JP5265975B2 - Manufacturing method and manufacturing apparatus for glass molded body - Google Patents

Abstract

Provided are a glass-formed body manufacturing method and a manufacturing device which can support formation of a large-volume glass block and fully improve the homogeneity of glass. A glass-formed body manufacturing device (10) is provided with a melting tank (20) in which a melt of a raw material is housed and which comprises plural electrodes (21a, 21'a) immersed in the melt, a feeder (30) which communicates with the melting tank (20), a heating unit (40) provided in the upper portion of the melting tank (20), a forming die (50) for forming molten glass led out from the feeder (30), and a stirring body (60) insertable into and removable from the melting tank (20).  The molten glass is fabricated by heating the molten solution from above the molten solution by the heating unit (40) while conductively heating the molten solution by electrically connecting the plural electrodes (21a, 21'a), inserting the stirring body (60) into the melting tank (20) from outside after the raw material is melted, and stirring the molten solution by the stirring body (60).

Description

  The present invention relates to a method for manufacturing a glass molded body and a manufacturing apparatus.

  Conventionally, as a melting apparatus for continuously obtaining glass, a melting tank, a clarification tank, and a stirring tank are sequentially provided, and the raw material is replenished so that the level of the melt is always substantially constant. A continuous melting furnace is often used in which the melted liquid is sequentially moved to a clarification tank and a stirring tank.

  However, in such a continuous melting furnace, the outflow amount of glass per unit time cannot be increased beyond a certain amount. For this reason, it is difficult to form a large volume glass block that requires a large amount of glass to flow out per unit time. Therefore, Patent Document 1 discloses a batch-type melting furnace (a melting furnace that stops the refilling of raw materials when a certain amount of melt is obtained while stopping the outflow of glass, and then starts outflow of glass). A technique for forming a large-capacity glass block using the same is disclosed.

By the way, in order to obtain a homogeneous glass, it is necessary to sufficiently stir the melt. Stirring can also be performed by convection or bubbling of the melt, but it is desirable to mechanically stir the melt with a stir bar or the like, particularly when the melt has a high viscosity.
JP 2006-117525 A

  However, in the batch-type melting furnace shown in Patent Document 1, when performing melting, clarification, and stirring in a single melting tank, undissolved raw materials in the melting step act, It has been difficult to install a mechanical stirrer because of problems such as damage and deterioration due to alloying with platinum. For this reason, in the conventional batch type melting furnace, it is necessary to perform stirring by a method other than mechanical stirring, and as a result, improvement in the homogeneity of the glass tends to be insufficient.

The present invention has been made in view of the above circumstances, and provides a method and apparatus for manufacturing a glass molded body that can cope with the molding of a large volume glass block and can sufficiently improve the homogeneity of the glass. Objective. Here, the large-volume glass block refers to, for example, a block having a size of 0.3 m ³ or more. In addition, in this invention, glass contains the crystallized glass which heat-processed and crystallized amorphous glass and amorphous glass.

  The present inventors heated the melt from above the melt while energizing and heating the melt, and inserting and removing the stirrer at an appropriate timing, so that the temperature of the melt is appropriately controlled, The inventors have found that the melt can be sufficiently stirred while suppressing damage, and have completed the present invention. Specifically, the present invention provides the following.

(1) A method for producing a glass molded body in which glass flows out from a feeder communicating with a melting tank containing a raw material melt into a mold,
Supplying a raw material to the dissolution tank having a plurality of electrodes in the melt;
Heating the melt from above the melt while conducting the heating of the melt by energizing the plurality of electrodes,
A manufacturing method in which, after the raw materials are dissolved, a stirring body is inserted from the outside into the dissolution tank, and the melt is stirred by the stirring body.

  (2) In the heating step, the temperature of the melt in the range of ¼ or less of the melt depth from the bottom of the dissolution tank is set to ¼ or less of the melt depth from the liquid surface. (1) The manufacturing method as described in (1) which has a temperature difference setting process made higher than the temperature of the melt in the range.

  (3) The manufacturing method according to (2), wherein the temperature difference is 10 ° C. or more.

  (4) As the plurality of electrodes, those having a cooling mechanism inside and projecting substantially horizontally inward of the dissolution tank are used, and the plurality of electrodes are cooled by the cooling mechanism (1) to (3 ) Any one of the manufacturing methods.

  (5) The production according to any one of (1) to (4), wherein an inner horizontal section at least at an installation position of the plurality of electrodes is an n-gon (n is an integer of 4 or more). Method.

  (6) The manufacturing method according to any one of (1) to (5), wherein the height of the liquid surface is detected, and the amount of raw material supply and / or melt derivation is adjusted based on the detected value.

  (7) When the height from the bottom of the dissolution tank to the liquid surface is H, and the height from the bottom of the dissolution tank to the top of the plurality of electrodes is h, h / H is 0.1 to 0.1. (6) The production method according to (6), wherein the supply amount of the raw material is adjusted to be 0.6.

  (8) The manufacturing method according to any one of (1) to (7), wherein heating of the melt from above is performed using a combustion burner provided on an upper furnace wall positioned above the melt.

  (9) The ratio (A: B) of the volume (A) above the liquid level in the dissolution tank and the volume (B) of the melt is 1.0: 1.0 to 1.5: (8) The production method according to (8).

  (10) As the melting tank, a part or all of the upper furnace wall and / or the lower furnace wall in which the melt is accommodated is selected from the group consisting of an electroformed refractory, a refractory brick, and a ceramic fiber. The production method according to (8) or (9), wherein a material formed of seeds or more is used.

(11) as said dissolving tank, a portion in contact with at least the melt of the lower furnace wall and ZrO ₂ as a main material, used further contains SiO ₂ and / or _Al 2 _{O 3} (10) according Production method.

  (12) As the melting tank, a flue having an adjustable opening is provided on the upper furnace wall, and the opening of the flue is adjusted so that the internal pressure of the melting tank falls within a predetermined range. (8) The manufacturing method in any one of (11).

  (13) The manufacturing method according to any one of (8) to (12), wherein the liquid level is set such that a difference in height between the center position of the opening of the combustion burner and the liquid level is 300 mm or more.

  (14) The manufacturing method according to any one of (8) to (13), wherein the combustion burner is disposed so as to open upward in the horizontal direction or in the horizontal direction.

