JP6591817B2 - Electrospinning device - Google Patents

Description

  The present invention relates to an electrospinning apparatus.

  The electrospinning method (electrospinning method) is attracting attention as a technology that can relatively easily manufacture a nano-sized diameter fiber (hereinafter referred to as nanofiber) without using mechanical force or thermal force. In the electrospinning method that has been performed so far, a solution of a substance that is a raw material for nanofibers is filled in a syringe, a needle-like nozzle attached to the syringe, and a collection electrode facing the needle-like nozzle 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, the solvent is instantly evaporated, and nanofibers are formed while the raw material is solidified. The nanofibers are deposited on the surface of the collecting electrode.

  In order to increase the productivity of the nanofiber manufacturing, in Patent Document 1, a high voltage is applied between the metal sphere and the opening of the spinning nozzle, and the path between the metal sphere and the opening of the spinning nozzle is applied. A high-speed airflow injection nozzle that ejects a high-speed airflow so as to be orthogonal to each other is provided, and the nanofiber spun from the spinning nozzle is scattered by the high-speed airflow injection nozzle, the course is changed, and the nanofiber that is scattered is dispersed. A method for producing nanofibers collected by a nanofiber collecting part is disclosed.

JP 2011-127234 A

  The productivity of the nanofiber is fundamentally determined by the amount of the raw material liquid injected from one raw material liquid injection nozzle per unit time. Therefore, it is necessary to increase the charge amount of the raw material liquid to be injected. However, it is difficult to improve productivity unless the tension of electrospinning can be made stable. In order to keep the electrospinning tension stable and constant, adjusting the spinning voltage is an important factor, and even when the spinning voltage is increased, the balance of the electrospinning tension is not lost, and electrospinning is performed. It has been desired to develop an electrospinning apparatus that can stably maintain a constant tension.

  On the other hand, in terms of increasing the charge amount of the raw material liquid and adjusting the spinning voltage, the technique described in Patent Document 1 is not sufficient, and it is difficult to obtain nanofibers with satisfactory productivity.

  Therefore, the subject of this invention is providing the electrospinning apparatus which can eliminate the fault which the prior art mentioned above has.

  The present invention provides a raw material injection unit having a conductive nozzle for injecting a raw material liquid, an electrode having a concave curved surface disposed in an electrically insulated manner from the nozzle, and a voltage between the nozzle and the electrode. An electrospinning apparatus comprising: a voltage generator to be generated; and an airflow injection unit that injects an airflow between the nozzle and the electrode, wherein the electrode has a substantially entire surface facing the nozzle, And the electrode is in contact with the covering, and the surface of the electrode that contacts the covering and the surface of the covering that contacts the electrode have the same shape, An electrospinning apparatus is provided in which the thickness of the opening end of the electrode in the direction in which the nozzle extends is thinner than the thickness of the covering positioned at the opening end.

  According to the present invention, the amount of charge of the raw material liquid can be increased as compared with the prior art, the balance of the electrospinning tension is not easily lost, and the electrospinning tension can be stably kept constant. Productivity can be increased as compared with the prior art.

FIG. 1 is an exploded perspective view showing a first 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. 3A is a side view showing a cross section of a preferred second embodiment of the electrospinning apparatus of the present invention, and FIG. 3B is a top view in FIG. FIG. 4 is a side view showing a cross section of another embodiment of the electrospinning apparatus shown in FIG. 5 is a cross-sectional view showing an example of the structure of a nozzle in the electrospinning apparatus shown in FIG. 1 and the electrospinning apparatus shown in FIG. FIG. 6 is a schematic view showing a cross-sectional structure in still another embodiment of the electrospinning apparatus of the present invention. FIG. 7 is a schematic view showing a cross-sectional structure of an electrospinning apparatus for producing the nanofiber of Reference Example 1. FIG. 8 is a scanning electron micrograph of the nanofiber manufactured by the nanofiber manufacturing apparatus of one embodiment of the present invention and the nanofiber manufactured by the electrospinning apparatus shown in FIG. FIG. 9 shows a fiber diameter measured from a scanning electron micrograph of the nanofiber manufactured by the nanofiber manufacturing apparatus according to the embodiment of the present invention and the nanofiber manufactured by the electrospinning apparatus shown in FIG. FIG.

