JP2002114530A - Method for manufacturing large-sized quartz glass body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently manufacturing a large-sized quartz glass body having high purity and high accuracy at a low cost. SOLUTION: A rod-like body 3 formed by serially connecting columnar or cylindrical carbon fiber reinforced carbon composite material members (C/C composites) in threaded parts is arranged in the central part of a heat resistant casting mold in the method for manufacturing the large-sized quartz glass body by packing silicon dioxide powder 2 into the heat resistant casting mold and forming molten glass in a heating furnace. The threaded parts are formed as trapezoidal shapes, and further, the threaded parts are provided with layers impregnated with carbon and/or subjected to coating, by which the strength of the threaded parts is improved.

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 large quartz glass body, and more particularly, to a method for producing a large-sized quartz glass body with high purity and high precision at low cost and with high yield.

[0002]

2. Description of the Related Art Conventionally, quartz glass tubes and rods for optical fiber preforms used in the production of optical fibers have been required to have high dimensional accuracy and high purity. A porous quartz glass base material (soot body) is formed by depositing, and then heated and heated to form a transparent vitrified glass material (VAD method).
Method), the MCVD method and the like have been adopted and put to practical use. Furthermore, in recent years, application of a sol-gel method or other synthetic methods, and development of a method combining the above methods (using an overcladding step such as a RIT / RIC method) have been advanced. And, for the future expansion of optical fiber demand,
It is expected that the size and length of the optical fiber preform will be further increased for mass production and cost reduction.
In order to further increase the size by the VAD method, the OVD method, the MCVD method, or a method based on a combination thereof, equipment such as a soot body manufacturing apparatus and a dehydration sintering furnace becomes large-scale, and the cost increases accordingly. And difficulties in handling are serious problems. Although the production of optical fiber preforms by the sol-gel method has great advantages in terms of equipment and handling, it still overcomes significant problems such as bubbles in quartz glass and other quality problems. Has not been put to practical use. Therefore,
Apart from the improvement of the manufacturing method, the manufacture of a quartz glass optical fiber preform using silicon dioxide powder as a starting material as disclosed in Japanese Patent Application Laid-Open No. 5-58656 and the like has been studied.

Also, in the field of semiconductor manufacturing, quartz glass tubes or ingots (in addition to blocks, plates or rods) used as materials for heat treatment jigs (core tubes, wafer boats, etc.) used in the manufacturing process. Since high purity and heat resistance are required, for example, the so-called Bernoulli method of melting and depositing while supplying quartz powder into an oxyhydrogen flame is employed. However, it takes a very long time to manufacture a large quartz glass body by the Bernoulli method, which leads to an increase in cost. For example, Japanese Patent Application Laid-Open No. 9-202632 discloses a method for manufacturing a large quartz glass body. As described in Japanese Unexamined Patent Publication, a method of filling silicon dioxide powder into a heat-resistant mold such as carbon and melting in a heating furnace to form a transparent glass (hereinafter referred to as a "mold melting method")
Has been proposed. This mold melting method can greatly reduce the work load and jigs and the like required for steps such as grinding and cutting as compared with a conventional method of forming a quartz glass block into a desired shape by machining. Not only is molding simple, but also the material yield is extremely high, so that it has a great advantage in cost.

[0004] As described above, in the method of manufacturing a quartz glass body using silicon dioxide powder as a starting material, a mold melting method is preferable in order to increase the size and reduce the cost. However, even with this mold melting method, in order to further increase the size and thickness, the size of the mold to be used is increased, and the rod-shaped body is made thinner and longer, and the silicon dioxide powder is placed in the mold. Need to be filled more. In the mold melting method described in the above publication, it is disclosed that a rod-shaped body made of quartz glass is inserted and arranged at the center of a carbon mold, but in practical use, ceramics such as alumina, zirconia, silicon carbide and silicon nitride are disclosed. It is also considered possible to use a graphitized carbon material (graphite carbon, hereinafter also referred to simply as "graphite"). However, a rod-shaped body made of quartz glass has a limitation in reducing the diameter in terms of strength or handling surface, and a rod-shaped body made of ceramics or carbon material has a problem in cost due to workability and high purity. Therefore, carbon fiber reinforced carbon composite is a material that excels in load resistance and heat resistance as well as workability, is easy to handle, etc., is also superior in price, and is also capable of high purity products. Materials (Carbon Fiber Rein
The use of a focused carbon composite (hereinafter "C / C composite") is considered suitable. However, in the case of a conventional C / C composite member, as the size of the member increases, problems in production of materials, molding and the like, and problems in processing accuracy increase. Practical use of the material was considered to involve great difficulties. Therefore, in order to increase the length, it is required to join a plurality of C / C composite members in series.

