spinneret

Abstract

To provide a spinneret in which laminated plates with different thicknesses are laminated, capable of being repeatedly used in a fiber manufacturing process, having excellent handleability and capable of long-term usage, without reducing fiber productivity in industrial use.SOLUTION: A spinneret in which laminated plates with two or more types of different thicknesses are laminated is characterized in that a positioning pin hole of the plate with the least thickness (laminated plate B) is bored based on the following formula: 0.010≤(b / a-1) / HAB (Formula 1). Here, a and b represent a short axis (a) and a long axis (b) of a perpendicular cross section of the positioning pin hole, and b / a represents an aspect ratio of the positioning pin hole. HAB represents a thickness ratio of the thickest laminated plate (laminated plate A) to the laminated plate B.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a spinneret for discharging a polymer in the form of a thread. [Background technology]

[0002] Currently, the uses of fibers are becoming more diverse, from clothing to industrial materials, and the required characteristics are becoming more diverse, so a wide variety of fiber element technologies have been proposed to meet these demands. For example, there are technologies such as finer single yarns and multifilament yarns aimed at providing a soft feel and high functionality by improving the yarn surface area, irregular cross-sections aimed at providing gloss and rigidity, and composite fibers aimed at high functionality by combining two or more types of polymers.

[0003] Generally, in order to produce these synthetic fibers, a spinneret for discharging the liquefied polymer is essential, but in order to stably produce fibers that satisfy the above-mentioned high functionality, it is essential to use a spinneret with a precisely designed flow path. Among them, in a spinneret capable of multifilamentation aimed at finer single yarns and a spinneret for compounding two or more polymers into a desired shape, the spinneret is composed of at least two types of laminated plates, a laminated plate for precisely controlling the polymer flow and a laminated plate for stably discharging the controlled polymer flow in a filamentous form. In this way, in order to precisely control the polymer flow and enable stable discharge, it is essential to apply a spinneret composed of multiple laminated plates, but high processing accuracy is required for the manufacture of such a spinneret. As a result, the manufacturing cost is also high, so from the viewpoint of industrial use, it goes without saying that it has long-term yarn production stability, and in addition, it is required to have excellent reusability and handleability.

[0004] The repeated use here means that after the spinneret is used to produce fibers, the laminates are disassembled, the polymer is removed and the laminates are washed, and then the laminates are reassembled and used to produce fibers. For example, in the case of melt spinning, the laminates are used in an environment where the polymer flow passes intermittently through the laminates while being fixed in the spin pack at high temperatures for a long period of time.

[0005] Thus, the spinneret is subjected to temperature changes and external shocks in several steps during its use. In general, a spinneret consisting of a plurality of laminates is assembled by adjusting the position using positioning pins, bolts, etc. so as not to unnecessarily block the flow path between the laminates, and then fixed and used for fiber production. However, the distortion of the laminates caused by use may become apparent, such as deformation of the laminates, such as bending and shrinkage. In this case, a slight deviation occurs in the center position of the positioning pin holes between the laminates, making it difficult to properly assemble the spinneret and making it difficult to reuse it. In addition, in a spinneret that aims to divide the polymer flow into a denser polymer flow and produce a complex fiber cross section, the number of laminates constituting the spinneret will be large, but considering that it is often designed to be applicable to existing fiber production equipment, the thickness of the laminates will be as thin as possible. In this case, distortion due to temperature changes and external shocks is likely to occur, which may encourage further assembly defects.

[0006] In response to such problems, Patent Document 1 proposes an integrated composite spinneret that does not require positioning pins by joining the laminated plates that make up the composite spinneret together.

[0007] Moreover, Patent Document 2 proposes a spinneret having a ceramic member that is less affected by thermal expansion compared to a metal member. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2008-38305 A [Patent Document 2] JP 2001-234421 A Summary of the Invention [Problem to be solved by the invention]

[0009] Patent Document 1 discloses a technique for assembling a spinneret that does not require a positioning pin, by forming a composite spinneret in which a group of polymer flow paths for distributing and transporting a plurality of polymers is processed and a group of spinneret plates divided into a plurality of parts are laminated together with their joint surfaces aligned to form an integrated spinneret. By using this spinneret, the spinneret plates are joined together to form an integrated spinneret, so that it is possible to eliminate the problem of assembly defects during repeated use. However, since it is an integrated spinneret in which each laminated plate is joined, a very complicated polymer flow path is formed inside the spinneret, and in a cleaning process after use, for example, a process of immersing the spinneret in a heated salt bath, it may be difficult to remove the polymer remaining in the flow path. Since poor cleaning may cause deterioration of operability, there have been cases in which it has not been possible to ensure stable fiber production.

