JPH0761877B2 - Method for manufacturing glass particulate deposit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a high-purity glass particle deposit, and the glass particle deposit according to the present invention can be used as a raw material for high-purity glass. INDUSTRIAL APPLICABILITY The present invention is advantageously used in the production of optical fibers and other fields requiring high-purity glass.

[Conventional technology]

As a method for producing high-purity glass, the conventional VAD method (Vapour Ph
ase Axial Deposition vapor phase method) or OVD method (Outside
Vapor Phase Oxidation Deposition (external attachment method) and the like are used to form a glass particle deposit, which is then sintered and made transparent to obtain glass. In this type of method, a combustion gas, a glass raw material gas, etc. are supplied to a burner for synthesizing glass particles, and the glass raw material is subjected to an oxidation reaction or a hydrolysis reaction in a flame formed in the burner. A fine glass particle deposit is formed by producing fine glass particles and adhering and depositing the fine glass particles in the direction of the rotation axis of a substantially cylindrical or cylindrical starting material that rotates itself.

[Problems to be solved by the invention]

By the way, in this kind of method, in the initial stage of the formation of the glass particulate deposits, the outer diameter of the glass particulate deposits is much smaller than that in the steady state, and the deposition efficiency of the glass particulate deposits (collected as deposits Amount of fine glass particles (weight) / total amount of glass raw material input (weight in terms of oxide)
X100 (%)] was very low.

In the present specification, "the initial stage of formation of a glass particle deposit" means that the synthesis burner is moved at a relatively constant speed in the rotational axis direction of the deposit after a certain amount of growth after the start of deposition in this type of method. By doing so, the deposit is grown to have a constant diameter, which means the "period during which the glass raw material is started to grow to a constant diameter". Also,
In the present specification, the "steady state" means "a state in which the deposit grows while maintaining a constant diameter".

Conventionally, a multi-tube burner is generally used as a burner for synthesizing glass particles of this type of manufacturing method, and at this time, the glass raw material is charged only in the innermost layer of the burner,
Alternatively, they were simultaneously charged from a plurality of layers including the innermost layer. From the viewpoint of preventing the diffusion of the glass raw material flow and improving the deposition efficiency, it is preferable that the glass raw material flow velocity is high,
On the other hand, if the flow rate is too high, the reaction time of the glass raw material in the flame becomes short, and the generation of glass fine particles becomes an indefinite amount, which lowers the deposition efficiency.

Therefore, the glass raw material flow rate is usually set so that the deposition efficiency becomes highest at the raw material flow rate in the steady state, and for this reason, in the initial stage of deposit formation until the steady state is reached, However, the convergence of the glass raw material flow is also poor, and it is considered that the deposition efficiency is significantly reduced.

Also, in the initial stage of glass deposit formation, the outer diameter of the glass particulate deposit is small and the collection efficiency is poor.Therefore, a method of gradually increasing the glass raw material input amount to improve the yield in the initial stage is adopted. ing. FIG. 3 shows the change over time in the amount of glass raw material charged in the conventional method. The vertical axis in the upper part of FIG. 3 is the glass raw material flow rate (arbitrary unit), and the vertical axis in the lower part of the figure is the ratio R of the raw material flow rate Vout of the other parts to the raw material flow rate Vin of the innermost layer of the burner. The axis shows time. In FIG. 3, the solid line 1 ″ is the total amount of glass raw material input, and is the sum of the glass raw material flow rate (one-dot chain line 2 ″) and the glass raw material flow rate (two-dot chain line 3 ″) that is input to parts other than the innermost layer. At this time, 1'is gradually increased from time 0 to t _0, but such an increase increases the amount of the raw material flowing in each layer at the same time in the innermost layer of the multi-tube burner or a plurality of layers including the innermost layer. That is, the ratio R = Vout / Vin of the glass material flow rate (3 ″) charged to the other part to the material flow rate (2 ″) charged to the innermost layer is shown by the solid line 4 ″ in the lower part of the figure. As shown in, the value was kept constant. However, even with such a method, the problem has not been solved sufficiently.

