Nozzle for special-shaped cross-section glass fiber and method for producing special-shaped cross-section glass fiber

Abstract

A nozzle (8) for irregular cross-section glass fibers is provided with a flat nozzle hole (6), the nozzle hole (6) having an inlet (6a) and an outlet (6b) for molten glass (2), a wall portion surrounding the nozzle hole (6) having a pair of short wall portions (12) opposed in the long diameter direction of the nozzle hole (6) and a pair of long wall portions (11) opposed in the short diameter direction, the nozzle (8) for irregular cross-section glass fibers is used to manufacture irregular cross-section glass fibers (2f) using molten glass (2) flowing out of the nozzle hole (6), and when the nozzle hole (6) is viewed from the outlet (6b) side, the average width of the bottom wall surface (12b) of the short wall portion (12) is wider than the average width of the bottom wall surface (11b) of the long wall portion (11).

Description

Technical Field

[0001] The present invention relates to a nozzle for producing irregular cross-section glass fibers having a flat cross-section shape using molten glass, and a method for producing the irregular cross-section glass fibers using the nozzle. Background Art

[0002] As one type of glass fiber, a flat cross-sectional glass fiber is manufactured (see Patent Document 1). The glass fiber can achieve a high reinforcing effect when compounded with a resin, and is therefore used in various fields such as fiber for fiber reinforced plastics (FRP).

[0003] When manufacturing a special-shaped cross-section glass fiber, for example, molten glass is supplied to an extruder from a feeder for circulating the molten glass, and the molten glass is drawn out from a plurality of nozzles provided in the extruder and cooled. The shape of the nozzle hole provided in the nozzle is generally a flat hole shape (rectangular, oblong, etc.).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2017 / 221471 Summary of the invention

[0007] Technical problem that the invention aims to solve

[0008] When producing a deformed cross-section glass fiber, there is the following problem to be solved: That is, the molten glass flowing out of the nozzle hole is deformed so that the surface area becomes small due to surface tension, and thus it is difficult to form a deformed cross-section glass fiber with a high flatness.

[0009] The present invention has been made in view of the above circumstances and has the technical problem of enabling the production of fibers with a high flatness ratio when producing a special-shaped cross-section glass fiber.

[0010] Technical solutions to the problem

[0011] The present invention for solving the above-mentioned problems is a nozzle for glass fibers with special cross-sections, characterized in that a flat nozzle hole is provided, the nozzle hole has an inlet and an outlet for molten glass, a wall portion surrounding the nozzle hole has a pair of short wall portions opposing each other in the long diameter direction of the nozzle hole and a pair of long wall portions opposing each other in the short diameter direction, the nozzle for glass fibers with special cross-sections is used to manufacture glass fibers with special cross-sections using molten glass flowing out of the nozzle hole, and the average width of the bottom wall surface of the short wall portion is wider than the average width of the bottom wall surface of the long wall portion.

[0012] When manufacturing a special-shaped cross-section glass fiber, in addition to the inner peripheral surface of the nozzle hole (including the inner wall surface of the short wall portion and the long wall portion), the bottom wall surface of the short wall portion and the long wall portion is also wetted by the molten glass. At this time, the bottom wall surface of the short wall portion and the long wall portion can respectively stretch the molten glass in the direction along the bottom wall surface, and the wider the width of the bottom wall surface (the width of the short wall portion along the thickness direction, or the width of the long wall portion along the thickness direction), the easier it is to stretch the molten glass. Moreover, in order to improve the flatness of the manufactured special-shaped cross-section glass fiber, it is advantageous to stretch the molten glass along the long diameter direction compared to the short diameter direction of the nozzle hole. Therefore, as shown in this structure, if the average width of the bottom wall surface of the short wall portion is wider than the average width of the bottom wall surface of the long wall portion, the molten glass can be effectively stretched along the long diameter direction of the nozzle hole. As a result, the special-shaped cross-section glass fiber can be formed into a high flatness.

[0013] In the above structure, the average width of the bottom wall surface of the short wall portion is preferably 1.5 times or more the average width of the bottom wall surface of the long wall portion.

[0014] This can effectively exert the effect of stretching the molten glass in the long-diameter direction of the nozzle hole, which is more advantageous in forming the irregular cross-section glass fiber with a high flatness.

