KR20090052848A - Glass-making processes - Google Patents

Abstract

Glass manufacturing method which can perform pressure reduction without generating a dolby, Glass manufacturing method which can perform pressure reduction defoaming, without foaming remaining in glassware by enlargement of bubble layer, Volatilization of specific component (boron etc.) in molten glass It provides the glass manufacturing method which can perform dark-pressure defoaming, suppressing this.

It is a glass manufacturing method which makes the water vapor concentration of the atmospheric gas of a vacuum degassing tank into 60 mol% or less in the process of vacuum-degassing a molten glass by a dark-pressure defoaming tank.

Glass production, molten glass, reduced pressure defoaming, atmosphere gas, water vapor concentration

Description

Glass manufacturing method {GLASS-MAKING PROCESSES}

This invention relates to the glass manufacturing method provided with the process of degassing under reduced pressure, the method of adjusting the water vapor concentration of the upper space in a pressure reduction degassing tank, and a vacuum degassing apparatus.

Conventionally, in order to improve the quality of the molded glass product, the clarification process which removes the bubble which generate | occur | produced in the molten glass before shape | molding the molten glass which melt | dissolved the raw material in the melting furnace with the shaping | molding apparatus is used.

In this clarification process, a molten glass is introduce | transduced in a reduced pressure atmosphere, the bubble in the molten glass flow which flows continuously in this reduced pressure atmosphere is largely grown, the bubble contained in a molten glass is raised, it is made to bubble, and it removes, Thereafter, a vacuum degassing method discharged from a reduced pressure atmosphere is known.

And in such a vacuum degassing method, the method which prescribed | regulated the pressure and temperature in a pressure reduction degassing tank is proposed in order to achieve preferable pressure reduction defoaming conditions (refer patent document 1, patent document 2).

Patent Document 1: Japanese Unexamined Patent Publication No. 2000-128422

Patent Document 2: International Publication No. 02/098810

Disclosure of the Invention

Problems to be Solved by the Invention

However, even if vacuum degassing | defoaming is performed on the above-mentioned preferable vacuum degassing | defoaming conditions, for example, during the vacuum degassing | defoaming process, the bubble layer which exists normally on the surface of a molten glass enlarges to 10 mm-several hundred mm, so-called Dolby (Iv) sometimes occurred. Dolby is a phenomenon in which bubbles reaching the glass surface that normally disappear with time are stably present for a long time by forming a layer without breaking, resulting in an increase in the molten glass interface (the molten glass surface). As a result, the problem that a bubble remains in the molten glass after pressure reduction defoaming arises.

Moreover, even if a dolby did not generate | occur | produce, as a result of the enlarged bubble layer, a bubble may remain | survive in glassware and may generate a defect.

In addition, even when decompression degassing is carried out under the above-mentioned preferable degassing | defoaming degassing conditions, when the specific component (boron etc.) in a molten glass volatilizes and a glass composition changes, when the flatness of the manufactured glass platen deteriorates, There was.

An object of the present invention is to provide a method for producing a glass in which vacuum degassing is performed with little generation of dolby.

Moreover, it is providing the glass manufacturing method which performs pressure reduction defoaming in which the bubble residual in the glassware resulting from enlargement of a bubble layer hardly arises.

Moreover, it is providing the glass manufacturing method which suppresses volatilization of specific component (boron etc.) in a molten glass, and performs pressure reduction defoaming.

Moreover, it is providing the method of adjusting the water vapor concentration of the atmospheric gas of the vacuum degassing tank which can be preferably applied for such a vacuum degassing | defoaming, and the vacuum degassing apparatus of the molten glass which can perform such vacuum degassing | defoaming.

Means to solve the problem

MEANS TO SOLVE THE PROBLEM This inventor examined the pressure reduction defoaming process conditions in the case where the bubble layer of the molten glass surface in a pressure reduction degassing tank enlarges, what is called a dolby generation, and produces a defect. And when the vapor density | concentration of the atmospheric gas in a pressure reduction degassing tank exceeded the specific value, it discovered that a bubble layer enlarged and many bubbles remain in a glass product. In addition, when the water vapor concentration exceeded another specific value which is higher than this specific value, it was found that the bubble layer was further enlarged and rubbing so that more bubbles remained in the glass product. And the glass manufacturing method which performs pressure reduction defoaming on the pressure reduction defoaming conditions below these specific values, the pressure reduction defoaming apparatus of the molten glass which can decompression degassing on such conditions, and the vapor concentration of the atmospheric gas in the pressure reduction defoaming tank of such apparatus are adjusted. It was found out how to solve the above problems, and completed the present invention.

The present invention provides the following (1) to (9).

(1) The glass manufacturing method provided with the process of carrying out the pressure reduction defoaming of the molten glass by making water vapor concentration of the atmospheric gas of a vacuum degassing tank into 60 mol% or less.

(2) The glass manufacturing method as described in said (1) which makes water vapor concentration of the said atmospheric gas into 60 mol% or less by introducing the low moisture gas into the atmospheric gas of the said vacuum degassing tank.

