JPS61281025A - Production of deposited material of glass fine particles - Google Patents

Abstract

PURPOSE:To stably and easily produce a deposited material glass fine particles without causing cracks, by attaching firstly a thin deposited layer of glass fine particles to the outer peripheral part of a starting raw material and forming a deposited material of glass fine particles on the thin deposited layer. CONSTITUTION:A combustion gas H2, an auxiliary combustion gas O2 and a raw material gas are sent to the burner 13 for synthesizing glass fine particles, the glass fine particles are formed in the formed flame 14 by a hydrolysis reaction and the glass fine particles are deposited on the outer peripheral part of the starting material 11 which is transferred relatively to the burner 13 for synthesizing the glass particles while being rotated, to form the deposited material 12 of glass fine particles. Besides this constitution, the burner 15 is set in front of the burner 13 forming the deposited material 12 of glass fine particles and the thin deposited layer 17 of glass fine particles are attached to the material. This deposited layer 17 of glass fine particles has a heat insulating effect to prevent heat losses caused by thermal conductivity of the starting material, and the deposited material 12 of glass fine particles formed in this shape does not lower the temperature of soot particles, consequently, the deposited material is effective for forming a hard deposited material.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for forming an aggregate of glass fine particles on the outer periphery of a cylindrical starting material. The present invention relates to a method for forming a glass fine particle deposit deposited on the outer periphery of a starting material, which is suitably used as an intermediate product during manufacturing.

[Conventional technology]

``Conventionally, as a method for manufacturing a base material for a quartz-based glass tube or an optical fiber, there is a so-called 1-external method disclosed in Japanese Patent Application Laid-Open No. 48-73522.

In this method, fine particulate glass such as SLC produced by the hydrolysis reaction of glass raw materials is deposited on the outer periphery of a rotating refractory starting material such as carbon, quartz glass, or alumina. After depositing a certain amount, the deposition is stopped, the starting material is pulled out, a pipe-shaped glass aggregate is formed, and this pipe-shaped glass aggregate is sintered into transparent glass in a high-temperature electric furnace to obtain a pipe-shaped glass. Or,
Using the same method as a starting material, a solid glass base material for fiber is used as a starting material to form a composite of the starting material and the glass fine particle deposits formed on its outer periphery. Another possible method is to further form a transparent glass layer on the outer periphery of the original fiber glass base material, which is the starting material, by heat-treating in a high-temperature furnace and sintering the part where the glass fine particles are deposited.

[Problems to be solved by the present invention]

Conventionally, in the above method, as shown in FIG. 5, the glass particle deposit body 12 is synthesized using one or more burners 13 for producing glass particles.Generally, H2a is produced as fuel gas from the tip of the burner. ○T14 e C*”m
etc., Os, air, etc. are supplied as combustion auxiliary gas, and the flame 14
form. Here, 5iC4, Gs(
,! , etc. are supplied, and by causing a hydrolysis reaction, shigasu fine particles 8101, Gaol, etc. are produced.

The glass particles adhere to the rotating starting material 1) to form a glass particle deposit 12.

A particular problem in producing a glass fine particle deposit by this method is the problem of cracking of the glass fine particle deposit. The cracking of the glass particle deposit occurs because the bulk density of the glass particle deposit is low, and the usual countermeasure is to increase the flow rate of fuel gas to harden the glass particle deposit. However, in the case of a glass particle deposit formed on the outer periphery of a rotating starting material, even a slight increase in fuel gas was insufficient as a countermeasure against cracking of the deposit. However, when the amount of fuel gas was increased significantly, a problem occurred in that the starting materials were deformed and moved around. When flaring occurs in the starting material, the starting material in the synthesized glass fine particle deposit becomes eccentric, making it impossible to obtain a base material with good axial symmetry. This problem of cracking of the base material becomes more noticeable as the outer diameter of the starting material increases. Further, when the amount of fuel gas is greatly increased, the flame temperature becomes too high and the burner flame flow becomes fast, resulting in a problem that the yield of the raw material becomes poor.

