JP5682577B2 - 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 process for producing a glass particulate deposit by an OVD method, a VAD method, and the like, and a transparency process for producing a transparent glass body by heating the glass particulate deposit. The manufacturing method containing is known (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 relationship, the occurrence of bubbles and cloudiness 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 the above is maintained, there is no description regarding the temperature gradient of the conduit.

  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 fine particle deposit, the glass fine particle deposit is produced by depositing the glass fine particles produced by the step on the starting rod in the reaction vessel, and the glass fine particle producing burner from the raw material container in the deposition step. At least part of the pipe up to 5 ° C./m or more is heated by the heating element on the burner side. It is characterized by controlling the temperature so as to distribution.

  Further, in the method for producing a glass particulate deposit according to the present invention, in the deposition step, at least a part of the piping from the raw material container to the glass particulate generation burner is heated to 15 ° C. on the burner side by a heating element. It is characterized in that the temperature is controlled so as to have a temperature gradient of at least / m.

  Further, in the method for producing a glass particulate deposit according to the present invention, in the deposition step, at least a part of the piping from the raw material container to the glass particulate generation burner is heated to a temperature of 25 ° C. on the burner side by a heating element. It is characterized in that the temperature is controlled so as to have a temperature gradient of at least / m.

  In the method for producing a glass particulate deposit according to the present invention, the heating element is a tape heater.

  Further, the method for producing a glass base material according to the present invention comprises producing a glass fine particle deposit by the method for producing a glass fine particle deposit, and heating the glass fine particle deposit produced in the deposition step to make it transparent. It is characterized by manufacturing a glass base material through a crystallization process.

  Further, the glass base material manufacturing method according to the present invention is characterized in that in the deposition step, a glass fine particle deposit is manufactured by an OVD method, a VAD method or an MMD method, and the glass base material is manufactured through the transparency step. It is said.

  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 the piping from the raw material container to the glass fine particle generating burner is heated to a temperature higher than 5 ° C./m by the heating element on the burner side. Since the temperature is controlled so as to be a gradient, the volume of the raw material gas in the pipe expands from the raw material container toward the burner, and the flow rate of the raw material gas is accelerated. As a result, the inertial force of the glass fine particles generated in the burner flame is increased, the straightness of the glass fine particles is promoted, and the glass fine particles are easily separated from the gas flow in the flame. Therefore, the adhesion efficiency of the glass fine particles to the starting rod and the glass fine particle deposit can be improved, and the raw material yield 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 the schematic which shows an example at the time of giving a temperature gradient to the gas supply piping in FIG. 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 held 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. Glass particulates 20 are deposited on the starting rod 13 to form a glass particulate 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 clad burner 18 as a glass fine particle producing burner is disposed below the inside of the reaction vessel 11, and a raw material gas and a flame forming gas are supplied to the clad 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 formed by 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. To do.

  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.

  In the method for producing a glass fine particle deposit according to the present embodiment, the temperature on the burner side of at least a part of the gas supply pipe 25 from the raw material container 22 to the cladding burner 18 is increased to a temperature gradient of 5 ° C./m or more. To control the temperature.

  At least a part of the gas supply pipe 25 from the raw material container 22 to the cladding burner 18 has a high temperature on the burner side so that the temperature gradient is preferably 15 ° C./m or more, more preferably 25 ° C./m or more. Control the temperature so that

  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. In the case of holding at temperature, the material of the gas supply pipe 25 is preferably a metallic material 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 can be kept low.

An example of temperature control of the gas supply pipe will be described.
As shown in FIG. 2, three types of tape heaters 26 </ b> A, 26 </ b> B, and 26 </ b> C are wound around the outer periphery of the gas supply pipe 25 from the temperature control booth 24 to the cladding burner 18. That is, the first tape heater 26A is wound on the clad burner 18 side, the second tape heater 26B is wound so as to be adjacent to the side, and the third tape heater 26C is wound on the temperature control booth 24 side. ing. For convenience, the length of the gas supply pipe 25 between the temperature control booth 24 and the cladding burner 18 is 1 m.

