JPH05345621A - Production of glass article - Google Patents

Abstract

PURPOSE:To prevent cracks from occurring by installing a protecting pipe at the tip of a synthetic burner, regulating the ratio of the outlet inside diameter to the inside diameter of the outermost port in a combustion gas blowoff port of the synthetic burner to a specific value and limiting the spreading of a flame. CONSTITUTION:A raw material gas such as SiCl4 is made to flow from the center of a concentric multitubular pipe burner 1 having a protecting pipe 2 installed at the tip thereof and a fuel gas such as H2, a combustion controlling gas such as Ar and a combustion improving gas such as O2 are made to flow on the outside thereof at a gas flow velocity V=QT/[1/4.pi.Dh<2>] (QT is the total gas flow rate; Dh is the outlet inside diameter of the protecting pipe) within the range of 0.75-1.25 (m<3>/sec). Thereby, a multiple flame is formed. The inside diameter (Dh) of the protecting pipe 2 is regulated to 1.9<=Dh/DC1.15 based on the inside diameter (DC) of the outermost port in the combustion gas blowoff port of the burner 1. As a result, the spreading of the flame is limited and glass fine particles produced by the flame hydrolytic reaction in the flame are deposited on a rotating starting rod to form a glass fine particle deposit 3, which is then heated at 1500-1650 deg.C to afford the objective glass article without causing cracks.

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 high-purity silica glass article, which is particularly suitable for producing a high-purity glass used for optical fiber preforms.

[0002]

2. Description of the Related Art High-purity quartz glass, particularly glass articles used for optical fiber preforms, are liquid glass raw materials such as SiC in order to prevent the inclusion of metallic impurities.
After vaporizing l ₄ , SiHCl _{3 and the} like into a gas state, high purity hydrogen or hydrocarbon is introduced into a flame formed as a fuel and high purity oxygen as an auxiliary combustion gas, and the glass is formed by a hydrolysis reaction or an oxidation reaction. Generate fine particles, deposit them on a target starting rod (rod), synthesize a glass fine particle deposit body, and make it transparent vitrified in a high temperature furnace.
It is manufactured by the so-called vapor phase synthesis method. VAD method (Vap
our-phase axial deposition method) or OVD
Method (Outside Vapor-phase deposition method) and the like are common. The glass articles used for optical fiber preforms and the like produced by this method may have their OH groups removed by a dehydration treatment before becoming transparent.

When glass particles are deposited on the tip of a starting rod to synthesize a glass particle deposit body, a columnar glass article of pure quartz can be obtained. On the other hand, if a dopant that changes the refractive index, such as GeCl _4, is mixed in the raw material gas, a core material having a high refractive index can be obtained. When a glass particle deposit is formed on the outer circumference of a glass-like starting rod having a core or a part of a clad and a clad, a clad or a second clad (also referred to as a jacket) is formed, and the optical fiber plug is formed. Reforms can be made and spun into fibers to give optical fibers.

Here, a concentric multi-tube burner is generally used as the burner for forming the flame, and in particular, in order to increase the synthesis rate of the glass particulate deposit (the weight of the glass synthesized per unit time). , A flame for synthesizing glass fine particles composed of a glass raw material gas, a fuel gas, and an auxiliary combustion glass, and a flame for heating a base material located at the outer periphery thereof are at least
So-called multiple flame burners, which have more than one set, are used. Generally, the spread of the flame is adjusted at the tip of this burner,
A protection tube is installed to prevent fluctuations in flames due to disturbance. For example, JP-A-56-45842 describes a method of controlling the diffusion of a dopant in a flame by attaching a protective tube and adjusting the length of the protective tube. JP-A-57-7834. The gazette describes that a rocking tube due to disturbance is prevented by installing a protective tube.
Further, Japanese Patent Application Laid-Open No. 57-11843 discloses a method of rotating a protective tube to further stabilize the flame. Further, Japanese Patent Laid-Open No. 63-79055 proposes a method of controlling the diffusion of glass fine particles formed in a flame by making the protective tube double and adjusting the length of each. In all of the above conventional methods, a protective tube has been proposed for protecting the flame from disturbance and controlling the diffusion of the dopant in the flame or the fine glass particles generated.

