RU2465221C2 - Method of making glass articles and device to this end - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to method of making glass articles and device to this end. Proposed method comprises glass feed into forming mould from feeder communicated with initial solution fusing chamber. Said chamber is furnished with electrodes arranged in fused solution to heat the latter by applying current to said electrodes. Then, fused solution is heated above fused solution after fusing initial material. Then, mixer is transferred into fusing chamber to mix fused solution.

EFFECT: increased glass homogeneity.

28 cl, 3 ex, 10 dwg

Description

Technical field

The invention relates to a method for producing a glass product and to a device for its production.

State of the art

Conventional continuous glass melting plants often include melting furnaces equipped with a melting tank, a clarifying tank, and a mixing tank. The starting material is usually added to maintain the level of the molten solution at a predetermined level. The molten solution of the molten starting material in the melting vessel is successively transferred to a clarification vessel and a mixing vessel.

However, in this type of continuous melting furnace, the glass yield per unit time cannot be increased above a predetermined amount. Corresponding difficulties are associated with the formation of glass blocks of large volume, which requires the release of a large amount of glass per unit time. In this regard, Patent Document 1 describes a process according to which large-volume glass blocks are obtained by using a batch melting furnace (a melting furnace in which it is planned to stop the production of glass, stop the supply of starting material when a certain amount of molten solution is reached, and then resume glass production).

However, sufficient mixing of the molten solution is required to obtain a uniform glass. Although the mixing can be carried out by convection flow or by bubbling, in particular when the molten solution has a high viscosity or the like. mechanical stirring using stirring rods or the like is required.

[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2006-117525

Description of the invention

However, in the batch furnace described in Patent Document 1, if melting, clarification, and stirring are carried out in a single melting vessel, installation of the mechanical stirring device is complicated due to problems associated with damage to the mechanical stirring device resulting from the action of the starting material, not melted during the melting stage, and wear as a result of fusion with platinum. As a result, mixing must be carried out in a traditional batch furnace using a method that excludes mechanical mixing, and therefore it is not possible to sufficiently improve the uniformity of the glass.

The present invention is presented in the light of the above circumstances and the aim of the invention is to provide a method for producing glass products and devices for its production, which is adapted to form blocks of glass of large volumes and can sufficiently improve the uniformity of the glass. As used here, a block of glass of large volume is, for example, a block with a volume of at least 0.3 m ³ . Glass in the present invention includes amorphous glass and crystalline glass, where amorphous glass is thermally treated to provide crystallization.

Applicants have implemented the present invention with the understanding that the temperature of the molten solution can be appropriately controlled, damage to the mixer can be suppressed, and sufficient mixing of the molten solution is possible by heating the molten solution on top of the molten solution, while at the same time providing electrical heating of the molten solution, and the installation and extracting the mixer at suitable time intervals. More specifically, the present invention includes the following.

1. A method of producing a glass product, in which glass is fed into a forming die from a feeder, which is connected to a melting tank containing a molten solution of the starting material.

The method includes:

a loading step for supplying the starting material to a melting vessel including electrodes in the molten solution, and

a heating step in which the molten solution is electrically heated by applying electric current to the electrodes, and further, the molten solution is heated on top of the molten solution.

After the starting material is melted, the mixer is installed from the external position to the internal position of the melting vessel, so that the molten solution is mixed with the mixer.

2. The production method, as indicated in paragraph (1) above, in which heating includes the step of setting the temperature difference, whereby the temperature of the molten solution at a level of ¼ or less than the depth of the molten solution from the bottom of the melting tank is higher than the temperature of the molten solution at ¼ or less than the depth of the molten solution from the surface of the solution.

3. The method of obtaining, as indicated in paragraph (2) above, in which the temperature difference is at least 10 ° C.

4. The production method, as indicated in any one of paragraphs (1) to (3) above, in which the inside of the electrodes includes a cooling device, the electrodes extend substantially horizontally in the melting tank, and the electrodes are cooled using a cooling device.

5. The method of obtaining, as indicated in any of paragraphs (1) to (4) above, in which the horizontal cross-sectional surface of the inner region of the melting vessel at least at the location of the electrodes has a n-gon configuration (n is an integer at least 4).

6. The production method, as indicated in any of paragraphs (1) to (5) above, in which the height of the surface of the solution is determined, and the amount of loading of the starting material and / or the amount of output of the molten solution is brought into correspondence based on the determined value.

7. The method of obtaining, as indicated in paragraph (6) above, in which the amount of feed of the starting material is adjusted so that the ratio h / H is 0.1-0.6, where H is the height from the bottom of the tank for melting to the surface solution, and h represents the height from the bottom of the vessel for melting to the very top of the electrodes.

8. The method of obtaining, as indicated in any of paragraphs (1) to (7) above, in which the heating of the molten solution from above is carried out using a combustion burner located in the upper part of the furnace wall above the molten solution.

9. The production method, as indicated in paragraph (8) above, in which the ratio (A: B) of the volume (A) above the surface of the solution in the melting vessel and the volume (B) of the molten solution is 1.0: 1.0- 1.5: 1.0.

10. The production method, as indicated in paragraph (8) or (9) above, in which partially or completely the upper part of the furnace wall and / or the lower part of the furnace wall containing the molten solution is made of at least one material selected from a group consisting of electrofused cast refractory, refractory brick or ceramic fiber.

11. The production method, as indicated in paragraph (10) above, in which at least a portion of the lower part of the furnace wall of the melting vessel that comes into contact with the molten solution is made mainly of ZrO ₂ and further includes SiO ₂ and / or Al ₂ O ₃ .

12. The production method, as indicated in any one of paragraphs (8) to (11) above, in which the melting vessel includes a gas outlet channel with an adjustable opening, where the channel is located on the upper part of the furnace wall and the opening of the gas outlet channel is adjusted so that the inner the pressure in the melting tank corresponds to a predetermined range.

13. The production method, as indicated in any of paragraphs (8) to (12) above, in which the surface of the solution is set so that the height difference between the center of the opening of the combustion burner and the surface of the solution is at least 300 mm.

14. The production method, as indicated in any one of paragraphs (8) to (13) above, in which the combustion burner is positioned so that the opening is directed in the horizontal direction or higher than the horizontal direction.

