Glass manufacturing – Processes – With shaping of particulate material and subsequent fusing...
Patent
1987-10-27
1989-05-09
Lindsay, Robert L.
Glass manufacturing
Processes
With shaping of particulate material and subsequent fusing...
65 33, 65 66, 65134, 65136, 65DIG8, C03C 1000, C03B 1902
Patent
active
048285951
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for the production of a glass by a vacuum melting method using silica as a raw material.
BACKGROUND TECHNOLOGY
In general, glasses as industrial products are produced by heating raw material powders prepared in a prescribed mixing proportion in a crucible or a tank furnace at temperatures higher than the liquids temperature to form a homogeneous mixture in the melted state and then cooling the mixture. In the production of a glass, the glass is usually made transparent, for example, by a means in which the bubbles in the melt formed from the adsorbed gas in the raw materials and the gas generated during the reaction are removed by elevating the temperature of the melt to reduce its viscosity sufficiently thereby allowing the gases and bubbles to float to its surface.
However, in the case of producing a glass from silica as the raw material, because of its high melting point, the temperature cannot be elevated to an extent effective for removing bubbles because of restrictions such as the high viscosity of the melt, refractoriness required for the crucible or furnace and for other reasons. If the temperature is elevated excessively, gases are generated by the volatilization of the raw material per se and the reaction between the raw material and the crucible forms all the more bubbles. Therefore, the above-described method cannot be employed. For the reasons set forth above, a method for the production of a transparent quartz glass using silica as the raw material is restricted to any one of the following methods:
(1) A method in which a silica powder is gradually fed into an argon-oxygen plasma flame or an oxygen-hydrogen flame and melted for glass formation and the resulting melt is deposited onto a stand. The generated gases are dissipated from the surface (Verneuil method);
(2) A method in which a porous body composed of silica fine particles is prepared and melted from one end thereof in the band-like state for glass formation. The generated gases leave from the unmelted porous body (zone melting method); and
(3) A method in which rock crystal powders prepared to have particle diameter of about 100 .mu.m are placed in a crucible and melted in a vacuum furnace for glass formation. The generated gases are removed by force (vacuum melting method).
However, with respect to the method (1) and method (2), it is well known that an extremely long period of time is required for producing one glass block and productivity is poor, and especially in the case of the Verneuil method, the yield is as low as 30% to 40%. Further, in the case that the argon-oxygen plasma flame is employed as a heat source, though a glass having a small number of residual OH groups and a relatively small number of bubbles can be obtained, the energy cost is high, whereas in the case that the oxygen-hydrogen flame which is low in the energy cost is employed, the problem is that the product has a large number of residual-OH groups. Still further, since the shape of ingots which can be produced is restricted to cylindrical and slender shapes, there is a disadvantage to the subsequent processings.
According to the vacuum melting method (3), though a relatively large-sized ingot having a small number of residual OH groups and a high viscosity at high temperatures can be obtained, since the raw material powder filled in a vessel such as a crucible is melted for glass formation, not only is there a difficulty in degassing but also a reaction gas caused by the contact with the vessel is generated, and the resulting glass has a relatively large number of bubbles. Therefore, glass having a high quality cannot be obtained. Further, since the rock crystal powders are used, bubbles tend to be generated due to low purity of the raw material per se. Also, there is a concern in the raw material supply due to exhaustion of the resources.
Under such a background, the present inventors have developed a process by which a transparent or functional, high-quality glass can be readily produced at a
REFERENCES:
patent: 805139 (1905-11-01), Hitchcock
patent: 1549597 (1925-08-01), Miller
patent: 1645080 (1927-10-01), Watson
patent: 2726487 (1955-12-01), Cummins et al.
patent: 3883337 (1975-05-01), Helgesson et al.
patent: 3927697 (1975-12-01), Baumler et al.
patent: 4013436 (1977-03-01), Van der Steen
patent: 4042361 (1977-08-01), Bihuniak et al.
patent: 4093771 (1978-06-01), Goldstein
patent: 4146379 (1979-03-01), Copley et al.
patent: 4225330 (1980-09-01), Kakuzen et al.
patent: 4414282 (1983-11-01), McCollister et al.
patent: 4416680 (1983-11-01), Bruning et al.
patent: 4429009 (1984-01-01), Pastor et al.
patent: 4465656 (1984-08-01), Pastor et al.
Vacuum, The International Journal and Abstracting Service for Vacuum Science and Technology, vol. 13, Pergamon Press, 1963, pp. ii, 47-52.
Boganov et al, "Threshold of Light Breakdown in Hydroxyl-Free High-Purity Vitreous Silica", Soviet Journal of Glass Physics and Chemistry, vol. 6, No. 5, Sep./Oct. 1980, pp. 383-390 (English language translation by Plenum Publishing Corporation).
Rabinovich et al, "Preparation of High-Silica Glasses from Colloidal Gels: I, Preparation for Sintering and Properties of Sintered Glasses", Journal of the American Ceramic Society, vol. 66, No. 10, Oct. 1983, pp. 683-688.
Kingery et al, Introduction to Ceramics, Second Edition, John Wiley & Sons, Inc., 1976, pp. 274-275.
Imayoshi Terukazu
Kikuchi Hitoshi
Morishita Hiroshi
Nakamura Akihiro
Japan Oxygen Co., Ltd.
Lindsay Robert L.
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