Bushings for glass fiber production and method for producing glass fibers

Abstract

The present invention relates to a bushing for glass fiber production, which has a plurality of nozzles made of platinum or the like for discharging molten glass and a base plate made of platinum or the like. In the present invention, a coating layer is formed on the outer circumferential surface of the tip portion on the glass discharge side of the nozzle, and the width of the coating layer is 5% or more and 95% or less with respect to the total length of the nozzle. The base plate includes a non-coating region without the coating layer in at least a portion. The regions of the nozzle and the base plate without the coating layer function as a sacrificial metal for protecting the tip portion of the nozzle where the coating layer is formed. In the present invention, in consideration of the function of the sacrificial metal, the coverage P calculated using a prescribed formula is preferably set to 5% or more and 350% or less with respect to the coating layer of the tip portion of the nozzle. The present invention identifies the main cause of abrasion occurring at the nozzle of the bushing for glass fiber production, and makes it difficult for the nozzle to be abraded even in the case of long-term use.

Description

Technical Field

[0001] This invention relates to a spinneret for manufacturing glass fibers from molten glass. Specifically, it relates to a spinneret for manufacturing glass fibers that can stably discharge a stream of molten glass and draw glass fibers during long-term use of the apparatus. Background Technology

[0002] Glass fibers are manufactured by refining and homogenizing molten glass obtained from heating raw glass at high temperatures, and then feeding the resulting glass preform into a stencil. In a glass fiber stencil, numerous nozzles are arranged on the bottom surface of a base plate. The glass preform is formed into fibers through these nozzles and discharged. As the glass preform exits the nozzles, it is cooled and wound into glass fibers. The base plate and nozzles of the glass fiber stencil are typically made of platinum-based materials such as platinum or platinum alloys.

[0003] The molten glass preform reaches temperatures exceeding 1000°C, and its velocity upon exiting the nozzle can sometimes reach several thousand meters per minute. Therefore, the environment surrounding the stencil is extremely harsh. Furthermore, even the slightest impurity is unacceptable in the glass fibers used in the final product. Consequently, all components of the stencil must be made of materials possessing high-temperature strength, high-temperature durability, and stability to prevent contamination of the glass preform. Platinum, the main component of platinum-based materials, exhibits excellent high-temperature strength, high-temperature creep characteristics, and chemical stability. Stencils constructed from platinum-based materials can draw glass fibers even under the high-temperature conditions of molten glass flow.

[0004] However, even platinum-based materials, which exhibit excellent strength and stability at high temperatures, cannot be said to be immune to breakage even under long-term operation in glass manufacturing equipment. To date, in glass fiber manufacturing plants, a decline in fiber quality has been reported with prolonged operation. One possible cause is the breakage of nozzles mounted on the base plate. Furthermore, the primary cause of this nozzle breakage is believed to be the effect of the high-temperature / high-speed airflow generated around the aforementioned sprue. It is known that platinum undergoes volatilization at high temperatures, and this volatilization is accelerated in areas exposed to high-temperature / high-speed airflow, resulting in wear on the nozzles.

[0005] The wear pattern of the nozzle varies depending on the manufacturing conditions of the glass fiber and the cooling structure in the sprue. Figure 1 The diagram illustrates the wear pattern of a nozzle caused by airflow. Figure 1 As shown, due to the wear caused by the high-temperature / high-speed airflow on the entire or part of the outer circumferential surface of the nozzle tip, the nozzle's cross-sectional shape becomes a figure-eight shape. Figure 1 (a) ), oblique shape ( Figure 1(b) and the like. If the abrasion of the nozzle becomes so severe, the desired fiber drawing of the glass fiber cannot be performed, and the life of the bushing ends even if the other parts than the nozzle are still intact.

[0006] For the problem of the breakage of the bushing for glass manufacturing as described above, several countermeasures can be mentioned. For example, in order to protect the nozzle from the above-mentioned air flow, there is a structure in which a windbreak is provided along the nozzle row of the outermost layer of the nozzle group arranged in the bottom plate (Patent Literature 1). This is because the part of the nozzle group that is most affected by the air flow is the nozzle tip of the nozzle row of the outermost layer of the nozzle group. In addition, for the same reason, there is also a bushing in which the nozzles of the nozzle row of the outermost layer of the nozzle group are plugged in advance to make dummy nozzles, so that they function as the above-mentioned windbreak (Patent Literature 2).

[0007] In addition, in addition to the provision of the member having the windbreak function as described above, a method of preventing the abrasion of the platinum-based material by forming a coating layer on the bottom plate and the nozzle of the bushing has also been proposed (Patent Literatures 3 and 4). In these prior arts, a heat-resistant ceramic such as stabilized zirconia is coated on the bottom plate or the nozzle or the entire bushing, and the platinum-based material is isolated from the external environment, thereby suppressing the abrasion.

