JPH0532426A - Production of quartz glass body - Google Patents

Abstract

PURPOSE:To provide a method for producing a quartz glass body in which bubbles can be prevented from forming in spite of the method for forming. CONSTITUTION:Humidified silica powder 10 is introduced and filled into a forming mold 1 made of rubber and a supporting cylinder 5 is coaxially set through a space 4 on the outer periphery of the forming mold 1. A top lid 3 is further attached to the upper part of the forming mold 1. A forming unit 6 assembled as described above is then placed in a high-pressure vessel 9 filled with a hydraulic medium 8 and a pressure is applied to the forming mold 1. Thereby, the humidified silica powder 10 in the interior is formed. The resultant formed body is subsequently placed in a thermostatic device and dried. The dried formed body is finally sintered in a helium atmosphere at about 1600 deg.C and transparently vitrified to afford a bubbleless quartz rod.

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 quartz glass body by a molding method for producing a quartz glass body used as an optical fiber preform for producing an optical fiber.

[0002]

2. Description of the Related Art Conventionally, when a quartz glass body is manufactured by a molding method, silica powder and powder containing silica powder as a main raw material are filled in a rubber molding die in a pressure vessel and molded by an external pressure. The obtained molded body was sintered to produce a quartz glass body.

[0003]

However, when the molded body obtained by such a molding method is sintered and vitrified, there is a problem that bubbles often occur in the quartz glass body. This is largely due to the non-uniform density and pores of the molded body.

An object of the present invention is to provide a method for producing a quartz glass body which can prevent the generation of bubbles even though it is a molding method.

[0005]

The means of the present invention for achieving the above object will be described below.

According to the first aspect of the present invention, silica powder, powder containing silica powder as a main raw material, granulated particles obtained by granulating silica powder, and powder containing silica powder as a main raw material are granulated in a molding die. When the quartz glass body is manufactured by filling a quartz glass body-forming powder or granules made of any of the above-mentioned granulated particles or a mixture thereof and molding the mixture with an external pressure, the quartz glass body The present invention is characterized in that the powder for body forming is moistened, and then the powder is filled into the forming die to perform the forming.

According to a second aspect of the present invention, a rod-shaped body is installed in the center of a molding die, and silica powder, a powder containing silica powder as a main raw material, and a silica powder are produced around the rod-shaped body in the molding body. Granulated granules, silica powder is used as a main raw material, and any one of granulated particles obtained by granulating powder or a mixture thereof is filled with a quartz glass body molding powder and molded by external pressure, When the obtained molded body is sintered to manufacture a quartz glass body, the quartz glass body-forming powder and granules are moistened, and then the molded body is filled and molded.

[0008]

As described above, if the quartz glass body molding powder and granules are humidified before being filled in the molding die, the bulk of the molded body is pressed by pressing during molding. The density can be improved. Further, the humidification can reduce the intake of air in the molded body. Furthermore, when granulated particles obtained by granulating silica powder, or granulated particles obtained by granulating powder having silica powder as a main raw material are used, the granulated particles can be easily crushed during molding to obtain uniform Quartz glass having a wide density distribution is obtained.

[0009]

【Example】

Example 1 A case of making a quartz rod will be described below with reference to FIG. In this example, commercially available silica powder was used as the powder particles for forming the quartz glass body. The particle size of the silica powder is about 8 μm and the water content is about 0.3%. This was placed in a thermo-hygrostat (not shown) and humidified. Humidification of this example,
The moisture content in silica powder is 3 at 40 ℃ and 70% humidity.
% Was performed. In this case, when the amount of water contained in the silica powder was 3% or more, cracks occurred during drying. The water content of the silica powder was measured with an infrared moisture meter.

The quartz glass body molding apparatus of this embodiment comprises a rubber-made cylindrical molding die 1, a lower lid 2 fitted to the lower portion thereof, an upper lid 3 fitted to the upper portion thereof, and a molding die. A mold 1 is provided with a support cylinder 5 which is coaxially arranged on the outer periphery of the mold 1 with a space 4 and whose both ends are supported by a lower lid 2 and an upper lid 3. A plurality of through holes 7 are dispersedly provided on the peripheral wall of the support cylinder 5. The molding unit 6 as described above is housed in a high-pressure container 9 filled with a pressurizing medium (lubricant) 8. The support cylinder 5 and the high-pressure container 9 are made of, for example, stainless steel.

