Electrospinning apparatus and fiber manufacturing method

Abstract

To provide an electrospinning device and a manufacturing method of a fiber, capable of suppressing deposition of a molten resin to an open end of a jet port while elevating wind velocity of a gas flow.SOLUTION: An electrospinning device 10 of the present invention includes: a nozzle 31 having an open end part for discharging a molten resin; an electrode 34 for forming an electric field between itself and the nozzle 31; and a gas jet part for ejecting a first gas flow A between the nozzle 31 and the electrode 34. The gas jet part includes: a first gas channel 40 arranged so as to surround the nozzle 31 and circulating the first gas flow A heated via a space formed in a space with an outer peripheral surface of the nozzle 31 to a discharge direction of the molten resin; and a jet port 41d for ejecting the first gas flow A circulating in the first gas channel 40 to the outside. An open end part of the jet port 41d has the smallest inner diameter among inner diameters of the first gas channel 40. The open end part of the nozzle 31 is arranged at a position projecting from an open end face of the jet port 41d.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electrospinning apparatus and a method for producing fibers. [Background technology]

[0002] Electrospinning has attracted attention as a technique that can easily and highly productively produce fiber sheets having nano-sized fibers by discharging a solution or melt of a raw resin. Generally, in electrospinning, a high voltage is applied between a nozzle for discharging the raw resin liquid and a collection electrode installed facing the nozzle at a predetermined distance, and the raw resin liquid is discharged under this condition. The raw resin liquid discharged from the tip of the nozzle is stretched by Coulomb force and then cooled and solidified, forming fine-diameter fibers.

[0003] As an apparatus for realizing such an electrospinning method, for example, there is an electrospinning apparatus described in Patent Document 1.

[0004] The electrospinning apparatus described in Patent Document 1 includes a first gas injection unit disposed so as to surround a nozzle and configured to be able to inject a heated gas flow from the rear end of the nozzle toward the front end along the extension direction of the nozzle, and a second gas injection unit located outside the first gas injection unit and configured to be able to inject a heated second gas flow from the rear end of the nozzle toward the front end. With this electrospinning apparatus, an electric field is generated between the nozzle and an electrode, and heated gas flows are injected from each of the first gas injection unit and the second gas injection unit, and a molten resin can be discharged from the nozzle to be spun, thereby making it possible to produce small-diameter fibers with relatively high production efficiency. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-011665 Summary of the Invention [Problem to be solved by the invention]

[0006] In an electrospinning apparatus such as that described in Patent Document 1, i.e., an electrospinning apparatus having an injection port for injecting an air flow around a nozzle, it is possible to further improve the productivity of small-diameter fibers by increasing the wind speed of the gas flow injected from the injection port. For example, one possible method for increasing the wind speed of the air flow is to increase the wind speed of the gas flow by increasing the driving force of the gas flow supply source, for example, the rotation speed of the drive source. However, if the driving force of the air flow supply source is increased to continuously produce fibers, the burden of maintenance and management, including running costs, is large.

[0007] This problem can be solved, for example, by narrowing the inner diameter of the nozzle. However, when the tip of the nozzle is positioned inside the nozzle, as in the electrospinning apparatus described in Patent Document 1, the molten resin discharged from the nozzle may adhere to the nozzle or its surroundings, which may hinder smooth gas flow from the nozzle. In such a case, it is not possible to stably and continuously produce small-diameter fibers, resulting in a decrease in fiber productivity.

[0008] The present invention is directed to providing an electrospinning apparatus and a method for producing fibers that can overcome the drawbacks of the prior art described above. [Means for solving the problem]

[0009] The present invention relates to an electrospinning apparatus including a nozzle having a discharge port for discharging a molten resin, an electrode for generating an electric field between the nozzle and the electrode, and a gas injection unit for injecting a gas flow between the nozzle and the electrode. The gas injection section is connected to a gas flow path that circulates the heated gas flow in the discharge direction of the molten resin, and the gas flow path is preferably arranged to surround the nozzle and has a space formed between the outer circumferential surface of the nozzle and a cylindrical wall portion arranged outside the nozzle, and an injection port arranged downstream of the space and injection of the gas flow flowing through the space to the outside. The injection port is preferably arranged in a minimum inner diameter flow path that has the smallest inner diameter among the inner diameters of the gas flow paths and has a minimum inner diameter portion located at the most downstream side of the minimum inner diameter flow path. The open end of the discharge port is preferably arranged in a position flush with the minimum inner diameter portion or in a position protruding from the open end face of the minimum inner diameter portion.

[0010] The present invention relates to a fiber manufacturing method for manufacturing fibers using an electrospinning apparatus including a nozzle having an outlet for discharging a molten resin, an electrode for generating an electric field between the nozzle and the electrode, and a gas injection unit for injecting a gas flow between the nozzle and the electrode. The gas injection unit is preferably connected to a gas flow path that circulates the heated gas flow in the direction of discharging the molten resin, and the gas flow path is preferably arranged to surround the nozzle and has a space formed between the outer circumferential surface of the nozzle and a cylindrical wall portion arranged outside the nozzle, and an injection port arranged downstream of the space and injecting the gas flow flowing through the space to the outside. The injection port is preferably arranged in a minimum inner diameter flow path that has the smallest inner diameter among the inner diameters of the gas flow paths and has a minimum inner diameter portion located furthest downstream of the minimum inner diameter flow path. The open end of the ejection port is preferably arranged flush with the minimum inner diameter portion or protruding from the open end face of the minimum inner diameter portion. The manufacturing method preferably includes a step of generating an electric field between the nozzle and the electrode and ejecting the molten resin from the nozzle while ejecting a heated gas flow from the injection port. [Effects of the Invention]

[0011] The electrospinning apparatus and fiber manufacturing method of the present invention have a simple configuration, but are capable of increasing the wind speed of the gas flow while suppressing adhesion of molten resin to the open end of the nozzle, thereby enabling stable production of small-diameter fibers with higher production efficiency. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional schematic diagram showing one embodiment of the electrospinning apparatus of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view of a main part of FIG. [Figure 3] FIG. 3 is a perspective schematic view of an orifice member attached to the front end of the inner cylinder of FIG. [Figure 4] FIG. 4 is an explanatory diagram for explaining the flow of air injected from the injection port of FIG. [Figure 5] FIG. 5 is a set of images showing the fiber diameters of fibers produced using the electrospinning apparatus, where (a) is an image of fibers produced using the electrospinning apparatus of Example 1, and (b) is an image of fibers produced using the electrospinning apparatus of Comparative Example 1. [Figure 6] FIG. 6 is a set of images showing the state of adhesion of molten resin to the nozzle when fibers are produced using the electrospinning apparatus, where (a) is an image when fibers are produced using the electrospinning apparatus of Example 1, and (b) is an image when fibers are produced using the electrospinning apparatuses of Comparative Examples 2 and 3. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will now be described based on preferred embodiments with reference to the drawings. Figure 1 shows one embodiment of an electrospinning apparatus of the present invention. As shown in the figure, the electrospinning apparatus 10 includes a kneading device 20 and a spinning unit 30.