[0008] Prior Art Documents

[0009] Patent Literature

[0010] Patent Literature 1: Japanese Patent No. 5813145

[0011] Patent Literature 2: Japanese Patent No. 5792104

[0012] Patent Literature 3: Japanese Patent No. 6624750

[0013] Patent Literature 4: Japanese Patent Application Publication No. 2020-040850 SUMMARY

[0014] PROBLEMS TO BE SOLVED BY THE INVENTION

[0015] Regarding the countermeasure for the wear of the bushing described above, there is a possibility that the windbreak wall increases the weight of the bushing, and the windbreak wall changes the air flow around the bushing, thereby changing the flow of the discharged molten glass. On the other hand, regarding the use of the dummy nozzle, since the nozzle that does not contribute to the drawing of the glass fiber is set, the use amount of the base metal of the platinum material is additionally increased while it is sometimes not appropriate from the viewpoint of the manufacturing efficiency of the glass fiber. In addition, the range in which the dummy nozzle and the like can cover the influence of the air flow is not so wide. On the contrary, regarding the coating, there is no problem caused by the windbreak wall and the dummy nozzle. In view of the heat resistance and the wear resistance of the ceramic used as the coating layer, if the coating layer is uniformly formed on the entire bushing, it can be expected that the coating layer can be used until the coating layer disappears.

[0016] However, according to the research by the present inventor, even the bushing for the glass fiber manufacturing having the coating layer so far has a problem of the breakage of the nozzle. In particular, it is confirmed that even in the case where the coating layer is formed on the entire bushing (the nozzle and the base plate), the wear of the nozzle occurs. The wear of the nozzle in the bushing having the coating layer does not occur with the peeling and the disappearance of the coating layer, but is not apparently observed from the appearance at the initial stage. However, with the passage of the running time, although the state of the coating layer does not greatly change, the wear and the penetration hole sometimes occur from the front end portion (the glass discharge portion) of the nozzle to the side surface. Furthermore, such wear and penetration hole of the nozzle sometimes occur in a shorter period than expected. The wear and the penetration hole occurring in the nozzle cause the disturbance of the glass flow, and thus cause the obstacle to the drawing of the glass fiber, resulting in the decrease in the production efficiency.

[0017] The present application is completed in view of the background described above, and aims to find the main cause of the wear of the nozzle described above for the bushing for the glass fiber manufacturing, and to provide the bushing in which the wear of the nozzle does not easily occur even in the case of long-term use.

[0018] Method for solving the problem

[0019] In order to solve the above problem, the present inventor first researched the main cause of the wear of the nozzle described above. Figure 2 is a photograph of the front end portion of the nozzle when the wear is reproduced by exposing the nozzle of the bushing for the glass fiber manufacturing, which is usually used, to the atmosphere at 1600°C or higher for 1 month after forming the ceramic coating layer on the entire surface of the outer periphery thereof. From Figure 2 It is known that the local wear portion is formed on the outer peripheral surface of the front end of the nozzle. Furthermore, as for the coating layer covering the nozzle, the crack and the hole are formed at the position corresponding to the hole. As described above, the wear of the platinum-based material is caused by the volatilization of the constituent metal such as platinum and rhodium. The volatilization of platinum and the like is caused by the fact that platinum and the like become the oxide having the volatility at high temperature in the oxidative atmosphere such as the atmosphere. From Figure 2The abrasion form shown is presumed to be that a minute crack and a hole are first generated in the coating layer, then a path for discharging a vapor of an oxide of platinum or the like is formed, and thus local abrasion of the nozzle is caused. The ceramic constituting the coating layer is a porous body and contains fine pores. It is considered that the coating layer generates a crack thereof by connection of the pores or the like due to thermal fluctuation. Further, the base metal surface of the nozzle is oxidized by air passing through the coating layer, and the generated oxide is discharged from the coating layer, thereby causing enlargement of the hole. Figure 2 The reproduction test is not a test accompanied by generation of air flow, but in an actual glass fiber manufacturing apparatus, a high-speed air flow is generated around the nozzle. The high-speed air flow has an effect of promoting movement of the relevant substances (invasion of air and discharge of oxide) in the formation process of the above-described abrasion, and thus it is predicted that the enlargement of the hole further accelerates.

[0020] As described above, it is ascertained that the abrasion at the tip portion and the side surface of the nozzle provided with the coating layer is caused by the following three main reasons: (1) occurrence of a crack and a hole in the coating layer; (2) oxidation reaction of platinum is performed in a concentrated and high-cycle manner due to being in a narrow space caused by the crack or the like; and (3) supply of air and discharge of oxide caused by a high-speed air flow in the vicinity of the tip of the nozzle. It is also considered that if even one of these main reasons can be eliminated, the abrasion at the tip portion and the side surface of the nozzle can be suppressed.

