JPH04295020A - Method for molding porous quartz glass body - Google Patents

Abstract

PURPOSE:To provide the method for rationally molding a quartz glass base material with high quality. CONSTITUTION:A quartz glass powder material 50A is packed into a mold 30A while the glass powder material 50A is subjected to a deaeration treatment at least in a part of a transporting route from a supply container 10A to the mold 30A at the time of packing the powder material 50A into the mold 30A, and compressing the material to mold the porous quartz glass body 60A. Since the powder material 50A is packed into the mold 30A while the material is subjected to the deaeration treatment in this transporting route, the high-density porous quartz glass base material 60A free from defects, such as nonuniform bulk densities and residual bubbles, is rationally molded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a silica-based porous glass body for producing optical fiber preforms, image fiber preforms, light guide preforms, rod lens preforms, etc. used in the fields of communication and optics. Regarding the molding method.

0002

[Prior Art] In the fields of communication and optics, when manufacturing silica-based glass base materials for optical fibers, image fibers, light guides, rod lenses, etc., first,
A widely used method is to mold a porous glass body and then turn the porous glass body into transparent glass.

[0003] As a method for manufacturing the above-mentioned silica-based porous glass body, those described in the following documents are known. Document 1: Japanese Patent Application Publication No. 60-210539 Document 2: Japanese Patent Application Publication No. 61-266325 Document 3: Glastech
．． Ber. 60 (1987) Nr. 3, pp.
．． 79-82

In the case of the manufacturing means disclosed in Documents 1 and 2, quartz-based glass powder material is filled into a cylindrical mold and compressed, and the glass powder material in the mold is heat-treated to form porous glass. Create a body. At this time, fine silica particles, fine doped silica particles, etc. are used as the quartz-based glass powder material, a screw conveyor is used as the means for transporting the glass powder material, and a mold made of quartz is used as the mold. When using the manufacturing method of Documents 1 and 2, a rod-shaped porous glass body (for core),
A tubular porous glass body (for cladding) or a composite of these rod-shaped and tubular porous glass bodies can be produced. The porous glass body thus produced becomes a transparent glass body after being subjected to treatments such as dehydration and sintering. The manufacturing method disclosed in Document 3 is also basically the same as that in Document 1.
, 2, and a core-clad porous glass body can be produced through this production method.

[0005]

[Problems to be Solved by the Invention] In the case of the above-mentioned manufacturing means, atmospheric air or other air is
It inevitably enters the inside of the screw conveyor, etc., and is mixed into the glass powder raw material. This air inclusion makes the bulk density of the glass powder raw material non-uniform during compression molding and prevents airtight filling, resulting in air bubbles remaining in the glass during sintering. This causes scattering loss, which deteriorates the transmission characteristics of the final product, the optical fiber, and makes the glass more likely to crack or break. In particular, these problems often occur when fine silica particles, which are easily sintered, are used as a raw material for glass powder.

[0006] In view of the above-mentioned technical problems, the present invention aims to provide a method by which a high-quality silica-based glass base material can be formed rationally.

In order to achieve the intended purpose, the present invention provides a method for forming a porous quartz glass body by filling and compressing a quartz glass powder material in a supply container into a mold using a transportation means including a screw conveyor. The method is characterized in that the glass powder material is filled into the mold while being degassed in at least a portion of the transport path from the supply container to the mold.

[0008]

[Operation] In the method of the present invention, when the quartz-based glass powder material in the supply container is filled and compressed into a mold by a predetermined transportation means to form a quartz-based porous glass body, the transportation route extends from the supply container to the mold. The glass powder material is filled into a mold while being deaerated in at least a portion of the glass powder material. In such cases, it is difficult for air bubbles to remain in the silica-based porous glass body formed in the mold, resulting in a high-density porous glass body that is free from defects such as uneven bulk density, air bubbles remaining during transparent vitrification, and cracks. A glass body is obtained. Moreover, since the degassing treatment of the glass powder material is performed in synchronization with the transportation of the material, the treatment time required for degassing does not lead to an increase in process time, and the porous glass body can be rationally formed.

