form of a nozzle, vent or tube.

Preferably, the silicon dioxide granules are introduced into the first chamber through the inlet of the furnace and warmed. This warming can be done in the presence of a gas or a combination of two or more gases. For this purpose a gas or a combination of two or more gases is present in the gas chamber of the first chamber. A gas chamber of the first chamber means a region of the first chamber not occupied by a solid or liquid phase. Suitable gases are, for example, hydrogen, oxygen, inert gases, and two or more thereof. Preferred inert gases are nitrogen, helium, neon, argon, krypton and xenon, with nitrogen, helium and combinations thereof being particularly preferred. Preferably, warming is performed in a reducing atmosphere. This can preferably be provided in the form of hydrogen or a combination of hydrogen and helium. Preferably, the silicon dioxide granules are warmed in the first chamber in a flow of gas or a combination of two or more gases.

More preferably, the silicon dioxide granules are warmed in the first chamber under reduced pressure, for example at a pressure of less than 500 mbar, or less than 300 mbar, such as 200 mbar or less.

Preferably, the first chamber has at least one device for moving the silicon dioxide granules. In principle, any device known to the person skilled in the art and deemed suitable for this purpose can be chosen. Stirring, shaking and swirling devices are preferred.

According to an embodiment of the first aspect, the temperature in the first chamber and the temperature in the further chamber are different. Preferably, the temperature in the first chamber is lower than the temperature in the further chamber. Preferably, the temperature difference between the first chamber and the further chamber is in the range 600-2400°C, such as in the range 1000-2000°C, or in the range 1200-1800°C, particularly preferably in the range 1500-1700°C. be. Furthermore, the temperature of the first chamber is preferably 600-2400° C., for example 1000-2000° C. or 1200-1800° C., particularly preferably 1500-1700° C., below the temperature of the further chamber.

According to one embodiment, the first chamber of the furnace is a preheating section, particularly preferably the preheating section described above with the characteristics described above. Preferably, the preheating section is connected to the further chamber via a passageway. Preferably, the silicon dioxide enters the further chamber from the preheating section via the passageway. A passageway between the preheating section and the further chamber can be closed so that gas introduced into the preheating section does not enter the further chamber through the passageway. Preferably, the passageway between the preheating section and the further chamber is closed so that the silicon dioxide does not come into contact with water. The passageway between the preheating section and the further chamber is separated from each other such that the gas chamber of the preheating section and the first chamber are separated from each other such that different gases or gas mixtures, different pressures, or both are present in the gas chamber. can be closed as Suitable passages are preferably as described in the embodiments above.

According to a further embodiment, the first chamber of the furnace is not a preheating section. For example, the first chamber may be a leveling chamber. A leveling chamber is a chamber of the furnace in which the throughput fluctuations of the upstream preheating section or the throughput difference between the preheating section and a further chamber are leveled. For example, a rotary kiln can be placed upstream of the first chamber, as described above. This throughput can typically vary by an amount up to 6% of the average throughput. Preferably, the silicon dioxide is maintained in the leveling chamber at the temperature it reached in the leveling chamber.

The furnace comprises a first chamber and a plurality of further chambers, such as 2 further chambers, 3 further chambers, 4 further chambers, 5 further chambers or more than 5 further chambers, particularly preferably 2 further chambers. It is also possible to have If the furnace has two further chambers, the first chamber is preferably the preheating section, the first of the further chambers is the leveling chamber, and the second of the further chambers is based on the material transport direction. The chamber is a melting chamber.

According to a further embodiment, an additive is present in the first chamber. Additives are preferably selected from the group consisting of halogens, inert gases, bases, oxygen, or combinations of two or more thereof.

In principle, elemental halogens and halogen compounds are suitable additives. Preferred halogens are selected from the group consisting of chlorine, fluorine, chlorine-containing compounds and fluorine-containing compounds. Particular preference is given to elemental chlorine and hydrogen chloride.

In principle all inert gases and mixtures of two or more thereof are suitable additives. Preferred inert gases are nitrogen, helium, or combinations thereof.

In principle, bases are also suitable additives. Preferred bases used as additives are inorganic bases and organic bases.

Additionally, oxygen is a preferred additive. Preferably the oxygen is present as an oxygen-containing atmosphere, for example in combination with an inert gas or a mixture of two or more inert gases, particularly preferably in combination with nitrogen, helium or nitrogen and helium. .

The first chamber can in principle contain any material suitable for heating silicon dioxide known to those skilled in the art. Preferably, the first chamber contains at least one component selected from the group consisting of quartz glass, refractory metals, aluminum, and combinations of two or more thereof, and particularly preferably the first chamber comprises Contains quartz glass or aluminum.

Preferably, the temperature in the first chamber does not exceed 600° C. when the first chamber contains polymer or aluminum. Preferably, the temperature in the first chamber is 100-1100° C. when the first chamber contains quartz glass. Preferably, the first chamber mainly contains quartz glass.

In principle, the silicon dioxide can be present in any state when it is transported from the first chamber to the further chamber through the passageway between the first chamber and the further chamber. Preferably, the silicon dioxide is present as a solid, eg as particles, powder or granules. According to one embodiment of the first aspect, the transfer of silicon dioxide from the first chamber to the further chamber takes place as granules.

According to a further embodiment, the further chamber is a crucible made from a metal sheet or sintered material, the sintered material comprising sintered metal, the metal sheet or sintered metal comprising molybdenum, tungsten and is selected from the group consisting of combinations of

The glass melt is removed from the furnace via an outlet, preferably via a nozzle.

step iii. )
A quartz glass body is produced from at least part of the glass melt. For this, preferably at least part of the glass melt produced in step ii) is removed and a quartz glass body is made therefrom.

Partial withdrawal of the glass melt produced in step ii) can in principle be carried out continuously from the melting furnace or melting chamber or after the production of the glass melt has ended. Preferably, a portion of the glass melt is withdrawn continuously. The glass melt is removed from the outlet of the furnace or the outlet of the melting chamber, preferably through a nozzle.

The glass melt can be cooled before, during or after removal to a temperature that allows formation of the glass melt. The increase in viscosity of the glass melt is related to the cooling of the glass melt. The glass melt is preferably cooled to such an extent that, in shaping, it retains the shape in which it was produced, while at the same time shaping is as easy and reliable as possible and can be carried out with little effort. A person skilled in the art can easily establish the viscosity of the glass melt for forming by varying the temperature of the glass melt in the forming tool. Preferably, the glass melt has a temperature in the range from 1750 to 2100.degree. C., for example in the range from 1850 to 2050.degree. Preferably, the glass melt is cooled after removal to a temperature below 500.degree. C., for example below 200.degree. C., below 100.degree.

The quartz glass body to be formed may be solid or hollow. A solid body means an object that is primarily made of a single material. Nonetheless, a solid body can have one or more inclusions, such as air bubbles. Such inclusions of hollow bodies generally have a size of 65 mm ³ or less, for example less than 40 mm ³ , or less than 20 mm ³ , or less than 5 mm ³ , or less than 2 mm ³ , particularly preferably less than 0.5 mm ³ . Preferably, the solid body comprises less than 0.02% by volume, such as less than 0.01% or less than 0.001% by volume of inclusions, in each case based on the total volume of the solid body.

The quartz glass body has an external shape (outer shape). External shape means the shape of the outer edge of the cross-section of the quartz glass body. The external shape of the cross-section of the quartz glass body is preferably circular, elliptical or polygonal with 3 or more corners, for example 4, 5, 6, 7 or 8 corners, particularly preferably , the quartz glass body is circular.

Preferably, the quartz glass body has a length in the range from 100 to 10000 mm, for example from 1000 to 4000 mm, particularly preferably from 1200 to 3000 mm.

Preferably, the quartz glass body has an outer diameter in the range from 1 to 500 mm, for example in the range from 2 to 400 mm, particularly preferably in the range from 5 to 300 mm.

Formation of the quartz glass body is performed using a nozzle. A glass melt is fed through a nozzle. The external shape of the quartz glass body formed through the nozzle is determined by the shape of the opening of the nozzle. If the opening is circular, a cylinder is created when forming the quartz glass body. If there is a structure in the nozzle opening, the structure is transferred to the external shape of the quartz glass body. A quartz glass body manufactured using a nozzle having a structure in the opening has an image of the structure in the longitudinal direction along the glass strand.

The nozzle is built into the melting furnace. Preferably, the nozzle is integrated into the melting furnace as part of the crucible, particularly preferably as part of the crucible outlet.

Preferably, at least part of the glass melt is withdrawn through the nozzle. The external shape of the quartz glass body is formed by removing at least part of the glass melt through a nozzle.

Preferably, the quartz glass body is cooled after forming so as to maintain its shape. Preferably, after shaping, the quartz glass body is brought to a temperature at least 1000° C. below the temperature of the glass melt during shaping, for example at least 1500° C. below or at least 1800° C. below, particularly preferably 1900 to 1950° C. below. Cooled. Preferably, the quartz glass body is cooled to a temperature below 500.degree. C., for example below 200.degree. C. or below 100.degree. C. or below 50.degree.

According to a preferred embodiment of the first aspect of the present invention, the quartz glass body obtained can be treated with at least one procedure selected from the group consisting of chemical treatment, thermal treatment or mechanical treatment. can.

Preferably, the quartz glass body is chemically aftertreated. Post-treatment relates to the treatment of already produced quartz glass bodies. Chemical post-treatments of quartz glass bodies are known in principle to those skilled in the art and are considered suitable for employing materials to alter the chemical structure and/or composition of the surface of the quartz glass body. means any procedure. Preferably, the chemical post-treatment includes at least one means selected from the group consisting of treatment with a fluorine compound and ultrasonic cleaning.

Possible fluorine compounds are in particular hydrogen fluoride and fluorine-containing acids such as hydrofluoric acid. The liquid preferably has a fluorine compound content in the range of 35 to 55 wt.%, more preferably in the range of 35 to 45 wt.%, these wt.% being in each case based on the total amount of the liquid. The remainder to 100% by weight is usually water. Preferably, the water is fully demineralized or deionized water.

Ultrasonic cleaning is preferably carried out in a liquid bath, particularly preferably in the presence of a cleaning agent. For ultrasonic cleaning, generally no fluorine compounds, such as hydrofluoric acid or hydrogen fluoride, are used.

Ultrasonic cleaning of the quartz glass body is preferably carried out under at least one, for example at least 2 or at least 3 or at least 4 or at least 5, particularly preferably under all of the following conditions.
- Ultrasonic cleaning performed in a continuous process.
- The device for ultrasonic cleaning has 6 chambers connected to each other by tubes.
- The holding time of the quartz glass body in each chamber can be set. Preferably, the retention time of the quartz glass body in each chamber is the same. Preferably, the retention time in each chamber ranges from 1 to 120 minutes, such as less than 5 minutes, or 1-5 minutes, or 2-4 minutes, or less than 60 minutes, or 10-60 minutes, or 20-50 minutes. minutes, particularly preferably in the range from 5 to 60 minutes.
- The first chamber contains a basic medium, preferably water and a base, and an ultrasonic cleaner.
- The third chamber contains an acidic medium, preferably including water and acid, and an ultrasonic cleaner.
- In the second and fourth to sixth chambers, the quartz glass body is washed with water, preferably demineralized water.
- The 4th to 6th chambers are operated with a water cascade. Preferably water is introduced only into the sixth chamber and flows from the sixth chamber to the fifth chamber and from the fifth chamber to the fourth chamber.

Preferably, the quartz glass body is thermally aftertreated. Thermal post-treatment of quartz glass bodies means in principle procedures which are known to the person skilled in the art and which are considered suitable for changing the morphology and/or structure of quartz glass bodies by means of temperature. Preferably, the thermal post-treatment includes at least one means selected from the group consisting of quenching, compression, expansion, stretching (drawing), welding, and combinations of two or more thereof. Preferably, the thermal post-treatment is not performed for the purpose of removing material.