Furthermore, since the heating efficiency of the glass fine particles is low in this initial stage, the adhered state of the glass fine particles is soft, and therefore cracks may occur at this stage, so that it is possible to obtain a stable high-quality glass fine particle deposit. There was also the problem of difficulty.

The present invention solves the above-mentioned problems in the manufacturing method using this type of multi-tube burner and stabilizes the deposition of the glass fine particle deposits without lowering the deposition efficiency or the occurrence of cracks even in the initial stage. It is an object of the present invention to provide a method capable of producing a high-quality glass particulate deposit.

[Means for solving problems]

According to the present invention, glass fine particles are synthesized by adhering and depositing glass fine particles synthesized by supplying a glass raw material into the flame of a multi-tube burner for synthesizing glass fine particles while adhering and depositing them on a rotating starting material, and depositing glass fine particles. a method for producing a body, a glass raw material was supplied to the plurality of layers of the burner, the ratio R of the glass raw material flow rate V _OUT to flow to portions other than the innermost layer of the plurality several layers, the glass raw material flow rate V _iN to be supplied to the innermost layer =
Glass fine particles characterized by including a process of gradually increasing V _OUT / V _IN to a steady-state value in the initial stage of forming glass fine particle deposits until the outer diameter of the glass fine particle deposits becomes constant. It is a method of manufacturing a deposit.

In the present invention, instead of the method of simultaneously increasing the flow rate of the raw material flowing in each layer in the initial stage of deposition as in the conventional method described above, the ratio of the raw material flowing in each layer is changed over time to finally achieve a stable state. The flow rate at.

When the flow rate of the glass raw material flowing in the innermost layer (center port) of the multi-tube burner is Vin and the total flow rate of the glass raw material flowing in the other layers (ports) is Vout, the ratio of the two is R =
It is defined as Vout / Vin, but in the present invention, in the initial stage of formation of the glass particulate body deposit body, that is, until the steady state in which the deposit grows while maintaining a constant diameter, R It is particularly preferable to change the input amount of the glass raw material so as to increase.

FIGS. 1 and 2 are graphs for explaining an example of changes over time in the flow rate of the raw material in the method of the present invention. The vertical axis and the horizontal axis in each figure are the same as those in FIG. 1 and 1 '
The solid line indicates the total amount of glass raw material input, and the glass raw material flow rate (one-dot chain line 2 and 2 ') and the glass raw material flow rate (two-dot chain line 3 and 3') other than the innermost layer.
And sum. Vout / Vin = R at this time is shown by the chain double-dashed line and 4 ', but it is the first value between time 0 and t ₀ .
In the figure, it increases from 0 to a constant value, and in FIG. 2, it increases from the value at the start to a constant value.

Thus, by increasing the ratio of the raw material flow rate to be flown to the innermost layer portion to the total input amount at the start of deposition, a sufficient raw material flow rate in the central portion and convergence of the raw material flow can be ensured, By increasing the ratio of the flow rate in the outer layer portion as the fine particle deposit grows, the amount of change in the raw material flow rate can be reduced and the deposition efficiency in the initial stage of formation can be improved. Therefore, the manufacturing yield of the glass fine particle deposit can be improved. Can be improved.

Furthermore, the heating efficiency of the glass raw material flown from the innermost layer is
Since it is the center of the flame, it is higher for particles flowing from its surroundings, and therefore the temperature of the glass particles tends to be higher. As a result, even in the initial stage of base material manufacturing,
Since the adhesion of the glass particles becomes hard, it is possible to prevent the base material from cracking.

As the glass raw material in the present invention, general raw materials used in this type of method, for example, SiCl ₄ , SiHCl ₃ , SiH ₂ Cl
₂ etc. are used, and additives such as GeCl ₄ , BCl ₃ , PCl ₅ are used.
Of course, it does not matter to add such as.

As the combustion gas, for example, H ₂ , CH ₄ , C ₂ H ₆ , C ₃ H
For example, hydrocarbons such as ₈ are, for example, O ₂ and CO as the supporting gas.
Etc. are used.