[0015] In the above configuration, it is preferred that the area of ​​the bottom wall surface of the short wall portion is larger than the area of ​​the bottom wall surface of the long wall portion.

[0016] This can effectively exert the effect of stretching the molten glass in the long-diameter direction of the nozzle hole, which is more advantageous in forming the irregular cross-section glass fiber with a high flatness.

[0017] Furthermore, the present invention for solving the above-mentioned problems is a method for manufacturing irregular cross-section glass fibers, characterized in that the irregular cross-section glass fibers are manufactured using a nozzle for the irregular cross-section glass fibers, the nozzle for the irregular cross-section glass fibers being provided with a flat nozzle hole, the nozzle hole having an inlet and an outlet for molten glass, the wall portion surrounding the nozzle hole having a pair of short wall portions opposing each other in the long diameter direction of the nozzle hole and a pair of long wall portions opposing each other in the short diameter direction, the manufacturing method being used to manufacture irregular cross-section glass fibers using molten glass flowing out of the nozzle hole, so that the average width of the bottom wall surface of the short wall portion is wider than the average width of the bottom wall surface of the long wall portion.

[0018] According to this method, the same actions and effects as those already described can be obtained for the above-mentioned nozzle for irregular-section glass fibers.

[0019] Effects of the Invention

[0020] According to the present invention, when producing a special-shaped cross-section glass fiber, a fiber with a high flatness can be produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a cross-sectional view schematically showing a method and apparatus for producing a deformed-cross-section glass fiber.

[0022] Figure 2 This is a cross-sectional view schematically showing the periphery of a nozzle for a special-shaped cross-section glass fiber.

[0023] Figure 3 This is a bottom view schematically showing the periphery of a nozzle for irregular-section glass fibers.

[0024] Figure 4 (a) is a side view of the nozzle for special-shaped cross-section glass fibers as viewed from the long wall portion side, (b) is a cross-sectional view, and (c) is a bottom view.

[0025] Figure 5 It is a cross-sectional view showing a glass fiber with a special cross section.

[0026] Figure 6 This is a bottom view of a nozzle for special-section glass fibers.

[0027] Figure 7 (a) is a side view of the nozzle for irregular-section glass fibers as viewed from the long wall portion side, (b) is a bottom view, and (c) is a cross-sectional view.

[0028] Figure 8 yes Figure 7 (c) Enlarged view of part A.

[0029] Explanation of symbols

[0030] 2 Molten Glass

[0031] 2f Special-section fiberglass

[0032] 6 Nozzle hole

[0033] 6a Inlet

[0034] 6b Outlet

[0035] 8 Nozzles for special-shaped cross-section glass fibers

[0036] 11 Longwall

[0037] 11b Bottom wall

[0038] 12 Short wall

[0039] 12b bottom wall surface

[0040] W1 Width

[0041] W2 Width DETAILED DESCRIPTION

[0042] Hereinafter, a nozzle for modified cross-section glass fibers and a method for producing modified cross-section glass fibers according to embodiments of the present invention will be described with reference to the drawings.

[0043] like Figure 1 As shown, the special-shaped cross-section glass fiber is manufactured by a manufacturing device 1. The manufacturing device 1 includes: a feeder 3 that flows a molten glass 2 generated by a melting furnace (not shown); an extruder 4 that is arranged at a position lower than the feeder 3; and a tube 5 that connects the feeder 3 and the extruder 4. The molten glass 2 is supplied from the feeder 3 to the extruder 4 via the tube 5. Then, the molten glass 2 flows out from the nozzle hole 6 of the extruder 4. The molten glass 2 is cooled to become a special-shaped cross-section glass fiber 2f (hereinafter, referred to as glass fiber 2f).

[0044] In the present embodiment, the molten glass 2 is made of E glass, but the present invention is not limited thereto, and the molten glass 2 may be made of other glass such as D glass, S glass, AR glass, or C glass.

[0045] The feeder 3 is connected to a glass melting furnace (not shown). The feeder 3 can flow the molten glass 2 continuously produced in the glass melting furnace. Inside the feeder 3, a liquid level 2a of the molten glass 2 is formed.

[0046] The extruder 4 has a base plate 7 at the bottom. A plurality of nozzles 8 for special-shaped cross-section glass fibers (hereinafter referred to as nozzles 8) and a cooling pipe 9 arranged near these nozzles 8 are provided on the base plate 7. The plurality of nozzles 8 have the same structure as each other. The details will be described later, and the nozzle hole 6 provided in each nozzle 8 is formed flat.

