Method for manufacturing a glass article

Abstract

The present invention provides a glass article manufacturing method capable of controlling the balance of raw material feeding speed and preventing the melting residue of glass raw materials in a cold top melting method. The glass article manufacturing method uses glass raw materials containing silica sand A and silica sand B, melts the glass raw materials by a cold top melting method, the volume-based median particle diameter of the silica sand A is larger than that of the silica sand B, the content of the silica sand B is adjusted in the range of 1 to 99 mass% relative to the total content of the silica sand A and the silica sand B, and the silica sand A and the silica sand B sufficiently satisfy the following necessary condition 1 and necessary condition 2. Necessary condition 1: the volume-based median particle diameter of the silica sand A and the volume-based median particle diameter of the silica sand B are both 300 μm or less. Necessary condition 2: the value obtained by subtracting the volume-based median particle diameter of the silica sand B from the volume-based median particle diameter of the silica sand A is 35 μm or more.

Description

Technical Field

[0001] This invention relates to a method for manufacturing glass articles. More specifically, this invention relates to a method for manufacturing glass articles using a cold-top melting method. Background Technology

[0002] As a method for melting glass raw materials during the manufacture of glass articles, examples include heating the glass raw materials in a melting tank using a burner or the like, and heating using Joule heat generated by passing electricity through the glass.

[0003] Among them, furnaces that use only the heat generated by passing electricity through the glass to melt it are also called all-electric furnaces.

[0004] All-electric furnaces are better in terms of high thermal efficiency and reduced energy consumption during manufacturing.

[0005] In addition, as a method for melting glass using an all-electric furnace, the cold-top melting method is known, which involves melting glass while the surface of the molten glass is covered by solid glass raw material.

[0006] As a method for manufacturing glass articles using an all-electric furnace, for example, the method using the electric furnace described in Patent Document 1 can be cited. It should be noted that paragraph 0030 of Patent Document 1 discloses that when manufacturing glass articles using the electric furnace described in Patent Document 1, it can be a cold-top type in which all the molten glass is covered by the glass raw material.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2018-080076 Summary of the Invention

[0010] In the existing cold-top melting method described in Patent Document 1, the heat generated by molten glass that is melted by electricity is generally used to melt the glass raw material. Glass raw material is then added from above the molten glass raw material to replenish it. Furthermore, the molten glass is discharged from the furnace at a predetermined rate for subsequent refining processes, etc.

[0011] In the cold-top melting method, the layer of unmelted glass material placed above the molten glass (hereinafter also referred to as the "blanket") can suppress heat dissipation from the molten glass, allowing the glass to melt in a state of high thermal efficiency.

[0012] As mentioned above, the thickness of the molten glass blanket is a crucial control factor in the cold-top melting method. Generally, the thickness of the blanket is determined by the balance between its melting rate and the rate at which the glass feedstock is fed relative to the blanket. Therefore, to maintain a constant blanket thickness, it is necessary to balance the melting rate of the blanket and the rate at which the glass feedstock is fed relative to the blanket. In other words, while maintaining a constant amount of molten glass in the furnace, the melting rate of the blanket is equal to the rate at which the molten glass is discharged. Considering the above, it can be said that to maintain a constant blanket thickness, it is necessary to balance the rate at which the glass feedstock is fed and the rate at which the molten glass is discharged.

[0013] In other words, to control the thickness of the blanket layer to a specified thickness, it is usually necessary to control the feeding rate of the glass raw material and the discharge rate of the molten glass to specified values. As mentioned above, in this specification, the feeding rate of the glass raw material when the thickness of the blanket layer is constant (i.e., the discharge rate of an equivalent amount of molten glass) is referred to as the "equilibrium raw material feeding rate". It should be noted that the unit of "equilibrium raw material feeding rate" in this specification is t / d / m. 2 d is expressed as the mass flow rate of glass raw material per unit melting area. Here, d represents one day (24 hours).

[0014] On the other hand, in the operation of the cold-top melting method, for example, in order to melt glass of different compositions, it is sometimes necessary to control the temperature of the molten glass in the furnace.

[0015] To address the requirements described above, one could consider increasing the amount of electricity applied to generate more heat, thereby raising the temperature of the molten glass. However, as the temperature of the molten glass increases, the thickness of the blanket layer decreases, resulting in more heat loss from the molten glass, making it difficult to maintain the temperature. Therefore, it can be said that raising the temperature of the molten glass is generally not easy.

[0016] In addition, as mentioned above, adjusting the power supply usually requires tap switching, and the cessation of power supply may cause significant changes in the conditions inside the kiln. Therefore, different methods are required to control the temperature of the molten glass.

[0017] On the other hand, in the operation of the cold top melting method, it is sometimes necessary to control the discharge rate of molten glass.

[0018] To address the requirements mentioned above, for example, if the amount of molten glass discharged is simply reduced, the thickness of the blanket layer decreases, and the heat dissipation from the molten glass increases, making it difficult to maintain the temperature of the molten glass.

[0019] In addition, as mentioned above, adjusting the power supply often requires tap switching and other work, and the cessation of power supply may cause significant changes in the kiln conditions, thus requiring different methods.

[0020] To meet the above requirements, it can be said that the thickness of the blanket layer needs to be controlled simultaneously with at least one of the molten glass temperature and the amount of molten glass discharged.

