KR20230135043A - Method of manufacturing glass articles - Google Patents

Abstract

Glass raw material 4 containing tin oxide powder is supplied onto the molten glass 2 contained in the glass melting furnace 1, and electrodes 7 and 8 are immersed in the supplied glass raw material 4 into the molten glass 2. ), in the method of manufacturing a glass article including a dissolution process of heating and dissolving, when 100 g of tin oxide powder is collected and passed through a 140 mesh sieve of ASTM standard E11, the mass remaining on the sieve is 0.01 g or less. It was decided to use a powder that is .

Description

Method of manufacturing glass articles

This disclosure relates to methods of making glass articles.

As is well known, glass articles such as glass plates, glass tubes, glass fibers, etc. are manufactured by heating and melting glass raw materials in a glass melting furnace and molding the resulting molten glass into a predetermined shape. Glass melting furnaces include all-electric melting furnaces in which heating is performed only with electrodes immersed in molten glass in the furnace (see Patent Document 1), and furnaces in which heating is performed using both electrodes and combustion burners.

Glass raw materials contain a fining agent for defoaming bubbles from molten glass, and tin oxide (SnO ₂ ) powder is widely used as a fining agent. For example, Patent Document 2 discloses the use of tin oxide powder with a median diameter D50 of 2 μm to 9 μm in order to produce a glass article with excellent foam quality.

Japanese Patent Publication No. 2003-183031 Japanese Patent Publication No. 2016-74598

However, when manufacturing glass articles using an all-electric melting furnace, the following problems sometimes occur when glass raw materials containing tin oxide powder are used.

That is, in the entire electric melting furnace, since heating by a combustion burner is not performed, the temperature in the upper space within the furnace is lowered, and as a result, a portion of the tin oxide powder is likely to remain undissolved. There have been cases where particulate tin occurred as a defect in glass articles manufactured as a result of this.

A technical problem that must be solved in consideration of the above-mentioned circumstances is to avoid the occurrence of defects in the glass article when using a glass raw material containing tin oxide powder in manufacturing a glass article using an all-electric melting furnace.

A method of manufacturing a glass article to solve the above problems involves supplying glass raw materials containing tin oxide powder onto molten glass contained in a glass melting furnace, and heating and dissolving the supplied glass raw materials with an electrode immersed in the molten glass. A method for manufacturing a glass article including a process, characterized in that when 100 g of tin oxide powder is collected and passed through a 140 mesh sieve of ASTM standard E11, a powder remaining on the sieve of 0.01 g or less is used. .

In this method, when 100 g of tin oxide powder is collected and passed through a 140 mesh sieve of ASTM standard E11, a powder with a mass remaining on the sieve of 0.01 g or less is used. When such tin oxide powder is used, it becomes possible to appropriately prevent dissolution residues of the tin oxide powder in the dissolution process. As a result, the occurrence of defects in glass articles can be avoided.

In the above method, it is preferable to use a tin oxide powder having a median diameter D50 of 1 μm to 80 μm.

If the median diameter D50 is too small, the particles contained in the tin oxide powder become correspondingly fine, and the cost increases to produce such fine particles, resulting in an increase in the production cost of glass raw materials including tin oxide powder. It becomes easier to become On the other hand, if the median diameter D50 is too large, it becomes difficult to meet the condition that the mass remaining on the sieve is 0.01 g or less per 100 g. However, if the median diameter D50 is 1㎛ to 80㎛, it becomes easy to satisfy the above-mentioned conditions while preventing an increase in the production cost of glass raw materials.

In the above method, it is preferable to use tin oxide powder having a median diameter D50 of more than 50 μm to 80 μm.

In this way, the production cost of glass raw materials can be reduced because the median diameter D50 exceeds 50 μm. In addition, because it is difficult for the tin oxide powder to contain excessively fine particles, it becomes possible to facilitate the handling of glass raw materials, for example, by making it easier to send the raw materials to a feeder when supplying glass raw materials to a glass melting furnace.

In the above method, it is preferable to combine the glass raw materials so that the molten glass contains 0.01% to 1.5% by mass of SnO ₂ .

In this way, bubbles can be appropriately defoamed from the molten glass.

In the above method, the molten glass is SiO ₂ : 50%~70%, Al ₂ O ₃ : 12%~25%, B ₂ O ₃ : 0%~12%, Li ₂ O+Na ₂ O+K ₂ in mass%. O (total amount of Li ₂ O, Na ₂ O, and K ₂ O): 0% to less than 1%, MgO: 0% to 8%, CaO: 0% to 15%, SrO: 0% to 12%, BaO : Glass raw materials may be combined to contain 0% to 15%.