[0005]

Conventionally, glass particulate deposits have been synthesized with this kind of structure, but in recent years, in order to improve the productivity of glass articles, attempts have been made in recent years to increase the synthesis rate of glass particulate deposits. Therefore, the above-mentioned multiple flame burner has been proposed in view of these requirements. However, when synthesizing the glass fine particle deposit, cracks occur in the glass fine particle deposit at the initial stage of starting to deposit glass fine particles on the starting rod, or when the synthesized glass fine particle deposit is made into transparent vitrification in a high temperature furnace. However, there was a frequent problem that cracks were generated near the deposition start end of glass particles. This is because the bulk density (the weight per unit volume including the pores, which represents the hardness) of the glass particulate deposit is unevenly borne, and the temperature heated during deposition is
This is due to the difference between the deposition start end and the steady part. That is, as shown in FIG. 2, when the glass particulate deposit body 6 is synthesized on the outer periphery of the starting rod 5 by the VAD method, the soft layer 7 that is not heated sufficiently by the flame and is deposited on the upper portion which is the starting end of the deposition. (Indicated by hatched lines in FIG. 2), which causes cracks during deposition due to thermal stress in the soot (generated during the cooling of the base material). Even if no cracks occur, the shrinkage rate varies depending on the difference in bulk density during transparent vitrification, so if there is a large difference in bulk density, cracks will still occur. In order to prevent this, measures have been taken such as changing the flow conditions of fuel gas, supporting gas, raw material gas, etc. at the time of glass particle deposition or changing the position of the burner 1, but there is a temporary effect, but it is essential. It was not a solution, and when the conditions were changed according to the product, the same problem occurred again, and reproducibility was lacking. In addition, 4 in a figure shows a protective tube. The present invention is
It is an object of the present invention to provide a method for manufacturing a glass article that solves such problems.

[0006]

[Means for Solving the Problems]

As a means for solving the above-mentioned problems, the present invention produces a glass fine particle by subjecting a glass raw material gas to a flame hydrolysis reaction or an oxidation reaction in a flame formed by a synthesis burner, and rotating the glass fine particle. In the method for producing a glass article by depositing on the tip or outer periphery of a starting rod that moves relative to the synthesizing burner, a protective tube is installed at the tip of the synthesizing burner, and the outlet inner diameter D _h of the protective tube is set. Is characterized by satisfying 1.4 ≦ D _h / D _c ≦ 1.65 with respect to the inner diameter D _c of the outermost port of the combustion gas of the burner for synthesis, thereby limiting the spread of flame and generating fine glass particles. And In the present invention, it is particularly desirable that the protective tube has a shape in which the inner diameter is enlarged in the flame ejection direction. Further, in the present invention, the total gas flow rate Q _T ejected from the synthesis burner is determined by the outlet inner diameter D _{h of the} protection tube.
It is also particularly desirable to adjust the flow velocity v = Q _T / [1/4 · π · (D _h ) ² ] defined by the formula 0.75 ≦ v ≦ 1.25 (m / sec). .. As a particularly preferred embodiment of the present invention, as the synthesis burner, a glass fine particle synthesis flame consisting of a glass raw material gas, a fuel gas and an auxiliary combustion gas is formed in the center, and a mother gas consisting of the fuel gas and the auxiliary combustion gas is formed around this flame. It is possible to use a burner in which at least one flame for heating the material is formed and the jet of the flame for heating the base metal projects in the jet direction of the flame with respect to the jet of the flame for synthesizing glass particles. .. The protective tube of the present invention may be made of quartz glass. Further, as the starting rod of the present invention, a transparent glass rod comprising a core or comprising a core and a part of a clad can be used to manufacture an optical fiber preform.

[0008]

The inventors of the present invention changed the protective tube attached to the tip of the burner variously, and the bulk density when synthesizing the glass particulate deposits, and the surface temperature at the time of synthesizing the glass particulate deposits, which is a factor that determines the bulk density. The relationship with the distribution was investigated. The surface temperature distribution was measured using the two-dimensional radiation thermometer 8 in the configuration of FIG. 3, and was arranged as the temperature distribution in the central axis direction of the glass particle deposit body 6. As a result, the following facts became clear. When cracks occur, the temperature distribution is as shown in FIG. That is, it was found that the high temperature maximum values existed at the upper and lower portions and the temperature at the upper portion was high. It was found that in the case where cracks did not occur comparatively, the temperature distribution had a lower upper maximum value as shown in FIG.

