TWI444344B - A method for producing a molten glass, a method for producing a vacuum degassing apparatus, and a glass product - Google Patents

Description

Method for producing molten glass, vacuum degassing device, and method for producing glass product Field of invention

The present invention relates to a method for producing a molten glass having a process for defoaming molten glass in a vacuum degassing vessel, a vacuum degassing device, and a method for producing a glass article.

Background of the invention

Conventionally, in order to improve the quality of a molded glass product, a clarification process for removing bubbles which have occurred in the molten glass is used before the molten glass in which the raw material has been melted in the melting furnace is subjected to molding by the molding apparatus.

In the clarification process, a known vacuum degassing method is: introducing molten glass into a reduced pressure environment, and in the reduced pressure environment, the bubbles in the continuously flowing molten glass flow are greatly grown to be contained in the molten glass. The bubbles float and are removed by breaking the bubbles on the surface of the molten glass, and then discharged from the reduced pressure environment.

In such a clarification process, when the bubble layer is enlarged on the surface of the molten glass, there is a fear that the decompression defoaming effect is lowered, and the bubbles remain in the molten glass after the clarification process is performed. Here, the vacuum degassing effect is an effect of removing the air bubbles contained in the molten glass by the above-described action, and foaming the bubbles on the surface of the molten glass to remove the bubbles.

It is difficult to remove the bubbles in the molten glass after the clarification process is performed, and there is a fear that defects will occur in the manufactured glass article. In addition, the foaming of the foam layer on the surface of the molten glass refers to a phenomenon in which the foam layer existing on the surface of the molten glass is generally increased to 10 mm to several hundreds of mm in a vacuum degassing process.

If the hypertrophy of the bubble layer is further carried out, a so-called bump will also occur. The term "bumping" refers to a bubble that reaches the surface of the glass, which is usually destroyed with time, and is stably present for a long time without breaking the foam and forming a layer, thereby causing a phenomenon in which the interface of the molten glass rises. If a bump occurs, there is a fear that the defoaming effect is lowered, and there is a problem that bubbles remain in the molten glass after the clarification process is performed, which is a problem.

In the patent documents 1 and 2, the applicant of the present invention proposes a method for producing a molten glass which can prevent the enlargement of the bubble layer on the surface of the molten glass or a reduced defoaming effect caused by the explosion, and a vacuum degassing apparatus for the molten glass. .

The method for producing a molten glass described in Patent Document 1 includes a process of introducing a low-moisture gas into an atmosphere of a vacuum degassing vessel to have a water vapor concentration of 60 mol% or less to defoam the molten glass under reduced pressure. Thereby, it is possible to prevent the enlargement or bumping of the bubble layer on the surface of the molten glass, and the decompression and defoaming effect caused by such conditions.

By preventing the bump, it is possible to prevent the molten glass from sticking to the wall or the top of the vacuum degassing tank and adhering the deposit, thereby preventing the formation of defects in the glass product caused by the falling, and improving the quality.

In addition, since the water in the environment in which the specific component (boron or the like) is volatilized is lowered, the effect of suppressing volatilization of a specific component (boron or the like) in the molten glass is achieved. Further, when a glass plate as a glass product is produced, deterioration in flatness can be suppressed.

The vacuum degassing apparatus for molten glass described in Patent Document 1 has a low-moisture gas introduction mechanism that can introduce a low-moisture gas into the upper space of the vacuum degassing tank.

On the other hand, in the method for producing molten glass described in Patent Document 2, a gas flow is formed above the molten glass flowing through the vacuum degassing vessel to eliminate the retention of the gas component from the molten glass, thereby preventing the bubble layer from being formed. Hypertrophy, and the reduction in decompression and defoaming effect caused by it.

Further, by eliminating the retention of the gas component from the molten glass, it is possible to prevent the decompression and defoaming effect caused by the cause other than the bubble layer from being lowered.

In order to form a gas flow over the molten glass flowing through the vacuum degassing tank, the vacuum degassing apparatus of the molten glass described in Patent Document 2 has a gas flow forming mechanism, and the gas flow forming mechanism is introduced by introducing the gas into the reduced pressure. A gas introduction mechanism for the upper space in the bubble tank and a gas introduction mechanism for guiding the gas from the upper space.

Advanced technical literature Patent literature

Patent Document 1: International Publication No. 2008-029649

Patent Document 2: International Publication No. 2008-093580

Depending on the use of the glass product, there are also strict requirements for the quality of the foam, that is, the number of bubble defects present in the glass product is extremely strict. Specific examples of such a glass product include a glass substrate for a flat panel display (FPD), an optical glass, and the like.

In order to manufacture such a glass product which is extremely strict with the requirements for the quality of the foam, it is required to further prevent the enlargement of the bubble layer on the surface of the glass and the reduction in the decompression and defoaming effect caused thereby.

In order to solve the above problems of the prior art, an object of the present invention is to provide a method for producing a molten glass which is excellent in a vacuum degassing effect, and more particularly to provide a method for preventing a decrease in defoaming effect caused by aeration of a bubble layer. A method of manufacturing molten glass.

Further, it is an object of the present invention to provide a vacuum degassing apparatus suitable for the method for producing molten glass of the present invention.

Further, it is an object of the present invention to provide a method for producing a glass article having a high foam quality, that is, a foam having few defects.

In order to achieve the above object, the present inventors have found that it is difficult to supply gas to the molten glass flowing in the vacuum degassing tank or to be difficult to be produced by the method for producing molten glass described in Patent Documents 1 and 2. The effect of decompression and defoaming effect is effectively exerted.

