EP3390300A1 - Fabrication d'un corps en verre de silice dans un creuset fritté debout - Google Patents

Fabrication d'un corps en verre de silice dans un creuset fritté debout

Info

Publication number
EP3390300A1
EP3390300A1 EP16815838.4A EP16815838A EP3390300A1 EP 3390300 A1 EP3390300 A1 EP 3390300A1 EP 16815838 A EP16815838 A EP 16815838A EP 3390300 A1 EP3390300 A1 EP 3390300A1
Authority
EP
European Patent Office
Prior art keywords
range
less
quartz glass
silica
ppm
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP16815838.4A
Other languages
German (de)
English (en)
Inventor
Matthias OTTER
Walter Lehmann
Michael HÜNERMANN
Nils Christian NIELSEN
Nigel Robert WHIPPEY
Boris Gromann
Abdoul-Gafar KPEBANE
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Heraeus Quarzglas GmbH and Co KG
Original Assignee
Heraeus Quarzglas GmbH and Co KG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Heraeus Quarzglas GmbH and Co KG filed Critical Heraeus Quarzglas GmbH and Co KG
Publication of EP3390300A1 publication Critical patent/EP3390300A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/06—Glass compositions containing silica with more than 90% silica by weight, e.g. quartz
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
    • B01J2/02—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by dividing the liquid material into drops, e.g. by spraying, and solidifying the drops
    • B01J2/04—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by dividing the liquid material into drops, e.g. by spraying, and solidifying the drops in a gaseous medium
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
    • C01B33/181—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by a dry process
    • C01B33/183—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by a dry process by oxidation or hydrolysis in the vapour phase of silicon compounds such as halides, trichlorosilane, monosilane
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B17/00—Forming molten glass by flowing-out, pushing-out, extruding or drawing downwardly or laterally from forming slits or by overflowing over lips
    • C03B17/04—Forming tubes or rods by drawing from stationary or rotating tools or from forming nozzles
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B19/00—Other methods of shaping glass
    • C03B19/10—Forming beads
    • C03B19/1005—Forming solid beads
    • C03B19/106—Forming solid beads by chemical vapour deposition; by liquid phase reaction
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B20/00—Processes specially adapted for the production of quartz or fused silica articles, not otherwise provided for
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B33/00—Severing cooled glass
    • C03B33/06—Cutting or splitting glass tubes, rods, or hollow products
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/012—Manufacture of preforms for drawing fibres or filaments
    • C03B37/01205—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments
    • C03B37/01211—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments by inserting one or more rods or tubes into a tube
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/012—Manufacture of preforms for drawing fibres or filaments
    • C03B37/01265—Manufacture of preforms for drawing fibres or filaments starting entirely or partially from molten glass, e.g. by dipping a preform in a melt
    • C03B37/01274—Manufacture of preforms for drawing fibres or filaments starting entirely or partially from molten glass, e.g. by dipping a preform in a melt by extrusion or drawing
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
    • C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
    • C03B37/027—Fibres composed of different sorts of glass, e.g. glass optical fibres
    • C03B37/02754—Solid fibres drawn from hollow preforms
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
    • C03B5/06—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture in pot furnaces
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
    • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
    • C03B5/167—Means for preventing damage to equipment, e.g. by molten glass, hot gases, batches
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
    • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
    • C03B5/235—Heating the glass
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C1/00—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels
    • C03C1/02—Pretreated ingredients
    • C03C1/026—Pelletisation or prereacting of powdered raw materials
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C2201/00—Glass compositions
    • C03C2201/02—Pure silica glass, e.g. pure fused quartz
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C2201/00—Glass compositions
    • C03C2201/06—Doped silica-based glasses
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C2201/00—Glass compositions
    • C03C2201/06—Doped silica-based glasses
    • C03C2201/08—Doped silica-based glasses containing boron or halide
    • C03C2201/11—Doped silica-based glasses containing boron or halide containing chlorine
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C2201/00—Glass compositions
    • C03C2201/06—Doped silica-based glasses
    • C03C2201/20—Doped silica-based glasses containing non-metals other than boron or halide
    • C03C2201/23—Doped silica-based glasses containing non-metals other than boron or halide containing hydroxyl groups
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C2201/00—Glass compositions
    • C03C2201/06—Doped silica-based glasses
    • C03C2201/30—Doped silica-based glasses containing metals
    • C03C2201/32—Doped silica-based glasses containing metals containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C2203/00—Production processes
    • C03C2203/20—Wet processes, e.g. sol-gel process
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
    • G01N21/412—Index profiling of optical fibres
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0005—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being of the fibre type
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02042—Multicore optical fibres
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00—Technologies relating to the processing of minerals
    • Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
    • Y02P40/57—Improving the yield, e-g- reduction of reject rates

Definitions

  • the invention relates to a method for producing a quartz glass body comprising the steps of i) providing a silica granule, ii) forming a glass melt from the silica granules in a furnace and iii) forming a quartz glass body from at least a part of the glass melt Sinter crucible includes.
  • the invention further relates to a quartz glass body obtainable by this method.
  • the invention relates to a light guide, a lighting means and a shaped body, which are each available by further processing of the quartz glass body.
  • Quartz glass, quartz glass products and products containing quartz glass are known.
  • various methods for producing quartz glass and quartz glass bodies are already known. Nevertheless, considerable efforts continue to be made to identify manufacturing processes by which silica glass of even higher purity, that is, absence of impurities, can be produced.
  • quartz glass and its processing products particularly high demands, for example, in terms of homogeneity and purity. This is, among other things, the case with quartz glass, which is processed into optical fibers or in light sources. Impurities can cause absorption here. This is disadvantageous because it leads to color changes and to the attenuation of the emitted light.
  • Another example of the use of high-purity quartz glass are production steps in semiconductor production. Here, any contamination of the glass body potentially leads to defects of the semiconductor, and thus to rejects in the production.
  • the high-purity, often synthetic quartz glass used for these methods are therefore produced very expensive. They are high priced.
  • quartz glass bodies Known methods for producing quartz glass bodies involve melting silica and forming into melted quartz glass bodies. Irregularities in a vitreous body, for example due to the inclusion of gases in the form of bubbles, can result in failure of the vitreous under load, especially at high temperatures, or preclude use for a particular purpose. Thus, impurities of the quartz glass-forming raw material can lead to the formation of cracks, bubbles, streaks and discoloration in the quartz glass. When used in processes for the manufacture and treatment of semiconductor devices, it is also possible to work out impurities in the glass body and transfer them to the treated semiconductor components. This is the case, for example, in etching processes and then leads to rejects in the semiconductor blanks.
  • a frequently occurring problem in the known production methods is consequently an insufficient quality of the quartz glass body.
  • Another aspect concerns the raw material efficiency. It seems to be advantageous to supply fumed silica and raw materials elsewhere as a by-product to industrial processing into quartz glass products instead of using these by-products as filler material, for example in building construction, or to dispose of it as waste in a costly manner. These by-products are often deposited as particulate matter in filters. The particulate matter raises further problems, in particular with regard to health, occupational safety and handling.
  • An object of the present invention is to at least partially overcome one or more of the disadvantages of the prior art.
  • components is meant in particular devices that can be used for or in reactors for chemical and / or physical treatment steps.
  • Homogeneity of a property or a substance is a measure of the uniformity of the distribution of that property or substance in a sample.
  • the homogeneity of the substance is a measure of the uniformity of the distribution of elements and compounds contained in the light guide, illuminant or semiconductor apparatus, in particular of OH, chlorine, metals, in particular aluminum, alkaline earth metals, refractory metals and dopants.
  • Another object is to further improve the processability of quartz glass bodies.
  • Another object is to further improve the manufacturability of quartz glass bodies.
  • Silica was produced, the silica granules having the following features:
  • the oven includes a standing sinter crucible.
  • a sintered crucible is a crucible made of a sintered material containing at least one sintered metal and having a density of not more than 96% of the theoretical density of the metal.
  • a sintered crucible is made by sintering the sintered material in a mold. The sintered material and the sintered metal in the sinter crucible are not rolled.
  • the sintered crucible is made of a sintered material including a sintered metal selected from the group consisting of molybdenum, tungsten, and a combination thereof.
  • the sintered metal of the sintered crucible has a density of 85% or more of the theoretical density of the sintered metal.
  • the BET surface area prior to step ii.) Is not reduced to less than 5 m 2 / g.
  • the standing sintered crucible has at least one of the following features:
  • ßol at least two sealed rings as side parts
  • Iii at least one gas outlet
  • silica powder wherein the silica powder has the following characteristics:
  • silica powder into a silica granule, the silica granule having a larger particle diameter than the silica powder, wherein preferably a silica granule is formed during processing with granules having a spherical morphology; wherein the processing is more preferably carried out by spray granulation or roll granulation.
  • step I wherein the silicon dioxide powder in step I has at least one of the following features:
  • f. a total content of metals other than aluminum of less than 1 ppm;
  • G. at least 70% by weight of the powder particles have a primary particle size in a range of 10 to 100 nm;
  • H a tamped density in a range of 0.001 to 0.3 g / cm 3 ; i. a residual moisture of less than 5 wt .-%;
  • wt .-%, ppm and ppb are each based on the total mass of the silica powder.
  • silica powder is preparable from a compound selected from the group consisting of siloxanes, silicon alkoxides and silicon halides.
  • silica granules have at least one of the following features:
  • G a pore volume in a range of 0.1 to 2.5 mL / g;
  • ppm and ppb are each related to the total mass of the silica granules.
  • a quartz glass body obtainable by a method according to one of the embodiments
  • C] has an aluminum content of less than 200 ppb
  • G a standard deviation of the OH content of not more than 10%, based on the OH content A] of the quartz glass body; H] a standard deviation of the Cl content of not more than 10%, based on the Cl content B] of the quartz glass body;
  • L has a tungsten content of less than 1000 ppb
  • M] has a molybdenum content of less than 1000 ppb
  • ppb and ppm are each based on the total weight of the quartz glass body.
  • a method for producing a light guide comprising the following steps:
  • Quartz glass body is first processed into a hollow body with at least one opening
  • a method for producing a luminous means comprising the following steps:
  • 12
  • a method for producing a shaped article comprising the following steps;
  • ßol at least two sealed rings as side parts
  • a use of a standing sintered crucible for producing products comprising quartz glass selected from the group consisting of a light guide, a lamp, the standing sintered crucible having the following features:
  • ßol at least two sealed rings as side parts
  • range indications also include the values called limits.
  • An indication of the kind "in the range of X to Y" with respect to a size A thus means that A can take the values X, Y and values between X and Y.
  • One-sided bounded areas of the kind "up to Y" for one size correspondingly, A means values Y and less than Y.
  • a first subject of the present invention is a method for producing a quartz glass body comprising the method steps:
  • the oven includes a standing sinter crucible.
  • the provision of the silica granules comprises the following method steps:
  • silica powder into a silica granule, the silica granule having a larger particle diameter than the silica powder.
  • a powder is understood as meaning particles of dry solids having a primary particle size in the range of 1 to less than 100 nm.
  • the silica granules can be obtained by granulating silica powder.
  • a silica granule typically has a BET surface area of 3 m 2 / g or more and a density of less than 1.5 g / cm 3 .
  • Granulating is understood as meaning the transfer of powder particles into granules.
  • Granulation forms aggregates of multiple silica powder particles, ie larger agglomerates called “silica granules.” These are often referred to as “silica granule particles” or “granule particles.” Granules form granules in their entirety, eg, the silica granules are “silica granules.” , The silica granules have a larger particle diameter than the silica powder. The process of granulation to convert a powder into granules will be explained later.
  • silicon dioxide granulation is understood as meaning silicon dioxide particles obtainable by comminuting a silicon dioxide body, in particular a quartz glass body.
  • a silica grain usually has a density of more than 1.2 g / cm 3 , for example in a range of 1.2 to 2.2 g / cm 3 , and more preferably about 2.2 g / cm 3 , More preferably, the BET surface area of a silica grain is generally less than 1 m 2 / g, determined according to DIN ISO 9277: 2014-01.
  • silica particles suitable to the person skilled in the art come into consideration as silica particles.
  • silica particles Preferably selected are silica granules and silica granules.
  • silicon dioxide powder from naturally occurring or from synthetically produced silicon dioxide.
  • synthetic silica powder is used.
  • Particular preference is given to using pyrogenically produced silicon dioxide powder.
  • the silica powder may be any silica powder having at least two particles. Any method which is familiar to the person skilled in the art and suitable for the present purpose can be considered as the production method.
  • the silica powder is produced in the production of quartz glass as a by-product, in particular in the production of so-called soot bodies. Silica of such origin is often referred to as "soot dust”.
  • a preferred source of the silica powder is silica particles obtained in the synthetic production of soot bodies using flame hydrolysis burners.
  • a rotating carrier tube which has a cylinder jacket surface, is reversibly moved back and forth along a row of burners.
  • the Flammhydrolysebrennern can be supplied as fuel gases each oxygen and hydrogen and the starting materials for the formation of Siliziumdioxidprimä articles.
  • the Siliziumdioxidprimä article preferably have a primary particle size of up to 100 nm.
  • the silica prima particles are recognizable in their shape by scanning electron microscopy and the primary article size can be determined.
  • Another part of the silicon dioxide particles is not deposited on the cylinder jacket surface of the support tube, but accumulates as dust, for example in a filter system.
  • the part of silicon dioxide particles deposited on the support tube is larger than the part of silica particles resulting from soot dust in the context of soot body production, based on the total weight of the silicon dioxide particles.
  • the soot dust is usually disposed of consuming and expensive as waste or spent without added value as a filler, e.g. in road construction, as additives in the dyestuff industry, as a raw material for tile production and for the production of hexafluorosilicic acid, which is used for the renovation of building foundations.
  • a filler e.g. in road construction, as additives in the dyestuff industry
  • it is suitable as a starting material and can be processed to a high quality product.
  • Silica produced by flame hydrolysis is commonly referred to as fumed silica. Fumed silica is usually in the form of amorphous silica primaries or silica particles.
  • the silica powder can be prepared by flame hydrolysis from a gas mixture.
  • the silica particles are also formed in the flame hydrolysis and discharged as silica powder before agglomerates or aggregates are formed.
  • the silica powder previously referred to as soot dust main product.
  • silica powder As starting materials for the formation of the silica powder are preferably siloxanes, silicon alkoxides and inorganic silicon compounds.
  • Siloxanes are understood as meaning linear and cyclic polyalkylsiloxanes.
  • Polyalkylsiloxanes preferably have the general formula
  • R is an alkyl group having 1 to 8 C atoms, preferably having 1 to 4 C atoms, particularly preferably a methyl group
  • siloxanes selected from the group consisting of hexamethyldisiloxane, hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) or a combination of two or more thereof.
  • D3 hexamethylcyclotrisiloxane
  • D4 octamethylcyclotetrasiloxane
  • D5 decamethylcyclopentasiloxane
  • Preferred silicon alkoxides are tetramethoxysilane and methyltrimethoxysilane.
  • Preferred inorganic silicon compounds as starting material for silica powder are silicon halides, silicates, Silicon carbide and silicon nitride. Particularly preferred as the inorganic silicon compound as a starting material for silica powder are silicon tetrachloride and trichlorosilane.
  • the silicon dioxide powder can be prepared from a compound selected from the group consisting of siloxanes, silicon alkoxides and silicon halides.
  • the silica powder can be prepared from a compound selected from the group consisting of hexamethyldisiloxane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane and
  • Decamethylcyclopentasiloxane tetramethoxysilane and methyltrimethoxysilane, silicon tetrachloride and trichlorosilane, or a combination of two or more thereof, for example, silicon tetrachloride and octamethylcyclotetrasiloxane, most preferably octamethylcyclotetrasiloxane.
  • a preferred composition of a suitable gas mixture includes a proportion of oxygen in the flame hydrolysis in a range of 25 to 40% by volume.
  • the proportion of hydrogen may be in a range of 45 to 60% by volume.
  • the proportion of silicon tetrachloride is preferably from 5 to 30% by volume, all of the abovementioned% by volume, based on the total volume of the gas stream.
  • the flame in the flame hydrolysis preferably has a temperature in a range from 1500 to 2500 ° C., for example in a range from 1600 to 2400 ° C., particularly preferably in one range from 1700 to 2300 ° C.
  • the silica particles formed in the flame hydrolysis are removed as silica powder before agglomerates or aggregates are formed.
  • the silica powder has the following characteristics:
  • a BET surface area in a range from 20 to 60 m 2 / g, for example from 25 to 55 m 2 / g, or from 30 to 50 m 2 / g, particularly preferably from 20 to 40 m 2 / g, and
  • the silicon dioxide powder preferably has at least one, for example at least two or at least three or at least four, more preferably at least five of the following characteristics:
  • G. at least 70% by weight of the powder particles have one in a range of 10 to less than 100 nm, for example in the range of 15 to less than 100 nm, more preferably in the range of 20 to less than 100 nm;
  • H. a tamped density in a range of 0.001 to 0.3 g / cm 3 for example in the range of 0.002 to 0.2 g / cm 3 or from 0.005 to 0.1 g / cm 3 , preferably in the range of 0.01 to 0.06 g / cm 3 , also preferably in the range of 0.1 to 0.2 g / cm 3 , or in the range of 0.15 to 0.2 g / cm 3 ; i. a residual moisture of less than 5 wt .-%, for example in the range of 0.25 to 3 wt .-%, particularly preferably in the range of 0.5 to 2 wt .-%;
  • a particle size distribution D 10 in the range of 1 to 7 ⁇ , for example in the range of 2 to 6 ⁇ or in the range of 3 to 5 ⁇ , more preferably in the range of 3.5 to 4.5 ⁇ ;
  • a particle size distribution D 90 in the range of 10 to 40 ⁇ , for example in the range of 15 to 35 ⁇ , particularly preferably in the range of 20 to 30 ⁇ ;
  • the silica powder contains silica.
  • the silica powder contains silica in an amount of more than 95% by weight, for example, in an amount of more than 98% by weight. or more than 99% by weight or more than 99.9% by weight, based in each case on the total weight of the silicon dioxide powder. More preferably, the silica powder contains silica in an amount of more than 99.99% by weight based on the total weight of the silica powder.
  • the silica powder has a metal content of metals other than aluminum of less than 5 ppm, for example less than 2 ppm, more preferably less than 1 ppm, each based on the total weight of the silica powder. Often, however, the silica powder has a content of metals other than aluminum in an amount of at least 1 ppb.
  • metals include sodium, lithium, potassium, magnesium, calcium, strontium, germanium, copper, molybdenum, tungsten, titanium, iron and chromium. These may be present, for example, as an element, as an ion, or as part of a molecule or an ion or a complex.
  • the silica powder has a total content of other ingredients of less than 30 ppm, for example less than 20 ppm, more preferably less than 15 ppm, the ppm each based on the total weight of the silica powder. Often, however, the silica powder has a content of other ingredients in an amount of at least 1 ppb.
  • Other constituents are understood as meaning all constituents of the silicon powder which do not belong to the following group: silicon dioxide, chlorine, aluminum, OH groups.
  • the indication of an ingredient when the ingredient is a chemical element means that it may be present as an element or as an ion in a compound or a salt.
  • aluminum also includes aluminum salts, aluminum oxides and
  • chlorine includes, in addition to elemental chlorine, chlorides such as Sodium chloride and hydrogen chloride. Often, the other ingredients are in the same state of matter as the substance in which they are contained.
  • the indication of an ingredient when the ingredient is a chemical compound or a functional group, means that the ingredient may be in said form, as a charged chemical compound, or as a derivative of the chemical compound.
  • the indication of the chemical ethanol includes ethanol as well as ethanol, for example, sodium ethanolate.
  • the term "OH group” also includes silanol, water and metal hydroxides
  • the term derivative in acetic acid also includes acetic acid ester and acetic anhydride.
  • At least 70% of the powder particles of the silica powder have a primary particle size of less than 100 nm, for example in the range of 10 to 100 nm or of 15 to 100 nm, and particularly preferably in the range of 20 to 100 nm up.
  • the primary article size is determined by dynamic light scattering according to ISO 13320: 2009-10.
  • At least 75% of the powder particles of the silica powder, based on the number of powder particles have a primary article size of less than 100 nm, for example in the range of 10 to 100 nm or of 15 to 100 nm, and particularly preferably in the region of 20 up to 100 nm.
  • at least 80% of the powder particles of the silica powder, based on the number of powder particles have a primary article size of less than 100 nm, for example in the range of 10 to 100 nm or 15 to 100 nm, and more preferably in the range of 20 up to 100 nm.
  • At least 85% of the powder particles of the silica powder have a primary particle size of less than 100 nm, for example in the range of 10 to 100 nm or 15 to 100 nm, and more preferably in the range of 20 to 100 nm up.
  • At least 90% of the powder particles of the silica powder have a primary article size of less than 100 nm, for example in the range of 10 to 100 nm or of 15 to 100 nm, and particularly preferably in the region of 20 up to 100 nm.
  • At least 95% of the powder particles of the silica powder have a primary particle size of less than 100 nm, for example in the range of 10 to 100 nm or 15 to 100 nm, and more preferably in the range of 20 to 100 nm up.
  • the silica powder has a particle size Di 0 in the range of 1 to 7 ⁇ , for example in
  • the silica powder has a particle size D 50 in the range of 6 to 15 ⁇ , for example in the range of 7 to 13 ⁇ or in the range of 8 to 1 1 ⁇ , more preferably in the range of 8.5 to 10.5 ⁇ .
  • the silica powder has a particle size D 90 in the range of 10 to 40 ⁇ , for
  • the silica powder has a specific surface area (BET surface area) in a range from 20 to 60 m 2 / g, for example from 25 to 55 m 2 / g, or from 30 to 50 m 2 / g, particularly preferably from 20 up to 40 m 2 / g.
  • BET surface area is determined according to the method of Brunauer, Emmet and Teller (BET) on the basis of DIN 66132 and is based on gas absorption at the surface to be measured.
  • the silica powder has a pH 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, more preferably in the range from 4.5 to 5.
  • Der pH value can be determined by means of a stick-in electrode (4% silicon dioxide powder in water).
  • the silicon dioxide powder preferably has the feature combination a./b./c. or a./b./f. or a./b./g. on, more preferably the combination of features a./b./c./f. or a./b./c./g. or a./b./f./g., particularly preferably the combination of features a./b./c./f./g.
  • the silicon dioxide powder preferably has the feature combination a./b./c. wherein the BET surface area is in a range of 20 to 40 m 2 / g, the bulk density is in a range of 0.05 to 0.3 g / ml, and the carbon content is less than 40 ppm.