[0014] The electrospinning apparatus 10 is equipped with a kneading device 20. The kneading device 20 melts a resin that is a raw material for the fibers and extrudes it into a spinning unit 30 (described later). The kneading device 20 has a cylinder and a screw (not shown) equipped with a heater inside, and is configured to melt and knead the raw material resin supplied into the kneading device 20 and extrude and supply it to the spinning unit 30.

[0015] The electrospinning apparatus 10 includes a spinning unit 30. The spinning unit 30 ejects the molten resin supplied from the kneading device 20 to the outside to spin the resin. The spinning unit 30 includes a hollow nozzle 31 that communicates with the kneading device 20. The nozzle 31 includes a tip region 32 and a main body region 33 having a cylindrical resin supply path 33a connected to the rear end of the tip region 32. The nozzle 31 is configured to eject the molten resin supplied from the kneading device 20 from the tip region 32 via the resin supply path 33a. From the viewpoint of improving chargeability, the tip region 32 of the nozzle 31 is preferably made of a conductor such as metal. Furthermore, from the viewpoint of improving heat resistance, the main body region 33 of the nozzle 31 is preferably made of metal. In the following description, unless otherwise specified, the direction of extension of the nozzle 31 (the left-right direction on the paper in FIG. 1) toward the kneading device 20 (the left side on the paper in FIG. 1) will also be referred to as the "rear" and the opposite direction (the right side on the paper in FIG. 1) will also be referred to as the "front." In addition, the kneading device 20 side will also be referred to as the "upstream side," and the opposite side will also be referred to as the "downstream side."

[0016] As shown in FIG. 2, the tip region 32 of the nozzle 31 has a connection portion connected to the main body region 33, and an open end portion connected to the connection portion and from which molten resin is discharged.

[0017] The inner diameter of the open end in the tip region 32 is preferably 50 μm or more, more preferably 100 μm or more, and is preferably 3000 μm or less, more preferably 2000 μm or less. By setting the inner diameter of the open end within this range, the molten resin can be discharged easily and quantitatively.

[0018] As shown in FIG. 1, the spinning unit 30 includes an electrode 34 for charging the tip region 32 of the nozzle 31 and generating an electric field between the tip region 32 and the electrode 34. The electrode 34 is made of a conductive material. The electrode 34 in FIG. 1 has a cylindrical shape and is arranged to surround the nozzle 31 in the circumferential direction. The surface 34a of the electrode 34 facing the nozzle 31 is formed as a concave curved surface on the inner surface of the cylinder. For convenience of explanation, in the following explanation, the surface 34a of the electrode 34 facing the nozzle 31 will also be referred to as the "concave curved surface 34a." The electrode 34 has an open end 34c on the tip side of the nozzle 31. The planar shape of the open end 34c is a circular shape, such as a perfect circle or an ellipse. The open end 34c is located forward of the tip of the tip region 32 of the nozzle 31. Although not shown, the open end 34c may be located on the same plane as the tip region 32 of the nozzle 31 or may be located rearward.

[0019] 1, electrical wiring 48 for applying a voltage between the electrode 34 and the nozzle 31 is drawn out from a surface 34b of the electrode 34 opposite to a surface 34a facing the nozzle 31. The electrical wiring 48 is connected to a high-voltage power supply device HV, and a positive or negative voltage is applied to the electrode 34 by the device HV.

[0020] The spinning unit 30 shown in FIG. 1 has a structure formed between the kneading device 20 and the tip region 32 of the nozzle 31. The structure includes a cylindrical main body region 33 that forms part of the nozzle 31, an inner tube 36 having a cylindrical wall portion that is disposed outward so as to surround the main body region 33, and an outer tube 37 that is positioned outside the inner tube 36. The rear end of the main body region 33 is connected to the kneading device 20, and molten resin supplied from the kneading device 20 can flow toward the tip region 32 of the nozzle 31 via a resin supply path 33a. The constituent materials of the inner tube 36 and the outer tube 37 are not particularly limited, but are preferably selected taking into consideration the electrostatic chargeability of the nozzle 31 and heat resistance to gas flow. For example, various metal materials or materials similar to the constituent materials of the surface coating portion 35a described below can be used.

[0021] The spinning unit 30 includes a first gas flow path 40 for injecting a gas flow between the nozzle 31 and the electrode 34. The first gas flow path 40 is a space formed between the nozzle 31 and a wall of the inner cylinder 36 including an optional orifice member, and specifically includes (1) a space formed between the main body region 33 of the nozzle 31 and the inner cylinder 36, (2) a space formed between the tip region 32 of the nozzle 31 and the inner cylinder 36, and (3) a space formed between the tip region 32 of the nozzle 31 and an orifice 41 (described later). A heated first gas flow A can flow through the first gas flow path 40. That is, the first gas flow path 40 is arranged to surround the nozzle 31 in the circumferential direction. As shown in FIG. 1, the first gas flow path 40 is formed so as to be able to spray a first gas flow A from the rear end side of the nozzle 31 (i.e., the kneading device 20 side) toward the tip region 32 along the extension direction of the nozzle 31.

[0022] A first gas injection unit 40a is connected to the rear end of the first gas flow path 40. The first gas injection unit 40a is connected to a first gas supply source (not shown), and supplies a heated first gas flow A supplied from the first gas supply source to the first gas flow path 40, causing the first gas flow A to circulate between the nozzle 31 and the electrode 34. From the viewpoint of convenience, the first gas flow A may be, for example, an air flow.

[0023] The first gas injection section 40a extends in a direction intersecting the extension direction of the first gas flow path 40. In the embodiment shown in Fig. 1, the extension direction of the first gas injection section 40a and the extension direction of the first gas flow path 40 are generally perpendicular to each other. Therefore, the first gas flow A supplied from a first gas supply source (not shown) flows through the first gas injection section 40a, and then its flow direction is changed by 90 degrees at the connection section between the first gas injection section 40a and the first gas flow path 40, and then the first gas flow A flows through the first gas flow path 40. In the device of the present invention, the angle of intersection between the first gas ejection part 40a and the first gas flow path 40 is not limited to 90 degrees, and they may intersect at another angle.

