MXPA00007575A

MXPA00007575A - Sinter materials and their processes of manufacture and uses, dispersions of silica granules and their uses, as well as uses of silica granules

Info

Publication number: MXPA00007575A
Application number: MXPA/A/2000/007575A
Authority: MX
Inventors: Mangold Helmut; Meyer Jurgen; Schneider Gerrit
Original assignee: Degussahüls Aktiengesellschaft*
Priority date: 1999-08-03
Filing date: 2000-08-02
Publication date: 2002-07-25

Abstract

Sintered materials, especially glasses, made by molding or compacting and optional purification and sintering, are made from granulates (IA, IB) made by compacting pyrogenic silica as described in DE 19601415-A1. The tamped density is (IA) 150-800, (IB) 220-700 g/l, average particle/grain size (IA) 150-800, (IB) 25-120 mu m and BET surface area (IA) 10-500, (IB) 40-400 m<2>/g. (IB) has a pore volume 0.5-2.5 ml/g, no pores finer than 5 nm, only meso- and macropores, and pH 3.6-8.5. Independent claims are also included for (a) dispersions containing 10-85 or 1-75 wt.%granulate (I) is various media;(b) the production of sintered materials,especially glasses, from pyrogenic silica.

Description

SINTERED MATERIALS FIELD OF THE INVENTION The invention relates to sintered materials (especially sintered glass), a process for the manufacture of sintered materials made of pyrogenic manufactured silicon dioxide, which is worked by means of a compression step carried out subsequently to obtain silicon dioxide granules. , as well as the use of corresponding silicon dioxide granules for the manufacture of sintered materials. BACKGROUND OF THE INVENTION It is known to react solutions of silicon oxide by the action of an acid to gel bodies which are dried and subjected to a sintering step (DE 30 01 792 C2). Such processes are generally referred to as the "gel solution process". The glazes produced in this way must be used in accordance with the invention for the manufacture of preformed bodies for further processing into light-conducting fibers. It is also known, nanoscaligo powder, as for example pyrogenically generated silicon dioxide, used for the manufacture of sintered glass bodies (US-A 5, 379, 364). Silica gel acid is used here as the starting material with a surface area of less than 100m2 / g and a dispersion with a solid material fraction of more than 30% by weight is produced. This gel dispersion after filling in a mold decreases the pH value. The gel body is then dried to a green body, this is subjected to a purification step and then sintered. In contrast to the process described in DE 30 01 792 C2, it is a process of the type such as US-A-5,379,364 called "solution-gel-coloration procedure". Known processes in which molded glass bodies are produced with the exclusive use of silicon alkoxide solutions corresponding to the "gel-solution process" have the disadvantage that the gel bodies during drying and during the sintering process shrink strongly. This shrinkage can be 60 and over 80% of the original measurements of the gel body. As a result of this strong shrinkage of drying and sintering bubbles and cracks of the finest within the body of glass produced, which negatively influence the qualities of the product. If by these bubbles and cracks the optical transmission of such glass molded bodies strongly decreases and optical homogeneity is damaged. Because of the resulting high optical damping, such glass molded bodies can not be used for the manufacture of high-value light-conducting fibers. In addition they have the known procedures "gel solution" the disadvantage, that the gel bodies have extremely fine pores and capillaries. The liquid contained in the gel bodies exerts a strong hydrodynamic pressure during the drying process in the capillaries, which in the drying process of the gel body also leads to ultrafine cracks, protrusions or bubbles. The procedures known as "solution-colloidal gel" have, on the contrary, the advantage compared to those of "solution-gel", a somewhat reduced shrinkage of drying and sintering. The cause for this decreased shrinkage is that used with pyrogenicly generated silicon dioxide, which allows a high degree of filling of this oxide within the dispersions, which are used for the manufacture of sintered glass. In spite of this they also present the procedures of gejL colloidal solution a strong shrinkage of drying and sintering. The shrinkage still occurs in a magnitude of 35 to 50% of the gel body stockings before drying. A further improvement of the optical properties of the sintered glass produced in this way establishes an increase in the degree of filling of the silicon dioxide powder within the technological manufacturing process with powder. These high degrees of filling that are needed can not however be achieved with the pyrogenically generated silicon dioxide powders, with low compression.