  • the silicon dioxide powder preferably has the feature combination a./b./f. wherein the BET surface area is in a range of 20 to 40 m 2 / g, the bulk density in a range of 0.05 to 0.3 g / ml, and the total content of metals other than aluminum are within a range from 1 ppb to 1 ppm.
  • the silicon dioxide powder preferably has the feature combination a./b./g. wherein the BET surface area is in a range of 20 to 40 m 2 / g, the bulk density is in a range of 0.05 to 0.3 g / ml, and at least 70 wt% of the powder particles have a primary particle size of a range of 20 to less than 100 nm.
  • the silicon dioxide powder more preferably has the feature combination a./b./c./f. wherein the BET surface area is in a range of 20 to 40 m 2 / g, the bulk density is in a range of 0.05 to 0.3 g / ml, the carbon content is less than 40 ppm, and the total content of metals , which are different from aluminum, is in a range of 1 ppb to 1 ppm.
  • the silicon dioxide powder more preferably has the feature combination a./b./c./g. wherein the BET surface area is in a range of 20 to 40 m 2 / g, the bulk density is in a range of 0.05 to 0.3 g / ml, the carbon content is less than 40 ppm and at least 70 wt. -% of the powder particles have a primary particle size in a range of 20 to less than 100 nm.
  • the silicon dioxide powder more preferably has the feature combination a./b./f./g. , wherein the BET surface area is in a range of 20 to 40 m 2 / g, the bulk density is in a range of 0.05 to 0.3 g / ml, the total content of metals other than aluminum, in a range of 1 ppb to 1 ppm and at least 70% by weight of the powder particles have a primary particle size in a range of 20 to less than 100 nm.
  • the silicon dioxide powder particularly preferably has the feature combination a./b./c./f./g. wherein the BET surface area is in a range of 20 to 40 m 2 / g, the bulk density is in a range of 0.05 to 0.3 g / ml, the carbon content is less than 40 ppm, the total content of metals which are different from aluminum, is in a range of 1 ppb to 1 ppm, and at least 70% by weight of the powder particles have a primary particle size in a range of 20 to less than 100 nm.
  • Step II the feature combination a./b./c./f./g. wherein the BET surface area is in a range of 20 to 40 m 2 / g, the bulk density is in a range of 0.05 to 0.3 g / ml, the carbon content is less than 40 ppm, the total content of metals which are different from aluminum, is in a range of 1 ppb to 1 ppm, and at least 70% by weight
  • the silicon dioxide powder is processed in step II to a granular silica, wherein the silica granules having a larger particle diameter than the silica powder.
  • Suitable in principle are all methods known to those skilled in the art, which lead to an increase in the particle diameter.
  • the silica granules have a particle diameter larger than the particle diameter of the silica powder.
  • the particle diameter of the silica granules is in a range of 500 to 50,000 times larger than the particle diameter of the silica powder, for example, 1,000 to 10,000 times larger, more preferably 2,000 to 8,000 times larger.
  • At least 90% of the silicon dioxide granules provided in step i) are preferably formed from pyrogenically produced silicon dioxide powder, for example at least 95% by weight or at least 98% by weight, more preferably at least 99% by weight or more, based in each case on the Total weight of silica granules.
  • the silica granules used have the following features:
  • the silica granules preferably have at least one, preferably at least two or at least three or at least four, more preferably all of the following features:
  • G a pore volume in a range of 0.1 to 2.5 mL / g, for example in a range of 0.15 to 1.5 mL / g; more preferably in a range of 0.2 to 0.8 mL / g;
  • ppm and ppb are each based on the total weight of the silica granules.
  • the granules of the silica granules preferably have a spherical morphology.
  • Spherical morphology refers to a round to oval shape of the particles.
  • the granules of the silica granules preferably have an average sphericity in a range of 0.7 to 1.3 SPHT3, for example, an average sphericity in a range of 0.8 to 1.2 SPHT3, more preferably an average sphericity in a range of 0 , 85 to 1.1 SPHT3 on.
  • the characteristic SPHT3 is described in the test methods.
  • the granules of the silica granules have a mean symmetry in a range of 0.7 to 1.3 Symm3, for example a mean symmetry in a range of 0.8 to 1.2 Symm3, more preferably a mean symmetry in a range of 0.85 to 1.1 Symm3.
  • Symm3 The feature of symmetry Symm3 is described in the test methods.
  • the silica granules have a metal content of metals other than aluminum of less than 1000 ppb, for example less than 500 ppb, more preferably less than 100 ppb, each based on the total weight of the silica granules. Often, however, the silica granules have a content of metals other than aluminum in an amount of at least 1 ppb.
  • the silica granules have a metal content of metals other than aluminum of less than 1 ppm, preferably in a range of 40 to 900 ppb, for example in a range of 50 to 700 ppb, more preferably in a range of 60 to 500 ppb, respectively based on the total weight of the silica granules.
  • metals include sodium, lithium, potassium, magnesium, calcium, strontium, germanium, copper, molybdenum, titanium, iron and chromium. These may be present, for example, as an element, as an ion, or as part of a molecule or an ion or a complex.
  • the silica granules may contain further constituents, for example in the form of molecules, ions or elements.
  • the silica granules contain less than 500 ppm, for example less than 300 ppm, more preferably less than 100 ppm, in each case based on the total weight of the silica granules, further constituents.
  • further ingredients are included in an amount of at least 1 ppb.
  • the further constituents may in particular be selected from the group consisting of carbon, fluoride, iodide, bromide, phosphorus or a mixture of at least two thereof.
  • the silica granules contain less than 10 ppm carbon, for example less than 8 ppm or less than 5 ppm, more preferably less than 4 ppm, each based on the total weight of the silica granules. Often, carbon in an amount of at least 1 ppb is contained in the silica granules.
  • the silica granules include less than 100 ppm, for example less than 80 ppm, more preferably less than 70 ppm, each based on the total weight of the silica granules other ingredients. Often, however, the other ingredients are included in an amount of at least 1 ppb.
  • step II includes the following steps:
  • a liquid is understood to be a substance or a mixture of substances which is liquid at a pressure of 1013 hPa and a temperature of 20 ° C.
  • a "slurry" means a mixture of at least two substances, the mixture having at least one liquid and at least one solid under the conditions under consideration.
  • liquids are selected from the group consisting of organic liquids and water.
  • the silica powder is soluble in the liquid in an amount of less than 0.5 g / L, preferably in an amount of less than 0.25 g / L, more preferably in an amount of less than 0.1 g / L, the g / L is given as g silica powder per liter of liquid.
  • Preferred liquids are polar solvents. These can be organic liquids or water.
  • the liquid is preferably selected from the group consisting of water, methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol and mixtures of more than one thereof.
  • the liquid is water.
  • the liquid includes distilled or deionized water.
  • the silica powder is processed into a slurry.
  • the silica powder is almost insoluble in the liquid at room temperature, but may be incorporated into the liquid in high weight fractions to obtain the slurry.
  • the silica powder and the liquid may be mixed in any manner.
  • the silica powder may be added to the liquid or the liquid to the silica powder.
  • the mixture may be agitated during addition or after addition. Most preferably, the mixture is agitated during and after adding. Examples of agitation are shaking and stirring, or a combination of both.
  • the silica powder may be added to the liquid with stirring. More preferably, a portion of the silica powder may be added to the liquid, with the mixture thus obtained being agitated, and the mixture subsequently mixed with the remainder of the silica powder.
  • a portion of the liquid may be added to the silica powder, the mixture thus obtained being agitated, and the mixture subsequently mixed with the remainder of the liquid.
  • the slurry is a suspension in which the silica powder is evenly distributed in the liquid.
  • uniformly it is meant that the density and composition of the slurry at each point does not differ by more than 10% from the average density and the average composition, each based on the total amount of slurry
  • a uniform distribution of the silica powder in the liquid can be made or obtained by moving as previously described, or both.
  • the slurry has a liter weight in the range of 1000 to 2000 g / L, for example in the range of 1200 to 1900 g / L or of 1300 to 1800 g / L, more preferably in the range of 1400 to 1700 g / L.
  • the weight per liter is determined by weighing a volume calibrated container.
  • the slurry has at least one, for example at least two or at least three or at least four, more preferably at least five of the following characteristics:
  • the slurry has a temperature of more than 0 ° C, preferably in a range of 5 to 35 ° C;
  • the slurry has a zeta potential at a pH of 7 in a range of 0 to -100 mA, for example from -20 to -60 mA, more preferably from -30 to -45 mA;
  • the slurry has a pH in a range of 7 or more, for example greater than 7 or a pH in the range of 7.5 to 13 or from 8 to 11, more preferably from 8.5 to 10 ;
  • the slurry has an isoelectric point of less than 7, for example in one
  • the slurry has a solids content of at least 40% by weight, for example in one
  • the slurry has a viscosity in accordance with DIN 53019-1 (5 rpm, 30 wt .-%) in a range of 500 to 2000 mPas, for example in the range of 600 to 1700 mPas, particularly preferably in the range of 1000 to 1600 mPas ;
  • the slurry has a thixotropy according to DIN SPEC 91143-2 (30 wt .-% in water, 23 ° C,
  • the silica particles in the slurry have in a 4 wt .-% slurry an average particle size in suspension according to DIN ISO 13320-1 in the range of 100 to 500 nm, for
  • the silica particles in a 4 wt .-% aqueous slurry has a particle size D 10 in a range of 50 to 250 nm, more preferably in the range of 100 to 150 nm.
  • the silica particles in a 4 wt .-% aqueous slurry has a particle size D 50 in the range of 100 to 400 nm, more preferably in the range of 200 to 250 nm.
  • the silica particles have, in a 4 wt .-% aqueous slurry has a particle size D 90 in the range of 200 to 600 nm, more preferably in a range of 350 to 400 nm.
  • the particle size is determined by means of DIN ISO 13320-1.
  • the term "isolectric point" is understood to mean the pH value at which the zeta potential assumes the value 0.
  • the zeta potential is determined in accordance with ISO 13099-2: 2012.
  • the pH of the slurry is adjusted to a value in the above range.
  • substances such as NaOH or NH 3 may be added , for example, as an aqueous solution of the slurry. The slurry is often moved.
  • the silica granules are obtained by granulating silica powder.
  • Granulating is understood as meaning the transfer of powder particles into granules.
  • aggregates of multiple silica powder particles form larger agglomerates, referred to as “silica granules.” These are often referred to as “silica particles,” “silica granule particles,” or “granule particles.”
  • granules form granules, e.g. In the present case, any granulation process known to those skilled in the art and suitable for granulating silica powder may in principle be selected.
  • a silica granule is formed with granules having a spherical morphology; wherein the processing is more preferably done by spray granulation or roll granulation.
  • silica granules containing granules having a spherical morphology include at most 50% granules, preferably at most 40% granules, more preferably at most 20% granules, more preferably between 0 and 50%, between 0 and 40%, or between 0 and 20 % o, or between 10 and 50%), between 10 and 40% o, or between 10 and 20% o granules that do not have a spherical morphology, the percentages in each case based on the total number of granules in the granules.
  • the granules with a spherical morphology have the already mentioned in this description SPHT3 values.
  • a silica granule is obtained by spray granulating the slurry.
  • Spray granulation is also referred to as spray drying.
  • the spray drying is preferably carried out in a spray tower.
  • the slurry is pressurized at elevated temperature.
  • the pressurized slurry is then released through a nozzle and sprayed into the spray tower.
  • droplets form, which dry instantly and initially form dry micro-particles ("germs.")
  • the micro-particles together with a gas stream acting on the particles, form a fluidized bed which holds them in suspension and thus allows a surface to dry further droplets form.
  • the nozzle through which the slurry is sprayed into the spray tower preferably forms an inlet into the interior of the spray tower.
  • the nozzle preferably has a contact surface with the slurry during spraying. Often, at least a portion of the nozzle is shaped as a tube through which the slurry is passed during spraying so that the inside of the hollow tube communicates with the slurry
  • the contact surface preferably contains a glass, a plastic or a combination thereof
  • the contact surface comprises a glass, more preferably quartz glass
  • the contact surface comprises a plastic
  • Preferred plastics are polyolefins, for example homopolymers or copolymers containing at least one olefin, more preferably homopolymers or copolymers comprising polypropylene, polyethylene, polybutadiene or combinations of two or more thereof n tact surface of a glass, a plastic or a combination thereof, for example selected from the group consisting of quartz glass and polyolefins, more preferably selected from
  • the contact surface and the other parts of the nozzle consist of the same or of different materials.
  • the other parts of the nozzle contain the same material as the contact surface.
  • the other parts of the nozzle contain a different material from the contact surface.
  • the contact surface may be coated with a suitable material, for example a glass or a plastic.
  • the nozzle is more than 70 wt .-%, based on the total weight of the nozzle, of an element selected from the group consisting of glass, plastic or a combination of glass and plastic formed, for example, more than 75 wt .-% or more than 80 wt .-% or more than 85 wt .-% or more than 90 wt .-% or more than 95 wt .-%, especially preferably more than 99% by weight.
  • the nozzle comprises a nozzle plate.
  • the nozzle plate is preferably formed of glass, plastic or a combination of glass and plastic.
  • the nozzle plate is formed of glass, particularly preferably quartz glass.
  • the nozzle plate is formed of plastic.
  • Preferred plastics are polyolefins, for example homo- or copolymers containing at least one olefin, more preferably homopolymers or copolymers comprising polypropylene, polyethylene, polybutadiene or combinations of two or more thereof.
  • the nozzle plate preferably contains no metals, in particular no tungsten, titanium, tantalum, chromium, cobalt, nickel, iron, vanadium, zirconium and manganese.
  • the nozzle preferably comprises a spiral screw.
  • the spiral screw is preferably made of glass, plastic or a combination of glass and plastic.
  • the spiral screw is formed of glass, more preferably quartz glass.
  • the spiral screw is formed from plastic.
  • Preferred plastics are polyolefins, for example homo- or copolymers containing at least one olefin, more preferably homopolymers or copolymers comprising polypropylene, polyethylene, polybutadiene or combinations of two or more thereof.
  • the spiral screw contains no metals, in particular no tungsten, titanium, tantalum, chromium, cobalt, nickel, iron, vanadium, zirconium and manganese.
  • the nozzle may further comprise other components.
  • Preferred further components are a nozzle body, particularly preferred is a nozzle body surrounding the spiral screw and the nozzle plate, a cross piece and a baffle plate.
  • a nozzle preferably comprises one or more, particularly preferably all, of the further components.
  • the other components can, independently of one another, in principle consist of any material known to the person skilled in the art and suitable for this purpose, for example of a metal-containing material, of glass or of a plastic.
  • the nozzle body is formed of glass, more preferably quartz glass.
  • the other components are formed from plastic.
  • Preferred plastics are polyolefins, for example homo- or copolymers containing at least one olefin, more preferably homopolymers or copolymers comprising polypropylene, polyethylene, polybutadiene or combinations of two or more thereof.
  • the other components preferably do not contain any metals, in particular no tungsten, titanium, tantalum, chromium, cobalt, nickel, iron, vanadium, zirconium and manganese.
  • the spray tower has a gas inlet and a gas outlet.
  • gas inlet gas can be introduced into the interior of the spray tower, and through the gas outlet, it can be discharged. It is also possible to introduce gas through the nozzle into the spray tower. Similarly, gas can be discharged through the outlet of the spray tower. Further preferably, gas may be supplied via the nozzle and a gas inlet of the spray tower, and discharged via the outlet of the spray tower and a gas outlet of the spray tower.
  • an atmosphere selected from air, an inert gas, at least two inert gases or a combination of air with at least one inert gas, preferably at least two inert gases, is present in the interior of the spray tower.
  • inert gases are preferably selected from the list consisting of nitrogen, helium, neon, Argon, krypton and xenon.
  • air, nitrogen or argon is present in the interior of the spray tower, more preferably air.
  • the atmosphere present in the spray tower is part of a gas stream.
  • the 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 parts of the gas stream through the nozzle and divert parts of the gas stream through a solids outlet.
  • the gas stream can take up additional components in the spray tower. These may originate from the slurry during spray drying and pass into the gas stream.
  • a dry gas stream is fed to the spray tower.
  • a dry gas stream is understood as meaning a gas or a gas mixture whose relative humidity is below the condensation point at the temperature set in the spray tower. A relative humidity of 100% corresponds to a water volume of 17.5 g / m 3 at 20 ° C.
  • the gas is preferably preheated to a temperature in a range of from 150 to 450 ° C, for example from 200 to 420 ° C or from 300 to 400 ° C, more preferably from 350 to 400 ° C.
  • the interior of the spray tower is preferably tempered.
  • the temperature in the interior of the spray tower is up to 550 ° C, for example 300 to 500 ° C, more preferably 350 to 450 ° C.
  • the gas stream at the gas inlet preferably has a temperature in a range from 150 to 450 ° C, for example from 200 to 420 ° C or from 300 to 400 ° C, particularly preferably from 350 to 400 ° C.
  • the withdrawn gas stream preferably has a temperature of less than 170 ° C, for example from 50 to 150 ° C, more preferably from 100 to 130 ° C. More preferably, the difference between the temperature of the gas stream at the time of introduction and the gas flow when discharged is in a range of 100 to 330 ° C, for example, 150 to 300 ° C.
  • the silica granules thus obtained are present as an agglomerate of individual particles of silica powder.
  • the individual particles of the silicon dioxide powder are still recognizable in the agglomerate.
  • the average particle size of the particles of the silica powder is preferably in the range of 10 to 1000 nm, for example, in the range of 20 to 500 nm or 30 to 250 nm or 35 to 200 nm or 40 to 150 nm, or more preferably in the range from 50 to 100 nm.
  • the average particle size of these particles is determined according to DIN ISO 13320-1.
  • the spray drying can be carried out in the presence of auxiliaries. In principle, all substances can be used as auxiliaries, which are known in the art and appear suitable for the present purpose.
  • auxiliaries are, for example, so-called binders.
  • suitable binders are metal oxides such as calcium oxide, metal carbonates such as calcium carbonate and polysaccharides such as cellulose, cellulose ethers, starch and starch derivatives.
  • spray drying is particularly preferably carried out without auxiliaries.
  • a portion thereof is separated.
  • the separation is done by sifting or sieving.
  • the sifting is preferably carried out by a cyclone, which is preferably arranged in the lower region of the spray tower, particularly preferably above the outlet of the spray tower.
  • the silica granules from the spray tower particles with a particle size of more than 1000 ⁇ , for example, with a particle size of more than 700 ⁇ particularly preferably separated with a particle size of more than 500 ⁇ by sieving.
  • the sieving of the particles can be carried out in principle by all methods known to the person skilled in the art and suitable for this purpose. Sieving is preferably carried out by means of a vibrating trough.
  • the spray-drying of the slurry through a nozzle into a spray tower is characterized by at least one, for example two or three, most preferably all of the following features:
  • a temperature of the droplets entering the spray tower in a range of 10 to 50 ° C, preferably in a range of 15 to 30 ° C, more preferably in a range of 18 to 25 ° C.
  • a temperature at the spray tower side of the nozzle in a range of 100 to 450 ° C, for example in a range of 250 to 440 ° C, more preferably from 350 to 430 ° C;
  • a slurry throughput through the die in a range of 0.05 to 1 m 3 / h, for example in a range of 0.1 to 0.7 m 3 / h or from 0.2 to 0.5 m 3 / h, more preferably in a range of 0.25 to 0.4 m 3 / h;
  • fj has a solids content of the slurry of at least 40% by weight, for example in a range of 50 to 80% by weight, or in a range of 55 to 75% by weight, particularly preferably in a range of 60 to 70% by weight .-%, in each case based on the total weight of the slurry; g] a gas flow in the spray tower in a range of 10 to 100 kg / min, for example in a range of 20 to 80 kg / min or from 30 to 70 kg / min, more preferably in a range of 40 to 60 kg / min; h] a temperature of the gas stream entering the spray tower in a range of 100 to 450 ° C, for example in a range of 250 to 440 ° C, more preferably 350 to 430 ° C;
  • the gas is selected from the group consisting of air, nitrogen and helium, or a combination of two or more thereof; preferably air;
  • m at least 50 wt .-% of the spray granules, based on the total weight of the resulting during spray drying silica granules, sets a flight distance of more than 20 m, for example, more than 30 or more than 50 or more than 70 or of more than 100 or more than 150 or more than 200 or in a range of 20 to 200 m or from 10 to 150 or from 20 to 100, particularly preferably in a range of 30 to 80 m.
  • the spray tower has a cylindrical geometry
  • a height of the spray tower of more than 10 m for example of more than 15 m or of more than 20 m or of more than 25 m or of more than 30 m or in a range of 10 to 25 m, particularly preferably in a range of 15 to 20 m;
  • the direction of the solder is understood to be the direction of the gravity vector.
  • the flight path means the path that a droplet of slurry travels from the exit of the nozzle into the headspace of the spray tower to form granules until completion of the flight and fall operation.
  • the flight and fall process will periodically end by impacting the granule at the bottom of the spray tower, or by granules coming into contact with other granules resting on the bottom of the spray tower, whichever comes first.
  • the flight time is the time it takes for a granule to cover the flight path in the spray tower.
  • the granules preferably have a helical trajectory in the spray tower.
  • at least 60% by weight of the spray granules, based on the total weight of the silica granules formed during the spray drying have an average flight distance of more than 20 m, for example greater than 30 or greater than 50 or greater than 70 or more than 100 or more than 150 or more than 200 or in a range of 20 to 200 m or from 10 to 150 or from 20 to 100, particularly preferably in a range of 30 to 80 m.
  • At least 70% by weight of the spray granules based on the total weight of the silica granules formed in the spray drying, have an average flight distance of more than 20 m, for example greater than 30 or greater than 50 or greater than 70 or more than 100 or more than 150 or more than 200 or in a range of 20 to 200 m or from 10 to 150 or from 20 to 100, particularly preferably in a range of 30 to 80 m.
  • At least 80% by weight of the spray granules based on the total weight of the silica granules formed in the spray drying, have an average flight distance of more than 20 m, for example greater than 30 or greater than 50 or greater than 70 or more than 100 or more than 150 or more than 200 or in a range of 20 to 200 m or from 10 to 150 or from 20 to 100, particularly preferably in a range of 30 to 80 m.
  • At least 90% by weight of the spray granules based on the total weight of the silica granules formed in the spray drying, have an average flight distance of more than 20 m, for example greater than 30 or greater than 50 or greater than 70 or more than 100 or more than 150 or more than 200 or in a range of 20 to 200 m or from 10 to 150 or from 20 to 100, particularly preferably in a range of 30 to 80 m.
  • a silica granule is obtained by roll granulating the slurry.
  • Roll granulation is done by stirring the slurry in the presence of a gas at elevated temperature.
  • Roll granulation preferably takes place in a stirred tank equipped with a stirring tool.
