Title of Invention

A FLOAT BATH BOTTOM REFRACTORY BRICK AND PROCESS OF PRODUCTION THEREOF

Abstract A float bath bottom refractory brick and process of production thereof are disclosed. The process comprises adding a potassium compound, as represented by mass percentage based on the following oxides, so that a K2O content in the float bath bottom refractory brick to be produced would be from 2 to 4% 10 to a clayey material comprising from 30 to 45% of Al2O3 and from 50 to 65% of SiO2, followed by firing. The float bath bottom refractory brick has a composition, as represented by mass percentage based on the following oxides, from 30 to 45% of A12O3, from 50 to 65% of Si2O2, at most 1% of Na2O and 2 to 4% of K2O.
Full Text DESCRIPTION
TECHNICAL FIELD
The present invention relates to a refractory brick
to be used for the bottom of a float bath i.e. a tin bath
in float process for production of plate glass, and a
process for its production.
BACKGROUND ART
In production of plate glass by float process, a
float bath on which molten glass is discharged from a
glass melting furnace and formed into a ribbon, comprises
a metal casing lined with a refractory brick, and is
filled with molten tin. Glass molten in the melting
furnace is discharged on the surface of the tin bath,
flows on the tin bath and advances to be formed into
smooth plate glass. As usual plate glass (soda lime
glass) for buildings, automobiles, etc., glass containing
about 15 mass% of Na2O is used. Such glass is in contact
with the molten tin at its bottom surface, and at the
interface, Na2O in the glass diffuses into the tin bath.
As a bottom refractory brick for such a float bath,
Chamotte brick containing Al2O3 and SiO2 as the main
components and having a mineral phase mainly comprising
Mullite and Cristobalite is employed in view of
characteristics, usefulness, cost, etc.
Na2O contained in the glass infiltrates from the
surface of the float bath bottom refractory brick into
its inside via the tin bath to form Nepheline, thereby to
form a metamorphic phase different from the matrix of the
refractory brick. The metamorphic phase increases in
thickness with time in a direction perpendicular to the
surface of the tin bath. Since Nepheline has a thermal
expansion coefficient about three times as high as that
of Mullite, peeling of the metamorphic phase from the
matrix due to volume expansion of the metamorphic phase
or due to thermal stress accompanying the change in
temperature conditions of the float bath, i.e. so called
flaking phenomena occur. The flakes, which have a
specific gravity smaller than that of the molten tin,
float up in the tin bath and scar the glass or generate
foreign matters, and they can be a major cause of
inhibiting smooth production of plate glass.
Heretofore, as a float bath bottom refractory brick
which inhibits such flaking phenomena, one having a total
alkali metal content up to 3% to a clay portion (Patent
Document 1) and one employing a silicate material
containing an alkali oxide having a particle diameter of
at most 0.09 mm in an amount of from 1 to 3 mass% (Patent
Document 2) have been disclosed. However, specifically,
they contain two alkali oxides i.e. from 0.1 to 0.4% of
Na20 and from 0.8 to 1.2% of K2O, and they will not
contain 2% or more of K2O. Further, one employing a
material having a particle diameter of at most 90 µm,
which has a total content of Na20 and K20 of at most 1
mass% (Patent Document 3) and the like have been known.
However, no document discloses effects of K20 as
disclosed in the present invention.
Patent Document 1: JP-A-6-122543
Patent Document 2: JP-A-6-340471
Patent Document 3: JP-A-2003-277134
DISCLOSURE OF THE INVENTION
PROBLEMS THAT THE INVENTION IS TO SOLVE
It is an object of the present invention to provide
a process for suitably producing a float bath bottom
refractory brick for production of glass plate which
suppresses the above-described flaking phenomena and
which is free from defects such as scars and foreign
matters. Further, it is to provide a float bath bottom
refractory brick which can suppress the above-described
flaking phenomena, and a float bath employing the above
float bath bottom refractory brick. Further, it is to
provide a process for producing glass by means of a float
bath employing the above float bath bottom refractory
brick.
MEANS OF SOLVING THE PROBLEMS
The present invention has been made to achieve the
above objects, and provides a process for producing a
float bath bottom refractory brick, which comprises