This has the consequence that the pre-molded body manufactured therefrom for the manufacture of light-conducting fibers has a worse optical transparency than would be desirable for the finally valuable product. The "solution-gel-colloidal" processes cause, in contrast to the "gel-solution" process, a somewhat better pore and capillary structure in the gel body. In the drying of the gel bodies produced by the colloidal solution gel process, fewer internal cracks, projections or bubbles than in the drying of gel bodies produced by the gel-solution process are produced for this reason, despite this If desired, the capital and porous structure should be further improved. The task of developing sintered materials with an improved capillary and porous structure is presented. The object of the invention is sintered materials, especially sintered glass, which by means of a molding or compression process, in the case of a purification, and possibly a successive sintering process, and which are characterized in that they are either manufactured pyrogenic generated silicon dioxide, which by means of a subsequent compression step according to DE 196 01 414 A1 are compressed into granules and have a density of 150 g / l to 800 g / l, preferably 200 to 500 g / l, a size of Grain grain from 10 to 800 μm and a BET surface from 10 to 500 m2 / g, preferably from 20 to 130 m2 / g, or used for their manufacture granulates according to DE 196 01 415 Al as base silicon dioxide generated pyrogenic with the following physical-guímicos data: average grain diameter : 25 to 120 μm, BET surface: 40 to 400 m2 / g, pore volume: 0.5 to 2.5 ml / g, pore distribution: none pore less 5nm, only meso and macro pores, pH value: 3.6 to 8.5, density stamping 220 to 700g / l. Examples for manufacturing processes of this type are the generation of an aqueous granulate dispersion, the filling of this dispersion in a mold and the gelation of the dispersion to form a gel body. This can be made by drying and sintering to high quality glass moldings. Another example for such a process is the dry pressing of silicon dioxide granules manufactured pyrogenically highly compressed to a solid molded body and subsequent sintering of this molded body to sintered glass. DESCRIPTION OF THE INVENTION The subject of the invention are the sintered materials mentioned above, which are characterized in that said granules are processed to sintered material by a process of the following type a) Manufacture of a dispersion made from 10% by weight up to 85% by weight weight preferably 25% to 70% by weight of solid fraction of the granulate and a polar or non-polar organic or non-organic liquid, preferably water, ethanol, or aliphatic hydrocarbons, subsequent filling of the dispersion in a mold or coating of surfaces with that dispersion , initiation of gelation of the dispersion and drying of the gel body or the coating in the form of gel body. The green body presented after the drying process or the coating in the form of a green body can, if necessary, be purified with gaseous substances such as chlorine or thionyl chloride at temperatures of 700 to 1000 ° C and then, if necessary, by means of of a sintering step at a temperature of 1000 to 1800 ° C, preferably 1100 to 1600 ° C, sintering in such a way that the sintered body produced or the sintered surface is completely sintered in a dense manner or is still partially porous; b) to take the corresponding granules without auxiliary take-up of a liquid into a mold or to put the granulate on a surface, if necessary then perform an additional compression step within which the molded body or the coating layer is pressed or compressed under high external mechanical pressure (pressing pressure in Example 1 and 120 MPa) in the presence of atmospheric pressure or at a reduced pressure, press and then compress. The molded body resulting from the pressing process or the compressed coating can be purified, if necessary, with a gaseous substance such as chlorine or thionyl chloride, at temperatures of 700 to 1000 ° C and by a sintering step a a temperature between 1000 to 1800 ° C, preferably 1100 at 1600 ° C sintered in such a way that the sintered body produced or the sintered surface is sintered fully dense or is still partially porous. c) the placement of corresponding granules in molding bodies or surfaces by a thermal and a highly energetic process, such as, for example, flame spraying, plasma coating, laser sintering or microwave sintering, within which a solid or A solid coating will be produced and the resulting sintered body or the resulting sintered surface will be fully sintered or still partially porous. Also objects of the invention are materials or glasses, which are characterized in that, in the manufacture of the materials or glasses, the granulates according to the invention by means of thermal, electrical, or electromagnetic energy, for example, by means of burners, suppliers of plasma or microwave radiation either before heating or in connection therewith are taken to a desired mold and then sintered, and the resulting sintered body or the resulting sintered surface is completely sintered or still present pores or partially or completely melts, before heating or in connection with it, putting it in a mold that is desired and solidifying in that mold or used to cover another material, such as glass or meta, and if necessary, follow it elaborating. The subject of the invention are glasses, which are characterized in that the sintering to a transparent glass body or a transparent glass layer is carried out within the range in the glass from 108 to 1012 dPas, preferably between 1010 and 1011 dPas. The object of the invention is glasses which are characterized in that the glasses are at least water resistant according to hydrolytic class 2, preferably water-resistant according to hydrolytically class 1. Glasses are characterized in that they are characterized in