JPH0511052B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial field of application] The present invention provides a method for supplying molten glass onto a molten metal bath,
Regarding the so-called float glass manufacturing plate in which molten glass is formed into a thin plate on a molten metal bath and then pulled out from the molten metal bath, specifically, thin plate glass with a thickness of 2 mm or less, particularly 1 mm or less is manufactured. The present invention relates to a method for manufacturing thin glass by a float method suitable for. [Prior art] When manufacturing glass sheets with a thickness less than the so-called equilibrium thickness using the float method, a traction force is applied after the exit of the molten metal bath to stretch the glass ribbon on the molten metal bath. It's here. However, in such a conventional method, since a shrinkage force acts in the width direction of the glass ribbon, a means for engaging a top roll with a side end of the glass ribbon is employed to counteract this shrinkage force.
Therefore, in the above-mentioned method, it is necessary that the side ends of the glass ribbon have a thickness sufficient to fully engage with the top roll. Once the thickness reaches a certain level, it is difficult to produce high-quality thin glass in a sufficiently stable manner, and in particular, it has been difficult to commercially produce thin glass having a thickness smaller than that. On the other hand, as an improvement for producing thinner plate glass using the float method,
-31012, a weir member is provided above the molten metal bath in a direction transverse to the flow of molten glass, and a pool of molten glass is formed on the molten metal bath by this weir member,
A method for manufacturing thin plate glass by passing the molten glass between the weir member and the molten metal bath surface while heating the molten glass with electricity in the area of the weir member is described, and Japanese Patent Publication No. 18611/1983 describes In the so-called float method, most of the thickness reduction is achieved by stretching the glass strip longitudinally, while preventing the width from being reduced by devices that engage the edges of the glass strip on both sides, and following the longitudinal stretching, A process has been described for the production of continuous glass sheets in which the glass band is laterally spread out by means of devices that engage the edges of the band on both sides, and the applicant has already made several proposals for the production of such thin glass sheets. For example, in Japanese Patent Publication No. 59-5529, molten glass is supplied onto a molten metal bath, a pool of molten glass is formed by a weir member provided across the molten metal bath on the surface of the molten metal bath, and the molten glass is In a method for manufacturing thin sheet glass in which glass is passed between a weir member and a molten metal bath surface and stretched between the weir member and the molten metal bath outlet, a portion of the weir member that comes into contact with the upper surface of the molten glass is The resistance of the molten glass against the weir member increases as it goes downstream, and the part of the weir member that finally comes into contact with the molten glass rises substantially vertically, thereby preventing the molten glass from colliding with the weir member. A method for manufacturing thin glass in a float glass plate in which the affinity force of 2 is applied perpendicularly to the distraction force, and various methods for manufacturing thin glass are known. [Problems to be Solved by the Invention] In the conventional method described in the above-mentioned Japanese Patent Publication No. 54-31012, when a glass plate having a thickness of 1 mm or less is produced, for example, the edges of the glass ribbon are difficult to stabilize. Sag (shrinking) is likely to occur, and bubbles are likely to occur due to multiple streaks in the drawing direction of the sheet glass or bubbles due to electrical heating in the area of the weir member, making it difficult to obtain high quality sheet glass, and furthermore, after cutting the edges. The width of the plate glass (net part) tends to be narrow, and the productivity is extremely low.