[0021] Here, the present inventors have achieved elimination of the above-described (2) main reason. Specifically, in the constitution of the bushing, the coating layer is selectively and preferentially formed at the tip portion of the nozzle, and on the other hand, for other portions, particularly the bottom plate, the coating layer is not formed but the base metal of the platinum material is exposed. Further, by confirming the effectiveness of this countermeasure, the present application is conceived.

[0022] That is, the present application is a bushing for glass fiber manufacturing, which has a plurality of nozzles constituted of platinum or platinum alloy and discharging molten glass, and a bottom plate constituted of platinum or platinum alloy, the plurality of nozzles being joined to the bottom plate, characterized in that a coating layer is formed on the outer peripheral surface of the tip portion on the glass discharge side of the plurality of nozzles, the width of the coating layer is 5% or more and 95% or less with respect to the full length of the nozzle, and the bottom plate contains a non-coating region without the coating layer in at least a part thereof.

[0023] With regard to the main causes of the nozzle abrasion described in (1) to (3) above, it is difficult to eliminate the occurrence of cracks in the coating layer of (1), the occurrence of holes, and the influence of the high-speed gas flow of (3). With regard to the main cause (1), as a means for inhibiting the occurrence of cracks and the like in the coating layer, a uniform thickness and density of the coating layer can be formed without gaps and unevenness. However, it is difficult to form such a coating layer on the entire nozzle. The present inventors believe that if a coating layer is formed on the entire nozzle, there is a possibility that the nozzle will be locally abraded due to the occurrence of unevenness. In addition, the high-speed gas flow near the front end of the nozzle of the main cause (3) is an environmental factor resulting from the production of glass fibers. Changing the production conditions of the glass fibers in order to eliminate the high-speed gas flow cannot be said to be a fundamental solution.

[0024] On the other hand, with regard to the main cause (2), it can be eliminated by preferentially causing the oxidation reaction of platinum in a region other than the nozzle. The oxidation / volatilization reaction of platinum and the like is inhibited by the increase in the volatile matter in the atmosphere. By oxidizing / volatilizing platinum and the like in a region other than the nozzle, the preferential reaction in the front end portion and the side surface of the nozzle is inhibited.

[0025] Furthermore, it is believed that, in addition to oxidizing / volatilizing platinum in a region other than the nozzle, it is effective to intentionally not form a coating layer on the base plate so as to expose the base metal of the platinum-based material on a part or the entire base plate. This means that the region of the base plate on which coating is not performed is used as a so-called sacrificial metal (sacrificial material), and this region is intentionally oxidized / volatilized. The base plate is a large area with respect to the area of each nozzle, and by oxidizing / volatilizing the base plate, volatile matter can be supplied to the periphery of the nozzle. As a result, it is expected that the volatilization inhibition effect can be imparted to all of the nozzles.

[0026] On the other hand, in the present application, a coating layer is required for the outer peripheral surface of the front end portion of the nozzle. As described above, the coating layer itself does not promote abrasion. From the viewpoint of the production of glass fibers, it is necessary to form a coating layer on the outer peripheral surface of the front end portion of the nozzle. Figure 2 It is also known that in the portion where no hole is generated, the base metal surface of the nozzle is not abraded, and thus it can be said that the coating layer has a protective effect. The side surface of the nozzle, and particularly the front end portion, is a site that is more affected by the high-speed gas flow with respect to the base plate. In order to reduce the influence of the high-speed gas flow as much as possible, a coating layer is necessary for the front end of the nozzle.

[0027] As described above, the glass fiber production bushing of the present application uses a coating layer, but the portion where the coating layer is intentionally formed is limited to the outer peripheral surface of the front end of the nozzle. Furthermore, it is provided that the entire or a part of the base plate is opened to expose the platinum-based material. Hereinafter, the configuration of the glass fiber production bushing of the present application will be described in more detail.

[0028] (I) Base plate

[0029] The bottom plate is a member for allowing the glass material in a molten state to stay, and is a plate-shaped member or a member having a box shape by bending processing. The material of the bottom plate is composed of platinum or a platinum alloy, and preferably platinum, a platinum-rhodium alloy (rhodium concentration: 5 to 20% by weight) is used. In addition to this, a dispersion type reinforced platinum or a dispersion type reinforced platinum-rhodium alloy is used for the purpose of improving strength. Note that the bottom plate has a through-hole at a position connected to the nozzle.