  (15) The ratio (a / b) of the combustion amount a (kcal / h) per unit time of the combustion burner to the supply amount b (L) of the raw material is set to 400 or less (1) to (14) Manufacturing method.

  (16) The manufacturing method according to any one of (1) to (15), wherein a ratio (b / c) of the supply amount b (L) of the raw material to the number c of the plurality of electrodes is 350 or less.

  (17) The manufacturing method according to any one of (1) to (16), wherein the stirrer has a refrigerant flow path therein and the refrigerant is circulated through the refrigerant flow path to cool the stirrer.

  (18) The manufacturing method according to any one of (1) to (17), wherein the plurality of electrodes are electrically connected to an AC power source having a frequency of 2.5 kHz or more.

  (19) The manufacturing method according to any one of (1) to (18), wherein the raw material is melted, clarified, and stirred in a single dissolution tank.

  (20) The manufacturing method according to any one of (1) to (19), wherein the feeder communicates with a substantial center of a bottom portion of the dissolution tank.

  (21) The manufacturing method according to any one of (1) to (20), which is applied to manufacturing a glass molded body having a melt viscosity of 1.5 poise or more at the maximum temperature during the heating step.

  (22) The production method according to any one of (1) to (21), wherein the obtained glass molded body has an OH group content of 570 ppm or less.

(23) The manufacturing method according to any one of (1) to (22), wherein the glass molded body is made of a SiO ₂ —Al ₂ O ₃ —Li ₂ O system or a SiO ₂ —Li ₂ O system.

(24) An apparatus for manufacturing a glass molded body,
A dissolution vessel having a plurality of electrodes in which a raw material melt is contained and immersed in the melt;
A feeder communicating with the dissolution tank;
Heating means provided in the upper part of the dissolution tank;
A mold for molding molten glass derived from the feeder;
A stirring device that can be inserted into and removed from the inside of the dissolution tank.

  (25) The stirrer has a refrigerant flow path therein, high-expansion ceramics are provided around the refrigerant flow path, and the high-expansion ceramics are coated with platinum or a platinum rhodium alloy (24 ) Manufacturing apparatus described.

  (26) The manufacturing apparatus according to (24) or (25), wherein each of the plurality of electrodes has a cooling mechanism inside and protrudes substantially inward of the dissolution tank.

  (27) The manufacturing apparatus according to any one of (24) to (26), wherein the dissolution tank has an n-sided horizontal cross section (n is an integer of 4 or more) at least at an installation position of the plurality of electrodes.

(28) The melting tank has a lower furnace wall for storing the melt, and an upper furnace wall provided on the upper part of the lower furnace wall,
The said heating means is a manufacturing apparatus in any one of (24) to (27) which has a combustion burner provided in the said upper furnace wall.

  According to the present invention, since the melt is heated by energization by the plurality of electrodes and is also heated from above, the raw materials are rapidly dissolved. Moreover, since the lower part of the melt is heated by energization heating, the convection of the melt is promoted, and clarification and homogenization are also quickly performed. And since a stirring body is inserted after fuse | melting a raw material, damage to a stirring body is suppressed, mechanical stirring becomes possible and the homogeneity of glass can fully be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a vertical sectional view of a glass molded body manufacturing apparatus 10 according to an embodiment of the present invention. FIG. 2 is a plan view of the manufacturing apparatus 10 before the raw material is charged (however, the upper wall 263 of the upper furnace wall 26 is seen through). The manufacturing apparatus 10 includes a dissolution tank 20, a feeder 30, a heating unit 40 as a heating unit, a mold 50, and a stirring body 60. Each component will be described in detail below.

[Dissolution tank]
The melting tank 20 contains a raw material melt. The raw material may be a batch (a mixture of raw material powders of each component) or a rough melt cullet obtained by vitrification of the batch, and is placed on a holding unit 73 provided at the front end of the main body 71 of the raw material supply unit 70. , And supplied through a supply hole 237 formed in the side wall 231′a. The supply hole 237 is formed so as to be openable and closable so that the temperature inside the dissolution tank 20 is not easily lowered, and is preferably opened when the raw material is supplied and closed during the rest.

  As shown in FIG. 2, the dissolution tank 20 has a plurality of electrodes 21a to 21d and 21′a to 21′d in the melt, and the plurality of electrodes 21a to 21d and 21′a to 21′d. Is electrically connected to a power source (not shown). When electricity is supplied from the power source to the electrodes 21a to 21d or 21'a to 21'd, energization is performed through the melt and the melt is heated. The temperature of the furnace and the melt are appropriately controlled in each step of melting, clarifying, and stirring the raw materials by heating by energization through the melt and heating from above of the melt by the heating unit 40 described later. Is possible. For example, when the raw material is melted from the state where the melting tank 20 is empty, the heating is performed only by the heating unit 40 until a certain amount of melt is obtained. Moreover, if the electrodes 21a to 21d and 21'a to 21'd are installed in the lower part of the dissolution tank 20, the electrodes 21a to 21d, 21'a to By increasing the degree of current heating by 21'd and relatively weakening the heating from above the melt, the temperature of the lower part of the melt becomes higher than the upper part. As a result, convection of the melt is promoted, and dissolution and clarification are rapidly performed. Can be

  The melt temperature in the range of ¼ or less of the melt depth from the bottom 233 of the dissolution tank 20 can be changed from the melt surface FL to the melt depth in that a strong melt convection can be easily obtained. It is preferable to make it higher than the temperature of the melt in a range of ¼ or less. This temperature difference is caused by the temperature sensors 22a to 22c provided inside the lower furnace wall 23 containing the melt and the temperature sensors (not shown) provided inside the electrodes 21a to 21d or 21'a to 21'd. May be performed by adjusting the degree of heating by the electrodes 21a to 21d or 21'a to 21'd and the heating unit 40 described later, based on the melt temperature of each part detected in step (b).