[0009]

[Example] First, the method of molding a silica-based porous glass base material according to the present invention will be described with reference to an example illustrated in FIGS. 1 and 2. In the case of the forming means illustrated in FIG.
0A, a screw conveyor 20A, and a mold 30A.

In FIG. 1, the supply container 10A has an inlet 11A on the upper surface equipped with an opening/closing lid, a hopper, etc., and an outlet 12A opened on the lower peripheral surface of its body.

In FIG. 1, a screw conveyor 20A
includes a screw 21A and a transport tube 22A with ventilation.
It consists of a combination of a decylinder 24A having a suction port 23A and a prime mover (motor) 25A. In the case of this screw conveyor 20A, after the transport cylinder 22A, which rotatably houses the screw 21A, and the decoupling cylinder 24A are fitted inside and out, the base end of the transport cylinder 22A is connected to the outlet 12A of the supply container 10A. , the base end of the decylinder 24A is attached to the body surface of the supply container 10A and/or the outer peripheral surface of the transport tube 22A. In this way screw conveyor 20A
is attached to the supply container 10A, the screw 21A
crosses the lower part of the supply container 10A, and its screw 2
A base end portion of the supply container 10A passes through the body wall surface of the supply container 10A and is connected to a prime mover 25A including a transmission system. In the case of such a screw conveyor 20A, as shown in FIG. 2, the inside of the transport cylinder 22A is a transport chamber 26A, and the space between the inner and outer peripheral surfaces of the decylinder 24A and the transport cylinder 22A is a vacuum chamber 27A. . Further, a suction piping system 40A including a vacuum pump, a valve, etc. is connected to the suction port 23A of the decylinder 24A.

In FIG. 1, a mold 30A includes a tubular or cylindrical molded container 31A with both ends open, a stopper 32A for closing one end opening of the molded container 31A, and a molded container 31A that can be slid freely into the molded container 31A. It consists of an internal seal ring 33A. The molded container 31A and the stopper 32A are assembled to each other in either a fixed or removable manner. In the case of a removable type, the plug 32A does not easily separate from the molded container 31A, and the two are fitted in an airtight manner. will be combined. The inner diameter of the molded container 31A is larger than the outer diameter of the vent cylinder 24A. The seal ring 33A has an inner diameter of 24A.
The outer diameter of the molded container 31A is approximately equal to the inner diameter of the molded container 31A. Therefore, when the mold 30A is placed over the outer periphery of the deducted cylinder 24A, the inner and outer circumferential surfaces of the seal ring 33A are brought into close contact with the outer circumferential surface of the deducted cylinder 24A and the inner circumferential surface of the molded container 31A.

The above-mentioned supply container 10A is made of metal, rubber,
It is made of any material such as synthetic resin (including FRP), quartz, ceramic, or a composite material thereof. For example, when the supply container 10A is made of a material other than quartz, the surface (particularly the inner surface) is coated with a coating material such as fluororesin (trade name: Teflon) in order to prevent contamination with the quartz-based glass powder material described below. or covered with a lining material. The screw 21A and decylinder 23A in the screw conveyor 20A, the molded container 31A and the stopper 32A in the mold 30A are also made of the above-mentioned arbitrary materials, and their surfaces are coated with the coating material or lining material as necessary. . The transport cylinder 22A of the screw conveyor 20A is made of a material with an open-cell structure, such as a porous material made of a sintered body of metal fibers, a porous ceramic, a hard open-cell synthetic resin, etc. It also has breathability. The seal ring 33A of the mold 30A is, for example,
It is made of silicone rubber and its surface is coated with fluororesin.