[0030] In the present application, the bottom plate has a function as a sacrificial metal for suppressing abrasion of the side surface and the tip end portion of the nozzle in addition to retaining the glass material as described above. However, no particular change is required to be made to the size and shape of the bottom plate, and the same as in the past can be provided. In the bottom plate including a non-coated region without a coated layer, even if volatilization of platinum or the like occurs, the abrasion caused by the volatilization is alleviated and is not localized. If the bottom plate is manufactured under the same design conditions (use temperature, capacity of the glass material to be retained, and the like) as in the past, it can be durable while functioning as a sacrificial metal.

[0031] Note that in the present application, although a sacrificial metal for protecting the nozzle from abrasion is required, an auxiliary member as a sacrificial metal is not provided outside the bottom plate, the nozzle, and the like. In the environment around the bushing in which a high-temperature high-speed gas flow exists, if the sacrificial metal is provided as a separate member, turbulence of the gas flow, abnormality of the temperature distribution, and the like occur, and stable fiber drawing is hindered, which can adversely affect the productivity. In addition, the addition of a separate member can cause an increase in the weight of the bushing. Furthermore, in the environment around the bushing, even if an auxiliary member as a sacrificial metal is used, it is difficult to make it function only as a sacrificial metal. For these reasons, the present inventors have found that it is most suitable to make the bottom plate function as a sacrificial metal, and have provided the above-described configuration.

[0032] (II) Nozzle

[0033] As for the nozzle, basically, the nozzle used in the bushing for manufacturing glass fibers in the past can be used. The nozzle is arranged in multiple numbers on the bottom surface of the bottom plate and is joined. The shape (outer shape, hole shape) of the nozzle is not particularly limited. It can be a straight pipe nozzle, a tapered nozzle having a thin tip, or a flat nozzle for manufacturing flat fibers. In addition, as for the material of the nozzle, platinum or the above-described platinum alloy can be used.

[0034] In the bushing for manufacturing glass fibers of the present application, the number of nozzles provided is not particularly limited, but generally, 200 to 10,000 nozzles are provided. In addition, as for the arrangement of the nozzles, the same as in the past can be provided. As for the arrangement of the nozzles, the groups of nozzles arranged at a certain interval can be arranged in multiple islands, or can be arranged relatively randomly.

[0035] (III) Coating layer of the front end portion of the nozzle and non-coating area in the base plate

[0036] (III-1) Coating layer of the front end portion of the nozzle

[0037] In the present application, as for the plurality of nozzles provided on the base plate, a coating layer is formed on the outer peripheral surface of the front end portion on the glass discharge side. This is because this is a portion of the bushing for manufacturing glass fibers that is particularly affected by high-speed airflow. Also, protection of the front end of the nozzle is particularly important in terms of continuous production of stable glass fibers. In the present application, the base plate as a sacrificial metal is mainly affected by volatilization of platinum or the like, and thus even if a crack or the like is present in the coating layer, local abrasion at this portion is suppressed. However, in view of the effects of high-speed airflow and the importance of protection of the front end of the nozzle, the coating layer must be present at the front end of the nozzle.

[0038] Figure 3 For the bushing of the present application, an example of the nozzle in which a coating layer is formed is shown. The coating area in which the coating layer is formed is the outer peripheral surface of the front end portion on the glass discharge side of the nozzle. The coating layer is not formed on the end surface of the nozzle. If the coating layer is present on the end surface of the nozzle, there is a possibility that wetting spread of the molten glass on the coating layer and turbulence of the molten glass stream will occur. Also, the coating layer is formed in a band shape on the outer periphery of the nozzle, and the width of the coating layer is set to 5% or more and 95% or less with respect to the entire length of the nozzle. This takes into account the range of effects due to high-speed airflow, and if the width of the coating layer is less than 5% with respect to the entire length of the nozzle, the coating layer is too narrow and protection of the front end of the nozzle becomes insufficient. On the other hand, the root side of the nozzle is not easily affected by high-speed airflow, and thus a coating layer having a width that is too large is not needed. Also, by providing a non-coating area on the root side of the nozzle, this area can function as a sacrificial metal together with the non-coating area of the base plate. The non-coating area of the nozzle is close to the coating area of the front end of the nozzle, and thus can exert an effective sacrificial metal effect. For this reason, the coating layer is not formed in an area that exceeds 95% of the entire length of the nozzle. Note that even if the root side of the nozzle functions as a sacrificial metal, as long as abrasion due to volatilization of platinum or the like is not local abrasion, the drawing of glass fibers is not affected. The width of the coating layer with respect to the entire length of the nozzle is preferably set to 6% or more and 80% or less, and more preferably 8% or more and 70% or less.