15. The method of obtaining, as indicated in any of paragraph (1) or (14) above, in which the ratio (a / b) of the heat released during combustion (kcal / h) per unit time of operation of the combustion burner, related to the amount of load b (l) starting material is 400 or less.

16. The production method, as indicated in any one of (1) or (15) above, in which the ratio (b / s) of the charge amount b (l) of the starting material to the amount from the electrodes is 350 or less.

17. The production method, as described in any one of paragraphs (1) to (16) above, in which the inside of the mixer includes a channel for a cooling medium, and the mixer is cooled by passing a cooling medium in a channel of a cooling medium.

18. The method of obtaining, as indicated in any of paragraphs (1) to (17) above, in which the electrodes are connected to an alternating current source with a frequency of at least 2.5 kHz.

19. The production method, as described in any of paragraphs (1) to (18) above, in which the melting, clarification and mixing of the source material is carried out in one vessel for melting.

20. The method of obtaining, as indicated in any of paragraphs (1) to (19) above, in which the feeder communicates essentially with the Central part of the bottom of the tank for melting.

21. The production method, as described in any one of paragraphs (1) to (20) above, in which it is obtained from a molten solution with a viscosity of at least 1.5 Poise at a maximum temperature of the heating step.

22. The production method, as indicated in any of paragraphs (1) to (21) above, in which the content of OH groups in the resulting glass product is 570 ppm (parts per million) or less.

23. The production method, as described in any of paragraphs (1) to (22) above, in which the glass product is obtained from SiO ₂ -Al ₂ O ₃ -Li ₂ O or SiO ₂ -LiO ₂ .

24. A device for producing glass products, including:

- a capacity for melting, containing the molten solution of the starting material and including electrodes immersed in the molten solution;

- a feeder connected to a vessel for melting,

- heating means located in the upper part of the melting tank,

- a forming die with which molten glass exiting the feeder is shaped, and

- a mixer made with the possibility of installation in the inner part of the tank for melting and extraction from this area.

25. The production device according to (24) above, in which the interior of the mixer includes a channel for a cooling medium, wherein ceramic material with a high coefficient of thermal expansion is provided on the outer circumferential region of the channel for a cooling medium, and ceramic material with a high coefficient of thermal expansion is coated platinum or platinum rhodium alloy.

26. The receiving device, as indicated in paragraph (24) or (25) above, in which the inner part of the electrodes includes a device for cooling, and the electrodes pass essentially in a horizontal direction into the melting tank.

27. The receiving device, as indicated in any one of paragraphs (24) - (26) above, in which the horizontal cross-sectional surface of the inner region of the melting vessel at least at the location of the electrodes has a n-gon configuration (n is an integer at least 4).

28. The production device, as indicated in any of paragraphs (24) to (27) above, in which the melting vessel includes a lower part of the furnace wall containing the molten solution and the upper part of the furnace wall located above the lower part of the furnace wall, and means heating includes a combustion burner provided on the upper part of the furnace wall.

According to the present invention, since the molten solution is subjected to electrical heating by means of electrodes, in addition to heating from above, the starting material is rapidly melted. Moreover, since the lower region of the molten solution is heated by electric heating, the convection flow of the molten solution is stimulated, and therefore, clarification and homogenization are also carried out quickly. Since the mixer is installed after the source material is melted, damage to the mixer can be suppressed, and therefore, mechanical mixing is possible, resulting in a significant improvement in glass uniformity.

Brief Description of the Drawings

figure 1 presents a view in vertical section of a device for producing glass products in accordance with the first embodiment of the present invention;

figure 2 presents a top view of the device for receiving, presented in figure 1;

figure 3 shows how the mixer is installed in the device for receiving, presented in figure 1;

figure 4 presents an incomplete enlarged sectional view of the mixer shown in figure 3;

5 shows a horizontal cross-sectional shape of a melting vessel according to another embodiment of the present invention;

6 is a view showing the uniformity of the inner region of a glass product obtained using the production method in accordance with a comparative example;

7 is a view showing the uniformity of the inner region of a glass product obtained using the production method in accordance with the first embodiment of the present invention, and

on Fig presents a surface image of a glass product obtained using the production method in accordance with the first embodiment of the present invention.

Embodiments of the present invention are described below with reference to the accompanying drawings.

Figure 1 presents a view in vertical section of a device 10 for producing a glass product in accordance with the first embodiment of the present invention. Figure 2 presents a top view of the device 10 for receiving in the state before loading the source material (the upper wall 263 of the upper part 26 of the furnace wall is presented as a through view). The receiving device 10 includes a melting vessel 20, a feeder 30, a heater 40 operating as a heating means, a forming die 50, and a mixer 60. Each of the above constituent elements is described in more detail below.

Melting tank

The molten solution of the starting material is placed in a tank 20 for melting. The starting material may be a batch (where the powdered starting material is mixed from various components) or a coarse fused glass break that is formed by vitrification of the batch. The source material is fixed in the holder 73 located at the far end of the main part 71 of the source material supply means 70, and is loaded through the loading hole 237 formed on the side wall 231 '. The opening 237 of the download can be opened and closed, thereby preventing a decrease in temperature in the inner region of the vessel 20 for melting, and preferably it is open during the loading of the source material and closed the rest of the time.

As shown in FIG. 2, the melting vessel 20 includes electrodes 21a-21d, 21'a-21'd in the molten solution. The electrodes 21a-21d, 21'a-21'd are connected to a power source (not shown). When electricity is supplied to the electrodes 21a-21d, 21'a-21'd from a power source, an electric current flows through the molten solution and thereby heats the molten solution. The temperature control of the molten solution and the inner furnace region can be appropriately carried out at each stage of melting, clarification, and mixing of the starting material by heating by allowing electric current to flow through the molten solution, and heating the molten solution from above by means of a heater 40, described below. For example, when melting the starting material from a state in which the melting vessel 20 is empty, heating by the heater 40 is only carried out to obtain a certain amount of molten solution. When the electrodes 21a-21d, 21'a-21'd are located at the bottom of the melting vessel 20, if a fixed amount of molten solution is placed, the convection flow of the molten solution, in addition to melting and clarification, can be stimulated by increasing the degree of electrical heating by electrodes 21a-21d, 21'a-21'd; and relative attenuation of the heating of the molten solution provided from above.

