JP4777936B2 - Glass tube forming sleeve and glass tube manufacturing method - Google Patents

Description

  The present invention relates to a sleeve used for forming a glass tube using the Danner method and a method for manufacturing a glass tube using the sleeve.

  The Danner method has been widely used as a method for mass-producing glass tubes. In the Danner method, molten glass is guided on a sleeve that is supported obliquely downward and axially rotated, and the molten glass is wound around the sleeve. The glass is formed into a tubular or rod shape by continuously drawing out the glass, and is characterized in that it can be manufactured with higher accuracy than other glass tube manufacturing methods.

  As the sleeve material used in the Danner method, conventionally fired refractory ceramics such as alumina, mullite and zircon have been generally used. In recent years, when manufacturing glass tubes with particularly strict quality requirements, or when the glass composition is erosive to the refractory sleeve material and the conventional ceramic refractory is used, the life of the sleeve is significantly shortened. In this case, a sleeve in which platinum or a platinum alloy is coated on a part or the entire surface of the refractory is used.

  On the other hand, with regard to the characteristics required for glass tubes, higher dimensional accuracy and appearance characteristics are required for parts used in the electronics field, etc., electrical characteristics such as dielectric constant, physical characteristics such as softening point, or UV protection Various high demands are made according to the use such as optical characteristics represented by the above. In order to produce and supply glass tubes that meet these various characteristic requirements, various research and development have been conducted to obtain glass compositions that satisfy these characteristics. However, in almost all cases, the glass composition thus developed is more difficult to manufacture because it tends to cause devitrification when the glass tube is formed by the Danner method than the conventional glass composition. . In the Dunner method, in order to form a highly accurate tube suitable for molding, the temperature at the tip of the sleeve is strictly controlled so that the viscosity is suitable for molding, and the contact time with the sleeve is long. There is. Therefore, as a method for producing glass that is easily devitrified, the Danner method is a method for producing devitrification more easily than the updraw method or the bellows method.

Patent Document 1 describes a method of adjusting the atmosphere in which the sleeve is placed in order to suppress generation of bubbles during glass processing using the Danner method and to reduce the viscosity of the glass. Patent Documents 2 and 3 describe a method of using a specific glass composition and a method of providing a sleeve on a sleeve as solutions for preventing devitrification occurring on the inner surface of the tube glass. Furthermore, Patent Document 3 discloses a method for preventing devitrification by covering the outer surface of a refractory sleeve with glass having a softening point higher than that of a molded glass tube by 30 ° C. and not causing a reaction product with the refractory. Are listed.
Japanese Patent Application Laid-Open No. 08-283031 JP 09-012332 A Japanese Patent Laying-Open No. 2005-22882

  In order to manufacture and supply a glass tube that satisfies various high-level characteristic requirements as described above, the present inventors need a Dunner method that can manufacture a glass tube with high accuracy. The research was conducted with the recognition that it is particularly important to prevent devitrification on the surface.

  When devitrification occurs on the inner surface of the tube, depending on its size, it can be a major drawback in the manufacture of fluorescent lamps, for example. Depending on the size of the devitrification, there is a possibility of causing unevenness in the step of applying the phosphor to the inner surface of the tube, or causing peeling in the baking step after the coating.

  Patent Document 1 describes controlling the atmosphere outside the sleeve in the Danner method. However, this atmosphere control acts on the outer surface side of the molded tube, and does not prevent devitrification on the inner surface of the tube of the present invention.

  Patent Document 2 describes that the composition of the tube glass that is the object of molding is specified in order to prevent devitrification of the glass in the Danner method. However, this method has a problem of devitrification in the production of glass outside the range, that is, various glass tubes satisfying the above various required characteristics, even if devitrification disappears for the composition specified in Patent Document 2. It does not help solve the problem.

  Further, Patent Document 3 describes means for preventing the devitrification product from being generated by the reaction between glass and refractory. However, it is not applicable to devitrification caused by some of the components of the glass composition rather than reaction with refractories.

  Therefore, a large amount of high dimensional accuracy tube glass is produced, and there is a problem in the manufacture of glass tubes in which devitrification is prevented from occurring on the inner surface of the tube, that is, a large amount of high dimensional accuracy tube glass is produced using the Danna method. However, there is no description or suggestion in Patent Documents 1 to 3 regarding prevention of devitrification that occurs on the inner surface of the glass tube and is caused by a part of the glass composition component.

  The present invention provides a glass tube forming sleeve capable of mass-producing glass tubes having high dimensional accuracy that meet various high-level characteristic requirements using the Danner method, and can prevent the occurrence of devitrification on the inner surface of the tube. A glass tube manufacturing method that can be used for mass production of glass tubes with high dimensional accuracy that meets various high-level characteristic requirements and that prevents the occurrence of devitrification on the inner surface of the tube using the Danner method. The issue is to provide.

  As a result of various experiments, the inventors of the present invention have provided, in a tube glass manufacturing method by the Danner method, a sleeve provided with a hollow portion, an introduction tube for introducing gas into the hollow portion, and an exhaust pipe, and an oxidation gas in the hollow portion. Or a sleeve having a structure for introducing a reducing gas, and by using the sleeve to control a gas component in an internal space of at least a part of the hollow structure, the oxidizing or reducing gas introduced into the sleeve The generation of devitrification on the inner surface of the tube glass can be suppressed or prevented by applying an oxidizing action or a reducing action to the glass passing through the sleeve and reaching the outer surface of the sleeve and contacting the sleeve interface. The present invention has been found and the present invention has been made.

