CS258184B1 - Charge composition for selenium rosaline glass - Google Patents

Abstract

The solution aims to slow down the reaction between iron Fe and selenium Se in selenium rosalin glass during heat treatment of semi-finished products or products made from it and to prevent the formation of an undesirable brown shade, especially in products polished by heat in an electric furnace. This is achieved by choosing a suitable composition of the charge, which contains in a mass concentration of 68 to 73% silicon dioxide SiC>2, 16 to 22% sodium oxide Na20 and potassium oxide K2O, 6 to 9% calcium oxide CaO or calcium oxide CaO and magnesium oxide MgO, 0.1 to 0.3% antimony oxide Sb2Oj, 0.07 to 0.2% selenium Se, while the mass content of fluorides F^- is 0.8 to 1.5%.

Description

The invention relates to a composition of a charge for selenium rosaline glass, intended in particular for the production of thermally polished beads.

Selenium rosalin glasses are known with a batch composition in mass concentration according to Table 1.

.Table 1

1. 2. silicon dioxide ^yes0 2 71.16 % 74.15 % sodium oxide ^At 2° 6.64 « 5.00 « potassium oxide ^To 2° 14.12 « 15.28 % calcium oxide CaO 2.74 % 5.35 % magnesium oxide MgO 1.01 % boron oxide BaO 1.82 % antimony trioxide _{Sb2O3 ​} 0.14 % 0.15 % selenium with 0.07 up to 0.12 * 0.06 up to 0.11% fluorides F ¹ " 1.28 % 1.0 ' and

Melting takes place at temperatures of 1,440 °C to 1,460 °C in a neutral to slightly oxidizing environment. The pink shade of selenium rosalin glass is due to the ability of selenium atoms SE to form an atomic solution, pyrosol, in the glass. However, the decisive factor influencing the pink color of glass is not only the presence of elemental selenium Se. The color is also affected by impurities present in the starting materials, the method of heat treatment of already shaped and ground glass products and the composition of the batch, especially the mutual ratio of sodium oxide Na ₂ 0 and potassium oxide K ₂ 0. With a predominance of potassium oxide KjO, more violet shades are obtained, with a predominance of sodium oxide Na ₂ O, undesirable yellowish shades arise. Of the impurities present in the starting materials, the iron content Fe mainly influences the resulting color. In already melted rosalin glass, its mass content, calculated as iron oxide Fe ₂ Oj, can be at most 0.03%. Thermal polishing is carried out at temperatures around 750 °C in polishing furnaces.

The colour of polished products does not change up to a temperature of 480 °C, in the temperature range of 480 to '600 °C they turn brown in direct dependence on the time during which they are exposed to the mentioned temperatures. During further heating and polishing at a temperature of 750 °C and further cooling down to a temperature of 600 °C, the polished products have a pink colour. The course of further cooling is decisive for their final colour. During polishing in an electric continuous furnace, cooling takes place only slowly and products made of selenium rosalin glass melted from a charge of known composition lose their characteristic pink shade and acquire a brown colour. If the products are cooled rapidly from a temperature of 600 °C, they remain pink. If the products are cooled rapidly from a temperature of 600 °C, they remain pink.

Until now, rapid cooling was achieved in a hazelnut polishing furnace. The operator had to manually move the hazelnuts with the stored products to the individual temperature zones of the furnace, which is a very physically demanding job, carried out in a difficult working environment. In addition, the quality of the products depends on the individual skills and experience of the worker. The shift output is low.

These disadvantages are eliminated by selenium rosalin glass, intended for thermal polishing of products made from it in an electric continuous furnace, with a charge composition according to the invention, the essence of which is that the charge contains the following components in mass concentration:

silicon dioxide SiO ₂ 68 to 73%, sodium oxide Na.O and potassium oxide K ₂ O 16 to 22%, calcium oxide CaO or calcium oxide CaO and magnesium oxide MgO 6 to 9%, antimony trioxide Sb ₂ O ₃ 0.1 to 0.3 0, selenium Se 0.05 to 0.2%, while the mass content of fluorides F ¹ " is 0.8 to 1.5% of the sum of the masses of the other components of the charge.

It is preferred that the charge contains neodymium oxide Nd ₂ O ₃ in a mass concentration of 0.03 to 0.15%. It is further preferred that the charge contains aluminum oxide Al ₂ O ₃ in a mass concentration of

0.2 to 2.0%. It is also preferred that the alkaline raw material contains no more than 0.05% by weight of SO ₄ disulfates.

