JP7293008B2 - Electrospinning apparatus and nanofiber manufacturing method - Google Patents

Description

The present invention relates to an electrospinning apparatus and a method for producing nanofibers.

The electrospinning method is attracting attention as a technique capable of easily producing a fiber sheet having nano-sized diameter fibers with high productivity 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 ejecting a raw material resin liquid and a collection electrode placed opposite to a position separated from the nozzle by a predetermined distance. Under this condition, the raw material resin liquid is discharged. 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 finer fibers. The present applicant has proposed an apparatus for producing fibers using this technology and a method for producing the same (Patent Documents 1 and 2).

Patent Literature 3 discloses a fine fiber manufacturing apparatus including first and second nozzles for jetting air with different jet pressures, and a discharge nozzle for supplying raw materials for fine fibers to be spun. The same document also discloses that the first and second nozzles are arranged so that the angle formed by the discharge nozzle is an acute angle or a right angle.

Further, in Patent Document 4, a row of orifices arranged at intervals in the width direction and capable of injecting a molten thermoplastic polymer and a pair of first slits for injecting hot air are provided. An apparatus is disclosed in which heated hot air is introduced so as to merge at the tip of the orifice row to produce a group of ultrafine fibers. The same document also discloses having slits that can be introduced to jet the gas in parallel on both sides of the hot air.

JP 2016-204816 A JP 2018-193658 A Japanese Patent Application Laid-Open No. 2019-2088 JP 2014-88639 A

By the way, in the electrospinning method using the melt of the raw material resin, drawing while maintaining the molten state of the raw material resin after the melt is discharged leads to a reduction in the diameter of the manufactured fiber and an improvement in production efficiency. The electrospinning apparatus described in Patent Document 1 maintains the heated state of the melt even after ejection, so that the melt is easily stretched. However, the spun fibers adhere to the electrodes arranged outside the discharge nozzle, making it difficult to continuously manufacture the fibers, or depending on the wind speed of the gas flow, the melt cannot be drawn sufficiently. However, there was room for improvement on these points.

The electrospinning apparatus described in Patent Literature 2 relates to the production of fibers using a resin solution, and does not discuss the fiber diameter reduction and production efficiency in the case of using a melt. In the manufacturing apparatus described in Patent Document 3, since the jetting direction of the nozzle for jetting gas and the extending direction of the discharge nozzle intersect, it is difficult to reduce the diameter of the fiber, and the production efficiency of the fiber is lowered. was there. Moreover, the production apparatus described in Patent Document 4 is not a technology related to the electrospinning method, and it was difficult to stably obtain desired ultrafine fibers.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electrospinning apparatus and a nanofiber manufacturing method using the same that can overcome the drawbacks of the prior art.

The present invention is an electrospinning apparatus comprising a nozzle for discharging a molten resin, an electrode for generating an electric field between the nozzle and the nozzle, and a gas injection unit,
The gas injection part is arranged so as to surround the nozzle, and is formed so as to be capable of injecting a heated first gas flow from the rear end toward the front end of the nozzle along the direction in which the nozzle extends. a first gas injection unit that is
a second gas injection part outside the first gas injection part and formed so as to be able to inject a heated second gas flow from the rear end of the nozzle toward the tip direction; It provides an apparatus.

The present invention also provides a nanofiber manufacturing method for manufacturing nanofibers using the electrospinning apparatus,
The molten resin is discharged from the nozzle in a state in which an electric field is generated between the nozzle and the electrode and heated gas flows are jetted from the first gas jetting portion and the second gas jetting portion, respectively. A method for producing nanofibers by spinning is provided.

According to the present invention, finer fibers can be produced with high production efficiency.

FIG. 1 is a schematic cross-sectional view showing one embodiment of the electrospinning apparatus of the present invention. FIG. 2 is a schematic cross-sectional view showing another embodiment of the electrospinning apparatus of the present invention. FIG. 3 is a schematic cross-sectional view showing still another embodiment of the electrospinning apparatus of the present invention. FIG. 4 is a schematic cross-sectional view showing still another embodiment of the electrospinning apparatus of the present invention. FIG. 5 is a schematic cross-sectional view showing still another embodiment of the electrospinning apparatus of the present invention. FIG. 6 is a schematic cross-sectional view showing still another embodiment of the electrospinning apparatus of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on its preferred embodiments with reference to the drawings. FIG. 1 shows the structure of one embodiment of the electrospinning apparatus of the present invention. As shown in the figure, the electrospinning device 10 includes a kneading device 20 and a spinning unit 30 .

The electrospinning device 10 has 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, which will be described later. The kneading device 20 has a cylinder equipped with a heater and a screw (not shown) therein, melt-kneads the raw material resin supplied into the kneading device 20, and extrudes and supplies it to the spinning unit 30. It has a structure that allows

The electrospinning apparatus 10 has a spinning unit 30 . The spinning unit 30 spun by discharging the molten resin supplied from the kneading device 20 to the outside. The spinning unit 30 has a hollow nozzle 31 communicating with the kneading device 20 . The nozzle 31 can discharge the molten resin supplied from the kneading device 20 from a nozzle tip 31a of the nozzle 31 through a resin supply path 31b, which will be described later. From the viewpoint of improving the chargeability of the nozzle 31, the nozzle 31 is preferably made of a conductor such as metal. In the following description, unless otherwise specified, the direction toward the kneading device 20 when viewed from the nozzle 31 (the left side of the drawing) is also referred to as the “rearward direction” or the “rear end direction”, and the opposite direction (the middle, right side of the paper) is also referred to as "forward" or "forward direction".