that the properties of the corresponding finer, sintered or melted powder particles coincide with the properties of a glass with identical chemical composition, which by means of a conventional melting process has been produced without the use of the aforementioned granulate. The manufacture of such sintered glass clearly requires lower sintering temperatures compared to the melting temperature, which is necessary for the manufacture of a glass with identical composition within a conventional melting process. In addition, the invention relates to dispersions, which are used "for the manufacture of sintered materials, and which are characterized by the following properties: a) Solid fractions of the granulates according to the invention from 10% by weight to 85% by weight , preferably from 25 to 70% by weight within a dispersion with a polar or non-polar organic or non-organic liquid, preferably water, ethanol, or aliphatic hydrocarbons, or b) solid fractions of the granulates according to the invention of 10 to 85% by weight, preferably 25 to 70% by weight, within an aqueous dispersion, having a pH value between pH = 1 and 6 or between pH = 8 and 12 and with organic acids, such as for example formic, citric or trichloroacetic acid, with inorganic acids such as, for example, nitric, phosphoric, or sulfuric acid, with organic bases such as for example triethyl amine, pyridine or tetramethyl ammonium hydroxide, and with inorganic bases such as, for example, potassium oxide, calcium hydroxide, or ammonium hydroxide, adjust in their pH value; or c) solid fractions of the granulates according to the invention from 10 to 85% by weight, preferably from 25 to 70% by weight, within an aqueous dispersion, having a pH value between pH = 6 and between pH = 8 and 12 adjusting the pH value with acids or organic or inorganic bases and also contain addition materials, which allow fractions of high granules and a better dispersion, such as for example polymers or ionic compounds, which contribute to an esteric or ionic stabilization of the dispersion and decrease the application of solid fractions or delay and / or prevent a gelation before time. d) solid fractions of the granulates according to the invention from 10 to 85% by weight, preferably 25 to 70% by weight, within an aqueous dispersion, having a pH value between pH = 6 and between pH = 8 and 12 adjusting the pH value with organic or inorganic acids or bases and also containing addition materials, which allow an improvement in the dispersion, gelling, drying, and purification as well as sintering of the sintered material subsequently, such as for example metal oxides of the formula Me ( 0R) x, where Me represents a metal, preferably silicon, - R an alkyl group "x" the valence of the metal ion. Such dispersions can also be combined with other organic binding materials such as for example polymers or resins, which likewise offer an improved product quality of the sintered material such as, for example, improved pore freedom or optical transmission or a process facilitated with higher grades of filling and less shrinkage during drying / sintering, or e) solid fractions of the granulates according to the invention from 10 to 85% by weight, preferably 25 to 70% by weight in an aqueous dispersion, which has a pH value between pH = 6 and between pH = 8 and 12, the pH value being adjusted with organic or inorganic acids or bases and also contains addition materials, such as metal oxides of the formula Me (OR) x, preferably tetraethoxysilane. To such dispersions, oxides generated pyrogenically in a weight fraction between 1 and 65% by weight, preferably 1 and 50% by weight, such as for example silicon dioxide, titanium dioxide, aluminum oxide, zirconium dioxide and mixed oxides can be added. the corresponding metals. the corresponding pyrogenic oxides can be added to the dispersion both uncompressed and also after performing a precompression of another type, as described in DE 196 01 415 A1. f) solid fractions of the granulates according to the invention of 1 to 75% by weight, preferably 5 to 50% by weight, within an aqueous dispersion, which has a pH value between pH = 6 and between pH = 8 and 12, the pH value being adjusted with organic or inorganic acids or bases and also contains addition materials, which allow an improvement in the dispersion, gelation, drying, and purification as well as sintering of the subsequently sintered material, such as for example metal oxides of the formula Me (OR) x, preferably tetraethoxysilane. Such dispersions can be combined according to the invention with salts or oxides of a metalloid and / or metal. The object of the invention is the use of the granulates according to the invention made of pyrogenically generated silicon dioxide for the manufacture of sintered materials, especially sintered glass, characterized in that the granulates used have the following properties: a) after a step of compression according to DE 196 01 415 Al having a printing density of 150 g / 1 up to 800 g / 1, preferably 200 to 4500 g / 1 a grain size of granulate from 10 to 800 μm and a BET surface area of 10 at 500 m3 / g, preferably 20 to 130 mz / g, or b) after a compression step in accordance with DE 196 01 415 A1 based on pyrogenically prepared silicon dioxide have the following physicochemical data; average grain diameter: 25 to 120 μm, BET surface 40 to 400 piVg, - pore volume: 0.5 to 2.5 ml / g, pore distribution, 1 no pore less than 5nm, only meso- and macropores, pH value; 3.6 up to 8.5, stamping density; 220 to 700 g / 1. The present invention relates to processes for the manufacture of sintered materials, especially sintered glasses, which are characterized in that pyrogenically produced silicon dioxide is compressed in a known manner and / or granulated, transformed into a dispersion, the dispersion gels, it dries, the green body produced is purified as well as subsequently sintered. The gelling