A sleeve for forming a glass tube of the present invention includes a cylindrical portion made of refractory, a blow pipe that passes through the cylindrical portion coaxially with the cylindrical portion, and a space between the cylindrical portion and the blow pipe as an axis of the cylindrical portion. A partition wall that is divided into a plurality of internal spaces at a surface intersecting with the internal space, and an introduction pipe and an exhaust pipe that communicate with at least one internal space of the plurality of internal spaces divided by the partition wall,
It is characterized in that the atmosphere in the internal space can be controlled by introducing gas from the introduction pipe into the internal space.

  In addition, the method for producing a glass tube of the present invention allows molten glass to flow down on a rotating glass tube forming sleeve having a cylindrical portion made of refractory with a blow pipe coaxially inserted, and from the tip of the sleeve. In a method of manufacturing a glass tube in which glass is continuously drawn and formed into a tubular shape, oxidizing or reducing gas is introduced into a hollow portion between a cylindrical portion of a sleeve and a blow pipe through an introduction tube, and is introduced into the sleeve interface. Devitrification generated on the inner surface of the glass tube is prevented by giving an oxidizing action or a reducing action to the glass in contact.

  According to the present invention, it is possible to effectively prevent devitrification on the inner surface of a tube when producing a tube glass that satisfies various high-level characteristic requirements and has a high dimensional accuracy by using the Danner method.

  Next, details of the present invention will be described by specifically describing embodiments of the present invention.

In the present invention, the refractory used for the sleeve is sprayed with a material that has low erosion due to contact with high-temperature glass, for example, a fired refractory such as alumina, mullite, or zircon, or a ceramic such as ZrO _{2 that} has high corrosion resistance Things can be used. If the apparent porosity of the refractory used in this sleeve is less than 1%, the gas inserted into the hollow portion may not sufficiently permeate to the interface, and the oxidation and reduction effects that occur at the sleeve / glass interface may not be sufficient. If the porosity exceeds 30%, the erosion resistance of the refractory to the glass is extremely lowered, and the life of the sleeve is significantly shortened. Therefore, the apparent porosity of the refractory used for the sleeve is preferably 1% or more, and more preferably 3% or more. Further, the apparent porosity of the refractory used for the sleeve is desirably 30% or less, and more desirably 25% or less.

  When molding glass that is highly eroded by refractory ceramics at high temperatures such as borosilicate glass, platinum material is used for part or all of the part that contacts the glass of the sleeve in order to maintain molding accuracy and quality. be able to.

  In this case, as the platinum material, at least one selected from platinum, a platinum rhodium alloy, or a platinum-gold alloy may be selected. As conditions for selecting these, the use temperature, the wettability of the glass, and the like are appropriately considered.

  As a method of forming a sleeve having a hollow portion by using platinum or a platinum alloy for at least a part of the sleeve, in addition to a method of processing and coating a platinum plate material on the refractory having the above porosity, the above refractory ceramics may be applied. There is a method in which platinum or a platinum alloy is coated by thermal spraying. It is also possible to give the platinum member itself strength and form a hollow structure with only the platinum material. In this case, in order to ensure mechanical strength, it is desirable to use a material such as platinum rhodium alloy, reinforced platinum, or reinforced platinum alloy.

In the present invention, examples of the gas used for each atmosphere adjustment include the following. Examples of the oxidizing gas include normal air containing oxygen gas and oxygen gas mixed with neutral gas. Examples of the reducing gas include H ₂ gas, CO gas, and hydrocarbon gas. Here, examples of the neutral gas include inert gases represented by N ₂ gas, CO ₂ gas, and Ar gas.

  Although the gas passes through the porous refractory ceramic sleeve, the passage of the gas is hindered at the site where platinum is used. Therefore, as a method of exerting a reducing action on the glass at the interface of the site where platinum is used, a gas containing hydrogen gas is used. It has been found that other gases cannot pass through platinum, but only hydrogen gas can pass through platinum and have a reducing action on the glass at the interface. It was also found that the hydrogen gas concentration must be 0.1% by volume or more in order to cause a reduction action using hydrogen gas.

  Since the sleeve is used at a high temperature, a slight gap is actually generated at a joint portion between the refractory ceramic sleeve and a metal member such as a fixture due to thermal expansion or the like. Then, hydrogen reacts with oxygen in the atmosphere leaking from the gaps, so it is necessary to add hydrogen excessively in order to keep the target portion reducible. A preferable hydrogen concentration for this purpose is 0.2% (volume%) or more. On the other hand, the upper limit of the hydrogen concentration in this case is intended to maintain the reducing property of the glass at the interface with the sleeve, so there is no particular limitation on the upper limit of the hydrogen concentration for this purpose. Since the environment in which the sleeve is arranged is in a high temperature state, in order to insert gas into this place, it is important to consider safety in handling. In order to avoid the explosion limit of hydrogen gas, the hydrogen concentration is preferably 4% or less. Therefore, considering the sleeve structure and safety, the desirable hydrogen concentration range is 0.2% to 4%.

As a result of earnest research, it has been found that the effect of adjusting the atmosphere in the present invention is particularly effective on the reducing action side, and particularly effective for glasses containing SiO ₂ , B ₂ O _{3, and} CeO ₂ . CeO ₂ -containing glass is unsuitable for dunner molding because of the high devitrification temperature of CeO ₂ itself, but the devitrification temperature is lowered by changing the devitrification species from CeO ₂ to CeBSiO ₅ . I found the fact that I can. This technique for lowering the devitrification temperature can be applied to borosilicate glass in which CeO ₂ is essential.