In this way, it becomes possible to enjoy the effect of avoiding the occurrence of defects when manufacturing a glass substrate for a display as a glass article.

In the above method, the cullet rate of the glass raw material may be 40% or less.

The lower the cullet rate of the glass raw material, the more likely it is that defects will occur in the glass article due to the dissolution residue of the tin oxide powder. Therefore, when the cullet rate is 40% or less, the effect of avoiding the occurrence of defects can be appropriately achieved by using tin oxide powder whose mass remaining on the sieve is 0.01 g or less per 100 g.

In the above method, the temperature corresponding to the viscosity of 10 ^2.5 Pa·s in the molten glass may be 1630°C or lower.

When the molten glass satisfies the above temperature conditions, defects are likely to occur in the glass article due to the melted residue of the tin oxide powder. Therefore, when the above conditions are met, the effect of avoiding the occurrence of defects can be appropriately achieved by using tin oxide powder whose mass remaining on the sieve is 0.01 g or less per 100 g.

According to the above-described glass article manufacturing method, it becomes possible to avoid the occurrence of defects in the glass article when using a glass raw material containing tin oxide powder in producing the glass article using an all-electric melting furnace.

1 is a cross-sectional view showing a method of manufacturing a glass article.
Figure 2 is a schematic diagram showing a method of manufacturing a glass article.

Hereinafter, a method for manufacturing a glass article according to an embodiment will be described with reference to the attached drawings. First, the glass melting furnace used in this manufacturing method will be explained.

The glass melting furnace 1 shown in FIG. 1 is an all-electric melting furnace provided with a melting chamber 3 that can accommodate molten glass 2. This glass melting furnace 1 performs a melting process (P1) in which the glass raw material 4 supplied on the surface 2a of the molten glass 2 in the melting chamber 3 is heated and melted, and a melting process is performed. It is configured to allow the molten glass 2 produced by (P1) to flow out of the dissolution chamber 3.

The melting chamber 3 includes a front wall 3a located at the upstream end in the flow direction D of the glass raw material 4 (molten glass 2) within the melting chamber 3, and a downstream end. It has a rear wall 3b located at, a pair of side walls 3c (only one side of the pair is shown in Fig. 1), a ceiling wall 3d, and a bottom wall 3e.

A screw feeder 5 is installed on the front wall 3a to continuously supply the glass raw material 4. The glass raw material 4 supplied from the screw feeder 5 melts while flowing in the flow direction D on the surface 2a of the molten glass 2. As a result, a portion of the surface 2a is covered with the glass raw material 4. As will be explained in detail later, the glass raw material 4 contains tin oxide (SnO ₂ ) powder as a clarifier. The rear wall 3b is formed with an outlet 6 for continuously flowing out the molten glass 2. Here, tin oxide powder refers to a powder containing SnO ₂ as a main component, and may contain impurities that are inevitably mixed during the manufacturing process or handling process. For example, the SnO ₂ content of tin oxide powder is 98% by mass or more.

On the bottom wall 3e, a plurality of rod-shaped electrodes 7 for heating the molten glass 2 by applying electricity are installed in a state immersed in the molten glass 2. In addition, a plurality of plate-shaped electrodes 8 for heating the molten glass 2 by applying electricity are installed on each of the pair of side walls 3c in a state immersed in the molten glass 2. As these electrodes 7 and 8 heat the molten glass 2, the glass raw material 4 on the surface 2a of the molten glass 2 is indirectly heated and sequentially melted.

In this glass melting furnace 1, after the start of continuous production of the molten glass 2 (after the start of the melting process P1), the heat energy applied to the molten glass 2 in the melting chamber 3 is supplied to the electrode ( It is generated only by 7, 8). As a result, an increase in the moisture content of the molten glass 2 within the dissolution chamber 3 can be suppressed, and the moisture content of the obtained glass (glass article) can be reduced. Additionally, the molten glass 2 can be produced while keeping the temperature in the upper space of the furnace low without heating by a combustion burner. For this reason, not only can the emission of greenhouse gases be reduced, but also the energy required for melting the glass raw material 4 can be reduced. In addition, in the step before the start of continuous production (the step of setting up the furnace to a state in which the melting process (P1) can be performed), molten glass (not shown) is formed, for example, by a combustion burner (not shown) installed on the side wall 3c. 2) and/or the glass raw material 4 may be heated.