As shown in FIG. 1, the spinning unit 30 has an electrode 32 for electrifying the nozzle 31 and generating an electric field between it and the nozzle 31 . Electrode 32 is made of a conductive material. The electrode 32 in the figure has a substantially bowl shape arranged so as to surround the nozzle 31 . The surface of the electrode 32 facing the nozzle 31 is formed into a concave surface. For convenience of explanation, the surface of the electrode 32 facing the nozzle 31 is also referred to as the "concave curved surface 32a" in the following description. The electrode 32 has an opening end 32c on the tip side of the nozzle 31, and the planar shape of the opening end 32c is a circular shape such as a perfect circle or an ellipse. The electrodes 32 are connected to a high voltage generator (not shown) by which a positive or negative voltage is applied.

The concave curved surface 32a is preferably curved at any position. The term "curved surface" as used herein refers to (a) a curved surface that does not have a flat portion at all, or (b) a shape that can be regarded as a concave curved surface as a whole by connecting a plurality of segments having a flat portion. or (c) a shape that can be regarded as a concave curved surface as a whole by connecting a plurality of annular segments having a belt-like portion with no curvature on one of the three mutually orthogonal axes. say.

From the viewpoint of facilitating the concentration of charge on the nozzle 31 and increasing the charge amount of the ejected molten resin, the concave curved surface 32a is formed so that the normal line at any position passes through the nozzle tip 31a or its vicinity. is preferable, and it is more preferable that the concave curved surface 32a has the same shape as the inner surface of the spherical shell of a true sphere. Similarly, the open end 32c is also preferably circular.

The spinning unit 30 shown in FIG. 1 includes a cylindrical resin supply path 31b between the kneading device 20 and the nozzle 31, an inner cylinder 36 arranged to surround the resin supply path 31b, and the inner cylinder 36. It has a structure formed with the outer cylinder 37 . The resin supply path 31b communicates with the kneading device 20 so that the molten resin supplied from the kneading device 20 can flow to the nozzle 31 side. A space formed between the resin supply path 31b and the inner cylinder 36 serves as a first gas injection portion 40 through which the heated first gas flow A can flow. That is, the first gas injection section 40 is arranged so as to surround the nozzle 31 . The first gas injection section 40 is connected to a first gas supply source (not shown) that supplies a heated first gas flow A to the gas injection section 40 through a first gas introduction port 40a. The first gas flow A can be supplied to each of the first gas injection sections 40,40. As shown in FIG. 1, the first gas injection part 40 directs the first gas flow from the rear end of the nozzle 31 (that is, the kneading device 20 side) toward the nozzle tip 31a and along the direction in which the nozzle 31 extends. It is designed to be able to inject A. From the viewpoint of convenience, the first gas flow A can be, for example, an air flow.

The first gas injection part 40 is formed in an annular shape so as to surround the outer periphery of the resin supply path 31b and the nozzle 31 from the viewpoint of drawing the discharged molten resin by the gas flow and making it easier to form ultrafine fibers. Alternatively, a plurality of the nozzles 31 are preferably arranged along the extending direction of the nozzles 31 so as to surround the nozzles 31 .

As shown in FIG. 1, the spinning unit 30 further includes a second gas injection section 50 for injecting the heated second gas flow B. As shown in FIG. The second gas injection section 50 is arranged outside the first gas injection section 40 with the position of the nozzle 31 as a reference when the spinning unit 30 is viewed from the front. The second gas injection part 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 nozzle tip 31a side. The second gas injection section 50 is connected to a second gas supply source (not shown) that supplies a heated second gas flow B to the gas injection section 50 via a second gas introduction port 50a. The second gas flow B can be supplied to each of the second gas injection sections 50,50. In the embodiment shown in the figure, the second gas injection section 50 is arranged inside the electrode 32 and outside the first gas injection section 40 with respect to the position of the nozzle 31 when the spinning unit 30 is viewed from the front. , so that the second gas flow B can be jetted along the direction in which the nozzle 31 extends. From the viewpoint of convenience, the second gas flow B can be, for example, an air flow.

In addition, "heated" in the first gas flow A and the second gas flow B refers to gas flows having a higher temperature than the standard temperature (20°C).

The electrospinning apparatus 10 may have a collection section (not shown) that collects the spun fibers at a position facing the nozzle 31 . A collecting electrode made of a conductive material such as metal is disposed in the collecting section, and the potential difference between the nozzle 31 and the collecting electrode causes the spun fibers to move on the collecting section. It is ready to be collected. The collection electrode preferably has a flat plate shape, 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 to each other. The collecting electrode is preferably grounded or energized by a high voltage power supply. In this case, it is also preferable that a voltage different from the voltage applied to the nozzle 31 is applied to the collecting portion. Moreover, the collection part may have 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 conveying means. When a collecting portion is provided, the distance between the tip of the nozzle 31 and the collecting portion is preferably 50 mm or more, more preferably 100 mm or more, preferably 2000 mm or less, and still more preferably, from the viewpoint of fiber collection efficiency. Set to be 1500 mm or less.