CeO ₂ but is often used in the glass as an absorbent of ultraviolet rays, the glass is likely to devitrify CeO ₂ is deposited comprising CeO _2. For this reason, the glass stays on the sleeve for a long time, and the moving speed of the glass becomes slower as it approaches the sleeve interface. Such glass is not suitable for tube forming by the Danner method. Since the occurrence of devitrification affects both temperature and time, devitrification is most likely to occur at the sleeve interface when the Danner method is used.

The effect of the present invention is that SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ — (Li ₂ O + Na ₂ O + K ₂ O) — (CaO + MgO + BaO + SrO) —CeO ₂ — (SnO + SnO ₂ ) — (ZrO ₂ + ZnO + Nb ₂ O ₅ ) This is particularly noticeable in the following composition range of the glass composition.

First, when the SiO ₂ is a network former of the glass exceeds 80% (wt%) reduced meltability, moldability of the glass, and in less than 55% decrease the chemical durability of the glass. When the chemical durability is lowered, it causes weathering or burns, and when used for a glass tube of a fluorescent lamp, it causes a decrease in luminance and uneven color. For this reason, the content of SiO ₂ is desirably 55 to 80%, and the content of SiO ₂ is more desirably 62 to 78%.

In addition, the inclusion of Al ₂ O ₃ has the effect of improving the devitrification property and chemical durability of the glass, and if the content of Al ₂ O ₃ exceeds 7%, striae occurs and the meltability is lowered. . Further, if the content of Al ₂ O ₃ is less than 1%, phase separation or devitrification is likely to occur, and the chemical durability of the glass is also lowered. For this reason, the content of Al ₂ O ₃ in the present invention is desirably in the range of 1 to 7%, and more desirably in the range of 2 to 5%.

B ₂ O ₃ is a component used for improving the meltability of the glass and adjusting the viscosity, but is very volatile, and if it exceeds 25%, it is difficult to obtain a homogeneous glass. Further, if the content is less than 1%, the meltability is remarkably lowered. For this reason, the content of B ₂ O ₃ in the present invention is 5% or more, more desirably 10% or more, and further desirably 12% or more.

Li ₂ O, Na ₂ O, and K ₂ O are components used to adjust the viscosity and thermal expansion coefficient while acting as a glass flux, improving the meltability of the glass. If the amount of each of these is less than the required content, the effect is not obtained, on the other hand, if the content of each exceeds the upper limit, the thermal expansion coefficient becomes too large, and the chemical durability Sex is reduced. The content of each component is preferably 0 to 3% for Li ₂ O, 0 to 8% for Na ₂ O, and ₂ to 12% for K ₂ O, and these may contain any of them alone. The inclusion of two or three types is desirable because effects such as improved insulation by mixed alkali can be expected. As for Na ₂ O, it is known that in the use of a fluorescent lamp, Na ₂ O reacts with mercury to form amalgam during lamp lighting. Excessive Na ₂ O in the glass results in a reduction in the amount of mercury that acts effectively in the fluorescent lamp, so from the environmental point of view of reducing the amount of mercury used, addition of Na ₂ O exceeding the above upper limit value. Is not desirable, more desirably 0 to 4%.

  CaO, MgO, BaO, and SrO are components that have the effect of lowering the viscosity of glass at high temperatures and improving the meltability, and can be added up to 5% in total if necessary. If the addition exceeds the upper limit, the glass state becomes unstable and devitrification tends to occur.

ZrO ₂ , ZnO, and Nb ₂ O ₅ are effective components for improving the resistance to ultraviolet solarization, so that they are added as necessary within a range not exceeding 5% when used in applications such as fluorescent lamps. When it exceeds 5%, devitrification becomes strong.

Further, CeO ₂ is a component that strongly absorbs ultraviolet rays, and is an essential component according to the present invention. When CeO ₂ is less than 0.1%, the effect of shielding ultraviolet rays is insufficient, and on the other hand, 5% When it exceeds, devitrification will become high, Therefore It is desirable to contain in the range between these.

Usually, Ce ions coexist in the state of Ce ³⁺ and Ce ⁴⁺ in glass, and Ce ³⁺ has an absorption band at 316 nm and Ce ⁴⁺ at 243 nm. Ce ³⁺ shows sharp absorption, whereas Ce ⁴⁺ shows broad absorption in the visible range, so that when the amount of addition increases, the glass is colored yellowish brown. In order to efficiently absorb ultraviolet light having a wavelength of 315 nm or less, which is ultraviolet light on the higher wavelength side, with colorless glass having no absorption in the visible region, the ratio of Ce ³⁺ needs to be increased. Since SnO has an effect of increasing the ratio of Ce ³⁺ , it is preferable to contain SnO, and 0.1% or more is contained in order to obtain this effect. However, if it exceeds 3%, devitrification becomes high, which is not desirable. Further, instead of SnO, it is possible to add C or an organic compound to produce the same effect. In this case, a clarification effect can be brought about at the same time by using Na ₂ SO ₄ together as a clarifier. Such a fining agent used in the glass melting of the present invention is desirably a reducing fining agent. A feature of the present invention is that good ultraviolet absorption characteristics can be obtained by controlling CeO ₂ used as an ultraviolet absorber to a state of Ce ³⁺ ions, and an oxidizing fining agent is not preferred. For similar reasons, the use of raw materials that act as oxidants should also be avoided. Specifically, NaCl or Na ₂ SO ₄ + C is desirable as the fining agent, and the use of Sb ₂ O ₅ or As ₂ O ₅ is not preferable. Also, alkaline component nitrates should not be used.

  Since the glass having the above composition is a borosilicate glass containing boric acid and an alkali metal oxide, it is desirable that at least a part of the surface of the sleeve material in contact with the glass is made of platinum from the viewpoint of erosion. If the glass contact surface is a refractory sleeve, the refractory is more or less eroded by the glass, forming a heterogeneous glass between the refractory and the glass. Accordingly, when the tube glass is formed, not only the forming accuracy of the tube is lowered, but also the roundness of the inner surface of the tube is lowered and the quality is remarkably lowered.