From the viewpoint of reducing the moisture content of glass, reducing greenhouse gas emissions, and promoting reduction of energy required for melting, in the melting process (P1), a single glass melting furnace (1) is used instead of using a plurality of glass melting furnaces (1). It is desirable to produce molten glass (2) using 1). From the viewpoint of promoting reduction of greenhouse gas emissions and energy required for melting, the maximum temperature of the molten glass 2 in the glass melting furnace 1 is preferably 1400°C to 1700°C, and the glass melting furnace 1 ), the residence time of the molten glass 2 is preferably 2 hours to 240 hours.

β-OH can be used as an indicator of the moisture content of glass. If this β-OH is lowered, the strain point can be increased. Moreover, even when the glass composition is the same, the smaller the β-OH, the smaller the thermal contraction rate at a temperature below the strain point. β-OH is preferably 0.30/mm or less, 0.25/mm or less, 0.20/mm or less, 0.15/mm or less, especially 0.10/mm or less. Additionally, if β-OH is too small, meltability tends to decrease. Therefore, β-OH is preferably 0.01/mm or more, especially 0.03/mm or more.

Here, “β-OH” refers to the value obtained by measuring the transmittance of glass using FT-IR and using the following formula 1.

[Number 1]

β-OH=(1/X)log(T1/T2)

X: plate thickness (mm)

T1: Transmittance (%) at reference wavelength 3846cm-1

T2: Minimum transmittance (%) around hydroxyl absorption wavelength 3600cm-1

Hereinafter, a method for manufacturing a glass article using the glass melting furnace 1 will be described. In this embodiment, the case of manufacturing a glass substrate for a display as a glass article is given as an example.

In this manufacturing method, as described above, the glass raw material 4 containing tin oxide powder is supplied onto the molten glass 2 contained in the glass melting furnace 1. For the tin oxide powder, 100 g of tin oxide powder was collected and passed through a 140 mesh sieve of ASTM standard E11 (a sieve with 105 ㎛ eye holes) for the purpose of preventing dissolution residues of the tin oxide powder in the dissolution process (P1). In this case, use tin oxide powder with a mass of tin oxide powder remaining on the sieve of 0.01 g or less. Additionally, the mass of tin oxide powder remaining on the sieve is preferably 0.005 g or less, and more preferably 0.001 g or less. On the other hand, the lower limit of the mass of tin oxide powder remaining on the sieve can be set to 0 g. The “tin oxide powder remaining on the sieve” herein means the tin oxide powder as follows. In other words, taking into account this fact that particles of tin oxide powder cause agglomeration, the tin oxide powder remaining on the sieve is pressed against the mesh of the sieve, and the tin oxide powder that still does not pass through the sieve is referred to as the “tin oxide powder remaining on the sieve.” 」.

From the viewpoint of preventing an increase in the production cost of the glass raw material 4 containing tin oxide powder and from the viewpoint of making it easier to satisfy the condition that the mass remaining on the sieve described above is 0.01 g or less per 100 g, The median diameter D50 is set at 1㎛~80㎛. Also, preferably, the median diameter D50 is set to exceed 50 μm to 80 μm. This makes it possible to stabilize the weighing and conveyance of the glass raw material 4.

The glass raw material 4 has a cullet rate of 40% or less. In addition, the glass raw material 4 is combined so that 0.01% to 1.5% by mass of SnO ₂ is contained when the glass raw material 4 is dissolved and the molten glass 2 is produced. In addition, the glass raw material 4 is SiO ₂ : 50% to 70%, Al ₂ O ₃ : 12% to 25%, and B ₂ O ₃ : 0% to 12% in mass% when the molten glass 2 is produced. , Li ₂ O+Na ₂ O+K ₂ O (total amount of Li ₂ O, Na ₂ O, and K ₂ O): 0% to less than 1%, MgO: 0% to 8%, CaO: 0% to 15 %, SrO: 0%~12%, BaO: 0%~15%. In addition, in this molten glass 2, the temperature corresponding to the viscosity of 10 ^2.5 Pa·s is 1630°C or lower.

As shown in FIG. 2, the molten glass 2 produced in the glass melting furnace 1 by performing the melting process (P1) is then subjected to a clarification process (P2), a stirring process (P3), a condition adjustment process (P4), It goes through the forming process (P5) sequentially.

A clarification tank (9) is used to carry out the clarification process (P2). In the clarification tank 9, the molten glass 2 flowing into the clarification tank 9 from the glass melting furnace 1 is heated and the molten glass 2 is melted by the action of a clarifier (tin oxide powder). Remove the air bubbles from (2).

To carry out the stirring process (P3), a stirring tank 10 and a stirrer 11 equipped with stirring blades are used. Specifically, the molten glass 2 flowing into the stirring tank 10 from the clarification tank 9 is stirred by the stirrer 11 to homogenize the molten glass 2.

