KR102413987B1 - Method for manufacturing molten glass and manufacturing method for glass articles - Google Patents

Abstract

The manufacturing method of the molten glass which can reduce the melt|dissolution delay of glass-making feedstock is provided. A glass raw material composition containing silica sand, aluminum oxide, and an alkali metal source is melted to contain 50 mol% or more of SiO ₂ , 5 mol% or more of Al ₂ O ₃ and a total of Li ₂ O, Na ₂ O, and K ₂ O is a method for producing a molten glass having a glass composition of 5 mol% or more, the silica sand has a D90 of 450 µm or more, and the difference between D90 and D10 is 350 µm or more, and the aluminum oxide has a D90 of 200 µm or less, and the mercury pressure The pore volume distribution in the range of 0.004-5 micrometers of pore diameters measured by law WHEREIN: The manufacturing method of the molten glass whose ratio of the volume of 0.1-5 micrometers of pore diameters is 60 % or more.

Description

Method for manufacturing molten glass and manufacturing method for glass articles

FIELD OF THE INVENTION The present invention relates to a method for producing a molten glass and a method for producing a glass article, in particular a method for producing an aluminosilicate glass and a method for producing a glass article.

Since strength is calculated|required by cover glass, such as a liquid crystal display device, alkali aluminosilicate glass is generally used. In addition, such glass is required to have high chemical resistance, high durability, few bubbles in the glass, high homogeneity, and high flatness. It is known that it is more difficult than the case in manufacture of glass.

In general, in the melting process of glass, it is important to uniformly and quickly dissolve silica sand, which is difficult to dissolve in the glass raw material composition, into the molten glass quickly, in order to improve the quality of the glass article and improve productivity. is considered

In patent document 1, as a manufacturing method of alkali aluminosilicate glass, by making the ratio of the specific surface area of the aluminum compound containing raw material contained in a glass raw material, and the specific surface area of a silica sand into a specific range, without making the particle size of silica sand fine, the glass raw material A method for producing alkali aluminosilicate glass having few quality defects such as bubbles by preventing dissolution residues of silica sand from the silica sand has been proposed.

International Publication No. 2014/103897

However, only reducing the dissolution residue of silica sand in the glass raw material composition may not be sufficient for uniform melting of the entire glass raw material composition. For example, in the melting of glass, a suspended matter layer (so-called scum layer or bubble layer) may be formed on the liquid level of the molten glass due to the delay in dissolution due to the difference in solubility of oxides contained in the glass raw material composition. The "floating material layer" is mainly composed of heterogeneous molten glass and bubbles, but the specific gravity of the heterogeneous molten glass is lower than that of the molten glass and has high viscosity, so it contains bubbles in the molten glass to form a layer floating on the surface layer of the molten glass liquid level do.

In a general glass melting method, when such a floating material layer is formed, in order to inhibit heat input from the upper combustion space, which is a heat source for melting the glass raw material composition, the temperature rise of the molten glass located under the floating material layer becomes insufficient, so that it is difficult to melt. A time difference arises in melting|fusing of glass-making feedstock and glass-making feedstock which is easy to melt|dissolve. When there is a time difference in melting, that is, when a dissolution delay occurs in a part of the glass raw material, heterogeneous molten glass having a specific gravity different from the composition of the target glass article is more likely to be formed, and at the same time, it is contained in the glass raw material powder. It becomes easy to enclose and enclose a bubble in a molten glass, and the uniformity of a glass article and bubble quality are easy to fall. Moreover, the problem that productivity in a glass melting process falls by melt|dissolution delay of some glass-making feedstock also arises.

The present invention has been made in view of the above circumstances, and by reducing the delay in dissolution of the glass raw material and reducing the formation of a suspended matter layer on the molten glass liquid level in the melting furnace, a glass article having excellent homogeneity and few bubbles in the glass is efficiently manufactured It aims at providing the manufacturing method of the molten glass which can be made, and the manufacturing method of a glass article.

The present inventors discovered that not only undissolved silica sand but many undissolved aluminum oxide remain|survived when the suspended matter layer formed on the liquid level of a molten glass was investigated and investigated. Moreover, while using silica sand with a large particle size distribution, by using the aluminum oxide which has a specific particle structure, it discovered that the dissolution delay of silica sand and aluminum oxide could be reduced simultaneously, and led to this invention.

The present invention has the following aspects. _In addition, in this invention, the component _of glass is represented by oxides, such as SiO2 _and Al2O3. Content (glass composition) of each component with respect to the whole glass is expressed by the molar percentage based on an oxide.