[0024] The inner cylinder 36 includes a cylindrical main body 36a and an annular flange 36b that protrudes radially inward from the inner circumferential surface of the front end of the main body 36a. The annular flange 36b can function as an orifice itself, but as will be described later, it can also function as a part that restricts the forward movement of an orifice member inserted into the inner cylinder 36. The term "orifice" as used herein broadly includes an orifice in which the cross-sectional area of ​​a gas flow path through which gas flows is partially reduced from the upstream side to the downstream side, and does not matter whether the orifice is formed integrally with the inner wall surface of the gas flow path or is separate from the inner wall portion of the flow path.

[0025] In this embodiment, an orifice member is attached to the inner surface of the front end of the inner cylinder 36. For example, an orifice 41, which will be described later, can be additionally provided in the annular member 36b of the inner cylinder 36, which can function as an orifice. 2 and 3, the orifice 41 typically has a stepped cylindrical shape in which a large-diameter cylindrical portion 41a and a small-diameter cylindrical portion 41b are integrally formed, and the cylindrical space formed concentrically between the large-diameter cylindrical portion 41a and the small-diameter cylindrical portion 41b serves as a gas flow path 41c through which the first gas flow A can flow. In the embodiment shown in FIGS. 2 and 3 (hereinafter referred to as "this embodiment"), such an orifice 41 is provided as an orifice member separate from the inner cylinder 36. The large-diameter cylindrical portion 41a has an outer diameter slightly smaller than the inner diameter of the main body portion 36a. The small-diameter cylindrical portion 41b has an outer diameter slightly smaller than the inner diameter of the annular flange portion 36b and is connected to the front end surface of the large-diameter cylindrical portion 41a.

[0026] When the orifice 41 serving as an orifice member is inserted into the inner cylinder 36, the large-diameter cylindrical portion 41a and the small-diameter cylindrical portion 41b are fitted into the main body portion 36a and the annular flange portion 36b, respectively, and the front end face of the large-diameter cylindrical portion 41a is positioned in contact with the rear end face of the annular flange portion 36b. In this embodiment, the gas flow path 41c of the orifice 41 has a cylindrical shape with the same diameter. Therefore, when the orifice portion 41 is attached to the inner cylinder 36, the gas flow path 41c becomes the smallest inner diameter flow path, which is the smallest inner diameter of the inner diameters of the first gas flow path 40, and the open end located at the most downstream side of the small inner diameter flow path becomes the open end of the small diameter cylindrical portion 41b. In this case, the open end of the small diameter cylindrical portion 41b located at the most downstream side of the gas flow path 41c (hereinafter also referred to as "injection port 41d") functions as the injection port for injecting the first gas flow A. Hereinafter, the open end of the small diameter cylindrical portion 41b will also be referred to as the injection port 41d. In other words, when an orifice 41 is provided in the inner tube 36, the inner diameter of the first gas flow path 40 is determined by the inner diameter of the gas flow path 41c of the orifice 41 at the front end, while it is determined by the inner diameter of the main body portion 36a of the inner tube 36 further upstream (see "inner diameter Id1" and "inner diameter Id2" in Figure 2).

[0027] In a configuration in which such an orifice 41 is not attached to the inner cylinder 36, the first gas flow A is injected through a hole formed in the annular flange 36b of the inner cylinder 36. That is, in such a configuration, the smallest inner diameter flow path of the first gas flow path 40 becomes the hole formed in the annular flange 36b, and the open end located most downstream of the smallest inner diameter flow path becomes the open end of the hole. In such a configuration, the inner diameter of the front end of the first gas flow path 40 is determined by the inner diameter of the hole formed in the annular flange portion 36b, and the open end of the hole functions as an injection port for injecting the first gas flow A.

[0028] In this way, by providing the orifice 41 in the inner cylinder 36 itself or by providing the annular flange portion 36b at the front end of the inner cylinder 36, it is possible to make the inner diameter of the first gas flow passage 40 smaller on the downstream side than on the upstream side. The outlet from which the first gas flow A is injected is the open end (injection port 41d) of the small-diameter cylindrical portion 41b when the orifice 41 is provided, and is the open end of a hole formed in the annular flange portion 36b when the orifice 41 is not provided. In other words, both of these are the end portions located most downstream of the small-diameter flow passage that constitutes the first gas flow passage 40 (hereinafter also referred to as the "minimum inner diameter portion"), and therefore it is possible to increase the wind speed of the first gas flow passage A injected from the minimum inner diameter portion.

[0029] Here, the wind speed of the first gas flow A injected from the minimum inner diameter portion will be described. The wind speed of the first gas flow A injected from the smallest inner diameter part (hereinafter also referred to as "outlet wind speed") is expressed as V, Q, where V is the outlet wind speed (m / s), Q is the supply wind speed (L / min), and m is the cross-sectional area of ​​the smallest inner diameter part. 2 ) is A, the initial temperature is T0 (K), and the heating temperature is T1 (K), it can be theoretically calculated using the following calculation formula (hereinafter referred to as the "theoretical value calculation formula"). V=(Q / A)×(T1 / T0)

[0030] For example, assuming that the inner diameter Id1 of the inner cylinder 36 is 13 mm, the inner diameter Id2 of the orifice 41 (smallest inner diameter portion) is 5 mm, the supply air velocity Q is 100 L / min, the initial temperature T0 is 25°C, and the outlet temperature is 300°C (heating temperature T1: 275°C), theoretically, the outlet air velocity V when the orifice 41 is attached to the inner cylinder 36 is 158 m / s. In contrast, when the first gas flow A is ejected from the inner cylinder 36 without the orifice 41 and the annular member 36b, that is, when the first gas flow A is ejected directly from the open end with an inner diameter Id1 of 13 mm, the outlet air velocity V is 23 m / s. In this way, by providing the orifice 41 in the inner cylinder 36, it is possible to dramatically improve the outlet air velocity V, i.e., the air velocity of the first gas flow A ejected from the ejection port 41d (smallest inner diameter portion).

[0031] When the orifice 41 is not attached to the inner cylinder 36 provided with the annular flange 36b, the inner diameter of the hole (smallest inner diameter portion) of the annular flange 36b that functions as an injection port is, for example, 9 mm, which is smaller than the inner diameter Id1 (13 mm) of the inner cylinder 36 without the annular flange 36b. This makes it possible to reliably improve the outlet wind velocity V of the first gas flow A injected from the hole (smallest inner diameter portion) of the annular member 36.

[0032] 2, in this embodiment, an inner cylinder 36 having an orifice 41 is disposed so as to surround the nozzle 31 in the circumferential direction. Therefore, in this embodiment, the heated first gas flow A can be sprayed in the discharging direction of the molten resin while covering the periphery of the molten resin discharged from the nozzle 31. That is, in this embodiment, an external force in the discharging direction of the molten resin by the spraying of the first gas flow A can be applied to the molten resin in addition to the Coulomb force. Therefore, the molten resin can be effectively stretched, and as a result, finer diameter fibers can be efficiently produced.

