JP2018095986A - Electrospinning device and electrospinning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrospinning device and an electrospinning method capable of removing solidified matter stuck to the vicinity of the tip of a nozzle without intermitting spinning.SOLUTION: Provided is an electrospinning device 1 comprising: a raw material jet part 2 provided with a nozzle 21 jetting a raw material liquid; an electrode 3 arranged so as to be electrically insulated from the nozzle 21; a voltage generation part 4 applying voltage to a space between the nozzle 21 and the electrode 3; and an air jet part 6 located in the rear than the tip 21a of the nozzle 21 and jetting air toward the tip 21a. In the air jet part 6, the jet direction of air is set in such a manner that solidified matter stuck to the vicinity of the tip of the nozzle 21 can be blown off and removed toward the recovery region of the solidified matter.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an electrospinning apparatus and an electrospinning method.

  The electrospinning method (electrospinning method) is attracting attention as a technology that can relatively easily manufacture a nano-sized diameter fiber (hereinafter also referred to as “nanofiber”) without using mechanical force or thermal force. In the electrospinning method performed so far, a syringe is filled with a solution of a material that is a raw material for nanofibers, a needle-like nozzle attached to the syringe, and a collection electrode facing the needle The operation of discharging the solution from the tip of the nozzle is performed under the condition that a high DC voltage is applied during the period. The discharged solution is stretched by Coulomb force, and the solvent is instantly volatilized, and nanofibers are formed while the raw material is solidified. The nanofibers are deposited on the surface of the collecting electrode.

  For example, in Patent Document 1, a polymer solution dissolved in a solvent is transported to a yarn discharging nozzle; while compressed air is discharged to the lower portion of the yarn discharging nozzle while the polymer solution is discharged through the yarn discharging nozzle to which a high voltage is applied. A method for producing nanofibers is described, comprising: threading a polymer solution onto a grounded intake collector under a threading nozzle; In this document, it is said that nozzle contamination can be minimized by injecting compressed air to the lower part of the yarn output nozzle.

JP 2005-520068 Gazette

  As described in Patent Document 1, in the electrospinning method, contamination of the nozzle from which the raw material liquid is discharged may be a problem. Although the technique described in this document is one of the means for solving the problem, it is only intended to minimize the contamination and no means for actively removing the contaminant is provided.

  Accordingly, an object of the present invention is to improve an electrospinning apparatus and an electrospinning method, and more specifically, to provide an electrospinning apparatus and an electrospinning method capable of successfully removing contaminants attached to a nozzle.

The present invention includes a raw material injection unit having a conductive nozzle for injecting a raw material liquid,
An electrode disposed electrically insulated from the nozzle;
A voltage generator for applying a voltage between the nozzle and the electrode;
An electrospinning apparatus including an air injection unit that is located behind the tip of the nozzle and that injects air toward the tip;
The air injection unit provides an electrospinning apparatus in which an air injection direction is set so that the solidified matter adhering to the vicinity of the tip of the nozzle can be blown off and removed toward a recovery region of the solidified matter. Is.

In addition, the present invention provides a raw material liquid from the raw material injection unit under a state in which a voltage is applied between the raw material injection unit having a conductive nozzle and an electrode that is electrically insulated from the nozzle. An electrospinning method comprising a step of injecting
When injecting the raw material liquid from the raw material injection unit, from the air injection unit located behind the tip of the nozzle, the air is injected toward the tip, the solidified material adhering to the vicinity of the tip, It is an object of the present invention to provide an electrospinning method in which the solidified product is removed by being blown off toward the recovery region.

  According to the present invention, the solidified material adhering to the vicinity of the tip of the nozzle can be removed without interrupting spinning, and spinning can be performed stably. In addition, according to the present invention, since the solidified material adhering to the vicinity of the tip of the nozzle is difficult to be mixed into the target product, it is possible to suppress deterioration in the quality of the product.

FIG. 1 is a perspective view showing a main part of a preferred embodiment of the electrospinning apparatus of the present invention. FIG. 2 is a schematic diagram showing a cross-sectional structure of the electrospinning apparatus shown in FIG. FIG. 3 is a schematic diagram showing the overall configuration of a preferred embodiment of the electrospinning apparatus of the present invention. FIG. 4 is a schematic view of the electrodes in the electrospinning apparatus shown in FIG. 1 as viewed from the front. FIG. 5 is an enlarged view of a main part showing the tip of the nozzle in the electrospinning apparatus shown in FIG.

  The present invention will be described below based on preferred embodiments with reference to the drawings. FIG. 1 shows a perspective view of a main part of a nanofiber manufacturing apparatus 1 by electrospinning, which is an embodiment of the electrospinning apparatus of the present invention. FIG. 2 is a schematic diagram showing a cross-sectional structure of the nanofiber manufacturing apparatus shown in FIG. As shown in these drawings, the nanofiber manufacturing apparatus 1 of the present embodiment basically employs a jet ESD method in which ESD (Electro-Spray Deposition) and a high-speed jet stream (jet) are combined. The apparatus 1 includes, for example, a raw material injection unit 2 having a conductive nozzle 21 for injecting a raw material liquid for producing nanofibers, and an electrode 3 having a concave curved surface portion 3A arranged in an electrically insulated manner from the nozzle 21. The voltage generator 4 for applying a voltage between the nozzle 21 and the electrode 3 is provided. Furthermore, the apparatus 1 according to the present embodiment includes an air injection unit 5 that is located near the base of the nozzle 21 and injects an air flow between the nozzle 21 and the electrode 3 along the direction in which the nozzle 21 extends.

  In the following description, as shown in FIG. 1, the extending direction of the electrode central axis CL passing through the centroid 3G of the plane defined by the open end 31a in the concave curved surface portion 3A is the Y direction, and the direction orthogonal thereto is the X direction. This will be described as a direction. The plane centroid 3G has the same concept as the center of gravity. However, since the plane defined by the open end 31a is a virtual plane and has no mass, it is not accurate to call it the center of gravity. Therefore, in this specification, it will be called the centroid instead of the center of gravity. .

