TW201720763A - Method for producing granulated bodies of glass starting material, method for producing molten glass, and method for producing glass article - Google Patents

Abstract

The present invention enables granulation of a glass starting material that contains a glass composition containing SiO2, P2O5 and Na2O. A method for producing granulated bodies of a glass starting material by granulating a glass starting material composition, which contains at least silica, a sodium oxide source, a magnesium oxide source and a phosphorus oxide source, in the presence of water. The glass starting material composition contains 3.6-8.4% by mass of magnesium hydroxide relative to the total solid content of the glass starting material composition.

Description

Method for producing glass raw material granules, method for producing molten glass, and method for producing glass articles

The present invention relates to a method for producing a glass raw material granule, a method for producing a molten glass using the glass raw material granule, and a method for producing a glass article.

In the production of glass, when the raw material powder is pulverized when the raw material powder is introduced into the melting furnace, problems such as a decrease in the homogeneity of the glass composition and a problem of waste of raw materials occur, and thus a method of granulating the raw material powder is proposed. . Patent Document 1 describes a white glass having a glass composition containing, in addition to SiO ₂ , P ₂ O ₅ which contributes to whitening, and Na ₂ O which is suitable for chemical strengthening treatment by ion exchange. Patent Document 1 produces white glass by a method of melting a raw material powder, but a method of granulating the raw material powder is not known.

In the following Patent Document 2, there is described a method of performing granulation by reacting cerium with caustic soda (sodium hydroxide) at a high temperature to thereby produce, for example, sodium metasilicate and sodium dicitrate. A water-soluble ceric acid salt, and the cerium salt is used as a binder to produce granules. However, there is no description of a method of granulating a glass raw material containing a phosphorus oxide. Advanced technical literature

Patent Document 1: International Publication No. 2014/119623 Patent Document 2: Japanese Patent Publication No. 56-37176

SUMMARY OF THE INVENTION Problems to be Solved by the Invention The present invention provides a method for producing a glass raw material granule, a method for producing a molten glass using the glass raw material granule, and a method for producing a glass article, wherein the method for producing the glass raw material granule is A glass raw material containing at least SiO ₂ , P ₂ O ₅ , and Na ₂ O as a glass composition can be appropriately granulated. Means to solve the problem

The present invention is the following [1] to [11]. [1] A method for producing a glass raw material granule, which comprises granulating a glass raw material composition in the presence of water to produce a glass raw material granule comprising at least a cerium oxide and a sodium oxide source And a magnesium oxide source and a phosphorus oxide source; and the glass raw material composition contains magnesium hydroxide in an amount of 3.6 to 8.4% by mass based on the total solid content of the glass raw material composition. [2] The method for producing a glass raw material granule according to [1], wherein an aqueous phosphoric acid solution is used as the phosphorus oxide source, and the phosphoric acid content is 4.7 to 16.9% by mass based on the total solid content of the glass raw material composition. . [3] The method for producing a glass raw material granule according to [1] or [2], wherein the magnesium hydroxide content is from 4.1 to 7.7% by mass based on the total solid content of the glass raw material composition. [4] The method for producing a glass raw material granule according to any one of [1] to [3], wherein sodium carbonate and/or sodium hydroxide is used as the source of the sodium oxide. [5] The method for producing a glass raw material granule according to any one of [1] to [4] wherein the average particle diameter of the cerium oxide is D50 of 5 to 350 μm. [6] The method for producing a glass raw material granule according to any one of [1] to [5] wherein the D50 of the average particle diameter of the glass raw material granule is 300 μm to 2 mm. [7] The method for producing a glass raw material granule according to any one of the items [1] to [6] wherein the glass composition derived from the glass raw material granule is represented by the oxide percentage based on the oxide as follows : The content of SiO ₂ is 50-74%, the content of B ₂ O ₃ is 0-8%; the content of Al ₂ O ₃ is 1~8%, the content of MgO is 3~18%, and the content of CaO is 0~ 7%, the content of SrO is 0~10%, the content of BaO is 0~12%, the content of ZrO ₂ is 0~5%, the content of Na ₂ O is 5~15%, and the content of P ₂ O ₅ is 2 ~10%, the total content of other components is below 9%; and the total content of CaO, SrO and BaO is 1~22%; the total content of MgO, CaO, SrO and BaO is 5~25%; and the content of CaO is The RO ratio CaO/RO is 0.7 or less. [8] A method for producing a molten glass, comprising the steps of: producing a glass raw material granule by the method according to any one of [1] to [7]; and, the glass melting step, the obtained glass raw material The granules are heated to form a molten glass. [9] The method for producing molten glass according to [8], wherein the glass melting step has a step of introducing granules on a molten glass surface in the melting furnace. [10] The method for producing molten glass according to [9], wherein the glass melting step comprises the steps of: melting the granules into a molten glass particle in a gas phase environment; and collecting the molten glass particles Into molten glass. [11] A method for producing a glass article, which comprises the method for producing a molten glass according to any one of [8] to [10], wherein the glass article is produced by the method comprising the steps of: melting the glass Step; forming step, forming the obtained molten glass; and quenching step, and cooling the formed glass. Effect of the invention

According to the method for producing a glass raw material granule of the present invention, a granulated body which is suitable for producing a glass containing at least SiO ₂ , P ₂ O ₅ and Na ₂ O as a glass composition can be obtained. According to the method for producing molten glass of the present invention, the granules can be used to produce a molten glass containing at least SiO ₂ , P ₂ O ₅ and Na ₂ O as a glass composition. According to the method for producing a glass article of the present invention, the granules can be used to produce a glass article containing at least SiO ₂ , P ₂ O ₅ and Na ₂ O as a glass composition.

