TWI394725B - Glass manufacturing method - Google Patents

Description

Glass manufacturing method

The present invention relates to a glass manufacturing method including a vacuum degassing step, a method of adjusting a water vapor concentration in an upper space in a vacuum degassing tank, and a vacuum degassing apparatus.

Conventionally, in order to improve the quality of the formed glass product, a clarification step of removing bubbles generated in the molten glass is performed before the molten glass in which the molten material is dissolved in the melting furnace is molded by a molding apparatus.

It is known that in the clarification step, the molten glass is introduced into the vacuum atmosphere, and under the vacuum atmosphere, the bubbles in the continuously flowing molten glass flow are greatly grown and the gas contained in the molten glass is floated, and A decompression degassing method in which a bubble is removed and then discharged from a vacuum atmosphere.

In such a vacuum degassing method, in order to achieve an appropriate vacuum degassing condition, a method of specifying the pressure and temperature in the vacuum degassing tank is proposed (see Patent Document 1 and Patent Document 2).

Patent Document 1: JP-A-2000-128422, Patent Document 2: International Publication No. 02/098810

However, for example, even if vacuum degassing is performed under the vacuum degassing condition as described above, in the vacuum degassing treatment, the bubble layer existing on the surface of the molten glass is usually about 10 mm or less, and is also enlarged toward 10 mm to several hundreds of mm. The so-called sudden boiling occurs. The term "bumping" refers to a bubble that reaches the surface of the glass, which usually disappears with time, does not break into bubbles, and becomes a layer and settles for a long period of time, resulting in a phenomenon in which the molten glass interface (the surface of the molten glass) rises. As a result, there is a problem that bubbles remain in the molten glass after vacuum degassing.

Further, even if no sudden boiling occurs, bubbles are left in the glass product as a result of the enlargement of the bubble layer, and defects occur.

Further, for example, even if vacuum degassing is performed under the vacuum degassing condition as described above, the specific component (boron or the like) in the molten glass is volatilized, and the glass composition is changed, resulting in deterioration of the flatness of the produced glass plate. .

It is an object of the present invention to provide a glass manufacturing method which performs vacuum degassing under sudden boiling.

Further, a glass production method in which bubbles are left in the glass product from which the bubble layer is enlarged and vacuum degassing is performed is provided.

Further, a glass production method for suppressing volatilization of a specific component (boron or the like) in the molten glass and performing vacuum degassing is provided.

Moreover, a method for adjusting the water vapor concentration of the atmosphere gas of the vacuum degassing tank which is preferably used under such vacuum degassing, and a vacuum degassing apparatus for the molten glass which can be vacuum degassed are provided.

The inventors of the present invention conducted a detailed review of the phenomenon that the surface of the molten glass surface in the vacuum degassing tank is enlarged, and the vacuum degassing treatment condition which causes a sudden boiling and defects. Thereafter, when the water vapor concentration of the atmosphere gas in the vacuum degassing tank was found to exceed a certain value, the bubble layer was enlarged and many bubbles remained in the glass product. Further, when the water vapor concentration is a specific value higher than the specific value, it is found that the bubble layer is further enlarged and swelled, so that bubbles remain in the glass product. Thereafter, a glass manufacturing method for vacuum degassing under vacuum degassing conditions below the specific value is found, a vacuum degassing device for molten glass which can be vacuum degassed under such conditions, and a vacuum degassing tank for adjusting such a device The method of the water vapor concentration of the atmosphere gas therein can solve the above problems and complete the present invention.

The present invention provides the following (1) to (8).

(1) A method for producing a glass, comprising the step of vacuum-degreasing a molten glass by a water vapor concentration of an atmosphere gas in a vacuum degassing tank of 60 mol% or less.

(2) The method for producing a glass according to the above (1), wherein the atmosphere gas introduced into the vacuum degassing tank by a low moisture content gas has a water vapor concentration of 60 mol% or less.

(3) The method for producing a glass according to the above (1) or (2), wherein the ambient gas has a water vapor concentration of 30 mol% or less.

(4) The method for producing a glass according to the above (2) or (3), wherein the oxygen concentration (% by volume) of the low moisture gas is lower than the oxygen concentration (% by volume) in the air.

(5) The method for producing a glass according to the above (4), wherein the low moisture gas has an oxygen concentration (% by volume) of 15% by volume or less.

A method for producing a glass, characterized in that a water vapor concentration of an atmosphere of a vacuum degassing tank for vacuum degassing molten glass is measured, and a low moisture gas is introduced into the vacuum based on a measurement result of the water vapor concentration. The atmosphere gas of the degassing tank is adjusted to adjust the water vapor concentration of the atmosphere gas in the vacuum degassing tank to 60 mol% or less.