  • the stirring container rotates in the opposite direction to the stirring tool.
  • the stirring vessel further comprises an inlet through which silica powder can be introduced into the stirring vessel, an outlet through which silica granules can be removed, a gas inlet and a gas outlet.
  • a pinworm is understood to mean a stirrer tool which is provided with a plurality of elongate pins whose longitudinal axis runs in each case coaxially with the axis of rotation of the stirrer tool.
  • the movement sequence of the pins preferably describes coaxial circles about the axis of rotation.
  • the slurry is adjusted to a pH of less than 7, for example to a pH in the range of 2 to 6.5, more preferably to a pH in the range of 4 to 6.
  • the pH - Value is preferably an inorganic acid used, for example, an acid selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, particularly preferably hydrochloric acid.
  • an atmosphere selected from air, an inert gas, at least two inert gases or a combination of air with at least one inert gas, preferably at least two inert gases.
  • inert gases are preferably selected from the list consisting of nitrogen, helium, neon, argon, krypton and xenon.
  • air, nitrogen or argon is present in the stirred tank, more preferably air.
  • the atmosphere present in the stirred tank is part of a gas stream.
  • the gas stream is preferably introduced into the stirred tank via the gas inlet and discharged via the gas outlet.
  • the gas stream can take up additional components in the stirred tank. These may originate from the slurry during roll granulation and pass into the gas stream.
  • the stirred tank is preferably supplied with a dry gas stream.
  • a "dry gas stream” is understood as meaning a gas or a gas mixture whose relative humidity is below the condensation point at the temperature set in the stirring vessel.
  • the gas is preferably at a temperature in a range from 50 to 300 ° C., for example from 80 to 250 ° C, more preferably preheated from 100 to 200 ° C.
  • 10 to 150 m 3 of gas per hour are preferably introduced per 1 kg of the slurry used into the stirred tank, for example 20 to 100 m 3 of gas per hour, more preferably 30 to 70 m 3 of gas per hour.
  • the gas stream dries the slurry while stirring to form silica granules.
  • the granules formed are removed from the stirred chamber.
  • the withdrawn granules are further dried.
  • the drying is carried out continuously, for example in a rotary kiln.
  • Preferred temperatures for drying are in a range of 80 to 250 ° C, for example in a range of 100 to 200 ° C, more preferably in a range of 120 to 180 ° C.
  • Continuously in the context of the present invention in relation to a method means that it can be operated continuously. This means that the supply and removal of substances and materials involved in the process can be carried out continuously during the execution of the process. It is not necessary to interrupt the procedure for this.
  • Continuously as an attribute of an object means that this object is designed so that a process occurring in it or a process step which takes place in it can be continuously carried out.
  • the granules obtained by roll granulation can be screened. Sieving can be done before or after drying. Preference is given to sieving before drying. Granules having a particle size of less than 50 ⁇ m, for example having a particle size of less than 80 ⁇ m, are particularly preferably screened out with a particle size of less than 100 ⁇ m.
  • the sieving of larger particles can be carried out in principle by all methods known to the person skilled in the art and suitable for this purpose.
  • the screening of larger particles preferably takes place by means of a vibrating trough.
  • roll granulation is characterized by at least one, for example two or three, most preferably all of the following features:
  • [b] granulation is carried out under a gas stream of 10 to 150 kg gas per hour and per 1 kg slurry;
  • Granules with a particle size of less than 100 ⁇ and more than 500 ⁇ are sieved;
  • the granules formed have a residual moisture of 15 to 30 wt .-%;
  • the granules formed are dried at 80 to 250 ° C, preferably in a continuous drying tube, more preferably up to a residual moisture content of less than 1 wt .-%.
  • the granulated silica preferably by spray or roll granulation, obtained silica granules, also referred to as silica granules I, treated before it is processed into quartz glass bodies.
  • This pretreatment can serve various purposes, which either facilitate the processing into quartz glass bodies or influence the properties of the resulting quartz glass bodies.
  • the silica granules I may be compacted, cleaned, surface modified or dried.
  • the silica granules I may be subjected to a thermal, mechanical or chemical treatment or a combination of two or more treatments to obtain a silica granule II.
  • the silica granules I have a carbon content Wcpj.
  • the carbon content Wcpj is preferably less than 50 ppm, for example in the range of 5 to 45 ppm or of 15 to 40 ppm, particularly preferably in the range of 25 to 35 ppm, in each case based on the total weight of the silica granulate I.
  • Silica granules I at least two particles.
  • the at least two particles can be a
  • a mixing In principle, mixing can be carried out in any desired manner.
  • a continuous furnace is selected for this purpose.
  • the at least two particles can preferably perform a relative movement to each other by being moved in a continuous furnace, for example a rotary kiln.
  • Continuous ovens are understood to mean furnaces in which the loading and unloading of the furnace, the so-called charging, takes place continuously.
  • Examples of continuous furnaces are rotary kilns, roller kilns, conveyor ovens, drive-through ovens, push-through ovens.
  • rotary kilns are used to treat the silica granules I.
  • the silica granule I is treated with a reactant to obtain a silica granule II.
  • the treatment is carried out to change the concentration of certain substances in the silica granules.
  • the silica granules I may have impurities or certain functionalities whose content is to be reduced, such as: OH groups, carbon-containing compounds, transition metals, alkali metals and alkaline earth metals.
  • the impurities and functionalities may originate from the starting material or be added during the process.
  • the treatment of the silica granulate I can serve various purposes.
  • the use of treated silica granules I may facilitate the processing of the silica granules into quartz glass bodies.
  • the properties of the resulting quartz glass body can be adjusted.
  • the silica granules I can be purified or surface-modified. The treatment of the silica granulate I can therefore be used to improve the properties of the resulting quartz glass body.
  • the reactants used are preferably a gas or a combination of several gases. This is also called gas mixture.
  • gases known to the person skilled in the art which are known and suitable for the said treatment.
  • a gas selected from the group consisting of HCl, Cl 2, F 2, 0 2, 0 3, H 2, C 2 F 4, C 2 F 6, HC10 4, air, inert gas, eg N 2, He, it is preferred Ne, Ar, Kr, or combinations of two or more of them.
  • the treatment is carried out in the presence of a gas or a combination of two or more as gases.
  • the treatment is carried out in a gas countercurrent, or in a gas direct current.
  • the reactant is selected from the group consisting of HCl, Cl 2 , F 2 , O 2 , O 3 or combinations of two or more thereof.
  • mixtures of two or more of the aforementioned gases are used to treat silica granules I.
  • metals contained as impurities in the silica granules I such as transition metals, alkali metals and alkaline earth metals can be removed.
  • the aforementioned metals with constituents of the gas mixture can undergo gaseous compounds under the process conditions, which are subsequently discharged and thus no longer present in the granules.
  • the OH Content in the silica granules I by the treatment of the silica granules I are reduced with these gases.
  • a gas mixture of HCl and Cl 2 is used as the reactant.
  • the gas mixture has a content of HCl in a range from 1 to 30% by volume, for example in a range from 2 to 15% by volume, particularly preferably in a range from 3 to 10% by volume.
  • the gas mixture has a content of CI 2 in a range from 20 to 70% by volume, for example in a range from 25 to 65% by volume, particularly preferably in a range from 30 to 60% by volume.
  • the remainder to 100% by volume may be supplemented by one or more inert gases, eg N 2 , He, Ne, Ar, Kr, or by air.
  • the proportion of inert gas in reactants is preferably in a range from 0 to less than 50% by volume, for example in a range from 1 to 40% by volume or from 5 to 30% by volume, more preferably in one range from 10 to 20% by volume, based in each case on the total volume of the reactant.
  • O 2 , C 2 F 2 , or mixtures thereof with Cl 2 are preferably used to purify silica granule I prepared from a siloxane or a mixture of several siloxanes.
  • the reactant in the form of a gas or gas mixture is preferably used as a gas stream or as part of a gas stream with a throughput in a range of 50 to 2000 L / h, for example in a range of 100 to 1000 L / h, more preferably in a range of 200 up to 500 L / h contacted with the silica granules.
  • a preferred embodiment of the contacting is a contact of gas flow and silica granules in a continuous furnace, for example a rotary kiln.
  • Another preferred embodiment of the contacting is a fluidized bed process.
  • a silica granule II having a carbon content Wcp By treating the silica granule I with the reactant, a silica granule II having a carbon content Wcp) is obtained.
  • the carbon content Wcpj of the silica granules II is smaller than the carbon content w C (i) of the silica granules I based on the total weight of the respective silica granules.
  • Preference is w C ß) by 0.5 to 99%, for example by 0.5 to 50% or 1 to 45%, more preferably by 1.5 to 40% less than w C (i).
  • the silica granule I is additionally subjected to a thermal or mechanical treatment or a combination of these treatments.
  • these additional treatments may be before or during the treatment with the reactant.
  • the additional treatment can also be carried out on the silica granules II.
  • the general term "silica granules" used below includes the alternatives “silica granules I” and “silicon dioxide granules II.” It is also possible to apply the treatments described below to both the “silicon dioxide granules I" and the treated silicon dioxide granules I, the "silicon dioxide granules II".
  • the treatment of silica granules can serve a variety of purposes, such as facilitating them
  • the treatment can also be the Properties of the resulting quartz glass body influence.
  • the silica granules may be compacted, cleaned, surface modified or dried.
  • the specific surface area (BET) may decrease.
  • bulk density and average particle size may increase due to agglomeration of silica particles.
  • the thermal treatment can be carried out dynamically or statically.
  • all furnaces are suitable for the dynamic thermal treatment, in which the silicon dioxide granules can be thermally treated and thereby moved.
  • the dynamic thermal treatment preferably continuous furnaces are used.
  • a preferred average residence time of the silica granules in the dynamic thermal treatment is quantity dependent.
  • the average residence time of the silica granules in the dynamic thermal treatment is preferably in the range from 10 to 180 minutes, for example in the range from 20 to 120 minutes or from 30 to 90 minutes.
  • the average residence time of the silica granules in the dynamic thermal treatment in the range of 30 to 90 min.
  • a defined portion of a stream of silica granules e.g. a gram, a kilogram or a ton. Beginning and end of the stay are determined here by running in and out of the continuous furnace operation.
  • the throughput of the silica granules in a continuous process for dynamic thermal treatment is in the range of 1 to 50 kg / h, for example in the range of 5 to 40 kg / h or 8 to 30 kg / h. Particularly preferred is the throughput in the range of 10 to 20 kg / h.
  • the treatment time results from the period between a loading and subsequent unloading of the furnace.
  • the throughput is in a range of 1 to 50 kg / h, for example in the range of 5 to 40 kg / h or 8 to 30 kg / h.
  • the throughput is particularly preferably in the range from 10 to 20 kg / h.
  • the throughput can be achieved by a batch of a certain amount treated for one hour.
  • the throughput may be achieved by a number of batches per hour, for example, the amount of a batch corresponding to the throughput per hour by the number of batches.
  • the treatment time then corresponds to the fraction of an hour, which results from 60 minutes by the number of batches per hour.
  • the dynamic thermal treatment of the silica granules preferably takes place at an oven temperature of at least 500 ° C., for example in the range from 510 to 1700 ° C. or from 550 to 1500 ° C. or from 580 to 1300 ° C., particularly preferably in the range from 600 to 1200 ° C.
  • the oven in the oven chamber has the specified temperature.
  • this temperature deviates upwards or downwards by less than 10% from the indicated temperature, based on the total Treatment time and the entire length of the oven both at any time of treatment and at any point in the oven.
  • the continuous process of a dynamic thermal treatment of the silica granules can be carried out at different furnace temperatures.
  • the oven may have a constant temperature over the treatment time, with the temperature varying in sections over the length of the oven. Such sections can be the same length or different lengths.
  • a temperature which increases from the inlet of the furnace to the outlet of the furnace is preferred.
  • the temperature at the inlet is at least 100 ° C lower than at the outlet, for example 150 ° C lower or 200 ° C lower or 300 ° C lower or 400 ° C lower. More preferably, the temperature at the exit is preferably at least 500 ° C., for example in the range from 510 to 1700 ° C.
  • the temperature at the inlet is preferably at least 300 ° C, for example from 400 to 1000 ° C or from 450 to 900 ° C or from 500 to 800 ° C or from 550 to 750 ° C, more preferably from 600 to 700 ° C.
  • each of the mentioned temperature ranges at the furnace inlet can be combined with each of the temperature ranges at the furnace outlet. Preferred combinations of furnace inlet and furnace outlet temperature ranges are:
  • crucibles preferably are used in an oven.
  • Crucibles or tin crucibles are suitable as crucibles.
  • a sintered crucible is a crucible made of a sintered material containing at least one sintered metal and having a density of not more than 96% of the theoretical density of the metal. The sintered material and the sintered metal in the sinter crucible are not rolled.
  • a crucible, referred to as a sheet crucible includes one or more rolled sheets. As a rule, rolled sheet bars are made of several, riveted plates. Examples of refractory metals are refractory metals, in particular tungsten, molybdenum and tantalum.
  • the crucibles may also be formed from graphite or, in the case of crucibles of refractory metals, be lined with graphite foil. More preferably, the crucibles may be formed of silicon dioxide. Particular preference is given to using silicon dioxide crucibles.
  • the average residence time of the silica granules in the static thermal treatment is quantity-dependent. Preferably, the average residence time of the silica granules in the static thermal treatment in an amount of 20 kg of silica granules I in the range of 10 to 180 minutes, for example in the range of 20 to 120 minutes, more preferably in the range of 30 to 90 min.
  • the static thermal treatment of the silica granules is carried out at an oven temperature of at least 800 ° C, for example in the range of 900 to 1700 ° C or 950 to 1600 ° C or 1000 to 1500 ° C or 1050 to 1400 ° C, especially preferably in the range of 1100 to 1300 ° C.
  • the static thermal treatment of the silicon dioxide granules I preferably takes place at a constant oven temperature.
  • the static thermal treatment can also be carried out at a varying oven temperature.
  • the temperature increases in the course of the treatment, wherein the temperature at the beginning of the treatment by at least 50 ° C is lower than at the end, for example 70 ° C lower or 80 ° C lower or 100 ° C lower or 110 ° C lower, and wherein the temperature at the end is preferably at least 800 ° C, for example in the range of 900 to 1700 ° C or 950 to 1600 ° C or 1000 to 1500 ° C or 1050 to 1400 ° C, more preferably in Range from 1100 to 1300 ° C. mechanically
  • the silicon dioxide granulate I can be treated mechanically.
  • the mechanical treatment can be carried out to increase the bulk density.
  • the mechanical treatment can be combined with the thermal treatment described above.
  • a mechanical treatment can be avoided that the agglomerates in the silica granules and thus the average particle size of the individual, treated Sihziumdioxidgranulen in silica granules are too large.
  • An enlargement of the agglomerates can complicate the further processing or have adverse effects on the properties of the quartz glass body produced by the method according to the invention, or a combination of the two effects.
  • Mechanical treatment of the silica granules also promotes uniform contact of the surfaces of the individual silica granules with the gas or gases. This is achieved in particular with a combination of simultaneous mechanical and chemical treatment with one or more gases. Thereby, the effect of the chemical treatment can be improved.
  • the mechanical treatment of the silica granules may be carried out by moving two or more silicon dioxide granules in a relative motion to one another, for example by rotating the tube of a rotary kiln.
  • the silicon dioxide granulate I is preferably treated chemically, thermally and mechanically. In particular, a simultaneous chemical, thermal and mechanical treatment of the silica granules I.
  • the silica granules I In the chemical treatment, the content of impurities in the silica granules I is reduced.
  • the silica granules I can be treated in a rotary kiln at elevated temperature under a chlorine- and oxygen-containing atmosphere. Water present in silica granules I evaporates, organic materials react to CO and CO 2 . Metal contaminants can be converted to volatile, chlorine-containing compounds.
  • the chlorine-containing atmosphere contains, for example, HCl or CI 2 or a combination of both. This treatment causes a reduction of the carbon content.
  • alkali and iron impurities are preferably reduced.
  • a reduction in the number of OH groups is preferably achieved. At temperatures below 700 ° C, long treatment times may result, at temperatures above 1100 ° C there is a risk that close pores of the granules, including chlorine or gaseous chlorine compounds.
  • the silicon dioxide granules I can be treated first in a chlorine-containing atmosphere and then in an oxygen-containing atmosphere.
  • the resulting low concentrations of carbon, hydroxyl groups and chlorine facilitate the melting of the silica granules II.
  • step II.2) is characterized by at least one, for example by at least two or at least three, more preferably by a combination of all of the following features:
  • the reactant includes HCl, CI 2 or a combination thereof;
  • the treatment is carried out at a temperature in a range of 600 to 900 ° C; N4) the reactant forms a countercurrent;
  • the reactant has a gas flow in a range of 50 to 2000 L / h, preferably 100 to 1000
  • L / h more preferably 200 to 500 L / h;
  • the reactant has a volume fraction of inert gas in a range of 0 to less than 50
  • the silica granules I have a particle diameter which is larger than the particle diameter of the silica powder.
  • the particle diameter of the silica granule I is up to 300 times larger than the particle diameter of the silica powder, for example up to 250 times greater or up to 200 times larger or up to 150 times larger or up to 100 times larger or up to 50 times larger or Up to 20 times larger or up to 10 times larger, more preferably 2 to 5 times larger.
  • silica granules thus obtained are also referred to as silica granules II. More preferably, the silica granules II are obtained from the silica granules I in a rotary kiln by means of a combination of thermal, mechanical and chemical treatment.
  • silica granulate provided in step i.) Is preferably selected from the group consisting of silica granules I, silica granules II and a combination thereof.
  • sicon dioxide granules I is meant granules of silicon dioxide which are produced by granulation of silicon dioxide powder which was obtained in the pyrolysis of silicon compounds in a fuel gas flame.
  • Silicon granules II is understood as meaning a granulate of silicon dioxide which is formed by post-treatment of the silicon dioxide granulate I. As after-treatment, chemical, thermal and / or mechanical treatments are contemplated in detail in the description of the provision of the silicon dioxide granules (process step II first object of the invention).
  • the silicon dioxide granulate I provided in step i.) Is particularly preferably the silicon dioxide granulate I.
  • the silicon dioxide granule I has the following features:
  • a BET surface area in the range of 20 to 50 m 2 / g for example in a range of 20 to 40 m 2 / g; more preferably in a range of 25 to 35 m 2 / g;
  • the microporous fraction preferably amounts to a BET surface area in the range from 4 to 5 m 2 / g; for example, in a range of 4.1 to 4.9 m 2 / g; more preferably in a range of 4.2 to 4.8 m 2 / g; and
  • [B] an average particle size in a range of 180 to 300 ⁇ .
  • the silicon dioxide granulate I is preferably characterized by at least one, for example by at least two or at least three or at least four, more preferably by at least five of the following features:
  • [C] has a bulk density in a range of 0.5 to 1.2 g / cm 3 , for example, in a range of 0.6 to 1.1 g / cm 3 , more preferably in a range of 0.7 to 1 , 0 g / cm 3 ;
  • [E] has an aluminum content of less than 200 ppb, preferably less than 100 ppb, for example less than 50 ppb or from 1 to 200 ppb or from 15 to 100 ppb, more preferably in a range from 1 to 50 ppb.
  • [G] a pore volume in a range of 0.1 to 1.5 mL / g, for example in a range of 0.15 to 1.1 mL / g; more preferably in a range of 0.2 to 0.8 mL / g,
  • Metal content of metals other than aluminum of less than 1000 ppb preferably in a range of 1 to 900 ppb, for example in a range of 1 to
  • [J] has a residual moisture of less than 10% by weight, preferably in a range of from 0.01% by weight to
  • wt .-% for example from 0.02 to 1 wt .-%, particularly preferably from 0.03 to 0.5 wt .-%; wherein the wt .-%, ppm and ppb are each based on the total weight of the silica granules I.
  • the OH content also hydroxy group content, is understood as meaning the content of OH groups in a material, for example in silica powder, in silicon dioxide granules or in a quartz glass body.
  • the content of OH groups is determined spectroscopically after in the infrared by comparing the first and the third OH band.
  • the chlorine content is understood as meaning the content of elemental chlorine or chloride ions in the silicon dioxide granules, the silicon dioxide powder or the quartz glass body.
  • the aluminum content is understood as meaning the content of elemental aluminum or aluminum ions in the silicon dioxide granules, the silicon dioxide powder or the quartz glass body.
  • the silica granule I has a microporous fraction in a range of 4 to 5 m 2 / g; for example, in a range of 4.1 to 4.9 m 2 / g; more preferably in a range of 4.2 to 4.8 m 2 / g.
  • the silica granulate I preferably has a density in a range of 2.1 to 2.3 g / cm 3 , more preferably in a range of 2.18 to 2.22 g / cm 3 .
  • the silicon dioxide granulate I preferably has an average particle size in a range from 180 to 300 ⁇ m, for example in a range from 220 to 280 ⁇ m, particularly preferably in a range from 230 to 270 ⁇ m.
  • the silica granulate I preferably has a particle size D 50 in a range of 150 to 300 ⁇ m, for example in a range of 200 to 280 ⁇ m, particularly preferably in a range of 230 to 270 ⁇ m. Further preferably, the silica granules I have a particle size D 10 in a range of 50 to 150 ⁇ , for example in a range of 100 to 150 ⁇ , more preferably in a range of 120 to 150 ⁇ on. Further preferably, the silica granules I a particle size D 90 in a range of 250 to 620 ⁇ , for example in a range of 300 to 550 ⁇ , more preferably in a range of 300 to 450 ⁇ on.
  • the silica granulate I preferably has the combination of features [A] / [B] / [C] or [A] / [B] / [E] or [A] / [B] / [G], more preferably the combination of features [A ] / [B] / [C] / [E] or [A] / [B] / [C] / [G] or [A] / [B] / [E] / [G], particularly preferably the combination of features [A] / [B] / [C] / [e] / [G].
  • the silica granulate I preferably has the combination of features [A] / [B] / [C], wherein the BET surface area in a range of 20 to 40 m 2 / g, the average particle size in a range of 180 to 300 ⁇ and the Bulk density is in a range of 0.6 to 1.1 g / mL.
  • the silica granulate I preferably has the combination of features [A] / [B] / [E], wherein the BET surface area in a range of 20 to 40 m 2 / g, the average particle size in a range of 180 to 300 ⁇ and the Aluminum content is in a range of 1 to 50 ppb.
  • the silica granulate I preferably has the combination of features [A] / [B] / [G], wherein the BET surface area in a range of 20 to 40 m 2 / g, the average particle size in a range of 180 to 300 ⁇ and the Pore volume is in a range of 0.2 to 0.8 mL / g.
