U.S. patent application number 13/346235 was filed with the patent office on 2012-06-28 for fining agents for silicate glasses.
Invention is credited to Matthew John Dejneka, Sinue Gomez.
Application Number | 20120159991 13/346235 |
Document ID | / |
Family ID | 40998909 |
Filed Date | 2012-06-28 |
United States Patent
Application |
20120159991 |
Kind Code |
A1 |
Dejneka; Matthew John ; et
al. |
June 28, 2012 |
FINING AGENTS FOR SILICATE GLASSES
Abstract
A fining agent for reducing the concentration of seeds or
bubbles in a silicate glass. The fining agent includes at least one
inorganic compound, such as a hydrate or a hydroxide that acts as a
source of water. In one embodiment, the fining agent further
includes at least one multivalent metal oxide and, optionally, an
oxidizer. A fusion formable and ion exchangeable silicate glass
having a seed concentration of less than about 1 seed/cm.sup.3 is
also provided. Methods of reducing the seed concentration of a
silicate glass, and a method of making a silicate glass having a
seed concentration of less than about 1 seed/cm.sup.3 are also
described.
Inventors: |
Dejneka; Matthew John;
(Corning, NY) ; Gomez; Sinue; (Corning,
NY) |
Family ID: |
40998909 |
Appl. No.: |
13/346235 |
Filed: |
January 9, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12392577 |
Feb 25, 2009 |
8158543 |
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13346235 |
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61067130 |
Feb 26, 2008 |
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Current U.S.
Class: |
65/66 ;
252/186.1; 252/186.21; 423/327.1; 423/328.3; 423/629; 423/641;
423/700; 65/134.3 |
Current CPC
Class: |
C03C 1/004 20130101;
C03C 3/095 20130101; C03C 3/083 20130101; Y02A 40/29 20180101; C03C
3/085 20130101; C03B 17/064 20130101; Y02A 40/28 20180101; C03C
21/002 20130101; C03C 3/087 20130101; C03B 5/225 20130101; Y10T
428/315 20150115; C03C 14/008 20130101; C03C 3/091 20130101 |
Class at
Publication: |
65/66 ; 65/134.3;
423/629; 423/641; 423/327.1; 423/700; 423/328.3; 252/186.1;
252/186.21 |
International
Class: |
C03B 5/225 20060101
C03B005/225; C01D 1/04 20060101 C01D001/04; C09K 3/00 20060101
C09K003/00; C01B 39/00 20060101 C01B039/00; C01B 33/42 20060101
C01B033/42; C01F 7/02 20060101 C01F007/02; C01B 33/40 20060101
C01B033/40 |
Claims
1. (canceled)
2. (canceled)
3. The method according to claim 20, wherein the metal hydrate is
one of a clay, a zeolite, a mica, and combinations thereof.
4. The method according to claim 20, wherein the metal hydroxide is
one of aluminum hydroxide, an alkali metal hydroxide, an alkaline
earth metal hydroxide, zirconium hydroxide, and combinations
thereof.
5. (canceled)
6. method according to claim 20, wherein the at least one oxidizer
is one of aluminum nitrate, an alkali metal nitrate, an alkaline
earth nitrate, zirconium nitrate, ammonium nitrate, and
combinations thereof.
7. The fining agent according to claim 12, wherein the silicate
glass is one of a soda lime glass, a borosilicate glass, an
aluminosilicate glass, and combinations thereof.
8. The fining agent according to claim 12, wherein the silicate
glass comprises: 60-72 mol % SiO.sub.2; 6-14 mol % Al.sub.2O.sub.3;
0-15 mol % B.sub.2O.sub.3; 0-1 mol % Li.sub.2O; 0-20 mol %
Na.sub.2O; 0-10 mol % K.sub.2O; 0-8 mol % MgO; 0-10 mol % CaO; 0-5
mol % ZrO.sub.2; 0-1 mol % SnO.sub.2; 0-1 mol % CeO.sub.2; less
than 50 ppm As.sub.2O.sub.3; and less than 50 ppm Sb.sub.2O.sub.3;
wherein 12 mol %.ltoreq.Li.sub.2O +Na.sub.2O+K.sub.2O.ltoreq.20 mol
% and 0 mol %.ltoreq.MgO+CaO.ltoreq.10 mol %, and wherein the
silicate glass is substantially free of antimony and arsenic.
9. (canceled)
10. (canceled)
11. (canceled)
12. A fining agent for silicate glasses, the fining agent
comprising an inorganic compound that acts as of a source of water
at a temperature at which a melt is formed, wherein the water
vaporizes and expands existing bubbles in the melt and allows the
expanded bubbles to rise to the surface of the melt and escape the
melt to reduce the seed concentration in the silicate glass to less
than about 1 seed/cm.sup.3, and wherein the fining agent is
substantially free of arsenic and antimony.
13. The fining agent according to claim 12, wherein the fining
agent comprises at least one of: a metal hydrate, a metal
hydroxide; and combinations thereof.
14. The fining agent according to claim 13, wherein the metal
hydrate is one of a clay, a zeolite, a mica, and combinations
thereof.
15. The fining agent according to claim 13, wherein the metal
hydroxide is one of aluminum hydroxide, an alkali metal hydroxide,
an alkaline earth metal hydroxide, zirconium hydroxide, and
combinations thereof.
16. The fining agent according to claim 15, wherein the fining
agent further comprises at least one multivalent metal oxide that
acts as a source of oxygen to the melt and, optionally, at least
one oxidizer.
17. The fining agent according to claim 16, wherein the at least
one oxidizer is one of aluminum nitrate, an alkali metal nitrate,
an alkaline earth nitrate, zirconium nitrate, ammonium nitrate, and
combinations thereof.
18. The fining agent according to claim 13, wherein the fining
agent acts as a flux that decreases the viscosity of the melt.
19. A method of reducing a concentration of seeds in a silicate
glass, the method comprising the steps of: a. providing a batch,
the batch comprising raw materials for the silicate glass and at
least one fining agent in an amount sufficient to generate one mole
of water vapor per kilogram of glass, wherein the at least one
fining agent is substantially free of arsenic and antimony and
comprises at least one inorganic compound that acts as of a source
of water at a temperature where a melt is formed; b. melting the
batch to form a melt, the melt having a surface; c. vaporizing the
water to form water vapor, wherein the water vapor expands existing
bubbles in the melt; d. allowing the expanded bubbles to rise to
the surface of the melt and escape the melt to reduce the
concentration of the plurality of seeds in the silicate glass melt
to less than about 1 seed/cm.sup.3; and e. removing at least a
portion of the plurality of bubbles from the melt.
20. The method according to claim 18, wherein the at least one
fining agent comprises at least one of: a metal hydrate, a metal
hydroxide; and combinations thereof.
21. The method according to claim 19, wherein the at least one
fining agent further comprises at least one multivalent metal oxide
that acts as a source of oxygen to the melt and, optionally, at
least one oxidizer.
22. A method of making a silicate glass having a seed concentration
of less than about 1 seed/cm.sup.3, the method comprising the steps
of a. providing a batch, the batch comprising raw materials for the
silicate glass and at least one fining agent in an amount
sufficient to generate one mole of water vapor per kilogram of
glass, wherein the at least one fining agent is substantially free
of arsenic and antimony and comprises at least one inorganic
compound that acts as of a source of water at a temperature where a
melt is formed; b. melting the batch to form a silicate glass melt;
c. vaporizing the water to form water vapor, wherein the water
vapor expands existing bubbles in the melt; d. allowing the
expanded bubbles to rise to the surface of the melt and escape the
melt to reduce the seed concentration in the melt below a
predetermined concentration; e. removing at least a portion of the
coalesced bubbles and seeds from the melt; and f. solidifying the
melt to form the silicate glass, wherein the glass has a seed
concentration of less than about 1 seed/cm.sup.3, wherein the
silicate glass comprises: 60-72 mol % SiO.sub.2; 6-14 mol %
Al.sub.2O.sub.3; 0-15 mol % B.sub.2O.sub.3; 0-1 mol % Li.sub.2O;
0-20 mol % Na.sub.2O; 0-10 mol % K.sub.2O; 0-8 mol % MgO; 0-10 mol
% CaO; 0-5 mol % ZrO.sub.2; 0-1 mol % SnO.sub.2; 0-1 mol %
CeO.sub.2; less than 50 ppm As.sub.2O.sub.3; and less than 50 ppm
Sb.sub.2O.sub.3; wherein 12 mol
%.ltoreq.Li.sub.2O+Na.sub.2O+K.sub.2O.ltoreq.20 mol % and 0 mol
%.ltoreq.MgO+CaO.ltoreq.10 mol %, and wherein the silicate glass is
substantially free of antimony and arsenic.
23. The method according to claim 22, wherein the at least one
fining agent comprises at least one of: a metal hydrate, a metal
hydroxide; and combinations thereof.
24. The method according to claim 23, wherein the at least one
fining agent further comprises at least one multivalent metal oxide
that acts as a source of oxygen to the melt and, optionally, at
least one oxidizer.
25. The method according to claim 23, wherein the metal hydrate is
one of a clay, a zeolite, a mica, and combinations thereof.
26. The method according to claim 23, wherein the metal hydroxide
is one of aluminum hydroxide, an alkali metal hydroxide, an
alkaline earth metal hydroxide, zirconium hydroxide, and
combinations thereof.
27. The method according to claim 23, wherein the at least one
oxidizer is one of aluminum nitrate, an alkali metal nitrate, an
alkaline earth nitrate, zirconium nitrate, ammonium nitrate, and
combinations thereof.
28. The method according to claim 19, wherein the silicate glass is
one of a soda lime glass, a borosilicate glass, an aluminosilicate
glass, and combinations thereof.