[0033] In addition, in this embodiment, as described above, the inner diameter of the first gas flow path 40 is reduced by the orifice 41, so that it is possible to increase the wind speed (initial speed) of the first gas flow A injected from the injection port 41d. As a result, the molten resin can be drawn more effectively, and finer diameter fibers can be produced efficiently.

[0034] In this embodiment, as shown in Fig. 2, the open end of the nozzle 31 is disposed so as to protrude from the minimum inner diameter portion of the ejection port 41d (see "protrusion amount L" in Fig. 2). That is, in this embodiment, the molten resin can be ejected from a position in front of the ejection port 41d while being subjected to external force by the ejection of the first gas flow A, which makes it possible to effectively prevent the molten resin from adhering to the ejection port 41d and its surroundings. As a result, in this embodiment, even when fiber production is performed continuously, a situation in which the smooth ejection of the first gas flow A is hindered due to the adhesion of the molten resin to the ejection port 41d is unlikely to occur, and thus small-diameter fibers can be stably produced.

[0035] As described above, according to this embodiment, even with a simple configuration, it is possible to increase the wind speed of the first gas flow A while suppressing adhesion of the molten resin to the injection port 41d and its surroundings, thereby enabling stable production of small-diameter fibers with higher production efficiency. Similarly, even when the first gas flow A is injected from the hole in the annular flange 36b without the orifice 41, it is possible to increase the wind speed of the first gas flow A, thereby suppressing adhesion of the molten resin to the annular flange 36b and its surroundings, and as a result, it is possible to stably produce small-diameter fibers with higher production efficiency.

[0036] In this embodiment, the inner diameter of the first gas flow path 40 through which the first gas flow A flows is smaller downstream than upstream, such that the inner diameter Id1 of the inner cylinder 36 on the upstream side and the inner diameter Id2 of the orifice 41 on the downstream side. That is, in this embodiment, the inner diameter of the first gas flow path 40 is gradually narrowed from the upstream side to the downstream side, so that the wind speed of the first gas flow A can be stably accelerated. As a result, in this embodiment, the first gas flow A can be stably ejected from the ejection port 41d at an increased speed, which allows the molten resin ejected from the nozzle 31 to be efficiently stretched, thereby efficiently thinning the fiber. Note that the same holds true when the first gas flow A is ejected from the hole in the annular flange portion 36b without the orifice 41 attached.

[0037] In this case, it is preferable that the cross-sectional area of ​​the first gas flow path 40 in a direction perpendicular to the flow direction of the first gas flow A (hereinafter referred to as the "perpendicular direction") is smaller on the downstream side than on the upstream side. Specifically, as shown in Fig. 2, if the inner diameter of the main body portion of the inner cylinder 36 is Id1, the inner diameter of the orifice 41 is Id2, the outer diameter of the main body region 33 of the nozzle 31 is Od1, the outer diameter of the open end of the nozzle 31 is Od2, and pi is the ratio of the circumference of a circle to its circumference, then The cross-sectional area of ​​the first gas flow path 40 on the upstream side is ·[(Id1 / 2×Id1 / 2)-(Оd1 / 2×Оd1 / 2)]×π The cross-sectional area of ​​the first gas flow path 40 on the downstream side is ·[(Id / 2×Id / 2)-(Оd1 / 2×Оd1 / 2)]×π Here, when the cross-sectional area of ​​the first gas flow path 40 on the upstream side is A and the cross-sectional area of ​​the first gas flow path 40 on the downstream side is B, A>B It is preferable that the following relational expression is satisfied.

[0038] When such a relational expression is satisfied, the cross-sectional area in the perpendicular direction through which the first gas flow A actually flows is gradually narrowed from the upstream side to the downstream side, so that the wind speed of the first gas flow A can be accelerated more stably, and as a result, the diameter of the fibers can be thinned more efficiently.

[0039] Furthermore, in this embodiment, as described above, the orifice member (orifice 41) is separately attached to the front end portion of the inner cylinder 36. That is, in this embodiment, if the orifice member is broken or damaged, not only can it be replaced, but also, by attaching an orifice member with a different inner diameter to the annular flange portion 36b, the wind speed of the first gas flow A ejected from the ejection port 40b can be changed, making it easy to adjust the wind speed.

[0040] From the viewpoint of easily replacing the orifice member, it is preferable that the outer diameters of the large-diameter cylindrical portion 41a and the small-diameter cylindrical portion 41b are such that a small gap is formed between the orifice member and the inner circumferential surface of the inner cylinder 36 when the orifice member is attached to the inner cylinder 36. Even with this configuration, when the first gas flow A is caused to flow through the inner cylinder 36, the front end face of the large-diameter cylindrical portion 41a is pressed against the rear end face of the annular flange portion 36b, so that no gap is formed between the inner cylinder 36 and the orifice member, and the first gas flow A can be suitably injected from the injection port 41d.

[0041] The protrusion amount L of the opening end of the nozzle 31 from the minimum inner diameter portion of the injection port 41d is preferably within 5 times the inner diameter Id2 of the orifice 41. For example, if the inner diameter Id2 of the orifice 41 is 5 mm, the protrusion amount L is preferably within 25 mm. When the nozzle 31 is protruded from the minimum inner diameter portion of the injection port 41d, the minimum protrusion amount L of the nozzle 31 is preferably More than 0mm , more preferably 0.5 mm or more, and further preferably 1 mm or more. Furthermore, being flush means that the protrusion amount L=0.

[0042] Here, the reason why the projection amount L of the open end of the nozzle 31 from the minimum inner diameter portion of the injection port 41d is set to within five times the inner diameter Id2 of the orifice 41 will be explained with reference to FIG. As shown in Figure 4, it is known that the gas flow ejected from the nozzle has a potential core region PA, a region where the wind speed does not decrease from the minimum inner diameter. The potential core region PA is eroded and reduced by the free mixing layers that develop on both sides of the minimum inner diameter, and therefore disappears at a certain distance from the nozzle. Generally, this distance is considered to be within a range of five times the nozzle diameter.

[0043] Considering the characteristics of the gas flow injected from such an injection port, and from the viewpoint of producing fibers with a smaller diameter, that is, from the viewpoint of ensuring that the high-speed first gas flow A comes into contact with the molten resin, it is preferable that the open end of the nozzle 31 be located within five times the inner diameter Id2 of the orifice 41 from the minimum inner diameter portion of the injection port 41d. This also applies to the case where the first gas flow A is injected from the hole (minimum inner diameter portion) of the annular flange 36b. That is, in this case, the position of the open end of the nozzle 31 is preferably located within five times the inner diameter of the hole from the hole of the annular flange 36b.

[0044] The gap D1 (see FIG. 1) of the first gas flow path 40 is preferably 1 mm or more, more preferably 2 mm or more, and is preferably 10 mm or less, more preferably 7 mm or less. By setting the gap D1 in this range, the first gas flow A can be adjusted to a desired air velocity and air volume, and the efficiency of stretching the molten resin can be further improved.