According to the electrospinning apparatus having the above configuration, the heated first gas flow A is jetted from the first gas jetting section 40 relatively close to the nozzle 31, so that the first gas flow A is jetted from the nozzle 31. It becomes easier to come into contact with the molten resin discharged from 31 . As a result, in addition to the Coulomb force, the molten resin can be drawn more effectively by the application of the external force due to the injection of the first gas stream, and finer fibers can be efficiently produced. Further, since the second gas flow B can be injected from the outside of the first gas injection part 40, the temperature of the space around the nozzle 31 in the molten resin discharge direction can be maintained at a high level, and the space can be formed in a wide range. can do. As a result, the cooling and solidification of the molten resin is delayed, the drawn state of the molten resin is maintained for a long period of time, and fibers having a smaller diameter can be efficiently produced. Furthermore, the second gas flow B can prevent the ejected molten resin or the fibers after being cooled and solidified from unintentionally adhering to the electrodes 32, so that the fibers can be transported in a desired direction to increase production efficiency. be able to.

From the viewpoint of making the above-mentioned effect more remarkable, the spinning unit 30 preferably has an electrically insulating wall portion 35 disposed at least on the concave curved surface 32a of the electrode 32 facing the nozzle 31. . As a result, electric discharge between the nozzle 31 and the electrode 32 can be prevented, and the fiber can be stably spun.

The wall portion 35 shown in FIG. 1 is in direct contact with the electrode 32 and covers the entire surface of the electrode 32 . With such a configuration, the wall portion 35 can also function as a support member that supports the electrode 32 . The wall portion 35 has an open end 35 c on the tip side of the nozzle 31 . The planar shape of the opening end 35c of the wall portion 35 may be a perfect circle or an ellipse. The surface of the wall portion 35 facing the nozzle 31 forms a wall surface 35b inclined toward the opening end 35c.

The wall portion 35 is preferably made of a dielectric for electrically insulating the nozzle 31 and the electrode 32 . By making the wall portion 35 dielectric, the charge amount of the nozzle 31 can be further increased, and fibers with a smaller diameter can be produced. The wall portion 35 may be composed of a single type of dielectric, or may be a laminate in which a plurality of types of dielectrics are laminated.

Dielectrics used for the wall portion 35 include insulating materials such as mica, alumina, zirconia, barium titanate, and other ceramic materials, bakelite (phenol resin), nylon (polyamide), vinyl chloride resin, polystyrene, polyester, and polypropylene. , polytetrafluoroethylene, and polyphenylene sulfide. Among these, it is preferable to use at least one insulating material selected from alumina, bakelite, nylon, and vinyl chloride resin, and it is particularly preferable to use nylon. As nylon, various polyamides such as 6 nylon and 66 nylon can be used. A commercially available product can also be used as nylon. Examples of such commercial products include MC nylon (registered trademark).

In addition, the dielectric used for the wall portion 35 can contain an antistatic agent. By containing an antistatic agent, it becomes difficult for charged molten resin, fibers, etc. to adhere to the wall portion 35, and the production efficiency of fibers can be improved. Known commercial products can be used as the antistatic agent, for example, Plectron (registered trademark, Sanyo Chemical Industries, Ltd.), Electrostripper (registered trademark, Kao Corporation), Rikemal (registered trademark, Riken Vitamin ( Co., Ltd.) and the like can be used.

Although each material constituting the first gas injection unit 40 and the second gas injection unit 50 is not particularly limited, it is preferable to select the materials in consideration of the chargeability of the nozzle 31 and the heat resistance to the gas flow. Similar materials can be used.

In the embodiment shown in FIG. 1, the electrode 32 is arranged outside the first gas injection section 40 and the second gas injection section 50 when the position of the nozzle 31 is used as a reference. is the same as the embodiment shown in FIG. 1, and the arrangement of the first gas injection unit 40 and the second gas injection unit 50 is different. You can also Even with such a configuration, the molten resin can be effectively stretched by further applying an external force due to the injection of the first gas flow in addition to the Coulomb force. In addition, since the cooling and solidification of the molten resin can be delayed and the drawn state of the molten resin can be maintained for a long period of time, fibers having a smaller diameter can be efficiently produced. The embodiment described below focuses on points that differ from the above-described embodiment, and the description of the above-described embodiment applies appropriately to points that are not particularly described. The same reference numerals are assigned to the same points as in the above-described embodiment, and the description thereof is omitted.

In the embodiment shown in FIGS. 2 and 3, the end positions of the injection ports of the first gas injection section 40 and the second gas injection section 50 are different. Specifically, in the embodiment shown in FIG. 2, the end position of the first gas injection port 40p in the first gas injection section 40 is substantially the same position as the nozzle tip 31a. On the other hand, the terminal end of the second gas injection port 50p in the second gas injection section 50 is located behind the nozzle tip 31a. With such a configuration, the second gas flow B is jetted in the direction of ejection of the molten resin, and the second gas flow B extends from the position of the nozzle 31 to the outside of the nozzle 31 when viewed from the front of the spinning unit 30. Since it becomes easy to jet while diffusing toward the nozzle 31, the space temperature around the nozzle 31 can be maintained at a high state, and the space can be formed in a wider range. As a result, the cooling and solidification of the molten resin is delayed, the drawn state of the molten resin is maintained for a long period of time, and fibers having a smaller diameter can be efficiently produced.

Further, in the embodiment shown in FIG. 3, the end position of the first gas injection port 40p in the first gas injection portion 40 is substantially the same as the nozzle tip 31a, and the second gas injection port 50p in the second gas injection portion 50 is positioned forward of the nozzle tip 31a. With such a configuration, the second gas flow B is jetted while being rectified along the ejection direction of the molten resin, so adhesion of the molten resin to the spinning unit 30 can be further suppressed.