(3) The glass manufacturing method as described in said (1) or (2) which makes water vapor concentration of the said atmospheric gas into 30 mol% or less.

(4) The glass manufacturing method as described in said (2) or (3) whose oxygen concentration (vol%) of the said low moisture gas is lower than the oxygen concentration (vol%) in air.

(5) The glass manufacturing method as described in said (4) whose oxygen concentration (vol%) of the said low moisture gas is 15 volume% or less.

(6) Measuring the water vapor concentration of the atmospheric gas of the vacuum degassing tank for degassing a molten glass under reduced pressure, and introduce | transducing a low moisture gas into the said atmospheric gas of the said vacuum degassing tank based on the measurement result of the water vapor concentration, The glass manufacturing method of adjusting the water vapor concentration of the said atmospheric gas of a vacuum degassing tank to 60 mol% or less.

(7) The pressure reduction degassing tank which is formed in this pressure reduction housing | suction, the pressure reduction degassing tank which is formed in this pressure reduction housing, and performs pressure reduction defoaming of molten glass, and this pressure reduction defoaming tank, and communicates with the molten glass before pressure reduction defoaming. A pressure reduction degassing apparatus of a molten glass, which is formed in communication with the pressure reduction degassing tank, which is introduced into the pressure reducing degassing tank, and has a derivation means for deriving the molten glass after pressure reduction degassing from the pressure reduction degassing tank. The vacuum degassing apparatus of the molten glass which further has a water vapor concentration measuring means which measures water vapor concentration, and the low moisture gas introduction means which introduces a low moisture gas into the upper space inside the said vacuum degassing tank.

(8) In the vacuum degassing apparatus, water vapor concentration control means capable of controlling the vapor concentration of the atmospheric gas to a desired value, and gas amount control means for controlling the amount of low moisture gas introduced by the signal from the control means. Furthermore, the pressure reduction defoaming apparatus as described in said (7).

(9) The vacuum degassing apparatus of the molten glass as described in said (7) or (8) in which the said low moisture gas introduction means is formed in the upstream of a vacuum degassing tank.

Effects of the Invention

The glass manufacturing method of this invention is equipped with the process of carrying out the pressure reduction defoaming of a molten glass by making the water vapor concentration of the atmospheric gas in a pressure reduction degassing tank into 60 mol% or less, and can perform pressure reduction defoaming of a molten glass without generating a dolby by this. It is effective. And it produces an effect that a defect which arises by the bubble which originates in Dolby remaining in a glass product remains. Moreover, since such a glass manufacturing method of this invention can prevent a dolby, glass manufacture can be continued stably.

This "stable manufacture" is a very important element in quality control in the glass manufacturing apparatus which drive | operates regardless of the day and night. Once quality deteriorates, it is necessary to shut down the plant for repair or adjustment. Moreover, since it can suppress that a fused object adheres to the wall or ceiling of a pressure reduction degassing tank, the molten glass which dripped can suppress defect formation of the glass product by the fall, and can aim at quality improvement.

Moreover, since the glass manufacturing method of this invention reduces water in the atmosphere which encourages volatilization of a specific component (boron etc.), it exhibits the effect that volatilization of a specific component (boron etc.) in a molten glass can be suppressed. . And when the glass platen is manufactured, deterioration of the flatness can be suppressed. In particular, in the glass for display, such as liquid crystal glass, the compositional specification is strictly prescribed | required from the viewpoint of the characteristic, but since boron tends to be very volatilized, it is necessary to strictly adjust content of boron. Therefore, according to the glass manufacturing method of this invention, the glass which has a composition and flatness within a standard range can be manufactured efficiently.

Moreover, it is preferable that the said water vapor concentration is 30 mol% or less in the glass manufacturing method of this invention. Thereby, in addition to not generating a dolby as mentioned above, the enlargement of a bubble layer is suppressed and it suppresses generation of many defects in a glassware (specifically, 0.5 piece / kg or less of bubbles per unit mass of glassware) Exert effect.

Moreover, the vacuum degassing apparatus of this invention can provide the vacuum degassing apparatus suitable for implementing such a glass manufacturing method of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the example of 1 structure of the vacuum degassing apparatus of this invention.

It is a figure which shows the pressure reduction defoaming apparatus etc. of this invention.

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

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

Explanation of the sign

1 vacuum degassing apparatus

3 atmosphere gas

3 'vented atmosphere gas

5 upper space

6 opening

7 low moisture gas

8 openings

9 opening

10 vacuum degassing device

11 pressure reducing housing

12 vacuum degassing tank

13 riser

14 downcomers

15 insulation

20 dissolution bath

22 upstream feet

24 downstream feet

28 pumps

30 Water vapor concentration measuring means

40 low moisture gas introduction means

41 low moisture gas generator

42 flow control valve

44 Flowmeter

G melt glass

Best Mode for Carrying Out the Invention

The glass manufacturing method of this invention is demonstrated.