[0039] Note that the width of the coating layer at the front end portion of the nozzle refers to the vertical length (W) between both end portions of the coating layer. Also, the entire length of the nozzle refers to the vertical length (L) between the joint portion of the nozzle and the base plate and the front end portion of the nozzle on the glass discharge side. Figure 3 Figure 3 ​h) in the above-described range. Further, the width of the coating layer at the tip of the entire nozzles can be in the above-described range. In addition, with respect to the nozzles, a portion (root of the nozzle) other than the region in which the coating layer is formed in the above-described width is not formed with the coating layer. Note that, as a specific dimension value of the width (W) of the coating layer of the nozzle, it is preferable that the width of 5 mm or less from the tip of the nozzle be set. Further, it is preferable that a non-coating region of the nozzle be formed adjacent to the coating layer of the width of 5 mm or less from the tip of the nozzle, so that a blank of the platinum-based material that becomes the sacrificial metal exists.

[0040] (III-2) Non-coating region of the bottom plate

[0041] In the present application, the coating layer is formed on the outer peripheral surface of the tip portion of the nozzle, and the bottom plate includes a non-coating region in at least a portion thereof that does not include the coating layer. With respect to the bottom plate, there is a case in which the coating layer is not formed on the entire surface thereof, and there is also a case in which the coating layer is formed partially. A point important in the subject matter of the present application is that the bottom plate other than the tip portion of the nozzle supplies the sacrificial metal necessary for protection of the tip portion of the nozzle, and if it is within a range in which this action occurs, the coating layer can exist on the bottom plate.

[0042] Examples of the form of the non-coating region of the bottom plate are shown in Figure 4 . As shown in Figure 4 (A), the periphery of the nozzle group is set as a non-coating region, and the coating layer can be formed on the peripheral portion of the bottom plate that is the remaining portion. With respect to the width of the coating layer at this time, there is no particular limitation, and the coating layer can be formed on either of the short side or the long side of the bottom plate. In addition, as shown in Figure 4 (B), the peripheral portion of the nozzle row is set as a non-coating region, and the coating layer is formed on the remaining portion. In these examples, the non-coating region is set in the vicinity of the nozzle in any of them. This is because, by setting the platinum-based material blank of the bottom plate in the vicinity of the nozzle as the sacrificial metal, protection of the tip of the nozzle can be appropriately performed. However, the shape of the non-coating region is not particularly limited. Note that, with respect to the surface area of the coating layer when the coating layer is formed on the bottom plate as such, it is described below.

[0043] (III-3) Surface area of the coating layer of the bottom plate of the present application

[0044] As described above, in the present application, the platinum-based material blank other than the tip portion of the nozzle and the non-coating platinum-based material blank of the bottom plate are used as the sacrificial metal to protect the tip of the nozzle on which the coating layer is formed. Therefore, the platinum-based material blank on which the coating layer is not formed is preferably within a prescribed range for the purpose. Specifically, it is preferable that the coverage rate P of the tip portion of the nozzle shown in the following equation be 5% or more and 350% or less.

[0045] P(%) = C / (NC1 + NC2) x 100

[0046] In the above formula, C is the total surface area of the coating layer of the tip portion of the nozzles in the entire nozzles. That is, the total surface area obtained by multiplying the surface area of the coating layer (width: 5% or more and 95% or less) formed in each nozzle by the number of nozzles. NC1 is the total surface area of the region without the coating layer of the nozzles in the entire nozzles. That is, the total surface area obtained by multiplying the surface area of the region without the coating layer of the nozzles by the number of nozzles. Further, NC2 is the surface area of the non-coating region provided in the base plate. In the case where there are a plurality of non-coating regions in the base plate, it is the total surface area thereof.

[0047] The coverage ratio P of the tip portion of the nozzles is set to 350% or less in order to supply the sacrificial metal necessary for protecting the region of the tip of the nozzles where the coating layer is present. On the other hand, the surface area of the region without the coating layer which becomes the sacrificial metal does not differ in terms of the protection effect even if it is excessive, and therefore it is appropriate to set the coverage ratio to 5% or more. The coverage ratio P of the tip portion of the nozzles is more preferably 5% or more and 300% or less, and further preferably 5% or more and 250% or less.

[0048] Note that even if the base plate is formed with a coating layer, its surface area is not used in the calculation of the coverage ratio P of the tip portion of the nozzles described above. This is because it is considered that the base plate is less affected by the high-speed airflow considered in the present application than the tip portion of the nozzles, and the effect of the sacrificial metal effect by the platinum-based material blank is small. In the first place, the non-coating region of the base plate becomes a supply source of the sacrificial metal to the tip portion of the nozzles, and therefore it is not desirable to actively form an excessive coating layer. With respect to the surface area of the coating layer formed in the base plate, the number (surface area) of the nozzles as the object of protection and the like should also be considered, and for example, it can be appropriately set to 70% or less, 55% or less, 40% or less with respect to the surface area of the base plate. The remaining portion of the surface of the base plate is the platinum-based material blank. Note that the surface area of the base plate here refers to the surface area of the face on one side of the base plate which is joined to the nozzles, and does not include the area of the other face. In addition, the area after excluding the area of the portion joined to the nozzles (nozzle cross-sectional area x number of nozzles) is the surface area of the base plate.