  For this reason, it is desirable to use platinum material for the glass erosion part where the most erosion occurs and the tip part which has a large influence on dimensional accuracy, and it is more desirable that the glass contact surface is made entirely of platinum or a platinum alloy. . The platinum material may be platinum, a platinum rhodium alloy, or a platinum-gold alloy, both of which are selected in a timely manner in consideration of operating temperature, glass wettability, and the like because they pass hydrogen gas. The hydrogen gas passes through the fired refractory having porosity, passes through the platinum material, reaches the glass interface, and can maintain the reducing action of the interface glass.

Next, the effect of the hydrogen-containing gas to be inserted will be described in detail. When the atmosphere of the sleeve hollow portion is not intentionally adjusted, CeO ₂ is in a state where Ce ³⁺ and Ce ⁴⁺ coexist in the glass, and Ce ions are likely to change in valence. For this reason, the glass at the interface of the sleeve is separated from the hydrogen of the OH group in the glass, the separated hydrogen passes through the platinum and diffuses into the sleeve, and the remaining oxygen converts Ce ³⁺ cerium ions in the glass to Ce ^4+. It is thought that it is oxidized. And it is thought that this is prevented by intentionally adjusting the atmosphere of the sleeve hollow portion. In particular, cerium ions in glass of this system have colorability in the Ce ⁴⁺ state, and may reduce the transmittance in the visible region when, for example, a fluorescent lamp is manufactured. For this reason, it is desirable that the Ce ions be in a Ce ³⁺ state in advance.

The present invention presupposes that a reducing agent such as SnO or carbon is added to the component in advance to melt in a reducing atmosphere and increase the ratio of Ce ³⁺ in the glass. In this case, the oxidation reaction is not suppressed, and the sleeve interface is in an oxidized state by the above-described reaction, which makes it easy to cause devitrification of CeO ₂ . In order to avoid this, hydrogen gas is inserted into the sleeve, and the interface glass can maintain the reduced state by the refractory and the hydrogen that has passed through the platinum. When the sleeve interface is maintained in a reduced state, CeO ₂ cannot be produced, and CeBSiO ₅ is likely to be preferentially generated. Not for purposes be generated devitrification CeBSiO ₅ in the present invention, generation of CeBSiO ₅ is compared to devitrification occurs temperature in the tube molding of CeO _2, found that low 50 ° C., the tube in the Danner method by doing so It has been found that devitrification generated on the surface can be prevented and more advantageous molding can be performed. In this way, even if the glass composition is the same, by maintaining the reducing atmosphere at the interface, it is possible to avoid the overlap between the forming viscosity and the devitrification temperature in actual tube forming, without causing devitrification on the inner surface of the tube. , Production can continue.

  Next, embodiments of the present invention will be described in more detail with reference to the drawings.

Example 1
FIG. 1 is a schematic cross-sectional view showing an embodiment of a glass tube forming sleeve according to the present invention. In FIG. 1, the sleeve 1 includes a sleeve shaft 4, a refractory cylinder 6, a heat-resistant metal fixing nut 8 and a fixture 9 that sandwich the cylinder 6 and fix it to the sleeve shaft 4. And a hollow portion 10 defined by being surrounded by a cylindrical portion 6 made of a refractory, a sleeve shaft 4, a fixing nut 8, and a fixture 9. Here, the cylindrical portion 6 made of refractory is made of a fired refractory such as alumina, mullite, or zircon. These fired refractories are permeable to gases such as hydrogen and oxygen. In the hollow portion 10, there is provided a partition wall 20 that crosses a sleeve tube axis formed of a refractory metal or the like, and the hollow portion 10 is divided into a sleeve front end side hollow portion 10a and a sleeve rear end side hollow portion 10b. ing.

  The sleeve shaft 4 fixed to the sleeve 1 is supported by the driving unit 5 so that the tip of the sleeve 1 is inclined downward, and is rotated. Heat resistant steel is preferably used for the sleeve shaft 4. The sleeve shaft 4 has a blow air supply hole 16 at its axis, and an opening at the upper part thereof is connected to a blow air supply device (not shown) via a blow pipe 17. Furthermore, a ring 13 is rotatably mounted on an annular concave groove provided in the fixture 9 by a plurality of bearings (not shown) to form an annular cavity 14 in which airtightness is maintained. A through pipe (introduction pipe) 12 a is attached to the hollow portion 14 so as to communicate with the distal end side hollow portion 10 a of the sleeve 1. A gas cylinder 11 filled with a gas whose components have been adjusted in advance is connected to the cavity 14 via a gas inlet pipe 18. Further, the distal end side hollow portion 10a communicates with a through hole 15 provided in the fixture 9 through a through pipe (exhaust pipe) 12b.

  In the glass tube forming apparatus having such a configuration, the refractory cylindrical portion 6 sandwiched between the fixing nut 8 and the fixture 9 via the sleeve shaft 4 by the drive portion 5 and fixed to the sleeve shaft 4 is centered on the axis. The molten glass A is supplied onto the outer surface of the rotating refractory cylinder 6, wound around the refractory cylinder 6 and moved to the tip of the sleeve 1, and then blow air supply device And is hollowed out by the air passing through the blow air supply hole 16 of the sleeve shaft 4, pulled out from the fixing nut 8 portion, and continuously formed into a glass tube.