  • the silica granulate I preferably has the combination of features [A] / [B] / [C] / [E], wherein the BET surface area in a range of 20 to 40 m 2 / g, the average particle size in a range of 180 to 300 ⁇ , the bulk density in a range of 0.6 to 1.1 g / mL and the aluminum content in a range of 1 to 50 ppb.
  • the silica granulate I preferably has the combination of features [A] / [B] / [C] / [G], wherein the BET surface area in a range of 20 to 40 m 2 / g, the average particle size in a range of 180 to 300 ⁇ , the bulk density in a range of 0.6 to 1.1 g / mL and the pore volume in a range of 0.2 to 0.8 mL / g.
  • the silica granulate I preferably has the combination of features [A] / [B] / [E] / [G], wherein the BET surface area in a range of 20 to 40 m 2 / g, the average particle size in a range of 180 to 300 ⁇ , the aluminum content in a range of 1 to 50 ppb and the pore volume in a range of 0.2 to 0.8 mL / g.
  • the silica granulate I preferably has the combination of features [A] / [B] / [C] / [E] / [G], wherein the BET surface area in a range of 20 to 40 m 2 / g, the average particle size in a Range from 180 to 300 ⁇ , the bulk density in a range of 0.6 to 1.1 g / mL, the aluminum content in a range of 1 to 50 ppb and the pore volume in a range of 0.2 to 0.8 mL / g is.
  • Particle size is understood to be the size of the particles composed of the primary particles which are present in a silica powder, in a slurry or in a silica granulate.
  • the mean particle size is understood as meaning the arithmetic mean of all particle sizes of said substance.
  • the D 50 value indicates that 50% of the particles, based on the total number of particles, are smaller than the specified value.
  • the D 10 value indicates that 10% of the particles, based on the total number of particles, are smaller than the specified value.
  • the D 90 value indicates that 90% of the particles, based on the total number of particles, are smaller than the specified value.
  • the particle size is determined by dynamic image analysis method according to ISO 13322-2: 2006-11. With particular preference, the silicon dioxide granules provided in step i.) Are the silicon dioxide granules
  • the silica granule II has the following characteristics: (A) a BET surface area in the range of 10 to 35 m 2 / g, for example in a range of 10 to 30 m 2 / g, more preferably in a range of 20 to 30 m 2 / g; and
  • the silicon dioxide granules II preferably have at least one, for example at least two or at least three or at least four, more preferably at least five of the following characteristics:
  • (C) a bulk density in a range of 0.7 to 1.2 g / cm 3 , for example, in a range of 0.75 to 1.1 g / cm 3 , particularly preferably in a range of 0.8 to 1 , 0 g / cm 3 ;
  • (G) a pore volume in a range of 0.1 to 2.5 mL / g, for example, in a range of 0.2 to 1.5 mL / g; more preferably in a range of 0.4 to 1 mL / g;
  • (H) a chlorine content of less than 500 ppm, preferably less than 400 ppm, for example less than 350 ppm or preferably less than 330 ppm or in a range from 1 ppb to 500 ppm or from 10 ppb to 450 ppm particularly preferred from 50 ppb to 300 ppm;
  • wt .-%, ppm and ppb are each based on the total weight of the silica granules II.
  • the silica granule II has a microporous fraction in a range of 1 to 2 m 2 / g, for example in a range of 1.2 to 1.9 m 2 / g, particularly preferably in a range of 1.3 to 1.8 m 2 / g on.
  • the silica granule II preferably has a density in a range from 0.5 to 2.0 g / cm 3 , for example from 0.6 to 1.5 g / cm 3 , particularly preferably from 0.8 to 1.2 g / cm 3 up.
  • the density is determined according to the method described in the test methods.
  • the silica granules II preferably has a particle size D 50 in a range of 150 to 300 ⁇ , to
  • the silica granules II has a particle size D 10 in a range of 50 to 150 ⁇ , for example in a range of 100 to 150 ⁇ , more preferably in a range of 120 to 150 ⁇ on. Further preferably, the granular silica II has a particle size D 90 in a range of 250 to 620 ⁇ , for example in a range of 300 to 550 ⁇ , more preferably in a range of 300 to 450 ⁇ on.
  • the silica granule II preferably has the feature combination (A) / (B) / (D) or (A) / (B) / (F) or (A) / (B) / (I), more preferably the combination of features (A ) / (B) / (D) / (F) or (A) / (B) / (D) / (I) or (A) / (B) / (F) / (I), particularly preferably the combination of features (A) / (B) / (D) / (F) / (I).
  • the silica granule II preferably has the feature combination (A) / (B) / (D), wherein the BET surface area is in a range of 10 to 30 m 2 / g, the mean particle size is in a range of 150 to 280 ⁇ and the carbon content is less than 4 ppm.
  • the silica granules II preferably has the combination of features (A) / (B) / (F), wherein the BET surface area in a range of 10 to 30 m 2 / g, the average particle size in a range of 150 to 280 ⁇ and the Tamping density is in a range of 0.8 to 1.0 g / mL.
  • the silica granules II preferably has the combination of features (A) / (B) / (I), wherein the BET surface area in a range of 10 to 30 m 2 / g, the average particle size in a range of 150 to 280 ⁇ and the Metal content of metals other than aluminum in a range of 1 to 400 ppb.
  • the silica granule II preferably has the feature combination (A) / (B) / (D) / (F), wherein the BET surface area is in a range of 10 to 30 m 2 / g, the average particle size in a range of 150 to 280 ⁇ , the carbon content is less than 4 ppm and the tamped density is in a range of 0.8 to 1.0 g / mL.
  • the silica granule II preferably has the feature combination (A) / (B) / (D) / (I), wherein the BET surface area is in a range of 10 to 30 m 2 / g, the average particle size in a range of 150 to 280 ⁇ , the carbon content is less than 4 ppm, and the metal content of metals other than aluminum is in a range of 1 to 400 ppb.
  • the silica granule II preferably has the feature combination (A) / (B) / (F) / (I), wherein the BET surface area in a range of 10 to 30 m 2 / g, the average particle size in a range of 150 to 280 ⁇ , the tamped density in a range of 0.8 to 1.0 g / mL and the metal content of metals other than aluminum, in a range of 1 to 400 ppb.
  • the silica granule II preferably has the feature combination (A) / (B) / (D) / (F) / (I), wherein the BET surface area is in a range of 10 to 30 m 2 / g, the average particle size in is a range of 150 to 280 ⁇ m, the carbon content is less than 4 ppm, the tamped density is in a range of 0.8 to 1.0 g / ml, and the metal content of metals other than aluminum is in a range of 1 to 400 ppb.
  • step ii. A glass melt is formed from the silica granules.
  • the silica granules are heated until a glass melt is obtained.
  • the heating of the silicon dioxide granules to a molten glass can in principle be carried out in any way known to the person skilled in the art for this purpose.
  • the formation of a glass melt from the silica granules can be carried out by a continuous process.
  • the silicon dioxide granules may preferably be introduced continuously into an oven or the glass melt may be removed continuously from the oven, or both. More preferably, the silica granules are continuously introduced into the furnace and the molten glass continuously removed from the furnace.
  • a furnace which has at least one inlet and at least one outlet.
  • An inlet means an opening through which silicon dioxide and optionally further substances can be introduced into the furnace.
  • An outlet means an opening through which at least part of the silicon dioxide can be removed from the oven.
  • the oven may be vertically and horizontally aligned.
  • the oven is vertically aligned.
  • at least one inlet is located above at least one outlet.
  • “Above” in connection with internals and features of a furnace, in particular an inlet and outlet means that the fixture or feature located "above” another occupies a higher position NormalNull (NN).
  • vertical is meant that the direct connection between the inlet and the outlet of the furnace has a deviation of not more than 30 ° to the direction of the solder.
  • the furnace includes a standing sintered crucible.
  • the silicon dioxide granules are introduced into the standing sintered crucible and heated to obtain a glass melt.
  • a sintered crucible is understood to mean a crucible made of a sintered material containing at least one sintered metal and wherein the sintered metal has a density of not more than 96% of the theoretical density of the metal.
  • the theoretical density of a material corresponds to the density of a nonporous and 100% dense material.
  • sintered metals is meant metals or alloys obtained by sintering metal powders.
  • the sintered material of the sintered crucible preferably has a density of 85% or more of the theoretical density of the sintered material, for example a density of 85% to 95% or of 90% to 94%, particularly preferably of 91% to 93%.
  • the sintered material can consist of all materials known to those skilled in the art and suitable for melting silicon dioxide.
  • the sintered material is made of at least one of the elements selected from the group consisting of refractory metals, graphite or graphite foil lined materials.
  • the sintered material includes a first sintered metal selected from the group consisting of molybdenum, tungsten and a combination thereof. More preferably, the sintered material further includes at least one other refractory metal other than the first sintered metal, more preferably selected from the group consisting of molybdenum, tungsten, rhenium, osmium, iridium, ruthenium, or a combination of two or more thereof.
  • the sintered material includes an alloy of molybdenum with a refractory metal, or tungsten with a refractory metal.
  • the alloying metal are rhenium, osmium, iridium, ruthenium or a combination of two or more thereof.
  • the sintered material includes an alloy of molybdenum with tungsten, rhenium, osmium, iridium, ruthenium, or a combination of two or more thereof.
  • the sintered material includes an alloy of tungsten with molybdenum, rhenium, osmium, iridium, ruthenium or a combination of two or more thereof.
  • the above-described sintered material may include a coating containing a refractory metal, in particular rhenium, osmium, iridium, ruthenium or a combination of two or more thereof.
  • the coating contains rhenium, osmium, iridium, ruthenium, molybdenum or tungsten, or a combination of two or more thereof.
  • the sintered material and its coating have various compositions.
  • a sintered material including molybdenum is coated with one or more layers of rhenium, osmium, iridium, ruthenium, tungsten, or each a combination of two or more thereof.
  • a sintered material including tungsten is coated with one or more layers of rhenium, osmium, iridium, ruthenium, molybdenum, or any combination of two or more thereof.
  • the sintered material may be rhenium alloyed molybdenum or rhenium alloyed tungsten, and may be coated on the inside of the crucible with one or more layers including rhenium, osmium, iridium, ruthenium or any combination of two or more thereof.
  • a sintered crucible is made by sintering the sintered material in a mold.
  • the sintered crucible can be made as a whole in one mold. It is also possible that individual parts of the sintered crucible are manufactured in a mold and subsequently processed into the sintered crucible.
  • the crucible is made of more than one part, for example, a bottom plate and one or more side parts. The side parts are preferably manufactured in one piece based on the circumference of the crucible.
  • the sintered crucible can be manufactured from a plurality of side parts arranged one above the other.
  • the side parts of the sintered crucible are sealed by screwing or by a tongue and groove joint.
  • Screwing is preferably done by making side pieces which have a thread at the edges.
  • a tongue and groove connection have two side parts to be joined at the edges each have a groove in the connecting third Part a spring is inserted so that a positive connection is formed perpendicular to the crucible wall level.
  • a sintered crucible is produced from more than one side part, for example from two or more side parts, particularly preferably from three or more side parts.
  • the parts of the stationary sinter crucible are connected by means of a tongue and groove connection.
  • the bottom plate can in principle be connected to the crucible wall by all measures known to the person skilled in the art and suitable for this purpose.
  • the bottom plate is provided with an external thread and is connected by screwing the bottom plate in the crucible wall with this.
  • the bottom plate is connected by means of screws with the crucible wall.
  • the bottom plate is suspended in the sintered crucible, for example by inserting the bottom plate on an inner collar of the crucible wall.
  • at least a part of the crucible wall and a thickened bottom plate are sintered in one piece.
  • the bottom plate and the crucible wall of the stationary sinter crucible are connected by means of a tongue and groove connection.
  • the bottom plate contained in a 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, more preferably 2 to 5 times thicker.
  • the sides preferably have a constant wall thickness over the circumference and over the height of the sintered crucible.
  • the sinter crucible has a nozzle.
  • the nozzle is formed of a nozzle material.
  • the nozzle material preferably comprises a precompressed material, for example with a density in a range of more than 95%, for example from 98 to 100%, particularly preferably from 99 to 99.999%, in each case based on the theoretical density of the nozzle material.
  • the nozzle material includes a refractory metal, for example, molybdenum, tungsten, or a combination thereof with a refractory metal.
  • a refractory metal for example, molybdenum, tungsten, or a combination thereof with a refractory metal.
  • Particularly preferred nozzle material is molybdenum.
  • a nozzle containing molybdenum may have a density of 100% of the theoretical density.
  • the hanging sintered crucible can in principle be heated in any manner familiar to the person skilled in the art and appear suitable for this purpose.
  • the hanging sintered crucible can be heated, for example, inductively or resistively.
  • inductive heating the energy is coupled directly by means of coils in the side wall of the sinter crucible and discharged from there to the inside of the crucible.
  • resistive heating the energy is coupled by radiation, the solid surface is heated from the outside and the energy is discharged from there to the inside.
  • the sintered crucible is preferably heated inductively.
  • the energy input into the sintered crucible is not effected by heating the sinter crucible, or a melt therein, or both, by means of a flame, such as a burner flame directed into the sinter crucible or crucible.
  • the sintered crucible has one or more than one heating zone, for example one or two or three or more than three heating zones, preferably one or two or three heating zones, particularly preferably a heating zone.
  • the heating zones of the sinter crucible can be brought to the same or different temperatures. For example, all heating zones may be heated to one temperature or all heating zones to different temperatures, or two or more heating zones to one and one or more heating zones independently of one another to different temperatures. Preferably, all heating zones are brought to different temperatures, for example, the temperature of the heating zones increases in the direction of material transport of the silica granules.
  • a standing sintered crucible is understood to mean a sinter crucible of the type described above, which is arranged standing in an oven.
  • the standing sintered crucible has at least one, for example at least two or at least three or at least four, particularly preferably all of the following features:
  • ßol at least two sealed rings as side parts, preferably at least two sealed by a tongue and groove joint rings as side parts;
  • Id a nozzle, preferably a nozzle fixedly connected to the crucible, particularly preferably a portion of the bottom of the crucible which is not formed as a standing surface;
  • Idl a mandrel, for example, a mandrel fixed to the nozzle with bars or a pin secured to webs on the lid or a mandrel connected from below the crucible with a holding rod;
  • Id at least one gas inlet, e.g. in the form of a filling tube or as a separate inlet;
  • Iii at least one gas outlet, e.g. as a separate outlet on the lid or in the wall of the crucible;
  • the standing sintered crucible preferably has a separation of the gas spaces in the furnace and in the area below the furnace. Under the area below the furnace, the area below the nozzle is understood, in which the withdrawn molten glass is located.
  • the gas spaces are preferably separated by the area on which the crucible stands. Gas, which is located in the gas space of the furnace between the furnace inner wall and the outer wall of the crucible, can not escape down into the area below the furnace.
  • the extracted molten glass has no contact with the gases from the gas space of the furnace.
  • glass melts taken from a furnace with a vertically arranged sintered crucible and quartz glass bodies formed therefrom have a higher surface purity than glass melts taken from a furnace with a sintered crucible arranged in a suspended position and quartz glass bodies formed therefrom.
  • the crucible is so connected to the inlet and the outlet of the furnace that through the inlet of the
  • Furnace silica granules can pass through the inlet of the crucible into the crucible and glass melt can be removed through the outlet of the crucible and the outlet of the furnace.
  • the crucible adjacent to the at least one inlet at least one opening, preferably a plurality of openings through which gas can be introduced and discharged.
  • the crucible comprises at least two openings, wherein at least one can be used as a gas inlet and at least one as a gas outlet. The use of at least one opening as gas inlet and at least one opening as gas outlet preferably leads to a gas flow in the crucible.
  • the silica granules are introduced into the crucible and then heated in the crucible.
  • the heating may be carried out in the presence of a gas or a mixture of two or more gases.
  • water bound to the silica granules may also pass into the gas phase to form another gas.
  • the gas or mixture of two or more gases is in the headspace of the crucible.
  • the gas space of the crucible is understood to mean the area inside the crucible which is not occupied by a solid or liquid phase. Suitable gases are, for example, hydrogen, inert gases and two or more thereof.
  • Inert gases are understood to mean those gases which do not react with the substances provided in the crucible up to a temperature of 2400 ° C.
  • Preferred inert gases are nitrogen, helium, neon, argon, krypton and xenon, more preferably argon and helium.
  • the heating is carried out in a reducing atmosphere.
  • This may preferably be provided by hydrogen or a combination of hydrogen and an inert gas, for example by a combination of hydrogen and helium, or of hydrogen and nitrogen, or of hydrogen and argon, more preferably by a combination of hydrogen and helium.
  • an at least partial gas exchange of air, oxygen and water to hydrogen, at least one inert gas, or against a combination of hydrogen and at least one inert gas is carried out on the silica granules.
  • the at least partial gas exchange is performed on the silica granules upon introduction of the silica granules, or before heating, or during heating, or during at least two of the aforementioned activities.
  • the silica granules are heated to melt in a gas stream of hydrogen and at least one inert gas, for example, argon or helium.
  • the dew point of the gas as it exits through the gas outlet is less than 0 ° C.
  • the dew point is understood to mean the temperature below which, under unchanged pressure, a constituent of the gas or gas mixture under investigation condenses. In general, this refers to the condensation of water.
  • the dew point is determined with a dew point mirror hygrometer according to the measuring method described in the Methods section
  • the furnace preferably also a crucible located therein, at least one gas outlet, is removed through the gas supplied to the furnace and formed during operation of the furnace.
  • the furnace may also have at least one dedicated gas inlet.
  • gas may be introduced through the solid feed, also referred to as solids inlet, for example together with the Silica particles, or before, after, or by a combination of two or more of the aforementioned possibilities.
  • the gas withdrawn from the furnace through the gas outlet, as it exits the furnace through the gas outlet has a dew point of less than 0 ° C, for example less than -10 ° C, or less than -20 ° C.
  • the dew point is determined according to the measuring method described in the method section at a slight overpressure of 5 to 20 mbar.
  • a device called "Optidew” from Michell Instruments GmbH, D-61381 Friedrichsdorf is suitable as a measuring device
  • the dew point of the gas is preferably determined at a measuring point at a distance of 10 cm or more from the gas outlet of the furnace this distance is between 10 cm and 5 m.
  • the distance of the measuring point from the gas outlet of the furnace is irrelevant for the result of the dew point measurement.
  • the gas is guided in a fluid-conducting manner from the outlet to the measuring point, for example in a hose or a pipe.
  • the temperature of the gas at the measuring point is often between 10 and 60 ° C, for example 20 to 50 ° C, in particular 20 to 30 ° C.
  • the gas or gas mixture before entry into the furnace has a dew point of less than -50 ° C, for example less than -60 ° C, or less than -70 ° C, or less than -80 ° C.
  • a dew point of -60 ° C is usually not exceeded.
  • the following ranges for the dew point when entering the oven from -50 to -100 ° C; from -60 to -100 ° C and from -70 to -100 ° C.
  • the dew point of the gas before entering the furnace is at least 50 ° C less than when it leaves the crucible, for example at least 60 ° C, or even 80 ° C.
  • the above information applies. The same applies to a measurement of the dew point before entering the furnace. Since no source of moisture entry and no condensation precipitation is provided between the location of the measurement and the oven, the distance from the measuring point to the gas inlet of the oven is not important here.
  • the furnace in particular the crucible, is operated at a gas exchange rate in a range from 200 to 3000 L / h.
  • the dew point is determined in a measuring cell, wherein the measuring cell is separated by a membrane from the gas passing through the gas outlet.
  • the membrane is preferably permeable to moisture.
  • a dew point mirror measuring device is used to determine the dew point.
  • the dew point at the gas outlet of the oven can be adjusted.
  • a method of adjusting the dew point at the outlet of the furnace includes the following steps:
  • the dew point can be adjusted to a range of less than 0 ° C, for example, less than -10 ° C, more preferably less than -20 ° C. More preferably, the dew point can be set in a range of less than 0 ° C to -100 ° C, for example, less than -10 ° C to -80 ° C, more preferably less than -20 ° C to -60 ° C become.
  • input material silica particles prepared for producing a quartz glass body, preferably silica granules, silica granules or combinations thereof
  • silicon dioxide particles, the granules and the granules are preferably characterized by the features described in the context of the first subject.
  • the furnace and the gas stream are preferably characterized by the features described in the context of the first subject.
  • the gas stream is formed by introducing a gas through an inlet into the furnace and discharging a gas through an outlet from the furnace.
  • the "gas exchange rate" is understood to mean the volume of gas that is passed out of the furnace per outlet through the outlet.
  • the gas exchange rate is also referred to as the flow rate of the gas or as the volume flow rate
  • increasing the residual moisture content of the input material may increase the dew point
  • decreasing the residual moisture of the input material may lower the dew point
  • increasing the rate of gas exchange may decrease the dew point
  • decreasing the gas exchange rate may increase the dew point have as a consequence.
  • the gas exchange rate of the gas stream is preferably in a range from 200 to 3000 L / h, for example from 200 to 2000 L / h, particularly preferably from 200 to 1000 L / h.
  • the residual moisture of the starting material is preferably in a range from 0.001% by weight to 5% by weight, for example from 0.01 to 1% by weight, particularly preferably from 0.03 to 0.5% by weight, in each case based on the total weight of the input material.
  • the dew point can preferably be influenced by further measures. Examples of such measures are the dew point of the gas stream entering the furnace, the furnace temperature and the composition of the gas stream. Reducing the dew point of the gas stream as it enters the furnace, reducing the furnace temperature, or decreasing the temperature of the gas stream at the outlet of the furnace may result in a reduction in the dew point of the gas stream at the outlet. The temperature of the gas stream at the exit of the furnace has no influence on the dew point, if it is above the dew point.
  • the gas exchange rate of the gas stream is varied.
  • the process is preferably characterized by at least one, for example at least two or at least three, more preferably at least four of the following features:
  • a gas exchange rate of the gas stream in a range from 200 to 3000 L / h, for example from 200 to 2000 L / h, more preferably from 200 to 1000 L / h;
  • an oven temperature in a range of 1700 to 2500 ° C, for example in a range of
  • VI ⁇ a temperature of the gas at the outlet in a range of 10 to 60 ° C, for example from 20 to
  • a gas stream with a high gas exchange rate and a low dew point at the inlet of the furnace when using a granular silica with a high residual moisture content.
  • a gas flow with a low gas exchange rate and a higher dew point can be used at the inlet of the furnace.
  • the gas exchange rate of a gas stream comprising helium and hydrogen is particularly preferably in the range from 200 to 3000 L / h.
  • the furnace temperature for melting the silica granules is preferably in the range of 1700 to 2500 ° C, for example, in the range of 1900 to 2400 ° C, more preferably in the range of 2100 to 2300 ° C.