A vacuum degassing device for molten glass, comprising: a vacuum housing that is vacuum-attracted; a vacuum degassing tank disposed in the vacuum enclosure for vacuum degassing of the molten glass; and the vacuum degassing The grooves are connected to each other, and the molten glass before the vacuum degassing is introduced into the vacuum degassing tank; the vacuum degassing tank is connected to the vacuum degassing tank, and the vacuum degassed glass is removed from the vacuum degassing tank. A vacuum degassing device for molten glass according to the derivation means, further comprising: a water vapor concentration measuring means for measuring a water vapor concentration of the atmosphere gas in the vacuum degassing tank; and introducing a low moisture gas into the vacuum degassing tank A low moisture gas introduction means for the inner upper space.

8. The vacuum degassing device according to (7) above, wherein the vacuum degassing device further comprises: a water vapor concentration control means capable of controlling a concentration of water vapor of the atmosphere gas to a desired value; The signal is used to control the amount of gas introduced by the low moisture gas.

9. The vacuum degassing apparatus for molten glass according to (7) or (8) above, wherein the low-moisture gas introduction means is provided on a flow side of the vacuum degassing tank.

The glass manufacturing method of the present invention comprises the steps of vacuum degassing the molten glass so that the water vapor concentration of the atmosphere gas in the vacuum degassing tank is 60 mol% or less, so that the boiling of the molten glass can be prevented from occurring. Degassing effect. Further, it is possible to achieve an effect that the glass product does not cause defects due to bubbles remaining in the boiling water. Further, since the glass manufacturing method of the present invention can prevent the boiling, it is possible to continue the glass production in stability.

This "stable manufacturing" is a very important factor in quality management for glass manufacturing equipment that does not require day and night operation. If the quality deteriorates, the equipment must be stopped due to repairs and adjustments. Further, since the molten glass which can suppress the sudden boiling adheres to the wall and the ceiling of the vacuum degassing tank, the falling of the glass can suppress the formation of defects in the glass product, and the quality is improved.

Further, in the method for producing a glass of the present invention, since the moisture in the atmosphere which promotes the volatilization of a specific component (boron or the like) can be reduced, the effect of suppressing the volatilization of a specific component (boron or the like) in the molten glass is achieved. In the case of producing a glass plate, deterioration in flatness can be suppressed. In particular, glass for displays such as glass for liquid crystals has strict specifications for composition because of its characteristics. On the other hand, since boron is very easily volatilized, it is necessary to strictly adjust the boron content. Therefore, according to the glass manufacturing method of the present invention, it is possible to efficiently manufacture a glass having a composition and flatness within a specification range.

Further, the glass production method of the present invention is preferably such that the water vapor concentration is 30 mol% or less. Thus, as described above, no sudden boiling occurs, and the enlargement of the bubble layer can be suppressed, and the effect of suppressing many defects of the glass product (specifically, the mass per unit mass of the glass product and 0.5 bubbles/kg or less) can be achieved.

Further, the vacuum degassing apparatus of the present invention can provide a suitable vacuum degassing apparatus for carrying out the glass manufacturing method of the present invention.

A method of manufacturing a glass according to the present invention will be described.

In the glass production method of the present invention, the water vapor concentration of the atmosphere gas in the vacuum degassing vessel is set to 60 mol% or less, and the molten glass is vacuum-degassed (hereinafter also referred to as "the vacuum degassing step of the present invention"). Next, it is preferable to have the raw material melting step as the pre-step, and it is preferable to have the forming step as the subsequent step. The raw material melting step and the forming step are not particularly limited, and may be, for example, a previously known step. There are other steps besides these steps.

In addition, the term "ambient gas" as used in the present invention means an atmosphere gas which is filled in the upper space (upper space) of the molten glass inside the vacuum degassing tank.

In the glass manufacturing method of the present invention, the vacuum degassing step of the present invention is a step of defoaming bubbles in the molten glass by flowing into the molten glass in a vacuum degassing tank in an internal vacuum state, if the vacuum is removed The vacuum degassing step of the atmospheric gas in the gas tank having a water vapor concentration of 60 mol% or less is not particularly limited.

For example, the water vapor concentration of the atmosphere gas in the vacuum degassing tank in the vacuum degassing apparatus is measured, and based on the measurement result of the water vapor concentration, the vacuum of the vacuum deaerator is adjusted by introducing a low moisture gas to be described later into the upper space. The method of the present invention can be carried out by adjusting the water vapor concentration of the atmosphere gas in the inside of the gas tank (hereinafter also referred to as "the moisture adjustment method of the present invention") by adjusting the water vapor concentration of the atmosphere gas to 60 mol% or less. Vacuum degassing step. The low moisture gas may be continuously introduced or intermittently introduced.

The vacuum degassing step of the present invention to which such a moisture adjusting method of the present invention is applied can be carried out, for example, using the vacuum degassing apparatus of the present invention.

A vacuum deaeration device according to the present invention will be described.

The vacuum degassing device of the present invention is a vacuum degassing device for vacuum degassing molten glass, and has a vacuum degassing tank that flows into the molten glass inside the vacuum state and degases the bubbles in the molten glass, and measures the foregoing a water vapor concentration measuring means for measuring the water vapor concentration of the atmosphere gas in the vacuum degassing tank, and a low moisture gas introducing means for introducing the low moisture gas into the upper space, reducing the water vapor concentration of the atmosphere gas, and vacuum removing the molten glass A vacuum degassing device, such as the vacuum degassing device shown in FIG.