Taking into account the problem of obtaining a strong convection flow in the molten solution, the temperature of the molten solution at a level of ¼ or less than the depth of the molten solution from the bottom 233 of the melting vessel 20 is preferably higher than the temperature of the molten solution at a level of ¼ or less than the depth of the molten solution from the surface of the molten solution FL . The temperature difference can be obtained by appropriate selection of the amount of heating provided by the heater 40, as described below, and the electrical heating provided by the electrodes 21a-21d, 21'a-21'd, based on the temperature of the molten solution in the corresponding positions recorded using sensors 22a -22c of the temperature provided on the inner side of the lower part 23 of the furnace wall that holds the molten solution, and temperature sensors (not shown) provided inside the electrodes 21a-21d, 21'a-21'd.

The temperature difference can be appropriately set depending on the viscosity or the like. molten solution and preferably at least 10 ° C. The lower limit of the temperature difference is more preferably 25 ° C and most preferably 40 ° C. Since the temperature difference suppresses the corrosion of the furnace walls caused by the molten solution, in addition to the cost increase due to electric heating, the temperature difference is preferably 150 ° C or less, more preferably 130 ° C or less, and most preferably 100 ° C or less. The temperature of the molten solution is measured as described hereinafter. A temperature sensor, such as a thermocouple or the like, coated with platinum, is inserted so that it passes into the molten solution from the hole located on the furnace wall, and measurements are carried out using a temperature sensor. Alternatively, measurements can also be made using a temperature sensor located inside the far end of the electrodes 21a-21d passing into the molten solution.

The interior of the electrodes 21a-21d, 21'a-21'd preferably includes a cooling device (not shown), and the electrodes preferably extend substantially horizontally in the melting vessel 20. Since the electrodes 21a-21d, 21'a-21'd are cooled by a cooling device, the wear caused by the molten high temperature solution can be suppressed. The cooling device may have a known configuration. Moreover, since the electrodes 21a-21d, 21'a-21'd extend substantially horizontally in the melting vessel 20, it is possible to quickly increase the temperature in the molten solution due to electric heating. In order to improve the efficiency of increasing the temperature of the molten solution, the lower limit of the length over which the electrodes extend is preferably 20 mm, more preferably 50 mm, and most preferably 100 mm. To minimize the amount of platinum or platinum rhodium alloy that corrodes in the molten solution due to electrical conductivity, the upper limit on the length of the electrodes is preferably 700 mm, more preferably 600 mm, and most preferably 450 mm.

The electrodes 21a-21d, 21'a-21'd are arranged in the opposite direction, as shown in FIG. 2, and current flows between a pair of electrodes 21a, 21a ', a pair of electrodes 21b, 21b', a pair of electrodes 21c, 21c ', a pair electrodes 21d, 21d '(the number of electrodes is eight pieces). To ensure uniformity of the molten solution by convection flow in the molten solution, the ratio (b / s) of the amount b (l) of the feed to the number of electrodes is preferably 350 or less. If the b / s ratio exceeds 350, the degree of electric heating in the molten solution will be insufficient, and as a result, the convection flow will be insufficient. The upper limit of the b / s ratio is more preferably 325 and, most preferably, 300. To ensure a compromise between the installation costs associated with the electrodes and the uniformity of the molten solution due to convection flow, the lower limit of the b / s ratio is preferably 50, more preferably , 60, and most preferably 75.

To prevent the formation of places with insufficient heating in the direction of the plane of the molten solution when using current, the horizontal surface of the inner region of the vessel 20 for melting at least at the location of the electrodes has an n-gon configuration (n is an integer of at least 4 and preferably an integer of at least 5). As shown in FIG. 5 (C), although it is possible to provide a horizontal cross section with n equal to four, this arrangement forms positions, as shown by the dashed line, in which electrical heating is relatively insufficient. If n is more preferably at least 5, and most preferably at least 6, less such positions result. In the present embodiment, as shown in FIG. 2, although in general the lower part 23 of the furnace wall has a horizontal cross-sectional surface in the shape of an n-gon, from the point of view of simplifying the configuration, the horizontal cross-sectional surface of the inner part, at least at the location of the electrodes, can be in the shape of an n-gon. To ensure uniform heating in the direction of the cross section of the molten solution, the horizontal surface of the inner region, at least at the location of the electrodes, is more preferably a regular n-gon.

In the present embodiment, the horizontal section surface is a regular octagon. However, the present embodiment is not limited to this, and, for example, the side walls 231a-231c, 231'a-231'c, as shown in Fig. 5 (A), can be smoothly connected by arched surfaces 232a-232h (in other words, without angular elements). As shown in FIG. 5 (B), the surface of the horizontal section can be rounded (for example, a circle or an oval), in other words, n can take on an infinite value. However, in order to facilitate the installation of the electrodes, the places where the electrodes 21a-21d, 21'a-21'd are mounted are preferably on a flat surface, as shown in FIG. 2 and the like.

The voltage source that is connected to the electrodes 21a-21d, 21'a-21'd is not particularly limited, but to improve the heating efficiency of the molten solution, an alternating current source with a frequency of at least 2.5 kHz is preferred.

Preferably, the solution surface height determination device 80 is provided in the melting vessel 20, and the feed amount of the starting material or the yield amount of the molten solution is preferably adjusted to the height of the surface of the solution FL of the molten solution determined by the solution surface height determination device 80. In other words, if the recorded surface height of the solution FL is within a predetermined range, the feed is stopped and the glass exit from the feeder 30 is provided as described below. If the registered value is below a predetermined range, the source material is loaded from the means 70 for supplying the source material. Thus, it is possible to improve the quality of the glass by preventing wear of the electrodes 21a-21d, 21'a-21'd from exposure to the gas environment. The device 80 for determining the height of the surface of the solution in accordance with the present invention is a device that emits radiation in the near infrared range from a semiconductor laser to the surface FL of the solution and detects reflected light. However, there are no restrictions in this regard.

More preferably, if the height from the bottom of the melting vessel to the surface of the solution is denoted by H, and the height from the bottom of the melting vessel to the very top of the electrodes is denoted by h, the amount of feed of the starting material is adjusted so that h / H is 0.1-0 , 6. Thus, the respective electrodes 21a-21d can be placed relative to the depth of the molten solution, so as to obtain an effective convection flow in the molten solution. When the surface height of the solution is too large, then the heating effect due to electric heating is insufficient, so the lower limit of the h / H ratio is more preferably 0.2 and most preferably 0.3. Moreover, due to difficulties in setting the temperature difference in the vertical direction of the molten solution, the upper limit of the h / H ratio is more preferably 0.55 and, most preferably, 0.52.