[0047] The tube 5 is formed into a cylindrical shape with a tube axis extending in the up-down direction. The upper end of the tube 5 is connected to the bottom of the feeder 3, and the lower end of the tube 5 is connected to the upper end of the extruder 4. It should be noted that as long as the tube 5 can connect the feeder 3 and the extruder 4, the shape and the direction in which the tube axis extends may be different from those in the present embodiment.

[0048] The extruder 4, the tube 5, the nozzle 8 and the cooling tube 9 are partially or entirely made of platinum or a platinum alloy (such as a platinum-rhodium alloy). In addition, in the present embodiment, the tube 5 among these components is entirely made of platinum or a platinum alloy.

[0049] The entire flow path from the connection portion between the feeder 3 and the tube 5 to the nozzle hole 6 of the extruder 4 is filled with the molten glass 2. Thus, the pressure (head pressure) for causing the molten glass 2 to flow out of the nozzle hole 6 is determined by the height difference H between the nozzle hole 6 and the liquid level 2a of the molten glass 2 in the feeder 3. Here, the height difference H can be adjusted by changing the length of the tube 5, for example.

[0050] The temperature and viscosity of the molten glass 2 when forming the glass fibers 2f are set to 1100°C to 1250°C (preferably 1150°C to 1200°C), 10 2.6 dPa·s~10 3.8 dPa·s (preferably 10 2.9 dPa·s~10 3.3 dPa·s). It should be noted that the "temperature and viscosity of the molten glass 2" referred to herein refers to the temperature and viscosity of the molten glass 2 at the position where it flows into the nozzle 8. The temperature and viscosity of the molten glass 2 can be adjusted, for example, by heating the extruder 4 and the tube 5 separately by any heating unit (for example, an electric heating device). In addition, the temperature and viscosity of the molten glass 2 can also be adjusted by heating the molten glass 2 and the feeder 3 in the glass melting furnace by electric heating.

[0051] The surface of the glass fiber 2f is coated with a sizing agent by an applicator (not shown). Thus, about several hundred to several thousand glass fibers 2f are spun as a strand 2s. The spun strand 2s is wound on a bobbin 10 as a winding device as a fiber bundle 2r. The strand 2s is cut into a length of about 1 mm to 20 mm, for example, and used as chopped strands.

[0052] like Figure 2 and Figure 3 As shown, the nozzle 8 has a pair of long wall portions 11, 11 and a pair of short wall portions 12, 12. The flat nozzle hole 6 is surrounded by these wall portions. The nozzle hole 6 has an inlet 6a for the molten glass 2 to flow in and an outlet 6b for the molten glass 2 to flow out. A notch portion 13 opening toward the outlet 6b side is provided on the pair of long wall portions 11, 11. Thus, the nozzle hole 6 is connected to the external space of the nozzle 8 through the notch portion 13.

[0053] The cooling pipe 9 circulates cooling water 14 inside thereof to cool the molten glass 2. The outer shape of the cooling pipe 9 is formed in a plate shape, and the plate surface is parallel to the long wall portion 11. Here, the cooling pipe 9 is provided integrally with the substrate 7, but it can also be provided at a position separated from the substrate 7. In addition, the cooling pipe 9 can also be formed in a circular tube shape.

[0054] The height position of the cooling pipe 9 can be adjusted according to the cooling condition of the molten glass 2. As an example, the cooling pipe 9 can be arranged at a position above the lower end of the nozzle 8 in a manner that the plate surface does not face the molten glass 2 drawn from the nozzle 8. On the other hand, the cooling pipe 9 can also be arranged across the upper and lower sides thereof with the lower end of the nozzle 8 as a reference in a manner that the plate surface faces the nozzle 8 and the molten glass 2 drawn from the nozzle 8. In addition, in the cooling of the molten glass 2, in addition to the cooling pipe 9, cooling fins cooled by air flow, etc. can also be used. In addition, the cooling pipe 9 is not a necessary structure and can be omitted.

[0055] A plurality of nozzle rows P are arranged in parallel at intervals on the substrate 7. Each nozzle row P has a plurality of nozzles 8. The plurality of nozzles 8 belonging to the same nozzle row P are arranged so that the nozzle holes 6 formed in the nozzles 8 are located on the same straight line.

