JP2017081772A - Glass preform manufacturing method - Google Patents

Abstract

A glass base material manufacturing method that enables fine pressure adjustment in a furnace and prevents product defects. In a method of manufacturing a glass base material 1 in which a porous glass base material 1 is sintered in a sintering furnace 100 in which core tubes 3 and 4 are disposed in a furnace body 7, the core tube is a first core. It has a double structure in which the second core tube 4 is arranged in the tube 3, and the flow rate is adjusted in the intermediate chamber 10 formed between the first core tube 3 and the second core tube 4 by the flow rate controller 13 a. Is supplied, and the flow rate regulator 13a is controlled so that the pressure of the intermediate chamber 10 is maintained within a predetermined pressure range, and the porous glass base material 1 is sintered. [Selection] Figure 1

Description

  The present invention relates to a method for producing a glass base material.

  Patent Document 1 is a method of placing a core tube in a furnace body and dehydrating and sintering an optical fiber preform. The method includes a first core tube and a second core tube arranged coaxially. The pressure in the intermediate chamber formed between the first core tube and the second core tube is determined from the pressure in the first core tube (core chamber) and the pressure in the furnace space (reactor chamber). It is disclosed that the gas supply to the intermediate chamber and the exhaust are performed independently at a low setting.

JP 2002-68770 A

  In the dehydration and sintering method described in Patent Document 1, the pressure in the core chamber, the furnace body chamber, and the intermediate chamber is adjusted by adjusting an exhaust valve provided at a gas exhaust port of each chamber. However, if pressure adjustment is performed using these exhaust valves, the pressure fluctuation in the intermediate layer increases due to the opening of the exhaust valve, and fine pressure adjustment is difficult. If the pressure cannot be finely adjusted, the pressure in the intermediate chamber cannot be maintained in a desired range, which may cause a defective product of the glass base material. In addition, an adjustment valve may be provided at the gas exhaust port of the intermediate chamber for pressure adjustment. However, this adjustment valve is likely to be clogged with silica fine particles contained in the exhaust gas. Since the power becomes weaker, it is necessary to adjust the exhaust pressure each time.

  An object of this invention is to provide the manufacturing method of the glass base material which enables the fine pressure adjustment in a furnace body, and prevents generation | occurrence | production of a product defect reliably.

The method for producing the glass base material of the present invention comprises:
A method for producing a glass base material, in which a porous glass base material is sintered in a sintering furnace in which a furnace core tube is disposed in the furnace body,
The reactor core tube is configured as a dual structure reactor core tube in which a second reactor core tube is disposed in the first reactor core tube,
Supplying a gas whose flow rate is adjusted by a flow controller to an intermediate chamber formed between the first core tube and the second core tube;
The porous glass base material is sintered by controlling the flow rate regulator so that the pressure in the intermediate chamber is maintained within a predetermined pressure range.

  According to the present invention, it is possible to finely adjust the pressure in the furnace body and prevent the occurrence of product defects.

It is the schematic of the dehydration sintering furnace using the core tube which concerns on the manufacturing method of the glass base material of this invention. (A) is a figure which shows the pressure fluctuation of the intermediate chamber which concerns on a comparative example, (B) is a figure which shows the pressure fluctuation of the intermediate chamber which concerns on an Example.

<Outline of Embodiment of the Present Invention>
First, an outline of an embodiment of the present invention will be described.
The method for producing a glass base material according to this embodiment is as follows:
(1) A method for producing a glass base material for sintering a porous glass base material in a sintering furnace in which a furnace core tube is disposed in the furnace body,
The reactor core tube is configured as a dual structure reactor core tube in which a second reactor core tube is disposed in the first reactor core tube,
Supplying a gas whose flow rate is adjusted by a flow controller to an intermediate chamber formed between the first core tube and the second core tube;
The porous glass base material is sintered by controlling the flow rate regulator so that the pressure in the intermediate chamber is maintained within a predetermined pressure range.
According to this configuration, it is possible to provide a method for manufacturing a glass base material that enables fine pressure adjustment in the furnace body and reliably prevents product defects.