When depositing the glass particulate deposit,
According to the deposition of the glass particles, the starting rod 5 is rotated and pulled up to synthesize the glass particle deposit body 6. For this reason,
If the growth of the glass particle deposits is slow at the start of deposition of the glass particle deposits 6, that is, most of the glass particles are attached by being directly heated by the flame. When the amount of glass particles adhered to the deposition surface is small, it is considered that the glass particles that have not adhered reach the upper end of the glass particle deposit body and are deposited without being heated so much. Therefore, when the temperature distribution as shown in FIG. 4 has two maximum values and the temperature of the upper portion is high, the glass fine particles are more likely to adhere to the upper end portion, and the glass fine particle deposit is higher than the lower portion. Tends to be large. In this case, the glass particle deposit does not grow easily, and the glass particle deposit attached to the upper part becomes larger. Even if the temperature of the upper part is high, the upper part is not completely covered with flames, and the soft layer becomes large due to this, and as shown in FIG.
Easier to form. On the other hand, in the case of the temperature distribution as shown in FIG. 5, since the temperature of the upper part is low and the temperature of the lower part is relatively high, the growth of the glass particle deposit in the lower part is fast and it becomes difficult to form a soft layer on the upper end. In other words, the glass particle deposit grows before forming the layer with a low bulk density,
Will be raised.

From these results, the burner temperature or the flow rate condition was changed so that the temperature distribution of the glass particulate deposit had an ideal shape as shown in FIG. 5, but finally, as shown in FIG. 1 or 6, The ratio D _h / D _c of the outlet inner diameter D _h of the protective tube 2 installed at the tip of the burner 1 to the inner diameter D _c of the combustion gas jet outermost port of the burner 1 is 1.4 to 1.65.
It has been found that it can be realized by setting the range of 1.45, preferably within the range of 1.45 to 1.55. D _h / D _c
Is less than 1.4, the temperature distribution becomes as shown in FIG. 4, and no improvement can be made no matter how the conditions are changed. On the other hand, if it is larger than 1.65, the flame spreads too much, and the upper temperature peak in FIG. 5 also lowers, resulting in a flat temperature distribution. Further, since the flow of the glass fine particles flowing through the flame center is too wide, the raw material yield (the ratio of the glass fine particles deposited to the produced glass fine particles calculated from the glass raw material gas fed into the burner) may decrease. all right. It is considered that this is because the flame appropriately expands in the protection tube and the temperature distribution becomes optimum. In a conventional burner with a protective tube, D _h is usually 20 to 80 mm, which is about 5 mm larger than D _c . Therefore, D _h / D _c is 1.06 ~
It is about 1.25.

Further, the gas flow velocity v ejected from the burner is
Total gas flow Q_TAnd protective tube outlet inner diameter D _hAnd v = Q_T/ [1 /
4 ・ π ・ (D_h)²], 0.75 ≦ v ≦ 1.
25, preferably 0.85 ≦ v ≦ 1.15
The effect can be further enhanced by adjusting the flow rate.
I understood. If the flow rate increases and the flow velocity increases, the inside of the protection tube
The effect of expanding the flame is reduced. That is, sufficient expansion
Since it reaches the deposition surface before it is completed,
The cloth will still look like Figure 4. Conversely, the flow velocity is slow
And the outlet diameter D of the protection tube_hHas the same effect as when
It is considered that temperature distribution tends to occur.

When a multi-tube burner is used as the burner, only the flame for heating the base material can be adjusted effectively, so that the effect of the present invention can be further enhanced. Further, the present invention is still effective when a glass fine particle deposit is synthesized at a high synthesis rate on the outer periphery of a glassy starting base material having a core or a part of a core and a clad using a multi-tube burner. Further, when the glass particulate deposit was synthesized with the constitution of the present invention, there was also an effect that the raw material yield was improved. A transparent glass article is obtained by heating the glass particle deposit produced by the present invention in a temperature range of 1500 ° C to 1650 ° C.

