JP2018193279A - Method for manufacturing glass fine particle deposit, method for manufacturing glass preform and glass fine particle deposit - Google Patents

Abstract

To provide a method for manufacturing a glass fine particle deposit without generating air bubbles in the inside of a glass preform obtained by the subsequent clarification step; a method for manufacturing a glass preform; and the glass fine particle deposit.SOLUTION: A method for manufacturing a glass fine particle deposit includes a deposition process of comprising: arranging a start rod 11 and a glass fine particle formation burner 22 in a reaction vessel 2; introducing a glass raw material into the burner 22; decomposing and reacting the glass raw material in flame formed by the burner 22 to form glass particles 30; depositing the formed glass particles 30 on the start rod 11 to prepare a glass fine particle deposit M. The content of organic based foreign matter included in the glass fine particle deposit M is 2 ppm or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a glass particulate deposit, a method for producing a glass base material, and a glass particulate deposit.

There is the following prior literature in a method for producing a glass fine particle deposit by using siloxane as a raw material and depositing glass fine particles on a starting rod by a gas phase synthesis method.
Patent Document 1 describes that a glass particulate deposit is formed using a siloxane raw material having a low concentration of high-boiling impurities.
Patent Document 2 describes that a raw material siloxane is subjected to a flame decomposition reaction in a liquid state.
Patent Document 3 describes that by adding an end-capping compound to a raw material cyclic siloxane, it is bonded to a site where the ring structure is opened to prevent further polymerization between siloxanes.

JP-A-9-156947 Special Table 2000-502040 JP-T-2001-50312

However, even when the techniques described in Patent Documents 1 to 3 are employed, there have been cases in which bubbles are observed inside the glass base material obtained by the transparentizing step after forming the glass fine particle deposit.
Accordingly, an object of the present invention is to provide a method for producing a glass particulate deposit, a method for producing a glass preform, and a glass particulate deposit, in which bubbles are not generated inside a glass preform obtained by a subsequent transparency step. And

The method for producing a glass particulate deposit according to the present invention comprises:
A starting rod and a glass fine particle generating burner are placed in a reaction vessel, a glass raw material is introduced into the burner, a glass raw material is subjected to a flame decomposition reaction in a flame formed by the burner to generate glass fine particles, and the generated glass A method for producing a glass particulate deposit comprising a deposition step of depositing particulate on the starting rod to produce a glass particulate deposit,
The content of organic foreign matter contained in the glass particulate deposit is set to 2 ppm or less.
Further, the method for producing a glass base material of the present invention produces a glass fine particle deposit by the method for producing a glass fine particle deposit, and heats the produced glass fine particle deposit to produce a transparent glass preform. It has a transparency process.
In the glass fine particle deposit of the present invention, the content of organic foreign matter is 2 ppm or less.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the glass fine particle deposit body from which a bubble does not generate | occur | produce inside the glass base material obtained by a subsequent transparentization process.

It is a block diagram which shows one form of the manufacturing apparatus which enforces the manufacturing method of the glass fine particle deposit body which concerns on 1 aspect of this invention.

[Description of Embodiment of the Present Invention]
First, the contents of the embodiment of the present invention will be listed and described.
A method for producing a glass particulate deposit according to an aspect of the present invention includes:
(1) A starting rod and a glass fine particle generating burner are arranged in a reaction vessel, a glass raw material is introduced into the burner, and a glass raw material is subjected to a flame decomposition reaction in a flame formed by the burner to generate glass fine particles, A method for producing a glass particulate deposit comprising a deposition step of depositing the generated glass particulate on the starting rod to produce a glass particulate deposit,
The content of organic foreign matter contained in the glass particulate deposit is set to 2 ppm or less.
According to this structure, the glass base material obtained through the transparentization process by subsequent heating (sintering) can be made free of bubbles and abnormal points (very small).