[0056] The cooling pipe 9 is arranged between two adjacent nozzle rows P and P in a manner extending in parallel with the nozzle row P. Thus, the molten glass 2 in the nozzle hole 6 is cooled by the notch portion 13 facing the cooling pipe 9. Specifically, the molten glass 2 is rapidly cooled from a temperature of more than 1000°C by the cooling pipe 9. Here, the cooling pipe 9 also has a function of suppressing the degradation of these components caused by heat by cooling the extruder 4 (substrate 7) and the nozzle 8, thereby improving durability.

[0057] like Figure 4 As shown in (a) to (c), the notch 13 provided in the long wall portion 11 of each nozzle 8 is in the shape of an isosceles trapezoid whose upper base is shorter than the lower base. As a result, the opening width of the notch 13 gradually increases from the inlet 6a side of the nozzle hole 6 toward the outlet 6b side. The depth of the notch 13 (the length along the axis 6x direction of the nozzle hole 6) is 0.1 mm to 2 mm. This is because, when the depth of the notch 13 exceeds 2 mm, in the cross section of the manufactured glass fiber 2f, the two ends in the longitudinal direction are too thin, and the glass fiber 2f is easily damaged.

[0058] The shape of the notch 13 is not limited to a trapezoid, and may be other shapes. For example, it may be a triangle, a semicircle, or a rectangle. However, even when these other shapes are adopted, the notch 13 preferably has an opening width that gradually expands from the inlet 6a side of the nozzle hole 6 toward the outlet 6b side.

[0059] like Figure 4As shown, in the present embodiment, a single nozzle hole 6 is provided in one nozzle 8. The nozzle hole 6 is formed in a long hole shape. A pair of long wall portions 11, 11 are opposed to each other in the short diameter direction of the long hole-shaped nozzle hole 6, and a pair of short wall portions 12, 12 are opposed to each other in the long diameter direction. Here, the aspect ratio (ratio of the long diameter to the short diameter) of the nozzle hole 6 is 2 to 5. The inner peripheral surface of the nozzle hole 6 including the inner wall surface 11a of the long wall portion 11 and the inner wall surface 12a of the short wall portion 12 is made of platinum or a platinum alloy. In addition, the inner wall surface 11a of the long wall portion 11 is as shown in FIG. Figure 4 (c) shows straight lines, which are parallel.

[0060] In addition, the boundary 15 between the long wall portion 11 and the short wall portion 12 is the inner wall surface relative to the Figure 4 At the point where the inclination in the left-right direction (Z direction) of (c) changes from 0, the portion where the inclination is 0 relative to the horizontal direction of the paper surface is the long wall portion 11 , and the portion where the inclination is not 0 is the short wall portion 12 .

[0061] The long wall portion 11 has a bottom wall surface 11b connected to the inner wall surface 11a. In addition, the bottom wall surface 11b at the position where the notch portion 13 is provided in the long wall portion 11 is a position corresponding to the upper base of the isosceles trapezoid or the side connecting the upper base and the lower base. In the present embodiment, the bottom wall surface 11b is a flat surface (a flat surface orthogonal to the axis 6x at a position corresponding to the upper base of the isosceles trapezoid). Similarly, the short wall portion 12 has a bottom wall surface 12b connected to the inner wall surface 12a. In the present embodiment, the bottom wall surface 12b is a flat surface orthogonal to the axis 6x. It should be noted that the bottom wall surface 11b and the bottom wall surface 12b are not necessarily flat surfaces, and can also be surfaces with concave and convex or curvature.

[0062] Here, if Figure 4 As shown in (c), when the nozzle hole 6 is viewed from the outlet 6b side, the average value of the width of the bottom wall surface 11b of the long wall portion 11 (the width along the short diameter direction) is set as the average width W1, and the average value of the width of the bottom wall surface 12b of the short wall portion 12 (the width along the long diameter direction) is set as the average width W2. At this time, the average width W2 is larger than the average width W1. Specifically, the average width W2 is 1.5 times or more of the average width W1, preferably 2 times or more. In addition, in the present embodiment, the thickness of the long wall portion 11 is W11 and is constant, so W1=W11, but the thickness of the short wall portion 12 is not constant (for example, W21≠W22≠W23). Therefore, the average width W2 is the average value of the thickness of each part of the short wall portion 12. In addition, in the present embodiment, the area of ​​the bottom wall surface 12b of the short wall portion 12 is larger than the area of ​​the bottom wall surface 11b of the long wall portion 11.

