MXPA98004935A - Method and apparatus for forming fused silice through the combustion of liqui reagents - Google Patents

Abstract

The present invention is directed to a method for manufacturing fused silica glass by introducing a liquid silicon-containing compound, preferably free of halides, directly into the flame of a burner, thereby forming an amorphous alcohol, this soot is deposited on a surface and consolidated to form a fused silica glass body. The invention also relates to an apparatus that includes a burner that generates a flame, an injector to supply a compound to the flame to convert the compound into soot and a surface on which the soot is deposited.

Description

METHOD AND APPARATUS FOR FORMING FUSED SILICA THROUGH THE COMBUSTION PE REACTIVE UQUIPOS FIELD PE UA INVENCIÓN The present invention relates to the formation of molten silica and more particularly to a method and apparatus for forming molten silica from liquid compounds containing silicon.

BACKGROUND OF THE INVENTION Various methods are known in the art that include the production of metal oxides from vaporous reagents. Such processes require a supply material solution "means for generating and transporting vapors from the supply material solution (hereinafter referred to as vaporous reagents) and an oxidant to a conversion reaction site, and an oxidation catalyst medium. and combustion coincidentally to produce finely divided spherical aggregates called soot. That soot can be collected on any deposition receiver in any number of ways ranging from a collection chamber to a rotary mandrel. It may be simultaneous or subsequently heat treated to form a high purity transparent and non-porous glass article. This procedure is usually carried out with specialized equipment having a unique arrangement of nozzles and burners. Some of the initial research that led to the development of such procedures focused on the production of bulk fused silica. The selection of suitable supply material was an important aspect of that work. Accordingly, it was determined at that time that a material capable of generating a vapor pressure of 200-300 millimeters of mercury (mm Hg) at a temperature below 100 ° C would be useful for making such bulk fused silica. The high vapor pressure of silicon tetrachloride (SiCl ^) suggested its usefulness as a convenient vapor source for soot generation and created the discovery and use of a series of similar chlorine-based sourcing materials. This factor, more than any other, is responsible for the currently accepted use of SiCl ^ »TeCl ^» POClß »and BC1-3 as vapor sources, even though these materials have certain chemically undesirable properties. Silicon »gerium» zirconium and titanium are metals commonly used in the form of halide as vaporous reagents to form metal oxide glasses. However, SiCl "has been the benchmark in the industry over the years for the production of high purity silica glass. As described in the patent of E.U.A. No. 3,698 »936. one of several reactions can be used to produce high purity fused silica by oxidation of SiC ^; namely: (1) S i Cl ^ + Oa-SiOat + SCl a »(2) SiCl ^ + ^^ Oa-SiOa + SCl a» O (3) S i Cl. "+ 2Hß0-Si 0ae + 4HCl, with which burners or jet assemblies are used to feed the gases and vapors of the reactant into a reaction space. It should be noted that reaction (2) rarely occurs or is used. There are inherent economic disadvantages for each of these reactions. Moreover, these reactions, which oxidize SiCl through pyrolysis and hydrolysis, have the disadvantage of producing chlorine or a very strong acid by-product. Although the first two reactions occur in theory, an auxiliary fuel is usually needed to achieve the pyrolytic temperature. Hydrolysis of SiCl2 results in the formation of hydrochloric acid (HCl). a by-product that is harmful not only to many deposition substrates and to the reaction equipment, but is also harmful to the environment. Emission abatement systems have proven to be very expensive due to the time at rest, loss and maintenance of the equipment caused by the corrosivity of HCl. Notwithstanding the problems with the handling and disposal of the HCl byproduct, the third reaction, the hydrolysis of SiCl2. it tends to be the commercial method that is most preferred to produce fused silica for economic reasons. Although hydrolysis of SiCl has been the industry's preference to produce high purity fused silica over the years, the increased global sensitivity to environmental protection has led to stricter government regulation of point source emissions, accelerating the search for less harmful solutions to the environment. Point source emission regulations require HCl. the by-product of hydrolyzing SiCl ^ "as well as many particulate pollutants are purified from the exhaust gases before their release into the atmosphere. The economic consequences of meeting these regulations have made the commercial production of fused silica from halide-based sourcing materials less attractive to the industry. As an alternative, high-purity silica or fused quartz has also been produced by the thermal decomposition and oxidation of silanes. However, this requires taking safety measures in handling due to the violent reaction that results from the introduction of air in a closed silos container. The reactors react with carbon dioxide, nitrous oxide, oxygen or water to produce high purity materials that are potentially useful for producing "among other things" semiconductor devices. However, silos have proven to be too expensive and reactive to be considered for commercial use except possibly for small-scale applications that require