JP2008019110A - Material for glass flow passage, apparatus for manufacturing glass and method for manufacturing glass articles - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material for a glass flow passage which is a specific platinum-based material, and can reduce the amount of air bubbles that remain in the glass articles even when using a platinum-based material as in the past and further even when defoaming them by using a defoaming apparatus, and to provide a method for manufacturing glass articles using the same. <P>SOLUTION: The material for a glass flow passage is a platinum-based material having an iron group metal content of not more than 60 ppm. Preferably the material for a glass flow passage has an iron group metal content of not more than 40 ppm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a glass channel material, a glass manufacturing apparatus, and a glass product manufacturing method.

  The quality required for glass products is becoming more sophisticated year by year. For example, in the field of liquid crystal display elements and display members for plasma displays, which have been increasingly used in recent years, even if a glass product (glass substrate) has a slight defect, it may interfere with the field of view. A glass product having a higher quality than ordinary window glass or the like, that is, having fewer defects, is demanded because it may cause a line on the surface to be disconnected.

Here, the defects are mainly foreign matters, striae and bubbles in the glass product.
The foreign matter is a small piece of refractory that is a constituent material of a glass melting furnace or the like in the glass manufacturing process, or a metal piece mixed in the manufacturing process. The striae are streaky amorphous bodies having a composition different from that of the matrix. Further, bubbles are mixed in the molten glass from the glass raw material or the like in the glass production process, and remain in the glass product without being separated by the clarification process or the like.
When a glass product having foreign matter or bubbles is used as a display member, the portion blocks light and display performance becomes insufficient. Further, when a glass product (substrate) having striae is used as a display member, for example, the refractive index is affected and the image is distorted.

It is considered that the occurrence of such defects is influenced by the material that contacts the molten glass in the manufacturing process. For example, refractories are conventionally used for materials such as kilns that store molten glass raw materials. In this case, if the refractory melts slightly into the molten glass and does not fully melt, May adversely affect composition.
Therefore, a specific high melting point noble metal such as a platinum-based material may be used instead of the refractory as the material used for the portion that contacts the molten glass in the manufacturing process. In this case, since the occurrence of foreign matter, striae and bubble defects is highly suppressed, defects in the manufactured glass product are significantly reduced.

  In addition, there is a case in which a defoaming apparatus that reduces the bubbles in the molten glass by passing the molten glass in a reduced-pressure atmosphere may be used for the purpose of reducing bubbles among defects. By using this defoaming device, the bubbles in the glass product can be significantly reduced.

As specific defoaming devices and defoaming methods aimed at reducing bubbles in glass products and suppressing the occurrence of defects, for example, those described in Patent Documents 1 to 3 have been proposed. Yes.
Patent Document 1 discloses a molten glass conduit made of platinum or a platinum alloy for flowing a molten glass in a horizontal direction while having a free surface, the width W of the cross section being the height H of the cross section. And a defoaming device using the molten glass conduit are described which are larger and have a cross-sectional contour that is a convex curve. Further, it is described that according to such a defoaming apparatus, impurities entering the molten glass can be reduced as much as possible, and a higher defoaming efficiency can be obtained, so that quality defects in the glass can be reduced.

  Further, Patent Document 2 is a metal conduit for flowing molten glass, and a portion that is continuously convex outward or inward in the circumferential direction is formed at least in one axial direction. The height H of the convex portion is 4 mm or more, and a molten glass conduit made of platinum, platinum alloy, dispersion strengthened platinum or dispersion strengthened platinum alloy is described. The vacuum degassing apparatus comprises a vacuum degassing tank, an ascending pipe for introducing molten glass into the vacuum degassing tank, and a downcomer pipe for discharging the molten glass from the vacuum degassing tank. In addition, there is described a vacuum degassing apparatus in which any one or more of the vacuum degassing tank, the riser pipe, and the downfall pipe is a conduit for molten glass as described above. And it is described that if such a molten glass conduit is used, the molten glass can be homogenized and improved in quality. Further, it is described that such a vacuum degassing apparatus can cope with expansion and contraction and vibration due to heat generated in the molten glass conduit when the molten glass is transferred.