The definitions of the terms used to implement the invention may be applied to cover the scope of the specification and the patent application. The components of the glass are represented by oxides such as SiO ₂ , P ₂ O ₅ and Na ₂ O. The content of each component with respect to the entire glass (glass composition) is expressed by the mass of the glass being 100% and based on the percentage of moles based on the oxygen oxide. The "glass raw material" is a raw material of a glass constituent component, and the "glass raw material composition" is a composition containing a plurality of glass raw materials. Examples of the glass raw material include oxides, composite oxides, and compounds which can be decomposed into oxides by thermal decomposition. Examples of the compound which can be decomposed into an oxide by thermal decomposition include hydroxides, carbonates, nitrates, sulfates, and halides. In the present specification, "granules" are obtained by granulating a glass raw material composition. The composition of the glass raw material composition in the present specification is expressed by mass% in terms of solid content. That is, the solid content of the glass raw material composition is 100% by mass and expressed by mass percentage, and when the glass raw material composition contains an aqueous solution, it is a composition containing the solid content in the aqueous solution. Further, the solid component contains water of crystallization. In the present specification, the "D50" of the glass raw material or the glass raw material composition is an average particle diameter expressed by a 50% particle diameter in the cumulative fraction. The "D50" of the glass material is a 50% particle diameter of the cumulative volume based on the volume measured by the laser diffraction method. The method of measuring the particle size by the laser diffraction method uses the method described in JIS Z8825-1 (2001). The "D50" of the granules is a 50% median diameter of the mass measured by a sieve or the like. In the present specification, the "~" of the numerical range is used as the lower limit and the upper limit, unless otherwise specified. The same meaning to use.

<Glass Raw Material Composition> In the present invention, the glass raw material composition is granulated in the presence of water to produce a glass raw material granule. That is, the glass raw material composition is used for granulation of a composition containing a total solid content. The glass raw material composition contains at least a source of cerium oxide, sodium oxide (hereinafter also referred to as "sodium source"), a source of magnesium oxide (hereinafter also referred to as "magnesium source"), and a source of phosphorus oxide.

[Ceria] Cerium oxide can be exemplified by cerium, quartz, attapulgite and amorphous cerium oxide. These may be used in combination of two or more kinds. In view of the ease of obtaining high-quality raw materials, sand is preferred. And they can be used in powder form. The cerium oxide content is preferably from 30 to 60% by mass, preferably from 35 to 55% by mass, more preferably from 40 to 50% by mass, based on the total solid content of the glass raw material composition. When the cerium oxide content is at least the lower limit of the above range, the granules are less likely to adhere to the wall surface of the granulator or the like and are easily handled. When the cerium oxide content is at most the upper limit of the above range, the strength of the granules tends to be high. The D50 of cerium oxide is preferably 5 to 350 μm. When the D50 of cerium oxide is 5 μm or more, it is easy to handle, and granulation is easy. When it is 350 μm or less, it is easy to obtain homogeneous granules.

[Sodium source] The sodium source is a compound which forms Na ₂ O in the production step of molten glass. Examples of the sodium source include sodium carbonate (sodium ash), sodium hydroxide (caustic soda), sodium sulfate, sodium nitrate, sodium chloride, sodium fluoride, and disodium hydrogen phosphate. Disodium hydrogen phosphate is also a source of phosphorus oxide. These may be used in combination of two or more kinds. A glass containing an alkali metal oxide such as Na ₂ O is suitable for ion exchange treatment to produce chemically strengthened glass. "Chemical strengthening by ion exchange treatment" is specifically an exchange of alkali metal ions (typically Li ions, Na ions) having a small ionic radius on the surface of the glass by ion exchange at a temperature below the glass transition point. An alkali ion having a large ionic radius (typically a Na ion or a K ion for Li ions and a K ion for a Na ion), thereby forming a compressive stress layer on the surface of the glass to increase the strength of the glass.

As a sodium source, in particular, when sodium carbonate (sodium ash) is used, it is preferable from the viewpoint of improving granulation property and preventing aggregation of granules. The D50 of sodium carbonate is not limited, but is preferably 50 to 400 μm, preferably 55 to 120 μm. When the D50 of sodium carbonate is in the above range, granulation is easy, and homogeneous granules are easily produced. The ratio of sodium carbonate is preferably from 70 to 100% by mass, preferably from 80 to 100% by mass, based on the total amount of the sodium source.

