JP2016011214A - Manufacturing method and manufacturing apparatus of float glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus capable of manufacturing high-quality glass which does not have a defect associated with attachment of droplets of molten tin on a bottom surface of a glass ribbon.SOLUTION: The present invention includes a process of lifting and conveying a glass ribbon, which is formed in a float bath housing molten tin, from a bath surface of the float bath by lift-out rolls parallelly disposed on a dross box part on a downstream side of the float bath, in which a space between a lift-out roll closest to the float bath in the dross box part provided with the lift-out rolls and a sidewall of the dross box part which adjacently faces the roll is partitioned as a closed space surrounded by the sidewall of the dross box part, the lift-out roll, and a pedestal of the lift-out roll, inert gas is sent into the closed space, the glass ribbon is conveyed from the float bath by the lift-out rolls while the closed space is filled with inert gas.

Description

  The present invention relates to a float glass manufacturing method and manufacturing apparatus.

In the glass manufacturing method by the float process, first, molten glass is continuously supplied to a horizontal bath surface of molten tin to form a belt-like glass (usually referred to as a glass ribbon). Pull up from the outlet side of the molten metal bath and pull out of the molten metal bath. Next, the glass ribbon is transported by a transport roll (lift-out roll), carried into a slow cooling furnace, slowly cooled while being moved in the slow cooling furnace, and cut into a required length by a cutting device, thereby obtaining a plate-like float glass. Is manufacturing.
In the float glass manufacturing method according to the above-described float method, one surface of the glass is formed by a molten metal bath surface, and the other surface of the glass is formed by spreading the molten glass on the molten metal. It can be made extremely high and is known as a production method suitable for mass production. For this reason, the float process is widely applied to the production of flat glass such as automotive glass and display glass.

FIG. 9 shows an example of a float glass manufacturing apparatus applied to this type of float process. The apparatus of this example includes a float bath 101 including a molten metal bath 100 of tin, and a downstream side of the float bath 101. It is comprised from the dross box 102 and the slow cooling furnace 103 installed in this. A plurality of lift-out rolls 105 are installed horizontally inside the dross box 102, and a plurality of layer rolls 106 are installed horizontally inside the slow cooling furnace 103 (see Patent Document 1).
In the manufacturing apparatus shown in FIG. 9, after the molten glass 107 is supplied to the bath surface of the molten metal bath 100 and stretched to the required thickness and width, the glass ribbon 108 is pulled out by the pulling force of the lift-out roll 105 and moved toward the slow cooling furnace 103 side. Can be transported.

As another example of this type of float glass manufacturing apparatus, a manufacturing apparatus is known in which an inert gas supply unit such as argon gas or nitrogen gas is provided above a lift-out roll provided in a dross box ( Patent Document 2).
The inert gas supply unit reverses the flow of gas to flow into the inside of the dross box from the outlet side of the float bath, and mixes the gas containing volatile tin present on the float bath side with the dross box side. It works not to let you. Since the dross box side tends to be cooler than the inside of the float bath, if volatile tin moves to the dross box side and adheres to the surface of the glass ribbon as fine metal oxide or dross, the glass surface is contaminated. So this contamination can be prevented.

Republished WO2009 / 014028 JP 2011-251897 A

  By the way, in the float process, when the glass ribbon is pulled up from the molten tin bath surface, the molten tin adheres to the lower surface of the glass ribbon, is taken out of the molten metal tank, and becomes tin oxide while remaining attached to the lower surface of the glass ribbon. There is a problem that becomes a defect of glass as a foreign substance. There is also a problem that molten tin adhering as a foreign matter adheres to the outer peripheral surface of the lift-out roll. The attached molten tin may adhere to the outer peripheral surface of the lift-out roll and generate an oxide that becomes a convex portion.

  For this reason, when pulling up the glass ribbon from the molten tin according to the float method, it is necessary to devise so that the molten tin does not adhere to the glass ribbon. Moreover, it is necessary to prevent oxygen from being mixed so as not to produce an oxide of molten tin. However, since the structure of the lift-out roll and its peripheral part is complicated, it is difficult to regulate the amount of oxygen that enters the inside of the dross box from the periphery of the dross box, and the part where the glass ribbon separates from the molten tin. There is a difficult problem in preventing oxygen from entering the surrounding area.

Based on these backgrounds, the present inventor studied the structure of a dross box provided with a lift-out roll, and conducted research on the molten metal adhering to the glass obtained by the float process. As a result, the glass ribbon was pulled up from the molten tin. It has been found that improving the structure and atmosphere of the portion provided with the liftout roll closest to the position can avoid the problem of glass contamination by tin oxide, and the present invention has been reached.
The present invention has been made based on the above-described background, and an object thereof is to provide a manufacturing method and a manufacturing apparatus capable of providing a high-quality float glass with few defects due to adhesion of tin oxide.

  The present invention lifts and conveys a glass ribbon formed by a float bath containing molten tin from a bath surface of the float bath by a lift-out roll disposed horizontally in a dross box provided on the downstream side of the float bath. A step between the liftout roll closest to the float bath and the side wall of the adjacent dross box portion in the dross box portion provided with the liftout roll, and the side wall of the dross box portion and the liftout A closed space surrounded by a roll and a base of the lift-out roll is partitioned and an inert gas is sent to the closed space, and the glass ribbon is removed from the float bath by the lift-out roll while filling the closed space with the inert gas. The present invention relates to a method for manufacturing a float glass to be conveyed.