Quenching is preferably carried out by quenching the quartz glass body in a furnace, preferably in the range of 900 to 1300°C, for example in the range of 900 to 1250°C or 1040 to 1300°C, particularly preferably in the range of 1000 to 1050°C or 1200 to 1300°C. by heating at a temperature of Preferably, in the heat treatment, a temperature of 1300° C. is not exceeded for a continuous period of more than 1 hour, particularly preferably a temperature of 1300° C. is not exceeded for the entire duration of the heat treatment. Quenching can in principle be carried out under reduced pressure, normal pressure, increased pressure, preferably reduced pressure, particularly preferably vacuum.

Compression is preferably carried out by heating the quartz glass body to a temperature of preferably about 2100° C. and then shaping it during a rotary swivel movement, preferably at a rotation speed of about 60 rpm. For example, a rod-shaped quartz glass body can be formed into a cylinder.

Preferably, the quartz glass body can be expanded by injecting gas into the quartz glass body. For example, a quartz glass body can be expanded to form a large diameter tube. For this, the quartz glass body is preferably heated to a temperature of about 2100° C., while a rotary swivel movement is preferably carried out at a rotation speed of about 60 rpm, and a pressure of up to about 100 mbar is preferably defined in the interior. Gas is flushed at a controlled internal pressure. A large diameter tube means a tube with an outer diameter of at least 500 mm.

The quartz glass body can preferably be drawn (drawn). Drawing is preferably performed by heating the quartz glass body to a temperature of preferably about 2100° C. and then drawing it to the desired outer diameter of the quartz glass body at a controlled drawing rate. For example, the lamp tube can be formed by drawing from a quartz glass body.

Preferably, the quartz glass body is post-treated mechanically. Mechanical post-treatment of quartz glass bodies is in principle known to the person skilled in the art and is suitable for changing the shape of the quartz glass body using abrasive means or for splitting the quartz glass body into pieces. means any procedure that seems to be In particular, the mechanical post-treatment is selected from the group consisting of grinding, drilling, honing, sawing, water jet cutting, laser cutting, roughening by sandblasting, milling, and combinations of two or more thereof. at least one means for

Preferably, the quartz glass body is treated by a combination of these procedures, for example a combination of chemical and thermal post-treatments, a combination of chemical and mechanical post-treatments, a combination of thermal and A combination with a mechanical aftertreatment, particularly preferably a combination of a chemical, a thermal and a mechanical aftertreatment. Furthermore, preferably, the quartz glass body can be independently subjected to several procedures as described above.

According to a further embodiment, the process comprises any of iv. ) forming a hollow body having at least one opening from said quartz glass body.

The hollow body produced has an internal shape and an external shape. Internal shape means the shape of the inner edge of the cross-section of the hollow body. The internal and external shapes in cross-section of the hollow body may be the same or different. The internal and external shape in cross-section of the hollow body can be circular, elliptical or polygonal with three or more corners, for example 4, 5, 6, 7 or 8 corners.

Preferably, the external shape of the cross section corresponds to the internal shape of the hollow body. Particularly preferably, the hollow body has a round inner shape and a round outer shape in cross section.

In another embodiment, the hollow bodies may have different internal and external shapes. Preferably, the hollow body has a circular external shape and a polygonal internal shape in cross section. Particularly preferably, the hollow body has a circular external shape and a hexagonal internal shape in cross section.

Preferably, the hollow body has a length in the range from 100 to 10000 mm, for example from 1000 to 4000 mm, particularly preferably from 1200 to 2000 mm.

Preferably, the hollow body has a wall thickness (wall thickness) in the range from 0.8 to 50 mm, for example in the range from 1 to 40 mm, from 2 to 30 mm or from 3 to 20 mm, particularly preferably in the range from 4 to 10 mm.

Preferably, the hollow body has an outer diameter in the range from 2.6 to 400 mm, such as from 3.5 to 450 mm, particularly preferably in the range from 5 to 300 mm.

Preferably, the hollow body has an internal diameter in the range from 1 to 300 mm, for example from 5 to 280 mm or from 10 to 200 mm, particularly preferably in the range from 20 to 100 mm.

The hollow body has one or more openings. Preferably, the hollow body contains one opening. Preferably, the hollow body has an even number of openings, for example 2, 4, 6, 8, 10, 12, 14, 16, 18 or 20 openings. Preferably, the hollow body has two openings. Preferably the hollow body is a tube. This form of hollow body is particularly preferred when the light guide comprises only one core. The hollow body can contain more than two openings. The openings are preferably arranged in opposite (opposite) pairs at the ends of the quartz glass body. For example, each end of the quartz glass body can have 2, 3, 4, 5, 6, 7 or more than 7 openings, particularly preferably 5, 6 openings. It has 1 or 7 openings. Preferred forms are, for example, tubes, twin tubes, ie tubes with two parallel channels, and multichannel tubes, ie tubes with more than two parallel channels.

Hollow bodies can in principle be formed by any method known to those skilled in the art. Preferably, the hollow body is formed using a nozzle. Preferably, the nozzle is provided in the center of its opening with a device for deflecting the glass melt during shaping. In this manner, a hollow body can be formed from the glass melt.

Hollow bodies can be produced by the use of nozzles and subsequent post-treatment. Suitable post-treatments are in principle all processes known to the person skilled in the art for producing hollow bodies from solid bodies, for example pressing channels, drilling, honing or grinding. Preferably, a suitable post-treatment is to pass the solid body over one or more mandrels, thereby forming a hollow body. A hollow body can also be made by introducing a mandrel into a solid body. Preferably, the hollow body is cooled after shaping.

Preferably, the hollow body is cooled after shaping to a temperature below 500°C, for example below 200°C, below 100°C or below 50°C, particularly preferably in the range from 20 to 30°C.

Pre-densification As a rule, step i. ), the silicon dioxide granules provided in step ii. ) to obtain a glass melt, it can be subjected to one or more pretreatment steps. Possible pretreatment steps are, for example, thermal or mechanical treatment steps. For example, the silicon dioxide granules can be produced by step ii. ) can be densified prior to warming. "Densification" means a decrease in BET surface area and a decrease in pore volume.

The silicon dioxide granules are preferably applied mechanically by heating the silicon dioxide granules or by applying pressure to the silicon dioxide granules, for example by rolling or pressing the silicon dioxide granules. It is densified by Preferably, the silicon dioxide granules are densified by heating. Particularly preferably, the densification of the silicon dioxide granules is carried out by heating with a preheating section connected to the melting furnace.

Preferably, the silicon dioxide is densified by heating at a temperature in the range 800-1400°C, for example in the range 850-1300°C, particularly preferably in the range 900-1200°C.

In one embodiment of the first aspect, the BET surface area of the silicon dioxide granules is determined by step ii. ) to less than 5 m ² /g, preferably less than 7 m ² /g, or less than 10 m ² /g, particularly preferably less than 15 m ² /g. Furthermore, the BET surface area of the silicon dioxide granules is determined by step i. ) compared to the silicon dioxide granules provided in step ii. ) is preferably not reduced prior to warming.

In one embodiment of the first aspect, the BET surface area of the silicon dioxide granules is less than 20 m ² /g, such as less than 15 m ² /g, or less than 10 m ² /g, or greater than 5 and less than 20 m ² /g. , or in the range from 7 to 15 m ² /g, particularly preferably in the range from 9 to 12 m ² /g. Preferably, the BET surface area of the silicon dioxide granules is determined by step i. ) compared to the silicon dioxide granules provided in step ii. ) is reduced by less than 40 m ² /g, for example 1 to 20 m ² /g, or 2 to 10 m ² /g, particularly preferably 3 to 8 m ² /g, and the BET surface area after densification is reduced by 5 m ² /g.

The compacted silicon dioxide granules preferably have at least one, such as at least 2, at least 3 or at least 4, particularly preferably at least 5, of the following properties.
A. a BET specific surface area of more than 5 to less than 40 m ² /g, for example in the range of 10 to 30 m ² /g, particularly preferably in the range of 15 to 25 m ² /g;
B. a particle size D ₁₀ in the range from 100 to 300 μm, particularly preferably in the range from 120 to 200 μm,
C. a particle size D ₅₀ in the range from 150 to 550 μm, particularly preferably in the range from 200 to 350 μm,
D. a particle size D ₉₀ in the range from 300 to 650 μm, particularly preferably in the range from 400 to 500 μm,
E. a bulk density in the range from 0.8 to 1.6 g/cm ³ , particularly preferably from 1.0 to 1.4 g/cm ³ ,
F. a tamping density in the range from 1.0 to 1.4 g/cm ³ , particularly preferably from 1.15 to 1.35 g/cm ³ ,
G. a carbon content of less than 5 ppm, such as less than 4.5 ppm, particularly preferably less than 4 ppm,
H. A Cl content of less than 500 ppm, particularly preferably between 1 ppb and 200 ppm.
The above ppm and ppb are in each case based on the total weight of the compacted silicon dioxide granules.

The compacted silicon dioxide granules preferably have characteristic A.1. /F. /G. or A. /F. /H. or A. /G. /H. , particularly preferably the characteristic A. /F. /G. /H. have a combination of

The compacted silicon dioxide granules preferably have characteristic A.1. /F. /G. with a BET specific surface area in the range of 10-30 m ² /g, a tamping density in the range of 1.15-1.35 g/mL and a carbon content of less than 4 ppm.

The compacted silicon dioxide granules preferably have characteristic A.1. /F. /H. with a BET surface area in the range of 10-30 m ² /g, a tamping density in the range of 1.15-1.35 g/mL and a chlorine content in the range of 1 ppb-200 ppm.

The compacted silicon dioxide granules preferably have characteristic A.1. /G. /H. with a BET specific surface area in the range of 10 to 30 m ² /g, a carbon content of less than 4 ppm and a chlorine content in the range of 1 ppb to 200 ppm.

The compacted silicon dioxide granules preferably have characteristic A.1. /F. /G. /H. having a BET specific surface area in the range of 10-30 m ² /g, a tamping density in the range of 1.15-1.35 g/mL, a carbon content of less than 4 ppm, and a chlorine content of is in the range of 1 ppb to 200 ppm.

In one embodiment of the first aspect, the melting energy is transferred to the silicon dioxide granules through the solid surface. Compressed silicon dioxide granules, for example, may be selected as the silicon dioxide granules.

A solid surface means a surface that is different from the surface of the silicon dioxide granules and that does not melt or disintegrate at the temperature at which the silicon dioxide granules are heated for melting. Materials suitable for solid surfaces are, for example, materials suitable as crucible material.

The solid surface can in principle be any surface known to the person skilled in the art and suitable for this purpose. For example, a crucible or a separate component that is not a crucible can be used as the solid surface.

In order to transfer the melting energy to the silicon dioxide granules, the solid surface can in principle be heated by any method known to the person skilled in the art and suitable for this purpose. Preferably, the solid surface is heated by resistive heating or induction heating. In the case of induction heating, energy is coupled directly to the solid surface by a coil and fed from there to its interior. In resistive heating, a solid surface is heated from the outside and transfers energy from there to the inside. In this connection, a heating chamber gas with a low heat capacity is advantageous, for example an argon atmosphere or an argon-containing atmosphere. For example, the solid surface can be heated electrically or by externally flaming the solid surface. Preferably, the solid surface is heated to a temperature capable of transferring a sufficient amount of energy to the silicon dioxide granules and/or partially melted silicon dioxide granules to melt the silicon dioxide granules.

According to one embodiment of the present invention, the introduction of energy into the crucible is by means of a flame, for example a burner flame, directed into or onto the crucible, the crucible or the bulk material present therein. , or both by warming.

When a separate component is used as the solid surface, this can be done in any manner, for example by placing the component on silicon dioxide granules or between granules of silicon dioxide granules. or by inserting the component between the crucible and the silicon dioxide granules, or by a combination of two or more of these. This component can be heated before, during, or both before and during transfer of the melting energy.

Preferably, the melting energy is transferred to the silicon dioxide granules via the inside of the crucible. In this case, the crucible is heated sufficiently to melt the silicon dioxide granules. The crucible is preferably resistively or inductively heated. Warmth travels from the outside of the crucible to the inside. A solid surface inside the crucible transfers the melting energy to the silicon dioxide granules.