[0049] Note that the coverage ratio P of the coating layer of the tip of the nozzle can change due to the operation of the trough (glass manufacturing apparatus), although the change is small. It is considered that this is due to abrasion caused by the high-speed airflow around the trough, a change in the area of the coating layer due to peeling / detachment of a small amount of the coating layer, a change in the size of the nozzle and the bottom plate that becomes a non-coating region. The above-mentioned coverage ratio P of the coating layer refers to the value at the time of manufacture (at the start of use). Regarding the change in the coverage ratio P due to the use of the trough, a change of about 40% to 80% is allowed. For example, when the coverage ratio P of the coating layer of the tip of the nozzle at the time of manufacture (at the start of use) is 60%, the coverage ratio P after use can be 24% to 48%.

[0050] The material of the coating layer is preferably composed of at least any one of zirconia, stabilized zirconia, alumina, silica, aluminosilicate, and magnesium oxide. These are substances determined in consideration of the inhibition of volatilization of platinum and the like at high temperatures and protection against abrasion caused by high-speed airflow at high temperatures. In particular, since the thermal expansion rate is close to that of platinum and the high-temperature durability is excellent, a coating material composed of stabilized zirconia is useful. In addition, the thickness of the coating layer is preferably in the range of 2 μm or more and 500 μm or less. If the coating layer is too thin, the protective effect of the tip of the nozzle cannot be expected. If the coating layer is too thick, there is a possibility that the coating layer will peel off due to slight deformation or impact of the nozzle. The coating layer can be provided as a single layer or multiple layers. For example, an alumina coating layer can be formed on the surface of the nozzle, and a stabilized zirconia coating layer can be formed thereon. Note that regarding the thickness of the coating layer, it is not necessarily uniform, and if it is in the above-mentioned range, there can be a difference based on the coating site.

[0051] As the method of forming the coating layer, various thermal spraying methods (atmospheric plasma thermal spraying (APS), suspension plasma thermal spraying (SPS), and the like), aerosol gas deposition (AD), sol-gel method, and physical vapor deposition method (PVD), chemical vapor deposition method (CVD), cold spraying method (CS), plating method, ion plating method, and the like can be given, but are not particularly limited.

[0052] Among these methods of forming the coating layer, the thickness of the coating layer can be adjusted. For example, in the AD method, a coating layer of about 2 to 10 μm can be formed, in the SPS method, a coating layer of about 50 to 150 μm can be formed, and in the APS method, a coating layer of about 50 to 500 μm can be formed. In addition, the ceramic layer (coating layer) based on these methods of forming has different densities. For example, the coating layer based on the AD method can be a dense ceramic layer even if it is thin, and can exert a volatilization inhibition effect. In the present application, the method of forming the coating layer and the thickness can be appropriately adjusted according to the size, shape, and use environment of the nozzle.

[0053] (IV) Other Constitutions

[0054] As to the bushing for glass fiber production of the present application, the combination of the above-described bottom plate and the plurality of nozzles provided with the coating layer at the front end is the basic configuration. However, additional members can be added to them. For example, as explained in the above-described prior art, a windbreak wall, a dummy nozzle after clogging can be provided around the nozzle group. This is because they have certain effectiveness for the protection of the front end of the nozzle. In this case, the coating layer can be formed on the windbreak wall, the dummy nozzle or not. Note that in the present application, whether or not the coating layer is formed on the windbreak wall or the like, even if the coating layer exists on them, they are not considered in the calculation of the coverage ratio P.

[0055] Effects of the Invention

[0056] As explained above, the bushing for glass fiber production of the present application is configured in such a manner that the coating layer is formed preferentially and necessarily on the outer peripheral surface on the nozzle front end side, and the platinum-based material is exposed on the remaining portion. Thereby, volatilization of platinum or the like occurs in the area without the coating layer, thereby suppressing the abrasion of the nozzle front end. According to the present application, in the glass fiber drawing process, it is possible to achieve long-term use of the device while suppressing the disturbance of the glass liquid flow due to the nozzle abrasion.

[0057] Note that the bushing for glass fiber production of the present application can be used for all forms of glass fiber production processes. As the process of glass fiber production, for example, there are: a downdraw method (DM method) in which a glass blank in a molten state adjusted to a target composition in a melting furnace is introduced into a feeder tank and then transferred to a bushing and directly drawn; a marvering method (MM method) in which a glass blank in a molten state is shaped into a glass ball or a glass rod of a certain diameter, and then drawn after re-melting; and the like. In addition, there are a bushing method in which glass melted and discharged from the bushing is blown out with a jet device to produce short fibers, and the like. In these production processes, glass fibers for various purposes can be produced at various temperatures or the like, and the bushing for glass fiber production of the present application can be used for any process. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 A drawing for explaining an example of the state in which the nozzle of the conventional bushing for glass production is abraded.

