JP2014005180A - Method of inserting electrode, method of manufacturing glass product, method of manufacturing glass melting tank, and glass melting tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of inserting an electrode into a glass melting tank.SOLUTION: There is provided a method of inserting an electrode that includes the steps of: arranging the electrode in a through hole in a bottom wall of the glass melting tank so that an upper end of the electrode is at a position which is 10 to 150 mm below a molten glass-side surface of the bottom wall; filling the through hole with a melt of first glass as alkali-free glass of 900 to 1,100°C in operation point; reserving a melt of second glass of larger than 1,100°C in operation point in the glass melting tank; and inserting the electrode so that the upper end of the electrode penetrates the melt of the first glass to enter the melt of the second glass.

Description

  The present invention relates to a method for inserting a heating electrode provided in a glass melting tank into a glass melt when manufacturing a high strain point glass, a method for manufacturing a glass product, a method for manufacturing a glass melting tank, and a glass melting tank. .

As one method for heating the glass melt, there is a method in which an electrode is inserted into the glass melt and energized. A metal such as molybdenum is used as an electrode material for current heating. The metal used for the electrodes may be oxidized, deteriorated or sublimated when exposed to hot air. Therefore, when the electrode is installed in the glass melting tank, a measure for cooling the electrode or a measure for blocking air is taken to protect the electrode.
When installing the electrode on the brick bottom wall of the glass melting tank, for example, as a method of inserting the electrode, first, a through hole is made in the bottom wall, and a rod-shaped electrode and an electrode holder for holding the electrode are installed in the bottom wall. The electrode holder is provided with cooling means such as a water cooling jacket. Next, when the electrode is inserted into the glass melting tank, the upper end of the electrode is kept inside the through hole in the bottom wall and cooled, and after the glass melt is stored in the glass melting tank, the electrode is inserted into the glass melt. It protrudes in (patent document 1).

JP 2007-119299 A

  In recent years, alkali-free glass having a high strain point has been used for liquid crystal display substrates and the like. Since these glasses have a higher viscosity than conventional soda lime glass, in order to soften to the same extent, it is necessary to raise the temperature to 100 ° C. or higher than soda lime glass. Therefore, it is difficult to insert into the glass melt while protecting the electrode by the above method. This is because if the temperature of the glass melting tank is raised in order to soften the glass to such an extent that the electrode can be inserted, the electrode also becomes hot and the electrode is easily oxidized. On the other hand, when the temperature of the glass melting tank is lowered in order to protect the electrode, the temperature of the glass melt is lowered, the viscosity becomes high, and the insertion of the electrode becomes difficult.

  Prior to storing the glass melt in the glass melting tank, the present inventor placed the melted soda lime glass cullet in the through hole where the electrode is waiting, and covered the electrode with molten soda lime glass. Protected. Next, the alkali-free glass was stored in a glass melting tank, and the electrode was inserted into the alkali-free glass melt. As a result, this method using soda lime glass facilitated the insertion of the electrode. However, when the glass melting tank is used for a long period of time, there is a problem that the heating efficiency of the alkali-free glass melt is lowered.

The present inventor considered that the cause of the problem was that the alkali metal component in the soda lime glass penetrated into the brick constituting the bottom wall of the glass melting tank and lowered the electrical resistivity of the brick. Specifically, it was considered that the electric resistivity of the brick decreases, so that the electric current that should flow in the alkali-free glass melt flows into the brick and the heating efficiency of the melt decreases. In addition, when current flows in the brick, abnormal heating occurs, so the brick may be dissolved.
From the above, the present inventor further needs to adopt a glass used for electrode protection not only having a low viscosity but also having no adverse effect on the electrodes and bricks in relation to the glass to be produced. We thought that there was, and led to the following invention.

That is, the present invention is a method for inserting an electrode of a glass melting tank, wherein the upper end of the electrode is 10 to 150 mm below the molten glass side surface of the bottom wall of the through hole in the brick bottom wall of the glass melting tank. Disposing the electrode at a position to become, filling the through hole with a melt of a first glass which is non-alkali glass having a working point of 900 ° C. or higher and 1100 ° C. or lower, and the glass A step of storing a melt of the second glass having a work point of over 1100 ° C. in the melting tank, and an upper end of the electrode penetrating the melt of the first glass and entering the melt of the second glass And inserting the electrode into the electrode.
The present invention includes a step of inserting an electrode into a glass melting tank by the electrode insertion method, heating the second glass melt with the electrode, and forming the second glass melt, And a step of slowly cooling the molded product.
The present invention provides a method for manufacturing a glass melting tank, wherein an electrode is inserted by the electrode insertion method.
The present invention is a glass melting tank for melting a second glass having a work point of over 1100 ° C., a brick bottom wall having a through hole, and an electrode inserted into the through hole of the bottom wall; And a first glass filled in the through hole, wherein the first glass provides a glass melting tank that is an alkali-free glass having a working point of 900 ° C. or higher and 1100 ° C. or lower.

