Electrospinning device and manufacturing method of fiber

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 manufacturing fibers.

Background Art

[0002] The electrospinning method has attracted attention as a technology that can simply and highly productively manufacture a fiber sheet having fibers with a nano-sized diameter by discharging a solution or melt of a raw material resin. Generally, in the electrospinning method, a high voltage is applied between a nozzle for discharging a raw material resin liquid and a collecting electrode installed to face a position at a predetermined distance from the nozzle, and the raw material resin liquid is discharged in that state. The raw material resin liquid discharged from the tip of the nozzle is cooled and solidified while being stretched by the Coulomb force, thereby 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 is arranged so as to surround the nozzle, and is formed so that a heated gas flow can be injected from the rear end of the nozzle toward the front end in the direction in which the nozzle extends, and a first gas injection part, and a second gas injection part that is outside the first gas injection part and is formed so that a heated second gas flow can be injected from the rear end of the nozzle toward the front end. According to such an electrospinning apparatus, an electric field is generated between the nozzle and the electrode, and molten resin is discharged from the nozzle and spun in a state where heated gas flows are injected from each of the first gas injection part and the second gas injection part, so that fine-diameter fibers can be manufactured with relatively high production efficiency.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] In an electrospinning apparatus like the one described in Patent Document 1, that is, an electrospinning apparatus equipped with nozzles for injecting airflow around the nozzle, it is possible to further improve the productivity of fine-diameter fibers by increasing the wind speed of the gas flow injected from the nozzles. For example, one method for increasing the wind speed of the airflow is to increase the driving force of the gas flow supply source, for example, by increasing the rotational speed of the drive source. However, if the driving force of the air flow supply source is increased to continuously manufacture fibers, the burden of maintenance and management, including running costs, becomes large.

[0007] Such inconveniences can be resolved, for example, by narrowing the inner diameter of the nozzle. However, if the nozzle tip is positioned inside the outlet, as in the electrospinning apparatus described in Patent Document 1, the molten resin discharged from the nozzle may adhere to the outlet and its surroundings, increasing the likelihood of obstructing the smooth ejection of gas from the outlet. In such cases, it becomes impossible to stably and continuously produce small-diameter fibers, resulting in a decrease in fiber productivity.

[0008] The present invention relates to providing an electrospinning apparatus and a method for manufacturing fibers that can overcome the drawbacks of the conventional technology described above. [Means for solving the problem]

[0009] The present invention relates to an electrospinning apparatus comprising a nozzle having a discharge port for discharging molten resin, an electrode for generating an electric field between the nozzle and the electrode, and a gas injection unit for injecting a gas stream between the nozzle and the electrode. The gas injection unit is preferably connected to a gas flow path that directs the heated gas flow toward 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 located outside the nozzle, and an injection port provided downstream of the space for injecting the gas flow flowing through the space to the outside. The injection port is preferably provided in the minimum inner diameter flow path, which is the smallest inner diameter of the gas flow path, and has the minimum inner diameter portion located furthest downstream of the minimum inner diameter flow path. The opening end of the discharge port is preferably positioned flush with the minimum inner diameter portion or protruding from the opening end surface of the minimum inner diameter portion.

[0010] The present invention relates to a method for producing fibers using an electrospinning apparatus comprising a nozzle having an outlet for discharging molten resin, an electrode for generating an electric field between the nozzle and the electrode, and a gas injection unit for injecting a gas stream between the nozzle and the electrode. Preferably, the gas injection unit is connected to a gas flow path that directs the heated gas flow toward the discharge direction of the molten resin, and the gas flow path is arranged to surround the nozzle and has a space formed between the outer circumferential surface of the nozzle and a cylindrical wall portion located outside the nozzle, and an injection port provided downstream of the space for injecting the gas flow flowing through the space to the outside. Preferably, the injection port is provided in the smallest inner diameter flow path, which is the smallest inner diameter of the inner diameter of the gas flow path, and has the smallest inner diameter portion located furthest downstream of the smallest inner diameter flow path. Preferably, the opening end of the discharge port is positioned flush with the smallest inner diameter portion or protruding from the opening end surface of the smallest inner diameter portion. Preferably, the manufacturing method includes a step of discharging molten resin from the nozzle while an electric field is generated between the nozzle and the electrode and a heated gas flow is injected from the injection port. [Effects of the Invention]