  • the residence time in the furnace is preferably in the range from 1 hour to 50 hours, for example 1 to 30 hours, particularly preferably 5 to 20 hours.
  • the residence time in the context of the present invention means the time required to remove a filling amount of the melting furnace according to the method during the implementation of the method according to the invention, the melting furnace in which the molten glass is formed.
  • the filling quantity is the total amount of silicon dioxide present in the melting furnace.
  • the silicon dioxide can be present as a solid and as a glass melt.
  • the furnace temperature increases over the length, in the direction of material transport.
  • the furnace temperature preferably increases over the length, in the direction of material transport by at least 100 ° C., for example by at least 300 ° C. or by at least 500 ° C. or by at least 700 ° C., more preferably by at least 1000 ° C.
  • the highest temperature in the oven is 1700 to 2500 ° C, for example 1900 to 2400 ° C, more preferably 2100 to 2300 ° C.
  • the increase in the oven temperature can be uniform or according to a temperature profile.
  • the oven temperature decreases before the glass melt is removed from the oven.
  • the oven temperature before the glass melt is removed from the oven by 50 to 500 ° C from, for example, to 100 ° C or 400 ° C, more preferably from 150 to 300 ° C.
  • the temperature of the glass melt during removal is preferably 1750 to 2100 ° C, for example 1850 to 2050 ° C, particularly preferably 1900 to 2000 ° C.
  • the furnace temperature increases over the length, in the direction of material transport and before the
  • the oven temperature takes over the length, in
  • Direction of material transport by at least 100 ° C for example by at least 300 ° C or by at least 500 ° C or by at least 700 ° C, more preferably by at least 1000 ° C.
  • the highest is
  • Temperature in the oven 1700 to 2500 ° C for example 1900 to 2400 ° C, more preferably 2100 to 2300 ° C.
  • the oven temperature before the glass melt is removed from the oven by 50 to 500 ° C from, for example, to 100 ° C or 400 ° C, more preferably from 150 to 300 ° C.
  • a molten glass can also be formed in a suspended sintered crucible.
  • This sinter crucible is suspended in the oven.
  • a suspension applied to the sintered crucible is often used, which is usually formed from a material different from the sintered crucible, for example aluminum, steel, iron, nickel or copper.
  • Such a suspension is usually equipped with a cooling, for example, a water cooling.
  • a quartz glass body obtained from a standing sintered crucible has less impurities on its surface than a quartz glass body obtained from a suspended sintered crucible.
  • a subsequent cleaning can be omitted or at least carried out less expensive than a hanging sintered crucible.
  • a glass melt can also be formed in a sheet metal crucible.
  • a sheet metal crucible is understood to mean a crucible which contains at least one rolled sheet.
  • a sheet metal crucible preferably has a plurality of rolled sheets.
  • a metal crucible suitable for melting silicon dioxide is made of sheets of a sintered and rolled material, in particular of sintered metal, for example of molybdenum, tungsten or a combination thereof. Such sheets regularly have a density of more than 96% of the theoretical density, for example a density of more than 96% to 98%, or of 98 to 99.95%.
  • the theoretical density of a material corresponds to the density of a nonporous and 100% dense material.
  • the density of the sheet can be obtained by sintering a sintered metal and then compacting, for example, rolling the sintered material.
  • Sheet metal bars are usually designed as hanging metal bars.
  • Gas diffusion of gases e.g. Argon, helium, hydrogen and nitrogen through the crucible walls are lower in a sintered crucible than in a crucible. These gases are used as an inert gas in the furnace around the crucible to prevent corrosion of the crucible from the outside, the heating elements and the furnace.
  • gases e.g. Argon, helium, hydrogen and nitrogen
  • a sinter crucible can be heated by induction. So a multi-zone heating is well feasible.
  • the stationary sinter crucible used according to the invention has the further advantage over all other crucibles that the crucible size has no design limit. Hanging crucibles are limited in crucible size by the retention capacity of the crucible wall and the carrying capacity of the crucible wall. preheating
  • the furnace has at least a first and a further chambers connected to each other through a passage, wherein the first and the further chamber have different temperatures, wherein the temperature of the first chamber is lower than the temperature of the further chamber.
  • a glass melt is formed from the silica granules.
  • This chamber is referred to below as the melting chamber.
  • a connected to the melting chamber via a fabric guide, but upstream chamber is also referred to as preheating. It is, for example, that in which at least one outlet is directly connected to an inlet of the melting chamber.
  • the aforementioned arrangement can also be formed in independent ovens.
  • the melting chamber is a melting furnace. With regard to the further description, however, the melting furnace can be understood to be synonymous with the melting chamber.
  • the remarks on the melting furnace also apply to the melting chamber, and vice versa.
  • the term preheating line is the same for both approaches.
  • the silica granules entering the furnace have a temperature in a range of 20 to 1300 ° C.
  • the silica granules are not tempered before entering the melting chamber.
  • the silica granules entering the oven have a temperature in a range of 20 to 40 ° C, more preferably 20 to 30 ° C.
  • silicon dioxide granules II are provided in accordance with step i.)
  • It preferably has a temperature in the range from 20 to 40 ° C., particularly preferably from 20 to 30 ° C., on entering the furnace.
  • the silica granules are tempered before entering the furnace to a temperature in a range of 40 to 1300 ° C.
  • Tempering means setting the temperature to a selected value.
  • the tempering can be carried out in principle on all known to those skilled and known for controlling the temperature of silica granules.
  • the tempering may be carried out in a furnace separate from the melting chamber or in an oven connected to the melting chamber.
  • the tempering takes place in a chamber connected to the melting chamber.
  • the furnace thus preferably comprises a preheating section in which the silicon dioxide can be tempered.
  • the preheating section itself is preferably a continuous furnace, particularly preferably a rotary kiln.
  • a continuous furnace is understood to mean a heated chamber which, during operation, causes a movement of the silicon dioxide from an inlet of the continuous furnace to an outlet of the continuous furnace.
  • the outlet is directly connected to the inlet of the melting furnace.
  • the silica granules from the preheating without further intermediate steps or measures can enter the furnace.
  • the preheating section comprises at least one gas inlet and at least one gas outlet.
  • gas inlet gas can enter the interior, the gas space of the preheating, and through the gas outlet, it can be discharged. It is also possible to gas over the inlet for that Introduce the silicon dioxide granules of the preheating section into the preheating section.
  • gas can be discharged via the outlet of the preheating section and subsequently separated from the silicon dioxide granulate.
  • gas can be supplied via the inlet for the silicon dioxide granules and a gas inlet to the preheating section, and discharged via the outlet of the preheating section and a gas outlet of the preheating section.
  • a gas flow is formed in the preheat section by using the gas inlet and the gas outlet.
  • gases are, for example, hydrogen, inert gases and two or more thereof.
  • Preferred inert gases are nitrogen, helium, neon, argon, krypton and xenon, more preferably nitrogen and helium.
  • a reducing atmosphere is present in the preheating section. This may preferably be provided by hydrogen or a combination of hydrogen and an inert gas, for example by a combination of hydrogen and helium or of hydrogen and nitrogen, more preferably by a combination of hydrogen and helium.
  • an oxidizing atmosphere is present in the preheating section. This may preferably be provided by oxygen or a combination of oxygen and one or more further gases, more preferably air. It is further preferably possible to temper the silicon dioxide at reduced pressure in the preheating section.
  • the silica granules entering the furnace have a temperature in the range of 100 to 1100 ° C or 300 to 1000 or 600 to 900 ° C. If silicon dioxide granules II are provided according to step i.), It preferably has a temperature in the range from 100 to 1100 ° C. or from 300 to 1000 or from 600 to 900 ° C. when entering the furnace.
  • the furnace includes at least two chambers.
  • the furnace includes a first and at least one further chamber.
  • the first and the further chambers are connected to each other by a passage.
  • the at least two chambers can in principle be arranged as desired in the oven, preferably vertically or horizontally, particularly preferably vertically.
  • the chambers are arranged in the furnace so that in the implementation of the method according to the first subject of the invention, silica granules pass through the first chamber and then heated in the further chamber to obtain a molten glass.
  • the further chamber preferably has the above-described features of the melting furnace and the crucible arranged therein.
  • each of the chambers includes an inlet and an outlet.
  • the inlet of the furnace is connected to the inlet of the first chamber through a passage.
  • the outlet of the furnace is connected to the outlet of the further chamber through a passage.
  • the outlet of the first chamber is connected by a passage to the inlet of the further chamber.
  • the chambers are arranged in the oven so that through the inlet of the furnace
  • Silica granules can get into the first chamber.
  • the chambers are preferably arranged in the furnace such that a silicon dioxide glass melt can be removed from the further chamber through the outlet of the furnace.
  • the silica granules in the first chamber arrive and be taken through the outlet of the furnace, a silica glass melt from another chamber.
  • the silica can pass as granules or powder in the direction predetermined by the method of transporting material from a first chamber to another.
  • Chambers connected by a passage include arrangements in which further intermediate elements are arranged between a first and a further chamber in the direction of material transport.
  • the passage can in principle happen gases, liquids and solids.
  • silica powders, slurries of silica powder and silica granules may pass the transition between a first and a further chamber.
  • all substances introduced into the first chamber can pass into the further chamber via the passage between the first and the further chambers.
  • the passage between the first and further chamber Preferably passes through the passage between the first and further chamber only silica in the form of granules or powder in the other chamber.
  • the passage between the first and the further chamber is closed by the silicon dioxide, so that the gas space of the first and the further chamber are separated from each other, preferably so that in the gas spaces different gases or gas mixtures, different pressures or both can be present.
  • the passage is formed by a lock, preferably by a rotary valve.
  • the first chamber of the furnace preferably has at least one gas inlet and at least one gas outlet.
  • the gas inlet may in principle have any shape which is known to those skilled in the art and suitable for introducing a gas, for example a nozzle, a valve or a pipe.
  • the gas outlet may in principle have any shape which is known to the person skilled in the art and suitable for discharging a gas, for example a nozzle, a valve or a pipe.
  • silica granules are introduced into the first chamber through the inlet of the furnace and heated. The heating may be carried out in the presence of a gas or a combination of two or more gases.
  • the gas or the combination of two or more gases is present in the gas space of the first chamber.
  • the gas space of the first chamber is understood to be the area of the first chamber which is not occupied by a solid or liquid phase.
  • gases are, for example, hydrogen, oxygen, inert gases and two or more thereof.
  • Preferred inert gases are nitrogen, helium, neon, argon, krypton and xenon, more preferably nitrogen, helium and a combination thereof.
  • the heating is carried out in a reducing atmosphere. This may preferably be provided by hydrogen or a combination of hydrogen and helium.
  • the silica granules in the first chamber are heated in a stream of the gas or the combination of two or more gases.
  • the silica granules in the first chamber be heated at a reduced pressure, for example at a pressure of less than 500 mbar or less than 300 mbar, for example 200 mbar or less.
  • the first chamber is provided with at least one device with which the silica granules are moved.
  • the temperatures in the first and in the further chamber are different.
  • the temperature in the first chamber is lower than the temperature in the other chamber.
  • the temperature difference between the first and the further chamber in a range of 600 to 2400 ° C, for example in a range of 1000 to 2000 ° C or from 1200 to 1800 ° C, more preferably in a range of 1500 to 1700 ° C. More preferably, the temperature in the first chamber is 600 to 2400 ° C, for example 1000 to 2000 ° C or 1200 to 1800 ° C, more preferably 1500 to 1700 ° C lower than the temperature in the other chamber.
  • the first chamber of the furnace is a preheating section, more preferably a preheating section as described above, having the features described above.
  • the preheating is connected by a passage with the other chamber.
  • silicon dioxide passes from the preheating section via an opening into the further chamber.
  • the passage between the preheating section and the further chamber may be closed, so that no gases introduced into the preheating section pass through the passage into the further chamber.
  • the passage between the preheating and the other chamber is closed, so that the silicon dioxide does not come into contact with water.
  • the passage between the preheating section and the further chamber can be closed, so that the gas space of the preheating section and the first chamber are separated from one another such that different gases or gas mixtures, different pressures or both can be present in the gas spaces.
  • the first chamber of the furnace is not a preheating section.
  • the first chamber is a compensation chamber.
  • a compensation chamber is understood to mean a chamber of the furnace in which throughput variations in an upstream preheating section or throughput differences between a preheating section and the further chamber are compensated.
  • the first chamber may be preceded by a rotary kiln as described above. This usually has a throughput that can vary by up to 6% of the average throughput.
  • silica is maintained in a compensation chamber at the temperature with which it enters the compensation chamber.
  • the furnace has a first chamber and more than one further chamber, for example two further chambers or three further chambers or four further chambers or five further chambers or more than five further chambers, particularly preferably two further chambers.
  • the first chamber is preferably a preheating section
  • the first of the further chambers is a compensation chamber
  • the second of the further chambers is the melting chamber, based on the direction of material transport.
  • an additive is present in the first chamber.
  • the additive is preferably selected from the group consisting of halogens, inert gases, bases, oxygen or a combination of two or more thereof.
  • halogens in elemental form and halogen compounds are suitable as additives.
  • Preferred halogens are selected from the group consisting of chlorine, fluorine, chlorine-containing compounds and fluorine-containing compounds. Particularly preferred are elemental chlorine and hydrogen chloride.
  • inert gases are nitrogen, helium or a combination thereof.
  • bases are also suitable as additives.
  • Preferred bases as additives are inorganic and organic bases.
  • oxygen is also suitable as an additive.
  • the oxygen is preferably 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 may in principle include any material known to those skilled in the art and suitable for heating silica.
  • the first chamber preferably contains at least one element selected from the group consisting of quartz glass, a refractory metal, aluminum and a combination of two or more thereof, particularly preferably the first chamber contains quartz glass or aluminum.
  • the temperature in the first chamber does not exceed 600 ° C when the first chamber includes a polymer or aluminum.
  • the temperature in the first chamber is 100 to 1100 ° C when the first chamber includes quartz glass.
  • the first chamber preferably contains essentially quartz glass.
  • the silicon dioxide When transporting the silicon dioxide from the first chamber to the further chamber through the passage between the first and the further chamber, the silicon dioxide can in principle be in any state.
  • the silicon dioxide is preferably present as a solid, for example as particles, powders or granules. According to a preferred embodiment of the first subject of the invention, the transport of the silicon dioxide from the first to the further chamber takes place as granules.
  • the further chamber is a crucible of a sheet metal or a sintered material, which contains a sintered metal, wherein the sheet or the sintered metal is selected from the group consisting of molybdenum, tungsten and a combination thereof.
  • the glass melt is removed through the outlet from the oven, preferably via a nozzle.
  • a quartz glass body is formed from at least part of the molten glass.
  • at least part of the glass melt produced in step ii) is preferably removed and the quartz glass body formed therefrom.
  • the removal of part of the glass melt produced in step ii) can, in principle, be carried out continuously from the melting furnace or the melting chamber, or after completion of the production of the glass melt.
  • a part of the molten glass is removed continuously.
  • the molten glass is removed through the outlet from the furnace or the outlet of the melting chamber, preferably via a nozzle.
  • the molten glass may be cooled before, during or after removal to a temperature which allows the molten glass to be molded.
  • the molten glass is preferably cooled to the extent that the formed form is retained during molding and molding can be carried out simultaneously as quickly as possible, reliably and with little effort.
  • the person skilled in the art can easily determine the viscosity of the molten glass for molding by varying the temperature of the molten glass on the mold.
  • When removing the molten glass preferably has a temperature in the range of 1750 to 2100 ° C, for example 1850 to 2050 ° C, particularly preferably 1900 to 2000 ° C.
  • the glass melt after removal to a temperature of less than 500 ° C, for example, less than 200 ° C or less than 100 ° C or less than 50 ° C, more preferably to a temperature in the range of 20 to 30 ° C cooled.
  • the formed quartz glass body may be a solid body or a hollow body.
  • a solid body is meant a body consisting essentially of a single material.
  • a solid body may have one or more inclusions, eg, gas bubbles.
  • inclusions in a solid body often 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 , more preferably less than 0.5 mm 3 .
  • a solid body contains less than 0.02% by volume of its volume, for example, less than 0.01% by volume or less than 0.001% by volume of inclusions, each based on the total volume of the solid body.
  • the quartz glass body has an outer shape.
  • the outer shape is understood to be the shape of the outer edge of the cross section of the quartz glass body.
  • the outer shape of the quartz glass body is preferably round, elliptical or polygonal in cross-section with three or more corners, for example 4, 5, 6, 7 or 8 corners, more preferably the quartz glass body is round.
  • the quartz glass body has a length in the range of 100 to 10,000 mm, for example from 1000 to 4000 mm, particularly preferably from 1200 to 3000 mm.
  • the quartz glass body has an outer diameter in the range of 1 to 500 mm, for example in a range of 2 to 400 mm, more preferably in a range of 5 to 300 mm.
  • the molding of the quartz glass body takes place by means of a nozzle.
  • the molten glass is passed through the nozzle.
  • the outer shape of a quartz glass body formed by the nozzle is determined by the shape of the opening of the nozzle.
  • a cylinder is formed as the quartz glass body is formed. If the opening of the nozzle has a structure, this structure is transferred to the outer shape of the quartz glass body.
  • a quartz glass body, which is formed by means of a nozzle with structures at the opening has an image of the structures in the longitudinal direction on the glass strand.
  • the nozzle is integrated in the furnace. Preferably, it is integrated as part of the crucible in the furnace, more preferably as part of the outlet of the crucible.
  • the at least part of the molten glass is removed through the nozzle.
  • the outer shape of the quartz glass body is formed by removing at least a portion of the glass melt through the nozzle.
  • the quartz glass body is cooled after forming to obtain its shape.
  • the quartz glass body is cooled after molding to a temperature which is at least 1000 ° C below the temperature of the glass melt during molding, for example at least 1500 ° C or at least 1800 ° C, more preferably 1900 to 1950 ° C.
  • the quartz glass body is cooled to a temperature of less than 500 ° C, for example of less than 200 ° C or less than 100 ° C or less than 50 ° C, more preferably to a temperature in the range of 20 to 30 ° C.
  • the resulting quartz glass body may be treated with at least one measure selected from the group consisting of chemical, thermal or mechanical treatment.
  • the quartz glass body is chemically treated.
  • Post-treatment refers to the treatment of an already formed quartz glass body.
  • chemical aftertreatment of the quartz glass body is understood in principle any measure which is known to the person skilled in the art and appears to be suitable for changing the chemical structure or the composition of the surface of the quartz glass body or both by the use of substances.
  • the chemical aftertreatment comprises at least one measure selected from the group consisting of treatment with fluorine compounds and ultrasonic cleaning.
  • Particularly suitable fluorine compounds are hydrogen fluoride and fluorine-containing acids, for example hydrofluoric acid.
  • the liquid preferably has a content of fluorine compounds in a range of 35 to 55 wt .-%, preferably in a range of 35 to 45 wt .-%, the wt .-% in each case based on the total amount of liquid.
  • the remainder to 100% by weight is usually water.
  • demineralized or deionized water is selected as the water.
  • Ultrasonic cleaning is preferably carried out in a liquid bath, more preferably in the presence of detergents.
  • detergents usually no fluorine compounds, for example, neither hydrofluoric acid nor hydrogen fluoride, are used.
  • the ultrasonic cleaning of the quartz glass body is preferably carried out under at least one, for example at least two or at least three or at least four or at least five, more preferably all of the following conditions:
  • the ultrasound leg is done in a continuous process.
  • the ultrasonic cleaning system has six chambers connected to each other by pipes.
  • the residence time of the quartz glass bodies in each chamber can be adjusted.
  • the residence time of the quartz glass bodies in each chamber is the same.
  • the residence time in each chamber is in a range of 1 to 120 minutes, for example less than 5 minutes or 1 to 5 minutes or 2 to 4 minutes or less than 60 minutes or 10 to 60 minutes or 20 to 50 minutes, more preferably in a range of 5 to 60 minutes.
  • the first chamber comprises a basic medium, preferably containing water and a base, and an ultrasonic cleaner.
  • the third compartment comprises an acidic medium, preferably containing water and an acid, and an ultrasonic cleaner.
  • the quartz glass body is cleaned with water, preferably demineralized water.
  • the fourth to sixth chamber is operated as a cascade with water, preferably desalted water.
  • the water is introduced only in the sixth chamber and runs from the sixth to the fifth and from the fifth to the fourth chamber.
  • the quartz glass body is thermally treated.
  • thermal aftertreatment of the quartz glass body is understood in principle any measure which is known to the person skilled in the art and appears suitable for changing the quartz glass body by the action of temperature in its shape or structure or both.
  • the thermal aftertreatment preferably comprises at least one measure selected from the group consisting of annealing, upsetting, inflation, drawing, welding and a combination of two or more thereof.
  • the thermal aftertreatment preferably takes place without the goal of material removal.
  • the annealing is preferably carried out by heating the quartz glass body in an oven, preferably at a temperature in a range of 900 to 1300 ° C, for example in a range of 900 to 1250 ° C or 1040 to 1300 ° C, more preferably in one range from 1000 to 1050 ° C or from 1200 to 1300 ° C.
  • a temperature of 1300 ° C is not exceeded for a continuous period of more than 1 h, more preferably, a temperature of 1300 ° C is not exceeded during the entire thermal treatment time.
  • the annealing can in principle be carried out at reduced pressure, at atmospheric pressure or at elevated pressure, preferably at reduced pressure, particularly preferably in vacuo.
  • the compression is preferably carried out by heating the quartz glass body, preferably to a temperature of about 2100 ° C, and then forming during a rotary rotary motion, preferably at a rotational speed of about 60 U / min.
  • a quartz glass body in the form of a rod can be reshaped by compression into a cylinder.
  • a quartz glass body can be inflated by blowing a gas into the quartz glass body.
  • a quartz glass body can be reshaped by blowing into a large pipe.
  • the quartz glass body preferably to a temperature of about 2100 ° C, while a rotary rotational movement, preferably at a rotational speed of about 60 U / min, is performed, heated and the interior is purged with a gas, preferably at a defined and regulated Internal pressure up to about 100 mbar.
  • a large pipe is understood to mean a pipe with an outer diameter of at least 500 mm.
  • a quartz glass body can preferably be pulled out.
  • the drawing is preferably carried out by heating the quartz glass body, preferably to a temperature of about 2100 ° C, and then drawing with a controlled drawing speed to the desired outer diameter of the quartz glass body.
  • lamp tubes can be formed by drawing out of quartz glass bodies.
  • the quartz glass body is mechanically aftertreated.
  • mechanical aftertreatment of the quartz glass body is understood in principle any measure which is known to the person skilled in the art and which appears suitable for changing the shape of the quartz glass body by an abrasive measure or for dividing the quartz glass body into several pieces.