adding a potassium compound to a clayey material
comprising, as represented by mass percentage based on
the following oxides, from 30 to 45% of Al203 and from 50
to 65% of SiO2, followed by firing.
The present invention further provides a process for
producing a float bath bottom refractory brick, which
comprises using a clayey material comprising, as
represented by mass percentage based on the following
oxides, from 30 to 45% of A12O3 and from 50 to 65% of SiO2
and having a Na20 content of at most 1%, wherein a
potassium compound is added so that the K20 content in
the float bath bottom refractory brick to be produced
would be from 2 to 4%.
The present invention further provides a process for
producing a float bath bottom refractory brick, which
comprises adding a potassium compound to a clayey
material comprising, as represented by mass percentage
based on the following oxides, from 30 to 45% of Al203
and from 50 to 65% of SiO2, kneading, molding, firing and
then crushing the material to obtain a granular
refractory material, kneading the granular refractory
material, and molding it, followed by firing, wherein
control is made so that in a fine granular portion having
a grain size less than 90 urn in the above granular
refractory material, the K2O content would be from 2 to
4%, and the Na2O content would be at most 1%.
The present invention further provides the above
process for producing a float bath bottom refractory
brick, wherein the granular refractory material contains
from 2 0 to 60 mass% of a fine granular portion having a
grain size less than 90 urn which contains from 2 to 4% of
K20 and at most 1% of Na20.
The present invention further provides the above
process for producing a float bath bottom refractory
brick, wherein control is made so that in a medium
granular portion having a grain size of from 9 0 µm to 1
mm and a fine granular portion having a grain size less
than 90 µm in the above granular refractory material, as
represented by mass percentage based on the following
oxides, the K20 content would be from 2 to 4%, and the
Na20 content would be at most 1%.
The present invention further provides the above
process for producing a float bath bottom refractory
brick, wherein the granular refractory material contains
from 20 to 6 0 mass% of the medium granular portion having
a grain size of from 90 µm to 1 mm.
The present invention further provides the above
process for producing a float bath bottom refractory
brick, which comprises kneading, molding, firing and then
crushing a clayey material comprising, as represented by
mass percentage based on the following oxides, from 3 0 to
45% of Al203 and from 50 to 65% of Si02, to obtain a
granular refractory material, adding a granular potassium
compound to the granular refractory material, kneading,
molding and firing the mixture, wherein control is made
so that the K20 content in the float bath bottom
refractory brick to be produced, would be from 2 to 4%.
The present invention further provides a float bath
bottom refractory brick having a composition which
comprises, as represented by mass percentage based on the
following oxides, from 30 to 45% of A1203, from 50 to 65%
of Si02, at most 1% of Na20 and from 2 to 4% of K20.
The present invention further provides the above
float bath bottom refractory brick, which has at most 10%
of a Cristobalite crystalline phase.
The present invention further provides the above
float bath bottom refractory brick, which has at least
20% of a Mullite crystalline phase.
The present invention further provides a float bath
having a bottom made of the above brick.
The present invention further provides a process for
producing plate glass, which comprises using the above
float bath.
EFFECTS OF THE INVENTION
The float bath bottom refractory brick to be produced
by the present invention has a glass phase rich in K20.
Therefore, infiltration of Na20 from the surface of the
refractory brick into the inside via the tin bath can be
suppressed, whereby formation of Nepheline can be
suppressed. Further, the glass phase absorbs volume
expansion of the formed Nepheline metamorphic phase and
suppresses flaking phenomena. Accordingly, the life of a
float bath employing the float bath bottom refractory
brick can be prolonged. Further, in a process for
producing plate glass employing the float bath, defects
(scars) of glass accompanying the flaking phenomena can
be reduced, whereby improvement in quality and rate of