[Magnesium Source] The magnesium source is a compound which forms MgO in the production step of molten glass. Examples of the magnesium source include magnesium hydroxide, magnesium oxide, magnesium carbonate, magnesium sulfate, magnesium nitrate, magnesium chloride, magnesium fluoride, and magnesium phosphate octahydrate. Magnesium phosphate octahydrate is also a source of phosphorus oxide. These may be used in combination of two or more kinds. In the present invention, at least magnesium hydroxide is used as the magnesium source. The granules can be produced by containing 3.6 to 8.4% by mass of magnesium hydroxide with respect to the total solid content of the glass raw material composition to obtain good granulation properties. When the amount of the magnesium hydroxide is 3.6 mass% or more, the granulation property is improved, and it is easy to granulate and it is easy to obtain a high-strength granule. When the magnesium hydroxide is 8.4% by mass or less, granules in the granulation can be prevented from aggregating each other, and the particle size of the granules can be easily controlled. Moreover, it is also difficult to cure after granulation, which is desirable. Further, in order to make the particle size of the granules more uniform, it is preferred to contain magnesium hydroxide in an amount of 4.1 to 7.7% by mass. The D50 of magnesium hydroxide is not limited, but is preferably 1 to 30 μm, preferably 2 to 10 μm. When the D50 of magnesium hydroxide is in the above range, granulation is easy, and homogeneous granules are easily produced.

As the magnesium source, magnesium oxide is preferably used in addition to magnesium hydroxide. The D50 of the magnesium oxide is not limited, but is preferably 1 to 30 μm, preferably 2 to 10 μm. When the D50 of the magnesium oxide is in the above range, granulation is easy, and homogeneous granules are easily produced. The ratio of magnesium hydroxide is preferably from 30 to 95% by mass, preferably from 45 to 90% by mass, based on the total amount of the magnesium source.

[Phosphorus Oxide Source] The phosphorus oxide source is a compound which forms P ₂ O ₅ in the production step of molten glass. The glass containing P ₂ O ₅ is suitable for forming a fine phase in the interior of the glass to produce a white glass. "Phase separation" means that the glass of a single phase is divided into two or more glass phases. Because the light will diffusely reflect and scatter at the interface of the phase separation, the appearance of the glass will be white. P ₂ O ₅ is an essential component for promoting such phase separation.

Examples of the phosphorus oxide source include phosphoric acid (H ₃ PO ₄ ), magnesium phosphate octahydrate, aluminum phosphate, and disodium hydrogen phosphate. In particular, when an aqueous solution of phosphoric acid (aqueous phosphoric acid) is used, the reaction with the basic substance is good, and the granulation rate is increased. Further, it is preferable that the phosphide component in the granule is easily homogenized because it is easily dispersed uniformly during granulation. Furthermore, the phosphoric acid aqueous solution is inexpensive and therefore economically advantageous. It is preferable that the phosphorus oxide source contains at least an aqueous solution of phosphoric acid (H ₃ PO ₄ ). The phosphorus oxide source may be used alone or in combination with the phosphoric acid aqueous solution, and one of magnesium phosphate octahydrate, aluminum phosphate, and disodium hydrogen phosphate may be used as the other phosphorus oxide source, or two or more kinds may be used in combination. . When an aqueous phosphoric acid solution is used, the content of phosphoric acid in the solid content of the raw material for granulation is preferably 4.7 to 16.9% by mass. When the content of the phosphoric acid is 4.7 mass% or more, the granulation property is improved, and high-strength granules are easily produced. On the other hand, when the content of the phosphoric acid is 16.9% by mass or less, the granules in the granulation can be prevented from aggregating each other, and the particle size of the granules can be easily controlled. Moreover, it is also difficult to cure by granules after granulation, and it is preferable to cure. Further, when the phosphoric acid content is 7.5 to 8.4% by mass, the curing after granulation can be remarkably suppressed, which is more preferable. Relative to the total amount of the oxide source of phosphorus, phosphoric ratio in terms of P ₂ O ₅ should be 70 to 100% by mass, preferably 80 to 100% by mass.

[Aluminum source] The glass raw material composition may also contain an aluminum source. The aluminum source is a compound that forms Al ₂ O ₃ in the manufacturing step of the molten glass. Examples of the aluminum source include alumina, aluminum hydroxide, aluminum phosphate, and feldspar. Aluminum phosphate is also a source of phosphorus oxide. These may be used in combination of two or more kinds.

The D50 of the aluminum hydroxide is not particularly limited, but is preferably 2 to 100 μm, preferably 5 to 60 μm. The D50 of the alumina is not particularly limited, but is preferably 2 to 100 μm, preferably 5 to 60 μm. The D50 of the aluminum phosphate is not particularly limited, but is preferably 20 to 300 μm, preferably 30 to 200 μm. The ratio of aluminum hydroxide in terms of Al ₂ O ₃ is preferably 60 to 100% by mass, preferably 70 to 100% by mass, based on the total amount of the aluminum source.

[Alkaline earth metal source other than magnesium] The glass raw material composition may contain an alkaline earth metal source other than magnesium. The alkaline earth metal other than magnesium in the present invention means Ca, Ba and Sr. The alkaline earth metal source is a compound which forms CaO, BaO and SrO in the production step of molten glass. Examples of the alkaline earth metal source include carbonates, sulfates, nitrates, oxides, hydroxides, chlorides, fluorides, and phosphates of the alkaline earth metals. These may be used in combination of two or more kinds. The alkaline earth metal phosphate is also a source of phosphorus oxide. The alkaline earth metal source is preferably a powder. Sulfate, chloride and fluoride of alkaline earth metals act as clarifying agents. Further, a composite oxide such as a composite carbonate such as dolomite or a sintered dolomite may be used.