(2) It is preferable to make content of the said organic type foreign material into 1 ppm or less.
According to this structure, the glass base material obtained through the transparentization process by subsequent heating (sintering) can be made free of bubbles and abnormal points (very small).
(3) The content of the organic foreign matter is preferably 0.5 ppm or less.
According to this structure, the glass base material obtained through the transparentization process by subsequent heating (sintering) can be further free of bubbles and abnormal points (very small).
(4) It is preferable to use siloxane as the glass raw material.
According to this configuration, since the raw material does not contain corrosive halogen, it is possible to eliminate the problem of corrosion of a manufacturing apparatus or the like caused by exhaust gas. Further, an exhaust gas treatment device is not required.
(5) It is preferable to use octamethylcyclotetrasiloxane (OMCTS) as the siloxane.
According to this configuration, the raw materials used can be easily obtained industrially, and can be stored and handled easily.
(6) It is preferable to make the glass raw material ejected from the burner into a liquid spray state.
According to this configuration, the flame decomposition reaction of the glass raw material can be promoted.
(7) It is preferable to make the glass raw material ejected from the burner into a gas state.
According to this configuration, the flame decomposition reaction of the glass raw material can be promoted.

(8) Moreover, the manufacturing method of the glass base material which concerns on 1 aspect of this invention manufactures a glass particulate deposit by the manufacturing method of the glass particulate deposit in any one of said (1)-(7), It has the transparentization process which heats the manufactured glass fine particle deposit body and manufactures a transparent glass base material.
According to this structure, it can be set as a glass base material without a bubble and an abnormal point (very small).

(9) Further, in the glass fine particle deposit according to one embodiment of the present invention, the content of the organic foreign matter is 2 ppm or less.
According to this structure, the glass base material obtained through the transparentization process by subsequent heating (sintering) can be made free of bubbles and abnormal points (very small).

[Details of the embodiment of the present invention]
[Outline of manufacturing method and equipment used]
Hereinafter, an example of an embodiment of a manufacturing method of a glass particulate deposition object and a manufacturing method of a glass base material concerning an embodiment of the present invention is described based on an accompanying drawing. As a manufacturing method shown below, an OVD (Outside Vapor Deposition) method will be described as an example, but the present invention is not limited to the OVD method. Similar to the OVD method, the present invention can be applied to a method of depositing glass from a glass raw material using a flame pyrolysis reaction, for example, VAD (Vapor Phase Axial Deposition) method, MMD (Multiburner Multilayer Deposition) method, etc. It is.

  FIG. 1 is a configuration diagram of a manufacturing apparatus 1 that performs the method for manufacturing a glass fine particle deposit according to the present embodiment. The production apparatus 1 includes a reaction vessel 2, an elevating and rotating device 3, a raw material supply device 21, a glass particle producing burner 22, and a control unit 5 that controls the operation of each unit.

The reaction container 2 is a container in which the glass particulate deposit M is formed, and includes an exhaust pipe 12 attached to a side surface of the container.
The lifting / lowering rotation device 3 is a device that moves the glass particulate deposit M up and down and rotates via the support rod 10 and the starting rod 11. The lifting / lowering rotation device 3 controls the operation of the support bar 10 based on a control signal transmitted from the control unit 5. The elevating and rotating device 3 elevates and lowers the glass particulate deposit M while rotating it.

The support rod 10 is disposed through a through hole formed in the upper wall of the reaction vessel 2, and a starting rod 11 is provided at one end portion (lower end portion in FIG. 1) disposed in the reaction vessel 2. Is attached. The other end (upper end in FIG. 1) of the support bar 10 is held by the elevating and rotating device 3.
The starting rod 11 is a rod on which glass fine particles are deposited, and is attached to the support rod 10.
The exhaust pipe 12 is a pipe for discharging glass fine particles and the like that have not adhered to the starting rod 11 and the glass fine particle deposit M to the outside of the reaction vessel 2.