  As shown in FIG. 1, the concave curved surface portion 3 </ b> A of the electrode 3 in the device 1 has a concave spherical shape as a whole, and particularly has a substantially bowl shape. The concave curved surface portion 3A is formed with a concave curved surface 3Af facing the nozzle 21, which is a substantially bowl-shaped inner surface. The surface 3Af facing the nozzle 21 of the concave curved surface portion 3A means the surface of the concave curved surface portion 3A that can face from the tip 21a of the nozzle 21 (opening portion through which the raw material liquid is discharged). In the apparatus 1, the surface is the same as the concave curved surface. As long as the inner surface of the concave curved surface portion 3A is a concave curved surface, the shape of the outer surface does not need to be a substantially bowl shape, and may be another shape. The concave curved surface portion 3A is made of a conductive material. The concave curved surface portion 3A is fixed to a base 30 made of an electrically insulating material.

  As shown in FIG. 1, when the surface (concave surface) 3Af facing the nozzle 21 in the concave curved surface portion 3A of the electrode 3 is viewed from the opening end portion 31a side, the peripheral edge of the opening end portion 31a is circular. . Accordingly, the plane defined by the open end 31a is circular, and the centroid 3G of the plane means the center of the circle. The peripheral edge of the opening end 31a means a contour on the nozzle 21 side of the opening end 31a, that is, an inner contour when the opening end 31a has a thickness. The circle defined by the open end 31a may be a perfect circle or an ellipse. From the viewpoint of concentrating the electric field on the tip of the nozzle 21, the peripheral edge of the opening end 31a is preferably a perfect circle.

  The surface (concave surface) 3Af facing the nozzle 21 in the concave surface portion 3A is a curved surface at any position on the inner surface as shown in FIG. The curved surface referred to here is (a) a curved surface having no flat surface portion, 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 surface portion. Say one of them. In the case of (b), a concave curved surface is formed by connecting segments having flat portions of the same or different sizes, for example, having a rectangular shape with a vertical and horizontal length of about 0.5 mm to 5 mm. It is preferable.

  The surface (concave surface) 3Af facing the nozzle 21 of the concave curved surface portion 3A preferably has a shape such that the normal line at an arbitrary position passes through the tip of the nozzle 21 or the vicinity thereof. From this viewpoint, it is particularly preferable that the concave curved surface has the same shape as the substantially hemispherical surface that is the inner surface of a true spherical shell.

  As shown in FIGS. 1 and 2, the bottom surface of a surface (concave surface) 3 </ b> Af facing the nozzle 21 of the concave surface portion 3 </ b> A of the electrode 3 is open, and the nozzle assembly that constitutes the raw material injection unit 2 in the opening portion. 20 is attached. Therefore, when the concave curved surface 3Af has the same shape as the inner surface of the true sphere, the concave curved surface 3Af of the concave curved surface portion 3A has the same shape as the inner surface of the spherical shell of the spherical band.

  As shown in FIGS. 1 and 2, the electrode 3 further includes an extending portion 3 </ b> B extending outward from the opening end portion 31 a in the concave curved surface portion 3 </ b> A. The shape of the extending portion 3B is not particularly limited as long as it extends outward from the opening end portion 31a. In the present embodiment, the extending portion 3B has a cylindrical shape extending from the entire periphery of the circular opening end portion 31b. As shown in FIG. 2, the boundary between the concave curved surface portion 3 </ b> A and the extending portion 3 </ b> B in the electrode 3 faces the nozzle 21 in the concave curved surface portion 3 </ b> A in a cross-sectional view along the extending direction (Y direction) of the electrode central axis CL. This is a position where the curvature in the Y direction of the surface (concave curved surface) 3Af becomes zero.

  As shown in FIG. 1, the extending portion 3 </ b> B has a cylindrical shape extending in the Y direction as a whole. In the extending portion 3B, a surface 3Bf that is a cylindrical inner surface and faces the nozzle 21 is formed in a concave curved surface. The surface 3Bf facing the nozzle 21 of the extending part 3B means the surface of the extending part 3B that can be faced from the tip 21a (opening through which the raw material liquid is injected) of the nozzle 21, and in this embodiment The same surface as the concave curved surface. As long as the inner surface of the extending portion 3B is a concave curved surface, the shape of the outer surface does not need to be a cylindrical shape, and may be another shape. The extending part 3B is made of a conductive material.

  As shown in FIG. 1, when the surface (concave curved surface) 3Bf facing the nozzle 21 in the extending portion 3B is viewed from the opening end portion 31b side, the peripheral edge of the opening end portion 31b is circular. When the opening end 31b has a thickness, the periphery of the opening end 31b is the same as the periphery of the opening end 31a of the concave curved surface portion 3A. , Means the inner contour. The circle defined by the open end 31b may be a perfect circle or an ellipse. In particular, the shape is preferably similar to the shape of the periphery of the open end 31a of the concave curved surface portion 3A. In particular, from the viewpoint of concentrating the electric field at the tip of the nozzle 21, it is preferable that the periphery of the opening end 31b is a perfect circle having the same shape as the periphery of the opening end 31a of the concave curved surface portion 3A.

  When the plane defined by the opening end portion 31b of the extending portion 3B is an ellipse, the electric field formed between the tip 21a of the nozzle 21 and the electrode 3 becomes strong, and a high charge amount can be obtained. Therefore, the eccentricity of the ellipse is preferably 0 or more and less than 0.6, more preferably 0 or more and less than 0.3, and particularly preferably a perfect circle with an eccentricity of 0.