In the embodiment shown in FIG. 4, the end position of the first gas injection port 40p in the first gas injection section 40 is substantially the same position as the nozzle tip 31a, and the end position of the second gas injection port 50p in the second gas injection section 50 is substantially the same. The end is positioned forward of the nozzle tip 31a. In addition, the second gas injection part 50 has a tapered shape in which the diameter of the injection port gradually increases from the rear to the front of the nozzle 31 . By having such a configuration, the second gas flow B is jetted while being rectified along the ejection direction of the molten resin, and the second gas flow B is positioned at the nozzle 31 in the front view of the spinning unit 30. Since it is easy to jet while diffusing outward from the nozzle 31, the temperature of the space around the nozzle 31 can be maintained at a high level, and the space can be formed in a wider range. As a result, it is possible to maintain the drawn state of the molten resin for a long time due to the delay in cooling and solidification of the molten resin, and to further suppress adhesion of the molten resin to the spinning unit 30 . Alternatively, the second gas injection part 50 may have a reverse tapered shape in which the injection diameter gradually decreases from the rear to the front of the nozzle 31 . In such a configuration, the second gas flow B is jetted together with the first gas flow A while surrounding the discharged molten resin, and the wind speed of the second gas flow B increases. , the effect of rectifying the gas flow caused by the second gas flow B is further enhanced, and adhesion of the molten resin to the spinning unit 30 can be more effectively suppressed.

Instead of the embodiment shown in FIGS. 1 to 4, the embodiment shown in FIG. 5 may be adopted. In the embodiment shown in FIG. 5, when the spinning unit 30 is viewed from the front, the electrode 32 is arranged between the first gas injection section 40 and the second gas injection section 50 with the position of the nozzle 31 as a reference. There is. The end position of the first gas injection port 40p in the first gas injection part 40 is substantially the same as the nozzle tip 31a, and the end of the second gas injection port 50p in the second gas injection part 50 is located at the nozzle tip 31a. located in front of the Even with such a configuration, the molten resin can be stretched more effectively by applying an external force by jetting the first gas stream in addition to the Coulomb force. In addition, cooling and solidification of the molten resin can be delayed, and the drawn state of the molten resin can be maintained for a long period of time, so fibers with a smaller diameter can be efficiently produced. In particular, in the embodiment shown in FIG. 5, the distance between the nozzle 31 and the electrode 32 is relatively short compared to the embodiments shown in FIGS. 1 to 4 and the embodiment shown in FIG. Also, the ejected molten resin can be more strongly charged, and as a result, it is possible to produce finer fibers due to the generation of the Coulomb force.

Instead of the embodiment shown in FIGS. 1 to 5, the embodiment shown in FIG. 6 may be adopted. In the embodiment shown in FIG. 6, when the spinning unit 30 is viewed from the front, the electrode 32 is arranged between the first gas injection section 40 and the second gas injection section 50 with the position of the nozzle 31 as a reference. there is Further, the end position of the first gas injection port 40p in the first gas injection section 40 is substantially the same position as the nozzle tip 31a. The end of the second gas injection port 50p of the second gas injection part 50 is located forward of the nozzle tip 31a, and the injection direction of the second gas flow B is arranged so as to intersect the direction in which the nozzle 31 extends. formed. Even with such a configuration, in addition to the Coulomb force, the molten resin can be stretched three-dimensionally by applying an external force due to the injection of the first gas flow A, and the molten resin can be stretched for a long time. Since the cooling and solidification of the molten resin can be delayed while maintaining it, fibers with a smaller diameter can be efficiently produced. In particular, in this embodiment, when the fibers to be spun are collected, it is possible to prevent the fibers from being unintentionally diffused in the plane direction of the collecting portion and collected, so that the fibers can be collected in a desired range. This has the advantage of increasing production efficiency.

Among these embodiments, when the spinning unit 30 is viewed from the front, the first gas injection part 40 and the second gas injection part 50 are positioned on two concentric circles with the nozzle 31 as the center and having different diameters. In addition, since the injection direction of the first gas flow A and the injection direction of the second gas flow B match, the second gas flow B can be injected so as to surround the first gas flow A. is preferred. That is, the embodiment shown in FIGS. 1 to 5 is preferable. With such a configuration, the second gas flow B flows between the first gas flow A and the outside air, and contact between the first gas flow A and the outside air can be prevented. An unintended temperature drop of the first gas flow A injected from the gas injection part 40 can be prevented. As a result, the drawing efficiency by spraying the first gas stream A onto the molten resin is further enhanced, and the advantage of efficiently obtaining fine-diameter fibers is exhibited.

Specifically, the first gas injection port 40p in the first gas injection unit 40 is arranged on a virtual circle with a relatively small diameter centered on the nozzle 31, and the second gas injection port 40p in the second gas injection unit 50 It is preferable that the injection ports 50p be arranged on a virtual circle centered on the nozzle 31 and having a relatively large diameter. In this case, when the spinning unit 30 is viewed from the direction opposite to the nozzle 31, both the first gas injection ports 40p and the second gas injection ports 50p are spaced apart at regular intervals in the circumferential direction of the virtual circle. A plurality of nozzles having a geometric shape such as a shape may be formed, or a continuous line-shaped nozzle may be formed along an imaginary circumference, or a combination of these may be used.

Next, items commonly applicable to each of the above-described embodiments will be described.
The inner diameter of the nozzle tip 31a can be set to preferably 50 μm or more, more preferably 100 μm or more, and preferably 3000 μm or less, more preferably 2000 μm or less. By setting the inner diameter of the nozzle tip 31a within this range, the molten resin can be easily and quantitatively discharged.