extremely high purity. A number of patents describe the production of high purity metal oxides, particularly fused silica, from a chloride based supply material. These patents describe equipment with a number of burner arrangements and supply material systems for achieving the oxidation of a metal chloride through hydrolysis or flame pyrolysis. Illustrative of this is the patent of E.U.A. No. 4,491,604 to Les K. et al., Wherein chlorosiline, dichlorosilane, and silicon tetrachloride are hydrolyzed with flame to form soot, and US Pat. No. 3,666,414 to Bayer, in which such halides as trichlorosi or chloroform are hydrolysed with flame. In similar procedures, the patents of E.U.A. Nos. 3 »486» 913 to Zirngibl ("Zirngibl") and 2 »269,059 to McLachlan (" McLac lan ") teach the oxidation of halides. The volatilized inorganic halide components such as TiCl ^. CrCla »CrO ^ Cla» If l ^. A1C1. "» ZrCl. FeCla »FeCl3» ZnClß or SnCl ^ that are oxidized with air »vapor or oxygen are used in Zirngibl» while the silicon halides »ethyl silicate» methyl borate »TiCl ^. A1C1, and ZrCl ^ are used by McLachlan. The patent of E.U.A. No. 3,416,890 to Best et al., Discloses a process for preparing finely divided metal or metalloid oxides by the decomposition of a metal or metalloid perhalogenide in a flame produced by the combustion of an oxidizing gas and an auxiliary fuel, such as sodium disulfide. carbon »carbon selenide sulfide» thiophosgene or other sulfur-containing hydrogen-free compounds directly bonded to carbon. The patent of E.U.A. No. 2 »239» 551 to Da1 ton describes a method for making glass by decomposing a gas mixture of glass-forming compounds in a combustible gas flame. The mixture is used in the formation of anhydrous oxides of silicon »aluminum and boron. Decomposable compounds such as ethyl or methyl silicate, trichlorosi, and silicon tetrachloride can be replaced by silicon tetrachloride. Methyl borate or boron hydride can be replaced by boron fluoride, etc. The patent of E.U.A. No. 2 »326» 059 to Nordberg »details the technique for manufacturing silica-rich ultra-low expansion glass by vaporizing Si and Ti tetrachlorides in the gas stream of any oxygen-gas burner» depositing the resulting mixture to make a preforms, vitrifying the preform at 1500 ° C to manufacture an opal glass and burning the opal preform at a higher temperature to cause it to become transparent. The patent of E.U.A. No. 2, 272, 432 to Hyde, discloses a method for producing glass articles containing vitreous silica by vaporizing a hydrolyzable silicon compound such as silicon chloride, tri chlorosil, methyl silicate, ethyl silicate, silicon fluoride, or mixtures thereof. using a water bath. The vapor of the silicon compound is hydrolyzed by water vapor in the flame of a burner and the resultant amorphous oxide is collected and subsequently concreted to a transparent glass. The patent of E.U.A. No. 4 »501» 602 to M 11er and others »describes the production of particulate metal oxide through the vapor phase arrangement of metal ß-diketonate complexes of groups IA» IB »HA» IIB »IIIA» IIIB. VAT IVB and the series of rare earths of the periodic table. Several patents in which silane compounds have been used to produce high purity fused silica are also cited in the art. Japanese patent application No. 9038-1985 to OKamoto et al., Discloses a method for impurifying quartz crystal using a silane ester expressed by the general formula R "Si (OR *) ^". ^ And one or more defined dopants by the formulas Ge (0Ra) 3 »BOR *) ^ and PHa,» where R * is a hydrogen atom »ethyl or methyl group; Ra is a methyl or ethyl group; R 'is a univalent hydrocarbon group and n is an integer ranging between 0 and 4. A large variety of organometallic compounds are described, including methyltrimethoxylamino-dimethyldimethoxysilane, tri-ethyl-1-methoxysi, or tetramethoxysilane, methyl-trietoxy-tin, and tetra-tetra? silane. The patent of E.U.A. No. 3 »117.838 to Sterling» describes a method for producing very pure quartz or fused silica by decomposition and combined thermal oxidation of silos, where either carbon dioxide, nitrous oxide or water vapor and a silane are fed to a burner or flame jet, and the flame is allowed to impact on a carbon substrate on which the silica is deposited. The patent of E.U.A. No. 4,810,673 to Freeman. describes a method for synthesizing high quality silicon oxides by the deposition of chemical vapor from a gas source mixture including a halogenated silane component and an oxygen source, namely chlorosilane and nitrous oxide. The patent of E.U.A. No. 4,242"487 to Hasegawa et al." Discloses a method for producing a heat-resistant semi-inorganic compound that is useful as a material for various heat-resistant materials, by reacting an organoborosilicon compound with at least one of the group of aliphatic polyhydric alcohols »aromatic alcohols» phenols and aromatic carboalic acids at 250 ° C-450 ° C in an inert atmosphere. As it is clear from the above description "it is highly desirable for both economic and environmental reasons" to find halide-containing silicon compounds to replace the silicon halide supply materials typically used to produce high purity silica glass. Such halide-free starting materials would produce carbon dioxide and water "instead of corrosive and harmful HCl" as by-products of the glassmaking process. The patent of E.U.A. No. 5,043,002 to Dobbins et al., The disclosure of which is incorporated herein by reference, discloses the usefulness of pol imetyl loxanes, in particular pol imethylcyclosiloxanes such as hexamet 1 cyclotrisi-1-oxane, octamet-1-cycoteote-1-oxane.