[1] A method for producing a molten glass having the following glass composition by melting a glass raw material composition containing silica sand, aluminum oxide and an alkali metal source, wherein the silica sand has a D90 of 450 µm or more, 600 µm or less, and D90 and The difference of D10 is 350 µm or more, the aluminum oxide has a D90 of 200 µm or less, and in the pore volume distribution in the range of 0.004 to 5 µm in pore diameter measured by the mercury intrusion method, the volume of the pore diameter is 0.1 to 5 µm The manufacturing method of the molten glass whose ratio is 60 % or more.

Glass composition (based on oxide): The content of SiO ₂ is 50 mol% or more, the content of Al ₂ O ₃ is 5 mol% or more, and the total content of Li ₂ O, Na ₂ O, and K ₂ O is 5 mol% or more .

[2] The method for producing a molten glass according to [1], wherein D10 of the silica sand is 90 µm or less.

[3] The method for producing a molten glass according to [1] or [2], wherein the volume ratio of the aluminum oxide having a pore diameter of 0.1 to 5 µm is 70% or more.

[4] The method for producing the molten glass according to any one of [1] to [3], wherein in the aluminum oxide, the average value of the ratio of the solid portion area in the binary image of the reflected electron image of the particles is 70% or less.

[5] in [1] to [3], wherein in the above aluminum oxide, the proportion of particles including non-solid parts in which the ratio of the solid part area in the binary image of the reflected electron image of the particle is 70% or less is 70% or more The manufacturing method of any one molten glass.

[6] The method for producing a molten glass according to any one of [1] to [5], wherein the molar ratio (on an oxide basis) of silica sand/aluminum oxide in the glass raw material composition is 2.5 to 15.

[7] The method for producing a molten glass according to any one of [1] to [6], wherein the glass raw material composition further contains at least one of boric acid and ZrO ₂ .

[8] In the glass composition of the molten glass, the total content of SiO ₂ , Al ₂ O ₃ , Li ₂ O, Na ₂ O, and K ₂ O is 60 to 100 mol%, [1] to [ 7] The manufacturing method of any one of molten glass.

[9] The method for producing a molten glass according to any one of [1] to [8], wherein the molten glass has the following glass composition.

Glass composition (based on oxide): SiO ₂ content of 50 to 75 mol%, Al ₂ O ₃ content of 5 to 20 mol%, B ₂ O ₃ content of 0-20 mol%, Li ₂ O, Na ₂ The total content of O and K ₂ O is 5 to 25 mol%, and the total content of MgO, CaO, SrO, and BaO is 0 to 20 mol%.

[10] A method for producing a glass article using the method for producing a molten glass according to any one of [1] to [9],

The manufacturing method of the glass article which has the melting process of manufacturing a molten glass with the said manufacturing method, the shaping|molding process of shape|molding the obtained molten glass, and the slow cooling process of annealing the glass after shaping|molding.

ADVANTAGE OF THE INVENTION According to the manufacturing method of the molten glass of this invention, the melt|dissolution delay of glass-making feedstock can be reduced and formation of the floating substance layer of the molten-glass liquid level in a melting furnace can be reduced.

ADVANTAGE OF THE INVENTION According to the manufacturing method of the glass article of this invention, the melt|dissolution delay of a glass raw material is reduced, it is excellent in homogeneity, and can manufacture the glass article with few bubbles in glass efficiently.

The measuring methods of "the particle diameter" in this invention, "the pore volume distribution by the mercury intrusion method of aluminum oxide", and "the ratio of the solid part area of aluminum oxide" are as follows.

<Measuring method of particle diameter>

"D50" is an average particle diameter expressed by the 50% diameter in an integrated fraction. D50 of the glass raw material is a 50% diameter in the volume-based integrated fraction obtained by the particle diameter measurement by the laser diffraction method.

"D90" is a 90% diameter in the volume-based integrated fraction obtained by particle diameter measurement by a laser diffraction method.

"D10" is a 10% diameter in the volume-based integrated fraction obtained by the particle diameter measurement by a laser diffraction method.

<Measuring method of pore volume distribution by mercury intrusion of aluminum oxide>

Using a fully automatic pore distribution measuring device (Pore Master 60-GT, manufactured by Quanta Chrome), the pore distribution was measured under the following conditions. : cm 3 /g) to obtain a pore volume distribution (Log differential pore volume distribution).

