Plant protecting and regulating compositions – Plant growth regulating compositions – Plural active ingredients
Reexamination Certificate
2000-07-27
2002-07-02
Group, Karl (Department: 1755)
Plant protecting and regulating compositions
Plant growth regulating compositions
Plural active ingredients
C501S007000
Reexamination Certificate
active
06413906
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to Li
2
O—Al
2
O
3
—SiO
2
crystallized glass and Li
2
O—Al
2
O
3
—SiO
2
crystallizable glass therefor.
2. Description of the Related Art
Conventionally, Li
2
O—Al
2
O
3
—SiO
2
crystallized glass has been used for front glass panels in kerosene heaters, wood stoves and the like, substrates for high-technology products, such as color filters, image sensors and the like, setters for baking electronic devices, shelf boards for microwave ovens, top plates for electromagnetic cooking devices, window glass for fire doors, and the like. For example, Japanese Examined Patent Publication(JP-B) No. S39-21,049, Japanese Examined Patent Publication (JP-B) No. S40-20,182, and Japanese Unexamined Patent Publication (JP-A) No. H01-308,845 disclose Li
2
O—Al
2
O
3
—SiO
2
crystallized glass having a &bgr;-quartz solid solution represented by the formula Li
2
O—Al
2
O
3
.nSiO
2
, in which n≧2, or a &bgr;-spodumene solid solution represented by the formula Li
2
O—Al
2
O
3
.nSiO
2
, in which n≧4, both of which are produced in the crystallized glass as a main crystal.
The Li
2
O—Al
2
O
3
—SiO
2
crystallized glass mentioned above has high mechanical strength and superior thermal characteristics, such as a low coefficient of thermal expansion. In addition, since the crystal produced in the Li
2
—O—Al
2
O
3
—SiO
2
crystallized glass is alterable by changing heating conditions in a crystallization process, transparent crystallized glass (a &bgr;-quartz solid solution is produced) and white and opaque crystallized glass (a &bgr;-spodumene solid solution is produced) can be produced from the same composition of raw glass material. Consequently, in accordance with the application, Li
2
O—Al
2
O
3
—SiO
2
crystallized glass suitable for the application can be selectively produced.
When this kind of crystallized glass is produced, heating to a high temperature above 1,400° C. for melting raw glass materials is required. Accordingly, as a fining agent added to one batch for glass production, arsenic oxide (As
2
O
3
) is used which is capable of evolving a great deal of gas for fining during melting at a high temperature. In melting in a batch production system, As
2
O
3
contained in raw glass materials is oxidized at 400 to 500° C. so as to form As
2
O
5
, and the As
2
O
5
is again reduced at 1,200 to 1,800° C. to form As
2
O
3
, whereby oxygen gas is evolved. The oxygen gas thus evolved diffuses into bubbles in the glass, and the bubbles enlarge, facilitating rising thereof, whereby the bubbles are removed. Since As
2
O
3
has the fining effect described above, As
2
O
3
has been widely used as a fining agent. In particular, As
2
O
3
is a very effective fining agent for Li
2
O—Al
2
O
3
—SiO
2
crystallized glass that must be subjected to melting at a high temperature.
In addition to the fining effect, As
2
O
3
has an effect of promoting crystallization. Accordingly, it is understood that AS
2
O
3
is an essential component in order to obtain desired characteristics of the crystallized glass described above.
However, As
2
O
3
is high toxic, and hence, environmental pollution may occur during a manufacturing process for glass, disposal of waste glass, and the like. Accordingly, it is desirable to reduce the, amount of As
2
O
3
used. However, when the amount of As
2
O
3
is simply decreased, the effects on fining and crystallization are degraded, and as a result, clarity and glass characteristics, which are equivalent to those obtained if the amount of As
2
O
3
were not decreased, cannot be obtained.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide Li
2
O—Al
2
O
3
—SiO
2
crystallized glass having clarity and glass characteristics equivalent to or superior to those of a conventional crystallized glass, even when the amount of As
2
O
3
used is decreased, and to provide Li
2
O—Al
2
O
3
—SiO
2
crystallizable glass as a raw glass material therefor.