can be carried out in different ways such as, for example, gel moldings, gel fibers, gelled layers or coatings on a glass or metal substrate. These bodies or layers of gel can after drying and purification be sintered in such a way as to produce a solid molded body or a solid coating, and the resulting sintered body or the sintered surface is completely hermetically or densely sintered or is still porous. The invention relates to processes for the manufacture of sintered materials, especially sintered glasses, which are characterized in that pyrogenically prepared silicon dioxide is granulated and / or compressed by known means, and then: a) the granulates without additional capture of a liquid is taken to a mold or applied to a surface, and then in any case another compression step is performed, within which the mold body or the layer under a strong mechanical pressure (pressure of for example 1 to 120 MPa) in the presence of atmospheric pressure or a decreased pressure are pressed and compressed further. The molded body produced after the pressing process or the compressed coating can, if appropriate, be purified with a gaseous substance, such as chlorine or thionyl chloride at temperatures of 700 to 1000 ° C and by a step of sintering at a temperature of 1000 to 1800 ° C, preferably from 1100 ° to 1600 ° C sintered in such a way that the sintered body or the sintered surfaces are completely dense in their sintering or are still porous; b) granulates are carried to a molded body or surfaces by high energy procedures either thermal or otherwise such as for example flame spraying, plasma coating or microwave sintering, within which a molded body or a solid coating is produced and the sintered body or the resulting sintered surfaces are fully sintered densely or are still partially porous; c) the granulates made of thermal, electrical or electromagnetic energy, for example by burners, plasma applicators or microwave radiation, either before heating or in connection with it, they are taken to a mold and then sintered; body or the sintered coating thus produced is fully dense in its sintering or is still partially porous, but the granulates are partially or completely fused, this before heating or in connection therewith is carried to whatever form is desired in that form or mold it is allowed to solidify or is used to coat another material such as glass or metal, and if necessary, it is continued with its elaboration. The object of the invention is the use of sintered materials, especially sintered glass or glass for the. manufacture of molded glass bodies such as: pre-molded bodies - glass conductor fibers (called "overcladding tubes" or "core rods") optical lenses, optical grids, glass mass (called Crucibles) electrical insulators, thermal insulators, magnetic insulators , prisms, devices or apparatus for the chemical or pharmaceutical industry, ingots, molding bodies for the electronics industry, glass bars as a raw material for further processing, shaped bodies with high demands on the accuracy of the shape after the process. The object of the invention is the application of sintered materials, especially sintered glass or glass, for the coating of other materials such as metal, synthetic material or glass, with layers of materials. The object of the invention is the application of sintered materials, especially sintered glass or glass, for the manufacture of materials in the form of fibers or fibers. The object of the invention is the application of granulates for the manufacture of glasses, especially sintered glass, ceramics, bonding materials, within which the granulates act as a reinforcing filler material, as a reinforcing filler material in metals, glasses, polymers, elastomers, lacquers or liquids. The object of the invention is the use of dispersions for the manufacture of glasses, especially sintered glass, as well as for polishing semiconductor materials or electrical connection circuits. In a preferred form of the invention, a pyrogenicly manufactured silicon dioxide can be used which, in a known manner according to DE 196 01 414 A1, is granulated or preferably compressed for the manufacture of sintered materials. The silicon dioxide compressed or preferably granulated in this manner can be a pyrogenicly manufactured oxide with a BET surface area of 10 to 500 m2 / g, with a stamping density of 150 to 800 g / 1 and a granulated grain size of 10 to 800 μm. Mixtures of compressed and non-compressed silicon dioxide can also be used according to the invention. The compressed pyrogenic silicon dioxide can be mixed in a dispersion with salts or oxides of a metalloid and / or metal. Mixtures of silicon dioxides manufactured pyrogenically compressed and non-compressed can also be prepared within the dispersion. Under the concepts "pyrogenicly generated silicic acid" pyrogenic silicon dioxide "they must be understood below as nanoscaligo powders of fine particles, which are prepared by the reaction of silicon tetrachloride in the form of a gas, such as for example methyl trichlorosilane or silicon tetrachloride in a high temperature flame,. where the flame is fed with hydrogen and oxygen and its water vapor if produced can be conducted. The term "granulate" is to be understood below as a pyrogenicly generated silicon dioxide powder which is compressed strongly by the compression method described in DE 19601 415 Al or analogously to that process. Under the concept of dispersion, it should be understood that this is an extremely uniform distribution of compressed or non-compressed pyrogenic silicon dioxide, that is granulated in a liquid such as water, ethanol or an organic solvent. Under the term "sintered material" or sintered glasses, materials or glasses are to be understood, which are produced from powders in fine particles by means of a technological process and powder formation and then a sintering step. The term "sintering process" should be