The glass manufacturing method of this invention is equipped with the process (henceforth a "pressure reduction defoaming process of this invention") of degassing a molten glass by making the water vapor concentration of the atmospheric gas of a vacuum degassing tank into 60 mol% or less. And it is preferable to provide a raw material melting process as a front process, and to provide a molding process as a post process. These raw material melting processes and molding processes are not particularly limited and may be, for example, conventionally known processes. In addition to these steps, other steps may be provided.

In addition, in this invention, "ambient gas" means the atmospheric gas which fills the space (upper space) of the upper part of a molten glass inside a pressure reduction degassing tank.

In the glass manufacturing method of this invention, the pressure reduction defoaming process of this invention is a process of defoaming the bubble in this molten glass by flowing a molten glass in the pressure reduction degassing tank which the inside was made into the pressure reduction state, It will not specifically limit, if it is a process of degassing under reduced pressure to make water vapor concentration 60 mol% or less.

For example, by measuring the water vapor concentration of the atmospheric gas of the vacuum degassing tank in a vacuum degassing apparatus, and introducing the low moisture gas mentioned later to the said upper space based on the measurement result of the steam concentration, the vacuum degassing of this vacuum degassing apparatus Applying a method for adjusting the water vapor concentration of the atmosphere gas in the tank (hereinafter also referred to as the "moisture adjustment method of the present invention"), and adjusting the water vapor concentration of the atmosphere gas to 60 mol% or less to degassing under reduced pressure of the present invention. The process can be carried out. The low moisture gas may be introduced continuously or intermittently.

The vacuum degassing | defoaming process of this invention to which such a moisture adjustment method of this invention is applied can be performed using the vacuum degassing apparatus of this invention, for example.

The vacuum degassing apparatus of this invention is demonstrated.

The pressure reduction defoaming apparatus of this invention is a pressure reduction defoaming apparatus which pressure-defoases a molten glass, flows a molten glass in the inside which was made into the pressure reduction state, and decompresses the bubble in this molten glass, and the atmosphere in the said pressure reduction degassing tank A water vapor concentration measuring means for measuring the water vapor concentration of the gas, and a low moisture gas introduction means for introducing a low moisture gas into the upper space, the water vapor concentration of the atmosphere gas is reduced, and the molten glass can be degassed under reduced pressure It is a vacuum degassing apparatus, for example, it is a vacuum degassing apparatus shown in FIG.

1 will be described. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1: is a figure which shows the vacuum degassing apparatus 1 which is one structural example of the vacuum degassing apparatus of this invention, the vacuum degassing tank 12 which the vacuum degassing apparatus of this invention has, the water vapor concentration measuring means 30, and low The moisture gas introduction means 40 is shown.

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

In the vacuum degassing apparatus 10 shown in FIG. 2, the cylindrical pressure reduction degassing tank 12 is arrange | positioned in the pressure reduction housing 11 so that the long axis may orientate in a horizontal direction. The rising pipe 13 which is oriented in a vertical direction is attached to the lower surface of one end of the pressure reduction degassing tank 12, and the descending pipe 14 is attached to the lower surface of the other end. A part of the rising pipe 13 and the falling pipe 14 is located in the pressure reduction housing 11.

And the upper surface of the pressure reduction degassing tank 12 has a some opening, The low moisture gas is supplied to the upper space 5 inside the pressure reduction degassing tank 12 from the exterior of the pressure reduction housing 11 via at least 1 opening 6. (7) can be introduced. In addition, the opening 8 formed in the pressure reduction housing 11 is connected to pressure reduction means (not shown in FIG. 2 as shown in FIG. 1 as the pump 28), such as a pump, and is an atmospheric gas which fills the upper space 5. (3) is discharged | emitted out of the pressure reduction housing 11 (it discharged is shown by atmosphere gas 3 '), and the inside of the pressure reduction degassing tank 12 can be depressurized. In addition, although the point of the opening 6 and the opening 8 is not limited to the point shown by the opening 6 and the opening 8 in FIG. 2, the opening 6 is an upstream side of the pressure reduction defoaming tank 12, It is preferable to form the opening 8 in the downstream side, respectively. By forming the opening 6 constituting a part of the low moisture gas introduction means upstream of the pressure reduction degassing tank 12, the low introduced into the upper space 5 inside the pressure reduction degassing tank 12 from the opening 6. The moisture gas 7 is flowed from the upstream side of the pressure reduction degassing tank 12 toward the downstream side in which the opening 8 is formed, and the upper space 5 inside the pressure reduction degassing tank 12 is uniformly low steam. Atmospheric gas of concentration can be used.

Further, the inside of the vacuum degassing vessel 12, for instance capable of measuring the pressure (P ₁₎ and the temperature (T ₁₎ of the atmospheric gas (3) is a known pressure gauge and thermometer installed (not shown) .

In addition, as shown in FIG. 2, the rising pipe 13 communicates with the vacuum degassing tank 12, and is an introduction means for introducing the molten glass G from the dissolution tank 20 into the vacuum degassing tank 12. . For this reason, the lower end part of the riser 13 is fitted in the opening end of the upstream pit 22, and is immersed in the molten glass G in this upstream pit 22. As shown in FIG.