[0045] 1, the spinning unit 30 further includes a second gas flow path 50 for spraying the heated second gas flow B. When the spinning unit 30 is viewed from the front, the second gas flow path 50 is disposed so as to surround the first gas flow path 40 at a position outside the first gas flow path 40 with respect to the position of the nozzle 31. When the spinning unit 30 is viewed from the front, the second gas flow path 50 is disposed inside the electrode 34 and outside the first gas flow path 40 with respect to the position of the nozzle 31. The second gas flow path 50 is a cylindrical space defined by the outer surface of the inner cylinder 36 and the inner surface of the outer cylinder 37.

[0046] The second gas flow path 50 is configured to be able to inject the heated second gas flow B from the rear end side of the nozzle 31 toward the tip region 32 along the extension direction of the nozzle 31. A second gas injection unit 50a is connected to the rear end of the second gas flow path 50. The second gas injection unit 50a is connected to a second gas supply source (not shown) and supplies a heated second gas flow B supplied from the second gas supply source to the second gas flow path 50, thereby injecting the second gas flow B between the nozzle 31 and the electrode 34. The second gas injection unit 50a extends in a direction intersecting the extension direction of the second gas flow path 50. In the embodiment shown in FIG. 1, the extension direction of the second gas injection unit 50a and the extension direction of the second gas flow path 50 are substantially perpendicular to each other.

[0047] From the viewpoint of convenience, for example, an air flow can be used as the second gas flow B. The gap D2 (see FIG. 1) of the second gas flow path 50 is preferably 1 mm or more, more preferably 5 mm or more, and is preferably 100 mm or less, more preferably 70 mm or less. By setting the gap D2 in this range, the second gas flow B can be adjusted to a desired air velocity and air volume, thereby further increasing the efficiency of stretching the molten resin.

[0048] Furthermore, the position of the front-to-rear end of the second gas flow path 50 is not particularly limited as long as the effects of the present invention are achieved, but when the position of the tip of the nozzle 31 in the tip region 32 is taken as the reference (zero), the position in front of the nozzle 31 is represented by a positive value and the position behind the nozzle 31 is represented by a negative value, it is preferably in the range of -50 mm or more and +50 mm or less. The term "heated" in the context of the first gas flow A and the second gas flow B refers to a gas flow whose temperature is higher than the standard temperature (20°C).

[0049] As described above, in the electrospinning apparatus 10 of this embodiment, when the spinning unit 30 is viewed from the front, the first gas flow path 40 is formed in an annular shape so as to surround the nozzle 31 outside the nozzle 31 with the position of the nozzle 31 as a reference, the second gas flow path 50 is formed in an annular shape so as to surround the first gas flow path 40 outside the first gas flow path 40, and further the electrode 34 is disposed in an annular shape outside the second gas flow path 50. The first gas flow path 40, the second gas flow path 50, and the electrode 34 are disposed concentrically around the nozzle 31.

[0050] The electrospinning apparatus 10 may have a collecting section (not shown) opposite the nozzle 31 to collect the spun fibers. A collecting electrode made of a conductive material such as metal is disposed in the collecting section, and the spun fibers can be collected on the collecting section due to the potential difference between the nozzle 31 and the collecting electrode. The collecting electrode is preferably flat, and it is also preferable that the plate surface of the collecting electrode is approximately perpendicular to the direction in which the nozzle 31 extends. The collecting electrode is preferably grounded or has a voltage applied thereto by a high-voltage power supply. In this case, it is also preferable that a voltage different from the charge polarity of the spun fibers is applied to the collecting section. The collecting section may also have a conveying means such as a belt conveyor disposed between the nozzle 31 and the collecting electrode. The fibers collected after spinning can be transported to a downstream process by the conveying means. When a collection section is provided, from the viewpoint of fiber collection efficiency, the distance between the tip of the nozzle 31 and the collection section is set to preferably 50 mm or more, more preferably 100 mm or more, preferably 2000 mm or less, and more preferably 1500 mm or less.

[0051] According to the electrospinning apparatus 10 having the above-described configuration, as described above, the heated first gas flow A is injected from the first gas flow path 40 that is relatively close to the tip region 32 of the nozzle 31, so that the first gas flow A is more likely to come into contact with the molten resin discharged from the tip region 32. As a result, the application of an external force by the injection of the first gas flow A in addition to the Coulomb force can more effectively stretch the molten resin, and finer fibers can be efficiently produced. Moreover, in this embodiment, the inner diameter of the first gas flow path 40 is reduced by the orifice 41, so that it is possible to increase the wind speed (initial speed) of the first gas flow A injected from the injection port 41d. Therefore, the electrospinning apparatus 10 according to this embodiment can more effectively draw the molten resin, and can efficiently produce fibers with a smaller diameter.

[0052] Furthermore, in this embodiment, the heated second gas flow B can be sprayed from a position further outward than the first gas flow path 40, thereby maintaining a high temperature in the space around the nozzle 31 in the direction of the molten resin discharge, and forming that space over a wide area. As a result, the cooling and solidification of the molten resin can be delayed, maintaining the stretched state of the molten resin for a long period of time, and efficiently producing fibers with a smaller diameter. Furthermore, the second gas flow B can prevent the discharged molten resin or the fibers after cooling and solidification from unintentionally adhering to the electrode 34, allowing the fibers to be transported in the desired direction, thereby improving production efficiency.

[0053] Furthermore, in this embodiment, the open end of the nozzle 31 is disposed at a position protruding from the minimum inner diameter portion of the ejection port 41d, and therefore the molten resin can be ejected from the front of the ejection port 41d while receiving an external force due to the ejection of the first gas flow A. As a result, it is possible to effectively prevent the molten resin from adhering to the ejection port 41d and its surroundings, and thus it is possible to stably produce small diameter fibers.

[0054] Moreover, since the electrode 34 is disposed outside the second gas flow path 50, the electrical wiring 48 that applies a high voltage to the electrode 34 can be drawn out from the surface 34b of the electrode 34 opposite to the surface 34a facing the nozzle 31. This facilitates the routing of the electrical wiring 48, which is made of a material with relatively low heat resistance. Furthermore, since the electrode 34 has a cylindrical shape, it is easy to miniaturize the electrospinning apparatus 10, and it is easy to integrate multiple electrospinning apparatuses 10. The ability to integrate multiple electrospinning apparatuses 10 greatly contributes to fiber productivity.

