METHOD AND SYSTEM FOR PRODUCING GLASS, IN WHICH CHEMICAL REDUCTION OF GLASS COMPONENTS IS AVOIDED

Abstract

In the method and system for producing glass reduction of reduction-sensitive ingredients in the glass is reduced or preferably is avoided during the melting and fining processes. The glass preferably has a high refractive index. During the process an oxidizing agent is inducted into a fining vessel and preferably also into a melt crucible made of a slit skull that is cooled by a cooling agent. The oxidizing agent is preferably oxygen. Furthermore a system for conducting the method is also described.

Description

BRIEF DESCRIPTION OF THE DRAWING

The objects, features and advantages of the invention will now be described in more detail with the aid of the following description of the preferred embodiments, with reference to the accompanying figures in which:

FIG. 1 is a schematic cross-sectional view of a first embodiment of a system according to the invention for producing glass in which chemical reduction of the components of the glass is avoided;

FIG. 2 is a schematic cross-sectional view of a second embodiment of a system according to the invention for producing glass in which chemical reduction of the components of the glass is avoided;

FIG. 3 is a schematic cross-sectional view of a third embodiment of a system according to the invention for producing glass in which chemical reduction of the components of the glass is avoided; and

FIG. 4 is a schematic cross-sectional view of a third embodiment of a system according to the invention for producing glass in which chemical reduction of the components of the glass is avoided.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In every FIG. 1 designates the melt and 2 designates the glass level. In the system shown in FIG. 1 a melt crucible 13 comprising skull walls cooled by a cooling agent 3 and a cover 6 made of flameproof material is connected via a heatable connection piece 5 made of noble metal or silicate glass to a fining vessel 14, which likewise comprises skull walls cooled by a cooling agent 3 and a cover 6 made of flameproof material. The melt crucible 13 and the fining vessel 14 are both encircled by inductors 4 and comprise bubbling nozzles 11 in the bottom area.

The fining vessel 14 comprises a glass melt flow influencing skull wall 12 in its interior and is connected via a cooling duct 7 made of noble metal or silicate glass to a homogenization unit 8. The homogenization unit 8 made of noble metal or silicate glass comprises a cover 6 made of flameproof material, an agitator 9 made of noble metal or silicate glass and a heatable feeder system 10 made of noble metal or silicate glass.

The system shown in FIG. 2 is different from that shown in FIG. 1 in such a way that the melt crucible 13 and the fining vessel 14 are connected to each other via a skull segment 5a. Also homogenisation unit 8 in the embodiment of FIG. 2 comprises a bubbling nozzle 11.

The system shown in FIG. 3 has a further modification in the homogenization system, which is a static homogenization unit 9a instead of an agitator. Furthermore the cooling duct and homogenization system are formed in one piece.

In contrast the cooling duct and the homogenisation system are not in one piece in the embodiment shown in FIG. 4. The embodiment of the system shown in FIG. 4 has as a connection between the homogenization system 8 and the fining vessel 14 that comprises cooling duct 7, which is made of noble metal or silicate glass.

Instead of the noble metal a noble metal alloy can also be used in every embodiment of the present invention. Instead of the bubbling nozzles 11 in every case foamed, porous or perforated cooled structures can be used, too.

The glass that can be produced using the method according to the present invention preferably comprises the compounds shown in table I.

TABLE I
Components                       Wt.-%
P2O5, B2O3, SiO2, F*             0-50
Nb2O5, Ta2O5, Bi2O3, Sb2O3, PbO  0-80
WO3, MoO3                        0-30
GeO2                             0-20
MgO, CaO, SrO, BaO               0-40
Li2O, Na2O, K2O, Rb2O, Cs2O      0-12
ZnO, TiO2                        0-8
Σ Nb2O5, Ta2O5, Bi2O3, Sb2O3, PbO 20-80
Σ WO3, MoO3, GeO2                0-40
Σ alkali metal oxide             0-15
Σ alkaline earth metal oxide     0-30

Here and in the following tables and enumerations, the enumeration of multiple components means that these components can be incorporated into the composition each independently in the indicated range.

The glasses that can be produced using the method according to the present invention particularly preferably comprise the compounds shown in table II.