When the glass ribbon is lifted and conveyed from the molten tin liquid surface, droplets of molten tin may adhere to the bottom surface side of the glass ribbon. According to the study by the present inventors, it was considered that the influence of oxygen is large that the droplets of tin are separated from the molten tin and adhere to the lower surface side of the glass ribbon. Therefore, when the relationship between the molten tin droplet and the oxygen atmosphere was examined, a phenomenon that the molten tin droplet wets with a time delay after a certain period of time on the glass surface occurred. It was found that there is a correlation with the oxygen concentration in the time until “secondary wetting”.
Therefore, for the liftout roll closest to the position where the glass ribbon separates from the molten tin liquid level in the dross box part, the space on the molten tin side from the liftout roll is closed and filled with a non-oxidizing gas. The droplets of molten tin that adhere to the lower surface side of the glass ribbon and are conveyed to the lift-out roll side can be suppressed.

In this invention, the shielding member which contacts the peripheral surface of the said lift-out roll is installed inside the side wall of the said dross box part nearest to the said float bath, and it obstruct | occludes between the side wall of the said dross box part and the said lift-out roll. can do.
If a closed member is configured by installing a shielding member between the lift-out roll closest to the position where the glass ribbon separates from the molten tin liquid level and the side wall of the adjacent dross box, the Oxygen is not supplied to the lower surface side of the glass ribbon. For this reason, the oxygen concentration can be reduced at the position where the lower surface of the glass ribbon is separated from the liquid surface of the molten tin, and the droplets of molten tin that adhere to the lower surface side of the glass ribbon and are conveyed to the lift-out roll side can be suppressed.

In this invention, a 2nd shielding member can be installed between the said glass ribbon both sides and the side wall of the said dross box part.
By installing the second shielding member on both sides of the glass ribbon, the oxygen concentration on the side where the lower surface of the glass ribbon separates from the liquid surface of the molten tin can be reduced, and it adheres to the lower surface side of the glass ribbon and lifts out. Molten tin droplets conveyed to the roll side can be suppressed.

In the present invention, the oxygen concentration at the position where the lower surface of the glass ribbon is separated from the liquid surface of the molten tin can be 3 ppm or less.
When molten tin droplets develop secondary wetting, there is an effect of oxygen concentration, and when the oxygen concentration is high to some extent, the time until secondary wetting appears is shortened. By suppressing the oxygen concentration to 3 ppm or less, the occurrence time of secondary wetting can be made sufficiently long, so that the tin droplets are separated from the molten tin at the position where the lower surface of the glass ribbon separates from the molten tin surface. Can be suppressed.

  The apparatus for producing a glass ribbon according to the present invention comprises a float bath for supplying molten glass to a liquid surface of molten tin to form a glass ribbon, and a lift-out roll for lifting and conveying the glass ribbon from the molten tin. An apparatus for producing a float glass having a dross box portion installed on the downstream side of a bus, wherein the dross box portion includes a casing body, one or more lift-out rolls disposed horizontally inside the casing body, and the lift The lift that is configured to include a pedestal that supports the bottom of the out-roll, the internal space of the casing body is partitioned into a plurality of regions by the lift-out roll and a pedestal below the lift, and the lift closest to the outlet of the float bath A shielding member having the region as a closed space between an out-roll and a side wall of the dross box portion opposed to the out-roll. It is location, and wherein the closed space in which a shielding member is gas supply means for supplying an inert gas is connected.

  For the lift-out roll closest to the position where the glass ribbon separates from the liquid surface of the molten tin, the space on the molten tin side from the lift-out roll is closed by a shielding member to fill the non-oxidizing gas therewith. Oxygen intrusion into the region separated from the liquid surface of the molten tin is suppressed. Accordingly, when the glass ribbon is separated from the liquid surface of the molten tin, the molten tin droplets adhering to the lower surface side of the glass ribbon are suppressed, and the molten tin droplets conveyed to the lift-out roll side are suppressed.

In this invention, the shielding member which contacts the peripheral surface of the said lift-out roll and closes between the said dross-box part and the said lift-out roll can be installed inside the side wall of the said dross box part nearest to the said float bath.
The shielding member closes a region between the lift-out roll and the side wall of the dross box portion while allowing the lift-out roll to rotate while contacting the lift-out roll. For this reason, a closed space is formed without hindrance to the operation of the lift-out roll, and adhesion of molten tin droplets to the glass ribbon is prevented.

In the present invention, a seal block is interposed between the lift-out roll and the pedestal below the lift-out roll to close the space between the lift-out roll and the pedestal while allowing the lift-out roll to rotate. Can be made.
By providing the seal block, the pedestal and the lift-out roll can be partitioned in an airtight manner while allowing the lift-out roll to rotate on the pedestal. For this reason, mixing of oxygen with respect to closed space can be prevented.