The state adjustment tank 12 is used to execute the state adjustment process (P4). In the condition adjustment tank 12, the temperature (viscosity), flow rate, etc. of the molten glass 2 are adjusted to bring the molten glass 2 into a state suitable for molding.

The molded body 13 is used to perform the molding process (P5). In the molded body 13, the glass ribbon 14 is continuously formed from the molten glass 2 by the overflow down-draw method. In addition, the molded body 13 may be formed by molding the glass ribbon 14 by another molding method such as the slot down-draw method, the re-draw method, or the float method.

After that, the glass substrate for display is obtained by going through various processes such as a cutting process to cut the glass plate that serves as the base of the glass substrate from the formed glass ribbon 14, a grinding/polishing process for the glass plate, a cleaning process, and an inspection process. This is manufactured. In addition, in this embodiment, a glass substrate for a display is manufactured as a glass article, but of course, glass articles other than this (e.g., glass tube, glass fiber, etc.) may be manufactured.

(Example)

Under the same mode as the above embodiment, as shown in [Table 1] below, when 100 g is collected and passed through a 140 mesh sieve of ASTM standard E11, four types of tin oxide with different masses remaining on the sieve are obtained. Glass substrates for displays were manufactured using each powder (Example: 3 types, Comparative Example: 1 type). Then, it was examined whether defects (particulate tin) derived from the dissolved residue of tin oxide powder occurred in the 100 kg glass substrate group manufactured. Specifically, the number of defects originating from the dissolved residue of tin oxide powder and having a length of 10 μm or more was counted.

Here, for the item of presence or absence of defects in [Table 1], “◎” means that the number of defects is 0.01 or less, and “○” means that the number of defects is more than 0.01, and also 0.1. It means that the number of defects was less than 0.1, and “△” means that the number of defects was more than 0.1 and less than 0.2, and “×” means that the number of defects was more than 0.2.

As shown in [Table 1], in Examples 1 to 3, it was possible to avoid the occurrence of defects in the glass substrate, unlike the comparative example. It is assumed that the reason such a result was obtained was that in Examples 1 to 3, unlike the Comparative Example, the dissolution residue of the tin oxide powder in the dissolution step (P1) was appropriately prevented. In addition, the glass raw material 4 of the comparative example and the glass raw material 4 of Examples 1 to 3 were used, respectively, and instead of the glass melting furnace 1, which is an all-electric melting furnace, a furnace using a combination of electrodes and a combustion burner was used. So, when glass substrates were manufactured, no defects occurred in any of them.

1: Glass melting furnace 2: Molten glass
4: Glass raw material 7: Electrode
8: Electrode P1: Dissolution process

Claims (7)

A method for producing a glass article comprising a dissolution step of supplying glass raw materials containing tin oxide powder onto molten glass contained in a glass melting furnace and dissolving the supplied glass raw materials by heating them with an electrode immersed in the molten glass. ,
A method for producing a glass article, characterized in that when 100 g of the tin oxide powder is collected and passed through a 140 mesh sieve of ASTM standard E11, a powder remaining on the sieve of 0.01 g or less is used. According to claim 1,
A method for producing a glass article, characterized in that using a powder having a median diameter D50 of 1 μm to 80 μm as the tin oxide powder. The method of claim 1 or 2,
A method for producing a glass article, characterized in that the tin oxide powder is used as a powder having a median diameter D50 of more than 50 μm to 80 μm. The method according to any one of claims 1 to 3,
A method for producing a glass article, characterized in that the glass raw materials are combined so that the molten glass contains 0.01% to 1.5% by mass of SnO ₂ . The method according to any one of claims 1 to 4,
The molten glass is SiO ₂ : 50% to 70%, Al ₂ O ₃ : 12% to 25%, B ₂ O ₃ : 0% to 12%, Li ₂ O+Na ₂ O+K ₂ O( (Total amount of Li ₂ O, Na ₂ O, and K ₂ O): 0% to less than 1%, MgO: 0% to 8%, CaO: 0% to 15%, SrO: 0% to 12%, BaO: 0 A method for producing a glass article, characterized in that the glass raw materials are combined to contain % to 15%. The method according to any one of claims 1 to 5,
A method for producing a glass article, characterized in that the cullet rate of the glass raw material is 40% or less. The method according to any one of claims 1 to 6,
A method for producing a glass article, characterized in that the temperature corresponding to the viscosity of 10 ^2.5 Pa·s in the molten glass is 1630°C or lower.