In the pore volume distribution in the range of 0.004 to 5 µm in pore diameter, the ratio of the volume of 0.1 to 5 µm in pore diameter is calculated. Specifically, the ratio of the integrated value of the pore volume in the pore diameter range of 0.1 to 5 μm to the integrated value of the pore volume in the pore diameter range of 0.004 to 5 μm is obtained, and “ratio of the volume of the pore diameter of 0.1 to 5 μm” ' to do.

[Measurement conditions of the fully automatic pore distribution measuring device]

Sample amount: about 0.3 to 0.4 g.

Pretreatment: Heat treatment is performed at 150° C. for 1 hour in a dryer.

Mercury contact angle: 140deg.

Mercury surface tension: 480 dyn/cm.

<Measuring method of ratio of solid part area of aluminum oxide>

First, a reflected electron image of aluminum oxide is imaged with an electron probe microanalyzer (EPMA). The obtained reflected electron image WHEREIN: With respect to one particle|grain, let the square or rectangle inscribed|inscribed on the image of the said particle|grain, and let the square whose area be the largest is set as an area measurement area. The area measurement area is image-processed to obtain a binary image. The ratio of the area of the high luminance region (white portion) in the area measurement area to the area (100%) of the area measurement area is calculated as "the ratio of the area of the solid portion (unit: %)".

For 100 randomly selected particles, the "ratio of the solid part area" is respectively calculated, and the average value obtained by dividing the total by 100 is defined as the "average value of the ratio of the solid part area (unit: %)".

In addition, let the particle|grains whose "ratio of a solid part area" is 70 % or less be "particles|grains containing a specific solid part". For 100 randomly selected particles, the “ratio of the area of the solid part” is obtained, respectively, and the ratio of the number of “particles including the specific solid part” among the 100 particles based on the number of the particles including the specific solid part (unit: %) )”.

[Reflection electron image shooting conditions by EPMA]

Voltage: 15kV.

Current: 9.2nA.

Contrast: 3200.

Luminance: 30-40.

Process time: 6.55 seconds.

Image size: 1280×960 pixels.

Magnification: 500x.

[Image processing conditions]

Image processing software: WinRoof Ver.6.1.

Binarization processing: Automatic binarization processing by the peak valet method.

Threshold: 31-255.

Area measurement area of high luminance region: A square or rectangle whose maximum area is inscribed with one particle.

<Method for producing molten glass>

The manufacturing method of the molten glass of this invention is a method of fusing|melting the glass raw material composition containing a silicon source, an aluminum source, and an alkali metal source, and manufacturing the molten glass which has a specific glass composition. A silicon source is _a compound used as SiO2 by melting. _An aluminum source is _a compound used as Al2O3 by melting.

In the present invention, the silicon source includes silica sand, and the aluminum source includes aluminum oxide.

[silk sand]

As for the particle size distribution of silica sand in the glass raw material composition, D90 is 450 µm or more and 600 µm or less, and the difference between D90 and D10 is 350 µm or more. That is, the silica sand contains large particles having a particle diameter of 450 µm or more and has a wide particle size distribution. By using silica sand having such a particle size distribution, the delay in dissolution of the glass raw material composition at the time of melting can be reduced favorably. 470 micrometers or more are preferable and, as for D90, 490 micrometers or more are more preferable. From the viewpoint of reducing the dissolution delay of silica sand, the upper limit of D90 is preferably 550 µm or less, and more preferably 500 µm or less. 90 micrometers or less are preferable and, as for D10, 80 micrometers or less are more preferable.

The difference between D90 and D10 of the silica sand is more preferably 400 µm or more, and still more preferably 420 µm or more.

In this invention, you may use 1 or more types of well-known silicon sources other than silica sand in the range which does not impair the effect of this invention.

[Aluminum Oxide]

The aluminum oxide in the glass raw material composition satisfies the following (a). In addition to (a), it is preferable to satisfy the following (b) or (c). However, in aluminum oxide, it is common to satisfy|fill following (b) and following (c) that following (a) is satisfied.

The following (a) shows the particle structure of the aluminum oxide used in the present invention by pore distribution, and the following (b) and (c) show the particle structure as a characteristic in the reflected electron image of the particle.

(a) D90 is 200 μm or less, and in the pore volume distribution in the range of 0.004 to 5 μm in pore diameter measured by the mercury intrusion method, the ratio of the volume of the pore diameter 0.1 to 5 μm (hereinafter simply referred to as “pore diameter 0.1 to The ratio of the volume of 5 µm”) is 60% or more.