[0005]

When a plurality of C / C composite members are joined in series, if the strength of the joining portion is insufficient, "bending" or "backlash" occurs at the connecting portion, and the rod-like member is formed. May be bowed.
This is particularly evident when the diameter of the rod-shaped body is reduced.If such "bending" occurs, the accuracy of the quartz glass body decreases, and the obtained quartz glass body is subjected to grinding, drilling, etc. Since a molding step is required, there is a problem that it is impossible to contribute to cost reduction in total. For example, as a method of joining a plurality of C / C composite members, a method of connecting a plurality of members using various various jigs, such as making a hole near an end of the member and locking it with a joining pin. Therefore, a rod-shaped body having a certain strength is also possible. However, when attempting to produce a larger quartz glass body by the mold melting method, the stress at the time of melt vitrification increases, and in the case of locking with a conventional joining pin, the pin cannot withstand excessive stress and cannot withstand excessive stress. Was broken. If the pins at the joints are damaged as described above, the rod-shaped body is deformed such as "bending", so that the accuracy of the obtained quartz glass body is reduced, and steps such as grinding and drilling are performed again. And the cost is limited.
Therefore, in order to further increase the length and diameter of the rod while maintaining excellent heat resistance and strength, a plurality of C /
An important issue is how to join the C composite members.

[0006]

Means for Solving the Problems In view of the above problems, the present inventors have conducted intensive studies and found that a plurality of C / C composite members having high purity, high strength and high heat resistance were screwed in series. By joining with, there is no strength of the joint part, there is no bending or backlash at the connection part, and a long, thin rod without bending is obtained, and it is the central part of the carbon mold It has been found that a large quartz glass body with high dimensional accuracy can be manufactured by disposing the glass material in a state where there is no deformation at the time of melt vitrification. And a trapezoidal screw is practical for the joining,
Furthermore, it has been found that by reinforcing the joint, the strength of the screw portion itself is improved, the diameter can be easily reduced, and a larger and thicker quartz glass body can be realized. In addition, the present inventors have found that when the rod-shaped body is reduced in diameter, a large amount of silicon dioxide powder can be filled and the size and thickness of the rod can be increased. For the problem that the possibility that the gas generated on the outer peripheral part side moves to the central part and the possibility of remaining as a bubble as it is because the melt vitrification is delayed may be increased,
It has been found that the improvement can be achieved by making the rod-shaped body disposed at the center part cylindrical. That is, by forming the hollow portion into a cylindrical shape by the rod-shaped body, it is possible to remove gas generated during the melt vitrification of the silicon dioxide powder from the hollow portion, and to reduce bubbles remaining in the quartz glass body. Becomes possible. Further, with respect to such "degassing", the present inventors have placed an intermediate material made of graphite between the rod and the silicon dioxide powder, or between the heat-resistant mold and the silicon dioxide powder, or both. Thus, the inventors have found that a path for discharging gas to the outside can be provided to further reduce bubbles remaining in the quartz glass body, and the present invention has been completed.
That is,

An object of the present invention is to provide a method for producing a large-sized quartz glass body of high purity at low cost using a rod-shaped body having excellent strength as well as heat resistance.

It is another object of the present invention to provide a method for producing a large-sized quartz glass body with high precision in a high yield, and to efficiently produce a large-sized quartz glass body containing less air bubbles. Is possible.

In order to achieve the above object, the present invention provides a method for producing a large quartz glass body in which a heat-resistant mold is filled with silicon dioxide powder and is melted and vitrified in a heating furnace. The present invention relates to a method for manufacturing a large quartz glass body, characterized in that a rod-shaped body in which cylindrical C / C composite members are joined in series by screw portions is arranged.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the accompanying drawings, but all are merely examples for explaining the technical idea of the present invention, and the present invention is thereby limited. It is not done.