[0063] Hereinafter, the main functions and effects of the method for producing a deformed cross-section glass fiber using the above-mentioned nozzle 8 will be described.

[0064] In the above-mentioned nozzle 8, when the bottom wall surface 11b of the long wall portion 11 and the bottom wall surface 12b of the short wall portion 12 are wetted by the molten glass 2, the bottom wall surfaces 11b and 12b stretch the molten glass 2 in the direction along the bottom wall surfaces 11b and 12b. Moreover, since the wider the width of the bottom wall surfaces 11b and 12b, the easier it is to stretch the molten glass 2, in the nozzle 8 in which the above-mentioned average width W2 is larger than the above-mentioned average width W1, the molten glass 2 can be effectively stretched along the long diameter direction of the nozzle hole 6. As a result, it is possible to manufacture Figure 5 Here, the cross-sectional shape of the glass fiber 2f is formed into a shape close to an oval.

[0065] Here, the nozzle for irregular cross-section glass fiber and the method for manufacturing irregular cross-section glass fiber involved in the present invention are not limited to the structure and mode described in the above-mentioned embodiment. For example, in the above-mentioned embodiment, the notch 13 is respectively provided in the pair of long wall parts 11, 11, but the notch 13 is not necessarily provided, and the notch 13 may be removed. In addition, the nozzle hole 6 may be an elliptical shape, a dumbbell shape, a rhombus shape, a triple perfect circle shape, a rectangular shape, etc. in addition to the long hole shape.

[0066] Next, a second embodiment different from the above-mentioned embodiment will be described. It should be noted that the structure other than the nozzle 8 is the same as that of the above-mentioned embodiment. Therefore, only the differences from the above-mentioned embodiment will be described.

[0067] like Figure 6 As shown, the nozzle 18 in the second embodiment includes a pair of long wall portions 21, 21 and a pair of short wall portions 22, 22. The pair of long wall portions 21, 21 are respectively provided with a notch portion 23 opening toward the outlet 6b. The shape of the notch portion 23 is the same as that of the above embodiment.

[0068] The long wall portion 21 has an inner wall surface 21a and a bottom wall surface 21b connected to the inner wall surface 21a. Moreover, in the second embodiment, unlike the above-mentioned embodiment, the inner wall surface 21a is not parallel to the horizontal direction of the paper surface, but is formed to approach the outer wall surface 21c of the long wall portion 21 as it becomes the central part of the inner wall surface 21a. Therefore, the width W13 of the central part of the bottom wall surface 21b of the long wall portion 21 is narrower than the width W12 of the bottom wall surface 21b of the long wall portion 21 on the short wall portion 22 side. Therefore, the average width W1 in the second embodiment is the average value of the thickness of each part of the long wall portion 22. In addition, in the second embodiment, the thickness of the bottom wall surface 22b of the short wall portion 22 is W24 and is fixed, so W2=W24. In addition, the average width W2 is larger than the average width W1.

[0069] In addition, unlike the above-mentioned embodiment, when the inner wall portion is not linear and parallel as in the present embodiment, the boundary 15 between the long wall portion 21 and the short wall portion 22 can be determined by the following method. Figure 6 As shown, a rectangle C described below in contact with the inner wall of the nozzle 18 is drawn, and each vertex of the rectangle C becomes a boundary 15. When the area of ​​the figure surrounded by the first side C1 of the rectangle C and the inner wall is set as D1, the area of ​​the figure surrounded by the second side C2 opposite to the first side C1 and the inner wall is set as D2, the area of ​​the figure surrounded by the third side C3 adjacent to the first side C1 and the inner wall is set as D3, and the area of ​​the figure surrounded by the fourth side C4 opposite to the third side C3 and the inner wall is set as D4, the rectangle C has a shape such that D1+D2=D3+D4.

[0070] In the second embodiment, since the average width W2 is larger than the average width W1, the molten glass 2 can be effectively stretched along the major diameter direction of the nozzle hole 16 in the nozzle 18. As a result, it is possible to manufacture Figure 5 Glass fiber 2f with high flatness as shown.

[0071] Next, a third embodiment different from the above two embodiments will be described. It should be noted that the structure other than the nozzle 8 is the same as that of the above embodiments. Therefore, only the differences from the above embodiments will be described.