  The concave curved surface portion 3A and the extending portion 3B of the electrode 3 are formed of separate members or formed as an integral member. When the concave curved surface portion 3A and the extending portion 3B are formed of separate members, the two are joined by a joining means such as an adhesive or a screw. By joining both with such a joining means, the concave curved surface portion 3A and the extending portion 3B can be easily manufactured and manufactured at low cost, and the length of the extending portion 3B can be easily adjusted. Become. When bonding the concave curved surface portion 3A and the extending portion 3B with an adhesive or a screw, from the viewpoint of stabilization of the bonding strength, the direction perpendicular to the opening end portion 31a (X direction) from the opening end portion 31a of the concave curved surface portion 3A ) And a flange 21 (not shown) extending outwardly opposite to the nozzle 21, and the nozzle 21 in a direction (X direction) perpendicular to the end of the extended portion 3 </ b> B on the concave curved surface portion 3 </ b> A side; It is preferable to provide a flange portion (not shown) extending outward on the opposite side, and to join the flange portion of the concave curved surface portion 3A and the flange portion of the extension portion 3B via an adhesive or a screw.

  As an adhesive that joins and fixes the concave curved surface portion 3A and the extending portion 3B, a known adhesive generally used in the field of electrospinning apparatus can be used. Specifically, an epoxy resin-based adhesive can be used. An adhesive etc. are mentioned. On the other hand, as a screw for joining and fixing the concave curved surface portion 3A and the extension portion 3B, a dielectric or wooden material of the same kind or different kind from a cover to be described later can be used. If the concave curved surface portion 3A and the extending portion 3B are joined by screws made of these materials, an air layer is less likely to be generated therebetween, and the electric field between the concave curved surface portion 3A and the extending portion 3B is stabilized. Can do. In the case of joining with a screw, for example, a through hole is formed in the flange portion of the concave curved surface portion 3A described above, a screw is passed through the through hole, and the screw is formed in the flange portion of the extension portion 3B. Can be joined and fixed by screwing into the screw holes.

  Each of the concave curved surface portion 3A and the extending portion 3B is made of metal or the like and has conductivity. Specifically, the concave curved surface portion 3A and the extending portion 3B are each formed of a sheet metal having a substantially uniform thickness, a conductive sheet, or the like. Examples of the sheet metal material include silver, gold, palladium, platinum, copper, nickel, and aluminum. Examples of the conductive sheet include a sheet made of metal such as silver, gold, palladium, platinum, copper, nickel, and aluminum, or a sheet containing conductive powder such as carbon-based filler such as carbon black and graphite powder. Etc. As the metal sheet, an aluminum tape, a household aluminum foil, or the like is preferably used from the viewpoint of cost and the lightness and thickness uniformity.

  In the electrode 3 having the above-described configuration, the concave curved surface portion 3A and the extending portion 3B have the same potential. The electrode 3 formed from the concave curved surface portion 3A and the extending portion 3B is connected to a DC high voltage power source 41, which is a voltage generating portion 4, as shown in FIG. 2, and a negative voltage is applied to the electrode 3. . Thus, the electrode 3 is configured such that the concave curved surface portion 3A and the extending portion 3B have the same potential in a state where the concave curved surface portion 3A and the extending portion 3B are electrically joined.

  As shown in FIGS. 1 and 2, the apparatus 1 of the present embodiment is provided with a nozzle assembly 20 constituting the raw material injection unit 2 at the bottommost opening of the concave curved surface portion 3 </ b> A of the electrode 3. The nozzle assembly 20 includes a nozzle 21 and a support portion 22 that supports the nozzle 21.

  The nozzle 21 is made of a conductive material, and is generally made of metal. The nozzle 21 is preferably composed of a needle-like straight pipe. A raw material liquid can be circulated in the nozzle 21. The lower limit of the inner diameter of the nozzle 21 is preferably set to 200 μm or more, more preferably 300 μm or more. On the other hand, the upper limit is preferably set to 3000 μm or less, more preferably 2000 μm or less. The inner diameter of the nozzle 21 can be set, for example, preferably from 200 μm to 3000 μm, and more preferably from 300 μm to 2000 μm. By setting the inner diameter of the nozzle 21 within this range, a raw material liquid containing a polymer and having viscosity can be sent easily and quantitatively, and an electric field concentrates in a narrow area around the nozzle, and the raw material liquid Is preferable because it can be charged efficiently.

  The support portion 22 is made of an electrically insulating material. Therefore, the electrode 3 and the nozzle 21 described above are electrically insulated by the support portion 22 as shown in FIG. The nozzle 21 is grounded. The tip 21a of the nozzle 21 is exposed in the electrode 3 formed from the concave curved surface portion 3A and the extending portion 3B. The nozzle 21 penetrates the support portion 22, and the rear end 21b of the nozzle 21 is exposed on the back side of the electrode 3 (that is, the surface opposite to the surface (concave surface) 3Af facing the nozzle 21). ing. The nozzle 21 does not necessarily have to penetrate the support portion 22, and the rear end 21 b of the nozzle 21 may be located in the middle of the raw material liquid supply through hole provided in the support portion 22. The through hole for supplying the raw material liquid provided in the rear end 21b of the nozzle 21 or the support portion 22 is connected to a raw material liquid supply source (not shown) for producing nanofibers, for example. The nozzle assembly 20 constitutes a raw material supply source and the raw material injection unit 2.

  As shown in FIG. 1 and FIG. 2, the nozzle 21 extends in such a way that it passes through the centroid 3G of the plane defined by the opening end 31a in the concave curved surface portion 3A or in the vicinity of the centroid 3G. Has been placed. Preferably, the nozzle 21 passes through the centroid 3G or the vicinity of the centroid 3G and the center of the opening provided at the bottom of the concave curved surface 3Af of the concave curved surface portion 3A or the vicinity of the center. Placed in. From the viewpoint of concentrating the electric field on the tip 21a of the nozzle 21, the extending direction of the nozzle 21 is parallel to the extending direction (Y direction) of the electrode central axis CL, and the nozzle 21 is arranged on the electrode central axis CL. Preferably it is. That is, it is preferable that the direction in which the nozzle 21 extends coincides with the direction in which the electrode center axis CL extends (Y direction).

