Method for producing borosilicate glasses
The process of producing a refined borosilicate glass includes preparing a glass batch with a composition in wt. % on the basis of oxide content of SiO 2, 65-82; Al 2 O 3 , 2-8; B 2 O 3 , 5-13; MgO+CaO+SrO +BaO+ZnO, 0-7; ZrO 2 , 0-2; and Li 2 O+Na 2 O+K 2 O, 3-10; adding 0.05 wt. % to 0.6 wt. % of sulfate(s) expressed as SO 3 to the glass batch as the refining agent; melting the glass batch including the refining agent to form melted glass; and then hot-shaping the borosilicate glass. The refining agent may also include from 0.01 wt. % to 0.6 wt. % of F − or from 0.015 wt. % to 0.6 wt. of Cl − . The sulfate is preferably an alkali metal and/or alkaline earth metal sulfate or sulfates.
1. A process of producing a refined borosilicate glass having a hydrolytic class 1, said process comprising the steps of:
a) preparing a glass batch with a composition, in wt. % on the basis of oxide content, consisting of:
SiO 2
65-82
Al 2 O 3
2-8
B 2 O 3
5-13
MgO + CaO + SrO + BaO + ZnO
0-7
ZrO 2
0-2
Li 2 O + Na 2 O + K 2 O
3-10
b) adding a refining agent to said glass batch, said refining agent consisting of from 0.01 wt. % to 0.8 wt. % of at least one sulfate, expressed as an equivalent amount of SO 3 , and from 0.005 wt. % to 1.0 wt. % of fluoride;
c) melting said glass batch including the refining agent added in step b) to form melted glass; and then
d) hot-shaping said glass.
2. The process as defined in claim 1 , in which from 0.05 wt. % to 0.6 wt. % of said at least one sulfate, expressed as an equivalent amount of SO 3, is added to said glass batch as said refining agent.
3. The process as defined in claim 1 , in which said refining agent consists of 0.01 wt. % to 0.8 wt. % of said at least one sulfate, expressed as an equivalent amount of SO 3, and from 0.01 wt. % to 0.6 wt. % of said fluoride.
4. The process as defined in claim 1 , in which said composition of said glass batch, in wt. % on the basis of oxide content, consists of:
SiO 2
75-82
Al 2 O 3
2-6
B 2 O 3
10-13
Na 2 O
3-5
K 2 O
0-1.
5. The process as defined in claim 1 , in which said composition of said glass batch, in wt. % on the basis of oxide content, consists of:
SiO 2
70-75
B 2 O 3
7-10
Al 2 O 3
3-7
Li 2 O
0-1
Na 2 O
6-8
K 2 O
0-3
Li 2 O + Na 2 O + K 2 O
6-10
MgO
0-1
CaO
0-2
BaO
0-4.
6. The process as defined in claim 1 , in which said composition of said glass batch, in wt. % on the basis of oxide content, consists of:
SiO 2
70-76
Al 2 O 3
2-7
B 2 O 3
5-13
MgO
0-1
CaO
0-3
BaO
0-4
ZnO
0-2
MgO + CaO + BaO + ZnO
0-7
ZrO 2
0-2
Li 2 O
0-1
Na 2 O
1-8
K 2 O
0-6
Li 2 O + Na 2 O + K 2 O
4-10.
7. The process as defined in claim 1 , in which said composition of said glass batch, in wt. % on the basis of oxide content, consists of:
SiO 2
72-75
Al 2 O 3
5-6
B 2 O 3
7-10
MgO
0-1
CaO
0.3-1
BaO
0-2.5
ZnO
0-3
MgO + CaO + BaO + ZnO
0.3-5
Li 2 O
0-1
Na 2 O
5.5-7.5
K 2 O
0-<1.5
Li 2 O + Na 2 O + K 2 O
5.5-7.5.
8. The process as defined in claim 1 , in which said at least one sulfate is one or more components selected from the group consisting of CaSO 4, ZnSO 4, MgSO 4, Na 2 SO 4 and BaSO 4 .
9. The process as defined in claim 1 , in which said at least one sulfate is Na 2 SO 4 .
10. The process as defined in claim 1 , wherein said at least one sulfate is selected from the group consisting of alkali metal sulfates and alkaline earth metal sulfates.
11. A process of producing a refined borosilicate glass having a hydrolytic class 1, said process comprising the steps of:
a) preparing a glass batch with a compositions, in wt. % on the basis of oxide content, consisting of:
SiO 2
70-75
Al 2 O 3
4.5-7
B 2 O 3
9.5-<11.5
MgO
0-2
CaO
0.5-2
SrO
0-3
BaO
0-1
ZnO
0-2
MgO + CaO + SrO + BaO + ZnO
1-7
ZrO 2
0-1
Li 2 O
0-1
Na 2 O
5-8
K 2 O
0-3
with Li 2 O + Na 2 O + K 2 O
5-9
b) adding a refining agent to said glass batch, said refining agent consisting of from 0.01 wt. % to 0.8 wt. % of at least one sulfate, expressed as an equivalent amount of SO 3 , and from 0.01 wt. % to 0.6 wt. % of fluoride;
c) melting said glass batch including the refining agent added in step b) to form melted glass; and then
d) hot-shaping said glass.
12. The process as defined in claim 11 , in which said composition of said glass batch, in wt. % on the basis of oxide content, consists of:
SiO 2
72-75
Al 2 O 3
4.5-6.5
B 2 O 3
9.5-<11
CaO
0.5-2
BaO
0-1
Li 2 O
0-1
Na 2 O
6-8
K 2 O
0-<1.5
with Li 2 O + Na 2 O + K 2 O
5-8.
13. The process as defined in claim 11 , wherein said at least one sulfate is selected from the group consisting of alkali metal sulfates and alkaline earth metal sulfates.
14. A process of producing a refined borosilicate glass having a hydrolytic class 1, said process comprising the steps of:
a) preparing a glass batch with a composition, in wt. % on the basis of oxide content, consisting of:
SiO 2
72-75
Al 2 O 3
4.5-6.5
B 2 O 3
9.5-<11.5
CaO
0.5-2
BaO
0-1
Li 2 O
0-1
Na 2 O
6-8
K 2 O
0-<1.5
with Li 2 O + Na 2 O + K 2 O
5-8;
b) adding a refining agent to said glass batch, said refining agent consisting of from 0.01 wt. % to 0.8 wt. % of at least one sulfate, expressed as an equivalent amount of SO 3 , and from 0.01 wt. % to 0.6 wt. % of fluoride;
c) melting said glass batch including the refining agent added in step b) to form melted glass; and then
d) hot-shaping said glass;
wherein said at least one sulfate is selected from the group consisting of alkali metal sulfates and alkaline earth metal sulfates.