(2) A gas whose flow rate is adjusted by a flow rate regulator is supplied into the second core tube,
It is preferable to sinter the porous glass base material by controlling the flow rate regulator so that the pressure in the second furnace core tube is maintained within a predetermined pressure range.
According to this configuration, it is possible to finely adjust the pressure in the second core tube that affects the pressure fluctuation in the intermediate chamber.

(3) supplying a gas whose flow rate is adjusted by a flow rate regulator to the outside of the first furnace core tube in the furnace body;
It is preferable to sinter the porous glass base material by controlling the flow rate regulator so that the pressure in the furnace body is maintained within a predetermined pressure range.
According to this configuration, it is possible to finely adjust the pressure in the furnace body that affects the pressure fluctuation in the intermediate chamber.

(4) The gas supplied into the second core tube preferably contains SiCl ₄ or SiF ₄ .
According to this configuration, since the exhaust gas containing silica fine particles that easily clog the exhaust-side regulating valve is exhausted, it is preferable to apply the invention according to (1) to (3).

<Details of Embodiment of the Present Invention>
Hereinafter, an example of an embodiment of a manufacturing method of a glass base material concerning the present invention is explained with reference to drawings.

FIG. 1 is a schematic view of a dehydration sintering furnace using a furnace core tube.
As shown in FIG. 1, the sintering furnace 100 includes a furnace core tube 3 (hereinafter referred to as a first core tube) disposed in a furnace body 7, and a second core tube 4 disposed in the first core tube 3. It is arranged so as to be coaxial with the core tube 3. A space (hereinafter referred to as an intermediate chamber) 10 is defined between the first core tube 3 and the second core tube 4.
The porous glass base material 1 made of SiO ₂ particles passes through the support rod 2 as a starting rod through the penetration portion 4a of the second core tube 4, the penetration portion 3a of the first core tube 3, and the penetration portion 7a of the furnace body 7. The suspension is supported at the center of the second reactor core tube 4. The first core tube 3 and the second core tube 4 are each made up of a plurality of cylindrical side wall members made of high-purity carbon and stacked in multiple stages. It is configured to be sealed with a material. Joint portions between the plurality of side wall members of the first core tube 3 and the second core tube 4 are defined as joint portions 3b and 4b. In addition, you may comprise the 1st core tube 3 and the 2nd core tube 4 by the division structure of quartz.
A heater 5 is disposed outside the first core tube 3, and the outside of the heater 5 is covered with a heat insulating material 6 to shield heat dissipation to the outside. The furnace body 7 is formed of a metal having excellent corrosion resistance, such as stainless steel, and surrounds the entire components including the first furnace core tube 3 and the second core tube 4 and completely seals them from the outside atmosphere.

  In the second furnace core tube 4, a gas supply pipe 11 that supplies gas for dehydration and sintering of the glass base material 1 and a gas exhaust pipe 12 that exhausts the gas in the second furnace core pipe 4 are independent of each other. Are connected. A gas supply pipe 13 to which an inert gas is supplied and a gas exhaust pipe 14 for exhausting the gas in the intermediate chamber 10 are independently connected to the intermediate chamber 10. A gas supply pipe 15 for supplying an inert gas and a gas exhaust pipe 16 for exhausting the gas in the furnace body are independently connected to the furnace body 7.

A gas for dehydration and sintering of the glass base material 1 is supplied from a gas supply pipe 11 to a core chamber 8 which is a space in the second core pipe 4. As this dehydrating and sintering gas, for example, a mixed gas of helium gas advantageous for glass transparency and chlorine gas advantageous for dehydration treatment is supplied. Further, the dehydration sintering gas includes a corrosive gas such as SiCl ₄ or SiF ₄ . Note that a fluorine compound gas that decomposes at a high temperature may be supplied to adjust the refractive index of the glass base material 1. The supply gas is not particularly limited to this example, and different types of gases are used depending on the glass base material manufacturing process.
The gas supply pipe 11 is provided with a mass flow controller (MFC) 11a that controls the flow rate of the supply gas as a flow rate regulator. By controlling the MFC 11 a by the gas pressure control device 19, the flow rate of the dehydration and sintering gas supplied into the core chamber 8 is adjusted. The pressure in the core chamber 8 is maintained within a predetermined range by adjusting the flow rate of the dehydration and sintering gas supplied into the core chamber 8 by the MFC 11a.