  For example, thermocouples are installed at both ends of the gas supply pipe 25 and at the outer periphery in the middle, and the respective temperatures are adjusted by the tape heaters 26A, 26B, and 26C. At this time, the temperature of the thermocouple installed at one end of the pipe (temperature control booth 24 side) is set to 120 ° C. by the third tape heater 26C, and the temperature of the thermocouple installed in the middle is set to 140 ° C. by the second tape heater 26B. If the temperature of the thermocouple installed at one end of the pipe (on the burner 18 side) is 160 ° C. by the first tape heater 26A, the temperature is controlled with a temperature gradient of 40 ° C./m.

  As described above, when the temperature of the gas supply pipe 25 from the temperature control booth 24 to the cladding burner 18 is controlled so that the temperature on the burner side is high and the temperature gradient is 5 ° C./m or more, the volume of the source gas in the gas supply pipe 25 is increased. Expands as it proceeds from the temperature control booth 24 to the cladding burner 18, and the flow velocity of the source gas is accelerated. Note that the above-described configuration of the three types of tape heaters 26A, 26B, and 26C is an example for realizing the present invention, and the present invention can be realized with another configuration. For example, even if a part of the tape heater 26B is controlled to be 140 ° C. and the other tape heaters (26A, 26C) are controlled with the same electric power as the tape heater 26B, the effect can be obtained. Note that at least part of the gas supply pipe 25 may be controlled to 5 ° C./m or more, but the entire pipe may be controlled to 5 ° C./m or more. For convenience, the length of the gas supply pipe 25 between the temperature control booth 24 and the cladding burner 18 is 1 m, but the length of the gas supply pipe 25 can be adjusted as appropriate.

  Thereby, the inertial force of the glass fine particles 20 generated in the burner flame is increased, the straightness of the glass fine particles 20 is promoted, and the glass fine particles 20 are easily separated from the gas flow in the flame. The adhesion efficiency of the glass fine particles 20 to the glass fine particle deposit 14 can be improved.

  Further, the pipe diameter is designed so that the Reynolds number (Re number) of the source gas flowing in the gas supply pipe 25 is 2000 or more, preferably 4000 or more, and more preferably 8000 or more. As a result, the flow of the raw material gas in the gas supply pipe 25 is turbulent, and the raw material gas is efficiently heated in the gas supply pipe 25 to easily increase the temperature. FIG. 4 shows the temperature of the raw material gas flowing in the gas supply pipe 25 when the entire length of the gas supply pipe 25 is heated to a constant value of 140 ° C. It can be seen from FIG. 4 that the higher the Re number, the easier the source gas flowing in the gas supply pipe 25 is heated. However, in the present invention, since the temperature of the gas supply pipe 25 is controlled to increase as it goes from the raw material container 22 to the cladding burner 18, the temperature of the raw material gas flowing in the gas supply pipe 25 is saturated on the cladding burner 18 side. Never do.

A manufacturing procedure of the glass fine particle deposit 14 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 lower end 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 clad burner 18. Deposit on starting rod 13.

  At this time, by energizing the tape heater 26 wound around the outer periphery of the gas supply pipe 25, the temperature of the gas supply pipe 25 is inclined at 5 ° C./m or more from the temperature control booth 24 toward the cladding burner 18. The temperature is controlled to be higher.

(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 in the deposition process will be briefly described. As shown in FIG. 3, the flame gas flow G containing the source gas such as SiCl ₄ formed by the cladding burner 18 hits the glass fine particle deposit 14 and the direction of the glass fine particle deposit 14 suddenly changes. It will bend in the outer circumferential direction.

  On the other hand, since the glass fine particles flowing along the flame gas flow G have a higher Stokes number as the flow rate is higher, the inertial force of the glass fine particles is increased and the straightness of the glass fine particles is improved. When the flame gas flow G hits the glass fine particle deposit 14 and the direction of flow suddenly changes in the outer peripheral direction of the glass fine particle deposit 14, the glass fine particle 20A having a large inertial force has high straightness, so that the glass fine particle deposit 14 is intact. Collide with. 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.

  In the present invention, at least a part of the gas supply pipe 25 is given a temperature gradient, the flow rate of the raw material gas flowing in the gas supply pipe 25 is accelerated toward the downstream side of the gas supply pipe 25, and the glass particles in the burner flame Increase inertia force by 20. As a result, the glass fine particles are easily separated 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 can be improved.

Next, an embodiment of the method for producing a glass base material of the present invention will be described.
In both Examples and Comparative Examples, a glass base material is produced using the following materials.
· Starting rod; diameter 25 mm, the input gas into the quartz glass cladding burner length 1000 mm; material gas _... SiCl 4 _(1~7SLM), flame formation gas _{... H 2 (100~150SLM), O} 2 (100~ 150 SLM), burner seal gas ... N ₂ (20-30 SLM)

  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.

