JP2003040626A - Method for producing fine glass particle heap - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing fine glass particle heap able to control effectively adhering or mixing of a foreign matter to it using its producing apparatus composed of a reaction vessel, an upper chimney and a lower chimney. SOLUTION: The apparatus to produce fine glass particle heap is contained in a vessel with an exhaust pipe. Clean air is introduced from a clean air introducing pipe and blending of outside air is prevented by adjusting inside pressure and outside pressure of the apparatus. The fine glass particle heap is performed while exhausting floating dust from the apparatus to the containing vessel where it is outside of the apparatus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a glass fine particle deposit by the OVD method, and more particularly to a method for producing a glass fine particle deposit with reduced contamination of foreign substances in the glass fine particle deposit.

[0002]

2. Description of the Related Art A burner for synthesizing glass particles is used,
SiCl ₄ and GeCl used as glass materials in oxyhydrogen flame
₄ is supplied and the flame hydrolysis reaction causes SiO ₂ and GeO.
_{2 When a} glass particle deposit is produced by the OVD method of generating glass particles and depositing the glass particles in the radial direction with respect to the starting lot, the glass particles generated by the burner are deposited around the starting rod. The glass particles not deposited on the body float in the space of the manufacturing apparatus including the reaction vessel and the upper and lower chimneys attached thereto. Since glass particles are easily flowed upward due to the influence of high temperature gas, the floating glass particles adhere to the inner wall surfaces of the manufacturing equipment, especially to the inner walls of the reaction vessel and the upper chimney, and when the amount of adhesion increases, the glass particle deposits fall off. Adheres as foreign matter to the surface of. Further, depending on the constituent material of the reaction device, metal-based dust may be generated.

If these foreign substances adhere to the glass particulate deposit, they will cause bubbles during the sinter-transparent process, and also will cause disconnection when drawing the optical fiber or increase the transmission loss of the optical fiber. There is a problem. Therefore, it is necessary to reduce the amount of foreign matter mixed in the glass particle deposit body as much as possible when manufacturing the glass particle deposit body, and various methods for that purpose have been studied and proposed.

For example, in Japanese Unexamined Patent Publication No. 5-116979 and Japanese Unexamined Patent Publication No. 5-116980, foreign matter is mixed into the glass particle deposit body by blowing clean air or oxyhydrogen flame onto the starting rod (glass particle deposit body) itself. A method of preventing this is disclosed. However, when clean air is blown directly onto the deposition surface, it peels off (cracks) into the glass particles.
Occurs. Further, when the deposition surface is roasted with an oxyhydrogen flame, there is a problem that the glass particulate deposit is likely to be deformed (especially when the soot bulk density is low). In addition, JP-A-8-2174
Japanese Patent No. 80 discloses an invention relating to a dew condensation preventing means for a reaction container for producing a porous base material that is stopped, and the formation of a metal oxide is suppressed by using Ni or a Ni-based alloy as the material of the reaction container. It is described that it is effective.
However, if Ni itself is also mixed in the glass particulate deposit,
It may cause fiber breakage and increase transmission loss.

[0005]

DISCLOSURE OF THE INVENTION According to the present invention, when a glass particle deposit is manufactured using a glass particle deposit manufacturing apparatus composed of a reaction vessel, an upper chimney and a lower chimney, foreign matter in the glass particle deposit is removed. An object of the present invention is to provide a method for producing a glass particle deposit body capable of effectively suppressing adhesion and mixture.