According to the electrode insertion method of the present invention, a non-alkali glass having a working point of 900 ° C. or higher and 1100 ° C. or lower is filled in the through hole in the bottom wall, so that the glass melt having a working point of more than 1100 ° C. is heated. Even in this case, the electrode placed in the through hole can be easily inserted into the melt, and the inserted electrode can be used stably for a long period of time.
According to the method for producing a glass product of the present invention, an electrode can be inserted into a high-strain-point glass melt without any problem and stable heating can be performed for a long period of time. it can.
According to the glass melting tank of the present invention, even when a glass having a work point of more than 1100 ° C. is melted, it is possible to carry out current heating stably for a long period of time while avoiding electrode deterioration.

It is sectional drawing which shows embodiment of the glass melting tank of this invention. It is sectional drawing which shows another embodiment of the glass melting tank of this invention. It is sectional drawing which shows another embodiment of the glass melting tank of this invention. It is sectional drawing which shows another embodiment of the glass melting tank of this invention. It is sectional drawing of the periphery of a bottom wall part explaining an example of the step which fills the through-hole with the melt of the 1st glass. It is a figure which shows an example of the step which stores the melt of 2nd glass. It is a flowchart which shows the manufacturing method of the glass product of this invention.

  Hereinafter, embodiments of an electrode insertion method, a glass product manufacturing method, a glass melting tank manufacturing method, and a glass melting tank (hereinafter simply referred to as “melting tank”) according to the present invention will be described with reference to the accompanying drawings. The present invention is not limited to the following embodiment.

[Melting tank]
FIG. 1 is a cross-sectional view schematically showing an embodiment of the melting tank of the present invention. FIG. 1 shows an image after the electrodes are inserted.
The melting tank 1 is a melting tank for heating a second glass melt G2 (hereinafter, simply referred to as “glass melt G2”) having an operating point of over 1100 ° C. Here, the working point is a characteristic value defined in ISO 7884-1 (1987) as an index representing the viscosity of glass, and is a standard of temperature suitable for glass forming. The working point can be measured by a method using a rotational viscometer (ISO 7884-2 (1987)) or the like.

  The melting tank 1 may be an apparatus for producing a glass melt G2 by melting glass raw materials, or for further melting and homogenizing the glass melt G2 made in another melting tank. The apparatus may be used. Although the melting tank 1 includes two electrodes 4 as heating means, it can include heating means other than the electrodes 4 separately. Usually, a burner for burning gas is provided on the side wall or ceiling.

  A bottom wall 2 made of brick is formed at the bottom of the melting tank 1. The bottom wall 2 can be configured by assembling a plurality of bricks. The material of the brick is not easily eroded by the glass melt G2 and the first glass melt described below (hereinafter simply referred to as “glass melt G1”) at a high temperature, and in the glass melts G1 and G2. An electrocast brick mainly composed of alumina, silica, and zirconia or a high zirconia electrocast brick is preferred because defects such as gravel and foam are less likely to occur. In addition, the bottom wall does not need to be horizontal, may be inclined, and the shape of the bottom wall is not limited.

A through hole for inserting the electrode 4 is formed in the bottom wall 2. The through hole has a size suitable for fitting the electrode holder 3 that holds the electrode, and can be, for example, a circle having a diameter of 50 to 120 mm.
In the through hole of the bottom wall 2, the electrode holder 3 is disposed below the bottom surface inside the melting tank 1 so as to form a space S. The bottom surface of the bottom wall 2 is cooled by outside air, but the top surface of the bottom wall 2 is in contact with the high-temperature glass melt. In order to avoid the electrode holder 3 from being eroded by contact with the high-temperature glass melts G <b> 1 and G <b> 2, the electrode holder 3 is accommodated in the through hole of the bottom wall 2. The position of the upper surface of the electrode holder 3 is preferably 50 to 150 mm below the inner bottom surface of the melting tank 1. The material of the electrode holder 3 is a metal such as stainless steel, for example.

Although the detailed structure of the electrode holder 3 is not shown, the electrode holder 3 includes a holding unit for holding the electrode 4 at an appropriate position and a cooling unit such as a water cooling jacket. The electrode holder 3 can also hold the upper end portion 4a of the electrode so as to be positioned in a space S surrounded by the inner surface of the through hole of the bottom wall 2 and the upper surface of the electrode holder 3, and the upper end portion 4a of the electrode can be held at the bottom. It can also be protruded from the wall 2 and held in the glass melt G2. The protrusion amount of the electrode 4 after being inserted into the glass melt G2 can be, for example, about 50 to 100 cm.
The electrode 4 is rod-shaped and fitted into the electrode holder 3, and the lower end 4b of the electrode is outside the glass melts G1 and G2 and connected to an external power source. When the upper end portion 4a of the electrode is inserted into the glass melt G2 and energized, Joule heat is generated by the resistance of the glass melt G2 existing between the electrodes 4, and the glass melt G2 is heated. Although two electrodes 4 are shown in FIG. 1, three or more electrodes 4 may be provided. The electrode 4 can be made into a round bar shape with a diameter of 40 to 100 mm, for example.

A space S surrounded by the inner surface of the through hole of the bottom wall 2 and the upper surface of the electrode holder 3 is filled with a glass melt G1. Therefore, before the electrode is inserted into the glass melt G2, the upper end portion 4a of the electrode is held so as to be positioned in the space S surrounded by the inner surface of the through hole of the bottom wall 2 and the upper surface of the electrode holder 3. Thus, the upper end portion 4a of the electrode is covered with the glass melt G1.
The glass melt G1 is a non-alkali glass melt having a working point of 900 ° C. or higher and 1100 ° C. or lower.

