Glass ceramic article and method and device for ceramizing glass

Patent metadata

Field	Value
Publication number	US-9302931-B2
Application number	US-201013262284-A
Country	US
Kind code	B2
Filing date	Mar 20, 2010
Priority date	Mar 31, 2009
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

The invention relates to a method and to a device for ceramizing green glass in a continuous furnace, with the ceramization being carried out directly on rollers.

First claim

The invention claimed is:

1. A method for ceramizing green glass, in particular in the form of a continuous green glass ribbon or individual green glass plates, the method comprising:
conveying the green glass directly on rollers at least during a volume crystallization,
wherein the entire ceramization process of at least one region of the green glass lasts between 0.5 and 4 hours, the at least one region being exposed to a maximum temperature between 750 and 1250° C. for 5 to 60 minutes during the volume crystallization,
carrying out the volume crystallization in a temperature range between 750 and 1250° C., the temperatures of the upper and lower faces of the at least one ceramizing region of the green glass being continuously measured and the heating being controlled using this information based on target values by a measuring and control apparatus, and
moving the at least one region forward on rollers during the volume crystallization at an advancing rate ranging between 0.2 and 10 m/min.,
wherein the viscosity of the at least one region of the green glass during the volume crystallization ranges, at least intermittently, between 10 7 and 10 11 dPa·s by adjusting the advancing rate and the temperature and
wherein the temperature and the advancing rate are controlled so that the following applies with respect to the distance x Roller of the roller axes:

x Roller 5 ≦360*(R a *t Pane 2 )/(ρ*g)*v*η, where R a is the maximum glass deflection, t Pane is the glass thickness, ρ is the glass density, g is the acceleration due to gravity, v is the advancing rate and η is the minimum viscosity of the glass.

2. The method according to claim 1 , wherein the green glass is conveyed and/or supported on rollers disposed at a distance from one another so that, at the prevailing parameters consisting of the temperature and advancing rate, a waviness of the ceramized green glass, measured between wave valley and wave peak, of less than 100 μm is generated.

3. A method according to claim 1 the green glass that is being ceramized has a composition from the following composition range:

60-73.0
wt. %
SiO 2 ,

15-25.0
wt. %
Al 2 O 3 ,

2.0-5.0
wt. %
Li 2 O,

0-5.0
wt. %
CaO + SrO + BaO,

0-5.0
wt. %
TiO 2 ,

0-5.0
wt. %
ZrO 2 ,

0-4.0
wt. %
ZnO

0-3.0
wt. %
Sb 2 O 3 ,

0-3.0
wt. %
MgO,

0-3.0
wt. %
SnO 2

0-2.0
wt. %
P 2 O 5 ,

0-1.5
wt. %
As 2 O 3 ,

0-1.2
wt. %
Na 2 O + K 2 O, with the respective

contents preferably being within

the ranges provided below,

0-1.0
wt. %
Na 2 O,

0-0.5
wt. %
K 2 O.

4. A method according to claim 1 the temperature is controlled so that it does not deviate in the furnace by more than −5° C. to +5° C. from a predefined target temperature T x over the width of the green glass T y to be ceramized, or a temperature difference between the upper and lower faces of the green glass to be ceramized in the furnace ranges between −0.5° and +1° C.

5. A method according to claim 1 the temperatures of the upper and lower faces of at least one ceramizing segment of the green glass are measured by temperature sensors having a response time of one second and the heating is controlled within 10 seconds.

6. A method according to claim 1 , wherein green glass plates are placed obliquely on the conveying apparatus so that one of the corners of the glass plate leads the remaining plate.

Assignees

• Gabel Falk
• Johansson Thoralf
• Martens Uwe
• Roos Christian
• Schroder Friedrich Georg
• Schott Ag

Inventors

• Gabel Falk
• Johansson Thoralf
• Martens Uwe
• Roos Christian
• Schroder Friedrich Georg

Classifications

• Y10T428/24488

  Differential nonuniformity at margin · CPC title

• C03B35/16

  by roller conveyors · CPC title

• C03B35/181

  Materials, coatings, loose coverings or sleeves thereof · CPC title

• C03B29/08

  Glass sheets · CPC title

• C03C10/0027

  containing SiO2, Al2O3, Li2O as main constituents · CPC title