[0010] Patent Document 2 discloses a spinneret technology for improving polymer release properties and stabilizing spinning production by using ceramic members for polymer discharge hole groups in a spinneret for melt spinning. This technology is said to be able to achieve excellent spinning stability by disposing ceramic members on the discharge laminate of the spinneret, which are less likely to accumulate foreign matter such as polymer thermal degradation products generated during spinning, compared to metal members such as SUS304, SUS630, and SUS316 that have been conventionally applied to spinnerets. Indeed, ceramic members have superior thermal dimensional stability compared to metal members, and there is a possibility that assembly defects due to bending and shrinkage during repeated use of the spinneret can be suppressed. However, since ceramic members are highly brittle and have low impact resistance, they may be chipped or cracked due to external impacts received during repeated use, making them difficult to handle.

[0011] In this way, in a spinneret constructed by stacking a plurality of laminated plates, warping and shrinkage due to repeated use become evident, and assembly of the spinneret when reused may become difficult. Therefore, there has been a demand for a spinneret that is excellent in repeated use and ease of handling while ensuring stable fiber production. [Means for solving the problem]

[0012] The above object can be achieved by the following means. (1) A spinneret in which a plurality of laminated plates are stacked, the laminated plates have two or more different thicknesses, and the positioning pin hole of the thinnest plate (laminate B) is drilled based on the following formula. 0.010≦(b / a-1) / H AB (Formula 1) Here, a and b are the minor axis (a) and major axis (b) of the positioning pin hole in the vertical cross section of the laminate, and b / a is the aspect ratio of the positioning pin hole. AB refers to the ratio of the thickness of the thickest laminate A to the thickness of laminate B. (2) The spinneret according to (1) above, wherein the laminate is made of stainless steel (SUS). (3) A spinneret according to the above (1) or (2), wherein the materials of the laminate A and the laminate B are different stainless steels (SUS). Effect of the Invention

[0013] The present invention makes it possible to provide a spinneret that can be used repeatedly in a fiber production process, does not impair fiber productivity even in industrial use, is easy to handle, and can be used for a long period of time. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram of a spinneret of the present invention, in which three laminated plates are stacked together. [Diagram 2] FIG. 2 is a schematic diagram of a positioning pin hole for explaining the aspect ratio of (Formula 1) of the present invention. [Diagram 3] 1 is a schematic plan view of a laminate B having positioning pin holes according to the present invention, the laminate B having positioning pin holes drilled in two places. Note that the polymer flow paths are omitted in the drawing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention will be described in detail below based on preferred embodiments. An example of a schematic diagram of a spinneret in which a plurality of laminates of different thicknesses are laminated according to the present invention is shown in Fig. 1. Fig. 1 illustrates a spinneret in which three laminates are laminated. The number of laminates in the present invention may be two or more, and is not particularly limited, but three or more is preferable.

[0016] The spinneret of the present invention may be a spinneret that discharges a single polymer, or it may be a composite spinneret for discharging a composite polymer stream composed of two or more types of polymers.

[0017] The spinneret in Figure 1 is composed of three laminated plates: an inlet plate 1, which is responsible for uniformly flowing the polymer components into the distribution plate 2; a distribution plate 2 for finely distributing the polymer components; and a discharge plate 3 for discharging the polymer in the form of threads. By using a spinneret having the above-mentioned configuration, it is possible to precisely control the polymer flow, and to suppress the deterioration of the polymer due to abnormal retention in the spinneret. In addition, it is possible to homogeneously subdivide the polymer flow, thereby ensuring the stability of spinning. Furthermore, it is possible to manufacture high-added-value fibers such as multifilament fibers and cross-section stabilization in composite spinning.

[0018] The thickness of each laminate plate in the spinneret of the present invention may be appropriately adjusted and set so that it fits into an existing spin pack while taking into consideration the back pressure when the polymer passes through. The spinneret in Fig. 1 is made up of three types of laminate plates with different thicknesses: an inlet plate 1 of 15 mm, a distributor plate 2 of 5 mm, and an outlet plate 3 of 30 mm.

[0019] In the spinneret of the present invention, when multiple laminates are laminated, the multiple laminates are fixed while adjusting their positions using a positioning pin 4 shown in Fig. 1 so as not to block the polymer flow path. In this case, in order to increase the accuracy of the position adjustment, it is preferable that at least two positioning pin holes are drilled in each laminate.