[0006]

The present invention comprises (1) a reaction vessel provided with a burner for synthesizing glass particles, an upper chimney and a lower chimney having an upper lid provided with a support rod insertion port,
Using a glass fine particle deposit production apparatus provided with a clean air introduction pipe for introducing clean air into the apparatus, the burner for synthesizing glass particles is arranged in opposition to a starting rod supported in the apparatus and rotating, In a method for producing a glass particle deposit by depositing glass particles on the outer periphery of a starting rod while reciprocating the starting rod up and down, an exhaust port is provided in at least one of the reaction vessel, the upper chimney or the lower chimney. The glass particulate deposit production apparatus is housed in a storage container equipped with an exhaust pipe, clean air is introduced into the apparatus through the clean air introduction pipe, and the pressure in the glass particulate deposit production apparatus is controlled by the device. It is maintained so that it is higher than the pressure of the space inside the outer storage container to prevent mixing of outside air into the device and to collect floating dust inside the device outside the device. A method of manufacturing a glass particle deposit body, characterized in that glass particles are deposited while being discharged into a container; 0.5 x 10 ⁴
The method for producing a glass fine particle deposit according to the above (1), characterized in that the clean air is not more than the number of particles / m ³ .

[0007]

DETAILED DESCRIPTION OF THE INVENTION The method of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic cross-sectional view schematically illustrating a configuration in which a glass particulate depositing body manufacturing apparatus for carrying out the method of the present invention is housed in a housing container. The glass particle deposit production apparatus 10 illustrated in FIG. 1 includes a reaction container 1 provided with a glass particle synthesizing burner 4 and an exhaust port 14, an upper chimney 2 having an upper lid 9 provided with a clean air introducing pipe 7, and It is composed of a lower chimney 3. In the method of the present invention, basically, a burner 4 for synthesizing glass particles is disposed in the manufacturing apparatus 10 so as to face a rotating starting rod 5 which is supported by a supporting rod 6, and the starting rod 5 is used.
Is a method of manufacturing the glass particle deposit body 8 by causing glass particles to be deposited on the outer circumference of the starting rod 5 while reciprocating vertically.

In the method of the present invention, this glass particulate deposit production apparatus 10 is provided with a storage container 1 equipped with an exhaust pipe 12.
1 and the clean air is introduced from the clean air introduction pipe 7 into the apparatus 10 to produce the glass particle deposit production apparatus 1
0 (upper chimney 2, reaction vessel 1, lower chimney 3) is maintained so as to be higher than the pressure in the space inside the storage container 11 outside the apparatus 10, and then into the apparatus for producing glass particle deposits 10. Of the outside air, and suspended dust in the apparatus 10 from the exhaust port 14 (the example shown in the figure is provided in the reaction vessel 1) (glass not deposited on the glass particle deposit body 8 in the apparatus 10). It is characterized in that glass particles are deposited while discharging (for example, particles) into the storage container 11 outside the apparatus 10.

That is, the pressure in the apparatus 10 is increased by adjusting the flow rate of the clean air introduced into the apparatus 10 from the clean air introduction pipe 7, and the pressure in the space inside the storage container 11 outside the apparatus 10 is higher than the pressure in the space. By keeping it high, it is possible to prevent external air from entering the device 10. Further, the apparatus 10 is provided with an exhaust port 14 so that dust such as glass particles that have not accumulated is discharged into the storage container 11 outside the apparatus 10 and further discharged from the exhaust pipe 12 to the outside. In addition,
The clean air introduction pipe 7 and the exhaust port 14 do not necessarily have to be provided in the upper lid 9 and the reaction container 1 as shown in FIG. 1, and may be provided in a plurality of places, such as the reaction container 1, the upper chimney 2 or the lower portion. It may be provided in at least one or more of the chimneys 3.

In the method of the present invention, a glass particulate deposit manufacturing apparatus 10 (upper chimney 2, reaction vessel 1, lower chimney 3)
The inside is managed as positive pressure, and the space inside the storage container 11 outside the device 10 is managed as negative pressure. Specifically, the relationship between the pressure P ₁ in the apparatus for producing glass particle deposits, the pressure P ₂ in the space inside the storage container outside the apparatus, and the atmospheric pressure P ₃ is P ₁ > P ₃ > P
₂ or P ₁ > P ₂ > P ₃ are held.

In order to maintain the cleanliness of the apparatus 10, the clean air introduced into the apparatus 10 through the clean air introducing pipe 7 has a dust number of 0.3 μm or more of 3.5 × 1.
It is desirable to use clean air of not more than 0 ⁴ pieces / m ³ (1000 pieces / CF, CF: ft ³ ).