  Although the said temperature difference may be suitably set according to the viscosity etc. of a melt, it is preferable that it is 10 degreeC or more. The lower limit of the temperature difference is more preferably 25 ° C, and most preferably 40 ° C. Further, the temperature difference is preferably 150 ° C. or less, more preferably 130 ° C. or less, and most preferably 100 ° C. or less in order to suppress an increase in cost spent for energization and erosion of the furnace wall by the melt. Here, the temperature of the melt is measured as follows. That is, a temperature sensor such as a thermocouple coated with platinum is projected into the melt from a hole provided in the furnace wall, and measurement is performed by the temperature sensor. Or you may measure with the temperature sensor provided in the front-end | tip part inside of the electrodes 21a-21d protruded in the melt.

  It is preferable that the electrodes 21a to 21d and 21'a to 21'd have a cooling mechanism (not shown) inside and protrude substantially inward into the dissolution tank 20. Since the electrodes 21a to 21d and 21'a to 21'd are cooled by the cooling mechanism, deterioration due to a high-temperature melt can be suppressed. The cooling mechanism may be a conventionally known one. Further, since the electrodes 21a to 21d and 21'a to 21'd protrude substantially inward into the dissolution tank 20, the temperature of the melt can be rapidly increased by energization. The lower limit of the protruding length is preferably 20 mm, more preferably 50 mm, and most preferably 100 mm from the viewpoint that the temperature rise of the melt can be made efficient. The upper limit of the protruding length is preferably 700 mm, more preferably 600 mm, and most preferably 450 mm so that the amount of platinum or a platinum rhodium alloy that erodes into the melt when energized is minimized.

  The electrodes 21a to 21d and 21'a to 21'd are arranged to face each other as shown in FIG. 2, and are a pair of electrodes 21a and 21'a, a pair of electrodes 21b and 21'b, and an electrode 21c and 21 Energization is performed between the pair of 'c and the pair of electrodes 21d and 21'd (the number of electrodes is eight). Here, it is preferable that the ratio (b / c) of the feed amount b (L) of the raw material to the number c of the plurality of electrodes is 350 or less in that homogenization of the melt by convection of the melt can be promoted. When b / c exceeds 350, the degree of current heating to the melt tends to be insufficient, and as a result, the promotion of convection tends to be insufficient. The upper limit of b / c is more preferably 325, and most preferably 300. Further, the lower limit of b / c is preferably 50, more preferably 65, and most preferably 75 in consideration of the installation cost of the electrode and the homogenization of the melt by convection.

  In order to prevent a portion where the heating is insufficient in the plane direction of the melt during such energization, the horizontal cross section inside the dissolution tank 20 at least at the electrode installation position is an n-square (n is an integer of 4 or more). And it is preferably an integer of 5 or more. That is, as shown in FIG. 5C, a horizontal cross section where n is 4 may be used, but in this case, there may be a place where current heating is relatively insufficient, such as a place surrounded by a dotted line. When n is preferably 5 or more, and most preferably 6 or more, such a portion is reduced. In the present embodiment, as shown in FIG. 2, the entire lower furnace wall 23 has an n-gonal horizontal section from the viewpoint of simplifying the configuration, but at least the internal horizontal section at the electrode installation position is an n-square shape. If it is. In order to make the heating of the melt in the plane direction uniform, it is more preferable that at least the internal horizontal cross section at the electrode installation position is a regular n-gon.

  In the present embodiment, the horizontal cross section is a regular octagon. However, the present invention is not limited to this, and for example, as shown in FIG. 5A, the side walls 231a to 231c and 231′a to 231′c are smooth with curved surfaces 232a to 232h. (That is, there is no corner), and the horizontal cross section may be a circle (for example, a perfect circle or an ellipse) as shown in FIG. 5B, that is, n may be infinite. However, from the viewpoint of easy installation of the electrodes, it is preferable that the portions where the electrodes 21a to 21d and 21'a to 21'd are installed are flat surfaces as shown in FIG.

  In addition, the power source connected to the electrodes 21a to 21d and 21'a to 21'd is not particularly limited, but may be an AC power source having a frequency of 2.5 kHz or more in that the heating efficiency of the melt can be improved. preferable.

  The dissolution tank 20 is provided with a liquid level detector 80. Based on the height value of the liquid level FL of the melt detected by the liquid level detector 80, the amount of supply of raw materials and / or derivation of the melt is determined. It is preferable to adjust. That is, when the detected value of the height of the liquid level FL falls within a predetermined range, the supply of the raw material is stopped, and the glass can flow out from a feeder 30 described later. When the detected value falls below the predetermined range, the supply of the raw material is performed. The raw material is supplied by the unit 70. Thereby, the quality of the glass can be stabilized, and deterioration due to the electrodes 21a to 21d and 21'a to 21'd being exposed to gas can be prevented. The liquid level detector 80 in the present embodiment is a device that emits near infrared rays from the semiconductor laser toward the liquid level FL and detects the reflected light, but is not limited thereto.

  Preferably, when the height from the bottom of the dissolution tank to the liquid surface is H and the height from the bottom of the dissolution tank to the top of the plurality of electrodes is h, h / H is 0.1 to 0. Adjust the feed rate of raw materials to be .6. Thereby, the relative positions of the electrodes 21a to 21d at the melt depth can be set to positions where effective convection of the melt can be obtained. If the liquid level becomes too high, the effect of heating by energization becomes insufficient, so the lower limit of h / H is more preferably 0.2, and most preferably 0.3. Moreover, since it becomes difficult to set the temperature difference in the vertical direction of the melt, the upper limit of h / H is more preferably 0.55, and most preferably 0.52.

[Heating section]
The heating unit 40 is provided in the upper part of the dissolution tank 20 and heats the melt from above the melt. As a result, the temperature is raised not only at the bottom but also at the top of the melt, so that it is possible to control the temperature of the melt in the vertical direction together with the current heating by the electrodes, and it is also advantageous in terms of speeding up the melting of the raw materials. is there. The heating unit 40 preferably has combustion burners 41a and 41b in terms of excellent temperature rise efficiency. These combustion burners 41a and 41b are provided in the upper furnace wall 26 located in the upper part of the lower furnace wall 23 which accommodates a melt. The combustion burners 41a and 41b in the present embodiment are arranged to face each other from the side wall 261 of the upper furnace wall 26 inward. Air combustion, oxyfuel combustion, or the like can be used as the combustion burners 41a and 41b, but oxyfuel combustion is preferred from the viewpoint of enabling high-temperature dissolution.