The injection port diameter D1 (see FIG. 1) of the first gas injection port 40p is preferably 1 mm or more, more preferably 2 mm or more, and preferably 10 mm or less, further preferably 7 mm or less. The injection port diameter D2 (see FIG. 1) of the second gas injection port 50p is preferably 10 mm or more, more preferably 20 mm or more, and preferably 100 mm or less, further preferably 70 mm or less. By setting the diameter of each injection port within such a range, the first gas flow A and the second gas flow B can be adjusted to desired wind speeds and wind volumes, and the drawing efficiency of the molten resin can be further enhanced.

From the viewpoint of successfully supplying the molten resin from the kneading device 20, a heating means (not shown) for heating or keeping the molten resin warm is provided between the kneading device 20 and the spinning unit 30. preferable. A known means such as a heater can be used as the heating means. As for the temperature for heating or keeping warm, it is preferable to heat or keep warm at or above the melting point of the raw material resin used in the production of the fiber. The resin supply path 31b is preferably made of, for example, metal from the viewpoint of thermal conductivity and mechanical strength, and is grounded from the viewpoint of preventing voltage load on the kneading device 20 in the melt electrospinning method. preferably.

The thickness of the dielectric used for the wall portion 35 is preferably 0.8 mm or more, more preferably 8 mm or more, from the viewpoint of increasing the charge amount of the molten resin. This thickness refers to the thickness of the wall portion 35 when the wall portion 35 is composed of a single type or multiple types of dielectrics (i.e., the thickness of the dielectric is equal to the thickness of the wall portion 35). . In addition, when the wall portion 35 is a composite containing metal particles or an air layer inside (the portion not exposed to the surface), the thickness of the wall portion 35 and the metal grains in the thickness direction of the wall portion 35 It refers to the thickness of the dielectric only after subtracting the sum of the diameter and the thickness of the air layer. Although the thickness of the wall portion 35 depends on the size of the electrode 32 and the positional relationship between the nozzle 31 and the electrode 32, it is preferably at least a value that does not allow the nozzle 31 and the wall portion 35 to come into direct contact with each other.

The end positions of the first gas injection port 40p and the second gas injection port 50p in the spinning unit 30 in the front-rear direction are not particularly limited as long as the effect of the present invention is exhibited, but the position of the nozzle tip 31a is 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. The end position of each gas injection port is the position of the front end of the outer member that constitutes each gas injection port, with the position of the nozzle 31 as a reference when the spinning unit 30 is viewed from the front. In addition, it is preferable that the end position of the first gas injection port 40p is the same as the tip position of the nozzle 31 or located in front of the tip. It is preferably located at the same position as or posterior to the tip.

The above is a description of the electrospinning apparatus 10 of the present invention. The electrospinning method using the apparatus 10 generates an electric field between the nozzle 31 and the electrode 32, and The molten resin is discharged from the tip 31a of the nozzle 31 while the two gas streams B are being jetted. The ejected molten resin is three-dimensionally stretched and finely divided by the Coulomb force generated therein and the jetting of the first gas flow A and the second gas flow B, and the resin is reduced. Cooling and solidification proceeds to form small-diameter fibers.

The fibers produced by the method of the present invention are small-diameter fibers called nanofibers having a fiber diameter of 30 μm or less when the fiber diameter is expressed as a circle-equivalent diameter. The nanofiber preferably has a fiber diameter of 0.1 µm or more, preferably 10 µm or less, more preferably 5 µm or less, and still more preferably 3 µm or less.

For the fiber diameter of the fiber, for example, 500 fibers arbitrarily selected from a two-dimensional image by scanning electron microscope (SEM) observation, excluding defects such as spun fiber clumps, fiber intersections, and polymer droplets, The fiber diameter can be measured by directly reading the length when a line perpendicular to the longitudinal direction of the fiber is drawn. A median fiber diameter is determined from the measured fiber diameter distribution, and is defined as the fiber diameter of the present invention.

When the first gas flow A and the second gas flow B are jetted in the production of fibers, it is preferable to jet the first gas flow A at a wind speed equal to or higher than the second gas flow B. By adjusting the wind speed of each gas stream, the ejected molten resin can be drawn more strongly by the external force generated by the ejection of the first gas stream, and as a result, finer fibers can be efficiently obtained. can be done.

Specifically, the ratio (A1/B1) of the wind speed A1 of the first gas flow A to the wind speed B1 of the second gas flow B is preferably 1 or more, more preferably 5 or more, and preferably 100 or less, more preferably is 80 or less.

The wind speed A1 of the first gas flow A is preferably 20 m/s or more, more preferably 30 m/s or more, and still more preferably 100 m/s or more, from the viewpoint of further stretching the discharged molten resin. 300 m/s or less is realistic from the viewpoint of preventing unintended breakage of the medium. Similarly, the wind speed B1 of the second gas flow B is preferably 1 m/s or more, more preferably 2 m/s or more, preferably 30 m/s or less, and 25 m/s or less, provided that the above ratio is satisfied. more preferred. These wind velocities are the values at the end of each gas injection port 40p, 50p. These wind velocities can be appropriately adjusted, for example, by changing the pressure of the gas flow supplied from each gas supply source or by changing the injection port diameter of each gas injection port.

