JP4183202B2 - Glass product manufacturing method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a glass product manufacturing method and apparatus for performing a molding step after removing bubbles contained in molten glass by a clarification step of molten glass.
[0002]
[Prior art]
The clarification process at the time of glass melting is usually performed by adding an appropriate clarifier in advance, and a representative example of this clarifier is mirabilite. Soot is decomposed at the fining temperature to generate SO ₃ bubbles, which mainly have a fining effect. In the decomposition temperature of the salt cake for the fining difficult matrix viscosity is too high due to sodium sulfate, and high decomposition temperature, for example As ₂ O ₃ and Sb ₂ O ₃ is used. However, when As ₂ O ₃ or Sb ₂ O ₃ is used in the float forming method, it reacts with tin in the float bath and causes defects due to this, which is not suitable for forming by the float method.
[0003]
Thus, a vacuum degassing method has been proposed for the purpose of clarifying a glass substrate having a high temperature viscosity, and a typical example thereof is JP-A-62-235222. This vacuum defoaming method introduces a molten glass substrate into a vacuum chamber maintained at atmospheric pressure or lower, so that the clarification effect itself is high, but a glass substrate having a composition containing a volatile component typified by B ₂ O ₃ is used. On the other hand, it is not necessarily suitable because volatile components are volatilized at the time of clarification.
[0004]
In this regard, the siphon-type vacuum degassing device already proposed by the present applicant is excellent in that volatilization of volatile components during clarification can be suppressed because the area exposed to the vacuum is limited only to the surface of the substrate. It has the characteristics. Techniques for performing defoaming under reduced pressure in the siphon system as described above, and further improvements and improvements thereof are disclosed in, for example, JP-A-2-188430, JP-A-2-221129, JP-A-3-33020, and JP-A-5 No. 58586 and JP-A-5-208830.
[0005]
As an example of this, the apparatus disclosed in Japanese Patent Laid-Open No. 3-33020 adopts a form in which molten glass is sequentially guided to a molding process through a melting tank, a riser pipe, a vacuum degassing tank, a downcomer pipe, and a storage tank. In the steady expansion state of the downcomer and the downcomer, the bending change amount of the flexible sealing member covered with the downcomer is suppressed, but this apparatus basically uses the siphon principle, The molten glass from is introduced into a vacuum defoaming tank and defoamed here to obtain a homogeneous molten glass, which is then molded to obtain a highly homogenous glass product.
[0006]
However, even in a siphon-type vacuum degassing apparatus, when a volatile component is volatilized from the surface, a deviation in composition occurs between the vicinity of the surface of the glass substrate (molten glass) and the inside. When this is severe, it causes product striae, and even when the deviation is not so severe, the quality of the product is deteriorated as a striation (Japanese Patent Laid-Open No. 2-188430). For this reason, in the above-mentioned Japanese Patent Application Laid-Open No. 5-208830, the substrate is homogenized by performing fairly strong substrate agitation after the vacuum degassing.
[0007]
[Problems to be solved by the invention]
However, such agitation of the substrate cannot be performed on all substrates. In a substrate having a low solubility of dissolved gas in molten glass (hereinafter also referred to as a melt as appropriate), even a little agitation causes reboil to cause generation of new bubbles, which does not make any sense of degassing under reduced pressure. Accordingly, an object of the present invention is to provide a clarification method and apparatus that eliminates the above-described drawbacks of the prior art and that can be applied to various substrates and simultaneously realizes a high degree of clarification and a high degree of homogenization.
[0008]
That is, the present invention relates to a glass product manufacturing method and apparatus that uses a siphon-type decompression tank for a clarification process of molten glass. In the siphon-type decompression tank, the flow of the molten glass is appropriately controlled by the foam layer and the barrier, To provide a glass product manufacturing method and apparatus capable of obtaining a uniform glass product at all times, with no fluctuation in glass composition until the molding process, by preventing the composition variation, greatly improving the product yield. With the goal.
[0009]
[Means for Solving the Problems]
The present invention relates to a method for producing a glass product by sequentially introducing molten glass through a stirring tank, a riser pipe, a decompression tank, a downcomer pipe, and a storage tank to a molding process. Provided is a method for producing a glass product characterized in that one or a plurality of barriers are provided to form a foam layer on the surface of the molten glass in a vacuum tank. In an apparatus for producing glass products by leading to a molding process through a tank, a riser, a decompression tank, a downcomer, and a storage tank, one or more barriers are installed in the molten glass decompression tank. An apparatus for producing a glass product characterized by the above is provided.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the dissolved gas is first made into fine bubbles by stirring in the agitation tank in the previous stage, and at least the non-uniformity of the substrate generated during dissolution is corrected. Of course, this stirring tank may also serve as a dissolution tank. This bubble becomes large in the decompression tank, takes in the dissolved gas, floats, and escapes from the substrate to the molten glass surface. In the present invention, a foam layer is formed on the surface of the molten glass with the above-described barrier installed, and convection in the matrix is suppressed by the barrier and the foam layer, thereby improving the homogeneity of the matrix in the vacuum tank. Can be improved.