  Moisture released from the glass base material 1 is hydrolyzed with a part of the supply gas to generate a corrosive harmful gas such as hydrogen chloride or hydrogen fluoride. Further, the generated gas contains dust particles such as silica fine particles. These gases are exhausted to the gas exhaust pipe 12 and processed by an abatement apparatus.

  Further, in the furnace body chamber 9 which is a space between the furnace body 7 and the first furnace core tube 3, an inert gas such as nitrogen or argon gas is used so that the heater 5 and the heat insulating material 6 do not deteriorate due to oxidation. Gas is supplied from the gas supply pipe 15 and exhausted to the gas exhaust pipe 16. The gas supply pipe 15 is provided with an MFC 15a as a flow rate regulator. By controlling the MFC 15 a by the gas pressure control device 19, the flow rate of the inert gas supplied into the furnace chamber 9 is adjusted. By adjusting the flow rate of the inert gas supplied into the furnace chamber 9 by the MFC 15a, the pressure in the furnace chamber 9 is maintained within a predetermined range.

  An intermediate chamber 10 formed between the first core tube 3 and the second core tube 4 blocks the core chamber 8 of the second core tube 4 and the furnace chamber 9 which is the space of the furnace body 7. In the intermediate chamber 10, for example, helium gas as an inert gas is supplied from a gas supply pipe 13 and exhausted to a gas exhaust pipe 14. The gas supply pipe 13 is provided with an MFC 13a as a flow rate regulator. By controlling the MFC 13 a by the gas pressure control device 19, the flow rate of the inert gas supplied into the intermediate chamber 10 is adjusted. By adjusting the flow rate of the inert gas supplied into the intermediate chamber 10 by the MFC 13a, the pressure in the intermediate chamber 10 is maintained within a predetermined range. Specifically, the pressure in the intermediate chamber 10 is adjusted by the MFC 13 a so that the pressure is slightly lower than the pressure in the core chamber 8 and the furnace body chamber 9. The pressure difference between the core chamber 8 and the intermediate chamber 10 is detected by a differential pressure gauge 17, and an MFC 11 a of the gas supply pipe 11 of the core chamber 8 and / or an MFC 13 a of the gas supply pipe 13 of the intermediate chamber 10 is detected by the gas pressure control device 19. Is controlled to adjust the pressure in the core chamber 8 and / or the intermediate chamber 10. On the other hand, the pressure difference between the furnace chamber 9 and the intermediate chamber 10 is detected by a differential pressure gauge 18, and the gas pressure control device 19 supplies the MFC 15 a of the gas supply pipe 15 of the furnace chamber 9 and / or the gas supply of the intermediate chamber 10. The pressure in the furnace chamber 9 and / or the intermediate chamber 10 is adjusted by controlling the MFC 13 a of the pipe 13.

  When the pressure in the intermediate chamber 10 is set to be slightly lower than the pressure in the core chamber 8, the gas in the second core tube 4 flows into the intermediate chamber 10 from the through-hole 4a and the joint 4b that are insufficiently airtight. There may be some leakage. However, the gas leaking into the intermediate chamber 10 is discharged to the outside from the gas exhaust pipe 14 and does not leak into the core chamber 8 on the higher pressure side. Further, when the pressure in the intermediate chamber 10 is set to be slightly lower than the pressure in the furnace chamber 9, the gas in the furnace body 7 flows from the through-hole 3 a and the joint 3 b of the first core tube 3 into the intermediate chamber 10. May leak a little. However, the gas leaking into the intermediate chamber 10 is discharged to the outside from the gas exhaust pipe 14 and does not leak into the furnace body chamber 9 on the higher pressure side.