Examples of the cerium oxide source include cerium carbonate, cerium nitrate, cerium sulfate, and cerium chloride. In particular, it is preferable to obtain cerium carbonate from the viewpoint of easy availability of the raw material and environmental aspects. The D50 of strontium carbonate is not particularly limited, but is preferably 2 to 30 μm, preferably 2 to 10 μm. The ratio of strontium carbonate is preferably 70 to 100% by mass, preferably 80 to 100% by mass, based on the total amount of the cerium oxide source.

[Other Glass Raw Materials] The glass raw material composition may contain, in addition to the above-exemplified compounds, other known compounds as a glass raw material within the range which does not impair the effects of the present invention. Examples of the other compound include a boron source such as boric acid and boron oxide; a zirconium source such as zirconium oxide, zircon and zirconium silicate; and a sulfur source such as sodium sulfate or aluminum sulfate. These may be used in combination of two or more kinds. In order to obtain a granulated body having high strength and homogeneity, the content of the other compound is preferably 20% by mass or less, preferably 10% by mass or less.

[Composition of Glass Raw Material Composition] The composition of the glass raw material composition is adjusted in such a manner that it is excluded from the component which is easily volatilized in the glass melting step, and is converted in the same manner as the composition of the glass article to be achieved by the oxide. .

[Glass composition] The glass composition of the granules obtained from the above-mentioned glass raw material composition is preferably the following composition (% by mole%). The following composition is suitable as a composition of white glass, and is particularly suitable as a composition of white glass for chemical strengthening treatment. The glass composition comprises: 50 to 74% SiO ₂ , 0 to 8% B ₂ O ₃ , 1 to 8% Al ₂ O ₃ , 3 to 18% MgO, 0 to 7% CaO, 0 to 10 % SrO, 0~12% BaO, 0~5% ZrO ₂ , 5~15% Na ₂ O and 2-10% P ₂ O ₅ ; and the total content of CaO, SrO and BaO is 1~ 22%; the total content of MgO, CaO, SrO and BaO is 5 to 25%; and the ratio of CaO content to RO is CaO/RO of 0.7 or less. The total amount of the other components other than the above is preferably 9% or less, preferably 6% or less.

SiO ₂ forms an essential component of the network structure of glass. When the content of SiO ₂ is 50% or more, it is easy to obtain good weather resistance, scratch resistance, and chemical resistance as glass. It is preferably 53% or more, preferably 55% or more, more preferably 57% or more. On the other hand, when the content of SiO ₂ is 74% or less, the melting temperature of the glass is not excessively high, and it is easy to obtain good scratch resistance. It is preferably 70% or less, preferably 68% or less, more preferably 65% or less.

Although B ₂ O ₃ is not an essential component, it contributes to an improvement in glass meltability, an increase in whiteness of glass, a decrease in thermal expansion rate, and an improvement in weather resistance. The content of B ₂ O ₃ is preferably 8% or less, and more preferably 7% or less, more preferably 6% or less, from the viewpoint of suppressing the whiteness unevenness of the white glass and easily improving the homogeneity of the whiteness. Here, "increased whiteness" or "high whiteness" means that the linear transmittance of the glass is low (the same applies hereinafter).

Al ₂ O ₃ has an effect of improving the chemical durability of the glass, and has a function of significantly improving the dispersion stability of SiO ₂ and other components, thereby imparting a function of uniformizing the phase separation of the glass, thereby improving the whiteness. Homogenization should preferably contain more than 1%. It is preferably 2% or more, more preferably 2.5% or more, and particularly preferably 3% or more. When the content of Al ₂ O ₃ is too large, the melting temperature of the glass becomes too high, and phase separation is hard to occur. The content of Al ₂ O ₃ is preferably 8% or less, preferably 7% or less, more preferably 6% or less from the viewpoint of easily obtaining high whiteness. If it is desired to use ion exchange to improve the chemical strengthening properties, it is preferably 3% or more.

The role of MgO is to help P ₂ O ₅ and Na ₂ O to promote phase separation and increase whiteness. However, once MgO is too much, phase separation is difficult to occur. The content of MgO is preferably 18% or less, preferably 15% or less, more preferably 13.5% or less. The lower limit of the MgO content is preferably 3% or more from the viewpoint of easily obtaining a whiteness improving effect.

CaO, SrO, and BaO are components which have an effect of increasing the whiteness, and it is preferable to contain one or more of them in order to obtain high whiteness. When CaO is contained, the content thereof is preferably 1% or more, preferably 2% or more. Further, in preventing devitrification, the content thereof is preferably 7% or less. It is preferably 6% or less, more preferably 5% or less. Here, the devitrification refers to a phenomenon in which transparency is lost due to crystallization (the same applies hereinafter). When SrO is contained, the content thereof is preferably 1% or more, preferably 2% or more. Moreover, in order not to devitrify, the content thereof is preferably 10% or less. It is preferably 8% or less. When BaO is contained, the content thereof is preferably 1% or more, preferably 3% or more. Moreover, in order not to devitrify, the content thereof is preferably 12% or less. It is preferably 10% or less, more preferably 9% or less. BaO promotes whitening more than other alkaline earth metal oxides. The total content of these components is preferably from 1 to 22% CaO + SrO + BaO. In order to obtain high whiteness, the content of the components is preferably 1% or more, preferably 2% or more, more preferably 3% or more. Further, in order to improve the stability of the glass and prevent devitrification, the total content is preferably 22% or less, preferably 15% or less, more preferably 13% or less, and particularly desirably 12% or less, more preferably It is below 10%.