In the present invention, the shielding member is made of carbon, is formed to have the same length as the lift-out roll, and the shielding member is disposed by bringing one surface of the shielding member into contact with the entire length of the peripheral surface of the lift-out roll. Can be configured.
By configuring the shielding member from carbon, the closed space can be closed without being affected by heat deformation as a shielding member that is excellent in heat resistance and is disposed in the vicinity of the region through which the high-temperature glass ribbon passes.

In this invention, it can be set as the structure which installed the 2nd shielding member in the both sides of the glass ribbon which moves along the said lift-out roll.
By installing the second shielding member on both sides of the glass ribbon, the oxygen concentration on the side where the lower surface of the glass ribbon separates from the liquid surface of the molten tin can be reduced, and it adheres to the lower surface side of the glass ribbon and lifts out. Molten tin droplets conveyed to the roll side can be suppressed.

According to the present invention, the space between the liftout roll closest to the float bath and the side wall of the dross box portion adjacent to the liftout roll is defined as a closed space, and the float bath is filled with the inert gas while the closed section is filled with the inert gas. It is conveyed while pulling up the glass ribbon from the molten tin. Thereby, it is possible to make it difficult to adhere the molten tin droplets at the portion where the glass ribbon is separated from the liquid surface of the molten tin, and therefore it is possible to manufacture high-quality glass that does not cause defects due to adhesion of the molten tin.
In order to make the space between the lift-out roll and the side wall of the dress box portion a closed space, a shielding member is provided on the side wall of the dross box portion, and the space between the side wall of the dross box portion and the lift-out roll can be closed.

Schematic which shows the whole structure of the float glass manufacturing apparatus of 1st embodiment which concerns on this invention. The block diagram which shows the 1st lift-out roll provided in the manufacturing apparatus, and its surrounding structure. The block diagram which shows the some lift-out roll provided in the manufacturing apparatus. Explanatory drawing for analyzing the conditions which the droplet of a molten metal adheres when pulling up a glass ribbon from the molten metal provided in the manufacturing apparatus. FIG. 5 (A) is a graph showing the relationship between the oxygen concentration and the time until the occurrence of secondary wetting, showing the relationship between the time until the onset of secondary wetting (latency time) and the oxygen concentration in molten tin droplets. FIG. 5B is an explanatory view showing the relation between the oxygen concentration and the molten tin droplet. The block diagram which shows the 1st lift-out roll in the case of performing the verification test of the manufacturing apparatus, and its surrounding structure. The graph which shows the relationship between the pressure of the area | region beside a lift-out roll obtained in the verification test of the manufacturing apparatus, and nitrogen gas flow rate. The graph which shows the relationship between the gas concentration of the glass ribbon lower area | region obtained in the verification test of the manufacturing apparatus, and the nitrogen gas flow rate of the area | region beside a lift-out roll. The block diagram which shows an example of the conventional float glass manufacturing apparatus.

Hereinafter, an embodiment of a float glass manufacturing apparatus according to the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiment described below.
As shown in FIG. 1, the float glass manufacturing apparatus 1 of the present embodiment causes the molten glass G supplied to the float bath 2 to flow along the surface of the molten tin 3 held in the float bath 2. A plate-shaped glass ribbon 5 is formed, and the glass ribbon 5 is drawn out by a lift-out roll 7 provided in the dross box section 6. In the apparatus of the present embodiment, the glass ribbon 5 is taken out from the outlet portion of the dross box portion 6 and then drawn into the slow cooling furnace 10 by the layer roll 9 to be cooled and washed, and then cut into a predetermined size. A size float glass is obtained.

  The molten glass G sent from the melting furnace (not shown) through the supply passage 11 is supplied to the inlet portion 2 a of the float bath 2 through the lip 12 provided at the terminal portion of the supply passage 11. Yes. A twill 13 for adjusting the flow of the molten glass G is installed in the supply passage 11 upstream of the lip 12. The supply passage 11 and the float bath 2 are each configured by assembling a plurality of heat-resistant materials such as refractory bricks, but are simplified in FIG.

As shown in FIG. 1, the float bath 2 is composed of a molten metal bath 2A filled with molten tin 3 and an upper structure 2B installed on the upper portion of the molten metal bath 2A. The atmosphere is cut off as much as possible.
A front lintel (front wall) 15 is formed at the entrance 2 a of the float bath 2, and the upper portion of the front lintel 15 is connected to the ceiling wall 16. A rear end wall 17 is provided on the downstream end side of the float bath 2 so as to be connected to the ceiling wall 16, and an outlet 18 of the glass ribbon 5 is formed in the rear end wall 17 at a position near the liquid level of the molten tin 3. ing. In the float bath 2, the upper structure 2 </ b> B is configured by the front lintel 15, the ceiling wall 16, and the rear end wall 17.

  The upper structure 2B is provided with a pipe (not shown). A reducing mixed gas composed of hydrogen and nitrogen is supplied from the pipe, and the internal space of the float bath 2 is always maintained in a reducing atmosphere at atmospheric pressure or higher. ing. The reducing atmosphere inside the float bath 2 slightly flows out from the outlet 18 from which the glass ribbon 5 is drawn to the dross box 6 side.