The downcomer 14 communicates with the vacuum degassing tank 12, and is a derivation means for lowering the molten glass G after vacuum degassing from the vacuum degassing tank 12 to lead to a treatment tank (not shown) in a later step. . For this reason, the lower end part of the downcomer 14 is fitted in the opening end of the downstream pit 24, and is immersed in the molten glass G in this downstream pit 24. As shown in FIG.

In the pressure reduction housing 11, heat insulation materials 15, such as a heat insulation brick which heat-insulates these, are arrange | positioned and formed around the pressure reduction degassing tank 12, the uprising pipe 13, and the downfalling pipe 14.

In the vacuum degassing apparatus 10 shown in FIG. 2, since the pressure reduction degassing tank 12, the rising pipe 13, and the downfall pipe 14 are the conduits of molten glass G, heat resistance and corrosion resistance with respect to a molten glass are It is manufactured using superior materials. For example, it is a hollow tube made of platinum or a platinum alloy. As a specific example of a platinum alloy, a platinum-gold alloy and a platinum- rhodium alloy are mentioned. Another example is a hollow tube made of a ceramic nonmetal inorganic material, that is, a dense refractory agent. Specific examples of the dense refractories include, for example, electroforming refractories such as alumina based electroforming refractory, zirconia based electroforming refractory, alumina-zirconia-silica based electroforming refractory, and dense alumina based refractory, dense zirconia- And dense calcined refractory materials such as silica-based refractory materials and dense alumina-zirconia-silica-based refractory materials.

The dimension of each component of such a vacuum degassing apparatus 10 can be suitably selected as needed. The size of the pressure reduction defoaming tank 12 can be suitably selected according to the pressure reduction defoaming apparatus to be used, regardless of whether the pressure reduction defoaming tank 12 is a platinum agent, a platinum alloy agent, or a dense refractory agent. In the case of the vacuum degassing tank 12 shown in FIG. 2, the specific example of the dimension is as follows.

Horizontal length: 1-20m

Internal diameter: 0.2 to 3 m (cross section)

When the pressure reduction degassing tank 12 is a platinum agent or a platinum alloy agent, it is preferable that thickness is 4 mm or less, More preferably, it is 0.5-1.2 mm.

The pressure reduction housing 11 is metal, for example, stainless steel, and has a shape and a dimension which can accommodate a pressure reduction degassing tank.

The rising pipe 13 and the falling pipe 14 can be appropriately selected depending on the vacuum degassing apparatus to be used, regardless of whether they are made of platinum, a platinum alloy, or a dense refractory. For example, the dimension of the riser 13 and the downtake 14 can be comprised as follows.

Internal diameter: 0.05-0.8m, More preferably, it is 0.1-0.6m

Length: 0.2-6 m, More preferably, 0.4-4 m

In the case where the riser 13 and the downtake 14 are made of platinum or a platinum alloy, the thickness is preferably 0.4 to 5 mm, more preferably 0.8 to 4 mm.

The vacuum degassing tank which the vacuum degassing apparatus of this invention has is a pressure reduction degassing tank 12 provided with such a structure, for example.

Next, the water vapor concentration measuring means 30 of the vacuum degassing apparatus of this invention is demonstrated.

In FIG. 1, the water vapor concentration measuring means 30 is connected to the downstream side of the pressure reduction degassing tank 12 by piping, etc., and the pump 28 which is a pressure reduction means is connected to the downstream side. By this pump 28, the atmospheric gas 3 'discharged | emitted from the pressure reduction degassing tank 12 can be sent to the water vapor concentration measuring means 30. As shown in FIG. Atmospheric gas 3 'discharged from pump 28 is purged as necessary and dissipated to the atmosphere.

The steam concentration measuring means 30 may be a commercial dew point meter, or may be a measuring means for measuring the pressure, temperature, gas flow rate and the like of the atmospheric gas 3 'discharged from the vacuum degassing tank 12. Each measuring means can use, for example, a conventionally known manometer, thermometer and gas flow meter. The water vapor concentration is a value indicating the amount of water vapor contained in the whole atmosphere gas.

The water vapor concentration (C) [mol%] of the atmospheric gas 3 'may be measured using a commercial dew point meter, and instead precipitates water contained in the atmospheric gas 3', and the amount thereof. It can also estimate by measuring (W) [g]. For example, the gas flow rate of the atmospheric gas 3 'discharged from the vacuum degassing layer 12 is F _out [m 3 / h], the gas outflow time is t _out [h], and the water vapor concentration measuring means 30 When the pressure and temperature of the atmospheric gas 3 'to be measured in P ₂ [Pa] and T ₂ [K] are set, the water vapor concentration (C) [mol%] in the atmospheric gas 3' is expressed by the following equation. It is represented by (1).

By setting the water vapor concentration calculated by the formula (1) to 60 mol% or less, vacuum degassing of the molten glass can be performed without generating dolby, and defects caused by bubbles remaining due to dolby remain in the glass product. It is effective.