In order to prevent the melting temperature from becoming too high and to reduce the melt viscosity, the total content of MgO, CaO, SrO and BaO should be set to 5% or more. It is preferably 10% or more, more preferably 12% or more. In order not to devitrify, the content thereof is preferably 25% or less, preferably 22% or less, more preferably 20% or less. In order not to devitrify, the CaO/RO ratio CaO/RO is preferably 0.7 or less, preferably 0.6 or less, more preferably 0.5 or less.

Although ZrO ₂ is not necessary, it contributes to the improvement of chemical durability. The content is preferably 5% or less, preferably 4% or less, more preferably 3% or less, from the viewpoint of not lowering the whiteness. Further, in order to increase the compressive stress at the time of ion exchange, when ZrO ₂ is contained, the content thereof is preferably 0.5% or more.

In order to improve the meltability of the glass, the content of Na ₂ O is preferably 5% or more. And it should be above 8%. In order to maintain weather resistance and to maintain whiteness, the content of Na ₂ O is preferably 15% or less. It is preferably 14% or less. In order to increase the surface compressive stress generated by the ion exchange treatment to increase the strength of the glass, the content of Na ₂ O is preferably 6% or more. It is preferably at least 7%, more preferably at least 8%.

P ₂ O ₅ is a basic component which significantly promotes glass whitening by phase separation, and its content is preferably 2% or more, preferably 3% or more. In order to suppress volatilization and reduce white unevenness and improve the appearance of the glass, the content thereof is preferably 10% or less, preferably 8% or less. When CaO is contained, the ratio of the content to the P ₂ O ₅ content, CaO/P ₂ O _{5 , is} preferably 1.5 or less in order to suppress devitrification. It is preferably 1.2 or less.

According to the present invention, it is possible to obtain a good granulation property by using a cerium oxide, a sodium source such as sodium carbonate, a phosphorus oxide source such as a phosphoric acid aqueous solution, and magnesium hydroxide as a glass raw material composition, thereby obtaining a suitable granulation property. Glass granules. For example, sodium carbonate, aqueous phosphoric acid, and magnesium hydroxide react in granulation to form disodium hydrogen phosphate hydrate, magnesium phosphate hydrate, and magnesium hydrogen phosphate hydrate, and it is estimated that these products will be produced. The granules function as a binder and exhibit the strength of the granules.

[Particle size of granules of glass raw material] The average particle diameter (D50) of the granules is not particularly limited. However, from the viewpoint of preventing scattering of the raw materials, it is preferably 300 μm or more, and more preferably 500 μm or more. Further, it is preferably 2 mm or less, preferably 1.5 mm or less, from the viewpoint of easy melting. The size of the granules should be selected according to the method of producing the molten glass using the granules, and an appropriate size is selected within the above range. When the granules are used in a method in which the granules are not melted by the melt method in the gas fusion method, the average particle diameter (D50) of the granules is 1 mm or more, that is, the generation of bubbles in the molten glass is easily suppressed. When the granules are melted by the gas fusion method, the average particle diameter (D50) of the granules is preferably 1000 μm or less, preferably 800 μm or less. When the average particle diameter of the granules is 1000 μm or less, it is preferable that the vitrification proceeds sufficiently into the granules when it is melted in the gas heating device.

<Method for Producing Glass Raw Material Granules> The method for producing granules according to the present invention has a granulation step of granulating a glass raw material composition in the presence of water. And as needed, it is preferred to have a heating and drying step which is heated and dried. As a method of supplying water to the glass raw material composition, a method of adding one part of the glass raw material to an aqueous solution can be used. The granulation step can be carried out by appropriately using a well-known granulation method. For example, a rolling granulation method, a stirring granulation method, a compression granulation method, or a method of crushing a molded body obtained by compression molding is preferably used. From the viewpoint of easily producing granules having a small particle size and homogeneity, a rolling granulation method is preferred.

[Rolling granulation method] A rolling granulation method is a method in which a container containing a raw material in which water or a binder is added to a powder is rotated, and the particles are rolled on a wall surface to allow other particles to adhere to the particles to be nuclei. The granulation method of growing particles around. Agitating blades and shredders can be provided in the container for rolling granulation. Excessively growing granules are crushed by agitating blades and choppers to produce granules of appropriate size. The rolling granulation method is exemplified by a method in which the powder in the glass raw material composition is placed in a container of a rolling granulation apparatus, and the raw material powder is mixed and stirred by vibrating and/or rotating the container, and simultaneously The raw material powder is sprayed with a predetermined amount of water mist for granulation. The container of the rolling granulator may be a dish-shaped, cylindrical, or conical rotating container or a vibrating container, and is not particularly limited. The rolling granulation device is not particularly limited, and for example, a container having a direction in which the direction perpendicular to the vertical direction is rotated as a rotation axis, and a rotor having a rotation in the opposite direction of the container around the rotation axis in the container can be used. Specific examples of the rolling granulation apparatus include EIRICH INTENSIVE MIXER (trade name, manufactured by EIRICH, Japan). The order of the addition of the glass raw material to the granulation apparatus is not particularly limited, and when the phosphoric acid aqueous solution is used, the method of preventing the local agglomeration is to add a phosphoric acid aqueous solution and water after mixing the powder raw material such as cerium oxide. It is appropriate. Further, in the case of using sodium hydroxide, from the viewpoint of preventing local agglomeration, a method of adding a sodium hydroxide aqueous solution with a powder containing cerium oxide and aluminum hydroxide in advance, or adding a particulate hydrogen A method of sodium oxide and water is preferred.