As described above, according to the production method of the present invention, a columnar or cylindrical C / C composite rod is placed at the center of a carbon mold, filled with silicon dioxide powder, and then melt-vitrified in a heating furnace. By doing so, a high-precision large quartz glass body is manufactured at low cost, and a schematic diagram of an example thereof is shown in FIG. In FIG. 1, reference numeral 1 denotes a heat-resistant mold, 2 denotes a silicon dioxide powder, 3 denotes a rod, 4 denotes a heater, 5 denotes an inert gas inlet, and 6 denotes an exhaust port.

The rod-shaped member 3 has a cylindrical or cylindrical C /
A C / C composite having a bulk density of 1.5 g / cm ³ or more and a bending strength of 100 MPa is a rod-shaped body in which two or more members made of a C composite are screw-connected in series.
As described above, those having a tensile strength of 100 MPa or more are preferred. If the C / C composite used is less than the above range, sufficient strength cannot be obtained, and when a large quartz glass body is melted and vitrified, the rod-shaped body may be deformed, which is not preferable. The C / C composite is formed, for example, by laminating a plurality of prepregs obtained by impregnating a carbon fiber cloth with a pitch or a resin, and molding the prepreg into a flat plate shape. Thereafter, carbonization treatment by baking, densification treatment such as re-impregnation with a pitch or resin and baking, and graphitization treatment are performed, and further, high purity treatment is performed using a halogen gas. As impurities in the C / C composite, Na, K, Fe and the like are preferably 1 ppm or less. As a result, contamination by impurities can be reduced, and when a quartz glass jig for manufacturing a semiconductor wafer is manufactured, contamination by a metal element or the like that becomes a semiconductor poison can be suppressed.
Also, when manufacturing a quartz glass tube for optical fiber preform,
A good optical fiber with little loss in transmission characteristics can be obtained.

[0013] As for the shape of the screw for joining the members made of the C / C composite in series with the screw portion, the "trapezoidal screw" having a "trapezoidal" cross-sectional shape has a large contact area between the male screw and the female screw. It is excellent in workability such as threading and joining, and a large quartz glass body can be manufactured more accurately and at low cost. In the present invention,
In addition to the trapezoidal screw, a “triangular screw”, a “square screw”, a “saw tooth screw” or the like can be appropriately used. FIG. 2 shows an example of a rod-shaped body provided with the trapezoidal screw. In FIG. 2, 7 is a C / C composite rod provided with a male thread on one side of both ends, 8 is a C / C composite rod provided with a female thread on one side of both ends, and 9 is a C / C composite. The male thread portion 10 of the rod 7 is a female thread portion of the C / C composite rod 8. Further, as shown in FIG. 3, the threaded portion of the C / C composite rod can be provided with a layer 11 impregnated with carbon and / or coated. When this layer 11 is provided, the strength of the thread portion is further improved, and the tensile strength of a rod having an outer diameter of 30 mm reaches about four times that of a graphite rod. Therefore, even if the rod-shaped body is made longer and smaller in diameter, the possibility of breakage in the screw portion is reduced, which is preferable. Further, as shown in FIG. 4, a reinforcing member 12 made of a C / C composite can be provided on the outer periphery of the screw portion to reinforce the screw portion. By providing this reinforcing member, the reinforcement of the threaded joint becomes stronger, the thermal expansion of the threaded part and the decrease in the contact area of the threaded part can be suppressed, a higher load resistance can be ensured, and the diameter can be reduced. It becomes possible. The C / C composite forming the reinforcing member is formed, for example, by winding a prepreg obtained by impregnating carbon fibers with a pitch or a resin on a columnar support, and forming the prepreg into a cylindrical shape. Thereafter, the carbonization treatment, the densification treatment, the graphitization treatment, and the high-purification treatment are performed, and a carbon impregnated and / or coated layer is provided. The carbon impregnation and / or
Alternatively, the generation of particles from the reinforcing member is suppressed by the coating, and a higher purity quartz glass body can be obtained. The reinforcing member may also be C / C without carbon impregnation and / or coating.
It can also be formed of a composite.