The raw material is supplied to the burner 22 by the raw material supply device 21. In FIG. 1, the gas supply device that supplies the flame forming gas is omitted.
The raw material supply device 21 includes a raw material container 24 that stores the liquid raw material 23, an MFC (Mass Flow Controller) 25 that controls the supply flow rate of the raw material gas, a supply pipe 26 that guides the raw material to the burner 22, a raw material container 24, and an MFC 25. And a temperature control booth 27 for maintaining a part of the supply pipe 26 at a predetermined temperature or higher.

  The liquid raw material 23 in the raw material container 24 is controlled to a temperature equal to or higher than the boiling point (for example, the standard boiling point in the case of OMCTS is 175 ° C.) in the temperature control booth 27 and is vaporized in the raw material container 24. The supply amount of the vaporized source gas to the burner 22 is controlled by the MFC 25. Note that the control of the supply amount of the source gas by the MFC 25 is performed based on a command value from the control unit 5.

  As for the material of the supply pipe 26, a fluororesin or the like is usually used. However, when the supply pipe 26 is held at a temperature of 200 ° C. or higher, it is preferable to use a metallic material such as SUS. Further, it is preferable that a tape heater 28 or the like as a heating element is wound around the outer periphery of the supply pipe 26 from the temperature control booth 27 to the burner 22 so that the supply pipe 26 is heated.

  The control unit 5 controls each operation of the elevating and rotating device 3, the raw material supply device 21, and the like. The controller 5 transmits a control signal for controlling the ascending / descending speed and the rotating speed of the glass particulate deposit M to the ascending / descending rotation device 3. Further, the control unit 5 transmits a control signal for controlling the flow rate of the raw material gas emitted from the burner 22 to the MFC 25 of the raw material supply device 21.

And various manufacturing conditions are set so that content of the organic type foreign material contained in the glass particulate deposit M may be 2 ppm or less.
The technique for setting the content of the organic foreign matter contained in the glass fine particle deposit M to 2 ppm or less is not particularly limited, but for example, appropriately setting the composition, flow rate, etc. of the flame forming gas. . Specifically, it is necessary to sufficiently supply hydrogen to form an oxyhydrogen flame in order to cause the siloxane to undergo a flame decomposition reaction. If the oxyhydrogen flame cannot be sufficiently formed, activation of the siloxane does not proceed. Oxygen is necessary to oxidize siloxane to form silica. If oxygen is insufficient, conversion to silica becomes insufficient. On the other hand, if hydrogen and oxygen are excessively supplied, it becomes a factor that inhibits the reaction in the flame.
Further, the content of the organic foreign matters contained in the glass fine particle deposit M is preferably 1 ppm or less from the viewpoint that the bubbles and abnormal points of the glass base material obtained through the subsequent transparentization step can be reduced. 0.5 ppm or less is more preferable.
The organic foreign matter contained in the glass fine particle deposit M includes a glass raw material component that remains unreacted when a glass raw material is subjected to a flame decomposition reaction to produce glass fine particles, and a glass raw material and a flame forming gas described later. This corresponds to a hydrocarbon-based by-product that is unexpectedly generated from the like.
Further, the method for measuring the content of the organic foreign matter contained in the glass fine particle deposit M is not particularly limited, but it is preferably performed by a gas chromatography mass spectrometry (GCMS) method.

The flame forming gas is not particularly limited as long as the burner can form a flame in order to cause the glass raw material to undergo a flame decomposition reaction to generate glass fine particles. In general, hydrogen (H ₂ ), which is a combustible gas, and oxygen (O ₂ ), which is an auxiliary combustion gas, are mixed as appropriate, and nitrogen or the like is further mixed as a seal gas. In this case, it is preferable that hydrogen, oxygen, and nitrogen are ejected from separate ejection ports and mixed after ejection.