In the method described in Publication No. 18611, the resulting glass is stretched to a thickness thinner than its equilibrium thickness by means that minimize deformation of the glass while supporting it on molten metal. The glass is passed through a relaxation zone with a long residence time using a roller, then passed through a zone where the upper surface of the edge of the glass band is stretched longitudinally with a transverse force applied with a roll, and then the glass is cooled sufficiently. It is extremely difficult to manufacture thin sheet glass, for example, thin glass of about 2 mm or less, especially in the 1 mm range.Moreover, the edges of the glass ribbon are difficult to stabilize, sag is likely to occur, and there are multiple streaks in the drawing direction of the glass ribbon. Moreover, the productivity is extremely low as the net portion becomes narrow after cutting the ears, and furthermore, the method described in Japanese Patent Publication No. 59-5529 filed by the applicant mentioned above can be used to obtain the desired results. When producing thin glass, although the problems of bubble formation and streak formation mentioned in Japanese Patent Publication No. 54-31012 have been solved, the edges of the glass ribbon are stabilized, and there is no sag, resulting in high quality. Therefore, it may not result in a wider net part, and it cannot be said that it can be manufactured stably and reliably all the time, and in rare cases, it may become unstable and uncertain, and the above-mentioned problems may occur. It was hot. In particular, the thinner the plate, the greater this tendency, and the more pronounced the tendency for productivity to deteriorate. [Means for Solving the Problems] The present invention has been made in view of the problems with the conventional methods as described above. By uniquely installing a boat-shaped side lining on the bath side lining, a step is created, making the width of the bath a little narrower than the original size, so that the edges of the molten glass are separated at this part, and the step is made as wide as possible. Provided is a method for manufacturing plate glass with a thickness of 2 mm or less, which solves the problems of the above-mentioned method by arranging at least one pair of first top rolls on both ends of the molten glass ribbon in the immediate vicinity. It is something to do. That is, in the present invention, molten glass is supplied onto a molten metal bath, a pool of molten glass is formed by a weir member provided on the surface of the molten metal bath across the molten metal bath, and this molten glass is used as a weir member. In a method for manufacturing a thin sheet glass having a thickness of 2 mm or less, the glass is stretched by passing between the molten metal bath surface and the molten metal bath side lining from the region corresponding to the weir member to the downstream region. A ship-shaped side lining is installed with a gap between both ends of the weir member, and a step is provided in both molten metal bath side linings downstream of the weir member, and a step is provided between both ends of the molten glass ribbon immediately after the step. The present invention provides a method for manufacturing thin glass, characterized in that at least an initial top roll is provided. Here, the material of the ship-shaped side lining, which is a step member provided in both molten metal bath side linings, is boron nitride, carbon graphite, etc., and is particularly preferably made of isotropic carbon having a porosity of 23% or less. Although it is graphite, approx.
Needless to say, it is desirable if the material does not get wet with the molten glass at a temperature of 1000±50°C, or does not get wet easily, has a specific gravity lower than that of the molten metal, and can withstand the above temperature. As a means, it may be fixedly provided on the conventional side lining, but it is also possible to install a ship-shaped side lining separately, and in particular, the length from the weir member to the downstream side is far away from the selvedge of the molten glass. It is most preferable that the length of the hull side lining coincides with the step part, and for this purpose it is preferable that the length of the hull side lining is adjustable, and therefore the downstream area of the weir member This refers to the range in which the edge of the molten glass separates from the side lining, but it also varies depending on the size of the molten metal bath, the amount of molten glass drawn out, the temperature, and the thickness of the thin glass to be manufactured. be. For example, the amount of molten glass drawn is approximately 200
When producing thin glass sheets with a thickness of about 0.5 to 1.5 mm in a molten metal bath with a molten metal bath of Kg/hour, the range downstream from the weir member is about 450 mm, preferably about 350 mm, and most preferably about 250 mm. It is. Regarding the width of the step, it is basically necessary to have a gap between both ends of the weir member and a distance sufficient to prevent the edge of the molten glass from coming into contact with the existing side lining again after it has separated at the step. often,
For example, if the withdrawal amount is the same as above, it is 30 to 150 mm.
about 40 to 100 mm, preferably about 40 to 100 mm. Next, the term "immediately after the step" means that at least the first top roll is placed to prevent the ends of the molten glass ribbon that have left the step of the side lining from shrinking toward the center.