[0011]
In this regard, conventionally, it has been considered that the homogeneity of the substrate is reduced by volatilization of the volatile components (mainly B ₂ O ₃ ) in the substrate in the vacuum degassing tank (Japanese Patent Laid-Open Nos. 2-188430 and 5-5). 208830 etc.). However, in the present invention, on the contrary, the substrate homogeneity can be improved in the decompression tank. The reason for this is unknown in detail, but it is probably because of the formation of a foam layer by installing the above-mentioned barrier. (1) The melt part in contact with the reduced-pressure atmosphere in the reduced-pressure tank is caused by evaporation of volatile components. Despite non-uniformity, (2) the uniformity of the melt is improved by the stirrer effect caused by the rising of bubbles, etc. (3) These two types of melts (1) and (2) are the foam layer. It is thought that it is difficult to be mixed with the presence of the barrier.
[0012]
That is, in the present invention, a barrier is present in the vacuum tank, but since this barrier is immersed in the melt, not only the foam layer on the melt surface is stopped, but also the flow of the melt surface portion is stopped. Works. This slows the flow of the melt surface and makes it stagnation. Therefore, it becomes difficult for the melt near the surface to descend along the decompression tank side wall or the like. Also, a foam layer is formed in front of the barrier by the barrier, and the presence of this foam layer inhibits convection inside the vicinity of the melt surface by the buoyancy or pressing force of the foam in contact with the melt surface.
[0013]
On the other hand, a part without a foam layer is formed at the rear part of the barrier, but since there are substantially no bubbles here, there is virtually no entrainment of the foam in the downcomer, thereby making the composition of the molten glass and this melting The homogeneity of the glass product formed with glass can be improved. In the present invention, the dissolved gas is microbubbled in the preceding agitation tank, and at least the non-uniformity of the substrate generated at the time of dissolution is corrected, and homogenization such as agitation after the decompression tank by the action of the barrier and the foam layer. Means are substantially unnecessary, but an auxiliary stirring operation may be added if necessary.
[0014]
In the present invention, the barrier and the foam layer formed thereby are used in this manner. However, as a prerequisite, an appropriate foam layer needs to be formed first, and the foam of the foam layer formed is easily formed on the melt surface. It is necessary to appropriately control the conditions for forming and maintaining the foam layer, that is, the viscosity of the melt. Among these, the generation of bubbles can be controlled by adjusting the amount of a component that vaporizes at a clarification temperature or a temperature slightly higher than that in a normal glass batch such as SO ₃ or Cl. The melt viscosity needs to be about log η = 2.6 or more in the case of a normal glass substrate, but can be appropriately set for each target batch depending on the composition of the molten glass.
[0015]
【Example】
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments or embodiments of a glass product manufacturing method and apparatus according to the present invention will be described below with reference to the accompanying drawings, but the present invention is of course not limited thereto. FIG. 1 is a cross-sectional view for explaining an embodiment of a glass product manufacturing apparatus according to the present invention, and FIG. 2 is an enlarged view of a portion indicated by A (◯) in FIG.
[0016]
In FIG. 1, 1 is a stirring tank, 2 is a first stirrer provided in the stirring tank 1, and the first stirrer 2 is rotatably supported in the stirring tank 1. 3 is a riser pipe of molten glass, 4 is a decompression tank, 5 is a downfall pipe, 6 is a storage tank, and 7 is a second stirrer provided in the storage tank 6. Among these, the riser 3, the decompression tank 4, and the downcomer 5 are housed in a casing 8, and heat insulation is prevented by a heat insulating material 9 packed therebetween, and is insulated from the outside air. The ascending pipe 3, the decompression tank 4 and the descending pipe 5 are heated by electric heating or other appropriate heating means (not shown) and maintained at a predetermined temperature, for example, about 1200 to 1450 ° C. by a temperature control system. In the figure, an arrow (→) indicates the flow of the molten glass, and 10 is a bypass pipe for the molten glass.
