JP5737241B2 - Fine glass particle deposit and method for producing glass matrix - Google Patents

Description

  The present invention is a glass for producing a glass fine particle deposit by depositing glass fine particles on a starting rod by VAD method (vapor phase axis attaching method), OVD method (external attaching method), MMD method (multi-burner multilayer attaching method) or the like. The present invention relates to a method for producing a fine particle deposit and a method for producing a glass base material by heating the glass fine particle deposit to make it transparent.

  As a conventional method for producing a glass base material, there are a deposition step for producing a glass particulate deposit by an OVD method, a VAD method or the like, and a transparency step for producing a transparent glass preform by heating the glass particulate deposit. (For example, refer patent documents 1-3).

  In the manufacturing method of Patent Document 1, glass raw material gas is heated and vaporized, and the glass raw material gas is guided to a glass fine particle forming burner by piping under reduced pressure. For example, the temperature of the piping is 55 ° C., and the heat resistance temperature is about 70 ° C. This makes it possible to use piping made of a vinyl chloride material.

  The manufacturing method of Patent Document 2 starts the deposition of glass fine particles after discarding the glass raw material gas for a predetermined time prior to the start of the deposition of the fine glass particles, and then discards the raw material gas, the volume of the piping, the pressure in the piping, and the piping. By satisfying the predetermined temperature, the occurrence of bubbles and cloudiness in the glass base material is avoided. The piping temperature is 82 ° C. or 85 ° C.

  In the manufacturing method of Patent Document 3, as a means for suppressing irregularities generated on the surface of the glass fine particle deposit, a conduit from a source gas generator for supplying source gas to a burner is formed at 90 ° C. over the entire length using a heater and a heat insulating material. Although it is described that it is held as described above, there is no description regarding the Reynolds number of the source gas flowing in the pipe.

  Patent Document 4 describes a method for suppressing the spread of the flame by introducing gas into the inner periphery of the hood installed at the tip of the burner flame as a means for increasing the raw material yield.

JP 2004-161555 A JP 2006-342031 A JP 2003-165737 A Japanese Patent Laid-Open No. 7-144927

  However, in the method for producing a glass base material described in Patent Documents 1 to 4, it is difficult to efficiently attach the generated glass fine particles to the starting rod or the glass fine particle deposit. That is, there is a limit to the ratio of the amount of glass fine particles deposited to the amount of glass raw material gas supplied.

  An object of the present invention is to provide a method for producing a glass fine particle deposit and a glass base material that can improve the efficiency of adhesion of the produced glass fine particles to a starting rod and a glass fine particle deposit.

  The method for producing a glass fine particle deposit according to the present invention capable of solving the above-mentioned problems is a method of heating and vaporizing a liquid glass raw material contained in a raw material container to form a glass raw material gas, and using the glass raw material gas as the raw material. The glass raw material gas is burned from the vessel to the glass fine particle producing burner, and the glass raw material gas is ejected from the glass fine particle producing burner, and a flame decomposition reaction (thermal decomposition reaction, flame hydrolysis reaction, thermal oxidation reaction, etc.) of the glass raw material gas. In the method for producing a glass particulate deposit including the deposition step of depositing the glass particulate generated by the above on a starting rod in a reaction vessel to form a glass particulate deposit, from the raw material container to the glass particulate generation burner in the deposition step And controlling at least a part of the piping to a temperature of 100 ° C. or higher by a heating element, The Reynolds number of the glass material gas flowing through the inside pipe et until the glass particles produced burners are characterized by a more than 2000.

  Further, in the method for producing a glass fine particle deposit according to the present invention, the Reynolds number of the glass raw material gas flowing in the pipe from the raw material container to the glass fine particle generating burner in the deposition step is 4000 or more, more preferably It is characterized by being 8000 or more.

  Further, the method for producing a glass base material according to the present invention is characterized in that the glass fine particle deposit produced in the method for producing a glass fine particle deposit is heated to become a glass preform through a transparentizing step. It is said.

  Further, the method for producing a glass base material according to the present invention comprises producing a glass fine particle deposit by any one of the VAD method, the OVD method, and the MMD method in the deposition step, and passing through the transparency step to obtain the glass base material. It is characterized by manufacturing.