  The fact that the nozzle 21 is arranged so that the extending direction of the nozzle 21 passes in the vicinity of the centroid 3G means that the longest diagonal line of the plane defined by the opening end 31a is L, and the figure is shown on the plane. When considering a virtual circle drawn with the same heart and having a radius of L / 10, the nozzle 21 is arranged so that the extending direction thereof passes through the inside of the virtual circle and the bottom of the concave curved surface 3Af. Is Rukoto. In particular, when the imaginary circle having a radius of L / 20 is considered, the nozzle 21 extends in the imaginary circle having a radius of L / 20 and the bottom of the concave curved surface 3Af. It is preferable to be arranged to pass through. The nozzle 21 is particularly preferably arranged so that the extending direction thereof passes through the centroid 3G and the bottom of the concave curved surface 3Af.

  As for the position of the tip 21a of the nozzle 21, as shown in FIG. 2, the tip 21a is located in the plane defined by the opening end 31a in the concave curved surface portion 3A, or is located in the vicinity of the plane. Thus, it is preferable that the nozzle 21 is disposed. Particularly preferably, the nozzle 21 is arranged so that the tip 21a of the nozzle 21 is located inside the opposed surface (concave curved surface) 3Af with respect to the plane. More preferably, the nozzle 21 is disposed on the inner side within a range of 1 mm to 10 mm from the plane. By setting the position of the tip 21a of the nozzle 21 in this way, the distance between the tip 21a of the nozzle 21 and the opposing surface (concave surface) 3Af becomes closer, the electric field is further concentrated, and a high charge amount is obtained. It is done. From this viewpoint, it is particularly preferable that the opposing surface (concave curved surface) 3Af of the concave curved surface portion 3A has a substantially hemispherical shape of a true spherical shell.

  As described above, the nozzle 21 is grounded, and a negative voltage is applied to the electrode 3 by the DC high voltage power supply 41 of the voltage generator 4. Therefore, the electrode 3 becomes a cathode and the nozzle 21 becomes an anode, and a voltage is applied between the electrode 3 and the nozzle 21 to form an electric field. In order to generate an electric field between the electrode 3 and the nozzle 21, instead of applying the voltage shown in FIG. 2, a positive voltage may be applied to the nozzle 21 and the electrode 3 may be grounded. . However, it is preferable to ground the nozzle 21 rather than applying a positive voltage to the nozzle 21 because an insulation measure can be simplified. The voltage generated by the voltage generator 4 is a DC voltage as long as the electrode 3 is kept at the cathode and the nozzle 21 is kept at the anode, that is, as long as the nozzle 21 is kept at a higher potential than the cathode. It is also possible to use a fluctuating voltage that is superimposed. From the viewpoint of keeping the charge amount of the raw material liquid constant and producing nanofibers of uniform thickness, the voltage is preferably a DC voltage.

  As the voltage generator 4, a known device such as a high voltage power supply device can be used. The potential difference applied between the electrode 3 and the nozzle 21 is preferably 1 kV or more, particularly 10 kV or more from the viewpoint that the raw material liquid can be sufficiently charged. On the other hand, this potential difference is preferably 100 kV or less, particularly 50 kV or less from the viewpoint of preventing discharge between the nozzle 21 and the electrode 3. For example, it is preferably 1 kV to 100 kV, particularly preferably 10 kV to 50 kV. When the voltage applied by the voltage generator 4 is a variable voltage, it is preferable that the time average of the potential difference generated between the electrode 3 and the nozzle 21 is within the above range.

  The air injection part 5 is located in the vicinity of the base part of the nozzle 21, as shown in FIG.1 and FIG.2. The air injection unit 5 has a through hole 51 in the vicinity of the base of the nozzle 21 in the nozzle assembly 20. The air injection part 5 is formed substantially parallel to the direction in which the nozzle 21 extends. “It is formed substantially in parallel” means that a virtual extension line extending in the direction in which the air injection section 5 extends extends in the space in which the members constituting the device 1 of the present embodiment are arranged. Says not intersecting the virtual extension line along the direction.

  When viewed from the opening end portion 31 b side of the electrode 3, two through holes 51 of the air ejecting portion 5 are provided so as to surround the nozzle 21. The through hole 51 is formed at a symmetrical position with the nozzle 21 in between. The air injection part 5 having the through hole 51 has an opening on the rear end side connected to an air flow supply source (not shown). By supplying air from this supply source, air is jetted from around the nozzle 21. The jetted air conveys the raw material liquid discharged from the tip 21a of the nozzle 21 toward the collection body 72 of the collection unit 7 shown in FIG. 3 described later, and contributes to stretching the nanofibers. 1 and 2 show a state in which two through holes 51 of the air injection unit 5 are provided. However, the number of the through holes 51 is not limited to this, and may be one or three or more. May be. Furthermore, the shape (cross-sectional shape) of the through hole 51 is not limited to a circle, but may be a rectangle, an ellipse, a double ring, a triangle, a honeycomb, or the like. From the viewpoint of obtaining a uniform air flow, an annular through hole 51 surrounding the nozzle 21 is desirable.

  The apparatus 1 of this embodiment is provided with the collection part 7 which collects electrospinning in the position facing the air injection part 5, as shown in FIG. In particular, a collection electrode 71 is disposed as a part of the collection unit 7. The collecting electrode 71 can be a flat plate made of a conductive material such as metal. The plate surface of the collecting electrode 71 and the air flow injection direction by the air injection unit 5 are substantially orthogonal to each other. The collecting electrode can be coated almost entirely on the surface with a cover with a dielectric exposed, and more preferably on the entire surface with a cover. Here, the substantially entire surface means a surface occupying an area of 90% or more of the total surface area of the surface. The entire surface means a surface that occupies 100% of the total surface area of the surface. In order to attract the positively charged nanofibers to the collecting electrode 71, it is preferable to apply a lower (negative) potential to the collecting electrode 71 than the nozzle 21 serving as the anode. In order to make the attraction more efficient, it is preferable to apply a lower (negative) potential than the electrode 3 which is a cathode.