  The manufacturing method of the glass tube which concerns on this invention can be implemented using the above apparatus structures. First, gas is fed into the hollow portion 10 of the sleeve 1 from the gas cylinder 11 through the gas feed pipe 18, the hollow portion 14, and the through pipe 12 a. When the gas is fed into the hollow portion 10, the gas penetrates into the refractory cylindrical portion 6. By maintaining this state, the selected glass exerts an oxidizing or reducing action on the molten glass A on the sleeve interface. As a result, the occurrence of devitrification at the interface between the molten glass A and the sleeve cylindrical portion 6 can be suppressed as described above.

At this time, for example, in the case of forming a glass tube with SiO ₂ , B ₂ O ₃ , or CeO ₂ -containing glass, by using a reducing gas such as H ₂ , CO, or hydrocarbon as an introduction gas, CeO ₂ crystal Precipitation can be prevented. Further, in this embodiment, by supplying gas only to the sleeve distal end side hollow portion 10a partitioned by the partition wall 20, devitrification precipitated in a relatively low temperature region on the sleeve can be effectively suppressed. became. According to this method, the intended purpose can be effectively achieved with a small amount of gas as compared with the case where gas is inserted into the entire hollow portion of the sleeve.

  In order to suppress devitrifying species that precipitate in a relatively high temperature region on the sleeve with respect to the glass tube forming temperature, the through pipe (introducing pipe) 12a and the through pipe (exhaust pipe) 12b are hollow on the sleeve rear end side. It is also possible to communicate with the portion 10b and supply gas to the rear end side hollow portion 10b.

(Example 2)
In the first embodiment, two sets of annular cavities 14 (rotary joints) are provided independently, and one of the cavities 14 communicates with the distal end side hollow portion 10a of the sleeve 1 through pipe (introducing pipe) 12a. The other cavity portion 14 is attached with a through pipe (introducing pipe) 12a so as to communicate with the sleeve rear end side hollow portion 10b, and provided with independent through pipes (exhaust pipes) 12b and 12b ′. It becomes possible to introduce different gases into the front end side hollow portion 10a and the rear end side hollow portion 10b. For example, in order to suppress devitrification deposited in a relatively low temperature region on the sleeve, a relatively high concentration or high pressure gas is supplied to the front end side hollow portion 10a corresponding to the devitrification temperature region, and the rear end side hollow portion is hollow. The portion 10b can be used in a preventive manner by supplying a gas having a relatively low concentration or low pressure, and the front-side hollow portion 10a is supplied with a highly reducing hydrogen-containing gas, and the rear-end-side hollow portion 10b can be used for supplying CO, hydrocarbon gas, or the like.

(Example 3)
FIG. 2 is a schematic cross-sectional view showing an embodiment of a glass tube forming sleeve according to the present invention. The sleeve 1 shown in FIG. 2 is coated with a platinum coating 7 on the outer surface of the sleeve tip side of the refractory cylindrical portion 6 constituting the sleeve 1 shown in FIG. 1 by a method such as plasma spraying or flame spraying. It was done. In addition, although platinum is used in the present Example, the metal selected from the group which consists of rhodium and those alloys other than platinum can be used similarly. By covering the outer surface of the sleeve tip side with platinum in this way, reaction between the molten glass and the refractory can be prevented, and deterioration of the glass tube forming accuracy due to erosion of the refractory can be prevented.

  Further, in this embodiment, the partition wall 20 is provided in the hollow portion 10 corresponding to the boundary between the site where the platinum coating 7 is applied and the site where it is not covered. In the sleeve configured as described above, the platinum-coated portion does not transmit a gas other than hydrogen. Therefore, by using a hydrogen-containing gas as the introduced gas, the glass on the platinum-coated 7 can be reduced. In the same manner as in Example A, the occurrence of devitrification can be suppressed at the platinum coating interface.

Example 4
In the same manner as in the third embodiment, in the sleeve in which the outer surface on the front end side of the sleeve of the refractory cylindrical portion 6 is coated with platinum 7, two sets of annular cavities 14 (rotary joints) are independently provided in the same manner as in the third embodiment. A through pipe (introduction pipe) 12a is attached to one of the hollow portions 14 so as to communicate with the distal end side hollow portion 10a of the sleeve 1, and the other hollow portion 14 communicates with the sleeve rear end side hollow portion 10b. A through-pipe (introducing pipe) 12a ′ is attached to each other, and independent through-pipes (exhaust pipes) 12b and 12b ′ are provided respectively, so that the hollow portion of the portion coated with platinum coating 7 and the hollow portion of the uncoated portion are provided. It is possible to control the internal atmosphere of the section independently.

  For example, a permeable hydrogen-containing gas is supplied to the front end side hollow portion 10a provided with the platinum coating 7, and CO, hydrocarbon gas, etc. are supplied to the rear end side hollow portion 10b not covered with platinum. The usage such as is possible.

  In Examples 2 and 4, an example in which the sleeve tip side surface is coated with platinum is shown. However, in order to prevent erosion of the refractory and to reduce bubble defects, a sleeve coated with platinum at a portion where high-temperature molten glass flows down is used. It is also possible to produce a glass tube using In that case, it is also possible to select an introduction gas corresponding to the platinum coating portion different from those of the above-described Examples 2 and 4.

(Examples 5-11, Comparative Examples 1-2)
In FIG. 3, the typical sectional drawing which showed the apparatus structure used by this Examples 5-11 and Comparative Examples 1-2 was shown. First, the raw material components of Examples 5 to 11 were weighed and mixed so as to have the composition shown in Table 1, and the obtained raw material mixture was placed in a quartz crucible or a platinum crucible, respectively, in an electric furnace 316. After being melted by heating at 1500 ° C. and sufficiently stirred and clarified, it was cast into a block shape. A portion without bubbles was selected from the glass block, cut into a shape of 3 mm thickness with a 20 mm square, and a sample 312 was prepared by mirror polishing so that bubbles were not caught on the interface side with platinum.