non-defective products will be achieved.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 illustrates results of X-ray diffraction
measurement in a case where a molded product of Example 1
is fired at 1,300°C.
Fig. 2 illustrates results of X-ray diffraction
measurement in a case where a molded product of Example 1
is fired at 1,350°C.
Fig. 3 illustrates proportions of crystalline phases
in a case where a molded product of Example 1 is fired at
1,300°C.
Fig. 4 illustrates proportions of crystalline phases
in a case where a molded product of Example 1 is fired at
1,350°C.
Fig. 5 illustrates results of X-ray diffraction
measurement in a case where a molded product of Example 2
is fired at 1,300°C.
Fig. 6 illustrates results of X-ray diffraction
measurement in a case where a molded product of Example 2
is fired at 1,350°C.
Fig. 7 illustrates proportions of crystalline phases
in a case where a molded product of Example 2 is fired at
1,300°C.
Fig. 8 illustrates proportions of crystalline phases
in a case where a molded product of Example 2 is fired at
1,350°C.
BEST MODE FOR CARRYING OUT THE INVENTION
As a raw material of the float bath bottom
refractory brick of the present invention, a clayey
material comprising, as represented by mass percentage of
the following oxides, from 30 to 45% of A120 and from 50
to 65% of SiO2 is employed. For the float bath bottom
refractory brick, as a clayey material, one having a Na20
content of at most 1% is used so as to reduce
infiltration of the sodium component from glass diffused
in the tin bath. In description of the composition in
the present invention, % represents mass% unless
otherwise specified.
As an additive to be a K20 source in the present
invention, various potassium compounds may be used, and
it is preferred to use potassium carbonate which is
easily available at a relatively low cost. If the K20
content is less than 2 mass%, the proportion of
Cristobalite tends to be large, whereby it tends to be
difficult to suppress the rate of infiltration of Na20
from glass into the refractory brick via the tin bath,
and it tends to be difficult to prevent flaking
phenomena. On the other hand, if the K20 content exceeds
4 mass%, the Mullite phase after firing tends to reduce,
and the glass phase tends to increase correspondingly,
whereby high temperature properties of the refractory
brick tend to be impaired.
As a specific process of using a clayey material
comprising from 30 to 45% of Al2O3 and from 50 to 65% of
SiO2 and having a Na2O content of at most 1%, and adding
a potassium compound so that the K2O content in the float
bath bottom refractory brick to be produced would be from
2 to 4%, a process of adding a potassium compound as a
K2O source to the above clayey material comprising from
30 to 45% of A12O3 and from 50 to 65% of SiO2, kneading,
molding, firing and then crushing the material to obtain
a granular refractory material, kneading the granular
refractory material, molding it into a shape of desired
float bath bottom refractory brick, followed by firing to
produce a float bath bottom refractory brick (hereinafter
referred to as a first production process) and a process
for producing a float bath bottom refractory brick, which
comprises adding a granular potassium compound to the
clayey material comprising from 3 0 to 45% of Al2O3 and
from 50 to 65% of SiO2, kneading and molding the mixture
into a shape of a desired float bath bottom refractory
brick, followed by firing (hereinafter referred to as a
second production process) may, for example, be
mentioned. However, the method is not limited thereto.
In a case where K2O is contained in the clayey
material in a small amount, the addition amount of the
potassium compound is adjusted so that the K20 content in
the float bath bottom refractory brick to be produced
would be from 2 to 4% considering the content of the K20
contained.
With respect to the reaction with Na20 at the surface
of the float bath bottom refractory brick, as described
above, the reaction rate with Na20 is suppressed by use
of the material containing from 2 to 4% of K20, and the
larger the specific surface area of the particles, the
higher the reactivity. On the other hand, the float bath
bottom refractory brick is produced by kneading, molding
and firing a granular refractory material for production
of the brick, and in view of characteristics required for
the refractory brick to be produced, usually as the
granular refractory material, one containing from 2 0 to