  In the apparatus 1 of this embodiment, in addition to the collection electrode 71, nanofibers are collected between the collection electrode 71 and the nozzle 21 so as to be adjacent to the collection electrode 71. A collecting body 72 is arranged as the collecting unit 7. As the collection body 72, insulators, such as a film, a mesh, a nonwoven fabric, and paper, can be used, for example.

  In the apparatus 1 of the present embodiment having the above configuration, the raw material liquid is charged using the principle of electrostatic induction. With electrostatic induction, when a positively charged object (charged body) is brought close to a stable conductor, for example, a negative charge moves to a part of the conductor close to the charged body, and conversely, a positive charge is charged. It is a phenomenon that becomes an electrostatic conductor away from the body. If a positively charged portion of the conductor is grounded while the charged body is kept close to the conductor, the positive charge is electrically neutralized and the conductor becomes a charged body having a negative charge. In the apparatus 1, since the electrode 3 is used as a negatively charged member, the nozzle 21 is a charged member having a positive charge. Therefore, when the raw material liquid flows through the positively charged nozzle 21, a positive charge is supplied from the nozzle 21, and the raw material liquid is positively charged.

  In the method of manufacturing nanofibers by the electrospinning method using the apparatus 1 having the above configuration, the raw material liquid is supplied from the tip 21a of the nozzle 21 under the state where an electric field is generated between the electrode 3 and the nozzle 21. Spray. Since the cations in the raw material liquid are attracted to the electrode 3 (cathode) side by the electric field, the raw material liquid ejected from the nozzle 21 contains a large amount of cations, and the raw material liquid is positively charged. Then, the raw material liquid is directed toward the collector (not shown) by injecting an air flow from the air injection unit 5 toward the injected raw material liquid. During this time, the fiber is thinned to nano-size by the self-repulsion chain of the charge of the raw material liquid, and at the same time, the volatilization of the solvent, the solidification of the polymer, and the like proceed to produce the nanofiber. The generated nanofibers are conveyed to the air flow ejected from the air ejecting unit 5 and are attracted to the electric field created by the collecting electrode 71, so that the collector 72 disposed at a position facing the air ejecting unit 5. Deposit on the surface. In order to attract positively charged nanofibers to the collector 72, a lower (negative) potential is applied to the collector electrode 71 than the nozzle 21 that is the anode. Alternatively, in order to make the attraction more efficient, a lower (negative) potential than the electrode 3 which is a cathode is given.

  In the case of producing nanofibers by the above electrospinning method, there is often a phenomenon that a solidified product generated by drying and solidifying the raw material liquid at the tip of the nozzle 21 adheres to the vicinity of the tip. This solidified product causes a defect in the raw material liquid droplets discharged from the nozzle 21 and causes a spinning failure. Eventually, it becomes a cause of lowering the production stability and quality stability of the nanofiber. In order to remove this solidified material, the operation of the apparatus 1 must be stopped temporarily. However, once the operation is stopped, it takes time to restart the operation, and troubles may occur. There is a risk that the production efficiency will be reduced. Therefore, in the apparatus 1 of the present embodiment, as shown in FIG. 2, the second air injection unit 6 that is located behind the tip 21 a of the nozzle 21 and injects air toward the tip 21 a of the nozzle 21 is provided on the electrode 3. In the concave curved surface portion 3A, the solidified product is removed while the operation of the apparatus 1 is continued.

  Specifically, one or a plurality of second through holes 61 are provided in the concave curved surface portion 3 </ b> A of the electrode 3 (a plurality of second through holes 61 in FIG. 2), and the second air injection unit 6 is configured from the second through holes 61. Has been. The second through hole 61 is formed such that a virtual extension line L along the direction in which the second through hole 61 extends is directed toward the tip 21 a of the nozzle 21. “Toward the tip 21a of the nozzle 21” means not only the position of the tip 21a itself of the nozzle 21, but also the virtual extension line L passing through the space of a sphere preferably having a radius of 30 mm or less centered on the tip 21a of the nozzle 21. Including the case. Further, “near the tip of the nozzle 21” is a region within 20 mm from the tip 21a of the nozzle 21.

  The second air injection unit 6 having the second through-hole 61 has a rear end opening connected to an air flow supply source (not shown). By supplying air from this supply source, air is jetted toward the tip 21 a of the nozzle 21 through the second through hole 61. When the electrospinning method using the apparatus 1 is performed, that is, when the raw material liquid is injected from the raw material injection unit 2, the tip of the nozzle 21 is injected by injecting air toward the tip of the nozzle 21. Unintentionally produced solidified material is blown off by the air flow and removed. Therefore, the solidified material adhering to the tip of the nozzle 21 can be removed without interrupting spinning. As a result, defects in the liquid droplets of the raw material liquid are less likely to occur, and poor spinning is less likely to occur. As a result, it is difficult for the solidified product to be mixed into the nanofiber that is the target product, and deterioration of the quality of the nanofiber that is the product can be suppressed. Furthermore, a decrease in production efficiency of nanofibers can be suppressed.

  The injection of air toward the tip 21a of the nozzle 21 by the second air injection unit 6 may be continuous or may be intermittent. Of these injection modes, intermittently injecting air is preferable because the discharge of the raw material liquid from the nozzle 21 is less affected. From the standpoint of making this effect even more prominent, the solidified material adhering to the vicinity of the tip 21a of the nozzle 21 becomes larger and peels off before being collected by the collecting unit 7 for collecting electrospinning. The apparatus 1 should just be set so that air may be injected from the 2nd through-hole 61 in the air injection part 6, It is preferable to set with the space | interval of 1 minute or more, More preferably, the space | interval of 5 minutes or more More preferably, the air is set to be ejected at intervals of 10 minutes or more. Further, it is preferably set so that air is injected at intervals of 60 minutes or less, more preferably at intervals of 40 minutes or less, and even more preferably at intervals of 20 minutes or less. Has been. Specifically, it is preferably set so that air is injected at intervals of 1 minute to 60 minutes, more preferably at intervals of 5 minutes to 40 minutes, and even more preferably at least 10 minutes to 20 minutes. It is set so that air is injected at intervals of.