("OMCTS") and decamethylcyclopentasiloxane, in a method for manufacturing fused silica glass. The method can be applied to the production of a non-porous body of doped silica glass with various oxide impurifiers and for the formation of optical waveguide fibers. The patent of E.U.A. No. 5,043,002 to Dobbins et al., Also discloses the use of hexamethyldisiloxane; see also reference to hexamethyldisiloxane of Japanese Patent Application No. 1-138145. The patent of E.U.A. No. 5,152,819 to Black ell et al., The disclosure of which is incorporated in the present reference manner, discloses additional halide-free silicon compounds, in partir. organo-1-nitrogen compounds having a basic Si-N-Si structure, if loxane zones having a Si-N-Si-O-Si basic structure and mixtures thereof, which can be used to produce silica glass high purity cast without the concomitant generation of corrosive and polluting by-products. Although the use of higher halide silicon compounds as supply materials for the production of fused silica glass, as described in the U.S. Patents. Nos. 5,043,002 and 5,152,819, prevents the formation of HCl "some problems still remain" partirly when the glass is designed for the formation of optical waveguide fibers. Applicants have discovered that "in the course of supplying a material for supplying polyalkyl 1 if vaporized 1-oxane to the burner" high-moler-weight species such as a gel can be deposited in the line carrying the vaporous reactants to the burner or inside the burner. burner itself. This leads to a reduction in the deposition rate of the soot preform that is subsequently consolidated into a part form from which a waveguide optical fiber is extracted. It also leads to imperfections in the part that will produce a defective or useless waveguide optical fiber from the affected portions of the part.