[0021] However, as mentioned above, when the thickness of the blanket layer is controlled to a predetermined thickness, there is usually a corresponding equilibrium feed rate for that thickness. Therefore, it is generally difficult to control the discharge rate of molten glass while controlling the thickness of the blanket layer. Furthermore, the aforementioned equilibrium feed rate changes with the temperature of the molten glass, making it generally difficult to control the temperature of the molten glass while controlling the thickness of the blanket layer.

[0022] Based on the above points, in the cold top melting method, a method is needed to control the balanced raw material input rate independently of the thickness of the blanket layer.

[0023] In addition, when melting glass raw materials using the cold-top melting method, it is required that no melt residue of glass raw materials be produced.

[0024] The present invention was made in view of the above-mentioned problems, and the problem is to provide a method for manufacturing glass articles in which the raw material input rate can be controlled and balanced in the cold top melting method and the melting residue of glass raw materials is not easily generated.

[0025] The inventors conducted in-depth research on the above-mentioned issues and found that by using two types of silica sand that fully meet the specified necessary conditions as silica sand for use as glass raw materials, and adjusting their mixing ratio, the rate of input of the aforementioned balanced raw materials can be controlled. Furthermore, it was found that by ensuring the silica sand fully meets the specified necessary conditions, no melting residue of the glass raw materials is generated.

[0026] That is, the inventors have discovered that the above-mentioned problems can be solved by the following configuration.

[0027] [1] A method for manufacturing a glass article, comprising using a glass raw material containing silica sand A and silica sand B, and melting the glass raw material by a cold-top melting method.

[0028] The median particle size of silica sand A, based on volume, is larger than the median particle size of silica sand B, based on volume.

[0029] The content of silica sand B is adjusted within the range of 1% to 99% by mass relative to the total content of silica sand A and silica sand B mentioned above.

[0030] The aforementioned silica sand A and silica sand B fully satisfy the following necessary conditions 1 and 2.

[0031] Necessary condition 1: The median particle size of the volume reference of silica sand A and the median particle size of the volume reference of silica sand B are both below 300μm.

[0032] Necessary condition 2: The value obtained by subtracting the median particle size of the volume reference of silica sand B from the median particle size of the volume reference of silica sand A is 35 μm or more.

[0033] [2] According to the method for manufacturing glass articles described in [1], the content of the silica sand B is adjusted in the range of 5% to 95% by mass relative to the total content of the silica sand A and the silica sand B.

[0034] [3] The method for manufacturing glass articles according to [1] or [2] wherein the content of the silica sand B is adjusted in the range of 10 to 90% by mass relative to the total content of the silica sand A and the silica sand B.

[0035] [4] A method for manufacturing a glass article according to any one of [1] to [3], wherein the following necessary condition 1-1 is further satisfied.

[0036] Necessary condition 1-1: The median particle size of the volume reference of the above-mentioned silica sand A is 100-300 μm, and the median particle size of the volume reference of the above-mentioned silica sand B is 20-150 μm.

[0037] [5] A method for manufacturing a glass article according to any one of [1] to [4], wherein the following necessary condition 2-1 is further satisfied.

[0038] Necessary condition 2-1: The value obtained by subtracting the median particle size of the volume reference of silica sand B from the median particle size of the volume reference of silica sand A is 50 μm or more.

[0039] [6] A method for manufacturing a glass article according to any one of [1] to [5], wherein the following necessary condition 2-2 is further satisfied.

[0040] Necessary condition 2-2: The value obtained by subtracting the median particle size of the volume reference of silica sand B from the median particle size of the volume reference of silica sand A is 60 μm or more.

[0041] [7] A method for manufacturing a glass article according to any one of [1] to [6], wherein the following necessary conditions 2-3 are further satisfied.

[0042] Necessary condition 2-3: The value obtained by subtracting the median particle size of the volume reference of silica sand B from the median particle size of the volume reference of silica sand A is less than 200 μm.

[0043] [8] A method for manufacturing a glass article according to any one of [1] to [7], wherein the total content of the aforementioned silica sand A and the aforementioned silica sand B in the aforementioned glass raw material is 30 to 90% by mass relative to the batch.

[0044] According to the present invention, a method for manufacturing glass articles that can control and balance the raw material input rate in the cold top melting method and is less likely to produce melting residues of glass raw materials can be provided. Attached Figure Description

[0045] Figure 1 This is a cross-sectional schematic diagram of the glass melting device used in the cold-top melting method.

[0046] Figure 2 This is a schematic diagram of a cross-section of a furnace used to determine the rate at which raw materials are fed into the furnace.

[0047] Figure 3 This is a graph showing the relationship between the value of the equilibrium feed rate measured in the actual test and the amount of silica sand remaining in the glass feed rate test.

[0048] Symbol Explanation

[0049] 1. Crucible

[0050] 1a Melting section

[0051] 1b Discharge section

[0052] 2a Induction heating device

[0053] 2b Electrically powered heating device

[0054] 10 Glass melting apparatus

[0055] 20 Melting bath

[0056] 22 First slot

[0057] 22a First lateral wall

[0058] 22b First bottom wall

[0059] 22c Flow port

[0060] 22d through hole

[0061] 24 Second slot

[0062] 24a Second sidewall

[0063] 24b Second bottom wall

[0064] 26. Take out the exit

[0065] 30 electrodes

[0066] 40 Electrode Holder

[0067] 50 Raw Material Supply Department Detailed Implementation

[0068] The following is a detailed description of one embodiment of the present invention.