In other words, in the method for producing molten glass described in Patent Documents 1 and 2, the gas supplied to the upper portion of the molten glass flowing through the vacuum degassing vessel can be decompressed from the atmosphere of the degassing vessel or from the molten glass. The surface is heated by radiant heat, but the temperature is much lower than the surface temperature of the molten glass flowing through the vacuum degassing tank, and is usually about room temperature. Supplying such a low-temperature gas causes a partial decrease in the temperature of the surface of the molten glass flowing in the vacuum degassing tank. Since the rate of foam breaking on the surface of the molten glass depends on the temperature of the surface of the molten glass, when the surface temperature of the molten glass is lowered, the rate of foaming at the surface is lowered, and there is a fear that the surface temperature is lowered. The defoaming effect is reduced.

The decrease in the surface temperature of the molten glass caused by the supply of the low-temperature gas and the reduction in the decompression and defoaming effect caused thereby are partially localized, but in glass products such as glass substrates for FPD which have strict requirements on the quality of the bubbles, , will become a problem.

The present invention provides a method for producing a molten glass, which is a process for defoaming molten glass in a vacuum degassing vessel, and heating the gas to 500 ° C, according to the above-mentioned inventors of the present invention. After the above temperature, it is supplied to the upper space of the molten glass which flows through the said pressure reduction degassing tank.

Moreover, the present invention provides a vacuum degassing apparatus for molten glass, comprising: a decompression housing sucked by a reduced pressure; and a vacuum degassing provided in the decompression housing to perform decompression defoaming of molten glass. a introducing means for communicating with the vacuum degassing tank to introduce the molten glass before decompression under reduced pressure into the decompression degassing tank; and being arranged to communicate with the decompression degassing tank to be a degassing vessel for defoaming the vacuum glass after degassing under reduced pressure, further comprising: a gas introduction mechanism for introducing a gas into the upper space inside the decompression degassing tank; and A heating mechanism for introducing gas into a space.

Further, the gas introduction mechanism of the vacuum degassing apparatus for molten glass of the present invention is constituted by a hollow tube, and the heating mechanism is provided along a line passing through the hollow tube to the inside of the decompression housing.

Moreover, the heating mechanism of the vacuum degassing apparatus for molten glass of this invention is provided in the inside of the piping of the said hollow tube.

Further, the vacuum degassing apparatus for molten glass of the present invention further includes a water vapor concentration measuring means for measuring the water vapor concentration of the ambient gas in the vacuum degassing tank.

Further, the gas introduction mechanism of the vacuum degassing apparatus for molten glass of the present invention is provided on the top or side of the vacuum degassing tank, and the vacuum degassing tank is attached to the molten glass inside the vacuum degassing tank. Formed with an upper space.

Furthermore, the present invention provides a method for producing a glass product, comprising: a vacuum degassing process using a vacuum degassing apparatus for melting glass, and a raw material melting process and a forming process as a process before and after the vacuum degassing process .

In the method for producing a molten glass according to the present invention, the gas heated to 500 ° C or higher is supplied to the upper space of the molten glass flowing through the vacuum degassing vessel, so that the surface temperature of the molten glass due to the gas supply is not lowered, and The resulting reduced pressure degassing effect is reduced, and the enlargement of the bubble layer and the reduced pressure defoaming effect caused by the foam layer are prevented.

Moreover, in the method for producing a molten glass of the present invention, since the decrease in the surface temperature of the molten glass due to the supply of the gas and the decrease in the defoaming effect under the reduced pressure can be prevented, the supply to the degassing defoaming tank can be increased. The amount of gas supplied to the upper space of the molten glass. Thereby, the effect of preventing the enlargement of the bubble layer and the resulting reduced pressure defoaming effect can be further enhanced.

The method for producing a molten glass of the present invention and the method for producing a glass product can obtain a molten glass or a glass product having excellent foam quality by the above-described effects. Therefore, it is suitable as a method for producing a glass substrate or an optical glass for FPD.

Simple illustration

Fig. 1 is a cross-sectional view showing a configuration example of a vacuum degassing apparatus of the present invention.

Fig. 2 is a view showing the flow direction of the gas flow formed above the molten glass G flowing through the vacuum degassing tank 12 shown in Fig. 1.

Detailed description of the preferred embodiment

Hereinafter, the present invention will be described with reference to the drawings.

Fig. 1 is a cross-sectional view showing a configuration example of a vacuum degassing apparatus of the present invention. In the vacuum degassing apparatus 10 shown in FIG. 1, the cylindrical decompression defoaming tank 12 is accommodated in the decompression housing 11 so that the long axis may be aligned in the horizontal direction. A riser pipe 13 that is oriented in the vertical direction is attached to the lower surface of the upstream side of the vacuum degassing tank 12, and a downcomer 14 is attached to the lower side of the downstream side. Further, the upstream side and the downstream side of the vacuum degassing tank 12 mean that the flow direction of the molten glass G flows through the vacuum degassing tank 12 (that is, flows in the lateral direction in the vacuum degassing tank 12). The upstream side and the downstream side. A portion of the riser 13 and the downcomer 14 are located within the decompression housing 11.

As shown in Fig. 1, the riser 13 is connected to the vacuum degassing tank 12, and the molten glass G from the melting tank 200 is introduced into the introduction mechanism of the vacuum degassing tank 12. Therefore, the lower end portion of the riser pipe 13 is fitted to the open end of the upstream pool 220, and is immersed in the molten glass G in the upstream pool 220.

The downcomer 14 is connected to the vacuum degassing tank 12, and the molten glass G which has been defoamed under reduced pressure is lowered by the vacuum degassing tank 12, and is led to a derivation mechanism of a processing tank (not shown) of a post-process. Therefore, the lower end portion of the downcomer 14 is fitted to the open end of the downstream pool 240, and is immersed in the molten glass G in the downstream pool 240.