BRIEF DESCRIPTION PE WA INVENTION The present invention is directed to a method for manufacturing fused silica glass. A liquid, preferably halide-free and silicon-containing compound capable of being converted by thermal oxidizing decomposition to SiOa is provided, and is directly introduced into the flame of a combustion burner, thereby forming finely divided amorphous soot. The amorphous soot is deposited on a receiving surface where, either substantially simultaneously with, or subsequent to its deposition, the soot can be consolidated into a fused silica glass body. The fused silica glass body can then be used to manufacture products directly from the molten body, or the molten body can be further treated, e.g., before extraction to fabricate a waveguide optical fiber; see also eg, the end uses described in the patent application of E.U.A. No. 08 / 574,961 entitled "Method for Purifying Polyalkylsiloxanes and the Resulting Products ", the contents of which are hereby incorporated by reference.The invention further comprises an apparatus for forming fused silica from liquid reagents, preferably halide-free and silicon-containing reactants, comprising: combustion which, during operation, generates a conversion site flame, an injector to supply a liquid compound containing silicon to the flame to convert the compound by thermal oxidant decomposition into a finely divided amorphous soot, and a receiving surface placed thereon to said combustion burner to allow deposition of the soot on the receiving surface The formation of amorphous molten SiOa soot particles from a supply material comprising a volatile silicon-containing compound typically involves vaporization of that compound before its introduction in a combustion burner. In the patent of E.U.A. No. 5, 04.002 to Dobbins and others previously mentioned »for example» a carrier gas such as nitrogen is bubbled through a reactive compound containing silicon »preferably a halide-free compound such as octameti iciclotetrasl loxane. A mixture of the reactive compound vapor and nitrogen is transported to the burner at the reaction site, where the reagent is combined with a gaseous fuel / oxygen mixture and brought to combustion. Although the use of halide-free silicon compounds as sourcing materials for the production of fused silica glass "as described in the U.S. Patents. Nos. 5,043,002 and 5,152,819. it prevents the formation of HCl »some problems still remain» particularly when the glass is designed for the formation of high-quality optical products such as waveguide optical fibers. The applicants have discovered »as described in the co-pending patent application of E.U.A. No. 08/574 »961 entitled" Method for Purifying Polyalkylsi loxanes and the Resulting Products "» that the presence of high-boiling impurities in, for example, a polyalkyl siloxane supply material, can result in the formation of gel deposits in the vaporization and supply systems that carry the vaporous reagents to the burner or inside the burner itself. Said polimerization and gelling of the siloxane supply material inhibits the control capacity and consistency of the silica manufacturing processes. This problem is aggravated when an oxidizing carrier gas such as oxygen is included in the reactive vapor stream »because the oxidants can catalyze the polymerization of the siloxane supply material. This leads to a reduction in the rate of deposition of the soot hole which is subsequently consolidated to a part form from which a waveguide optical fiber is extracted. Furthermore, particles of high molecular weight and high boiling impurities can be deposited on the piece of waveguide optical fiber »resulting in" defect "or" cluster defect "imperfections that adversely affect the quality of the the waveguide optical fiber extracted subsequently and which may require the scraping of a complete part. The defects are small bubbles (ie »0.1 to 4.0 mm in diameter) in a glass body. These can be formed in the fused silica by an impurity such as gelled and non-combusted polyalkyl loxane. A very small particle of siloxane gel may be the initiation site for a defect. The siloxane decomposes at high temperature after being deposited on the glass body, giving rise to gases that cause the formation of the defect. Thermophoresis is the process by which soot is attracted to the preform. In fact, it produces the driving force that moves the particles towards the coolest preform. The hot gases that come from the burner pass around the preform during the placement »the soot particles do not have enough time for the combustion to hit the preform alone. Thermophoresis moves the particles in a temperature gradient from the hot regions to colder regions. Burned gases that come from a burner are hotter than the preform. As these gases pass around the preform, a temperature gradient is produced. The molecules of the hot gas have a higher velocity than the molecules of the cold gas. When the molecules of the hot gas hit a particle, they transmit more momentum to the particle than the cold gas molecule. In this way »the particles are directed towards the molecules of the coldest gas and» in turn »towards the preform. Cluster defects are larger glass defects found in fiber optic guide preforms wave. They are constituted by a series of defects in the form of a line or a cluster in the form of funnel or flower. A large gel particle may be the initiation site for a cluster defect. After the gel particle has attacked the porous preform, it causes a raised area to erupt from the surface of the preform. Because the cluster defect is a high site »more heat transfer passes over this place. Because of this increased heat transfer, "more thermophoresis occurs at this site" causing the imperfection to grow and leave behind a row of defects. As a result of cluster defect »the affected portion of the waveguide optical fiber preform can not be normally consoli- dated» and the consequent unevenness in the part produces a defective waveguide optical fiber. In the case of a typical 100-kilometer consolidated piece, which has a diameter of 70 millimeters (mm >); and a length of 0.8 meters (m), the presence of a cluster defect on the surface of the piece will typically result in the loss of 5 kilometers of waveguide optical fiber in the extraction. In the case of a larger consolidated part, the negative impact of a single cluster defect is proportionally greater. In a consolidated piece of 250 kilometers having a diameter of 90 mm and a length of 1.8 m »a cluster defect on the surface of the piece will typically result in the loss of 8 kilometers of waveguide optical fiber in the extraction . The applicants have now discovered that the problem described above is inhibited by supplying the siloxane supply material in liquid form to the conversion site during the silica manufacturing process. By supplying the siloxane sourcing material as a liquid instead of as a vapor, the gel of the siloxane supply material is avoided since the exposure of the siloxane supplying material to the high temperature environments of a siloxane is avoided. vaporizer and a steam supply system. This improves the performance and quality of the fused silica produced and also reduces the maintenance requirements of the production system.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram of a reagent delivery system according to the present invention. Figure 2 is a schematic representation of a liquid reagent provided to the flame of a burner from a syringe according to the present invention. Figure 3 is a schematic representation of liquid reagent particles that are flame-blown from a transducer according to the present invention. Figure 4 is a schematic representation of an atomizer incorporated in the structure of a burner according to the present invention.