(b) D90 is 200 micrometers or less, and the average value of the ratio of the solid part area in the binary image of the reflected electron image of particle|grains is 70 % or less.

(c) D90 is 200 μm or less, and the ratio (number %) of “particles including non-solid parts” to aluminum oxide in which the ratio of the solid part area in the binary image of the reflected electron image of the particle is 70% or less 70% or more.

By using such aluminum oxide, the delay in dissolution of the glass raw material composition at the time of melting can be reduced favorably.

150 micrometers or less are preferable, as for D90 of aluminum oxide, 100 micrometers or less are more preferable, 90 micrometers or less are still more preferable, and 85 micrometers or less are especially preferable.

In this invention, you may use 1 or more types of well-known aluminum sources other than aluminum oxide in the range which does not impair the effect of this invention.

In the above (a), the ratio of the volume with a pore diameter of 0.1 to 5 µm is preferably 70% or more, more preferably 80% or more, still more preferably 90% or more, since the dissolution delay of aluminum oxide is reduced. do.

In the above (b), the average value of the ratio of the area of the solid portion of the aluminum oxide particles is preferably 60% or less, more preferably 50% or less, and 45% or less because the dissolution delay of aluminum oxide is reduced. more preferably. Although the lower limit of the average value of the ratio of the said solid part area can be set suitably, when the ratio of a solid part becomes low, the volume (volume) of aluminum oxide will increase. For this reason, it is preferable to set it as the range in which conveyance is possible and supply is easy with respect to the target glass composition. Realistically, 15 % or more is preferable, and 20 % or more is more preferable.

In said (c), as for the ratio (number %) of the said "particles containing a specific solid part" with respect to aluminum oxide, 90 % or more is more preferable. In addition, all the aluminum oxides except the aluminum oxide which are unavoidably contained in another raw material may be "particles containing a specific solid part".

[Alkali Metal Source]

The alkali metal in the present invention refers to Na, K, and Li. _An alkali metal source is _a compound used as Na2O, K2O, _and Li2O by melting. Examples of the alkali metal source include carbonates, sulfates, nitrates, oxides, hydroxides, chlorides and fluorides of alkali metals. These may be 1 type or may use 2 or more types together. In addition, the particle diameter is not specifically limited, A well-known alkali metal source can be used. As an example of an alkali metal carbonate, sodium carbonate, potassium carbonate, lithium carbonate, etc. are preferable, and especially sodium carbonate (soda ash) can be applied suitably from the point of handling easiness.

[Alkaline Earth Metal Source]

The glass raw material composition may contain an alkaline earth metal source in addition to the above components.

The alkaline earth metal in this specification refers to Mg, Ca, Ba, and Sr. An alkaline earth metal source is a compound which forms MgO, CaO, BaO, and SrO by melting. Examples of the alkaline earth metal source include carbonates, sulfates, nitrates, oxides, hydroxides, chlorides and fluorides of alkaline earth metals. These may be 1 type or may use 2 or more types together. In addition, the particle diameter is not specifically limited, A well-known alkaline-earth metal source can be used. Moreover, complex carbonates, such as dolomite, and complex oxides, such as calcined dolomite, can also be used.

[Boron Source]

The glass raw material composition may contain a boron source. Examples of the boron source include boric acid, boric oxide (B ₂ O ₃ ), and colemanite. These may be 1 type or may use 2 or more types together.

Examples of boric acid include orthoboric acid (H ₃ BO ₃ ), metaboric acid (HBO ₂ ), and tetraboric acid (H ₂ B ₄ O ₇ ).

[Other Glass Raw Materials]

The glass raw material composition may contain compounds other than those known as glass raw materials, as long as the effects of the present invention are not impaired.

Tin oxide, titanium oxide, zirconium oxide, zircon, cerium oxide, antimony oxide, iron oxide, cobalt oxide, chromium oxide, copper oxide, nickel oxide etc. are mentioned as a compound other than the above. These may be 1 type or may use 2 or more types together.

[Glass raw material composition]

A glass raw material composition is prepared by mixing glass raw materials, such as a silicon source, an aluminum source, and an alkali metal source, so that it may become a target glass composition. The glass composition of the glass raw material composition is adjusted so as to be substantially the same as the target glass composition of the molten glass, in terms of oxide, except for components that are liable to volatilize during melting. The glass composition of a molten glass is the same as the glass composition of the glass article obtained by shape|molding this molten glass. Moreover, you may mix the oxide which has a clarifier and a clarification action|action as a component which volatilizes easily.