  The dross box portion 6 provided on the rear stage side of the float bath 2 includes a lower casing 6A and an upper casing 6B. In the present embodiment, three lift-out rolls 7 are provided horizontally on the lower casing 6A. The lift-out roll 7 is generally composed of a roll body portion made of, for example, quartz and a shaft that supports the roll body portion. The number of liftout rolls 7 is not limited to three as in this embodiment, and any number of liftout rolls 7 may be provided as long as the glass ribbon 5 can be conveyed to the slow cooling furnace 10 side. The lower casing 6A has a side wall 6a on the float bath 2 side and a side wall 6b on the slow cooling furnace 10 side on the bottom wall 6c, and other side walls (not shown) erected on both sides in the width direction of these side walls 6a and 6b. ) And is configured in a box shape in which the upper surface side of each side wall is open.

  Below the lift-out roll 7, a graphite seal block 21 and a wall-shaped pedestal 22 are disposed in order to block the air flow between the molten metal bathtub 2 </ b> A and the slow cooling furnace 10. The seal block 21 is installed on the pedestal 22 so that the upper surface of the seal block 21 is in contact with the roll surface of the lift-out roll 7, and the seal block 21 is partitioned so as to be somewhat airtight with the peripheral surface of the lift-out roll 7. ing. The base 22 is formed in a wall shape from a thick metal piece such as ductile cast iron, and is provided so as to partition the inside of the lower casing 6A.

  In the lower casing 6A, three combinations of the base 22, the seal block 21, and the lift-out roll 7 are arranged at a predetermined interval in the conveying direction of the glass ribbon 6, so that the inside of the lower casing 6A is The space is partitioned into four regions R1, R2, R3, and R4. Of these four regions, the region R1 closest to the outlet 18 of the float bath 2 is the first lift-out roll 7 closest to the outlet 18 of the float bath 2, and the seal block 21 installed therebelow. And a region surrounded by the base 22 and the side wall of the lower casing 6A. Since both end portions of each lift-out roll 7 are arranged close to a peripheral wall portion (not shown) of the lower casing 6A, the regions R1, R2, R3, and R4 are box-like regions that are open on the upper surface side. Yes. In addition, it is possible to adopt a structure in which each lift-out roll 7 passes through the side wall of the lower casing 6A as it is. In that case, a gap between the side wall and the lift-out roll is formed to be as small as possible so as to have a sealed structure. The gap can be covered with a heat-resistant cloth.

  A carbon shielding member 27 supported by a support member 26 is provided on the upper side of the region R1. The shielding member 27 has an inverted trapezoidal cross section and is formed to have the same length as the lift-out roll 7. The shielding member 27 closes between the lift-out roll 7 and the side wall 6a of the lower casing 6A adjacent to the lift-out roll 7 over almost the entire length of the lift-out roll 7 accommodated in the lower casing 6A, thereby making the region R1 a closed space. Has the effect of

As shown in an enlarged view in FIG. 2, the shielding member 27 has a bottom surface 27 a that is installed on a heat-resistant metal comb-like support member 26 that is horizontally disposed. The first side surface 27b and the second side surface 27c rising to the edge in the width direction of the bottom surface 27a, and a ceiling surface 27d formed so as to connect to these side surfaces are formed in an inverted trapezoidal cross section. . The first side surface 27b of the shielding member 27 rises vertically from one side edge of the bottom surface 27a and is in close contact with the side wall 6a side of the lower casing 6A. The second side surface 27c extends from the other side edge of the bottom surface 27a so as to approach the lift-out roll 7 side, and its upper end portion is brought into light contact with the peripheral surface of the lift-out roll 7.
The support member 26 is fixed to a double wall structure portion incorporated in the side wall 6a of the lower casing 6A. The double wall structure is configured by disposing an internal wall 29 with a refrigerant flow path 28 opened with respect to the side wall 6a of the lower casing 6A on the float bath 2 side. A comb-like support member 26 is horizontally attached to the inner wall 29 via a base member 30, and the shielding member 27 is installed on the support member 26 as described above.

  Below the lift-out roll 7, a supply pipe 23 for ejecting either an inert gas such as nitrogen or a reducing gas such as hydrogen or a non-oxidizing gas such as a mixed gas thereof is installed. ing. In the present embodiment, the non-oxidizing gas ejected from the supply pipe 23 is preferably ejected after preheating to 400 to 600 ° C. This is to prevent the glass ribbon 5 from being locally cooled by the ejection of the non-oxidizing gas.

As shown in FIG. 3, the supply pipes 23 are provided in each of the regions R1, R2, and R3, and each supply pipe 23 is pulled out to the outside of the dross box portion 6 and is gathered into one extension pipe 32. The outlet pipe 32 is connected to a non-oxidizing gas supply source 33 such as nitrogen gas or hydrogen gas. With this structure, a non-oxidizing gas can be supplied from the non-oxidizing gas supply source 33 to each of the regions R1, R2, and R3. When the non-oxidizing gas is supplied to the region R1 through the supply pipe 23, the region R1 is sealed by the shielding member 27, so that the region R1 can be positively pressured.
The dross box 6 is provided with a heater (not shown) so that the temperature of the glass ribbon 5 can be adjusted.