29. The method according to claim 19, wherein the silicate glass
comprises: 60-72 mol % SiO.sub.2; 6-14 mol % Al.sub.2O.sub.3; 0-15
mol % B.sub.2O.sub.3; 0-1 mol % Li.sub.2O; 0-20 mol % Na.sub.2O;
0-10 mol % K.sub.2O; 0-8 mol % MgO; 0-10 mol % CaO; 0-5 mol %
ZrO.sub.2; 0-1 mol % SnO.sub.2; 0-1 mol % CeO.sub.2; less than 50
ppm As.sub.2O.sub.3; and less than 50 ppm Sb.sub.2O.sub.3; wherein
12 mol %.ltoreq.Li.sub.2O+Na.sub.2O+K.sub.2O.ltoreq.20 mol % and 0
mol %.ltoreq.MgO+CaO.ltoreq.10 mol %, and wherein the silicate
glass is substantially free of antimony and arsenic.
30. The method according to claim 22, wherein solidifying the melt
to form the silicate glass comprises down-drawing the melt.
31. The method according to claim 22, further comprising ion
exchanging the silicate glass, wherein the silicate glass, when ion
exchanged, has a surface compressive stress of at least about 200
MPa and a surface compressive layer having a depth of at least
about 30 .mu.m.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of and claims the benefit
of priority from U.S. patent application Ser. No. 12/392,577, filed
on Feb. 25, 2009, which claims the benefit of priority under 35
U.S.C. .sctn.119(e) of U.S. Provisional Application Ser. No.
61/067,130 filed on Feb. 26, 2008, the contents of which are
incorporated by reference herein in their entirety.
BACKGROUND
[0002] During glass formation from the melt, contaminants in the
melt tend to form gas bubbles, also referred to in the art as
"seeds." Such seeds affect the performance and quality of the
glass, and efforts are made to remove or "fine" them from the
glass.
[0003] Seed formation is problematic for silicate glasses. In
particular, aluminosilicate glasses and other silicate glasses that
melt at high temperature are much more difficult to fine than other
glasses. The high viscosities of such glasses slow the rate of
bubble removal by via Stokes fining; i.e., allowing the bubbles to
rise to the surface of the melt due to buoyancy.
[0004] Fining agents such as As.sub.2O.sub.3, Sb.sub.2O.sub.3, and
halides have been used to remove bubbles from aluminosilicate
glasses. These chemical fining packages work by releasing gas to
existing bubbles, causing them to increase in size and rise more
quickly to the top of the melt. However, these components are
toxic, hazardous to handle, expensive, and undesirable for
environmentally green products and processes. Sulfate fining agents
have also been used in soft glasses. However, they contribute to
sulfur emissions and actually exacerbate seed formation in
aluminosilicate glasses.
SUMMARY
[0005] Environmentally friendly fining agents for reducing the
concentration of seeds or bubbles in a silicate glass are provided.
The fining agent includes at least one inorganic compound, such as
a hydrate or a hydroxide, which acts as a source of water. In one
embodiment, the fining agent further includes at least one
multivalent metal oxide and, optionally, an oxidizer. A fusion
formable and ion exchangeable silicate glass having a seed
concentration of less than about 1 seed/cm.sup.3 is also provided.
Methods of reducing the seed concentration of a silicate glass, and
a method of making a silicate glass having a seed concentration of
less than about 1 seed/cm.sup.3 are also described.
[0006] Accordingly, one aspect of the disclosure is to provide a
silicate glass. The silicate glass has a seed concentration of less
than about 1 seed/cm.sup.3, wherein a batch or raw materials that
form the silicate glass includes at least one fining agent. The
fining agent comprises at least one inorganic compound that acts as
of a source of water at a temperature where a melt is formed.
[0007] Another aspect of the disclosure is to provide a fining
agent for silicate glasses. The fining agent comprises an inorganic
compound that acts as of a source of water at a temperature where a
melt is formed, wherein the water vaporizes and expands existing
bubbles in the melt and allows the expanded bubbles to rise to the
surface of the melt and escape the melt to reduce the seed
concentration in the silicate glass to less than about 1
seed/cm.sup.3.
[0008] A third aspect of the disclosure is to provide a method of
reducing a concentration of seeds in a silicate glass. The method
comprises the steps of: providing a batch comprising raw materials
for the silicate glass and at least one fining agent, wherein the
at least one fining agent comprises at least one inorganic compound
that acts as of a source of water at a temperature where a melt is
formed; melting the batch to form the melt; vaporizing the water to
form water vapor, wherein the water vapor expands existing bubbles
in the melt; allowing the expanded bubbles to rise to the surface
of the melt and escape the melt to reduce the seed concentration in
the melt below a predetermined concentration; and removing at least
a portion of the coalesced bubbles and seeds from the melt.
[0009] A fourth aspect of the disclosure is to provide a method of
making a silicate glass having a seed concentration of less than
about 1 seed/cm.sup.3. The method comprises the steps of: providing
a batch comprising raw materials for the silicate glass and at
least one fining agent, wherein the at least one fining agent
comprises at least one inorganic compound that acts as of a source
of water at a temperature of a melt; melting the batch to form the
melt; vaporizing the water to form water vapor, wherein the water
vapor expands existing bubbles in the melt; allowing the expanded
bubbles to rise to the surface of the melt and escape the melt to
reduce the seed concentration in the melt below a predetermined
concentration; removing at least a portion of the coalesced bubbles
and seeds from the melt; and solidifying the melt to form the
silicate glass, wherein the silicate glass has a seed concentration
of less than about 1 seed/cm.sup.3.
[0010] These and other aspects, advantages, and salient features
will become apparent from the following detailed description, the
accompanying drawings, and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a photograph of polished cross sections of glasses
obtained from melts containing fining agents;
[0012] FIG. 2 is a photograph of polished cross sections of glasses
obtained from melts showing the effect of different fining agents
on the concentration of seeds within the melt; and
[0013] FIG. 3 is a photograph of polished cross sections of glasses
obtained from melts comparing the effectiveness of hydroxide fining
agents in reducing seed formation.
DETAILED DESCRIPTION
[0014] In the following description, like reference characters
designate like or corresponding parts throughout the several views
shown in the figures. It is also understood that, unless otherwise
specified, terms such as "top," "bottom," "outward," "inward," and
the like are words of convenience and are not to be construed as
limiting terms. In addition, whenever a group is described as
comprising at least one of a group of elements and combinations
thereof; it is understood that the group may comprise, consist of,
or consist essentially of any number of those elements recited,
either individually or in combination with each other. Similarly,
whenever a group is described as consisting of at least one of a
group of elements or combinations thereof, it is understood that
the group may consist of any number of those elements recited,
either individually or in combination with each other. Unless
otherwise specified, a range of values, when recited, includes both
the upper and lower limits of the recited range.
[0015] Referring to the drawings in general and to FIG. 1 in
particular, it will be understood that the illustrations are for
the purpose of describing particular embodiments and are not
intended to limit the disclosure and appended claims thereto.
[0016] Glasses having relatively high viscosities (i.e., 200 Poise
viscosities of between about 1500.degree. C. and 1675.degree. C.)
may require melting to obtain a glass having low levels of
inclusions. Gaseous inclusions, blisters, or bubbles, which are
also referred to herein as "seeds," tend to have an adverse affect
of the optical quality and properties of the glass. For example,
the presence of seeds affects the refractive index, density, and
transmission of light through the glass. To aid in eliminating or
reducing the concentration of these gaseous inclusions, it is, in
some instances, useful to add chemical fining agents. Such fining
agents fill early-stage bubbles with gas, thus increasing the
velocity at which the bubbles rise through the melt. Typical fining
agents include, but are not limited to: oxides of arsenic,
antimony, tin and cerium; metal halides (fluorides, chlorides and
bromides); metal sulfates; and the like. Arsenic oxides are
particularly effective fining agents because they release oxygen
very late in the melt stage. However, arsenic and antimony are
generally regarded as hazardous materials. Therefore, it may be
advantageous in particular applications to completely avoid using
arsenic or antimony, and instead use a nontoxic component to
produce a fining effect.
[0017] As described herein, the number of seeds within silicate
glasses is reduced by providing fining agents that comprise at
least one inorganic compound that acts as a source of water at a
temperature of a melt formed by the mixture of raw materials (also
referred to herein as the "batch" or "batch materials") that are
used to form the silicate glass. The inorganic compound may melt or
decompose at a temperature below the temperature of the melt,
generating water. The water is initially dissolved as a vapor in
the melt. As the temperature of the melt increases, the water vapor
comes out of solution and is captured by bubbles already present in
the melt. The captured water vapor fills the bubbles with steam and
expands the bubbles, causing them to rise more quickly to the
surface of the melt and escape. For example, aluminum hydroxide
(Al(OH).sub.3, which is used as a fining agent, decomposes to form
boehmite (AlO.(OH)) and water at temperatures below those at which
a melt initially appears. The boehmite will decompose at higher
temperatures to form alumina (Al.sub.2O.sub.3) and water. The water
produced by this two-step decomposition will eventually be captured
by bubbles already present in the melt, increasing the size of
these bubbles and causing them to rise to the surface of the melt,
where they escape. The fining agent is also substantially free of
arsenic and antimony.
[0018] In one embodiment, the water source comprises at least one
of a hydrate, a metal hydroxide, and combinations thereof. Hydrates
are solid inorganic compounds that contain water molecules, which
are either bound to a metal or silicon center or crystallized with
a metal complex. Such hydrates are said to contain "water of
crystallization" or "water of hydration." With the exception of
boric acid, such hydrates may include hydrates of oxides or salts
formed by any of the constituents (e.g., alumina, alkali and
alkaline earth metals, zirconium) of the silicate glass. Metal
hydroxides are compounds that comprise a metal and the diatomic
hydroxyl OH.sup.- anion.
[0019] Non-limiting examples of inorganic or metal hydrates and
hydroxides include, but are not limited to: phyllosilicates, such
as clays and micas; zeolites; other hydrated silicates; and the
like. Clays that may be used as a water source in the fining agent
include, but are not limited to: aluminum silicate hydroxides, such
as kaolinite and pyrophillite; talc (magnesium silicate hydroxide);
montmorillonite-smectite (e.g., Bentonite); and combinations
thereof, such as clinochlore
((Mg.sub.5Al)(AlSi.sub.3)O.sub.10(OH).sub.8). Zeolites are hydrated
aluminosilicates having symmetrically stacked alumina and silica
tetrahedra that form an open, stable, three-dimensional honeycomb
structure having a negative charge. Zeolites that may be used as a
water source in the fining agent include, but are not limited to:
mineral zeolites, such as analcime, chabazite, heulandite,
natrolite, phillipsite, stilbite, and mordenite. Natrolite
(Na.sub.2Al.sub.2Si.sub.3O.sub.10.2H.sub.2O) has a formula that is
typical of such mineral zeolites. Synthetic zeolites such as
zeolite A, ZSM-5, and the like may also be used in the fining
agent.