In FIG. 1, the glass powder material 50A is
As an example, it is made of pure silica glass particles (SiO2 particles = silica particles), and as another example, it is made of doped quartz-based glass particles with an average particle size of 100 μm or less, which is made by adding appropriate amounts of GeO2, P2 O5, etc. to silica particles. . As yet another example, the glass powder material 50A may be made of a mixture of the above glass fine particles and a solvent. Examples of this solvent include pure water, polyvinyl alcohol, polyvinyl butyral, polyethylene glycol, methylcellulose, carboxymethylcellulose,
Organic materials such as ethyl cellulose, hydroxypropyl cellulose, and glycerin are employed. The amount of solvent added in the glass powder material 50A is 35% relative to the glass fine particles.
It is desirable that it is less than wt%, usually 20wt%
It is set to a certain degree.

In the embodiment shown in FIG. 1, when molding a quartz-based porous glass body using a mold 30A set on the outer periphery of the screw conveyor 20A, the prime mover 25
Screw 21 of screw conveyor 20A via A
While rotating A, suction is drawn between the inner and outer circumferential surfaces of the de-cylinder 24A and the transport cylinder 22A, that is, the inside of the vacuum chamber 27A, via the suction piping system 40A. When the apparatus of FIG. 1 is operated in this manner, the glass powder material 50A in the supply container 10A is transferred to the transport chamber 20 via the screw conveyor 20A.
A to the mold 30A side, and during the transportation, the air mixed in the glass powder material 50A is transported to the vacuum chamber 27A adjacent to the air-permeable transport tube 22A.
It is removed (degassed) via the piping system 40A. When the degassed glass powder material 50A reaches the mold 30A, the preceding glass powder material 50A is filled and filled into the mold 30A by the subsequent glass powder material 50A, which is continuously transported via the screw conveyor 20A. Since it is compressed, a compressed glass powder material 50A, that is, a porous glass body 60A is formed in the mold 30A. Hereinafter, the glass powder material 50A that is subsequently transported causes the porous glass body 60 in the mold 30A to
A grows in the axial direction, and as the porous glass body 60A grows, the mold 30A moves in the direction of the arrow in FIG. When the porous glass body 60A grows to a predetermined length,
The operation of each part is stopped and the mold 30A is removed from the screw conveyor 20A.

When the molded container 31A of the mold 30A has heat resistance, the porous glass body 60A formed in this manner is dried together with the molded container 31A from which the stopper 32A and the seal ring 33A have been removed. When the molded container 31A of the mold 30A does not have heat resistance, the molded container 31A is dried after being released from the mold 30A. The porous glass body 60A after the drying process undergoes known dehydration treatment and transparent vitrification treatment (sintering treatment) to become a transparent glass body. Note that when the molded container 31A of the mold 30A is made of pure quartz or doped quartz, it may be subjected to drying, dehydration, and transparent vitrification treatments together with the molded container 31A, and then integrated with the container glass.

Next, a method of forming a silica-based porous glass base material according to the present invention will be described with reference to an example illustrated in FIG. In the case of the forming means illustrated in FIG. 3, the supply container 10A
, the screw conveyor 20A is the same as that in FIG. 1, but the structure of the mold 30B is different from that in FIG. That is, in the case of the mold 30B shown in FIG.
1 is formed, and an outer tube b4 is provided with a single (or a plurality of) suction ports b3.
5 and a telescopic tube b6 inserted into the inner tube b2 and having both ends fixed to the outer peripheral surface of the outer tube b4 constitute a molded container 31B, and the molded container 31B has the same configuration as in FIG. A plug body 32B and a seal ring 33B are combined. A suction piping system (not shown) is connected to the suction port b3 of the double pipe b5. As the double pipe b5, a material with high mechanical properties and hardness is used from among the materials mentioned above, and as the telescopic pipe b6, for example,
Silicone rubber coated with fluororesin is used.

In the molding means illustrated in FIG. 3, the other components except the mold 30B are the same as described with reference to FIGS. 1 and 2.