  Furthermore, Patent Document 3 describes a glass sheet manufacturing system having a platinum component.

Thus, in a glass manufacturing apparatus, when a platinum-type material is used for the member which contacts molten glass, generation | occurrence | production of a foreign material, a striae, and the defect of a bubble can be suppressed highly. Moreover, if it defoams using a defoaming apparatus, a bubble can be reduced further. Furthermore, if a vacuum degassing apparatus using a platinum-based material as a member in contact with molten glass as described in Patent Documents 1 to 3 above is used, the occurrence of defects is highly suppressed and defoaming is performed. Therefore, it is preferable because bubbles can be reduced.
International Publication No. 2004/060820 Pamphlet International Publication No. 2004/070251 Pamphlet International Publication No. 2004/083134 Pamphlet

However, even when a platinum-based material is used as described above and a defoaming apparatus is used, a small amount of bubbles may remain in the molten glass, and thus in the glass product. It is preferable that such bubbles are as few as possible. Particularly, when glass products are used as the display member as described above, the demand is strong.
The object of the present invention is to use a platinum-based material at a site in contact with the molten glass, so that the amount of bubbles remaining in the glass product can be reduced as compared with the conventional platinum flow-through material, which is a specific platinum-based material. And a method of manufacturing a glass product using the same. In addition, the said effect can be exhibited at higher level by using a vacuum degassing apparatus.

  The present inventor has conducted earnest research, and even when using a platinum-based material as described above and further defoaming using a defoaming device, the generation of bubbles remaining in a small amount in a glass product is usually in the platinum-based material. Has been found to be related to iron group elements contained in small amounts. Further research has been carried out, and it has been found that the use of a platinum-based material having the iron group element content of a specific value or less can also reduce the amount of bubbles in the glass product, thereby completing the present invention.

The present invention includes the following (1) to (5).
(1) A glass channel material that is a platinum-based material and has an iron group metal content of 60 ppm or less.
(2) The glass channel material according to (1), wherein the iron group metal content is 40 ppm or less.
(3) An apparatus for glass flow path using the glass flow path material according to (1) or (2) above for at least a part of a member in contact with molten glass.
(4) A vacuum degassing apparatus comprising a vacuum degassing tank, a riser pipe for introducing molten glass into the vacuum degassing tank, and a downcomer pipe for discharging the molten glass from the vacuum degassing tank. A vacuum degassing apparatus, wherein at least one selected from the group consisting of the vacuum degassing tank, the riser pipe and the downfall pipe is made of the glass flow path material according to the above (1) or (2).
(5) A method for producing a glass product, comprising a clarification step of degassing molten glass using the vacuum degassing apparatus according to (4) above.

  In addition, in this invention, the display regarding the content rate of each component in platinum-type materials, such as an iron group metal content rate, shall all mean mass ratio.

  According to the present invention, by using a platinum-based material at a site in contact with molten glass, a glass channel material, which is a specific platinum-based material that can reduce the amount of bubbles remaining in a glass product as compared with the prior art. And a method for producing a glass product using the same. Further, it is possible to provide a vacuum degassing apparatus that can reduce the amount of bubbles to a higher level using the glass flow path material.

The present invention is a glass channel material, a glass manufacturing apparatus, and a glass product manufacturing method.
First, the glass channel material of the present invention will be described.
The glass flow path material of the present invention is a platinum flow path material having an iron group metal content of 60 ppm or less.