[0011] According to the electrospinning apparatus and fiber manufacturing method of the present invention, despite its simple configuration, it is possible to increase the airflow velocity of the gas while suppressing the adhesion of molten resin to the opening end of the nozzle, thereby enabling the stable production of fine-diameter fibers with higher production efficiency. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic cross-sectional view showing one embodiment of the electrospinning apparatus of the present invention. [Figure 2] Figure 2 is an enlarged cross-sectional view of the main part of Figure 1. [Figure 3] Figure 3 is a schematic perspective view of the orifice member that is attached to the front end of the inner cylinder shown in Figure 1. [Figure 4] Figure 4 is an explanatory diagram illustrating the airflow ejected from the nozzle shown in Figure 1. [Figure 5] Figure 5 is an image showing the fiber diameter of fibers produced using an 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] Figure 6 is an image showing the adhesion of molten resin to the nozzle when fibers are produced using an electrospinning apparatus. (a) shows the image when fibers are produced using the electrospinning apparatus of Example 1, and (b) shows the image when fibers are produced using the electrospinning apparatus of Comparative Examples 2 and 3. [Modes for carrying out the invention]

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

[0014] The electrospinning device 10 includes a kneading device 20. The kneading device 20 melts the resin that is the raw material of the fiber and discharges it to the spinning unit 30 described later. The kneading device 20 has a cylinder equipped with a heater and a screw (not shown) inside it, and is structured 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 device 10 includes a spinning unit 30. The spinning unit 30 discharges the molten resin supplied from the kneading device 20 to the outside and spins it. The spinning unit 30 includes a hollow nozzle 31 that communicates with the kneading device 20. The nozzle 31 is composed of 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 discharge the molten resin supplied from the kneading device 20 from the tip region 32 through the resin supply path 33a. From the perspective of improving the chargeability, it is preferable that the tip region 32 of the nozzle 31 is composed of a conductor such as metal. Also, from the perspective of improving the heat resistance, it is preferable that the main body region 33 of the nozzle 31 is composed of metal. In the following description, unless otherwise specified, in the extending direction of the nozzle 31 (the left - right direction of the paper surface in FIG. 1), the direction on the side of the kneading device 20 (the left side of the paper surface in FIG. 1) is also referred to as "rearward", and the direction opposite to this direction (the right side of the paper surface in the figure) is also referred to as "forward". Also, the side of the kneading device 20 is also referred to as "upstream side", and the opposite side is also referred to as "downstream side".

[0016] As shown in FIG. 2, the tip region 32 of the nozzle 31 has a connection part connected to the main body region 33 and an opening end part connected to the connection part that discharges the molten resin.

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

[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 the figure has a cylindrical shape arranged so as to surround the nozzle 31 along its circumferential direction. The surface 34a of the electrode 34 facing the nozzle 31 is formed in a concave curved surface shape of the inner surface of the cylinder. For the sake of convenience of explanation, in the following description, the surface 34a of the electrode 34 facing the nozzle 31 is also 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 in front of the tip portion in 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 behind it.

[0019] As shown in FIG. 1, an electrical wiring line 48 for applying a voltage between the electrode 34 and the nozzle 31 is drawn out from the surface 34b on the side opposite to the surface 34a of the electrode 34 facing the nozzle 31. The electrical wiring line 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 by a cylindrical main body region 33 that forms part of the nozzle 31, an inner cylinder 36 having a cylindrical wall portion arranged outward so as to surround the main body region 33, and an outer cylinder 37 located outside the inner cylinder 36, between the kneading device 20 and the tip region 32 of the nozzle 31. The rear end of the main body region 33 communicates with the kneading device 20, and the molten resin supplied from the kneading device 20 can flow toward the tip region 32 side of the nozzle 31 through the resin supply path 33a. The constituent materials of each of the inner cylinder 36 and the outer cylinder 37 are not particularly limited, but it is preferable to select them in consideration of the chargeability of the nozzle 31 and the heat resistance against the gas flow. For example, various metal materials and the same materials as the constituent materials of the surface coating portion 35a described later can be used.

[0021] The spinning unit 30 includes a first gas flow path 40 that injects 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 the wall portion of an inner cylinder 36 which includes an optional orifice member, and more 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, which will be described later. The heated first gas flow A is able to flow through the first gas flow path 40. In other words, the first gas flow path 40 is arranged to surround the nozzle 31 along its circumferential direction. As shown in Figure 1, the first gas flow path 40 is formed to allow the injection of the first gas flow A along the extending direction of the nozzle 31, from the rear end side of the nozzle 31 (i.e., the side of the mixing device 20) toward the tip region 32.

[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 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. For convenience, for example, an airflow can be used as the first gas flow A.

[0023] The first gas injection section 40a extends in a direction intersecting the extending direction of the first gas flow path 40. In the embodiment shown in Figure 1, the extending direction of the first gas injection section 40a and the extending direction of the first gas flow path 40 are approximately perpendicular. Therefore, the first gas flow A supplied from the first gas supply source (not shown) flows through the first gas injection section 40a, and at the connection between the first gas injection section 40a and the first gas flow path 40, the flow direction is changed by 90 degrees and flows through the first gas flow path 40. In the apparatus of the present invention, the intersection angle between the first gas injection section 40a and the first gas flow path 40 is not limited to 90 degrees, and they may intersect at other angles.