[0017]
2 (a) is an enlarged view of a portion corresponding to A in FIG. 1, and FIG. 2 (b) is a perspective view of a cross section taken along line BB ′ in FIG. 2 (a). Are using the same symbols. Reference numeral 12 in FIG. 2 denotes a foam layer formed by damming by the barrier 11. In addition, one barrier 11 is provided in the figure, but in the present invention, two or more barriers 11 can be arranged at an appropriate interval, whereby a foam layer can be more reliably formed. it can.
[0018]
The space S in the decompression tank 4 is divided into a portion S1 having a foam layer on the molten glass surface upstream of the barrier 11 and a portion S2 having no foam layer on the molten glass surface downstream of the barrier 11 by the barrier 11. Divided. Of these, the S1 portion with a foam layer stagnates in the melt surface, making it difficult for the melt in the vicinity of the surface to descend along the side wall of the decompression tank, and the buoyancy of the foam in contact with the melt surface due to the presence of the foam layer. Or the convection in the vicinity of the surface of the melt is hindered by the pressing force.
[0019]
Next, operations and effects of the glass manufacturing apparatus configured as described above will be described. The molten glass melted in a melting tank (not shown) and stored in the stirring tank 1 is stirred by the first stirrer 2, the dissolved gas is microbubbled by this stirring, and the base material non-uniformity generated when the raw material is melted Is corrected. The flow of the molten glass to the ascending pipe 3, the decompression tank 4 and the descending pipe 5 is based on Sanphon's principle. Therefore, the liquid level of the molten glass in the storage tank 6 is higher than the liquid level of the molten glass in the stirring tank 1. The inside of the decompression tank 4 is kept in a decompressed state by the head pressure difference. In the decompression tank 4, the molten glass flows toward the downcomer 5 while maintaining the liquid level L and the space S.
[0020]
Although the molten glass contains occluded gas, the occluded gas is occluded in the molten glass in a gaseous state under normal pressure. In the present invention, it is indispensable to stir the molten glass in front of the decompression tank 4, and the first stirrer 2 plays this role in the apparatus of the illustrated embodiment. First, dissolved gas is made into fine bubbles by this stirring, and the unevenness of the substrate generated when the raw material is dissolved is corrected. The amount of agitation needs to be within a range where a foam layer having a thickness of 10 mm or more (a foam layer formed by the barrier 11) can be formed in the decompression tank 4 and the foam layer does not flow out of the tank.
[0021]
At this time, the viscosity and temperature conditions for the molten glass can be appropriately set depending on the composition of the molten glass, etc., but usually, for example, the viscosity is log η = about 2.7 to 4.2, and the temperature is about 1450 to 1200 ° C. To do. The molten glass that occludes the fine bubbles is guided to the lower end portion of the riser 3, rises in the riser 3 by the siphon principle, and is introduced into the decompression tank 4. The inside of the decompression tank 4 is set to a decompression state below atmospheric pressure, for example, a decompression state of 1/20 to 1/3 atm. As a result, the fine bubbles in the molten glass that have been lifted up the riser 3 and led to the decompression tank 4 are reboiled at an early stage to form a foam layer on the surface of the molten glass. After that, it was confirmed that there was substantially no generation of new bubbles in the vacuum tank.
[0022]
The location of the barrier 11 in the decompression tank 4 can be placed at an appropriate place in the decompression tank 4, but if it is near the center of the interior of the tank or in front of it, that is, close to the riser 3, the foam layer again in the space S 2. In order to stop the flow of the melt, the vicinity of the downstream in the decompression tank 4 (the vicinity of the downcomer pipe 5) where the bubble removal is substantially eliminated is important. If the bubbles are removed, the stirring effect is lost, and the vicinity of the downcomer pipe 5 has a high effect of blocking the melt flow by the barrier. Therefore, at least one barrier should be installed near the downcomer pipe 5 in the decompression tank 4. Is preferred.
[0023]
When two or more barriers 11 are provided at an appropriate interval, at least one of the barriers 11 is provided at an appropriate location, for example, at the center after taking the above considerations into consideration when it is one. Can be placed before and after the department. Further, as shown in FIG. 1, when the vacuum defoaming tank 4 is viewed in the melt flow direction, it is actually observed as the first tank, the second tank, and the third tank in order from the left depending on whether the barrier is left or right. The thickness was 100 mm or more in the first tank, and almost no bubbles were confirmed in the third tank. Thus, considering that there is almost no foam layer in the third tank, it is preferable that this portion has a minimum area where the ground level can be confirmed. The barrier is effective and effective if it is immersed in the melt at least 30 mm or more, and the immersion depth is preferably 50 mm or more.