  In order to make this device imitate a sleeve having a hollow structure, a refractory was processed and manufactured to produce a structure 315 having a hollow portion in the refractory. A refractory ceramic having a predetermined porosity was selected as the structure 315, and platinum coating 313 was applied to the refractory ceramic. A heat-resistant metal tube 314 for introducing a gas was provided inside the structure 315. A leak portion was provided below the platinum-coated refractory so that the internal pressure would not rise too much, and a gas having a flow rate of 50 ml / min was sent into the hollow refractory to adjust the atmosphere.

  In Examples 5 to 9, a refractory having porosity is coated with a platinum material by the above-described method. In Examples 10 to 11, a sleeve of refractory ceramics having no porosity and having porosity is used. Using.

As the insertion gas, a gas cylinder adjusted in advance to a predetermined concentration is prepared, and N ₂ is selected and added to hydrogen as a balance gas in this cylinder. The balance gas does not need to be nitrogen in particular, and there is no problem as a balance gas as long as it is a chemically stable gas that does not react with hydrogen, such as argon and carbon dioxide. In order to match the devitrification occurrence conditions to tube forming as much as possible, after raising the temperature to 1250 ° C. which is a temperature range where devitrification does not occur so that the temperature gradient on the actual sleeve is maintained, Log η = 4.0, 4.8, 5.5 (where the unit of η is dPa · s), which is the viscosity of molding of each sample glass assuming the glass on the sleeve at the molding temperature of the dunner. The temperature was lowered to a predetermined temperature and maintained for 4 hours, and the interface glass with platinum was observed with a microscope to confirm the occurrence of devitrification. Viscosity log η set here is 4.0 (here, the unit of η is dPa · s), assuming the central part from the outlet of the sleeve, log η = 4.8 (here, the unit of η is dPa · s) is the sleeve This is the viscosity at the lowest temperature on the sleeve at the tip. The viscosity of log η = 5.5 (where the unit of η is dPa · s) is not the original molding viscosity on the sleeve, but devitrification was intentionally generated to investigate the crystal morphology. is there.

In the examples, no devitrification was observed at the platinum interface of the sample treated with log η = 4.0, 4.8 (here, the unit of η is dPa · s) on the sleeve. Devitrification was confirmed only at log η = 5.5, which is not the viscosity of the above. When the generated devitrification was analyzed by X-ray diffraction, the devitrification species was CeBSiO ₅ for the conditions of this example.

Next, Comparative Examples 1 and 2 for the above examples are summarized in Table 2. These comparative examples are described in Example No. 1 and no. Using the one sampled from the same sample glass of composition 4, devitrification occurred under the same processing conditions except that the hydrogen concentration in the atmosphere was processed under the condition of 0.1% by volume or less, Devitrification was confirmed at any viscosity. This devitrification, devitrification of CeBSiO ₅ and CeO ₂ Comparative Example 1 was subjected to analysis of devitrification in the same X-ray diffraction and embodiments mixed, Comparative Example 2 was confirmed only CeO ₂ .

  FIG. 4 is an X-ray diffraction chart for the samples of Example 5 and Comparative Example 2. From this figure, it can be seen that the form of devitrification at the interface changes with the reducing atmosphere.

From the above test, the glass treated with the same composition and the same temperature is maintained by reducing the atmosphere at the interface between the glass and the sleeve, and the devitrification of the interface is changed from CeO ₂ to CeBSiO ₅ , thereby forming the Danner method. It was found that devitrification is less likely to occur at temperature. In addition, it has been found that by using hydrogen gas, hydrogen has an internal gas tightness, thereby passing through the refractory and passing through platinum to bring about a reducing effect on the interface glass.

(Example 12, Comparative Example 3)
FIG. 5 is a diagram schematically showing the basic configuration of the glass tube manufacturing apparatus using the Danner method used in this example. In this glass tube manufacturing apparatus, the sleeve 501 is supported in an obliquely downward direction, and is rotated by a rotation driving device 503 in the axial direction about the sleeve shaft 502. In this configuration, the molten glass 505 flowing down from the trough 504 at a predetermined temperature is wound on the sleeve 501, and the tube glass is continuously formed while supplying blow air from the tip portion through the shaft 502 from the upper portion of the shaft 502.

  In the sleeve 501 having this hollow structure, a refractory cylinder made of a refractory is sandwiched and held by a fixing jig called a holding collar 506 made of a heat-resistant metal to form a hollow portion. Although not shown in the drawing, the presser collar is fixed by a spring from the upper part of the shaft so as to release the expansion of the shaft and the refractory ceramics.

  A sleeve shaft 502 for fixing the sleeve has a blow air supply hole 507, and an opening on the upper side thereof is connected to a blow air supply device (not shown in the drawing) via a blow pipe.

  Further, a rotatable jig called a rotary joint is attached to the upper portion of the presser collar 506, and has a structure that can constantly supply gas to the sleeve hollow portion while the gas introduction tube 509 is rotating. The hollow portion of the sleeve has a structure that keeps hermeticity so that the internal atmosphere can be controlled as described above.

  The introduction pipe 509 is made of a heat-resistant metal typified by SUS310S, for example, and the material is selected according to the operating temperature. Further, the number of tubes is not limited to one, and a plurality of tubes are attached to the front and rear of the sleeve hollow portion and the circumferential direction so as to effectively permeate the refractory and effectively give the interface glass a redox action. It is also effective.