  • the mechanical aftertreatment includes at least one measure selected from the group consisting of grinding, drilling, honing, sawing, water jet cutting, laser beam cutting, thawing by sand blasting, milling and a combination of two or more thereof.
  • the quartz glass body with a combination of these measures for example with a combination of a chemical and a thermal aftertreatment or a chemical and a mechanical aftertreatment or a thermal and a mechanical aftertreatment, particularly preferably with a combination of a chemical, a thermal and a treated mechanical aftertreatment.
  • the quartz glass body can each be subjected, independently of one another, to a plurality of the aforementioned measures.
  • the method includes the following method step:
  • the formed hollow body has an inner and an outer shape.
  • Inner form is understood to mean the shape of the inner edge of the hollow body in cross section.
  • the inner and outer shape of the cross section of the hollow body may be the same or different.
  • the inner and outer shapes of the hollow body may be round, elliptical or polygonal in cross-section with three or more corners, for example 4, 5, 6, 7 or 8 corners.
  • the outer shape of the cross section corresponds to the inner shape of the cross section of the hollow body.
  • the hollow body in cross section has a round inner and a round outer shape.
  • the hollow body may differ in the inner and outer shape.
  • the hollow body in cross section has a round outer shape and a polygonal inner shape.
  • the hollow body has a round outer shape and a hexagonal inner shape in cross section.
  • the hollow body has a length in the range of 100 to 10,000 mm, for example from 1000 to 4000 mm, more preferably from 1200 to 2000 mm.
  • the hollow body has a wall thickness in a range of 0.8 to 50 mm, for example in a range of 1 to 40 mm or from 2 to 30 mm or from 3 to 20 mm, particularly preferably in a range of 4 to 10 mm ,
  • the hollow body has an outer diameter of 2.6 to 400 mm, for example in a range of 3.5 to 450 mm, more preferably in a range of 5 to 300 mm.
  • the hollow body preferably has an inner diameter of 1 to 300 mm, for example in a range of 5 to 280 mm or of 10 to 200 mm, particularly preferably in a range of 20 to 100 mm.
  • the hollow body contains one or more openings.
  • the hollow body includes an opening.
  • the hollow body preferably contains an even number of openings, for example 2, 4, 6, 8, 10, 12, 14, 16, 18 or 20 openings.
  • the hollow body contains two openings.
  • the hollow body is a tube. This shape of the hollow body is particularly preferred when the optical fiber includes only one core.
  • the hollow body may contain more than two openings.
  • the openings are preferably in pairs opposite each other in the ends of the quartz glass body. For example, each end of the quartz glass body has 2, 3, 4, 5, 6, 7 or more than 7 openings, more preferably 5, 6 or 7 openings.
  • Preferred shapes are, for example, tubes, twin tubes, ie tubes with two parallel channels, multi-channel bars, ie tubes with more than two parallel channels.
  • the hollow body can in principle be formed in any way known to those skilled in the art.
  • the hollow body is formed by means of a nozzle.
  • the nozzle in the center of its opening contains a device which dissipates the molten glass during molding.
  • a hollow body can be formed from a molten glass.
  • a hollow body can be done by using a nozzle and subsequent aftertreatment.
  • all processes known to the person skilled in the art for producing a hollow body from a solid body for example the swaging of channels, drilling, honing or grinding, are suitable as aftertreatment.
  • As a post-treatment it is preferable to guide the solid body over one or more spikes, whereby a hollow body is formed.
  • the mandrel can be introduced into the solid body to form a hollow body.
  • the hollow body is cooled after forming.
  • the hollow body is after forming at a temperature of less than 500 ° C, for example less than 200 ° C or less than 100 ° C or less than 50 ° C, more preferably at a temperature in the range of 20 to 30 ° C cooled. supercharging
  • step i) it is in principle possible to subject the silicon dioxide granules provided in step i) to one or more pretreatment steps before it is heated in step ii) until a glass melt is obtained.
  • pretreatment steps for example, thermal or mechanical treatment steps into consideration.
  • the silica granules are compacted before heating in step ii.).
  • reaction is meant a reduction in BET surface area and a reduction in pore volume.
  • the silica granules are preferably densified thermally by heating the silica granules or mechanically by applying a pressure to the silica granules, for example, rolling or pressing the silica granules.
  • the silica granules are compacted by heating.
  • the compacting of the silicon dioxide granules is carried out by heating by means of a preheating section connected to the melting furnace.
  • the silica is densified by heating at a temperature in a range of 800 to 1400 ° C, for example, at a temperature in a range of 850 to 1300 ° C, particularly preferably at a temperature in a range of 900 to 1200 ° C.
  • the BET surface area of the silica granule prior to heating in step ii.) Is not reduced to less than 5 m 2 / g, preferably not less than 7 m 2 / g or not less than 10 m 2 / g, more preferably not less than 15 m 2 / g. It is further preferred that the BET surface area of the silica granules prior to heating in step ii.) Is not reduced over the silica granules provided in step i.).
  • the BET surface area of Siliziumdioxidgranulats is reduced to less than 20 m 2 / g, for example less than 15m 2 / g, or less than 10 m 2 / g, or to a range from more than 5 to less than 20 m 2 / g or from 7 to 15 m 2 / g, more preferably in a range from 9 to 12 m 2 / g.
  • the BET surface area of the silica granules is reduced by less than 40 m 2 / g, for example by 1 to 20 m 2 / g or by 2 to 10, prior to heating in step ii.) Over the silica granules provided in step i.) m 2 / g, more preferably around 3 to 8 m 2 / g, wherein the BET surface area after compaction is more than 5 m 2 / g.
  • the compacted silica granules are referred to below as silica granules III.
  • the silicon dioxide granules III preferably have at least one, for example at least two or at least three or at least four, more preferably at least five of the following characteristics:
  • a particle size D 10 in a range of 100 to 300 ⁇ , more preferably in a range of 120 to 200 ⁇ ;
  • D. a particle size D 90 in a range of 300 to 650 ⁇ , more preferably in a range of 400 to 500 ⁇ ;
  • E a bulk density in a range of 0.8 to 1.6 g / cm 3 , more preferably from 1.0 to 1.4 g / cm 3 ;
  • G an amount of carbon of less than 5 ppm, for example less than 4.5 ppm, more preferably less than 4 ppm;
  • ppm and ppb are each based on the total weight of the silica granules III.
  • the silica granule III preferably has the feature combination A./F./G. or A./F./H. or A./G./H. on, particularly preferably the combination of features A./F./G./H.
  • the silica granule III preferably has the feature combination A./F./G. wherein the BET surface area is in a range of 10 to 30 m 2 / g, the tamped density is in a range of 1.15 to 1.35 g / mL, and the carbon content is less than 4 ppm.
  • the silica granules III preferably has the combination of features A./F./H. wherein the BET surface area is in a range of 10 to 30 m 2 / g, the tapped density is in a range of 1.15 to 1.35 g / ml, and the chlorine content is in a range of 1 ppb to 200 ppm.
  • the silica granules III preferably has the feature combination A./G./H. wherein the BET surface area is in a range of 10 to 30 m 2 / g, the carbon content is less than 4 ppm, and the chlorine content is in a range of 1 ppb to 200 ppm.
  • the silica granules III preferably has the feature combination A./F./G./H. wherein the BET surface area is in a range of 10 to 30 m 2 / g, the tamped density is in a range of 1.15 to 1.35 g / ml, the carbon content is less than 4 ppm and the chlorine content in one Range from 1 ppb to 200 ppm.
  • a silicon component other than silicon dioxide is added.
  • the addition of a silicon component other than silicon dioxide is also referred to below as Si doping.
  • the Si doping can be carried out in any method step.
  • the Si doping is preferably carried out in step i) or in step iL).
  • the silicon component other than silicon dioxide can in principle be added in any desired form, for example as a solid, as a liquid, as a gas, in solution or as a dispersion.
  • the silicon dioxide-different silicon component is added as a powder.
  • the silicon dioxide-different silicon component is added as a liquid or as a gas.
  • the silicon dioxide-non-silicon component is preferably added in an amount within a range of 1 to 100,000 ppm, for example, in a range of 10 to 10,000 ppm or 30 to 1,000 ppm or in a range of 50 to 500 ppm, more preferably in one Range of 80 to 200 ppm, more preferably in a range of 200 to 300 ppm, each based on the total weight of silica.
  • the silicon dioxide-different silicon component may be solid, liquid or gaseous. If it is solid, it preferably has an average particle size of up to 10 mm, for example of up to 1000 ⁇ of up to 400 ⁇ or in a range of 1 to 400 ⁇ , for example 2 to 200 ⁇ or 3 to 100 ⁇ , more preferably in a range of 5 to 50 ⁇ .
  • the particle size data are based on the state of the non-silicon dioxide silicon component at room temperature.
  • the silicon component preferably has a purity of at least 99.5 wt .-%, for example of at least 99.8 wt .-% or of at least 99.9 wt .-%, or of at least 99.99 wt .-%, more preferably of at least 99.999 wt .-%, each based on the total weight of the silicon component.
  • the silicon component has an amount of carbon of not more than 10 ppm, for example not more than 50 ppm, more preferably not more than 1 ppm, in each case based on the total weight of the silicon component. This is particularly preferred for silicon used as a silicon component.
  • the silicon component has an amount of impurities selected from the group consisting of Al, Ca, Co, Cr, Cu, Fe, Ge, Hf, K, Li, Mg, Mn, Mo, Na, Nb, Ni, Ti, V, W, Zn, Zr of not more than 250 ppm, for example not more than 150 ppm, more preferably not more than 100 ppm, in each case based on the total weight of the silicon component.
  • This is particularly preferred for silicon used as a silicon component.
  • a silicon component other than silicon dioxide is preferably added.
  • the silica component other than silicon dioxide is added to a silica granule during processing of the silica powder (step II).
  • the silicon dioxide-different silicon component may be added to the silica before, during, or after granulation.
  • the silica may be Si-doped by adding the silicon dioxide-disparate silicon component to the slurry including silica powder.
  • the silicon dioxide-dissimilar silicon component is mixed with silica powder and then slurried in a liquid, or the silicon dioxide-non-silicon component is added to a slurry of silica powder in a liquid and slurried, or the silica powder becomes a slurry or solution of Silicon dioxide various silicon component in a liquid and slurried.
  • the silicon dioxide can be Si-doped by adding the silicon dioxide-different silicon component during granulation. It is possible in principle, different from silicon dioxide
  • the silicon dioxide-different silicon component can be sprayed, for example, through the nozzle together with the slurry in the spray tower.
  • the silicon dioxide-different silicon component may preferably be added in solid form or as a slurry, for example, after the slurry is introduced into the stirred tank.
  • the silica may be Si-doped by adding the silicon dioxide-disparate silicon component after granulation.
  • the silica may be doped to the silica granules II, preferably by adding the non-silica silicon component during the thermal or mechanical treatment of the silica granules I.
  • the silica granules II is doped with the silicon dioxide-different Sihziumkomponente. More preferably, the silicon dioxide-different Sihziumkomponente be added during several of the aforementioned sections, in particular during and after the thermal or mechanical treatment of the silica granules I to the silica granules II.
  • the silicon component which is different from silicon dioxide, may in principle be silicon or any compound containing silicon which is known and has a reducing effect on the person skilled in the art.
  • the silicon component other than silicon dioxide is preferably silicon, a silicon-hydrogen compound, for example a silane, a silicon-oxygen compound, for example silicon monoxide, or a silicon-hydrogen-oxygen compound, for example disiloxane.
  • a silicon-hydrogen compound for example a silane
  • a silicon-oxygen compound for example silicon monoxide
  • silicon-hydrogen-oxygen compound for example disiloxane.
  • Examples of preferred silanes are monosilane, disilane, trisilane, tetrasilane pentasilane, hexasilane heptasilane, higher homologs and isomers of the aforementioned, as well as cyclic silanes such as cyclopentasilane.
  • a silicon component other than silicon dioxide is preferably added.
  • the silicon dioxide-free Sihziumkomponente can be added together with the silica granules directly into the crucible.
  • silicon may be added to the crucible as the silicon dioxide-disassociated silicon component together with the silica granules.
  • the silicon is preferably added as a powder, in particular in the particle size already mentioned for the silicon dioxide-different silicon component.
  • the silica component other than silicon dioxide is added to the silica granules prior to introduction into the crucible.
  • the addition can in principle be carried out at any time after the formation of the granules, for example in the preheating section, before or during the precompression of the silicon dioxide granules II or to the silicon dioxide granules III.
  • a obtained by adding a Sihziumkomponente different from silicon dioxide is a Sihziumkomponente different from silicon dioxide
  • Si-doped granules are referred to below as "Si-doped granules.”
  • [I] has a BET surface area in a range of more than 5 to less than 40 m 2 / g, for example, 10 to 30 m 2 / g, particularly preferably in a range of 15 to 25 m 2 / g;
  • a particle size D 10 in a range of 100 to 300 ⁇ , more preferably in a range of 120 to 200 ⁇ ;
  • a particle size D 90 in a range of 300 to 650 ⁇ , more preferably in a range of 400 to 500 ⁇ ;
  • an amount of carbon of less than 5 ppm, for example less than 4.5 ppm, more preferably less than 4 ppm;
  • [I I] has a residual moisture content of less than 3% by weight, for example in a range from 0.001% by weight to 2% by weight, particularly preferably from 0.01 to 1% by weight;
  • wt .-%, ppm and ppb are each based on the total weight of the Si-doped granules.
  • the melting energy is transferred to the silica granules via a solid surface.
  • a solid surface is understood to mean a surface which is different from the surface of the silica granules and which does not melt or decompose at temperatures to which the silica granules are heated to melt.
  • Suitable materials of the solid surface are, for example, the materials suitable as crucible materials.
  • the solid surface may, in principle, be any surface known to those skilled in the art and suitable for these purposes.
  • the crucible or a separate component other than the crucible may be used as a solid surface.
  • the solid surface can in principle be known to those skilled in the art and suitable for this purpose
  • the solid surface is heated by resistive heating or induction heating.
  • resistive heating or induction heating.
  • the solid surface may be heated electrically or by firing the solid surface with a flame from the outside.
  • the solid surface is heated to a temperature that can transfer an amount of energy sufficient to melt the silica granules to the silica granules and / or partially melted silica granules.
  • the energy input into the sintered crucible is not effected by heating the sinter crucible, or a melt therein, or both, by means of a flame, such as a burner flame directed into the sinter crucible or crucible.
  • a separate component is used as the solid surface, it can be brought into contact with the silicon dioxide granules in any manner, for example by placing the component on the silica granules or by introducing the component between the granules of the silicon dioxide granules or by pushing the component between crucible and silicon dioxide granules or by a combination of two or more of them.
  • the component may be heated before or during or before and during the transfer of the melting energy.
  • the melting energy is transferred via the crucible inside to the silica granules.
  • the crucible is heated to the point where the silica granulate melts.
  • the crucible is preferably heated resistively or inductively. The heat is transferred from the outside to the inside of the crucible.
  • the solid surface of the inner crucible transmits the melting energy to the silica granules.
  • the melting energy is not transferred to the silica granules via a gas space on the silica granules. More preferably, the melting energy is not transferred to the silica granules by firing the silica granules with a flame. Examples of these excluded energy transmission paths are directing one or more burner flames from the top into the crucible, or onto the silica, or both.
  • the above-described method according to the first aspect of the invention relates to the production of a quartz glass body.
  • the quartz glass body preferably has at least one of the following features, for example at least two or at least three or at least four, particularly preferably at least five of the following features:
  • C] has an aluminum content of less than 200 ppb, for example less than 100 ppb, more preferably less than 80 ppb;
  • 3-10 15 / cm 3 more preferably in a range of 0.5-101 1 5 J to 2.0-101 1 5 J / cm 3 J ;
  • a metal content of metals other than aluminum of less than 1 ppm, for example less than 0.5 ppm, more preferably less than 0.1 ppm;
  • G a standard deviation of the OH content of not more than 10%, preferably not more than 5%, based on the OH content A] of the quartz glass body;
  • L has a tungsten content of less than 1000 ppb, for example less than 500 ppb or less than 300 ppb or less than 100 ppb or in a range of from 1 to 500 ppb or from 1 to 300 ppb, more preferably in one range from 1 to 100 ppb;
  • M] has a molybdenum content of less than 1000 ppb, for example less than 500 ppb or less than 300 ppb or less than 100 ppb or in a range of from 1 to 500 ppb or from 1 to 300 ppb, more preferably in one range from 1 to 100 ppb,
  • ppb and ppm are each based on the total weight of the quartz glass body.
  • the quartz glass body preferably 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 quartz glass body. Often, however, the quartz glass body has a content of metals other than aluminum in an amount of at least 1 ppb.
  • metals include sodium, lithium, potassium, magnesium, calcium, strontium, germanium, copper, molybdenum, titanium, iron and chromium. These may be present, for example, as an element, as an ion, or as part of a molecule or an ion or a complex.
  • the quartz glass body may include other ingredients.
  • the quartz glass body contains less than 500 ppm, for example less than 450 ppm, more preferably less than 400 ppm of further constituents, the ppm being in each case based on the total weight of the quartz glass body.
  • Other constituents which may be considered are, for example, carbon, fluorine, iodine, bromine and phosphorus. These may be present, for example, as an element, as an ion, or as part of a molecule or an ion or a complex. Often, however, the quartz glass body has a content of other constituents in an amount of at least 1 ppb.
  • the quartz glass body contains carbon in an amount of less than 5 ppm, for example less than 4.5 ppm, more preferably less than 4 ppm, each based on the total weight of the Quartz glass body.
  • the silica glass body has a content of carbon in an amount of at least 1 ppb.
  • the quartz glass body preferably has a homogeneously distributed OH amount, Cl amount or Al amount.
  • An indicator of the homogeneity of the quartz glass body can be expressed in the standard deviation of OH amount, Cl amount or AI amount.
  • the standard deviation is the measure of the spread of the values of a variable, here the OH quantity, amount of chlorine or amount of aluminum, by their arithmetic mean.
  • the content of the component to be determined in the sample e.g. OH, chlorine or aluminum, determined at at least seven measuring points.
  • the quartz glass body preferably has the combination of features A] / B] / C] or A] / B] / D] or A] / B] / F], more preferably the combination of features A] / B] / C] / D] or A] / B] / C] / F] or A] / B] / D] / F], particularly preferably the combination of features A] / B] / C] / D] / F].
  • the quartz glass body preferably has the combination of features A] / B] / C], wherein the OH content is less than 400 ppm, the chlorine content less than 100 ppm and the aluminum content less than 80 ppb.
  • the quartz glass body preferably has the combination of features A] / B] / D], the OH content is less than 400 ppm, the chlorine content is less than 100 ppm and the ODC content is in a range of 0.1 -10 15 to 3 -10 15 / cm 3 lies.
  • the quartz glass body preferably has the combination of features A] / B] / C] / D], wherein the OH content is less than 400 ppm, the chlorine content less than 100 ppm, the aluminum content less than 80 ppb and the ODC content in one Range from 0, M0 15 to 3-10 15 / cm 3 .
  • a second object of the present invention is a quartz glass body obtainable by the method according to the first aspect of the invention.
  • the quartz glass body preferably has at least one of the following features, for example at least two or at least three or at least four, particularly preferably at least five of the following features:
  • C] has an aluminum content of less than 200 ppb, for example less than 100 ppb, more preferably less than 80 ppb;
  • 3-10 15 / cm 3 more preferably in a range of 0.5-101 1 5 J to 2.0-10 1 1 5 J / cm 3 J ;
  • L has a tungsten content of less than 1000 ppb, for example less than 500 ppb or less than 300 ppb or less than 100 ppb or in a range of from 1 to 500 ppb or from 1 to 300 ppb, more preferably in one range from 1 to 100 ppb;
  • M] has a molybdenum content of less than 1000 ppb, for example less than 500 ppb or less than 300 ppb or less than 100 ppb or in a range of from 1 to 500 ppb or from 1 to 300 ppb, more preferably in one range from 1 to 100 ppb,
  • ppb and ppm are each based on the total weight of the quartz glass body.
  • a third object of the present invention is a method for producing a light guide comprising the following steps:
  • AI deploy All of a hollow body having at least one opening obtainable by a method according to the first subject of the invention including step iv.), Or
  • Quartz glass body is first processed into a hollow body with at least one opening
  • step C pulling the precursor from step B / in the heat to obtain a light guide having one or more cores and a cladding Ml.
  • the quartz glass body provided in step AJ is a hollow body having at least one opening.
  • the quartz glass body provided in step AJ is preferably characterized by the features according to the second aspect of the invention.
  • the quartz glass body provided in step AJ is preferably obtainable by a method according to the first aspect of the invention as step iv.) Forming a hollow body having at least one opening of the quartz glass body.
  • the quartz glass body obtainable in this way has the features according to the second subject of the invention.
  • One or more core rods are introduced through the at least one opening of the quartz glass body (step B /).
  • a core rod in the context of the present invention, an object is referred to, which is intended to be in a shell, for example, a shell Ml, introduced and processed into a light guide.
  • the core rod has a core of quartz glass.
  • the core rod includes a core of quartz glass and a first cladding layer MO surrounding the core.
  • Each core rod has a shape chosen to fit within the quartz glass body.
  • the outer shape of a core rod is in the form of an opening of the quartz glass body.
  • the quartz glass body is a tube and the core rod is a rod with a round cross section.
  • the diameter of the core rod is less than the inner diameter of the hollow body.
  • the diameter of the core rod is 0.1 to 3 mm smaller than the inner diameter of the hollow body, for example 0.3 to 2.5 mm smaller or 0.5 to 2 mm smaller or 0.7 to 1.5 mm smaller, especially preferably 0.8 to 1.2 mm smaller.
  • the ratio of the inside diameter of the quartz glass body to the diameter of the core rod is in the range of 2: 1 to 1,0001: 1, for example in the range of 1.8: 1 to 1.01: 1 or in the range of 1.6: 1 to 1.005: 1 or in the range of 1.4: 1 to 1.01: 1, more preferably in the range of 1.2: 1 to 1.05: 1.
  • a region within the quartz glass body which is not filled by the core rod can be filled with at least one further component, for example a silica powder or a silica granulate.
  • a core rod already located in at least one further quartz glass body to be introduced into a quartz glass body.
  • the 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 can also already be located in two or more further quartz glass bodies, for example in 3 or 4 or 5 or 6 or more further quartz glass bodies.
  • the precursor is pulled hot (step C /).
  • the product thus obtained is a light guide with one or more cores and at least one shell Ml.
  • Preference is given to drawing the precursor at a rate in the range from 1 to 100 m / h, for example at a rate in the range from 2 to 50 m / h or from 3 to 30 m / h.
  • the drawing of the quartz glass body takes place at a speed in the range of 5 to 25 m / h.