Explain Figure 1. 1 is a view showing a vacuum degassing apparatus 1 which is a configuration example of a vacuum degassing apparatus of the present invention, and shows a vacuum degassing tank 12 and a water vapor concentration measuring means 30 which the vacuum degassing apparatus of the present invention has. And a low moisture gas introduction means 40.

First, this vacuum degassing tank 12 will be described using FIG. FIG. 2 is a view (cross-sectional view) illustrating the vacuum degassing apparatus 10 of the present invention including the vacuum degassing tank 12 (the water vapor concentration measuring means and the low moisture gas introducing means are not described).

In the vacuum degassing apparatus 10 shown in FIG. 2, the vacuum degassing tank 12 which is formed in a cylindrical shape is aligned in the horizontal direction of the long axis, and is accommodated in the vacuum envelope 11. The riser 13 which is vertically aligned below one end of the vacuum degassing tank 12 and the downcomer 14 are installed below the other end. The riser 13 and the downcomer 14 are located in the vacuum enclosure 11 with a portion thereof.

Next, a plurality of openings are formed in the upper surface of the vacuum degassing tank 12, and the low moisture gas 7 can be introduced into the upper space 5 inside the vacuum degassing tank 12 through the outside of the vacuum envelope 11 through the at least one opening 6. Further, the opening 8 formed by the vacuum envelope 11 is a decompression means (not shown in Fig. 2, shown by the pump 28 in Fig. 1) connected to a pump or the like, and the atmosphere gas 3 filled in the upper space 5 is evacuated to the vacuum envelope. When the outer discharge is 11 (the discharge is indicated by the atmosphere gas 3'), the inside of the vacuum degassing tank 12 can be decompressed. Further, the openings 6 and the openings 8 are not limited to the openings 6 and the openings 8 shown in FIG. 2, and the openings 6 are provided on the upstream side of the vacuum degassing tank 12, and the openings 8 are provided on the downstream side thereof. good. The opening 6 constituting a part of the low-moisture gas introduction means is disposed on the upstream side of the vacuum degassing tank 12, so that the opening 6 is directed toward the low-moisture gas 7 introduced into the upper space 5 inside the vacuum degassing tank 12, The upstream side of the vacuum degassing tank 12 flows toward the downstream side of the installation opening 8, so that the upper space 5 inside the vacuum degassing tank 12 can be made into a uniform low water vapor concentration atmosphere.

Further, inside the vacuum degassing tank 12, for example, a known pressure gauge and a thermometer (not shown) capable of measuring the pressure (P ₁ ) and temperature (T ₁ ) of the atmosphere gas 3 are provided.

Moreover, as shown in FIG. 2, the riser pipe 13 is an introduction means that communicates with the vacuum degassing tank 12 and introduces the molten glass G from the dissolution tank 20 into the vacuum degassing tank 12. Therefore, the lower end portion of the riser pipe 13 is fitted into the open end of the upstream pit 22, and is impregnated by the molten glass G in the upstream pit 22.

The downcomer 14 is a deriving means that is connected to the vacuum degassing tank 12, and is a vacuum degassing glass G which is evacuated by the vacuum degassing tank 12 and which is led out in a processing tank (not shown) in the subsequent step. Therefore, the lower end portion of the downcomer 14 is fitted into the open end of the downstream pit 24, and is impregnated by the molten glass G in the downstream pit 24.

In the vacuum envelope 11, a heat insulating material 15 such as a heat insulating brick which is thermally insulated and covered is disposed around the vacuum degassing tank 12, the riser pipe 13, and the down pipe 14.

In the vacuum degassing apparatus 10 shown in FIG. 2, since the vacuum degassing tank 12, the riser pipe 13, and the downcomer 14 are the ducts of the molten glass G, it is manufactured using the material excellent in the heat resistance and the corrosion resistance of the molten glass. When an example is given, it is a hollow tube made of platinum or a platinum alloy. Specific examples of the platinum alloy include a platinum-gold alloy and a platinum-rhodium alloy. Moreover, as another example, it is a ceramic-type non-metal inorganic material, that is, a hollow tube made of a dense refractory. Specific examples of the dense refractory include an electroformed refractory such as an alumina-based electroformed refractory, a zirconia-based electroformed refractory, or an alumina-zirconia-ceria-based electroforming refractory. And a dense calcined refractory such as a dense alumina refractory, a dense zirconium dioxide-cerium oxide refractory, and a dense alumina-zirconia-ceria-based refractory.

The size of each component of such a vacuum degassing device 10 can be appropriately selected as needed. The size of the vacuum degassing tank 12 can be appropriately selected depending on the vacuum deaerator used, regardless of whether the vacuum degassing tank 12 is made of platinum or a platinum alloy or a dense refractory. In the case of the vacuum degassing tank 12 shown in Fig. 2, specific examples of the dimensions thereof are as follows.