[0055] In order to prevent unintended discharge between the electrode 34 and the nozzle 31 during operation of the electrospinning apparatus 10, the spinning unit 30 preferably includes an electrically insulating surface coating 35a disposed at least on the concave curved surface 34a of the electrode 34 facing the nozzle 31. This prevents discharge between the nozzle 31 and the electrode 34, enabling stable fiber spinning. The surface coating 35a shown in FIG. 1 is in direct contact with the electrode 34 and covers the entire surface of the electrode 34 facing the nozzle 31. The surface coating 35a is a concave curved surface on the inner surface of a cylinder. The surface coating 35a is disposed so as to surround the nozzle 31 in the circumferential direction.

[0056] The spinning unit 30 preferably also includes an electrically insulating back surface covering part 35b disposed on the convex curved surface 34b, which is the surface of the electrode 34 opposite to the concave curved surface 34a, which is the surface facing the nozzle 31. The back surface covering part 35b is a convex curved surface on the outer surface of a cylinder. Furthermore, as shown in Fig. 1, the spinning unit 30 preferably includes end covering portions 35c on the outer side of both ends in the extending direction of the electrode 34. In other words, as shown in Fig. 1, it is preferable that the entire area of ​​the electrode 34 is covered. With this configuration, the covering portions 35a, 35b, 35c can also function as support members for supporting the electrode 34.

[0057] The surface covering portion 35a, the back covering portion 35b, and the end covering portion 35c are preferably made of a material that electrically insulates the nozzle 31 from the electrode 34. In this specification, electrical insulation means a material having a volume resistivity of 10 or more at 25°C. 8 This refers to materials with a resistance of Ω·cm or more.

[0058] To ensure sufficiently high electrical insulation, the thickness of each of the front surface covering portion 35a and the back surface covering portion 35b is preferably 2 mm or more, more preferably 4 mm or more. From the viewpoint of electrical insulation, there is no particular upper limit to the thickness, but from the viewpoint of preventing the electrospinning apparatus 10 from becoming large, the thickness is preferably 30 mm or less, more preferably 15 mm or less.

[0059] Materials constituting each of the covering portions 35a, 35b, and 35c include dielectric ceramic materials such as mica, alumina, zirconia, and barium titanate, and resin-based materials such as Bakelite (phenolic resin), nylon (polyamide), vinyl chloride resin, polystyrene, polyester, polypropylene, polytetrafluoroethylene, and polyphenylene sulfide. Other examples include composite materials such as glass cloth, laminated plates obtained by impregnating glass cloth with a heat-resistant binder, glass wool, rock wool, and silica cloth. Among these, it is preferable to use at least one selected from alumina, Bakelite, glass cloth, laminated plates obtained by impregnating glass cloth with a heat-resistant binder, and composite materials such as glass wool, rock wool, and silica cloth. It is particularly preferable to use a laminated plate obtained by impregnating glass cloth with a heat-resistant binder.

[0060] In order to ensure a smooth supply of the molten resin from the kneading device 20, it is preferable that a heating means (not shown) for heating or maintaining the temperature of the molten resin be provided between the kneading device 20 and the spinning unit 30. Known means such as a heater can be used as the heating means. The temperature for heating or maintaining the temperature is preferably equal to or higher than the melting point of the raw resin used in fiber production. From the viewpoints of thermal conductivity and mechanical strength, the main body region 33 is preferably made of, for example, metal, and is preferably grounded to prevent voltage load on the kneading device 20 during the melt electrospinning method.

[0061] The above has been a description of the electrospinning apparatus 10. A method for producing fibers using the electrospinning apparatus 10 (electrospinning method) will now be described. In the fiber manufacturing method using the electrospinning apparatus 10, an electric field is generated between the nozzle 31 and the electrode 34, and a molten resin is discharged from the tip region 32 of the nozzle 31 while a first gas flow A and a second gas flow B are being jetted. The discharged molten resin is three-dimensionally stretched and refined by the Coulomb force generated inside the nozzle 31 and the jetting of the first gas flow A and the second gas flow B, and at the same time, the resin is cooled and solidified, forming fine fibers.

[0062] The fibers produced by the method of the present invention are thin fibers called nanofibers, with a fiber diameter of 30 μm or less when expressed as an equivalent circle diameter. The nanofibers preferably have a fiber diameter of 0.1 μm or more, preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less.

[0063] The fiber diameter of a fiber can be measured by, for example, randomly selecting 500 fibers from a two-dimensional image obtained by scanning electron microscope (SEM) observation, excluding defects such as spun fiber clumps, intersections between fibers, and polymer droplets, and directly reading the length of a line drawn perpendicular to the longitudinal direction of the fiber as the fiber diameter. The median diameter is determined from the distribution of the measured fiber diameters, and this is defined as the fiber diameter in this specification.

[0064] In fiber production, when the first gas flow A and the second gas flow B are sprayed, it is preferable to spray them so that the wind speed of the first gas flow A is equal to or greater than the wind speed of the second gas flow B. By adjusting the wind speed of each gas flow, the discharged molten resin can be stretched more strongly by the external force generated by the spraying of the first gas flow, and as a result, fibers with an even smaller diameter can be obtained efficiently.

[0065] The molten resin used in the present invention is a fluid resin composition containing a thermoplastic resin having a melting point. The term "having a melting point" means that when the resin is heated in differential scanning calorimetry, it exhibits an endothermic peak resulting from a phase change from solid to liquid before thermal decomposition. The melting point of the thermoplastic resin can be measured, for example, using a melting point / dropping point measuring device (manufactured by Mettler-Toledo, Model No. DP90 Automatic Dropping Point / Softening Point Measuring System) in accordance with JIS K 0064 or JIS K 2220.

[0066] Examples of thermoplastic resins include polyolefin resins such as polyethylene, polypropylene, and ethylene-α-olefin copolymers; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polylactic acid, and liquid crystal polymers; polyamide resins such as nylon 6 and nylon 66; vinyl polymers such as polyvinyl chloride, polyvinylidene chloride, and polystyrene; acrylic polymers such as polyacrylic acid, polyacrylic acid esters, polymethacrylic acid, and polymethacrylic acid esters; polyvinyl acetate and polyvinyl acetate-ethylene copolymers. These resins can be used alone or in combination. Among these thermoplastic resins, polyolefin resins such as polyethylene, polypropylene, and ethylene-α-olefin copolymers are preferred because of their ease of spinning due to their properties such as low melting point, high fluidity, and high ductility.