  According to the method for producing a glass fine particle deposit and a glass base material according to the present invention, at least a part of piping from the raw material container to the glass fine particle generating burner is controlled to a temperature of 100 ° C. or higher by the heating element, and the raw material container The glass material gas flowing through the pipe from the glass particle burner to 2000 or more, the Reynolds number of the glass raw material gas is 2000 or more, turbulent the flow of the glass raw material gas in the pipe, the raw material gas flowing in the pipe from the pipe length The heating time of the source gas can be lengthened by following a long path length, and the temperature of the source gas can be easily increased.

  By increasing the temperature of the raw material gas, the flame hydrolysis reaction is promoted in the burner flame, the number of glass fine particles generated in the flame is increased, and the outer diameter of the glass fine particles is also increased. In addition, the increase in particle diameter promotes aggregation (bonding between particles) due to turbulent diffusion. By these effects, the inertial force of the glass fine particles is increased, the glass fine particles are easily detached from the flow of the flame gas, and the adhesion efficiency of the glass fine particles to the starting rod and the glass fine particle deposit can be improved.

It is a block diagram of the manufacturing apparatus explaining the manufacturing method of the glass fine particle deposit body which concerns on this invention. It is a schematic diagram explaining the behavior at the time of glass particulates depositing on a glass particulate deposit. It is a graph which shows the temperature change of the raw material gas in a part of longitudinal direction in gas supply piping.

  Hereinafter, a method for producing a glass fine particle deposit and a glass base material according to an embodiment of the present invention will be described with reference to the drawings. In the following, the VAD method will be described as an example, but the present invention is not limited to the VAD method. The present invention can also be applied to other methods for producing a glass fine particle deposit such as an OVD method and an MMD method.

  As shown in FIG. 1, a manufacturing apparatus 10 that performs the method for manufacturing a glass fine particle deposit according to the present embodiment deposits glass fine particles by the VAD method. The starting rod 13 is attached to the lower end of the support rod 12. An exhaust pipe 21 is attached to the side surface of the reaction vessel 11.

  The upper end of the support bar 12 is gripped by the lifting / lowering rotation device 15 and is lifted / lowered by the lifting / lowering rotation device 15 together with the rotation. The raising / lowering rotation device 15 is controlled by the control device 16 so that the outer diameter of the glass fine particle deposit 14 is uniform. A cladding burner 18 which is a burner for generating glass particles is disposed below the reaction vessel 11, and glass particles 20 are ejected toward the starting rod 13 to form a glass particle deposit 14. Further, the glass fine particles 20 in the reaction vessel 11 that have not adhered to the starting rod 13 or the glass fine particle deposit 14 are exhausted through the exhaust pipe 21.

  A raw material gas and a flame forming gas are supplied to the cladding burner 18 by a gas supply device. The cladding burner 18 is a multi-tube burner such as an eight-fold tube. In FIG. 1, a gas supply device for supplying the flame forming gas is omitted.

The cladding burner 18 is charged with SiCl ₄ as a source gas, H ₂ and O ₂ as a flame forming gas, and N ₂ as a burner seal gas. In the oxyhydrogen flame of the cladding burner 18, glass fine particles 20 are generated by a flame hydrolysis reaction, and the glass fine particles 20 are deposited on the starting rod 13 to produce a glass fine particle deposit 14 having a predetermined outer diameter.

  The gas supply device 19 includes a raw material container 22 for storing the liquid raw material 28, an MFC 23 for controlling the supply flow rate of the raw material gas, a gas supply pipe 25 for guiding the raw material gas to the cladding burner 18, a raw material container 22, the MFC 23, and a gas supply pipe 25. The temperature control booth 24 keeps a part of the temperature above a predetermined temperature.

  The liquid raw material 28 in the raw material container 22 is controlled to a temperature equal to or higher than the boiling point in the temperature control booth 24, vaporized in the raw material container 22, and the supply amount of the raw material gas supplied to the cladding burner 18 by the MFC 23 is controlled. The Note that the control of the raw material gas supply amount by the MFC 23 is performed based on a command value from the control device 16.