The composition of the charge according to the invention has the following advantages. The color reaction between iron Fe and selenium Se is so inhibited, especially due to the increase in the content of calcium oxide CaO in the charge, that even when the thermally polished products made of glass melted from this charge are slowly cooled according to the temperature curve of the relevant electric continuous furnace, their browning does not occur. Therefore, thermal polishing can be carried out in an electric continuous furnace. which brings technological advantages, eliminates physical strain for the operator and the influence of the operator on the quality of the products. These have the desired pink color.

Examples of embodiments are described below, without limiting the scope of the invention. Table 2 shows the weight composition of the charge according to the invention in percent corresponding to the examples.

Table 2

1 2 3 4 5 silicon dioxide SiO ₂ 72.30 72.20 73.00 71.84 72.34 sodium oxide Na ₂ O 8.18 8.18 8.17 8.10 8.17 potassium oxide K ₂ 0 11.60 11.60 11.69 11.59 11.69 calcium oxide CaO 7.70 7.70 4.08 7.66 5.77 magnesium oxide Mgo - - 2.87 - 0.82 , aluminum oxide A1 ₂ O ₃ - - - 0.52 0.90 antimony trioxide Sb ₂ O ₃ 0.14 0.14 0.14 0.14 0.14 neodymium oxide Nd ₂ O ₃ ' - 0.10 - 0.10 0.12 selenium Se 0.08 0.08 0.05 0.05 0.05 where the mass content of fluorides F ^1- is 1.20 1.20 1.10 1.20 1.10 sum other components bets

Example 1

Selenium rosalin glass was prepared by melting a charge with a chemical composition according to column 1 of table 2. For the introduction of potassium oxide K,0, the alkaline raw material potash 2K ₂ CO ₃ anhydrous was used, which contained 0.05% of sulfates SO ₄ . The charge was melted in neutral to weakly oxidizing conditions at a temperature of 1,440 to 1,460 °C. Rods with a diameter of 35 mm were mechanically pulled from the glass, shaped from the rods and then ground into beads. These were polished in an electric continuous polishing furnace. The polished beads had the desired pink color.

Example 2

Selenium rosaline glass was prepared by melting a charge with a chemical composition according to column 2 of table 2. For the introduction of potassium oxide _K2O , the alkaline raw material potash _K2CO3 anhydrous was used, as in example 1. The conditions for melting, manufacturing and processing of the products were the same as in example 1. The polished beads had the _desired pink color.

Example 3

Selenium rosaline glass was prepared by melting a charge with a chemical composition according to column 3 of table 2. Ground dolomite CaMg(CO ₃ > ₂ was used to introduce calcium oxide CaO and magnesium oxide MgO. The iron content Fe was 0.03% by weight in the glass. The conditions for melting, manufacturing and processing the products were the same as in example 1. The polished products had the desired pink color.

Example 4

Selenium rosaline glass was prepared by melting a charge with a chemical composition according to column 4 of table 2. The charge contained 40% by weight of shards of the same composition. Cryolite Na^AlFg was used to introduce aluminum oxide AljOj ^and F ^3- hylo. The conditions of melting, manufacturing and processing of the products were the same as in example 1. The polished beads had the desired pink color.

Attached

Selenium resaline glass was prepared by melting a batch with the chemical composition according to column 5 of table 2. An oxidative melting method was chosen, which ensured an increased addition of potassium nitrate KNO ₃ to the batch. The rod drawing, shaping and machining of the pieces were the same as in example 1. The polished beads had the desired pink color.

Claims (4)

1. Composition for the charge resalinové Se glass, designed in particular for producing heat-polished glass beads, characterized in that it comprises, in a concentration by weight from 68 to 73% of silica SiO, 16-22% sodium oxide Na ₂ 0 and potassium oxide K ₂ 0, 6 to 9% CaO or CaO and MgO, 0.1 to 0.3% antimony trioxide Sb ₂ O ₃ , 0.05 to 1.2% selenium Se, the F ³ fluoride content by weight being 0.8 to 1.5% of the sum of the weights of the other batch components. Second batch composition according to claim 1, characterized in that it comprises neodymium oxide NG ₂ O ₃ in a concentration of from 0.03 to 0.15%. A charge composition according to claim 1 or 2, characterized in that it contains alumina Al ₂ O ₃ in a concentration by weight of 0.2 to 2.0%. 4. The charge composition according to claim 1 or 2 or 3, characterized in that the alkaline raw material 2 contains not more than 0.05% by weight of sulphate SO4 Severography, n. P., MOST