[0020] In the spinneret of the present invention, from the viewpoint of improving handleability and sealing property to improve spinning stability, it is also preferable to drill bolt holes in the laminated plates and integrate the spinneret with bolts. The spinneret in Fig. 1 has a bolt hole drilled in the center of the multiple laminated plates stacked together, and the spinneret is integrated with a bolt 5.

[0021] In the spinneret of the present invention, the positioning pin holes of the thinnest plate (laminate plate B) among the multiple laminate plates are drilled based on the above (Formula 1). This makes it possible to eliminate assembly defects caused by bending or shrinkage of the laminate plates during repeated use of the spinneret.

[0022] When used for melt spinning, the spinneret is exposed to a high-temperature atmosphere of 200°C or higher, and the laminates that make up the spinneret undergo thermal expansion. The degree of this thermal expansion depends on the temperature, material, and shape. For this reason, even if a spinneret made of multiple laminates of the same material and shape is left in a high-temperature atmosphere of 200°C or higher, no distortion due to thermal expansion occurs.

[0023] However, in the case of a spinneret of the present invention that is composed of a plurality of laminated plates having different thicknesses, bending or shrinkage of the laminated plates may occur for reasons that will be described later using the spinneret of FIG. 1 as an example.

[0024] The spinneret of the present invention, which is composed of a plurality of laminates, is firmly fixed in order to maximize the sealing property in the spin pack and prevent polymer leakage. The thermal expansion of the laminate increases according to the thickness of each laminate, so that the laminate expands thermally in the thickness direction and in the discharge surface direction. In this case, since the laminates constituting the spinneret of the present invention are integrated with positioning pins, the other laminates thermally expand to follow the thickest laminate A (discharge plate 3), and as a result, the thinnest laminate B (distribution plate 2) is most distorted. When the polymer flow passes through the distribution plate 2 in this state or an external impact is applied, the distortion of the laminate B may become apparent as a minute deflection in the polymer discharge direction, or the laminate B may shrink to eliminate the distortion during the disassembly process. As a result, when the laminate B (distribution plate 2) is reused, the center position of the positioning pin hole is misaligned with the other laminates (introduction plate 1, discharge plate 3), which may cause a failure in the spinneret assembly and make it difficult to reuse it.

[0025] In order to solve this problem, the spinneret of the present invention is a spinneret in which the positioning pin holes in the thinnest plate (laminated plate B) are drilled based on the following (Equation 1), and a spinneret that combines excellent handleability and repeated use has been discovered. 0.010≦(b / a-1) / H AB (Formula 1) Here, a and b are the minor axis (a) and major axis (b) of the positioning pin hole in the vertical cross section of the laminate, and b / a is the aspect ratio of the positioning pin hole. AB is the ratio of the thickness of laminate A to the thickness of laminate B.

[0026] By drilling the positioning pin hole of the above formula 1 in the thinnest laminate B, it is possible to reduce distortion caused by differences in thermal expansion between multiple laminates of different thicknesses, and also to reduce deviation of the center position of the positioning pin hole caused by bending and shrinkage that become evident during the fiber production process. This allows the positioning pin holes of multiple laminates to maintain communication and multiple laminates to be stacked without blocking the polymer flow path, resulting in a spinneret that is excellent in fiber production stability, fiber quality, and repeated use.

[0027] The positioning pin hole drilled based on (Formula 1) in the spinneret of the present invention has an elliptical shape with an aspect ratio b / a greater than 1, as exemplified in Fig. 2. At least one elliptical positioning pin hole may be drilled in one laminate. From the viewpoint of increasing the positioning accuracy when stacking a plurality of laminates, it is preferable that at least one circular positioning pin hole is drilled in addition to the elliptical positioning pin hole.

[0028] FIG. 3 shows an example of laminate B in which one oval positioning pin hole 6 and one circular positioning pin hole 7 of the above formula 1 are drilled in one place. The aspect ratio b / a of the oval positioning pin hole 6 in the spinneret of the present invention is such that the larger the aspect ratio, the more the distortion caused by the difference in thermal expansion with other laminates can be reduced, and the more the deviation of the center position of the positioning pin hole caused by bending or shrinkage that becomes evident through the fiber production process can be compensated for. On the other hand, in order to smoothly arrange the polymer flow path and adjust the position when assembling the spinneret, the aspect ratio b / a is preferably 1.1 to 2.0.