[0069] The following description of the necessary conditions is sometimes based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.

[0070] The meanings of the terms used in this instruction manual are as follows.

[0071] The range of values ​​represented by “~” refers to the range including the values ​​recorded before and after “~” as the lower and upper limits.

[0072] "ppm" is an abbreviation for parts-per-million, which refers to 1 part per million (ppm). -6 ).

[0073] In this specification, "silica sand" refers to powder primarily composed of silicon dioxide (SiO2). The silicon dioxide content in the silica sand is generally 95% by mass or more, preferably 98% by mass or more, and more preferably 99% by mass or more, relative to the total mass of the silica sand. Furthermore, silica sand can be composed entirely of silicon dioxide. That is, the silicon dioxide content in the silica sand can be 100% by mass.

[0074] <Methods for Manufacturing Glass Articles>

[0075] The method for manufacturing glass articles of the present invention is to melt the glass raw material by means of a cold-top melting method using a glass raw material comprising silica sand A and silica sand B, which will be described later.

[0076] First, the cold top melting method will be explained with reference to the attached diagram.

[0077] [Cold Top Melting Method]

[0078] Figure 1 This is a cross-sectional schematic diagram of the glass melting device 10 used in the cold-top melting method.

[0079] The glass melting apparatus 10 melts the glass raw material GS supplied by the raw material supply unit 50 to produce molten glass GL. The glass raw material GS is usually prepared by mixing multiple materials. In addition, the glass raw material GS includes silica sand A and silica sand B, which will be described later.

[0080] The glass raw material GS is described in detail below.

[0081] The glass melting apparatus 10 includes: a melting tank 20 for containing glass raw material GS and molten glass GL formed by melting the glass raw material GS, and multiple electrodes 30 for electrically heating the molten glass GL.

[0082] Glass raw material GS is fed from the supply section 50 into the liquid surface LS of molten glass GL, forming a blanket layer of glass raw material GS on the liquid surface LS.

[0083] The layers (blankets) of the glass raw material GS are slowly melted by heat transferred from the molten glass GL.

[0084] In order to suppress the loss of heat or evaporation components from the molten glass GL, the layer (blanket layer) of the glass raw material GS preferably covers more than 80% of the liquid surface LS of the molten glass GL, and more preferably more than 90% of the liquid surface LS.

[0085] In addition, the maximum surface temperature of the layer (blanket layer) of the glass raw material GS is preferably below 500°C, more preferably below 350°C, and even more preferably below 200°C.

[0086] The glass melting apparatus 10 is preferably an all-electric furnace that melts the glass raw material GS solely by electrically heating the molten glass GL. The all-electric furnace has only a plurality of electrodes 30 as the heating source for melting the glass raw material GS.

[0087] It should be noted that the glass melting apparatus 10 can be of a form other than an all-electric furnace, and can melt the glass raw material GS by using both electric heating of the molten glass GL and combustion heat such as gas or heavy oil. Preferably, the heat generated by electric heating accounts for 80% or more of the heat generated per unit time in melting the glass raw material GS. It should be noted that in an all-electric furnace, this proportion is 100%.

[0088] Figure 1 The melting tank 20 in the glass melting apparatus 10 shown has a double-layer structure (shelf structure), having a first tank 22 and a second tank 24 disposed on the lower side of the first tank 22.

[0089] The first groove 22 has a first sidewall 22a surrounding the molten glass GL, a first bottom wall 22b supporting the molten glass GL from below, and a flow port 22c forming through the first bottom wall 22b. The molten glass GL moves from the first groove 22 to the second groove 24 via the flow port 22c.

[0090] It should be noted that the larger the surface area of ​​the molten glass GL is, the more the amount of glass raw material GS can be added per unit time, and the more the production capacity of molten glass GL can be increased.

[0091] The second groove 24 has a second sidewall 24a extending downward from the periphery of the flow port 22c, and a second bottom wall 24b supporting the molten glass GL from below. An outlet 26 is provided on the second sidewall 24a.

[0092] The outlet 26 of the molten glass GL can be located on the second bottom wall 24b.

[0093] It should be noted that the melting tank 20 may not have a shelf structure. That is, the melting tank 20 only needs to have a first groove 22, and may not have a second groove 24. It should also be noted that if the melting tank 20 does not have a second groove 24, a flow port 22c is not formed on the first bottom wall 22b. In addition, if the melting tank 20 does not have a second groove 24, the outlet 26 for the molten glass GL may be located on the first side wall 22a or on the first bottom wall 22b.

[0094] The melting tank 20 is made of refractory bricks, for example. Examples of refractory bricks include zirconia-based electroformed bricks, alumina-based electroformed bricks, alumina-zirconia-alumina electroformed bricks, alumina-zirconia-silica (AZS) electroformed bricks, and dense fired bricks.

[0095] The melting tank 20 can be made of various refractory bricks.

[0096] exist Figure 1 In the manner shown, electrode 30 is rod-shaped and protrudes obliquely upward from the first bottom wall 22b.

[0097] There are no particular limitations on electrode 30; for example, a molybdenum electrode can be used.