Length in the horizontal direction: 1~20m inner diameter: 0.2~3m (cross section)

When the vacuum degassing tank 12 is made of platinum or a platinum alloy, the thickness is preferably 4 mm or less, and preferably 0.5 to 1.2 mm.

The vacuum envelope 11 is made of metal, for example, made of stainless steel, and has a shape and a size that can accommodate a vacuum degassing tank.

The riser pipe 13 and the downcomer pipe 14 are made of platinum or a platinum alloy or a compact refractory, and can be appropriately selected depending on the vacuum degassing device to be used. For example, the sizes of the riser 13 and the downcomer 14 are configured as follows.

Inner diameter: 0.05 to 0.8 m, preferably 0.1 to 0.6 m Length: 0.2 to 6 m, preferably 0.4 to 4 m

When the riser pipe 13 and the downcomer pipe 14 are made of platinum or a platinum alloy, the thickness is preferably 0.4 to 5 mm, and preferably 0.8 to 4 mm.

The vacuum degassing tank provided in the vacuum degassing apparatus of the present invention is, for example, a vacuum degassing tank 12 having such a configuration.

Next, the water vapor concentration measuring means 30 included in the vacuum degassing apparatus of the present invention will be described.

The water vapor concentration measuring means 30 in Fig. 1 is a pump 28 that is connected to a downstream side of the vacuum degassing tank 12 by piping or the like, and is connected to a downstream side of the decompression means. By the pump 28, the atmosphere gas 3' discharged from the vacuum degassing tank 12 can be sent to the steam concentration measuring means 30. The atmosphere gas 3' discharged from the pump 28 is treated as it is and discharged to the atmosphere.

The water vapor concentration measuring means 30 may be a commercially available dew point meter, and may be a measuring means for measuring the pressure, temperature, and gas flow rate of the atmosphere gas 3' discharged from the vacuum degassing tank 12. For each measurement means, for example, a previously known pressure gauge, a thermometer, and a gas flow meter can be used. The water vapor concentration is a value indicating the amount of water vapor contained in the entire atmosphere.

The water vapor concentration (C) [mole %] of the atmosphere gas 3' can be measured using a commercially available dew point meter, and the water contained in the atmosphere 3' can be precipitated, and the amount (W) [g] is measured. And the estimate is also possible. For example, the gas flow rate of the atmosphere gas 3' discharged from the vacuum degassing tank 12 is regarded as F _out [m ³ /h], the gas outflow time is regarded as t _out [h], and the water vapor concentration measuring means 30 is measured. When the pressure and temperature of the atmosphere gas 3' are regarded as P ₂ [Pa] and T ₂ [K], the water vapor concentration (C) [mol%] in the atmosphere gas 3' is represented by the following formula (1).

When the water vapor concentration calculated by the formula (1) is 60 mol% or less, the vacuum degassing of the molten glass can be performed without causing ablation, and the effect of causing no defects due to bubbles remaining in the glass product can be obtained.

The individual units are as follows.

C: mol%, W: g, T ₂ : K, P ₂ : Pa, F _out : m ³ /h, t _out : h, R (gas constant): J. K/mol

Next, the low-moisture gas introduction means 40 of the vacuum degassing apparatus of the present invention will be described.

The low-moisture gas introduction means 40 in Fig. 1 is connected to a pipe or the like on the upstream side of the vacuum degassing tank 12. Then, the low-moisture gas 7 can be introduced by the low-moisture gas introduction means 40 by the piping or the like.

In the low-moisture gas introduction means 40, for example, the low-moisture gas generating device 41 and the vacuum degassing tank 12 are connected by piping or the like, and the low-moisture gas 7 generated by the low-moisture gas generating device 41 can be introduced. The upper space 5 of the vacuum degassing tank 12. Next, between the low-moisture gas generating device 41 and the vacuum degassing tank 12, a flow rate control valve 42 and a flow meter 44 are sequentially provided, whereby the introduction amount of the low-moisture gas 7 can be adjusted.

In addition, the arrangement of the flow control valve 42 and the flow meter 44 may be reversed.

Here, the low-moisture gas introduction means 40 may have an introduction means (for example, a high-pressure fan or the like) for actively introducing the low-moisture gas 7 into the upper space 5 of the vacuum degassing tank 12. At this time, since the low-moisture gas 7 can be efficiently introduced into the upper space 5, it is preferable.

Moreover, when the atmosphere is used as the low-moisture gas 7, the above-described low-moisture gas generator 41 is unnecessary. For example, one of the pipes connecting the upper space 5 and the like is opened in the atmosphere via the opening and closing of the flow rate control valve 42, and the atmosphere may be decompressed through the pipe and introduced into the upper space 5.

In addition, when the inert gas or the like other than the atmosphere is used as the low-moisture gas 7, the above-described water vapor concentration measuring means 30 is preferably a gas component measuring instrument having a gas component capable of measuring the atmospheric gas 3' discharged from the upper space 5.