According to one aspect of the present invention, there is provided a Li
2
O—Al
2
O
3
—SiO
2
crystallized glass which contains, by weight, 0.05 to 4% Sb
2
O
3
, in which the content of &bgr;-OH is 0.3 to 4/mm.
According to another aspect of the present invention, there is provided a Li
2
O—Al
2
O
3
—SiO
2
crystallizable glass which contains, by weight, 0.05 to 4% Sb
2
O
3
, in which the content of &bgr;-OH is 0.15 to 2/mm.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Description will first be made in detail as regards a Li
2
O—Al
2
O
3
—SiO
2
crystallizable glass and a Li
2
O—Al
2
O
3
—SiO
2
crystallized glass according to the present invention.
The Li
2
O—Al
2
O
3
—SiO
2
crystallized glass of t he present invention has a &bgr;-quartz solid solution or a &bgr;-spodumene solid solution produced as a main crystal therein. By the production of the crystal Mentioned above, the Li
2
O—Al
2
O
3
—SiO
2
crystallized glass is obtained, which has a low coefficient of thermal expansion of approximately −10 to 30×10
−7
/° C. (30 to 750° C.) and high mechanical strength. When a metastable &bgr;-quartz solid solution is produced as a main crystal, transparent crystallized glass is obtained, and when a metastable &bgr;-quartz solid solution is inverted to a stable &bgr;-spodumene solid solution by heating at a high temperature, white and opaque crystallized glass is obtained.
Instead of As
2
O
3
, antimony oxide (Sb
2
O
3
) is used in the crystallized glass of the present invention. Sb
2
O
3
is oxidized to Sb
2
O
5
at approximately 400° C. under melting conditions, and in a high temperature range of 1000° C. or more, a great deal of oxygen gas is evolved by a reaction caused by a change in valence of the antimony (Sb) ion. The gas evolved diffuses into bubbles remaining in the glass and increases the diameters of the bubbles, so that the bubbles rise and escape, resulting in the fining of the glass. In addition, it was understood through the research by the inventors of the present invention that Sb
2
O
3
functions to promote crystallization in the glass just as As
2
O
3
does.
However, the effects of Sb
2
O
3
on fining and promotion of crystallinity are smaller than those of As
2
O
3
. When the content of Sb
2
O
3
is increased, the effects described above are enhanced; however, since Sb
2
O
3
facilitates coloration of glass due to impurities (in the present invention, coloration caused by impurity Fe
2
O
3
in the presence of TiO
2
) more strongly than As
2
O
3
, Sb
2
O
3
cannot be added to the glass in an amount sufficient to obtain the effects of Sb
2
O
3
on fining and promotion of crystallinity. Through the intensive research by the present inventors of the present invention, it was discovered that clarity and crystallinity of glass can be improved when the content of water in the glass is increased. In this connection, even though the promotion of crystallinity of glass can be achieved by increasing the content of MgO, ZnO, Na
2
O, K
2
O, and the like, MgO and ZnO promote coloration due to impurities, and coefficient of thermal expansion is significantly increased when Na
2
O or K
2
O is added. Accordingly, the components mentioned above cannot be added to glass in an amount sufficient to promote crystallinity. In contrast, water can improve clarity and crystallinity of glass without promoting coloration due to impurities and increasing coefficient of thermal expansion.
In the present invention, the content of water in glass is represented by the content of &bgr;-OH.
The content of &bgr;-OH in Li
2
O—Al
2
O
3
—SiO
2
crystallized glass of the present invention is calculated by the following equation based on the data obtained in an infrared absorption spectrum; the content of &bgr;-OH (/mm)={log(T
3850
/T
3500
)}/t, in which T
3850
is the transmittance in the vicinity of 3,850 cm
−1
, T
3500
is the minimum transmittance in the vicinity of 3,500 cm
−1
, and t is the thickness of the crystallized glass used for spectrum measurement (mm, actual measured value 3 mm).
In addition, th
Sakamoto Akihiko
Shimatani Narutoshi
Yamada Hiroyuki
Collard & Roe P.C.
Group Karl
Nippon Electric Glass Co. Ltd.
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