Each unit is as follows.

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

Next, the low moisture gas introduction means 40 which the vacuum degassing apparatus of this invention has is demonstrated.

In FIG. 1, the low moisture gas introduction means 40 is connected with the upstream side of the pressure reduction degassing tank 12, and piping. And the low moisture gas 7 can be introduce | transduced from the low moisture gas introduction means 40 via this piping etc.

For example, as shown in FIG. 1, the low moisture gas introduction unit 40 is connected to a low moisture gas generator 41 and a reduced pressure degassing tank 12 by a pipe or the like, and has a low moisture gas generator 41. ) Can be introduced into the upper space 5 of the vacuum degassing tank 12. And the flow control valve 42 and the flowmeter 44 are provided in this order between the low moisture gas generator 41 and the pressure reduction degassing tank 12, and these introduce | transduce the low moisture gas 7 with these. Can be adjusted.

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

Here, the low moisture gas introduction means 40 may have the introduction means (for example, a high pressure fan etc.) for actively introducing the low moisture gas 7 into the upper space 5 of the pressure reduction degassing tank 12. do. In this case, since the low moisture gas 7 can be efficiently introduced into the upper space 5, it is preferable.

In addition, if the atmosphere is used as the low moisture gas 7, the low moisture gas generator 41 is not necessary. For example, one end of a pipe or the like connected to the upper space 5 is opened to the atmosphere by opening and closing the flow control valve 42, and the atmosphere is introduced into the upper space 5 which is decompressed through the piping. If you can.

In addition, when using inert gas etc. other than air | atmosphere as a low moisture gas 7, for example, the said water vapor concentration measuring means 30 of the atmospheric gas 3 'discharged | emitted from the upper space 5 is carried out. It is preferable to have a gas component measuring system which can measure a gas component.

In addition, in this invention, a low moisture gas means the gas whose moisture (water vapor concentration) is lower than the atmospheric gas 3 in the upper space 5. As shown in FIG. The low moisture gas may be atmospheric air, dry air, or an inert gas such as N ₂ or Ar, and may be one or more. It is preferable that the water vapor concentration of low moisture gas is 0-20 mol%, It is more preferable that it is 0-5 mol%, It is still more preferable that it is 0-1 mol%. In addition, the water vapor concentration of low moisture gas can be measured using a commercial dew point meter.

The vacuum degassing apparatus of this invention is a vacuum degassing apparatus 1 which has such a vacuum degassing tank 12, the water vapor concentration measuring means 30, and the low moisture gas introduction means 40, for example.

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

For example, since the water vapor concentration (C) obtained by the above equation (1) and the target water vapor concentration (C ₁ ) have a relationship of the following equation (2), the amount of introduction into the upper space of the low moisture gas ( By adjusting F _in ) and the introduction time (t _in ), the discharge from the upper space of the atmosphere gas (F _OUT ) and the discharge time (t _OUT ), and the water vapor concentration (S) [mol%] of the low moisture gas, It can be set as a value aimed at concentration.

The meaning and unit of each symbol is as follows.

C ₁ : [mol%], V (volume of upper space): [m 3], V _in : [m 3], V _out : [m 3]

Here, V _in is an upper portion of the introduced gas volume F _in × t _in [m 3] determined from the introduction amount F _in [m 3 / h] and the introduction time t _in [h] measured by the flowmeter 44. It is conversion amount in space temperature and pressure. Similarly, V _out is the discharge gas volume F _out determined from 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. t _out ) [m3] The converted amount in the temperature and pressure of the upper space.

In addition, when the pressure in the upper space is kept constant, it is necessary to set V _in = V _out .

For example, _in order to reduce the water vapor concentration (C) = 20 mol% in the upper space of volume (V) = 1 m 3 to the target water vapor concentration (C ₁ ) = 10 mol%, when V _in = V _out , The amount of water gas introduced (V _in ) = 0.53 m 3.

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

In practice, it is necessary to constantly adjust because moisture evaporation from the molten glass, the device component, or the like, or a change in the water vapor concentration due to leakage gas occurs.

In addition, it is preferable to monitor and control this water vapor concentration normally during manufacture of a glass product. Specifically, the vacuum degassing apparatus preferably has steam concentration control means capable of controlling the vapor concentration of the atmosphere gas to a desired value, and the amount of low moisture gas introduced is controlled by a signal from the control means. It is preferable to further have a gas amount control means.

For example, T ₂ , P ₂ , F _OUT , t _OUT , W ₂ , S, F _IN, and t _IN are measured normally, these data are collected on a computer, and the computer allows the water vapor concentration in the upper space to the desired value. It is preferable that the vacuum degassing apparatus of this invention has the water vapor concentration control means which can be controlled so that it may be controlled. Moreover, it is preferable that the pressure reduction defoaming apparatus of this invention makes it possible to control the opening and closing of the flow control valve 42 by this computer, and the gas amount control means by which the data of the flowmeter 44 is fed back to this computer. . In addition, in order to keep the production performance constant, it is preferable to adjust the flow rate while controlling to the desired pressure.