[0024] The inner cylinder 36 is composed of a cylindrical main body 36a and an annular flange 36b projecting 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 the orifice member fitted into the inner cylinder 36. In this context, "orifice" broadly refers to a gas flow channel in which the cross-sectional area decreases partially from the upstream to the downstream side, and does not require whether it is formed integrally with the inner wall of the gas flow channel or is separate from the inner wall of the channel.

[0025] In this embodiment, an orifice member is mounted on the inner surface of the front end of the inner cylinder 36. For example, an additional orifice 41, which will be described later, can be provided on the annular member 36b of the inner cylinder 36, which can function as an orifice. As shown in Figures 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 Figures 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 is formed with an outer diameter slightly smaller than the inner diameter of the main body portion 36a. The small-diameter cylindrical portion 41b is formed with an outer diameter slightly smaller than the inner diameter of the annular flange portion 36b and is connected to the front end face of the large-diameter cylindrical portion 41a.

[0026] The orifice 41, as an orifice component, is inserted into the inner cylinder 36 so that 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 in contact with the rear end face of the annular flange portion 36b. In this embodiment, since the gas flow path 41c of the orifice 41 has a cylindrical shape of the same diameter, when the orifice portion 41 is installed inside the inner cylinder 36, the gas flow path 41c becomes the smallest inner diameter flow path, which is the smallest inner diameter of the first gas flow path 40, and the open end located at the downstream end of the smallest 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 downstream end of the gas flow path 41c (hereinafter also referred to as the "injection port 41d") functions as an 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 cylinder 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 further upstream it is determined by the inner diameter of the main body portion 36a of the inner cylinder 36 (see "Inner Diameter Id1" and "Inner Diameter Id2" in Figure 2).

[0027] In the case where 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 portion 36b of the inner cylinder 36. That is, in this configuration, the smallest inner diameter flow path of the first gas flow path 40 becomes the hole formed in the annular flange portion 36b, and the opening end located at the downstream end of the smallest inner diameter flow path becomes the opening end of the hole. In this 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 an orifice 41 in the inner cylinder 36 itself, or by providing an 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 path 40 smaller on the downstream side than on the upstream side. The nozzle for injecting the first gas flow A becomes the open end (injection nozzle 41d) of the small-diameter cylinder portion 41b when an orifice 41 is provided, and the open end of the hole formed in the annular flange portion 36b when an orifice 41 is not provided. In other words, since both of these are the ends located at the downstream end of the smallest inner diameter flow path constituting the first gas flow path 40 (hereinafter also referred to as the "smallest inner diameter portion"), it is possible to increase the wind speed of the first gas flow A injected from the smallest inner diameter portion.

[0029] Here, we will explain the wind speed of the first gas flow A ejected from the smallest inner diameter section. The wind speed of the first gas flow A ejected from the smallest inner diameter section (hereinafter also referred to as the "outlet wind speed") is given by: outlet wind speed (m / s) = V, supply wind speed (L / min) = Q, and cross-sectional area of ​​the smallest inner diameter section (m 2 If we let A be the initial temperature, T0 (K), and T1 (K), then the theoretical value can be calculated using the following formula (hereinafter referred to as the "theoretical value calculation formula"). V = (Q / A) × (T1 / T0)

[0030] For example, if the inner diameter Id1 of the inner cylinder 36 is 13 mm, the inner diameter Id2 of the orifice 41 (minimum inner diameter section) 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), then theoretically, the outlet air velocity V when the orifice 41 is installed in the inner cylinder 36 is 158 m / s. In contrast, if the orifice 41 is not installed and the annular member 36b is not provided, and the first gas flow A is injected from the inner cylinder 36, that is, if the first gas flow A is injected directly from the opening end with an inner diameter Id1 of 13 mm, the outlet air velocity V is 23 m / s. Thus, by providing the orifice 41 in the inner cylinder 36, it is possible to dramatically increase the outlet air velocity V, that is, the air velocity of the first gas flow A injected from the nozzle 41d (minimum inner diameter section).

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

[0032] As shown in Figure 2, in this embodiment, the inner cylinder 36 having an orifice 41 is arranged to surround the nozzle 31 along its circumferential direction. Therefore, in this embodiment, it is possible to inject the heated first gas flow A along the discharge direction of the molten resin while covering the molten resin discharged from the nozzle 31. In other words, in this embodiment, in addition to the Coulomb force, an external force in the discharge direction of the molten resin due to the injection of the first gas flow A can be applied to the molten resin, so that the molten resin can be effectively stretched, and as a result it is possible to efficiently manufacture finer diameter fibers.

[0033] Furthermore, in this embodiment, as described above, since the inner diameter of the first gas flow path 40 is reduced by the orifice 41, it is possible to increase the wind speed (initial velocity) of the first gas flow A injected from the nozzle 41d. As a result, the molten resin can be stretched more effectively, and even smaller diameter fibers can be manufactured more efficiently.

