DE1496396C - Process for melting glass containing volatile components - Google Patents

Description

The invention relates to a method for melting glass that contains volatile constituents contains. In particular, it relates to a process for treating raw glass at the time in which poisonous and volatile substances such as selenium, sulfur, arsenic, antimony and tellurium in the glass melting furnace can be entered as additions.

Numerous types of glass have become known so far, the selenium, sulfur, arsenic, antimony and / or Contain tellurium. In the manufacture of such additives alone or in combination Glass, these additives are added to the glass melting furnace as an element, as a chemical compound or as this Raw material containing constituents is added and melted in the furnace, as is the case with melting other raw glass materials is the case in a conventional melting furnace. However, since the boiling temperatures of selenium, sulfur, arsenic, antimony and tellurium are low, most of it evaporates, and consequently, only an extremely small proportion of the effective additives actually remain in the glass.

Selenium is an effective additive for optical filter glass, glass for absorbing rays Wavelengths and gray glass known. Such glasses are then described in the examples. For example, it is necessary to use selenium in amounts of 0.1 to 0.2 percent by weight, based on the molten glass to be fed to the melting furnace to produce glass with a selenium content of 0.001 percent by weight to manufacture.

The invention is therefore based on the object to create conditions that when melting Glass types with a content of volatile elements such as arsenic, antimony, sulfur, selenium and / or tellurium, these remain in the glass in as high an effective proportion as possible. This goal is achieved according to the Invention achieved by pulverized broken glass with arsenic, antimony, sulfur, selenium or Tellurium in a ratio of 0.05 to 30 percent by weight, based on the amount of broken glass, mixed, the mixture is pressed and the compact is sintered at a temperature between 500 and 1200 ° C and that Enter the sintered product together with the desired material of the raw glass in a melting furnace.

A method for sintering glass batches is already known (German patent specification 884 400), in the case of arsenic or cerium oxide or calcium sulphate the components of the batch as correction surcharges be added to the melting process and the subsequent refining of the glass bath to favorable influence. In addition to arsenic, there are compounds that have the problem of volatility does not occur as with the elements in question according to the invention, not even with the Elements of said compounds.

Furthermore, a method for the production of a mixture for melting glass from the German Patent specification 1,053,746 is known. In this> process, the cullet makes the one with respect to the normal Raw batch one or more components are missing, an essential component of the batch out. The problem arises that the broken glass, if it is a larger batch constituent forms, separates from the constituents of the raw mixture, whereby an inhomogeneous one during melting Glass is created. To solve this problem, according to f { the German patent 1 053 746 describes a method according to which one refining agents or other Compensating substances directly with the cullet and not as part of the raw mixture, d. h., the unmelted batch ingredients. The missing ingredients are in aqueous solution applied to the broken glass and the greater part of the water before introducing the broken glass into the mixture evaporates.

The person skilled in the art does not receive any suggestion for the present invention from these literature references underlying problem to be solved in the manner described and claimed.

Said prior art can not of the inventive method are taken from the specific conditions, after which once pressed prior to sintering the mixture and sintering the compact at temperatures between 500 and 1200 ⁰ C.

It is advantageous to press the mixture under a pressure of 60 to 500 kg / cm ^2. If necessary, a suitable binder can be added.

Arsenic, antimony, sulfur, selenium and tellurium can be added in elemental form as a chemical compound or be used in the form of a corresponding glass.

In order to increase the amount of additives that remain in the molten glass, it is desirable that the viscosity of the broken glass near the boiling point of the additives is more than ΙΟ ⁷ Ρ.

For example, if selenium is used with a boiling point of 688 ⁰ C, the viscosity of the glass breakage is at 600 to 700 ° C, preferably 10 ¹⁰ to 10 ⁷ P.
The following example illustrates the invention.

example

A. 100 parts of powdered broken glass are mixed thoroughly with 0.4 parts by weight of powdered metallic selenium and sintered at 965 ° C.
B. A mixture similar to the above is pressed at a pressure of 500 kg / cm ² into a rod with a diameter of 26 mm and a length of 30 mm and sintered at 950 ° C.

The remaining amount (%) of selenium in the sintered Materials A and B was A = 50%, B = 70%.

Further, the sintered bodies A and B with raw glass and broken glass were described below mixed and melted. The remaining amount of selenium (in percent by weight) in the glass was

Sintered body

6.0 parts
4.3 parts

Raw glass

60 parts
60 parts

Broken glass

IO

34 pieces
35.7 parts

Remaining Percentage Se, Percentage Se Amount in the glass, based on the In the glas related to Se im all in all (%) Sintered body used Se 0.0018 A. 15.0 7.5 0.0020 B. 18.1 11.6

crowd additions and remaining amount (%) As Sb Te (Weight percent) 88 92 75 of additives 88 92 75 per 100 parts Se S. 88 92 75 Broken glass 70 65 86 91 73 0.01 70 65 84 90 70 0.05 70 65 0.5 68 65 1.0 65 63 5.0

crowd additions and remaining amount (%) As Sb Te (Weight percent) 81 87 65 of additives 75 86 56 per 100 parts Se S. 70 85 52 Broken glass 60 59 60 75 45 10.0 50 49 20.0 45 45 30.0 40 38 40.0

On the other hand, if pressing is performed before sintering, the relationship between Compression pressure and remaining amount of additives in the sintered material:

A comparison with the usual method shows that the remaining selenium content (%) with respect to the total charge weight with the same amount of selenium used according to the usual method 0.15% and the major portion evaporates, while according to the method of the present invention 5 to 10% selenium remains in the glass.

The test results with regard to the mixing ratio of raw additives (Se and S were in elemental form, As, Sb and Te used as oxides), pulverized broken glass and remaining The amount of additives in the sintered body is as follows:

The mixture was pressed at a pressure of 400 kg / cm ² and then sintered at 700 to 1000 ⁰ C.

Remaining portion (%) Se S. in the sintered material Sb Te Press pressure of additives 50 48 As 58 55 (kg / cm ² ) 60 62 57 81 67 0 63 64 63 85 71 30th 65 63 79 90 73 60 67 64 85 91 73 100 68 64 87 91 74 200 69 65 87 92 75 300 70 68 89 93 76 400 70 68 90 93 77 500 70 68 90 93 77 600 90 700

Furthermore, there is the following relationship between the sintering temperature and the remaining amount of additives in the sintered material:

Sintering temperature Se Remaining portion (%) in sintered material Sb Te 40 Γ C) 18th of additives As 35 25th 500 20th 40 • 63 42 700 25th 55 80 60 45 800 70 78 85 77 900 65 80 89 80 1000 64 85 75 70 1100 30th 70 65 40 50 1200 60 S. 30th 40 45 65 50 35 30th

Claims (3)

Patent claims: 1. A method for melting glass which contains volatile components, characterized in that pulverized broken glass with arsenic, antimony, sulfur, selenium and / or tellurium in a ratio of 0.05 to 30 percent by weight, based on the amount of broken glass, mixed, the mixture is pressed and the compact is sintered at a temperature between 500 and 1200 ⁰ C and the sintered product is introduced into a melting furnace together with the desired material of the raw glass. 2. The method according to claim 1, characterized in that the mixture is pressed ^{under a pressure of 60 to 500 kg / cm 2.} 3. The method according to claims 1 and 2, characterized in that said elements be added as such, as compounds or in the form of a corresponding glass.