Heater

A heater 40 is provided at the top of the melting vessel 20 to heat the molten solution on top of the molten solution. Thus, since the temperature of both the upper part and the lower part of the molten solution increases, temperature control in the vertical direction of the molten solution is possible in combination with electric heating by means of electrodes, and therefore there is an advantage in increasing the melting rate of the starting material. The heater 40 preferably includes combustion burners 41a, 41b to improve the temperature rise efficiency. These combustion burners 41a, 41b are located on the upper part 23 of the furnace wall, which holds the molten solution. The burners 41a, 41b of the combustion in accordance with the present embodiment are located opposite each other and extend from the side wall 261 of the upper part 26 of the furnace wall inward. Although combustion can use air or oxygen or the like. in combustion burners 41a, 41b, the use of oxygen is preferred to allow melting at high temperatures.

If the combustion reaction is carried out using combustion burners 41a, 41b, OH groups are formed in the gas atmosphere. OH groups can reduce the thermal stability of glass when mixed with a molten solution, in particular, when obtaining crystalline glass or the like, they lead to unstable crystal growth, due to differences in crystallization rate resulting from the distribution of OH groups. To prevent deterioration or concomitant cracking, it is imperative to suppress the mixing of OH groups with the molten solution. The ratio (A: B) of the volume (A) above the surface FL of the solution in the melting vessel 20 and the volume (B) of the molten solution is preferably 1.0: 1.0-1.5: 1.0. If A is too large relative to B, the durability of the refractory starting materials is reduced, since the amount of heat is significantly higher. If A is too small relative to B, there is a possibility of obtaining glass with a high content of OH groups. A: B is more preferably 1.0: 1.0-1.4: 1.0, and most preferably 1.0: 1.0-1.35: 1.0. As used here, the volume (A) above the surface FL of the solution in the melting vessel means the volume occupied by the gas in the melting vessel, and is usually equal to the volume calculated by subtracting the volume of the molten solution from the total volume of the melting vessel 20. Typically, the regulation of the A: B ratio is carried out by changing the volume of the molten solution, using the charge of the starting material and / or the amount of output of the molten solution. However, in this sense there are no restrictions, and such regulation can be performed by changing the volume of the melting vessel 20.

The surface FL of the solution is preferably set so that the height difference α between the centers of the openings 43a, 43b of the burners 41a, 41b of the combustion and the surface FL of the solution is at least 300 mm. Thus, the suppression of mixing OH groups with the molten solution can be improved since the openings 43a, 43b, which are the source of OH groups, are sufficiently separated from the molten solution. The lower limit of the height difference α is more preferably 350 mm and, most preferably, 400 mm. If the height difference α is too large, there is a danger that the molten solution will not heat up efficiently enough, and thus, the upper limit of the height difference α is preferably 850 mm, more preferably 700 mm, and most preferably 650 mm. Installation (task selection) the surface of the FL solution can be carried out by the amount of output of the molten solution and / or loading of the source material.

The burners 41a, 41b are preferably arranged so that the openings are directed in the horizontal direction, as in the preferred embodiment, or above the horizontal direction. If the openings of the burners are directed below the horizontal direction, the risk of mixing OH groups with the molten solution increases, since the flame is oriented in the direction of the molten solution. However, since this risk is reduced according to the above configuration, preventing mixing of OH groups with the molten solution can be improved. To achieve the same effect, the upper part 26 of the furnace wall in the present embodiment has a configuration with a wider diametrical shape than the side wall 231 of the lower part 23 of the furnace wall, so as to cover the openings 43a, 43b of the burners 41a, 41b from the molten solution. However, there are no restrictions in this regard.

In order to improve the suppression of mixing OH groups with the molten solution, the ratio (a / b) of the heat released during combustion (kcal / h) per unit time of operation of the burners 41a, 41b of the combustion to the amount b (l) of the feed of the starting material is preferably 400 or less. If the a / b ratio is too large, in other words, if excessive combustion occurs relative to the charge amount of the starting material that is heated, the number of OH groups mixed with the molten solution per unit time can increase. The upper limit of the a / b ratio is more preferably 350 and, most preferably 330. Given that the melting process is slowed down due to insufficient heating of the molten solution if the ratio a / b is too small, the lower limit of the a / b ratio is preferably 50, more preferably 70 and most preferably 100. The heat generated during combustion (kcal / h) is calculated relative to the amount of gas supplied (eg, gaseous oxygen, gaseous hydrocarbons) to the combustion burners 41a, 41b. The amount b (l) of the feed of the starting material is the volume of the feed (units: liters) charged to obtain the amount of molten solution that is in the melting tank at that moment.

In the present embodiment, although the heater 40 consists of combustion burners 41a, 41b, there are no restrictions, and MoSi ₂ based heating elements (e.g., Kanthal Super manufactured by Kanthal Co., Ltd) can be used or SiC-based heating elements (e.g., an Erema heating element manufactured by Tokai Konetsu Kogyo Co., Ltd) or the like.

Returning to the description of the melting tank, part and all of the upper part 26 of the furnace wall and / or the lower part 23 of the furnace wall is made of at least one material selected from the group consisting of electrofused cast refractory, refractory brick or ceramic fiber. Thus, the wear of the upper part 26 of the furnace wall caused by the burners 41a, 41b of the combustion, and / or the wear of the lower part 23 of the furnace wall caused by the contact or the like. with molten high temperature solution, can be suppressed. In order to maximize this effect, the entire lower part of the furnace wall 23 and the upper part 26 of the furnace wall are preferably formed from at least a material selected from the group consisting of electrofused cast refractory, refractory brick or ceramic fiber.

At least a portion of the bottom 23 of the furnace wall that is in contact with the molten solution preferably consists of a main component Zr ₂ O and further includes SiO ₂ and / or Al ₂ O ₃ . Durability can be improved by using Zr ₂ O as the main component. The simultaneous use of SiO ₂ and / or Al ₂ O ₃ can improve the stability of Zr ₂ O and possibly significantly improve the corrosion resistance of the furnace from the molten solution. This effect is especially noticeable for glass made from SiO ₂ —Al ₂ O ₃ —Li ₂ O. In order to simplify the configuration of the present embodiment, although the entire lower part 23 of the furnace wall is made of an element of essentially the same composition, at least the portions that are in contact with the molten solution can be made of such an element of the above composition. Corrosion prevention can be achieved by cooling the area susceptible to corrosion on the surface of water glass, as the case may be, in particular by cooling a portion of the molten FL solution at the top.