[0034] In this embodiment, as shown in Figure 2, the opening end of the nozzle 31 is positioned to protrude from the smallest inner diameter portion of the injection port 41d (see "Protrusion Amount L" in Figure 2). That is, in this embodiment, the molten resin can be discharged from a position in front of the injection port 41d while an external force is applied by the injection of the first gas flow A, so that adhesion of the molten resin to the injection port 41d and its surroundings can be effectively suppressed. As a result, in this embodiment, even if fiber production is carried out continuously, situations such as the smooth injection of the first gas flow A being hindered by the adhesion of the molten resin to the injection port 41d are unlikely to occur, so that 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 the adhesion of molten resin to the injection port 41d and its surroundings, thereby enabling the 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 portion 36b without the orifice 41 installed, it is possible to increase the wind speed of the first gas flow A, thereby suppressing the adhesion of molten resin to the annular flange portion 36b and its surroundings, and as a result, it is possible to stably produce small-diameter fibers with higher production efficiency.

[0036] Furthermore, in this embodiment, the inner diameter of the first gas flow path 40 through which the first gas flow A flows is formed such that it is smaller downstream than upstream, with the inner diameter Id1 being that of the inner cylinder 36 upstream and the inner diameter Id2 being that of the orifice 41 downstream. In other words, in this embodiment, the inner diameter of the first gas flow path 40 is narrowed in stages from upstream to downstream, making it possible to stably accelerate the wind speed of the first gas flow A. As a result, in this embodiment, the accelerated first gas flow A can be stably ejected from the nozzle 41d, so that the molten resin discharged from the nozzle 31 can be stretched efficiently, and as a result, the diameter of the fibers can be efficiently reduced. The same can be said when the first gas flow A is injected from the hole in the annular flange portion 36b without the orifice 41 installed.

[0037] In this case, it is preferable that the cross-sectional area of ​​the first gas flow path 40 in the 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 Figure 2, if the inner diameter of the main body of the inner cylinder 36 is Id1, the inner diameter of the orifice 41 is Id2, the outer diameter of the main body area 33 of the nozzle 31 is Od1, the outer diameter of the opening end of the nozzle 31 is Od2, and pi is π, The cross-sectional area of ​​the upstream first gas flow path 40 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 This is the result. Here, if the cross-sectional area of ​​the upstream first gas flow path 40 is A and the cross-sectional area of ​​the downstream first gas flow path 40 is B, A > B It is preferable that the following relationship is satisfied.

[0038] When this relationship is satisfied, the cross-sectional area in the orthogonal direction through which the first gas flow A actually flows is gradually narrowed from the upstream side to the downstream side. As a result, the wind speed of the first gas flow A can be accelerated more stably, and consequently, the diameter of the fibers can be reduced more efficiently.

[0039] Furthermore, in this embodiment, as described above, an orifice member (orifice 41) is separately attached to the front end of the inner cylinder 36. In other words, in this embodiment, if the orifice member is damaged or broken, it can be replaced, and 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 nozzle 40b can be changed, making it possible to easily adjust the wind speed.

[0040] Furthermore, from the viewpoint of facilitating the replacement of the orifice member, it is preferable that a small gap is formed between the outer diameters of the large-diameter cylindrical portion 41a and the small-diameter cylindrical portion 41b when the orifice member is installed in the inner cylinder 36. Even with this configuration, when the first gas flow A is circulated within the inner cylinder 36, the front end surface of the large-diameter cylindrical portion 41a is pressed against the rear end surface of the annular flange portion 36b, so that no gap is created between the inner cylinder 36 and the orifice member, and the first gas flow A can be effectively injected from the nozzle 41d.

[0041] Furthermore, the amount L of the protrusion 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 protrudes 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 The protrusion is more preferably 0.5 mm or more, and even more preferably 1 mm or more. Furthermore, "flush" means that the protrusion amount L = 0.

[0042] Here, the reason why the amount of protrusion L of the opening end of the nozzle 31 from the minimum inner diameter portion of the injection port 41d is set to be within 5 times the inner diameter Id2 of the orifice 41 will be explained with reference to Figure 4. As shown in Figure 4, it is known that the gas flow ejected from the nozzle contains a potential core region PA, a region where the airflow velocity from the smallest inner diameter does not decrease. The potential core region PA is eroded and reduced by the free mixing layer that develops from both sides of the smallest inner diameter, and therefore disappears at a predetermined distance from the nozzle. Generally, this distance is considered to be within a range of five times the nozzle diameter.