  • the drawing is performed in the heat at a temperature of up to 2500 ° C, for example, at a temperature in the range of 1700 to 2400 ° C, more preferably at a temperature in the range of 2100 to 2300 ° C.
  • the precursor is passed through an oven which heats the precursor from outside.
  • the precursor is extended until the desired thickness of the optical fiber is achieved.
  • the precursor is elongated to 1,000 to 6,000,000 times the length, for example, 10,000 to 500,000 times or 30,000 to 200,000 times, each based on the length of the quartz glass body provided in step AI. More preferably, the precursor is elongated to 100,000 to 10,000,000 times the length, for example, 150,000 to 5,800,000 times or 160,000 to 640,000 times or 1,440,000 to 5,760,000 times or 14,400,000 1,440,000 to 2,560,000 times the length, based in each case on the length of the quartz glass body provided in step AI.
  • the diameter of the precursor is reduced by elongation by a factor in a range of 100 to 3,500, for example, in a range of 300 to 3,000 or 400 to 800, or 1,200 to 2,400, or 1,200 to 1,600 in diameter of the quartz glass body provided in step AI.
  • the light guide also referred to as an optical waveguide, may include any material that is suitable for conducting or guiding electromagnetic radiation, in particular light.
  • conducting or guiding radiation is meant the extension of the radiation over the longitudinal extent of the optical fiber without substantial obstruction or attenuation of the intensity of the radiation.
  • the radiation is coupled into the conductor via one end of the light guide.
  • the optical waveguide conducts electromagnetic radiation in a wavelength range from 170 to 5000 nm.
  • the attenuation of the radiation through the optical waveguide in the respective wavelength range is preferably in a range of 0.1 to 10 dB / km.
  • the optical fiber has a transmission rate of up to 50 Tbit / s.
  • the light guide preferably has a curl parameter of more than 6 m.
  • the curl parameter according to the invention the bending radius of a fiber, e.g. a light guide or a sheath Ml, understood that adjusts itself to a freely movable fiber without external force.
  • the light guide is preferably configured bendable. Bendable in the sense of the invention means that the light guide is characterized by a bending radius of 20 mm or less, for example 10 mm or less, particularly preferably less than 5 mm or less. By a bend radius is meant the narrowest radius that can be formed without causing breakage of the light guide and directing radiation without affecting the ability of the light guide.
  • An impairment is present at an attenuation of the transmitted light by a bend of the light guide by more than 0.1 dB.
  • the attenuation is preferably given at a reference wavelength of 1550 nm.
  • the quartz preferably consists of silicon dioxide with less than 1% by weight of other substances, for example less than 0.5% by weight of other substances, more preferably less than 0.3% by weight of other substances, based in each case on the total weight of the quartz. More preferably, the quartz contains at least 99% by weight of silica, based on the total weight of the quartz.
  • the light guide preferably has an elongated shape.
  • the light guide is defined in its shape by its longitudinal extent L and its cross-section Q.
  • the light guide preferably has a round outer wall along its longitudinal extent L. A cross-section Q of the light guide is always determined in a plane which is perpendicular to the outer wall of the light guide.
  • the light guide preferably has a diameter d L in a range of 0.04 to 1.5 mm.
  • the light guide preferably has a length in a range of 1 m to 100 km.
  • the optical fiber includes one or more cores, for example one or two cores or three cores or four cores or five cores or six cores or seven cores or more than seven cores, more preferably a core.
  • more than 90%, for example more than 95%, more preferably more than 98%, of the electromagnetic radiation conducted through the optical fiber is guided in the cores.
  • the material of the cores is preferably selected from the group consisting of glass or quartz glass, or a combination of the two, particularly preferably quartz glass.
  • the cores can be made of the same material or independently consist of different materials. Preferably, all cores made of the same material, more preferably made of quartz glass.
  • Each core has a, preferably round, cross-section Q K and has an elongated shape with the length L K.
  • the cross section Q K of a core is independent of the cross section Q K of each other core.
  • the cross sections Q K of the cores may be the same or different.
  • the cross sections QK of all cores are the same.
  • a cross section Q K of a core is always determined in a plane that is perpendicular to the outer wall of the core or the optical fiber outer wall. If a core is curved in the longitudinal extent, the cross section QK is determined perpendicular to the tangent at a point on the outer wall of this core.
  • the length L K of a core is independent of the length L K of each other core.
  • the lengths L K of the cores may be the same or different.
  • the lengths L K of all cores are the same.
  • Each core preferably has a length L K in a range of 1 m to 100 km.
  • Each core has a diameter d.
  • the diameter d of a core is independent of the diameter d K of each other core.
  • the diameters d K of the cores may be the same or different.
  • the diameters d K of all cores are the same.
  • the diameter d K of each core in a range of 0.1 to 1000 ⁇ , for example from 0.2 to 100 ⁇ or from 0.5 to 50 ⁇ , more preferably from 1 to 30 ⁇ on.
  • Each core has at least one refractive index profile perpendicular to the maximum core extent.
  • 'Refractive index curve' means that the refractive index is constant or changes perpendicular to the maximum core extent.
  • the preferred refractive index profile corresponds to a concentric refractive index profile, for example a concentric refractive index profile, in which a first region with the maximum refractive index is in the center of the core, followed by another region with a lower refractive index.
  • each core has only one refractive index profile over its length L K.
  • the refractive index profile of a core is independent of the refractive index profile of each additional core.
  • the refractive index profiles of the cores may be the same or different.
  • the refractive index profiles of all cores are the same. It is also possible in principle for a core to have a multiplicity of different refractive index profiles.
  • Each refractive index profile perpendicular to the maximum core extent has a maximum refractive index n K.
  • Each refractive index profile perpendicular to the maximum core extent may also have further lower refractive indices.
  • the lowest refractive index of the refractive index profile is preferably not more than 0.5 lower than the maximum refractive index n K of the refractive index profile.
  • the lowest refractive index of the refractive index profile is preferably around 0.0001 to 0.15, for example around 0.0002 to 0.1, particularly preferably around 0.0003 to 0.05, less than the maximum refractive index n K of the refractive index profile.
  • n K refractive index
  • the refractive index n K of a core is regardless of the refractive index n K of each other core.
  • the refractive indexes n K of the cores may be the same or different.
  • the refractive indexes n K of all cores are equal.
  • each core of the optical fiber has a density in a range of 1.9 to 2.5 g / cm 3 , for example in a range of 2.0 to 2.4 g / cm 3 , particularly preferably in a range of 2, 1 to 2.3 g / cm 3 .
  • the cores preferably have 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 a nucleus is independent of the density of each additional nucleus.
  • the densities of the cores can be the same or different. Preferably, the densities of all cores are the same.
  • At least the sheath Ml is made of silicon dioxide and has at least one, preferably several or all of the following features:
  • 3-10 15 / cm 3 more preferably in a range of 0.5-101 1 5 J to 2.0-10 1 1 5 J / cm 3 J ;
  • h) a standard deviation of the OH content of not more than 10%, preferably not more than 5%, based on the OH content a) of the shell Ml;
  • a transformation point Tg in a range from 1150 to 1250 ° C, particularly preferably in a range from 1180 to 1220 ° C,
  • ppb and ppm are each based on the total weight of the shell Ml.
  • the sheath has a refractive index homogeneity of less than 1 - 10 "4 on the refractive index homogeneity is the maximum deviation of the refractive index at each point of a sample, such as a sheath.
  • the shell Ml preferably 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 shell Ml. Often, however, the shell M1 has a content of metals other than aluminum in an amount of at least 1 ppb.
  • metals include sodium, lithium, potassium, magnesium, calcium, strontium, germanium, copper, molybdenum, titanium, iron and chromium. These may be present, for example, as an element, as an ion, or as part of a molecule or an ion or a complex.
  • the shell Ml may include other ingredients.
  • the shell M1 contains less than 500 ppm, for example less than 450 ppm, more preferably less than 400 ppm of further constituents, the ppm being in each case based on the total weight of the shell M1.
  • Other constituents which may be considered are, for example, carbon, fluorine, iodine, bromine and phosphorus. These may be present, for example, as an element, as an ion, or as part of a molecule or an ion or a complex. Often, however, the shell M1 has a content of further constituents in an amount of at least 1 ppb.
  • the shell M1 preferably contains carbon at less than 5 ppm, for example less than 4 ppm or less than 3 ppm, more preferably less than 2 ppm, based in each case on the total weight of the shell M1. Often, however, the shell M1 has a content of carbon in an amount of at least 1 ppb.
  • the shell Ml has a homogeneously distributed OH amount, Cl amount or Al amount.
  • the shell Ml has a weight fraction of at least 80 wt .-%. for example, at least 85 wt .-%, particularly preferably at least 90 wt .-%, each based on the total weight of the shell Ml and the cores on.
  • the shell Ml has a weight fraction of at least 80 wt .-%. for example, at least 85 wt .-%, particularly preferably at least 90 wt .-%, each based on the total weight of the shell Ml, the cores and lying between the shell Ml and the cores other shells, on.
  • the shell Ml has a weight fraction of at least 80 wt .-%. for example, at least 85 wt .-%, particularly preferably at least 90 wt .-%, each based on the total weight of the optical fiber on.
  • the shell Ml has a density in a range of 2.1 to 2.3 g / cm 3 , more preferably in a range of 2.18 to 2.22 g / cm 3 .
  • Another aspect relates to a light guide obtainable by a method including the following steps:
  • step C pulling the precursor from step B / in the heat to obtain a light guide having one or more cores and a cladding Ml.
  • the steps AI, B / and C / are preferably characterized by the features described in the context of the third object.
  • the light guide is preferably characterized by the features described in the context of the third article.
  • a fourth subject of the present invention relates to a method for producing a luminous means, comprising the following steps:
  • a hollow body is provided.
  • the hollow body provided in step (i) includes at least one opening, for example one opening or two openings or three openings or four openings, particularly preferably one opening or two openings.
  • a hollow body having at least one opening obtainable by a method according to the first subject of the invention including step iv.), Is provided (step (i-1)).
  • the hollow body has the features described in the context of the first or second object of the invention.
  • a hollow body which is obtainable from a quartz glass body according to the second subject of the invention (step (i-2)).
  • a quartz glass body according to the second subject of the invention for processing a quartz glass body according to the second subject of the invention to form a hollow body, several possibilities come into consideration.
  • a hollow body having two openings can be formed analogously to step iv.) Of the first article of the invention from a quartz glass body.
  • the processing of the quartz glass body to a hollow body with an opening can in principle by means of all the
  • the resulting hollow body preferably has the features described in the context of the first and second objects of the invention.
  • the hollow body is made of a material containing silicon dioxide, preferably in an amount in a range of 98 to 100 wt .-%, for example in a range of 99.9 to 100 wt .-%, particularly preferably 100 wt .-% , in each case based on the total weight of the hollow body.
  • the material from which the hollow body is made preferably has at least one, preferably several, for example two, or preferably all of the following features:
  • a silicon dioxide content of preferably more than 95% by weight, for example more than
  • HC2. a density in a range of 2.1 to 2.3 g / cm 3 , more preferably in a range of 2.18 to 2.22 g / cm 3 ;
  • HC3. a light transmittance at least one wavelength in the visible range of 350 to
  • HK4 an OH content of less than 500 ppm, for example less than 400 ppm, more preferably less than 300 ppm;
  • HK5. a chlorine content of less than 200 ppm, preferably less than 100 ppm, for example less than 80 ppm, more preferably less than 60 ppm;
  • HK6 an aluminum content of less than 200 ppb, for example less than 100 ppb, more preferably less than 80 ppb;
  • HK7 a carbon content of less than 5 ppm, for example less than 4.5 ppm, more preferably less than 4 ppm;
  • HK11 HK11. a transformation point Tg in a range of 1150 to 1250 ° C, more preferably in a range of 1180 to 1220 ° C;
  • the hollow body from step (i) is filled with a gas, preferably with two electrodes, before it is filled with a gas.
  • the electrodes are connected to an electrical power supply.
  • the electrodes are connected to a lamp base.
  • the material of the electrodes is preferably selected from the group of metals. In principle, any metal may be selected as the electrode material that will not be oxidized, corroded, melted or otherwise impaired as an electrode in its shape or conductivity during the operating conditions of the lamp.
  • the electrode material is preferably selected from the group consisting of iron, molybdenum, copper, tungsten, rhenium, gold and platinum or at least two thereof, with tungsten, molybdenum or rhenium being preferred.
  • the hollow body provided in step (i) and optionally equipped with electrodes in step (ii) is filled with a gas.
  • the filling can be carried out in any manner known to those skilled in the art and suitable for filling.
  • a gas is passed through the at least one opening in the hollow body.
  • the hollow body is evacuated prior to filling with a gas, preferably to a pressure of less than 2 mbar.
  • a gas preferably to a pressure of less than 2 mbar.
  • the hollow body is filled with the gas.
  • These steps can be repeated to minimize contamination with air, especially with oxygen.
  • these steps are repeated at least twice, for example at least three times or at least four times, more preferably at least five times until the amount of impurities with other gases such as air, in particular oxygen, is sufficiently low. This procedure is particularly preferred for filling hollow bodies with an opening.
  • a hollow body contains two or more openings
  • the hollow body is preferably filled through one of the openings.
  • the air located in the hollow body before filling with the gas can escape through the at least one further opening.
  • the gas is passed through the hollow body until the amount of contamination with other gases such as air, in particular oxygen is sufficiently low.
  • the hollow body is filled with an inert gas or a combination of two or more inert gases, for example with nitrogen, helium, neon, argon, krypton, xenon or a combination of two or more thereof, more preferably with krypton, xenon or a combination of Nitrogen and argon.
  • inert gas or a combination of two or more inert gases for example with nitrogen, helium, neon, argon, krypton, xenon or a combination of two or more thereof, more preferably with krypton, xenon or a combination of Nitrogen and argon.
  • Further preferred fillers for hollow bodies of lamps are deuterium and mercury.
  • the hollow body is closed after filling with a gas, so that the gas in the other
  • Closure can be done by melting or attaching a closure.
  • Suitable closures are, for example, quartz glass closures, which are for example melted out onto the hollow body, or
  • the lighting means according to the fourth aspect of the invention includes a hollow body and optionally electrodes.
  • the illuminant preferably has at least one, for example at least two or at least three or at least four, more preferably at least five of the following features:
  • a volume in a range of 0.1 cm 3 to 10 m 3 for example in a range of 0.3 cm 3 to 8 m 3 , particularly preferably in a range of 0.5 cm 3 to 5 m 3 ;
  • a radiation angle in a range of 2 to 360 ° for example in a range of 10 to 360 °, particularly preferably in a range of 30 to 360 °;
  • a radiation of light in a wavelength range of 145 to 4000 nm, for example in a range of 150 to 450 nm, or of 800 to 4000 nm, particularly preferably in a range of 160 to 280 nm;
  • v. a power in a range of 1 mW to 100 kW, more preferably in a range of 1 kW to 100 kW, or in a range of 1 to 100 watts.
  • Another aspect relates to a lighting device obtainable by a method comprising the following steps:
  • steps (i), (ii) and (iii) are preferably characterized by the features described in the context of the fourth subject.
  • the lighting means is preferably characterized by the features described in the context of the fourth subject.
  • a fifth subject of the present invention relates to a method for producing a shaped article comprising the following steps:
  • the quartz glass body provided in step (1) is a quartz glass body according to the second aspect of the invention or obtainable by a method according to the first aspect of the invention.
  • the provided quartz glass body has the features of the first or second object of the invention.
  • the quartz glass body is formed into a shaped body as described in the first, third and fourth articles of the invention. More preferably, the shaped body can be formed by means of techniques known to glass blowers.
  • the shaped body can assume any shape which can be shaped from quartz glass.
  • Preferred shaped bodies are, for example:
  • Hollow body with at least one opening such as round-bottomed flasks and stand-up flasks,
  • Tubes and hollow cylinders for example reaction tubes, profile tubes, rectangular chambers,
  • Rods, rods and blocks for example in round or square, symmetrical or asymmetrical
  • bent parts for example convex or concave surfaces and plates, bent bars and tubes.
  • the shaped body can be treated after molding.
  • all methods described in connection with the first subject of the invention which are suitable for reworking the quartz glass body come into consideration.
  • the shaped body can be mechanically processed, for example by drilling, honing, external grinding, crushing or drawing.
  • Another aspect relates to a molded article obtainable by a method including the following steps:
  • the steps (1) and (2) are preferably characterized by the features described in the context of the fifth subject.
  • a sixth subject of the present invention is the use of a standing sintered crucible for producing products comprising quartz glass selected from the group consisting of a light guide, a light source, a lamp and a shaped body, wherein in the standing sintered crucible a silicon dioxide granulate having the following properties is processed:
  • FIG. 5 shows a flow chart (method for producing a luminous means)
  • Fig. 6 is a schematic representation of a standing crucible in an oven
  • FIG. 7 schematic representation of a spray tower
  • Fig. 8 is a schematic representation of a cross section of a light guide
  • Fig. 9 is a schematic representation of a plan view of a light guide
  • FIG. 1 shows a flow chart containing the steps 101 to 104 of a method 100 for producing a quartz glass body according to the present invention.
  • a silica granulate is provided in a first step 101.
  • a glass melt is formed from the silica granules in a second step 102.
  • molds are used for melting, which can be introduced into an oven and removed from it again.
  • Such forms are often made of graphite. They result in a negative mold of the casting.
  • the silica granules are filled into the mold, first melted in the mold in the third step 103.
  • the quartz glass body is formed in the same mold by cooling the melt.
  • This is then removed from the mold and processed further, for example in an optional step 104.
  • This procedure is discontinuous.
  • the formation of the melt is preferably carried out under reduced pressure, in particular under vacuum. It is also possible to temporarily charge the furnace with a reducing, hydrogen-containing atmosphere during step 103.
  • a quartz glass body is formed.
  • the formation of the quartz glass body is preferably carried out here by removing at least a portion of the glass melt from the crucible and cooling. The removal takes place preferably through a nozzle at the lower end of the crucible.
  • the shape of the quartz glass body can be determined by the design of the nozzle. For example, massive bodies can be obtained. Hollow bodies are obtained, for example, if a mandrel is additionally provided in the nozzle.
  • This exemplary method for the production of quartz glass bodies, and in particular step 103 is preferably carried out continuously. From a solid quartz glass body can be formed in an optional step 104, a hollow body.
  • FIG. 2 shows a flow chart containing the steps 201, 202 and 203 of a method 200 for producing a silicon dioxide granulate I.
  • a silicon dioxide powder is provided.
  • a silica powder is preferably obtained from a synthetic process in which a silicon-containing material, for example, a siloxane, a silicon alkoxide or a silicon halide is converted to silica in a pyrogenic process.
  • the silica powder is mixed with a liquid, preferably water, to obtain a slurry.
  • the silica contained in the slurry is transferred to a silica granule.
  • the granulation takes place by means of spray granulation. For this, the slurry is sprayed through a nozzle into a spray tower and dried to form granules, with the contact surface between the nozzle and the slurry including a glass or plastic.
  • FIG. 3 shows a flow chart containing the steps 301, 302, 303 and 304 of a method 300 for producing a silica granulate II.
  • the steps 301, 302 and 303 run in accordance with the steps 201, 202 and 203 according to FIG in step 303, silica granules I obtained are processed into a silica granulate II. This is preferably done by heating the silica granules I in a chlorine-containing atmosphere.
  • FIG. 4 shows a flowchart containing the steps 401, 403 and 404 as well as the optional step 402 of a method for producing a light guide.
  • a quartz glass body is provided, preferably a quartz glass body produced according to method 100.
  • Such a quartz glass body may be a solid or a hollow quartz glass body.
  • a hollow quartz glass body corresponding to step 104 is formed in a second step 402.
  • one or more than one core rod is introduced into the hollow quartz glass body.
  • the quartz glass body provided with one or more than one core rod is processed to form a light guide.
  • the quartz glass body provided with one or more than one core rod is preferably heated to soften and elongated until the desired optical fiber thickness is reached.
  • FIG. 5 shows a flowchart containing the steps 501, 503 and 504 as well as the optional step 502 of a method for producing a luminous means.
  • a quartz glass body is provided, preferably a quartz glass body produced according to method 100.
  • Such a quartz glass body may be a solid or a hollow quartz glass body.
  • the quartz glass body provided in step 501 is solid, it is optionally formed into a hollow quartz glass body according to step 104 in a second step 502.
  • the hollow quartz glass body is equipped with electrodes.
  • a solid quartz glass body is initially provided (501), shaped into a hollow body (502), equipped with electrodes (503) and filled with a gas (504).
  • FIG. 6 shows a preferred embodiment of a furnace 900 with a vertical crucible.
  • the crucible 901 is arranged standing in the furnace 900.
  • the crucible 901 has a footprint 902, a solids inlet 903 and a nozzle 904 as an outlet.
  • the crucible 901 is filled via the inlet 903 with silica granules 905.
  • silicon dioxide granules 905 are present in the upper region of the crucible, while a glass melt 906 is present in the lower region of the crucible.
  • the crucible can be heated by heating elements 907, which are arranged on the outside of the crucible wall 910.
  • the furnace also has an insulation layer 909 between the heating elements 907 and the furnace outer wall 908.
  • the space between the insulating layer 909 and the crucible wall 910 may be filled with a gas, and has a gas inlet 91 1 and a gas outlet 912 thereto. Through the nozzle 904, a quartz glass body 913 can be removed from the crucible 901.
  • FIG. 7 shows a preferred embodiment of a spray tower 1100 for spray granulating silica.
  • the spray tower 1 100 comprises a feed 1 101, through which a pressurized slurry containing silica powder and a liquid is supplied to the spray tower.
  • a nozzle 1102 At the end of the line is a nozzle 1102, through which the slurry is finely distributed in the spray tower is introduced.
  • the nozzle is oriented obliquely upwards so that the slurry is sprayed as fine droplets in the direction of the nozzle alignment in the spray tower and then falls down in a bow driven by gravity.
  • the spray tower 1100 also comprises a sighting device 1104 and a screening device 1 105.
  • the sighting device 1 104 particles are sucked off, which fall below a defined particle size, and removed by the discharge 1 106. According to the particle size of the particles to be sucked, the suction power of the sighting device 1104 can be regulated.
  • the sieve device 1105 particles above a defined particle size are screened off and removed through the discharge 1107.
  • the sieve permeability of the sieve device 1105 can be selected according to the particle size of the particles to be sieved. The remaining particles, a silica granule of the desired particle size, are withdrawn through the outlet 1 108.
  • FIG. 8 schematically shows a cross section through an optical waveguide 1200 according to the invention, which has a core 1201 and a sheath M1 1202 surrounding the core 1201.