  The glass base material manufacturing method of the present embodiment controls at least a part of the gas supply pipe 25 from the temperature control booth 24 to the cladding burner 18 to a temperature of 100 ° C. or more by a tape heater 26 as a heating element, The Reynolds number Re of the source gas flowing in the gas supply pipe 25 from the source container 22 to the cladding burner 18 is set to 2000 or more. In general, the gas flow flowing in the pipe is laminar when the Reynolds number is less than 2000, is a transition region between 2000 and 4000, and becomes turbulent when 4000 or more. In order to promote the flame hydrolysis reaction of the raw material gas in the burner flame, at least a part of the gas supply pipe 25 may be controlled to 100 ° C. or higher, but the entire pipe is controlled to 100 ° C. or higher. May be.

The Reynolds number Re of the raw material gas flowing in the gas supply pipe 25 is expressed by the following equation, where D is the inner diameter of the pipe, V is the average gas flow velocity in the pipe, and v is the kinematic viscosity coefficient of the gas in the pipe.
Re = DV / ν
The kinematic viscosity coefficient ν of SiCl ₄ at a temperature of 100 ° C. is about 3.1 × 10 ⁻⁶ (m ² / s).

  The Reynolds number Re is preferably 4000 or more, more preferably 8000 or more. By doing in this way, the source gas flowing in the gas supply pipe 25 from the source container 22 to the cladding burner 18 becomes more turbulent. By increasing the turbulent strength of the raw material gas flowing in the gas supply pipe 25, the raw material gas is introduced into the cladding burner 18 along a path length longer than the pipe length.

  Therefore, the source gas is sufficiently heated in the gas supply pipe 25 by the tape heater 26 and the temperature rises. As a result, the raw material gas ejected from the burner is accelerated in the flame hydrolysis reaction in the burner flame.

  When the flame hydrolysis reaction is promoted in the burner flame, the number of glass fine particles generated in the flame increases. Further, since the growth of the glass fine particles proceeds, the outer diameter of the glass fine particles also increases. Furthermore, when the particle diameter increases, aggregation (bonding between particles) due to turbulent diffusion is promoted. Due to these effects, the inertial force of the glass fine particles in the burner flame is increased, and the glass fine particles are easily detached from the flow of the flame gas (see FIG. 2), and the glass fine particles 20 to the starting rod 13 and the glass fine particle deposit 14 are obtained. The adhesion efficiency of can be improved.

  As for the material of the gas supply pipe 25, when the gas supply pipe 25 is held at a temperature of less than 200 ° C., the material of the gas supply pipe 25 may be fluororesin (Teflon (registered trademark)), but it is 200 ° C. or more. When the temperature is maintained, the material of the gas supply pipe 25 is preferably a metal such as SUS having excellent heat resistance. A tape heater 26 as a heating element is wound around the outer periphery of the gas supply pipe 25 from the temperature control booth 24 to the cladding burner 18. The tape heater 26 is a flexible heater in which an ultra fine stranded wire of a metal heating element or a carbon fibrous surface heating element is covered with a protective material. When the tape heater 26 is energized, the gas supply pipe 25 is heated.

  In addition, it is preferable that the heat insulation tape 27 which is a heat insulating material is wound around the outer periphery of the tape heater 26. When the heat insulating tape 27 is wound, the power consumption of the tape heater 26 can be kept low.

  In addition, the temperature distribution in the longitudinal direction of the gas supply pipe 25 is preferably controlled so that the temperature increases from the raw material container 22 side toward the cladding burner 18 side. As a result, the flow velocity of the raw material gas flowing in the piping is accelerated, so that the glass fine particles 20 generated in the flame are aggregated (bonded between particles) by turbulent diffusion, and the bonded particles are separated from the flow of the flame gas. It becomes easy, and the adhesion efficiency of the glass fine particles 20 to the starting rod 13 and the glass fine particle deposit 14 can be further improved. Specifically, the deposition efficiency of the glass fine particles 20 can be increased by setting the temperature gradient of the gas supply pipe 25 to 5 ° C./m or more, preferably 15 ° C./m or more, more preferably 25 ° C./m or more. it can.