The melting tank 1 is used by storing the high-temperature glass melt G2 and then inserting the electrode 4 into the glass melt G2. In a state where the glass melt G2 is stored in the melting tank 1, the temperature of the space S surrounded by the inner surface of the through hole of the bottom wall 2 and the upper surface of the electrode holder 3 is about 900 to 1100 ° C. Since the first glass is a glass having a working point of 900 ° C. or higher and 1100 ° C. or lower, it has an appropriate viscosity at this time. If the working point of the first glass is higher than 1100 ° C., the viscosity becomes too high, so that it becomes difficult to insert the electrode 4. If the working point of the first glass is less than 900 ° C., the viscosity becomes too low, and the first glass may leak out from the gap between the through hole of the bottom wall 2 and the electrode holder 3. The working point of the first glass is more preferably 1000 to 1080 ° C.
The first glass preferably has a liquidus temperature of 1100 ° C. or lower. Glass having a liquidus temperature higher than 1100 ° C. tends to produce crystals in the glass melt at a temperature range of 1100 ° C. or lower, and fluidity may be lost. If the fluidity of the first glass filled in the space in the through hole of the bottom wall 2 is lost, the electrode 4 may be difficult to insert or may be broken due to a large load applied during insertion. is there.

  In addition, liquid phase temperature can be calculated | required by observing the glass sample heat-processed, for example using the temperature gradient furnace. In this specification, a glass sample is set on a platinum holder, and after heat treatment in a furnace maintained at a fixed temperature gradient, the crystal grown in the glass is observed with a microscope, and the start of crystal generation The glass temperature is the liquidus temperature. As a simple method, for example, it is possible to determine whether the liquidus temperature is higher or lower than 1100 ° C. by observing the presence or absence of crystals after holding a glass piece in a platinum container in a furnace kept at 1100 ° C. .

The first glass preferably has a higher specific gravity than the second glass. Thereby, it is possible to prevent the glass melt G1 from being mixed into the glass melt G2. For example, when the specific gravity of the second glass is 2.50, the specific gravity of the first glass is preferably 2.51 or more, and more preferably 2.60 or more. That is, the specific gravity of the second glass is preferably greater than or equal to 0.01 and more preferably greater than or equal to 0.1 relative to the specific gravity of the first glass.
The composition of the first glass will be described later.

  Another embodiment of the melting tank of the present invention includes an oxygen burner and / or a plasma torch for forming a high-temperature gas phase atmosphere at the top, and raw material particles obtained by granulating a glass raw material in the high-temperature gas phase atmosphere Can be provided with a raw material supply means. In this case, it is preferable that the oxygen burner and / or the plasma torch be installed downward on the ceiling of the melting tank. Thereby, the raw material particles can be dissolved in a high temperature gas phase atmosphere to form molten glass particles in the gas phase. FIG. 2 is a diagram illustrating an example of the embodiment. A downward oxygen burner 5 is provided on the ceiling of the melting tank 11. The oxygen burner 5 of FIG. 2 includes a raw material supply nozzle in addition to a nozzle for forming a flame, but the oxygen burner and the raw material supply port may be provided separately. The second glass raw material particles G20 are charged into a high-temperature flame from the raw material supply nozzle of the burner 5, and become second glass molten glass particles G21, which are stored in the melting tank 11.

  Another embodiment of the melting tank of the present invention may have a glass inlet to which glass melt is supplied from another melting tank. FIG. 3 is a diagram showing an example. The melting tank 12 is connected to another melting tank 100. The raw material of the second glass charged into the other melting tank 100 from the raw material supply port 72 is melted by the heat of the burner 52 provided on the side wall of the other melting tank 100 to become a glass melt G2. It flows into the melting tank 12 from the inlet 6. The glass melt G2 flowing into the melting tank 12 is heated using the electrode 4 and is homogenized by defoaming or the like.

  Another embodiment of the melting tank of the present invention can include a raw material supply port for charging the raw material onto the glass melt. In this case, the raw material to be input may be a powder of oxide, hydroxide, carbonate, or the like, raw material particles obtained by granulating them, or a mixture thereof. FIG. 4 is a diagram showing an example. There is a raw material supply port 7 at one end of the melting tank 13. The raw material of the second glass is charged from the raw material supply port 7 onto the glass melt in the melting tank 13 and melted to become a glass melt G2. The melting tank 13 includes an electrode 4 installed on the bottom wall 2 as a heating unit, but can include a burner or the like as an auxiliary heating unit. In the melting tank 13, the electrode 4 can be an auxiliary heating means, and a burner can also be a main heating means. Even when the electrode 4 is used as a main heating means, when the glass melt G2 is stored before the electrode 4 is inserted into the glass melt G2, the glass raw material is melted using the burner or the like.

Next, the electrode insertion method of the present invention will be described step by step.
[Step of placing electrodes]
As shown in FIG. 5, the electrode 4 has an upper end portion 4 a of the electrode inserted into the through hole of the bottom wall 2 before the glass melt G <b> 2 is stored in the melting tank 1. It is arrange | positioned so that it may be located below 150 mm. At this time, the upper end portion 4 a of the electrode stands by above the upper surface of the electrode holder 3 and below the bottom wall, and is cooled by the effect of the cooling means provided in the electrode holder 3.