TABLE II
Components                       Wt.-%
P2O5, B2O3, SiO2, F              0-30
Nb2O5, Ta2O5, Bi2O3, Sb2O3, PbO  0-60
WO3, MoO3                        0-30
GeO2                             0-20
MgO, CaO, SrO, BaO               0-30
Li2O, Na2O, K2O, Rb2O, Cs2O      0-12
ZnO, TiO2                        0-8
Σ Nb2O5, Ta2O5, Bi2O3, Sb2O3, PbO 20-60
Σ WO3, MoO3, GeO2                0-40
Σ alkali metal oxide             2-15
Σ alkaline earth metal oxide     0-30

The glasses that can be produced using the method according to the present invention exceptionally preferably comprise the compounds shown in table III.

TABLE III
Components                      Wt.-%
P2O5, B2O3, SiO2, F             8-30
Nb2O5, Ta2O5, Bi2O3, Sb2O3, PbO 10-50
WO3, MoO3                       0-30
GeO2                            0-20
MgO, CaO, SrO, BaO              0-22
Li2O, Na2O, K2O, Rb2O, Cs2O     0-12
ZnO, TiO2                       0-8
Σ Nb2O5, Ta2O5, Bi2O3, Sb2O3,   20-60
PbO
Σ WO3, MoO3, GeO2               0-40
Σ alkali metal oxide            2-15
Σ alkaline earth metal oxide    0-30

The glasses that can be produced using the method according to the present invention most exceptionally preferably comprise the compounds shown in table IV.

TABLE IV
Components                       Wt.-%
P2O5, B2O3, SiO2, F              8-30
Nb2O5, Ta2O5, Bi2O3, Sb2O3, PbO  10-50
WO3, MoO3                        0-16
GeO2                             0-10
MgO, CaO, SrO, BaO               0-22
Li2O, Na2O, K2O, Rb2O, Cs2O      0-12
ZnO, TiO2                        0-8
Σ Nb2O5, Ta2O5, Bi2O3, Sb2O3, PbO 20-50
Σ WO3, MoO3, GeO2                0-20
Σ alkali metal oxide             2-15
Σ alkaline earth metal oxide     0-20

Preferably the glasses have low contents of silicate and/or noble metals, particularly preferred the glasses are free of silicate and/or noble metals.

EXAMPLES

Examples 1 to 4 describe examples of glass produced according to the present invention and their properties (n_d=refractive index; v_d=Abbe number; ΔP_g,F, τ_i=internal transmittance). The invention is not limited by these concrete examples.

Example 1

A glass of the following composition was produced:

P₂O₅: 21.0%

Σ Nb₂O₅, Ta₂O₅, Sb₂O₃: 50.5%

Σ MgO, CaO, SrO, BaO: 19.0%

Σ Li₂O, Na₂O, K₂O, Rb₂O, Cs₂O: 4.5%

Σ ZnO, TiO₂: 5.0%

A melting skull crucible and a fining skull crucible consisting of AlMgSi1, connection segment, homogenization unit, agitator and feeder consisted of PtIr1 were used in the process.

The following melting parameters were used:

Melting: 1200° C.-1210° C., O₂-Bubbling: 3×50 l/h

Fining: 1220° C.-1230° C., O₂-Bubbling: 2×20 l/h

Mixing: 1180° C.

Feeder: 1150° C.

Ingots were produced.

The following optical values were measured:

n_d=1.92773;v_d=20.61;

ΔP_g,F=−0.0312

τ_i (400 nm; 25 mm)=0.104; 0.002¹; 0.1152² τ_i (420 nm; 25 mm)=0.435; 0.232¹; 0.495² τ_i (460 nm; 25 mm)=0.812; 0.748¹; 0.846² τ_i (500 nm; 25 mm)=0.898; 0.858¹; 0.932²

The given reference values (¹) have been measured in a glass of the same composition that has been melted in a melting skull crucible made of AlMgSi1 at 1210° C. and fined in a conventional fining chamber made of PtIr1 at 1230° C. The cooling duct, the homogenization unit, the agitator and the feeder consisted of PtIr1. The reference melt was not bubbled with oxygen.

The given values (²) were achieved by additional O₂-bubbling through the melt at in other respects identical melting conditions as above. For that purpose the melt was bubbled with oxygen in a mixing crucible with 1×15 l/h at 1175 to 1180° C.

