MX2009010663A - Process for the preparation of ceramic glass material in the form of sheets, sheets thus obtained and use thereof. - Google Patents

Abstract

A process allowing to obtain ceramic glass material in the form of sheets of large dimensions usable in constructions for panelling or for flooring is described.

Description

PROCESS FOR THE PREPARATION OF GLASS MATERIAL CERAMIC IN THE FORM OF LEAVES. LEAVES OBTAINED FROM THIS FORM AND USE OF THE SAME Field of the Invention The present invention relates to the field of ceramic materials and manufacturing processes thereof.

Background of the Invention As is known, glass is an amorphous material obtained by the fusion of crystalline compounds, usually oxides, and subsequent cooling of the melt.

However, to obtain ceramic glass materials, appropriate mixtures of oxides are melted, the melt thus obtained is subjected to rapid cooling by means of forming operations (by roller pressing or static, centrifugation, injection, blowing, extrusion, hot-bent) then the semi-finished product is subjected to appropriate thermal cycles in which (homogeneous or heterogeneous) the crystalline nuclei develop and subsequently grow.

The presence of crystalline phases and the particular microstructure determined by the contemporary presence of these with the amorphous matrix, imparts physical-chemical characteristics superior to those of the initial glass in the final material (hardness, brightness, resistance to stress and etching, etc.). ) which becomes particularly useful in several fields and which have nothing in common with the analogous properties of glass.

The processing cycles of the glass and ceramic glass are obviously completely different, also because it is not possible to continuously process the molten oxide mass which, as mentioned above, constitutes the first stage of preparation and is rapidly cooled by means of several operations of shape (roller pressing or static). On the other hand, it is obvious how useful it would be to be able to subject the melt of precursors of ceramic glass materials to the normal manufacturing cycles used for the manufacture of glass because of the simplicity of the process and because this would make it possible to obtain the final material with extreme ease and in formats of any desired dimension.

Brief Description of the Invention The Applicant has now devised a process with which it is possible to process the molten oxide mass for ceramic glass material by implementing the same operations and taking advantage of the same industrial equipment commonly used for the processing and manufacture of glass.

Detailed Description of the Invention The present invention consists of overcoming the aforementioned problems by virtue of a process comprising the fusion of a mixture of appropriate oxides, the processing of the melt according to the normal glass manufacturing processes (rolling, forming, blowing, etc.). .) and the subsequent treatment of the material thus obtained in appropriate crystallization cycles.

According to the invention, the mixture of initial oxides consists essentially of Si02, Al203 and Li20 possibly in the presence of other oxides.

Preferably, according to the invention, the percentages of the three aforementioned components (expressed by weight with respect to the total weight of the final mixture) are: Si02: 50% -80%; Al203: 5% -30%; Li20 3% -20% The other oxides possibly present are chosen from the group consisting of, ZnO, P205, K20, Na20, CaO, MgO, BaO.

More preferably, the aforementioned oxides, if present in the mixture, represent a weight percentage respectively comprising: ZnO: 0.1-3%; P205: 0.1-5%; K20: 1-5%, Na20: 0.1-6%, CaO: 0.1-6%; MgO: 0.1-6%, BaO: 0.1-5%; Zr02: 0.1-4%.

The oxide mixtures as described above have a melting point from 1500 to 1550 ° C and can, therefore, be melted in normal gas furnaces used to melt glass and the melted materials are free of lots of stones and bubbles and with a viscosity to allow the subsequent process of forming them.

The forming process and the subsequent annealing is carried out under normal processing conditions used for the formation of glass.

/ For example, the molten material is laminated by passing it through a roller system that at the same time squeezes the laminate to the required thickness and then feeds it. Subsequently, the continuous sheet formed in this way enters a temperature controlled oven called an annealing furnace which allows to relieve possible mechanical stresses caused to the glass during the roll forming stage. At the exit of the annealing furnace, the edges of the sheet are cut, possibly straightened and cut according to appropriate sizes, the process allows, for example, the continuous manufacture of sheets of large dimensions. Preferably, the dough is processed at a viscosity of about Log? = 4 Normally, the melt during the processing process is subjected to rapid cooling, at a temperature corresponding to \ ogr \ = 13, where the accumulated stresses dissipate in a time of about 1 hour.

Furthermore, in the composition of the mixture, the thermal crystallization cycle is also important for the process according to the invention.

The thermal cycle must be performed at a temperature of 550 ° C to 920 ° C and for times from 2 to 6 hours, the total cycle lasts 12-25 hours.

By varying the times and the temperature within the aforementioned ranges it is also possible to vary the appearance characteristics of each material.

For example, starting at a temperature of 550 ° C and varying it by increasing in steps of 20 ° C, it is possible to obtain a range comprising the blue effect due to the Tyndall phenomenon, from semi-transparent to a perfectly opaque target.

Some examples of preparation of ceramic glass materials according to the invention are shown below.

Example 1 A mixture of oxides having the following composition: Oxides% by weight Si02 78.61 Al203 5.35 ZnO 0.52 Li20 11.23 P2Os 1.95 K20 2.34 It was melted in a gas oven (oxygen-methane) at a temperature of 1450 ° C. After about 36 hours, the molten material appears perfectly refined, and therefore a temperature processing is performed (log? = 4) and formed according to the known technique for processing the glass, in the desired shape and dimensions. In this case, the melt during the pressing process is subjected to a rapid cooling, at a temperature corresponding to logn, = 13, and kept constant so that the accumulated stresses dissipate in a time of about 1 hour.

AND! The crystallization cycle was carried out by keeping the leaf at 820 ° C for 1 hour and then constantly decreasing the temperature to reach room temperature in approximately 12 hours.