In the present invention, the amount of raw material input to each layer of the burner is performed as described above, but the way of flowing the combustion gas and the auxiliary combustion gas is not particularly limited, and does not increase, decrease, or change with respect to the raw material flow rate. Note that various adjustments may be made.

〔Example〕

Example 1. A glass fine particle deposit was produced by the method of the present invention using an octagonal tube burner as a burner for synthesizing glass fine particles. Silicon tetrachloride is used as the glass raw material, the flow rate of the innermost layer is 600cc / min at the start of deposition, the raw material flow rate from the other layers is 0cc / min, hydrogen 40 / min, oxygen 40 / min,
Flushed with argon 15 / min. The flow rate of the raw material in the innermost layer was kept constant at 600 cc / min until and during the steady state. On the other hand, the raw material flow rate from the other parts increased from 0 at the beginning to 400 cc / min in 40 minutes and then 400 c / min.
Holds c / min. At this time, R increased from 0 to 0.66 (see Fig. 1). The deposition efficiency in the initial stage of sooting is about 70
%, And no cracks occurred at all.

Example 2. In Example 1, only the glass raw material (silicon tetrachloride) flow rate was set to 500 cc / min for the innermost layer at the start of deposition and 100 cc / min for the other layers.
The innermost layer is 600cc / min in 40 minutes, and the other layers are 400cc / min.
The glass particulate deposit was produced under the same conditions as in Example 1 except that the amount was increased so as to correspond to the above. At this time, R increased from 0.2 to 0.66 (see Fig. 2). Under these conditions, the deposition efficiency at the initial stage of sooting is about 65.
%, And when a total of 10 glass fine particle deposits were produced under these conditions, no cracks occurred.

Comparative Example 1 In Example 1, only the glass raw material flow rate was set to 360 cc / min for the innermost layer at the start of deposition and 240 cc / min for the other layers, and increased to 600 cc / min and 400 cc / min for 40 minutes, respectively. A glass particle deposit was prepared under the same conditions except that the above procedure was performed.
At this time, R was constant at 0.66 from the initial stage of deposition (see FIG. 3). Under these conditions, the raw material yield was about 62%, which was lower than that in Example 1, and cracking at the initial stage of sooting occurred in 3 out of 10 deposits produced.

From the results of the above Examples and Comparative Examples, it is clear that the method of the present invention is superior to the conventional method in terms of deposition efficiency and prevention of cracking.

〔The invention's effect〕

As described in detail above, the present invention can improve the deposition efficiency in the production of glass particle deposits by using a multi-tube burner, and can solve the cracking problem in the initial stage of production. This is an excellent method that has a large economic effect and a high quality improving effect that it can be used for preparing a material and that a high quality product can be stably obtained while reducing the manufacturing cost.

[Brief description of drawings]

In FIGS. 1 and 2, the upper part shows the flow of the glass raw material into the multi-tube burner according to the present invention, and the lower part shows the glass raw material input to the layers other than the innermost layer with respect to the glass raw material input amount Vin of the burner inner layer at that time. It is the figure which represented ratio R = Vout / Vin of quantity Vout as a graph with respect to each elapsed time. Fig. 3 shows the flow of glass raw material and R in the conventional method in Fig. 1,
It is the figure made into the graph similar to FIG.

Claims (1)

[Claims] 1. A glass material produced by supplying a glass raw material into the flame of a multi-tube burner for synthesizing glass particles, and adhering and depositing the glass particles on a rotating starting material while allowing the glass material to grow in the rotation axis direction of the starting material. In the method for producing a fine particle deposit, a glass raw material is supplied to a plurality of layers of the burner, and a glass raw material flow rate V _OUT flowing to a portion other than the innermost layer of the plurality of layers and a glass raw material flow rate V _IN flowing to the innermost layer. In the initial stage of forming glass particulate deposits until the outer diameter of the glass particulate deposits becomes constant, the ratio R = V _OUT / V _IN is gradually increased to a steady-state value. A method for manufacturing a glass particle deposit body.