In the decompression housing 11, a heat insulating material 18 such as a heat insulating brick for insulating such a coating is disposed around the decompression defoaming tank 12, the riser pipe 13, and the down pipe 14.

In the vacuum degassing apparatus 10 shown in Fig. 1, since the vacuum degassing tank 12, the riser pipe 13, and the down pipe 14 are pipes of the molten glass G, the heat resistance and the corrosion resistance of the molten glass are used. Production. For example, a hollow tube made of platinum or platinum alloy. Specific examples of the platinum alloy include a platinum-gold alloy and a platinum-ruthenium alloy. Moreover, as another example, it is a hollow tube made of a ceramic-based non-metallic inorganic material, that is, a hollow tube made of a dense refractory material. Specific examples of the dense refractory include electroforming of an alumina-based electroformed refractory, a zirconia-based electroformed refractory, and an alumina-zirconia-silica-based electroforming refractory. A dense refractory refractory such as a refractory material, a dense alumina refractory, a dense zirconia-yttria-based refractory, and a dense alumina-zirconia-yttria-based refractory. The decompression housing 11 for accommodating the decompression degassing tank 12 and accommodating one of the riser 13 and the downcomer 14 is made of metal, for example, made of stainless steel.

In the vacuum degassing apparatus 10 of the present invention shown in Fig. 1, windows 15 and 16 for monitoring the inside of the vacuum degassing tank 12 are provided on the upstream side and the downstream side of the top of the vacuum degassing tank 12. The windows 15 and 16 are hollow tubes made of platinum or platinum alloy or dense refractories, one end of which is connected to the upstream side and the downstream side of the top of the vacuum degassing tank 12, and the other end penetrates the decompression housing 11 The wall surface is located outside the decompression housing 11.

The window 15 provided on the upstream side of the vacuum degassing tank 12 is inserted with a ceramic hollow tube 17 made of platinum or platinum alloy or containing alumina or zirconia. The hollow tube 17 is a gas introduction mechanism that introduces the gas 100 into the upper space inside the decompression degassing tank 12.

In addition, the upper space inside the decompression degassing tank 12 means a space portion which flows over the molten glass G of the vacuum degassing tank 12. In the vacuum degassing tank 12, the front end of the hollow tube 17 is located above the molten glass G.

Further, for example, the window 16 provided on the downstream side of the vacuum degassing tank 12 is connected to a pressure reducing mechanism (not shown) such as a pump, and discharges the ambient gas of the upper space to the decompression housing 11 Externally, the inside of the vacuum degassing tank 12 can be decompressed.

Although not shown, a heating mechanism (for example, a heater) for heating the gas 100 introduced into the upper space inside the decompression degassing tank 12 is provided inside the hollow tube 17. In addition, when a heater is used as the heating means, the heat generation method is not particularly limited, and various heat generation methods such as a method of heating and heating the electric heating body can be used.

The vacuum degassing apparatus of the present invention has a heating mechanism that introduces a gas into a space above the inside of the vacuum degassing vessel and a heating mechanism that heats the gas introduced into the head space. The gas is supplied to the upper space of the molten glass which flows through the vacuum degassing tank.

In addition, the type of the gas introduced by the gas introduction means and the temperature of the heated gas are described in the description of the method for producing molten glass of the present invention to be described later.

The gas introduction means in the vacuum degassing apparatus of the present invention is not limited to the one shown in Fig. 1 as long as the gas can be introduced into the upper space inside the decompression degassing tank.

For example, in the vacuum degassing apparatus 10 shown in Fig. 1, a hollow tube 17 having a straight tube shape with a distal end downward is shown. However, the shape of the hollow tube is not limited thereto, and the shape of the hollow tube can be appropriately selected. For example, in order to induce the gas 100 introduced into the upper space inside the decompression degassing tank 12 in the downstream direction, a hollow tube whose front end is curved in the downstream direction may be used. Further, the gas introduction mechanism may be disposed on the side instead of above the vacuum degassing tank.

Further, in the vacuum degassing apparatus 10 shown in Fig. 1, the hollow tube 17 is inserted into the window 15 provided on the upstream side, but the hollow tube 17 which is the gas introduction means may be inserted downstream. Side window 16. Further, the window 15 or the window itself may be used as the gas introduction mechanism without using the hollow tube 17.

However, when the heated gas is supplied to the space above the molten glass G flowing through the vacuum degassing tank 12, the hollow tube 17 inserted into the window 15 or the window 16 is used as a gas introduction mechanism. In use, the heated gas does not become cold before being supplied to the upper space of the molten glass G, so that it is preferable. Further, in the above-described manner, the heated gas is introduced into the upper space of the molten glass flowing through the vacuum degassing vessel to prevent the bubble layer on the surface of the molten glass from being enlarged, and thus the decompression and defoaming effect is lowered. In the case where the gas flow is formed above the molten glass flowing through the vacuum degassing vessel, the hollow tube 17 inserted into the window 15 or the window 16 is preferably used as a gas introduction mechanism.

Further, when the bubble layer on the surface of the molten glass is easily enlarged to the point which is generated on the upstream side of the vacuum degassing tank, it is preferable to insert the window 15 provided on the upstream side of the vacuum degassing tank 12 or insert it into The hollow tube 17 of the window 15 is used as a gas introduction mechanism.

Further, in the above, for the purpose of monitoring the inside of the vacuum degassing tank 12, the windows 15, 16 provided at the top of the vacuum degassing tank 12, or the hollow tubes 17 inserted into the windows 15, 16 are used as The gas introduction mechanism is used, but a gas introduction mechanism may be provided in addition to the parts.

For example, a hollow tube structure similar to the windows 15, 16 may be provided at a portion other than the top of the vacuum degassing tank, for example, an upstream side end surface, a downstream side end surface, or a side surface of the vacuum degassing tank. The tube structure is used as a gas introduction mechanism.