[0043] In view of the characteristics of the gas flow ejected from such an injection port, and from the viewpoint of manufacturing finer diameter fibers, that is, from the viewpoint of ensuring that the high-speed first gas flow A reliably comes into contact with the molten resin, it is preferable that the opening end of the nozzle 31 is positioned 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 when the first gas flow A is ejected from the hole (minimum inner diameter portion) of the annular flange portion 36b. In this case, the position of the opening end of the nozzle 31 is preferably within five times the inner diameter of the hole in the annular flange portion 36b.

[0044] The gap D1 of the first gas flow path 40 (see Figure 1) is preferably 1 mm or more, more preferably 2 mm or more, preferably 10 mm or less, and even more preferably 7 mm or less. By having the gap D1 within this range, the first gas flow A can be adjusted to the desired wind speed and airflow rate, thereby further increasing the stretching efficiency of the molten resin.

[0045] As shown in Figure 1, the spinning unit 30 further includes a second gas channel 50 for injecting a heated second gas flow B. When the spinning unit 30 is viewed from the front, the second gas channel 50 is positioned outside the first gas channel 40, with reference to the position of the nozzle 31, and surrounds the first gas channel 40. Also, when the spinning unit 30 is viewed from the front, the second gas channel 50 is positioned inside the electrode 34 and outside the first gas channel 40, with reference to the position of the nozzle 31. The second gas channel 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 inject a heated second gas flow B along the extending direction of the nozzle 31, from the rear end of the nozzle 31 toward the tip region 32. 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 heated second gas flow B, supplied from the second gas supply source, to the second gas flow path 50, 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 extending direction of the second gas flow path 50. In the embodiment shown in Figure 1, the extending direction of the second gas injection unit 50a and the extending direction of the second gas flow path 50 are generally perpendicular.

[0047] From a convenience standpoint, for example, an airflow can be used as the second gas flow B. Furthermore, the gap D2 of the second gas flow path 50 (see Figure 1) is preferably 1 mm or more, more preferably 5 mm or more, preferably 100 mm or less, and even more preferably 70 mm or less. By having the gap D2 within this range, the second gas flow B can be adjusted to the desired wind speed and airflow rate, thereby further increasing the stretching efficiency of the molten resin.

[0048] Furthermore, the end position of the second gas flow path 50 in the front-rear direction is not particularly limited as long as the effects of the present invention are achieved. However, when the position of the tip in the tip region 32 of the nozzle 31 is taken as the reference (zero), the forward position of the nozzle 31 is represented by a positive value, and the rear position of 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. In the context of the first gas flow A and the second gas flow B, "heated" 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, a first annular gas flow path 40 is formed outside the nozzle 31, surrounding the nozzle 31, with the position of the nozzle 31 as the reference point. A second annular gas flow path 50 is formed outside the first gas flow path 40, surrounding the first gas flow path 40. Furthermore, electrodes 34 are arranged 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 electrodes 34 are arranged concentrically around the nozzle 31.

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

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

[0052] Furthermore, in this embodiment, since the heated second gas flow B can be injected from the outer circumference of the first gas flow path 40, the ambient temperature around the nozzle 31 in the direction of molten resin discharge can be maintained at a high level, and this ambient temperature can be formed over a wide area. As a result, the cooling and solidification of the molten resin can be delayed, the stretched state of the molten resin can be maintained for a longer period of time, and finer diameter fibers can be efficiently produced. Moreover, the second gas flow B can prevent the discharged molten resin or the cooled and solidified fibers from unintentionally adhering to the electrode 34, allowing the fibers to be transported in the desired direction and increasing production efficiency.

[0053] Furthermore, in this embodiment, since the opening end of the nozzle 31 is positioned to protrude from the smallest inner diameter portion of the injection port 41d, the molten resin can be discharged from the front of the injection port 41d while an external force is applied by the injection of the first gas flow A. As a result, adhesion of the molten resin to the injection port 41d and its surroundings can be effectively suppressed, making it possible to stably manufacture small-diameter fibers.

[0054] Furthermore, since the electrode 34 is positioned outside the second gas flow path 50, the electrical wiring 48 for applying high voltage to the electrode 34 can be routed from the surface 34b opposite to the surface 34a facing the nozzle 31. This makes it easier to handle the electrical wiring 48, which is made of a material with relatively low heat resistance. Moreover, because the electrode 34 is cylindrical, the electrospinning apparatus 10 can be easily miniaturized, and multiple electrospinning apparatuses 10 can be easily integrated. The ability to integrate multiple electrospinning apparatuses 10 greatly contributes to fiber productivity.

[0055] Furthermore, in order to prevent unintended discharge from occurring between the electrode 34 and the nozzle 31 during operation of the electrospinning apparatus 10, it is preferable that the spinning unit 30 is provided with an electrically insulating surface coating portion 35a, which is at least disposed on the concave curved surface 34a of the electrode 34 that faces the nozzle 31. This prevents discharge between the nozzle 31 and the electrode 34, allowing for stable fiber spinning. The surface coating portion 35a shown in Figure 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 portion 35a is a concave curved surface on the inner surface of a cylinder. The surface coating portion 35a is arranged to surround the nozzle 31 along its circumferential direction.