PESCRIPCIQN PETA LAPA PE THE INVENTION The present invention is directed to a method for manufacturing a high purity fused silica glass. The invention provides a method for inhibiting the gelation of a siloxane sourcing material in the silica manufacturing process by supplying the siloxane sourcing material to the conversion site in liquid form. Since the hot environments of the vaporizer and the steam supply system "which promote the formation of problematic gels" are avoided, the silica manufacturing process is improved. The siloxane supply material is supplied to the conversion site as a liquid and does not evaporate until just before or at the same time it is converted to amorphous fused silica soot. The amorphous silica soot is then deposited on a receiving surface. Either substantially simultaneously with or subsequent to its deposition, the soot can be consolidated into a fused silica glass body from which eg a waveguide optical fiber can be formed by extraction. The invention further comprises a silica manufacturing apparatus which includes a tank of liquid siloxane supply material for containing the liquid loxane supply material and a liquid siloxane supply material transport line for supplying the liquid supply material. liquid siloxane to an injector that injects the liquid supply material at the conversion site where it is decomposed by a combustion burner flame to form a finely divided amorphous silica soot that is deposited on a receiving surface. The fused silica glass body can be impurified with an oxide impurifier where, in addition to the liquid siloxane supply material, a dopant compound which is capable of being converted by oxidation or flame hydrolysis is introduced into the burner flame. in a member of the group consisting of Pa0B and a metal oxide having a metal component selected from groups IA »IB, HA, IIB, IIIA, IIIB, IVA, VA, and from the series of rare earths of the table periodical of the elements. The fused silica glass impurified with oxide obtained in this way can be. e.g. »extracted to form a waveguide optical fiber. Figure 1 schematically illustrates a system for supplying liquid siloxane supply material and »optionally» impurifer-supplying compounds to the burner 10. A siloxane supply material such as polymethylcyclosi loxane is stored in the material tank. supply 11. The supply material tank 11 is connected to the liquid supply material injector 15 at the reagent introduction site by means of a liquid supply material conduit system which can, if desired, include a liquid source pump. dosage 12, an optional filter 13 and a preheater 14. Said liquid supply material transport conduit has a first terminal end 51 and a second terminal end 52. The liquid of siloxane supply material coming from tank 11 is transferred to through the transport conduit of liquid supply material by the pump 12 through the filter 13 to the optional preheater 14. The liquid supplied through the filter 13 is under a pressure sufficient to prevent and substantially prevent its volatilization in the preheater 14. which is it optionally employs to heat the liquid reagent prior to its introduction into the burner 10. and avoids the high temperatures of a vaporizer that normally promote gel formation. The burner is preferably provided with an internal protective gas, an external protective gas and a mixture of methane and oxygen for the flame, as described, for example »in the patent of E.U.A. No. 4,165,223 to D.R. Powers »which is incorporated herein by reference. The liquid reagent is conveyed from the optional filter 13 or optional preheater 14 through the second terminal end 52 to the liquid injector 15 »which supplies the liquid to the burner 10. The injector 15 comprises a device for supplying the liquid reagent» either as a liquid stream or with atomized liquid particles, directly to the flame of the burner 10. In the present description, the reagent is generally referred to as being in "liquid" form. What is meant by this expression is that the reagent is in a substantial liquid state. A small portion of the reagent may be in the form of vapor, particularly when the preheater 14 is employed, or when a nitrogen blanket is employed on the liquid. A small portion of the reagent may be in the form of vapor when delivered to the combustion site without adversely affecting the function of the product. The liquid injector 15 may comprise, for example, a syringe provided with a fine needle, by means of which a liquid stream may be injected at high speed into the burner flame. Although a syringe can be used on a small scale, commercial operations will require a larger scale equivalent eg an atomizer. Various types of atomization media capable of forming very small particles of liquid are known in the art of atomization "as described in" Atomization and Sprays ". by Arthur H. Lefebure »Hemisphere Publishing Co .. 1989» which is incorporated herein by reference. The atomizers can be operated by various energy sources such as liquid »gas» mechanical, electric and vibratory, and can be categorized as »for example» jet »swirl, jet-swirl» pneumatic, rotary »acoustic» ultrasonic and electrostatic Preferably "a jet atomizer is used" even very preferably, the jet atomizer is a jet-swirl atomizer, which swirls to the liquid and then, as the atomizers generally do »ejects the liquid in the form of a jet at high speed through a small hole. Several types of atomizers are described in "Liquid Atomization", by L. Bayvel and Z. Orzecho ski »Taylor &; Francis. (1993). which is incorporated herein by way of reference. Another preferred type is a pneumatic atomizer operated by nitrogen or air pressure. In particularly preferred embodiments. The atomizer can be incorporated in the structure of the combustion burner. The atomized particles of the reactive siloxane compound are brought to combustion in a burner having a fuel of. Preferably, a combination of methane and oxygen. The atomized reagent particles can be transported from the atomizer to the burner flame by a carrier gas such as nitrogen, which is preferably the atomizing gas. Figure 2 schematically illustrates an apparatus according to the present invention, in which the syringe 21 injects a stream of liquid reagent 22 to the flame of the conversion site 23 produced by the burner 24. The thermal oxidant decomposition of the reagent produces a soot finely divided amorphous 25 which is deposited on a rotating mandrel 26. Figure 3 is a schematic representation of another embodiment of the apparatus of the present invention, in which the atomizer 31 injects small particles of liquid reagent 32 into the flame 23 produced by the burner 24. Combustion of the reagent produces soot 25. which is deposited on a rotating mandrel 26. Figure 4 is a cross-sectional view of a preferred embodiment of the apparatus of the present invention. Here, the burner 40 incorporates within its structure an atomizer 41 that injects finely atomized liquid reagent particles into the flame 23. As with the embodiments described previously, the amorphous soot produced by the combustion of the liquid reagent is collected on the rotating mandrel 26. As shown in Fig. 4 »the burner 40 comprises a series of concentric channels surrounding the atomizer 41. A stream of nitrogen can be supplied via the inner channel 43 to prevent premature contact of the reagent particles 42 with oxygen "which can be supplied to the flame 23 through channels 44 and 45. An oxygen premix and a fuel such as methane is conducted to the flame through the external channel 46. A burner equipped with an injector of atomization, such as the embodiment illustrated in FIG. 4 »produces a broad stream of soot which achieves an improved concentricity of the center and facing regions of a waveguide optical fiber formed subsequently. The atomizer unit 53 of the invention that is most preferred as shown in Figure 4 is comprised of an air jet atomizer. With said air jet atomizer, the liquid siloxane supply material is atomized by the kinetic energy of a gas stream flowing from the internal channel 43. High velocity gas is used to atomize the supply material. This produces atomized liquid projections 42 with a speed on the scale of 0.5 to 50.0 m / sec. The use of an inert gas is preferred with the air jet atomizer. The Na gas with the invention is particularly preferred, but a non-inert gas such as 0a may also be used. but it will not help to prevent the combustion of the supply material before the complete evaporation of the liquid supply material. The use of Na gas as the air jet gas helps to protect the supply material from the oxygen in the flame and prevents the accumulation in the burner. With the use of the air jet atomizer in the invention, the high velocity jet gas is effectively delivered to achieve a beneficial atomization level of the siloxane in the burner and in the mist. In the practice of the invention, even though it is preferred to have an atomizing unit 53 as an integral part of the burner unit, it is possible to use an air jet atomizer which is separate from the burner especially as with the atomizers. and 31 of figures 2 and 3.