In the present invention, the glass flow path material means a material used in a path (flow path) through which molten glass passes in a glass manufacturing process, and used for a portion in contact with molten glass.
For example, in the vacuum degassing apparatus as described in Patent Documents 1 and 2, the material for the glass flow path of the present invention is used as a material for a vacuum defoaming tank, a riser pipe, a downfall pipe, and the like that are in contact with molten glass. Can be used. In addition, for example, in the melting process of a general glass manufacturing process, the glass flow path material of the present invention is used instead of a refractory or a refractory brick used on the inner surface of a tank in which molten glass is stored. Can be used.
Further, the glass flow path material of the present invention can also be used for the platinum components 16, 18, 20, 22, 24, 26 and 28 in the glass apparatus 10 as described in FIG.
Furthermore, the glass channel material of the present invention can also be used as a material for a sword portion when glass is produced by the fusion method.

In the present invention, the platinum-based material means platinum or a platinum alloy, and may be dispersion strengthened platinum or dispersion strengthened platinum alloy.
Furthermore, this platinum alloy is an alloy of platinum and other noble metal elements, and examples of the other noble metal elements include an alloy of platinum and at least one selected from the group consisting of Rh, Au, Ir, and Ru. It is done. In addition, even if these metals contact | connect a molten glass, they are hardly eluted like platinum. Although the content rate of noble metal components (rhodium etc.) other than platinum in the platinum alloy is not particularly limited, it is preferably 20% by mass or less, more preferably 1 to 15% by mass, and 5 to 12% by mass. More preferably it is. The reason is that if the amount is too small, the intended effect of solid solution strengthening cannot be obtained sufficiently, and if the amount is too large, the workability as a material is impaired.

  Further, this platinum-based dispersion strengthened alloy means a dispersion strengthened alloy in which fine ceramic particles are dispersed in the platinum or the matrix of the platinum alloy. Use of such a platinum-based dispersion strengthened alloy for the glass flow path material of the present invention is preferable because mechanical properties at high temperatures such as creep strength are increased and the durability life of the apparatus is shortened. Examples of the ceramic particles include zirconium oxide, calcium oxide, and yttrium oxide particles. The content of the ceramic particles in the platinum-based dispersion strengthened alloy is not particularly limited, but is preferably 1.0% by mass or less, more preferably 0.05 to 0.5% by mass, More preferably, it is -0.2 mass%. The reason is that if the amount is too small, the effect of improving the high-temperature mechanical properties is not remarkable, and if the amount is too large, it is difficult to process into a thin plate suitable for forming an apparatus by a normal rolling method or the like. In addition, since the ceramic particle here is solid-dissolved in platinum, it hardly melt | dissolves in a molten glass normally, and does not increase the bubble in a glass product.

The glass channel material of the present invention is such a platinum-based material, but the platinum-based material usually contains a small amount of impurities.
Examples of the impurity include Cu, Fe, Ni, Co, Ag, Al, B, Ca, Cr, Mg, Mn, Mo, Pb, Si, Sn, Ti, and Zn. Such impurities are usually contained in an amount of about 0.1% by mass or less.

The glass channel material of the present invention is the platinum-based material having a total content of iron group metal elements (Fe, Ni, Co and Cr) of 60 ppm or less among such impurities.
This content is preferably 40 ppm or less, and more preferably 30 ppm or less.
When the glass flow path material of the present invention is used, the generation of bubbles remaining in a small amount in the glass product can be suppressed, and the amount of bubbles in the glass product can be reduced as compared with the prior art.
Further, among iron group metal elements, the content of Fe is usually the largest. The Fe content is preferably 50 ppm, particularly 40 ppm.