  When a combustion reaction is performed by the combustion burners 41a and 41b, OH groups are generated in the atmosphere. Since this OH group tends to lower the thermal stability of the glass when mixed in the melt, in particular in the case of producing crystallized glass, an unstable crystal due to the difference in the crystallization rate due to the OH group distribution. From the standpoint of preventing quality degradation and cracking caused by growth and the occurrence thereof, it is highly necessary to suppress the mixing of OH groups into the melt. Therefore, the ratio (A: B) of the volume (A) above the liquid level FL in the dissolution tank 20 and the volume (B) of the melt is set to 1.0: 1.0 to 1.5: 1. It is preferably 0. When A is excessive with respect to B, the amount of combustion becomes excessive and the life of the refractory is likely to be shortened, and when A is excessively small with respect to B, glass containing a high amount of OH groups is likely to be produced. A: B is more preferably 1.0: 1.0 to 1.4: 1.0, and most preferably 1.1: 1.0 to 1.35: 1.0. Here, the “volume (A) above the liquid level FL in the dissolution tank” refers to the volume occupied by gas in the dissolution tank, and is usually a value obtained by subtracting the volume of the melt from the total volume of the dissolution tank 20. be equivalent to. Usually, it is assumed that the adjustment of A: B is performed by increasing / decreasing the melt volume B through the supply of raw materials and / or the derived amount of the melt. You may go.

  The liquid level FL is preferably set so that the height difference α between the center position of the openings 43a and 43b of the combustion burners 41a and 41b and the liquid level FL is 300 mm or more. Accordingly, the openings 43a and 43b, which are generation sources of OH groups, are sufficiently separated from the melt, so that mixing of OH groups into the melt can be further suppressed. The lower limit of the height difference α is more preferably 350 mm, and most preferably 400 mm. In addition, if the height difference α is excessive, the heating efficiency of the melt may be insufficient. Therefore, the upper limit of the height difference α is preferably 850 mm, more preferably 700 mm, and most preferably 650 mm. The liquid level FL may be set through the supply of raw materials and / or the amount of melt derived.

  Moreover, it is preferable that the combustion burners 41a and 41b are arranged so as to open in the horizontal direction or upward in the horizontal direction as in the present embodiment. If the combustion burner is opened downward from the horizontal direction, the flame is directed to the melt, so that there is an increased risk of mixing OH groups into the melt. However, according to the above configuration, such a risk is reduced. Therefore, mixing of OH groups into the melt can be further suppressed. The upper furnace wall 26 in this embodiment has a shape in which the side wall 261 has a diameter larger than that of the side wall 231 of the lower furnace wall 23 for the same effect, and the openings 43a, 41a, 41b of the combustion burners 41a, 41b. Although 43b is hidden from the melt, it is not limited to such a configuration.

  The ratio (a / b) of the combustion amount a (kcal / h) per unit time of the combustion burners 41a and 41b to the supply amount b (L) of the raw material is 400 in that mixing of OH groups into the melt can be further suppressed. The following is preferable. If a / b is excessive, that is, if excessive combustion is performed with respect to the supply amount of the raw material to be heated, the amount of OH groups mixed into the melt per unit amount tends to increase. The upper limit of a / b is more preferably 350, and most preferably 330. Considering that heating of the melt becomes insufficient and dissolution is delayed when a / b is too small, the lower limit of a / b is preferably 50, more preferably 70, and most preferably 100. It is. The combustion amount a (kcal / h) can be calculated based on the supply amount of gas (for example, oxygen gas or hydrocarbon gas) supplied to the combustion burners 41a and 41b. The raw material supply amount b (L) is the volume (unit: liter) of the raw material supplied to obtain the amount of melt accommodated in the dissolution tank at that time.

In the present embodiment, the heating portion 40 the combustion burner 41a, was constructed in 41b, is not limited thereto, MoSi ₂ heating element (e.g. Kanthal Corp. of "Cantal Super") or SiC heating elements (e.g. Tokaikonetsukogyo Co. Elema heating element) or the like.

  Returning to the explanation of the melting tank again, a part or all of the upper furnace wall 26 and / or the lower furnace wall 23 is formed of at least one selected from the group consisting of electroformed refractories, refractory bricks, and ceramic fibers. It is preferable. Thereby, deterioration of the upper furnace wall 26 due to a high temperature atmosphere generated by combustion in the combustion burners 41a and 41b and / or deterioration of the lower furnace wall 23 due to contact with a high temperature melt can be suppressed. In addition, in the point which can enjoy such an effect to the maximum, all of the lower furnace wall 23 and the upper furnace wall 26 are formed with one or more types selected from the group consisting of electroformed refractories, refractory bricks, and ceramic fibers. It is preferable that

In the lower furnace wall 23, it is preferable that at least a portion in contact with the melt is mainly composed of ZrO ₂ and further includes SiO ₂ and / or Al ₂ O ₃ . The durability can be improved by using ZrO ₂ as the main material, and the stability of ZrO ₂ can be improved by using SiO ₂ and / or Al ₂ O ₃ together, which greatly improves the erosion of the furnace wall by the melt. it can. This effect is particularly noticeable in SiO ₂ —Al ₂ O ₃ —Li ₂ O glass. In the present embodiment, the entire lower furnace wall 23 is formed of a material having substantially the same composition from the viewpoint of simplification of the configuration. However, it is only necessary that at least a portion in contact with the melt is formed of the material having the above composition. Further, depending on the situation, a portion where the glass liquid surface is easily eroded, particularly the melt FL portion, can be cooled from the outside to prevent erosion.

  The upper furnace wall 26 of the melting tank 20 is provided with a flue 28 whose opening degree can be adjusted, and the opening degree of the flue 28 may be adjusted so that the internal pressure of the melting tank 20 falls within a predetermined range. preferable. Thereby, while being able to stabilize the quality of a glass molded object, since it is suppressed that OH group accumulate | stores in the dissolution tank 20, mixing of the OH group to a melt can be suppressed more. In the present embodiment, the opening of the flue 28 is adjusted by the regulating valve, but is not limited to this.