  That is, the corrosive harmful gas generated in the second furnace core tube 4 does not leak into the furnace chamber 9 of the furnace body 7 even though it leaks into the intermediate chamber 10. Similarly, the gas containing impurities generated from the heat insulating material and the metal of the main body of the furnace body 7 may leak into the intermediate chamber 10 in the furnace body 7, but the core room 8 of the second core tube 4. Will not leak. In this way, the first reactor core tube 3 and the second reactor core tube 4 which are partition walls separating the gas in the second reactor core tube 4 and the gas in the furnace body 7 are joined to the joint portion 3b having insufficient hermeticity, Even if 4b and the penetration parts 3a and 4a exist, the gas separated from each other is prevented from leaking.

  Since the pressure difference between the intermediate chamber 10 and the core chamber 8 and the furnace chamber 9 only needs to prevent the gas from flowing from the intermediate chamber 10 side to the core chamber 8 and the furnace chamber chamber 9 side, It is sufficient if a pressure difference exists. Specifically, the pressure P in the intermediate chamber 10 is 101.3 to 102.3 KPa (atmospheric pressure is 101.325 KPa), and the pressure in the core chamber 8 is P + (0.01 to 0.2) KPa. The pressure in the furnace chamber 9 is in the range of P + (0.1 to 1.0) KPa.

  As described above, in the present embodiment, the gas whose flow rate is adjusted by the MFC 13 a is supplied to the intermediate chamber 10 formed between the first core tube 3 and the second core tube 4. The porous glass base material 1 is dehydrated and sintered by controlling the MFC 13a so that the pressure is maintained within a predetermined pressure range. According to this configuration, since the pressure of the inert gas supplied to the intermediate chamber 10 is adjusted by the MFC 13 a provided in the gas supply pipe 13 of the intermediate chamber 10, fine pressure adjustment is performed in the intermediate chamber 10. Thus, the pressure in the intermediate chamber 10 can be stably maintained within a desired range. Therefore, the pressure difference between the core chamber 8 and the intermediate chamber 10 or the pressure difference between the furnace chamber 9 and the intermediate chamber 10 is reversed, that is, the pressure in the intermediate chamber 10 is the pressure in the core chamber 8 and the furnace chamber 9. Thus, a pressure rise phenomenon that becomes higher than the above does not occur, and product defects can be reliably prevented.

  In addition, when the adjustment valve for adjusting the exhaust pressure is provided in the gas exhaust pipe as in the past, dust particles contained in the exhaust gas are likely to adhere to the adjustment valve and become clogged. A pressure reversal phenomenon may occur in which the pressure in the intermediate chamber is higher than the pressure. However, according to the configuration of the present embodiment, the gas exhaust pipe 12 is not provided with a regulating valve or the like, so that the pressure inversion between the intermediate chamber 10, the core chamber 8, and the furnace body chamber 9 due to the clogging of the gas exhaust pipe 12. The occurrence of a phenomenon cannot occur.

  In the present embodiment, the dehydration sintering gas whose flow rate is adjusted by the MFC 11a is supplied into the second core tube 4 so that the pressure in the second core tube 4 is maintained within a predetermined pressure range. In addition, the porous glass base material 1 is sintered by controlling the MFC 11a. According to this configuration, since the pressure in the second core tube 4 that affects the pressure fluctuation in the intermediate chamber 10 can be finely adjusted, the pressure difference between the core chamber 8 and the intermediate chamber 10 is set to a desired range. Can be maintained.

  Further, in the present embodiment, the gas whose flow rate is adjusted by the MFC 15 a is supplied into the furnace body chamber 9 which is defined inside the furnace body 7 and outside the first furnace core tube 3. The porous glass base material 1 is sintered by controlling the MFC 15a so that the internal pressure is maintained within a predetermined pressure range. According to this configuration, the pressure in the furnace body chamber 9 that affects the pressure fluctuation in the intermediate chamber 10 can be finely adjusted, so that the pressure difference between the furnace body chamber 9 and the intermediate chamber 10 is set to a desired range. Can be maintained.