Measure the outer peripheral temperature of the gas supply pipe at three points along the longitudinal direction of the pipe, and evaluate the minimum temperature gradient between the measurement points; T (° C./m), raw material yield of glass fine particles; X (%) . In addition, the raw material yield X of the glass fine particles is the mass ratio of the glass fine particles actually deposited on the starting rod and the glass fine particle deposit body with respect to SiO ₂ mass when the SiCl ₄ gas to be input chemically reacts with 100% SiO _2. And

Specifically, in the embodiment, the gas supply pipe from the temperature control booth to the cladding burner is heated to a high temperature on the burner side by a heating element, and the minimum temperature gradient T is gradually increased from 5 ° C./m to 40 ° C./m. Control and calculate the raw material yield at each temperature gradient. On the other hand, in the comparative example, the raw material yield is calculated when the temperature gradient is not managed and the minimum temperature gradient T is less than 5 ° C./m.
As a result, the results shown in Table 1 are obtained.

As is clear from Table 1, in Examples 1 to 5 in which the minimum temperature gradient T is 5 ° C./m or more, the raw material yield X is 32% or more. When the minimum temperature gradient T in Example 5 is 40 ° C./m, the raw material gas temperature immediately before being introduced into the burner is 270 ° C., that is, the raw material gas temperature is 212.12 higher than the standard boiling point of SiCl _{4 as} the raw material gas. At this time, the raw material yield X is improved to 40%. On the other hand, in Comparative Examples 1 and 2, since the minimum temperature gradient T is less than 5 ° C./m, the raw material yield X is as low as 27% or less, and the minimum temperature gradient T of Comparative Example 2 is 3 ° C./m. In this case, the raw material yield X is 24%, and it can be seen that only about one-fourth of the SiCl ₄ gas to be introduced adheres as glass fine particles.

  In addition, the manufacturing method of the 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. However, all other glass base material manufacturing methods using a flame decomposition reaction such as the OVD method and the MMD method. It is effective for.

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, what is necessary is just to manage the temperature of the gas supply piping which connects a raw material container and a burner at the temperature more than the boiling point of source gas, for example, the temperature of 100 degreeC or more.
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 (7)

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 generating burner by piping,
The glass raw material gas is ejected from the glass fine particle producing burner,
In a method for producing a glass fine particle deposit comprising a deposition step of depositing glass fine particles generated by a flame decomposition reaction of the glass raw material gas on a starting rod in a reaction vessel to produce a glass fine particle deposit,
The temperature of at least a part of the piping from the raw material container to the glass fine particle generating burner in the deposition step is controlled by a heating element so that the temperature of the burner becomes high and a temperature gradient of 5 ° C./m or more. A method for producing a glass particulate deposit. In the manufacturing method of the glass fine particle deposit body according to claim 1,
The temperature of at least a part of the pipe from the raw material container to the glass fine particle generating burner in the deposition step is controlled by a heating element so that the temperature of the burner becomes high and a temperature gradient of 15 ° C./m or more. A method for producing a glass particulate deposit. In the manufacturing method of the glass fine particle deposit body according to claim 1,
The temperature of at least a part of the piping from the raw material container to the glass particle generation burner in the deposition step is controlled by a heating element so that the temperature of the burner becomes high and a temperature gradient of 25 ° C./m or more. A method for producing a glass particulate deposit. In the manufacturing method of the glass particulate deposits according to any one of claims 1 to 3,
The method for producing a glass particulate deposit, wherein the heating element is a tape heater. A glass particulate deposit is produced by the method for producing a glass particulate deposit according to any one of claims 1 to 4,
A method for producing a glass base material, comprising: producing a glass base material through a transparentizing step of heating and transparentizing the glass fine particle deposit produced in the deposition step.   6. The method for producing a glass base material according to claim 5, wherein a glass fine particle deposit is produced by the OVD method, the VAD method or the MMD method in the deposition step, and the glass base material is produced through the clarification step. .   In the manufacturing method of the glass particulate deposits according to any one of claims 1 to 4,
  The method for producing a glass particulate deposit, wherein the number of lay nozzles of the glass raw material gas flowing in the pipe is 2000 or more.

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