A gas outlet channel 28, including an adjustable opening, is located in the upper part 26 of the furnace wall of the melting vessel 20 and, preferably, the opening of the gas outlet channel 28 is adjusted so that the internal pressure in the melting vessel corresponds to a predetermined range. Thus, the quality of the glass product can be stabilized and the accumulation of OH groups in the melting vessel 20 can be suppressed, thereby increasing the suppression of mixing OH groups with the molten solution. In the present embodiment, although the opening of the gas outlet channel 28 is controlled by means of an adjustable valve, there is no limitation in this regard.

In the present embodiment, the horizontal sectional surface of the upper part 26 of the furnace wall has a square configuration and a gas outlet 28 is provided on the surface of the side wall 261, on which there are no burners 41a, 41b of combustion. The guide tube 29 is located on the opposite surface relative to the gas outlet channel 28, and the guide tube 29 communicates the inner region of the melting vessel 20 with the external atmosphere. Atmospheric air is supplied to the melting tank 20 from the guide pipe 29, depending on the opening of the gas outlet channel 28. This external air displaces the internal air containing OH groups from the melting vessel 20 out through the gas exhaust channel 28. Considering the suppression of mixing of OH groups with molten solution, the vent pipe 28 and / or the guide tube 29 is preferably mounted at the same height as the burners 41a, 41b, or lower.

Mixer

The mixer 60 is configured to allow retractable installation in the interior of the melting vessel. After the starting material is melted, the mixer 60 is set from an external position to an internal position in the melting vessel 20 so as to mix the molten solution. In other words, since the mixer 60 is located on the outside of the melting vessel 20 during the melting stage, in which there is a risk of contact of the mixer elements with the unmelted starting material, wear of the mixer 60 can be suppressed. The deterioration in glass quality caused by the components of the mixer 60 coming into contact with the molten solution can also be suppressed.

Figure 3 shows how the mixer 60 is installed in the tank 20 for melting. If stirring is not carried out, the opening 235 made with the possibility of opening and closing, provided above the surface of the solution FL of the molten solution on the side wall 231, is closed, which ensures a tight closure of the melting vessel 20. After the completion of the melting stage, immediately before the mixing stage, as shown in FIG. 3 (A), the opening 235 is openable and openable, whereby the channel 236 openable for opening and closing is opened and the mixer 60 can be installed. The mixer in the present embodiment includes a bar-shaped main body 61 connected to the drive and curved substantially at a right angle in a bend portion 63 located in the middle of the main part 61, passing further to the remote zu 65. operable to open and close the channel 235 has a transverse dimension greater than the distance of the bending portion 63 to the distal end 65, and a vertical size larger than the diameter of the main portion 61 (usually, it has a shape extending in the longitudinal direction). The mixer 60 is set so that a portion from the bend portion 63 to the distal end 65 is brought into a horizontal position (FIG. 3 (B)). If the distal end 65 is inserted into the inner region of the melting vessel 20, the body 61 is rotated and the distal end 65 is immersed in the molten solution (Figure 3 (C)). After that, the distal end 65 moves inside the molten solution due to the operation of the drive, and thus, the molten solution is mechanically mixed. If the distal end 65 moves in a desired orbit in the molten solution, the transverse width of the channel 236 with the possibility of opening and closing it must be large enough to avoid the walls of the hole 235 opening and closing contacting the main body 61. After mixing, the mixer 60 and the opening 235 capable of opening and closing is returned sequentially to the state shown in FIG. 3 (B), (A), and the mixer 60 is returned to the external position of the container 20 avleniya.

Figure 4 presents an incomplete enlarged sectional view of the mixer 60 shown in Figure 3. The interior of the mixer includes a channel 66 for the cooling medium. Ceramic material 67 with a high coefficient of thermal expansion provide on the outer peripheral region of the channel 66 for the cooling medium. Ceramic material 67 with a high coefficient of thermal expansion is preferably coated with platinum or platinum rhodium alloy 68. Since platinum or platinum rhodium alloy 68 exhibits excellent stability, they inhibit the entry of unwanted impurities into the molten solution, which allows mixing. Moreover, the wear of the mixer 60, due to the passage of the cooling medium through the channel 66 of the cooling medium, can be suppressed. The amount of platinum or platinum rhodium alloy used can be reduced by placing ceramic material between platinum or platinum rhodium alloy 68 and the cooling medium channel 66, which reduces manufacturing costs. Damage to the mixer 60 due to deformation can be suppressed by using a ceramic material with a high coefficient of thermal expansion as a ceramic material and approximating the thermal expansion characteristic caused by temperature changes to that characteristic for platinum or platinum rhodium alloy 68. Thus, a ceramic material with a high thermal coefficient expansion is a ceramic material exhibiting a characteristic of thermal expansion in temperature urnyh step mixing conditions, approximate to a characteristic of platinum or platinum-rhodium alloy, and may be selected depending on the temperature conditions. However, mainly ceramic materials based on Al ₂ O ₃ —CaO or the like can be used. There are no particular restrictions on the cooling medium flowing through the channel 66 for the cooling medium, and the medium may include water, liquids such as oil or the like, and air or the like.

A large amount of molten glass per unit time can be obtained from the feeder 30, as described below, by melting, clarifying and mixing the starting material in one melting tank 20, and while allowing the formation of large volume glass blocks. However, there are no restrictions in this regard, and various melting vessels are used to carry out the melting, clarification and mixing of the starting material.

Feeder

The feeder 30 allows you to start and end the feed using a product control device (not shown), connects the melting container 20 to the external environment and introduces the molten glass from the melting container 20 into the forming die 50. More specifically, the molten glass flows into the connecting hole 33, facing the molten solution, and the glass comes from the injection hole 35, through the main part 31 and into the forming die 50. This type of feeder 30 is made of platinum or platinum rhodium with melt to suppress the flow of unwanted impurities into molten glass.