As for the glass composition (oxide basis) of the molten glass in this invention, content _of SiO2 is 50 mol% or more, content of Al2O3 is ₅ mol% or _more , Furthermore, _Li2O , _Na2O , _K2O Total content is 5 mol% or more, and these sum total is 60-100 mol%.

The ratio of silica sand/aluminum oxide (molar ratio based on oxide) in the glass raw material is 2.5 or more, and more preferably 4 or more, in preventing the dissolution residue of aluminum oxide. Moreover, in preventing the dissolution residue of silica sand, 15 or less are preferable and 12 or less are more preferable.

In addition, the glass raw material composition may further include at least one of boric acid and ZrO ₂ , in addition to silica sand, aluminum oxide, and an alkali metal source. Even with a glass composition containing boric acid or ZrO ₂ that has a significantly different melting point from silica or alumina, for example, alkali aluminosilicate glass, it is possible to prevent a delay in dissolution of the raw material to form a uniform molten glass.

The following compositions (1) to (4) are mentioned as a preferable glass composition (100 mol% in total) of a molten glass.

Composition (1): SiO ₂ is 50 to 75 mol%, Al ₂ O ₃ is 5 to 20 mol%, B ₂ O ₃ is 0 to 20 mol%, Li ₂ O, Na ₂ O, the total of K ₂ O is 5 to 25 mol%, and 0 to 20 mol% in total of MgO, CaO, SrO, and BaO.

Composition (2): 50 to 75 mol% of SiO ₂ , 5 to 20 mol% of Al ₂ O ₃ , 5 to 25 mol% of the total of Li ₂ O, Na ₂ O, and K ₂ O, MgO, CaO, SrO , BaO is 0 to 20 mol%, ZrO ₂ , TiO ₂ is 0 to 5 mol%, Fe ₂ O ₃ content is 0 to 5 mol%, and Co ₃ O ₄ content is 0 to 5 mol %.

Composition (3): 50 to 75 mol% of SiO ₂ , 5 to 20 mol% of Al ₂ O ₃ , 5 to 25 mol% of the total of Li ₂ O, Na ₂ O, and K ₂ O, and B ₂ O ₃ 1 to 20 mol%, and 0 to 25 mol% in total of MgO, CaO, SrO, and BaO.

Composition (4): 50 to 75 mol% of SiO ₂ , 5 to 20 mol% of Al ₂ O ₃ , 5 to 25 mol% of the total of Li ₂ O, Na ₂ O, and K ₂ O, B ₂ O ₃ 1 to 15 mol%, the total of MgO, CaO, SrO, and BaO is 0 to 15 mol%, the total of ZrO ₂ and TiO ₂ is 0 to 5 mol%, the content of Fe ₂ O ₃ is 0 to 5 mol%, Moreover, the content of Co ₃ O ₄ is 0 to 5 mol%.

Moreover, in the alkali aluminosilicate glass containing at least ₁ sort(s) of boric acid and ZrO2, 0-6 mol% is preferable and, as for content _{of B2O3} , 6-10 mol% is more preferable. 0-2 mol% is preferable and, as for content of ZrO2, _2-5 mol% is more preferable.

The following composition (6) is mentioned as a preferable composition in case _a boric acid and ZrO2 are further included in some cases.

Composition (6): 50 to 75 mol% of SiO ₂ , 5 to 20 mol% of Al ₂ O ₃ , 1 to 15 mol% of the total of Li ₂ O, Na ₂ O, and K ₂ O, B ₂ O ₃ 1 to 15 mol%, the total of MgO, CaO, SrO, and BaO is 0 to 15 mol%, the total of ZrO ₂ and TiO ₂ is 0 to 5 mol%, the content of Fe ₂ O ₃ is 0 to 5 mol%, Moreover, the content of Co ₃ O ₄ is 0 to 5 mol%.

[melting process]

The melting process of implementing the manufacturing method of the molten glass of this invention can be performed by a well-known method. Preferably, it is carried out by pouring the glass raw material composition into a melting furnace and melting it.

In the method of pouring a glass raw material composition into a melting furnace and melting it, a suspended material layer is formed on the molten glass liquid level in the melting furnace due to the delay in dissolution of the glass raw material composition, and heat from above the liquid level is blocked by the floating material layer. Insufficiency and heating unevenness are easy to occur. For this reason, the effect of improving the meltability of a glass raw material composition by applying this invention is large.

The melting furnace is not particularly limited and may be of a batch type or a continuous type.