[0098] It should be noted that an insertion hole 22d for inserting the electrode 30 is formed in the first bottom wall 22b. Furthermore, an electrode holder 40 is provided in the insertion hole 22d. The electrode holder 40 holds the electrode 30 and cools the electrode 30, preventing molten glass GL from leaking out of the melting tank 20 through the insertion hole 22d. Cooling of the electrode holder 40 is achieved by supplying a refrigerant such as water. It should be noted that the electrode holder 40 can hold the lower end of the electrode 30. Additionally, in Figure 1 In the manner shown, the electrode holder 40 does not protrude above the paper from the through hole 22d, but it can protrude.

[0099] It should be noted that, of course, the present invention can use... Figure 1 Glass melting apparatus 10 other than those shown.

[0100] [Glass raw materials]

[0101] In this invention, the glass raw material melted by the cold top melting method includes silica sand A and silica sand B.

[0102] Here, the median particle size of silica sand A in terms of volume is larger than the median particle size of silica sand B in terms of volume. Furthermore, the content of silica sand B is adjusted within the range of 1 to 99% by mass relative to the total content of silica sand A and silica sand B.

[0103] Furthermore, silica sand A and silica sand B fully satisfy the following necessary conditions 1 and 2.

[0104] Necessary condition 1: The median particle size of both silica sand A and silica sand B in terms of volume reference is below 300 μm.

[0105] Necessary condition 2: The value obtained by subtracting the median particle size of silica sand B from the median particle size of silica sand A in volumetric reference is 35 μm or more.

[0106] That is, the median particle size of silica sand A based on volume is set as D. 50A (Unit: μm), the median particle size of silica sand B based on volume is set as D. 50B (Unit: μm) D 50A and D 50B The following relationships (1), (2) and (3) are satisfied.

[0107] (1) D 50A >D 50B

[0108] (2) D 50A ≤300, D 50B ≤300

[0109] (3) D 50A -D 50B ≥35

[0110] In the glass article manufacturing method of the present invention, the mechanism by which the raw material input rate can be controlled and balanced in the cold top melting method and the melting residue of glass raw materials is not easily generated has not been clearly defined, but the inventors speculate as follows.

[0111] In the manufacturing method of the glass article of the present invention, the glass raw materials mostly include silica sand (SiO2) and other raw materials. Generally, the melting point of SiO2 is often higher than that of other raw materials, and the other raw materials are mostly melted by dehydration and decomposition to generate a liquid phase mainly composed of the other raw materials. It is considered that the process of melting SiO2 in molten glass is carried out in sequence as a melting step in which SiO2 melts in the generated liquid phase and a diffusion step in which SiO2 diffuses in the molten glass. It is considered that in the process of melting SiO2 in molten glass, the diffusion step is longer than the melting step. That is, in the process of melting SiO2 in molten glass, the diffusion step in which the molten SiO2 diffuses in the molten glass is considered to be the rate control step.

[0112] In the case of mixing two types of silica sand with different particle sizes (median particle size), as in the glass article manufacturing method of the present invention, it can be said that the melting of the smaller-sized silica sand (the aforementioned silica sand B) takes precedence. It is believed that if the smaller-sized silica sand melts first, a state will occur where a large amount of melt containing a large amount of SiO2 generated by the melting of the smaller-sized silica sand (the aforementioned silica sand A) exists around the larger-sized silica sand.

[0113] When the SiO2-rich melt, as described above, exists around large-particle silica sand, the aforementioned diffusion steps limit the melting rate of the large-particle silica sand, which can be said to cause the silica sand to melt more slowly. If the silica sand melts more slowly, the melting rate of the blanket layer decreases, resulting in a smaller value for the equilibrium feed rate.

[0114] Furthermore, it can be said that the amount of SiO2-rich melt (i.e., the thickness of the SiO2 diffusion layer) as described above can be adjusted by the content of small-particle-size silica sand contained in the glass raw material.

[0115] In summary, by adjusting the particle size difference and mixing ratio of large and small silica sand, the melting rate of the blanket layer can be adjusted, thereby allowing for control of the raw material input rate independently of the blanket layer thickness.

[0116] On the other hand, when the particle size of silica sand is large, the melting time of the silica sand tends to be longer, which can easily lead to melting residue in the glass raw material. In the glass article manufacturing method of the present invention, it is believed that by making the median particle size of the silica sand contained in the glass raw material in a volume reference of 300 μm or less, melting residue in the glass raw material is less likely to occur.

[0117] The median particle size of silica sand A and silica sand B based on volume (D above) 50A and D 50B This refers to obtaining a particle size distribution curve using a laser-based particle size distribution measuring device, where the cumulative frequency of the particle size distribution, expressed as a volume percentage, represents the 50% particle size. Specifically, the particle size distribution curve is obtained using a laser-based particle size distribution measuring device under the following apparatus and conditions.

[0118] • Device Name: LA960S2 (Made by Horiba Manufacturing Co., Ltd.)

[0119] • Dispersion medium: water

[0120] • Pre-measurement treatment: Ultrasonic treatment (1 minute)

[0121] The median particle size, D, of silica sand A based on volume is... 50A (Unit: μm) As long as the above necessary conditions are fully met, there are no special restrictions. Preferably, it is 80 μm or more, more preferably 100 μm or more, and even more preferably 200 μm or more.

[0122] In addition, D 50A The upper limit is 300 μm or less, preferably 280 μm or less, and more preferably 250 μm or less. D 50A It can be below 200μm or below 100μm.