[Step of filling glass melt G1]
In FIG. 5, a glass melt G 1, which is a non-alkali glass melt having a working point of 900 ° C. or higher and 1100 ° C. or lower, is formed on the inner surface of the through hole provided in the bottom wall 2 of the melting tank 1 and the upper surface of the electrode holder 3. The space S surrounded by is shown filled. At this time, the upper end 4a of the electrode is covered with the glass melt G1. By filling the through-hole with the glass melt G1, by covering the portion of the electrode that may be oxidized with the glass melt G1 before the electrode is inserted, deterioration due to the oxidation of the electrode can be prevented. The portion where the electrode may be deteriorated is a portion where the temperature of the electrode becomes high before being inserted into the glass melt G2. In other words, the part where the electrode may deteriorate is the upper region of the electrode. When the electrode is held by the electrode holder, the gap between the electrode and the electrode holder, or when the electrode is held by brick Including the gap between the electrode and the brick. In FIG. 5, the upper ends 4a of the two electrodes are covered with the glass melt G1 in each space S, but the glass melts G1 in the plurality of spaces S are connected as shown in FIG. It may be in a state.

  Various methods can be adopted as the method of filling the glass melt G1. For example, the glass melt G1 is obtained by dissolving the glass melt G1 obtained by melting the first glass raw material in another melting tank or the like with the inner surface of the through hole provided in the bottom wall 2 and the upper surface of the electrode holder 3. It may be filled by a method of pouring the space S surrounded by. The first glass raw material may be melted in the melting tank 1. Since the deterioration due to oxidation of the electrode 4 can be prevented and the operation is simple, the step of filling the glass melt is to place the first glass cullet inside or around the through hole (the cullet is arranged). It is preferable to melt the arranged cullet to form a glass melt G1 (step of melting the cullet).

[Step of placing the first glass cullet]
A first glass cullet is disposed inside or around the through hole. The first glass cullet is disposed at an appropriate position in a sufficient amount to cover the upper end portion 4a of the electrode with the glass melt G1 in the step of melting the cullet described later. The first glass cullet may be disposed on the surface of the bottom wall 2 near the through hole, or may be disposed so as to close the through hole.
The first glass cullet is preferably crushed and disposed so as to fill the space of the through hole in the bottom wall 2, that is, the space S surrounded by the inner surface of the through hole and the upper surface of the electrode holder 3. For example, filling the space S with the first glass cullet crushed into particles having a major axis of about 1 mm to 20 mm is because the upper end 4a of the electrode is quickly covered with the glass melt G1 after the cullet is melted. Particularly preferred. Placing a flat plate-like cullet after filling the space S with the crushed cullet is more preferable because high-temperature air can be blocked from the upper end portion 4a of the electrode.

[Step of melting first glass cullet]
The first glass cullet filled in the through hole of the bottom wall is melted when the temperature of the melting tank is increased using a heating burner provided on the side wall or the ceiling of the melting tank 1, etc. G1. Even when most of the inside of the melting tank 1 is at a high temperature of about 1500 ° C., the inside of the through hole in the bottom wall 2 is a cooling means provided in the electrode holder 3 to prevent the electrode 4 from being oxidized. For example, it is cooled to about 500 ° C. to 800 ° C. Since the first glass is a glass having a working point of 900 ° C. or higher and 1100 ° C. or lower, it has a certain degree of fluidity in this temperature range and is in a molten state.

[Step of storing glass melt G2]
After the glass melt G1 is filled into the space S, the glass melt G2 is stored in the melting tank 1. At this time, the temperature of the glass melt G2 is, for example, 1500 ° C. or higher. The glass melt G2 will be described later.
FIG. 6 is a cross-sectional view of the melting tank 1 showing a state in which the glass melt G2 is stored before the electrodes are inserted into the glass melt G2. As a method for storing the glass melt G2, for example, the following method can be employed.

  As an example of a method for storing glass melt G2, molten glass particles formed by melting raw material particles obtained by granulating the second glass raw material in an oxyfuel flame and / or thermal plasma are deposited. The method of doing is mentioned. In this method, there is a method in which a burner for melting raw material particles is installed in the upper part of the melting tank 1 and the raw material particles introduced into the oxyfuel flame are dropped and deposited as molten glass particles in the gas phase in the melting tank 1. Can be adopted.

  For example, in the melting tank 11 of FIG. 2, the downward oxygen burner 5 is provided on the ceiling. The oxygen burner 5 includes a nozzle for supplying a raw material in addition to a nozzle for forming a flame. The second glass raw material particles G20 are charged into the high-temperature oxyfuel flame from the raw material supply nozzle of the oxygen burner 5 by airflow conveyance. The second glass raw material particles G20 are made of a mixture of raw materials such as oxides and carbonates, and are granulated into particles of about 1 mm or less, for example. The second glass material particles G20 are melted in a high-temperature gas phase formed by burning the oxygen burner 5, and become second glass molten glass particles G21. The molten glass particles G21 of the second glass are deposited and stored in the melting tank 11 in a state where the upper end portion 4a of the electrode remains in the bottom wall 2.

