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
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B19/00—Other methods of shaping glass
  • C03B19/14—Other methods of shaping glass by gas- or vapour- phase reaction processes
  • C03B19/1415—Reactant delivery systems
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2201/00—Type of glass produced
  • C03B2201/02—Pure silica glass, e.g. pure fused quartz
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2201/00—Type of glass produced
  • C03B2201/06—Doped silica-based glasses
  • C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
  • C03B2201/40—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn
  • C03B2201/42—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn doped with titanium
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2207/00—Glass deposition burners
  • C03B2207/30—For glass precursor of non-standard type, e.g. solid SiH3F
  • C03B2207/32—Non-halide
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2207/00—Glass deposition burners
  • C03B2207/30—For glass precursor of non-standard type, e.g. solid SiH3F
  • C03B2207/34—Liquid, e.g. mist or aerosol
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2207/00—Glass deposition burners
  • C03B2207/80—Feeding the burner or the burner-heated deposition site
  • C03B2207/85—Feeding the burner or the burner-heated deposition site with vapour generated from liquid glass precursors, e.g. directly by heating the liquid
• • 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
  • C03C2201/40—Doped silica-based glasses containing metals containing transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn
  • C03C2201/42—Doped silica-based glasses containing metals containing transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn containing titanium
• • 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
  • C03C2203/40—Gas-phase processes