The apparatus may also be provided with a dopant supply tank 16"shown in Figure 1. which contains a compound capable of being converted" by oxidation or flame hydrolysis "into Pa0ß or into a metal oxide whose metal component is selected of groups IA »IB» HA »IIB, IIIA, IIIB, VAT. IVB. GOES. and of the series of rare earths of the periodic table. These oxide dopants are combined with the silica generated in the burner to provide doped fused silica glass which can be substantially formed in the form of waveguide optical fibers. The compound supplying the silica glass dopant can be provided to the feed tank 11 from the docter supply 16 of Figure 1. Alternatively the doping agent can be supplied from the supply 16 to the liquid injector 15 by means of a separate dosing pump "and optionally a filter (not shown) analogous to the delivery system used for the silica-containing compound. According to the invention, the silicon-containing and preferably halide-free reactive compound preferably comprises a polyalkyloxy loxane, for example heme ameti di si loxane. Most preferably, the polyalkyl siloxane comprises a polymethylcyclosi loxane. More preferably, the polymethyl loxane is selected from the group consisting of hexamethylcitric acid loxane, octane, and cyclosotene loxane. decamethylcyclopentasi loxane, dodecamethylcyclohexasi loxane and mixtures thereof. As described in the patent application of E.U.A. No. 08 / 574,961, the use of siloxane sourcing materials such as octamethylcycotetra-si-loxane involves problems with conventional silica manufacturing processes, since the siloxane sourcing material is prone to be pooled and form gels which are clogged and obstructed to the supply material vaporizer and the vaporized supply material supply system. The following examples further illustrate the invention.