In this embodiment, the silica powder 10 moistened as described above is charged and filled in the rubber mold 1. During the charging and filling, the lower lid 2 fitted to the lower part of the mold 1 was vibrated. The mold 1 used in this example has a size of about 35 mmφ (outer diameter) × 25 mmφ (inner diameter) × 170 mm (length, of which length the filling portion is 150 mm). The amount of humidified silica powder 10 was about 80 g. Next, the support cylinder 5 was set concentrically on the outer periphery of the molding die 1 through the space 4, and the upper lid 3 was attached to the upper part of the molding die 1. Although not shown, the surface of the lower lid 2 and the upper lid 3 that the humidified silica powder 10 comes into contact with is coated with a fluororesin.

The molding unit 6 assembled in this manner is placed in a high-pressure container 9 filled with a pressure medium (lubricant) 8 and pressure is applied to the rubber molding die 1 to wet the silica powder inside. 10 was molded. Molding pressure: about 500Kgf /
cm ² , pressure application time: about 1 minute. The obtained molded body could be taken out from the mold 1 without damage.

Next, the obtained molded body was placed in a thermostat (not shown) and dried. Drying was performed under the conditions of a temperature of 110 ° C. and a time of about 24 hours. The humidity at this time is 0%.

Finally, when the molded body was sintered in a helium atmosphere at about 1600 ° C. to form a transparent glass, the outer diameter was 17 mm.
A φ-free quartz rod was obtained.

Next, the case of producing a quartz pipe will be described below with reference to FIG. In this example, silica granules obtained by granulating silica powder were used as the quartz glass body molding powder. The silica granulated particles have a primary particle size of about 0.7 μm before granulation and a particle size of about 50 μm after granulation. The amount of water contained in the silica granulated particles is about 0.5%. The silica granulated particles were placed in a thermo-hygrostat (not shown) and humidified. Humidification conditions are temperature 40 ℃,
The moisture content in the silica granulated particles was adjusted to 5% at a humidity of 95%. When the amount of water contained in the silica granulated particles was 5% or more, a part of the silica granulated particles returned to the primary particles, and the filling property deteriorated. The amount of water contained in the silica granulated particles was measured with an infrared moisture meter.

The apparatus for molding a quartz glass body of this embodiment comprises a rubber molding die 11, a cylindrical lower lid 12 arranged in a lower portion of the molding die 11 and an upper lid thereof. A cylindrical upper lid 13 and a lower punch 14 fitted to the lower lid 12.
And the upper punch 15 fitted to the upper lid 13 and the molding die 11
A pressure rubber die 16 disposed on the outer periphery of the pressure rubber die 16 supported at both ends by the lower lid 12 and the upper lid 13, and coaxially disposed on the outer periphery of the pressure rubber die 16 with a space 17 at both ends. A high-pressure container 18 liquid-tightly supported by the upper lid 13 and a pressurizing medium inlet 19 penetrating the peripheral wall of the high-pressure container 18.
And is configured. A pressurizing medium (lubricating oil) 20 is press-fitted from a pressurizing medium inlet 19 into a space 17 defined by the pressurizing rubber mold 16 and the high-pressure container 18.

In this embodiment, the upper punch 15 is opened, the moistened silica granulated particles 21 moistened as described above are charged and filled in the molding die 11, and then the upper punch 15 is closed.
At this time, since the upper end of the glass rod 23 is previously supported by the holding jig 22 provided in the center of the lower surface of the upper punch 15, the glass rod 23 is closed by closing the upper punch 15.
Is inserted into the humidified silica granulated particles 21 along the center of the mold 11, and the lower part of the glass rod 23 is positioned in the recess 24 provided in the center of the upper surface of the lower punch 14. The molding die 11 of this embodiment has an inner diameter of about 50 mmφ and a filling portion length of about 250 mm. The glass rod 23 has an outer diameter of about 20 mmφ. The amount of the humidified silica granulated particles 21 charged is about 350 g. The surfaces of the lower punch 14 and the upper punch 15 in contact with the humidified silica granulated particles 21 are coated with a fluororesin to prevent contamination from both punches 14 and 15.