The mold 30B of the embodiment shown in FIG.
The telescopic tube b6 is suctioned and held on the inner peripheral surface of the inner tube b2 by suction in the double tube b5 through the suction port b3, and after the stopper 32B and the seal ring 33B are assembled thereto,
It is set on the outer periphery of the screw conveyor 20A. Hereinafter, as described in the embodiment shown in FIGS. 1 and 2, the steps from forming the porous glass body 60A to making it transparent vitrification are carried out.

Next, a method of forming a silica-based porous glass base material according to the present invention will be described with reference to an example illustrated in FIG. The molding means illustrated in FIG. 4 includes two supply containers, two screw conveyors, and one mold.

In FIG. 4, one supply container 10A has an inlet 11A and an outlet 12A, and the other supply container 10B has an inlet 11A and an outlet 12A.
It also has an inlet 11B and an outlet 12B. These supply containers 10A and 10B are spaced apart from each other in the front and back.

One screw conveyor 20 shown in FIG.
A is a breathable transport tube 22A with a built-in screw 21A.
passes through the supply container 10A, the base end of the transport cylinder 22A is connected to the outlet 12A of the supply container 10A, and a de-cylinder 24A installed between both supply containers 10A and 10B is connected to the transport cylinder. It covers a part of the outer peripheral surface of 22A. In the case of the transport tube 22A shown in FIG. 4, the portion covered by the de-cylinder 24A has air permeability, but the other portions do not have air permeability. The other configuration regarding this screw conveyor 20A is substantially the same as that described with reference to FIG.

The other screw conveyor 20 shown in FIG.
B includes a screw 21B and a transport tube 22 with ventilation.
B, a decylinder 24B having a suction port 23B, and a prime mover. This screw conveyor 20B
The screw 21B consists of a hollow rotating shaft that can be closely fitted relative to the transport tube 22A, and a screw blade attached to the outer circumferential surface of the hollow rotating shaft. In the case of this screw conveyor 20B, the screw 21
B is rotatably inserted into the transport cylinder 22B, and the transport cylinder 22
After the screw 21B in the transport cylinder 22B and the transport cylinder 22A are relatively fitted inside and outside, the base end of the transport cylinder 22B is connected to the outlet 12B of the supply container 10B, The proximal end of the decylinder 24B is attached to the body surface of the supply container 10B and/or the outer peripheral surface of the transport tube 22B. In this way, the screw conveyor 20
When B is attached to the supply container 10B, the screw 21
B crosses the lower part of the supply container 10B, and the base end of the screw 21B passes through the wall surface of the body of the supply container 10B and is connected to a prime mover (not shown). In the case of such a screw conveyor 20B, the inside of the transport cylinder 22B is the transport chamber 26.
B, and the space between the inner and outer circumferential surfaces of the de-cylinder 24B and the transport cylinder 22B becomes a vacuum chamber 27B. Further, a suction piping system 40B including a vacuum pump, a valve, etc. is connected to the suction port 23B of the decylinder 24B.

The materials of each part regarding the supply containers 10A, 10B and screw conveyors 20A, 20B described above are the same as those described in FIG. 1.

In the embodiment of FIG. 4, the mold is
, and those described in FIG. 3 can be arbitrarily adopted, and as an example, the mold 30A in FIG. 1 is adopted.

In the embodiment of FIG. 4, one supply container 1
The glass powder material 50A contained in 0A is made of, for example, the doped quartz material described in FIG. 1. In FIG. 4, the glass powder material 50B is made of, for example, pure silica glass particles (SiO2 particles = silica particles), and as another example, an appropriate amount of F, B, etc. is added to the silica particles.
It consists of doped quartz-based glass fine particles with an average particle size of 100 μm or less to which 2 O3 and the like are added. As yet another example, the glass powder material 50B may be made of a mixture of the glass fine particles and the solvent. The amount of solvent added to the glass powder material 50B may be the same as described above.