  From the same viewpoint as described above, the solidified material adhering to the vicinity of the tip 21a of the nozzle 21 is blown off toward the collection region of the solidified material by jetting air from the second through hole 61 in the second air jetting section 6. It is sufficient that the time required for the apparatus 1 is set in the apparatus 1, and it is preferable that the air is jetted over a period of 0.5 seconds or more, and more preferably over a period of 0.7 seconds or more. More preferably, the air is set to be jetted over a time of 1.0 second or longer. In addition, it is preferable that air is set to be jetted over a period of 3 seconds or less, more preferably 2.0 seconds or less, and even more preferably 1.5 seconds or less. Is set to Specifically, it is preferably set so that air is injected over a time period of 0.5 seconds or more and 3 seconds or less, more preferably 0.7 seconds or more and 2.0 seconds or less, and even more preferably The air is set to be jetted over a period of 1.0 second to 1.5 seconds.

  In relation to intermittently injecting air toward the tip of the nozzle 21 by the second air injection unit 6, the device 1 detects a solidified substance adhering to the tip of the nozzle 21 (FIG. (Not shown). As a method for detecting the solidified material, a method of detecting the size of the solidified material by image recognition using a camera, a method of detecting the tip position of the solidified material from the tip 21a of the nozzle 21 using a laser, or the like is preferable. The sensor is connected to a controller (not shown), and when the raw material liquid is injected from the raw material injection unit 2, the controller detects the solidified substance detection signal (for example, the size of the solidified substance and the tip position of the solidified substance are set values. It is preferable that a command for air injection is issued to the second air injection unit 6 when a signal is received from the sensor. As described above, it is preferable for the second air injection unit 6 to start the injection of air when the solidified substance is detected by the sensor because it is difficult to affect the discharge of the raw material liquid from the nozzle 21. Then, while the air injection command is issued to the second air injection unit 6, the controller determines that the solidified product removal signal (for example, the size or tip position of the solidified product is below the set value and the solidified product has been removed. If the sensor detects a signal generated when the second air injection unit 6 is set so as to stop the injection of air from the second air injection unit 6, This makes it more difficult to affect the discharge of water. Moreover, it is preferable that the set value of the detection signal and the removal signal of the solidified product is provided with hysteresis from the viewpoint of preventing chattering.

  By the way, by injecting air toward the tip of the nozzle 21, the solidified material adhering to the tip of the nozzle 21 can be blown away and the solidified material can be removed, but the removed solidified material is blown away. When the electrode 3 or the collector 72 is reached, the significance of removing the solidified material from the tip of the nozzle 21 is diminished. Therefore, in the second air injection unit 6 in the present embodiment, the air injection direction is set so that the solidified material adhering to the tip of the nozzle 21 can be blown off and removed toward the recovery region of the solidified material. . Thereby, it is possible to effectively prevent the degradation of the quality of the nanofiber caused by the removed solidified material adhering to the electrode 3 or the collector 72. As shown in FIG. 2 and FIG. 3, the “solidified material recovery region” is a three-dimensional structure including a virtual extension line L that is located in front of the tip of the nozzle 21 and extends in the direction in which the second through hole 61 extends. It is a space or a two-dimensional region, and is a three-dimensional space or a two-dimensional region that does not include each member constituting the device 1, and is a position indicated by a symbol S in FIG. In FIG. 3, the position indicated by the symbol S is two-dimensionally represented, but this position may be a three-dimensional space.

  In order for the solidified material blown off to successfully reach the collection region, it is advantageous to adjust the position of the second through-hole 61 in the second air injection unit 6. For example, when there are a plurality of second through holes 61 constituting the second air injection unit 6, each of the second through holes 61 is arranged such that the combined vector of the injection direction of the air injected from each second through hole 61 faces the recovery region. Two through-holes 61 are preferably arranged. Specifically, as shown in FIG. 4, when the nozzle 21 is viewed from a direction opposite to the extending direction, each second through hole 61 constituting the second air injection unit 6 causes the nozzle 21 to be 180 degrees. It is preferable that they are arranged so as to surround within a range of less than. In particular, as shown in the figure, the second through holes 61 are arranged on the circumference centered on the nozzle 21, and the second through holes 61 located at both ends of the second through holes 61. If the second through holes 61 are arranged so that the angle θ between the nozzle 21 and the nozzle 21 is preferably less than 180 degrees, more preferably 150 degrees or less, and even more preferably 120 degrees or less, the blown solidified material is successfully removed. Reach the collection area. The angle is preferably 30 degrees or more, particularly 60 degrees or more, particularly 90 degrees or more. “The combined vector of the injection direction of the air injected from the second through holes 61 faces the recovery region” means that the combined vector of all the vectors of the injection directions of the air injected from the respective second through holes 61 is virtual. An extension line refers to passing at least part of the collection area.

  From the same viewpoint as described above, as shown in FIG. 5, the injection direction D of the air injected from the second air injection unit 6 is such that the angle Q with respect to the orthogonal plane P passing through the tip 21 a of the nozzle 21 is 20 degrees or more. Preferably, it is 30 degrees or more, more preferably 40 degrees or more. The angle Q is preferably 80 degrees or less, more preferably 70 degrees or less, and still more preferably 60 degrees or less. The angle Q is preferably 20 degrees or more and 80 degrees or less, more preferably 30 degrees or more and 70 degrees or less, and further preferably 40 degrees or more and 60 degrees or less.

  As the raw material liquid used in the apparatus 1 of the above embodiment, a solution in which a polymer compound capable of forming a fiber is dissolved or dispersed in a solvent or a melt obtained by heating and melting a polymer compound can be used. The electrospinning method using a polymer solution as a raw material liquid is sometimes called a solution method, and the method using a polymer melt is sometimes called a melting method. The solution or melt can be appropriately mixed with inorganic particles, organic particles, plant extracts, surfactants, oil agents, electrolytes for adjusting ion concentration, and the like.