In this state, the pressurizing medium (lubricant) 20 was press-fitted from the pressurizing medium inlet 19. With this pressure medium 20, a pressure of about 1000 kgf / cm ² was applied to the pressure rubber mold 16 for about 1 minute. As a result, from the pressure rubber mold 16 to the molding mold 1
The pressure is transmitted to 1, and the humidified silica granulated particles 21 are compression molded. In this embodiment, the mold 11 is made of nitrile rubber (NBR). Then, in order to prevent cracks and cracks due to the rapid restoring force of the mold 11, the pressure was slowly reduced over about 20 minutes.

By the above operation, a porous base material having no cracks was obtained. After pulling out the glass rod 23 from the center of the released porous base material, the porous base material was sufficiently dried by a thermostat (not shown).

This porous matrix was vitrified into a transparent glass in a helium atmosphere at about 1650 ° C. No bubbles were observed in the obtained quartz pipe.

Next, an example of producing an optical fiber preform will be described with reference to FIG. In this example, silica granulated particles were used as the powder particles for forming the quartz glass body. The silica granulated particles have a primary particle size of about 0.7 μm and a granulated particle size of about 50 μm. The amount of water contained in the silica granulated particles is about 0.5%. The silica granulated particles were placed in a thermo-hygrostat (not shown) for humidification. Humidification conditions are
At a temperature of 40 ° C. and a humidity of 70%, the amount of water contained in the silica granulated particles was set to 3%. The amount of water contained in the silica granulated particles is 5
When it is more than 100%, a part of the silica granulated particles is returned to the primary particles, and the filling property is deteriorated. The amount of water contained in the silica granulated particles was measured with an infrared moisture meter.

The upper punch 15 is opened, the humidified silica granulated particles 21 produced as described above are charged and filled in the molding die 11, and then the upper punch 15 is closed. The mold 11 has an inner diameter of about 50 mmφ and a filling portion length of about 250 mm. A glass rod 23 is attached to the upper punch 15 in advance by a holding jig 22. In this way, like the above,
When the upper punch 15 is closed, the glass rod 23 is inserted into the humidified silica granulated particles 21 along the center of the mold 11, and the recess 2 provided in the center of the upper surface of the lower punch 14 is inserted.
The lower part of the glass rod 23 is positioned at 4. The glass rod 23 is manufactured by a vapor phase method, and has a core / cladding ratio of 1/4 and dimensions of 10.6 mmφ × 270 mm. The amount of the humidified silica granulated particles added was about 420 g. Furthermore, each punch 14,1
The surface of No. 5 that contacts the humidified silica granulated particles 21 is coated with a fluororesin so as to prevent contamination from both punches.

In this state, the pressurizing medium (lubricant) 20 was press-fitted from the pressurizing medium inlet 19. With this pressure medium 20, a pressure of about 1000 kgf / cm ² was applied to the pressure rubber mold 16 for about 1 minute. As a result, from the pressure rubber mold 16 to the molding mold 1
The pressure was transmitted to No. 1, and the humidified silica granulated particles 21 were compression molded. In this embodiment, the mold 11 is made of nitrile rubber (NBR). Then, in order to prevent cracks and cracks due to the rapid restoring force of the mold 11, the pressure was slowly reduced over about 20 minutes.

By the above operation, a porous base material having no cracks was obtained. The porous base material was sufficiently dried with a thermostat.

An optical fiber preform was produced by dehydrating and vitrifying this porous preform under the same conditions as in the vapor phase method. The dehydration and vitrification conditions are the same as those in the ordinary vapor phase method. No bubbles were observed in the obtained optical fiber preform. This optical fiber preform was drawn by an ordinary method to form an optical fiber. The obtained optical fiber had the same characteristics as the fiber produced by the vapor phase method or the like.