In the production of fibers, when the first gas flow A and the second gas flow B are jetted, it is also preferable to jet the air volume of the second gas flow B so that it is equal to or greater than the air volume of the first gas flow A. . By adjusting the air volume of each gas flow, it is possible to maintain the temperature of the space around the nozzle 31 in the direction of ejection of the molten resin at a high state and to form the space in a wider range. As a result, the cooling and solidification of the molten resin can be delayed while the drawn state of the molten resin is maintained for a long period of time, so that fibers having a smaller diameter can be efficiently produced.

Specifically, the ratio (B2/A2) of the air volume B2 of the second gas flow B to the air volume A2 of the first gas flow A is preferably 1 or more, more preferably 2 or more, and still more preferably 5 or more. is 200 or less, more preferably 100 or less, still more preferably 20 or less.

The air volume A2 of the first gas flow A is preferably 10 L/min or more, more preferably 60 L/min or more, and 300 L/min from the viewpoint of achieving both improvement in drawing efficiency of the discharged molten resin and prevention of breakage. The following is preferable, and 200 L/min or less is more preferable. Similarly, the air volume B2 of the second gas flow B is preferably 100 L/min or more, more preferably 500 L/min or more, and preferably 4000 L/min or less, and 3000 L/min or less, provided that the above ratio is satisfied. is more preferred. These air volumes are the values at the end of each gas injection port. These air volumes can be appropriately adjusted, for example, by changing the flow rate of the gas flow supplied from each gas supply source or by changing the injection port diameter of each gas injection port.

In particular, from the viewpoint of maintaining the space temperature around the nozzle 31 in the ejection direction of the molten resin at a higher state to increase the drawing efficiency of the molten resin and to manufacture fibers with a smaller diameter, It is also preferable to inject the second gas stream B at a higher temperature. The solidification temperature of a molten resin refers to the melting point of a resin composition containing a thermoplastic resin, which will be described later.

The temperature of each of the heated gas streams A and B can be appropriately changed depending on the type of raw material resin and its melting point. preferably 500° C. or lower, more preferably 400° C. or lower. The temperature of the second gas flow B is preferably 25° C. or higher, more preferably 100° C. or higher, and preferably 300° C. or lower, more preferably 200° C. or lower. These temperatures are the values at the end of each gas injection port. These temperatures can be adjusted as appropriate, for example, by changing the degree of heating in each gas source.

The molten resin used in the present invention is a fluid of a resin composition containing a thermoplastic resin having a melting point. In addition, "having a melting point" means that when the resin is heated in the differential scanning calorimetry (DSC method), the phase changes from solid to liquid before the resin thermally decomposes. It is said to show an endothermic peak that The melting point of the thermoplastic resin is measured according to JIS K 0064 or JIS K 2220 using, for example, a melting point/dropping point measuring device (manufactured by Mettler Toledo, model number: DP90 automatic dropping point/softening point measuring system). can be done.

Examples of thermoplastic resins include polyolefin resins such as polyethylene, polypropylene, and ethylene-α-olefin copolymers; polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polylactic acid, and liquid crystal polymers; nylon 6 and nylon 66, and the like. Polyamide resin; vinyl polymers such as polyvinyl chloride, polyvinylidene chloride and polystyrene; acrylic polymers such as polyacrylic acid, polyacrylate, polymethacrylic acid and polymethacrylate; polyvinyl acetate, polyvinyl acetate- Examples include ethylene copolymers. These resins can be used singly or in combination of two or more. Among these thermoplastic resins, polyolefin resins such as polyethylene, polypropylene, and ethylene-α-olefin copolymers are preferably used from the viewpoint of ease of spinning due to properties such as low melting point, high fluidity, and high ductility.

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 charging agents, antioxidants, neutralizers, light stabilizers, ultraviolet absorbers, lubricants, antistatic agents, metal deactivators, hydrophilizing agents, and the like. Examples of charging agents include metal soaps, acylalkyltaurate salts, and alkylsulfonates, which are metal salts of organic acids such as stearic acid, lauric acid, and ricinoleic acid, and metals such as Ca, Li, Zn, and Ba. and ionic surfactants such as quaternary ammonium salts. Examples of antioxidants include phenol-based antioxidants, phosphite-based antioxidants, and thio-based 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, benzophenones and the like. Examples of lubricants include higher fatty acid amides such as stearamide. Examples of antistatic agents include fatty acid partial esters such as glycerin fatty acid monoester. Examples of metal deactivators include phosphones, epoxies, triazoles, hydrazides, oxamides and the like. Examples of hydrophilizing agents include nonionic surfactants such as polyhydric alcohol fatty acid esters, ethylene oxide adducts, and amine-anomide-based surfactants.

When the molten resin contains an additive, the content of the additive is preferably 0.5% by mass or more and 50% by mass or less, more preferably 1% by mass or more and 40% by mass or less, from the viewpoint of successful electrospinning. More preferably, it is 3% by mass or more and 30% by mass or less. That is, the molten resin used for producing the nanofiber of the present invention is mainly composed of thermoplastic resin.

The method of producing the molten resin is not particularly limited, and for example, it can be produced by heating and melting a thermoplastic resin, adding additives as necessary, and heating and kneading them. Such a molten resin may be produced as a masterbatch by melt-kneading in advance. At the time of production, the thermoplastic resin and, if necessary, additives are supplied to the kneading device 20, and in the kneading device 20 It may be manufactured by heating, melting and kneading.