  In the present embodiment, the upper furnace wall 26 has a rectangular horizontal cross section, and the flue 28 is provided on one side of the side wall 261 where the combustion burners 41a and 41b are not provided. An introduction pipe 29 is provided on the opposite side of the flue 28, and the introduction pipe 29 communicates the inside of the dissolution tank 20 with the outside air. Depending on the opening of the flue 28, outside air is introduced into the dissolution tank 20 from the introduction pipe 29, and this outside air pushes the inside air of the dissolution tank 20 containing OH groups to the outside through the flue 28. It is preferable that the flue 28 and / or the introduction pipe 29 are provided at the same height as or lower than the combustion burners 41a and 41b in that the OH group can be further prevented from being mixed into the melt.

[Stirring body]
The stirring body 60 is configured to be inserted into and removed from the inside of the dissolution tank. After the raw materials are dissolved, the stirring body 60 is inserted from the outside into the dissolution tank 20 to stir the melt. That is, since the stirrer 60 is disposed outside the dissolution tank 20 during the melting step in which undissolved raw materials that may attack the stirrer exist, deterioration of the stirrer 60 can be suppressed. Moreover, the deterioration of the quality of the glass by the component which comprises the stirring body 60 being taken in into a melt can also be suppressed.

  FIG. 3 is a view showing an aspect in which the stirring body 60 is inserted into the dissolution tank 20. While not in the stirring step, the open / close window 235 provided above the melt surface FL in the side wall 231 is closed to seal the inside of the dissolution tank 20. On the other hand, after the dissolution step is completed, immediately before the stirring step. Then, as shown in FIG. 3A, the opening / closing window 235 opens to form the opening / closing port 236, and the stirring member 60 can be inserted. Here, the stirrer 60 in the present embodiment has a rod-like base 61 connected to a drive source, and bends at a substantially right angle at a bent portion 63 provided in the middle of the base 61 to reach the tip 65. . The opening / closing port 236 has a width dimension larger than the length from the bent portion 63 to the distal end portion 65 and a vertical width dimension larger than the diameter of the base portion 61 (usually has a horizontally long shape). The stirring body 60 is inserted in a state where the part from the tip part 65 to the tip part 65 is laid down horizontally (FIG. 3B). When the tip 65 is inserted into the dissolution tank 20, the base 61 is rotated and the tip 65 is immersed in the melt (FIG. 3C). Thereafter, by operating the drive source, the tip 65 moves in the melt, and the melt is mechanically agitated. Here, the lateral width of the opening / closing port 236 should have such a dimension that the opening / closing window 235 does not contact the base 61 when the tip 65 moves in a desired path in the melt. When the stirring is finished, the stirring body 60 and the opening / closing window 235 are sequentially returned to the states shown in FIGS. 3B and 3A, and the stirring body 60 is returned to the outside of the dissolution tank 20.

FIG. 4 is a partially enlarged cross-sectional view of the stirring body 60. The stirrer 60 has a refrigerant flow channel 66 inside, a high expansion ceramic 67 is provided around the refrigerant flow channel 66, and the high expansion ceramic 67 is covered with platinum or a platinum rhodium alloy 68. preferable. Since platinum or the platinum rhodium alloy 68 is excellent in stability, the stirring can be performed while suppressing the mixing of foreign matters into the melt, and the deterioration of the stirring body 60 can be suppressed by the coolant flowing through the coolant channel 66. In addition, by interposing ceramics between platinum or platinum rhodium alloy 68 and refrigerant flow channel 66, the amount of platinum or platinum rhodium alloy used can be reduced to reduce manufacturing costs, and high expansion ceramics can be used as ceramics. As a result, the expansion characteristics accompanying the temperature change approximate to that of platinum or the platinum rhodium alloy 68, and as a result, damage to the stirrer 60 due to deformation can be suppressed. Thus, high expansion ceramics refers to ceramics whose expansion characteristics under the temperature conditions in the stirring process are similar to those of platinum or platinum rhodium alloys, and are appropriately selected according to the temperature conditions. Al ₂ O ₃ —CaO-based ceramics can be used. In addition, the refrigerant | coolant which distribute | circulates the refrigerant | coolant flow path 66 is not specifically limited, Liquids, such as water and oil, and gas, such as air, may be sufficient.

  In this way, by performing melting, clarification, and stirring of the raw materials in the single dissolution tank 20, a large amount of molten glass can be derived per unit time from a feeder 30 described later. Can be used for molding. However, the present invention is not limited to this, and melting, clarification, and stirring of raw materials may be performed in combination with a plurality of dissolution tanks.

[feeder]
The feeder 30 can start and stop the outflow by an outflow control means (not shown), communicates the melting tank 20 to the outside world, and guides the molten glass in the melting tank 20 to the mold 50. Specifically, molten glass flows into the communication port 33 facing the melt and is led out from the outlet 35 to the molding die 50 through the main body 31. Such a feeder 30 is formed of platinum or a platinum alloy so as to suppress foreign matters from being mixed into the molten glass.

  The feeder 30 is preferably provided at the bottom portion 233 of the melting tank 20 and more preferably provided substantially at the center of the bottom portion 233 in that molten glass with higher homogeneity can be derived. Here, the approximate center of the bottom is a similarity in which, in the projection of the bottom along the vertical axis direction of the dissolution tank 20, the center of gravity of the projection of the bottom coincides with the center of gravity, and the area is 10% of the area of the projection of the bottom. It refers to any point in the area surrounded by the shape.

  The communication port 33 of the feeder 30 is preferably arranged above the bottom portion 233 in terms of being able to lead out molten glass with higher homogeneity. However, the electrodes 21a to 21d, 21 ′ are not so disturbed as to prevent current heating. It must be located below the installation height of a to 21′d.

[Molding mold]
The mold 50 molds molten glass led out from the feeder 30. The mold 50 has a size that matches the desired size of the glass molded body. For example, when a large volume glass block is desired, the large volume mold 50 is used. In addition, it is preferable to provide a mechanism that can increase or decrease the distance between the outlet 35 and the mold 50. As a result, even if the amount of molten glass derived and accumulated in the mold 50 is successively increased, the falling distance of the molten glass derived from the outlet 35 is always kept at a minimum. Mixing of bubbles and striae can be suppressed.