60% of a fine granular portion having a grain size less
than 90 urn, from 20 to 60% of a medium granular portion
having a grain size of from 90 urn to 1 mm and from 20 to
60% of a coarse granular portion having a grain size
exceeding 1 mm, is usually used. With respect to a float
bath bottom refractory block produced by using such a
granular refractory material, a portion comprising the
fine granular portion is most likely to be infiltrated
and eroded by the sodium component from glass diffused in
the tin bath, the medium granular portion is second
likely to be eroded, and the coarse granular portion is
relatively less likely to be eroded. Accordingly, in
order to reduce particularly the infiltration of sodiµm,
it is preferred to use a granular refractory material
controlled so that in the fine granular portion having a
grain size less than 90 µm, the K20 content would be from
2 to 4% and the Na20 content would be at most 1%.
Further, it is more preferred to employ one controlled so
that in the fine granular portion having a grain size
less than 90 µm and in the medium granular portion having
a grain size of from 90 µm to 1 mm, the K20 content would
be from 2 to 4% and the Na20 content would be at most 1%.
It is more preferred to employ one controlled so that in
the coarse granular portion having a grain size exceeding
1 mm, the K20 and Na20 contents are as defined above,
that is, in all granular portions, the K20 content would
be from 2 to 4% and the Na20 content would be at most 1%.
As mentioned above, by use of a refractory brick having a
fine granular portion comprising the above material, for
the float bath bottom, the rate of formation of Nepheline
at the surface can be suppressed, and flaking phenomena
can preferably be prevented.
In the first production process, it is preferred
that the granular refractory material containing the K20
source is kneaded,, molded and dried, and then the
resulting molded product is fired at a temperature of
from 1,200°C to 1,400°C. If the molded product is fired
at a temperature lower than 1,200°C, the fired product
will not be stable in terms of mineral phase, and if it
is fired at a temperature higher than 1,400°C, the
Mullite phase after firing tends to be small,
specifically, the proportion of the Mullite crystalline
phase will be less than 20%, and the glass phase tends to
excessively increase correspondingly, whereby high
temperature properties of the refractory brick may be
impaired. The fired molded product is crushed by a
crusher and classified into coarse particles having grain
sizes exceeding 1 mm, medium particles having grain sizes
of from 90 µm to 1 mm and fine particles having grain
sizes less than 90 µm. In such a manner, a material for
production of a float bath bottom refractory brick,
controlled so than the K20 content would be from 2 to 4
mass%, is obtained. Then, the material is kneaded and
molded into a shape of a desired float bath bottom
refractory brick, dried and fired at a temperature within
a range of from 1,200°C to 1,400°C to obtain a float bath
bottom refractory brick.
In the second production process, in a case where
the clayey material is kneaded, molded, fired and then
crushed to obtain a granular refractory material, to
which a granular potassium compound as a K20 source is
added, the additive as the K20 source has to be uniformly-
dispersed in the Al203-Si02 clayey material, and
accordingly the particles size is preferably at least
matched to the particles size of the material. More
preferably, the addit ive as the K20 source is
preliminarily finely pulverized to a particle size
smaller than that of the fine granular portion of the
material and then kneaded with the clayey material.
When the clayey material originally contains a
desired amount of K20, namely, when a clayey material
comprising from 30 to 45% of Al203, from 50 to 65% of
Si02, at most 1% of Na20 and from 2 to 4% of K20 is used
to produce a float bath bottom refractory brick, which is
used for the float bath bottom, the rate of formation of
Nepheline at the surface can be suppressed, and flaking
phenomena can preferably be prevented.
In the float bath bottom refractory brick
comprising, on the basis of the following oxides, from 3 0
to 45% of Al203, from 50 to 65% of Si02 and at most 1% of
Na20, a proportion of the Cristobalite crystalline phase
higher than 10% means a relatively small amount of the
glass phase in the refractory brick, and absorption of
volume expansion of Nepheline formed on the surface by a