Another example of the method for storing the glass melt G2 is to melt the glass melt G2 obtained after melting the raw material of the second glass outside the melt tank 1 (for example, another melt tank). The method of storing glass melt G2 by making it flow in the tank 1 is mentioned. In this case, the melting tank 1 can be used as a tank for homogenizing the glass melt G2.
For example, in the melting tank 12 of FIG. 3, the second glass raw material is charged into the other melting tank 100 from the raw material supply port 72. The raw material of the second glass is melted by the heat of the burner 52 provided on the side wall of the other melting tank 100 to form a glass melt G2. The obtained glass melt G2 flows from the glass inlet 6 into the melting tank 12 where the upper end 4a of the electrode remains in the bottom wall 2 and is stored.

Still another example of the method for storing the glass melt G2 is a method for storing the glass melt G2 by charging the raw material of the second glass into the melting tank 1 and melting it. In this method, after the raw materials of the second glass are mixed and put into the melting tank 1, they can be melted by a burner provided on the side wall or ceiling of the melting tank 1.
For example, in the melting tank 13 of FIG. 4, the second glass raw material is introduced from the raw material supply port 7 into the melting tank 13 where the upper end 4a of the electrode remains in the bottom wall 2 and heated by a burner or the like. The glass melt G2 is stored by melting.

[Step of inserting electrode]
After storing the glass melt G2, the upper end portion 4a of the electrode is inserted by pushing up the electrode 4 so as to penetrate the glass melt G1 and enter the glass melt G2. At this time, most of the inside of the melting tank 1 in which the glass melt G2 is stored is at a high temperature of about 1500 ° C., but the inside of the through hole of the bottom wall 2 is cooled by a cooling means or the like provided in the electrode holder 3. For example, it is cooled to about 500 ° C to 800 ° C. When the temperature of the glass melt G1 covering the upper end portion 4a of the electrode is raised to about 900 to 1100 ° C. by a method such as stopping water cooling of the electrode holder 3 for several minutes, the viscosity of the glass melt G1 decreases. It will flow moderately. Therefore, the electrode 4 can be pushed up without applying a large weight. Furthermore, since the glass melt G2 is heated by a burner or the like to the high temperature, the electrode 4 can be inserted and protruded into the glass melt G2 without applying a large load. The position of the upper end portion 4a of the electrode is set to an appropriate height for heating the glass melt G2.
After the upper end 4a of the electrode is inserted into the glass melt G2, when an electric current is passed between the electrodes, a current flows in the glass, Joule heat is generated, and the glass melt G2 is heated.

[First glass]
The first glass is alkali-free glass. That is, the first glass does not contain alkali metal components such as Na ₂ O, K ₂ O, and Li ₂ O above the impurity level. Even if it contains an alkali metal component, the total in glass is 1 mol% or less. In the case of glass containing an alkali metal component, the alkali metal component may enter the brick constituting the bottom wall 2 of the melting tank 1 to reduce the electrical resistivity of the brick. When the electrical resistivity of the brick decreases, a current that should flow through the glass melt G2 flows into the brick, and the heating efficiency of the glass melt decreases. Further, when an electric current flows in the brick, the brick may be abnormally heated and melted.
The first glass is SiO ₂ 52-64%, B ₂ O ₃ 3-25%, Al ₂ O ₃ 2-10%, MgO 0-11%, CaO, expressed as mol% on oxide basis. 0 to 11%, and any one or more oxides selected from SrO and BaO are preferably contained in a total amount of 2 to 30%. Such a glass is alkali-free glass but has a viscosity as low as soda lime glass, and since the liquidus temperature is low, crystallization hardly occurs and the electrode is not easily oxidized.

Hereinafter, the composition of this preferable glass will be described by simply describing “mol%” as “%”.
SiO ₂ is an oxide that forms a glass network and is essential. The content of SiO ₂ is preferably 52% or more, and more preferably 54% or more. Further, the content of SiO ₂ is preferably 64% or less, and more preferably 62% or less. This is because if the content of SiO ₂ is not less than the above lower limit value, the glass is stable and hardly devitrified, and if it is not more than the above upper limit value, the temperature required for vitrification does not become too high.

Al ₂ O ₃ is a component that stabilizes the glass, and is preferably contained in an amount of 2% or more. Al ₂ O ₃ is preferably 2% or more because the effect of stabilizing the glass is high. When Al ₂ O ₃ is 10% or less, vitrification does not require a high temperature and the liquidus temperature does not become too high, which is preferable.
SiO ₂ and Al ₂ O ₃ are components that increase the working point of glass. In order to set the working point to 1100 ° C. or lower, the total content of SiO ₂ and Al ₂ O ₃ is preferably 68% or lower, and more preferably 66% or lower. In order to set the working point to 900 ° C. or higher, the total content of SiO ₂ and Al ₂ O ₃ is preferably 57% or higher, and more preferably 60% or higher. By setting the total content of SiO ₂ and Al ₂ O _{3 in} the above range, a glass having a preferable work point can be obtained. The total content of SiO ₂ and Al ₂ O ₃ is more preferably 60 to 66%.

B ₂ O ₃ is a component that forms a glass network and is a component that lowers the viscosity. The content of B ₂ O ₃ is preferably 3% or more, and more preferably 5% or more because the viscosity of the glass can be lowered. The content of B ₂ O ₃ is preferably 25% or less, and more preferably 20% or less because the acid resistance and water resistance of the glass can be increased.