For example, a glass raw material composition and, if necessary, a cullet having the same glass composition as the target molten glass are continuously introduced into a melting furnace, heated to about 1600 to 1700°C, and melted to obtain a molten glass. In addition, cullet is glass debris discharged|emitted in the manufacturing process of glass, etc.

<Method for manufacturing glass article>

The manufacturing method of the glass article of this invention is a method of manufacturing a glass article using the manufacturing method of the molten glass of this invention.

After shape|molding the molten glass obtained by the above-mentioned melting|fusing process into the shape made into the objective by a shaping|molding process, it cools slowly at a slow cooling process as needed. Then, a glass article is obtained by performing subsequent processing by a well-known method, such as cutting|disconnection and grinding|polishing, in a subsequent processing process as needed.

When a glass article is plate-shaped, a glass article is obtained by shape|molding into the target shape by well-known methods, such as a float method, a down-draw method, and a fusion method, in a shaping|molding process, and slow cooling as needed.

<Operation and mechanism>

According to the present invention, in a glass raw material composition comprising silica sand, aluminum oxide and an alkali metal source, silica sand having a large particle size distribution is used and a pore volume distribution having a pore diameter of 0.004 to 5 µm in a pore volume distribution of 0.1 to 5 µm By using aluminum oxide having a particle structure in which the ratio of the volume to is large, in the melting process of the glass raw material composition, the delay in dissolution of silica sand or aluminum oxide can be reduced.

Further, in a glass raw material composition containing silica sand, aluminum oxide and an alkali metal source, silica sand having a large particle size distribution is used and the particle structure in which the ratio of the solid part area in the binary image of the reflected electron image of the particles becomes small. By using the aluminum oxide having

Although the reason is not clear, it is guessed as follows.

The above-mentioned floating material layer is comprised from a heterogeneous molten glass and a bubble. In the heterogeneous molten glass, the concentration of SiO ₂ and Al ₂ O ₃ is higher than that of the molten glass of the target composition, and in the dissolution process of the glass raw material composition, silica sand and aluminum oxide are delayed compared to other raw material compositions. Moreover, the melt|dissolution rate of the silica sand with respect to a heterogeneous molten glass is inferior to those with respect to the molten glass of the objective composition. Therefore, the silica sand and aluminum oxide once delayed in dissolution tends to have a higher ratio in the heterogeneous molten glass, and the time required for the silica sand and aluminum oxide having delayed dissolution to melt to the end is longer.

In contrast, in the present invention, when the glass raw material composition is heated, silica sand and an alkali metal source react rapidly to react with a low melting point (xSiO ₂ -yA ₂ O (A represents an alkali metal. x, y represent a reaction ratio) .)) is formed, and aluminum oxide is dissolved in the reactant. At this time, when silica sand with a large particle size distribution is used, since silica sand with a large particle diameter is relatively difficult to react, the ratio (x/y) of SiO ₂ in the reactant (xSiO ₂ -yA ₂ O) can be controlled low. have. For this reason, while suppressing the viscosity _of the said reactant low, reactivity with aluminum oxide can be maintained highly by maintaining the ratio (y/x) of A2O in a reactant high.

Since the aluminum oxide which has the said specific particle structure melt|dissolves favorably in such a reaction material, it is thought that the dissolution delay of aluminum oxide can be reduced. At this time, by making the particle diameter of silica sand into a certain size or less, dissolution delay of silica sand can also be reduced collectively. In this way, by reducing the delay in dissolution of both silica sand and aluminum oxide, the formation of heterogeneous molten glass and aggregation of silica sand and aluminum oxide delayed in dissolution can be reduced.

Example

Hereinafter, the present invention will be described in more detail using Examples, but the present invention is not limited to these Examples.

<Measurement of particle diameter>

The particle size distribution was measured by wet laser diffraction using a laser diffraction/scattering particle size distribution analyzer (manufactured by Horiba Seisakusho, product name: LA-950) to determine D10, D50 or D90. When the particles were aggregated in the dispersion medium, the aggregate was dispersed by ultrasonic waves, and the particle size distribution of the primary particles constituting the aggregate was measured.

<Method for measuring crucible bottom temperature and floating material layer thickness (evaluation of dissolution delay of glass raw material composition)>

Silica sand, aluminum oxide, an alkali metal source, and other raw materials were prepared so as to obtain alkali aluminosilicate glass having a predetermined glass composition to obtain a glass raw material composition.

The prepared glass raw material composition and cullet were mixed in a predetermined ratio, put into a crucible, and melted in the crucible. The crucible bottom temperature during glass melting was measured, and the degree of dissolution retardation of silica sand or alumina oxide was compared.