  It is preferable to apply the manufacturing method of the glass molded object using the above manufacturing apparatus 10 to manufacture of the glass molded object whose viscosity of the melt in the highest temperature during a heating process is 1.5 poise or more. Thus, even in a glass whose melt is highly viscous, clarification is promoted by convection and mechanical stirring is performed by the stirring body 60, so that the homogeneity of the glass can be sufficiently improved. The lower limit of the melt viscosity at the highest temperature during the heating step is more preferably 1.7 poise, most preferably 1.8 poise. On the other hand, if the melt viscosity is excessive, the viscosity of the melt at the highest temperature during the heating process, taking into account that manufacturing costs are likely to increase as a result of the enormous energy required for convection and mechanical stirring. The upper limit is preferably 3.0 poise, more preferably 2.8 poise, and most preferably 2.7 poise.

  Moreover, content of OH group of the glass molded body obtained in this way is 570 ppm or less. Such a glass molded body is useful as a low expansion glass product excellent in heat resistance. The upper limit of the OH group content in the glass molded body is more preferably 540 ppm, and most preferably 500 ppm. Further, considering the balance between the effect obtained by reducing the OH group content and the accompanying increase in production cost, the lower limit of the OH group content of the glass molded body is preferably 50 ppm, more preferably 150 ppm, most preferably 200 ppm.

The OH group content in the glass molded body can be calculated using the following Lambert-Beer equation.
C = log ₁₀ (Ta / Tb) / αt
(In the formula, C is the content (ppm) of OH molecules, and α is the molar absorption coefficient of water (8.6 L).
/ Mol · mm), t is the thickness of the polished glass (mm), Ta and Tb are the transmissivity (%) at each wavelength, and more specifically, Ta is a maximum value near a wavelength of 2.0 μm. Tb is a transmittance showing a minimum value in the vicinity of a wavelength of 2.21 μm. )

The glass molded body is preferably made of a SiO ₂ —Al ₂ O ₃ —Li ₂ O system. Such a SiO ₂ —Al ₂ O ₃ —Li ₂ O-based glass molded body is a low-expansion glass molded body useful for various applications such as an exposure apparatus for semiconductor manufacturing and an astronomical telescope, but the melting temperature of raw materials. It is also known that the viscosity of the melt is extremely high. However, according to the manufacturing method of the present invention, by using heating from above with the combustion burners 41a and 41b and energization heating with the electrodes 21a to 21d and 21'a to 21'd in combination, the raw material can be quickly and sufficiently obtained. Is dissolved, and clarification is performed quickly and sufficiently by promoting convection, so that a SiO ₂ —Al ₂ O ₃ —Li ₂ O-based glass molded article excellent in homogeneity can be produced. Moreover, since mixing of OH groups into the melt is suppressed, an extremely low expansion glass molded body can be obtained. The production method of the present invention is also suitable for producing amorphous glass for hard disk substrates, crystallized glass for hard disk substrates, and crystallized glass for optical communication filters made of SiO ₂ —Li ₂ O.

[Temperature conditions]
It is preferable that the temperature conditions of each step when manufacturing the SiO ₂ —Al ₂ O ₃ —Li ₂ O-based glass using the above manufacturing apparatus 10 are set to the following values.

  First, when the batch is charged from the state where the dissolution tank 20 is completely empty to obtain a melt, the temperature of the internal space of the dissolution tank 20 is set to 1530 to 1550 ° C. by the heating unit 40 so that the melt can be obtained quickly. It is preferable to do.

  Once the dissolution tank 20 is filled with a certain amount of melt, the melt in the dissolution tank 20 is prevented from becoming less than a certain amount unless the glass composition is changed. That is, the amount of melt is controlled so that a certain amount of melt remains in the melting tank 20 even after the amount of molten glass necessary for manufacturing one glass block has flowed out.

  After finishing one outflow for manufacturing the glass block, the raw materials are supplied and melted in the melt until reaching a certain level (dissolution step). The temperature in this step is preferably 1450 ° C. to 1550 ° C., more preferably 1460 ° C. to 1540 ° C., and most preferably 1480 in the upper part of the melt so that platinum deterioration and undissolved residue (cause of foreign matter) can be suppressed. ℃ -1500 ℃.

  After the raw materials are completely dissolved, clarification and stirring are simultaneously performed (clarification / stirring step). The temperature in this step is preferably 1480 ° C. to 1580 ° C., more preferably 1500 ° C. from the viewpoint of reducing combustion energy by the heating unit 40 and suppressing crystal precipitation on the glass surface in the upper part of the melt. -1560 ° C, most preferably 1510 ° C-1540 ° C. The temperature at the lower part of the melt is preferably 1530 ° C. to 1600 ° C., more preferably 1540 ° C. to 1595 ° C., and most preferably so that homogenization of the melt by convection can be promoted and deterioration of platinum can be suppressed. 1550 ° C to 1590 ° C.

<Example 1>
Using the glass molded body manufacturing apparatus 10 described above, 54.5 to 57% SiO ₂ component, 6.0% to 8.5% P ₂ O ₅ component, 22.0 to 20% by mass based on oxide. 26.0% Al ₂ O ₃ component, 3.5-4.2% Li ₂ O component, 0.6-1.6% MgO component, 0.4-1.4% ZnO component, 0 0.7-2.0% CaO component, 0.6-1.7% BaO component, 1.6-2.7% TiO ₂ component, 1.0-2.2% ZrO ₂ component, and A batch raw material containing 0.8 to 1.2% of As ₂ O ₃ component is charged, and oxygen is supplied to the combustion burners 41a and 41b in a state where the height H from the bottom 233 of the dissolution tank 20 to the liquid level is 976 mm. Is applied to the electrodes 21a to 21d and 21'a to 21'd, which are burned and protrude horizontally 120 to 130 mm inward of the dissolution tank. It melt | dissolved by supplying alternating current of 0.0kHz, Then, the stirring body 60 was inserted, and clarification and stirring were performed. During this time, the temperature in the electrode provided with a temperature sensor (the detected value is referred to as an upper temperature) provided with a height of 750 mm from the bottom 233 and an electrode provided with a height of 230 mm from the bottom 233. When measured with a sensor (the detected value is referred to as the lower temperature), the upper temperature was 1516-1530 ° C, the lower temperature was 1580-1589 ° C, and the lower temperature was higher than the upper temperature with a temperature difference of about 60 ° C. . Thereby, it is estimated that the convection of the melt is promoted. At this time, the volume (A) above the melt level FL in the dissolution tank 20 is 2.766 m ³ , the melt volume (B) is 3.281 m ³ , and A: B = 1.19. : 1. The height difference between the center position of the opening of the combustion burner and the liquid level was 612 mm. The raw material supply amount b was 1020 (L), the combustion amount a per unit time was 240000 (kcal / h), and a / b was 235.2. The height h up to the top of the plurality of electrodes was 400 mm. Since the number c of electrodes was 8, b / c was 127.5.