[0123] The median particle size, D, of silica sand B is a volume-based standard. 50B (Unit: μm) There are no particular limitations as long as the above-mentioned necessary conditions are fully met; preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more. It should be noted that D... 50B It can be 50μm or larger, or 100μm or larger.

[0124] In addition, D 50B The upper limit is 265 μm or less, preferably 200 μm or less, and more preferably 150 μm or less.

[0125] In addition, regarding silica sand A and silica sand B, it is also preferable to further satisfy the following necessary condition 1-1.

[0126] Necessary condition 1-1: The median particle size of silica sand A in volumetric reference is 100-300 μm, and the median particle size of silica sand B in volumetric reference is 20-150 μm.

[0127] It should be noted that silica sand A and silica sand B fully meet the above-mentioned necessary condition 2.

[0128] Regarding silica sand A and silica sand B, it is also preferable to further satisfy the following necessary conditions 1-2.

[0129] Necessary conditions 1-2: The median particle size of silica sand A in volumetric reference is 130-250 μm, and the median particle size of silica sand B in volumetric reference is 30-150 μm.

[0130] It should be noted that silica sand A and silica sand B fully meet the above-mentioned necessary condition 2.

[0131] In addition, regarding silica sand A and silica sand B, it is also preferable to further satisfy the following necessary condition 2-1.

[0132] Necessary condition 2-1: The value obtained by subtracting the median particle size of silica sand B from the median particle size of silica sand A in volume reference is greater than 50 μm.

[0133] It should be noted that silica sand A and silica sand B fully satisfy the above-mentioned necessary conditions 1 and 2.

[0134] In addition, regarding silica sand A and silica sand B, it is also preferable to further satisfy the following necessary condition 2-2.

[0135] Necessary condition 2-2: The value obtained by subtracting the median particle size of silica sand B from the median particle size of silica sand A in volume reference is 60 μm or more.

[0136] It should be noted that silica sand A and silica sand B fully satisfy the above-mentioned necessary conditions 1 and 2.

[0137] In addition, regarding silica sand A and silica sand B, it is also preferable to further satisfy the following necessary conditions 2-3.

[0138] Necessary condition 2-3: The value obtained by subtracting the median particle size of silica sand B from the median particle size of silica sand A in volume reference is less than 200 μm.

[0139] It should be noted that silica sand A and silica sand B fully satisfy the above-mentioned necessary conditions 1 and 2.

[0140] In addition, regarding silica sand A and silica sand B, it is also preferable to further satisfy the following necessary conditions 2-4.

[0141] Necessary condition 2-4: The value obtained by subtracting the median particle size of silica sand B from the median particle size of silica sand A in volume reference is less than 150 μm.

[0142] It should be noted that silica sand A and silica sand B fully satisfy the above-mentioned necessary conditions 1 and 2.

[0143] Regarding silica sand A and silica sand B, if the above necessary conditions are met, the particle size distribution of silica sand A and silica sand B can be unimodal or multimodal, but unimodal is preferred.

[0144] As described above, the glass raw material includes silica sand A and silica sand B. From the viewpoint of facilitating control over the rate of raw material input, the combined content of silica sand A and silica sand B in the glass raw material is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more relative to the batch.

[0145] In addition, the combined content of silica sand A and silica sand B in the glass raw material is mostly 95% by mass or less relative to the batch, preferably 90% by mass or less, and more preferably 80% by mass or less.

[0146] It should be noted that the batch of glass raw materials mentioned above refers to glass raw materials other than the crushed glass raw materials described later. Typically, the batch consists of silica sand A, silica sand B, and other raw materials described later.

[0147] The content of raw materials in batches relative to glass raw materials is typically above 40% by mass, and mostly above 50% by mass. Alternatively, the content of raw materials in batches relative to glass raw materials can be 100% by mass, but is mostly below 95% by mass.

[0148] Other raw materials included in glass raw materials besides silica sand A and silica sand B include compounds containing elements included in the glass composition, as described later.

[0149] Other raw materials may be appropriately compounds of elements contained in the glass composition described later, i.e., raw materials in the form commonly used as glass raw materials.

[0150] Other raw materials include, for example, oxides, hydroxides and chlorides of elements contained in the glass composition described later, as well as carbonates, nitrates and sulfates containing elements contained in the glass composition described later.

[0151] The median particle size of the other raw materials, based on volume, is preferably 5 μm or more, and more preferably 10 μm or more. Furthermore, the median particle size of the other raw materials, based on volume, is preferably 1000 μm or less, and more preferably 500 μm or less.

[0152] The median particle size of other raw materials based on volume can be determined using the same method as the median particle size of silica sand A and silica sand B based on volume.

[0153] In addition to the batches mentioned above, glass raw materials may also include crushed glass raw materials.

[0154] Crushed glass raw materials refer to raw materials obtained by crushing glass. For example, crushed glass raw materials are obtained by crushing scrap glass and out-of-specification glass items during other processes described later. The composition of crushed glass raw materials is usually consistent with the composition of molten glass obtained by melting the glass raw materials.

[0155] The content of cullet relative to the main glass material is mostly above 5% by mass. Additionally, the content of cullet relative to the main glass material is typically below 60% by mass, and mostly below 50% by mass. It should be noted that the main glass material may not contain cullet.