As the crucible, an alumina crucible (product name: SSA-S, manufactured by Nikkato Co., Ltd., inner diameter 240 mm, height 245 mm) was used.

As the melting furnace, in order to reproduce the heating state of the upper combustion space in which the molten glass is heated from above in a continuous melting furnace, a two-chamber type equipped with a movable crucible holder, a large electric furnace provided with a heater at the top of each furnace room was used. . The alumina crucible covered the side and bottom of the crucible with an insulating board having a thickness of 20 cm or more to block heat input from the side and bottom to the glass raw material composition in the crucible.

In order to reproduce the temperature history of the glass melting furnace in actual production, immediately after heating under the conditions of 1350 ° C. for 30 minutes (dew point 50 ° C.) in the first furnace chamber, 1600 ° C. for 180 minutes (dew point) in the second furnace chamber 50 ℃) was set to be heated.

In order to evaluate the degree of the melt|dissolution retardation of glass raw material, the crucible bottom temperature was measured by the following procedure.

First, the glass raw material composition and the cullet were mixed in a predetermined ratio at room temperature and put into a crucible. The total amount of the glass raw material composition and the cullet was 2 kg in terms of glass mass.

Then, the crucible was accommodated in the first furnace and heated under the above conditions, then transferred into the second furnace and heated under the above conditions, and taken out from the second furnace. During this time, the temperature of the outer surface of the bottom of the crucible was measured with a thermocouple, and the highest temperature was recorded as the crucible bottom temperature.

It shows that there are few interruption|blocking of the heat|fever by the float layer of the molten-glass liquid level in a crucible, and the temperature of a molten glass rose efficiently by the heat from a heater, so that crucible bottom temperature is high.

Moreover, the crucible taken out from the 2nd furnace chamber was cooled slowly to room temperature, and the molten glass in the crucible was solidified. After cooling and solidification, the inner side of the crucible was observed, and the difference between the height wetted with glass and the height of the glass surface was recorded as the thickness of the floating material layer.

<Measuring method of the number of bubbles>

After measuring the crucible bottom temperature and floating material layer thickness, the center of the glass solidified by cooling in the crucible was cut out into a cylindrical shape with an outer diameter of 35 mm, and the cut out glass was cut out to a thickness of 1 mm to obtain a glass sample. As for the glass sample, both surfaces were mirror-polished, and the area|region of 2 cm<2> or more divided with respect to the cross-sectional direction was visually observed using the optical microscope, and the number of bubbles which can be confirmed was measured.

Since the viscosity of a molten glass will fall when there is little melt|dissolution delay of glass-making feedstock and there are few suspended substance layers, ie, when the temperature rise of a molten glass is favorable, since the defoaming reaction is also accelerated|stimulated when a clarifier is contained, bubble in glass melting easy to fall out Therefore, the direction with few bubble numbers means that the melt|dissolution delay of glass-making feedstock was suppressed.

<Glass raw material>

The following glass raw materials were used.

Silica sand: Five types of silica sand A to E shown in Table 1 were used.

Aluminum oxide: 4 types of alumina S to V shown in Table 2 were used.

Alkali metal source: soda ash (1) (D50=400 μm).

Magnesium source: magnesium oxide (1) (D50=10 μm).

Other Ingredients: Glauber's salt (clarifier).

[Examples 1 to 5]

Examples 1 and 2 are Examples, and Examples 3 to 5 are comparative examples. The silica sand, aluminum oxide, alkali metal source, magnesium source, and clarifier shown in Table 3 were prepared so that it might become the following glass composition (i), and it was set as the glass-making feedstock composition. The addition amount of a clarifier was 1.4 mol% with respect to the glass-making feedstock composition.

For the glass raw material composition of each example, the crucible bottom temperature, the thickness of the suspended matter layer, and the number of bubbles were measured by the above method. The mass ratio of the glass raw material composition to the cullet was 50:50. The results are shown in Table 3.

<Glass composition (i)>

SiO ₂ : 68.0 mol%, Al ₂ O ₃ : 10.0 mol%, MgO: 8.0 mol%, Na ₂ O: 14.0 mol%. The molar ratio of SiO ₂ /Al ₂ O ₃ is 6.8.