The layer impregnated and / or coated with carbon is a CVI treatment using a hydrocarbon gas or the like.
Alternatively, the C / C composite is subjected to CVD treatment or resin impregnation / coating, curing, baking treatment, etc.
(I) a layer formed by impregnating and coating pyrolytic carbon from the surface to the inside of pores by CVI treatment or by impregnating a substance such as glassy carbon by resin treatment or the like;
i) a layer formed by coating the surface with pyrolytic carbon by CVD processing, or coating the surface with a substance such as glassy carbon by resin treatment, or (iii) pyrolytic carbon by CVI processing. Is impregnated and coated from the surface to the inside of the pores, or is impregnated with a substance such as glassy carbon by resin treatment, and the surface is coated with pyrolytic carbon by CVD processing, or the resin is treated. Etc. means a layer formed by coating the surface with a substance such as glassy carbon. In the above-mentioned "impregnation" and "coating", mechanical surface treatment and finishing as necessary before and after the step of forming these layers are generally performed industrially.

In the production of the large quartz glass body, C
/ C between the rod and silicon dioxide powder and / or the heat-resistant mold and silicon dioxide powder to prevent adhesion between the composite rod and the quartz glass and / or the adhesion between the heat-resistant mold and the quartz glass. And an intermediate material made of graphite is preferably interposed between them. Specific examples of the graphite intermediate material include a graphite sheet and / or graphite felt, and the graphite sheet and / or graphite felt is used to cover the outer periphery of the rod or cover the inside of the mold to form the rod. And / or the adhesion between the mold and the quartz glass body can be prevented, so that the quartz glass body can be easily extracted and the C / C composite rod or heat-resistant mold can be reused, and the life thereof can be extended. It is also possible to measure. Furthermore, the coating reduces the stress associated with the vitrification of the silicon dioxide powder, thereby preventing deformation and breakage of the mold, and the elasticity and gas permeability of graphite reduce gas generated during vitrification. Since a path to escape to the outside is provided, it is possible to further reduce bubbles remaining in the quartz glass body. In the case where the rod-shaped body or the mold is coated with a graphite intermediate material, either one of a graphite sheet or graphite felt may be used, and the graphite felt may be further coated on the graphite sheet. As disclosed in Japanese Patent Application Laid-Open No. H11-278857, different materials may be used for the bottom part and the side part of the mold.

The silicon dioxide powder used in the production method of the present invention can be appropriately selected according to the application and cost. For example, a semiconductor jig which requires a high purity and a high heat resistance above a certain level is required. In the case of quartz glass body for
Purified crystalline silica powder obtained by pulverizing natural quartz (quartz), silica sand, silica stone, or the like is preferable in terms of cost, and amorphous silica powder obtained by fusing them is also usable. When a powder having higher purity is required, for example, when manufacturing a cylindrical quartz glass body for manufacturing a base material for an optical fiber, a silicon alkoxide, a silicon halide (such as silicon tetrachloride), a silicate, It is preferable to use a synthetic quartz glass powder obtained by a sol-gel method, a soot method, a flame combustion method, or the like, using soda or another silicon compound as a starting material. In addition, fumed silica, precipitated silica, and the like can be used.

The size of the crystalline or amorphous silicon dioxide powder may be appropriately selected according to the heating and melting conditions and the like. Preferred examples thereof include powders having a particle size in the range of 1 to 1000 μm, A more preferred example is a powder having a particle size in the range of 10 to 300 μm. If the particle size of the silicon dioxide powder to be used is too large, it is difficult to obtain a uniform vitreous glass because the packing density of the powder is reduced, and a homogeneous quartz glass body may not be obtained. It is desirable not to use silicon powder. If the particle size is too small, there may be a problem in handling. Therefore, it is desirable not to use silicon dioxide powder having a particle size of less than 1 μm. In particular, when using synthetic quartz glass powder, the melting of the powder is accelerated, which promotes the remaining of bubbles, and as a result, there is a possibility that the number of contained bubbles may be increased. However, it is desirable to use a powder having a relatively large particle size. Further, in the present invention, natural or synthetic or crystalline or amorphous silicon dioxide powder or the like can be appropriately used depending on the use of the quartz glass body and the like. Specifically, natural quartz powder, natural stone It can be appropriately selected from English glass powder, synthetic quartz glass powder and synthetic quartz powder, and elements (aluminum, nitrogen, hydrogen) having a specific action (improving heat resistance, improving light transmittance, etc.) in the above-mentioned various powders , Etc.) can be used. Further, from the viewpoint of controlling the filling density and melting rate of the above-mentioned silicon dioxide powder or the like, it is also effective to mix or combine the various silicon dioxide powders. For example, a particle size of 1 to 1000 μm
Within this range, it is possible to increase the packing density and promote uniform melt vitrification by mixing quartz powder with a certain degree of particle size within the range described above. Is filled, and the outside (near the outer peripheral portion) is filled with quartz powder, so that the melting of the outside can be prevented from becoming too fast, and the inclusion of bubbles can be suppressed.