Further, in the vacuum degassing apparatus 10 shown in Fig. 1, the windows 15 and 16 for monitoring the inside of the vacuum degassing tank 12 are provided on the upstream side and the downstream side of the top of the vacuum degassing tank 12, but The window for monitoring the inside of the vacuum degassing tank 12 may be disposed at a portion other than the upstream side and the downstream side of the top portion of the vacuum degassing tank 12 (for example, the intermediate portion), and the window may be inserted or inserted into The hollow tube of the window is used as a gas introduction mechanism.

Further, in the vacuum degassing apparatus 10 shown in Fig. 1, one gas introduction means is provided. However, the number of the gas introduction means in the vacuum degassing apparatus of the present invention is not particularly limited, and may be plural.

For example, in the vacuum degassing apparatus 10 shown in Fig. 1, in addition to the hollow tube 17 inserted into the window 15 on the upstream side, the hollow tube can be inserted into the window 16 on the downstream side as a gas introduction mechanism. use.

Further, the gas introduction means may be provided with a mechanism (for example, a gas flow rate control valve) for controlling the amount of gas introduced, or a valve mechanism (for example, a solenoid valve) for stopping the introduction of the gas after the gas is introduced as needed.

The heating mechanism in the vacuum degassing apparatus of the present invention is not limited to the above-described aspect as long as it can heat the gas introduced into the upper space of the inside of the vacuum degassing vessel by the gas introduction mechanism.

For example, the above description is that a heating mechanism for heating the gas 100 is provided inside the hollow tube 17 of the gas introduction mechanism, but the heating mechanism may be provided on the outer circumference of the hollow tube 17. In this case, for example, a heater as a heating means may be wound around the outer circumference of the hollow tube 17.

Further, the heating means is preferably provided along the piping of the hollow tube 11 in the decompression housing 11. In this case, the temperature of the gas to be introduced into the vacuum degassing tank does not decrease. Further, the heating means is preferably provided inside the conduit of the hollow tube 17 as the gas introduction means. In this case, the gas can be heated more efficiently. Further, the above-described heating mechanism is provided along the pipe of the hollow pipe, and includes a case where the entire pipe is included in the decompression casing 11 and is provided continuously, and the pipe is provided at a predetermined interval. Or it is set in the field of entering the decompression degassing tank.

Further, as described above, when the window 15 or the window 16 itself is used as the gas introduction mechanism without using the hollow tube 17, a heating mechanism may be provided in the window 15 or the window 16.

Further, the hollow tubes 17 inserted into the windows 15, 16 or the windows 15, 16 may be provided with heating means, but may be provided for feeding to the windows 15, 16 or to the windows 15, 16 A heating mechanism in which the gas before the tube 17 is preheated. As a specific example of providing such a heating means, a heating means for supplying a gas supply source such as a pump or a heating means for providing a gas supply pipe on the upstream side of the comparative gas hollow pipe 17 is provided.

In addition to the above-described constituent elements, the vacuum degassing apparatus of the present invention may have a function of preventing the molten glass surface from being introduced into the upper space of the molten glass flowing through the vacuum degassing tank, which will be described later. The foam layer is enlarged, and the resulting decompression and defoaming effect is reduced, and other suitable components are suitable.

For example, in order to form a gas flow over the molten glass flowing through the vacuum degassing vessel, the foaming layer on the surface of the molten glass is prevented from being enlarged, and the resulting decompression and defoaming effect is reduced. In addition to the gas introduction mechanism into which the gas 100 is introduced into the upper space inside the decompression degassing tank 12, a gas outlet means for guiding the gas from the upper space is required. The details will be described in detail later, but in the case of the vacuum degassing apparatus 10 shown in Fig. 1, the downstream side window 16 can be used as a gas discharge mechanism.

Further, in order to form a gas flow in the vicinity of the surface (liquid surface) of the molten glass G, an obstacle plate 19 for guiding the gas flow to the lower side may be provided inside the top of the vacuum degassing tank 12.

In addition, when the water vapor concentration of the ambient gas in the vacuum degassing vessel is 60 mol% or less, the foaming layer on the surface of the molten glass is prevented from being enlarged, and the decompression and defoaming effect caused thereby is lowered. It is preferable to provide a water vapor concentration measuring means for measuring the water vapor concentration of the ambient gas, and the gas introducing means should control the gas introduction amount in accordance with the water vapor concentration measured by the water vapor concentration measuring means.

As the water vapor concentration measuring means, a commercially available dew point meter may be used, and water contained in the environmental gas discharged from the vacuum degassing tank as described in Patent Document 1 may be used, and the amount may be measured by measuring the amount. Estimate the water vapor concentration of the ambient gas.

In the vacuum degassing apparatus of the present invention, in order to decompress the upper space in the decompression degassing tank, for example, a groove opening is provided in the top of the vacuum degassing tank which is housed in the decompression housing, and A suction opening is provided at a top portion of the decompression housing corresponding to the opening of the slot, and a vacuum pump for decompressing the decompression degassing tank is connected to the suction opening, and decompression of the molten glass is performed by operation of the vacuum pump. .

In addition, when a gas introduction mechanism is provided on the side of the window 15 on the upstream side of the decompression degassing tank 12 as described above, a pressure reduction mechanism such as a vacuum pump may be connected to the side of the window 16 provided on the downstream side. The ambient gas in the upper space of the vacuum degassing tank is discharged to the outside of the decompression housing 11 to decompress the inside of the vacuum degassing tank 12. In addition, when a gas introduction mechanism is provided on the side of the window 16 on the downstream side of the decompression degassing tank 12, a pressure reduction mechanism such as a vacuum pump may be connected to the window 15 provided on the upstream side thereof to decompress the pressure. The ambient gas in the upper space of the defoaming tank is discharged to the outside of the decompression housing 11, and the inside of the vacuum degassing tank 12 is decompressed.