Definitions

• This invention relates to ultra-low expansion glasses composed of Si0 2 and Ti ⁇ 2. More particularly, the invention relates to environmentally friendly methods for making such glasses. BACKGROUND OF THE INVENTION Historically, ultra-low expansion glasses composed of Si ⁇ 2 and TiO 2 have been made by flame hydrolysis (flame deposition) of SiCLj and TiCL.
• the deposition process is carried out in a furnace composed of a refractory crown, which carries a series of soot producing burners, and a refractory cup, which collects the soot produced by the burners to form a glass "boule.”
• the Ti ⁇ 2 concentration in the finished glass is typically in the 5-11% by weight range (e.g., approximately 7% by weight) and the glass has an expansion coefficient of less than 5xlO- 7 /°C. See U.S. Patent No. 2,326,059.
• SiCl and TiCLj are clearly chlorine-containing compounds.
• these raw materials result in the production of various chlorine -containing by-products, e.g., CI2 and HC1, which can cause environmental damage.
• these by-products can be collected by scrubbing the emission gases which exit the glass making furnace, such scrubbing is expensive and complicates the glass making process.
• halide- free polymethylsiloxanes have been used in the production of silica- containing glasses.
• Ti-Ipox is exceedingly sensitive to even the smallest amounts of water and/or hydroxyl groups in OMCTS; and (2) OMCTS as commercially supplied contains amounts of dissolved water and silanols (SiOH) well above the levels to which Ti-Ipox is sensitive, even though OMCTS is considered in the art to be a hydrophobic material, e.g., commercially available OMCTS typically has a water content of around 10 ppm but can have water levels as high as 200 ppm or even higher.
• FIG. 1 shows storage tanks 10 and 12 for OMCTS and Ti-Ipox, respectively, each storage tank being equipped with appropriate heating equipment (not shown) for converting its contents into vapor form.
• gas e.g., nitrogen
• tanks 10 and 12 are supplied to tanks 10 and 12 through feed lines 14 and 16, respectively, and serves to carry vaporized OMCTS and vaporized Ti-Ipox to static mixer 18 by means of conduits 20 and 22.
• static mixer 18 the mixed vapors pass through conduit 24 to distribution manifold 26 and from there to burners 28 by means of conduits 30.
• the OMCTS and Ti-Ipox vapors are only in contact between joint 13 and burners 28. This corresponds to a contact time of only a few seconds.
• the water/hydroxyl groups in OMCTS were found to hydrolyze the Ti-Ipox resulting in the formation of a white precipitate at all points downstream of joint 13. This precipitate, which is believed to be Ti ⁇ 2, accumulates on, among other things, burners 28 resulting in pressure increases in distribution manifold 26 and deviations in the composition of the boule.
• the invention in accordance with certain of its aspects provides a method for producing a silica-titania glass which comprises the steps of:
• soot particles from the third gas stream using at least one burner, e.g., forming soot particles from the gas stream in conduit 24 by means of distribution manifold 26, conduits 30, and burners 28; and (e) producing the desired silica-titania glass from the soot particles, e.g., by collecting the soot particles produced by burners 28 to form a boule, with the boule being consolidated as the soot particles are collected or alternatively, but less preferred, after the particles are collected; wherein the concentration of water and/or hydroxyl groups in the first gas stream is sufficiently low so that mixing of the first and second gas streams does not result in the formation of a substantial amount of a precipitate as a result of hydrolysis of Ti-Ipox.
• a "substantial amount" of precipitate is an amount which necessitates premature shut down of the glass making process for precipitate removal before a desired quantity of glass has been produced.
• the concentration of water in the OMCTS prior to its incorporation in the first gas stream is less than 2 ppm and, most preferably, less than 1 ppm.
• a low concentration of water is preferably achieved by pre-drying the OMCTS before it is introduced into tank 10.
• the inert gas provided to tank 10 by conduit 14 must also be dry so that water is not reintroduced into the OMCTS.
• the inert gas provided to tank 12 by conduit 16 must also be dry.
• OMCTS and Ti-Ipox are the preferred starting materials for producing silica-titania glasses, other halide-free compounds can be -5-
• Figure 1 is a schematic diagram of apparatus which can be used in the practice of the invention to produce silica-titania glasses.
• Figure 2 is a schematic diagram of apparatus which can be used to produce "dry" OMCTS.
• FIG. 2 shows suitable equipment for producing an OMCTS feedstock having a low water content.
• OMCTS which is to be dried (the "wet" OMCTS) is introduced into tank 32 through conduit 34 which is equipped with shut off valve 36.
• the wet OMCTS is heated to a temperature of, for example, 140°F, after which dry nitrogen is pumped into the tank through conduit 38.
• Conduit 38 can be equipped with a sparger so as to produce numerous small bubbles which flow upward -6-
• a nitrogen flow rate of 12.5 scfm has been found suitable to dry approximately 300 gallons of OMCTS in about 3.5 hours.
• the heating of the OMCTS is preferably performed by hot oil tracing of tank 32. Although electric heating can be used, hot oil heating is preferred since it reduces the chances of hot spots along the surface of the tank which can result in undesirable polymerization of the OMCTS. Even with hot oil heating, the temperatures of the OMCTS and of the hot oil need to be monitored to avoid excessive heating and thus polymerization of the OMCTS. Because the vapor pressure of water is substantially greater than that of OMCTS, the temperature of the wet OMCTS does not have to be raised above 212°F to achieve effective water removal but only to a temperature of around 140°F.
• Moisture sensor 44 can, for example, be a PANAMETRICS brand sensor manufactured by Panametrics Incorporated, Waltham, MA. Although this sensor gives somewhat qualitative results, it has been found to work successfully in practice.
• the flow of nitrogen is shut off and the dried OMCTS is transferred to storage tank 50 using pump 48.
• conduit 52 By means of conduit 52, a blanket of dry nitrogen is maintained over the "dry" OMCTS as it is being pumped into tank 50, as well as during storage in that tank.
• the dry OMCTS is transferred to tank 10 of Figure 1 using outlet conduit 54 of tank 50 and an appropriate inlet conduit (not shown) to tank 10. -7-
• the apparatus of Figures 1 and 2 is preferably made of stainless steel, e.g., 304L SS, except for conduits 30 in Figure 1 which are preferably PFA TEFLON.
• Tanks 10 and 12 in Figure 1, as well as the conduits shown in that figure, are preferably hot oil traced.
• tank 32 in Figure 2 is also hot oil traced, as are the various conduits associated with that tank which carry OMCTS.
• the invention has been described in terms of producing glass boules of ultra-low expansion silica-titania glasses, it can also be used in the production of other silica glasses which contain titanium.
• the invention can be used in the preparation of titanium-doped preforms from which optical waveguide fibers can be drawn.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Glass Compositions (AREA)
• Glass Melting And Manufacturing (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=22172934

Family Applications (1)

Country Status (3)

Cited By (8)

Citations (7)

• 1999
  • 1999-04-21 WO PCT/US1999/008777 patent/WO1999054259A1/en not_active Application Discontinuation
  • 1999-04-21 EP EP99919954A patent/EP1094990A1/de not_active Withdrawn
  • 1999-04-21 JP JP2000544606A patent/JP2002512169A/ja not_active Withdrawn

Patent Citations (7)

Also Published As

Similar Documents

Legal Events