[0059] Figure 2 A photograph for showing an example of the local abrasion occurring at the nozzle front end portion of the bushing for glass fiber production in which the entire surface is coated.

[0060] Figure 3 A drawing for explaining an example of the shape of the coating layer at the nozzle front end.

[0061] Figure 4A photograph showing a specific example of the shape of the bushing in which the coating layer is formed on the base plate according to the present application.

[0062] Figure 5 A photograph showing the results of the heating test at 1200°C, 1600°C of the sample in which the coating layer is formed on the entire surface of the nozzle in the pretest of the present embodiment.

[0063] Figure 6 A photograph showing the results of the heating test at 1200°C, 1600°C of the sample in which the coating layer is selectively formed on the tip end of the nozzle in the pretest of the present embodiment. DETAILED DESCRIPTION

[0064] Hereinafter, an embodiment of the present application will be described. In the present embodiment, a pretest was conducted to confirm the effectiveness when the coating layer is formed on the outer peripheral surface of the tip end portion of the nozzle. Then, a glass fiber manufacturing bushing in which the coating layer is formed on the tip end portion of the nozzle was actually manufactured, and the drawing of the glass fiber was conducted.

[0065] [Pretest]

[0066] In the pretest, a sample imitating the bushing as a product was prepared, and a heating test was conducted after forming various coating layers. A nozzle made of platinum (a conical cylindrical body having an outer diameter of 2.70 mm (outer diameter of the upper end portion) x 1.55 mm (outer diameter of the lower end portion), a wall thickness of 0.3 mm, and a total length of 3.5 mm) used in the actual glass fiber manufacturing bushing was placed on one of the plates (size 15 mm x 30 mm, thickness 1.5 mm) made of platinum alloy (Pt-10 wt% Rh) imitating the base plate, thereby preparing the sample. With respect to the sample, two kinds of samples were prepared: a sample 1 in which the coating layer is formed on the entire surface of the nozzle (the entire surface of the nozzle side surface and the entire surface of the platinum plate surface), and a sample 2 in which the coating layer is formed on the tip end of the nozzle with a width of 1.75 mm (50% of the total length of the nozzle). The coating layer was composed of stabilized zirconia, and was formed with a thickness of 150 μm using a thermal spraying method (APS). Then, a heating test was conducted on these samples 1, 2 under two heating conditions of 1200°C x 1 month and 1600°C x 1 month in the atmosphere, and the presence or absence of local abrasion at the tip end of the nozzle was confirmed.

[0067] With respect to the pretest, the photograph of the nozzle after the heating test at 1200°C of the sample 1 on which the entire surface was coated is Figure 5 , and the photograph of the nozzle after the heating test at 1600°C of the sample 2 is the above Figure 2 In the sample 1 on which the entire surface of the bushing was coated, almost no local abrasion was observed in the heating at 1200°C. However, the sample 2 on which the entire surface was coated was locally abraded at many places due to the heating at 1600°C.

[0068] On the other hand, the results of the heating test (1200°C heating, 1600°C heating) of the sample 2 in which the front end portion of the nozzle was coated are shown in Figure 6 In the sample 2 in which the front end portion of the nozzle was coated, no local abrasion was observed at all in the heating at 1200°C. Also, as to the sample after the heating test at 1600°C, no local abrasion was observed as in the case of 1200°C.

[0069] From the results of the above pre-test, the effectiveness of the selective coating layer on the outer peripheral surface of the front end portion of the nozzle can be confirmed. Note that in the sample 1 in which the coating layer was formed on the entire surface of the nozzle, although no local abrasion was observed much at the heating at 1200°C, it is predicted that the abrasion will progress in the case of a longer heating time.

[0070] [Manufacture of a bushing for glass fiber production, field test]

[0071] As described above, by forming the coating layer preferentially on the outer peripheral surface of the front end portion of the nozzle, the inhibitory effect of the local abrasion due to the volatilization of platinum or the like can be confirmed. Therefore, an actual bushing for glass fiber production was manufactured, and a field test of producing glass fibers was performed. As to the bushing for glass fiber production manufactured in this embodiment, a bottom plate made of platinum alloy (Pt-20% Rh) having a bottom surface size of 155 mm x 550 mm and a thickness of 1.5 mm was joined with 4000 nozzles made of platinum alloy (Pt-20% Rh) having the same size as the nozzle used in the above pre-test.