If the amount of water used is too large, it needs to be dried for a long time. If the amount of water is too small, the strength of the granules will be insufficient. Therefore, it is preferable to set them so as not to cause such an inconvenience. For example, the amount of water present at the time of granulation is preferably 5 to 25 parts by mass, preferably 6 to 15 parts by mass, based on 100 parts by mass of the total solid content of the glass raw material composition. If the amount of water is insufficient relative to the solid content of the glass raw material composition, it is difficult to obtain a strong granule, and if it is excessive, it tends to adhere to the surface of a device such as a mixer when mixed. The particle size of the granules can be controlled by the stirring strength and the stirring time. After granulation by a rolling granulator, the obtained particles are preferably dried by heating. It can be carried out by a known heat drying method. For example, the following method can be used: heating at a temperature of 100 ° C to 200 ° C for 1 hour to 12 hours using a hot air dryer.

<Manufacturing Method of Molten Glass> The method for producing molten glass of the present invention has a glass melting step (hereinafter also referred to as "melting step") in which the granules obtained by the present invention are heated to obtain molten glass. The melting step can be carried out using a crucible kiln or a Siemens-type glass melting furnace or the like, or can be performed by electric melting. These can be implemented in a well-known manner.

[Melting Step] The melting step is a step of introducing granules on the liquid surface thereof when molten glass is melted in the glass melting furnace, and granulating the granules by a burner or the like (also called a granule) The batch pile, the batch pile is heated, so that the block is melted from the surface, and the molten glass is slowly formed. Alternatively, the granules are placed in a raw material layer formed on the molten glass surface, and a portion which is in contact with the molten glass heated by electrofusion or the like is melted, and the molten glass is gradually formed. In the case where a large amount of glass is produced by using a large-scale apparatus, the raw material batch, the glass plate, etc. are crushed, and the obtained glass swarf is mixed and input. Since the granules obtained by the present invention have high strength, they are preferable because they are difficult to collapse even when the raw material batch and the glass cullet which are composed of the granules obtained by the present invention are mixed and fed.

[In-Gas Melting Method] In one aspect of the method for producing molten glass of the present invention, the granule obtained by the present invention may be formed into molten glass particles by a gas fusion method; The molten glass particles are collected to form a molten glass. Specifically, the granules are first introduced into a high temperature gas phase environment of a gas heating apparatus. A known device can be used for the in-air heating device. Since the granules obtained by the present invention have excellent strength, it is possible to suppress the occurrence of fine powder even when particles collide with each other during transport or introduction, and particles collide with the inner wall of the transport path. Next, the molten glass particles which have been melted in the gas heating device are collected to obtain a glass melt, and the molten glass taken out therefrom is supplied to the next forming step. The method of collecting the molten glass particles can, for example, receive the molten glass particles dropped in the gas phase environment due to the weight of the body, and collect them in a heat-resistant container provided in a lower portion of the gas phase environment.

<Method for Producing Glass Article> The method for producing a glass article of the present invention is a method for producing a glass article using the method for producing molten glass of the present invention. First, the molten glass obtained in the melting step is formed into a desired shape after the forming step, and then subjected to a cold cooling step as required. Thereafter, a glass article is obtained by performing post-processing in a well-known method such as cutting or grinding in a post-processing step. When the glass article is in the form of a plate, the forming step is a floating glass method, a downdraw method, a slit down draw method, a fusion method, a roll method (roll). After a well-known method such as out method) and a method of introduction are formed into a desired shape, the glass article is obtained by subjecting it to coldness as needed.

When a white glass article is produced, after the cold step, a post-processing step is performed as needed, and a phase separation step of heat-treating the glass to separate the phases is provided. A well-known method can be used for the heat treatment for phase separation. The heat treatment conditions for phase-separating the glass are preferably 50 to 400 ° C higher than the glass transition point or the cold point, preferably 100 to 300 ° C. The heat treatment time of the glass is preferably from 1 to 64 hours, preferably from 2 to 32 hours. From the viewpoint of mass production, it is preferably 24 hours or less, more preferably 12 hours or less. In addition, in the steps of melting, homogenizing, forming, quenching or shape processing of the glass, the phase separation treatment may not be performed intentionally, but by heat treatment for melting, homogenization, forming, cold cooling or shape processing. Let the glass phase. At this time, the phase separation step of the glass phase separation is set to be included in the step of melting or the like. Whether or not the glass is phase-separated can be judged by SEM (scanning electron microscope). That is, when the glass is phase-separated, it can be observed that it is divided into two or more phases by SEM observation.