In the above-described fiber manufacturing method, for convenience of explanation, a mode in which the electrospinning apparatus 10 including one spinning unit 30 is used alone has been described, but the present invention is not limited to this mode. Specifically, electrospinning may be performed using a plurality of electrospinning apparatuses 10 each having one spinning unit 30, or electrospinning may be performed using a single or a plurality of electrospinning apparatuses 10 each having a plurality of spinning units 30. Good (hereinafter, these forms are collectively referred to as "multiple arrangement forms"). In particular, by arranging the electrospinning devices 10 or the spinning units 30 close to each other and electrospinning in that state, even when the air volume B2 of the second gas flow is reduced, the space around and in front of the nozzle 31 The temperature can be maintained in a high state and the space can be formed in a wider range. As a result, it is possible to delay the cooling and solidification of the molten resin, and to produce fine-diameter fibers more effectively. In addition, since the fibers can be produced by a plurality of spinning units 30 at once, there is an advantage that the production efficiency of the fibers can be further improved while reducing the supply cost of the heated gas flow.

The arrangement positions of the plurality of electrospinning devices 10 or the spinning units 30 can be appropriately selected according to the production environment and the application of the fibers to be produced. One or more spinning unit rows in which the spinning units 30 are arranged along one direction may be arranged, or adjacent spinning units 30 may be arranged so as to be alternately positioned in front and behind in the conveying direction in the collection section.

The air volume B2 of the second gas flow B in the multiple arrangement form described above is preferably 50 L/min or more, and preferably 100 L/min or more, on the condition that the air volume A2 of the first gas flow A and the B2/A2 ratio are satisfied. More preferably, 2000 L/min or less is preferable, and 1500 L/min or less is even more preferable. If the air volume B2 in the multiple arrangement form is within such a range, the discharged molten resin can be sufficiently drawn, and the diameter of the fibers can be efficiently reduced. This air volume B2 is a value at the end of the gas injection port, and is appropriately adjusted by, for example, changing the flow rate of the gas flow supplied from the gas supply source or changing the injection port diameter of each gas injection port. be able to.

The nanofibers produced by the electrospinning method using the electrospinning apparatus 10 described above or a deposit thereof can be used for various purposes as a fiber molded article in which the nanofibers are accumulated. The shape of the molded body includes a sheet, cotton-like body, filamentous body and the like. The fiber molding may be used by being laminated with other sheets, or containing various liquids, fine particles, fibers, and the like. The fiber sheet adheres to human skin, teeth, gums, hair, non-human mammalian skin, teeth, gums, plant surfaces such as branches and leaves, etc. for medical purposes, cosmetic purposes, decorative purposes and other non-medical purposes. It is preferably used as a sheet to be applied. In addition, it can be suitably used as a high-performance filter with high dust collection and low pressure loss, a battery separator that can be used at high current density, a cell culture substrate having a high pore structure, and the like. A cotton-like body of fibers is suitably used as a soundproofing material, a heat insulating material, or the like.

Although the present invention has been described above based on its preferred embodiments, the present invention is not limited to the above embodiments.

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

[Examples 1 and 2]
Using the electrospinning apparatus 10 having the structure shown in FIG. 2 alone, polypropylene (PP; manufactured by PolyMirae, MF650Y, melting point 155° C.) is contained in an amount of 95% by mass as a raw material thermoplastic resin, and acylalkyl taurine is used as an additive. A molten resin composed of a resin composition containing 5% by mass of salt (N-stearoyl-N-methyltaurate sodium; manufactured by Nikko Chemicals Co., Ltd., Nikkor SMT) was spun by a melt electrospinning method to produce fibers. The electrospinning conditions were as follows. Table 1 below shows the temperature, wind speed ratio, and wind volume ratio of the first gas flow A and the second gas flow B, and the relationship between the position of the nozzle tip 31a and the end position of each gas injection port 40p, 50p.

[Conditions for manufacturing fibers]
・Manufacturing environment: 18-25°C, 50% RH
・Discharge rate of molten resin: 2 g/min
・Inner diameter of nozzle 31: 0.25 mm
・Applied voltage to nozzle tip 31a (made of stainless steel): -20 kV
- The wind speed A1 of the first gas flow: The wind speed ratio (A1/B1) was set in the range of 30 m/s or more and 300 m/s or less so as to satisfy the conditions shown in Table 1 below.
The wind speed B1 of the second gas flow: The wind speed ratio (A1/B1) was set in the range of 2 m/s or more and 30 m/s or less so as to satisfy the conditions shown in Table 1 below.
The air volume A2 of the first gas flow: The air volume ratio (B2/A2) was set in the range of 20 L/min or more and 180 L/min or less so as to satisfy the conditions shown in Table 1 below.
Air volume B2 of the second gas flow: Air volume ratio (B2/A2) was set in the range of 100 L/min or more and 3000 L/min or less so as to satisfy the conditions shown in Table 1 below.

[Examples 3 to 6]
Using the electrospinning apparatus 10 having the structure shown in FIG. Electrospinning was performed under the same conditions as in Example 1, except that the relationship with the terminal position of 50p was changed as shown in Table 1 below to produce fibers.

[Example 7]
Using the electrospinning apparatus 10 having the structure shown in FIG. Electrospinning was performed under the same conditions as in Example 1, except that the relationship with the terminal position of 50p was changed as shown in Table 1 below to produce fibers.

[Examples 8 and 9]
A plurality of electrospinning apparatuses 10 having the structure shown in FIG. 2 were used and arranged at regular intervals and close to each other. The temperature of the first gas flow A and the second gas flow B, the wind speed ratio, the wind volume ratio, and the relationship between the position of the nozzle tip 31a and the terminal position of each gas injection port 40p, 50p were changed as shown in Table 1 below. Otherwise, electrospinning was carried out under the same conditions as in Example 1 to produce fibers.