[0156] The batch of raw materials may contain silica materials other than silica sand A and silica sand B, but it is preferable that they do not contain silica materials other than silica sand A and silica sand B.

[0157] When the batch raw materials include silica raw materials other than silica sand A and silica sand B (other silica raw materials), the median particle size of the other silica raw materials based on volume is preferably below 2300 μm.

[0158] Furthermore, in the method for manufacturing the glass article of the present invention, the content of silica sand B is adjusted within a range of 1 to 99% by mass relative to the total content of silica sand A and silica sand B. From the viewpoint of easier control over the rate of raw material input, it is preferable to adjust the content of silica sand B within a range of 5 to 95% by mass relative to the total content of silica sand A and silica sand B, more preferably within a range of 10 to 90% by mass, and even more preferably within a range of 15 to 85% by mass.

[0159] The adjustment of the content of silica sand B in glass raw materials relative to the total content of silica sand A and silica sand B can be carried out by known methods.

[0160] In the above Figure 1 In this method, the glass raw material GS supplied from the raw material supply unit 50 is supplied, for example, after the powders constituting the glass raw material GS are mixed together. Here, when mixing the powders constituting the glass raw material GS, the aforementioned content of silica sand B can be adjusted simply by adjusting the amount of silica sand A and silica sand B used.

[0161] Furthermore, when continuously supplying glass raw material GS, it is preferable to provide a raw material mixing section (not shown) between the raw material supply section 50 and multiple raw material receiving sections (not shown) that contain each raw material. Here, when adjusting the above-mentioned content of silica sand B, the supply speed of silica sand A from the raw material receiving section containing silica sand A to the raw material mixing section, and the supply speed of silica sand B from the raw material receiving section containing silica sand B to the raw material mixing section can be adjusted.

[0162] [Glass Composition]

[0163] In the method for manufacturing glass articles of the present invention, a preferred composition of molten glass obtained by the cold-top melting method will be described. That is, a preferred glass composition of glass articles obtained by the method for manufacturing glass articles of the present invention will be described.

[0164] The glass composition can be one that contains alkali components (e.g., soda glass, soda-lime glass, borosilicate glass, and aluminosilicate glass) or one that is substantially free of alkali components (alkali-free glass).

[0165] Essentially, "not containing the above-mentioned alkaline components" means that the total content of alkali metal oxides (Li2O, Na2O, K2O) is less than 1000 ppm by mass.

[0166] As a composition of alkali-free glass, for example, a composition containing, by mass percent (based on oxides): 54%–73% SiO2, 10%–23% Al2O3, 0.1%–12% B2O3, 0%–12% MgO, 0%–15% CaO, 0%–16% SrO, 0%–15% BaO, totaling 8%–26% MgO, CaO, SrO, and BaO. Here, B2O3, MgO, CaO, SrO, and BaO are not essential components but are optional.

[0167] Other components of alkali-free glass include, for example, a composition containing, by mass percent, 57–67.5% SiO2, 17–25% Al2O3, 0.1–5.5% B2O3, 2–8.5% MgO, 1.5–8.5% CaO, 0.5–10% SrO, and 0–2.5% BaO.

[0168] In addition, other components of alkali-free glass include, for example, a composition containing 45-75% SiO2, 1-15% Al2O3, 1-30% B2O3, 0.1-13% MgO, 0.1-13% CaO, 0.1-13% SrO, and 0-13% BaO, expressed as a percentage by mass based on oxides.

[0169] [Other processes]

[0170] The method for manufacturing glass articles of the present invention may include other steps besides those described above.

[0171] Other processes include, for example, a clarifying process to clarify molten glass, a forming process to shape molten glass, and a processing process to process already shaped glass articles.

[0172] That is, in the glass article manufacturing method of the present invention, the obtained molten glass can be clarified, and the clarified molten glass can be shaped to obtain a glass article.

[0173] The aforementioned clarifying, molding, and processing steps can be carried out using known methods.

[0174] <Glass items>

[0175] Glass articles can be obtained by the glass article manufacturing method of the present invention described above.

[0176] There are no particular restrictions on the use of the obtained glass articles; they can be appropriately used for purposes where existing glass articles are suitable.

[0177] Example

[0178] The present invention will be described in more detail below based on embodiments.

[0179] The materials, amounts, proportions, processing contents, and processing steps shown in the following embodiments can be appropriately modified as long as they do not depart from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as limited to the embodiments shown below.

[0180] <Test on the melting rate of glass raw materials>

[0181] Prepare the glass raw material in the manner described below. It should be noted that the following composition is expressed as a percentage by mass based on oxides.

[0182] SiO2: 60%, Al2O3: 17%, B2O3: 8%, MgO: 3%, CaO: 4%, SrO: 8%

[0183] It should be noted that, as a raw material for SiO2, the median particle size (D) based on volume is used. 50) is silica sand with the following values ​​1 to 6.

[0184] ·Silica sand 1:D 50 37μm

[0185] ·Silica sand 2:D 50 51μm

[0186] ·Silica sand 3:D 50 125μm

[0187] ·Silica sand 4:D 50 147μm

[0188] ·Silica sand 5:D 50 214μm

[0189] ·Silica sand 6:D 50 319μm

[0190] ·Silica sand 7:D 50 273μm

[0191] Glass raw materials containing two types of silica sand selected from silica sand 1 to 7 were uniformly mixed and placed in a crucible. The mixture was heated to 1550°C and then subjected to heat treatment without a time limit, including a step of removal from the furnace. In this heat treatment, the heating rate was 10°C / min, and the raw materials were water-cooled after removal from the furnace. The sample weight of the glass raw material was 15g, and the test was conducted under a large atmosphere.