When a white chemically strengthened glass article is produced, a chemical strengthening step of performing ion exchange treatment is performed after processing into a desired shape by a forming step. In addition, in the case of a phase separation step, the chemical strengthening step is carried out after the phase separation step. The ion exchange treatment method, for example, by ion immersing glass in a heated potassium nitrate (KNO ₃ ) molten salt, is known to ion exchange the Na ions of the glass surface layer with the K ions in the molten salt. Example

The invention will be explained in more detail using the following examples, but the invention is not limited to the examples. Production Examples 1 to 9 are examples, and Production Examples 10 to 12 are comparative examples. [Glass composition] For the glass composition obtained from the glass raw material granulation system, five kinds of glass materials of A to E shown in Table 1 were used. The glass composition of Table 1 is expressed as the percentage of moles based on the oxide (unit: % by mole). [Glass Raw Material] The raw materials used in the respective glass materials A to E are shown in Table 2.

[Table 1]

[Table 2]

<Production Examples 1 to 12: Production of Glass Raw Material Granules> [Mixed Glass Raw Material Composition] The blending of the glass raw materials of the respective examples is shown in Tables 3 and 4. The caustic soda (aqueous sodium hydroxide solution) is a blending amount of NaOH as a sodium source, and the remainder is a blending amount of water. The phosphoric acid aqueous solution is also a blending amount of phosphoric acid (H ₃ PO ₄ ) as a source of phosphorus oxide, and the remainder is used as a blending amount of water.

Glass raw material granules were produced by blending (solid content and water) and production conditions (granulation time) shown in Tables 3 and 4. Table 5 is a table in which the blending (unit: parts by mass) of the glass raw material compositions of Tables 3 and 4 is converted into a mass percentage (unit: mass%) with respect to the total solid content. The granulator used EIRICH INTENSIVE MIXER (product name, manufactured by EIRICH, Japan, type: R02 type, capacity 5L, rotor: star type). Specifically, the amount of water added to the liquid raw material is calculated so that the ratio of the total solid content of the glass raw material to be granulated to the total amount of water and the water can be a value shown in the table. The water is premixed with the liquid raw material to prepare a mixed liquid. The raw materials other than the liquid raw materials were placed in a granulator, and preliminary mixing was carried out for 60 seconds at a turntable rotation number of 42 rpm and a rotor rotation number of 900 rpm. After the preliminary mixing, the water and the aqueous phosphoric acid solution were charged while maintaining the number of revolutions of the turntable at 42 rpm. Thereafter, the number of revolutions of the rotor was 3000 rpm, and after granulation was carried out in the granulation time shown in the table, it was taken out from the granulator and dried by a tray dryer at a heating chamber temperature of 120 ° C. The glass raw material granules were obtained for 15 hours. Photographs of the granules obtained in Production Examples 2, 5, 7, 8, 11, and 12 are shown in Figs. A unit length of 1 mm is displayed on the upper left of each photo.

<Evaluation> [D50 of granules (unit: μm)] The obtained granules were subjected to particle size distribution using an automatic sieving measuring instrument (SEISHIN ENTERPRISE CO., LTD., product name: Robot Sifter RPS-105). And determination of the average particle size (D50). Further, the mesh opening sizes of the eight sieves used in the automatic screening tester were: 106 μm, 250 μm, 355 μm, 500 μm, 710 μm, 1000 μm, 1400 μm, and 2000 μm. The measurement results of this D50 are shown in Tables 3 and 4. [Micronized powder (unit: mass%)] 15 g of the obtained granules were shaken for 60 minutes with a shaker (product name: AS-1N, manufactured by AS ONE Corporation) (simulation failure test), and then measured by an automatic sieve analyzer to be smaller than The content of the micropowder of 106 μm (unit: mass%), that is, the micropowder ratio was measured. The results are shown in Tables 3 and 4. The lower the micronized rate, the higher the strength of the granules.

[Pelletizing property] When the granulation time shown in Tables 3 and 4 is granulated, the particles do not grow and most of the particles are powdery, and it is judged as "x" (poor), and the particles grow. The case where the granules were obtained was judged as "○" (good). [Curability after granulation] About 2 kg of the granules obtained by the granulation described above were placed in a sealed plastic bag for one hour, and then opened, and the granules were adhered to each other and were inseparably cured. It is judged as "○" (good) in the case where "x" (defective) is used, and most of the granules are independent or can be easily separated under the impact of shaking the plastic bag.

[table 3] In Table 3, Production Example 1 was vigorously cured, and the D50 and the fine powder ratio could not be measured. Further, in Production Examples 10 to 12, D50, fine powder ratio, and curability were not measured because predetermined granules were not formed. Therefore, these manufacturing examples are indicated by "-".

[Table 4]

[table 5]

As shown in the results of Tables 3, 4, and 5, in the production examples 1 to 9 in which the content of magnesium hydroxide (Mg(OH) ₂ ) was 3.6 to 8.4% by mass based on the total solid content of the glass raw material composition, The particles of the glass raw material composition grow to produce a good glass raw material granule. On the other hand, when magnesium hydroxide is less than 3.6% by mass, the granulation property is remarkably lowered to make granulation difficult. When the content is more than 8.4% by mass, the adhesive force becomes too strong, so that the granules abruptly aggregate with each other and easily become a large agglomerate, so that the particle size control of the granules is actually difficult.

