Process for the preparation of ceramic glass material in the form of sheets, sheets thus obtained and use thereof
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.
1. A process suitable for manufacturing ceramic glass material in the form of sheets, the process comprising:
melting an oxide mixture used for manufacturing ceramic glass material to form a vitreous mass;
refining the vitreous mass thus obtained to form a molten glass material;
passing the molten glass material through a roller system to form a continuous sheet, wherein the sheet has a dimension of about 2×3 meters;
annealing the continuous sheet; and
subjecting the continuous sheet to a thermal crystallization cycle after said annealing, wherein said oxide mixture comprises: SiO 2 : 50%-80%; Al 2 O 3 : 5%-30%; and Li 2 O: about 7% to about 11%, wherein the ceramic glass material consists essentially of one or more of lithium phyllodisilicate and β-spodumene phase, and wherein the thermal crystallization cycle comprises a last stage of the process before final cooling and is conducted at a temperature from 550° C. to 920° C. for 2 to 6 hours, having a total cycle lasting for 12-25 hours.
2. A process according to claim 1 , wherein the oxide mixture further comprises other oxides chosen from the group consisting of ZnO, P 2 O 5 , K 2 O, Na 2 O, CaO, MgO, BaO, and ZrO 2 .
3. A process according to claim 2 , wherein said other oxides, if present in the mixture, represent a percentage by weight comprised between respectively: ZnO: 0.1-3%; P 2 O 5 : 0.1-5%; K 2 O: 1-5%; Na 2 O: 0.1-6%; CaO: 0.1-6%; MgO: 0.1-6%; BaO: 0.1-5%; and ZrO 2 : 0.1-4%.
4. A process according to claim 1 , wherein the thermal crystallization cycle is conducted beginning from 550° C. and varying the temperature in 20° increases.
5. The process of claim 1 wherein the oxide mixture comprises one of the following compositions represented as a percentage by weight:
a) SiO 2
78.57
Al 2 O 3
5.35
ZnO
0.52
Li 2 O
11.23
P 2 O 5
1.95
K 2 O
2.34;
b) SiO 2
74.47
Al 2 O 3
9.35
ZnO
0.52
Li 2 O
11.23
P 2 O 5
1.95
K 2 O
2.34;
c) SiO 2
75.50
Al 2 O 3
8.35
ZnO
0.50
Li 2 O
9.75
P 2 O 5
1.95
K 2 O
2.35
Na 2 O
1.00
CaO
0.50;
d) SiO 2
77.51
Al 2 O 3
5.35
ZnO
1.52
Li 2 O
10.23
P 2 O 5
2.95
K 2 O
2.34;
e) SiO 2
78.46
Al 2 O 3
5.35
ZnO
4.52
Li 2 O
7.23
P 2 O 5
1.95
MgO
1.00;
f) SiO 2
78.59
Al 2 O 3
5.36
ZnO
0.52
Li 2 O
11.24
P 2 O 5
1.95
MgO
3.00
K 2 O
2.34; or
g) SiO 2
75.13
Al 2 O 3
8.31
ZnO
0.52
Li 2 O
9.68
P 2 O 5
1.94
K 2 O
2.33
BaO
0.93
ZrO 2
0.93.
6. The process according to claim 1 , wherein the oxide mixture comprises a melting point of 1500° C. to 1550° C.
7. The process according to claim 1 , wherein said annealing is carried out in a controlled temperature oven to relieve mechanical stresses caused to the glass during said passing the molten glass material through a roller system.
8. The process according to claim 7 , wherein said annealing is carried out for approximately 1 hour.