Example 1 - Generation of Soot by Invention of Liquid Reagent in a Flame with a Syringe A stream of octamethyl cyclictetrasi liquid loxane (OMCTS) was injected into the burner flame of a lathe equipped with a glass bar using a syringe provided with a needle of 0.254 mm in diameter. The resulting porous soot particles containing S 0w were collected on the rotating glass rod of 25.4 mm in diameter. This procedure demonstrates the possibility of obtaining Si0 ~. by combustion of the compound siloxane supply material in liquid form.

Example 2 - Generation of soot using an ultrasensitive transducer atomizer as injector Octameti lciclotetras liquid loxane (OMCTS) was supplied to a combustion burner by means of an ultrasonic transducer Vibra-Ce11"20-khz (available from Sonics & Materials, Inc. »Danbury» CT) inserted below the center line of the burner The atomizer was surrounded by two internal oxygen supply rings and a pre-blended CH ^ / Oa outer ring.The following flow rates were employed: octa ethylcyclotetrasiloxane (OMCTS) »11 grams per minute, oxygen» 10 normal liters per minute (SLPM), pre-mix »10 SLPM of CH" and 8.4 SLPM of 0. The combustion was continued for approximately minutes. A suitable Si0a deposit was collected on the mandrel »further demonstrating the practicality of producing Si03 from a loxane supply material introduced as small liquid particles in the burner flame.

Example 3 - Generation of Soap N by a Burning Combustion Burner An atomization burner as illustrated in Figure 4 was constructed. Various dimensions of the atomizer 41 and the surrounding channels were tested as follows: atomizer 41: 0.177 to 0.381 mm internal diameter of channel 43: 0.914 to 0.1.27 mm outer diameter of channel 43: 1.21 to 1.60 mm Using an atomizer 41 having an internal diameter of 0.381 mm, soot particles were generated from octameti Iciclotetrasi loxane (OMCTS) for 65 minutes. The flow rates were as follows: pre-mix through channel 46: 10 SPLM of CH ^ and 8 SPLM of 0a. 0a through channels 44 and 45: 26 SPLM. Na through channel 43: 5.6 SLPM. Octameti Iciclotetrasi loxane (OMCTS) through the atomizer 41: 6 milliliters per minute (ml / min) during the first five minutes »then 10 ml / min for the next 60 minutes. The target or decoy »a 25.4 mm diameter glass rod was programmed to rotate between 1 and 5 rotations per second» traveling forward and backward at approximately 15 meters per minute. The distance of the burner to the decoy receiving surface was approximately 165 mm. Complete combustion of the octameti reagent Icyclotetrasi loxane (OMCTS) was achieved and the target weight increased by 247 grams during the 65 minute decomposition period (3.8 grams / ml). The soot was subsequently consolidated in an oven »producing a clear glass free of visual defects. These results demonstrate the successful use of an atomization burner of the invention to combust a liquid siloxane supply material and deposit soot on a receiving surface at a suitable rate. The invention has been described in detail for purposes of illustration, but it is understood that said detail is solely for that purpose and that variations may be made thereto by those skilled in the art without departing from the spirit and scope of the invention. defined by the following re vindications.

Claims (23)

NOVELTY OF THE INVENTION CLAIMS

1. - A method for inhibiting the gelation of a siloxane supply material during the manufacture of silica. Said method comprises the steps of: a) obtaining a liquid siloxane supply material; b) supplying said liquid siloxane supply material in liquid form to a conversion site; c) atomizing said liquid siloxane supply material at the conversion site; d) converting said atomized siloxane sourcing material into silica at the conversion site.

2. A method according to claim 1, further characterized in that said step of atomizing said liquid silo-liquid supply material at the conversion site further comprises the step of atomizing by air jet said liquid siloxane supply material .