Next, the procedure of the method for producing the glass fine particle deposit and the glass base material will be described.
[Deposition process]
Glass fine particles are deposited by the OVD method (external method) to produce a glass fine particle deposit M. First, as shown in FIG. 1, with the support rod 10 attached to the elevating and rotating device 3, and with the start rod 11 attached to the lower end of the support rod 10, a part of the start rod 11 and the support rod 10 are placed in the reaction vessel. Put it in 2.
Subsequently, the MFC 25 supplies the source gas to the burner 22 while controlling the supply amount based on the control signal transmitted from the control unit 5.
The raw material gas and the flame forming gas are supplied to the burner 22, and the glass fine particles 30 are generated by oxidizing the raw material in the flame.
The burner 22 continuously deposits the glass particles 30 generated in the flame on the starting rod 11 that rotates and moves up and down.
The elevating and rotating device 3 moves up and down and rotates the starting rod 11 and the glass particulate deposit M deposited on the starting rod 11 based on a control signal from the control unit 5.

[Transparency process]
Next, the obtained glass fine particle deposit M 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 obtain a transparent glass base material. Such a glass base material is repeatedly manufactured.

[Various manufacturing conditions]
In addition, although the aspect mentioned above makes the glass raw material which was a liquid gas state, and it ejects from the burner 22, it is good also as an aspect which ejects from the burner 22 in the state of a liquid spray, without making a glass raw material gas state. . In a mode in which the glass raw material is ejected from the burner 22 in a liquid spray state, the liquid raw material ejected from the liquid raw material port (not shown) of the burner 22 is atomized by applying a gas jetted from a jet gas port (not shown). Examples of the gas to be ejected from the ejection gas port include nitrogen (N ₂ ), oxygen (O ₂ ), argon (Ar), and the like, and each is ejected alone or mixed.

Further, the glass raw material is not particularly limited as long as it is capable of generating glass fine particles by the flame decomposition reaction in the above-described embodiment. Examples include silicon tetrachloride (SiCl ₄ ), siloxane, and the like. Among them, siloxane is preferable because it does not generate corrosive gas such as chlorine as a result of using it in comparison with SiCl ₄ . Of the siloxanes, cyclic ones are preferred from the viewpoint of industrial availability and easy storage and handling. Among them, OMCTS is more preferred.

[Function and effect]
When high boiling point impurities are present in the glass raw material, a gel-like substance may be generated inside the supply pipe and the burner itself. Moreover, a gel-like substance may be produced in the process of turning a liquid glass raw material into a gas state. Furthermore, when a cyclic siloxane such as OMCTS is used as the glass raw material, the ring-opened siloxanes may be bonded together to form a gel-like substance due to the opening of the ring structure. When such a gel-like substance adheres to the glass fine particle deposit, it causes bubbles in the glass base material obtained by a subsequent transparentization process.

In the aforementioned Patent Documents 1 to 3 and the like, by making the glass raw material have a low concentration of high-boiling impurities, causing the glass raw material to undergo a flame decomposition reaction while being in a liquid state, adding an end-capping compound to the glass raw material, etc. It has been studied to suppress the formation of gel-like substances.
However, even in the glass fine particle deposit obtained by the above-described technique, there has been an example in which bubbles are observed inside the glass base material obtained by the subsequent clarification process.
This is because when a glass raw material is subjected to a flame decomposition reaction to produce glass fine particles, unreacted glass raw material components, and hydrocarbon-based foreign matters that are unexpectedly by-produced from the glass raw material and flame forming gas, etc. It is estimated that it adheres to the glass particulate deposit.

  Therefore, in the embodiment of the present invention, by controlling the content of the organic foreign matter contained in the glass fine particle deposit to 2 ppm or less, the generation of bubbles inside the glass base material obtained by the subsequent clearing step is suppressed. I was able to.

  Hereinafter, the results of evaluation tests using examples and comparative examples according to the present invention will be shown, and the present invention will be described in more detail. The present invention is not limited to these examples.

  1 is deposited by the OVD method, that is, the glass particulate deposit M is produced [deposition step]. Further, the obtained glass fine particle deposit M 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 [translucent step].