[0029] In addition, the thickness ratio H of the laminated plate in the spinneret of the present invention AB It is preferable that H is in the range of 1.1 to 40. AB By making the value 40 or less, the distortion that tends to occur in the laminate B can be suppressed, the ease of assembling a plurality of laminates into the spinneret can be improved, and a spinneret with excellent reusability can be obtained.

[0030] In the spinneret of the present invention, it is sufficient that a positioning pin hole based on the above (Formula 1) is drilled in laminate B, but the positioning pin holes in the other laminates may also be drilled with positioning pin holes based on the above (Formula 1).

[0031] In the spinneret of the present invention, from the viewpoint of assembling the spinneret by stacking the laminated plates without impairing the accuracy of position adjustment, it is preferable that the center positions of the positioning pin holes of each laminated plate are communicated in the vertical direction.

[0032] The positioning pin hole in the spinneret of the present invention may be drilled anywhere as long as it does not interfere with the polymer flow path. However, as illustrated in FIG. 3, it is preferable that the centers of the oval positioning pin hole 6 and the circular positioning pin hole 7 based on the above formula 1 are on the same circumference.

[0033] The minor axis a of the vertical cross section of the oval-shaped positioning pin hole in the spinneret of the present invention is preferably +0.05 mm to +0.20 mm relative to the outer diameter of the positioning pin, and more preferably +0.10 mm to +0.15 mm to further improve the accuracy of position adjustment.

[0034] In addition, it is preferable that the long axis b of the oval-shaped positioning pin hole in the spinneret of the present invention is set toward the center of the laminate, which can reduce the bending and shrinkage that occurs in the laminate B toward the center of the laminate.

[0035] The laminated plate constituting the spinneret of the present invention is preferably made of stainless steel (SUS), which has high strength, excellent dimensional stability, excellent workability of fine holes, and is resistant to rust, making it suitable for the spinneret of the present invention used in melt spinning, which is exposed to high temperatures for long periods of time.

[0036] In addition, the materials of the laminates constituting the spinneret of the present invention may be different for each laminate, as long as the object and effect of the present invention are not impaired. As the SUS material, SUS630 material (linear expansion coefficient 1.2×10 -5 / ℃), SUS316 material (linear expansion coefficient 1.6×10 -5 / ℃), SUS304 material (linear expansion coefficient 1.7×10 -5 / °C). For example, by using SUS630 material for the thickest laminate A and SUS316 material for the thinnest laminate B, the difference in thermal expansion can be suppressed and the resulting distortion can be reduced.

[0037] The shape of the spinneret of the present invention is not limited to a circular shape, but may be a polygonal shape such as a square.

[0038] The pinhole diameter of the positioning pin 4 used in the spinneret of the present invention is not particularly limited, but is preferably φ3 mm to φ10 mm. A pinhole diameter of φ3 mm or more can prevent breakage, and a pinhole diameter of φ10 mm or less can facilitate the arrangement of the polymer flow path. Furthermore, the material of the positioning pin used in the spinneret of the present invention is preferably stainless steel (SUS) from the viewpoints of heat resistance, strength, and ease of handling.

[0039] The method of using the spinneret of the present invention has been described based on the melt spinning method, but it can also be applied to the melt blowing method and the spunbonding method, and further to solution spinning methods such as wet and dry-wet. EXAMPLES

[0040] The effects of the composite spinneret of the present invention will be specifically described below with reference to examples. The examples and comparative examples were evaluated as follows.

[0041] A. Laminate thickness The thickness of each laminate constituting the spinneret was measured in mm at three points using a vernier caliper, and the average value was rounded off to the nearest tenth to determine the thickness of the laminate.

[0042] B. Short axis (a) and long axis (b) of the vertical cross section of an oval-shaped locating pin hole For laminate B, which is the thinnest of the laminates constituting the spinneret, an image was taken with a KEYENCE digital microscope at a magnification that included the positioning pin hole, and the short axis and long axis were measured in mm using image processing software (WINROOF). The values ​​rounded to the first decimal place were defined as the short axis (a) and the long axis (b), respectively, and the aspect ratio (b / a) was calculated.

[0043] C. Spinneret assembly For each Example, the assembly property of the spinneret that had been repeatedly used 10 times was evaluated using the following two-stage scale. Note that "repeated use" refers to the process of disassembling each laminated plate after use, removing the polymer, and cleaning the plate, and then reassembling the plate, and disassembly and assembly are counted as one time. Good A: Can be assembled without any problems. Defective C: Unable to assemble after less than 10 uses.