As the burner 4 for synthesizing glass fine particles,
Although a conventionally used type may be used, for example, the multi-tube type burner shown in FIG. 2 can be preferably used. In FIG. 2, reference numeral 15 is a raw material and hydrogen gas ejection port, 16 and 19 are argon gas ejection ports, 17 is a hydrogen gas ejection port, and 18 and 20 are oxygen gas ejection ports.

[0013]

EXAMPLES The method of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. (Embodiment 1) As shown in FIG. 1, a reaction vessel 1 made of Ni (diameter 500 mm), an upper chimney 2 (diameter 400 mm) and a lower chimney 3 (diameter 400 m) accommodated in an accommodation vessel 11.
m) was used to deposit glass particles around the starting rod 5 to manufacture a glass particle deposit body. On the upper part of the upper chimney 12, there is provided an upper lid 9 having a hole for inserting the support rod 6 and having a clean air introducing pipe 7 attached thereto. The reaction vessel 1 has three burners 4 for synthesizing glass particles and an exhaust port 14 (diameter of 300 m) for discharging dust such as glass particles floating in the reaction vessel 1 without accumulating into the container 11.
m) is installed.

A starting rod 5 is manufactured by welding dummy rods made of quartz glass to both ends of a core rod (length: 500 mm) having a core / clad portion and having a diameter of 30 mm, and the starting rod 5 is rotated vertically at 40 rpm. Glass particulates produced from the burner 4 for synthesizing glass particulates were successively deposited while traversing up and down 1100mm at a speed of 200 mm / min to prepare a glass particulate deposit body 11. As the burner 4, three burners each having a diameter of 30 mm and having a structure shown in FIG.
It was installed at m. Silicon tetrachloride as a raw material for each of the three burners 4: 4 SLM (standard liter /
Min), hydrogen: 80 SLM and oxygen: 40 SLM to form a flame, and Ar: 2 SL as a sealing gas.
M was supplied.

During the deposition period of the glass particles, the number of dust particles having a size of 0.3 μm or more is 1.4 from the clean air introducing pipe 7.
~ 2.1 x 10 ³ air / m ³ clean air
Introduced at ³ / min. The number of dust particles having a size of 0.3 μm or more in the atmosphere outside the storage container 11 is 3.5 × 10 ^6.
The number was about pcs / m ³ . The number of dust is Met / On
It was measured by a particle counter, Model 237B manufactured by e. Further, the pressure P ₁ in the apparatus for producing glass particle deposits 10, the pressure P ₂ in the space inside the container 11 outside the apparatus and the atmospheric pressure P ₃ are P ₁ = 101600P, respectively.
a, P ₂ = 101000Pa, P ₃ = 101300Pa
Met.

This operation was repeated in order to obtain the final target glass layer thickness of 30 mm (glass diameter: 93 mm), and the glass fine particle deposit 11 having an outer diameter of 200 mm was produced by traversing 150 times. Obtained glass particulate deposit 1
1 was heated at a high temperature to form a transparent glass and then formed into a fiber. When a screening test was performed on the obtained optical fiber, the number of disconnection was 100 km and was once. The screening test here was performed under a load (1.8 to 2.2 kgf) that results in a tensile elongation of 2% in the longitudinal direction of the fiber.
This is a fiber strength test for checking the presence or absence of wire breakage by applying (about).

Comparative Example 1 A glass fine particle deposit was produced in the same manner as in Example 1. During the deposition period of the glass particles, clean air having a size of 0.3 μm or more and a dust number of 1.4 to 2.1 × 10 ³ particles / m ³ was introduced from the clean air introduction pipe 7 at an air flow rate of 20 m ³ / min. The number of dust particles having a size of 0.3 μm or more in the atmosphere outside the storage container 11 was about 3.5 × 10 ⁶ particles / m ³ . Also, by adjusting the exhaust pressure of the exhaust pipe 12 and the opening area of the exhaust port 14,
The pressure P ₁ in the glass particle deposit production apparatus 10, the pressure P ₂ in the space inside the storage container 11 outside the apparatus, and the atmospheric pressure P
₃ are P ₁ = 101100 Pa and P ₂ = 1011 respectively
00Pa, was set to be P ₃ = 101300Pa.

