Melting and clarifying method of medium borosilicate medicinal glass

Abstract

The invention discloses a melting and clarifying method for medium borosilicate medicinal glass, which is carried out in a medium borosilicate medicinal glass tank furnace, and comprises the following steps: arranging 4-8 rows of tin oxide electrodes on the tank wall and / or the tank bottom in a range of 30-60% from the rear wall of the tank furnace, and the distance between two adjacent rows of tin oxide electrodes is 300-600mm; and adding a strontium sulfate clarifying agent into the medium borosilicate medicinal glass batch. The tin oxide electrode is matched with the strontium sulfate clarifying agent, so that the clarifying effect of the medium borosilicate medicinal glass can be optimal; through system application and verification, the number of bubbles of the medium borosilicate medicinal glass can be stably controlled to be (5-12) per 10kg of glass, the high-quality melting and clarification target of the medium borosilicate medicinal glass is effectively achieved, and the problem of melting and clarification of the medium borosilicate medicinal glass is well solved.

Description

technical field [0001] The invention relates to the technical field of glass clarification, in particular to a method for melting and clarification of medium borosilicate medical glass. Background technique [0002] Medium borosilicate pharmaceutical glass packaging is recognized as the most stable quality pharmaceutical packaging. Since 1911, German SCHOTT company began to produce medium borosilicate pharmaceutical glass products. It has a history of more than 100 years. At present, only German SCHOTT, Companies such as NEC Glass and Corning of the United States can mass-produce this type of glass with high quality and large scale. [0003] For the typical chemical composition of borosilicate pharmaceutical glass, please refer to Table 1-1 on page 3 of the main text of "Pharmaceutical Glass". 2 70~75, Al 2 o 3 5~7, B 2 o 3 9.5%~10.3, CaO+BaO 1~3.5 and Na 2 O+K 2 O 7~9, 20℃~300℃ linear thermal expansion coefficient is α=(4.9~5.4)×10 -6 / °C, the glass melting tempe...

AI Technical Summary

Problems solved by technology

With the increase in the use of rare earth cerium oxide, the price of cerium oxide has increased significantly, which has brought greater cost pressure to the application of medium borosilicate pharmaceutical glass; so people began to use sodium chloride clarifying agent commonly used in high borosilicate glass, but chlorine The clarification mechanism of sodium chloride belongs to the high-temperature volatile type, and generally requires a melting temperature greater than 1465°C to function, while the melting time of medium borosilicate pharmaceutical glass in the tank kiln with a melting temperature greater than 1465°C is less than 30 minutes

Because the molybdenum electrode is easily oxidized, if too much oxidant is used in the batch material, the molybdenum electrode will be consumed rapidly; therefore, the medium borosilicate pharmaceutical glass that uses the molybdenum electrode for fluxing cannot use oxidizing clarifiers, such as sulfuric acid Barium, calcium sulfate, cerium oxide, tin oxide, nitrate, etc., so medium borosilicate pharmaceutical glass can only widely use chloride clarifiers, such as sodium chloride, calcium chloride, etc., but this will induce the surface of the glass tube Gas line appearance quality defects

[0006] In order to discharge air bubbles and homogenize the glass liquid, in the 1990s, the borosilicate pharmaceutical glass industry began to learn from and apply the platinum channel scheme used in the production of TFT-LCD substrate glass and optical glass, relying on the independent electric heating and upward tilt of the platinum channel The pipe structure further promotes the bubbles in the medium borosilicate medical glass melt to float and overflow on the upward inclined pipe, which can make the glass liquid achieve better clarification effect; but the platinum channel uses the alloy material formed by platinum and rhodium, which is very expensive

The weight of a platinum channel is about 30 kg to 70 kg. According to the current market price, the investment is as high as 20 million to 40 million RMB, or even more. The investment of a platinum channel is almost equivalent to that of a kiln, which seriously affects the technology. application and promotion

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