When the content of the iron group metal element contained in the platinum-based material is the above value, the mechanism capable of suppressing the generation of bubbles is not necessarily clear, but the present inventor thinks as follows. .
When the platinum-based material is used as the glass channel material, Fe contained in a trace amount is dissolved in the molten glass. Fe exists in the molten glass as divalent or trivalent ions, and the quantity ratio affects the characteristics of the molten glass. Thus, when Fe is dissolved from the platinum-based material, the divalent ion is locally present. Alternatively, the amount ratio of trivalent Fe ions changes. As a result of this change, it is considered that a part of oxygen in the oxide in the molten glass is released, or dissolved gas in the molten glass is precipitated due to the generation of molten glass having different characteristics, thereby generating bubbles.
Moreover, it is thought that it acts similarly about iron group metals other than Fe.
Note that the total content of impurities other than iron group metal elements (Cu, Ag, Al, B, Ca, Mg, Mn, Mo, Pb, Si, Sn, Ti, Zn, etc.) Considering durability, contamination of glass, and the like, it is preferably 100 ppm or less, particularly preferably 50 ppm or less.

Such a glass channel material of the present invention, that is, the platinum-based material having an iron group metal element content of 60 ppm or less cannot be produced by the conventional platinum purification method, and this platinum purification method is repeated. Can be manufactured.
Specifically, a platinum-based material having a higher iron group metal element content than the above values, that is, a platinum-based material used in a conventional glass manufacturing process is, for example, a dissolution method, a solvent extraction method, or the like. The glass channel material of the present invention can be produced by repeating the same purification method several times more than when producing a conventionally used platinum-based material. It can be manufactured by doing.

Next, the glass manufacturing apparatus of the present invention will be described.
The glass manufacturing apparatus of the present invention is a glass manufacturing apparatus using the glass flow path material of the present invention as at least a part of a member in contact with molten glass.
As such an apparatus for producing glass, for example, a vacuum degassing tank, a riser pipe for introducing molten glass into the vacuum degassing tank, a downcomer pipe for discharging the molten glass from the vacuum degassing tank, A vacuum degassing apparatus having at least one selected from the group consisting of the vacuum degassing tank, the riser pipe and the downfall pipe is made of the glass flow path material of the present invention. .

An example of such a vacuum degassing apparatus is the one shown in FIG.
The vacuum degassing apparatus 10 of the aspect shown in FIG. 1 is an upstream transfer tank 30A that supplies molten molten glass 21, and a lift that raises the molten glass 21 vertically upward at the downstream end of the upstream transfer tank 30A. From the pipe 22U, the decompression defoaming tank 20 provided substantially horizontally from the upper end of the ascending pipe 22U, the descending pipe 22L for guiding the molten glass 21 vertically downward from the downstream end of the decompression defoaming tank 20, and the descending pipe 22L A downstream transfer tank 30B that guides the molten glass 21 to the downstream side is provided.
The ascending pipe 22U, the vacuum degassing tank 20 and the descending pipe 22L are formed in a gate shape, and the molten glass 21 is lifted up to the vacuum degassing tank 20 by the siphon principle, and the molten glass 21 is formed by the differential pressure. Remove contained foam. The defoamed molten glass 21 is guided to the downstream transfer tank 30B through the downcomer 22L and transferred to the molding process.

The ascending pipe 22U, the vacuum degassing tank 20, and the descending pipe 22L are covered with a casing 23.
The upstream transfer tank 30A is provided with a first stirrer 31a, and the downstream transfer tank 30B is provided with a second stirrer 31b. The molten glass 21 being supplied from the upstream transfer tank 30A is agitated by the first stirrer 31a to make the dissolved gas into microbubbles and to make the molten glass 21 uniform.

The glass manufacturing apparatus of the present invention is, for example, such a vacuum degassing apparatus, and at least one selected from the group consisting of the vacuum degassing tank, the riser pipe, and the downfall pipe is the glass flow path of the present invention. This is a vacuum degassing device made of a material for use.
In such a vacuum degassing apparatus of the present invention, the thickness, shape, etc. of the glass flow path constituting the vacuum degassing tank, the riser pipe and the downfall pipe are not particularly limited. For example, in a vacuum degassing tank, a wall thickness of 0.4 to 1.6 mm and an elliptical cross-sectional diameter can be preferably used.

