Glass manufacturing – Processes – Fining or homogenizing molten glass
Reexamination Certificate
1999-06-08
2001-11-20
Vincent, Sean (Department: 1731)
Glass manufacturing
Processes
Fining or homogenizing molten glass
C065S134300, C065S134900
Reexamination Certificate
active
06318126
ABSTRACT:
The present invention relates to a vacuum degassing method for molten glass, to remove bubbles from molten glass continuously supplied.
Heretofore, it has been common to carry out vacuum degassing to remove bubbles from molten glass melted in a melting tank by conducting degassing treatment of the molten glass in a vacuum degassing apparatus under a predetermined reduced pressure condition, prior to forming the molten glass by a forming apparatus, in order to improve the quality of the formed glass product. Above the molten glass in the vacuum degassing apparatus, there exists an upper space in a reduced pressure state. The molten glass subjected to degassing treatment in the vacuum degassing apparatus will be supplied to a forming apparatus via e.g. a discharge pipe.
At the time of carrying out the vacuum degassing, there is a bubble layer formed on the molten glass surface. When the flow rate of the molten glass to be subjected to vacuum degassing, is small, the forming rate of this bubble layer is lower than the rate at which bubbles constituting the bubble layer break to diminish the bubble layer, and the bubble layer will be extinguished or diminished towards the downstream in the vacuum degassing apparatus, thus leading to no serious problem. However, if the flow rate of the molten glass is large and the bubble layer remains in the vacuum degassing apparatus in a thickness not negligible, the following problems will be brought about.
(1) Bubbles in the bubble layer will be carried along the flow of molten glass and will be sent from the vacuum degassing apparatus via e.g. a discharge pipe to a forming apparatus. Such bubbles will be defects in the glass product.
(2) Radiational heat transfer from the molten glass of a high temperature to the upper space is hindered by the bubble layer, and the temperature of the upper space decreases. Consequently, the temperature of the upper surface of the bubble layer which is in contact with the upper space, decreases, and the bubbles on the upper surface of the bubble layer tend to hardly break, whereby the bubble layer will further increase. If the bubble layer increases, the bubble layer is likely to be in contact with e.g. the ceiling of the vacuum degassing apparatus and erode the material constituting the vacuum degassing apparatus, thus leading to shortening of the useful life of the vacuum degassing apparatus or increase in the defects in the glass product resulting from inclusion of the corroded constituting material in the molten glass.
The present invention has been made in view of the above circumstances, and it is an object of the present invention to suppress formation of the bubble layer or extinguish or diminish the formed bubble layer in a short period of time, to improve the degassing efficiency and to make it possible to reduce the size of the degassing apparatus, in the vacuum degassing method for molten glass to remove bubbles from the molten glass continuously supplied.
The present invention provides a vacuum degassing method for molten glass, which comprises introducing molten glass into a vacuum degassing apparatus, subjecting it to degassing treatment under a predetermined reduced pressure condition and then withdrawing it for a subsequent step, wherein during the degassing treatment, a metal compound which is at least one compound of metal selected from the group consisting of aluminum, titanium, silicon, zinc, magnesium, iron, chromium, cobalt, cerium and calcium, is supplied from outside of the vacuum degassing apparatus to the surface of a bubble layer formed in the molten glass to diminish or extinguish the bubble layer.
Now, the present invention will be described in detail with reference to the preferred embodiments.
The metal compound may be in any state at the time of being supplied, so long as it will become before reaching the bubble layer a fine powder of a metal or a metal oxide or fine droplets of a molten metal or a molten metal compound. However, it is preferably supplied in the form of a solution, a suspension, a powder or a gas.
The above metal compound may be mixed into air or oxygen for combustion and a fuel is burned together with such a gas for combustion, and the above-mentioned metal compound contained in such a combustion exhaust gas, may be supplied to the bubble layer.
Otherwise, a fine powder of the above metal compound may be mixed in air and directly supplied to the bubble layer.
It is preferred that the above metal compound is supplied in a form of a solution having dissolved in water or an organic solvent at least one compound selected from the group consisting of an organic aluminum compound, an organic titanium compound, an organic silicon compound, an organic zinc compound, an organic magnesium compound, an organic iron compound, an organic chromium compound, an organic cobalt compound, an organic cerium compound and an organic calcium compound.
Further, it is preferred that the above metal compound is supplied in the form of a suspension having suspended in water or an organic solvent at least one powder selected from powders of aluminum oxide, titanium oxide, silicon oxide, zinc oxide, magnesium oxide, iron oxide, chromium oxide, cobalt oxide and cerium oxide.
It is also preferred that the above metal compound is supplied in the form of a solution having dissolved in water or an organic solvent a hydroxide, a sulfate, a nitrate and/or a chloride of at least one member selected from the group consisting of aluminum, titanium, silicon, zinc, magnesium, iron, chromium, cobalt and calcium.
Otherwise, the above metal compound is titanium tetrachloride or silicon tetrachloride and may be supplied to the bubble layer in the form of a gas.
The above degassing treatment is preferably carried out in a vacuum degassing apparatus made of a refractory.
Now, the vacuum degassing method for molten glass of the present invention will be described in further detail with reference to a preferred embodiment as shown in the attached drawing.
REFERENCES:
patent: 1598308 (1926-08-01), Pike
patent: 3350185 (1967-10-01), Rough
patent: 3519412 (1970-07-01), Olink
patent: 3649235 (1972-03-01), Harris
patent: 4002449 (1977-01-01), Spanoudis
patent: 4339254 (1982-07-01), Gridley
patent: 4704153 (1987-11-01), Schwenninger et al.
patent: 4794860 (1989-01-01), Welton
patent: 4849004 (1989-07-01), Schwenninger et al.
patent: 5316563 (1994-05-01), Ishimura et al.
patent: 5665137 (1997-09-01), Huang
patent: 5785726 (1998-07-01), Dorfeld et al.
patent: 5849058 (1998-12-01), Takeshita et al.
patent: 5851253 (1998-12-01), Pet et al.
patent: 5851258 (1998-12-01), Ando et al.
patent: 0 556 576 (1993-08-01), None
patent: 0 775 671 (1997-05-01), None
patent: 984 301 (1964-01-01), None
patent: 1 121 883 (1968-07-01), None
patent: 1 445 825 (1976-08-01), None
patent: 2-221129 (1990-09-01), None
patent: 3-33020 (1991-02-01), None
patent: 3-69516 (1991-03-01), None
patent: 4-31325 (1992-02-01), None
patent: 5-58646 (1993-03-01), None
patent: 5-208845 (1993-08-01), None
patent: 5-208830 (1993-08-01), None
patent: 5-229831 (1993-09-01), None
patent: 6-305735 (1994-11-01), None
Patent Abstracts of Japan, vol. 097, No. 007, Jul. 31, 1997, JP 09 059029, Mar. 4, 1997.
Kijima Takashi
Matsuwaki Masataka
Sasaki Michito
Takei Yusuke
Tanigaki Atsushi
Asahi Glass Company Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Vincent Sean
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