[0056] Preferably, the spinning unit 30 also includes an electrically insulating back surface covering portion 35b located on the convex curved surface 34b opposite to the concave curved surface 34a of the electrode 34, which faces the nozzle 31. The back surface covering portion 35b is a convex curved surface on the outer surface of the cylinder. Furthermore, as shown in Figure 1, it is preferable that the spinning unit 30 has end coverings 35c outside both ends in the extending direction of the electrode 34. In other words, as shown in Figure 1, it is preferable that the entire area of ​​the electrode 34 is covered. With this configuration, each covering portion 35a, 35b, and 35c can also function as a support member for the electrode 34.

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

[0058] To ensure sufficiently high electrical insulation, the thickness of the surface coating portion 35a and the back coating portion 35b are preferably 2 mm or more, and more preferably 4 mm or more, independently of each other. From the viewpoint of electrical insulation, there is no particular upper limit on the thickness, but from the viewpoint of suppressing the enlargement of the electrospinning apparatus 10, the thickness is preferably 30 mm or less, and more preferably 15 mm or less.

[0059] Examples of materials constituting each of the coating portions 35a, 35b, and 35c include ceramic materials such as dielectrics like 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 glass cloth, laminates made by impregnating glass cloth with a heat-resistant binder, glass wool, rock wool, and silica cloth. Of these, it is preferable to use at least one selected from alumina, bakelite, glass cloth, laminates made by impregnating glass cloth with a heat-resistant binder, glass wool, rock wool, and silica cloth, and it is particularly preferable to use a laminate made by impregnating glass cloth with a heat-resistant binder.

[0060] Furthermore, from the viewpoint of successfully supplying 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 is provided between the kneading device 20 and the spinning unit 30. Known means such as a heater can be used as the heating means. It is preferable that the temperature for heating or maintaining the temperature be above the melting point of the raw material resin used in the manufacture of the fibers. In addition, the main body area 33 is preferably made of metal, for example, from the viewpoint of thermal conductivity and mechanical strength, and is preferably grounded from the viewpoint of preventing voltage load on the kneading device 20 in the molten electrospinning method.

[0061] The above was a description of the electrospinning apparatus 10. The method for manufacturing fibers using the electrospinning apparatus 10 (electrospinning method) will be described below. In the method for manufacturing fibers using the electrospinning apparatus 10, an electric field is generated between the nozzle 31 and the electrode 34, and 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 injected. The discharged molten resin is finely divided as it is stretched three-dimensionally by the Coulomb force generated inside it and the injection of the first gas flow A and the second gas flow B, and at the same time, the cooling and solidification of the resin proceeds, forming fine-diameter fibers.

[0062] The fibers produced by the method of the present invention are small fibers called nanofibers, with a fiber diameter of 30 μm or less when expressed as an equivalent circular 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, for example, by selecting 500 fibers arbitrarily from a two-dimensional image obtained by scanning electron microscopy (SEM), removing defects such as spun fiber clumps, fiber intersections, 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 referred to as the fiber diameter in this specification.

[0064] In the manufacturing of fibers, when injecting the first gas flow A and the second gas flow B, it is preferable to inject the first gas flow A at a velocity equal to or greater than that of the second gas flow B. By adjusting the velocity of each gas flow, the discharged molten resin can be stretched more strongly by the external force generated by the injection of the first gas flow, and as a result, even finer diameter fibers can be efficiently obtained.

[0065] The molten resin used in the present invention is a fluid resin composition containing a thermoplastic resin having a melting point. "Having a melting point" means that, in differential scanning calorimetry, when the resin is heated, it exhibits an endothermic peak due to a phase change from solid to liquid before thermal decomposition of the resin. The melting point of the thermoplastic resin can be measured, for example, using a melting point / dropping point analyzer (Mettler Toledo Co., Ltd., model number: DP90 automatic dropping point / softening point analyzer) 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 copolymer; polyester resins such as polyethylene terephthalate and 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; and polyvinyl acetate and polyvinyl acetate-ethylene copolymers. These resins can be used individually or in combination of two or more. Of these thermoplastic resins, polyolefin resins such as polyethylene, polypropylene, and ethylene-α-olefin copolymer are preferred because they are easy to spin 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 a thermoplastic resin, as long as the effects of the present invention are not impaired. Examples of additives include antistatic agents, antioxidants, neutralizing agents, light stabilizers, ultraviolet absorbers, lubricants, antistatic agents, metal deactivators, and hydrophilic agents. Examples of antistatic 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 acylalkyl 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 ultraviolet absorbers include hindered amines, nickel complex compounds, benzotriazoles, and benzophenones. Examples of lubricants include higher fatty acid amides such as stearate amide. Examples of antistatic agents include fatty acid partial esters such as glycerol fatty acid monoesters. Examples of metal deactivators include phosphores, epoxy compounds, triazoles, hydrazides, and oxamides. Examples of hydrophilic agents include polyhydric alcohol fatty acid esters, ethylene oxide adducts, and nonionic surfactants such as amine anamides.