Further, the term "low moisture gas" as used in the present invention means a gas having a lower moisture (water vapor concentration) than the atmosphere gas 3 in the upper space 5. Examples of the low moisture gas include air, dry air, inert gas such as N ₂ and Ar, and the like, and may be one type or plural types. The water vapor concentration of the low moisture gas is preferably 0 to 20 mol%, more preferably 0 to 5 mol%, and further preferably 0 to 1 mol%. Further, the water vapor concentration of the low moisture gas can be measured using a commercially available dew point meter or the like.

The vacuum degassing device of the present invention is, for example, a vacuum degassing device 1 having such a vacuum degassing tank 12, a water vapor concentration measuring means 30, and a low moisture gas introducing means 40.

In the vacuum degassing apparatus of the present invention, the concentration of the ambient gas water vapor in the upper space is measured by the water vapor concentration measuring means, and when the concentration is higher than the desired water vapor concentration, the low moisture gas introduction means is introduced low. The moisture gas can be adjusted to the desired concentration in the upper space by appropriately repeating the adjustment.

For example, the water vapor concentration (C) obtained by the above formula (1) and the target water vapor concentration (C ₁ ) have the relationship of the following formula (2), so that the introduction amount of the low moisture gas into the upper space is adjusted (F) _In ) and the introduction time (t _in ), the amount of ambient gas discharged from the upper space (F _out ) and the discharge time (t _out ), and the water vapor concentration (S) [mol%] of the low moisture gas, The water vapor concentration is set to a target value.

The meaning and unit of each mark are as follows: C ₁ : [mol%], V (volume of the upper space): [m ³ ], V _in : [m ³ ], V _out : [m ³ ]

Here, V _in is the introduced gas volume (F _in ×t _in ) obtained by the introduction amount (F _in [m ³ /h]) and the introduction time (t _in [h]) measured by the flow meter 44 [ m ³ ] The amount of temperature and pressure converted in the upper space. Similarly, V _out is the discharge gas volume determined by the discharge amount (F _out [m ³ /h]) and the discharge time (t _out [h]) measured by the flow meter included in the water vapor concentration measuring means 30. (F _out ×t _out ) [m ³ ] The converted value of the temperature and pressure in the upper space.

Also, when the pressure in the upper space is kept constant, V _in = V _out must be used.

For example, the water vapor concentration (C) = 20 mol% in the upper space of the volume (V) = 1 m ³ is reduced to the target water vapor concentration (C ₁ ) = 10 mol%, and when V _in = V _out , the low moisture gas The amount of introduction (V _in ) = 0.53 m ³ .

Therefore, when the temperature of the upper space (T ₁ )=1673K and the pressure (P ₁ )=25 kPa, the introduction gas temperature (T ₃ )=298K and the pressure (P ₃ )=101 kPa at the position of the flow meter 44 introduce the gas volume ( F _in × t _in ) is 0.023 [m ³ ].

Actually, since the water from the molten glass and the constituent material of the device evaporates or the water vapor concentration changes due to the air leakage, it is necessary to continuously adjust.

In addition, in the manufacture of glass products, this water vapor concentration is often monitored and controlled. Specifically, it is preferable that the vacuum degassing device has a water vapor concentration control means capable of controlling a water vapor concentration of the atmosphere gas to a desired value, and further has a method of controlling a low moisture gas based on a signal from the control means. The amount of gas to be introduced is preferably controlled.

For example, the vacuum degassing device of the present invention has constant measurements T ₂ , P ₂ , F _out , t _out , W ₂ , S, F _in and t _in , and collects such data on a computer, according to which the computer will be upper It is preferred that the water vapor concentration of the space is controlled to a desired value of the water vapor concentration. Further, it is preferable that the vacuum deaerator of the present invention has a gas amount control means for controlling the opening and closing of the flow rate control valve 42 by this computer and inputting the data of the flow meter 44 to the computer. Moreover, in order to keep the production performance constant, it is desirable to adjust the flow rate while controlling the desired pressure.

The glass manufacturing method of the present invention is preferably carried out using such a vacuum degassing device of the present invention, but other methods may be applied. For example, it is not necessary to introduce a gas into the upper space in the vacuum degassing tank according to the vacuum degassing device of the present invention, and to reduce the concentration of the gas water vapor in the vacuum envelope when the vacuum degassing tank is connected to the atmosphere in the vacuum enclosure. Just fine.

In the glass production method of the present invention, the vacuum degassing treatment conditions are not particularly limited as long as they are in the usual range. The normal vacuum decompression condition means that the pressure (P ₁ ) of the atmosphere in the upper space inside the vacuum degassing tank is 38 to 460 mmHg (51 to 613 hPa), and the temperature (T ₁ ) is 1100 ° C to 1500 ° C. In particular, the treatment conditions for vacuum degassing treatment are carried out at 1250 ° C to 1450 ° C.

In the vacuum degassing step of the present invention provided in the glass production method of the present invention, the water vapor concentration of the atmosphere inside the vacuum degassing tank is 60 mol% or less. If so, the degassing of the bubbles in the molten glass can be carried out under vacuum conditions without causing a sudden boiling.