[0020] In one embodiment, the fining agent includes at least one
metal hydroxide. Such hydroxides may include the hydroxides formed
by any of the constituents (e.g., alumina ((Al(OH).sub.3); alkali
(e.g., NaOH, KOH, LiOH) and alkaline earth (Mg(OH).sub.2,
Ca(OH).sub.2, Sr(OH).sub.2, Ba(OH).sub.2) metals; and zirconium
(Zr(OH).sub.4)) of the silicate glass. Additionally, the fining
agent may comprise the mineral hydroromarchite
(Sn.sub.3O.sub.2(OH).sub.2), and/or hydroxides of zinc
(Zn(OH).sub.2) and gallium (Ga(OH).sub.3).
[0021] In another embodiment, the fining agent further includes at
least one multivalent metal oxide that acts as a source of oxygen
to the melt and, optionally, an oxidizer. These multivalent metal
oxides are reduced in the glass melt, releasing oxygen, which may
also form bubbles. Non-limiting examples of such oxides include,
but are not limited to, tin(IV) oxide (SnO.sub.2), ceria or cerium
oxide (CeO.sub.2), and the like. The fining agent, in one
embodiment, comprises up to 0.5 mol % SnO.sub.2, up to 0.5 mol %
CeO.sub.2, and, optionally, 0-4 mol % of oxidizer.
[0022] Oxidizers such as, but not limited to, aluminum nitrate,
alkali metal nitrates, alkaline earth metal nitrates, zirconium
nitrate, ammonium nitrate, and the like re-oxidize the multivalent
metal oxides in the melt, thus enhancing the effectiveness of the
fining agent. Rather than be consumed by tramp contaminants and
organic compounds, the oxygen produced by the reduction of
multivalent metal oxides such as tin(IV) oxide and ceria are
absorbed by the oxidizer and reused in the fining process.
[0023] The fining agents described herein are "batched in" with the
rest of the raw materials that are used to formulate the silicate
glass. The inorganic compounds that are added as sources of water,
such as the hydrates and hydroxides, upon release of water, form
oxides that account for a portion of the glass composition.
[0024] The source of water decomposes to release water, which is
first dissolved in the initial melt and later comes out of solution
and vaporizes into the melt as steam (water vapor). The steam is
captured by bubbles that are generated by impurities and already
exist in the melt. The steam fills these existing bubbles, causing
them to expand and increase in size. The larger bubbles rise more
quickly to the top surface of the melt and escape the melt. Each
mole of aluminum hydroxide, for example, decomposes in the melt to
first form boehmite, which then decomposes to form alumina
(aluminum oxide), ultimately releasing 1.5 moles of water according
to the reactions
Al(OH).sub.3.fwdarw.AlO.(OH)+H.sub.2O, and
AlO.(OH).fwdarw.1/2Al.sub.2O.sub.3+1/2H.sub.2O.
Expressed in terms of the amount of alumina that is initially
introduced, or batched, into the glass as aluminum hydroxide, each
mole of Al.sub.2O.sub.3 that is batched provides 3 moles of water
vapor to the melt. Given that 1 mole of any gas occupies 22.4
liters at standard temperature and pressure (1 kPa (1 bar)
pressure, 273 K), or STP, each mole of Al.sub.2O.sub.3 batched as
Al(OH).sub.3 (molecular weight 156 grams) releases 67 liters of
gas. Because the gas is released at the temperature of the melt,
the actual volume of gas released by each mole of alumina batched
as Al(OH).sub.3 will be much greater than 67 liters. At
1000.degree. C. (1273 K), for example, each mole of alumina batched
as Al(OH).sub.3 releases a volume of about 312 liters of gaseous
water.
[0025] Similarly, a mole of sodium hydroxide decomposes to form
sodium oxide and water vapor according to the reaction
NaOH.fwdarw.1/2Na.sub.2O+1/2H.sub.2O.
The amount Na.sub.2O batched as sodium hydroxide provides one mole
of water vapor to the melt. At STP, one mole of a gas has a volume
of 22.4 liters. As previously described above, gaseous water is
released at the temperature of the melt, and the actual volume of
gas released by each mole of sodium oxide batched as NaOH will be
much greater than 22.3 liters.
[0026] In one embodiment, at least 1 mole of water per kilogram of
glass is used to effectively "fine" the glass--i.e., reduce the
number of seeds or bubbles in the glass. In another embodiment,
5-50 moles H.sub.2O/kg of glass are used to fine the glass. The
amount of water needed to fine the glass depends in part on the
density of the glass and other factors, such as the composition of
the glass and the viscosity and temperature of the melt. Depending
on the parameters for a particular glass, it may be possible in
some instances to use less than 1 mole H.sub.2O/kg glass to
effectively fine the glass.
[0027] The fining agents described herein are capable of providing
at least 0.25 moles, and, in one embodiment, 0.5 moles of gas
(water vapor, oxygen, or the like), per mole of fining agent to the
melt. The fining agents are capable of producing a seed
concentration within the silicate glass of less than about 1
seed/cm.sup.3 or, alternatively, about 5 seeds per pound (454
grams) of silicate glass. In one embodiment, the fining agents
described herein are capable of producing a silicate glass that is
substantially free of seeds.
[0028] The fining agents described herein may also act as
"fugitive" fluxes that reduce the viscosity of the melt, causing
the bubbles to rise to the top of the melt more rapidly.
[0029] A silicate glass having a seed concentration of less than
about 1 seed/cm.sup.3 or, alternatively, about 5 seeds per pound
(454 grams) of silicate glass, is also provided. In one embodiment,
the silicate glass is substantially free of seeds. At least one of
the fining agents described hereinabove is added to a batch
comprising raw materials for the silicate glass. Such raw materials
for making the silicate glasses described herein are known in the
art. After adding the at least one fining agent to the batch, the
batch is melted. The fining agent comprises at least one inorganic
compound that acts as of a source of water at a temperature of a
melt. The silicate glass may be one of a soda lime glass, a
borosilicate glass, an aluminosilicate glass, and combinations
thereof, such as, for example an aluminoborosilicate glass.
[0030] In one embodiment, the silicate glass comprises: 60-70 mol %
SiO.sub.2; 6-14 mol % Al.sub.2O.sub.3; 0-15 mol % B.sub.2O.sub.3;
0-15 mol % Li.sub.2O; 0-20 mol % Na.sub.2O; 0-10 mol % K.sub.2O;
0-8 mol % MgO; 0-10 mol % CaO; 0-5 mol % ZrO.sub.2; 0-1 mol %
SnO.sub.2; 0-1 mol % CeO.sub.2; less than 50 ppm As.sub.2O.sub.3;
and less than 50 ppm Sb.sub.2O.sub.3; wherein 12 mol
%.ltoreq.Li.sub.2O+Na.sub.2O+K.sub.2O.ltoreq.20 mol % and 0 mol
%.ltoreq.MgO+CaO.ltoreq.10 mol %. In another embodiment, the
silicate glass comprises: 63.5-66.5 mol % SiO.sub.2; 8-12 mol %
Al.sub.2O.sub.3; 0-3 mol % B.sub.2O.sub.3; 0-5 mol % Li.sub.2O;
8-18 mol % Na.sub.2O; 0-5 mol % K.sub.2O; 1-7 mol % MgO; 0-2.5 mol
% CaO; 0-3 mol % ZrO.sub.2; 0.05-0.25 mol % SnO.sub.2; 0.05-0.5 mol
% CeO.sub.2; less than 50 ppm As.sub.2O.sub.3; and less than 50 ppm
Sb.sub.2O.sub.3; wherein 14 mol
%.ltoreq.Li.sub.2O+Na.sub.2O+K.sub.2O.ltoreq.18 mol % and 2 mol
%.ltoreq.MgO+CaO.ltoreq.7 mol %.
[0031] The largest single constituent of the silicate glass is
SiO.sub.2, which forms the matrix of the glass and is present in
the inventive glasses in a concentration ranging from about 60 mol
% up to and including about 70 mol %. SiO.sub.2 serves as a
viscosity enhancer that aids formability and imparts chemical
durability to the glass. At concentrations that are higher than the
range given above, SiO.sub.2 prohibitively raises the melting
temperature. Glass durability suffers at concentrations below the
60-70 mol % SiO.sub.2 range. In addition, lower SiO.sub.2
concentrations can cause the liquidus temperature to increase
substantially in glasses having high alkali or alkaline earth oxide
concentrations.
[0032] The greater alkali metal oxide content of the silicate glass
facilitates melting, softens the glass, enables ion exchange,
decreases melt resistivity, and breaks up the glass network, which
increases thermal expansion and decreases durability. Mixtures of
alkali metal oxides help depress the liquidus temperature and may
enhance ion exchange as well. While Li.sub.2O provides fast ion
exchange, low density, and high modulus, it is also quite
expensive. Na.sub.2O is very desirable for ion exchange with
K.sup.+ ions for chemical strengthening and makes stable glasses
with respect to devitrification. Small amounts of K.sub.2O relative
to Na.sub.2O actually help increase the rate exchange of K.sup.+
ions for Na.sup.+ ions and decrease the liquidus temperature, but
also increase the thermal expansivity of the glass.
[0033] Alumina (Al.sub.2O.sub.3) and, to a lesser extent, zirconia
(ZrO.sub.2) have the opposite effect of the alkali metal oxides. In
addition, Al.sub.2O.sub.3 scavenges non-bridging oxygens (NBOs) to
form AlO.sub.4 tetrahedra while making the glass thermally harder.