As the heating and melting conditions of the silicon dioxide powder, for example, the conditions described in JP-A-9-202632 are preferably used. That is, from room temperature to 1600 ° C, from 200 to 600 ° C / hour, from 1600 ° C to the melting temperature of quartz powder, at a rate of 10 to 100 ° C / hour, at least 30 minutes per 5 cm thickness of the filled silicon dioxide powder layer. In short, it is heated and melted while exhausting the gas in the filled silicon dioxide powder. After the heating and melting, the temperature is maintained at the above-mentioned melting temperature for at least 2 hours, preferably 3 to 5 hours. By adopting the melting conditions, even if the quartz glass body is further enlarged,
It is possible to reduce the air bubbles remaining inside.
More preferably, if the C / C composite rod is made cylindrical and melted while discharging gas from the hollow portion, there is an effect of further suppressing the remaining of bubbles. Note that the above description is based on the premise that a transparent quartz glass body is manufactured.However, even when an opaque quartz glass body having heat-shielding properties and light-shielding properties is to be obtained, the manufacturing method of the present invention is not required. In this case, it is possible to add a foaming agent to the filled silicon dioxide powder, or to appropriately change the temperature profile at the time of heating.

As described above, the C / C composite rod used in the production method of the present invention has high purity and high heat resistance and strength. A large quartz glass body having high dimensional accuracy and containing few bubbles can be manufactured at low cost without deformation or center deviation even during transfer or transportation.

[0020]

Now, the present invention will be described in further detail with reference to Examples. However, these Examples are illustrative only.
The present invention is not limited thereby.

Example 1 A prepreg was manufactured by impregnating a 6K plain weave cloth of carbon fiber (Torayca T-300) manufactured by Toray Industries Co., Ltd. with a phenol resin, cut into about 820 mm × 410 mm, and laminated.
Perform hot press molding at 160 ° C, about 820mm x 4
A compact having a size of 10 mm × 35 mm was obtained. The molded body was heated to 800 ° C. in an electric furnace and heated to obtain a fired body. The fired body is densified by repeatedly performing pitch impregnation and firing, and then heat-treated at 2,000 ° C. to about 820 m
A flat C / C composite of mx 410 mm x 35 mm was obtained. When the physical properties of the C / C composite plate were measured, the bulk density was 1.62 g / cm ³ and the bending strength was 1
It was 55 MPa and the tensile strength was 220 MPa. This flat, length 800 mm, to prepare 12 a cylindrical rod having a diameter of 30 mm?, The two of which rods, while the trapezoidal male thread from the end surface to 50mm in length by Grinding the one end periphery, another The inner circumference of the end of the book is formed into a trapezoidal female screw by grinding, and after performing high-purity treatment with a halogen gas, the two pieces are connected in series and joined to form a length of 15 mm.
A C / C composite rod having a diameter of 50 mm and a diameter of 30 mm was obtained. The obtained rod was attached to a tensile tester, and the breaking load was measured with a static tensile load at a transition speed of 0.5 mm / min. As a result, the thread was broken, and the breaking load at that time was 14,200 N (Newton), confirming that the joint had sufficient strength.

Further, regarding the remaining ten rods,
A trapezoidal male screw and a trapezoidal female screw were provided in the same manner as described above. (Here, one rod has only one male screw at one end, eight rods have one male screw at one end, and the other has a female screw at the other end. Only one female screw was provided on one end side of each of the rods), and a high-purity treatment was performed with a halogen gas. Then, these ten rods are joined at nine locations with male and female threads in the same manner as described above, and a length of 755
A C / C composite rod A (3) having a diameter of 0 mm and a diameter of 30 mm was obtained.