According to a further embodiment of the invention, the melting energy is not transferred to the silicon dioxide granules via the gas compartment. Further, preferably, melting energy is not transferred to the silicon dioxide granules by burning the silicon dioxide granules with a flame. Examples of these excluded energy transfer means are directing one or more burner flames from above into the melting crucible, or onto the silicon dioxide, or both.

A fifth aspect of the present invention is a quartz glass body obtained by the method according to the fourth aspect. Preference is therefore also given to a method for producing a quartz glass body, in which the method according to the first aspect of the invention is performed, in particular steps (i) to (v) are performed, and silicon dioxide granules are formed. From this, as already mentioned above, a glass melt and finally a quartz glass body are formed.

In one embodiment, the quartz glass body has at least one, preferably two or more, and up to all of the following properties.
A] a chlorine content of less than 1 ppm,
B] an aluminum content of less than 200 ppb,
C] content of atoms other than Si, O, H, C less than 5 ppm,
D] 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 ~ log ₁₀ (η (1300 ° C) / dPas) = 12.2, or log ₁₀ (η (1350 ° C) / dPas) = 10.5 to log ₁₀ (η (1350 ° C) / dPas) = 11.5 range of viscosities (p=1013 hPa),
E] refractive index homogeneity of less than 10 ⁻⁴ ,
F] Cylindrical morphology,
G] a tungsten content of less than 5 ppm,
H] molybdenum content less than 5 ppm.
The above ppb and ppm are in each case based on the total weight of the quartz glass body.

A sixth aspect of the present invention is a method for manufacturing a fiber optic light guide (light guide), comprising:
A/ Providing a quartz glass body according to the fifth aspect of the present invention or any one of its embodiments, or obtainable according to the fourth aspect, which quartz glass body is first processed , obtaining a hollow body having at least one opening;
B/ inserting one or more core rods into said quartz glass body through said at least one opening to obtain a precursor;
C/drawing the precursor from step B/ while heating to obtain an optical fiber light guide having one or more cores and a jacket M1.

Process A/
The quartz glass body provided in step A/ is preferably characterized by the features of the fourth and/or fifth aspect of the invention. Furthermore, this quartz glass body may be shaped by a reshaping process to give a hollow body with at least one opening. Particularly preferably, the quartz glass body thus obtained has the properties of the fifth aspect.

Process B/
One or more core rods are introduced through at least one opening in the quartz glass body (step B/). A core rod in the context of the present invention means an object designed to be introduced into a jacket, eg jacket M1, and processed to obtain a light guide. The core rod has a core of quartz glass. Preferably, the core rod includes a quartz glass core and a jacket layer M0 surrounding the core.

Each core rod has a configuration selected to fit within the quartz glass body. Preferably, the external shape of the core rod corresponds to the shape of the opening of the quartz glass body. Particularly preferably, the quartz glass body is a tube and the core rod is a rod-like body with a circular cross section.

The diameter of the core rod is smaller than the inner diameter of the hollow body. Preferably, the diameter of the core rod is 0.1 to 3 mm smaller than the inner diameter of the hollow body, such as 0.3 to 2.5 mm smaller, or 0.5 to 2 mm smaller, or 0.7 to 1.5 mm smaller, in particular Preferably 0.8 to 1.2 mm smaller.

Preferably, the ratio of the inner diameter of the quartz glass body to the diameter of the core rod is in the range of 2:1 to 1.0001:1, such as in the range of 1.8:1 to 1.01:1, or in the range of 1.6:1 to 1.005:1, or 1.4:1 to 1.01:1, particularly preferably 1.2:1 to 1.05:1.

Preferably, the areas not filled by the core rod inside the quartz glass body can be filled with at least one further component, for example silicon dioxide powder or silicon dioxide granules.

It is also possible to introduce a core rod already present in a further quartz glass body into the quartz glass body. In this case, this further quartz glass body has an outer diameter which is smaller than the inner diameter of the quartz glass body. The core rod introduced into the quartz glass body may already enter two or more further quartz glass bodies, for example three or four or five or six or more further quartz glass bodies.

A quartz glass body having one or more core rods thus obtained is hereinafter referred to as a "precursor".

Process C/
The precursor is stretched while being heated (step C/). The resulting product is a light guide with one or more cores and at least one jacket M1.

Preferably the stretching of the precursor is carried out at a speed in the range 1-100 m/h, for example in the range 2-50 m/h or 3-30 m/h. Particularly preferably, the drawing of the quartz glass body is carried out at a speed in the range from 5 to 25 m/h.

Stretching is preferably carried out with heating at temperatures up to 2500°C, for example at temperatures in the range from 1700 to 2400°C, particularly preferably at temperatures in the range from 2100 to 2300°C.

Preferably, the precursor is sent through a furnace that heats the precursor from the outside.

Preferably, the precursor is stretched until the desired thickness of the light guide is obtained. Preferably, the precursor is in each case 1,000 to 6,000,000 times the length of the quartz glass body provided in step A/, for example 10,000 to 500,000 times the length. Stretched to double the length, or 30,000 to 200,000 times the length. Particularly preferably, the precursor is 100,000 to 10,000,000 times the length, for example 150,000 to 5,000,000 times the length of the quartz glass body provided in step A/ in each case. 800,000 times as long, 160,000 to 640,000 times as long, or 1,440,000 to 5,760,000 times as long, or 1,440,000 to 2,560,000 times as long is stretched to the length of

Preferably, the diameter of the precursor is in the range of 100 to 3,500, such as in the range of 300 to 3,000, or in the range of 400 to 800, in each case based on the diameter of the quartz glass body provided in step A/. or a multiple in the range of 1,200 to 2,400, or in the range of 1,200 to 1,600.

Optical conductors, also called optical waveguides, can comprise any material suitable for conducting or guiding electromagnetic radiation, in particular light.

Conducting or directing radiation means propagating the radiation along the length of the light guide without significantly impeding or attenuating the intensity of the radiation. For this, the radiation is coupled into the guide (waveguide) via one end of the light guide. Preferably, the light guide conducts electromagnetic radiation in the wavelength range of 170-5000 nm. Preferably, the attenuation of radiation by the light guide in this wavelength range is in the range 0.1-10 dB/km. Preferably, the light guide has a transmission rate of up to 50 Tbit/s.

The light guide preferably has a curl parameter greater than 6m. Curl parameter in this context means the bending radius of a fiber, eg a light guide or jacket M1, which exists as a free moving fiber free from external forces.

The light guide is preferably made flexible. Flexibility in the context of the present invention means that the light guide features a bending radius of 20 mm or less, for example 10 mm or less, particularly preferably 5 mm or less. Bending radius means the smallest radius that can be formed without destroying the light guide and without compromising the light guide's ability to conduct radiation. A fault occurs if there is more than 0.1 dB of light attenuation at the bent portion of the light guide. This attenuation is preferably defined at a reference wavelength of 1550 nm.

Preferably, the quartz contains silicon dioxide and less than 1% by weight of other substances, for example less than 0.5% by weight, particularly preferably 0.3% by weight, in each case based on the total weight of the quartz. % of other substances. Further, preferably the quartz comprises at least 99% by weight silicon dioxide, based on the total weight of the quartz.

The light guide preferably has an elongated shape. The shape of the light guide is defined by an extension L of its length and Q of its cross section. The light guide preferably has a rounded outer wall along the extension L of its length. The cross section Q of the light guide is always determined in a plane perpendicular to the outer wall of the light guide. If the light guide is curved on the length extension L, the cross section Q is determined perpendicular to the tangent at a point on the outer wall of the light guide. The light guide preferably has a diameter d _L in the range 0.04-1.5 mm. Preferably, the light guide has a length in the range from 1 m to 100 km.

The light guide has one or more cores, for example 1 core or 2 cores or 3 cores or 4 cores or 5 cores or 6 cores or 7 cores or more than 7 cores, particularly preferably may contain one core. Preferably, more than 90%, for example more than 95%, particularly preferably more than 98%, of the electromagnetic radiation conducted through the light guide is conducted within the core. For the transport of light within the core, the preferred wavelength range applies, as already mentioned for light guides. Preferably, the material of the core is selected from the group consisting of glass or fused silica or a combination of both, with fused silica being particularly preferred. The multiple cores can be made from the same material, or can be made from different materials, independently of each other. Preferably, all cores are made from the same material, particularly preferably from quartz glass.

Each core has an elongated shape, preferably circular, with a cross-section _QK and a length _LK . The cross-section _QK of one core is independent of the cross-section _QK of each other core. The cross-sections _QK of those cores may be the same or different. Preferably, all cores have the same cross-section _QK . The cross-section _QK of the core is always determined in a plane perpendicular to the outer wall of the core or the outer wall of the light guide. If the core is curved in extension of its length, the cross-section _QK will be perpendicular to the tangent at a point on the outer wall of the core. The length L _K of a core is independent of the length L _K of each other core. Their core lengths L _K may be the same or different. Preferably, all core lengths _LK are the same. Each core preferably has a length L _K ranging from 1 m to 100 km. Each core has a diameter _dK . The diameter _dK of one core is independent of the diameter _dK of each other core. Their core diameters _dK may be the same or different. Preferably, all cores have the same diameter _dK . Preferably, the diameter _dK of each core ranges from 0.1 to 1000 μm, for example from 0.2 to 100 μm or from 0.5 to 50 μm, particularly preferably from 1 to 30 μm.

Each core has at least one refractive index profile perpendicular to the maximum extension of the core. By "refractive index profile" is meant a constant or varying refractive index in the direction perpendicular to the maximum extension of the core. A preferred refractive index profile is a concentric refractive index profile, e.g., at the center of the core there is a first region of highest refractive index, surrounded by further regions of lower refractive index. It corresponds to a concentric profile of refractive indices. Preferably, each core has only one refractive index profile over its length L _K . The refractive index profile of one core is independent of the refractive index profile of each other core. The refractive index profiles of those cores may be the same or different. Preferably, all cores have the same refractive index profile. In principle, it is also possible for one core to have several different refractive index profiles.

Each refractive index profile perpendicular to the maximum extension of the core has a maximum refractive index _nK . Each refractive index profile perpendicular to the maximum extension of the core can also have a lower refractive index. The minimum refractive index of the refractive index profile is preferably less than the maximum refractive index _nK of the refractive index profile by 0.5 or less. The minimum refractive index of the refractive index profile should be 0.0001 to 0.15, for example 0.0002 to 0.1, particularly preferably 0.0003 to 0.05 smaller than the maximum refractive index n _K of the refractive index profile. preferable.

Preferably, the core has a range of 1.40 to 1.60, measured at a reference wavelength λ _r =589 nm (sodium D line), in each case at a temperature of 20° C. and normal pressure (p=1013 hPa), For example, it has a refractive index n _K in the range from 1.41 to 1.59, particularly preferably in the range from 1.42 to 1.58. See the Test Methods section for further details on this point. The refractive index _nK of a core is independent of the refractive index _nK of each other core. The refractive indices _nK of those cores may be the same or different. Preferably, all cores have the same refractive index _nK .

Preferably, each core of the light guide has a weight in the range 1.9-2.5 g/cm ³ , such as in the range 2.0-2.4 g/cm ³ , particularly preferably 2.1-2.3 g/cm 3 It has a density in the range of ³ . Preferably, the core has a residual moisture content of less than 100 ppb, for example less than 20 ppb or less than 5 ppb, particularly preferably less than 1 ppb, in each case based on the total weight of the core. The density of one core is independent of the density of each other core. The densities of those cores may be the same or different. Preferably, all cores have the same density.

If the light guide comprises multiple cores, each core has the above characteristics independently of the other cores. All cores preferably have the same characteristics.

According to the invention, the core is surrounded by at least one jacket M1. Jacket M1 preferably surrounds the core over its entire length. Preferably, the jacket M1 surrounds the core for at least 95%, for example at least 98% or at least 99%, particularly preferably 100%, of the outer surface of the core, ie the entire outer wall of the core. In many cases the core is entirely surrounded by a jacket M1 up to the edge (in any case the last 1-5 cm). This helps protect the core from mechanical failure.