[0067] The molten resin may be a resin composition containing additives in addition to the thermoplastic resin, as long as the effects of the present invention are not impaired. Examples of additives include electrostatic agents, antioxidants, neutralizing agents, light stabilizers, UV absorbers, lubricants, antistatic agents, metal deactivators, and hydrophilizing agents. Examples of electrostatic agents include metal soaps in which organic acids such as stearic acid, lauric acid, and ricinoleic acid form metal salts with metals such as Ca, Li, Zn, and Ba, as well as ionic surfactants such as acyl alkyl taurine salts, alkyl sulfonates, and quaternary ammonium salts. Examples of antioxidants include phenolic antioxidants, phosphite antioxidants, and thio antioxidants. Examples of neutralizing agents include higher fatty acid salts such as calcium stearate and zinc stearate. Examples of light stabilizers and UV absorbers include hindered amines, nickel complex compounds, benzotriazoles, and benzophenones. Examples of lubricants include higher fatty acid amides such as stearic acid amide. Examples of antistatic agents include fatty acid partial esters such as glycerin fatty acid monoesters. Examples of metal deactivators include phosphones, epoxies, triazoles, hydrazides, and oxamides. Examples of hydrophilizing agents include polyhydric alcohol fatty acid esters, ethylene oxide adducts, and nonionic surfactants such as amine anamides.

[0068] When the molten resin contains an additive, the content of the additive is preferably 0.5% by mass to 50% by mass, more preferably 1% by mass to 40% by mass, and even more preferably 3% by mass to 30% by mass, from the viewpoint of successful electrospinning. In other words, the molten resin used in the production of the nanofiber of the present invention is mainly composed of a thermoplastic resin.

[0069] The method for producing the molten resin is not particularly limited, and it can be produced, for example, by adding additives as necessary to a thermoplastic resin that has been heated and melted, and then heating and kneading them. Such a molten resin may be produced by melting and kneading the thermoplastic resin in advance as a master batch, or by supplying the thermoplastic resin and additives as necessary to a kneading device 20 during production, and then heating, melting, and kneading them in the kneading device 20.

[0070] Nanofibers or their deposits produced by electrospinning using the electrospinning apparatus 10 described above can be used for various purposes as fiber molded articles. Examples of the molded articles include sheets, cotton-like bodies, and filaments. The fiber molded articles may be laminated with other sheets or may contain various liquids, fine particles, fibers, and the like. Fiber sheets are suitable for medical purposes and non-medical purposes, such as cosmetic and decorative purposes, as sheets attached to human skin, teeth, gums, and hair, as well as to the skin, teeth, gums, and plant surfaces such as branches and leaves of non-human mammals. They are also suitable for use as high-performance filters with high dust collection and low pressure loss, battery separators capable of use at high current densities, and cell culture substrates with highly porous structures. Fiber cotton-like bodies are suitable for use as soundproofing materials, heat insulating materials, and the like.

[0071] Although the present invention has been described above based on preferred embodiments, the present invention is not limited to these embodiments. For example, in this embodiment, the open end of the nozzle 31 is positioned protruding from the minimum inner diameter portion of the orifice 41's jetting port 41d. However, it may be positioned flush with the minimum inner diameter portion of the jetting port 41d. Even with this configuration, the molten resin can be discharged from a position flush with the jetting port 41d while being subjected to external force from the jetting of the first gas flow A. This makes it possible to prevent adhesion of the molten resin to the jetting port 41d and its surroundings. Therefore, even in this case, when fiber production is performed continuously and continuously, it is unlikely that smooth jetting of the first gas flow A will be hindered due to adhesion of the molten resin to the jetting port 41d, and stable production of small-diameter fibers can be expected.

[0072] In addition, in this embodiment, the inner diameter of the injection port that injects the first gas flow A is reduced by using the orifice 41, but the inner diameter of the inner cylinder 36 itself may be reduced toward the front.

[0073] Furthermore, in this embodiment, an outer cylinder 37 is provided outside the inner cylinder 36 and configured to inject the second gas flow B, but it is also possible, for example, to omit the outer cylinder 37 and configure the second gas flow B not to be injected. [Example]

[0074] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to such examples.

[0075] In the following Examples 1 and 2, and Comparative Examples 1 to 3 as comparative examples, tests were conducted to produce fibers by spinning a molten resin made of polypropylene as a raw thermoplastic resin by melt electrospinning using the electrospinning apparatus 10 of Fig. 1 under the production conditions shown in Table 1. In Examples 1 and 2, and Comparative Examples 1 to 3, the fiber diameters of the produced fibers were measured, and the presence or absence of adhesion of the molten resin (fibers) to the injection nozzle 41d and its surroundings was confirmed.

[0076] [Table 1]

[0077] [Examples 1 and 2] In Examples 1 and 2, fibers were produced under the following production conditions. Inner diameter Id1 of the main body 36a of the inner cylinder 36: 16 mm Orifice member inner diameter Id2: 5mm Outer diameter Od1 of the main body region 33 of the nozzle 31: 12 mm Outer diameter Od2 of the opening end of the nozzle 31: 0.5 mm First gas flow A air volume Q: 100L / min Temperature of the first gas flow A injected from the injection port 41d (outlet temperature): 300°C In this case, the cross-sectional area of ​​the first gas flow path 40 in the perpendicular direction is 88 mm at the location where the main body region 33 of the nozzle 31 is disposed inside the inner cylinder 36. 2 , 19.4 mm at the location where the injection port 41d is located. 2 This becomes: The wind speed V of the first gas flow A (theoretical outlet wind speed V) calculated using the above-mentioned theoretical value calculation formula was 158 m / s. In Examples 1 and 2, the fiber was produced by varying the value of the protrusion amount L of the opening end of the nozzle 31 from the minimum inner diameter part of the injection port 41d. Specifically, the protrusion amount L was set to 2 mm in Example 1 and 0 mm in Example 2.

[0078] [Comparative Example 1] In Comparative Example 1, fibers were produced under the following production conditions. Inner diameter Id1 of the main body 36a of the inner cylinder 36: 13 mm Outer diameter Od1 of the main body region 33 of the nozzle 31: 12 mm Outer diameter Od2 of the opening end of the nozzle 31: 0.5 mm First gas flow A air volume Q: 100L / min Temperature of the first gas flow A injected from the injection port 41d (outlet temperature): 300°C Amount of protrusion L of the opening end of the nozzle 31 from the opening end face of the injection port 41d: 1 mm In this case, the cross-sectional area of ​​the first gas flow path 40 in the perpendicular direction is 19.6 mm 2 at the portion where the main body region 33 of the nozzle 31 is disposed inside the inner cylinder 36. 2 , 132.5 mm at the location where the injection port 41d is located. 2 The wind speed V of the first gas flow A (theoretical outlet wind speed V) calculated using the above-mentioned theoretical value calculation formula is 24 m / s. Thus, Comparative Example 1 is similar to Examples 1 and 2 in that the opening end of the nozzle 31 protrudes a predetermined amount from the minimum inner diameter portion of the injection port 41d, but differs in that it does not have an orifice 41 attached and does not have an annular flange portion 36b.

[0079] [Comparative Examples 2 and 3] In Comparative Examples 2 and 3, the only difference from Examples 1 and 2 is that the open end of the nozzle 31 does not protrude from the minimum inner diameter portion of the injection port 41d, and tests were conducted under the same manufacturing conditions.