Pure quartz glass is used as the starting rod 11.
A starting rod 11 and a glass fine particle producing burner 22 were disposed in the reaction vessel 2, and OMCTS was introduced into the burner 22 as a glass raw material in a gaseous state. The OMCTS was subjected to a flame decomposition reaction in the flame formed by the burner 22 to generate glass particles, and the generated glass particles 30 were deposited on the starting rod 11 to produce a glass particle deposit M. At this time, as flame decomposition reaction conditions, five different conditions (Nos. 1 to 5, as shown in Table 1 below) in which the flow rate of each gas supplied to the burner was changed were examined. When gas chromatography mass spectrometry (GCMS) was performed on each of the five kinds of glass fine particle deposits M produced, the contents of unreacted OMCTS and hydrocarbon-based foreign matters were as shown in Table 1 below.
In the measurement by GCMS, no. Glass particulates were sampled from 1 to 5 glass particulate deposits and heated at 300 ° C. for 5 minutes to analyze the generated gaseous substances.
Further, the produced five kinds of glass fine particle deposits M were heated to produce a transparent glass base material. When the produced glass base material was evaluated for bubbles and abnormal points, it was as shown in Table 1 below.
In the evaluation of bubbles and abnormal points, halogen lamp light is irradiated from the side surface of the glass base material, the inside of the glass base material is visually observed, and the number of bubbles having a size of 1 mm or more and colored foreign matters that can be visually confirmed. Was evaluated by the number of bubbles and abnormal points contained in the glass base material per 100 km converted length when the line was drawn.
In Table 1 below, no. 1 to 3 are examples. 4 to 5 are comparative examples.

No. in Table 1 above. 1-3 were able to sufficiently supply oxygen and hydrogen gas to form an oxyhydrogen flame and decompose OMCTS, so that the content of OMCTS and hydrocarbon-based foreign matter in the glass particulate deposit was 2 ppm or less. Thereafter, there were almost no bubbles or abnormal points in the glass base material produced thereafter.
In contrast, No. 1 in Table 1 above. 4-5, since the supply amount of oxygen was insufficient and a sufficient oxyhydrogen flame could not be formed, the content of OMCTS and hydrocarbon-based foreign matter in the glass particulate deposit exceeded 2 ppm, and thereafter A relatively large number of bubbles and abnormal points were observed in the glass base material prepared in the above.

1: Manufacturing device 2: Reaction vessel 3: Lifting and rotating device 5: Control unit 10: Support rod 11: Starting rod 21: Raw material supply device 22: Burner 23: Liquid raw material 24: Raw material container 25: MFC
26: Supply piping 27: Temperature control booth 28: Tape heater 30: Glass particulate M: Glass particulate deposit

Claims (9)

A starting rod and a glass fine particle generating burner are placed in a reaction vessel, a glass raw material is introduced into the burner, a glass raw material is subjected to a flame decomposition reaction in a flame formed by the burner to generate glass fine particles, and the generated glass A method for producing a glass particulate deposit comprising a deposition step of depositing particulate on the starting rod to produce a glass particulate deposit,
A method for producing a glass particulate deposit, wherein the content of organic foreign matter contained in the glass particulate deposit is 2 ppm or less.   The method for producing a glass particulate deposit according to claim 1, wherein the content of the organic foreign matter is 1 ppm or less.   The method for producing a glass particulate deposit according to claim 2, wherein the content of the organic foreign matter is 0.5 ppm or less.   The method for producing a glass particulate deposit according to any one of claims 1 to 3, wherein siloxane is used as the glass raw material.   The method for producing a glass particulate deposit according to claim 4, wherein octamethylcyclotetrasiloxane (OMCTS) is used as the siloxane.   The method for producing a glass particulate deposit according to any one of claims 1 to 5, wherein the glass raw material ejected from the burner is in a liquid spray state.   The method for producing a glass particulate deposit according to any one of claims 1 to 5, wherein the glass raw material ejected from the burner is in a gas state.   A glass particulate deposit is produced by the method for producing a glass particulate deposit according to any one of claims 1 to 7, and the produced glass particulate deposit is heated to produce a transparent glass base material. The manufacturing method of the glass base material which has a transparency process.   A glass particulate deposit having an organic foreign matter content of 2 ppm or less.

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