MgO, CaO, SrO, and BaO are all optional components that increase the stability of the glass and are components that lower the viscosity, and are preferably contained in a total of 10 to 40%. In order to improve the stability of the glass, it is more preferable to contain any two or more of them. In order to lower the liquidus temperature, the total amount of MgO, CaO, SrO and BaO is preferably 40% or less, and more preferably 30% or less. In order to reduce the viscosity of the glass, the total amount of MgO, CaO, SrO and BaO is preferably 10% or more, more preferably 15% or more, and further preferably 20% or more.
When it contains MgO, it is more preferable that the content is 1 to 11% from a viewpoint of the devitrification property of glass.
When it contains CaO, it is more preferable that the content is 1 to 11% from a viewpoint of the devitrification property of glass.
SrO and BaO are components that greatly increase the viscosity of the glass and increase the specific gravity. The total amount of any one or more oxides selected from SrO and BaO is preferably 2% or more, more preferably 5% or more from the viewpoint of viscosity and specific gravity. The total amount of one or more oxides selected from SrO and BaO is preferably 30% or less and more preferably 25% or less from the viewpoint of devitrification of the glass.

In addition to the above, the first glass can appropriately contain one or more components selected from ZnO, ZrO ₂ , TiO ₂ , La ₂ O ₃ , and P ₂ O ₅ . The total amount of these is preferably 10% or less, and more preferably 5% or less.
The first glass preferably does not contain As ₂ O ₃ , Sb ₂ O ₃ , PbO, and Bi ₂ O ₃ . These components have a strong tendency to oxidize the electrode.

[Second glass]
The second glass is a glass having a working point exceeding 1100 ° C. Such a glass is useful as a glass having high heat resistance because of its high strain point.
The second glass is a SiO ₂ 60 to _75% by mol% based on _oxides, B 2 _{O 3} 0-20%, the _{Al 2 O 3 5~20%, MgO} , CaO, from SrO and BaO It is preferably an alkali-free glass containing 5 to 25% in total of any one or more selected oxides and more than 68% in total of SiO ₂ and Al ₂ O ₃ . The glass having such a composition has a high strain point, and is suitable for a substrate glass used for a liquid crystal display panel or the like from the viewpoint of thermal expansion coefficient, acid resistance, and other characteristics.

This glass composition will be described.
SiO ₂ is an oxide that forms a glass network and is essential. The content of SiO ₂ is preferably 60% or more, and more preferably 65% or more because the strain point of the glass can be increased. The content of SiO ₂ is preferably 75% or less, and more preferably 70% or less because the temperature required for vitrification can be lowered.
Al ₂ O ₃ is a component that increases the strain point together with SiO ₂ , and the content of 5% or more can increase the strain point. If the content of Al ₂ O ₃ is 20% or less, the glass is less likely to become unstable.

In order to increase the strain point of the glass, the total content of SiO ₂ and Al ₂ O ₃ is preferably more than 68%, and more preferably 70% or more. From the viewpoint of easy manufacturing of glass, the total content of SiO ₂ and Al ₂ O ₃ is preferably 85% or less, and more preferably 80% or less.
B ₂ O ₃ is an optional component that lowers the viscosity of the glass. In order to increase the acid resistance of the glass, the content of B ₂ O ₃ is preferably 20% or less, and more preferably 15% or less. When B ₂ O ₃ is contained, the content is preferably 1% or more, and more preferably 5% or more, from the viewpoint of the viscosity of the glass.
MgO, CaO, SrO and BaO are all optional components that lower the viscosity of the glass, and in order to lower the viscosity of the glass, it is preferable that any one or more oxides are contained in a total amount of 5% or more. It is more preferable to contain above. The total amount of MgO, CaO, SrO and BaO is preferably 25% or less, and more preferably 20% or less, from the viewpoint of glass stability.

In addition to the above, the second glass may contain one or more components selected from ZnO, CuO, CoO, Fe ₂ O ₃ , ZrO ₂ , TiO ₂ , La ₂ O ₃ , and P ₂ O _5. . The total amount of these is preferably 5% or less.

[Glass product manufacturing method]
Embodiment of the manufacturing method of the glass product of this invention is a method of manufacturing the glass product which consists of 2nd glass, and has the step which heats the glass melt G2 using the above-mentioned electrode insertion method.
FIG. 7 is a flowchart showing an example of a general glass product manufacturing method. The glass product is obtained by melting a glass raw material to obtain a glass melt, step S01 for homogenizing the obtained glass melt G2, step S03 for shaping the glass melt G2 into a plate shape, and the like. It can be obtained through step S04 of slowly cooling the object.
The step of heating the glass melt G2 includes one or both of a step S01 for melting the raw material to obtain the glass melt G2 and a step S02 for homogenizing the obtained glass melt G2. It is preferable to heat the glass melt G2 using the electrode inserted by the insertion method.

  When the step S01 for obtaining the glass melt G2 using the electrode inserted by the electrode insertion method of the present invention is performed, the second glass material is a melting tank in which the electrode is inserted by the electrode insertion method of the present invention. 1 is dissolved. For example, in FIG. 4, the second glass raw material is charged on the glass melt G2 in the melting tank 13 from the raw material supply port 7, and is melted using the electrode 4 inserted by the electrode insertion method of the present invention. . When the electrode insertion method of the present invention is used in step S01 for obtaining the glass melt G2, the raw material may be dissolved using a burner or the like as a main heating means, and the electrode 4 may be used as an auxiliary heating means.