[0080] [Fiber diameter measurement] The fiber diameter of the fibers was measured by SEM observation according to the measurement method described above.

[0081] [Whether or not molten resin is attached] Under each production condition of the examples and comparative examples, whether or not the molten resin (fiber) discharged from the nozzle 31 adhered to the injection port 41d of the orifice 4 and its surroundings was visually evaluated according to the following criteria. The results are shown in Table 1. "Yes": The molten resin (fiber) discharged from the nozzle 31 adheres to the injection port 41d and its surroundings, and the fiber production efficiency is poor. "None": The molten resin (fiber) discharged from the nozzle 31 does not adhere to the injection port 41d and its surroundings, allowing for continuous fiber production and improving fiber production efficiency.

[0082] [Test evaluation] As shown in Table 1, in Examples 1, 2, Comparative Examples 2, and 3, which have an orifice 41 (theoretical outlet wind speed V of first gas flow A: 158 m / s), fibers with a small diameter, for example, 0.5 μm (Examples 1 and 2), were produced. In contrast, in Comparative Example 1, which does not have an orifice 41 (theoretical outlet wind speed V of first gas flow A: 24 m / s), fibers with a larger diameter, for example, 3.8 μm, were produced. Note that FIG. 5(a) shows an image of fibers produced using the electrospinning apparatus 10 of Example 1, and FIG. 5(b) shows an image of fibers produced using the electrospinning apparatus 10 of Comparative Example 1. From these test results, it can be seen that increasing the wind speed V of the first gas flow A ejected from the ejection port 41d allows for more efficient production of fibers with a smaller diameter.

[0083] On the other hand, in Examples 1 and 2 and Comparative Example 1, in which the protrusion amount L of the opening end of the nozzle 31 was set to 0 mm or more, it was confirmed that the molten resin (fiber) did not adhere to the injection port 41d and its periphery. In contrast, in Comparative Examples 2 and 3, in which the protrusion amount L was set to less than 0 mm, it was confirmed that the molten resin (fiber) adhered to the injection port 41d and its periphery. Note that FIG. 6(a) shows an image of the injection port 41d and its periphery when fibers were produced using the electrospinning apparatus 10 of Example 1, and FIG. 6(b) shows an image of the injection port 41d and its periphery when fibers were produced using the electrospinning apparatus 10 of Comparative Examples 2 and 3. These test results show that by setting the protrusion amount L of the opening end of the nozzle 31 from the opening end face of the injection port 41d to 0 mm or more, it is possible to effectively prevent adhesion of molten resin (fiber) to the injection port 41d and its surrounding area, i.e., continuous production of fibers is possible and fiber production efficiency is high.

[0084] The above test results demonstrate that, in order to achieve the "continuous production" of "smaller diameter" fibers, it is necessary to (1) increase the wind speed V of the first gas flow A ejected from the nozzle 41d and (2) set the protrusion amount L of the opening end of the nozzle 31 from the minimum inner diameter part of the nozzle 41d to 0 mm or more. As described above, it is preferable to set the protrusion amount L of the opening end of the nozzle 31 to within a range of 5 times the inner diameter of the orifice 41 (see FIG. 4).

[0085] In the above embodiment, the opening end (injection port 41d) of the small diameter cylindrical portion 41b is set as the minimum inner diameter portion when the orifice 41 is provided, and the opening end of the hole formed in the annular flange portion 36b is set as the minimum inner diameter portion when the orifice 41 is not provided, and the protrusion amount L of the opening end of the nozzle 31 is set based on the position of this minimum inner diameter portion. However, the position of the minimum inner diameter portion is not limited to the opening end as described above, and it can also be set at a position upstream of the opening end, provided that it is the most downstream position in the smallest inner diameter flow path of the gas flow path. The present invention has been described above based on the preferred embodiments and modifications thereof, but the present invention is not limited to the above-described embodiments and modifications. [Explanation of symbols]

[0086] 10. Electrospinning device 32c Opening end (discharge port) 34 electrodes 36 Inner cylinder 40 first gas flow path 40a First gas injection section 41d injection port

Claims

1. a nozzle having a discharge port for discharging molten resin; an electrode for generating an electric field between the electrode and the nozzle; an electrospinning apparatus including a gas injection unit that injects a gas flow between the nozzle and the electrode, the gas injection unit is connected to a gas flow path that causes the heated gas flow to flow in a discharge direction of the molten resin, the gas flow path is disposed so as to surround the nozzle, and includes a space formed between an outer peripheral surface of the nozzle and a cylindrical wall portion disposed outside the nozzle, and an injection port provided downstream of the space and for injecting the gas flow passing through the space to the outside, the injection port is provided in a minimum inner diameter flow path that has the smallest inner diameter among the inner diameters of the gas flow paths, and has a minimum inner diameter portion that is located at the most downstream side of the minimum inner diameter flow path, an opening end of the discharge port is located at a position flush with the minimum inner diameter portion or at a position protruding from the opening end surface of the minimum inner diameter portion;

2. The electrospinning apparatus according to claim 1 , wherein the inner diameter of the gas flow path is smaller on the downstream side than on the upstream side.

3. 3. The electrospinning apparatus according to claim 1, wherein a cross-sectional area of ​​the space in a direction perpendicular to a flow direction of the gas flow is smaller at the minimum inner diameter portion than at a cross-sectional area on an upstream side of the injection port.

4. 3. The electrospinning apparatus according to claim 1, wherein a protrusion amount of the discharge port from the minimum inner diameter portion is within 5 times the inner diameter of the open end of the injection port.

5. A method for producing fibers using an electrospinning apparatus including a nozzle having a discharge port for discharging a molten resin, an electrode for generating an electric field between the nozzle and the electrode, and a gas injection unit for injecting a gas flow between the nozzle and the electrode, The gas injection unit is a gas flow path that is disposed so as to surround the nozzle and that allows the heated gas flow to flow in a discharge direction of the molten resin through a space formed between the nozzle and an outer peripheral surface of the nozzle; an injection port that injects the gas flow passing through the gas flow path to the outside, the injection port is provided in a minimum inner diameter flow path that has the smallest inner diameter among the inner diameters of the gas flow paths, and has a minimum inner diameter portion that is located at the most downstream side of the minimum inner diameter flow path, an opening end of the discharge port is disposed at a position flush with a minimum inner diameter portion located at the most downstream side of the minimum inner diameter flow path or at a position protruding from an opening end surface of the minimum inner diameter portion, The manufacturing method includes: A method for producing fibers, comprising the steps of generating an electric field between the nozzle and the electrode, and discharging molten resin from the nozzle while spraying a heated gas flow from the nozzle.

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