understood as meaning processes in which powders in fine particles by the application of heat are transformed into solid moldings or solid layers, which already only partially possess or no longer possess them. Under the concept 'body of gel' must be understood bodies, that after the gelation, this is after solidifying they appear in humid or soaked state and possess a skeleton of particles united one with the other, that this full of liquid. Under the concept "green body" should be understood body of dry gel, in which the liquid was removed from the skeleton of the particles and which have a high porosity. l The advantages of the sintered materials according to the invention, especially sintered glass, are the improved optical transparency of the glasses, the improved optical homogeneity, the improved chemical or mechanical resistance of the layers on substrate materials as well as the chemical loading capacity or The mechanics of molded bodies or fibers compared to materials or glasses, which are manufactured by the hitherto usual methods of "sol-gel", colloidal sol-gel "or by means of a conventional melt process. The following advantages: With the highly compressed powders a higher degree of filling of the dispersions is allowed to occur.The higher degree of filling of the dispersion causes in the materials thus produced better properties of the product, such as better transparency, by a number Reduced bubble entrances and fewer cracks Simultaneously produced by the application The use of highly compressed powders is also a technical advantage of the process. Thus, for example, dispersions with the aid of easily understood powder are allowed to produce, the technical advantages of the process in the use of highly filled dispersions also consist of sintered materials in the reduction of the shrinkage of the green or shrinkage bodies when sintering. The use of such powders causes other technical advantages for the process. This can be due to the influence of the fine particles of the powder used or the porosity of the green body, reducing the sintering temperature both, as would not be possible with the use of other powders or another manufacturing process without loss of quality for the future material. Sintered The use according to the invention of highly compressed powder further leads to a better possibility of processing within the manufacturing process of the powder technology by an improved capillary or porous structure of the gel body. By applying such high-understanding powders, it is possible to simplify the drying of the gel body and improve the quality of the future product. The sintered materials described, especially sintered glass or glass, can be used commercially for the manufacture of glass molded bodies such as for example preformed bodies of light-conducting fiber (so-called "overcladding Tubes" or "Core Rods") optical lenses, optical grids, masses of glass called "Crucibles") electrical insulators, thermal insulators, magnetic insulators, prisms, parts or appliances for the chemical or pharmaceutical industry, ingots, moldings for the electronics industry, glass bars as a raw material for further processing, moldings with high demands on the accuracy of the shape after the process. In addition such sintered materials can be used commercially for the coating of other materials such as metal, synthetic material, or glass with sintered glass or glass layers. It is possible to use the sintered materials according to the invention, such as sintered glass or glass also for the manufacture of materials in the form of fibers or fibers. The granulates described can be used for the manufacture of glasses, especially sintered glasses, ceramics, or bonding materials, within which the granulates act as reinforcing filler material as well as serve as reinforcing fillers in metals, glasses, polymers, elastomers, lacquers or liquids. The dispersions according to the invention can be used for the manufacture of glasses, in particular glass, as well as for polishing semiconductor materials or electrical connection circuits. Example 1 A pyrogally generated silicon dioxide with a BET surface area of 90 m2 / g and an agitation density of 35 g / 1 and a printing density of 59 g / l is compressed according to DE 196 014 14 Al to a granulate. The compressed silicon dioxide has a BET surface area of 90 m2 / g and a printing density of 246 g / 1. Then 180 ml of distilled water are placed in a container and the pH is adjusted to 11 with a 30% solution of KOH before the beginning of the granulation. Then, by means of a solvent with a dissolver disc, 120 g is put and always this quantity of the granulate in the water; the number of revolutions of the solvent is approximately 1000 r. p m.After the granulate has been fully worked in the dispersion, the dispersion is treated with another 30 minutes approximately. After that time the pre-dispersed dispersion is dispersed for 120 minutes with an Ultra-Turrax Rotor-Stator aggregate dispersion at 10000 r.p.m. and during that dispersion it cools. After the dispersion step a dispersion is obtained, which after a resting time of 24 hours has a viscosity in the range of 200 to 250 mPas / s at 50 r.p. m, (measured with a Brookfield vicosymmetry with cuff 2). The content of solid material is 405 in 'weight in reference to the dispersion. Example 2 (comparison example). A pyrogenically generated silicon dioxide with a BET surface area of 90 m2 / g and a printing density of 59 g / l is used without compression. For this, 180 ml of distilled water is placed in a container and adjusted to a pH value of 11 with a solution of 30% KOH before the beginning of the powder addition. Subsequently, by means of a dissolver with a dissolving disk, the uncompressed powder is added to the water, the number of revolutions of the dissolver is 10000 rpm. Of the uncompressed silicon dioxide, however, only 96 g are allowed to stir without the