  When step S02 for homogenizing glass melt G2 using the electrode inserted by the electrode insertion method of the present invention is performed, step S01 for obtaining glass melt G2 can be performed by any method. That is, the glass melt G2 is formed by melting the raw material by an arbitrary method using another melting tank or the like, and is poured into the melting tank 1 in which the electrode is inserted by the electrode insertion method of the present invention to be homogenized. Can do. In the case of this homogenization, other heating means can be used in combination as appropriate. For example, in FIG. 3, the glass melt G <b> 2 is charged with the second glass raw material from the raw material supply port 72 into the other melting tank 100, and the heat of the burner 52 provided on the side wall of the other melting tank 100 The raw material is dissolved and formed. The obtained glass melt G2 can be poured into the melting tank 12 from the glass inlet 6 and heated using the electrode 4 inserted by the electrode insertion method of the present invention, and homogenized such as defoaming.

The second glass raw material particles are melted by being introduced into an oxyfuel flame and / or thermal plasma to form molten glass particles, and the obtained molten glass particles are inserted into the electrode of the present invention. You may homogenize, supplying to the melting tank which inserted the electrode by the method. For example, in FIG. 2, a downward oxygen burner 5 is provided on the ceiling of the melting tank 11, and the oxygen burner 5 includes a nozzle for supplying glass raw material particles in addition to a nozzle for forming an oxyfuel flame. . The second glass material particles G20 are fed into the high-temperature oxyfuel flame from the material supply nozzle of the oxygen burner 5 by airflow conveyance. The second glass raw material particles G20 are made of a mixture of raw materials such as oxides and carbonates, and are granulated into particles of about 1 mm or less, for example. The second glass raw material particles G20 are melted in a high-temperature gas phase formed by burning the oxygen burner 5, and become second glass molten glass particles G21 and fall into the melting tank 11. The obtained molten glass particles G21 of the second glass can be stored in the melting tank 11 and homogenized by heating using the electrode 4 inserted by the electrode insertion method of the present invention.
The step S03 for forming the glass melt G2 into a plate shape and the step S04 for gradually cooling the formed product can be performed by a known method.

Tables 1 and 2 show the glass compositions and physical property values expressed in mol% based on oxides for the examples of the first glass and the second glass. Examples 1 to 10 are examples of the first glass, Examples 11 and 12 are comparative examples, Example 13 is an example of the second glass, and is also a comparative example of the first glass.
As raw materials for glass, commonly used oxides, carbonates, hydroxides, etc. are used so that the composition shown in the columns from SiO ₂ to Na ₂ O in Tables 1 and ₂ is obtained. Formulated and mixed. The mixed raw materials were put into a platinum crucible and melted by heating to 1500 ° C. for Examples 1, 2, and 12 and 1600 ° C. for Example 13 using an indirect resistance heating type electric furnace. Examples 1 and 2 are examples of the first glass. Example 12 is soda lime glass.

A cullet and a glass block for measuring physical properties were obtained from the obtained molten glass, and the working point of each glass was measured with a rotational viscometer. The results are shown in the work point column of Table 1.
Further, the liquidus temperature was measured by a method using a temperature gradient furnace. The results are shown in the liquid phase temperature column of Table 1. Furthermore, the specific gravity column of Table 1 shows the result of measuring the specific gravity by applying “JISZ 8807-1976 Solid Specific Gravity Measurement Method 4. Measurement Method for Weighing in Liquid”.
The physical property values of the glass are actually measured values for Examples 1, 2, 12, and 13, and estimated values from the glass composition for Examples 3 to 11.

For the glasses having the compositions of Examples 1, 2, 12, and 13, the following experiment was conducted in order to evaluate the effect. In the experiment, first, a high zirconia electroformed brick (trade name ZB-X9540: manufactured by AGC Ceramics) was provided with two through holes with a diameter of 70 mm and fitted with an electrode holder on the bottom wall of the melting tank, A molybdenum rod having a diameter of 48 mm was inserted as an electrode into the electrode holder.
Next, in the experiment, after adjusting the upper end of the electrode to be 20 mm below the bottom of the melting tank, 1.5 kg each of the glass cullet of Example 1 as the first glass, the upper part of each through hole in the bottom wall The electrode holder was heated until the temperature measured at a position 50 mm above the bottom of the melting tank reached 1600 ° C. while cooling the electrode holder with water. This melted the first glass cullet. At this time, the inside of the through hole is cooled by the water cooling function of the electrode holder, but is estimated to be about 500 to 800 ° C.
Further, in the experiment, after the glass melt of Example 13 melted at 1600 ° C. as the second glass was stored in the melting tank, the cooling of the electrode holder was stopped for 5 minutes, and the electrode was pushed upward. Insertion was possible up to a height (500 mm) without any problems. When the operation of the melting tank was continued for 2 months thereafter, the temperature of the glass melt was always kept properly, and a high-quality glass product could be produced.