[0013]

EXAMPLES Example 1 A concentric 12-tube burner was used. This burner flows SiCl ₄ as a glass raw material gas from the center, hydrogen as a fuel gas, argon as a combustion control gas, and
Oxygen is flowed as a combustion supporting gas, and argon is further used on the outside.
The structure is such that two sets of flames for heating the base material are formed in the order of hydrogen, argon, and oxygen. Oxygen gas was caused to flow in the combustion gas outermost layer port of this burner in the twelfth layer, and the inner diameter of this twelfth pipe was 72 mm. For this reason, the protective tube has the structure shown in Fig. 1, and the inner diameter of the mounting part with the burner is 76 m.
m, the jet outlet inner diameter D _h was 110 mm, and the protrusion length L from the burner was 70 mm. The material was quartz glass. The gas flow rate is 290 liters / minute for hydrogen and 240 for oxygen.
L / min, argon 40 L / min, glass raw material gas 18 L / min. The total gas flow rate is 588 liters / minute, and v is 1.03 m / sec, which satisfies the limited range of the present invention. With this configuration, when 10 glass deposits were synthesized on the outer periphery of the glass rod including the core and a part of the clad synthesized by the VAD method and made into transparent glass, cracks of the glass particulate deposit and No cracks occurred at the time of transparent vitrification. The raw material yield at this time was 58%.
The transparentization was performed by heating at 1600 ° C.

[0014] Most of the same configuration as Comparative Example 1 Example 1, burner mounting portion 76mm as a protective tube, used as the spout 96 mm, the glass particles deposit on the outer periphery of the glass rod and a part of the core and the cladding Synthesized. As a result, it was found that 2 out of 10 cracks occurred during synthesis and 6 cracked during transparency.
The clearing temperature is 1600 ° C. Raw material yield is 47
% Was low. D _h / D _c = 1.33 (outside the scope of the present invention), is v = 1.35m / sec.

COMPARATIVE EXAMPLE 2 Almost the same structure as in Example 1, except that a protective tube having a burner mounting portion of 76 mm and a jetting outlet of 125 mm was used, and a glass fine particle deposit was formed on the outer periphery of the glass rod including the core and a part of the clad. Synthesized. As a result, it was found that 3 out of 10 cracks were generated during synthesis, and 4 cracks were generated during transparency. The clearing temperature is 1600 ° C. The raw material yield was significantly reduced to 44%. D _h / D _c = 1.74 (outside the range of the present invention) and v = 0.80 m / sec.

EXAMPLE 2 Using a concentric 16-tube burner, a glass raw material gas SiCl ₄ was made to flow from the center, and hydrogen, argon and oxygen were made to flow to the outside thereof to form a flame for synthesizing glass fine particles, and further to the outside thereof argon. The gas was flowed so that three combinations of flames for heating the base material of hydrogen, argon, and oxygen were created. The inner diameter of the 16th pipe forming the outermost 16th port of the combustion gas oxygen was 96 mm. This burner is also shown in Figure 1.
A protective tube made of quartz glass having an inner diameter of the burner attachment portion of 100 mm and an inner diameter D _{h of the} ejection port of 145 mm was installed in the shape shown in FIG. D _h / D _c = 1.51. With this configuration, hydrogen 440 liters / minute, oxygen 380 liters / minute, argon 90 liters / minute, glass source gas 19 liters / minute
Minutes The total gas flow rate is 929 liters / minute,
Is 0.94 m / sec, which satisfies the particularly desirable range of the present invention. With this structure, a glass particulate deposit was synthesized from the tip of the starting rod to form a columnar base material. 16
It became transparent at 00 ° C. By this method, 10 base materials were synthesized, but good transparent glass articles could be obtained from all 10 base materials. The raw material yield was as good as 56%.