Further, the lower the water vapor concentration, the smaller the foam layer tends to be. Therefore, the water vapor concentration of the atmosphere inside the vacuum degassing tank is preferably 50 mol% or less, and more preferably 40 mol% or less. When the water vapor concentration is 30 mol% or less, the foam layer tends to be thinner, which is not preferable. Further, depending on the glass composition, one bubble sometimes shrinks or breaks, so that the bubble layer becomes thinner, so it is preferable. Further, it is preferable that it is difficult to remain a bubble which is considered to be a defect in the degree of defects in the glass product. When the water vapor concentration is further lowered, the probability of occurrence of defects in the glass product is preferably lower, preferably 25 mol% or less, more preferably 20 mol% or less, still more preferably 15 mol% or less, and 10 mol% or less. More preferably, it is preferably 5 mol% or less.

Further, the present inventors have found that, in addition to the above, the shrinkage of such bubbles is found to be particularly remarkable in the molten glass of a specific composition.

Specifically, when the molten glass is total tellurite glass, if the water vapor concentration is 30 mol% or less, the bubbles tend to shrink significantly. Therefore, the glass manufacturing method of the present invention, the vacuum degassing apparatus of the present invention and the moisture adjusting method of the present invention are more preferably used in the production of perrhensilicate glass.

The so-called total tellurite glass here has the following composition.

Composition range: SiO ₂ : 55 to 74, Al ₂ O ₃ : 10 to 20, B ₂ O ₃ : 5 to 12, Al ₂ O ₃ / B ₂ O ₃ : 1.5 to 3, MgO: 0 to 5, CaO : 0~5, SrO: 0~12, BaO: 0~12, SrO+BaO: 6~12 (unit is mass%).

There has been no review of the water vapor concentration in the pressure and temperature conditions in the vacuum degassing tank which has been suggested above. The present inventors have made efforts to review the cause of sudden boiling and bubble layer hypertrophy even if degassing under the previously suggested vacuum degassing condition, and have found that the problem can be solved by focusing on the previously unfocused water vapor concentration.

Moreover, the present inventors have found that when the water vapor concentration is 60 mol% or less, the effect of suppressing the volatilization of a specific component (boron or the like) in the molten glass can be achieved. By suppressing the volatilization of a component such as boron, the composition fluctuation of boron or the like can be prevented, and the deterioration of the flatness due to the composition variation can be suppressed.

Further, the volatile component, for example, the volatilization of Cl, F, S or the like can be suppressed, so that the composition variation of these components can be prevented, and the deterioration of the flatness due to the composition variation can be suppressed.

These Cl, F, S and other components are greatly affected by water volatilization. For example, F is in the HF type and S is in the H ₂ SO ₄ type. Therefore, when the water concentration in the vacuum degassing tank is equal to or less than a certain amount, the fluctuation of the above-mentioned components accompanying the evaporation of water can be suppressed.

Further, the characteristics of the glass are very fine specifications depending on the use thereof, and a glass composition having a very detailed structure is appropriately substituted for such a specification. For example, there is of course a specification regarding the content of boron, but in the prior method, since boron is volatilized, it is necessary to use a large amount of boron as a raw material. Further, conventionally, the amount of boron to be volatilized varies depending on conditions, and as the case may be, the specification of the boron content may exceed. In the present invention, it is useful to solve such problems.

From this point of view, the glass manufacturing method of the present invention, the vacuum degassing device of the present invention and the moisture adjusting method of the present invention are of course not preferred for use in ordinary glass, and particularly for the production of perrhenate glass. use.

Further, in the present invention, the low moisture gas introduced into the upper space inside the vacuum degassing tank preferably has a lower oxygen concentration than the oxygen concentration in the air. The oxygen concentration is preferably 15% by volume or less, more preferably 10% by volume, and even more preferably 5% by volume or less. Further, the low moisture gas is preferably a gas containing no oxygen, such as N ₂ gas, Ar gas, CO ₂ or the like.

When the oxygen concentration of the low-moisture gas introduced into the upper space is such a value, the foam layer can be thinned as described above, and when platinum or a platinum alloy is used as the material of the vacuum degassing tank, the platinum can be suppressed. Oxidation, prolonging the life of the vacuum degassing tank, and further suppressing the formation of defects from the platinum in the glass product is preferable.

As described above, the glass production method of the present invention is preferably provided with the vacuum degassing step of the present invention, and includes a raw material melting step and a forming step as the pre-step and the post-step. This raw material melting step can be, for example, a previously known step, for example, a step of melting the raw material by heating at about 1400 ° C or more depending on the type of glass. The raw material to be used is not particularly limited as long as it is suitable for the raw material of the glass to be produced. For example, a raw material obtained by blending a previously known substance such as tannic acid, boric acid or limestone with a composition of the final glass product can be used. This raw material may also contain the desired clarifying agent. Further, the forming step may be, for example, a previously known step, and examples thereof include a float forming step, a roll-out forming step, a melt forming step, and the like.

Example

Hereinafter, the present invention will be specifically described based on examples. However, the invention is not limited thereto.

