JP7437612B2 - Method for manufacturing glass articles - Google Patents

Description

The present invention relates to a method of manufacturing a glass article by changing the substrate of molten glass.

A glass melting furnace generates molten glass by heating a glass raw material input into a melting tank (melting tank) from a raw material supply section (inlet) using a heating device such as a burner or an electrode. The generated molten glass is discharged from the glass melting furnace and is formed into a glass article by a forming device or the like.

When changing the type of glass article, the base material of the molten glass is changed. As a method for changing the substrate, a substrate extraction method and an extrusion method are known (see, for example, Patent Document 1). For example, in the extrusion method, the first type of molten glass that was previously generated in the glass melting furnace is pushed downstream by the second type of molten glass that is generated later, and then the second type of molten glass is Manufacturing of glass articles will begin.

JP 2017-65933 Publication

When changing the base of molten glass in a glass melting furnace by the extrusion method, the molten glass of the first type is extruded from the glass melting furnace by the molten glass of the second type, but all of it is discharged from the glass melting furnace. Instead, some of it may remain in the glass melting furnace. Specifically, the molten glass that has reached the stagnation layer present above the molten glass in the glass melting furnace may remain in the glass melting furnace. The molten glass in the stagnant layer is likely to change in quality and become foreign glass due to volatilization of some components or incorporation of foreign substances.

In this case, if the molten glass of the first type remaining in the stagnation layer in the glass melting furnace mixes with the molten glass of the second type during and after the substrate change, bubble defects etc. may occur in the glass article. There is a risk that this may occur, leading to quality deterioration.

The present invention has been made in view of the above circumstances, and its technical objective is to prevent quality deterioration of glass articles manufactured during and after substrate change.

The present invention is intended to solve the above-mentioned problems, and is a method for manufacturing a glass article from molten glass having a liquid level in a refractory tank made of a refractory, the refractory tank comprising: a preparation step of having an outlet for discharging molten glass, and preparing a state in which the difference between the height of the liquid level of the molten glass in the refractory tank and the height of the upper end of the outlet is 170 mm or more; a type changing step of changing the type of the molten glass discharged from the discharge port by an extrusion method from a first type to a second type, and in the type changing step, the height of the liquid level of the molten glass is changing the type of the molten glass discharged from the discharge port from the first type to the second type while maintaining a state in which a difference between the height of the glass and the height of the upper end of the discharge port is 170 mm or more; It is characterized by

According to this configuration, in the product type change process, by setting the difference between the height of the liquid level of the molten glass and the height of the upper end of the outlet in the refractory tank to be 170 mm or more, the refractory tank is removed after the product type change process is completed. The molten glass of the first type remaining in the stagnation layer inside is difficult to mix with the molten glass of the second type being discharged from the discharge port. Thereby, it is possible to prevent the occurrence of defects in the glass article due to the contamination of the molten glass related to the first type. Therefore, it is possible to prevent quality deterioration of glass articles of an intermediate type between the first type and second type manufactured during the type change process, and of glass articles of the second type manufactured after the type change process is completed. can.

In this method, the capacity of the molten glass in the refractory tank may be 15 m ³ or more. The refractory tank may include a first refractory tank and a second refractory tank connected to the first refractory tank. The discharge port may include a first discharge port formed in the first refractory tank and a second discharge port formed in the second refractory tank. In the preparation step and the type changing step, the difference between the height of the liquid level of the molten glass in the first refractory tank and the height of the upper end of the first discharge port is 170 mm or more, and A difference between the height of the liquid level of the molten glass in the second refractory tank and the height of the upper end of the second discharge port may be 170 mm or more.

According to this configuration, since the capacity of the first refractory tank and the second refractory tank is 15 m ³ or more, the capacity is large, and the amount of stagnant layer also tends to be large. In this case, in the type change process, by setting the difference between the height of the liquid level of molten glass in each refractory tank and the height of the upper end of each outlet in each refractory tank to be 170 mm or more, Later, a large amount of the molten glass of the first type existing in the stagnation layer can be prevented from mixing with the molten glass of the second type for a long period of time.