The manufacturing procedure of the glass fine particle deposit and the glass base material will be described.
(Deposition process)
As shown in FIG. 1, the support rod 12 is attached to the lifting / lowering rotation device 15, and the starting rod 13 attached to the tip of the support rod 12 is placed in the reaction vessel 11. Next, while the starting rod 13 is rotated by the elevating and rotating device 15, the raw material gas is chemically changed into the glass fine particles 20 by the flame hydrolysis reaction in the oxyhydrogen flame formed by the cladding burner 18, and the starting rod 13 is made of glass. Fine particles 20 are deposited.

  At this time, the gas supply pipe 25 for supplying the raw material gas to the cladding burner 18 has a pipe inner diameter D designed so as to obtain a desired Reynolds number Re. Further, the tape heater 26 wound around the outer periphery of the gas supply pipe 25 is energized to control at least a part of the gas supply pipe 25 to a temperature of 100 ° C. or higher. Thereby, the average flow velocity of the raw material gas flowing in the pipe is controlled so that a desired Reynolds number Re can be obtained.

  That is, when the flow rate of the source gas flowing in the gas supply pipe 25 is constant, the Reynolds number Re of the source gas flowing in the pipe is changed by changing the pipe inner diameter D of the gas supply pipe 25 and the temperature of the gas supply pipe 25. Can be controlled. Further, when the temperature of the source gas flowing through the gas supply pipe 25 changes, the kinematic viscosity coefficient of the source gas also changes.

  The glass fine particle deposit 14 in which the glass fine particles 20 are deposited on the starting rod 13 is pulled up by the elevating and rotating device 15 in accordance with the growth rate of the lower end of the glass fine particle deposit 14.

(Transparent process)
Next, the obtained glass fine particle deposit 14 is heated to 1100 ° C. in a mixed atmosphere of an inert gas and a chlorine gas, and then heated to 1550 ° C. in a He atmosphere to perform transparent vitrification. Such a glass base material is repeatedly manufactured.

The behavior of the glass fine particles 20 in the flame gas flow will be briefly described.
As shown in FIG. 2, the flame gas flow G containing a source gas such as SiCl ₄ formed by the cladding burner 18 strikes the glass particulate deposit 14 and the flowing direction abruptly becomes the glass particulate deposit 14. It will bend in the outer peripheral direction.

  On the other hand, the glass fine particles 20 generated in the flame gas flow G flow along the flame gas flow G, and the inertial force thereof is determined by the Stokes number of the glass fine particles 20. The Stokes number is proportional to the square of the particle diameter and the flow velocity of the particle. As the Stokes number increases, the inertial force of the glass fine particle 20 increases and the straightness of the glass fine particle 20 improves.

  When the flame gas flow G hits the glass fine particle deposit 14 and its flow direction suddenly changes in the outer peripheral direction of the glass fine particle deposit 14, the glass fine particle 20A having a large inertia force has high straightness, and thus directly collides with the glass fine particle deposit 14. To do. However, since the glass fine particles 20B having a small inertia force flow along the flame gas flow G, they flow away in the outer peripheral direction of the glass fine particle deposit 14. Accordingly, it is important how to increase the inertial force of the glass fine particles 20.

  As described above, at least a part of the gas supply pipe 25 from the temperature control booth 24 to the cladding burner 18 is controlled to a temperature of 100 ° C. or more by the tape heater 26 as a heating element, and from the raw material container 22 to the cladding burner 18. The Reynolds number of the raw material gas flowing through the gas supply pipe 25 is 2000 or more, preferably 4000 or more, and more preferably 8000 or more.

  Thereby, the flow of the raw material gas in the gas supply pipe 25 becomes turbulent, and the raw material gas is sufficiently heated in the gas supply pipe 25 by the tape heater 26 and the temperature rises. As a result, the raw material gas ejected from the burner is accelerated in the flame hydrolysis reaction in the burner flame.