<Example 1> In order to reproduce an atmosphere which was subjected to vacuum degassing, a platinum crucible containing a glass raw material was placed in a vacuum decompression vessel. The crucible was heated to melt the glass so that the temperature of the molten glass was 1420 °C. Thereafter, the absolute pressure in the vacuum decompression vessel was 26.7 kPa.

Here, the composition of the glass raw materials used is as follows.

SiO ₂ : 59.4%, Al ₂ O ₃ : 17.6%, B ₂ O ₃ : 7.9%, MgO: 3.2%, CaO: 3.7%, SrO: 7.9%, and BaO: 0.1%.

Further, Examples 1 to 3 were carried out by using a platinum tantalum placed in molten glass instead of the vacuum degassing tank 12 in Fig. 1, and the experimental results of this crucible can be regarded as the result of the vacuum degassing tank 12 in Fig. 1. Equivalent.

Next, the atmosphere adjusted to the desired water vapor concentration is introduced into the vacuum decompression vessel, and the water vapor concentration (mol%) of the atmosphere in the vacuum decompression vessel is adjusted in various numerical values. Regarding the respective water vapor concentrations, bubbles in the molten glass were photographed using a CCD camera from an observation window provided in the vacuum decompression device. After 30 minutes passed, the molten glass in the crucible was quenched and solidified, and the number of bubbles (counting diameters of 100 μm or more) present in the sample after curing was measured, and the bubble density (number/kg) was determined. Here, the mass of the molten glass is 5.0 kg, and the number of the bubbles in the glass before the pressure reduction is about the same value in the case of the respective water vapor concentrations.

The results are shown in Figure 3.

It is confirmed from Fig. 3 that the higher the water vapor concentration of the atmosphere in the vacuum decompression container, the more the bubbles remain. In FIG. 3, the horizontal axis represents the water vapor (moisture) concentration of the atmosphere, and the vertical axis represents the value of the number of bubbles represented by Log.

Further, when the water vapor concentration is more than 60 mol%, the interface of the molten glass sharply rises when observed by a CCD camera, and a so-called sudden boiling phenomenon occurs.

<Example 2> Next, the thickness of the bubble layer was measured using the apparatus similar to the above-mentioned Example 1, and the water vapor density of the atmosphere in the vacuum pressure reduction container was 70 mol%, 47 mol%, 31 mol%, and 3 mol%. Further, in the first embodiment, the low-moisture gas in the atmosphere was N ₂ , CO ₂ , and Ar, and the water vapor concentration in the atmosphere in the vacuum decompression vessel was less than 1 mol%, respectively, and the same test was carried out. The glass composition was the same as in Example 1.

The results are shown in Table 1.

As described above, when the water vapor concentration is 70 mol%, the thickness of the bubble layer is 20 mm or more, and the so-called sudden boiling is confirmed. Further, when the water vapor concentration is 3 to 47 mol%, a bubble layer having a thickness of about 1 to 2 mm is formed, but no sudden boiling is confirmed. Further, if the atmosphere is N ₂ , CO ₂ or Ar (the water vapor concentration is less than 1 mol%), no bubble layer is formed. From the above results, the water vapor concentration must be 60 mol% or less. Further, the thickness of the bubble layer is preferably about 15 mm or less.

<Example 3> In the same test as in Example 2, the bubble shrinkage rate in the bubble layer of various atmospheres was measured. Here, the molten glass was the same as the silicate glass of Example 1.

The results are shown in Figure 4. In addition, the bubble diameter in FIG. 4 is a value which shows normalization. The term "normalization" refers to the ratio of the diameter of the bubble in the interior of the molten glass reaching the bubble layer to the diameter of the bubble at each time. Therefore, when the bubble reaches the bubble layer, the elapsed time Os is obtained, and the bubble diameter at this time is 1.0.

4, in the case of an atmosphere having a water vapor concentration of 31 mol%, an atmosphere having a water vapor concentration of 3 mol%, and a water vapor concentration of 1 mol% or less of N ₂ , CO ₂ or Ar, the bubble shrinkage speed is increased.

As a result, it is judged that the lower the water vapor concentration in the atmosphere, the more easily the bubble shrinks, that is, the bubble easily disappears.

<Example 4> Next, the bubble was floated up to the surface of the molten glass by vacuum degassing treatment, and then foamed and destroyed, and the water vapor concentration (1 mol%, 9 mol%, 13 mol%, 19 mol%, 22 mol) was used in various atmospheres. %, 35 mol%, 70 mol%) and glass composition (soda lime glass: composition A, composition B, composition C) were measured. Here, a 50 cc transparent quartz glass beaker was used as a container to observe the appearance of the bubbles, and the thickness of the bubble layer when about 50 g of the glass was dissolved was measured. Further, the number of bubbles (Bs) floating on the surface of the molten glass and the number of bubbles (B _B ) which reached the surface of the molten glass and broke and disappeared were counted by a CCD camera, and the value of the bubble breaking rate (B _B /B) was calculated. _S %). The thickness (mm) of the foam layer and the foam breaking rate (%) are shown in Table 2 below.