It is better to be as close to the step as possible. For example, the above-mentioned withdrawal amount is within about 200 mm from the step, preferably within about 150 mm. It goes without saying that one pair of the first top rolls can be provided on both the left and right sides, and that one or more top rolls can be arranged in pairs on the downstream side depending on the situation at the appropriate time. . [Function] As described above, the present invention provides a weir member and a unique combination of steps on both molten metal bath side linings in the ship-type side lining in the downstream region of the weir member, and provides a step difference immediately after the step. Since both ears of the molten glass ribbon are engaged by the top roll, a part of the molten glass pool flows through the gap between the weir member and the hull side lining, and flows along the long sides of the hull side lining. In addition, the molten glass that has passed between the weir member and the molten metal surface is made less susceptible to the so-called refloat phenomenon in which it tries to shrink to an equilibrium plate thickness, and the molten glass is allowed to flow down to the level difference, and at this point the side of the hull is By separating the ends of the molten glass from the lining, the edges of the glass ribbon to be formed are less affected by other factors and are always constant, and even though the distraction force due to the traction force of the transfer rolls is still weak, the top rolls are engaged. The top roll is engaged with both ears of the molten glass ribbon immediately after the step, which is at a temperature suitable for refloating, to suppress the gradual increase in the stretching force against the refloat action. When separating the edges of molten glass and forming an edge using a side lining that has a flat contact surface, the separation position tends to be unstable depending on various factors, and furthermore, the separation position tends to be unstable after separation. In the molten glass that has passed through both ears of the molten glass ribbon that has passed through the gap between the weir member and the side lining and the lower end of the weir member,
In particular, the refloat phenomenon is likely to occur in the ear member, and furthermore, in the case of the top roll, both ears of the glass ribbon immediately after separation shrink and become thicker, making it difficult to set them too close together and forcing them to be set downstream to some extent. However, according to the present invention, this problem can be solved, and the fluctuation of both ears of the molten glass ribbon is eliminated, and the effect of using topprol is reduced. The width of the glass ribbon, thickness distribution and thickness variation in both flow directions have been improved, and the width of the glass ribbon and the net portion (cutting width) have been increased.
It was also possible to further improve the occurrence of streaks and warpage. [Example] An example of the implementation of the present invention will be described below based on the accompanying drawings. 1 and 2 are a horizontal cross-sectional view and a longitudinal cross-sectional view showing a thin glass manufacturing apparatus in the case of carrying out the present invention, and FIG. FIG. 2 is an enlarged schematic diagram of main parts. In the figure, 5 is a refractory bottom, 1 is molten glass,
11 is a molten glass reservoir, 2 is a refractory twill, 3 is a lip tile, 9 is a wet bag tile, 4 is a molten metal bath, 8 is a molten metal, 10 is a weir member, 14 is a heater, and 18 to 20 are nozzles. 1 to 3 top rolls, 21 is a side lining, 15 is a boat-shaped side lining, and 32 is a cooler. The amount of molten glass 1 melted in a glass melting tank kiln (not shown) is suppressed by a twill 2,
It flows over the lip tile 3 and is fed onto the molten metal bath 4 . The molten glass 1 forms a molten glass reservoir 11 on the molten metal bath 4 by the side lining 21, the wet bag tile 9, and the weir member 10. The molten glass 1 supplied to the molten glass reservoir 11 passes between the weir member 10 and the molten metal 8 surface of the molten metal bath 4 , while a portion of the molten glass 1 passes between both ends of the weir member 10 and the molten metal. Bath 4 both side walls 2
The water flows into the gap 28 provided between the side lining 21 of No. 7 and the side lining 15 attached to the ship, and separates from the long side 17 of the side lining 15 at the stepped portion 16 of the downstream area 22 of the weir member 10. The ear portion 23 is formed, and a first top roll 18, which is a first top roll, is disposed at a portion 34 immediately after the ear portion 23 is formed, and the first top roll 18 is engaged with the ear portion 23, thereby causing a so-called refloat phenomenon. Glass ribbon 2 while suppressing shrinkage in the width direction
4 so that the plate width 25 is expanded and maintained,