Alumina and zirconia also provide lower expansion and greater
durability but, at high concentrations, make the glass more
difficult to melt. In most ion exchangeable glasses,
R.sub.2O>Al.sub.2O.sub.3 (where R.sub.2O represents at least one
alkali metal oxide, such as Li.sub.2O, Na.sub.2O, K.sub.2O) since
glasses in which R.sub.2O.dbd.Al.sub.2O.sub.3 are very difficult to
melt unless B.sub.2O.sub.3 is present.
[0034] Alkaline earth oxides help create a steeper viscosity curve
for the glasses. Replacing alkali metal oxides with alkaline earth
metal oxides generally raises the anneal and strain points of the
glass while lowering the melting temperatures needed to make high
quality glass. MgO and CaO are less expensive than SrO and BaO and
do not increase the density as much as the heavier oxides. BaO is
also considered to be a hazardous or toxic material, and its
presence is therefore undesirable. Accordingly, in one embodiment,
the glass is substantially free of barium. Large amounts of MgO
tend to increase the liquidus temperature, as the oxide is prone to
form forsterite (Mg.sub.2SiO.sub.4) at low MgO concentrations in
sodium aluminosilicate glasses.
[0035] B.sub.2O.sub.3 may be used as a flux to soften glasses,
making them easier to melt. B.sub.2O.sub.3 also helps scavenge
non-bridging oxygen atoms (NBOs), converting the NBOs to bridging
oxygen atoms through the formation of BO.sub.4 tetrahedra, which
increases the toughness of the glass by minimizing the number of
weak NBOs. B.sub.2O.sub.3 also lowers the hardness of the glass
which, when coupled with the higher toughness, decreases the
brittleness, thereby resulting in a mechanically durable glass.
[0036] Arsenic and antimony are widely regarded as hazardous or
toxic materials, and their presence is therefore undesirable.
Accordingly, the silicate glass, in another embodiment, is
substantially free of at least one of arsenic, antimony, and
barium.
[0037] In one embodiment, the silicate glass has a liquidus
viscosity of at least 100 kilopoise (kpoise). In another
embodiment, the liquidus viscosity is at least 160 kpoise, and, in
a third embodiment, the liquidus viscosity is at least 220 kpoise.
As used herein, the term "liquidus viscosity" refers to the
viscosity of a molten glass at the liquidus temperature, wherein
the liquidus temperature refers to the temperature at which the
very last crystals melt away as temperature is increased from room
temperature. These properties permit these silicate glasses to be
down-drawable; i.e., the glass is capable of being formed into
sheets using down-draw methods such as, but not limited to, fusion
draw and slot draw methods that are known to those skilled in the
art. Such down-draw processes are used in the large-scale
manufacture of ion-exchangeable flat glass.
[0038] The fusion draw process uses a drawing tank that has a
channel for accepting molten glass raw material. The channel has
weirs that are open at the top along the length of the channel on
both sides of the channel. When the channel fills with molten
material, the molten glass overflows the weirs. Due to gravity, the
molten glass flows down the outside surfaces of the drawing tank.
These outside surfaces extend down and inwardly so that they join
at an edge below the drawing tank. The two flowing glass surfaces
join at this edge to fuse and form a single flowing sheet. The
fusion draw method offers the advantage that, since the two glass
films flowing over the channel fuse together, neither outside
surface of the resulting glass sheet comes in contact with any part
of the apparatus. Thus, the surface properties of the glass sheet
are not affected by such contact.
[0039] The slot draw method is distinct from the fusion draw
method. Here the molten raw material glass is provided to a drawing
tank. The bottom of the drawing tank has an open slot with a nozzle
that extends the length of the slot. The molten glass flows through
the slot/nozzle and is drawn downward as a continuous sheet
therethrough and into an annealing region. Compared to the fusion
draw process, the slot draw process provides a thinner sheet, as
only a single sheet is drawn through the slot, rather than two
sheets being fused together, as in the fusion down-draw
process.
[0040] Down-draw processes produce surfaces that are relatively
pristine. Because the strength of the glass surface is controlled
by the amount and size of surface flaws, a pristine surface that
has had minimal contact has a higher initial strength. When this
high strength glass is then chemically strengthened, the resultant
strength is higher than that of a surface that has been a lapped
and polished. Chemical strengthening or tempering by ion exchange
also increases the resistance of the glass to flaw formation due to
handling. Down-drawn glass may be drawn to a thickness of less than
about 2 mm. In addition, down drawn glass has a very flat, smooth
surface that can be used in its final application without costly
grinding and polishing.
[0041] In one embodiment, the silicate glass described herein is
substantially free of lithium. As used herein, "substantially free
of lithium" means that lithium is not intentionally added to the
glass or glass raw materials during any of the processing steps
leading to the formation of the alkali aluminosilicate glass. It is
understood that a silicate glass or a silicate glass article that
is substantially free of lithium may inadvertently contain small
amounts of lithium due to contamination. The absence of lithium
reduces poisoning of ion exchange baths, and thus reduces the need
to replenish the salt supply needed to chemically strengthen the
glass. In addition, due to the absence of lithium, the glass is
compatible with continuous unit (CU) melting technologies such as
the down-draw processes described above and the materials used
therein, the latter including both fused zirconia and alumina
refractories and zirconia and alumina isopipes.
[0042] In one embodiment, the silicate glass comprises at least one
alkali metal oxide and is ion exchangeable. As used herein, the
term "ion-exchangeable" is understood to mean that the glass is
capable of being strengthened by ion exchange processes that are
known to those skilled in the art. Such ion exchange processes
include, but are not limited to, treating the heated alkali
aluminosilicate glass with a heated solution containing ions having
a larger ionic radius than ions that are present in the glass
surface, thus replacing the smaller ions with the larger ions.
Potassium ions, for example, could replace sodium ions in the
glass. Alternatively, other alkali metal ions having larger atomic
radii, such as rubidium or cesium, could replace smaller alkali
metal ions in the glass. Alternatively, the smaller alkali metal
ions could be replaced by Ag.sup.+ ions. Similarly, other alkali
metal salts such as, but not limited to, sulfates, halides, and the
like may be used in the ion exchange process. In one embodiment,
the down-drawn glass is chemically strengthened by placing it a
molten salt bath comprising KNO.sub.3 for a predetermined time
period to achieve ion exchange. In one embodiment, the temperature
of the molten salt bath is about 430.degree. C. and the
predetermined time period is about eight hours.
[0043] Surface compressive stress refers to a stress caused by the
substitution during chemical strengthening of an alkali metal ion
contained in a glass surface layer by another alkali metal ion
having a larger ionic radius. In one embodiment, potassium ions are
substituted for sodium ions in the surface layer of the glass
described herein. The glass has a surface compressive stress of at
least about 200 MPa. In one embodiment, the surface compressive
stress is at least about 600 MPa. The alkali aluminosilicate glass
has a compressive stress layer that has a depth of at least about
30 .mu.m and, in another embodiment, the depth of the compressive
stress layer is at least about 40 .mu.m.
[0044] The replacement of smaller ions by larger ions at a
temperature below that at which the glass network can relax
produces a distribution of ions across the surface of the glass
that results in a stress profile. The larger volume of the incoming
ion produces compressive stress (CS) on the surface and tension in
the center (central tension, or CT) of the glass. The compressive
stress is related to the central tension by the following
relationship:
CS=CT.times.(t-2DOL)/DOL;
where t is the thickness of the glass and DOL is the depth of
exchange, also referred to as depth of layer.
[0045] The silicate glass is resistant to both chipping and
scratching, making it well suited for use in cover plates, touch
screens, watch crystals, solar concentrators, windows, screens,
containers, and other applications that require strong and tough
glass with good scratch resistance.
[0046] A method of reducing the concentration of seeds in a
silicate glass is also provided. A batch comprising raw materials
for the silicate glass and at least one fining agent, as described
herein, is first provided. Such raw materials include, but are not
limited to, sand, alumina, nepheline syenite (a mineral comprising
Na.sub.2O.Al.sub.2O.sub.3.2SiO.sub.2), boric acid, soda ash,
potassium carbonate, magnesia, limestone, and the like. The batch
containing the at least one fining agent is then melted to form a
silicate glass melt. The fining agent comprises at least one
inorganic compound that acts as of a source of water at the
temperature of the melt. In one embodiment, the fining agent
comprises at least one of a metal hydrate, a metal hydroxide, and
combinations thereof. In another embodiment, the fining agent may
further include at least one multivalent metal oxide that acts as a
source of oxygen to the melt and, optionally, at least one
oxidizer, all of which have been previously described herein.
[0047] As previously described herein, the inorganic compound that
acts as source of water at the temperature of the melt may
decompose below the temperature of the melt, generating water vapor
that is initially dissolved in the solid or melt. As temperature
increases the water vapor (steam) comes out of solution. The water
vapor is captured by bubbles that already exist in the melt. The
water vapor fills these existing bubbles, causing them to expand
and increase in size. The expanded bubbles rise more quickly to the
top surface of the melt and escape the melt. At least a portion of
the expanded bubbles are then removed from the melt, usually by
allowing them to rise to the surface of the melt, where the gases
in the bubbles escape into the atmosphere above the melt and the
seed concentration in the resulting silicate glass is reduced to a
concentration below a predetermined level. In one embodiment, the
bubbles are allowed to rise and the gases allowed to escape by
maintaining the temperature of the melt at or above a predetermined
temperature. For example, some aluminosilicate glasses are first
melted at about 1525.degree. C. and then heated to about
1600.degree. C. to allow gases to escape from the melt.
[0048] A method of making the silicate glasses described herein is
also provided. A batch comprising raw materials for a silicate
glass and at least one fining agent, as described herein, is first
provided. Such raw materials include, but are not limited to, sand,
alumina, nepheline syenite (a mineral comprising
Na.sub.2O.Al.sub.2O.sub.3.2SiO.sub.2), boric acid, soda ash,
potassium carbonate, magnesia, limestone, and the like. The batch
containing the at least one fining agent is then heated to a
temperature at which a melt begins to form. The fining agent
comprises at least one inorganic compound that acts as of a source
of water at the temperature of the melt. In one embodiment, the
fining agent comprises at least one of a metal hydrate and a metal
hydroxide. In another embodiment, the fining agent may further
include at least one multivalent metal oxide that acts as a source
of oxygen to the melt and, optionally, at least one oxidizer, all
of which have been previously described herein.