The method and structure for decompressing the pressure in the vacuum degassing tank are the most suitable methods and structures for the structure of the vacuum degassing apparatus.

The size of each component of the vacuum degassing apparatus 10 of the present invention can be appropriately selected as needed. The size of the vacuum degassing tank 12 is not limited to that of the vacuum degassing tank 12 made of platinum or platinum alloy or a dense refractory material, and may be used in accordance with the vacuum degassing apparatus or the vacuum degassing tank 12 Shape is appropriately selected. In the case of the cylindrical decompression degassing tank 12 shown in Fig. 1, one example of the size is as follows.

‧ Length in horizontal direction: 1~20m

‧Inner diameter: 0.2~3m (round section)

When the vacuum degassing tank 12 is made of platinum or platinum alloy, the thickness is preferably 4 mm or less, and more preferably 0.5 to 1.2 mm.

The vacuum degassing tank is not limited to a cylindrical shape having a circular cross section, and may have a cylindrical shape having an elliptical or semicircular cross section or a tubular shape having a rectangular cross section.

The size of the riser 13 and the downcomer 14 is not limited to platinum or platinum alloy or dense refractory, and may be appropriately selected depending on the vacuum degassing apparatus to be used. For example, in the case of the vacuum degassing apparatus 10 shown in Fig. 1, one example of the dimensions of the riser 13 and the downcomer 14 is as follows.

‧Inner diameter: 0.05~0.8m, preferably 0.1~0.6m

‧ Length: 0.2~6m, preferably 0.4~4m

When the riser 13 and the downcomer 14 are made of platinum or platinum alloy, the thickness is preferably 0.4 to 5 mm, and more preferably 0.8 to 4 mm.

Next, a method of producing a molten glass of the present invention will be described.

The method for producing a molten glass according to the present invention comprises the steps of defoaming the molten glass under reduced pressure in a vacuum degassing tank, and heating the gas for preventing the bubble layer on the surface of the molten glass from heating to a temperature of 500 ° C or higher. The upper space of the molten glass flowing through the vacuum degassing tank.

Here, the gas supplied to the upper space of the molten glass flowing through the vacuum degassing tank is preferably at least one selected from the group consisting of hydrogen (H ₂ ), nitrogen (N ₂ ), oxygen (O ₂ ), air, carbon monoxide. (CO), carbon dioxide (CO ₂ ), argon (Ar), helium (He), neon (Ne), krypton (Kr), xenon (Xe), hydrocarbon-based gas, carbonized fluorine-based gas, and ammonia (NH ₃ ) The gas in the group is further preferably at least one selected from the group consisting of nitrogen, air, carbon dioxide, argon (Ar), helium (He), neon (Ne), krypton (Kr) and xenon (Xe). Further, it is preferable that the gas of the group is at least one selected from the group consisting of nitrogen, air, carbon dioxide, and argon.

In addition, it is preferable to use a gas selected from the above-mentioned group because the gas supplied to the space above the molten glass is used to prevent the bubble layer from being enlarged on the surface of the molten glass to be described later, and the effect of reducing the decompression and defoaming effect. Therefore, it is better. More specifically, by forming a gas stream above the molten glass flowing through the vacuum degassing vessel, it is possible to prevent the bubble layer from being enlarged on the surface of the molten glass and to reduce the decompression and defoaming effect. Preferably. In addition, by setting the water vapor concentration of the ambient gas in the vacuum degassing tank to 60 mol% or less, it is preferable to prevent the bubble layer on the surface of the molten glass from being enlarged and the decompression and defoaming effect of the molten glass to be reduced. Moreover, it does not adversely affect molten glass or manufactured glass products, and glass manufacturing equipment (especially vacuum degassing apparatus).

In addition, it is known that at least one type of gas selected from the above-mentioned group can supply any one of the above-mentioned groups to the upper space of the molten glass, and two or more kinds of mixed gases can be supplied to the molten glass. The upper space.

Further, when the constituent material of the vacuum degassing tank is platinum or platinum alloy, if air is used as the gas supplied to the upper space of the molten glass flowing through the vacuum degassing tank, it is preferable that the oxygen concentration is higher than that in the air. Lower concentration gas. By using a gas having a lower oxygen concentration than the oxygen concentration in the air, oxidation of platinum which is a constituent material of the vacuum degassing vessel can be suppressed, the life of the vacuum degassing vessel can be prolonged, and generation of the glass product can be suppressed. The defect of platinum is preferred.

In order to obtain the above effects, the oxygen concentration in the gas is preferably 15% by volume or less, more preferably 10% by volume or less, and most preferably 5% by volume or less.

Moreover, when the flow rate of the gas supplied to the upper space of the molten glass is 5 standard liters per minute or more, the effect of preventing the bubble layer from being enlarged and the resulting reduced pressure defoaming effect can be further improved. Preferably.

When at least one gas selected from the above group is heated to a temperature of 500 ° C or higher and supplied to the upper space of the molten glass flowing through the vacuum degassing vessel, the reduction of the present invention described in FIG. 1 is used. Press the defoaming device.

In the method for producing a molten glass according to the present invention, a gas heated to a temperature of 500 ° C or higher is supplied to the upper space of the molten glass flowing through the vacuum degassing vessel, so that the temperature of the molten glass surface due to the supply of the gas can be greatly reduced. Moreover, the reduction in the pressure reduction defoaming effect caused by the temperature decrease of the surface of the molten glass can be greatly reduced.

Further, since the supply of the gas can prevent the surface temperature of the molten glass from decreasing and the pressure reduction and defoaming effect from being lowered, the amount of gas supplied to the upper space of the molten glass flowing through the vacuum degassing tank can be increased. Thereby, the effect of preventing the enlargement of the bubble layer described later and the resulting reduced pressure defoaming effect can be further enhanced.