reaction with Na20 from glass infiltrated into the
refractory brick via the tin bath, by the glass phase,
tends to be difficult, and prevention of flaking
phenomena tends to be difficult, such being unfavorable.
The proportion of the Cristobalite crystalline phase
is represented by the percentage of (the mass of
Cristobalite)/{(the mass of Cristobalite)+(the mass of
Mullite)}, and the mass of Cristobalite and the mass of
Mullite can be obtained by employing analytical curves
preliminarily prepared from intensity peaks of
Cristobalite and Mullite measured by an X-ray diffraction
apparatus (8/29 method, Cu-Kal rays).
As a measurement method by an X-ray diffraction
apparatus, the intensity peak of a powdered sample is
measured by a powder X-ray diffraction apparatus, which
is compared with an analytical curve preliminarily
prepared by peak intensities of samples having the
proportions of Cristobalite and Mullite changed in five
stages, thereby to determine the proportion.
On the other hand, in the float bath bottom
refractory brick, a proportion of the Mullite crystalline
phase less than 20% means a relatively large amount of
the glass phase in the refractory brick, and in such a
case, high temperature properties of the refractory brick
tend to be impaired.
The proportion of the Mullite crystalline phase is
represented by the percentage of (the mass of
Mullite)/{(the mass of Cristobalite)+(the mass of
Mullite)}, and the mass of Cristobalite and the mass of
Mullite are measured by the above-described method of
employing an X-ray diffraction apparatus.
If a large brick such as the float bath bottom
refractory brick is produced by press molding by means of
e.g. an oil hydraulic press, laminar defects (lamination)
may form in a plane direction perpendicular to the
direction of the pressure. If the refractory brick is
used for the float bath bottom in a state where the
defects are in parallel with glass in the float bath,
peeling of Nepheline formed by a reaction with Na20 from
glass infiltrated into the refractory brick via the tin
bath from the surface of the refractory brick due to its
volume expansion, i.e. flaking phenomena may be more
accelerated. Accordingly, the direction of pressure at
the time of press molding is preferably such a direction
that the possible direction of lamination would be
perpendicular to glass in the float bath, considering the
direction of installation of the refractory brick in the
float bath.
The float bath bottom refractory brick produced by
any one of the above processes preferably have a porosity
within a range of from 15 to 20%, a bulk specific gravity
within a range of from 2.1 to 2.3 and a compressive
strength within a range of from 3 0 to 70 MPa, so as to
satisfy mechanical strength, etc. as a structure.
Further, in the float bath for production of plate
glass employing the above float bath bottom refractory
brick, flaking phenomena of the float bath bottom
refractory brick can be suppressed, that is, the life of
the float bath bottom refractory brick can be prolonged,
whereby the time period until the float bath bottom
refractory brick is exchanged with the float bath shut
down, will be prolonged. Accordingly, the efficiency of
the float bath will improve, and the cost for exchange
relative to the operation time, can be suppressed to be
relatively low.
Further, in the process for producing glass
employing the float bath employing the above float bath
bottom refractory brick, defects (scars) of glass
accompanying flaking phenomena are reduced, the quality
tends to improve, and the rate of non-defective products
tends to increase. Accordingly, the cost for production
of glass can be suppressed low.
EXAMPLES
Now, the present invention will be explained in
further detail with reference to Examples and Comparative
Examples.
With respect to an X-ray diffraction measurement
method, measurement was carried out by means of X Pert-
MPD (?/2? method, Cu-Ka1 rays) manufactured by PHILIPS
employing a powder as a sample. Five types of samples
with ratios of Mullite to Cristobalite of 100:0, 75:25,
50:50, 25:75 and 0:100 were preliminarily subjected to
measurement to obtain an analytical curve from the ratios
and the X-ray peak intensities.
Chemical analysis values of Al203-Si02 materials used
in Examples 1 and 2, as represented by mass percentage
based on oxides, are shown in Table 1. The clayey-
material of the material A contains 1.1 massl of K20, and
the clayey material of the material B contains 0.3 massl
of K20.