  • FIG. 9 schematically shows a plan view of an optical waveguide 1300 which has a cable-like structure.
  • a part of the core 1301 without cladding M1 1302 was shown.
  • typical is the cladding of the core 1301 over its entire length with the shell Ml 1302.
  • FIG. 10 shows a flow chart containing steps 1601 and 1602 of a method for producing a shaped body.
  • a quartz grass body is provided, preferably a quartz glass body produced according to method 100.
  • Such a quartz glass body may be a solid or a hollow quartz glass body
  • REPORTED SHEET (RULE 91) ISA / EP be. From a solid quartz glass body provided in step 1601, moldings are formed in a second step 1602.
  • the fictive temperature is determined by means of Raman spectroscopy on the basis of the Raman scattering intensity at about 606 cm -1
  • the procedure and evaluation is described in the article by Pfleiderer et al., The UV-induced 210 nm absorption band in fused silica with different thermal history and stoichiometry "; Journal of Non-Crystalline Solids, Vol. 159 (1993), pages 145-153.
  • the OH content of the glass is determined by infrared spectroscopy.
  • the method "Optical Determinations of OH in Fused Silica” (JAP 37, 3991 (1966)) specified by DM Dodd & DM Fraser is used instead of the device specified therein, an FTIR spectrometer (Fourier transform infrared spectrometer, current
  • the analysis of the spectra can in principle be carried out both at the absorption band at about 3670 cm-1 and at the absorption band at about 7200 cm-1.
  • the selection of the band used is carried out according to the rule in that the transmission loss due to the OH absorption is between 10 and 90%.
  • Oxygen Deficiency Centers ODCs
  • ODC (I) absorption at 165 nm is determined by means of a transmission measurement on a 1-2 mm thick sample using a vacuum UV spectrometer, model VUVAS 2000, from McPherson, Inc. (USA).
  • N defect concentration [1 / cm 3 ]
  • the digestion vessel is opened and thermally further treated at 100 ° C until the solution is completely evaporated. Meanwhile, the digestion tank is filled 3x with 15ml ultrapure water. Add 1ml HN0 3 to the digestion vessel to dissolve any separated contaminants and make up to 15ml with ultrapure water. Thus the measuring solution is ready. d-2) Measurement ICP-MS / ICP-OES
  • OES or MS depends on the expected element concentration. Typical determination limits for the MS are lppb, for the OES lOppb (in each case based on the weighted sample amount).
  • the determination of the element concentration with the measuring instruments is carried out in accordance with the equipment manufacturers (ICP-MS: Agilent 7500ce, ICP-OES: Perkin Elmer 7300 DV) and using certified reference liquids for calibration.
  • the element concentration in the solution (15 ml) determined by the devices is then converted to the original sample weight (2 g).
  • a well-defined volume of the liquid is weighed into a measuring vessel which is inert with respect to the liquid and its constituents, the empty weight and the weight of the filled vessel being measured.
  • the density results from the difference between the two weight measurements divided by the volume of liquid introduced.
  • the sample is rinsed several times with ultrapure water, then dried.
  • 2 g of the sample are weighed into a nickel crucible and covered with 10 g Na 2 C0 3 and 0.5 g ZnO.
  • the crucible is closed with a Ni cover and annealed at 1000 ° C for one hour.
  • the nickel crucible is filled with water and boiled until the melt cake has completely dissolved.
  • the solution is transferred to a 200 ml volumetric flask and made up to 200 ml with ultrapure water.
  • the determination of the fluoride content of the measurement solution is carried out by means of an ion-sensitive (fluoride) electrode, suitable for the expected concentration range, and display device according to the manufacturer, here a fluoride ion-selective electrode and reference electrode F-500 with R503 / D on a pMX 3000 / pH / ION of the companyticianlich-Technische Werkmaschinen GmbH.
  • an ion-sensitive (fluoride) electrode suitable for the expected concentration range
  • display device here a fluoride ion-selective electrode and reference electrode F-500 with R503 / D on a pMX 3000 / pH / ION of the companyticianlich-Technische Werkmaschinen GmbH.
  • the measuring solution has a pH in the range between 5 and 7.
  • the determination of the chloride content of the measuring solution is carried out by means of ion-sensitive (chloride) electrode, suitable for the expected concentration range, and display device according to the manufacturer's instructions here a type Cl-500 electrode and reference electrode type R-503 / D on a pMX 3000 / pH / ION the company Scientific-Technical Workshops GmbH.
  • chloride ion-sensitive
  • Chlorine contents ⁇ 50 ppm up to 0.1 ppm in quartz glass are determined by neutron activation analysis (NAA).
  • NAA neutron activation analysis
  • 3 drill bits each with a diameter of 3 mm and a length of 1 cm each are drawn from the quartz glass body to be examined.
  • quartz glass samples The transmission of quartz glass samples is determined using commercial grid or FTIR spectrometers from Perkin Elmer (Lambda 900 [190-3000nm] or System 2000 [1000-5000nm]). The choice depends on the required measuring range.
  • the specimens are polished in a plane-parallel manner (surface roughness RMS ⁇ 0.5 nm) and the surface after polishing is freed of all residues by ultrasonic treatment.
  • the sample thickness is 1cm. In the case of expected high transmission loss due to contamination, doping, etc., a thicker or thinner sample can also be selected to remain within the instrument's measuring range.
  • a sample thickness (measuring length) is selected in which, due to the passage of light through the sample, only slight artifacts occur and at the same time a sufficiently detectable effect is measured.
  • the sample is placed in front of an Ulbrich sphere in the beam path.
  • the refractive index distribution of tubes / rods can be determined by means of a York Technology Ltd. Preform Profiler PI 02 or PI 04.
  • the rod is placed horizontally in the measuring chamber and this sealed. Thereafter, the measuring chamber is filled up with an immersion oil which has a refractive index at the test wavelength of 633nm, which is very similar to the outermost glass layer at 633nm.
  • the laser beam then passes through the measuring chamber. Behind the measuring chamber (in beam direction) a detector is mounted, which determines the deflection angle (jet entry in opposite to jet exit from the measuring chamber).
  • the diametric refractive index profile can be reconstructed by means of an inverse Abel transformation.
  • the refractive index of a sample is analogous to the above description with the York Technology Ltd. Preform Profiler PI 04 determined. In the case of isotropic samples, only one value is obtained even when measuring the refractive index distribution, the refractive index.
  • the quantitative determination of the surface carbon content of silica granules and silica powder is carried out on a carbon analyzer RC612 from Leco Corporation, USA, by the complete oxidation of all surface carbon contaminants (except SiC) with oxygen to carbon dioxide.
  • a carbon analyzer RC612 from Leco Corporation, USA
  • 4.0 g of a sample are weighed and introduced into the carbon analyzer in a quartz glass boat.
  • the sample is lapped with pure oxygen and heated to 900 ° C for 180 seconds.
  • the resulting C0 2 is detected by the infrared detector of the carbon analyzer. Under these measurement conditions, the detection limit is ⁇ 1 ppm (ppm by weight) carbon.
  • a quartz glass boat suitable for this analysis on the above-mentioned carbon analyzer is available as a consumable for LECO analyzer having LECO number 781-335 im
  • Such a boat has the dimensions of width / length / height of about 25mm / 60mm / 15mm.
  • the quartz glass boat is filled halfway up with sample material.
  • Silica powder can be achieved so a weight of 1.0 g of sample material.
  • the lower one Detection limit is then ⁇ 1 ppm by weight carbon.
  • a weight of 4 g of a silica granules is reached (average particle size in the range of 100 to 500 ⁇ ).
  • the lower detection limit is then about 0.1 ppm by weight of carbon.
  • the Curl parameter (also called: “Fiber Curl") is determined in accordance with DIN EN 60793-1-34: 2007-01 (German version of the standard IEC 60793-1-34: 2006) in the
  • the damping is determined in accordance with DIN EN 60793-1-40: 2001 (German version of IEC 60793-1- 40: 2001). Measured according to the method described in Annex ("cut-back method") in a
  • the slurry is adjusted with demineralized water (Direct-Q 3UV, Millipore, water quality: 18.2 MQcm) to a concentration of 30% solids by weight. Subsequently, the demineralized water (Direct-Q 3UV, Millipore, water quality: 18.2 MQcm) to a concentration of 30% solids by weight. Subsequently, the demineralized water (Direct-Q 3UV, Millipore, water quality: 18.2 MQcm) to a concentration of 30% solids by weight. Subsequently, the demineralized water (Direct-Q 3UV, Millipore, water quality: 18.2 MQcm) to a concentration of 30% solids by weight. Subsequently, the demineralized water (Direct-Q 3UV, Millipore, water quality: 18.2 MQcm) to a concentration of 30% solids by weight. Subsequently, the demineralized water (Direct-Q 3UV, Millipore, water quality: 18.2 MQcm)
  • Viscosity was measured on a MCR102 of the company Anton pair. For this purpose, the viscosity is measured at 5 revolutions / minute (rpm). It is measured at a temperature of 23 ° C and an air pressure of 1013 hPa. o. Thixotropy
  • the slurry is adjusted to a concentration of 30% solids by weight with demineralized water (Direct-Q 3UV, Millipore, water grade: 18.2 MQcm). Subsequently, the thixotropy is determined with a MCR102 of the Fa. Anton pair with a cone-plate arrangement. For this purpose, the viscosity is measured at 5 and at 50 revolutions / minute (rpm). The quotient of the first and the second value gives the thixotropic index. The measurement is measured at a temperature of 23 ° C. p. Zeta potential of the slurry
  • zeta potential measuring cell Flow Cell, Beckman Coulter
  • demineralized water Direct-Q 3UV, Millipore, water quality: 18.2 MQcm
  • the pH is brought to 7 by adding FINO 3 -
  • the pH is varied by adding HNO 3 solutions having the concentrations of 0.1 mol / L and 1 mol / L and a NaOH solution having the concentration of 0.1 mol / L.
  • the isoelectric point is the pH at which the zeta potential is zero. It is measured at a temperature of 23 ° C. r. pH of the slurry
  • the pH of the slurry is determined by means of a WTW 3210 from the Scientific-Technical Committee.
  • the electrode used is the pH 3210 Set 3 from WTW. It is measured at a temperature of 23 ° C.
  • the bulk density is determined according to the standard DIN ISO 697: 1984-01 with a SMG 697 from Powtec.
  • the bulk material (silica powder or granules) does not form lumps. u. Tamped density (granulate)
  • the tamped density is measured according to DIN ISO 787: 1995-10. v. Determination of the pore size distribution
  • the pore size distribution is determined according to DIN 66133 (with a surface tension of 480 mN / m and a contact angle of 140 °).
  • Pascal 400 from Porotec is used.
  • pore sizes from 3.7 nm to 100 ⁇ Pascal 140 is used by the company. Porotec.
  • the sample is subjected to a pressure treatment before the measurement.
  • a Manual Hydraulic Press (Order No. 15011 from Specac Ltd., River House, 97 Cray Avenue, Orpington, Kent BR5 4HE, U.K.) is used.
  • sample material 250 mg are weighed into a "pellet die" with a 13 mm inner diameter from Specac Ltd. and loaded with 1 t as indicated.This load is held for 5 s and readjusted if necessary, then the sample is decompressed and allowed to stand for 4 h 105 ⁇ 2 ° C dried in a convection oven.
  • the weight of the sample in the Penetrometer Type 10 is 0.001 g and is accurate for a good
  • Hg volume to fill the penetrometer ranges between 20% to 40% of the total Hg volume. Subsequently, the penetrometer is slowly evacuated to 50 ⁇ Hg and for 5 min at this
  • the primary particle size is measured by means of a scanning electron microscope (SEM) model Zeiss Ultra 55.
  • SEM scanning electron microscope
  • the sample is suspended in demineralized water (Direct-Q 3UV, Millipore, water quality: 18.2 MQcm) to obtain an extremely dilute suspension.
  • the suspension is treated with the ultrasonic probe (UW 2070, Bandelin electronic, 70 W, 20 kHz) for 1 min and then applied to a carbon adhesive pad.
  • UW 2070 Ultrasonic probe
  • the mean particle size in suspension is measured by means of a Mastersizer 2000, available from Malvern Instruments Ltd., UK, according to their instruction manual using the laser diffraction method.
  • the sample is suspended in demineralized water (Direct-Q 3UV, Millipore, water quality: 18.2 MQcm) to obtain 20 mL suspension at a concentration of 1 g / L.
  • the suspension is treated with the ultrasonic probe (UW 2070, Bandelin electronic, 70 W, 20 kHz) for 1 min. y. Particle size and grain size of the solid
  • the particle size and grain size of the solid are measured by means of a Camsizers XT available from Retsch Technology GmbH, Germany according to their instruction manual.
  • the software gives the D10,
  • Quantachrome available), which operates according to the SMART method ("Sorption Method with Adaptive Dosing Rate") .
  • the reference materials are Alumina SARM-13 and SARM-214, available from Quantachrome, and the tare weight of the measuring cells used (clean and dry)
  • the type of measuring cell is chosen so that the supplied sample material and the filling rod fill the measuring cell as much as possible and the dead space is reduced to a minimum 10-20 m 2 / g
  • the measuring cells are fixed in the baking stations of the BET measuring device (without filling rod) and evacuated to ⁇ 200 mbar The speed of the evacuation is set so that no M aterial escapes from the measuring cell.
  • Nitrogen gas (N2 4.0) is measured.
  • the measuring cell is evacuated and is using a nitrogen bath cooled down to 77 K
  • the dead space is measured by helium gas (He 4.6). It will be evacuated again.
  • a multipoint analysis with at least 5 measuring points is carried out.
  • Adsorptive N2 4.0 is used.
  • the specific surface area is given in m2 / g. za. Viscosity of vitreous bodies
  • the viscosity of the glass is measured by means of the beam bending viscometer type 401 - TA Instruments with the manufacturer software WinTA (currently version 9.0) under Windows 10 according to the standard DIN ISO 7884-4: 1998-02.
  • the span between the supports is 45mm.
  • Sample sticks with a rectangular cross section are cut from areas of homogenous material (top and bottom of the sample with fine grinding of at least 1000 grains).
  • RA 0.15 ⁇ .
  • the dew point is determined by means of a Taupunk mirror hygrometer with the designation "Optidew” from Michell Instruments GmbH, D-61381 Friedrichsdorf
  • Dew point mirror hygrometer is located at a distance of 100 cm from the gas outlet of the furnace.
  • the measuring device with the measuring cell is connected via a T-piece and a hose (Swagelok PFA, outer diameter: 6 mm) to the gas outlet of the furnace in a gas-conducting manner.
  • An overpressure of 10 ⁇ 2 mbar is applied to the measuring cell.
  • the flow of gas through the measuring cell is 1-2 standard liters / min.
  • the measuring cell is located in a room with a temperature of 25 ° C, 30% relative humidity and a mean air pressure of 1013 hPa. Zc. Residual moisture (water content)
  • the determination of the residual moisture of a sample of silica granules is carried out with the aid of a moisture analyzer HX204 from Mettler Toledo.
  • the device works on the principle of thermogravimetry.
  • the HX204 is equipped with a halogen heater as heating element.
  • the drying temperature is 220 ° C.
  • the starting weight of the sample is 10 g ⁇ 10%.
  • the measuring method "Standard" is selected and drying is continued until the change in weight does not exceed 1 mg / 140 s
  • Residual moisture results from the difference between the start weight of the sample and the final weight of the sample, divided by the start weight of the sample.
  • the aerosol formed from the atomization of a siloxane with air (A) is introduced under pressure into a flame formed by ignition of a mixture of oxygen-enriched air (B) and hydrogen. Furthermore, an air stream (C) surrounding the flame is introduced and the process mixture subsequently cooled with process gas. The product is deposited on a filter.
  • the process parameters are given in Table 1 and the characteristics of the resulting products in
  • OMCTS octamethylcyclotetrasiloxane
  • SiC silicon tetrachloride
  • a particle stream of silica powder is introduced over the top of a standing column. Water vapor at a temperature (A) and air is supplied via the foot of the column. The column is held by an internal heater to a temperature (B) at the column head and a second temperature (C) at the column base. After leaving the column (residence time (D)), the silica powder has in particular the properties shown in Table 6. The process parameters are given in Table 5.
  • the silica powders obtained in Examples C-1 and C-2 each have a low one
  • Example C-2 Chlorine content, as well as in suspension to a moderate pH.
  • the carbon content of Example C-2 is higher than that of C-1.
  • a particle stream of silica powder is introduced over the top of a standing column. About the foot of the column, a neutralizing agent and air is supplied. The column is held by an internal heater to a temperature (B) at the column head and a second temperature (C) at the column base. After leaving the column (residence time (D)), the silica powder has in particular the properties shown in Table 8. The process parameters are given in Table 7. Table 7
  • silica granules from silica powder
  • Installation height distance between nozzle and lowest point of the spray tower interior in the direction of the S chwerkraftverktors.
  • C 006011 graphite powder, max. Particle size: 75 ⁇ , high purity (available from Goodfellow GmbH, Bad Nauheim (Germany);
  • the granules are all porous, show a uniform and spherical shape (all microscopic examination). They are not prone to caking or sticking.
  • Sihziumdioxidgranulat is first treated in a rotary kiln, optionally at a temperature Tl with oxygen or nitrogen (see Table 11). Subsequently, the Sihziumdioxidgranulat is treated in cocurrent with a chlorine-containing component, wherein the temperature is increased to a temperature T2.
  • the process parameters are given in Table 11, the properties of the resulting treated granules in Table 12.
  • the throughput was chosen as the controlled variable. This means that during operation the mass flow emerging from the rotary kiln is weighed and then the rotational speed and / or the inclination of the rotary kiln are adjusted accordingly. For example, an increase in throughput can be achieved by a) increasing the rotational speed, or b) increasing the inclination of the rotary tube from the horizontal, or a combination of a) and b).
  • the throughput was chosen as the control variable. This means that during operation the mass flow emerging from the rotary kiln is weighed and then the rotational speed and / or the inclination of the rotary kiln are adjusted accordingly. For example, an increase in throughput can be achieved by a) increasing the rotational speed, or b) increasing the inclination of the rotary tube from the horizontal, or a combination of a) and b).
  • the granules after the cleaning step show a significantly reduced carbon content (such as low-carbon granules, e.g., Fl-1) in the case of Fl-2, F2-1 and F3-2.
  • Fl-2, Fl-5, F2-1 and F3-2 show a significantly lower content of alkaline earth metals. SiC formation was not observed.
  • Sihziumdioxidgranulat is subjected to a temperature upstream of the melting furnace upstream and with this via a further intermediate chamber material leading connected antechamber in the form of a rotary kiln.
  • the rotary kiln is characterized by a rising in the conveying direction temperature profile.
  • a further treated silicon dioxide granulate was obtained.
  • Example G-4-2 was dispensed with a heat treatment during mixing in the rotary kiln.
  • the process parameters are given in Table 13, the properties of the resulting treated granules in Table 14.
  • the throughput was chosen as the controlled variable. This means that during operation the mass flow emerging from the rotary kiln is weighed and then the rotational speed and / or the inclination of the rotary kiln are adjusted accordingly. For example, an increase in throughput can be achieved by a) increasing the rotational speed, or b) increasing the inclination of the rotary tube from the horizontal, or a combination of a) and b).
  • G3-1 and G3-2 have a significantly lower alkaline earth metal content compared to before (F3-1 and F3-2, respectively) as a result of this treatment.
  • Silica granules according to line 2 of Table 15 are used to make a quartz glass tube in a vertical crucible drawing process.
  • the construction of the standing furnace for example H5-1 including a stationary crucible is shown schematically in FIG.
  • the silica granules are added via the solids feed and the interior of the crucible is purged with a gas mixture.
  • a glass melt forms, on which a bulk cone of silicon dioxide granules sits.
  • molten glass is taken from the molten glass via a die (possibly with a dome) and drawn down vertically as a pipe string.
  • the throughput of the system is obtained.
  • the flow rate can be adjusted to the desired size.
  • the process parameters are given in Table 15, the properties of the quartz glass bodies formed in Table 16.
  • the liquid used for the aforementioned treatment is characterized before and after treatment by the properties given in Table 17.

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Abstract

L'invention concerne un procédé pour produire un corps en verre de silice, ledit procédé comprenant les étapes suivantes consistant à : i.) préparer un granulat de dioxyde de silicium, ii.) former un bain de verre fondu à partir du granulat de dioxyde de silicium dans un four et iii.) former un corps en verre de silice à partir d'au moins une partie du bain de verre fondu, le four contenant un creuset fritté debout. L'invention concerne également un corps en verre de silice pouvant être obtenu au moyen de ce procédé. L'invention concerne en outre un guide d'ondes optiques, un moyen d'éclairage et un corps moulé pouvant être obtenus respectivement par traitement ultérieur du corps en verre de silice.
EP16815838.4A 2015-12-18 2016-12-16 Fabrication d'un corps en verre de silice dans un creuset fritté debout Withdrawn EP3390300A1 (fr)

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TWI813534B (zh) 2015-12-18 2023-09-01 德商何瑞斯廓格拉斯公司 利用露點監測在熔融烘箱中製備石英玻璃體
CN108698892A (zh) 2015-12-18 2018-10-23 贺利氏石英玻璃有限两合公司 从二氧化硅颗粒制备石英玻璃体
TW201731782A (zh) 2015-12-18 2017-09-16 何瑞斯廓格拉斯公司 在多腔式爐中製備石英玻璃體
WO2017103125A1 (fr) 2015-12-18 2017-06-22 Heraeus Quarzglas Gmbh & Co. Kg Granulation par atomisation de dioxyde de silicium lors de la fabrication de verre de silice
TWI812586B (zh) 2015-12-18 2023-08-21 德商何瑞斯廓格拉斯公司 石英玻璃體、其製備方法與應用、及用於控制烘箱出口處之露點
KR20180095619A (ko) 2015-12-18 2018-08-27 헤래우스 크바르츠글라스 게엠베하 ＆ 컴파니 케이지 실리카 유리 제조 동안 규소 함량의 증가
CN108698887B (zh) 2015-12-18 2022-01-21 贺利氏石英玻璃有限两合公司 由均质石英玻璃制得的玻璃纤维和预成形品
TWI733723B (zh) 2015-12-18 2021-07-21 德商何瑞斯廓格拉斯公司 不透明石英玻璃體的製備
CN111495383B (zh) * 2020-04-22 2023-03-10 陕西延长石油（集团）有限责任公司 一种己二醇与氨气制备己二胺的方法及催化剂
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CN108779014A (zh) 2018-11-09
TW201731781A (zh) 2017-09-16
US20190031554A1 (en) 2019-01-31
KR20180095617A (ko) 2018-08-27
JP2019502632A (ja) 2019-01-31

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