In the embodiment shown in FIG. 4, when a quartz-based porous glass body is molded using a mold 30A set on the outer periphery of the screw conveyor 20B, the screw conveyors 20A and 20B are The screws 21A, 21B are rotated to suck the inside of each vacuum chamber 27A, 27B via both piping systems 40A, 40B for suction. When the apparatus of FIG. 4 is operated in this manner, one of the glass powder materials 50A is transferred to the screw conveyor 20.
A, the glass powder material 5 is transported from the inside of the supply container 10A to the transport chamber 26A and the mold 30A.
The mixed air in 0A is removed (degassed) by the piping system 40A as described above, and at the same time, the other glass powder material 50B is also transported from the supply container 10B to the transport chamber via the screw conveyor 20B. 26B, mold 30A
The entrained air in the glass powder material 50B is transported to the vacuum chamber 2 adjacent to the air-permeable transport tube 22B.
It is removed (degassed) via piping system 40B via 7B. When the degassed glass powder materials 50A, 50B reach the inside of the mold 30A, the preceding glass powder materials 50A
, 50B are continuously transported via screw conveyors 20A, 20B.
A and 50B fill and compress the mold 30A, so that the mold 30A contains the compressed glass powder materials 50A and 50B, that is, the glass powder material 50A.
A porous glass body 60A for the core (axis) and a porous glass body 60B for the cladding (outer periphery) made of the glass powder material 50B are integrally molded. Thereafter, the composite porous glass body (60A+60B) in the mold 30A grows in the axial direction by the glass powder materials 50A and 50B that are subsequently transported, and as the composite porous glass body grows, the mold 30A Move in the direction of arrow 4. When the composite porous glass body has grown to a predetermined length, the operation of each part is stopped and the mold 30A is transferred to the screw conveyor 2.
Remove from 0B.

The composite porous glass body thus formed is subjected to the drying treatment, dehydration treatment, and transparent vitrification treatment (sintering treatment) described above to become a transparent glass body.

A silica-based glass base material (transparent glass body) for optical fibers, image fibers, light guides, and rod lenses can be made from the porous glass body produced by the method of the present invention. . All of these base materials are made from high-quality porous glass, so
Final products such as optical fibers, image fibers, light guides, and rod lenses can also be obtained with good characteristics.

[0030]

Effects of the Invention The method of the present invention, when filling and compressing a silica-based glass powder material into a mold to form a silica-based porous glass body, deaerates the glass powder material in at least a part of its transportation route. Since it is filled into the mold while being processed, it is possible to rationally mold a high-density silica-based porous glass base material without defects such as uneven bulk density or residual bubbles.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the method of the present invention together with a molding apparatus used therein.

FIG. 2 is a partially enlarged sectional view of the molding apparatus illustrated in FIG. 1;

FIG. 3 is a sectional view showing another embodiment of the method of the present invention together with a molding apparatus used therein.

FIG. 4 is a sectional view showing still another embodiment of the method of the present invention together with a molding apparatus used therein.

[Explanation of symbols]

10A supply container 10B Supply container 12A Entrance of supply container 12B Entrance of supply container 13A Supply container outlet 13B Supply container outlet 20A screw conveyor 20B Screw conveyor 21A screw 21B screw 22A Transport tube 22B Transport tube 23A Suction port 23B Suction port 24A Decylinder 24B De-cylinder 25A Prime mover 26A Transport room 26B Transport room 27A Vacuum chamber 27B Vacuum chamber 30A mold 30B mold 31A Molded container 31B Molded container 32A Plug body 32B Plug body 33A Seal ring 33B Seal ring 40A Piping system 40B Piping system 50A Glass powder material 50B Glass powder material 60A porous glass body 60B Porous glass body

Claims (1)

[Claims] Claim 1: A method for forming a porous silica glass body by filling and compressing a quartz-based glass powder material in a supply container into a mold using a transportation means including a screw conveyor, comprising: a transportation path from the supply container to the mold; A method for molding a quartz-based porous glass body, which comprises filling a mold with a glass powder material while degassing the glass powder material at least in part.