Example 3 Using a concentric octuple burner, SiCl ₄ as a glass raw material gas was passed from the center, and hydrogen, argon, and oxygen were made to flow to the outside in this order to form a flame for synthesizing glass particles, and the inside was made to the outer periphery. Argon, hydrogen, argon, and oxygen were flowed in this order. The inner diameter of the eighth pipe forming the oxygen outlet of the eighth port of the burner was 40 mm. Figure 6 here
A protective tube as shown in (1) was attached, and a glass particle deposit was synthesized on the outer circumference of a starting rod having a core and a part of a clad. The inner diameter of the straight portion of the protective tube is 45 mm, the inner diameter of the outlet end is 61 mm, and D _h / D _c = 1.53.
The gas flow rate is 72 liters / minute for hydrogen and 63 liters / for oxygen.
Min, argon 14 l / min, SiCl ₄ 7 l / min. The total gas flow is 156 liters / minute,
v became 0.89 m / sec. Ten glass fine particle deposits were synthesized with this configuration, and when heat-transparent at 1620 ° C., all glass articles became transparent. This glass article was a good preform for optical fibers. The raw material yield was also as good as 58%.

Although the concentric burners have been described in the above embodiments, the same effect can be obtained when the protective tube is attached regardless of whether they are circular or concentric.

[0019]

As described above, according to the present invention, the temperature distribution of the glass particulate deposit heated by the flame is
An appropriate distribution that does not form a soft volume portion can be obtained, and a good glass article without cracks can be manufactured. Therefore, the present invention is particularly effective for producing a glass article that can be suitably used as an optical fiber preform.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of a specific example of a protective tube of the present invention.

FIG. 2 is a schematic diagram illustrating a shape state of a soft layer in a configuration according to a conventional method.

FIG. 3 is a schematic diagram showing a configuration of temperature measurement by a two-dimensional radiation thermometer.

FIG. 4 is a graph showing a temperature distribution when a soft layer is formed.

FIG. 5 is a graph showing a good temperature distribution.

FIG. 6 is a schematic view showing the shape of a protection tube according to another embodiment of the present invention.

[Explanation of sign]

 1 burner 2 protective tube 3 glass particulate deposit body 4 protective tube 5 starting rod 6 glass particulate deposit body 7 soft part of glass particulate deposit body 8 two-dimensional radiation thermometer

Claims (6)

[Claims] 1. A starting point for producing glass fine particles by subjecting a glass material gas to a flame hydrolysis reaction or oxidation reaction in a flame formed by a synthesis burner, and moving the glass fine particles relative to the synthesis burner while rotating the glass fine particles. In the method for producing a glass article by depositing on the tip or the outer periphery of a rod, a protective tube is installed at the tip of a synthesizing burner, and the outlet inner diameter D _h of the synthesizing burner is the outermost port of the combustion gas ejection port. A method for producing a glass article, characterized in that by satisfying 1.4 ≦ D _h / D _c ≦ 1.65 with respect to an inner diameter D _c, the spread of a flame is restricted to produce fine glass particles. 2. The method for producing a glass article according to claim 1, wherein the protective tube has a shape in which the inner diameter is enlarged in the flame ejection direction. 3. A flow rate v = Q _T / [1/4 · π · (D _h ) ² ] defined by the total gas flow rate Q _T ejected from the synthesis burner by the outlet inner diameter D _h of the protection tube. Against 0.75 ≦
The method for producing a glass article according to claim 1, wherein the glass article is adjusted so as to satisfy v ≦ 1.25 (m / sec). 4. The method for manufacturing a glass article according to claim 1, wherein the protective tube is made of quartz glass. 5. A flame for synthesizing glass particles, comprising a glass raw material gas, a fuel gas, and an auxiliary combustion gas at the center, and a flame for synthesizing a base material, comprising the fuel gas and the auxiliary combustion gas, formed around the periphery of the combustion burner. At least one or more of the above are formed, and a burner is used in which the ejection port of the flame for heating the base material projects in the ejection direction of the flame with respect to the ejection port of the flame for synthesizing glass fine particles. Item 5. A method for manufacturing a glass article according to any one of Items 4. 6. A transparent glass rod comprising a core or a part of a core and a clad is used as the starting rod,
A method for manufacturing a glass article according to any one of claims 1 to 5, wherein a preform for an optical fiber is manufactured.