The C / C composite rod A (3)
Is placed in the center of a cylindrical carbon mold 1 having an inner diameter of 155 mmφ and a length of 1000 mm, and then filled with quartz powder 2 (total metal impurities 30 ppm or less, particle size distribution 60 to 280 μm, average particle size 180 μm) while applying vibration. And a height of about 950 mm. The density of the packing is about 1.45g
/ Cm ³ . The entire carbon mold 1 was set in a vacuum furnace, the pressure was reduced to a degree of vacuum of 1 × 10 ⁻⁴ mmHg or less, and then the temperature was raised. Using a carbon resistance heater 4 as a heating source, the temperature is measured from room temperature to 1780 ° C. for 7 hours while the temperature is measured with a thermocouple, and the temperature is maintained at 1780 ° C. for 2 hours, and then the vacuum in the furnace is broken with nitrogen gas. Then, the pressure was returned to the atmospheric pressure, and the pressure was maintained at the atmospheric pressure until the completion of the melting and slow cooling, thereby producing a large quartz glass body having a hollow cylinder shape. The obtained quartz glass body did not contain bubbles, had good dimensional accuracy without bending or eccentricity, and was a quartz glass hollow body suitable as a base material for optical fibers.

Example 2 As in Example 1, twelve cylindrical rods having a length of 800 mm and a diameter of 30 mm were produced. Of the two rods, the outer circumference of one end was ground 50 mm from the end face.
A trapezoidal female screw was formed by grinding the inner periphery of the other end while a trapezoidal male screw was formed up to the length. The two rods having these threaded portions are subjected to a high-purity treatment with a halogen gas, then put into a vapor deposition furnace, and impregnated and coated with pyrolytic carbon by a CVI treatment. The rods are connected in series and joined, and the length is 1550 mm,
A C / C composite rod having a diameter of 30 mm was obtained.
About the obtained C / C composite rod-shaped body, when the breaking load by the static tensile load was measured in the same manner as in Example 1, the thread was broken, and the breaking load at that time was 167.
00N, and it was confirmed that it had a strength that was even better than that of Example 1.

Further, for the remaining ten rods,
After performing the purification treatment with halogen gas, the screw portion is impregnated and coated with pyrolytic carbon by the CVI treatment in the same manner as described above, and the trapezoidal male screw and the trapezoidal female screw are used in the same manner as in the rod-shaped body of Example 1 to obtain 9 parts. Join the parts, length 7550mm,
30 mmφ diameter C / C composite rod B (3)
Got.

The C / C composite rod B (3)
Is covered with a graphite sheet, and the rod B is placed at the center of a cylindrical carbon mold 1 having an inner diameter of 155 mmφ and a length of 1000 mm, and then a quartz powder 2 (total metal impurities 30 ppm or less, particle size distribution 60 to 280 μm) ,
(Average particle size: 180 μm) while applying vibration, and packed to a height of about 950 mm. The whole carbon mold 1 filled with the quartz powder was heated in a vacuum furnace under the same conditions as in Example 1 to produce a large hollow cylindrical quartz glass body. The obtained quartz glass body did not contain bubbles, had good dimensional accuracy without bending or eccentricity, and was a quartz glass hollow body suitable as a base material for optical fibers. Further, the C / C composite rod-shaped body B (3) from which the graphite sheet was peeled off did not show any deterioration such as deterioration on its surface, indicating that it could be used repeatedly.