Feeder 30 is preferably placed on the bottom 233 of the melting vessel 20 to provide molten glass with improved uniformity, and more preferably, placed substantially in the center of the bottom 233. The expression “substantially in the center of the bottom” means an arbitrary position in a region including a shape similar to projection of the bottom along the vertical axis of the vessel 20 for melting, the center of gravity of the form coincides with the center of the projection of the bottom and has 10% of the surface area from the projection of the bottom.

Although the connecting hole 33 of the feeder 30 is preferably located above the bottom 233 to allow the exit of molten glass exhibiting improved uniformity, placement below the placement height of the electrodes 21a-21d, 21'a-21'd is necessary to avoid exposure to electric heating.

Forming stamp

The forming die 50 enables the molding of molten glass coming from the feeder 30. The forming die 50 has dimensions matching the required dimensions of the glass product. For example, a large forming die 50 is used if a large glass product is contemplated. Preferably, a mechanism is provided for varying the distance between the injection hole 35 and the forming die 50. Thus, even if the amount of molten glass that enters and accumulates in the forming die 50 increases gradually, since the falling distance of the molten glass coming from the injection hole 35 is usually maintain minimal grooves or air bubbles or the like. in a glass product can be suppressed.

The method for producing a glass product using the manufacturing device 10 described below is preferably suitable for the manufacture of a glass product in which the viscosity of the molten solution at the maximum temperature during the heating step is at least 1.5 Poise. Since even such a high viscosity liquid glass makes it possible to ensure transparency due to convection flow and mechanical stirring with a mixer 60, a sufficient improvement in the uniformity of the glass is possible. The lower viscosity limit of the molten solution at maximum temperature during the heating step is more preferably 1.7 Poise and, most preferably, 1.8 Poise. If the viscosity of the molten solution is too high, a large amount of energy is required to provide convection flow and mechanical mixing, which leads to an increase in manufacturing costs. Thus, the upper viscosity limit of the molten solution at maximum temperature during the heating step is preferably 3.0 Poise, more preferably 2.8 Poise and, most preferably 2.7 Poise.

The OH group content of the glass product obtained by the above method is 570 ppm or less. This type of glass product is used as a glass product with a low thermal coefficient of expansion exhibiting excellent heat resistance characteristics. The upper limit of the OH group content of the glass product is more preferably 540 ppm and, most preferably, 500 ppm. In light of the combined effect of reducing the content of OH groups and the resulting increase in manufacturing cost, the lower limit of the content of OH groups in a glass product is preferably 50 ppm, more preferably 150 ppm and, most preferably, 200 ppm.

The OH group content of the glass product can be calculated using the Lambert-Behr equation, as described below.

C = log ₁₀ (Ta / Tb) / αt,

where C means the content of OH molecules (ppm), alpha means the molar absorption coefficient of water (8.6 l / mol · mm), t is the thickness of the frosted glass (mm), Ta and Tb are the transmittance (%) for each wavelength. More specifically, Ta is a transmittance having a maximum value near a wavelength of 2.0 μm, and Tb is a transmittance having a minimum value near a wavelength of 2.21 μm.

The glass product is preferably obtained from SiO ₂ —Al ₂ O ₃ —Li ₂ O.

The SiO ₂ —Al ₂ O ₃ —Li ₂ O glass product is a low expansion coefficient glass product used in various fields, including an astronomical telescope or an exposure device in a semiconductor manufacturing facility. It is known that the melting temperature of the starting material and the viscosity of the molten solution are extremely high. However, according to the production method in accordance with the invention, the combination of heating using the above burners 41a, 41b of combustion and electric heating by means of electrodes 21a-21d, 21'a-21'd provides quick and sufficient melting of the starting material, in addition to quick and sufficient lightening due to the convection flow. Therefore, an SiO ₂ —Al ₂ O ₃ —Li ₂ O glass article with excellent uniformity can be obtained. Since the addition of OH groups to the molten solution is suppressed, a glass product with a particularly low coefficient of thermal expansion is obtained. In addition, the production method in accordance with the present invention is suitable for producing amorphous glass used in substrates of hard disks formed from SiO ₂ -Li ₂ O, or crystalline glass used in substrates of hard disks, or crystalline glass used for optical communication filters .

Temperature conditions

The temperature conditions at each stage in the preparation of SiO ₂ -Al ₂ O ₃ -Li ₂ O glass using the device 10 for obtaining, as described above, it is preferable to use the following.

If the charge is loaded in a state in which the melting vessel 20 is completely empty so as to obtain a molten solution, the temperature in the interior of the melting vessel 20 provided by the heater 40 is preferably 1530-1550 ° C.

After the melting vessel 20 is filled with a certain amount of molten solution, except in cases of changing the composition of glass or the like, the molten solution in the melting vessel 20 is adjusted so that it is not less than a predetermined amount. In other words, even after the desired amount of molten glass is exited upon receipt of the glass blocks, the amount of molten solution is controlled so that a certain amount of molten solution remains in the melting vessel 20.

After completing one pass to obtain a glass block, the starting material is fed into the molten solution and melted until a certain level is reached (melting step). To prevent platinum wear or damage from the melting residue (resulting in undesirable impurities), the temperature at this stage is preferably 1450-1550 ° C at the top of the molten solution, more preferably 1460-1540 ° C and, most preferably, 1480-1500 ° C.

After completion of the melting of the starting material, clarification and mixing are performed simultaneously (clarification and mixing stages). To reduce the use of combustion energy from the heater 40 and suppress the precipitation of crystals on the glass surface, the temperature during this step is preferably 1500-1560 ° C and, most preferably, 1510-1540 ° C. The temperature of the lower part of the molten solution is preferably 1530-1600 ° C, more preferably 1540-1595 ° C, and most preferably 1550-1590 ° C, to ensure uniformity of the molten solution by convection flow and suppress the deterioration caused by the presence of platinum.