[0192] After heat treatment, the contents of the crucible were removed and subjected to X-ray diffraction to quantify the amount of residual silica sand. It should be noted that the amount of residual silica sand was quantified based on a pre-established SiO2 / ZnO intensity ratio relative to the SiO2 / ZnO mass ratio, which determined the amount of residual SiO2 (the amount of residual silica sand) after heat treatment. The results are shown in Table 1.

[0193] It should be noted that in Table 1, the column "Content of Silica Sand A" represents the content of Silica Sand A relative to the total content of Silica Sand A and Silica Sand B.

[0194] Additionally, in Table 1, the column "Difference from Linear Interpolation" represents the difference between the amount of residual silica sand when the content of silica sand A is 50% by mass and the linear interpolation values ​​when the content of silica sand A is 0% by mass and 100% by mass. The larger the value in the "Difference from Linear Interpolation" column, the greater the variation in the amount of residual silica sand when silica sand A and silica sand B are mixed.

[0195]

[0196] Based on the results shown in Table 1, it was confirmed that if two types of silica sand are mixed, the amount of residual silica sand changes after heat treatment.

[0197] Among them, when comparing Examples 1, 3 and 5, which fully satisfy the above-mentioned necessary condition 2, with Examples 2 and 6, which do not fully satisfy the above-mentioned necessary condition 2, it was confirmed in Examples 1, 3 and 5 that the amount of residual silica sand varied more when the two types of silica sand were mixed.

[0198] Furthermore, when comparing Examples 1, 3, and 5, which fully satisfy the above-mentioned necessary condition 1, with Example 4, which does not fully satisfy the above-mentioned necessary condition 1, it was confirmed in Examples 1, 3, and 5 that even when the two types of silica sand were mixed, the amount of residual silica sand did not exceed a certain value (specifically, the amount of residual silica sand in Example 7 was 6.90% by mass).

[0199] The following study investigates the relationship between the amount of residual silica sand after heat treatment and the rate of input of equilibrium raw materials.

[0200] Furthermore, the following describes the results of a study on the relationship between the amount of silica sand remaining after the aforementioned heat treatment and the melting residue of the glass raw material. Specifically, the relationship between the amount of silica sand remaining after heat treatment exceeding 6.90% by mass and the melting residue of the glass raw material was studied.

[0201] <Determination of the Rate of Feeding Raw Materials into Balance>

[0202] Based on the above principles, it is believed that the amount of residual silica sand in the above glass raw material melting rate test is related to the melting rate of the blanket layer. That is, in the above test, it is believed that when the amount of residual silica sand is large, the melting rate of the blanket layer can be controlled in a smaller direction, and when the amount of residual silica sand is small, the melting rate of the blanket layer can be controlled in a larger direction.

[0203] Here, in practice, the equilibrium feed rate when a specified mixture of silica sand is used as a glass raw material was measured using an actual machine.

[0204] Specifically, a glass raw material is used that mixes the aforementioned silica sand with other raw materials. Figure 2 The furnace shown is used to measure the rate at which raw materials are fed into equilibrium.

[0205] Figure 2 The furnace shown has a roughly funnel-shaped crucible 1. The opening at the top of the crucible 1 is the inlet for feeding glass raw materials. While feeding glass raw materials through the inlet, molten glass is discharged from the bottom of the furnace, thereby continuously producing molten glass.

[0206] An induction heating device 2a is provided on the outer periphery of the melting section 1a at the upper part of the crucible 1, which enables the heated material in the crucible 1 to have a temperature gradient from the low-temperature region at the upper part of the melting section 1a to the high-temperature region at the lower part of the melting section 1a. An electrically energized heating device 2b is provided in the discharge section 1b at the lower part of the crucible 1, and the discharge rate can be adjusted by adjusting the temperature of the glass flowing inside the discharge section 1b.

[0207] In this example, a platinum crucible with a diameter of 100 mm, a height of 250 mm, and a length of 140 mm for the discharge section 1b is used as crucible 1. Heating is performed with the molten glass temperature (set temperature) within the melting section 1a set at 1600°C. It should be noted that a temperature control position is defined as a location 200 mm below the top of the melting section 1a, and the temperature at this position is used as the set temperature of the melting section 1a.

[0208] In addition, a position 120mm above the lower end of the discharge section 1b is designated as the temperature control position of the discharge section 1b, and the temperature at this position is used as the set temperature of the discharge section 1b. The set temperature range of the discharge section 1b is 1250℃~1350℃.

[0209] The temperature of the discharge section 1b of crucible 1 is adjusted, and the discharge rate is adjusted to continuously feed glass raw material at a feeding rate corresponding to the discharge rate. When the feeding and discharge rates are balanced, the material is filled with molten glass for approximately 100 mm from the bottom of the melting section 1a and with raw material for approximately 140 mm from the top of the crucible 1. The mass flow rate (t / d / m²) of the glass raw material per unit melting area under this balanced state is measured. 2 This serves as a balancing factor for the rate at which raw materials are input.