While the second and third top rolls 19, 20, etc. are provided at appropriate times to further exert a holding force for expanding the plate width, a weir member is provided on the outside of the exit side of the molten metal bath 4 (not shown), for example, by a traction means of a conveyor roll. While being cooled by, for example, a cooler 32, which is an atmosphere cooling device, while applying the action of the distraction force generated between the glass ribbon 24 and the glass ribbon 10, a strip-shaped glass ribbon 24 is formed by being thinly stretched and having a larger net portion 26, as shown in FIG. The outside of the molten metal bath 4 (not shown) is transferred to subsequent steps such as slow cooling and cutting. In addition, the ship-shaped side lining 15 is arranged in a region from both ends of the weir member 10 to the downstream part 22 of the weir member, with respect to the side lining 21 provided inside the side wall 27 of the molten metal bath 4. In order to bring the molten glass 1 into close contact with the side lining 21 and move it smoothly without any steps on the upstream side, it is fixed with a holding fitting 29 so as to be substantially flush with the side lining 21 and in a floating state. The ceiling structure above the molten glass reservoir 11 is composed of a flat arch 12, which is higher than other ceiling parts, and a heat insulating front wall 34 is provided at the downstream end of the flat arch 12. A heater 14 is provided as a heating means in order to prevent and equalize the temperature of the molten glass pool 11 located upstream of the weir member 10 due to natural heat radiation. Downstream space 31 formed by ceiling 33 after wall 34
A cooler 32, which is an atmosphere cooling device, is provided at appropriate times to lower the temperature of the molten glass 1 and form the glass ribbon 24. Although not shown, a heating device is sometimes installed on the ceiling 33 in the wide part of the molten metal bath 4 in the downstream space 31 so that it can be heated. Furthermore, in the illustrated apparatus, the structure of the bottom 5 of the molten metal bath 4 consists of a low deep part 6 and a shallow bottom part 7, so that the molten metal is Convection is controlled. Instead of the device of this embodiment, the bottom 5 of the molten metal bath 4 may be structured to have a uniform depth and other convection control means may be provided. Furthermore, although not shown, the downstream space 31
A mixed gas of nitrogen and hydrogen is supplied to the ceiling 33 of the molten metal 8 to prevent oxidation of the molten metal 8 while maintaining a positive pressure relative to the atmospheric pressure and preventing uneven cooling of the glass ribbon 24. It also has an auxiliary effect of keeping the atmosphere in the downstream space 31 at a set temperature. On the other hand, the weir member 10 is fixed with a water cooling support 30.
For example, Japanese Patent Publication No. 59-5529, Japanese Patent Publication No. 59-39376, which the present applicant has already applied for.
Needless to say, it is better to use the method proposed in Japanese Patent Publication No. 61-38131. Next, a more specific example of operation using the apparatus configured as described above is shown.
Kg/hour, the molten glass temperature in the molten glass reservoir 11 is approximately 1100°C, and the pulling speed of the glass ribbon 24 by the transport roll is approximately 1.2 m/min.
A glass ribbon having an average thickness of 1.0 mm can be obtained continuously, but the ears 23 of the glass ribbon 24 can be stabilized, and the sag improvement rate is 10 to 30%.
As a result, the width of the net portion 26, which is the cutting width, can be increased, and in some cases, the width 25 of the glass ribbon 24 can also be increased, and the thickness distribution can be improved in both the flow direction and the width direction. Both of these improvements have been made, making it possible to achieve stable operation within the final target of plate thickness variation of 0.01 to 0.02 mm. [Effects of the Invention] As described above, according to the present invention, a step is provided in the weir member and the molten metal bath side lining in the downstream region of the weir member, and the first top roll is disposed immediately after the step. Because of this unique combination, the edges of molten glass can be manufactured in a more stable state,
It is possible to increase the board width and cutting width while preventing the thickening of the edges, resulting in a more uniform board thickness distribution, and the generation of streaks can be further controlled, resulting in high-quality boards with a thickness of 2 mm or less. It is possible to obtain thin glass.

[Brief explanation of the drawing]

Fig. 1 is a horizontal sectional view showing an example of a device for carrying out the present invention, Fig. 2 is a longitudinal sectional view mainly showing the vicinity of the weir member in Fig. 1, and Fig. 3 is a side lining of the hull form in Fig. 1. FIG. 2 is an enlarged schematic diagram of main parts showing the configuration near the installation. 1... Molten glass, 4 ... Molten metal bath, 10...
... Weir member, 16 ... Step portion, 15 ... Ship-shaped side lining, 18 ... First top roll, 21 ...
...Side lining, 24...Glass ribbon.

Claims (1)

[Claims] 1. Molten glass is supplied onto the molten metal bath, a pool of molten glass is formed on the molten metal bath surface by a weir member provided across the molten metal bath, and this molten glass is transferred between the molten metal bath surface and the molten metal bath surface. In the method for producing thin glass having a thickness of 2 mm or less, the side lining of both molten metal baths extends from the area corresponding to the weir member to the downstream area, and the side linings of both ends of the weir member and A ship-shaped side lining is installed with a gap, and a step is provided in both molten metal bath side linings in the downstream region of the weir member, and the first top roll is placed on both ears of the molten glass ribbon immediately after the step. A method for producing thin glass, characterized in that at least the following steps are taken: