JPH11292558A - Reactor for production of glass fine particle deposit for optical fiber glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress such a problem that detection of the top end of a glass deposit by a laser detector is inhibited by deposition of glass fine particles on the inner wall of a VAD reactor when porous glass fine particles are deposited on the top end of a rotating seed rod while the rod is drawn to grow a porous glass fine particle deposited body, by adding a gas permeating function to the reactor. SOLUTION: The wall of the reactor is composed of a two-layer structure, and the inner wall 22 of the reactor 21 is composed of a material having gas-permeability (such as a PTFE porous material) and a clean gas is passed between the inner wall and the outer wall 23. The supply pressure of the clean gas is controlled higher by about 10 mm Aq than the inner pressure of the reactor 21 so that the gas can flow into the inside of the reactor 21. Since the outer wall 23 is not exposed to high temp. or hydrochloric gas, it may be made of plastics or general metals. The source gas and H2 , O2 are supplied from burners 3 to deposit glass fine particles on the top end of a seed rod 4, and the rod is drawn to grow the deposit of the glass fine particles. In this device, fine particles hardly deposit on the light-transmitting part or observation window of a top end laser detector 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called VA in which porous glass fine particles are deposited on the tip of a rotating seed rod and the seed rod is pulled up to grow a porous glass fine particle deposit.
The present invention relates to a reaction vessel for producing a glass fine particle deposit for an optical fiber by a method D.

[0002]

2. Description of the Related Art A VAD method is one of the methods for producing a glass particle deposit for an optical fiber. As shown in FIG. 3, the production of a glass fine particle deposit by the VAD method is performed using a glass material (S
iCl ₄ , GeCl ₄ etc.) and combustion gas (H ₂ , O ₂ )
Is spouted from the burner 31 to hydrolyze the glass raw material in the flame, and the seed rod 32 which rotates the generated glass fine particles
This is a method in which a seed rod is pulled up and grown while being deposited on the tip of the seed. The container 33 for producing the glass particle deposit in this manner is selected based on the following criteria. That is, 1. 200 ° C to 300 ° C generated by hydrolysis reaction
1. Does not deteriorate in high temperature chlorine or high temperature hydrochloric acid atmosphere. 2. The inside of the container is kept in a clean atmosphere; The inside can be observed. As a material satisfying such conditions, a reaction vessel made of quartz glass was generally used. In the drawing, reference numeral 34 denotes a laser tip detector, which controls the rise of the seed rod 32 by catching the growth of the fine particles 35 by applying the laser light from the outside of the reaction vessel 33 to the lowermost end of the glass fine particle deposit body 35. It is. In the figure, 36 is an exhaust duct, and 37 is a viewing window. In addition, with the increase in the size of the VAD device, the inner surface of a metal container having a water cooling jacket is processed with Teflon,
Large-scale devices provided with quartz glass viewing windows have also been used.

[0003]

In recent years, the demand for optical fibers has increased, and accordingly, the production equipment has become larger, and the manufacturing time of the glass fine particle deposit has been greatly increased. V
One of the most problematic points in the production of a glass particle deposit by the AD method is that glass particles hydrolyzed in a burner (flame) adhere to a seed rod as a target or a growing porous glass particle deposit. And adheres to the inner wall surface of the reaction vessel without being discharged outside the vessel. As described above, as the manufacturing time of the glass fine particle deposit increases, the amount of the fine particles attached to the inner wall surface of the reaction vessel increases in proportion thereto, and the laser beam of the laser tip detector 34 is blocked to reduce the growth rate during the deposition. The catch 35 cannot be obtained, and a deposit 35 of uniform quality cannot be manufactured. In addition, since the adhered fine particles are peeled off from the inner wall surface and mixed into the growing glass fine particle deposit, a problem such as a bubble remaining in the product occurs, so that it is impossible to manufacture for a long time. For this reason, it is necessary to frequently clean the inner wall surface of the reaction vessel, and the productivity of the glass particle deposit is extremely deteriorated. The present invention has been made to solve the conventional problems and to provide a reaction vessel capable of coping with a long-time reaction and having no adverse effect on the glass fine particle deposit.

[0004]

SUMMARY OF THE INVENTION According to the present invention, there is provided a glass particle deposit for an optical fiber, wherein a porous glass particle deposit is grown by pulling up the seed rod while depositing porous glass particles on the tip of a rotating seed rod. The object of the present invention is to provide a reaction vessel for producing a glass fine particle deposit for an optical fiber, wherein the reaction vessel has a gas permeation function in the reaction vessel for producing a porous glass fine particle. Further, the present invention provides a reaction container for producing a glass microparticle deposit for an optical fiber, wherein the reaction container has a double wall, an outer wall does not substantially transmit gas, and an inner wall has a gas transmission function. To provide.