[0049] As previously described herein, the inorganic compound that
acts as source of water at the temperature of the melt may
decompose below the temperature of the melt, generating water vapor
that is initially dissolved in the solid or melt. As temperature
increases, the water vapor (steam) comes out of solution. The water
vapor is captured by bubbles that already exist in the melt. The
water vapor fills these existing bubbles, causing them to expand
and increase in size. The expanded bubbles rise more quickly to the
top surface of the melt and escape the melt. At least a portion of
the expanded bubbles are then removed from the melt, usually by
allowing them to rise to the surface of the melt where the gases in
the bubbles escape into the atmosphere above the melt, thus
reducing the concentration of bubbles or seeds in the melt to a
concentration below a predetermined level. In one embodiment, the
bubbles are allowed to rise and the vapors allowed to escape by
maintaining the temperature of the melt above a predetermined
temperature. The silicate glass, having a seed concentration of
less than about 1 seed/cm.sup.3, is then solidified.
EXAMPLES
[0050] The following examples illustrate the features and
advantages of the invention and in no way are intended to limit the
disclosure and appended claims thereto.
Example 1
[0051] Example 1 serves to illustrate the effectiveness of the
fining agents described herein. Nine samples of aluminosilicate
crucible melts were prepared. The batch materials used for each
sample are listed in Table 1a. Different combinations of the fining
agents of the present invention were added to samples 11-18. Sample
19 did not contain any of the fining agents described hereinabove,
and thus served as a control sample. In samples 12, 13, 14, and 18,
the fining agent aluminum hydroxide (Al(OH).sub.3) was substituted
for alumina (Al.sub.2O.sub.3) in the batch. Sodium hydroxide (NaOH)
was substituted for soda ash in samples 15 and 16. Ceria and
tin(IV) oxide were added to samples 11-18, and the oxidizer sodium
nitrate (NaNO.sub.3) was added to samples 17 and 18.
[0052] The batched samples were melted at 1525.degree. C. for one
hour and then heated at 1600.degree. C. for one hour to facilitate
the removal of bubbles from the melt. The compositions of the
resulting glasses, expressed in weight percent and mole percent,
are listed in Tables 1b and 1c, respectively. Tables 1b and 1c also
include the averages concentration of seeds or bubbles in the glass
samples, expressed as seeds/cm.sup.3.
[0053] As previously described herein, upon the release of water,
the inorganic compound fining agents, such as the hydrates and
hydroxides that are added as sources of water, form oxides that
account for a portion of the glass composition. This is shown in
tables 1c, 2c, and 3c.
[0054] Polished cross-sections of glasses obtained from the melts
in Example 1 are shown in FIG. 1. Sample 19, which contained none
of the fining agents, has an average seed concentration of 930
seeds/cm.sup.3. The addition of 0.1 mol % SnO.sub.2 and 0.1 mol %
CeO.sub.2 alone (sample 11) drastically reduces the concentration
of seeds or bubbles in the glass to 79.1 seeds/cm.sup.3. The use of
the oxidizer (NaNO.sub.3) with SnO.sub.2 and CeO.sub.2 alone
(sample 17) also further reduces the concentration of bubbles or
seeds to 0.061 seeds/cm.sup.3.
[0055] The addition of either Al(OH).sub.3 (samples 12, 13, 14,
18), or NaOH (samples 15 and 16) adds water in the form of
hydroxides. Either of these fining agents reduces the seed
concentration to levels below those observed when a combination of
tin(IV) oxide and ceria alone (sample 11) is used, whereas addition
of even higher levels of these hydroxides virtually eliminate seeds
or bubbles under the melting conditions used. The addition of
Al(OH).sub.3 reduces the seed concentration to values ranging from
0.610 seeds/cm.sup.3 (sample 14, in which 359 g of nephelene
syenite were added to the batch) to 0.183 seeds/cm.sup.3 (sample
18, in which 247 g (Al(OH).sub.3 were added to the batch). The
addition of NaOH reduces seed concentration to values ranging from
0.580 seeds/cm.sup.3 (sample 15, 87 g NaOH added to the batch) to
0.677 seeds/cm.sup.3 (sample 16, 173 g NaOH added to the batch).
Use of the oxidizer NaNO.sub.3 with SnO.sub.2, CeO.sub.2, and a
hydrate (sample 18) reduces the number of bubble/seeds in the glass
to a concentration of 0.183 seeds/cm.sup.3.
Example 2
[0056] Example 2 illustrates the amount of fining agent (or agents)
that effectively reduce the concentration of bubbles/seeds in
silicate glasses. Nine samples of aluminosilicate crucible melts
were prepared. The batch materials used for each sample are listed
in Table 2a. Ceria and tin(IV) oxide were added to samples 21-29,
and are the only fining agents present in sample 29. The fining
agent aluminum hydroxide (Al(OH).sub.3) was substituted for alumina
(Al.sub.2O.sub.3) in the batch in samples 21 and 22, and sodium
hydroxide (NaOH) was substituted for soda ash in samples 23 and 24.
Samples 21 and 23 each contain an amount of hydroxide fining agent
(Al(OH).sub.3 in sample 21 and NaOH in sample 23) to generate three
moles of H.sub.2O, whereas samples 22 and 24 each contain an amount
of hydroxide fining agent ((Al(OH).sub.3) in sample 21 and NaOH in
sample 23) to generate six moles of H.sub.2O. Sodium nitrate was
added as an oxidizer to samples 27 and 28.
[0057] Varying amounts of tall oil, an organic fatty acid, were
added to samples 25 and 26. Tall oil burns at melt temperatures,
consuming O.sub.2 to yield CO, CO.sub.2, and water as combustion
products.
[0058] The batched samples were melted at 1525.degree. C. for one
hour and then heated at 1600.degree. C. for one hour to facilitate
the removal of bubbles from the melt. The compositions of the
resulting glasses, expressed in weight percent and mole percent,
are listed in Tables 2b and 2c, respectively.
[0059] Polished cross-sections of glasses obtained from the melts
in Example 2 are shown in FIG. 2. Both aluminum hydroxide and
sodium hydroxide fining agents effectively fine the glass. For a
given amount of water generated by the fining agents (i.e.,
comparing sample 21 vs. sample 23 and sample 22 vs. sample 24),
NaOH appears to be more effective than Al(OH).sub.3 in reducing the
bubble/seed count in the glass.
[0060] Based on these experiments, tall oil does not act as a
fining agent. Instead, as seen in samples 25 and 25 in FIG. 2, the
addition of tall oil to the melt leads to an increase bubble/seed
formation in the glass.
Example 3
[0061] Example 3 compares the effectiveness of the hydroxide fining
agents to hydrogen permeation. The batch materials used for each
sample are listed in Table 3a.
[0062] Samples 31 and 32 were identical samples, each containing
aluminum hydroxide, tin(IV) oxide, and ceria. Samples 31 and 32
were placed in platinum crucibles. Sample 32 was melted with glass
on both sides of the crucible to effectively shut off hydrogen
permeation into the sample. Sample 32 was further contained by a
second refractory crucible backer.
[0063] Samples 33 and 34 were identical samples, containing tin(IV)
oxide, ceria, and 52.78 g of sodium nitrate oxidizer. Sample 33 was
melted with glass on both sides of the crucible to effectively shut
off hydrogen permeation into the sample. Samples 35, 36, and 37
contained SnO.sub.2, CeO.sub.2, and 26.39, 105.55 g, and 52.78 g,
respectively, of NaNO.sub.3. Sample 38 contained SnO.sub.2 and
NaNO.sub.3, but no ceria, whereas sample 9 contained ceria and
NaNO.sub.3, but no tin(IV) oxide.
[0064] The batched samples were melted at 1525.degree. C. for one
hour and then heated at 1600.degree. for one hour to facilitate the
removal of bubbles from the melt. The compositions of the resulting
glasses, expressed in weight percent and mole percent, are listed
in Tables 3b and 3c, respectively.
[0065] Polished cross-sections of glasses obtained from the melts
in Example 3 are shown in FIG. 3. Comparison of samples 31 and 32
shows no apparent difference in the number of bubbles/seeds,
indicating the hydrogen permeation is not the mechanism for
fining/bubble reduction in the melt.
[0066] Samples 33 and 34 do not contain hydride fining agents. In
this case, the glass where H.sub.2 permeation was shut off (sample
33) has fewer bubbles, again showing that H.sub.2 permeation is not
the effective mechanism of the fining package of the present
invention.
[0067] Samples 35-37 demonstrate that varying the amount of
oxidizer has little effect on the number of bubbles/seeds in the
melt. These samples all exhibit low concentrations of
bubbles/seeds, compared to glasses that do not contain the fining
agents described herein (see, for example, sample 39 in FIG. 1).
Similarly, melts containing oxidizer and either tin(IV) oxide alone
(sample 38) or ceria alone (sample 39) yield low concentrations of
bubbles/seeds, showing that the presence of just one of these
fining agents and an oxidizer is still effective in removing
bubbles/seeds.
Example 4
[0068] Example 4 identified fining agent or agents that effectively
reduces the concentration of bubbles/seeds in soda lime glasses.
Nine samples of soda lime crucible melts were prepared. The batch
materials used for each sample are listed in Table 4a.
[0069] The batched samples were melted at 1425.degree. C. for one
hour and then heated at 1525.degree. C. for one hour to facilitate
the removal of bubbles from the melt. The compositions of the
resulting glasses, expressed in weight percent and mole percent,
are listed in Tables 4b and 4c, respectively.