Although it is preferable to implement the glass manufacturing method of this invention using such a vacuum degassing apparatus of this invention, you may apply another method. For example, it is not necessary to introduce gas into the upper space in the vacuum degassing tank like the vacuum degassing apparatus of the present invention, and when the atmosphere in the vacuum degassing tank and the pressure reduction housing are connected, the water vapor concentration of the gas in the vacuum degassing housing. This can be reduced.

In the glass manufacturing method of this invention, pressure reduction defoaming treatment conditions will not be specifically limited if it is a normal range. The normal pressure-reducing treatment conditions mean that the pressure P ₁ of the atmospheric gas 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 processing conditions which perform pressure reduction defoaming treatment as 1250 degreeC-1450 degreeC are said.

In the vacuum degassing | defoaming process of this invention with which the glass manufacturing method of this invention is equipped, the water vapor concentration of the atmospheric gas inside a pressure reduction degassing tank is 60 mol% or less. Then, defoaming of the bubble in a molten glass can be performed under reduced pressure conditions, without generating what is called a dolby.

Moreover, since the bubble layer tends to become thinner as this water vapor concentration is lower, it is preferable that the water vapor concentration of the atmospheric gas inside a vacuum degassing tank is 50 mol% or less, and it is more preferable that it is 40 mol% or less. And since a bubble layer tends to become thinner if the water vapor concentration is 30 mol% or less, it is preferable. In addition, depending on the glass composition, one by one bubble may shrink or break, which is preferable because the bubble layer becomes thinner. Moreover, since the bubble of the magnitude | size of the grade regarded as a defect in glass goods becomes difficult to remain, it is preferable. If the water vapor concentration is even lower, the probability of defects occurring in the glass product is further lowered, more preferably 25 mol% or less, more preferably 20 mol% or less, still more preferably 15 mol% or less, and even more preferably 10 mol% or less. And it is more preferable that it is 5 mol% or less.

In addition to the above, the inventors have found that such shrinkage of bubbles is a phenomenon which is particularly remarkable for molten glass of a specific composition.

Specifically, when the molten glass is borosilicate glass, bubbles tend to shrink significantly when the water vapor concentration is 30 mol% or less. Therefore, the glass manufacturing method of this invention, the vacuum degassing apparatus of this invention, and the moisture adjustment method of this invention can be used more preferably, when manufacturing borosilicate glass.

The borosilicate glass here is the following composition, for example.

Range of composition: 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%).

Conventionally, although the pressure and temperature conditions in the pressure reduction degassing tank were preferable, there was no example which examined the water vapor concentration. MEANS TO SOLVE THE PROBLEM This inventor can solve such a problem by earnestly examining the cause of dolby or the bubble layer enlargement, even if it performs defoaming under the pressure reduction defoaming condition shown previously, and paying attention to the water vapor concentration which was not paid attention conventionally. I found out.

Moreover, this inventor discovered also that the effect which can suppress volatilization of a specific component (boron etc.) in a molten glass is made by making water vapor concentration into 60 mol% or less. By suppressing volatilization of components such as boron, it is possible to prevent composition fluctuations such as boron and to suppress deterioration of flatness caused by composition fluctuations.

In addition, since volatilization such as volatile components, such as Cl, F, and S, can also be suppressed, variation in the composition of these components can be prevented, and deterioration of flatness resulting from the variation in the composition can be suppressed. can do.

It is thought that these components, such as Cl, F, and S, are largely influenced by the volatilization of water. For example, as the F HF, S is considered to be volatilized as H ₂ SO _4. Therefore, it is thought that the fluctuation | variation of the said component volatilized with volatilization of water can be suppressed by making water concentration in a vacuum degassing tank below a certain amount.

In addition, the very fine specification exists in the characteristic of glass according to the use, and the composition of glass is determined over very detailed thing so that it may conform to the specification. For example, although a standard exists naturally with respect to content of boron, in the conventional method, since boron was volatilized, it was necessary to use more boron as a raw material. In addition, conventionally, the amount which boron volatilizes differs according to conditions, and there exists a possibility that it may exceed the specification of boron content in some cases. In this invention, such a problem is solved and it is useful.

Also in this respect, it can be said that the glass manufacturing method of this invention, the vacuum degassing apparatus of this invention, and the moisture adjustment method of this invention can be used suitably especially when manufacturing borosilicate glass, not to mention normal glass. have.

Moreover, in this invention, it is preferable that the low moisture gas introduce | transduced into the upper space inside a pressure reduction degassing tank is gas whose oxygen concentration is lower than the oxygen concentration in air. It is preferable that this oxygen concentration is 15 volume% or less, It is more preferable that it is 10 volume% or less, It is further more preferable that it is 5 volume% or less. In addition, the low moisture gas is preferably a gas containing no oxygen, for example, N ₂ gas, Ar gas, CO _{2 and the} like.