[0044] D. Spinning stability For each Example, spinning was performed using a spinneret that had been used repeatedly 10 times, and the spinning stability was evaluated on the following three-level scale based on the number of yarn breaks per 1 million meters. Good A: Number of yarn breaks < 1.0 / million m Acceptable B: 1.0 times / million m≦Number of thread breaks<2.0 times / million m Defective C: Number of yarn breakages ≧2.0 times / million m.

[0045] E. Section formability For each Example, the sea-island composite fibers produced using the spinneret that had been used repeatedly 10 times were embedded in epoxy resin, frozen using a Reichert FC-4E cryosectioning system, and cut using a Reichert-Nissei ultracut N (ultramicrotome) equipped with a diamond knife, and the cut surfaces were photographed using a transmission electron microscope (TEM) at a magnification that allowed observation of all the island components in one sea-island composite fiber for 10 different sea-island composite fibers. From these images, the island component diameters of all 10 sea-island composite fibers were measured using image processing software (WINROOF), and the average value and standard deviation were calculated. From these results, the island component diameter variation CV% was calculated based on the following formula, and the cross section formability was judged based on the following. Island component diameter variation CV% = (standard deviation / average value) x 100 Good A: Island component diameter variation <20.0 Poor C: Island component diameter variation ≧ 20.0.

[0046] [Example 1] The spinneret is composed of three laminated plates, the inlet plate 1 having a thickness of 15 mm, the distribution plate 2 having a thickness of 5 mm, and the discharge plate 3 having a thickness of 30 mm (thickness ratio H AB = 6.0) and for sea-island composite fibers with 70 islands. The aspect ratio (b / a) of the oval positioning pin holes drilled in the distribution plate 2, i.e., laminate plate B, was 1.4. Using this spinneret, sea-island composite fibers were produced as follows.

[0047] Polyethylene terephthalate (PET1, melt viscosity 160 Pa s) was used as the island component, and polyethylene terephthalate copolymerized with 8.0 mol% 5-sodium sulfoisophthalic acid and 10 mass% polyethylene glycol with a molecular weight of 1000 (copolymerized PET, melt viscosity 121 Pa s) was used as the sea component. The spinning temperature was set to 285°C, and the polymer was flowed into the spin pack, and a composite polymer flow was discharged from the discharge hole of the spinneret so that the composite weight ratio of the sea component / island component was 20 / 80. The melt-discharged yarn was cooled and solidified, and then an oil agent was applied, and the yarn was drawn 3.3 times between rollers heated to 85°C and 150°C, and wound up at 4000 m / min to produce a sea-island composite fiber of 66 dtex-9 filaments. The spinneret was then disassembled from the spin pack, washed, and reassembled, and the same operation was repeated nine times to produce a sea-island composite fiber.

[0048] After 10 uses, the spinneret could be assembled without any problems because the elliptical positioning pin holes in the laminated plates maintained communication with each other through the oval positioning pin holes drilled in laminated plate B. The spinning stability was also excellent (0 yarn breakages) and the cross-section formability was also good (CV%=4.7), demonstrating excellent reusability. The results are shown in Table 1.

[0049] [Examples 2 and 3] The spinneret was carried out in the same manner as in Example 1, except that the aspect ratio of the oval positioning pin hole drilled in the laminate B was changed to 1.1 (Example 2) and 2.0 (Example 3).

[0050] In both spinnerets, the oval shaped positioning pin holes played a role in reducing distortion caused by the difference in thermal expansion with other laminates in the spin pack, and the positioning pin holes of each laminate were in a connected state, which showed good spinneret assembly properties and no problems with repeated use. The results are shown in Table 1.

[0051] [Comparative Example 1] As the spinneret, laminate B was used in which the positioning pin hole was round, i.e., the aspect ratio (b / a) was 1.0, outside the range of the (Equation 1) specified in the present application, and all other operations were carried out in the same manner as in Example 1.

[0052] With this spinneret, minute deflections and shrinkage occurred in laminate B with repeated use, causing slight misalignment in the center positions of the positioning pin holes between the laminates, making it impossible to properly assemble the spinneret after five uses, and resulting in inferior reusability compared to Example 1. The results are shown in Table 1.

[0053] [Comparative Example 2] As for the spinneret, the same procedure as in Example 1 was repeated except that the aspect ratio of the oval positioning pin hole drilled in laminate B was set to 1.05, which was outside the range of (Formula 1) specified in the present application.