[0070] Sample 41, which contained no fining agent or oxidizer, had
numerous seeds. A substantial reduction in seed concentration was
observed in sample 48, in which talc and tin(IV) oxide were added
to the batch. Lesser reductions in seed concentration was observed
in samples 42 (containing only one fining agent: tin(IV) oxide); 43
(containing tin(IV) oxide and sodium nitate oxidizer); 44
(containing only one fining agent: NaOH); 45 (containing tin(IV)
oxide and NaOH); 46 (containing tin(IV) oxide, NaOH and sodium
nitrate); 47 (containing tin(IV) oxide and calcium hydroxide); and
49 (containing tin(IV) oxide and sodium sulfate oxidizer).
Example 5
[0071] Example 5 identified fining agent or agents that effectively
reduces the concentration of bubbles/seeds in aluminosilicate
glasses that are used in liquid crystal display (LCD) applications.
Nine samples of aluminosilicate crucible melts were prepared. The
batch materials used for each sample are listed in Table 5a.
[0072] The batched samples were melted at 1550.degree. C. for one
hour and then heated at 1625.degree. C. for one hour to facilitate
the removal of bubbles from the melt. The compositions of the
resulting glasses, expressed in weight percent and mole percent,
are listed in Tables 5b and 5c, respectively.
[0073] Very few seeds were observed in sample 54, in which fining
agents aluminum hydroxide and tin(IV) oxide, and barium nitrate
oxidizer were added to the batch. A substantial reduction in seed
concentration was observed for samples 52 (containing tin(IV) oxide
and half the amount of aluminum hydroxide in sample 54) a; 53
(containing tin(IV) oxide and the same amount of aluminum hydroxide
as in sample 54); and 57 (containing sodium hydroxide, the same
amount of aluminum hydroxide as in sample 54, and barium nitrate
oxidizer). The reduction in seed concentration observed in samples
51 and 58 (both containing tin(IV) oxide and barium nitrate
oxidizer) was less than that observed in samples 54, 52, 53, and
57, but still significant. No reduction in seed concentration was
observed in samples 55 (containing twice the tin(IV) oxide
concentration of samples 51-54 and 57-59, and barium nitrate) and
56 ((containing three times the tin(IV) oxide concentration of
samples 51-54 and 57-59, and barium nitrate oxidizer).
Example 6
[0074] Example 6 identified fining agent or agents that effectively
reduces the concentration of bubbles/seeds in aluminosilicate
glasses having high boron concentrations. First and second sets of
samples of crucible melts were prepared. The batch materials used
for each of the first and second set of samples are listed in Table
5a1, respectively.
[0075] The first set of batched samples was melted at 1525.degree.
C. for one hour and then heated at 1625.degree. C. for one hour to
facilitate the removal of bubbles from the melt. The compositions
of the resulting glasses, expressed in weight percent and mole
percent, are listed in Tables 5b1 and 5c1, respectively. The second
set of batched samples was melted at 1529.degree. C. for one hour
and then heated at 1625.degree. C. for one hour to facilitate the
removal of bubbles from the melt. The compositions of the resulting
glasses, expressed in weight percent and mole percent, are listed
in Tables 5b2 and 5c2, respectively.
[0076] Samples 63 and 64 were substantially free of seeds. The
batch material for sample 3 included fining agents tin(IV) oxide
and hydrated alumina, whereas the batch material for sample 64
comprised fining agents arsenic pentoxide, tin(IV) oxide, and
sodium nitrate as an oxidizer. The results obtained for samples 63
and 64 show that the addition of water (in the form of hydrated
alumina) and tin(IV) oxide works as effectively as arsenic. A
substantial reduction in seed concentration was also observed for
samples 61 and 62, in which the batch materials included water (in
the form of hydrated alumina) as the sole fining agent. The results
obtained for samples 61 and 62 indicate that water-containing
hydrates can effectively act as fining agents for glasses over a
range of boron contents.
[0077] Substantial reduction in seed count were also observed for
samples 65 and 66. Fining agents added to the batch materials for
sample 65 included hydrated alumina, cerium oxide, and tin(IV)
oxide. Fining agents added to the batch materials for sample 66
included hydrated alumina, sodium hydroxide, cerium oxide, and
tin(IV) oxide. The results obtained for these samples also
demonstrate the efficacy of water in the form of hydrated alumina
as a fining agent for boron-containing glasses.
[0078] While typical embodiments have been set forth for the
purpose of illustration, the foregoing description should not be
deemed to be a limitation on the scope of the above disclosure and
appended claims. Accordingly, various modifications, adaptations,
and alternatives may occur to one skilled in the art without
departing from the spirit and scope of the present disclosure.
TABLE-US-00001 TABLE 1a Compositions of batch materials, expressed
in grams, for crucible melts described in Example 1. Batch Material
11 12 13 14 15 16 17 18 19 Sand 616.56 616.57 616.59 396.99 616.57
616.58 616.56 616.59 619.67 Alumina 161.71 82.33 0 0 161.71 161.71
161.71 0 162.51 Aluminum hydroxide 0.00 121.40 247.30 120.15 0.00
0.00 0.00 247.30 0.00 Nepheline Syenite 0.00 0.00 0.00 359.48 0.00
0.00 0.00 0.00 0.00 Boric Acid 12.06 12.06 12.06 12.06 12.06 12.06
12.06 12.06 12.06 Soda Ash 227.86 227.84 227.81 165.45 112.69 0
194.96 194.90 228.89 Sodium Hydroxide 0.00 0.00 0.00 0.00 87.27
172.67 0.00 0.00 0.00 Sodium Nitrate 0.00 0.00 0.00 0.00 0.00 0.00
52.78 52.78 0.00 Potassium Carbonate 52.69 52.69 52.69 27.29 52.69
52.69 52.66 52.66 52.98 Magnesia 37.86 37.86 37.86 37.92 37.87
37.87 37.86 37.86 38.07 Limestone 8.23 8.23 8.23 6.30 8.50 8.77
8.31 8.31 8.23 Tin (IV) Oxide 2.31 2.31 2.31 2.31 2.31 2.31 2.31
2.31 0.00 Cerium (IV) Oxide 2.72 2.72 2.72 2.72 2.72 2.72 2.72 2.72
0.00
TABLE-US-00002 TABLE 1b Compositions of glasses prepared from
crucible melts described in Example 1, expressed in weight percent.
Composition (wt %) 11 12 13 14 15 16 17 18 19 SiO.sub.2 61.37 61.37
61.38 61.38 61.37 61.37 61.37 61.37 61.69 Al.sub.2O.sub.3 16.23
16.24 16.24 16.24 16.23 16.23 16.23 16.23 16.32 B.sub.2O.sub.3 0.68
0.68 0.68 0.68 0.68 0.68 0.68 0.68 0.68 Na.sub.2O 13.33 13.33 13.33
13.33 13.33 13.33 13.33 13.33 13.39 K.sub.2O 3.57 3.57 3.57 3.57
3.57 3.57 3.57 3.57 3.59 MgO 3.66 3.66 3.66 3.66 3.66 3.66 3.66
3.66 3.68 CaO 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50
SnO.sub.2 0.23 0.23 0.23 0.23 0.23 0.23 0.23 0.23 0.00 CeO.sub.2
0.27 0.27 0.27 0.27 0.27 0.27 0.27 0.27 0.00 Fe.sub.20.sub.3 0.02
0.02 0.01 0.01 0.02 0.02 0.02 0.01 0.02 Average seeds/cm.sup.3
79.11 0.482 0.384 0.610 0.580 0.677 0.061 0.183 929.7
TABLE-US-00003 TABLE 1c Compositions of glasses prepared from
crucible melts described in Example 1, expressed in mole percent.
Composition (mol %) 11 12 13 14 15 16 17 18 19 SiO.sub.2 65.89
65.89 65.89 65.89 65.89 65.89 65.89 65.89 65.89 Al.sub.2O.sub.3
(Alumina) 10.27 5.27 0 0 10.27 10.27 10.27 0 10.27 Al.sub.2O.sub.3
(Al(OH).sub.3) 0 5 10.27 5 0 0 0 10.27 0 Al.sub.2O.sub.3
(Nepheline) 0 0 0 5.27 0 0 0 0 0 B.sub.2O.sub.3 0.63 0.63 0.63 0.63
0.63 0.63 0.63 0.63 0.63 Na.sub.2O (Soda Ash) 13.91 13.91 13.91
13.91 6.91 0 11.91 11.91 13.91 Na.sub.2O (NaOH) 0 0 0 0 7 13.91 0 0
0 Na.sub.2O (NaNO.sub.3) 0 0 0 0 0 0 2 2 0 K.sub.2O 2.45 2.45 2.45
2.45 2.45 2.45 2.45 2.45 2.45 MgO 5.86 5.86 5.86 5.86 5.86 5.86
5.86 5.86 5.86 CaO 0.57 0.57 0.57 0.57 0.57 0.57 0.57 0.57 0.57
SnO.sub.2 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0 CeO.sub.2 0.10
0.10 0.10 0.10 0.10 0.10 0.10 0.10 0 Average seeds/cm.sup.3 79.11
0.482 0.384 0.610 0.580 0.677 0.061 0.183 929.7
TABLE-US-00004 TABLE 2a Compositions of batch materials, expressed
in grams, for crucible melts described in Example 2. Batch Material
21 22 23 24 25 26 27 28 29 Sand 616.56 616.56 616.56 616.56 616.56
616.56 616.56 189.49 616.56 Alumina 145.77 129.94 161.71 161.71
161.71 161.71 161.71 0 161.71 Aluminum hydroxide 24.22 48.59 0.00
0.00 0.00 0.00 0.00 0.00 0.00 Nepheline Syenite 0.00 0.00 0.00 0.00
0.00 0.00 0.00 699.16 0.00 Boric Acid 12.06 12.06 12.06 12.06 12.06
12.06 12.06 12.06 12.06 Soda Ash 227.86 227.85 178.50 129.15 227.86
227.86 194.96 73.63 227.86 Sodium Hydroxide 0.00 0.00 37.40 74.81
0.00 0.00 0.00 0.00 0.00 Sodium Nitrate 0.00 0.00 0.00 0.00 0.00
0.00 52.78 52.78 0.00 Potassium Carbonate 52.69 52.69 52.69 52.69
52.69 52.69 52.66 3.27 52.69 Magnesia 37.86 37.86 37.86 37.87 37.86
37.86 37.86 37.97 37.86 Limestone 8.23 8.23 8.35 8.46 8.23 8.23
8.31 4.56 8.23 Tin (IV) Oxide 2.31 2.31 2.31 2.31 2.31 2.31 2.31
2.31 2.31 Cerium (IV) Oxide 2.72 2.72 2.72 2.72 2.72 2.72 2.72 2.72
2.72 Fatty Acid, Tall Oil 1.00 5.00
TABLE-US-00005 TABLE 2b Compositions of glasses prepared from
crucible melts described in Example 2, expressed in weight percent.