In another experiment, when the glass cullet of Example 12 was used instead of the glass cullet of Example 1 as the first glass, there was no problem until the electrode was inserted. After continuing, there was a problem that the temperature of the glass melt decreased, and the quality of the glass product became unstable.
In addition, when the glass cullet of Example 13 was used as the first glass instead of the glass cullet of Example 1, the viscosity of the glass was too high even when the temperature of the electrode holder was stopped for 5 minutes and the temperature was raised. The electrode could not be inserted. When the same experiment was performed using the glass of Examples 2 to 10 as the first glass, the glass had the preferable viscosity without containing an alkali metal oxide. Similar effects can be expected.
Furthermore, since the specific gravity of the glasses of Examples 1 to 10 is larger than that of the glass of Example 13, when the melt of the glass of Example 13 is stored as the second glass, the first glass and the second glass are mixed. Is considered to be difficult to occur.
Since the glass of Example 11 has a high CaO content and a high liquidus temperature, the glass may crystallize when the electrode is inserted, and the electrode may be damaged.

  The present invention is applicable to the production of high strain point glass such as alkali-free glass.

DESCRIPTION OF SYMBOLS 1, 11, 12, 13: Melting tank 2: Bottom wall 3: Electrode holder 4: Electrode 4a: Upper end part 4b of electrode: Lower end part 5, 52 of electrode: Burner 6: Glass inflow port 7, 72: Raw material supply port 100: Other melting tank G1: First glass melt G2: Second glass melt G20: Second glass raw material particles G21: Second glass molten glass particles

Claims (15)

A method for inserting an electrode of a glass melting tank,
Disposing the electrode at a position where the upper end of the electrode is 10 to 150 mm below the molten glass side surface of the bottom wall in a through hole in the brick bottom wall of the glass melting tank;
Filling the through hole with a melt of a first glass which is an alkali-free glass having a working point of 900 ° C. or higher and 1100 ° C. or lower;
Storing a second glass melt having a work point of over 1100 ° C. in the glass melting tank;
Inserting the electrode so that the upper end of the electrode penetrates the melt of the first glass and enters the melt of the second glass;
An electrode insertion method comprising: The first glass is SiO ₂ 52 to 64%, B ₂ O _{3 3} to 25%, Al ₂ O ₃ 2 to 10%, MgO 0 to 11%, expressed in mol% based on oxide. The method for inserting an electrode according to claim 1, comprising 0 to 11% of CaO and 2 to 30% in total of any one or more oxides selected from SrO and BaO.   The step of filling the melt of the first glass comprises a step of arranging the cullet of the first glass in the through hole, and a step of melting and filling the cullet arranged. 3. The method for inserting an electrode according to 2. Said second glass is SiO ₂ 60-75%, B ₂ O ₃ 0-20%, Al ₂ O ₃ 5-20%, MgO, CaO, SrO and BaO in terms of mole percent on oxide basis. 5-25% in total of either one or more oxides selected from, and 68% greater than the SiO ₂ and _Al 2 _{O 3} in total, any one of claims 1 to 3 which is an alkali-free glass containing The method for inserting an electrode according to claim 1.   The step of storing the melt of the second glass is a step of depositing and storing molten glass particles formed by putting raw material particles in an oxyfuel flame and / or thermal plasma in the glass melting tank. The electrode insertion method according to any one of claims 1 to 4.   The method for inserting an electrode according to any one of claims 1 to 4, wherein the step of storing the melt of the second glass includes a step of storing the melted raw material after flowing the raw material into the glass melting tank.   5. The electrode according to claim 1, wherein the step of storing the melt of the second glass includes a step of charging a raw material into the glass melting tank and dissolving and storing the raw material. Insertion method. Inserting the electrode into the glass melting tank by the electrode insertion method according to any one of claims 1 to 7, and heating the melt of the second glass with the electrode;
Forming a melt of the second glass;
Gradually cooling the molded article,
A method for producing glass products including   An electrode is inserted by the electrode insertion method according to claim 1, wherein the glass melting tank is produced. A glass melting tank for melting a second glass having a work point of over 1100 ° C.,
A brick bottom wall having a through hole, an electrode inserted into the through hole of the bottom wall, and a first glass filled in the through hole,
Said 1st glass is a glass melting tank which is a non-alkali glass whose work point is 900 degreeC or more and 1100 degrees C or less. The first glass is SiO ₂ 52 to 64%, B ₂ O _{3 3} to 25%, Al ₂ O ₃ 2 to 10%, MgO 0 to 11%, expressed in mol% based on oxide. The glass melting tank according to claim 10, which is an alkali-free glass containing 0 to 11% of CaO and 2 to 30% in total of any one or more oxides selected from SrO and BaO. Said second glass is SiO ₂ 60-75%, B ₂ O ₃ 0-20%, Al ₂ O ₃ 5-20%, MgO, CaO, SrO and BaO in terms of mole percent on oxide basis. 12. The glass melt according to claim 10, which is an alkali-free glass containing 5 to 25% in total of any one or more oxides selected from the group consisting of more than 68% in total of SiO ₂ and Al ₂ O _3. Tank.   13. An oxygen burner and / or a plasma torch for forming a high temperature gas phase atmosphere, and a material supply means for introducing the second glass material particles into the high temperature gas phase atmosphere. The glass melting tank as described in any one of Claims.   The glass melting tank as described in any one of Claims 10-12 in which the melt of said 2nd glass has a glass inflow port supplied from another glass melting tank.   The glass melting tank as described in any one of Claims 10-12 in which the said glass melting tank has a raw material supply port which throws in the raw material of said 2nd glass.

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