When the oxygen concentration of the low moisture gas introduced into the upper space is such a value, in addition to the above-described layer thickness of the bubble layer, when platinum or a platinum alloy is used as the material of the vacuum degassing tank, the platinum It is preferable because the oxidation of the catalyst can be suppressed to increase the life of the vacuum degassing tank, and in the glass product, the generation of defects derived from platinum can be suppressed.

As mentioned above, it is preferable that the glass manufacturing method of this invention is equipped with the vacuum degassing | defoaming process of this invention, and has a raw material melting process and a shaping | molding process as a front process and a post process. This raw material melting process may be a conventionally well-known thing, for example, and is a process of melting a raw material by heating to about 1400 degreeC or more according to the kind of glass, for example. The raw material to be used is not particularly limited as long as it is a raw material suitable for glass to be produced. For example, a raw material obtained by combining conventionally known ones such as silica sand, boric acid, limestone and the like with the composition of the final glass product can be used. This raw material may also contain a desired clarifier. In addition, this molding process may be a conventionally well-known thing, for example, A float molding process, a roll out molding process, a fusion molding process, etc. are mentioned, for example.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated concretely based on an Example. However, the present invention is not limited thereto.

<Example 1>

In order to reproduce the atmosphere in which vacuum degassing | defoaming is carried out, the crucible made from platinum containing the glass raw material was arrange | positioned in the vacuum pressure reduction container. The crucible was heated to melt the glass, and 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 used glass raw material 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%, BaO: 0.1%

In addition, although Examples 1-3 were experimented using the crucible made from the platinum made from molten glass instead of the pressure reduction degassing tank 12 of FIG. 1, the experimental result of this crucible was the pressure reduction degassing tank of FIG. Can be regarded as equivalent to

Subsequently, the atmosphere adjusted to the desired water vapor concentration was introduced into the vacuum decompression vessel, and adjusted by changing the water vapor concentration (mol%) in the atmosphere in the vacuum decompression vessel to various values. In the case of each steam concentration, the bubble in the molten glass was image | photographed using the CCD camera from the observation window formed in the vacuum decompression device. And after 30 minutes passed, the molten glass was quenched and solidified in the crucible, the number of bubbles (counting 100 micrometers or more in diameter) which existed in the sample after solidification was measured, and bubble density (piece / kg) was calculated | required. Here, the mass of the molten glass was 5.0 kg, and the number of bubbles in the glass before pressure reduction was about the same value in the case of each vapor concentration.

The results are shown in FIG.

It can be seen from FIG. 3 that bubbles remain as the concentration of water vapor in the atmosphere in the vacuum decompression vessel is higher. In FIG. 3, the horizontal axis represents the concentration of water vapor (moisture) in the atmosphere, and the vertical axis represents the value of the number of bubbles taken as Log.

Moreover, when water vapor concentration was more than 60 mol%, when observing with a CCD camera, a molten glass interface rose rapidly and what is called a Dolby phenomenon.

<Example 2>

Next, using the apparatus similar to the said Example 1, the thickness of the bubble layer was measured as 70 mol%, 47 mol%, 31 mol%, and 3 mol% of the water vapor concentration of the atmosphere in a vacuum pressure reduction container. Further, in Example 1 in the low-moisture gas was air with N _2, CO _2, Ar, and with the water vapor concentration in the atmosphere of the vacuum pressure vessel is less than 1mol%, respectively, it was carried out the same experiment. The glass composition is the same as in Example 1.

The results are shown in Table 1.

Thus, when water vapor concentration was 70 mol%, the thickness of the bubble layer became 20 mm or more, and it was confirmed that what is called dolby. Moreover, when the water vapor concentration was 3 to 47 mol%, a bubble layer having a thickness of about 1 to 2 mm was formed, but no dolby was confirmed. Further, the atmosphere is N _2, is CO ₂ or Ar (water vapor concentration is less than 1mol%) fabric layer did not occur. From the above results, the water vapor concentration needs to be 60 mol% or less. Moreover, it is preferable that the thickness of a bubble layer is about 15 mm or less.

<Example 3>

In the same test as in Example 2, the shrinkage rate of the bubbles in the bubble layer for each of various atmospheres was measured. Here, the borosilicate glass similar to Example 1 was used for the molten glass.

The results are shown in FIG. In addition, the bubble diameter has shown the normalized value in FIG. Normalization is the ratio of the bubble diameter in each time with respect to the bubble diameter when the bubble inside a molten glass rises and it reaches | attained the bubble layer. Therefore, when the bubble reaches the bubble layer, the elapsed time is 0s, and the bubble diameter at that time is 1.0.

From FIG. 4, in the case of the atmosphere with a water vapor concentration of 31 mol%, in the case of the atmosphere having a water vapor concentration of 3 mol% and N ₂ , CO ₂ or Ar having a water vapor concentration of 1 mol% or less, the shrinkage rate of the bubbles was increased.

From this result, it turned out that the one where the water vapor concentration in atmosphere is low tends to shrink | contract, and in other words, it is easy to lose | disappear bubbles.