Compo- sition (wt %) 21 22 23 24 25 26 27 28 29 SiO.sub.2 61.38
61.37 61.37 61.37 61.37 61.37 61.37 61.38 61.37 Al.sub.2O.sub.3
16.23 16.23 16.23 16.23 16.23 16.23 16.23 16.24 16.23
B.sub.2O.sub.3 0.68 0.68 0.68 0.68 0.68 0.68 0.68 0.68 0.68
Na.sub.2O 13.33 13.33 13.33 13.33 13.33 13.33 13.33 13.33 13.33
K.sub.2O 3.58 3.57 3.57 3.57 3.57 3.57 3.57 3.57 3.57 MgO 3.66 3.66
3.66 3.66 3.66 3.66 3.66 3.66 3.66 CaO 0.50 0.50 0.50 0.50 0.50
0.50 0.50 0.50 0.50 SnO.sub.2 0.23 0.23 0.23 0.23 0.23 0.23 0.23
0.23 0.23 CeO.sub.2 0.27 0.27 0.27 0.27 0.27 0.27 0.27 0.27 0.27
Fe.sub.2O.sub.3 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.00 0.02
TABLE-US-00006 TABLE 2c Compositions of glasses prepared from
crucible melts described in Example 2, expressed in mole percent.
Composition (mol %) 21 22 23 24 25 26 27 28 29 SiO.sub.2 65.89
65.89 65.89 65.89 65.89 65.89 65.89 65.89 65.89 Al.sub.2O.sub.3
(Alumina) 9.27 8.27 10.27 10.27 10.27 10.27 10.27 0 10.27
Al.sub.2O.sub.3 (Al(OH).sub.3) 1 2 0 0 0 0 0 0 0 Al.sub.2O.sub.3
(Nepheline) 0 0 0 0 0 0 0 10.27 0 B.sub.2O.sub.3 0.63 0.63 0.63
0.63 0.63 0.63 0.63 0.63 0.63 Na.sub.2O (Soda Ash) 13.91 13.91
10.91 7.91 13.91 13.91 11.91 11.91 13.91 Na.sub.2O (NaOH) 0 0 3 6 0
0 0 0 0 Na.sub.2O (NaNO.sub.3) 0 0 0 0 0 0 2 2 0 K.sub.2O 2.45 2.45
2.45 2.45 2.45 2.45 2.45 2.45 2.45 MgO 5.86 5.86 5.86 5.86 5.86
5.86 5.86 5.86 5.86 CaO 0.57 0.57 0.57 0.57 0.57 0.57 0.57 0.57
0.57 SnO.sub.2 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10
CeO.sub.2 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10
TABLE-US-00007 TABLE 3a Compositions of batch materials, expressed
in grams, for crucible melts described in Example 3. Batch Material
31 32 33 34 35 36 37 38 39 Sand 616.59 616.59 616.56 616.56 616.56
616.56 188.45 616.76 616.36 Alumina 0 0 161.71 161.71 161.71 161.71
0 161.71 161.61 Aluminum hydroxide 247.30 247.30 0.00 0.00 0.00
0.00 0.00 0.00 0.00 Nepheline Syenite 0.00 0.00 0.00 0.00 0.00 0.00
699.16 0.00 0.00 Boric Acid 12.06 12.06 12.06 12.06 12.06 12.06
12.06 12.06 12.06 Soda Ash 227.81 227.81 194.96 194.96 211.41
162.05 73.33 194.97 194.78 Sodium Nitrate 0.00 0.00 52.78 52.78
26.39 105.55 52.78 52.78 52.78 Potassium Carbonate 52.69 52.69
52.66 52.66 52.67 52.64 3.15 52.66 52.66 Magnesia 37.86 37.86 37.86
37.86 37.86 37.86 37.97 37.86 37.86 Limestone 8.23 8.23 8.31 8.31
8.27 8.38 4.55 8.31 8.31 Tin (IV) Oxide 2.31 2.31 2.31 2.31 2.31
2.31 2.31 4.71 0.00 Cerium Oxide 2.72 2.72 2.72 2.72 2.72 2.72 2.72
0.00 5.35
TABLE-US-00008 TABLE 3b Compositions of glasses prepared from
crucible melts described in Example 3, expressed in weight percent.
Compo- sition (wt %) 31 32 33 34 35 36 37 38 39 SiO.sub.2 61.38
61.38 61.37 61.37 61.37 61.37 61.38 61.40 61.36 Al.sub.2O.sub.3
16.24 16.24 16.23 16.23 16.23 16.23 16.24 16.24 16.23
B.sub.2O.sub.3 0.68 0.68 0.68 0.68 0.68 0.68 0.68 0.68 0.68
Na.sub.2O 13.33 13.33 13.33 13.33 13.33 13.33 13.33 13.33 13.32
K.sub.2O 3.57 3.57 3.57 3.57 3.57 3.57 3.57 3.57 3.57 MgO 3.66 3.66
3.66 3.66 3.66 3.66 3.66 3.66 3.66 CaO 0.50 0.50 0.50 0.50 0.50
0.50 0.50 0.50 0.50 SnO.sub.2 0.23 0.23 0.23 0.23 0.23 0.23 0.23
0.47 0.00 CeO.sub.2 0.27 0.27 0.27 0.27 0.27 0.27 0.27 0.00 0.53
Fe.sub.2O.sub.3 0.01 0.01 0.02 0.02 0.02 0.02 0.00 0.02 0.02
TABLE-US-00009 TABLE 3c Compositions of glasses prepared from
crucible melts described in Example 3, expressed in mole percent.
Composition (mol %) 31 32 33 34 35 36 37 38 39 SiO.sub.2 65.89
65.89 65.89 65.89 65.89 65.89 65.89 65.89 65.89 Al.sub.2O.sub.3
(Alumina) 0 0 10.27 10.27 10.27 10.27 0 10.27 10.27 Al.sub.2O.sub.3
(Al(OH).sub.3) 10.27 10.27 0 0 0 0 0 0 0 Al.sub.2O.sub.3
(Nepheline) 0 0 0 0 0 0 10.27 0 0 B.sub.2O.sub.3 0.63 0.63 0.63
0.63 0.63 0.63 0.63 0.63 0.63 Na.sub.2O (Soda Ash) 13.91 13.91
11.91 11.91 12.91 9.91 11.91 11.91 11.91 Na.sub.2O (NaNO.sub.3) 0 0
2 2 1 4 2 2 2 K.sub.2O 2.45 2.45 2.45 2.45 2.45 2.45 2.45 2.45 2.45
MgO 5.86 5.86 5.86 5.86 5.86 5.86 5.86 5.86 5.86 CaO 0.57 0.57 0.57
0.57 0.57 0.57 0.57 0.57 0.57 SnO.sub.2 0.10 0.10 0.10 0.10 0.10
0.10 0.10 0.2 0 CeO.sub.2 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0
0.2
TABLE-US-00010 TABLE 4a Compositions of batch materials, expressed
in grams, for crucible melts described in Example 4. Batch Material
41 42 43 44 45 46 47 48 49 Sand 584.01 564.43 564.43 584.02 564.44
558.44 584.59 519.71 584.01 Alumina 13.55 13.59 13.58 13.54 13.58
13.44 13.67 13.71 13.55 Soda Ash 191.49 190.94 176.68 84.28 84.00
83.18 191.49 191.41 184.36 Sodium Nitrate 0.00 0.00 22.87 0.00 0.00
22.65 0.00 0.00 0.00 Magnesia 32.25 32.17 32.17 32.25 32.18 31.86
32.48 0 32.25 Limestone 104.02 103.88 103.91 104.28 104.14 102.96 0
104.25 104.03 Sodium hydroxide 0.00 0.00 0.00 81.25 81.04 80.21*
0.00 0.00 0.00 Lime hydrate 0.00 0.00 0.00 0.00 0.00 0.00 94.99
0.00 0.00 Talc 0.00 0.00 0.00 0.00 0.00 0.00 0.00 103.47 0.00 Tin
(IV) Oxide 0.00 20.00 20.00 0.00 20.00 20.00 0.00 0.00 0.00 Sodium
sulfate 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 9.53 *CaOH
substituted for NaOH
TABLE-US-00011 TABLE 4b Compositions of glasses prepared from
crucible melts described in Example 4, expressed in weight percent.
Compo- sition (wt %) 41 42 43 44 45 46 47 48 49 SiO.sub.2 72.94
72.75 72.75 72.94 72.75 72.00 72.94 72.86 72.46 Al.sub.2O.sub.3
1.89 1.89 1.89 1.89 1.89 1.87 1.89 1.89 1.88 Na.sub.2O 13.96 13.92
13.92 13.97 13.92 14.81 13.96 13.95 13.87 MgO 4.08 4.07 4.07 4.08
4.07 4.03 4.08 4.07 4.05 CaO 7.09 7.08 7.08 7.09 7.08 7.00 7.09
7.08 7.04 SnO.sub.2 0.00 0.25 0.25 0.00 0.25 0.25 0.00 0.00 0.00
SO.sub.3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.67
Fe.sub.2O.sub.3 0.04 0.04 0.04 0.04 0.04 0.04 0.05 0.15 0.04
TABLE-US-00012 TABLE 4c Compositions of glasses prepared from
crucible melts described in Example 4, expressed in mole percent.
Composition (mol %) 41 42 43 44 45 46 47 48 49 SiO.sub.2 72. 72.
72. 72. 72. 72. 72. 72. 72. Al.sub.2O.sub.3 1.1 1.1 1.1 1.1 1.1 1.1
1.1 1.1 1.1 Na.sub.2O (Soda Ash) 13.4 13.4 12.4 5.9 5.9 5.9 13.4
13.4 12.9 Na.sub.2O (NaNO.sub.3) 0 0 1 0 0 1 0 0 0 MgO 6 6 6 6 6 6
6 0 6 CaO 7.5 7.5 7.5 7.5 7.5 7.5 0 7.5 7.5 Na.sub.2O 0 0 0 7.5 7.5
7.5 0 0 0 CaO 0 0 0 0 0 0 7.5 0 0 MgO 0 0 0 0 0 0 0 6 0 SnO.sub.2 0
0.1 0.1 0 0.1 0.1 0 0 0 Na.sub.2O 0 0 0 0 0 0 0 0 .5
TABLE-US-00013 TABLE 5a Compositions of batch materials, expressed
in grams, for crucible melts described in Example 5. Batch Material
51 52 53 54 55 56 57 58 59 Sand 555.02 555.04 555.06 553.96 553.92
552.82 550.55 623.69 623.73 Alumina 192.23 99.12 0 0 191.84 191.54
0 182.65 0 Alumina, hydrated 0 142.40 293.98 293.37 0 0 291.70 0
279.33 Magnesia 14.06 14.06 14.06 13.96 13.96 13.96 13.96 29.26
29.26 Limestone 59.39 59.39 59.39 59.39 59.39 59.21 59.02 79.24
79.24 Strontium carbonate 5.16 5.16 5.16 5.16 5.16 5.16 5.02 29.34
29.34 Barium carbonate 51.92 51.92 51.92 51.79 51.79 51.79 51.53
80.48 80.48 Lanthanum oxide 111.63 111.63 111.63 111.42 111.42
111.22 110.72 0 0 Yttrium oxide 29.40 29.40 29.40 29.30 29.30 29.30
29.20 0 0 Tin (IV) Oxide 2.01 2.01 2.01 3.91 3.91 5.92 1.91 2.21
2.21 Barium nitrate 34.32 34.32 34.32 34.15 34.15 34.15 33.97 38.61
38.61 Boric acid 0.00 0.00 0.00 0.00 0.00 0.00 0.00 22.70 22.70
Sodium hydroxide 9.81
TABLE-US-00014 TABLE 5b Compositions of glasses prepared from
crucible melts described in Example 5, expressed in weight percent.
Compo- sition (wt %) 51 52 53 54 55 56 57 58 59 SiO.sub.2 54.74
54.74 54.74 54.65 54.64 54.52 54.31 61.45 61.45 Al.sub.2O.sub.3
19.08 19.08 19.08 19.05 19.05 19.01 18.94 18.14 18.14 MgO 1.42 1.42
1.42 1.41 1.41 1.41 1.41 2.91 2.91 CaO 3.19 3.19 3.19 3.19 3.19
3.18 3.17 4.25 4.25 SrO 0.42 0.42 0.42 0.42 0.42 0.41 0.41 2.10
2.10 BaO 5.90 5.90 5.90 5.88 5.88 5.88 5.85 8.31 8.31
La.sub.2O.sub.3 10.93 10.93 10.93 10.92 10.92 10.89 10.85 0.00 0.00
Y.sub.2O.sub.3 2.90 2.90 2.90 2.89 2.89 2.89 2.88 0.00 0.00
SnO.sub.2 0.20 0.20 0.20 0.39 0.39 0.58 0.19 0.22 0.22
B.sub.2O.sub.3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.26 1.26
Na.sub.2O 0.00 0.00 0.00 0.00 0.00 0.00 0.79 0.00 0.00
Fe.sub.2O.sub.3 0.03 0.02 0.02 0.02 0.03 0.03 0.02 0.03 0.03
NO.sub.2 1.19 1.19 1.19 1.18 1.18 1.18 1.17 1.33 1.33 Cl.sup.- 0.01
0.01 0.01 0.01 0.01 0.01 0.01 0.00 0.00
TABLE-US-00015 TABLE 5c Compositions of glasses prepared from
crucible melts described in Example 5, expressed in mole percent.
Compo- sition (mol %) 51 52 53 54 55 56 57 58 59 SiO.sub.2 70.86
70.86 70.86 70.86 70.86 70.86 70.86 70.6 70.6 Al.sub.2O.sub.3 14.56
7.56 0 0 14.56 14.56 0 12.28 0 Al.sub.2O.sub.3 0 7 14.56 14.56 0 0
14.56 0 12.28 MgO 2.74 2.74 2.74 2.74 2.74 2.74 2.74 4.99 4.99 CaO
4.43 4.43 4.43 4.43 4.43 4.43 4.43 5.23 5.23 SrO .31 .31 .31 .31
.31 .31 .31 1.40 1.40 BaO 1.99 1.99 1.99 1.99 1.99 1.99 1.99 2.74
2.74 La.sub.2O.sub.3 2.61 2.61 2.61 2.61 2.61 2.61 2.61 0 0
Y.sub.2O.sub.3 1.00 1.00 1.00 1.00 1.00 1.00 1.00 0 0 SnO.sub.2
0.10 0.10 0.10 0.2 0.2 0.3 0.10 0.10 0.10 BaO 1 1 1 1 1 1 1 1 1
B.sub.2O.sub.3 0 0 0 0 0 0 0 1.25 1.25 Na.sub.2O 0 0 0 0 0 0 1 0
0
TABLE-US-00016 TABLE 6a1 Compositions of batch materials, expressed
in grams, for crucible melts described in Example 6. Batch Material
61 62 63 64 Sand 608.27 616.75 568.66 609.37 Alumina 84.32 72.69
81.04 173.87 Boric oxide 29.38 52.59 118.86 118.76 Soda Ash 199.39
176.49 98.95 82.7 Potassium carbonate 46.21 40.91 23.11 23.1
Lithium carbonate 10.49 21.23 52.2 51.95 Magnesia 29.26 22.14 -0.13
-0.14 Limestone 6.004 4.321 -0.48 -0.45 Tin (IV) oxide 0 0 46 0
Arsenic Pentoxide 0 0 0 6.986 Sodium nitrate 0 0 0 26.04 Alumina,
hydrated 143.32 145 142.4 0
TABLE-US-00017 TABLE 6a2 Compositions of batch materials, expressed
in grams, for crucible melts described in Example 6. Batch Material
66 67 Sand 350.12 350.11 Alumina 0 79.05 Alumina, hydrated 241.72
119.71 Boric acid 116.71 116.71 Soda ash 195.24 97.92 Sodium
hydroxide 0 73.77 Potassium carbonate 57.69 57.69 Magnesia 15.07
15.07 Limestone 3.956 4.191 Tin (IV) oxide 230 230 Cerium (IV)oxide
26 26
TABLE-US-00018 TABLE 6b1 Compositions of glasses prepared from
crucible melts of batch compositions listed in Table 6a1 and
described in Example 6, expressed in weight percent. Composition
(wt %) 61 62 63 64 SiO.sub.2 60.66 61.5 60.83 60.74 Al.sub.2O.sub.3
17.89 16.84 17.49 17.46 B.sub.2O.sub.3 2.9 5.19 11.73 11.72
Na.sub.2O 11.69 10.35 5.82 5.81 K.sub.2O 3.14 2.78 1.57 1.57 MgO
0.42 0.85 2.09 2.08 CaO 2.89 2.19 0 0 SnO.sub.2 0.39 0.29 0 0
As.sub.2O.sub.3 0 0 0.46 0 SO.sub.3 0 0 0 0.6 Sb.sub.2O.sub.3 0 0 0
0 Fe.sub.2O.sub.3 0 0 0 0 H.sub.2O 0.02 0.02 0.01 0.02 Cl-- 0 0 0
0
TABLE-US-00019 TABLE 6b2 Compositions of glasses prepared from
crucible melts of batch compositions listed in Table 6a2 and
described in Example 6, expressed in weight percent. Composition
(wt %) 65 66 SiO.sub.2 60.03 60.03 Al.sub.2O.sub.3 15.77 15.77
B.sub.2O.sub.3 6.58 6.58 Na.sub.2O 11.45 11.45 K.sub.2O 3.92 3.92
MgO 1.49 1.49 CaO 0.26 0.26 SnO.sub.2 0.23 0.23 CeO.sub.2 0.26 0.26
Fe.sub.2O.sub.3 0.01 0.01 H.sub.2O 0 0 Cl-- 0 0
TABLE-US-00020 TABLE 6c1 Compositions of glasses prepared from
crucible melts of batch compositions listed in Table 6a1 and
described in Example 6, expressed in mole percent. Composition (wt
%) 61 62 63 64 SiO.sub.2 66.04 66.21 66.7 66.7 Al2O.sub.3 5.48 4.68
5.3 11.3 B.sub.2O.sub.3 2.72 4.82 11.1 11.1 Na.sub.2O 12.37 10.83
6.2 5.2 K.sub.2O 2.18 1.91 1.1 1.1 Li.sub.2O 0.92 1.84 4.6 4.6 MgO
4.69 3.52 0 0 CaO 0.46 0.34 0 0 SnO.sub.2 0 0 0.2 0 As.sub.2O.sub.3
0 0 0 0.2 Na.sub.2O 0 0 0 1 Al.sub.2O.sub.3 6 6 6 0
TABLE-US-00021 TABLE 6c2 Compositions of glasses prepared from
crucible melts of batch compositions listed in Table 6a2 and
described in Example 6, expressed in mole percent. Composition (wt
%) 65 66 SiO.sub.2 65.23 65.23 Al.sub.2O.sub.3 0 5.1
Al.sub.2O.sub.3 10.1 5 B.sub.2O.sub.3 6.17 6.17 Na.sub.2O 12.1 6.1
Na.sub.2O 0 6 K.sub.2O 2.72 2.72 MgO 2.41 2.41 CaO 0.3 0.3
SnO.sub.2 0.1 0.1 CeO.sub.2 0.1 0.1
* * * * *