Example 2

A glass of the following composition was produced:

P₂O₅: 22.8%

Σ Nb₂O₅, Ta₂O₅, Sb₂O₃: 47.0%

Σ MoO₃, WO₃: 14.0%

Σ MgO, CaO, SrO, BaO: 2.0%

Σ Li₂O, Na₂O, K₂O, Rb₂O, Cs₂O: 9.2%

Σ TiO₂, GeO₂: 5.0%

A melting skull crucible and a fining skull crucible consisting of AlMgSi1, connection segment, cooling duct, homogenization unit, agitator and feeder consisted of PtIr1 were employed in the process.

The following melting parameters were adjusted:

Melting: 1110° C.-1120° C., O₂-Bubbling: 3×30 l/h

Fining: 1130° C.-1150° C., O₂-Bubbling: 2×150 l/h

Mixing: 1110-1120° C.

Feeder: 1100° C.

Ingots were produced.

The following optical values were measured:

n_d=1.97242;v_d=22.65;

ΔP_g,F=0.0223

τ_i (400 nm; 25 mm)=0.070 (0.06)τ_i (420 nm; 25 mm)=0.423 (0.36)τ_i (500 nm; 25 mm)=0.875 (0.668)

The reference values given in brackets have been measured in a glass of the same composition that has been melted in a melting skull crucible made of AlMgSi1 at 1120° C. and fined in a conventional fining chamber made of PtIr1 at 1150° C. The cooling duct, the homogenization unit, the agitator and the feeder consisted of PtIr1. The reference melt was not bubbled with 3×30 l/h of oxygen in the melting skull.

Example 3

A glass for optical and electronic purposes of the following composition was produced:

Σ B₂O₃, SiO₂: 10.5%

Σ Sb₂O₃, Bi₂O₃: 77.0%

Σ MgO, CaO, ZnO: 12.5%

A melting skull crucible, connection segment, cooling duct and feeder consisting of PtIr1 were used.

The following melting parameters were adjusted:

Melting: 1000° C.-1050° C., O₂-Bubbling: 3×50 l/h

Cooling track: 900-950° C.

Feeder: 850° C.

Glass flakes were produced.

The following optical values were measured:

n_d=2.101

Example 4

An optical glass of the following composition was produced:

SiO₂: 29.0%

Σ PbO, Sb₂O₃: 64.3%

Σ MgO, CaO, SrO, BaO: 2.0%

Σ Li₂O, Na₂O, K₂O, Rb₂O, Cs₂O: 6.7%

A melting skull crucible and a fining skull crucible consisting of AlMgSi1, connection segment, cooling track, homogenization unit, agitator and feeder consisted of PtIr1 were used.

The following melting parameters were adjusted:

Melting: 1200° C.-1210° C., O₂-Bubbling: 3×30 l/h

Fining: 1275° C., O₂-Bubbling: 2×20 l/h

Mixing: 1180-1190° C.

Feeder: 1150° C.

Ingots were produced.

The following optical values were measured:

n_d=1.75815;v_d=26.64;

ΔP_g,F=0.6067

τ_i (400 nm; 25 mm)=0.984

The above-mentioned glass is essentially free of other components. This is supposed to mean in the sense of the present invention that further components are not added to the glass and, if present at all, are present in the form and amount of impurities.

PARTS LIST

• 1—glass melt
• 2—melt surface
• 3—skull walls cooled by cooling agent
• 4—inductor
• 5—heatable connection piece made of noble metal or silicate glass
• 5 a—skull connection element
• 6—cover made of flame proof material
• 7—heatable or coolable cooling ductmade of noble metal or silicate glass
• 8—heatable homogenization system made of noble metal or silicate glass
• 9—agitator made of noble metal or silicate glass
• 9 a—static homogenization unit made of noble metal
• 10—heatable feeder system made of noble metal or silicate glass
• 11—bubbling nozzles
• 12—skull wall cooled by cooling agent (influencing the stream)
• 13—melt crucible
• 14—fining vessel

Claims

1. A process for producing glass, said process comprising conducting at least one oxidizing agent into a fining vessel for a glass melt, in which a fining process is taking place in the glass melt so that reduction of reduction-sensitive components in the glass melt is avoided or reduced.

2. The process according to claim 1, wherein the reduction of the reduction-sensitive components in the glass melt is additionally reduced or avoided during a glass melting process by conducting oxidizing agents into a melt crucible in which the glass melting process is taking place to form the glass melt.