This operation was repeated in order to obtain the final target glass layer thickness of 30 mm (glass diameter: 93 mm). However, since there were many suspended glass particles in the reaction vessel 1, foreign matter adhered to the surface of the deposit at the 50th traverse. (Protrusions were generated in the effective part of the glass particulate deposit), and the process was terminated halfway.
In this case, outside air enters the storage container 11 through the gaps around the clean air introduction pipe 7, the exhaust pipe 12, and the support rod 6 of the storage container 11, and further the gap between the upper lid 9 and the support rod 6 and the exhaust port 14 are provided.
It is considered that the suspended glass fine particles were not smoothly discharged due to invasion into the reaction vessel 1 from the above.

(Comparative Example 2) In place of the clean air introduced from the clean air introducing pipe 7, an air having a dust number of 50 x 10 ⁴ particles / m ³ having a size of 0.3 µm or more was introduced. A glass fine particle deposit was manufactured in the same manner as above. This operation was repeated in order to obtain the final target glass layer thickness of 30 mm (93 mm in glass diameter), and the glass fine particle deposit 11 having an outer diameter of 200 mm was produced with 150 traverses. Obtained glass particulate deposit 11
Was heated at a high temperature to form a transparent glass and then formed into a fiber. When a screening test was performed on the obtained optical fiber, the number of disconnection was 100 km and 10 times.

[0020]

EFFECTS OF THE INVENTION According to the method of the present invention, dust such as undeposited glass particles floating in the manufacturing apparatus during the manufacture of the glass particle deposition body can be efficiently discharged to the outside of the apparatus, and stable. Quality glass particulate deposits can be produced.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view schematically illustrating a configuration in which a glass particle deposit production apparatus for carrying out the method of the present invention is housed in a housing container.

FIG. 2 is a sectional view showing the structure of a multi-tube type glass fine particle synthesizing burner used in the examples.

[Explanation of symbols]

1 Reaction Vessel 2 Upper Chimney 3 Lower Chimney 4 Burner 5 Starting Rod 6 Support Rod 7 Clean Air Introducing Tube 8 Glass Fine Particle Deposit 9 Upper Lid 10 Glass Fine Particle Deposit Manufacturing Equipment 11 Storage Container 12 Exhaust Pipe 14 Exhaust Port 15 Raw Material and Hydrogen Gas Ejection port 16 Argon gas ejection port 17 Hydrogen gas ejection port 18 Oxygen gas ejection port 19 Argon gas ejection port 20 Oxygen gas ejection port

Claims (2)

[Claims] 1. A clean air introducing pipe for introducing clean air into the apparatus, which comprises a reaction container provided with a burner for synthesizing glass particles, an upper chimney and a lower chimney having an upper lid provided with a support rod insertion port. The glass particle deposit manufacturing apparatus is used to dispose a burner for synthesizing glass particles so as to face a rotating starting rod supported in the apparatus, and the glass particles are started and reciprocated while the starting rod is moved up and down. In the method for producing a glass fine particle deposit by depositing on the outer periphery of the above, an exhaust port is provided in at least one of the reaction vessel, the upper chimney or the lower chimney, and the glass fine particle deposit producing apparatus is equipped with an exhaust pipe. It is stored in a storage container, clean air is introduced into the device from the clean air introduction pipe, and the pressure inside the device for producing glass particle deposits is controlled outside the device. The pressure in the storage container is kept higher than the pressure in the storage container to prevent the mixing of the outside air into the device, and the floating dust in the device is discharged into the storage container outside the device to deposit glass particles. A method for producing a glass particulate deposit, comprising: 2. Clean air introduced into the apparatus,
The number of dust particles with a size of 0.3 μm or more is 3.5 × 10 ⁴ /
The method for producing a glass particle deposit according to claim 1, wherein the clean air is m ³ or less.