The refractory tank may include a melting tank that heats glass raw materials to produce the molten glass, and a clarification tank that performs defoaming treatment of the molten glass. Dissolution tanks and clarification tanks tend to have a large capacity, and the amount of stagnant layer also tends to increase. If the present invention described above is applied to such a melting tank and a clarification tank, the effect of being able to manufacture high-quality glass articles with few bubble defects etc. will be remarkable.

The refractory tank may include a distribution tank including a plurality of the discharge ports. A stagnant layer may also form within the distribution tank. If the present invention described above is applied to such a distribution tank, a high quality glass article with few bubble defects etc. can be manufactured.

The density of the molten glass related to the second type may be greater than the density of the molten glass related to the first type. In the type changing step, the molten glass of the second type with higher density flows so as to sneak under the molten glass of the first type with lower density. As a result, the molten glass of the first type tends to remain above the second molten glass in the refractory tank, and is less likely to mix with the molten glass of the second type even after the type change step is completed.

In this method, the number of bubbles of 100 μm or more contained in the glass article manufactured during the product change step may be 0.05 bubbles/kg or less. In this way, it is possible to maintain high quality of the glass article that is an intermediate type between the first type and the second type that is manufactured during the execution of the type changing process. Accordingly, it is possible to maintain high quality of the glass article related to the second type that is manufactured immediately after the execution of the type changing step.

According to the present invention, it is possible to prevent quality deterioration of glass articles manufactured during and after the substrate change.

FIG. 2 is a side view showing an apparatus for manufacturing glass articles. It is a sectional view showing a glass melting furnace and a clarification tank. It is a sectional view of a glass melting furnace and a clarification tank showing a substrate changing process. It is a sectional view of a glass melting furnace and a clarification tank showing a substrate changing process.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. 1 to 4 show an embodiment of a method for manufacturing a glass article according to the present invention.

1 and 2 show an apparatus for manufacturing glass articles. The manufacturing apparatus 1 includes, in order from the upstream side, a glass melting furnace 2 that heats glass raw materials to produce molten glass GM, a clarification tank 3 that performs defoaming treatment of the molten glass GM, and a molding device that molds the molten glass GM. 4 is mainly provided.

The glass melting furnace 2 includes a first melting tank 5, a second melting tank 6, a connecting part (hereinafter referred to as "first connecting part") 7 that connects the first melting tank 5 and the second melting tank 6, Equipped with.

The first melting tank 5 is a refractory tank (first refractory tank) made of refractories. Examples of refractories include refractory bricks (for example, zirconia-based electroformed bricks, alumina-based electroformed bricks, alumina-zirconia-based electroformed bricks, AZS (Al-Zr-Si)-based electroformed bricks, dense fired bricks, etc.). It will be done. The capacity (volume) of the molten glass GM in the first melting tank 5 is preferably 15 m ³ or more, more preferably 30 m ³ or more. On the other hand, the upper limit of the capacity is, for example, 600 m ³ .

As shown in FIG. 2, the first melting tank 5 includes a raw material supply section 8 that supplies glass raw materials, a heating device (not shown) such as a burner and an electrode that heats the glass raw materials and molten glass GM, and a molten glass GM. It mainly includes a discharge port (hereinafter referred to as "first discharge port") 9 for discharging.

As shown in FIG. 2, the molten glass GM produced by the first melting tank 5 has a liquid surface (free surface) FS. Here, the "liquid surface (free surface)" refers to the surface of the molten glass GM that comes into contact with the gas phase (interface with the gas phase) (the same applies hereinafter).

The second melting tank 6 is a refractory tank (second refractory tank) made of a refractory. As the refractory material for the second melting tank 6, refractory bricks or the like are used as in the first melting tank 5. The capacity of the molten glass GM in the second melting tank 6 is preferably 15 m ³ or more, more preferably 30 m ³ or more. On the other hand, the upper limit of the capacity is, for example, 600 m ³ .

The second melting tank 6 includes a heating device (not shown) such as a burner and an electrode that heats the molten glass GM, a supply port 10 connected to the first connection part 7, and discharges the molten glass GM into the clarification tank 3. A discharge port (hereinafter referred to as "second discharge port") 11 is provided. The molten glass GM accommodated in the second melting tank 6 has a liquid level FS.