3. The process according to claim 1, wherein the reduction of the reduction-sensitive components in the glass melt is additionally decreased or avoided during a homogenization process by conducting oxidizing agents into a homogenization vessel in which the homogenization process is taking place in the glass melt.

4. The process according to claim 1, wherein the at least one oxidizing agent is oxygen and/or ozone.

5. The process according to claim 1, wherein the glass is a high-index glass with a refractive index of at least 1.7.

6. The process according to claim 5, wherein the glass has a composition, in wt. %, comprising:

7. The process according to claim 1, further comprising heating a melt crucible in which a glass melting process takes place to form the glass melt and/or the fining vessel inductively with a high-frequency electromagnetic alternating field.

8. The process according to claim 1, further comprising heating a melt crucible in which a glass melting process takes place to form the glass melt and/or the fining vessel by cooled electrodes and wherein said cooled electrodes are made of platinum, gold, SnO2 or iridium.

9. The process according to claim 1, further comprising heating with a burner supplied with fossil fuels to initiate a glass melting process to form the glass melt.

10. The process according to claim 1, further comprising conducting the at least one oxidizing agent into the glass melt via bubbling nozzles located in a bottom of a melt crucible, in which the glass melting process is taking place to form the glass melt, and/or located in the fining vessel.

11. The process according to claim 1, wherein the at least one oxidizing agent is conducted in a laminar flow into the glass melt by foamed, porous or perforated structures arranged in a bottom of a melt crucible, in which the glass melting process is taking place to form the glass melt, and/or located in the fining vessel.

12. The process according to claim 1, further comprising transferring the glass melt from a melt crucible, in which the glass melting process is taking place to form the glass melt, into the fining vessel though a heatable platinum pipe or through a silicate glass pipe.

13. The process according to claim 1, further comprising transferring the glass melt from a melt crucible, in which the glass melting process is taking place to form the glass melt, to the fining vessel via a skull segment.

14. The process according to claim 1, wherein the glass is a heavy metal phosphate glass comprising at least 40 percent by weight of heavy metals and at least 8 percent by weight and a maximum of 50 percent by weight of P2O5.

15. The process according to claim 1, wherein the glass is a heavy metal borate glass comprising at least 40 percent by weight of heavy metals, at least 8 percent by weight and a maximum of 50 percent by weight of B2O3.

16. The process according to claim 1, wherein the glass is a heavy metal silicate glass comprising at least 40 percent by weight of heavy metals, at least 8 percent by weight and a maximum of 50 percent by weight of SiO2.

17. A system for performing a process for producing glass, said system comprising a melt crucible (13) and a fining vessel (14), said fining vessel (14) comprising means for conducting at least one oxidizing agent into the fining vessel and said process comprising conducting the at least one oxidizing agent into a glass melt in the fining vessel so that reduction of reduction-sensitive components in the glass melt is avoided or reduced.

18. The system according to claim 17, wherein said at least one oxidizing agent is oxygen and/or ozone.

19. The system according to claim 17, wherein the melt crucible (13) comprises means for conducting at one oxidizing substance into the melt crucible.

20. The system according to claim 19, wherein said at one oxidizing substance is oxygen and/or ozone.

21. The system according to claim 17, wherein said means for conducting the at least one oxidizing agent comprises at least one bubbling nozzle (11).

22. The system according to claim 17, wherein said means for conducting the at least one oxidizing agent comprises foamed, porous or perforated cooled structures.

23. The system according to claim 17, in which the melt crucible (13) and/or the fining vessel (14) are a unit, said unit is heatable with a high-frequency alternating electromagnetic field, said melt crucible (13) and/or said fining vessel (14) consist of a metallic skull crucible comprising walls, said walls of which are cooled by a cooling agent and are provided with high-frequency permeable slits with respective slit widths of from 1.5 mm up to and including 4.0 mm

24. The system according to claim 23, wherein the slit widths are from 2.0 mm up to and including 3.0 mm.

25. The system according to claim 17, wherein the melt crucible is cooled with a cooling agent and consists of coated or uncoated metal or consists of a coated or uncoated metal alloy.

26. The system according to claim 25, wherein the metal or the metal alloy is an aluminium alloy, a nickel basis alloy, copper, brass, a noble metal or a steel.

27. The system according to claim 25, wherein the metal or the metal alloy is coated with a synthetic material containing fluorine.