  The exhaust pipe 510 is also determined according to the introduction pipe, and the diameter, length, the number of exhaust pipes, and the like are determined in consideration of pressure loss in order to maintain the positive pressure in the hollow portion.

  It is desirable to control the pressure to be more positive than atmospheric pressure so that the gas passes through the sleeve refractory inserted in the hollow portion and the gas is smoothly oxidized and reduced with respect to the glass at the sleeve interface.

  A cylinder 511 for supplying gas is installed in the upstream portion of the gas introduction pipe attached inside so as to adjust the atmosphere inside the sleeve. The cylinder 511 has a pressure regulator and a flow meter for making a constant pressure, and has a structure capable of supplying a constant pressure and a constant amount of gas. It is preferable to use a gas cylinder that has been adjusted to a predetermined concentration in order to obtain a desired atmosphere in the sleeve because it is convenient for stable gas supply.

  In the present invention, in order to control the atmosphere of at least a part of the sleeve hollow portion, a structure having an introduction pipe and an exhaust pipe for controlling a gas component is adopted. It is sufficient to concentrate and concentrate on the devitrification generation region of the interface glass to control at least a part, and it is not necessary that all the hollow portions have the same atmosphere. Further, depending on the purpose, the atmosphere can be divided into an oxidizing atmosphere, a reducing atmosphere and a neutral atmosphere. For example, when oxidation is strengthened, deterioration of the shaft made of refractory metal is expected to increase. Therefore, an oxidizing gas is efficiently introduced and controlled only in an area where devitrification of the interface glass occurs. In order to prevent oxidation of the shaft, reduction or neutral gas introduction can be controlled. In this case, as will be described later, the atmosphere can be individually controlled by providing a partition in the sleeve hollow portion with a heat-resistant metal partition plate and adjusting the amount and pressure of each gas.

For the danna sleeve used in this example, a member made of SiO ₂ -Al ₂ O ₃ based high alumina (84%) refractory ceramics with a porosity of 24% was used, and the entire surface in contact with the glass was used. The platinum coating 508 of FIG. 5 is formed by performing thermal spraying so that the platinum thickness becomes 0.3 mm with respect to the refractory having a thickness of 50 mm in the cylindrical portion. A danna sleeve, in which this refractory is fixed to a shaft that also serves as a blow pipe in the axial direction, was placed in a temperature gradient furnace called a muffle.

  This sleeve was attached to a tube glass forming apparatus, and glass having the composition shown in Table 3 was formed into a glass tube by the Danner method. Molding is caused to flow down on the sleeve at a glass temperature of 1200 ° C., and a temperature gradient is set so that the glass temperature at the sleeve tip has a viscosity of log η = 4.8 (where the unit of η is dPa · s) suitable for molding. I put it on. The rotary joint part behind the sleeve is provided with piping from a cylinder installed away from the furnace by a copper tube.

  As a hydrogen gas to be inserted into the sleeve, a cylinder filled with a mixed gas in which a hydrogen concentration was 1% and nitrogen was previously contained as a balance gas was prepared. The pressure was adjusted to 0.2 MPa with a regulator, and a mixed gas having an insertion amount of 1 L / min with a flow meter was continuously inserted into the sleeve from this cylinder. The tube was continuously formed by adjusting the blow pressure and the drawing machine installed downstream of the sleeve so that the outer diameter was 4 mm and the inner diameter was 3 mm.

Thus, the glass adjusted to have the glass composition of Example 12 was melted in a melting furnace and clarified and homogenized. This glass was allowed to flow down from the trough onto the sleeve to form a tube. On the other hand, in Comparative Example 3, the same glass was used in a normal atmosphere without introducing gas into the sleeve. As described above, devitrification was compared for the same glass under the condition that the internal atmosphere of the sleeve was different. For devitrification, the tube-formed tube is cut at 1 m, 100 m of the tube is continuously collected, the inner surface of the tube is observed with a 10-fold magnifier, the presence of devitrification is confirmed, and the frequency of devitrification is investigated. It was done by the method. Table 3 shows the results. Here, the value of devitrification frequency in Table 3 is the number of devitrification per meter observed after the displayed continuous operation elapsed time.

  Thus, like the results of the previous Examples 5 to 11, in the actual molding by the Danner method, the tube molded by the method of the present invention is more devitrified than the one molded by the conventional method. It has been shown that the occurrence can be significantly reduced.

In the present invention, the invention relates to the Danner method using a hollow cylindrical cylinder called a sleeve. By passing hydrogen through a furnace material such as platinum or a fired refractory, CeO ₂ crystals There is a significant feature in that CeBSiO ₅ crystals can be precipitated, and the devitrification temperature can be lowered by this, and the effect has been confirmed. This method is not limited to tube glass, and in borosilicate glass containing CeO ₂ , if a countermeasure against devitrification is required due to overlapping molding temperature and devitrification temperature, for example, devitrification of the interface through refractory or platinum is required. Since the generated temperature can be lowered, the present invention can be applied to plate forming such as the fusion method and the slit down draw method as well as a manufacturing method in which a devitrification preventing effect can be obtained by providing hydrogen gas to the furnace wall with a sealed structure.

According to the present invention, a tube glass that is molded using the Danner method can be manufactured without devitrification even if it contains an easily devitrifying component such as CeO ₂ . For example, when this glass tube is used as a glass tube of a fluorescent lamp, it is possible to provide a tube that is effective in cutting ultraviolet rays and transmits visible light well.