<Example 4>

Next, the bubble rises on the molten glass surface by the vacuum degassing | defoaming process, and it blows up and annihilates it, and various atmosphere vapor concentrations (1 mol%, 9 mol%, 13 mol%, 19 mol%, 22 mol%, 35 mol%, 70 mol) %) And glass composition (soda lime glass: composition A, composition B, composition C). Here, the thickness of the bubble layer at the time of melt | dissolving about 50 g of glass was measured using the 50 cc transparent quartz glass beaker as a container so that the bubble state can be observed. In addition, molten number of injured cell by the free surface (B _S dog) and the melt reaches the glass surface to Resistencia, the number of extinction of the bubble count by looking at (B _B dog) with a CCD camera, and the value of Resistencia rate (B _B / B _S %) was calculated. The thickness (mm) and the breaking rate (%) of the bubble layer are shown in Table 2 below.

In addition, also in the case of any sample, the temperature of the molten glass was heated at 1200 degreeC. The absolute pressure in the container was 18.7 kPa for the composition A, 10.3 kPa for the composition B, and 14.4 kPa for the composition C. In addition, the content rate of each component in composition A, the composition B, and the composition C was as showing in following Table 3. % In Table 3 represents the mass%.

From Table 2, it can be confirmed that the higher the water vapor concentration of the atmosphere in the container, the lower the breakage rate, and the bubbles remain. Specifically, when the vapor concentration in the atmosphere exceeds 60 mol%, the bubble layer becomes 20 mm or more thick, but when it is 60 mol% or less, it can be confirmed that the bubble layer becomes thin. Moreover, when water vapor concentration was more than 60 mol%, when observing with a CCD camera, a molten glass interface rose rapidly and what is called a Dolby phenomenon. Moreover, when the water vapor concentration of the atmosphere in a container is less than 15 mol%, a breakage rate became high and it turned out that it is preferable. That is, when the water vapor concentration of the atmosphere in the container is 60 mol% or less, the dolby phenomenon can be prevented, the bubble layer can be made thin, and when the water vapor concentration is further lowered, the breakage rate becomes higher and the bubbles disappear.

This invention is applicable to the glass manufacturing method provided with the vacuum degassing apparatus and pressure reduction defoaming process of a molten glass, and it is especially suitable for manufacture of the high quality glass for displays with few bubbles.

In addition, all the content of JP Patent application 2006-233441, a claim, drawing, and the abstract for which it applied on August 30, 2006 is referred here, and it introduces as an indication of the specification of this invention.

Claims (9)

The glass manufacturing method provided with the process of carrying out the pressure reduction defoaming of the molten glass by making water vapor concentration of the atmospheric gas of a pressure reduction degassing tank into 60 mol% or less. The method of claim 1, The glass manufacturing method which makes water vapor concentration of the said atmospheric gas into 60 mol% or less by introduce | transducing a low moisture gas into the atmospheric gas of the said vacuum degassing tank. The method according to claim 1 or 2, The glass manufacturing method which makes water vapor concentration of the said atmospheric gas into 30 mol% or less. The method of claim 2 or 3, The oxygen production concentration (vol%) of the said low moisture gas is lower than the oxygen concentration (vol%) in air. The method of claim 4, wherein The oxygen concentration (vol%) of the said low moisture gas is 15 volume% or less, The glass manufacturing method. The vacuum degassing tank is measured by measuring the vapor concentration of the atmospheric gas of the vacuum degassing tank for degassing the molten glass under reduced pressure, and introducing a low moisture gas into the atmospheric gas of the vacuum degassing tank based on the measurement result of the steam concentration. The glass manufacturing method of adjusting the water vapor concentration of the said atmospheric gas to 60 mol% or less. The pressure reduction degassing | defoaming tank formed in this pressure reduction housing | suction, the pressure reduction defoaming tank which carries out the pressure reduction defoaming of molten glass, and this pressure reduction defoaming tank formed in this pressure reduction housing | suction, and introduce | transduces the molten glass before pressure reduction defoaming tank to the said pressure reduction defoaming tank As a pressure reduction defoaming apparatus of the molten glass formed in communication with the said introduction means and the said pressure reduction degassing tank, and having a derivation means which derives the molten glass after pressure reduction defoaming from the said pressure reduction degassing tank, Water vapor concentration measuring means for measuring the water vapor concentration of the atmospheric gas of the vacuum degassing tank; The pressure reduction defoaming apparatus of the molten glass which further has a low moisture gas introduction means which introduces a low moisture gas into the upper space inside the said vacuum degassing tank. The method of claim 7, wherein The vacuum degassing apparatus further includes steam concentration control means capable of controlling the vapor concentration of the atmospheric gas to a desired value, and gas amount control means for controlling the amount of low moisture gas introduced by a signal from the control means. Vacuum degassing apparatus. The method according to claim 7 or 8, The low pressure degassing apparatus of the molten glass with which the said low moisture gas introduction means is formed in the upstream of a pressure reduction degassing tank.

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