In addition, any sample heated the temperature of the molten glass at 1200 °C. The absolute pressure in the container was 18.7 kPa in the case of composition A, 10.3 kPa in the case of composition B, and 14.4 kPa in the case of composition C. Further, the content ratios of the components A in the composition A, the composition B, and the composition C are as shown in Table 3 below. The % in Table 3 indicates the mass %.

It is confirmed from Table 2 that the higher the water vapor concentration of the atmosphere in the container, the lower the bubble breaking rate and the remaining bubbles. Specifically, when the water vapor concentration of the atmosphere is more than 60 mol%, the foam layer has a thickness of 20 mm or more, and when it is 60 mol% or less, it is confirmed that the bubble layer is thin. Further, when the water vapor concentration is more than 60 mol%, the interface of the molten glass sharply rises when observed by a CCD camera, and a so-called sudden boiling phenomenon occurs. Moreover, when the water vapor concentration of the atmosphere in the container is less than 15 mol%, the foam breaking rate is high, and it is known that it is preferable. In other words, when the water vapor concentration of the atmosphere in the container is 60 mol% or less, the phenomenon of bumping can be prevented and the bubble layer can be made thin, and if the water vapor concentration is further lowered, the bubble breaking rate is increased and the bubbles are eliminated.

[Industrial availability]

The present invention can be applied to a glass manufacturing method including a vacuum degassing device for molten glass and a vacuum degassing step, and is particularly suitable for the production of high quality display glass having few bubbles.

In addition, the entire contents of the specification, the patent application, the drawings and the abstract of the Japanese Patent Application No. 2006-233441, filed on August 30, 2006, are hereby incorporated by reference.

1. . . Vacuum degassing device

3. . . Atmosphere gas

3’. . . Exhausted atmosphere

5. . . Upper space

6. . . Opening

7. . . Low moisture gas

8. . . Opening

9. . . Opening

10. . . Vacuum degassing device

11. . . Vacuum cover

12. . . Vacuum degassing tank

13. . . Riser

14. . . Drop tube

15. . . Insulation material

20. . . Dissolution tank

twenty two. . . Upflow pit

twenty three. . . Downflow pit

28. . . Pump

30. . . Water vapor concentration measuring means

40. . . Low moisture gas introduction means

41. . . Low moisture gas generating device

42. . . Flow control valve

44. . . Flow meter

G. . . Dissolved glass

Fig. 1 is a view showing a configuration example of a vacuum degassing apparatus of the present invention.

Fig. 2 is a view showing a vacuum degassing apparatus and the like of the present invention.

Fig. 3 is a view showing the result of Example 1 of the present invention.

Fig. 4 is a view showing the result of Example 3 of the present invention.

Claims (10)

A method for producing a glass, comprising: introducing a low-moisture gas into an atmosphere gas in a vacuum degassing tank, wherein a water vapor concentration of the atmosphere gas is 60 mol% or less, and vacuuming the molten glass The step of degassing. The method for producing a glass according to claim 1, wherein the low moisture content gas is nitrogen, argon, carbon dioxide or the atmosphere. The method for producing a glass according to claim 1 or 2, wherein the ambient gas has a water vapor concentration of 30 mol% or less. The method for producing a glass according to claim 1 or 2, wherein an oxygen concentration (% by volume) of the low moisture gas is lower than an oxygen concentration (% by volume) in the air. The method for producing a glass according to the fourth aspect of the invention, wherein the low-moisture gas has an oxygen concentration (% by volume) of 15% by volume or less. A method for producing glass, characterized in that a water vapor concentration of an atmosphere of a vacuum degassing tank for vacuum degassing molten glass is measured, and a low moisture gas is introduced into the vacuum degassing according to a measurement result of the water vapor concentration. The atmosphere gas in the tank is adjusted so that the water vapor concentration of the atmosphere gas in the vacuum degassing tank is 60 mol% or less. The method for manufacturing glass according to item 6 of the patent application, the low moisture content gas is nitrogen, argon, and dioxane. Carbon or atmosphere. A vacuum degassing device for molten glass, comprising: a vacuum housing that is vacuum-attracted; a vacuum degassing tank disposed in the vacuum enclosure for vacuum degassing of the molten glass; and the vacuum degassing tank is connected thereto And an introduction means for introducing the molten glass before vacuum degassing into the vacuum degassing tank; and being disposed in communication with the vacuum degassing tank, the molten glass after vacuum degassing is derived from the vacuum degassing tank A vacuum degassing device for molten glass according to the present invention, further comprising: a water vapor concentration measuring means for measuring a water vapor concentration of the atmosphere gas in the vacuum degassing tank; and introducing a low moisture gas into the vacuum degassing tank Low moisture gas introduction means in the upper space. The vacuum degassing device of claim 8, wherein the low moisture content gas is nitrogen, argon, carbon dioxide or the atmosphere. The vacuum degassing device for molten glass according to claim 8 or 9, wherein the low moisture content gas is introduced into the flow side of the vacuum degassing tank.