EXAMPLE 1
To 10 g of the clayey material A, potassium
carbonate as a K20 source was added in an amount of not
added (1.1%), 2, 3 or 4% as calculated as K20 mass% after
mixing. The material having no potassium carbonate added
corresponds to sample 1 (Comparative Example 1), and
mixtures having potassium carbonate added in an amount of
2%, 3% and 4% correspond to sample 2 (Example 1), sample
3 (Example 1) and sample 4 (Example 1), respectively. As
potassium carbonate, one preliminarily pulverized in a
mortar was employed. Kneading was carried out in a
mortar. The kneaded product was put in a mold, and
molded into pellets by means of a pressing machine. The
molded product was fired at 1,3 00°C for 24 hours.
The fired product was crushed into granules, and the
obtained granular refractory material was kneaded, molded
into two molded products with a shape of a desired float
bath bottom refractory brick, and the two molded products
were dried and fired at 1,300°C and 1,350oC,
respectively, to obtain two types of float bath bottom
refractory brick. The granular refractory material
comprised 30% of a fine granular portion having a grain
size less than 90 µm, 30% of a medium granular portion
having a grain size of from 90 µm to 1 mm and 40% of a
coarse granular portion having a grain size exceeding 1
mm. The composition of the prepared brick is
substantially the same as the composition of the
material.
Results of X-ray diffraction measurement of test
specimens of the obtained float bath bottom refractory
brick and proportions of crystalline phases are shown in
Figs. 1, 2, 3 and 4. Fig. 1 illustrates results of X-ray
diffraction measurement with respect to test specimens
obtained by firing the molded products at 1,300°C, Fig. 2
illustrates results of X-ray diffraction measurement with
respect to test specimens obtained by firing the molded
products at 1,350°C. Fig. 3 illustrates proportions of
crystalline phases with respect to test specimens
obtained by firing the molded products at 1,3 00°C, and
Fig. 4 illustrates proportions of crystalline phases with
respect to test specimens obtained by firing molded
products at 1,350°C. The vertical axis represents the
peak intensity of each crystal, and the horizontal axis
represents mass% of K20.
It is confirmed from Figs. 1 and 2 that the peak
intensities representing the proportions of Cristobalite
and quartz decrease, as the mass% of K20 increases to 2,
3 and 4% (Example 1) as compared with no potassium
carbonate is added (proportion of the Cristobalite
crystalline phase is 11%) (Comparative Example 1).
Further, it is confirmed that the proportion of the
cristobalite crystalline phase also decreases. Such
phenomena indicate that a glass phase rich in K20
increases, which suppresses a reaction with Na20 at the
surface of the refractory brick to be used for a float
bath bottom.
Further, as evident from Figs. 3 and 4, the
proportion of the Cristobalite crystalline phase exceeds
10% in a case where no potassium carbonate is added
(Comparative Example 1), and the proportion of the
Cristobalite crystalline phase is less than 10% in a case
where potassium carbonate is added so that the massl of
K20 would be 2, 3 or 4% (Example 1).
Accordingly, it is estimated that flaking phenomena
can be suppressed by use of the float bath bottom
refractory brick of Example 1.
EXAMPLE 2
In the same manner as in Example 1, to 10 g of the
clayey material B, potassium carbonate as a K20 source
was added in an amount of 0.3 (not added), 2, 3, 4 or 6%
as calculated as K20 mass% after mixing. The material
having no potassium carbonate added corresponds to sample
5 (Comparative Example 2), and mixtures having potassium
carbonate added in an amount of 2%, 3%, 4% and 6%
correspond to sample 6 (Example 2), sample 7 (Example 2),
sample 8 (Example 2) and sample 9 (Comparative Example
3), respectively. As potassium carbonate, one
preliminarily pulverized in a mortar was employed.
Kneading was carried out in a mortar. The kneaded
product was put in a mold and molded into pellets by
means of a pressing machine. The molded product was
fired at 1,300°C for 24 hours.
The fired product was crushed into granules, and the
obtained granular refractory material was kneaded and
molded into two molded products with a shape of a desired
float bath bottom refractory brick, and the two molded
products were dried and fired at 1,300°C and 1,350°C,
respectively, to obtain two types of float bath bottom
refractory brick. The above granular refractory material
comprised 3 0% of a fine granular portion having a grain
size less than 90 urn, 30% of a medium granular portion
having a grain size of from 90 urn to 1 mm and 40% of a
coarse granular portion having a grain size exceeding 1
mm. The composition of the obtained brick is
substantially the same as the composition of the
material.
Results of X-ray diffraction measurement with
respect to test specimens of the obtained float bath
bottom refractory brick and proportions of crystalline
phases are shown in Figs. 5, 6, 7 and 8. Fig. 5
illustrates results of X-ray diffraction measurement with
respect to test specimens obtained by firing the molded
products at 1,300°C, and Fig. 6 illustrates results of X-
ray diffraction measurement with respect to test
specimens obtained by firing the molded product at
1,350°C. Fig. 7 illustrates proportions of crystalline
phases with respect to test specimens obtained by firing
the molded products at 1,300°C, and Fig. 8 illustrates
proportions of crystalline phases with respect to test
specimens obtained by firing the molded products at
1,350°C. The vertical axis represents the proportion of
each crystalline phase, and the horizontal axis represent
mass% of K20.