The first connecting portion 7 constitutes a flow path that transfers the molten glass GM from the first melting tank 5 to the second melting tank 6. The first connection part 7 connects the first discharge port 9 of the first dissolution tank 5 and the supply port 10 of the second dissolution tank 6. The first connecting portion 7 is hollow and made of a refractory such as firebrick, platinum, a platinum alloy, or the like. The molten glass GM flowing through the first connection portion 7 does not have a liquid surface (free surface).

The clarification tank 3 performs a defoaming process on the molten glass GM supplied from the second melting tank 6. The clarification tank 3 is made of refractory material such as firebricks. The clarification tank 3 includes a heating device (not shown) that heats the molten glass GM to a predetermined temperature gradient, a supply port 12 for the molten glass GM, and a discharge port 13. The molten glass GM accommodated in the clarification tank 3 has a liquid level FS.

The clarification tank 3 is connected to the second dissolution tank 6 via a connection part (hereinafter referred to as "second connection part") 14. The second connection part 14 constitutes a flow path that transfers the molten glass GM from the second melting tank 6 to the clarification tank 3. The second connection part 14 connects the second discharge port 11 of the second dissolution tank 6 and the supply port 12 of the clarification tank 3. The second connecting portion 14 is hollow and made of a refractory material such as a firebrick, platinum, a platinum alloy, or the like. The molten glass GM flowing through the second connection portion 14 does not have a liquid level.

The outlet 13 of the fining tank 3 is connected to the molding device 4 via a glass supply path 15. The molten glass GM flowing through the glass supply path 15 does not have a liquid level. A stirring tank for stirring the molten glass with a stirrer and a conditioning tank for adjusting the state of the molten glass (for example, viscosity and flow rate) may be provided on the path of the glass supply path 15, if necessary.

The molding device 4 includes a molded body (not shown) that molds the molten glass GM supplied from the glass supply path 15 into a predetermined shape. The molded body is formed by molding molten glass GM into a predetermined shape such as a glass ribbon by an overflow down-draw method or other various molding methods. In addition, the molding device 4 may be configured to mold the molten glass GM by a float method.

Hereinafter, a method for manufacturing a glass article using the manufacturing apparatus 1 having the above configuration will be described.

This method includes a melting process in which glass raw materials are heated in a glass melting furnace 2 to produce molten glass GM, a fining process in which the molten glass GM is defoamed, and a forming process in which the molten glass GM is molded into a predetermined shape. The main preparation is as follows.

In the melting step, the glass raw material supplied from the raw material supply section 8 into the first melting tank 5 is heated by a heating device. As a result, the glass raw materials are melted and molten glass GM is generated. Molten glass GM flows into the second melting tank 6 through the first connection part 7. In the second melting tank 6, the temperature of the molten glass GM is maintained constant by heating the molten glass GM. Molten glass GM in the second melting tank 6 flows into the clarification tank 3 through the second connection part 14.

A fining agent is blended into the glass raw material, and gas (bubbles) is generated in the molten glass GM heated in the fining tank 3 due to the action of this fining agent. In the clarification process, gas contained in the molten glass GM is removed in the clarification tank 3. Thereafter, the molten glass GM is transferred from the refining tank 3 to the molding device 4 through the glass supply path 15.

In the forming process, the molten glass GM supplied from the refining tank 3 through the glass supply path 15 is formed into a predetermined shape by a molded body. When forming a glass ribbon, the formed glass ribbon becomes a glass article (glass plate) through various processes such as an annealing process, a cutting process, and an inspection process. In the cutting process, after the glass plate is cut out from the glass ribbon, the edges of the glass plate are removed. If necessary, a re-cutting process, an end face processing process, and a cleaning process may be provided. In the re-cutting process, the glass plate is cut to the desired dimensions. In the end face processing process, microcracks are removed by grinding and polishing the end face of the glass plate. In the cleaning process, the glass plate is mainly Remove dirt adhering to the surface. The glass plate thus obtained is suitable for use as a glass substrate and cover glass for displays, for example.

In the method for manufacturing a glass article described above, when manufacturing a glass article having a composition different from that of the glass article being manufactured, a substrate changing step is performed. In the substrate changing step, while continuing the operation of the manufacturing apparatus 1, the type of molten glass GM produced in the glass melting furnace 2 is changed from the first type to the second type by an extrusion method. Hereinafter, the molten glass related to the first type of glass article will be referred to as first molten glass GM1, and the molten glass produced from the glass raw material related to the second type of glass article will be referred to as second molten glass GM2.