EXAMPLES

Example 1

Using the device 10 to obtain a glass product, as described below, load the mixture of the starting material, in terms of the amount of oxides, wt.%, Including 54.5-57% SiO ₂ , 6.0-8.5% P ₂ O ₅ , 22.0-26.0% Al ₂ O ₃ , 3.5-4.2% Li ₂ , 0.6-1.6% MgO, 0.4-1.4% ZnO, 0.7-2, 0 CaO, 0.6-1.7% BaO, 1.6-2.7% TiO ₂ , 1.0-2.2% ZrO ₂ and 0.8-1.2% As ₂ O ₃ . A height H from the bottom 233 of the melting vessel 20 to the surface of the liquid is set to 976 mm and oxygen is supplied to the burners 41a, 41b of the combustion, which activate. An alternating current with a frequency of 3.0 kHz is connected to the electrodes 21a-21d, 21'a-21'd, which pass 120-130 mm horizontally into the melting tank, in order to thereby carry out the melting process. After that, the mixer 60 is installed to carry out clarification and mixing. When the temperature of the molten solution during this period is measured using a temperature sensor provided at a height of 750 mm from the bottom 233 (the recorded value refers to the temperature of the upper part) and a temperature sensor in electrodes located 230 mm from the bottom 233 (the recorded value refers to temperature of the lower part), the temperature of the upper part is 1516 ° C-1530 ° C, and the temperature of the lower part is 1580 ° C-1589 ° C. The temperature of the lower part is higher than the temperature of the upper part with a temperature difference of approximately 60 ° C. Thus, it can be assumed that convection flow in the molten solution is ensured. The volume (A) on top of the surface FL of the molten solution in the melting vessel 20 is 2.766 m ³ , the volume (B) of the molten solution is 3.281 m ³ and A: B = 1.19: 1. The height distance between the center of the opening of the combustion burner and the surface of the solution is 612 mm. The b loading amount of the starting material is 1020 (l), the amount of heat generated by combustion per unit time is 240,000 (kcal / h) and the a / b ratio is 235.2. The height h to the very top of the electrodes is 400 mm. Since the number of electrodes with is 8, the b / s ratio is 127.5.

The molten glass obtained by the above method is fed into a forming die 50 and, after cooling and annealing, a glass product with a diameter of 1700 mm and a thickness of 400 mm is obtained. The mixer 60 is rotated until the exit of the molten glass to the forming die 50 is completed and after the supply of the molten glass is completed, the mixer 60 is returned to the upper position of the melting vessel 20. This glass product is cut to a thickness of approximately 10 mm and after applying a polarizing adhesive film to the surface of the cut parts, surface images were obtained using graphics software. The results are presented in Fig.7. The OH group content of the glass product is 424-566 ppm, as calculated by the Lambert-Behr equation above.

Comparative Example 1

Except for the fact that there are no electrodes 21a-21d, 21'a-21'd, a device with the same configuration as the receiving device 10 is used to manufacture a glass product in the same manner as in Example 1. In the course melting, clarification and mixing, the temperature of the upper part is 1602-1604 ° C and the temperature of the lower part is 1544-1546 ° C. Therefore, the temperature of the upper part is higher than the temperature of the lower part. Thus, it can be assumed that convection flow in the molten solution is not provided. The image of the surface of the cut parts is presented in Fig.6.

As can be seen from Fig. 7, the glass product obtained in Example 1 is homogeneous and has a particularly low number of stripes. In contrast, as shown in FIG. 6, the glass product obtained in accordance with comparative example 1 has poor uniformity and, as a consequence, the occurrence of strips.

Basic example 1

The following tests were performed to verify that the ratio of the volume (A) above the molten solution to the surface of the solution FL and the volume (B) of the molten solution affects the OH group content of the glass product. Except that the starting material was loaded so that the volume (A) above the surface of the FL of the molten solution in the melting vessel 20 was 1.369 m ³ and the volume (B) of the molten solution was 1.768 m ³ (A: B = 0.77: 1), the glass product was obtained in the same order as in example 1. The content of OH groups in the glass product is 953-998 ppm when calculated according to the Lambert-Behr equation indicated above. The transmittance is measured using a 270-30 infrared spectrometer manufactured by Hitachi Ltd., using a glass product sample before crystallization heat treatment, polished to a thickness of 10 mm. The maximum transmittance near the wavelength of 2.0 μm is taken as Ta, and the minimum transmittance near the wavelength of 2.21 microns is taken as Tb. Loss of reflection from the surface is included in the transmittance.

Basic example 1

The following tests were performed to verify that the ratio of the number of electrodes and the loading amount of the starting material affects the OH group content of the glass product. In basic example 2-1, a glass product was made in the same order as in example 1, using a receiving device containing four electrodes (the horizontal section surface of the lower part of the furnace wall 23 is a square), and in basic examples 2-2 ~ 2-7, a production device was used containing eight electrodes (the horizontal cross-sectional surface of the lower part 23 of the furnace wall is a regular octagon), except that the conditions shown in table 1 were changed. In the basic example 2-7, the mixing time is shorter than in other basic examples, while it is 3/5 of the time in other basic examples.

Basic example 2

In comparative example 2, except that stirring is not carried out, the glass product is obtained in the same order as in basic example 2-1.

The content of OH groups, the number of bands and the level of undesirable impurities entering the glass product, obtained in basic example 2 and comparative example 2, are presented in table 1. In table 1, the symbols for the appearance of the bands are presented as follows: A - not observed, B - almost not observed, C: a small amount is observed, D: there are many bands. Designations of unwanted impurities are presented as follows: A: no impurities, B: almost no impurities, C: small amount of impurities, D: high level of impurities.

As shown in table 1, when compared with comparative example 2, the number of bands and undesirable impurities in the base examples 2-1 ~ 2-7 was acceptable. Thus, strips and undesirable impurities obtained in a glass product can be reduced by mixing. In the basic examples 2-2 ~ 2-6, the number of bands and undesirable impurities is low, and therefore excellent glass products can be obtained.

Basic example 3

Results showing that the OH group content also affects the crystallization of the glass was verified using SiO ₂ —Al ₂ O ₃ —Li ₂ O glass with the same composition as in Example 1 to prepare batches of glass with a correspondingly different OH group content. These glass samples were crystallized by appropriate heat treatment and then the quality of crystallization and the processing characteristics after crystallization were evaluated. The results are presented in table 2. In table 2, A means good quality, B means average quality, and C means poor quality.

table 2 The content of OH groups (ppm) 778 752 672 605 578 548 540 518 510 466 424 Crystallization C C C B B A A A A A A Processing characteristics after crystallization C C A A A A A A

As shown in table 2, glass with an OH group content of at least 578 ppm does not show good crystallization and does not show good processing characteristics after crystallization. In contrast, glass with an OH group content of 548 ppm or less exhibits good crystallization and good processing characteristics after crystallization. Thus, it was confirmed that the improvement of crystallization and processing characteristics after crystallization is provided by a decrease in the content of OH groups.