It is found that the peak intensities of
Cristobalite and quartz when no potassium carbonate is
added (Comparative Example 2) are still higher than those
of Example 1. This means that the amount of the glass
phase in the refractory brick is small, and accordingly a
reaction with Na20 at the surface of the refractory brick
to be used for a float bath bottom can not be suppressed.
To such a material, potassium carbonate is added in an
amount of 2, 3, 4 or 6% as calculated as K20 mass% after
mixing, followed by firing, whereby the peak intensities
of Cristobalite and quartz reduce in a case where the K2O
content is 2, 3 or 4% (Example 2), and the reaction with
Na20 as described in Example 1 is suppressed. If the
potassium carbonate is added in an amount of 6%
(Comparative Example 3) as calculated as K20 mass% after
mixing, followed by firing, whereby reduction of the peak
intensity of Mullite is remarkable, and the proportion of
Mullite remarkably decreased to at most 2 0% as shown in
Figs. 7 and 8. Namely, the amount of the glass phase is
in excess, and the high temperature properties of the
refractory brick may be impaired. Accordingly, it is
estimated that flaking phenomena can be suppressed by use
of the float bath bottom refractory brick of Example 2.
INDUSTRIAL APPLICABILITY
The present invention is useful for production of a
float bath bottom refractory brick, since high effect of
suppressing flaking phenomena can be obtained.
The entire disclosure of Japanese Patent Application
No. 2004-325473 filed on November 9, 2004 including
specification, claims and summary is incorporated therein
by reference in its entirety.
WE CLAIM:
1. A process for producing a float bath bottom refractory brick, which comprises adding
a potassium compound, as represented by mass percentage based on the following oxides, so
that a K2O content in the float bath bottom refractory brick to be produced would be from 2
to 4% 10 to a clayey material comprising from 30 to 45% of AL12O3 and from 50 to 65% of
SiO2, followed by firing.
2. A process for producing a float bath bottom refractory brick, which comprises using a
clayey material comprising, as represented by mass percentage based on the following
oxides, from 30 to 45% of Al2O3 and from 50 to 65% of SiO2 and having a Na20 content of at
most 1%, wherein a potassium compound is added so that the K20 content in the float bath
bottom refractory brick to be produced would be from 2 to 4%, and firing the clayey material.
3. The process for producing a float bath bottom refractory brick as claimed in claim 1,
which comprises adding a potassium compound to a clayey material comprising, as
represented by mass percentage based on the following oxides, from 30 to 45% of Al2O3 and
from 50 to 65% of SiO2, kneading, molding, firing and then crushing the material to obtain a
granular refractory material, kneading the granular refractory material, molding it into a
shape of a desired float bath bottom refractory brick, followed by firing, wherein control is
made so that in a fine granular portion having a grain size less than 90 µm in the above
granular refractory material, the K20 content would be from 2 to 4%, and the Na20 content
would be at most 1%.
4. The process for producing a float bath bottom refractory brick as claimed in claim 3,
wherein the granular refractory material contains from 20 to 60 mass % of a fine granular
portion having a grain size less than 90 µm which contains from 2 to 4% and at most 1% of
Na2O.
5. The process for producing a float bath bottom refractory brick as claimed in claim 3,
wherein control is made so that in a medium granular portion having a grain size of from 90 µm to 1 mm and a fine granular portion having a grain size less than 90 µm in the above
granular refractory material, as represented by mass percentage based on the following
oxides, the K20 content would be from 2 to 4%, and the Na20 content would be at most 1%.
6. The process for producing a float bath bottom refractory brick as claimed in claim 5,
wherein the granular refractory material contains from 20 to 60 mass% of the medium
granular portion having a grain size of from 90 µm to 1 mm.
7. The process for producing a float bath bottom refractory brick as claimed in claim 1,
which comprises kneading, molding, firing and then crushing a clayey material comprising,
as represented by mass percentage based on the following oxides, from 30 to 45% of Al2O3
and from 50 to 65% of Si2O2, to obtain a granular refractory material, adding a granular
potassium compound to the granular refractory material, kneading and molding the mixture it
into a shape of a desired float bath bottom refractory brick, followed by firing, wherein
control is made so that the K2O content in the float bath bottom refractory brick to be
produced, would be from 2 to 4%.
8. A float bath bottom refractory brick having a composition which comprises, as
represented by mass percentage based on the following oxides, from 30 to 45% of Al2O3,
from 50 to 65% of Si2O2, at most 1% of Na2O and 2 to 4% of K2O.
9. The float bath bottom refractory brick as claimed in claim 8, which has at most 10%
of a cristobalite crystalline phase.
10. The float bath bottom refractory brick as claimed in claim 8 or 9, which has at least
20% of a mullite crystalline phase.
11. A float bath having a bottom made of the brick as claimed in any one of claims 8 to
10.
12. A process for producing plate glass, which comprises discharging molten glass
floating on tin in a float bath and forming smooth plate glass therefrom, wherein the float
bath is as defined in claim 11.
13. The float bath bottom refractory brick as claimed in claim 8, wherein the K2O content
is from 3 to 4%.