dispersion becoming too viscous. This corresponds to a mass fraction of 35% by weight within the dispersion, compared to 120 g according to example 1 of the invention, this is clearly a lower amount. After the pole has been completely made in the suspension, it is still dispersed another 30 minutes with the dissolver. After that time the pre-dispersed dispersion is dispersed for 120 minutes with an Ultra-Turrax Rotor-Stator aggregate dispersion at 10000 r.p.m. and during that dispersion it cools. After the dispersion step a dispersion is obtained, which after a resting time of 24 hours has a viscosity in the range of 330 to 460 mPas / s at 50 r.p. m, (measured with a Brookfield vicosymmetry with sleeve 2). Compared to Example 1 with a solid fraction of 405 by weight of granulate in the dispersion only 355 by weight in a dispersion are left of the uncompressed powder. Furthermore, the viscosity of the dispersion is clearly higher, than according to Example 1, which makes the sol-gel colloidal process difficult. Example 3 (according to the invention). A pyrogenically generated silicon dioxide with a BET surface area of 50 m2 / g and a printing density of 130 g / l is compressed to a granulate according to DE 196 014 14 Al. The compressed silicon dioxide has a BET surface area of 50 m2 / g. a stamping density of 365 g / 1. 180 ml of water are then placed in a container and adjusted to a pH value of 11 with a 30% by weight KOH solution before the start of the powder introduction. Then by means of a dissolver quantities of 220 g of the granulate are put in the water; the number of revolutions of the dissolver is lOOOr.p.m. After the granulate has been completely processed in the dispersion, the dispersion is dispersed for another 30 minutes with the dissolver. Then dispersion by means of an Ultra-Turrax - • Rotor-Stator aggregate dispersion is dispersed at 10000r.p.m. for 120 minutes and during the dispersion it is cooled. The dispersion obtained has a solid fraction of about 55% by weight. Example 4 (Comparison example) A pyrogenically generated silicon dioxide has a BET surface area of 50 m2 / g and a stamping density of 130 g / l. This non-compressed powder is used to compare with Example 3. For this, 180 ml of water is placed in a container and adjusted to a pH value 11 before the start of the introduction of the powder with a 30% by weight KOH solution. It is then added to the powder with a dissolver disk dissolver, ei. number of revolutions of 1000r / min. However, uncompressed powder can only be added 180g without the dispersion becoming too viscous. This corresponds to a mass fraction of 50% by weight in the dispersion. Compared to the 220 g according to Example 3 this is clearly lower. After the powder has been made in the dispersion the suspension is still dispersed by the dissolver for another 30 minutes. Then the dispersion by means of an Ultra-Turrax-Rotor-Stator aggregate dispersion is dispersed at 10000r.p.m. for 120 minutes and during the dispersion it is cooled. Compared to Example 3, in which there is a solid content of 55% by weight with the uncompressed powder, only a dispersion with a solid content of approximately 50% by weight is allowed to be produced. Example 5 (according to the invention) A pyrogenically generated silicon dioxide with a BET surface area of 90 m2 / g and an agitation density of 35 g / 1 and a printing density of 59 g / 1 is compressed to a granulate according to DE 196 014 14 Al. Compressed silicon dioxide has a BET surface area of 90 m2 / g and a printing density of 246 g / 1. 17.2 g of this powder are stirred with 27 ml of distilled water and 2.57 ml of tetramethylammonium hydroxide in a homogeneous dispersion as described in Examples 1-4. After the termination of the dispersion, 1 ml of ethyl acetate is added and the dispersion is immediately poured into a mold. After 12 minutes the gelled dispersion is present, and the gel body produced is removed after one hour of the mold and Dry at room temperature for 6 days. By drying a microporous green body is produced. This is sintered by a vacuum zone sintering at 1400 ° C for 4 hours. A sintered glass body is produced without bubbles or visible pores. Example 6 (according to the invention) A pyrogenically generated silicon dioxide with a BET surface area of 300 m2 / g and an agitation density of 30 g / 1 and a stamping density of 50 g / 1 is compressed to a granulate according to DE 196 014 14 Al. The compressed silicon dioxide has a BET surface area of 300 m2 / g and a printing density of 289 g / 1. 11.2 g of this powder are stirred with 27 ml of distilled water and 2.57 ml of tetramethylammonium hydroxide in a homogeneous dispersion as described in examples 1-4. After the termination of the dispersion, 1 ml of acetic acid ethyl ester is added and the dispersion is immediately poured into a mold. After 20 minutes the gelled dispersion is present, and the gel body produced is removed after one hour from the mold and Dry at room temperature for 7 days. By drying a microporous green body is produced. This by means of a sintering of vacuum zone at 1400 ° C is sintered 4 hours. A sintered glass body is produced without bubbles or visible pores. Example 7 (according to the invention) A pyrogenically generated silicon dioxide with a BET surface area of 200 m2 / g a stirring density of 35 g / 1 and a printing density of 50 g / 1 is compressed to a granulate according to the invention. DE 196 014 14 Al. The silicon dioxide compressed has a BET surface area of 200 m2 / g and a printing density of 219 g / 1. 18 g of this powder are dried 24 hours in a drying apparatus at 105 ° C. After the dried powder is pressed to a molded body with a diameter of 10mm. The pressing is done in a steel mold with a pressing pressure of 51.2 Mpa and a pressing time of 90 seconds. The molded body is sintered in a sintering furnace in vacuum zones at 1500 ° C for 5 hours. A sintered glass body is produced without bubbles or visible pores. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims

Having described the invention as above, property is claimed as contained in the following: CLAIMS 1. Sintered materials, especially sintered glass, which are produced by means of a modeling or compression process, if necessary a subsequent purification and, if necessary, a subsequent sintering process, and are characterized in that, a) it is used for manufacture of pyrogenicly produced silicon dioxide, which by means of a subsequent process step according to DE 196 01 415 A1 are compressed to granules and have a printing dty of 150 g / 1 to 800 g / 1, granulate grain size from 10 to 800 μm and a BET surface from 10 to 500 m2 / gb). For its manufacture granulates are used according to the 196 01 415 Al based on pyrogenic prepared silicon dioxide with the following physical-chemical data: average grain diameter: 25 to 120 μm, BET surface: 40 to 400 m2 / g, pore volume: 0.5 to 2.5 ml / g, pore distribution: no pore less than 5 nm, only meso and macro pores, pH value: 3.6 to 8.5, printing dty 220 to 700 g / 1. 2. - Sintered materials according to claim 1, characterized in that the granulates mentioned in claim 1 are made to sintered material by a process of the following type a) manufacture of a dispersion made from 10% by weight up to 85% by weight, preferably 25% 70% by weight of solid fraction of the granulate and a polar or non-polar organic or non-organic liquid, preferably water, ethanol, or aliphatic hydrocarbons, subsequent filling of the dispersion in a mold or coating of surfaces with that dispersion, initiation of the gelation of the dispersion and drying of the body gel or the coating in gel body form, the green body presented after the drying process or the coating in the form of a green body, can possibly be purified with gaseous substances such as chlorine or chloride of thionyl at temperatures of 700 to 1000 ° C and then, if necessary, by means of a sintering step at a temperature of and 1000 to 1800 ° C in such a way that the sintered body produced or the sintered surface is completely sintered in a d manner or is still partially porous; b) bringing the corresponding granules without auxiliary take-up of a liquid to a mold or placing the granulate on a surface, if necessary then carrying out an additional compression step within which the molded body or the coating layer is pressed or compressed under a high external mechanical pressure in the presence of atmospheric pressure or at a reduced pressure is pressed and then compressed, the molded body resulting from the pressing process or the compressed coating can be purified, if necessary, with a gaseous substance such as chlorine or thionyl chloride, at temperatures of 700 to 1000 ° C and for a sintering step to a temperature between 1000 to 1800 ° C in such a way that the sintered body produced or the sintered surface is sintered fully d or is still partially porous, c) the application of corresponding granules in molding bodies or surfaces by a thermal process and other highly energetic, such as for example flame spraying, plasma coating, laser sintering or microwave sintering, within which a solid molded body or a solid coating is produced and the resulting sintered body or the resulting sintered surface is fully sintered or still partially porous. 3. - Sintered materials according to claim 1, characterized in that, in their preparation, granulates according to claim 1 are used by means of making thermal, electrical or electromagnetic energy a) before heating or in connection therewith they are brought to a desired shape and then sintered in such a way that the sintered bodies or the sintered surface produced are dly sintered fully or are still partially porous; b) they are completely or partially melted before the heating in connection with it, taking it to a desired shape and in this way they are solidified or used to cover other materials and, if necessary, they are then worked on. 4. Glasses according to claims 1 to 3, characterized in that the sintering is carried out to a transparent glass body or to a transparent glass layer within the viscosity field of the glass between 108 to 1012 dPas. 5. Glasses according to claims 1 to 4, characterized in that the glasses are at least water resistant according to hydrolytic class 2. 5. Glasses according to claims 1 to 5, characterized in that, the properties of the glasses Sintered or fused glass of powder particles of the finest match the properties of a glass with identical chemical composition, which has been manufactured by means of a conventional melting process without the use of the granulates according to claim 1, where the preparation of such sintered glass clearly requires lower sintering temperatures than the melting temperature, which is necessary for the preparation of a glass with the same composition within a conventional melting process. 7. Dispersions characterized by the following properties: a) solid fractions of granules according to claim 1 from 10% to 85% by weight within the dispersion with a polar or non-polar inorganic or organic liquid b) solid fractions of granules according to claim 1 from 10% to 85% by weight within an aqueous dispersion, which has a pH value between pH = 6 and between pH = -8 and 12 and is adjusted to the corresponding pH value by means of acids organic, with inorganic acids, with organic bases and with inorganic bases. c) the solid fraction of granules according to claim 1 from 10% to 85% by weight within an aqueous dispersion, which has a pH value between pH = l and 6 or between pH = 8 and 12 and is adjusted to the value corresponding pH by means of organic acids, with inorganic acids, with organic bases and with inorganic bases, and contains additives, which allow a higher fraction of granulate and an improved dispersion, which contribute to an esteric or ionic stabilization of the dispersion and prevent