JPS61163132A - Preparation of quartz glass tube - Google Patents

Abstract

PURPOSE:To prepare uniformly died quartz glass tubes having high purity and high precision with good productivity and high yield by the sol-gel method by performing drying of tubular gel while revolving the tubular gel around an axis of the tube. CONSTITUTION:In the prepn. of quartz glass tube by the sol-gel method using alkyl silicate and fine powdery silica as main starting material, quartz glass tubes having high level of quality are obtd. inexpensively by performing drying while revolving tubular gel 1 around a tube axis. An example for the drying vessel 3 (a closed vessel having perforations provided to the top surface of the vessel with a specified opening degree) is shown; 2 are revolvable rolls.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for molding a quartz glass tube using a sol-gel method.

[Conventional technology]

A method for producing quartz glass using a sol-gel method using alkyl silicate and finely powdered silica as main raw materials has attracted much attention because high-quality quartz glass can be produced at low cost. In addition, a silica sol made mainly of alkyl silicate and finely powdered silica is placed in a cylindrical container, gelled while rotating around the tube axis, and then evaporated to dryness to form a dry gel.The resulting tubular gel is sintered. A method for producing a quartz glass tube in which vitrification is performed is very important as a method for producing high-quality quartz glass tubes at low cost.

In the conventional method for manufacturing quartz glass tubes using the sol-gel method, the gel is dried by placing the tubular gel in a drying container and leaving it at a predetermined temperature.

[Problem that the invention seeks to solve]

However, in the above-mentioned conventional technology, the part of the tubular gel that is in contact with the drying container during gel drying dries more slowly than other parts, resulting in uneven drying and the tubular gel cracking during drying. It may warp. Furthermore, due to uneven vapor pressure of water or alcohol in the drying container, the tubular gel may dry unevenly, and the tubular gel may crack or warp during drying. In addition, when drying a tubular gel with its tube axis horizontal, the water alcohol contained in the gel accumulates on the inner periphery of the tubular gel, making the inner periphery dry unevenly and causing the tubular gel to dry during drying. It may crack or warp. If the drying rate is reduced by reducing the opening ratio of the drying container to avoid such non-uniform drying, it will take a long time to dry, which will significantly impair mass production, making it impractical. Furthermore, in the early stages of drying, the gel is still soft and deforms due to gravity. Therefore, unless the tubular gel is dried with the tube axis vertical,
The roundness of the resulting tube becomes poor. This problem does not occur if the tubular gel is dried with its axis vertical, but long tubular gels cannot be made because they collapse under their own weight. The present invention aims to solve these problems all at once.The purpose of the present invention is to dry the tubular gel uniformly and quickly without deformation, with a high yield, and to produce high-quality quartz. An object of the present invention is to provide a method for manufacturing a quartz glass tube for obtaining glass tubes with good mass productivity.

[Means for Solving the Problems] The method for manufacturing a quartz glass tube of the present invention is characterized in that, in the method for manufacturing a quartz glass tube by the sol-gel method, drying is performed while rotating the tubular gel around the tube axis. shall be.

[Effect]

By drying the tubular gel while rotating it around the tube axis, the outer periphery of the tubular gel comes into even contact with the drying container, which eliminates uneven drying and prevents the tubular gel from cracking or warping during drying. No more stuffing away. Also,
Even if there is unevenness in the vapor pressure of water or alcohol in the drying container, it can be ignored, and unevenness in drying is eliminated.
The tubular gel no longer cracks or warps during drying. In addition, even if the water or alcohol contained in the gel accumulates on the inner periphery of the tubular gel, the inner periphery is evenly wetted by rotation, which eliminates uneven drying of the inner periphery and prevents the tubular gel from cracking during drying. No more bunching up or warping. As described above, according to the present invention, non-uniform drying is eliminated, so even if the drying rate is increased, the tubular gel will not crack or warp during drying.

Furthermore, since gravity is applied evenly in the radial direction of the tubular gel, the roundness of the resulting tube will not deteriorate. As described above, according to the present invention, a tubular gel can be dried quickly, uniformly, and with a high yield without being deformed.

[Example-1] Commercially available ethyl silicate (51(oc2Hs)4) 90
0 d and 0.02 N hydrochloric acid 365- were mixed, vigorously stirred to perform hydrolysis, and further fine powdered silica 297 f and water 565- A high silica sol was obtained. In addition, even when the above raw materials are mixed at the same time and the same dispersion treatment is performed,
A similar silica sol was prepared. This sol contains 0. I
After adding N ammonia water and adjusting the pH value to 5, it was filtered, and the 1,400-meter solution was put into a 5 crsφ x 1 m polyvinyl chloride pipe, plugged at both ends of the pipe, and heated at 1,100 orp around the pipe axis. Rotate for hours to gel. At the point when contraction begins after gelation, the tubular gel is
Transfer to the drying container shown in the figure, and set the opening ratio of the top surface of the drying container to 15.
% and rotated at the speed shown in Table 1 at 60°C.
After drying it for 2 weeks, it became 55cr11φ×70cWI.
A dry gel was obtained. Note that 100 samples of each sample were prepared under the same conditions.

From Table 1, it can be seen that the sample dried while rotating had a higher yield than the sample dried without rotating.

It can be seen that both the anti-shaft and roundness are clearly improved.

Even though the rotation speed is relatively slow as CLOlrpm,
It can be seen that even a relatively high rotation speed of 1100 rpm is sufficiently effective. When the obtained dried gel was sintered according to a predetermined program, a quartz glass tube of 2.5 cn1φ x 50 mm was obtained with a yield of 100%.

[Example-2] A silica sol was prepared and gelated in the same manner as in Example-1 to create a tubular gel, which was dried at 60°C under the conditions shown in Table 2. 70 m of dry gel was obtained. Note that 100 samples of each sample were prepared under the same conditions.

From Table 2, it can be seen that the yield of the samples dried while rotating was clearly improved compared to the samples dried without rotating. Moreover, the faster the drying speed, the
It can be seen that there is a significant improvement. Therefore, it can be seen that if drying is performed while rotating, the period required for drying can be significantly shortened. When the obtained dried gel was sintered according to a predetermined program, a quartz glass tube of λ53φ×5000 was obtained with a yield of 100%.

Note that in this example, a tubular gel was created by gelling a cylindrical container while rotating it around the tube axis, but the present invention is also applicable to tubular gels created by any other method. be able to.

[Effect]

As described above, according to the present invention, since the tubular gel is dried while being rotated around the tube axis, the drying becomes uniform, the yield 9 is improved, and warpage is reduced. Also, since gravity is applied evenly in the radial direction, roundness is improved. Furthermore, since the drying speed can be increased, the drying period can be significantly shortened, and mass productivity can be significantly improved.

Therefore, not only in fields where quartz glass tubes have been used up until now, but also in terms of quality, high-purity, high-precision quartz glass tubes can be manufactured easily and domestically, making them suitable for semiconductor applications. We believe that it can be widely applied to core tubes for diffusion furnaces, jacket tubes for optical fibers, etc.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a drying container showing one embodiment of the present invention. 1... Tubular gel 2... Roller 5 that rotates in conjunction with...
・Airtight container (however, there are holes on the top surface to achieve the specified opening ratio)

Claims (1)

[Claims] A method for producing a quartz glass tube by a sol-gel method using an alkyl silicate and finely powdered silica as main raw materials, the method comprising drying the tubular gel while rotating it around the tube axis.