The substrate changing process includes a preparation process and a type changing process. In the preparation process, a difference ΔHa (ΔHa =H1-H2) is 170 mm or more, preferably 300 mm or more. On the other hand, the upper limit of the difference ΔHa is, for example, 1200 mm.

In the preparation process, a difference ΔHb (ΔHb =H3-H4) is 170 mm or more, preferably 300 mm or more. On the other hand, the upper limit of the difference ΔHb is, for example, 1200 mm.

In the preparation process, the difference ΔHc (ΔHc=H5-H6) between the height H5 of the liquid level of the first molten glass GM1 in the clarification tank 3 and the height H6 of the upper end 13a of the discharge port 13 in the clarification tank 3 is , 170 mm or more, preferably 300 mm or more. On the other hand, the upper limit of the difference ΔHc is, for example, 1200 mm.

These height differences ΔHa to ΔHc can be adjusted, for example, by changing conditions such as the amount of glass raw material input into the first molten glass GM1 and the heating temperature by the heating device.

In the melting process and the preparation process, as shown in FIGS. 2 and 3, in the first melting tank 5, the wall side where the first discharge port 9 is formed, and is lower than the first discharge port 9. A layer (stagnant layer) SL in which the molten glasses GM and GM1 stagnate is formed at the upper position. Similarly, a stagnant layer SL is formed in the second dissolution tank 6 and the clarification tank 3 as well. Note that the stagnation layer SL in the second dissolution tank 6 and the clarification tank 3 is formed not only on the wall side where the discharge ports 11 and 13 are formed, but also on the wall side where the supply ports 10 and 12 are formed. may also be formed (formed entirely).

The first molten glass GM in the stagnation layer SL of the first melting tank 5, second melting tank 6, and clarification tank 3 is altered and has different properties due to volatilization of some components from the liquid surface or mixing of foreign substances. It tends to become glass.

In the type change step, the glass raw material of the second type is supplied from the raw material supply unit 8 into the first melting tank 5, and the heating device of the first melting tank 5 heats the glass raw material.

As shown in FIG. 3, in the type change step, the glass raw material of the second type supplied to the first melting tank 5 is heated by the heating device, thereby generating the second molten glass GM2. Thereby, in the first melting tank 5, the first molten glass GM1 and the second molten glass GM2 are mixed.

The second molten glass GM2 is mixed with the first molten glass GM1 while extruding the first molten glass GM1, and the second molten glass GM2 is mixed with the first molten glass GM1, and is connected to the first connection part 7, the second melting tank 6, the second connection part 14, the clarification tank 3 and the glass supply path. 15 and is supplied to the molding device 4. Hereinafter, the molten glass in which the first molten glass GM1 and the second molten glass GM2 are mixed may be referred to as "mixed molten glass."

In the product type change step, the difference ΔHa between the height H1 of the liquid level of the molten glasses GM1 and GM2 in the first melting tank 5 and the height H2 of the upper end 9a at the first discharge port 9 of the first melting tank 5 is determined. The height H1 of the liquid level is adjusted so as to maintain a state of 170 mm or more, preferably 300 mm or more.

Thereby, in the first melting tank 5, a state in which the first molten glass GM1 of the stagnation layer SL is difficult to flow is maintained, so the second molten glass GM2 flows so as to sneak under the stagnation layer SL. Therefore, due to the generation and flow of the second molten glass GM2 in the first melting tank 5, most of the first molten glass GM1 in the first melting tank 5, except for the first molten glass GM1 in the stagnation layer SL, , is pushed out from the first discharge port 9. Moreover, in the stagnation layer SL of the first melting tank 5, the first molten glass GM1 continues to remain in the first melting tank 5 for a long period of time even after the product type change process is finished.

The difference ΔHb between the height H3 of the liquid level of the molten glasses GM1 and GM2 in the second melting tank 6 and the height H4 of the upper end 11a at the second discharge port 11 of the second melting tank 6 is 170 mm or more, Preferably, the height H3 of the liquid level is adjusted so as to maintain a state of 300 mm or more.