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

[0069] There are no particular restrictions on the method for producing the molten resin. For example, it can be produced by heating and melting a thermoplastic resin, adding additives as needed, and then heating and kneading the mixture. Such a molten resin may be produced by pre-melting and kneading it as a masterbatch, or the thermoplastic resin and additives as needed may be supplied to a kneading device 20 at the time of production, and then heated, melted, and kneaded within the kneading device 20.

[0070] Nanofibers or their deposits produced by the electrospinning method using the electrospinning apparatus 10 described above can be used for various purposes as a fibrous molded body formed by accumulating them. Examples of molded body shapes include sheets, cotton-like bodies, and thread-like bodies. The fibrous molded body may be used by laminating it with other sheets or by incorporating various liquids, fine particles, fibers, etc. Fiber sheets are suitably used as sheets attached to human skin, teeth, gums, hair, the skin, teeth, gums of non-human mammals, and the surfaces of plants such as branches and leaves for non-medical purposes such as medical, cosmetic, and decorative purposes. They are also suitably used as high-performance filters with high dust collection and low pressure loss, battery separators that can be used at high current densities, and cell culture substrates with a highly porous structure. Cotton-like fibrous bodies are suitably used as soundproofing materials and heat insulating materials.

[0071] Although the present invention has been described above based on its preferred embodiments, the present invention is not limited to the above embodiments. For example, in this embodiment, the opening end of the nozzle 31 is positioned to protrude from the minimum inner diameter portion of the injection port 41d in the orifice 41, but it may also be positioned flush with the minimum inner diameter portion of the injection port 41d. Even with this configuration, the molten resin can be discharged from a position flush with the injection port 41d while an external force is applied by the injection of the first gas flow A, so it is possible to suppress the adhesion of molten resin to the injection port 41d and its surroundings. Therefore, even in this case, when fiber manufacturing is carried out continuously and steadily, it is unlikely that the smooth injection of the first gas flow A will be hindered by the adhesion of molten resin to the injection port 41d, so stable production of small diameter fibers can be expected.

[0072] Furthermore, in this embodiment, the inner diameter of the nozzle into which the first gas flow A is injected is reduced using the orifice 41, but the inner diameter may also be reduced by reducing the inner diameter of the inner cylinder 36 itself toward the front.

[0073] Furthermore, in this embodiment, an outer cylinder 37 is provided outside the inner cylinder 36 to inject the second gas flow B. However, it is also possible to omit the outer cylinder 37 and configure the system so that the second gas flow B is not injected. [Examples]

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

[0075] In Examples 1 and 2, and Comparative Examples 1 to 3, described below, tests were conducted to produce fibers by spinning a molten resin made of polypropylene as the thermoplastic resin raw material using the molten electrospinning method with the electrospinning apparatus 10 shown in Figure 1, according to the manufacturing conditions shown in Table 1 below. In Examples 1 and 2, and Comparative Examples 1 to 3, the fiber diameter of the produced fibers was measured, and the presence or absence of adhesion of molten resin (fibers) to the 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 manufacturing conditions. • Inner diameter Id1 of the main body 36a of the inner cylinder 36: 16mm • Inner diameter of orifice component Id2: 5mm • Outer diameter of nozzle 31 body area 33 Od1: 12mm • Outer diameter Od2 of the opening end of nozzle 31: 0.5 mm • Airflow rate Q of the first gas flow A: 100 L / min • Temperature of the first gas stream A ejected from nozzle 41d (outlet temperature): 300℃ In this case, the cross-sectional area of ​​the first gas flow path 40 in the perpendicular direction is 88 mm² at the location where the main body area 33 of the nozzle 31 is located inside the inner cylinder 36. 2 At the location of the nozzle 41d, 19.4 mm 2 This is the result. Furthermore, the wind speed V (theoretical outlet wind speed V) of the first gas flow A, calculated using the theoretical value calculation formula described above, is 158 m / s. In addition, in Example 1 and Example 2, the value of the protrusion amount L of the opening end of the nozzle 31 from the minimum inner diameter portion of the injection port 41d was differed during fiber production. Specifically, the protrusion amount L was set to 2 mm in Example 1 and to 0 mm in Example 2.