or decrease a decrease in solid fractions and / or prevent gelling ahead of time; d) solid fractions of granules according to claim 1 from 10% to 85% by weight within an aqueous dispersion, which has a pH value between pH = l and 6 or between pH = 8 and 12 and is adjusted to the corresponding pH value by means of organic acids, with inorganic acids, with organic bases and with inorganic bases, and contains additives, which allow improved dispersion, gelling, drying and purification as well as improved sintering of future sintered materials, where such dispersions can also be mixed with other organic bonding materials, which also allow an improved product quality of the sintered material; e) solid fractions of granules according to claim 1 from 1 to 75% by weight in an aqueous dispersion, which has a pH value between pH = l and 6 or between pH = 8 and 12 and is adjusted to the corresponding pH value with organic or inorganic acids or bases and optionally may contain other additives, where pyrogenically generated oxides in a weight fraction of 1 to 65% by weight can be added to such dispersions and the corresponding pyrogenic oxides of the dispersion may not be compressed or afterwards of performing a pre-compression add, as described in DE 196 01 415 Al; f) solid fractions of granules according to claim 1 from 1 to 75% by weight, within an aqueous dispersion, having a pH value between pH = l and 6 or between pH = 8 and 12 and adjusting to the corresponding pH value with inorganic or organic acids or bases and optionally may contain other additives, which allow an improvement in the dispersion, gelling, drying and purification as well as sintering of future sintered materials, where such dispersions according to the invention can be mixed with salts or oxides of a metalloid and / metal. 8. Use of granules made of pyrogenically generated silicon dioxide for the preparation of sintered materials, especially sintered glasses according to claim 1, characterized in that, the granulates used have the following properties: a) the granulates have after a compression step Subsequent according to DE 196 01 415 At a stamping density of 150 g / 1 to 800 g / 1, a grain size of granulate of 10 to 800 μm and a BET surface of 10 to 500 m2 / g; b) granulates according to DE 196 01 415 Al based on pyrogenicly prepared silicon dioxide possess the following physical-chemical data: average grain diameter: 25 to 120 μm, BET surface: 40 to 400 m2 / g, volume pore: 0.5 to 2.5 ml / g, pore distribution: no pore less than 5nm, only meso and macro pores, pH value, 3.6 to 8.5, stamping density 220 to 700 g / 1. 9. - Process for the preparation of sintered materials especially sintered glass according to claim 1, characterized in that the pyrogenically prepared silicon dioxide is compressed by known means and / or granulated, transformed into a dispersion, the dispersion is gelled , it is dried, the green body produced, if necessary, is purified as well as then sintered. 10. Process for the preparation of sintered materials, especially sintered glass according to claim 1, characterized in that the pyrogenically prepared silicon dioxide is compressed in a known manner and / or granulated, and then: a) to take the granulates according to the invention. to claim 1 without auxiliary taking of a liquid into a mold or placing the granulate on a surface, if necessary then performing an additional compression step within which the molded body or the coating layer is pressed or compressed under an elevated external mechanical pressure in the presence of atmospheric pressure or at a reduced pressure, pressed and then compressed, the molded body resulting from the pressing process or the compressed coating can be purified, if necessary, with a gaseous substance such as chlorine or thionyl chloride, at temperatures from 700 to 1000 ° C and by a sintering step at a temperature between 1000 up to 1800 ° C, preferably 1100 to 1600 ° C, sintering in such a way that the sintered body produced or the sintered surface is sintered fully dense or is still partially porous; b) the placement of granules according to claim 1 in molding bodies or surfaces by a thermal and other highly energetic process, such as for example flame spraying, plasma coating, laser sintering or microwave sintering, within which a solid molded body or a solid coating are produced and the resulting sintered body or the resulting sintered surface is fully sintered or still partially porous; c) the granulates mentioned in claim 1, by means of making thermal, electrical or electromagnetic energy, either before heating before heating or in connection therewith are brought to a desired shape and then sintered in such a way that the sintered bodies or the sintered surface produced are densely sintered fully or are still partially porous; or they are completely or partially melted before the heating in connection with it, taking it to a desired shape and in this way they are solidified or used to cover other materials and, if necessary, their elaboration is continued. 11. Use of sintered materials, especially sintered glass or glass corresponding to claims 1-6 for the manufacture of glass moldings. 12. -Use of sintered bodies, especially sintered glass or glass to cover other materials. 13. Use of sintered materials, especially sintered glasses or glasses corresponding to claims 1-6 for the manufacture of materials of the fiber or fiber type. 14. Use of granules according to claim 1 for the preparation of glasses, especially sintered glass, ceramics, bonding materials, within which the granulates act as a reinforcing filler material, as reinforcing fillers in metals, glazes, polymers, elastomers, lacquers or liquids. 15. Use of dispersions according to claims 2 and 7 for the manufacture of glasses or glazes, especially sintered glass according to claims 1-6 as well as for polishing semiconductor materials or electrical connection circuits.