Thereby, in the second melting tank 6, a state in which the first molten glass GM1 of the stagnation layer SL is difficult to flow is maintained, so the second molten glass GM2 flows so as to sneak under the stagnation layer SL. Due to the flow of the second molten glass GM2, most of the first molten glass GM1 in the second melting tank 6 is pushed out from the second discharge port 11, except for the first molten glass GM1 in the stagnation layer SL. Moreover, in the stagnation layer SL of the second melting tank 6, the first molten glass GM1 continues to remain in the second melting tank 6 for a long period of time even after the product type change process is finished.

The difference ΔHc between the height H5 of the liquid level of the molten glasses GM1 and GM2 in the clarification tank 3 and the height H6 of the upper end 13a at the outlet 13 of the clarification tank 3 is 170 mm or more, preferably 300 mm or more. The height H5 of the liquid level is adjusted so that the state is maintained.

Thereby, in the clarification tank 3, the state in which the first molten glass GM1 of the stagnation layer SL is difficult to flow is maintained, so the second molten glass GM2 flows so as to sneak under the stagnation layer SL. Due to the flow of this second molten glass GM2, most of the first molten glass GM1 in the refining tank 3 is pushed out from the discharge port 13, except for the first molten glass GM1 in the stagnation layer SL. Moreover, in the stagnation layer SL of the clarification tank 3, the first molten glass GM1 continues to remain in the clarification tank 3 for a long period of time even after the product type change process is finished. As a result, the state shown in FIG. 4 is reached, and the product type change process is completed.

According to the method for manufacturing a glass article according to the present embodiment described above, in the preparation process and the type change process, the liquid level heights H1, H3, H5 of the molten glasses GM1 and GM2 and the first melting glass which is the refractory tank are determined. By setting the differences ΔHa, ΔHb, and ΔHc between the heights of the upper ends 9a, 11a, and 13a of the respective discharge ports 9, 11, and 13 of the tank 5, the second dissolving tank 6, and the clarification tank 3 to 170 mm or more, the type change process During and after the execution, the first molten glass GM1 (foreign glass) remaining in the stagnation layer SL of the first melting tank 5, second melting tank 6, and clarification tank 3 flows into each discharge port 9, 11, 13. It becomes difficult to do.

Therefore, it is possible to prevent bubble defects and the like in the glass article caused by the first molten glass GM1 (different glass) of the stagnation layer SL being mixed into the mixed molten glass and the second molten glass GM2. This makes it possible to prevent the quality of the glass article of the second type from deteriorating during and after the substrate change process is completed.

Here, while the product type change step is being executed, a glass article manufactured using mixed molten glass (hereinafter referred to as "intermediate grade glass article") is inspected (inspection step). In this inspection process, the presence, type, size, etc. of foreign objects and bubbles in the intermediate grade glass article are inspected. In the type change process, the liquid level heights H1, H3, H5 of molten glass GM1, GM2 and the respective discharge ports 9, 11, By setting the difference ΔHa, ΔHb, ΔHc between the heights of the upper ends 9a, 11a, and 13a of 13 to 170 mm, the number of bubbles with a maximum dimension of 100 μm or more is 0.05 pieces/kg in an intermediate type glass article. and remained at the same level even after the product change process was completed. Furthermore, when the height differences ΔHa, ΔHb, and ΔHc were 300 mm, the number of bubbles was 0.03 bubbles/kg, which remained at the same level even after the product type change process was completed. On the other hand, when the height differences ΔHa, ΔHb, and ΔHc were set to 100 mm, the number of bubbles increased to 3.0 bubbles/kg. In each case, the capacity of the first dissolution tank 5 was 500 m ³ , the capacity of the second dissolution tank 6 was 150 m ³ , and the capacity of the clarification tank 3 was 150 m ³ .

It is preferable that the density of the second molten glass GM2 is greater than the density of the first molten glass GM1. In this case, the second molten glass GM2 flows and easily reaches the lower layer, and the first molten glass GM1 flows and easily reaches the upper layer. For this reason, the first molten glass GM1 in the stagnation layer SL tends to remain there during and after the product change step, and it is possible to more reliably prevent the occurrence of bubble defects and the like in the glass article.