  The molten glass obtained in this way was led out to a mold 50 and slowly cooled after molding to produce a glass molded body having a diameter of 1700 mm and a thickness of 400 mmt. The stirrer 60 was rotated until the molten glass was led out to the mold 50, and returned to the outside of the melting tank 20 after the molten glass was led out. The glass molded body was cut to a thickness of about 10 mm, and a polarizing adhesive film was adhered to the surface of the cut piece, and then a surface image was obtained with graphic software. The result is shown in FIG. Moreover, when content of OH group in a glass molded object was computed based on the above-mentioned Lambert-Beer formula, it was 424-566 ppm.

(Comparative Example 1)
A glass molded body is manufactured in the same manner as in Example 1 except that the electrodes 21a to 21d and 21'a to 21'd are not installed, and a manufacturing apparatus having the same configuration as the manufacturing apparatus 10 is used. did. The upper temperature during dissolution, clarification, and stirring was 1602-1604 ° C., and the lower temperature was 1544-1546 ° C. The upper temperature was higher than the lower temperature. Thereby, it is estimated that the convection of the melt is not performed. A surface image of the cut piece is shown in FIG.

  As shown in FIG. 7, it was found that the glass molded body produced in Example 1 was homogeneous and striae were extremely suppressed. In contrast, as shown in FIG. 6, the glass molded body produced in Comparative Example 1 was found to have low homogeneity and striae.

<Reference Example 1>
In order to verify the effect that the ratio of the volume (A) above the melt level FL and the volume (B) of the melt has on the OH group content in the glass molded body, the following test was conducted. . First, the volume (A) above the melt level FL in the dissolution tank 20 is 1.369 m ³ and the melt volume (B) is 1.768 m ³ (A: B = 0.77: 1). ) A glass molded body was produced in the same procedure as in Example 1 except that the raw materials were added as described above. It was 953-998 ppm when content of OH group in this glass molded object was computed based on the above-mentioned Lambert-Beer formula. Here, the transmittance was measured using a 270-30 type infrared spectrophotometer manufactured by Hitachi, Ltd. using a glass molded body polished to a thickness of 10 mm before crystallization heat treatment as a sample, and at a wavelength of about 2.0 μm. The maximum value of the transmittance was Ta, and the minimum value of the transmittance around the wavelength of 2.21 μm was Tb. These transmittances include the surface reflection loss.

<Reference Example 2>
In order to verify the effect of the ratio of the number of electrodes and the supply amount of raw materials on the OH group content in the glass molded body, the following test was performed. In Reference Example 2-1, a manufacturing apparatus with four electrodes (the horizontal cross section of the lower furnace wall 23 is square) is used, and in Reference Examples 2-2 to 2-7, a manufacturing apparatus with eight electrodes (lower part). A glass molded body was manufactured in the same procedure as in Example 1 except that the horizontal cross section of the furnace wall 23 was a regular octagon) and the conditions shown in Table 1 were changed. In Reference Example 2-7, the stirring time was set shorter than that of the other reference examples, and the stirring time was set to 3/5 of the other reference examples.

(Comparative Example 2)
In Comparative Example 2, a glass molded body was produced in the same procedure as in Reference Example 2-1, except that stirring was not performed.

  Table 1 also shows the OH group content, the degree of striae, and the degree of foreign matter contamination in the glass molded bodies produced in Reference Example 2 and Comparative Example 2. In Table 1, the standard of striae means ◎: not observed at all, ○: almost not observed, △: observed slightly, x: generated a lot, respectively. (Double-circle): It does not mix at all, (circle): Almost not mixed, (triangle | delta): It mixed a little, and x: It was mixed in large quantities, respectively.

  As shown in Table 1, in Reference Examples 2-1 to 2-7, the degree of striae and foreign matter was better than that in Comparative Example 2. Thereby, it turned out that the striae and foreign material mixing which arise in a glass molded object can be suppressed by stirring. Moreover, in Reference Examples 2-2 to 2-6, it was found that the degree of striae and foreign matters is low, and an excellent glass molded body can be produced.

<Reference Example 3>
In order to verify the effect of the OH group content in the glass on crystallization, the SiO ₂ —Al ₂ O ₃ —Li ₂ O glass having the same composition as that of Example 1, each having a different OH group content. A series of glasses were prepared, and each glass was crystallized by heat treatment, and the good crystallization and the workability after crystallization were evaluated. The results are shown in Table 2. In Table 2, ◯ indicates good, Δ indicates intermediate, and X indicates poor.

  As shown in Table 2, a glass having an OH group content of 578 ppm or more is not good in crystallization and has poor workability after crystallization, whereas a glass having an OH group content of 548 ppm or less. Was found to be excellent in both crystallization and workability after crystallization. Thereby, it was confirmed that crystallization and the workability after crystallization can be improved by reducing the OH group content.

  Moreover, the surface image of the glass molded object after the crystallization whose content of OH group was 778 ppm and 548 ppm was acquired. The results are shown in FIG. 8 ((a) corresponds to 778 ppm and (b) corresponds to 548 ppm). As shown in FIG. 8, it was confirmed that the glass molded body having an OH group content of 778 ppm was cracked, but the glass molded body having an OH group content of 548 ppm was confirmed to be cracked. could not. Thereby, it was confirmed that generation | occurrence | production of the crack in the glass molded object at the time of crystallization can be suppressed by reducing OH group content.