  The present invention will be described below based on preferred embodiments with reference to the drawings. FIG. 1 is an exploded perspective view of a nanofiber manufacturing apparatus which is a first 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 1A of the first embodiment basically employs a jet ESD method in which ESD (Electro-Spray Deposition) and a high-speed jet stream (jet) are combined. 1A of manufacturing apparatuses are the raw material injection part 2 provided with the conductive nozzle 21 which injects the raw material liquid for nanofiber manufacture, for example, The electrode 3 which has the concave curved surface 3f arrange | positioned electrically insulated from the nozzle 21, The voltage generator 4 that generates a voltage between the nozzle 21 and the electrode 3 and the airflow injection unit 5 that injects an airflow between the nozzle 21 and the electrode 3 are provided. In the manufacturing apparatus 1A, the electrode 3 is covered with a covering 6 with a dielectric exposed on the entire surface of the surface 3f facing the nozzle 21. The surface 3f facing the nozzle 21 of the electrode 3 means the surface of the electrode 3 that can be faced from the tip 21a (opening portion through which the raw material liquid is injected) of the nozzle 21, and will be described later in the manufacturing apparatus 1A. Further, it is the same surface as the concave curved surface 3f.

  In the manufacturing apparatus 1A, as shown in FIG. 1, the electrode 3 has a concave spherical shape as a whole, and particularly has a substantially bowl shape. The electrode 3 is formed with a concave curved surface 3f that faces the nozzle 21, which is a substantially bowl-shaped inner surface. As long as the inner surface of the electrode 3 is a concave curved surface 3f, the outer surface of the electrode 3 does not need to be substantially bowl-shaped, and may have other shapes. The electrode 3 is made of a conductive material. The electrode 3 is fixed to a base 30 made of an electrically insulating material. In addition, the electrode 3 is connected to a DC high voltage power supply 41 which is a voltage generating unit 4 as shown in FIG. 2, and a negative voltage is applied thereto.

  When the surface (concave surface) 3f facing the nozzle 21 of the electrode 3 is viewed from the opening end portion 31 side, the periphery of the opening end portion 31 is circular. This circle may be a perfect circle or an ellipse, but from the viewpoint of concentrating the electric field on the tip of the nozzle 21, the peripheral edge of the opening end 31 is preferably a true circle. On the other hand, the surface (concave curved surface) 3f facing the nozzle 21 is a curved surface at any position on the inner surface. The curved surface referred to here is (a) a curved surface that does not have a flat surface 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 surface portion. Or (c) one of the three axes orthogonal to each other is connected to a plurality of annular segments having a belt-like portion with no curvature, and has a shape that can be regarded as a concave curved surface as a whole. Say. 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. In the case of (c), for example, it is preferable to form the concave curved surface 3f by connecting annular segments made of a plurality of flat cylinders having different radii and heights of about 0.001 mm to 5 mm. In this annular segment, among the three axes orthogonal to each other, that is, the X-axis, Y-axis, and Z-axis, the X-axis and Y-axis including the cross section of the cylinder have a curvature, and Z is the height direction of the cylinder It is preferred that the axis has no curvature.

  It is preferable that the surface (concave curved surface) 3f facing the nozzle 21 of the electrode 3 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 inner surface of a true spherical shell.

  In the manufacturing apparatus 1A, as shown in FIGS. 1 and 2, the bottom of the surface (concave surface) 3f facing the nozzle 21 of the electrode 3 is open, and the nozzle assembly that forms the raw material injection unit 2 in the opening. 20 is attached. The nozzle assembly 20 includes a nozzle 21 and a support portion 22 that supports the nozzle 21.