Example 3 As in Examples 1 and 2, the length was 800 mm and the diameter was 30 m.
Twelve cylindrical rods of mφ were prepared, and of two rods, the outer periphery of one end was ground from the end face by grinding.
While a trapezoidal male screw was formed up to the length of mm, the inner periphery of the other end was ground to form a trapezoidal female screw. Next, the outer peripheral portion of the female screw portion was cut by a depth of 1 mm and a length of 30 mm. This is for attaching a cylindrical C / C composite reinforcing member for reinforcing around the circumference to the cut portion. The two rods having these threaded portions are subjected to a high-purity treatment with a halogen gas, then put into a vapor deposition furnace, and impregnated and coated with pyrolytic carbon by a CVI treatment. Rods are connected in series and joined to form a 1550 mm long, 30 mm diameter C /
A C composite rod was obtained. The reinforcing member is formed by molding a carbon fiber (Torayca T-300) 12K filament manufactured by Toray Industries, Inc. into a cylindrical shape while impregnating a phenolic resin with a filament winding device, and repeatedly performing pitch impregnation and firing on the molded body several times. After densification, heat treatment was performed at 2000 ° C. This cylinder-shaped product was cut into a width of 20 mm, and a metal jig divided into two was inserted therein. The tensile strength was measured by a method of pulling up and down using a tensile tester. The tensile strength was 300 MPa. The inner and outer diameters and lengths of the reinforcing member were machined so as to match the outer peripheral portion of the female screw portion of the C / C composite rod, and fitted to the outer peripheral portion of the internal thread portion as shown in FIG.
The reinforcing member was subjected to a high-purity treatment with a halogen gas and impregnation / coating with pyrolytic carbon in the same manner as in Example 2. About the obtained C / C composite rod,
When the measurement of the breaking load by the static tensile load was performed in the same manner as in Examples 1 and 2, the thread was broken, and the breaking load at that time was 21,000 N, and the strength was higher than that of Example 2. Was confirmed.

Further, regarding the remaining ten rods,
After high purity treatment with halogen gas, the screw portion is impregnated and coated with pyrolytic carbon by CVI treatment as described above, and a trapezoidal male screw and cylindrical C / C are formed as described above.
Nine places are joined by a trapezoidal female screw to which a composite reinforcing member is attached in the same manner as the rods of Examples 1 and 2 to form a C / C composite rod C (3) having a length of 7550 mm and a diameter of 30 mmφ. Obtained.

The inner wall surface of a cylindrical carbon mold 1 having an inner diameter of 155 mm and a length of 1000 mm is covered with graphite felt, and the C / C composite rod C (3) is arranged at the center of the mold 1 and then quartz. Powder 2 (total metal impurities 30 ppm or less, particle size distribution 60 to 280 μm, average particle size 180 μm) is filled while applying vibration, and a height of about 95
Packed to 0 mm. The entirety of the carbon mold 1 filled with the quartz powder was heated in a vacuum furnace under the same conditions as in Examples 1 and 2, to produce a large quartz glass body having a hollow cylinder shape. The obtained quartz glass body did not contain bubbles, had good dimensional accuracy without bending or eccentricity, and was a quartz glass hollow body suitable as a base material for optical fibers. In addition, the inner wall of the carbon mold 1 from which the graphite felt was peeled off did not show any deterioration such as deterioration on its surface, indicating that the inner wall could be used plural times.

COMPARATIVE EXAMPLE 1 Twelve cylindrical rods having a length of 800 mm and a diameter of 30 mmφ were made of high-purity isotropic high-density graphite (trade name: ISO-630, manufactured by Toyo Carbon Co., Ltd.), and two rods were prepared. Were connected in series with a trapezoidal male screw and a trapezoidal female screw to obtain a high-purity isotropic high-density graphite rod having a length of 1550 mm and a diameter of 30 mmφ. The high-purity isotropic high-density graphite used had a bulk density of 1.82 g / cm ³ and a tensile strength of 53.
It was 9 MPa and the ash content was 10 ppm or less. When the breaking load by static tensile load was measured on the obtained rod-shaped body in the same manner as in Examples 1 to 3, the thread was broken, and the breaking load at that time was 3900N. Further, after performing the purification treatment on the remaining 10 rods, nine places are joined by a trapezoidal male screw and a trapezoidal female screw, and a rod made of high-purity isotropic high-density graphite having a length of 7550 mm and a diameter of 30 mmφ is formed. Body E (3) was obtained.

In the same manner as in Example 1, the high-purity isotropic high-density graphite rod-shaped body E (3) is placed at the center of the cylindrical carbon mold 1, and then the quartz powder 2 is filled into the mold 1. Stuffed. The whole carbon mold 1 filled with the quartz powder 2 was heated in a vacuum furnace under the same conditions as in Examples 1 to 3,
A large quartz glass body having a hollow cylinder shape was manufactured. Since the used rod-shaped body was slightly deformed, an error in dimensional accuracy was found on the inner peripheral side (hollow portion) of the quartz glass body.