[0024]
On the other hand, on the downstream side of the barrier 11, a portion S2 having no foam layer is formed on the surface of the molten glass, but here no foam layer is formed (no foam layer). Bubbles are not caught and bubbles do not enter the molten glass flowing to the downcomer 5. In the present invention, since the bubble layer is not formed on the surface of the molten glass in the space portion S2, it is possible to accurately measure the ground level of the molten glass here without any error. As described above, it is preferable that the measurement portion has a minimum area where the ground level can be confirmed.
[0025]
The barrier 11 is fixed by placing predetermined gaps 13 and 14 at the lower and upper parts around the liquid surface of the molten glass as shown in the figure. A flow passage is formed. The shape of the barrier 11 needs to be a width that can hold the above-mentioned predetermined gaps 13 and 14 on the top, bottom, left and right of the cross section in the decompression tank 4, but the other points are thin plate-like as long as the installation purpose can be achieved. Other suitable shapes can be used, and platinum or a platinum rhodium alloy is preferably used as the constituent material.
[0026]
Next, the molten glass descends in the downcomer 5 in this state, is squeezed out from the decompression tank 4 and guided to the storage tank 6, and is agitated and homogenized by the second stirrer 7 in the storage tank 6. Is done. In the present invention, the second stirrer 7 is not necessarily required, but in the illustrated embodiment, it is installed as an auxiliary. As described above, in the present invention, since the volatilization of boric acid and other volatile components from the mother glass (molten glass) to the gas phase is suppressed by the foam layer, the molten glass is formed in a homogenized state in terms of composition. And is molded into various glass products with high homogeneity.
[0027]
Using an apparatus as shown in FIG. 1, an operation was performed on an aluminosilicate glass containing boric acid having a high temperature viscosity. The barriers 11 were installed in two places, the center of the decompression tank 4 and the downstream quarter. The barrier 11 is effective if it is immersed in molten glass at least 30 mm or more, and preferably 50 mm or more. In this example, both barriers were immersed by about 65 mm. As operation conditions, the first stirrer 2 was set to around 5 rpm, and the second stirrer 7 was carried out under a stirring condition of about 3 rpm or less. As a result, a glass plate having a foam number of 0.1 to 0.2 pieces / kg or less in the molded glass product and a better homogeneity than before (striation is not noticeable) was obtained.
[0028]
【The invention's effect】
As described above, according to the present invention, a high degree of clarification and high degree of homogenization that can be applied to various substrates are realized simultaneously by installing a barrier in a vacuum tank and forming a foam layer on the molten glass surface. can do. In addition, it is possible to measure the ground level of the molten glass in the downstream space portion in the decompression tank, and to obtain an effective effect that the homogenizing means after the decompression tank is substantially unnecessary.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view for explaining an embodiment of a glass product manufacturing apparatus according to the present invention.
FIG. 2 is an enlarged view of a portion indicated by A in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Stirring tank 2 1st stirrer 3 riser pipe 4 decompression tank 5 descending pipe 6 storage tank 7 2nd stirrer 8 housing 9 heat insulating material 10 bypass pipe 11 barrier 12 foam layer S space S1 in decompression tank space S2 with foam layer S2 foam Space S2 without layers
13 Lower part gap 14 Upper part gap

Claims (6)

  In a method for producing glass products by sequentially introducing molten glass to a molding process through a stirring tank, a riser pipe, a decompression tank, a downcomer pipe, and a storage tank, the molten glass is stirred in the stirring tank and one piece in the decompression tank. Alternatively, a method for producing a glass product, comprising providing a plurality of barriers to form a foam layer on the surface of the molten glass in the vacuum tank. The method for producing a glass product according to claim 1, wherein the barrier is immersed in the melt by at least 30 mm or more. The method for producing a glass product according to claim 1 or 2, wherein at least one of the barriers is installed in the vicinity of a downcomer in a decompression tank.   In a glass product manufacturing apparatus in which molten glass is sequentially led to a molding process through a stirring tank, a riser pipe, a decompression tank, a downcomer pipe, and a storage tank, one or more barriers are installed in the decompression tank. An apparatus for producing glass products, characterized in that 5. The glass product manufacturing apparatus according to claim 4, wherein the barrier is immersed in the melt by at least 30 mm or more. 6. The glass product manufacturing apparatus according to claim 4, wherein at least one of the barriers is installed near a downcomer in a decompression tank.

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