[0005]

FIG. 1 is an explanatory view showing an embodiment of the present invention. In this embodiment, the VAD method is installed in a room where the atmosphere is clean and controlled, such as a clean room. 1 is a room where the atmosphere is clean and controlled, and 2 is a reaction container installed in the room 1. Reference numeral 3 denotes a burner, 4 denotes a seed rod that can move upward while rotating, 5 denotes a glass fine particle deposit on which glass fine particles are deposited, 6 denotes a lowermost point of the glass fine particle deposit, and the upper part of the seed rod is detected. A laser tip detection device that controls the movement.
Is provided with a laser light transmission window. In the figure, reference numeral 11 denotes a seed rod or a duct for driving out glass particles that have not been deposited on the glass particle deposit, out of the reaction vessel 2, and 12 denotes a viewing window. The reaction vessel 2 in the present invention is made of a material having gas permeability. As a gas-permeable material, a porous material of polytetrafluoroethylene (PTFE) satisfies the conditions as a VAD container and is suitable.

A reaction vessel 2 made of a porous material of polytetrafluoroethylene (PTFE) is set in a clean room 1, and the pressure in the reaction vessel 2 is reduced by -10 with respect to the external pressure.
mmAq, clean air was allowed to flow in from outside the reaction vessel 2, and SiCl ₄ and GeCl ₄ were supplied to the burner 3.
Raw material gas and H ₂ equal, fuel gas O _2, and if necessary by supplying an inert gas to generate glass particles by hydrolysis, depositing the glass particles on the tip of the seed rod 4, the seed rod 4 The glass fine particle deposit 5 is grown by pulling up while rotating. In this example, the temperature of the wall surface did not rise so much because the gas passed through the wall surface of the reaction vessel 2 and was 90 ° C. at the maximum. Further, there was no adhesion of glass particles on the inner wall surface, and the adhesion to the laser beam transmitting portion and the observation window 12 was extremely small as compared with the conventional reaction vessel, thereby enabling long-term production. In addition, as a result of manufacturing for a long time, conventionally, the glass fine particle deposits were stained by falling off of the glass fine particles attached to the tube wall, and an accident that bubbles remained at the time of vitrification occurred, but in the present embodiment, such an accident occurred. No problems occurred. As described above, in the present invention, since a clean gas is supplied into the vessel from the outside of the reaction vessel, the temperature of the wall surface of the reaction vessel does not rise so much, and chlorine and hydrochloric acid generated by the hydrolysis reaction are generated in the reaction vessel. Since it does not come in contact with the wall surface, a glass fiber filter material,
A polypropylene porous material, a carbon fiber filter material or the like can be used.

FIG. 2 is an explanatory view showing a second embodiment of the present invention. This embodiment is an example in which the VAD method is performed in an atmosphere where there is concern about cleanliness. The wall of the reaction vessel has a double structure, and clean air or an inert gas is injected between the outer wall and the inner wall. The gas is blown into the reaction vessel through the inner wall. That is, in the figure, reference numeral 21 denotes a reaction vessel, which comprises an inner wall 22 and an outer wall 23,
Between the inner wall 21 and the outer wall 22, there is a space 24 through which clean gas flows. The same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The inner wall 22 of the reaction vessel 21 is made of a material having gas permeability (for example, PTFE porous material).
, And a clean gas flows in the space 24 between the outer wall 23. The supply pressure of the clean gas is set to a pressure (about 10 mmAq) slightly higher than the pressure in the reaction vessel 21 such that the gas flows into the reaction vessel. Since the outer wall 23 is not exposed to a high temperature or exposed to corrosive gas such as chlorine or hydrochloric acid by forming the clean gas to flow into the reaction vessel in this manner, the material of the outer wall 23 is not required. For example, plastic, iron, aluminum or the like can be used.

In the present invention, as described above, at least the inner wall surface of the reaction vessel has a gas permeation function. As described above, by providing the inner wall surface with a gas permeation function, the inner wall surface is not exposed to corrosive gas and the temperature does not become high, so that it is possible to manufacture a deposit for a long time, and it is possible to deposit large glass fine particles. Body production becomes possible. Further, since the adhesion of the glass particles to the wall surface is substantially suppressed, foreign matter is not mixed into the deposit, and a high-quality glass particle deposit can be manufactured.

[0009]

As described in detail above, according to the present invention,
By providing a gas permeable function to the inner wall of the reaction vessel of the VAD method, the temperature rise on the wall can be suppressed. Therefore, even in a device for manufacturing a large-sized glass particle deposit by enlarging the reaction vessel, the wall can be cooled. There is no need to install equipment,
Adhesion of glass particles to the inner wall surface can be prevented by the gas flowing into the inside, and a high-quality glass particle deposit can be manufactured without being affected by cleaning.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory view showing a second embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating a conventional VAD method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Room with clean atmosphere 2 Reaction vessel 3 Burner 4 Seed stick 5 Glass fine particle deposit 6 Laser tip detector 21 Reaction vessel 22 Inner wall 23 Outer wall

Claims (2)

[Claims] 1. A porous glass particle deposition for producing an optical fiber glass particle deposit by growing a porous glass particle deposit by pulling up the seed rod while depositing porous glass particles on the tip of a rotating seed rod. A reaction vessel for producing a glass fine particle deposit for an optical fiber, wherein the reaction vessel has a gas permeation function. 2. The method according to claim 1, wherein the reaction vessel has a double wall, the outer wall is substantially impermeable to gas, and the inner wall has a gas permeable function. For reaction vessel.