  Generally, as a polymer compound for producing nanofiber, polypropylene, polyethylene, polystyrene, polyvinyl alcohol, polyurethane, polyethylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, poly-m-phenylene terephthalate, poly-p-phenylene isofura Tate, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polyvinylidene chloride-acrylate copolymer, polyacrylonitrile, polyacrylonitrile-methacrylate copolymer, polycarbonate, polyarylate, polyester carbonate, nylon , Aramid, polycaprolactone, polylactic acid, polyglycolic acid, collagen, polyhydroxybutyrate , Polyvinyl acetate, polypeptides and the like. The polymer compound to be used is not limited to one type, and any plurality of types can be used in combination from the exemplified polymer compounds.

  When a solution in which a polymer compound is dissolved or dispersed in a solvent is used as the raw material liquid, the solvent includes water, methanol, ethanol, 1-propanol, 2-propanol, hexafluoroisopropanol, tetraethylene glycol, triethylene glycol, Dibenzyl alcohol, 1,3-dioxolane, 1,4-dioxane, methyl ethyl ketone, methyl isobutyl ketone, methyl-n-hexyl ketone, methyl-n-propyl ketone, diisopropyl ketone, diisobutyl ketone, acetone, hexafluoroacetone, phenol, Formic acid, methyl formate, ethyl formate, propyl formate, methyl benzoate, ethyl benzoate, propyl benzoate, methyl acetate, ethyl acetate, propyl acetate, dimethyl phthalate, diethyl phthalate, dipropyl phthalate, Methyl chloride, ethyl chloride, methylene chloride, chloroform, o-chlorotoluene, p-chlorotoluene, carbon tetrachloride, 1,1-dichloroethane, 1,2-dichloroethane, trichloroethane, dichloropropane, dibromoethane, dibromopropane, bromide Methyl, ethyl bromide, propyl bromide, acetic acid, benzene, toluene, hexane, cyclohexane, cyclohexanone, cyclopentane, o-xylene, p-xylene, m-xylene, acetonitrile, tetrahydrofuran, N, N-dimethylformamide, pyridine, etc. Can be illustrated. The solvent to be used is not limited to one type, and a plurality of arbitrary types may be selected from the exemplified solvents and mixed.

  In particular, when water is used as a solvent, it is preferable to use the following natural and synthetic polymers having high solubility in water. Examples of natural polymers include pullulan, hyaluronic acid, chondroitin sulfate, poly-γ-glutamic acid, modified corn starch, β-glucan, gluco-oligosaccharide, heparin, keratosulfuric acid and other mucopolysaccharides, cellulose, pectin, xylan, lignin, glucomannan. Galacturonic acid, psyllium seed gum, tamarind seed gum, gum arabic, tragacanth gum, soy water soluble polysaccharide, alginic acid, carrageenan, laminaran, agar (agarose), fucoidan, methylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose and the like. Examples of the synthetic polymer include partially saponified polyvinyl alcohol, low saponified polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide, and sodium polyacrylate. These polymer compounds can be used alone or in combination of two or more. Among these polymer compounds, from the viewpoint of easy preparation of nanofibers, natural polymers such as pullulan and synthetic polymers such as partially saponified polyvinyl alcohol, low saponified polyvinyl alcohol, polyvinyl pyrrolidone and polyethylene oxide should be used. Is preferred.

  Moreover, although it is not highly soluble in water, it can be insolubilized after formation of nanofibers, partially saponified polyvinyl alcohol that can be crosslinked after formation of nanofibers in combination with a crosslinking agent, partially saponified polyvinyl alcohol, poly (N-propanoylethyleneimine) ) Oxazoline-modified silicones such as graft-dimethylsiloxane / γ-aminopropylmethylsiloxane copolymer, acrylic resin such as twein (main component of corn protein), polyester, polylactic acid (PLA), polyacrylonitrile resin, polymethacrylic acid resin, etc. , High molecular compounds such as polystyrene resin, polyvinyl butyral resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyurethane resin, polyamide resin, polyimide resin, polyamideimide resin Rukoto can. These polymer compounds can be used alone or in combination of two or more.

  The nanofiber manufactured by the apparatus 1 of the above embodiment is generally 10 nm or more and 3000 nm or less, particularly 10 nm or more and 1000 nm or less when the thickness is represented by a circle equivalent diameter. The thickness of the nanofiber can be measured, for example, by observation with a scanning electron microscope (SEM).

  The nanofiber manufactured using the electrospinning apparatus of the present invention can be used for various purposes as a nanofiber molded body in which the nanofiber is integrated. Examples of the shape of the molded body include a sheet, a cotton-like body, and a thread-like body. The nanofiber molded body may be used by laminating with other sheets or containing various liquids, fine particles, fibers and the like. The nanofiber sheet is suitably used as a sheet attached to human skin, teeth, gums and the like for non-medical purposes such as medical purposes and cosmetic purposes. Further, it is also suitably used as a high-performance filter with high dust collection and low-pressure loss, a battery separator that can be used at a high current density, a cell culture substrate having a high pore structure, and the like. The nanofiber cotton-like body is suitably used as a soundproofing material or a heat insulating material.

  As mentioned above, although this invention was demonstrated based on the preferable embodiment, this invention is not restrict | limited to the said embodiment. For example, the electrode 3 in the above embodiment is composed of a combination of the concave curved surface portion 3A and the cylindrical extending portion 3B, but instead of this, the extending portion 3B expands toward the opening end. A cylindrical body having a diameter (that is, a side surface of the truncated cone) may be used. Moreover, you may provide further the 2nd extension part (not shown) which is connected with the opening end of the cylindrical extension part 3B, and diameter-reduces toward a front-end | tip.

  Further, as the electrode 3, an electrode that does not have an extending portion and is formed only of the concave curved surface portion 3 </ b> A may be used. Further, as the electrode 3, a flat electrode having no curved surface may be used.