The upper casing 6B of the dross box section 6 is configured as a steel sealing gate, a ceiling wall 24 installed between the float bath 2 and the slow cooling furnace 10, and a stainless steel drape 25 suspended from the ceiling wall 24. And is installed on the upper side of the lower casing 6A. Among the plurality of drapes 25 depending on the ceiling wall 24, the inner three drapes 25 are arranged along the upper position of the contact position between the three lift-out rolls 7 and the glass ribbon 5 moving thereabove. Yes. That is, these drapes 25 are arranged above the central axis of the lift-out roll 7 so as to extend over the entire length of the lift-out roll 7, and partition the internal space of the upper casing 6B into a plurality.
A plurality of layer rolls 9 are installed horizontally in the slow cooling furnace 10, and the glass ribbon 5 that has moved through the dross box portion 6 can be conveyed through the slow cooling furnace 10 by the plurality of layer rolls 9.

  Since the region R1 is configured as a closed space by the shielding member 27 to supply a non-oxidizing gas, a detection tube 35 for pressure measurement is provided inside the region R1 as shown in FIG. Is preferably measurable. In addition, an atmosphere gas measuring pipe 36 is provided in a region R5 above the shielding member 27 and defined by the shielding member 27, the lift-out roll 7 and the glass ribbon 5 passing therethrough. It is preferable that the atmospheric gas in the region R5 can be analyzed. In addition, what is shown by the code | symbol 37 in FIG. 2 is the below-mentioned test tracer gas introduction pipe | tube installed in area | region R2.

By the way, in the manufacturing apparatus 1 of the present embodiment, the shielding member 27 is provided in order to make the region R1 a closed space, but 2 on both sides of the region through which the glass ribbon 5 passes inside the dross box portion 6 in FIG. You may arrange | position the 2nd shielding member 39 as shown with a dashed-dotted line. The 2nd shielding member 39 can be comprised with a heat insulating material etc., and can be arrange | positioned so that it may extend along the edge side of the some lift-out roll 7. FIG. By closing the openings present on both sides of the glass ribbon 5 inside the dross box 6 with the second shielding member, the lower casing 6A side of the dross box 6 can be more strictly sealed.
The second shielding member 39 is provided, and the sealing structure on the lower casing 6A side can be further enhanced, whereby oxygen that enters the lower surface side of the glass ribbon 5 can be suppressed, and molten tin is formed on the lower surface side of the glass ribbon 5. There is an effect of suppressing the phenomenon of adhesion of the liquid droplets.

Next, a method for manufacturing float glass using the float glass manufacturing apparatus 1 having the above-described configuration will be described.
In order to manufacture the glass ribbon 5 using the manufacturing apparatus having the configuration shown in FIGS. 1 to 3, the molten glass G is supplied from the melting furnace to the supply path 11, and the flow rate of the molten glass G flowing on the lip 12 is changed to the front. The molten glass G is supplied onto the molten tin 3 at the inlet portion 2a of the float bath 2 while being adjusted by the amount of damming of the twill 13. In the float bath 2, the molten glass G flowed on the molten tin 3 is formed into a strip-shaped glass ribbon 5 having a predetermined width and a predetermined thickness. The glass ribbon 5 is pulled from the liquid surface of the molten tin 3 by the lift-out roll 7 and moved to the dross box 6 side, and then the glass ribbon 5 is cooled while being conveyed through the slow cooling furnace 10 by the layer roll 9. After the glass ribbon 5 cooled in the slow cooling furnace 10 is cooled, the glass ribbon 5 is cut into a length and a width necessary for the cutting step, whereby a float glass having a desired width and length can be manufactured.

  When the molten glass G is supplied to the molten tin 3 to form the glass ribbon 5, the glass ribbon 5 is formed while supplying a non-oxidizing gas to each region R 1, R 2, R 3, R 4 of the dross box portion 5. In the region where the non-oxidizing gas is supplied, the region R1 is a region where the glass ribbon 5 is separated from the liquid surface of the molten tin 3 and pulled up, that is, a region closest to the so-called pickup position. It is considered that the influence on the state of the glass ribbon 5 is the largest. Further, since the glass ribbon 5 is conveyed above the region R1 while being in contact with the lift-out roll 7, the atmosphere on the lower surface side of the glass ribbon 5 at the above-described pickup position is considered to be greatly influenced by the atmosphere of the region R1.

  Therefore, the shielding member 27 is provided in the region R1 to close the upper portion of the region R1 to be a closed space, and the non-oxidizing gas is supplied to the closed space so that the gas in the region R1 does not move to the lower surface side of the glass ribbon 5. The non-oxidizing gas penetrates into the lower surface side of the glass ribbon 5 even if some gas penetrates. In addition, if the non-oxidizing gas is injected into the region R1 to fill the region R1 with the non-oxidizing gas and the region R1 is positively pressured with the non-oxidizing gas, oxygen from the periphery of the dross box portion 6 is introduced into the region R1. Therefore, the oxygen concentration on the lower surface side of the glass ribbon 5 is not improved. When supplying the non-oxidizing gas to the region R1, it is preferable to set the pressure to about atmospheric pressure + 10 Pa. Since the internal space of the float bath 2 is always maintained in a reducing atmosphere at atmospheric pressure or higher, a mixed gas of hydrogen gas and nitrogen gas constituting the reducing atmosphere flows out from the outlet 18 of the float bath 2. Yes.