A more detailed investigation of the above-mentioned phenomenon of base material side deviation revealed that when the base material cracks, the glass fine particle deposits crack as if to burst, and most of them peel off from the starting material. From this, it is expected that the glass particle deposits attached near the surface of the starting material will be extremely soft. After successful synthesis, we measured the bulk density distribution in the radial direction of the glass particle deposit, and as shown in Figure 4, we found that the bulk density near the surface of the starting material was lower than that outside. Ta. From this, it has become clear that the main cause of cracks in glass fine particle deposits is that soft glass particles are deposited near the surface of the starting material when the glass fine particle deposit is formed to be thick.

It is thought that the reason why soft glass particles are deposited near the surface of the starting material is that the conductivity of the starting material removes heat from the starting material itself, which prevents the temperature of the glass particles adhering near the surface from rising sufficiently. As a countermeasure to this, the present inventors installed all heating burners 19 in front of the burner 15 for synthesizing the glass fine particle deposit as shown in FIG. 5, and while heating the starting material 1)'t-, Glass fine particle deposit 1
We also devised a method to form 2.

This method can prevent temperature drop due to heat conduction of the starting materials to some extent. However, even in this method, the starting material heating burner 19 is replaced by the flame 14 of the glass particle synthesis burner 15.
It must be installed in a position that does not disturb the
Since it is not possible to get sufficiently close to the deposition surface of the glass particle deposit, the present invention is further intended to provide a method that overcomes such interlayers.

[Means for solving problems]

The present invention aims to overcome the above-mentioned problems and stably produce a glass fine particle deposit. Prior to forming the glass fine particle deposit on the outer periphery of a rotating starting material, first:
By depositing a thin glass particle deposit layer and forming the glass particle deposit thereon, it is possible to stably and easily manufacture the glass particle deposit Xt.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described below based on embodiments with reference to diagram t-81. Fuel gas H to burner 13 for glass particle synthesis! , heating gas 01, raw material gas 1) IE, and in the flame 14 formed by this burner 15, rainbow glass fine particles are formed by a hydrolysis reaction. The glass fine particles are deposited on the outer periphery of the starting material 1) which rotates and moves relative to the glass fine particle synthesis burner, and the glass fine particle deposit body 12
form. In the present invention, in addition to this configuration, a burner 15 is installed in front of the burner 15 that forms the glass fine particle deposit body 12t'', and a thin glass fine particle deposit layer 17 is deposited. It has an insulating effect that prevents heat loss due to heat conduction inside the glass, and is formed on this.In glass fine particle deposits, it is effective in forming a hard deposit without lowering the temperature of the soot particles. I'll go.

Generally the starting material is quartz glass, SLA.

Graphite and metallic materials may be used, but the thermal conductivity of these materials is approximately 1 for graphite.
00 kCal/mh2”℃, about 7°kaal at N1,
/mhrc, 810 is as high as about 50 kaa1/mhrc, and even silica glass, which has the worst thermal conductivity, has a high thermal conductivity of about 1 to 2 koa.
It has a thermal conductivity of l/mhrTl:. On the contrary,
According to actual measurement results, the thermal conductivity of the glass fine particle deposit is about 1 (L O' 5 keal/mhrc), which is two digits lower than that of quartz glass, and the heat loss is small.

Therefore, once a thin layer of glass fine particles is formed, due to the heat insulating effect of the glass fine particle layer, the glass fine particles formed thereon are not deprived of heat from the starting material, and form a deposit with high bulk density. becomes easier to form. In addition, when the entire powder aggregate is attached to the solid surface, the adhesion is poor and causes the aggregate to peel off after the glass particle aggregate is manufactured. The adhesion of fine particles is good (1), and it is effective in solving this problem.

However, if the thickness of the glass fine particle deposit layer that is initially deposited is too thick, the same problem as in the conventional method will occur because heat will be taken away from the vicinity of the starting material surface of the deposited layer by the starting material. Become. As a result of careful consideration of this point, it was found that the above-mentioned problem does not occur if the thickness of the deposited layer of glass particles initially deposited is 50% or less of the diameter of the starting material.

In addition, even if a thin glass particle deposit layer is formed, if the bulk density of this glass particle layer is small, problems similar to those of the conventional method (Matsu9) occur, and it has been found that Fi is not effective in preventing cracks in the deposit. . When the bulk density t of the glass fine particle deposited layer was changed, it was found that the problem of cracking did not occur as long as the bulk density was α2 f/- or more.