[0072] Then, in the bushing for glass fiber production, a coating layer made of stabilized zirconia was formed on the outer peripheral surface of the front end portion of all the nozzles. Specifically, the coating layer was formed on a width of 1.75 mm from the discharge side end portion of the nozzle (1.75 mm from the root of the nozzle). The width of the coating layer was 50% with respect to the entire length of the nozzle. The base metal (platinum alloy) was exposed on the other portions of the nozzle and the bottom plate. The thickness of the coating layer was in the range of 50 μm to 300 μm at any portion of the coating layer. Also, the coverage ratio P of the front end portion of the nozzle of the bushing for glass fiber production was 40.2%.

[0073] As to the manufacture of the bushing for glass fiber production, the nozzles processed to the above size were arranged and joined to the bottom plate by punching. In the joining of the nozzles, through holes were formed in advance in the nozzle mounting portions of the bottom plate, the nozzles were inserted into the through holes, and pre-joining was performed by heating in an electric furnace, and the root of the joined portion was welded by YAG laser. Thus, a bushing before coating was manufactured. Then, before the formation of the coating layer, the range to be a non-coating region was masked, and the coating layer was selectively formed on the outer peripheral surface of the front end of the nozzle. After the formation of the coating layer, the mask was removed, and thus the bushing for glass fiber production of this embodiment was obtained.

[0074] In the manufacturing test of the glass fiber using the glass fiber manufacturing bushing of the present embodiment, first, the bushing is joined to the terminal for electric current passage heating and the side flange of the box shape. Then, the bushing is assembled to the downstream side of the melting tank of the glass manufacturing apparatus. The glass fiber discharged from the bushing is properly wound.

[0075] The glass fiber manufacturing apparatus provided with the glass fiber manufacturing bushing of the present embodiment is used to manufacture the glass fiber for 6 months (the heating temperature of the bushing is 1300°C). During this period, no significant abnormality in appearance is observed in the nozzles of the bushing. Moreover, the glass fiber drawing is also stably performed. After the apparatus is operated for half a year, the glass manufacturing apparatus is first shut down, the bushing is removed, and the inspection of the bottom plate and the nozzles is performed.

[0076] In the inspection results, regarding the nozzles, no local abrasion like a hole is observed in any of the nozzles. On the other hand, the bottom plate is observed and the abrasion amount is confirmed, and as a result, there is a tendency that the plate thickness abrasion of the bottom plate increases from the central portion to both side end portions, but there is no conspicuous abrasion site as a whole, and the result of the measurement is that although there is a site where the plate thickness is abraded by a maximum of about 7% with respect to the plate thickness at the time of manufacturing, the plate thickness abrasion is about 1.7% or so in total. However, no abnormality in the temperature distribution or the like is observed during the apparatus operation for the half year, and there is no particular problem in the quality of the manufactured glass fiber.

[0077] Industrial applicability

[0078] The glass fiber manufacturing bushing according to the present embodiment can realize stable use during a long operation period for the glass manufacturing apparatus, and can efficiently manufacture the glass fiber with excellent quality.

Claims

1. A bushing for glass fiber production, comprising a plurality of nozzles made of platinum or platinum alloy and discharging molten glass, and a base plate made of platinum or platinum alloy, the plurality of nozzles being joined to the base plate, characterized in that, a coating layer is formed on the outer peripheral surface of the tip portion on the glass discharge side of the plurality of nozzles, the width of the coating layer being 5% or more and 95% or less with respect to the full length of the nozzle, the coating layer is not formed on the end surface on the glass discharge side of the plurality of nozzles, and the base plate includes a non-coating region having no coating layer in at least a part thereof.

2. The bushing for glass fiber production according to claim 1, wherein the coverage ratio P of the tip portion of the nozzle represented by the following formula is 5% or more and 350% or less, P(%) = C / (NC1+NC2) x 100 wherein C is the total surface area of the coating layer of the tip portion of the nozzle in the entire nozzle, NC1 is the total surface area of the region of the nozzle having no coating layer in the entire nozzle, and NC2 is the surface area of the non-coating region of the base plate.

3. The bushing for glass fiber production according to claim 1 or claim 2, wherein the thickness of the coating layer is in the range of 2 μm or more and 500 μm or less.

4. The bushing for glass fiber production according to claim 1 or claim 2, wherein the coating layer is made of at least any one of zirconia, stabilized zirconia, alumina, silica, aluminosilicate, and magnesium oxide.

5. A method for producing a glass fiber using the bushing for glass fiber production according to claim 1 or claim 2, wherein a glass blank in a molten state is circulated from the bushing for glass fiber production, and a glass blank in a fiber form is discharged. ​ ​ ​ ​ ​ ​ ​ ​ ​

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