  Since the glass ribbon 5 passes through the dross box 6 and a plurality of lift-out rolls 7 are provided inside the dross box 6, the inside of the dross box 6 is completely sealed. It cannot be. For this reason, it is effective to provide the shielding member 27 to make the region R1 a closed space, to provide the supply pipe 23 to supply the non-oxidizing gas to the region R1, and to make the region R1 positive with the non-oxidizing gas. It is.

In the present embodiment, the region R1 is referred to as a closed space, but the lift-out roll 7 and the shielding member 27 in contact with the region R1 are only in contact with each other. A slight amount of gas flows out from between 7 and the shielding member 27. Further, since only the lift-out roll 7 and the seal block 21 are in contact with each other, a slight amount of gas can escape from between the lift-out roll 7 and the shielding member 27 by making the region R1 positive. Have sex. Further, gas is slightly released from the portions in contact with the side walls of the dross box portion 6 on both ends of the lift-out roll 7. In the present embodiment, the state in which the region R1 is closed to such an extent that gas escape from these portions is collectively referred to as a closed space.
By filling the non-oxidizing gas with the region R1 as a closed space and making the region R1 into a positive pressure, the portion where the glass ribbon 5 separates from the liquid surface of the molten tin 3 and the surrounding oxygen concentration can be made lower than before. . For this reason, there is less possibility that molten tin droplets adhere to the lower surface side of the glass ribbon 5, and there is less possibility that tin oxide will adhere to the lower surface side of the glass ribbon 5.

By the way, even if the reducing gas is simply introduced into the region R1 without providing the shielding member 27, the amount of oxygen on the lower surface side of the glass ribbon 5 cannot be reduced. For example, since there is a temperature difference between the inside of the upper casing 6A and the inside of the lower casing 6B in the dross box section 6, a pressure difference also arises, and due to these, oxygen slightly enters the inside of the lower casing 6B from the surroundings. Come in. Although the temperature is about 600 ° C. in the dross box section 6, even if hydrogen is introduced as a reducing gas into this oxygen amount environment, the oxygen remains present without being consumed. In this situation, when the non-oxidizing gas is introduced into the region R1 without providing the shielding member 27 and the introduction pressure of the non-oxidizing gas is increased, the non-oxidizing gas slightly containing oxygen from the opening side of the region R1 is glass. Since it goes to the ribbon 5 side, the purpose of reducing oxygen cannot be achieved. Rather, if the air flow rate of the non-oxidizing gas is increased, dust may be blown off and the glass ribbon 5 may be contaminated. In this respect, it is significant that oxygen on the lower surface side of the glass ribbon 5 can be reduced by providing the shielding member 27 and adding the atmospheric pressure to the region R1 as a closed space to make the region R1 a positive pressure.
The non-oxidizing gas to be added to the region R1 from the supply pipe 23 may always flow, or is stopped when the pressure is measured and reaches a desired positive pressure state, and is added again only when the pressure decreases. Any supply state such as supply may be used.

Hereinafter, a description will be given of a state in which molten tin adheres to the lower surface side of the glass ribbon 5 and a state in which molten tin droplets are difficult to adhere when the oxygen concentration is low.
In FIG. 4, when the molten tin 3 exists on the refractory material 34 such as a brick, the thin glass ribbon 5 moves along the liquid surface, and the glass ribbon 5 is pulled up obliquely upward at an arbitrary position. A state in which a droplet of molten tin 3 is separated from an end portion of tin 3 and slightly moved together with glass ribbon 5 while adhering to the lower surface of glass ribbon 5 as dross 3a is shown.
In order to prevent molten tin droplets from adhering to the lower surface of the glass ribbon 5, the balance of the forces acting parallel to the glass surface at the triple point (the point where the glass ribbon 5 is separated from the molten tin 3) is When working in the direction of pulling back to the side, it is considered that molten tin droplets are not brought to the glass ribbon 5.

When the force in the direction parallel to the lower surface of the glass ribbon 5 is taken out as shown in FIG. 4, γ _GS (change in surface energy of the atmosphere and glass) surface tension changes in the direction taken to the glass ribbon 5. In the direction of pulling back to the molten tin side, mgsin η (parallel component of gravity), γ _LS (surface energy change between liquid tin and atmosphere), surface tension change, γ _LG cos θ (surface energy change between liquid tin and atmosphere) The surface tension changes.

In summary, mgsin η + γ _LG cos θ + γ _LS = γ _GS , and the direction of this equilibrium equation is determined by γ _LG cos θ which is a fluctuating value, and since γ _LG is constant, the value of θ is considered to be dominant. It is done.
As a result, the larger the wetting angle θ (90 ° to 180 °) of tin, the greater the force on the side pulled back to the molten tin, and there is a tendency that molten tin droplets do not adhere to the glass ribbon 5. Recognize.
In order to determine whether or not the molten tin droplets adhere to the glass ribbon side, the inventor conducted the following test. In the following tests, according to the knowledge of the present inventor, in the state where the molten tin is in contact with the lower surface of the glass ribbon 5, a phenomenon of secondary wetting appears in the molten tin droplet, and the molten tin droplet The phenomenon of changing the wetting angle will be described below.