[0072] like Figure 7 As shown, the nozzle 28 in the third embodiment has a pair of long wall portions 31, 31 and a pair of short wall portions 32, 32. A notch portion 33 opening toward the outlet 6b side is provided in each of the pair of long wall portions 31, 31. The shape of the notch portion 33 is the same as that of the above-mentioned embodiment. In addition, the widths of the long wall portion 31 and the short wall portion 32 when viewed from above are both W3 and fixed.

[0073] like Figure 8 As shown, the short wall portion 32 has an inner wall surface 32a and a bottom wall surface T connected to the inner wall surface 32a. The bottom wall surface T has: a vertical bottom wall surface 32b, which is perpendicular to the inner wall surface 32a; and an inclined bottom wall surface 32c, which is connected to the vertical bottom wall surface 32b and the inner wall surface 32a and is inclined relative to the inner wall surface 32a. Moreover, in the third embodiment, the thickness of the short wall portion 32 is fixed as in the second embodiment. Figure 8 As shown, the width of the vertical bottom wall surface 32b is L2, and the width of the inclined bottom wall surface 32c is L1. Here, the average width W2 of the bottom wall surface T is (L1+L2).

[0074] By providing the inclined bottom wall surface 32c in this way, the average width W2 of the bottom wall surface T can be made longer (L1-L3) compared to the case where the inclined bottom wall surface 32c is not provided (in this case, the width of the bottom wall surface is L2+L3=W3). The relationship between L1 and L3 is L1=L3 / cosθ. For example, when θ=55°, L1=1.74×L3.

[0075] In the third embodiment, the average width W2 (L2+1.74L3) is 0.74L3 longer than the average width W1 (W3), so that the molten glass 2 can be effectively stretched along the major diameter direction of the nozzle hole 26 in the nozzle 28. As a result, it is possible to manufacture Figure 5 Glass fiber 2f with high flatness as shown.

Claims

1. A nozzle for special-shaped cross-section glass fiber, characterized in that: A flat nozzle hole is provided, the nozzle hole having an inlet and an outlet for molten glass, The wall portion surrounding the nozzle hole includes a pair of short wall portions facing each other in the long diameter direction of the nozzle hole and a pair of long wall portions facing each other in the short diameter direction. The nozzle for the special-shaped cross-section glass fiber is used to manufacture the special-shaped cross-section glass fiber by using the molten glass flowing out from the nozzle hole. The average width of the bottom wall surface of the short wall portion is wider than the average width of the bottom wall surface of the long wall portion, and on the bottom wall surface of the long wall portion, the inner wall surface of the long wall portion is formed to approach the outer wall surface of the long wall portion toward the central portion.

2. The nozzle for special-shaped cross-section glass fiber according to claim 1, characterized in that: The average width of the bottom wall surface of the short wall portion is 1.5 times or more the average width of the bottom wall surface of the long wall portion.

3. The nozzle for special-shaped cross-section glass fiber according to claim 1 or 2, characterized in that: The area of ​​the bottom wall surface of the short wall portion is larger than the area of ​​the bottom wall surface of the long wall portion.

4. The nozzle for special-shaped cross-section glass fiber according to claim 1 or 2, characterized in that: The inner wall surface and the outer wall surface of the short wall portion are arc-shaped.

5. The nozzle for special-shaped cross-section glass fiber according to claim 1 or 2, characterized in that: The thickness of the bottom wall surface of the short wall portion is constant.

6. A method for manufacturing a special-shaped cross-section glass fiber, characterized in that: The glass fiber is manufactured using a nozzle for a special-shaped cross-section, wherein the nozzle for the special-shaped cross-section glass fiber is provided with a flat nozzle hole, the nozzle hole has an inlet and an outlet for molten glass, and a wall portion surrounding the nozzle hole has a pair of short wall portions opposed in the long diameter direction of the nozzle hole and a pair of long wall portions opposed in the short diameter direction. The manufacturing method is used to manufacture special-shaped cross-section glass fibers by using molten glass flowing out of the nozzle hole. The average width of the bottom wall surface of the short wall portion is made wider than the average width of the bottom wall surface of the long wall portion, and on the bottom wall surface of the long wall portion, the inner wall surface of the long wall portion is formed to approach the outer wall surface of the long wall portion toward the central portion.

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