  Moreover, in the said embodiment, although the 2nd air injection part 6 was provided in 3 A of concave curved surface parts of the electrode 3, the position which provides the 2nd air injection part 6 is not restricted here. Furthermore, in the said embodiment, although the 2nd air injection part 6 was comprised from the through-hole, the hole which comprises the 2nd air injection part 6 does not need to be a through-hole.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, “%” means “mass%”.

[Example 1]
Electrospinning was performed using the electrospinning apparatus 1 configured as shown in FIGS. 1 to 4 to produce nanofibers. The apparatus 1 was operated in an environment of 23 ° C. and 20% RH. The collecting electrode 71 was arranged at a position 1200 mm away from the tip of the nozzle 21. The electrode 3 was grounded, and a DC voltage of +25 kV was applied to the nozzle 21 and −30 kV was applied to the collecting electrode 71. The raw material liquid was discharged at a discharge rate of 20 mL / min in a state where air was injected from the air injection unit 5 at 100 L / min. As the raw material liquid, a model raw material liquid in which a solidified product is easily generated was used. This model raw material liquid consisted of an aqueous solution containing 22% sodium bicarbonate.

  Air was injected at 100 L / min from the second air injection unit 6 toward the tip 21a of the nozzle 21 (total amount of all air flows). The injection time was 2 seconds. Further, as shown in FIG. 5, the air injection direction D was set so that the angle Q with respect to the orthogonal plane P passing through the tip 21 a of the nozzle 21 was 40 degrees. This angle Q is an angle at which the solidified material adhering to the vicinity of the tip of the nozzle 21 can be blown off toward the collection region. In this example, since the model raw material liquid in which a solidified product was easily generated was used, air was injected every time the solidified product was visually generated. Therefore, the time of the injection interval was not set.

[Examples 2 to 4]
The electrospinning apparatus 1 was operated in the same manner as in Example 1 except that the conditions shown in Table 1 below were adopted. The angle Q shown in the table is an angle at which the solidified material adhering to the vicinity of the tip of the nozzle 21 can be blown off toward the collection region.

[Examples 5 to 10]
The perforation angle of each second through hole 61 was changed so that the direction of the air injected from each second through hole 61 of the second air injection unit 6 passed through a position 5 mm ahead of the tip 21 a of the nozzle 21. The conditions shown in Table 1 below were adopted. Except for these, the electrospinning apparatus 1 was operated in the same manner as in Example 1.

[Comparative Example 1]
In Example 1, the 2nd air injection part 6 did not inject the air. The electrospinning apparatus 1 was operated in the same manner as in Example 1 except for this.

[Evaluation]
The adhesion state of the solidified substance at the tip 21a of the nozzle 21 after electrospinning performed in the examples and comparative examples was visually observed and evaluated according to the following criteria. The results are shown in Table 1 below.
○: The solidified substance adhering to the vicinity of the tip of the nozzle could be removed toward the collection region, and no solidified substance was observed near the tip.
X: The solidified substance remained adhering to the vicinity of the tip of the nozzle.

  As is clear from the results shown in Table 1, it can be seen that in each example, the solidified material adhering to the vicinity of the tip of the nozzle 21 can be removed toward the collection region. On the other hand, in the comparative example, it can be seen that the solidified material remains attached near the tip of the nozzle, and the solidified material could not be removed.

1 Nanofiber production equipment (electrospinning equipment)
2 Raw material injection unit 20 Nozzle assembly 21 Nozzle 21a Tip 22 Support unit 3 Electrode 3A Concave surface 3Af Concave surface 31a Open end 3B Extension 3Bf Concave surface 31b Open end 30 Base 4 Voltage generator 41 DC high voltage power supply 5 Air injection part 51 Through hole 6 Second air injection part 61 Second through hole 7 Collection part 71 Collection electrode 72 Collection body

Claims (8)

A raw material injection section having a conductive nozzle for injecting the raw material liquid;
An electrode disposed electrically insulated from the nozzle;
A voltage generator for applying a voltage between the nozzle and the electrode;
An electrospinning apparatus including an air injection unit that is located behind the tip of the nozzle and that injects air toward the tip;
The electrospinning apparatus, wherein the air injection unit is configured such that the air injection direction is set so that the solidified material adhering to the vicinity of the tip of the nozzle can be blown off and removed toward the recovery region of the solidified material.   2. The electrospinning apparatus according to claim 1, wherein the air injection unit is set so that air is injected at an interval of 1 minute to 60 minutes and over a time of 0.5 seconds to 3 seconds. A sensor for detecting solidified material adhering to the tip of the nozzle;
2. The electrospinning according to claim 1, wherein the air injection unit is set to start air injection when solidified matter is detected by the sensor and stop air injection when the solidified material is removed. apparatus. The air injection part has a plurality of holes for injecting air;
The electrospinning apparatus according to any one of claims 1 to 3, wherein each hole is arranged so that a combined vector of an injection direction of air injected from each hole faces the recovery region. A step of injecting a raw material liquid from the raw material injection unit under a state in which a voltage is applied between the raw material injection unit having a conductive nozzle and an electrode disposed in an electrically insulated manner from the nozzle; An electrospinning method comprising:
When injecting the raw material liquid from the raw material injection unit, from the air injection unit located behind the tip of the nozzle, the air is injected toward the tip, the solidified material adhering to the vicinity of the tip, An electrospinning method in which the solidified product is removed by blowing off toward the recovery region.   The electrospinning method according to claim 5, wherein air is injected from the air injection unit at intervals of 1 minute to 60 minutes and over a time period of 0.5 seconds to 3 seconds.   When the raw material liquid is being injected from the raw material injection section, the solidified substance adhering to the vicinity of the tip of the nozzle is detected by a sensor, and when the solidified substance is detected by the sensor, air injection is started, and the The electrospinning method according to claim 5 or 6, wherein the air injection is stopped when the solidified product is removed. The air injection part has a plurality of holes for injecting air;
8. The air is injected from the air injection portion in which each hole is arranged so that a combined vector of the injection directions of the air injected from each of the holes faces the recovery region. The electrospinning method according to item.

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