From the viewpoint of the above effects, it is preferable to supply a gas heated to 550 ° C or higher to the upper space of the molten glass flowing through the vacuum degassing vessel, and it is more preferable to supply a gas heated to 600 ° C or higher.

In the method for producing a molten glass according to the present invention, the gas heated to a temperature of 500 ° C or higher is introduced into the upper space of the molten glass flowing through the vacuum degassing vessel, thereby preventing the bubble layer on the surface of the molten glass from being enlarged, and thus The effect of reducing the decompression and defoaming effect produced can be roughly classified into the following two effects. The method for producing a molten glass of the present invention may be either of these effects, or may be used in either case.

In the first action, a gas flow is formed above the molten glass flowing through the vacuum degassing vessel, and the retention of the gas component from the molten glass is eliminated, thereby preventing the bubble layer on the surface of the molten glass from being enlarged and thus decompressing. The bubble effect is reduced.

As described above, the vacuum degassing method removes the bubbles contained in the molten glass by placing the molten glass under a reduced-pressure atmosphere, and removes the bubbles on the surface of the molten glass to remove the bubbles. The gas component (hereinafter referred to as "the gas component derived from the molten glass" which is generated by the bubble breaking on the surface of the molten glass is retained above the molten glass flowing in the vacuum degassing vessel, above the molten glass Since the ambient gas (the upper space inside the vacuum degassing tank) has a high partial pressure of the gas component from the molten glass, bubbles floating on the surface of the molten glass are less likely to be broken, and the defoaming effect under reduced pressure is lowered.

Further, the gas component from the molten glass may differ depending on the glass composition, and examples thereof include, for example, HCl, H ₂ SO ₄ , a boric acid compound, HF, and the like.

As shown in Fig. 2, when the gas 100 is supplied to the upper space of the molten glass G flowing through the vacuum degassing tank 12 by the hollow tube 17 as the gas introduction means, the formation of the molten glass G is reduced. The gas flow g flowing to the downstream side of the upstream side of the pressure degassing tank 12 is performed. The gas component from the molten glass is transported by the gas stream g and is discharged to the outside by the window 16 as a gas discharge means. As a result, the retention of the gas component from the molten glass can be eliminated. By eliminating the retention of the gas component from the molten glass, it is possible to prevent the bubble layer on the surface of the molten glass from being enlarged, and the resulting vacuum defoaming effect is reduced.

In addition, in the second figure, although the flow direction of the gas stream g and the flow direction of the molten glass G (that is, the flow direction of the molten glass indicated by the arrow) are the same direction, as long as it can be eliminated by the formation of the gas flow When the gas component of the molten glass is retained, the flow direction of the gas stream g is not limited thereto.

For example, the flow direction of the gas stream g and the flow direction of the molten glass G may be opposite directions. In this case, the gas 100 is supplied from the gas introduction means provided in the downstream side window 16, and a gas flow which flows from the downstream side of the decompression degassing tank 12 to the upstream side is formed. Further, in this case, the window 15 on the upstream side functions as a gas discharge mechanism.

Further, although the vacuum degassing tank 12 shown in Fig. 2 has a vertically long shape which is long in the flow direction of the molten glass G, the vacuum degassing tank has a short length and a width in the flow direction of the molten glass G. A wider shape. In the case of such a vacuum degassing vessel, a gas flow in the width direction of the vacuum degassing vessel (that is, a direction perpendicular to the flow direction of the molten glass G) may be formed.

In addition, in the second drawing, the gas flow g in the same direction as the flow direction of the molten glass G is formed in the entire longitudinal direction of the vacuum degassing tank 12, but a plurality of gas flows may be formed above the molten glass G. Gas flow. The plurality of gas streams may be in the same direction as the flow direction of the molten glass G or in the opposite direction. Further, the plurality of gas streams may be in the same direction of flow, or may be in opposite directions.

Further, when a gas flow in the vertical direction is formed with respect to the flow direction of the molten glass G, or when a plurality of gas flows are formed above the molten glass G, the gas introduction mechanism and the gas discharge can be arranged in consideration of the flow direction of the formed gas flow. mechanism.

However, if the bubble layer on the surface of the molten glass is easily enlarged to the point where it is generated on the upstream side of the vacuum degassing tank, it is preferable to insert the hollow tube 17 into the window 15 on the upstream side as shown in Fig. 2 . The gas 100 is supplied, and then a gas flow g in the same direction as the flow direction of the molten glass G is formed.

The second action is to introduce a gas (low moisture gas) which is low in moisture to prevent the bubble layer of the molten glass surface from being introduced into the ambient gas of the vacuum degassing tank, and the water vapor concentration of the ambient gas is When it is 60 mol% or less, it is possible to prevent the bubble layer on the surface of the molten glass from being enlarged, and the resulting decompression and defoaming effect is lowered.

Further, as described in Patent Document 1, when the water vapor concentration of the ambient gas in the vacuum degassing tank exceeds a specific value, the bubble layer on the surface of the molten glass is enlarged, and when it exceeds a specific value higher than the specific value, The bubble layer enlargement will further proceed and the bump will occur. However, by introducing the low-moisture gas into the ambient gas of the vacuum degassing tank, the water vapor concentration of the ambient gas is 60 mol% or less, thereby preventing the bubble on the surface of the molten glass. The layer is enlarged, and the resulting decompression and defoaming effect is reduced. Then, of course, by preventing the bubble layer on the surface of the molten glass from being enlarged, it is possible to prevent the bump and the resulting decompression and defoaming effect from being lowered.