  When the flame hydrolysis reaction is promoted in the burner flame, the number of glass fine particles generated in the flame increases. Further, since the growth of the glass fine particles proceeds, the outer diameter of the glass fine particles also increases. Furthermore, the increase in particle diameter promotes aggregation (bonding between particles) due to turbulent diffusion. By these effects, the inertial force of the glass fine particles in the burner flame is increased, the glass fine particles are easily detached from the flow of the flame gas, and the adhesion efficiency of the glass fine particles 20 to the starting rod 13 and the glass fine particle deposit 14 is improved. Can be made.

  Further, when the temperature of the raw material gas flowing through the gas supply pipe 25 is increased, the volume of the raw material gas is expanded, and the flow rate of the glass fine particles 20 generated in the burner flame is also increased. As described above, the inertial force of the glass fine particles 20 flowing along the flame gas flow G is determined by the Stokes number. Since the Stokes number is proportional to the flow velocity of the particles, when the raw material gas temperature in the gas supply pipe 25 rises and the flow velocity of the glass fine particles 20 rises, the inertial force of the glass fine particles 20 increases. With these effects, the adhesion efficiency of the glass fine particles 20 to the starting rod 13 and the glass fine particle deposit 14 can be improved.

Next, an embodiment of the method for producing a glass fine particle deposit and a glass base material according to the present invention will be described. In both Examples and Comparative Examples, a glass fine particle deposit is manufactured using the following materials.
・ Starting rod: quartz glass with a diameter of 20 mm and a length of 1000 mm ・ Input gas to a cladding burner: raw material gas: SiCl ₄ (1-3 SLM), flame forming gas: H ₂ (40-70 SLM), O ₂ (40- 70 SLM), burner seal gas ... N ₂ (8-14 SLM)
・ Gas supply pipe between raw material container and clad burner; pipe temperature 100 ° C., 150 ° C., 260 ° C., 270 ° C., pipe inner diameter 2.7-19 mm

  Glass fine particles are deposited by the VAD method. The obtained glass fine particle deposit is heated to 1100 ° C. in a mixed atmosphere of an inert gas and a chlorine gas, and then heated to 1550 ° C. in a He atmosphere to perform transparent vitrification.

In the above-described deposition process, the pipe inner diameter D and pipe temperature of the gas supply pipe are appropriately selected, the Reynolds number Re is changed, and the Reynolds number Re of the source gas flowing in the pipe when the source gas flow rate becomes 3 SLM, and the glass The raw material yield X (%) of the fine particles is evaluated. The raw material yield X is the mass ratio of the glass fine particles actually deposited on the starting rod and the glass fine particle deposit to the SiO ₂ mass in the case where the SiCl ₄ gas to be added chemically reacts with 100% SiO ₂ .
As a result, the results shown in Table 1 are obtained.

As is clear from Table 1, in Examples 1 to 6 in which the Reynolds number Re is 2000 or more, the raw material yield X is 28% or higher, and the higher the Re, the higher the raw material yield X. In particular, in the case of Re4008, the raw material yield X is 30%, and in the case of Re8253, the raw material yield X is 31%. Example 4 is an example in which the gas supply pipe temperature is 150 ° C., that is, the gas supply pipe temperature is 92.4 ° C. higher than the standard boiling point of SiCl _{4 as} the raw material gas, but the Re number is 10408, and the raw material yield X Is improved to 32%. Further, Example 5 is an example in which the gas supply pipe temperature is 260 ° C., that is, the pipe temperature is 202.4 ° C. higher than the standard boiling point of SiCl _{4 as} the raw material gas, but the Re number is 11546 and the raw material yield X is 35%. Go up. Further, in Example 6, the temperature gradient of the gas supply pipe is increased from the raw material container toward the burner with a slope of 50 ° C./m, and the temperature of the gas supply pipe near the burner is 270 ° C., that is, the gas supply pipe temperature is the source gas. This is an example of 212.4 ° C. higher than the normal boiling point of SiCl ₄ . The Reynolds number Re is 11554, and the effect of providing a temperature gradient in the longitudinal direction of the gas supply pipe promotes the turbulent diffusion of the glass particles in the flame, and the raw material yield X jumps up to 37%.
On the other hand, in Comparative Examples 1 to 3 in which the Reynolds number Re is less than 2000, the raw material yield X is as low as 25% or less, and in Comparative Example 3 in which Re is less than 1500, the raw material yield X is 23%. In Comparative Examples 1 to 3, it can be seen that only about one-fourth of the SiCl ₄ gas to be introduced adheres.