[0054] In this spinneret, the effect of the oval-shaped positioning pin hole was small, so that the deformation of laminate B was likely to progress with repeated use, and a slight misalignment occurred in the center position of the positioning pin hole between the laminates, and as a result, the spinneret could not be assembled after seven uses. The results are shown in Table 1.

[0055] [Examples 4 to 6] In Example 4, the thickness ratio H AB = 10.0, and in Example 5, the thickness ratio H AB = 30.0, and in Example 6, the thickness of the laminate B was changed so that the thickness ratio H AB The same procedure as in Example 1 was repeated, except that the thicknesses of the laminates A and B were changed so that the σ=16.7.

[0056] In all spinnerets, even when the thickness ratio was increased compared to Example 1, the spinnerets could be used repeatedly without impairing the assembly properties, and showed good spinning stability and cross section formability. The results are shown in Table 1.

[0057] [Comparative Example 3] The spinneret is composed of laminated plates, the distribution plate 2 having a thickness of 1 mm and the discharge plate 3 having a thickness of 50 mm, i.e., a thickness ratio of H AB The same procedure as in Example 1 was repeated except that the value was set to 50.0, which is outside the range of the formula 1 defined in the present application.

[0058] This spinneret is designed so that the distortion caused in laminate B by repeated use is the thickness ratio H AB Since the positioning pin holes remained connected after 10 uses, the laminate B was easily warped and shrunk with repeated use, and although it was possible to assemble it, the polymer flow paths between the laminates were misaligned, causing the polymer to be abnormally retained locally, resulting in polymer degradation, and the number of yarn breakages was high at 6.7 times / million meters, and the island component sizes were also non-uniform in the fiber cross section, resulting in inferior spinning stability and cross section formability compared to Example 1. The results are shown in Table 1.

[0059] [Examples 7 to 9] Example 7 was carried out according to Example 1, except that the inlet plate 1 and the distribution plate 2 were integrated into a laminate having a thickness of 20 mm, and the number of laminated discharge plates 3 (thickness 30 mm) was two. Example 8 was carried out according to Example 1, except that the distribution plate 2 was 3 mm thick and three plates were laminated (a total of five inlet plates 1 and discharge plates 3), and Example 9 was carried out according to Example 1, except that the distribution plate 2 was 3 mm thick and six plates were laminated (a total of eight inlet plates 1 and discharge plates 3).

[0060] In all spinnerets, the spinnerets were easy to assemble even after 10 uses, and were excellent in terms of reusability. In particular, in Examples 8 and 9, by increasing the number of layers, the polymer flow could be made more homogenous, and the cross-sectional formability was superior to that of Example 1. The results are shown in Table 2.

[0061] [Examples 10 to 12] Examples 10 and 11 were carried out in the same manner as Example 1, except that the material of the laminate was changed to SUS304 (Example 10) and SUS316 (Example 11), and Example 12 was carried out in the same manner as Example 1, except that the material of laminate B was changed to SUS316.

[0062] In all spinnerets, good repeated usability was obtained even when the material was changed. In particular, in Example 12, by using a material with a different linear expansion coefficient for laminate B, the distortion caused by the thermal expansion difference was reduced as much as possible, and the deformation of laminate B due to repeated use was suppressed, so that the spinning stability and cross-sectional formability were as excellent as those of Example 1. The results are shown in Table 2.

[0063] [Table 1]

[0064] [Table 2] [Explanation of symbols]

[0065] a: Minor axis of the vertical cross section of the oval shaped positioning pin hole b: Long axis of the vertical cross section of the oval shaped positioning pin hole 1: Introduction board 2: Distribution plate 3: Discharge plate 4: Positioning pin 5: Bolt 6: Oval shaped positioning pin hole 7: Circular positioning pin hole

Claims

1. A spinneret in which a plurality of laminated plates are stacked, the laminated plates have two or more different thicknesses, and the positioning pin hole of the thinnest plate (laminate plate B) is drilled based on the following formula. 0.010≦(b / a-1) / H ＡＢ (Formula 1) Here, a and b are the minor axis (a) and major axis (b) of the positioning pin hole in the vertical cross section of the laminate, and b / a indicates the aspect ratio of the positioning pin hole. ＡＢ refers to the ratio of the thickness of the thickest laminate A to the thickness of laminate B.

2. 2. The spinneret according to claim 1, wherein the laminate is made of stainless steel (SUS).

3. 3. The spinneret according to claim 1 or 2, wherein the laminated plate A and the laminated plate B are made of different stainless steels (SUS).

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