Here, the low moisture gas system means a gas having a water vapor concentration lower than that of the atmospheric pressure degassing tank. The water vapor concentration of the low moisture gas is preferably 60 mol% or less, preferably 50 mol% or less, more preferably 40 mol% or less, more preferably 30 mol% or less, still more preferably 25 mol% or less, and preferably 20 mol% or less. Preferably, it is 15 mol% or less, more preferably 10 mol% or less, and particularly preferably 5 mol% or less.

Further, any of the gases supplied to the upper space of the molten glass flowing through the vacuum degassing tank can be supplied as a low moisture gas.

Further, since the lower the water vapor concentration of the ambient gas having the vacuum degassing tank, the bubble layer on the surface of the molten glass tends to be thinner, so the water vapor concentration of the ambient gas is preferably 50 mol% or less, and 40 mol%. The following are preferred. Further, when the water vapor concentration is 30 mol% or less, the bubble layer tends to be thinner, which is preferable.

Further, when the water vapor concentration of the ambient gas is low, some of the glass composition may be caused by a bubble shrinkage or foaming, whereby the bubble layer becomes thinner, so that it is preferable. Specifically, when the molten glass is borosilicate glass, if the water vapor concentration is 30 mol% or less, the bubbles tend to shrink remarkably. Here, the borosilicate glass is composed of, for example, the following composition in terms of oxide.

Composition range: SiO ₂ : 50~66, Al ₂ O ₃ : 10.5~22, B ₂ O ₃ : 0~12, MgO: 0~8, CaO: 0~14.5, SrO: 0~24, BaO: 0 ~13.5, MgO+CaO+SrO+BaO: 9~29.5 (unit is mass%).

Further, when the water vapor concentration of the ambient gas is low, it is preferable that the bubble which is considered to be a defect is likely to remain in the glass product produced by defoaming under reduced pressure. When the water vapor concentration of the ambient gas becomes lower, the probability of defects in the glass product produced by defoaming under reduced pressure becomes lower, so it is preferably 25 mol% or less, and 20 mol% or less. Preferably, it is preferably 15 mol% or less, more preferably 10 mol% or less, and still more preferably 5 mol% or less.

Further, by suspending the water vapor concentration of the ambient gas to 60 mol% or less, volatilization of a specific component (boron or the like) in the molten glass can be suppressed. By suppressing the volatilization of the components such as boron, it is possible to prevent the composition of boron or the like from changing, and it is possible to suppress the deterioration of the flatness due to the composition variation.

Further, since volatilization of other components which are easily volatilized, for example, Cl, F, and S, can be suppressed, it is possible to prevent variations in composition of the components, and it is possible to suppress deterioration of flatness due to composition variation.

The volatilization of such Cl, F, S and the like is considered to be very much affected by the moisture in the ambient gas. For example, it is conceivable that F is volatilized as HF, and S is volatilized as H ₂ SO ₄ . Therefore, by ordering the water vapor concentration of the ambient gas to be 60 mol% or less, it is considered that the volatilization of the above components and the compositional variation of the above components can be suppressed.

In the conventional method, since boron is volatilized from the molten glass, more boron must be used as a raw material. Moreover, the amount of boron volatilization varies depending on conditions, and therefore there is a problem that the composition of the glass varies microscopically.

The method for producing a molten glass of the present invention can suppress the volatilization of boron from molten glass, and can solve such problems.

From this point of view, the method for producing a molten glass of the present invention is suitably used in the production of general glass, and can be said to be particularly suitable for use in the production of borosilicate glass.

In the method for producing molten glass of the present invention, as long as the first or second action described above can be exerted, it is not always necessary to continuously supply the gas 100 to the upper space of the molten glass G flowing through the vacuum degassing tank 12.

In the case of the first action, as long as the retention of the gas component from the molten glass can be solved, the gas flow can be periodically formed during the vacuum degassing, for example, it can be formed every hour for 1 to 30 seconds. Left and right gas flow. Therefore, the gas 100 may be periodically supplied to the upper space of the molten glass G flowing through the vacuum degassing tank 12.

Further, in the case of the second action, in the implementation of the vacuum degassing, the water vapor concentration of the ambient gas in the vacuum degassing tank 12 may be monitored, and when the water vapor concentration of the ambient gas exceeds 60 mol%. In the case of krypton, the gas 100 is supplied as a low-moisture gas to the upper space of the molten glass G flowing through the vacuum degassing tank 12.

In the method for producing a molten glass according to the present invention, at least one gas selected from the group of gases supplied to the upper space of the molten glass flowing through the vacuum degassing vessel described above is heated to a temperature of 500 ° C or higher. It can be carried out in the same manner as the conventional method for producing molten glass, except that it is supplied to the upper portion of the molten glass flowing through the vacuum degassing vessel. For example, when vacuum degassing is carried out, the vacuum degassing vessel 12 is preferably heated to a temperature ranging from 1100 ° C to 1600 ° C, particularly preferably from 1150 ° C to 1450 ° C. Further, the inside of the vacuum degassing tank 12 should be decompressed to an absolute pressure of 38 to 460 mmHg (51 to 613 hPa), and a pressure reduction to 60 to 350 mmHg (80 to 467 hPa) is preferred. Further, from the viewpoint of productivity, the flow rate of the molten glass G flowing through the vacuum degassing tank 12 is preferably from 1 to 2,000 tons/day.

The method for producing a glass product of the present invention includes the vacuum degassing process, and includes a raw material melting process and a molding process as a front process and a post process. The raw material melting process can be, for example, a well-known person, for example, a process of melting a raw material by heating to about 1400 ° C or more in response to the type of glass. The raw material to be used is not particularly limited as long as it is a material suitable for the glass to be produced. For example, a raw material which blends with a known person such as cerambi, boric acid or limestone in combination with the composition of the final glass product may be used. Desirable clarifier. Further, the molding process may be, for example, a well-known person, and may be, for example, a floating molding process, a roll forming process, a melt forming process, or the like.