Comparative Example A molded body was prepared by the method shown in Example 2 using silica granulated particles which were not humidified. Table 1 shows a comparative example of the compact density and porosity of the compact formed using the humidified silica granulated particles and the compact formed using the non-humidified silica granulated particles. By humidifying, the density of the molded body was improved and the porosity was also reduced. It is clear that the reduced porosity also reduces the amount of air contained in the molded body, and also reduces the bubbles contained in the quartz glass.

[0027]

[Table 1]

In the above embodiment, an example was shown in which silica powder and granulated particles obtained by granulating silica powder were used as the quartz glass molding powder, but the present invention is not limited to this. For example, a powder containing silica powder as a main raw material such as a powder obtained by adding a dopant to silica powder, or granulated particles obtained by granulating a powder containing the powder as a main raw material can be used.

In addition to the above, the following particles and the like can be used as the powder particles for forming the quartz glass body.

(A) A mixture of silica powder and granulated particles obtained by granulating silica powder.

(B) a powder whose main raw material is silica powder,
A mixture with granulated particles obtained by granulating powder having silica powder as a main raw material.

(C) A mixture of silica powder and granulated particles obtained by granulating powder having silica powder as a main raw material.

(D) A powder containing silica powder as a main raw material,
A mixture with granulated particles obtained by granulating silica powder.

[0034]

As described above, in the method for producing a quartz glass body according to the present invention, before filling the quartz glass body-forming powdery granules in the molding die, Since it is humidified, the bulk density of the molded product can be improved by applying pressure during molding. Further, the humidification can reduce the intake of air in the molded body. Therefore, by improving the density of the molded body and reducing the intake of air, it becomes possible to suppress the generation of bubbles when the molded body is made into a transparent glass. Therefore, according to the present invention, high-quality quartz glass bodies can be mass-produced with high yield.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an embodiment of a molding apparatus for carrying out the manufacturing method of the present invention.

FIG. 2 is a vertical sectional view of another embodiment of the molding apparatus for carrying out the manufacturing method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Mold, 2 ... Lower lid, 3 ... Upper lid, 4 ... Space, 5 ... Support cylinder, 6 ... Molding unit, 7 ... Through hole, 8 ... Pressurizing medium, 9
... high-pressure container, 10 ... humidified silica powder, 11 ... mold, 12 ... lower lid, 13 ... upper lid, 14 ... lower punch, 15 ...
Upper punch, 16 ... Pressurized rubber mold, 17 ... Space, 18 ... High pressure container, 19 ... Pressurized medium injection port, 20 ... Pressurized medium, 21 ...
Humidified silica granulated particles, 22 ... Holding jig, 23 ... Glass rod, 24 ... Recessed portion.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuaki Yoshida             2-6-1, Marunouchi, Chiyoda-ku, Tokyo             Kawa Electric Industry Co., Ltd.

Claims (2)

[Claims] 1. A silica powder, a powder containing silica powder as a main raw material, a granulated particle obtained by granulating silica powder, or a granulated particle obtained by granulating a powder containing silica powder as a main raw material in a molding die. Alternatively, when a quartz glass body-forming powder or granules composed of a mixture of these is filled and molded by external pressure, and a quartz glass body is manufactured by sintering this, the quartz glass body-forming powder or granules are A method of manufacturing a quartz glass body, which comprises humidifying and then filling the molding die to carry out molding. 2. A rod-shaped body is installed in the center of a molding die, and silica powder, a powder containing silica powder as a main raw material, and granulated particles obtained by granulating silica powder are provided around the rod-shaped body in the molding body.
A silica glass powder is used as a main raw material, and any one of the granulated particles obtained by granulating the powder or a mixture thereof is filled with a quartz glass body molding powder and molded by external pressure. A method for producing a quartz glass body, comprising the steps of humidifying the quartz glass body-forming powder and then filling the molding die and performing molding when the quartz glass body is produced by sintering.