The relationship between the time until the second wetting (seconds) and the oxygen concentration (ppm) is shown below for the wetting angle of the molten tin droplets performed by the present inventors.
In the absence of oxygen with respect to the glass surface, the wetting angle of the molten tin droplet 40 is constant at 113 ° in an environment of 500 to 900 ° C. When oxygen is present in the periphery of the molten tin droplet 40, oxygen begins to enter the droplet 40 as shown in FIG. The oxygen concentration in the droplet increases as time passes after it begins to penetrate, but the wetting angle θ hardly changes, and an oxide film starts to form on the droplet surface when the saturation solubility is exceeded at a certain time. At the same time, since the surface energy changes rapidly, a phenomenon that can be referred to as a secondary wetting phenomenon occurs, and the wetting angle θ ₂ decreases. This phenomenon is called a secondary wetting phenomenon.

When this secondary wetting phenomenon occurs, the wetting angle decreases, so that the force on the side of pulling the droplet 40 back to the molten tin in the direction of the above-mentioned equilibrium is reduced, and the droplet 40 is applied to the moving glass ribbon 5. It became clear by the inventor's test that it tends to adhere.
The graph of FIG. 5A shows the result of measuring the relationship between the time until secondary wetting (latency time) and the oxygen concentration (ppm). This test shows the result of measuring the time until the occurrence of secondary wetting for each oxygen concentration when the oxygen concentration is changed at 700 ° C.
From the graph shown in FIG. 5A, the time until the occurrence of secondary wetting occurs in a short time close to 0 at an oxygen concentration of 30 ppm, but it takes about 250 seconds at an oxygen concentration of 10 ppm, but it takes about 300 seconds at 5 ppm. It was found that the concentration suddenly increased from 3 ppm to about 500 seconds, and increased significantly to about 1500 seconds at 1 ppm. For this reason, it is thought that as the time for generating the secondary wetting is longer, the molten tin droplet is less likely to adhere to the lower surface side of the glass ribbon.
For this reason, it is considered important to provide the shielding member 27 as described above to seal the region R1 and supply the non-oxidizing gas to make the region R1 have a positive pressure.

Examples of the present invention will be described below to further explain the present invention.
Using the glass ribbon manufacturing apparatus having the configuration shown in FIGS. 1 and 2, as shown in FIG. 6, the liftout roll 7 closest to the float bath 2, the glass ribbon 5 passing thereover, and the upper side wall of the lower casing 6A A region surrounded by the shielding member 27 is defined as a room A. Next, a region R1 surrounded by the liftout roll 7 closest to the float bath 2, the seal block 21 below it, the base 22, the bottom wall 6a of the lower casing 6A and the side wall 6a, and the shielding member 27 is defined as a B chamber.
A quartz roll having a diameter of 250 mm and a length of 3 m was used as the lift-out roll 7, and the glass ribbon was conveyed so that the glass ribbon having a thickness of 0.7 mm moved on the lift-out roll 7. The shielding member is made of carbon having an inverted trapezoidal shape having a bottom side of 20 mm, an upper surface of 40 mm, and an oblique side of 30 mm that contacts the surface of the lift-out roll, and the lift-out roll 7 is brought into contact with the surface of the lift-out roll 7 by its own weight. The following tests were conducted while conveying the glass ribbon 5 by the above method.

Using the apparatus configured as described above, a first test was performed in which nitrogen gas was supplied to the B chamber at a rate of (0, 4, 8, 16) m ³ / h from the supply pipe 23 installed in the B chamber. . Next, a second test was performed in which CO ₂ gas was supplied to the region R2 as a tracer gas from the tracer gas supply pipe 37 provided in the region R2 behind the lift-out roll 7 at a rate of 1.2 m ³ / h. . Moreover, it tested about each with and without the shielding board 27 provided in each test condition.
FIG. 7 shows the pressure change in the B chamber accompanying the first test when the shielding plate is provided and when the shielding plate is omitted.

As is clear from the results shown in FIG. 7, when the shielding plate was not provided, the pressure in the B chamber slightly increased as the nitrogen gas flow rate was increased, but suddenly decreased when the flow exceeded 8 m ³ / h. This is because no shielding plate is provided, so nitrogen gas leaks from the contact portion between the seal block and the lift-out roll, or the contact portion between the lift-out roll and the glass ribbon, which has sealed the B chamber, and a strong air flow generated by them. It seems that the negative pressure part occurred locally. On the other hand, when the shielding plate was provided, the pressure in the B chamber increased proportionally as the nitrogen gas flow rate was increased.
From the above, it can be seen that by providing the shielding plate, the A room and the B room can be partitioned to make the B room a closed space.