The molten glass and the glass article produced by the present invention are not limited in composition as long as they are produced by a heat fusion method. Therefore, it may be an alkali-free glass or an alkali-lime vermiculite glass or an alkali-boric glass-like alkali glass typified by soda-lime glass. The present invention is particularly suitable for the production of alkali-free glass, and is more suitable for the production of alkali-free glass for liquid crystal substrates.

Further, according to the present invention, since a glass product having extremely excellent foam quality, that is, a glass having few defects, can be obtained, it is suitable as a method for producing a glass substrate or an optical glass for FPD.

Industrial availability

According to the method for producing a molten glass of the present invention, since the decrease in the surface temperature of the molten glass due to the supply of the gas and the decrease in the defoaming effect under the reduced pressure are prevented, the growth of the bubble layer is prevented, and the resulting layer is formed. Since the effect of defoaming under reduced pressure is lowered, it is possible to obtain a molten glass or a glass product which is excellent in foam quality, and is suitable as a method for producing a glass substrate for FPD or an optical glass.

The entire disclosure of the specification, the drawings, and the abstract of the Japanese Patent Application No. 2009-167512, the entire disclosure of which is hereby incorporated by reference.

10. . . Vacuum degassing device

11. . . Pressure reducing housing

12. . . Vacuum degassing tank

13. . . Riser

14. . . Drop tube

15,16. . . window

17. . . Hollow tube (gas introduction mechanism)

18. . . Insulation material

19. . . Obstruction board

100. . . gas

200. . . Melting tank

220. . . Upstream pool

240. . . Downstream pool

G. . . Molten glass

g. . . Gas flow

Fig. 1 is a cross-sectional view showing a configuration example of a vacuum degassing apparatus of the present invention.

Fig. 2 is a view showing the flow direction of the gas flow formed above the molten glass G flowing through the vacuum degassing tank 12 shown in Fig. 1.

10. . . Vacuum degassing device

11. . . Pressure reducing housing

12. . . Vacuum degassing tank

13. . . Riser

14. . . Drop tube

15,16. . . window

17. . . Hollow tube (gas introduction mechanism)

18. . . Insulation material

19. . . Obstruction board

100. . . gas

200. . . Melting tank

220. . . Upstream pool

240. . . Downstream pool

G. . . Molten glass

Claims (11)

A method for producing a molten glass, which comprises a process for defoaming a molten glass under reduced pressure in a vacuum degassing vessel, wherein the gas is heated to a temperature of 500 ° C or higher and then supplied to the reduced pressure degassing The upper space of the molten glass of the tank. The method for producing a molten glass according to the first aspect of the invention, wherein the gas system supplied to the upper space of the molten glass flowing through the vacuum degassing vessel is at least one selected from the group consisting of hydrogen (H ₂ ) and nitrogen (N ₂ ). ), oxygen (O ₂ ), air, carbon monoxide (CO), carbon dioxide (CO ₂ ), argon (Ar), helium (He), neon (Ne), krypton (Kr), xenon (Xe), hydrocarbon-based gas, A gas of a group of carbonized fluorine-based gas and ammonia (NH ₃ ). The method for producing a molten glass according to claim 1 or 2, wherein the gas supplied to the space above the molten glass flowing through the vacuum degassing vessel is air having an oxygen concentration of 15% by volume or less. The method for producing a molten glass according to claim 1 or 2, wherein the ambient gas of the vacuum degassing vessel can be obtained by supplying the gas to an upper space of the molten glass flowing through the vacuum degassing vessel. The water vapor concentration is 60 mol% or less. The method for producing a molten glass according to claim 1 or 2, wherein the gas is supplied to the upper portion of the molten glass flowing through the vacuum degassing vessel, and is melted in the vacuum degassing vessel. Above the glass, at least one gas stream selected from the flow direction of the molten glass, a gas flow opposite to the flow direction of the molten glass, and a gas perpendicular to the flow direction of the molten glass are formed. The gas flow of the group of streams. A vacuum degassing device for molten glass, comprising: a decompression housing sucked by a reduced pressure; and a vacuum degassing tank provided in the decompression housing to perform decompression defoaming of molten glass; The vacuum degassing tank is connected to the introduction mechanism for introducing the molten glass before decompression under reduced pressure into the decompression degassing tank; and is provided in communication with the decompression degassing tank to be used for the decompression defoaming tank The apparatus for deriving the molten glass after defoaming under reduced pressure further includes: a gas introduction mechanism that introduces a gas into the upper space inside the decompression degassing tank; and a gas that introduces the gas introduced into the upper space Heating mechanism. The vacuum degassing apparatus for molten glass according to Item 6 of the patent application, wherein the gas introduction mechanism is constituted by a hollow tube, and the heating mechanism passes through the pipeline of the hollow tube to pass through the decompression housing. And set. The vacuum degassing apparatus for molten glass according to claim 7, wherein the heating mechanism is disposed inside a pipe of the hollow pipe. The vacuum degassing apparatus for molten glass according to any one of claims 6 to 8, further comprising a water vapor concentration measuring means for measuring a water vapor concentration of an ambient gas in the vacuum degassing tank. The vacuum degassing apparatus for molten glass according to any one of claims 6 to 8, wherein the gas introduction mechanism is disposed at a top or a side of the vacuum degassing tank, and the vacuum degassing tank is attached to An upper space is formed on the molten glass inside the vacuum degassing tank. A method for producing a glass product, comprising: a vacuum degassing process using a vacuum degassing device for molten glass according to any one of claims 6 to 10, and a process before the vacuum degassing process and The post-process raw material melting process and forming process.