Production Example 1 in which the content of magnesium hydroxide (Mg(OH) ₂ ) is 3.6 to 8.4% by mass and the content of phosphoric acid (H ₃ PO ₄ ) is 4.7 to 16.9% by mass based on the total solid content of the glass raw material composition Granules having good granulation properties were obtained in ~9. On the other hand, in Examples 10 to 12 in which the content of phosphoric acid (H ₃ PO ₄ ) was in the range of 4.7 to 16.9% by mass, but the content of magnesium hydroxide (Mg(OH) ₂ ) was still less than 3.6% by mass, granulation was difficult.

The content of magnesium hydroxide (Mg(OH) ₂ ) is 4.1 to 7.7% by mass relative to the total solid content of the glass raw material composition, and the content of phosphorus oxide (H ₃ PO ₄ ) relative to the total solid content is In Production Examples 4 to 8 of 7.5 to 8.4% by mass, more excellent granules which did not solidify after granulation were obtained. Further, since the fine powder ratio of the granules is less than 1%, granules having sufficient strength are obtained. Industrial availability

According to the production method of the present invention, a glass raw material granule suitable for producing glass containing at least SiO ₂ , P ₂ O ₅ and Na ₂ O can be obtained. Further, when the glass raw material granules are melted, it is possible to prevent the granules from collapsing and to form a plurality of fine powders, and to suppress the solidification of the granules. Therefore, the glass raw material granules obtained by the production method of the present invention are easily transported, and it is difficult to form fine powder even when transported or introduced in a high-temperature gas phase environment, and it is suitable for glass production and other use by a gas fusion method. Glass melting furnace glass manufacturing. In addition, the entire contents of the specification, the scope of the application, the drawings and the abstract of the Japanese Patent Application No. 2015-183969, filed on Sep.

Fig. 1 is a photograph of the granules obtained in Production Example 2. Fig. 2 is a photograph of the granules obtained in Production Example 5. Fig. 3 is a photograph of the granules obtained in Production Example 7. Fig. 4 is a photograph of the granules obtained in Production Example 8. Fig. 5 is a photograph of the granules obtained in Production Example 11. Fig. 6 is a photograph of the granules obtained in Production Example 12.

(no)

Claims (11)

A method for producing a glass raw material granule, which comprises granulating a glass raw material composition in the presence of water to produce a glass raw material granule comprising at least a cerium oxide, a sodium oxide source, and a magnesium oxide The source material and the phosphorus oxide source; and the glass raw material composition contains magnesium hydroxide in an amount of 3.6 to 8.4% by mass based on the total solid content of the glass raw material composition. The method for producing a glass raw material granule according to claim 1, wherein a phosphoric acid aqueous solution is used as the phosphorus oxide source, and the phosphoric acid content is 4.7 to 16.9% by mass based on the total solid content of the glass raw material composition. The method for producing a glass raw material granule according to claim 1 or 2, wherein the magnesium hydroxide content is from 4.1 to 7.7% by mass based on the total solid content of the glass raw material composition. The method for producing a glass raw material granule according to any one of claims 1 to 3, wherein sodium carbonate and/or sodium hydroxide is used as the source of the sodium oxide. The method for producing a glass raw material granule according to any one of claims 1 to 4, wherein the average particle diameter of the cerium oxide is D50 of 5 to 350 μm. The method for producing a glass raw material granule according to any one of claims 1 to 5, wherein the D50 of the average particle diameter of the glass raw material granule is 300 μm to 2 mm. The method for producing a glass raw material granule according to any one of claims 1 to 6, wherein the glass composition derived from the glass raw material granule is represented by the oxide percentage based on the oxide: the content of SiO ₂ is 50 ~74%; B ₂ O ₃ content is 0~8%; Al ₂ O ₃ content is 1~8%; MgO content is 3~18%; CaO content is 0~7%; SrO content is 0~10%; BaO content is 0~12%; ZrO ₂ content is 0~5%; Na ₂ O content is 5~15%; P ₂ O ₅ content is 2~10%; other components The total content of CaO, SrO and BaO is 1~22%; the total content of MgO, CaO, SrO and BaO is 5~25%; and the ratio of CaO content to RO is CaO/RO 0.7 or less. A method for producing a molten glass, comprising the steps of: producing a glass raw material granule by the method according to any one of claims 1 to 7; and, in the glass melting step, heating the obtained glass raw material granule Made of molten glass. The method for producing molten glass according to claim 8, wherein the glass melting step has a step of feeding the granules on the molten glass surface in the melting furnace. The method for producing molten glass according to claim 9, wherein the glass melting step comprises the steps of: melting the granules into a molten glass particle in a gas phase environment; and collecting the molten glass particles to form a molten glass. . A method for producing a glass article, which is characterized in that the method for producing a molten glass according to any one of claims 8 to 10, wherein the method for producing the glass article comprises the steps of: the glass melting step; the forming step, The obtained molten glass is shaped; and the cold-cold step is performed to cool the formed glass.