FIG. 8 shows the change in the CO ₂ concentration in the room A accompanying the second test when the shielding plate is provided and when the shielding plate is omitted.
As shown in FIG. 8, when the shielding plate is not provided, the pressure in the chamber A once decreases as the nitrogen gas flow rate is increased, but the pressure rapidly increases when the nitrogen gas flow rate exceeds 8 m ³ / h. As shown in FIG. 7, this correlates with the result that the pressure in the B chamber rapidly decreases when the nitrogen gas flow rate exceeds 8 m ³ / h.
On the other hand, when the shielding plate is provided, the CO ₂ concentration in the A chamber can be decreased sequentially by increasing the nitrogen gas flow rate. When the nitrogen gas flow rate exceeds 8 m ³ / h, the CO ₂ concentration in the A chamber is reduced to approximately 0 ppm. We were able to.

Therefore, when applied to an actual float glass manufacturing apparatus, even if air (oxygen) is present in the region adjacent to the B chamber, the amount of oxygen in the air reaching the A chamber is considered to be extremely small. .
For this reason, when the manufacturing apparatus having the structure shown in FIG. 6 is used, oxygen can be reduced to almost 0 ppm with respect to the region where the glass ribbon is separated from the liquid surface of the molten tin. In this way, the time until the secondary leakage of molten tin droplets can be increased. For this reason, there is less risk of molten tin droplets adhering to the lower surface of the glass ribbon, and there is a feature that a high-quality float glass free from defects due to tin oxide adhesion can be produced.

  The technique of the present invention can be widely applied to glass ribbon production techniques in general by the float process.

  G ... glass ribbon, R1, R2, R3, R4, R5 ... area, 1 ... float glass manufacturing apparatus, 2 ... float bath, 2A ... molten metal bath, 2a ... inlet, 3 ... molten tin, 5 ... glass ribbon , 6 ... Dross box part, 6A ... Lower casing, 6a ... Side wall, 6B ... Upper casing, 6b ... Side wall, 7 ... Lift-out roll, 8 ... Glass ribbon, 9 ... Layer roll, 10 ... Slow cooling furnace, 11 ... Supply passage, 12 Lip, 13 twill, 15 front lintel, 17 rear wall, 18 outlet, 21 seal block, 22 pedestal, 23 supply pipe, 25 drape, 26 support member, 27 shielding member , 29 ... inner wall, 35 ... pressure detection tube, 36 ... gas measurement pipe, 37 ... tracer gas introduction pipe, 39 ... second shielding member.

Claims (10)

  A step of lifting and conveying a glass ribbon formed by a float bath containing molten metal from a bath surface of the float bath with a lift-out roll disposed horizontally in a dross box provided downstream of the float bath. In the dross box part provided with the lift-out roll, the side wall of the dross box part, the lift-out roll, and the lift are provided between the lift-out roll closest to the float bath and the side wall of the dross box part adjacent thereto. Float glass that conveys the glass ribbon from the float bath by the lift-out roll while partitioning it as a closed space surrounded by the pedestal of the out roll, sending an inert gas to the closed space, and filling the closed space with the inert gas Manufacturing method.   The shielding member which contacts the peripheral surface of the said lift-out roll is installed inside the side wall of the said dross box part nearest to the said float bath, The block between the side wall of the said dross box part and the said lift-out roll is obstruct | occluded. The manufacturing method of the float glass of description.   A seal block that seals between the lift-out roll and the pedestal while interposing the lift-out roll and allowing the rotation of the lift-out roll between the lift-out roll and a pedestal therebelow is interposed. A method for producing a float glass according to 1 or 2.   The manufacturing method of the float glass as described in any one of Claims 1-3 which installs a 2nd shielding member between the said glass ribbon both sides and the side wall of the said dross box part.   The oxygen concentration of the said area | region shall be 3 ppm or less, The manufacturing method of the float glass as described in any one of Claims 1-4 characterized by the above-mentioned. A dross box installed on the downstream side of the float bath, including a float bath for supplying molten glass to the liquid surface of the molten tin to form a glass ribbon, and a lift-out roll for lifting and conveying the glass ribbon from the molten tin A float glass manufacturing apparatus comprising a section,
The dross box part is configured to include a casing body, one or more liftout rolls disposed horizontally inside the casing body, and a pedestal that supports the bottom of the liftout roll, and the internal space of the casing body is the The region is divided into a plurality of regions by a lift-out roll and a pedestal below the lift-out roll, and the region is defined as a closed space between the lift-out roll closest to the outlet of the float bath and the side wall of the dross box portion adjacent thereto. An apparatus for producing float glass in which a shielding member is disposed, and gas supply means for supplying an inert gas is connected to a closed space provided with the shielding member.   The shielding member which contacts the peripheral surface of the said lift-out roll and closes between the said dross-box part and the said lift-out roll inside the side wall of the said dross box part nearest to the said float bath is installed. Float glass manufacturing equipment.   A seal block is interposed between the lift-out roll and a pedestal below the lift-out roll and closes the lift-out roll and the pedestal while allowing the lift-out roll to rotate and allowing the lift-out roll to rotate. The float glass manufacturing apparatus according to 6 or 7.   The said shielding member consists of carbon, it is formed in the same length as the said lift-out roll, The said shielding member is arrange | positioned by making one surface of the said shielding member contact the partial full length of the surrounding surface of the said lift-out roll. The apparatus for producing float glass according to any one of 6 to 8.   The apparatus for producing float glass according to any one of claims 6 to 9, wherein a second shielding member is installed on both sides of the glass ribbon that moves along the lift-out roll.

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