Comparative Example 2 As in Examples 1 to 3, a length of 800 mm and a diameter of 30 mm
Twelve φ cylindrical rods were produced. Then two of them
Using one rod, the end of one cylindrical rod 13 is slit 16 and inserted into another cylindrical rod, and a pin insertion hole 14 as shown in FIG. The two rods were fixed to obtain a C / C composite rod having a length of 1550 mm and a diameter of 30 mmφ. When the breaking load of the obtained rod-shaped body was measured by a static tensile load in the same manner as in Examples 1 to 3, the pin was broken, and the breaking load at that time was 9,500 N. Further, after the remaining 10 rods were subjected to a high-purification treatment, 9 places were joined together by pin fixing in the same manner as described above, and a C / C composite rod F (3) having a length of 7550 mm and a diameter of 30 mmφ was used. Got.

As in Example 1 and Comparative Example 1, the C /
After the C composite rod F (3) is placed at the center of the cylindrical carbon mold 1, the quartz powder 2 is filled and the mold 1
Packed in. Carbon mold 1 filled with this quartz powder 2
The whole was heated in a vacuum furnace under the same conditions as in Examples 1 to 3 and Comparative Example 1, to produce a large quartz glass body having a hollow cylinder shape. Since the used rod-shaped body was bent at the pin fixing part, it was difficult to pull it out of the quartz glass body.When the bar was forcibly pulled out by heating and load, the inner peripheral side of the quartz glass body was greatly deformed. Was.

[0034]

According to the production method of the present invention, a large-sized quartz glass body with high purity and high precision can be produced at low cost and with high yield. The obtained quartz glass body is suitably used as a material for a quartz glass jig for manufacturing a semiconductor and also as a material for quartz glass for an optical fiber preform, and its industrial value is high.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view when a heat-resistant mold for carrying out the present invention is filled with silicon dioxide powder.

FIG. 2 is a schematic sectional view of a joint portion of a rod-shaped body used for manufacturing a large quartz glass body of the present invention.

FIG. 3 is a schematic cross-sectional view of a joint portion of a rod-like body having a layer in which a thread is impregnated and / or coated with carbon.

FIG. 4 is a schematic cross-sectional view of a joint portion of a rod-shaped body in which a reinforcing member is formed on the outer periphery of a screw portion.

FIG. 5 is a schematic cross-sectional view of a joint portion of a rod-shaped body fixed in a pin and connected in series.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Heat resistant mold 2 Silicon dioxide powder 3 Rod 4 Heater 5 Inert gas introduction port 6 Exhaust port 7 Rod (Rod with male screw on one end) 8 Rod (Rod with female screw on one end) 9 Male thread portion of rod 7 10 Female thread portion of rod 8 11 Layer impregnated and / or coated with carbon 12 Reinforcing member made of C / C composite 13 Rod (rod with slit on one end side) 14 pin Insertion hole 15 Pin 16 Slit

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Atsuyuki Shimada 88, Kawakubo, Kanaya, Tamura-cho, Koriyama-shi, Fukushima Prefecture Inside the Koriyama Plant, Shin-Etsu Quartz Co., Ltd. Toyo Carbon Co., Ltd. F-term (reference) 4G014 AH08

Claims (6)

[Claims] 1. A method for producing a large quartz glass body in which a heat-resistant mold is filled with silicon dioxide powder and melted and vitrified in a heating furnace, wherein a columnar or cylindrical carbon fiber reinforced carbon composite material member is formed by a screw portion. A method for producing a large quartz glass body, comprising: disposing a rod-shaped body joined in series at the center of the heat-resistant mold. 2. The method for manufacturing a large quartz glass body according to claim 1, wherein the screw portion for joining the members made of carbon fiber reinforced carbon composite material is a trapezoidal screw. 3. The method for producing a large quartz glass body according to claim 1, wherein the thread portion is impregnated with carbon and / or coated. 4. A reinforcing member made of carbon fiber reinforced carbon composite material is provided on the outer periphery of the screw portion.
4. The method for producing a large quartz glass body according to any one of items 3 to 3. 5. A rod-like body having a cylindrical shape having a hollow portion,
The method for producing a large quartz glass body according to any one of claims 1 to 4, wherein gas is discharged from the hollow portion. 6. An intermediate material made of graphite is interposed between the rod and the silicon dioxide powder and / or between the heat-resistant mold and the silicon dioxide powder. 2. The method for producing a large quartz glass body according to 1.