It is a typical sectional view showing one embodiment of a sleeve for glass tube fabrication concerning the present invention. It is a typical sectional view showing other embodiments of a sleeve for glass tube fabrication concerning the present invention. It is sectional drawing which showed typically the apparatus structure used in the Example of this invention. 3 is an X-ray diffraction chart of glass samples of Example 1 and Comparative Example 2. FIG. 14 is a schematic cross-sectional view of a glass tube forming sleeve used in Example 12. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Sleeve, 4 ... Sleeve shaft, 6 ... Refractory cylindrical part, 7 ... Platinum coating, 8 ... Fixing nut, 9 ... Fixing tool, 10 ... Hollow part, 10a ... Sleeve front side hollow part, 10b ... Sleeve rear end Side hollow part, 12a ... through pipe (introducing pipe), 12b ... through pipe (exhaust pipe), 13 ... ring, 14 ... hollow part, 15 ... through hole, 16 ... blow air supply hole, 17 ... blow pipe, 20 ... Bulkhead, 316 ... Electric furnace, 315 ... Structure with hollow part, 314 ... Heat-resistant metal tube, 313 ... Platinum coating, 501 ... Sleeve, 502 ... Sleeve shaft, 503 ... Rotary drive, 504 ... Trough, 505 ... Melting Glass, 506, presser collar, 507, blow air supply hole, 508, platinum coating, 509, gas introduction pipe, 510, gas exhaust pipe, 511, gas cylinder, A, molten glass.

Claims (16)

A refractory cylinder,
A blow pipe penetrating into the cylindrical portion coaxially with the cylindrical portion;
A partition wall that divides the space between the cylindrical portion and the blow pipe into a plurality of internal spaces at a plane intersecting the axis of the cylindrical portion;
An introduction pipe and an exhaust pipe communicating with at least one of the plurality of internal spaces divided by the partition walls, and introducing an atmosphere from the introduction pipe into the internal space, thereby changing the atmosphere of the internal space A glass tube forming sleeve characterized by being controllable.   The glass tube molding according to claim 1, wherein each of the plurality of internal spaces divided by the partition wall has an introduction pipe and an exhaust pipe, and each of the plurality of internal spaces can be controlled to have a different atmosphere. Sleeve.   The glass tube forming sleeve according to claim 1 or 2, wherein the refractory constituting the sleeve is made of a refractory ceramic having an apparent porosity of 1% or more and 30% or less.   4. The glass tube forming sleeve according to claim 1, wherein a part or the entire surface of the outer surface of the sleeve that is in contact with glass is covered with platinum or a platinum alloy.   A portion of the outer surface of the sleeve that is in contact with the glass is covered with platinum or a platinum alloy, and the partition corresponds to a boundary portion between the portion covered with platinum or the platinum alloy and the portion not covered with platinum. The glass tube forming sleeve according to claim 4, wherein the glass tube forming sleeve is provided.   6. The gas according to claim 1, wherein the gas is an oxidizing gas or a reducing gas, and the gas that has permeated the sleeve gives an oxidizing action or a reducing action to the glass in contact with the sleeve interface. A sleeve for forming a glass tube according to 1.   Glass that has a cylindrical portion made of refractory with a blow pipe inserted coaxially, and flows molten glass onto a rotating glass tube forming sleeve, and continuously draws the glass from the tip of the sleeve to form a tube. In the method of manufacturing a tube, an oxidizing or reducing gas is introduced into a hollow portion between the cylindrical portion of the sleeve and the blow pipe through an introducing tube, and an oxidizing action is exerted on the glass in contact with the sleeve interface. Or the devitrification which generate | occur | produces in a glass tube inner surface by giving a reducing effect | action is prevented, The manufacturing method of the glass tube characterized by the above-mentioned.   The glass tube forming sleeve according to claim 1 is used as the sleeve, and an oxidizing gas or a reducing gas is applied to an internal space corresponding to a region having a temperature at which the glass in contact with the sleeve interface is likely to be devitrified. The glass tube manufacturing method according to claim 7, wherein:   The glass tube forming sleeve according to claim 2 is used as the sleeve, and at least one of the type, concentration, and pressure of the gas to be introduced is made different for each internal space divided by the partition wall. The manufacturing method of the glass tube of Claim 7.   The glass tube forming sleeve according to claim 5 is used as the sleeve, and a reducing gas containing hydrogen is introduced into an internal space corresponding to a portion where the sleeve surface is covered with platinum or a platinum alloy, and comes into contact with the sleeve interface. The method for producing a glass tube according to claim 7 or 9, wherein a reducing action is imparted to the glass being processed.   The method for producing a glass tube according to any one of claims 7 to 10, wherein the refractory constituting the sleeve is made of refractory ceramics having an apparent porosity of 1% to 30%.   The method for manufacturing a glass tube according to any one of claims 7 to 9, wherein a part or the entire surface of the outer surface of the sleeve that is in contact with glass is covered with platinum or a platinum alloy.   The method for producing a glass tube according to any one of claims 7 to 9 or 11 to 12, wherein the gas introduced into the hollow portion is a reducing gas containing hydrogen.   The method for producing a glass tube according to claim 13, wherein the reducing gas contains 0.1% by volume or more of hydrogen. Glass to be formed into a glass _{tube, SiO 2, B 2 O 3} , and a manufacturing method of a glass tube according to claim 13 or 14, characterized in that comprising CeO _2. The glass contains, by mass% _{notation, SiO 2 55~80%, Al 2} O 3 1~10%, B 2 O 3 1~25%, Li 2 O + Na 2 O + K 2 O1~15%, CaO + MgO + BaO + SrO0~10%, _{CeO 2 0.1~5%, SnO + SnO} 2 0~5%, the process of claim 15 glass tube, wherein the containing 2 O 5 0~5% ZrO 2 + ZnO + Nb.

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