  Among such vacuum degassing apparatuses, it is preferable that at least the vacuum degassing tank is made of the glass channel material of the present invention. In the vacuum defoaming tank, the contact area between the inner surface of the glass channel material of the present invention and the molten glass is large, and the flow rate of the molten glass is relatively slow, so the glass channel material of the present invention is used. This is because the amount of the iron group metal that melts into the molten glass is high in suppressing effect.

  As an apparatus for producing glass of the present invention, in addition to the above-mentioned vacuum degassing apparatus, for example, in a melting furnace for melting glass raw materials, the glass flow path of the present invention is provided on the inner surface of a tank for storing the obtained molten glass. The material used for the application is in the form of a plate. Similarly, there is an apparatus in which at least a part of a portion in contact with the molten glass in the float forming step is formed of the glass flow path material of the present invention.

Next, the manufacturing method of the glass product of this invention is demonstrated.
The manufacturing method of the glass product of this invention is a manufacturing method of the glass product which comprises the clarification process which defoams molten glass using the vacuum degassing apparatus using the glass flow-path material of said invention. .
In order to produce a glass product, in addition to such a clarification step, a dissolution step as a pre-process and a molding step as a post-process are usually required. These steps other than are not particularly limited, and for example, a conventionally known method can be applied.
For example, as a conventionally known melting step, there is a step in which a commonly used glass raw material is charged into a melting furnace and melted at a temperature of about 1500 to 1650 ° C.
For example, a conventionally known molding process includes a float molding process.

  The clarification process which the manufacturing method of the glass product of this invention comprises will not be specifically limited if it is a process performed using the reduced pressure degassing apparatus using the glass flow-path material of said this invention. For example, the vacuum degassing apparatus of the aspect shown in FIG. 1 can be used.

In the method for producing a glass product of the present invention, the operating conditions of the vacuum degassing apparatus (pressure in the vacuum degassing tank, etc.) are not particularly limited.
For example, molten glass is allowed to flow in the horizontal direction while having a free surface in the vacuum degassing vessel, and the pressure of the atmosphere on the free surface is 0.05 to 0.6 atm, preferably 0.08 to 0.5 atm. More preferably, the molten glass can be defoamed by holding at 0.12 to 0.3 atm. Defoaming at such a pressure is preferable because it can efficiently perform degassing under reduced pressure. On the other hand, it is caused by the inclusion of iron group metal in the platinum-based material forming the degassing tank. There is a tendency for the amount of bubbles to increase. Here, when the platinum-based material forming the vacuum degassing tank is not the glass channel material of the present invention and the iron group metal content is more than 60 ppm, the amount of generated bubbles becomes particularly remarkable. . Therefore, when the iron group metal content is 60 ppm or less, a vacuum degassing tank made of the glass flow path material of the present invention is used. Since generation | occurrence | production of the bubble resulting from an iron group metal containing in the material to suppress is suppressed, since the glass product which does not contain a bubble more can be manufactured, it is preferable.
In the glass product of the present invention, the target glass is not limited in terms of composition as long as it is a glass produced by a heat melting method. Therefore, alkali glass such as lime silica glass or borosilicate glass may be used. However, since it is difficult to remove bubbles during vacuum degassing and it is used for applications that require particularly few defects such as display glass substrates, alkali-free glass (substantially contains alkali content). Glass) is preferred. Specifically, if it is non-alkali glass (glass having a strain point of 600 ° C. or higher), melting at a higher temperature than normal glass is required. It is possible to use.

Samples of three platinum alloys (platinum-10 mass% rhodium alloy) having different iron group metal contents are immersed in a borosilicate glass for liquid crystal substrates (hereinafter referred to as “molten glass A”) at 1500 ° C., respectively. The number of bubbles generated was compared.
This will be specifically described below.