A float bath bottom refractory brick and process of production thereof are disclosed.
The process comprises adding a potassium compound, as represented by mass percentage
based on the following oxides, so that a K2O content in the float bath bottom refractory brick
to be produced would be from 2 to 4% 10 to a clayey material comprising from 30 to 45% of
Al2O3 and from 50 to 65% of SiO2, followed by firing. The float bath bottom refractory brick
has a composition, as represented by mass percentage based on the following oxides, from 30
to 45% of A12O3, from 50 to 65% of Si2O2, at most 1% of Na2O and 2 to 4% of K2O.

Documents:

01631-kolnp-2007-abstract.pdf

01631-kolnp-2007-assignment.pdf

01631-kolnp-2007-claims.pdf

01631-kolnp-2007-correspondence others 1.1.pdf

01631-kolnp-2007-correspondence others 1.2.pdf

01631-kolnp-2007-correspondence others.pdf

01631-kolnp-2007-description complete.pdf

01631-kolnp-2007-drawings.pdf

01631-kolnp-2007-form 1.pdf

01631-kolnp-2007-form 3 1.1.pdf

01631-kolnp-2007-form 3.pdf

01631-kolnp-2007-form 5.pdf

01631-kolnp-2007-gpa.pdf

01631-kolnp-2007-international publication.pdf

01631-kolnp-2007-international search report.pdf

01631-kolnp-2007-others.pdf

01631-kolnp-2007-pct request form.pdf

01631-kolnp-2007-priority document.pdf

1631-KOLNP-2007-ABSTRACT 1.1.pdf

1631-KOLNP-2007-AMANDED CLAIMS.pdf

1631-KOLNP-2007-AMANDED PAGES OF SPECIFICATION.pdf

1631-KOLNP-2007-ASSIGNMENT.pdf

1631-KOLNP-2007-CORRESPONDENCE 1.1.pdf

1631-KOLNP-2007-CORRESPONDENCE.pdf

1631-KOLNP-2007-DESCRIPTION (COMPLETE) 1.1.pdf

1631-KOLNP-2007-EXAMINATION REPORT.pdf

1631-KOLNP-2007-FORM 1-1.1.pdf

1631-KOLNP-2007-FORM 18 1.1.pdf

1631-KOLNP-2007-FORM 2.pdf

1631-KOLNP-2007-FORM 3-1.2.pdf

1631-KOLNP-2007-FORM 3.pdf

1631-KOLNP-2007-FORM 5.pdf

1631-kolnp-2007-form-18.pdf

1631-KOLNP-2007-FORM-27.pdf

1631-KOLNP-2007-GPA.pdf

1631-KOLNP-2007-GRANTED-ABSTRACT.pdf

1631-KOLNP-2007-GRANTED-CLAIMS.pdf

1631-KOLNP-2007-GRANTED-DESCRIPTION (COMPLETE).pdf

1631-KOLNP-2007-GRANTED-DRAWINGS.pdf

1631-KOLNP-2007-GRANTED-FORM 1.pdf

1631-KOLNP-2007-GRANTED-FORM 2.pdf

1631-KOLNP-2007-GRANTED-SPECIFICATION.pdf

1631-KOLNP-2007-OTHERS 1.1.pdf

1631-KOLNP-2007-OTHERS 1.2.pdf

1631-KOLNP-2007-OTHERS.pdf

1631-KOLNP-2007-PA.pdf

1631-KOLNP-2007-PETITION UNDER RULE 137.pdf

1631-KOLNP-2007-PRIORITY DOCUMENT.pdf

1631-KOLNP-2007-REPLY TO EXAMINATION REPORT.pdf

1631-KOLNP-2007-TRANSLATED COPY OF PRIORITY DOCUMENT.pdf

abstract-01631-kolnp-2007.jpg


Patent Number 250160
Indian Patent Application Number 1631/KOLNP/2007
PG Journal Number 50/2011
Publication Date 16-Dec-2011
Grant Date 13-Dec-2011
Date of Filing 07-May-2007
Name of Patentee ASAHI GLASS COMPANY, LIMITED
Applicant Address 12-1, YURAKUCHO, 1-CHOME, CHIYODA-KU, TOKYO
Inventors:
# Inventor's Name Inventor's Address
1 KABASHIMA, SHUJI C/O ASAHI GLASS COMPANY, LIMITED 1-1, SUEHIRO-CHO, TSURUMI-KU, YOKOHAMA-SHI, KANAGAWA 2300045
2 YOKOTANI, MASAMICHI C/O ASAHI GLASS COMPANY, LIMITED 1-1, SUEHIRO-CHO, TSURUMI-KU, YOKOHAMA-SHI, KANAGAWA 2300045
3 SAKAI, KOUZOU C/O ASAHI GLASS COMPANY, LIMITED 1-1, SUEHIRO-CHO, TSURUMI-KU, YOKOHAMA-SHI, KANAGAWA 2300045
PCT International Classification Number C03B 18/16
PCT International Application Number PCT/JP2005/020478
PCT International Filing date 2005-11-08
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2004-325473 2004-11-09 Japan