[0210] The results of the measurement of the equilibrium feed rate are shown in Table 2 and... Figure 3 The figure is shown below. It should be noted that in Table 2, the column for "Content of Silica Sand A" represents the total content of Silica Sand A relative to the contents of Silica Sand A and Silica Sand B. Additionally, in Table 2, the values ​​for the equilibrium raw material input rate are normalized values ​​based on the equilibrium raw material input rate in the case of Example 8.

[0211]

[0212] exist Figure 3 In the graph, the horizontal axis represents the amount of silica sand remaining in the above-mentioned glass raw material melting rate test, and the vertical axis represents the value of the equilibrium raw material feeding rate measured in the actual test. It should be noted that the value of the equilibrium raw material feeding rate shown on the vertical axis represents the value obtained by normalizing the value of the equilibrium raw material feeding rate in Example 8.

[0213] like Figure 3 As shown, a strong negative correlation was found between the amount of residual silica sand in the glass raw material melting rate test and the measured equilibrium raw material feeding rate in the actual test. That is, it was confirmed that if the amount of residual silica sand in the glass raw material melting rate test increases, the equilibrium raw material feeding rate decreases.

[0214] Therefore, referring to Tables 1 and 2 above and Figure 3The results confirm that mixing the two types of silica sand allows for a wider range of control over the rate of raw material input.

[0215] That is, it can be said that when glass raw materials containing silica sand A and silica sand B are used and the glass raw materials are melted by the cold top melting method, when the median particle size of the volume reference of silica sand A is greater than the median particle size of the volume reference of silica sand B, the content of silica sand B is adjusted within a specified range relative to the total content of silica sand A and silica sand B, and when silica sand A and silica sand B fully meet the above-mentioned necessary condition 2, the raw material input rate can be controlled and balanced.

[0216] It should be noted that in the above-mentioned glass raw material melting rate test, the equilibrium raw material feeding rate was measured using glass raw materials with a residual silica sand content exceeding 6.90% by mass during the heat treatment (for example, the glass raw material with a silica sand A content of 100% by mass in Example 4). As a result, melt residue of the glass raw material was confirmed in the extracted molten glass. On the other hand, the equilibrium raw material feeding rate was measured using glass raw materials with a residual silica sand content of 6.90% by mass or less during the heat treatment (for example, the glass raw material with a silica sand A content of 100% by mass in Example 6, etc.). As a result, no melt residue of the glass raw material was observed in the extracted molten glass.

[0217] That is, when at least one of the median particle size of silica sand A and the median particle size of silica sand B exceeds 300 μm (i.e., when necessary condition 1 is not fully satisfied), it can be said that there is a tendency to produce melting residue of glass raw materials.

[0218] On the other hand, when the above-mentioned necessary condition 1 is fully met, it can be said that it is not easy to produce melting residue of glass raw materials.

[0219] This application is based on Japanese Patent Application 2024-212420, filed on December 5, 2024, the contents of which are incorporated herein by reference.

Claims

1. A method for manufacturing a glass article, comprising using a glass raw material containing silica sand A and silica sand B, and melting the glass raw material by a cold-top melting method. The median particle size of silica sand A, based on volume, is larger than the median particle size of silica sand B, based on volume. The content of silica sand B is adjusted within the range of 1% to 99% by mass relative to the total content of silica sand A and silica sand B. The silica sand A and the silica sand B fully satisfy the following necessary conditions 1 and 2. Necessary condition 1: The median particle size of both silica sand A and silica sand B, based on volume, is below 300 μm. Necessary condition 2: The value obtained by subtracting the median particle size of the volume reference of silica sand B from the median particle size of the volume reference of silica sand A is 35 μm or more.

2. The method for manufacturing glass articles according to claim 1, wherein, The content of silica sand B is adjusted within the range of 5% to 95% by mass relative to the total content of silica sand A and silica sand B.

3. The method for manufacturing glass articles according to claim 1, wherein, The content of silica sand B is adjusted within the range of 10% to 90% by mass relative to the total content of silica sand A and silica sand B.

4. The method for manufacturing a glass article according to any one of claims 1 to 3, wherein, Furthermore, the following necessary condition 1-1 must be met. Necessary condition 1-1: The median particle size of the volume reference of the silica sand A is 100-300 μm, and the median particle size of the volume reference of the silica sand B is 20-150 μm.

5. The method for manufacturing a glass article according to any one of claims 1 to 3, wherein, Furthermore, the following necessary condition 2-1 must be met. Necessary condition 2-1: The value obtained by subtracting the median particle size of the volume reference of silica sand B from the median particle size of the volume reference of silica sand A is 50 μm or more.

6. The method for manufacturing a glass article according to any one of claims 1 to 3, wherein, Furthermore, the following necessary condition 2-2 must be met. Necessary condition 2-2: The value obtained by subtracting the median particle size of the volume reference of silica sand B from the median particle size of the volume reference of silica sand A is 60 μm or more.

7. The method for manufacturing a glass article according to any one of claims 1 to 3, wherein, Furthermore, the following necessary conditions 2-3 must be met. Necessary condition 2-3: The value obtained by subtracting the median particle size of the volume reference of silica sand B from the median particle size of the volume reference of silica sand A is less than 200 μm.

8. The method for manufacturing a glass article according to any one of claims 1 to 3, wherein, The total content of silica sand A and silica sand B in the glass raw material is 30-90% by mass relative to the batch.

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