  In the manufacturing apparatus 1A, the nozzle 21 of the raw material injection unit 2 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. The lower limit of the outer diameter of the nozzle 21 is preferably set to 300 μm or more, more preferably 400 μm or more. On the other hand, the upper limit value can be set to preferably 4000 μm or less, and more preferably 3000 μm or less. The outer diameter of the nozzle 21 can be set, for example, preferably from 300 μm to 4000 μm, and more preferably from 400 μm to 3000 μm. By setting the inner diameter and outer diameter of the nozzle 21 within this range, it is possible to easily and quantitatively feed a viscous raw material liquid containing a polymer, and an electric field concentrates in a narrow area around the nozzle. It is preferable because the raw material liquid can be charged efficiently.

  In the manufacturing apparatus 1A, the extending direction of the nozzle 21 is the center of the circle defined by the opening end 31 on the surface (concave surface) 3f facing the nozzle 21 of the electrode 3 or the vicinity of the center, It is preferably arranged so as to pass through the center of the opening provided at the bottom of the opposing surface (concave surface) 3f or the vicinity of the center. In particular, it is preferable that the plane including the circle defined by the opening end 31 of the opposing surface (concave curved surface) 3f and the direction in which the nozzle 21 extends are orthogonal. By arranging the nozzle 21 in this way, the electric field is further concentrated on the tip 21 a of the nozzle 21.

  As for the position of the tip 21a of the nozzle 21, the tip 21a is located in or near the plane including the circle defined by the open end 31 on the surface (concave surface) 3f facing the nozzle 21 of the electrode 3. It is preferable to do. In particular, it is preferable to arrange the nozzle 21 so as to be located inside the opposing surface (concave curved surface) 3f rather than the plane. Specifically, it is preferable to dispose 1 to 10 mm inside the plane. By making the position of the tip 21a of the nozzle 21 in this way, the raw material liquid sprayed from the tip 21a of the nozzle 21 becomes difficult to be drawn to the facing surface (concave surface) 3f of the electrode 3, and the facing surface The (concave curved surface) 3f is hardly contaminated by the raw material liquid. From this viewpoint, it is particularly preferable that the facing surface (concave curved surface) 3f of the electrode 3 has a substantially hemispherical shape of a true spherical shell.

  In 1 A of manufacturing apparatuses, the support part 22 of the raw material injection part 2 is comprised from the electrically insulating material. Therefore, the electrode 3 and the nozzle 21 described above are electrically insulated by the support 22 as shown in FIG. The nozzle 21 is grounded. The tip 21a of the nozzle 21 is exposed in the electrode 3 formed in a concave curved surface. The nozzle 21 penetrates the support portion 22, and the rear end 21 b of the nozzle 21 is exposed on the back side of the electrode 3 (that is, the surface opposite to the surface (concave surface) 3 f 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 through hole for supplying the raw material liquid 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.

  In the manufacturing apparatus 1A, the distance (shortest distance) between the tip 21a of the nozzle 21 and the surface (concave surface) 3f facing the nozzle 21 of the electrode 3 is preferably set to 20 mm or more, particularly 30 mm or more. If it is narrower than this, the raw material liquid sprayed from the tip of the nozzle 21 and in the form of a fiber tends to adhere to the concave curved surface of the electrode 3. The upper limit value of the distance between the tip 21a of the nozzle 21 and the surface (concave surface) 3f facing the nozzle 21 of the electrode 3 is preferably set to 100 mm or less, particularly 50 mm or less. If it is wider than this, the electric field formed between the nozzle 21 and the electrode 3 becomes weak, and it becomes difficult to obtain a high charge amount. From such a viewpoint, for example, the distance (shortest distance) between the two is preferably set to 20 mm or more and 100 mm or less, and more preferably set to 30 mm or more and 50 mm or less.

  In the manufacturing apparatus 1A, as described above, the nozzle 21 is grounded as shown in FIG. 2, and a negative voltage is applied to the electrode 3 by the DC high-voltage power supply 41 of the voltage generator 4. ing. Therefore, the electrode 3 becomes a cathode and the nozzle 21 becomes an anode, and a voltage is generated 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.

  In the manufacturing apparatus 1 </ b> A, a known device such as a high-voltage power supply device can be used for the voltage generator 4. 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.