However, when used as a glass material for original fibers, it is required to have low loss due to the original transmission characteristics.

If there is a large amount of O)I group' contained inside the glass, OH
The absorption loss of light by the base increases, and the properties of the optical fiber deteriorate. In the case of glass fine particle deposits, the issue is whether or not OH groups can escape.
The H characteristic depends on the bulk density of the deposit, and in general, α
69/ is required to be 1 or less. This means that
The case of the thin glass particle deposit layer according to the present invention is no exception, and considering the above-mentioned measures against cracking, the bulk density is α2
~α6f/2 is required.

〔Example〕

In the configuration shown in Figure 1, a concentric multi-tube burner was used to form a glass particle deposit on the outer periphery of a quartz glass tube with an outer diameter of 2 (Isφ). From 15, Hg = 6 t
/win, 02 = 10 t/min.

Mr = 5 t/winS81014 = 40 Q
Gas f was flowed at Q/min. From the burner 16 for forming the glass fine particle deposit body formed on this, Hg = 52 t
/min, o.

= 65 t/min, Ar = 21 t/m
BICla = as combustion gas and raw material gas in
2500 cc/min was input. As a result, a good glass particle deposit could be obtained at a deposition rate of 4.1 t/Win. In the production of this deposit, there is no problem of the base material cracking, and the process can be carried out in an extremely stable manner. When we measured the structure and bulk density distribution of one of the manufactured base materials, we found that the thickness of the thin glass particle deposit layer initially attached to the trap was 1°8cm (9% of the outer diameter of the starting material). ), the bulk density is (L 55 f/cn?
It was found that the glass particles were firmly attached.

As shown in Figure 2, the bulk density (f10r/') distribution of the glass fine particle deposits formed on the outer periphery is slightly smaller near the starting material surface (the outer diameter of the starting material is indicated by the chain line in the figure). Although there were inflection points, there were no dents in the bulk density as shown in Figure 4, indicating a good distribution. The base material could be manufactured at a high level of raw material yield of 6°.

In this example, gold was shown when only 5Icz4 was used as the glass raw material, but aec14゜poaz
Even if raw materials such as , etc. are mixed, the same effect can be obtained.

Although only one burner was used for forming the glass particle deposit in this embodiment, a plurality of burners may be used.

〔Effect of the invention〕

The present invention has the advantage that when a glass particle deposit is synthesized on the outer periphery of a starting material such as quartz glass, the glass particle deposit can be produced stably and easily.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating an embodiment of the present invention, and FIG. 2 is a graph showing a radial bulk density distribution of a glass fine particle deposit obtained in an example of the present invention. Figure 3 is a diagram explaining the conventional method, Figure 4 is a graph showing the radial bulk density distribution of the glass particle deposit produced by the conventional method, and Figure 5 is an explanation of the method using a burner for heating the starting material. figure.

Claims (4)

[Claims] (1) From near one end of a substantially cylindrical or cylindrical starting material that is rotating about its own axis, a glass raw material is introduced into the flame of a burner for synthesizing glass fine particles onto the outer periphery of the starting material. By starting to deposit the glass particles generated by supplying the material and moving the burner relatively parallel to the axis of the starting material, a deposited body of glass particles is formed in the axial direction on the outer periphery of the starting material. In terms of how to
1. A method for producing a glass particle deposit, which comprises first depositing a thin glass particle deposit layer, and then forming a glass particle deposit thereon. (2) The method for manufacturing a glass particle deposit according to claim (1), wherein the thickness of the glass particle deposit layer initially deposited is 50% or less of the outer diameter of the starting material. (3) Glass fine particle deposition according to claim (1) or (2), wherein the bulk density of the glass fine particle deposition layer to be deposited first is 0.2 to 0.6 g/cm^3 How the body is manufactured. (4) Claims (1) to (3) in which the first glass particle deposit layer and the glass particle deposit layer formed thereon are synthesized using separate burners.
2. A method for producing a glass fine particle deposit according to any one of the above.