[Comparative Example 1]
Spinning was carried out in the same manner as in Example 1, except that the second gas flow B was not jetted and the voltage applied to the nozzle tip 31a was set to zero to produce a fiber. In this comparative example, no electric field is generated between the nozzle 31 and the electrode 32, and electrospinning is not performed.

[Comparative Example 2]
Electrospinning was carried out under the same conditions as in Example 1, except that the second gas flow B was not jetted, to produce fibers.

[Comparative Examples 3 and 4]
The relationship between the temperature, wind speed ratio, and wind volume ratio of the first gas flow A and the second gas flow B, and the position of the nozzle tip 31a and the end positions of the gas injection ports 40p and 50p are shown in Table 1 below. Spinning was carried out in the same manner as in Example 1, except that the voltage applied to the nozzle tip 31a was changed to zero to produce a fiber. In each comparative example, no electric field was generated between the nozzle 31 and the electrode 32, and electrospinning was not performed.

[Measurement of median fiber diameter]
The fiber diameter of the spun fibers was measured by the method described above under each manufacturing condition of the examples and comparative examples. Table 1 shows the results.

[Evaluation of adhesion of fibers to electrodes]
Whether or not the spun fibers adhered to the electrode 32 and its vicinity under each manufacturing condition of the examples and comparative examples was visually evaluated according to the following criteria. Table 1 shows the results.
- "Yes": Spun fibers and deposits thereof adhere to the electrode 32 and its vicinity, and the production efficiency of the fibers is poor.
"None": The spun fibers and deposits thereof are not adhered to the electrode 32 and its vicinity, continuous production of the fibers is possible, and the production efficiency of the fibers is good.

As shown in Table 1, in each example in which the first gas flow and the second gas flow were jetted so as to have a predetermined air velocity ratio and air volume ratio, compared with each comparative example, a fine-diameter nanofiber called nanofiber was used. It can be seen that the fibers can be produced efficiently. Also, by injecting the second gas flow, it is possible to prevent the spun fibers from adhering to the electrodes.

Specifically, when comparing Example 1 and Comparative Example 3, and Example 7 and Comparative Example 4, in which the first gas flow A and the second gas flow B were jetted under the same conditions, a comparative example in which electrospinning was not performed Compared to Example 3 and Comparative Example 4, Example 1 and Example 7, in which electrospinning was performed, can produce finer fibers. From this, it can be seen that the electrospinning method is a method capable of efficiently producing fine-diameter fibers.

Further, as shown in Examples 5, 6, 8, and 9, the wind speed A1 of the first gas flow A is made higher than the wind speed B1 of the second gas flow, or As shown in 9, it can also be seen that by increasing the temperature of the second gas stream B, fibers with a small fiber diameter can be efficiently produced. In particular, Examples 3, 4, 6 and 9 in which the wind speed A1 of the first gas flow A is higher than the wind speed B1 of the second gas flow and the temperature of the second gas flow B is higher than the melting point of the thermoplastic resin According to the method, fibers with a smaller diameter can be produced with high production efficiency.

REFERENCE SIGNS LIST 10 electrospinning device 20 kneading device 30 spinning unit 31 nozzle 31a nozzle tip 32 electrode 32a concave curved surface 35 wall portion 35a wall surface 40 first gas injection portion 50 second gas injection portion A first gas flow B second gas flow

Claims (9)

An electrospinning apparatus comprising a nozzle for discharging a molten resin, an electrode for generating an electric field between the nozzle and the nozzle, and a gas injection unit,
The gas injection part is arranged so as to surround the nozzle, and is formed so as to be capable of injecting a heated first gas flow from the rear end toward the front end of the nozzle along the direction in which the nozzle extends. a first gas injection unit that is
a second gas injection part outside the first gas injection part and formed so as to be able to inject a heated second gas flow from the rear end of the nozzle toward the tip direction; Device. The electrospinning apparatus according to claim 1, wherein the electrode is arranged outside the first gas injection section and the second gas injection section. The electrospinning apparatus according to claim 1, wherein the electrode is arranged between the first gas injection section and the second gas injection section. The first gas injection unit and the second gas injection unit are positioned on concentric circles centered on the nozzle,
4. An electrospinning apparatus according to any one of claims 1 to 3, wherein the second gas stream is jettably arranged to surround the first gas stream. 5. The electrospinning apparatus according to any one of claims 1 to 4, comprising an electrically insulating wall portion arranged on a surface of the electrode facing the nozzle. A nanofiber manufacturing method for manufacturing nanofibers using the electrospinning apparatus according to any one of claims 1 to 5,
The molten resin is discharged from the nozzle in a state in which an electric field is generated between the nozzle and the electrode and heated gas flows are jetted from the first gas jetting portion and the second gas jetting portion, respectively. A method for producing nanofibers by spinning. The method for producing nanofiber according to claim 6, wherein the gas flow is jetted so that the ratio of the wind speed of the first gas flow to the wind speed of the second gas flow is 1 or more and 100 or less. The method for producing nanofiber according to claim 6 or 7, wherein the gas flow is jetted so that the ratio of the air volume of the second gas flow to the air volume of the first gas flow is 1 or more and 200 or less. The method for producing nanofibers according to any one of claims 6 to 8, wherein the second gas flow having a temperature higher than the solidification temperature of the molten resin is jetted.

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