The diffraction analysis shows how after crystallization at 820 ° C for 130 minutes the following phases are present: beta-quartz [11-0252] and lithium silicate Li2Si205 [40-0376] (JCPDS numbering (Joint Committee on Powder Diffraction Standards ).

Mechanical characteristics: Microhardness: 740 Hv (load = 100 g) Other features: Resistance to EN 102 Must pass freezing test Chemical resistance EN 106 - EN Must pass 122 test P'o 2 A mixture of oxides that have the following composition Oxides% by weight S Sii0022 74.61 Al203 9.35 ZnO 0.52 Li20 11.23 P205 .95 K2? 00 2.34 It was melted in a gas oven (oxygen-methane) at a temperature of 1450 ° C. After approximately 36 hours, the molten material appears perfectly refined, and therefore the shape and temperature processing (log? = 4) was performed according to the technique, desired shape and dimensions.

In this case, the melt during the pressing process was subjected to rapid cooling, at a temperature corresponding to log? = 13, and kept constant so that the accumulated stresses dissipated in a time of about 1 hour.

The crystallization cycle was carried out by keeping the leaf at 900 ° C for 1 hour and then constantly lowering the temperature to reach room temperature in 12 hours.

The diffraction analysis shows after the crystallization at 900 ° C for 60 minutes the following phases that are present, lithium aluminum silicate [35-0794] and lithium silicate Li2Si205 [40-0376] Mechanical characteristics: Microhardness 832 Hv (load = 100 g) Other features: peep 3 A mixture of oxides having the following composition Oxides% by weight S02 75.60 Al203 8.35 ZnO 0.50 Li20 9.75 K20 2.35 Na20 1.00 CaO 0.50 It was melted in a gas oven (oxygen-methane) at a temperature of 1450 ° C. After approximately 36 hours, the molten material appears perfectly refined, and therefore the shape and temperature processing was performed (log? = 4) according to the technique, desired shape and dimensions.

In this case, the melt during the pressing process was subjected to rapid cooling, at a temperature corresponding to log? = 13, and kept constant so that the accumulated stresses dissipated in a time of about 1 hour.

The crystallization cycle was carried out maintaining the leaf at 820 ° C in approximately 4 hours, keeping it constant for 4 hours, and then lowering it again to reach room temperature in 12 hours.

F The diffraction analysis shows after crystallization at 820 ° C for 4 hours the lithium aluminum silicate [21-0503] and lithium silicate Li2Si205 [40-0376] Mechanical characteristics: Microhardness 830 Hv (load Other features: Similar to that described in the previous examples, similar results have been obtained using the following oxide mixtures: Formulation Formulation Formulation Formulation A B C D Si02 77.61 78.46 75.59 75.13 LÍ20 10.23 7.23 11.24 9.68 AI203 5.35 5.49 5.36 8.31 K20 2.34 2.34 2.34 2.33 P205 2.95 1.95 1.95 1.94 ZnO 1.52 4.52 0.52 0.52 MgO - 1.00 3.00 - BaO - - - 0.93 Zr02 - - 1.14 Proceeding as shown in the examples, sheets of considerable size have been obtained, for example up to 2.00 x 3.00 meters, which by virtue of the exceptional properties shown above can be used in constructions for coating with panels and coatings.

Claims (9)

1. A process for manufacturing ceramic glass material in the form of sheets, wherein: - the oxide mixtures used to make the ceramic glass material melt; - the vitreous mass thus obtained is processed using the operations and equipment commonly used for the processing and manufacture of glass; - the material thus obtained is subjected to a thermal crystallization cycle.

2. A process according to claim 1, wherein the oxides of the ceramic glass material consist of mixtures of oxides comprising: Si02, Al203 and Li20.

3. A process according to claim 2, wherein the mixtures consist of: Si02: 50% -80%; Al203: 5% -30%; LizO 3% -20% possibly in the presence of other oxides.

4. A process according to claim 3, wherein the other oxides are selected from the group consisting of ZnO, P205, K20, Na20, CaO, MgO, BaO.

5. A process according to claim 4, wherein the oxides, if present in the mixture, represent a weight percentage comprised respectively of: ZnO: 0.1-3%; P2Os: 0.1-5%; K20: 1-5%, Na20: 0.1-6%, CaO: 0.1-6%; MgO: 0. 1-6%, BaO: 0.1-5%; Zr02: 0.1-4%.

6. A process according to claim 1-6, wherein the thermal crystallization cycle, which constitutes the last stage of the process before final cooling, is conducted at a temperature from 550 ° C to 920 ° C and for times of 2 to 6 hours, the total cycle lasts 12-25 hours.

7. A process according to claim 6, wherein the crystallization cycle is conducted from 550 ° C and with a temperature variation that increases every 20 ° C.

8. Oxide mixtures for a process according to claims 1-7, which has the following compositions: a) Si02 78.57 Al203 5.35 ZnO 0.52 Li20 11.23 p2o5 1.95 ?2? 2.34 b) Si02 74.47 Al203 9.35 ZnO 0.52 Li20 11.23 p2o5 1.95 K20 2.34 c) Si02 75.50 Al203 8.35 ZnO Li20 P205 K20 Na20 CaO d) SiO AI203 ZnO Li20 P205 K2O e) SiO Al203 ZnO LizO p2o5 MgO f) SÍO; Al203 ZnO Li20 P205 MgO K20 g) s¡o2 AI2O3 ZnO Li20 P205 K20 Beam Zr02

9. Sheets of ceramic glass material that have dimensions up to 2.00 x 3.00 meters.