  FIG. 3 shows the temperature of the raw material gas flowing in the gas supply pipe when the entire length of the gas supply pipe is heated to a constant value of 140 ° C. From this figure, in the laminar flow state where the Reynolds number Re is 1870 (broken line in the figure), the temperature rises gradually along the longitudinal direction of the pipe, but the Reynolds number Re is 2000 (dashed line in the figure) or 4000 (shown in the figure). In the turbulent state of the middle two-dot chain line), it can be seen that the temperature rises rapidly on the upstream side of the pipe. In Examples 1 to 6, the Reynolds number Re is 2000 or more. Therefore, in Examples 1 to 5, the temperature of the raw material gas supplied to the burner is equal to the temperature of the gas supply pipe. In Example 6, the Reynolds number Re is input to the burner. The temperature of the raw material gas is equal to the temperature of the gas supply pipe near the burner.

  In addition, the manufacturing method of the glass fine particle deposit body and glass base material of this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably. For example, in the present embodiment, the case where the glass fine particle deposit is manufactured by the VAD method in the deposition step has been described as an example, but all other glass fine particle deposits and glass using flame decomposition reaction such as the OVD method and the MMD method are used. It is effective for the manufacturing method of the base material.

In this embodiment, only SiCl ₄ is used as the source gas. However, the core glass synthesis using SiCl ₄ and GeCl ₄ is also effective in improving the source yield. A similar effect can be obtained with a source gas other than SiCl ₄ .

  In addition, the material, shape, dimension, numerical value, form, number, arrangement location, and the like of each component in the above-described embodiment are arbitrary and are not limited as long as the present invention can be achieved.

  DESCRIPTION OF SYMBOLS 10 ... Manufacturing apparatus, 11 ... Reaction container, 12 ... Support rod, 13 ... Departure rod, 14 ... Glass particulate deposit, 15 ... Elevating and rotating device, 16 ... Control device, 18 ... Burner for clad, 19 ... Gas supply device, 20 ... Glass fine particles, 22 ... Raw material container, 23 ... MFC, 24 ... Temperature control booth, 25 ... Gas supply piping, 26 ... Tape heater (heating element), 27 ... Heat insulation tape

Claims (5)

The liquid glass raw material contained in the raw material container is heated and vaporized to form a glass raw material gas,
The glass raw material gas is led from the raw material container to a glass fine particle producing burner by piping, and the glass raw material gas is ejected from the glass fine particle producing burner,
In the method for producing a glass particulate deposit including a deposition step in which glass particulates generated by a flame decomposition reaction of the glass raw material gas are deposited on a starting rod in a reaction vessel to form a glass particulate deposit,
While controlling at least a part of the piping from the raw material container in the deposition step to the glass particulate generation burner to a temperature of 100 ° C. or higher by a heating element,
A method for producing a glass fine particle deposit, wherein the Reynolds number of a glass raw material gas flowing in the pipe from the raw material container to the glass fine particle producing burner is 2000 or more. In the manufacturing method of the glass fine particle deposit body according to claim 1,
A method for producing a glass particulate deposit, wherein the Reynolds number of the glass source gas flowing in the pipe from the source container to the glass particulate generation burner in the deposition step is 4000 or more. In the manufacturing method of the glass fine particle deposit body according to claim 1,
A method for producing a glass particulate deposit, wherein the Reynolds number of the glass source gas flowing in the pipe from the source container to the glass particulate generation burner in the deposition step is 8000 or more.   The glass fine particle deposit produced in the method for producing a glass fine particle deposit according to any one of claims 1 to 3 is made into a glass base material through a transparentization step of heating to make it transparent. Manufacturing method of glass base material. In the manufacturing method of the glass base material of Claim 4,
The method for producing a glass base material, wherein the glass fine particle deposition method in the deposition step is any one of a VAD method, an OVD method, and an MMD method.

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