First, samples 1 to 3 having the compositions shown in Table 1 (showing compositions other than platinum) were prepared.
The iron group metal content is 25 ppm for sample 1, 37 ppm for sample 2, and 73 ppm for sample 3. In addition, the content rate of each component was calculated | required by performing GDMS analysis (glow discharge mass spectrometry) with respect to the surface after grinding each sample surface about 0.2 mm deep. “Nd” in Table 1 indicates that it is below the analysis limit.

Next, the number of bubbles generated from each sample immersed in the molten glass A was measured by the bubble generation number measuring device shown in FIG.
The bubble generation number measuring apparatus 50 shown in FIG. 2 has a double crucible 43 installed in an electric furnace 44 and is immersed in a molten glass 42 (molten glass A) filled in a crucible 43 a inside the double crucible 43. In this apparatus, bubbles generated from the sample 41 can be observed by a video camera 45 installed at the top of the electric furnace 44 and recorded on a recording computer 46.

  In such a bubble generation number measuring device 50, during the measurement, the heating temperature of the electric furnace 44 is adjusted so that the temperature of the molten glass 42 is always maintained at 1500 ° C. Further, the molten glass A was constantly supplied from the inlet 47 so that the composition of the molten glass 42 (molten glass A) filled in the crucible 43a inside the double crucible 43 was always constant. The molten glass A overflowed from the inner crucible 43a is temporarily accumulated in the outer crucible 43b and discharged from the outlet 48 to the outside of the electric furnace 44.

  With such a bubble generation number measuring device 50, the number of bubbles generated between 2 hours and 10 hours after each sample was immersed in the molten glass A was measured. The results are shown in Table 2. The number of bubbles was shown as the number in the unit surface area of each sample. In addition, the measurement was performed 5 times and the average value was calculated.

  Thus, in Sample 1 and Sample 2 in which the iron group metal content is 60 ppm or less, the number of bubbles generated was very small. On the other hand, in the sample 3 having an iron group metal content of more than 60 ppm, the number of bubbles generated increased.

  From the above examples, if a glass product is produced using a glass production apparatus using a platinum-based material having an iron group metal content of 60 ppm or less as a member in contact with molten glass, the iron group metal content is 60 ppm. Compared with the case where a glass product is manufactured using an apparatus for manufacturing a glass using an ultra-high one, it is considered that the bubble content is significantly reduced.

FIG. 1 is a schematic longitudinal sectional view of a vacuum degassing apparatus showing an example of the vacuum degassing apparatus of the present invention. FIG. 2 is a schematic diagram of the bubble generation number measuring device used in the examples and comparative examples of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Depressurization degassing apparatus 20 Depressurization defoaming tank 21 Molten glass 22U Rising pipe 22L Downfalling pipe 23 Casing 30A Upstream transfer tank 30B Downstream transfer tank 31a First stirrer 31b Second stirrer 41 Sample 42 Molten glass 43 Double crucible 43a Inside Crucible 43b Outer crucible 44 Electric furnace 45 Video camera 46 Recording computer 47 Inlet port 48 Outlet port 49 Observation window 50 Bubble generation number measuring device

Claims (5)

  A glass channel material that is a platinum-based material and has an iron group metal content of 60 ppm or less.   The glass channel material according to claim 1, wherein the iron group metal content is 40 ppm or less.   The apparatus for glass manufacture which used the material for glass flow paths of Claim 1 or 2 for at least one part of the member which contacts molten glass. A vacuum degassing apparatus having a vacuum degassing tank, a riser pipe for introducing molten glass into the vacuum degassing tank, and a downcomer pipe for discharging the molten glass from the vacuum degassing tank,
The vacuum degassing apparatus in which at least one selected from the group consisting of the vacuum degassing tank, the riser pipe, and the downfall pipe is made of the glass channel material according to claim 1 or 2.   The manufacturing method of glass products which comprises the clarification process which defoams molten glass using the vacuum degassing apparatus of Claim 4.

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