Jacket M1 may comprise any material, including silicon dioxide, that has a lower refractive index than at least one point P along the profile of cross-section _QK of the core. Preferably, this at least one point in the cross-sectional _QK profile of the core is a point located in the center of the core. Furthermore, preferably the point P in the cross-sectional profile of the core is the point with the highest refractive index n _Kmax in the core. Preferably, the jacket M1 has a refractive index n _M1 that is at least 0.0001 lower than the refractive index n _K of the core at at least one point in the profile of the cross-section Q of the core. Preferably, the jacket M1 has an amount in the range 0.0001 to 0.5, such as in the range 0.0002 to 0.4, particularly preferably in the range 0.0003 to 0.3, above the refractive index n _K of the core. has a lower refractive index _nM1 .

Preferably, jacket M1 has a refractive index n _M1 in the range 0.9 to 1.599, for example in the range 1.30 to 1.59, particularly preferably in the range 1.40 to 1.57. Preferably, the jacket _M1 forms a region of the light guide with constant refractive index nM1. A region with constant refractive index means a region in which the refractive index does not deviate from the average value of _nM1 by more than 0.0001.

In principle, the light guide can contain a further jacket. Particularly preferably at least one, preferably several or all of the further jackets have a refractive index lower than the refractive index _nK of the respective core. Preferably, the light guide has one or two or three or four or more than four further jackets surrounding jacket M1. Preferably, the further jacket surrounding jacket _M1 has a refractive index lower than the refractive index nM1 of jacket M1.

Preferably, the light guide has one or two or three or four or more than four further jackets surrounding the core and surrounded by the jacket M1, i.e. located between the core and the jacket M1. have. Furthermore, preferably the further jacket located between the core and the jacket _M1 has a refractive index higher than the refractive index nM1 of the jacket M1.

Preferably, said refractive index decreases from the core of the light guide towards the outermost jacket. The decrease in refractive index from the core to the outermost jacket can occur stepwise or continuously. The index drop can have different intervals. Further, preferably the refractive index can be graded in at least one section and continuous in at least one other section. The steps (lowering amounts) may be of the same height or of different heights. It is certainly possible to arrange portions of increasing refractive index between portions of decreasing refractive index.

Different refractive indices of different jackets can be configured, for example, by doping the jacket M1, further jackets and/or the core.

Depending on how the core is prepared, the core may already have the first jacket layer M0 after preparation. This jacket layer M0, which is directly adjacent to the core, is sometimes called an embedded jacket layer. Jacket layer M0 is located closer to the midpoint of the core than jacket M1 and further jackets, if present. The jacket layer M0 generally does not function for light transmission or radiation transmission. Rather, the jacket layer M0 plays a greater role in retaining the radiation inside the core through which the radiation is transported. Radiation conducted in the core is therefore preferably reflected at the interface from the core to the jacket layer M0. This core-to-jacket layer M0 interface is preferably characterized by a change in refractive index. The refractive index of the jacket layer M0 is preferably lower than the refractive index _nK of the core. Preferably, the jacket layer M0 comprises the same material as the core, but has a lower refractive index than the core due to doping or additives.

Preferably, at least jacket M1 is made of silicon dioxide and has at least one, preferably several or all of the following characteristics.
a) an OH content of less than 5 ppm, particularly preferably less than 1 ppm,
b) a chlorine content of less than 200 ppm, preferably less than 100 ppm, such as less than 80 ppm, particularly preferably less than 60 ppm,
c) an aluminum content of less than 200 ppb, preferably less than 100 ppb, such as less than 80 ppb, particularly preferably less than 60 ppb,
d) less than 5·10 ¹⁵ /cm ³ , for example in the range from 0.1·10 ¹⁵ to 3·10 ¹⁵ /cm ³ , particularly preferably in the range from 0.5·10 ¹⁵ to 2.0·10 ¹⁵ /cm ³ ODC content of
e) a metal content of metals other than aluminum of less than 1 ppm, such as less than 0.5 ppm, particularly preferably less than 0.1 ppm,
f) log ₁₀ (η(1250°C)/dPas) = 11.4 to log ₁₀ (η(1250°C)/dPas) = 12.9 and/or log ₁₀ (η(1300°C)/dPas) = 11 .1 to log ₁₀ (η (1300° C.)/dPas)=12.2, and/or log ₁₀ (η (1350° C.)/dPas)=10.5 to log ₁₀ (η (1350° C.)/dPas)= viscosity in the range of 11.5 (p=1013 hPa),
g) Curl parameters greater than 6m;
h) a refractive index homogeneity of less than 1·10 ⁻⁴ ;
i) a transformation point Tg in the range from 1150°C to 1250°C, particularly preferably in the range from 1180°C to 1220°C.
The above ppb and ppm are each based on the total weight of jacket M1.

Preferably, the jacket has a refractive index homogeneity of less than 1·10 ⁻⁴ . The refractive index homogeneity indicates the maximum deviation of the refractive index at each position of the sample, eg jacket M1 or quartz glass body, relative to the mean value of all refractive indices measured for that sample. To determine the average value, the refractive index is measured at at least 7 measurement positions.

Preferably, the jacket M1 has a metal content of metals other than aluminum of less than 1000 ppb, for example less than 500 ppb, particularly preferably less than 100 ppb, in each case based on the total weight of the jacket M1. However, in many cases jacket M1 has a content of metals other than aluminum of at least 1 ppb. Such metals are, for example, sodium, lithium, potassium, magnesium, calcium, strontium, germanium, copper, molybdenum, titanium, iron and chromium. They can be present, for example, as elements, as ions, as part of molecules, as part of ions, or as part of complexes.

Jacket M1 may include further components. Jacket M1 preferably contains less than 5 ppm, for example less than 4.5 ppm, particularly preferably less than 4 ppm, of other constituents, which ppm is in each case based on the total weight of jacket M1. Further constituents that may be considered are for example carbon, fluorine, iodine, bromine and phosphorus. These may be present as elements, as ions, or as part of molecules or ions or complexes, but the jacket M1 may contain at least 1 ppb of atoms other than Si, O, H, C, Cl. many.

Preferably, the jacket M1 contains less than 5 ppm, such as less than 4 ppm, less than 3 ppm, particularly preferably less than 2 ppm of carbon, in each case based on the total weight of the jacket M1. However, often the jacket M1 has a carbon content of at least 1 ppb.

Preferably, the jacket M1 has a uniform distribution of OH-content, Cl-content or Al-content.

In one embodiment of the light guide, the jacket M1 accounts for at least 80% by weight, such as at least 85% by weight, particularly preferably at least 90% by weight, in each case based on the total weight of the jacket M1 and the core. . Preferably, the jacket M1 comprises at least 80% by weight, for example at least 85% by weight, in each case based on the total weight of the jacket M1, the core and a further jacket located between the jacket M1 and the core, Particularly preferred is at least 90% by weight. Preferably, jacket M1 accounts for at least 80% by weight, for example at least 85% by weight, particularly preferably at least 90% by weight, in each case based on the total weight of the light guide.

Preferably, jacket M1 has a density in the range from 2.1 to 2.3 g/cm ³ , particularly preferably in the range from 2.18 to 2.22 g/cm ³ .

A further aspect is
A/ A quartz glass body according to the fifth aspect of the present invention or a quartz glass body obtainable by the method according to the fourth aspect is provided, which quartz glass body is first processed to form at least one opening. obtaining a hollow body having
B/ inserting one or more core rods into the quartz glass body through at least one opening to obtain a precursor;
C/drawing the precursor from step B/ while heating to obtain a light guide having one or more cores and jackets M1.

Steps A/, B/ and C/ are preferably characterized by the properties described in the fourth aspect.

The light guide is preferably characterized by the properties described in the sixth aspect.

A seventh aspect of the present invention is a method for manufacturing a light emitter,
(i) providing a quartz glass body according to the fifth aspect of the invention or a quartz glass body obtainable by the method according to the fourth aspect, and first processing this quartz glass body to obtain a hollow body; ,
(ii) attaching electrodes to the hollow body as required;
(iii) filling the hollow body with a gas.

step (i)
In step (i) a quartz glass body is provided. The quartz glass body provided in step (i) is first processed to have at least one opening, for example one opening or two openings or three openings or four openings, particularly preferably one opening. A hollow body containing one or two openings is obtained.

A quartz glass body obtained by the method according to the fifth aspect or the method according to the fourth aspect is preferred for step (i). This quartz glass body preferably has the properties according to the fourth or fifth aspect.

A plurality of possibilities are conceivable for processing the quartz glass body according to the seventh aspect.

Said quartz glass body may in principle be processed to give an open hollow body by any means known to the person skilled in the art and suitable for the production of open glass hollow bodies. Suitable methods include, for example, compression, blowing, suction, or combinations thereof. It is also possible to produce a hollow body with one opening from a hollow body with two openings by closing one opening, for example by melting.

The hollow bodies preferably contain silicon dioxide in an amount in the range from 98 to 100% by weight, for example in the range from 99.9 to 100% by weight, particularly preferably 100% by weight, in each case based on the total weight of the hollow bodies. It is made up of materials that contain

The material used to prepare the hollow bodies preferably has at least one, preferably more than, for example two, or preferably all of the following characteristics.
HK1. a silicon dioxide content of preferably more than 95% by weight, such as more than 97% by weight, particularly preferably more than 99% by weight, based on the total weight of the material;
HK2. a density in the range from 2.1 to 2.3 g/cm ³ , particularly preferably in the range from 2.18 to 2.22 g/cm ³ ,
HK3. visible range from 350 to 750 nm in the range from 10 to 100%, for example in the range from 30 to 99.99%, particularly preferably in the range from 50 to 99.9%, based on the amount of light generated inside the hollow body light transmission at at least one wavelength of
HK4. an OH content of less than 500 ppm, such as less than 400 ppm, particularly preferably less than 300 ppm,
HK5. a chlorine content of less than 200 ppm, preferably less than 100 ppm, such as less than 80 ppm, particularly preferably less than 60 ppm,
HK6. an aluminum content of less than 200 ppb, such as less than 100 ppb, particularly preferably less than 80 ppb,
HK7. a carbon content of less than 5 ppm, such as less than 4.5 ppm, particularly preferably less than 4 ppm,
HK8. ODC content less than 5·10 ¹⁵ /cm ³ ,
HK9. a metal content of metals other than aluminum of less than 1 ppm, such as less than 0.5 ppm, particularly preferably less than 0.1 ppm;
HK10. log ₁₀ η (1250° C.)=11.4 to log ₁₀ η (1250° C.)=12.4 and/or log ₁₀ η (1300° C.)=11.1 to log ₁₀ η (1350° C.)=11.7 and/or a viscosity in the range of log ₁₀ η(1350° C.)=10.5 to log ₁₀ η(1350° C.)=11.1 (p=1013 hPa),
HK11. A transformation point Tg in the range from 1150 to 1250°C, particularly preferably in the range from 1180 to 1220°C.
The above ppm and ppb are each based on the total weight of the hollow body.

step (ii)
Preferably, the hollow body of step (i) is fitted with electrodes, preferably two electrodes, before filling with gas. Preferably the electrodes are connected to a current source. Preferably, the electrode is connected to the socket of the light emitter.

The material of the electrodes is preferably selected from the group of metals. In principle, the electrode material can be selected from any metal that does not oxidize, corrode, melt, etc. under the conditions of use of the emitter and does not impair its shape and conductivity as an electrode. The electrode material is preferably selected from the group consisting of iron, molybdenum, copper, tungsten, rhenium, gold and platinum, or at least two selected therefrom, preferably tungsten, molybdenum or rhenium.

step (iii)
The hollow body provided in step (i) and optionally fitted with electrodes in step (ii) is filled with a gas.

The filling can be done by any process known to those skilled in the art and suitable for filling. Preferably, the gas is supplied to the hollow body through at least one opening.

Preferably, the hollow body is evacuated before filling with gas, preferably to a pressure of less than 2 mbar. The hollow body is then filled with the gas by introducing the gas. These steps can be repeated to reduce airborne impurities, especially oxygen. Preferably, these steps are repeated at least two times, for example at least three times, or at least four times, particularly preferably at least five times, until the amount of other gas impurities such as air, especially oxygen, is sufficiently low. This procedure is particularly preferred when filling hollow bodies with one opening.

For hollow bodies containing more than one opening, the hollow body is preferably filled through one of the openings. Air present in the hollow body prior to filling with gas can exit through at least one further opening. Gas is fed through the hollow body until the amount of other gas impurities such as air, especially oxygen, is sufficiently low.

The hollow body contains an inert gas or a combination of two or more inert gases such as nitrogen, helium, neon, argon, krypton, xenon or a combination of two or more thereof, particularly preferably krypton, xenon, Or preferably filled with a combination of nitrogen and argon. Further preferred filling materials for the hollow body of the phosphor are deuterium and mercury.

Preferably, the hollow body is closed after filling with gas in order to keep out the gas during further processing and/or to keep out air from the outside during further processing. This closure can be done by melting or putting on the cap. A suitable cap is, for example, a quartz glass cap or a luminous socket, the quartz glass cap being fused onto the hollow body, for example. Preferably, the hollow body is closed by melting.

The light emitter includes a hollow body and optional electrodes. Preferably, the light emitter has at least one, for example at least two, or at least three, or at least four, particularly preferably at least five, of the following characteristics.
I. ) having a volume in the range 0.1 cm ³ to 10 m ³ , for example in the range 0.3 cm ³ to 8 m ³ , particularly preferably in the range 0.5 cm ³ to 5 m ³ ,
II. ) lengths in the range from 1 mm to 100 m, for example in the range from 3 mm to 80 m, particularly preferably in the range from 5 mm to 50 m;
III. ) radiation angles in the range from 2 to 360°, for example in the range from 10 to 360°, particularly preferably in the range from 30 to 360°,
IV. ) emission of light in the wavelength range from 145 to 4000 nm, such as from 150 to 450 nm, or from 800 to 4000 nm, particularly preferably from 160 to 280 nm;
V. ) power in the range from 1 mW to 100 kW, particularly preferably in the range from 1 kW to 100 kW or in the range from 1 to 100 W;

A further aspect is
(i) providing a quartz glass body according to the fifth aspect of the invention or obtainable according to the fourth aspect of the invention, and first processing this quartz glass body to obtain a hollow body; When,
(ii) attaching electrodes to the hollow body as required;
(iii) filling the hollow body with a gas.

Steps (i), (ii) and (iii) are preferably characterized by the properties mentioned in the course of the seventh aspect.

The light emitter is preferably characterized by the properties described in the seventh aspect.

An eighth aspect of the present invention is a method for producing a molded article,
(1) providing a quartz glass body according to the fifth aspect of the present invention or a quartz glass body obtained by the method according to the fourth aspect;
(2) molding the quartz glass body to obtain a molded body;

The quartz glass body provided in step (1) is the quartz glass body according to the fifth aspect of the invention or the quartz glass body obtained by the method according to the fourth aspect of the invention. The quartz glass body provided preferably has the properties of the first aspect or the fifth aspect.

Step (2)
For shaping the quartz glass body provided in step (1), in principle any process known to the person skilled in the art and suitable for shaping quartz glass is possible. Preferably, the quartz glass body is shaped as described in the context of the first, fourth and fifth aspects to obtain a shaped body. Furthermore, preferably, the shaped bodies may be shaped by techniques known to those skilled in the art of glass blowing.

The shaped body can in principle have any shape that can be formed from quartz glass. Preferred shaped bodies are for example - hollow bodies with at least one opening, such as round-bottomed and flat-bottomed flasks,
- fittings and caps for such hollow bodies,
– uncovered items such as bowls and boats (wafer carriers),
- crucibles arranged uncovered or closable,
- seats and windows,
- cuvettes,
- tubes and hollow cylinders, such as reaction tubes, section tubes, cuboid chambers,
- symmetrical or asymmetrical rods, bars and blocks, for example round or square,
- tubes and hollow cylinders closed at one or both ends,
- domes and bells,
- flanges,
- lenses and prisms,
- parts welded together,
- Curved parts, such as convex or concave surfaces and sheets, curved rods and tubes.

According to one embodiment, the molded body can be treated after molding. For this purpose, in principle all processes described in connection with the first embodiment are possible, which are suitable for the post-treatment of quartz glass bodies. Preferably, the compact can be processed mechanically, for example by drilling, honing, external grinding, size reduction or stretching.

A further aspect is
(1) providing a quartz glass body according to the fifth aspect of the invention or a quartz glass body obtained by the method according to the fourth aspect of the invention;
(2) It relates to a molded article obtained by a method including the step of molding the quartz glass body to obtain a molded article.

Steps (1) and (2) are preferably characterized by the properties mentioned in the course of the eighth aspect.

The shaped body is preferably characterized by the properties mentioned in the course of the eighth aspect.

A ninth aspect of the invention is a method of making a coating on a substrate, comprising:
|A| providing a silicon dioxide suspension obtained according to the first aspect or an embodiment thereof, and a substrate;
|B| applying (forming) a layer of the silicon dioxide suspension to a substrate;
A method by which a coating is formed on a substrate.

The silicon dioxide suspension provided in step |A| is obtained by the method according to the first aspect of the invention. This silicon dioxide suspension may have further properties corresponding to the embodiments described in relation to the first aspect.

The application (forming) in step |B| can in principle be carried out by all methods known to the person skilled in the art and suitable for carrying out coatings, the substrate being at least partially coated with the silicon dioxide suspension. be done.

In further embodiments, the application may be by depositing a silicon dioxide suspension onto the substrate, dipping the substrate into the silicon dioxide suspension, or a combination of both forms. Application by deposition of a silicon dioxide suspension is, for example, spin-coating, impregnating, casting, dripping, sputtering, spraying, doctor-blading, brushing, or printing via a dispensing pump, or inkjet-printing, screen-printing onto the substrate, It may be done by gravure printing, offset printing or pad printing. The silicon dioxide suspension may be applied in a pre-dried film thickness in the range 0.01 μm to 250 μm, such as in the range 0.1 μm to 50 μm.

"Applying" is also taken to mean that the silicon dioxide suspension used is applied to the substrate via an auxiliary material. The silicon dioxide suspension used for coating may be sprayed onto the substrate through a nozzle, sputtered, or applied through a slot nozzle. Other methods of interest are curtain casting and spin coating. The silicon dioxide suspension may be applied to the surface of the substrate via rolls or rollers. Known spraying or sputtering methods are, for example, microdispensers through nozzles or digital printing. In this case, force may be applied to the silicon dioxide suspension used for coating, or the silicon dioxide suspension may simply be dropped onto the substrate.

In the case of immersion, the substrate may be dragged through the silicon dioxide suspension in a bath. If the substrate is only partially coated, only the surface to be coated may be immersed in the silicon dioxide suspension and removed again, eg dip coating. Repeated dipping may result in different coating thicknesses, which may be set by the viscosity and solids content of the silicon dioxide suspension. Thereby, coating thicknesses of the silicon dioxide suspension before drying may be obtained in the range from 0.5 to 1000 μm, preferably in the range from 5 to 250 μm, particularly preferably in the range from 10 to 100 μm.

This may, but need not, be followed by a step |C| to reduce the liquid content of the coating. Step |C| is performed until the liquid content of the coating reaches or falls below a set point based on the total weight of the coating. This set point may be, for example, 10 wt%, 5 wt%, 2 wt% or even 0.2 wt%, where wt% is in each case based on the total weight of the coating. In principle, all methods known to the person skilled in the art and which appear suitable to him may come into consideration, in particular drying by heat, drying by superimposing the coating with a gas or gas mixture, drying in the surroundings of reduced pressure. At least one selected from the group comprising evaporating the liquid with pressure, e.g. moving molecules of the liquid with microwaves, etc. may be considered. Combinations of two or more of the above methods are also contemplated, which combinations may be spatially and/or temporally the same, spatially and/or temporally consecutive, spatially and/or may overlap in time. In this context, "overlapping" means that the first method has not yet completed when the subsequent method is started.

The present invention will now be described with reference to the drawings. The figures are not true to scale and are not intended to limit the invention.

DETAILED DESCRIPTION OF THE FIGURES FIG. 1 illustrates a method for producing a silicon dioxide suspension comprising at least (i) step 101 of providing a silicon dioxide powder, (ii) step 102 of providing a liquid, (iii) mixing the silicon dioxide powder with the liquid to obtain a slurry (103); (iv) sonicating the slurry to obtain a precursor suspension (104); and passing 105 at least a portion of the precursor suspension through a first multi-stage filter device.

FIG. 2 schematically shows a filter arrangement comprising three filter stages with a first filter 211, a second filter 212 and a third filter 213 respectively. They are arranged in downstream order.

FIG. 3 schematically shows a further filter arrangement comprising three filter stages. After passing the silicon dioxide suspension through the first filter stage with filter 311, this suspension is split on its way to the second filter stage and a portion of the suspension is passed through the second filter stage. , and another part of the suspension passes through filter B 313 . The suspension is then recombined and passed through a third filter stage with filter 314 .

FIG. 4 schematically shows a method of manufacturing a quartz glass body including steps 411, 412, and 413. FIG. step i. ) 411, silicon dioxide granules are provided. step ii. ) 412, a glass melt is formed from the silicon dioxide granules. step iii. ) 413, a quartz glass body is formed from at least a portion of the glass melt.

Graph a) in FIG. 5 shows, by way of example, a slurry of silicon dioxide powder on which the method of the invention is based. The graph shows a certain amount of well-dispersed particles of particle size below 1 μm, but also shows a series of agglomerates in the range of 1-5 μm and 10-100 μm. Graph b) shows the particle size distribution of the silicon dioxide suspension obtained by dispersing the silicon dioxide slurry according to graph a). In this figure all particles are dispersed. Particle sizes for silicon dioxide particles greater than 1 μm are not given. Subsequent filtration retains the particle size distribution of FIG. 5b) of the silicon dioxide particles, but separates particles that are not silicon dioxide.

FIG. 6 shows a comparative image of a (hot) glass body of approximately 1 m after removal from the melting pot. In these figures, the melt used is a) granules formed from an unfiltered silicon dioxide suspension and b) the melt used is silicon dioxide filtered according to the invention. The vitreous body is a suspension granule, c) the melt used is a granule as in Example 15-4, i. Glass bodies previously ball-milled (zircon oxide balls and polyurethane-coated cups).

FIG. 7 shows two cooled quartz glass bodies. The quartz glass body in image a) was made from a suspension of silicon dioxide particles that had not been treated according to the invention. Contains many large bubbles. The quartz glass body in image b) was made on the basis of the silicon dioxide suspension according to the invention. Almost no air bubbles are seen.

Test method a. OH Content The OH content of the glass is determined by infrared spectroscopy. D. M. Dodd and D. M. Fraser, "Optical Determinations of OH in Fused Silica" (JAP 37, 3991 (1966)) is adopted. Instead of the apparatus described therein, an FTIR spectrometer (Fourier Transform Infrared Spectrometer, Perkin Elmer's current System 2000) is employed. Analysis of the spectrum is possible in principle with either the absorption band at about 3670 cm ^-1 or the absorption band at about 7200 cm ^-1 . The selection of absorption bands is based on a 10-90% reduction in transmittance due to OH absorption.

b. Oxygen Deprivation Center (ODC)
For quantitative detection, ODC(I) absorption was measured at 165 nm by transmission measurements in a probe with a thickness of 1-2 mm by McPherson, Inc. (McPherson) (USA) vacuum UV spectrometer, model VUVAS 2000.
then,
N=α/σ
In the above formula,
N = defect concentration [1/cm ³ ]
α=optical absorption of ODC(I) band [1/cm, base e]
σ = effective cross-sectional area [cm ³ ]
However, the effective cross-sectional area is set to σ=7.5·10 ⁻¹⁷ cm ² (L. Skuja, “Color Centers and Their Transformations in Glassy SiO ₂ ”, Lectures of the summer school “Photosensitivity in Optical Waveforms , 13-18 July 1998, Vitznau, Switzerland).

c. Elemental Analysis c-1) Pulverize a solid sample. About 20 g of the sample is then cleaned by introducing it all into an HF-resistant container, covering it with HF and heat-treating it at 100° C. for 1 hour. After cooling, the acid is discarded and the sample is washed several times with high-purity water. The container and sample are then dried in a dry cabinet.

Next, about 2 g of solid sample (ground material cleaned as above; dust without pretreatment, etc.) is weighed into an HF-resistant extraction vessel and 15 ml of HF (50% by weight) is added. dissolves in The extraction vessel is sealed and heat treated at 100° C. until the sample is completely dissolved. The extraction vessel is then opened and further heat treated at 100° C. until the solution has completely evaporated. Meanwhile, the extraction vessel is filled three times with 15 ml of high-purity water. In order to dissolve the separated impurities, 1 ml of HNO ₃ is introduced into the extraction vessel and filled up to 15 ml with high-purity water. The sample solution is now ready.

c-2) ICP-MS/ICP-OES measurement Whether to adopt OES or MS depends on the expected element concentration. Typically, MS measures 1 ppb and OES measures 10 ppb (both based on weighed samples). The elemental concentration is measured by the above-described measuring device according to the specifications of the device manufacturer (ICP-MS: Agilent 7500ce, ICP-OES: Perkin Elmer 7300 DV) and using a certified standard solution for calibration. The element concentrations in solution (15 ml) measured by the instrument are then converted based on the original weight of the probe (2 g).

Note: It should be noted that the acid, container, water, and equipment must be sufficiently pure to measure the elemental concentration of interest. This is confirmed by extracting a blank sample without fused silica.

The following elements are thus determined: Li, Na, Mg, K, Ca, Fe, Ni, Cr, Hf, Zr, Ti, (Ta), V, Nb, W, Mo, Al.

c-3) Measurements of samples present as liquids are performed as described above, omitting the sample preparation according to step c-1). A 15 ml liquid sample is introduced into the extraction flask. No conversion is made based on the original sample weight.

d. Determination of the Density of a Liquid To determine the density of a liquid, a precisely defined volume of liquid is weighed into a measuring device inert to the liquid and its constituents, and the empty weight and the filled weight of the container are determined. to measure. Density is given as the difference between the two weight measurements divided by the volume of liquid introduced.

e. Fluoride Determination A 15 g quartz glass sample is ground and cleaned by treatment with nitric acid at 70.degree. The sample is then washed several times with high-purity water and then dried. A 2 g sample is weighed into a nickel crucible and covered with 10 g Na ₂ CO ₃ and 0.5 g ZnO. The crucible is closed with a Ni lid and calcined at 1000° C. for 1 hour. Water is then added to the nickel crucible and boiled until the molten crust is completely dissolved. Transfer this solution to a 200 ml volumetric flask and fill up to 200 ml with high purity water. After sedimentation of undissolved components, 30 ml is taken and transferred to a 100 ml volumetric flask, 0.75 ml glacial acetic acid and 60 ml TISAB are added and topped up with high purity water. Transfer this sample solution to a 150 ml glass beaker.

Determination of the fluoride content in the sample solution was performed here by Wissenschaftlich-Technische Werkstaetten GmbH using an ion-sensitive (fluoride) electrode suitable for the expected concentration range and a display device specified by the manufacturer. Fluoride ion selective and reference electrodes F-500 and R503/D connected to pMX 3000/pH/ION from Senschaftlich Technische Werkstetten. The fluoride concentration in the quartz glass is calculated using the fluoride concentration in the solution, the dilution ratio, and the weight of the sample.

f. Measurement of chlorine (50ppm or more)
A 15 g quartz glass sample is ground and cleaned by treatment with nitric acid at about 70°C. The sample is then washed several times with high-purity water and then dried. 2 g of sample are then filled into a PTFE insert for a pressure vessel, dissolved in 15 ml of NaOH (c=10 mol/l), closed with a PTFE lid and placed in the pressure vessel. The pressure vessel is closed and heat treated at about 155° C. for 24 hours. After cooling, remove the PTFE insert and transfer the entire solution to a 100 ml volumetric flask. Add 10 ml of HNO ₃ (65 wt %) and 15 ml of acetate buffer, cool and fill up to 100 ml with high purity water. Transfer this sample solution to a 150 ml glass beaker. This sample solution has a pH value in the range of 5-7.

Measurement of the chloride content in the sample solution is performed using an ion-sensitive (chloride) electrode suitable for the expected concentration range and a display device specified by the manufacturer, here pMX from Wissenschaftlich-Technische Werkstaetten GmbH. 3000/pH/ION with model number Cl-500 electrode and model number R-503/D reference electrode.

g. Chlorine content (less than 50 ppm)
A chlorine content of less than 50 ppm to 0.1 ppm in quartz glass is determined by neutron activation analysis (NAA). For this, three bores with a diameter of 3 mm and a length of 1 cm are taken from the quartz glass body to be measured. These are sent for analysis to a research institute, this time the Institute for Nuclear Chemistry at the Johannes-Gutenberg University in Mainz, Germany. To eliminate sample contamination by chlorine, the samples were thoroughly cleaned in an HF bath on site just prior to the measurements. Each bore is measured several times. The results and bore are then returned from the laboratory.

h. Optical Properties The transmittance of fused silica samples is measured using a commercial grating or FTIR spectrometer from Perkin Elmer (Lambda 900 [190-3000 nm] or System 2000 [1000-5000 nm]). The choice depends on the required measuring range.

To measure the absolute transmittance, the sample body is polished on parallel planes (surface roughness RMS<0.5 nm) and all surface residues are removed by sonication. The sample thickness is 1 cm. If a strong transmittance reduction due to impurities, dopants, etc. is expected, a thicker or thinner sample can be chosen to stay within the measurement range of the instrument. A sample thickness (measuring length) is chosen such that a sufficiently detectable effect is measured at the same time with only minor artifacts occurring when the radiation passes through the sample.

For opacity measurements, the sample is placed in front of the integrating sphere. Opacity is determined by the formula O=1/T=I ₀ /I, using the measured transmittance value T
Calculated by

i. Refractive Index and Refractive Index Profiles in Tubes or Rods Refractive index profiles for tubes/rods are manufactured by York Technology Ltd.; (York Technologies) Preform Profiler P102 or P104. For this, the rod is placed lying down in the measuring chamber and the chamber is tightly closed. The measurement chamber is then filled with immersion oil having a refractive index at 633 nm that is very close to the refractive index of the outermost glass layer at the test wavelength of 633 nm. A laser beam then passes through the measurement chamber. Behind the measuring chamber (in the direction of the radiation) is mounted a detector that measures the angle of deviation (of the radiation entering the measuring chamber compared to the radiation leaving the measuring chamber). Assuming that the rod index profile is radially symmetric, the diametric index profile can be reconstructed by the inverse Abel transformation. These calculations are performed by the equipment manufacturer York's software.

The refractive index of the sample was measured by York Technology Ltd. is measured with a Preform Profiler P104. For isotropic samples, measuring the refractive index profile gives only one value, the refractive index.

j. Carbon Content Quantitative measurement of the surface carbon content of silicon dioxide granules and silicon dioxide powders was performed using a Leco Corporation, USA carbon analyzer RC612 to measure all surface carbon contamination (SiC ) are completely oxidized with oxygen to give carbon dioxide. For this, 4.0 g of sample is weighed, placed in a quartz glass dish and introduced into the carbon analyzer. The sample is immersed in pure oxygen and heated to 900° C. for 180 seconds. The _CO2 produced is measured by the infrared detector of the carbon analyzer. Under these measurement conditions, the detection limit is less than 1 ppm (ppm by weight) of carbon.

A quartz glass boat suitable for this analysis using the carbon analyzer described above is available on the laboratory market as a consumable for LECO analyzers with LECO number 781-335, in this case Deslis Laborhandel (Fleurstrand). It is available from Flurstrasse 21, D-40235 Düsseldorf (Germany) as Deslis No. LQ-130XL. Such boats have width/length/height dimensions of about 25mm/60mm/15mm. The quartz glass boat is filled to half its height with sample material. In the case of silicon dioxide powder, sample weights of 1.0 g of sample material can be reached. The lower limit of detection is then less than 1 ppm by weight of carbon. In the same boat, for the same fill height, a sample weight of 4 g of silicon dioxide granules is reached (average particle size in the range of 100-500 μm). In that case, the lower limit of detection is about 0.1 ppm by weight of carbon. The lower limit of detection is reached when the measured area integral of the sample is less than or equal to three times the measured area integral of the blank sample (blank sample = method as above, but with an empty quartz glass boat).

k. Curl Parameter The curl parameter (also called “fiber curl”) is measured according to DIN EN 60793-1-34:2007-01 (German version of standard IEC 60793-1-34:2006). Measurements are as described in Annex A, Section A. 2.1, A. 3.2, and A. It is carried out according to the method described in 4.1 (“extrema technique”).
Measurements shall be made in accordance with Annex A A. 2.1, A. 3.2 and A. It is carried out according to the method described in section 4.1 (“extrema technique”).

l. Attenuation Attenuation is measured according to DIN EN 60793-1-40:2001 (German version of standard IEC 60793-1-40:2001). The measurement is performed at a wavelength of λ=1550 nm according to the method described in the appendix (“cutback method”).

m. Viscosity of Slurries or Suspensions Slurries are made with demineralized water (Direct-Q 3UV, Millipore, water quality: 18.2 MΩcm) at a solids concentration of 30% by weight. The viscosity is then measured with an MCR102 from Anton-Paar. For this, the viscosity is measured at 5 revolutions per minute (5 rpm). The measurements are made at a temperature of 23° C. and a pressure of 1013 hPa. The same procedure is used for suspensions.

n. thixotropy and rheopexy--n1. A thixotropic slurry or suspension is made with demineralized water (Direct-Q 3UV, Millipore, water quality: 18.2 MΩcm) at a solids concentration of 30% by weight. The thixotropy is then measured with an MCR102 from Anton-Paar in a cone-plate configuration. For this, the viscosity is measured at 5 revolutions per minute (5 rpm) and 50 revolutions per minute (50 rpm). The quotient of the first value and the second value indicates the thixotropic index. Measurements are made at a temperature of 23°C.

- n2. A rheopexy slurry or suspension is made with demineralized water (Direct-Q 3UV, Millipore, water quality: 18.2 MΩcm) to a solids concentration of 60% by weight. The viscosity of the slurry or suspension, which was then adjusted to 25° C., was measured by Malvern Panalytical Ltd. (Malvern Panalytical) Kinexus pro+ rheometer with paddle stirrer at constant shear rate of 25/s or 100/s for 15 minutes.

o. Zeta Potential of Slurries For zeta potential measurements, a zeta potential cell (Flow Cell, Beckman Coulter) is used. The sample is dissolved in demineralized water (Direct-Q 3UV, Millipore, water quality: 18.2 MΩcm) to obtain a 20 mL solution with a concentration of 1 g/L. The pH is set to 7 through the addition of HNO ₃ solutions with concentrations of 0.1 mol/L and 1 mol/L and NaOH solutions with a concentration of 0.1 mol/L. Measurements are made at a temperature of 23°C.

p. Isoelectric Point of Slurries or Suspensions Isoelectric point, zeta potential measuring cell (Flow Cell, Beckman Coulter) and automatic titrator (DelsaNano AT, Beckman Coulter) are used. The sample is dissolved in demineralized water (Direct-Q 3UV, Millipore, water quality: 18.2 MΩcm) to obtain a 20 mL solution with a concentration of 1 g/L. The pH is changed by adding HNO ₃ solutions with concentrations of 0.1 mol/L and 1 mol/L and NaOH solutions with a concentration of 0.1 mol/L. The isoelectric point is the pH value at which the zeta potential is equal to zero. Measurements are made at a temperature of 23°C.

q. pH Value of Slurries or Suspensions The pH value of slurries is determined using a WTW 3210 from Wissenschaftlich-Technische-Werkstaetten GmbH. A pH 3210 Set 3 from WTW is used as the electrode. Measurements are made at a temperature of 23°C.

r. Solids Content A weighed portion m ₁ of the slurry or suspension material is heated to 500° C. for 4 hours and re-weighed (m ₂ ) after cooling. The solid content w is given as m ₂ /m ₁ ×100 [% by weight].

s. Bulk Density The bulk density of bulk materials is measured on an SMG 697 from Powtec according to standard DIN ISO 697:1984-01. Bulk materials (silicon dioxide powder or granules) do not form agglomerates.

t. Tamping Density The tamping density of bulk material is determined according to standard DIN ISO 787:1995-10. Silicon dioxide powders and silicon dioxide granules are particularly suitable as bulk material.

u. Measurement of Pore Size Distribution The pore size distribution is determined according to DIN 66133 (at a surface tension of 480 mN/m and a contact angle of 140°). For measurements of pore sizes smaller than 3.7 nm, a Pascal 400 from Porotec is used. For pore size measurements from 3.7 nm to 100 μm, Pascal 140 from Porotec is used. Samples are subjected to pressure treatment prior to measurement. For this, a manual hydraulic press is used (Specac Ltd.) (River House, 97 Cray Avenue, Orpington, Kent BR5 4HE, UK). ), order number 15011). 250 mg of sample material was weighed into a Specac Ltd. It is placed in a "pellet die" with an inner diameter of 13 mm manufactured by the manufacturer and a load of 1 t is applied according to the display. This load is maintained for 5 s and readjusted as necessary. The load on the sample is then removed and the sample is dried in a recirculating air drying cabinet for 4 hours at 105±2°C.

The sample is weighed into a Type 10 penetrometer with an accuracy of 0.001 g. In order to provide good reproducibility of the measurements, the penetrometer should have a "stem volume used", i.e. the percentage of Hg volume used to fill the penetrometer should be between 20% of the total Hg volume. Select to be in the 40% range. The penetrometer was then slowly evacuated to 50 μm Hg and left at this pressure for 5 minutes. The following parameters, total pore volume, total pore surface area (assuming cylindrical pores), average pore radius, modal pore radius (most common pore radius), second peak pore Radius (μm), is provided directly by the software of the measurement device.

v. Primary Particle Size Primary particle size is measured using a scanning electron microscope (SEM) model Zeiss Ultra 55. The sample is suspended in demineralized water (Direct-Q 3UV, Millipore, water quality: 18.2 MΩcm) to obtain a very dilute suspension. The suspension is treated with an ultrasonic probe (UW 2070, Bandelin electronic, 70 W, 20 kHz) for 1 minute and then applied to a carbon sticky pad.

w. Average Particle Size in Suspension Average particle size in suspension was measured by Malvern Instruments Ltd. A Mastersizer 2000 available from (UK) is used according to the user's manual and measured using the laser deflection method. The sample is suspended in demineralized water (Direct-Q 3UV, Millipore, water quality: 18.2 MΩcm) to obtain a 20 mL suspension with a concentration of 1 g/L. The suspension is treated with an ultrasonic probe (UW 2070, Bandelin electronic, 70 W, 20 kHz) for 1 minute.

x. Particle Size and Core Size of Solids Particle size and core size of solids are measured using a Camsizer XT available from Retsch Technology GmbH (Germany) according to the user manual. The software gives D10, D50, and D90 values for the samples.

y. BET Measurement For the determination of the specific surface area, the static volumetric BET method is used according to DIN ISO 9277:2010. For BET measurements, use "NOVA 3000" or "Quadrasorb" (available from Quantachrome) operating according to the SMART method ("Sorption Method with Adaptive dosing Rate"). Micropore analysis was performed using the t-plot method (p/p0=0.1-0.3) and mesopore analysis was performed using the MBET method (p/p0=0.0-0.3). 3) Using standard alumina SARM-13 and SARM-214 available from Quantachrome as reference materials Tare the measuring cell (clean and dry) Sample material introduced and Select the type of measuring cell so that the filler rod fills the measuring cell as much as possible and dead space is reduced to a minimum.The sample material is introduced into the measuring cell.The expected value of the measurement is 10-20 m. Select the amount of sample material so that it corresponds to ² /g.Fix the measuring cell in the firing position of the BET measuring device (without filler rod) and evacuate to <200 mbar.The rate of evacuation depends on the material The measuring cell is set so that it does not leak.Baking is carried out in this state for 1 hour at 200° C.After cooling, the measuring cell filled with sample is weighed (raw value).The tare weight is then taken to the raw value. = net weight = weight of the sample.Then the filling rod is introduced into the measuring cell, which is also fixed in the measuring position of the BET measuring device.Before starting the measurement, the identification of the sample and the Enter the weight into the software Start the measurement Measure the saturation pressure of nitrogen gas (N2 4.0) Evacuate the measuring cell and cool it to 77 K using a nitrogen bath Dead space is helium Measurement is performed using gas (He 4.6).The measuring cell is evacuated again.Multipoint analysis with at least 5 measuring points is carried out.N2 4.0 is used as absorbent.Specific surface area is m ² /g.

z. Glass Body Viscosity The viscosity of the glass was measured using a TA Instruments model 401 beam bending viscometer with the manufacturer's software WinTA (current version 9.0) running on Windows 10 using DIN Measure according to ISO 7884-4:1998-02 standard. The support width between supports is 45 mm. A sample rod with a rectangular cross-section is cut from an area of homogeneous material (the top and bottom surfaces of the sample have a finish of at least 1000 grains). The sample surface after processing has a grain size = 9 μm and RA = 0.15 μm. The sample rod has the following dimensions: Length = 50 mm, Width = 5 mm, and Height = 3 mm (written in the order length, width, height, as in standard documents). Three samples are measured and the average is calculated. A thermocouple in close contact with the sample surface is used to measure the sample temperature. The following parameters are used: heating rate = 25 K to a maximum of 1500°C, load weight = 100 g, maximum bending = 3000 µm (differs from standard documentation).

EXAMPLES The present invention will now be described with reference to examples. The invention is not limited to the examples.

E. 1. Preparation of Silicon Dioxide Granules from Silicon Dioxide Powder E15-x: A slurry of calcined silica (BET=30 m ² /g, average particle size in suspension=100 nm) was mixed in a mixer with stirrer/paddle geometry. Placed in deionized water (L=0.1 μS/cm) and homogenized. The solids content of the homogenized mixture was 55% by weight. For E15-2, E15-3, the suspension was then sonicated as shown in Table 2. All suspension E15-x was then passed through a filter arrangement. Particle size and elemental analysis before filtration are shown in Table 3.

In examples E15-1 to E15-4, three filters numbered 1 . ~3. (downstream sequence from 1. through 2. to 3.) was selected. This was as follows.
1. Filter: Acura Multiflow (registered trademark) (PP multilayer depth filter), filter opening 10 μm, separation rate 80%,
2. Filter: Acura Promelt (registered trademark) (PP depth filter), filter opening 1 μm, separation rate 99.9%,
3. Filter: Acura Multiflow (registered trademark) (PP multi-layer depth filter), filter opening 0.5 μm, separation rate 80%.

Example E15-1 was prepared as above but was not sonicated.

For E15-2, model UIP 1000 hdT-230 ultrasonicator (Hielscher Ultrasonics GmbH, Teltow) with booster B4-1.2 and titanium probe BS4d55 with FC100L1K-1S through flow cell (Teltow (Germany)) was selected. A power density of 950 W/liter and a throughput of 180 l/h were chosen.

For E15-3, a vortex reactor block WB4-1604 ultrasonicator from Bandelin (Berlin, Germany) with a power density of 550 W/liter and a throughput of 250 l/h was selected.

In example E15-4, the procedure was as described in E-15-x, but instead of ultrasound, the following operating parameters were used before microfiltration: speed 900 rpm, throughput 250 l/h, mill Processing was carried out in a ball mill model Diskus 20 from Netzsch Feinmahltechnik GmbH, Selb (Germany) with a ball size of 500 μm.

Comparing Example 15-1 with other Examples E15-2 through E15-4 reveals an average particle size in the suspension compared to the comparative suspension that was not additionally dispersed after the dispersing step. , and the particle size distribution is clearly narrow.

Dispersion by ultrasound at a power density of 950 W/liter shows good homogenization with a small average particle size, but the proof of analysis shows an increased content of elements other than Si, O, H, C and Cl, especially metal atoms. is doing. For further processing into quartz glass, these mean the formation of insoluble particles or gas bubbles. These particles are only partially retained in the filter arrangement. Equivalent and more pronounced findings are observed when a ball mill is used for dispersion.

Examples E15-2 and E15-3 according to the invention show good and consistent dispersion and low contents of elements other than Si, O, H, C and Cl. The largest fraction of particles of elements other than Si, O, H, C and Cl is retained in the filter arrangement.

The filter arrangements of Examples E15-3 and E15-4 show at least 8 times longer service life before replacement (filter arrangement service life) compared to Example E15-1, whereas E15-4 , the dose of metal ions implanted by the ball-mill dispersion process is considerably higher than that of E15-3.

This results in a purer silicon dioxide suspension and at the same time increases the service life of the filter arrangement.

Metals (Ca, Co, Cr, Cu, Fe, Ge, Hf, K, Li, Mg, Mn, Mo, Na, Nb, Ni, Ti, V, W, Zn, Zr) when dispersed in a ball mill The injection volume is much higher than with ultrasonic dispersion.

2. Different filter combinations in filter placement E16-x: A slurry of calcined silica (BET=30 m ² /g, average particle size in suspension=100 nm) was added to deionized water in a mixer equipped with an agitator/paddle geometry. (L=0.1 μS/cm) and homogenized as before. The solids content of the homogenized mixture was 63% by weight. All slurries were then treated with an ultrasonic generator (Rating: 550 W/liter, throughput: 250 l/h, treatment time: 30 seconds). All E16-x suspensions were then passed through the filter arrangement. The filter arrangement consists of three filters numbered 1 . ~3. (sequence downstream from 1. through 2. to 3.).
The filters used were as follows (Table 4).

Multiflow filters are available from Fuhr GmbH, 55270 Klein-Winternheim (Germany). The filters were used in the following configuration: height: 20 (20 inches (50.8 cm)), material: polypropylene, gradation: 4 (4 layers), adapter: F3 (222 adapter with fins).

Promelt filters are also available from Fuhr GmbH. These filters are used in the configuration Height: 20 (20 inches (50.8 cm)), Material: Polypropylene, Gradation: 1 (β rate = 1000) (4 layers), Adapter: F3 (222 adapter with fins) did.

amaPure TS filters are obtained from Filtration Group GmbH, Schleifbachweg 45, 74613 Oehringen (Germany) (formerly Mahle Industryfiltration). can. The filters were used in the following configuration: height: 20 inches (50.8 cm), material: polypropylene, version: X8.

Table 5 shows each combination of three filters in the filter arrangement.

Observations i. The granulation properties of the suspensions contained in E16-1 to E16-8 were found to be "good". "Good" means that all suspensions are suitable for granulation.
ii. The fused silica blisters produced from the granules of each example were "good" for Examples E16-1 to E16-3 and E16-7 and E16-8. "Good" means marketable quartz glass quality with few bubbles. Such a quartz glass is shown in FIG. 7b). Blistering of Examples E16-4 through E16-6 was rated as "moderate". "Medium" means a quality of quartz glass that has a high number of bubbles and is considered to be available only on a limited basis.
iii. The dose of metal ions was radically low and the particle size distribution, expressed as the ratio of D90 to D10, was also low.
iv. Short service lives (less than 1000 liters) and long service lives (>1000 liters) were observed, depending on the service life of the filter.

3. Ultrasonication E17-x: A slurry of calcined silica (BET=30 m ² /g, average particle size in suspension=100 nm) was added to deionized water (L=0 .1 μS/cm) as before. The solids content of the homogenized mixture was 63% by weight. All slurries were then treated with an ultrasonicator. The sonication parameters are summarized in Table 6. All suspensions E17-x were subsequently passed through the same filter arrangement as example E15-x.

Observations i. At high ultrasonic power, the average particle size of the suspension upstream of the filter is somewhat lower than at low ultrasonic power. At the same time, the content of metal ions and (and thus) ions other than Si, O, H, C, Cl is clearly high.
ii. At the same treatment time (10 seconds (s)), the dose of metal ions implanted at an ultrasonic power of 550 W/liter is clearly lower than at 950 W/liter. The particle size distributions of D10/D90 are only slightly different. When the treatment time at 550 W/liter is doubled to 20 seconds, the same particle size and distribution as the treatment at 950 W/liter and 10 seconds is obtained by sonication at a significantly lower metal ion concentration.
iii. The longer the treatment time, the higher the metal ion concentration.

101 step (i)
102 step (ii)
103 step (iii)
104 step (iv)
105 step (v)
211 first filter 212 second filter 213 third filter 311 first one filter step using filter 312 second filter step, filter A
313 second filter step, filter B
314 third filter step 411 using filter step i. )
412 step ii. )
413 step iii. )

Claims (21)

A method for producing a silicon dioxide suspension, comprising:
(i) providing silicon dioxide powder;
(ii) providing a liquid;
(iii) mixing the silicon dioxide powder with the liquid to obtain a slurry;
(iv) sonicating the slurry to obtain a precursor suspension;
(v) passing at least a portion of the precursor suspension through a first multi-stage filter device,
said first multi-stage filter device having at least first, second and third filter stages;
each filter step includes at least one filter;
said second filter stage is positioned downstream of said first filter stage and said third filter stage is positioned downstream of said second filter stage;
The first filter step has a filter opening of 5 μm or more,
The second filter step has a filter opening in the range of 0.5 to 5 μm,
The third filtering step has a filter opening of 1 μm or less,
at least one of said filter steps selected from said first, second and third filter steps has a separation rate of 99.5% or more;
The separation ratios are stated according to ISO 16889 and are in each case based on said filters,
and said filter opening indicates what the minimum particle size that said filter will hold. 2. The method of claim 1, wherein the silicon dioxide suspension of step (v) is obtained after passing through a multi-stage filter device. The first filter device has the following characteristics:
(a) the first filter step has a separation rate of 90% or less;
(b) the first filtering step has a filter opening in the range of 5 to 15 μm;
(c) said second filter step has a separation rate of 95% or greater;
(d) the second filter step has a filter opening of 0.5 to 2 μm,
(e) the third filtering step has a separation rate of 99.5% or greater;
3. A method according to claim 1 or claim 2, characterized by at least one of or a combination of two or more thereof. 4. Method according to any one of claims 1 to 3, wherein at least one filter of the first filter device in one of the filter steps is designed as a depth filter. 5. A method according to any one of the preceding claims, wherein the treatment of said slurry with ultrasound lasts at least 10 seconds. 6. A method according to any one of the preceding claims, wherein the treatment of said slurry by ultrasound is characterized by power densities up to 600 W/liter. 7. The method of any one of claims 1-6, wherein the slurry has less than 5% by weight of additives for stabilizing the slurry, said weight% being based on the total weight of the slurry. . 8. The method of any one of claims 1-7, wherein the silicon dioxide powder can be made from a compound selected from the group consisting of siloxanes and silicon alkoxides. The silicon dioxide powder has the following properties:
a. a carbon content of less than 100 ppm;
b. a chlorine content of less than 500 ppm;
c. an aluminum content of less than 200 ppb;
d. Content of atoms other than Si, O, H, C, Cl less than 5 ppm,
e. at least 70% by weight of the powder particles have a primary particle size in the range of 10-100 nm;
f. a tamping density in the range of 0.001 to 0.3 g/ ^cm3 ;
g. residual moisture less than 5% by weight,
h. at least one of the BET surface areas less than 35 g/m ² or characteristic a. ~ h. having a combination of two or more of
9. The method of any one of claims 1-8, wherein the weight percent, ppm and ppb are in each case based on the total amount of the silicon dioxide powder. The slurry has the following properties:
a. ) a solids content of at least 20% by weight, based on the dry weight of said slurry;
b. ) as a 4 wt% slurry, said slurry having a pH value in the range of 3 to 8;
c. ) at least 90% by weight of the silicon dioxide particles have a particle size in the range of 1 nm to less than 10 μm;
d. ) content of atoms other than Si, O, H, C, and Cl of 5 ppm or less;
e. 10. The method of any one of claims 1 to 9, wherein the slurry is characterized by at least one of being rheopexic, and wherein the weight percentages and ppm are always based on the total solids content of the slurry. The silicon dioxide suspension has the following properties:
A. rheopexic properties at temperatures below 45° C. and solids concentrations in the range of 20-70 wt %, said wt % being based on total solids in said suspension;
B. at least 90% by weight of said silicon dioxide particles, based on the total weight of all silicon dioxide particles, having a particle size in the range of 1 nm to less than 10 μm;
C. As a 4 wt% suspension, said suspension has a pH value in the range of 3 to 8, said wt% being based on the solids content of said suspension;
D. a chlorine content of less than 500 ppm;
E. an aluminum content of less than 200 ppb;
F. Content of atoms other than Si, O, H, C, Cl less than 5 ppm,
and wherein said ppm and ppb are in each case based on the total amount of silicon dioxide particles. A silicon dioxide suspension obtainable by the method according to any one of claims 1 to 11. A process for the production of silicon dioxide granules, wherein the silicon dioxide suspension according to claim 12 or the silicon dioxide suspension obtained by the process according to any one of claims 1 to 11 is treated to obtain silicon dioxide granules, said silicon dioxide granules having a larger particle size than the silicon dioxide particles present in said silicon dioxide suspension. Said processing of said silicon dioxide suspension is spray drying, said spray drying having the following characteristics:
a] spray granulation in a spray tower,
b] said silicon dioxide suspension at the nozzle is up to 40 bar, for example in the range from 1.3 to 20 bar, from 1.5 to 18 bar, from 2 to 15 bar or from 4 to 13 bar, particularly preferably in the range from 5 to 12 bar , this pressure is stated in absolute value (relative to p=0 hPa),
c] the droplets entering said spray tower are at a temperature in the range from 10 to 50°C, preferably in the range from 15 to 30°C, particularly preferably in the range from 18 to 25°C,
d] the temperature on the side of the nozzle facing the spray tower is in the range from 100 to 450° C., for example in the range from 250 to 440° C., particularly preferably in the range from 320 to 430° C.
e] in the range from 0.05 to 1 m ³ /h, for example from 0.1 to 0.7 m ³ /h or from 0.2 to 0.5 m ³ /h, particularly preferably from 0.25 to 0.4 m ³ /h Throughput of the silicon dioxide suspension through the nozzle in the range of h,
f] at least 40% by weight, for example in the range from 50 to 80% by weight, or in the range from 55 to 75% by weight, particularly preferably from 60 to 70% by weight, in each case based on the total weight of said silicon dioxide suspension solids content of said silicon dioxide suspension in the range of
g] gas inflow to the spray tower in the range 10-100 kg/min, for example in the range 20-80 kg/min or in the range 30-70 kg/min, particularly preferably in the range 40-60 kg/min;
h] the temperature of the gas stream upon entering said spray tower in the range 100-450° C., for example in the range 250-440° C., particularly preferably in the range 320-430° C.;
i] the temperature of the gas stream upon exiting said spray tower of less than 170°C;
j] said gas is selected from the group consisting of air, nitrogen and helium or a combination of two or more thereof, preferably air;
k] less than 5 wt%, such as less than 3 wt%, or less than 1 wt%, or 0.01 to 0.5, in each case based on the total weight of said silicon dioxide granules resulting from said spray drying residual moisture of the granules when removed from the spray tower in the range by weight, particularly preferably in the range from 0.1 to 0.3% by weight;
l] At least 50% by weight of the spray granules, based on the total weight of the silicon dioxide granules resulting from the spray-drying, for a time in the range 1 to 100 seconds, such as 10 to 80 seconds, particularly preferably 25 seconds. complete a flight time of ~70 seconds,
m] at least 50% by weight of said spray granules, based on the total weight of said silicon dioxide granules resulting from said spray drying, is greater than 20m, such as greater than 30m, or greater than 50m, or greater than 70m, or greater than 100m , or complete a flight path of more than 150 m, or more than 200 m, or in the range of 20-200 m, or in the range of 10-150 m, or in the range of 20-100 m, particularly preferably in the range of 30-80 m,
n] said spray tower has a cylindrical shape,
o] the height of the spray tower above 10 m, for example above 15 m, or above 20 m, or above 25 m, or above 30 m, or in the range from 10 to 25 m, particularly preferably in the range from 15 to 20 m,
p] filtering out particles with a size of less than 90 μm before removing the granules from the spray tower;
q] After removing the granules from the spray tower, preferably on a vibrating chute, filtering out particles with a size greater than 500 μm,
r] the droplets of the silicon dioxide suspension leave the nozzle at an angle of 30-60° to the vertical, particularly preferably at an angle of 45° to the vertical,
14. The method of claim 13, characterized by at least one of: The silicon dioxide granules have the following properties:
A) an angle of repose in the range 23-26°;
B) a BET specific surface area in the range of 20-50 m ² /g;
C) bulk density in the range of 0.5 to 1.2 g/ ^cm3 ;
D) an average particle size of the silicon dioxide particles in the range of 50-500 μm E) a carbon content of less than 50 ppm;
F) a chlorine content of less than 500 ppm;
G) an aluminum content of less than 200 ppb;
H) content of atoms other than Si, O, H, C less than 5 ppm;
I) tamping density of silicon dioxide granule particles in the range of 0.7 to 1.3 g/cm ³ ;
J) pore volume of silicon dioxide granule particles in the range of 0.1 to 2.5 mL/g;
K) the particle size distribution D ₁₀ of the silicon dioxide granule particles in the range from 50 to 150 μm,
L) the particle size distribution D ₅₀ of the silicon dioxide particles in the range 150-300 μm,
M) the particle size distribution D ₉₀ of the silicon dioxide particles in the range 250-620 μm;
and wherein said ppm and ppb are in each case based on the total weight of said silicon dioxide granules. A method for manufacturing a quartz glass body, comprising at least i. ) providing silicon dioxide granules obtained by the method according to any one of claims 13 to 15;
ii. ) forming a glass melt from the silicon dioxide granules;
iii. ) forming a quartz glass body from at least a portion of said glass melt. A quartz glass body obtainable by the method according to claim 16 . The following characteristics:
A] a chlorine content of less than 500 ppm,
B] an aluminum content of less than 200 ppb,
C] content of atoms other than Si, O, H, C less than 5 ppm,
D] 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 ~ log ₁₀ (η (1300 ° C) / dPas) = 12.2, or log ₁₀ (η (1350 ° C) / dPas) = 10.5 to log ₁₀ (η (1350 ° C) / dPas) = 11.5 range of viscosities (p=1013 hPa),
E] refractive index homogeneity of less than 10 ⁻⁴ ,
F] Cylindrical morphology,
G] a tungsten content of less than 5 ppm,
H] molybdenum content less than 5 ppm,
18. The fused silica body of claim 17, wherein said ppb and ppm are in each case based on the total weight of said fused silica body. A method of manufacturing a light guide, comprising:
A/Providing a quartz glass body according to claim 17 or claim 18 or obtainable by the method according to claim 16, said quartz glass body being first processed to form at least one opening. obtaining a hollow body having
B/ inserting one or more core rods into said hollow body from step A/ through said at least one opening to obtain a precursor;
C/ drawing said precursor while heating to obtain a light guide having one or more cores and a jacket M1. A method for manufacturing a light emitter,
(i) providing a quartz glass body according to claim 17 or claim 18 or obtainable by the method according to claim 16, said quartz glass body being first processed to form at least one aperture; obtaining a hollow body having parts;
(ii) attaching electrodes to the hollow body as required;
(iii) filling the hollow body from step (i) with a gas. A method for manufacturing a molded body,
(1) providing a quartz glass body according to claim 17 or 18 or a quartz glass body obtained by the method according to claim 16;
(2) A method including the step of molding the quartz glass body to obtain a molded body.

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