An image was made of the surface of a glass product after crystallization with OH groups of 778 ppm and 548 ppm. These results are presented in Fig. 8 ((A) corresponds to 778 ppm, corresponds to 548 ppm). As shown in FIG. 8, it is confirmed that cracks are formed in the glass product with an OH group content of 778 ppm, and such cracks are absent in the glass product with an OH group content of 548 ppm. Thus, it was confirmed that the formation of cracks in a glass product during crystallization can be suppressed by a decrease in the content of OH groups.

List of Symbols

10 device for the production of glass

20 capacity for melting

21 electrodes

23 lower part of the furnace wall

233 bottom

26 upper part of the furnace wall

28 gas outlet

30 feeder

40 heater (heating means)

41 burner

43 hole

50 forming stamp

60 mixer

66 channel for the cooling medium

67 high thermal expansion ceramic

68 platinum or platinum rhodium alloy

Claims (28)

1. A method of producing a glass product, in which glass is fed into a forming die from a feeder, which is connected to a melting tank containing a molten solution of the starting material, comprising the following stages:
supplying the starting material to a melting vessel including electrodes in the molten solution, and
heating the molten solution by applying an electric current to the electrodes and heating the molten solution on top of the molten solution, and
after the initial material has melted, the mixer is installed from an external position to an internal position of the melting vessel in order to mix the molten solution with a mixer. 2. The production method according to claim 1, in which the heating step includes the step of setting the temperature difference at which the temperature of the molten solution at a level of 1/4 or less than the depth of the molten solution from the bottom of the melting tank is higher than the temperature of the molten solution at 1/4 or less than the depth of the molten solution from the surface of the solution. 3. The production method according to claim 2, in which the temperature difference is at least 10 ° C. 4. The production method according to claim 1, in which the inner part of the electrodes includes a cooling device, the electrodes extend substantially horizontally in the melting tank, and the electrodes are cooled using a cooling device. 5. The production method according to claim 1, wherein the horizontal cross-sectional surface of the inner region of the melting vessel at least at the location of the electrodes has a n-gon configuration (n is an integer of at least 4). 6. The production method according to claim 1, wherein the height of the surface of the solution is determined, and the amount of loading of the starting material and / or the amount of output of the molten solution is brought into correspondence based on the determined value. 7. The production method according to claim 6, in which the load amount of the starting material is adjusted so that the h / H ratio is 0.1-0.6, where H is the height from the bottom of the melting tank to the surface of the solution, and h is height from the bottom of the melting tank to the very top of the electrodes. 8. The production method according to claim 1, in which the heating of the molten solution from above is carried out using a combustion burner located in the upper part of the furnace wall above the molten solution. 9. The production method according to claim 8, in which the ratio (A: B) of the volume (A) above the surface of the solution in the melting tank and the volume (B) of the molten solution is 1.0: 1.0-1.5: 1, 0. 10. The production method according to claim 8 or 9, in which partially or completely the upper part of the furnace wall and / or the lower part of the furnace wall containing the molten solution is made of at least one material selected from the group consisting of electrofused cast refractory, refractory bricks or ceramic fibers. 11. The production method according to claim 10, in which at least a portion of the lower part of the furnace wall of the melting vessel that comes into contact with the molten solution is made mainly of ZrO ₂ and further includes SiO ₂ and / or Al ₂ O ₃ . 12. The production method of claim 8, in which the melting tank includes a gas outlet with an adjustable hole, where the channel is located in the upper part of the furnace wall and the opening of the gas outlet is adjusted so that the internal pressure in the melting vessel corresponds to a predetermined range. 13. The production method of claim 8, in which the surface of the solution is set so that the height difference between the center of the opening of the combustion burner and the surface of the solution is at least 300 mm. 14. The production method of claim 8, in which the combustion burner is located so that the hole is directed in the horizontal direction or above the horizontal direction. 15. The production method according to claim 1, in which the ratio (a / b) of the heat released during combustion (kcal / h) per unit time of operation of the combustion burner, related to the amount of loading b (l) of the starting material, is 400 or less. 16. The production method according to claim 1, in which the ratio (b / c) of the charge amount b (l) of the starting material to the amount from the electrodes is 350 or less. 17. The production method according to claim 1, in which the inner part of the mixer includes a channel for a cooling medium, and the mixer is cooled by passing a cooling medium in the channel of the cooling medium. 18. The production method according to claim 1, in which the electrodes are connected to an alternating current source with a frequency of at least 2.5 kHz. 19. The production method according to claim 1, in which the melting, clarification and mixing of the source material is carried out in one tank for melting. 20. The production method according to claim 1, in which the feeder communicates essentially with the Central part of the bottom of the tank for melting. 21. The production method according to claim 1, in which the glass product is obtained from a molten solution with a viscosity of at least 1.5 Poise at a maximum temperature of the heating stage. 22. The production method according to claim 1, in which the content of OH groups in the resulting glass product is 570 million ^-1 or less. 23. The production method according to claim 1, in which the glass product is obtained from SiO ₂ -Al ₂ O ₃ -Li ₂ O or SiO ₂ -LiO ₂ . 24. A device for producing glass products, including:
a melting tank containing the molten solution of the starting material and including electrodes immersed in the molten solution;
a feeder connected to a melting tank,
heating means located at the top of the melting tank,
a forming die with which molten glass exiting the feeder is shaped; and
a mixer made with the possibility of installation in the inner part of the tank for melting and extraction from this area. 25. The receiving device according to paragraph 24, in which the inner part of the mixer includes a channel for a cooling medium, and ceramic material with a high coefficient of thermal expansion is provided on the outer peripheral region of the channel for a cooling medium, and ceramic material with a high coefficient of thermal expansion is coated with platinum or platinum rhodium alloy. 26. The receiving device according to paragraph 24, in which the inner part of the electrodes includes a device for cooling, and the electrodes pass essentially in a horizontal direction into the melting tank. 27. The device for producing according to paragraph 24, in which the horizontal surface of the inner region of the vessel for melting at least at the location of the electrodes has a n-gon configuration (n is an integer of at least 4). 28. The device for producing according to any one of paragraphs.24-27, in which the capacity for melting includes the lower part of the furnace wall containing the molten solution, and the upper part of the furnace wall located above the lower part of the furnace wall, and
the heating means includes a combustion burner provided on the upper part of the furnace wall.

Images