From the results in Table 3, D90 is 200 µm or less, the ratio of the volume with a pore diameter of 0.1 to 5 µm is 60% or more, and the average value of the ratio of the solid part area is 70% or less. Examples 1 and 2 using silica sands A and B of 450 μm or more, and the difference between D90 and D10 of 350 μm or more, have a higher crucible bottom temperature and a thin floating material layer than Examples 3 to 5 using silica sand C to E, There are few bubbles. It is seen that the melt|dissolution delay of glass-making feedstock reduced.

[Examples 6 to 9]

Examples 6 to 8 are Examples, and Example 9 is a comparative example. The silica sand, aluminum oxide, alkali metal source, magnesium source, and clarifier shown in Table 4 were prepared so that it might become the said glass composition (i), and it was set as the glass-making feedstock composition. The addition amount of a clarifier is the same as that of Example 1.

With respect to the glass raw material composition of each example, evaluation of the dissolution delay of the glass raw material and the measurement of the number of bubbles were performed by the above method. The mass ratio of the glass raw material composition to the cullet was set to 35:65. The results are shown in Table 4.

From the result of Table 4, while using the said silica sand A, D90 is 200 micrometers or less, the ratio of the volume of 0.1-5 micrometers of pore diameters is 60% or more, and the average value of the ratio of the solid part area is 70% or less Alumina S Examples 6 to 8 using U to U had a higher crucible bottom temperature than Example 9 in which alumina V having a pore diameter of 0.1 to 5 µm, a volume ratio of 56%, and an average value of the ratio of the solid portion area of 75%, was high. , the thickness of the floating material layer is thin and the number of bubbles is small. It is recognized that the melt|dissolution delay of glass-making feedstock was reduced.

In addition, the specification of Japanese Patent Application No. 2016-221713 for which it applied on November 14, 2016, a claim, and the abstract are referred to this specification, and it takes in as an indication of the specification of this invention.

Claims (10)

A method for producing a molten glass having the following glass composition by melting a glass raw material composition containing silica sand, aluminum oxide and an alkali metal source,
The silica sand has a D90 of 450 μm or more and 600 μm or less, and the difference between D90 and D10 is 350 μm or more,
The said aluminum oxide has a D90 of 200 micrometers or less, and in the pore volume distribution in the range of 0.004-5 micrometers of pore diameters measured by the mercury intrusion method, the ratio of the volume of 0.1-5 micrometers of pore diameters is 60% or more of molten glass manufacturing method.
Glass composition (based on oxide): The content of SiO ₂ is 50 to 75 mol%, the content of Al ₂ O ₃ is 5 to 20 mol%, and the total content of Li ₂ O, Na ₂ O, and K ₂ O is 5 to 25 mol%. The manufacturing method of the molten glass of Claim 1 whose D10 of the said silica sand is 90 micrometers or less. The manufacturing method of the molten glass of Claim 1 or 2 whose ratio of the volume of the said pore diameter of 0.1-5 micrometers of the said aluminum oxide is 70 % or more. The manufacturing method of the molten glass of Claim 1 or 2 whose average value of the ratio of the solid part area in the binary image of the reflected electron image of particle|grains is 70 % or less in the said aluminum oxide. The molten glass according to claim 1 or 2, wherein in the aluminum oxide, the proportion of the particles including the non-solid portion in which the ratio of the area of the solid portion in the binary image of the reflected electron image of the particle is 70% or less is 70% or more. manufacturing method. The method for producing a molten glass according to claim 1 or 2, wherein the molar ratio (on an oxide basis) of silica sand/aluminum oxide in the glass raw material composition is 2.5 to 15. The method for producing a molten glass according to claim 1 or 2, wherein the glass raw material composition further contains at least one of boric acid and ZrO ₂ . _{The total} content _of SiO2, Al2O3, Li2O, Na2O, and K2O in _the glass composition of the said molten glass in Claim ₁ or ₂ is 60-100 mol% A method for manufacturing phosphorus molten glass. The manufacturing method of the molten glass of Claim 1 or 2 in which the said molten glass has the following glass composition.
Glass composition (based on oxide): SiO ₂ content of 50 to 75 mol%, Al ₂ O ₃ content of 5 to 20 mol%, B ₂ O ₃ content of 0-20 mol%, Li ₂ O, Na ₂ The total content of O and K ₂ O is 5 to 25 mol%, and the total content of MgO, CaO, SrO, and BaO is 0 to 20 mol%. It is a method of manufacturing a glass article using the manufacturing method of the molten glass of Claim 1 or 2,
The manufacturing method of the glass article which has the melting process of manufacturing a molten glass with the said manufacturing method, the shaping|molding process of shape|molding the obtained molten glass, and the slow cooling process of annealing the glass after shaping|molding.