3. A method according to claim 2, further characterized in that said step of atomizing by air jet said liquid siloxane supply material further comprises the step of atomizing the liquid siloxane supply material with kinetic energy of a stream of flowing gas.

4. A method according to claim 2 »further characterized in that said step of atomizing by air jet said liquid siloxane supply material further comprises the step of releasing a jet of inert gas to said liquid siloxane supply material.

5. A method according to claim 4. further characterized in that said step of throwing a jet of inert gas into said liquid siloxane supply material comprises the step of throwing a jet of nitrogen gas at said supply material of s liquid loxane.

6. A method according to claim 1 »further characterized in that said step of atomizing said liquid siloxane supply material at the conversion site further comprises imparting a rate of more than

0. 5 m / sec to the atomized siloxane supply material.

7. A method according to claim 1 further characterized in that said step of converting said atomized siloxane supply material into silica at the conversion site further comprises the step of decomposing said atomized sxanoxane supply material into a call.

8. A method of using a liquid loxane at a conversion site, where the sole is converted into silica soot. This method comprises the steps of: a) containing a liquid silo in a location far from said conversion site; b) supplying said liquid silo in liquid form to the conversion site; c) vaporizing said liquid silo supplied at the conversion site; d) converting said siloxane supplied and vaporized into silica soot at the conversion site.

9. A method according to claim 8 »further characterized in that said step of supplying said liquid siloxane in liquid form to the conversion site further comprises the step of inhibiting the vaporization of the liquid silo.

10. A method according to the claim 8 »further characterized in that said step of vaporizing said supplied liquid silo or anode further comprises the step of ejecting a jet of inert gas into said liquid silo.

11.- A method in accordance with the claim 8 »said method further comprises the step of impurifying said silica soot with at least one member of a group consisting of Pa0B and a metal oxide having a metal component selected from the groups IA» IB »HA» IIB »IIIA » IIIB. VAT IVB. VA, and of the series of rare earths of the periodic table of the elements.

12. An apparatus for the manufacture of silica comprising: a tank of liquid siloxane supply material containing a liquid siloxane supply material; a supply conduit for liquid silo supply material having a first terminal terminal and a second terminal terminal, said first terminal terminal connected to said tank of liquid silo supply material?; an injector of liquid silo supply material, said injector connected to the second terminal end of said liquid supply silo supply material conduit »a conversion site of σilo? anus to silica close to said injector , further characterized in that said silo? anus that is ejected from said injector is converted into silica.

13. A silicone manufacturing apparatus according to claim 12. further characterized in that said injector of liquid silo supply material comprises an atomization means.

14. An apparatus according to claim 13. further characterized by said atomization means comprises an air jet atomizer.

15. An apparatus according to claim 14 »further characterized in that said air jet atomizer is adjacent to a burner.

16. An apparatus according to claim 12 »further characterized in that said site of conversion from silo-ano to silica comprises a flame.

17. An apparatus in accordance with the claim 13 »further characterized in that said atomization means comprises an electrostatic atomizer.

18. An apparatus according to claim 13 »further characterized in that said atomization means comprises a pneumatic atomizer.

19. An apparatus according to claim 13. further characterized in that said atomization means comprises a jet atomizer.

20. A method for manufacturing silica soot, said method comprising: providing a conversion site, said conversion site for converting silica into a silica-producing supply material; placing an air jet atomizer near said conversion site; supplying a liquid-producing silica-producing supply material to said air-jet atomizer »atomizing said silica-producing gas-supply material with a gas.

21. A method for manufacturing silica soot "said method comprises: providing a conversion site, said conversion site for converting silica into a silica-producing supply material; placing an electrostatic atomizer near said conversion site; supplying a silica-producing material in liquid form to said electrostatic atomizer; electrostatically atomizing said silica-producing supply material with an electric charge.

22. A method for manufacturing silica soot, said method comprising: providing a conversion site, said conversion site for converting into silica a silica-producing supply material; placing a pneumatic atomizer near said conversion site; supplying a silica-producing material in liquid form to said pneumatic atomizer; pneumatically atomizing said silica-producing supply material.

23. A method for manufacturing silica soot. Said method comprises: providing a conversion site, said conversion site for converting silica into a silica-producing supply material; placing a jet atomizer near said conversion site; supplying a material for producing silica in liquid form to said jet atomizer; spraying said silica-producing supply material.