It is a vertical sectional view of the manufacturing device of the glass forming object concerning one embodiment of the present invention. It is a horizontal top view of the manufacturing apparatus of FIG. It is a figure which shows the aspect of insertion of the stirring body which comprises the manufacturing apparatus of FIG. It is a partial expanded sectional view of the stirring body of FIG. It is a figure which shows the horizontal cross-sectional shape of the dissolution tank which comprises the modification of the said embodiment. It is an image which shows the homogeneity inside the glass molded object manufactured with the manufacturing method which concerns on a comparative example. It is an image which shows the homogeneity inside the glass molded object manufactured with the manufacturing method which concerns on one Example of this invention. It is a surface image of the glass molded object manufactured with the manufacturing method which concerns on one Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Glass forming body manufacturing apparatus 20 Melting tank 21 Electrode 23 Lower furnace wall 233 Bottom part 26 Upper furnace wall 28 Flue 30 Feeder 40 Heating part (heating means)
41 Combustion burner 43 Opening 50 Molding die 60 Stirrer 66 Refrigerant flow path 67 High expansion ceramics 68 Platinum or platinum rhodium alloy

Claims (28)

A method for producing a glass molded body in which glass flows out from a feeder communicating with a melting tank containing a raw material melt into a mold,
Supplying a raw material to the dissolution tank having a plurality of electrodes in the melt;
Heating the melt from above the melt while conducting the heating of the melt by energizing the plurality of electrodes,
A manufacturing method in which, after the raw materials are dissolved, a stirring body is inserted from the outside into the dissolution tank, and the melt is stirred by the stirring body.   In the heating step, the temperature of the melt in a range of ¼ or less of the melt depth from the bottom of the dissolution tank is set in a range of ¼ or less of the melt depth from the liquid surface. The manufacturing method of Claim 1 which has a temperature difference setting process made higher than the temperature of a melt.   The manufacturing method of Claim 2 which makes a temperature difference 10 degreeC or more.   4. The plurality of electrodes according to claim 1, wherein the plurality of electrodes have a cooling mechanism inside and project substantially horizontally toward the inside of the dissolution tank, and the plurality of electrodes are cooled by the cooling mechanism. 5. Production method.   The manufacturing method according to any one of claims 1 to 4, wherein the dissolution tank is one having an n-sided horizontal cross section (where n is an integer of 4 or more) at least at an installation position of the plurality of electrodes.   The manufacturing method according to claim 1, wherein the height of the liquid surface is detected, and the amount of raw material supply and / or melt discharge is adjusted based on the detected value.   When the height from the bottom of the dissolution tank to the liquid surface is H and the height from the bottom of the dissolution tank to the top of the plurality of electrodes is h, h / H is 0.1 to 0.6. The manufacturing method according to claim 6, wherein the supply amount of the raw material is adjusted so that   The manufacturing method according to any one of claims 1 to 7, wherein the heating of the melt from above is performed using a combustion burner provided on an upper furnace wall located above the melt.   The ratio (A: B) of the volume (A) above the liquid level in the dissolution tank and the volume (B) of the melt is 1.0: 1.0 to 1.5: 1.0. The manufacturing method of Claim 8.   As the melting tank, a part or all of the upper furnace wall and / or the lower furnace wall in which the melt is accommodated is at least one selected from the group consisting of electroformed refractories, refractory bricks, and ceramic fibers. The manufacturing method of Claim 8 or 9 using what was formed. The manufacturing method according to claim 10, wherein at least a portion of the lower furnace wall that contacts the melt is made of ZrO ₂ as a main material and further contains SiO ₂ and / or Al ₂ O ₃ as the melting tank.   9. The smelter opening is adjusted so that the inner pressure of the smelting tank is within a predetermined range by using a melting tank having a flue whose opening is adjustable provided on the upper furnace wall. To 11. The production method according to any one of 11 to 11.   The manufacturing method according to any one of claims 8 to 12, wherein the liquid level is set so that a height difference between a center position of the opening of the combustion burner and the liquid level is 300 mm or more.   The manufacturing method according to any one of claims 8 to 13, wherein the combustion burner is disposed so as to open in a horizontal direction or upward from the horizontal direction.   The manufacturing method according to any one of claims 1 to 14, wherein a ratio (a / b) of a combustion amount a (kcal / h) per unit time of the combustion burner to a supply amount b (L) of the raw material is 400 or less.   The manufacturing method according to claim 1, wherein a ratio (b / c) of the supply amount b (L) of the raw material to the number c of the plurality of electrodes is set to 350 or less.   The manufacturing method according to any one of claims 1 to 16, wherein the agitator has a refrigerant flow path therein, and the agitator is cooled by circulating the refrigerant through the refrigerant flow path.   The manufacturing method according to claim 1, wherein the plurality of electrodes are electrically connected to an AC power source having a frequency of 2.5 kHz or more.   The manufacturing method according to any one of claims 1 to 18, wherein the raw material is melted, clarified, and stirred in a single dissolution tank.   The said feeder is a manufacturing method in any one of Claim 1 to 19 connected to the approximate center of the bottom part of the said dissolution tank.   The manufacturing method according to any one of claims 1 to 20, which is applied to manufacture of a glass molded body having a melt viscosity of 1.5 poise or more at a maximum temperature during the heating step.   The production method according to any one of claims 1 to 21, wherein the glass molded body to be obtained has an OH group content of 570 ppm or less. The process according to any one of claims 1 22 for the glass molded body made of _{SiO 2 -Al 2 O 3 -Li 2} O system or _SiO 2 -Li ₂ O system. An apparatus for manufacturing a glass molded body,
A dissolution vessel having a plurality of electrodes in which a raw material melt is contained and immersed in the melt;
A feeder communicating with the dissolution tank;
Heating means provided in the upper part of the dissolution tank;
A mold for molding molten glass derived from the feeder;
A stirring device that can be inserted into and removed from the inside of the dissolution tank.   25. The stirrer has a refrigerant flow path therein, high-expansion ceramics are provided around the refrigerant flow path, and the high-expansion ceramics are coated with platinum or a platinum rhodium alloy. manufacturing device.   26. The manufacturing apparatus according to claim 24 or 25, wherein the plurality of electrodes have a cooling mechanism therein and project substantially horizontally inward of the dissolution tank.   27. The manufacturing apparatus according to any one of claims 24 to 26, wherein the dissolution tank has an n-sided horizontal cross section (n is an integer of 4 or more) at least at an installation position of the plurality of electrodes. The melting tank has a lower furnace wall for storing the melt, and an upper furnace wall provided on the upper part of the lower furnace wall,
The manufacturing apparatus according to any one of claims 24 to 27, wherein the heating means includes a combustion burner provided on the upper furnace wall.