Note that the present invention is not limited to the configuration of the embodiment described above, nor is it limited to the effects described above. The present invention can be modified in various ways without departing from the gist of the invention.

In the embodiment described above, the manufacturing apparatus 1 is illustrated as having two dissolving tanks (the first dissolving tank 5 and the second dissolving tank 6), but the present invention is not limited to this configuration. The present invention is also applicable to the case where a glass article is manufactured by the manufacturing apparatus 1 having only one melting tank (first melting tank 5).

The glass melting furnace 2 may include a distribution tank downstream of the clarification tank 3. The distribution tank is connected to the clarification tank 3 via a hollow connection. The distribution tank includes a supply port connected to the connection part and a plurality of discharge ports. A molding device 4 is connected to each of the plurality of discharge ports via a glass supply path 15.

With this configuration, the distribution tank can distribute molten glass to the plurality of glass supply paths 15 and the plurality of forming devices 4. The molten glass in the distribution tank has a liquid level. In the substrate change process (preparation process and type change process), the difference between the height of the liquid level of the molten glass in the distribution tank and the height of the upper end of each outlet in the distribution tank is 170 mm or more, preferably It is 300 mm or more. The capacity of the molten glass in the distribution tank is preferably 15 m ³ or more, more preferably 30 m ³ or more.

3 Clarifying tank 5 First melting tank (first refractory tank)
6 Second dissolution tank (second refractory tank)
9 First discharge port 9a Upper end of the first discharge port 11 Second discharge port 11a Upper end of the second discharge port 13 Discharge port 13a of the clarification tank Upper end of the discharge port of the clarification tank FS Liquid surface (free surface)
GM1 First molten glass GM2 Second molten glass H1 Height of the liquid level of molten glass in the first melting tank H2 Height of the upper end of the first outlet in the first melting tank H3 Molten glass in the second melting tank H4 Height of the upper end of the second discharge port in the second melting tank H5 Height of the liquid level of molten glass in the clarification tank H6 Height of the upper end of the discharge port in the clarification tank ΔHa Molten glass Difference between the height of the liquid level of the molten glass and the height of the upper end of the first discharge port ΔHb Difference between the height of the liquid level of the molten glass and the height of the upper end of the second discharge port ΔHc The height of the liquid level of the molten glass and the height of the fining tank The difference between the height of the upper end of the outlet and

Claims (5)

A method of manufacturing a glass article from molten glass having a liquid level in a refractory tank configured with a refractory, the method comprising:
The refractory tank has an outlet for discharging the molten glass,
a preparation step of preparing a state in which the difference between the height of the liquid level of the molten glass in the refractory tank and the height of the upper end of the discharge port is 170 mm or more; A type change step of changing the type of molten glass from the first type to the second type,
In the type changing step, the molten glass discharged from the discharge port is maintained such that the difference between the height of the liquid level of the molten glass and the height of the upper end of the discharge port is 170 mm or more. changing the variety from the first variety to the second variety ;
A method for manufacturing a glass article , wherein the density of the molten glass of the second type is greater than the density of the molten glass of the first type . The capacity of the molten glass in the refractory tank is 15 m3 ^or more,
The refractory tank includes a first refractory tank and a second refractory tank connected to the first refractory tank,
The outlet includes a first outlet formed in the first refractory tank and a second outlet formed in the second refractory tank,
In the preparation step and the type changing step, the difference between the height of the liquid level of the molten glass in the first refractory tank and the height of the upper end of the first discharge port is 170 mm or more, and The method for manufacturing a glass article according to claim 1, wherein a difference between the height of the liquid level of the molten glass in the second refractory tank and the height of the upper end of the second outlet is 170 mm or more. The method for manufacturing a glass article according to claim 1 or 2, wherein the refractory tank includes a melting tank that heats glass raw materials to produce the molten glass, and a clarification tank that performs defoaming treatment of the molten glass. . The method for manufacturing a glass article according to any one of claims 1 to 3, wherein the refractory tank includes a distribution tank including a plurality of the discharge ports. The method for manufacturing a glass article according to any one of claims 1 to 4 , wherein the number of bubbles of 100 μm or more contained in the glass article manufactured during execution of the product type changing step is 0.05 bubbles/kg or less.

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