In the present embodiment, the gas supplied to the second furnace tube 4 preferably contains SiCl ₄ or SiF _4. In the case of a configuration in which a regulating valve is provided in the gas exhaust pipe as in the prior art, when exhaust gas containing silica fine particles is exhausted, silica fine particles are likely to adhere to the regulating valve and become clogged. However, there is a high possibility that a pressure reversal phenomenon occurs when the pressure in the intermediate chamber 10 is high. However, according to the above configuration, the problem that the pressure reversal phenomenon occurs due to the silica fine particles adhering to the regulating valve is eliminated, so that the gas supplied into the second reactor core tube 4 is made of silica fine particles such as SiCl ₄ or SiF _4. Even if the gas is generated, problems such as product defects and equipment troubles do not occur.

(Example)
FIG. 2A is a diagram showing pressure fluctuations in the intermediate chamber according to the comparative example, and FIG. 2B is a diagram showing pressure fluctuations in the intermediate chamber according to the example.
In the comparative example shown in FIG. 2A, an adjustment valve is provided in the gas exhaust pipe (gas exhaust pipe 14 in FIG. 1) of the intermediate chamber, and the internal pressure of the intermediate chamber is adjusted by opening and closing the adjustment valve. The pressure fluctuation was measured over 1 hour. On the other hand, in the embodiment shown in FIG. 2B, as described above, an MFC is provided as a flow regulator in the gas supply pipe (gas supply pipe 13 in FIG. 1) of the intermediate chamber, and the flow rate of the MFC is increased in the intermediate chamber. A regulated gas was supplied and the pressure fluctuation in the intermediate chamber was measured over 1 hour.
As a result, in the comparative example shown in FIG. 2 (A), the pressure fluctuation range of the intermediate chamber was about 1.4 KPa, but in the example shown in FIG. 2 (B), the pressure fluctuation range of the intermediate chamber was It was suppressed to about 0.9 KPa. Thereby, instead of the regulating valve provided on the gas exhaust pipe side, an MFC is provided on the gas supply pipe side, and the pressure of the gas supplied to the intermediate chamber is adjusted, so that the pressure in the intermediate chamber is set to a desired value. It was confirmed that the range could be stably maintained.

  While the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. In addition, the number, position, shape, and the like of the constituent members described above are not limited to the above-described embodiments, and can be changed to a number, position, shape, and the like that are suitable for carrying out the present invention.

1: Glass base material (porous glass base material)
2: support rod 3: first reactor core tube 4: second reactor core tube 5: heater 6: heat insulating material 7: reactor body 8: reactor chamber 9: reactor chamber 10: intermediate chamber 11, 13, 15: gas supply tube 11a, 13a, 15a: MFC (flow rate regulator)
12, 14, 16: Gas exhaust pipe 17, 18: Differential pressure gauge 19: Gas pressure control device

Claims (4)

A method for producing a glass base material, in which a porous glass base material is sintered in a sintering furnace in which a furnace core tube is disposed in the furnace body,
The reactor core tube is configured as a dual structure reactor core tube in which a second reactor core tube is disposed in the first reactor core tube,
Supplying a gas whose flow rate is adjusted by a flow controller to an intermediate chamber formed between the first core tube and the second core tube;
A method for producing a glass base material, wherein the flow rate controller is controlled to sinter the porous glass base material so that the pressure in the intermediate chamber is maintained within a predetermined pressure range. In the second furnace core tube, a gas whose flow rate is adjusted by a flow rate regulator is supplied,
The glass base material according to claim 1, wherein the porous glass base material is sintered by controlling the flow rate controller so that the pressure in the second furnace core tube is maintained within a predetermined pressure range. Manufacturing method. A gas whose flow rate is adjusted by a flow rate regulator is supplied to the outside of the first furnace core tube inside the furnace body,
The glass matrix according to claim 1 or 2, wherein the porous glass matrix is sintered by controlling the flow rate regulator so that the pressure in the furnace body is maintained within a predetermined pressure range. A method of manufacturing the material. The method for producing a glass base material according to any one of claims 1 to 3, wherein the gas supplied into the second furnace core tube includes SiCl ₄ or SiF ₄ .

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