[0078] [Comparative Example 1] In Comparative Example 1, fibers were manufactured under the following manufacturing conditions. • Inner diameter Id1 of the main body 36a of the inner cylinder 36: 13mm • Outer diameter of nozzle 31 body area 33 Od1: 12mm • Outer diameter Od2 of the opening end of nozzle 31: 0.5 mm • Airflow rate Q of the first gas flow A: 100 L / min • Temperature of the first gas stream A ejected from nozzle 41d (outlet temperature): 300℃ • Protrusion amount L of the opening end of the nozzle 31 from the opening end face of the spray 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 mm² in the portion where the main body area 33 of the nozzle 31 is located inside the inner cylinder 36. 2 At the location of nozzle 41d, the distance is 132.5 mm. 2 Furthermore, the wind speed V (theoretical outlet wind speed V) of the first gas flow A, calculated using the theoretical value calculation formula described above, 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 by a predetermined amount from the minimum inner diameter portion of the injection port 41d, but it differs in that it does not have an orifice 41 and does not have an annular flange portion 36b.

[0079] [Comparative Example 2 and Comparative Example 3] Comparative Examples 2 and 3 differed from Examples 1 and 2 only in that the opening end of the nozzle 31 did not protrude beyond the minimum inner diameter of the injection port 41d; all other manufacturing conditions were the same for the tests.

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

[0081] [Presence or absence of molten resin adhesion] Under the manufacturing conditions of both the examples and comparative examples, the molten resin (fiber) discharged from the nozzle 31 was visually evaluated according to the following criteria to determine whether it adhered to the injection port 41d of the orifice 4 and its surroundings. The results are shown in Table 1. • "Yes": Molten resin (fiber) discharged from nozzle 31 adheres to the nozzle 41d and its surroundings, resulting in poor fiber production efficiency. • "None": The molten resin (fiber) discharged from the nozzle 31 does not adhere to the nozzle 41d and its surroundings, enabling continuous fiber production and resulting in high fiber production efficiency.

[0082] [Test Evaluation] As shown in Table 1, in Examples 1, 2, Comparative Examples 2, and 3 (theoretical outlet wind speed V of the first gas flow A: 158 m / s), which have an orifice 41, it was possible to produce fibers with a small diameter, such as 0.5 μm (Examples 1 and 2). In contrast, in Comparative Example 1 (theoretical outlet wind speed V of the first gas flow A: 24 m / s), which does not have an orifice, the result was that fibers with a larger diameter, such as 3.8 μm, were produced. Figure 5(a) is an image of the fibers produced using the electrospinning apparatus 10 of Example 1, and Figure 5(b) is an image of the fibers produced using the electrospinning apparatus 10 of Comparative Example 1. These test results show that increasing the wind speed V of the first gas stream A ejected from nozzle 41d allows for the efficient production of small-diameter fibers.

[0083] On the other hand, in Examples 1, 2, and Comparative Example 1, where 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 nozzle 41d and its surroundings. In contrast, in Comparative Examples 2 and 3, where the protrusion amount L was set to less than 0 mm, adhesion of the molten resin (fiber) to the nozzle 41d and its surroundings was confirmed. Figure 6(a) shows an image of the nozzle 41d and its surroundings when fibers were produced using the electrospinning apparatus 10 of Example 1, and Figure 6(b) shows an image of the nozzle 41d and its surroundings 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 molten resin (fiber) from adhering to the injection port 41d and its surroundings, meaning that continuous fiber production is possible and fiber production efficiency is high.

[0084] From the above test results, it has been demonstrated that in order to achieve 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 amount of protrusion L of the opening end of the nozzle 31 from the smallest inner diameter portion of the nozzle 41d to 0 mm or more. The amount of protrusion L of the opening end of the nozzle 31 is preferably set to a range within 5 times the inner diameter of the orifice 41, as described above (see Figure 4).

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

[0086] 10. Electrospinning apparatus 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 a molten resin; an electrode for generating an electric field between the electrode and the nozzle; An electrospinning apparatus comprising: 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 portion formed between an outer circumferential surface of the nozzle and a cylindrical wall portion disposed outside the nozzle, and an injection port provided downstream of the space portion and configured to inject the gas flow passing through the space portion to the outside, the injection port is provided in a minimum inner diameter flow passage that has a smallest inner diameter among inner diameters of the gas flow passage, and has a minimum inner diameter portion located on the most downstream side of the minimum inner diameter flow passage, an opening end of the discharge port is disposed at a position flush with the minimum inner diameter portion or at a position protruding from the opening end face of the minimum inner diameter portion.

2. The electrospinning apparatus according to claim 1 , wherein an inner diameter of the gas flow passage 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 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 an inner diameter of an open end of the injection port.

5. A method for producing 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 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 circumferential 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 passage that has a smallest inner diameter among inner diameters of the gas flow passage, and has a minimum inner diameter portion located on the most downstream side of the minimum inner diameter flow passage, an opening end of the discharge port is disposed in a position flush with a minimum inner diameter portion located at the most downstream side of the minimum inner diameter flow path or in a position protruding from an opening end face 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 ejecting molten resin from the nozzle while ejecting a heated gas flow from the nozzle.

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