  In the manufacturing apparatus 1 </ b> A, the airflow injection unit 5 has a through hole 51 in the vicinity of the base of the nozzle 21 in the nozzle assembly 20 as shown in FIGS. 1 and 2. The airflow injection unit 5 is formed along the direction in which the nozzle 21 extends. Furthermore, the airflow injection part 5 is formed so as to be able to inject a high-speed airflow toward the tip 21 a of the nozzle 21. When viewed from the opening end 31 side of the electrode 3, two through holes 51 of the airflow ejection unit 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 flow injection section 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 is a collection unit (not shown), which will be described later, disposed at a position facing the airflow jetting unit 5 from the raw material liquid jetted from the tip 21a of the nozzle 21 and elongated by the action of an electric field. Contributes to stretching the nanofiber while being transported toward the surface. In the manufacturing apparatus 1A, a state in which two through holes 51 of the airflow injection unit 5 are provided is shown. 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.

  As the air flow ejected from the air flow ejecting unit 5, for example, one dried by a dryer or the like to a humidity of 30% RH or less can be used. The air flow is preferably maintained at a constant temperature so that the state of the manufactured nanofibers is maintained constant. The wind speed of the airflow is preferably, for example, 10 m / sec or more, particularly 20 m / sec or more. If it is slower than this, it becomes difficult to convey the traveling direction of the nanofiber in the direction in which the collecting portion is present against the electric field between the nozzle 21 and the electrode 3. The upper limit of the wind speed of the air flow is preferably 60 m / sec or less, particularly 50 m / sec or less, for example. If the wind speed is faster than this, the air flow may cause the fiber to break. From such a viewpoint, the wind speed of the airflow is preferably 10 m / sec or more and 60 m / sec or less, and particularly preferably 20 m / sec or more and 50 m / sec or less.

  In the manufacturing apparatus 1A, as shown in FIGS. 1 and 2, the covering 6 is formed on the surface of the electrode 3 that is a cathode, on the substantially entire surface (concave surface) 3f facing the nozzle 21, with a dielectric on the surface. An exposed covering 6 is disposed. Here, “substantially the entire surface” means an area that occupies an area of 90% or more of the total surface area (100%) of the surface (concave surface) 3 f facing the nozzle 21 of the electrode 3. Further, the covering 6 with a dielectric exposed on the surface is a covering 6 in which substantially the entire surface (area of 90% or more) is composed only of a dielectric. It is preferable that the entire surface (100% area) of the covering 6 is composed only of a dielectric. That is, the covering 6 is preferably a covering in which a dielectric is exposed on the surface and no conductor such as metal is present on the surface. A typical example is a covering made up of a single type of dielectric, but the covering may be a composite of multiple types of dielectrics, or the surface may be made up of only a dielectric. For example, it may be a composite containing metal particles, a metal or air layer, or the like inside (a portion not exposed on the surface).

  In the manufacturing apparatus 1A, as shown in FIG. 2, the electrode 3 and the covering 6 are in contact with each other. From the viewpoint of strengthening the bonding between the electrode 3 and the covering 6, it is preferable that the electrode 3 and the covering 6 are in close contact with each other. The surface (concave surface) 3f in contact with the cover 6 in the electrode 3 and the surface 6f in contact with the electrode 3 in the cover 6 have the same shape. Here, the surface 3 f in contact with the covering 6 in the electrode 3 is the same surface as the surface (concave surface) 3 f facing the nozzle 21 of the electrode 3. In the manufacturing apparatus 1 </ b> A, the covering 6 has a hollow convex portion 61 having a shape complementary to the electrode 3 having a surface (concave curved surface) 3 f facing the nozzle 21. In other words, as shown in FIGS. 1 and 2, the shape of the electrode 3 having the opposing surface (concave surface) 3 f and the shape of the portion in contact with the electrode in the covering 6 are similar. Here, the part in contact with the electrode in the covering 6 means a hollow convex portion 61, and the shape of the electrode 3 and the shape of the convex portion 61 are similar to each other.

  In the manufacturing apparatus 1A, as shown in FIGS. 1 and 2, the top of the convex portion 61 of the covering 6 is opened, and the nozzle assembly 20 is fitted into the opening. The convex portion 61 covers a surface (concave curved surface) 3 f facing the nozzle 21 in the surface of the electrode 3. The covering 6 has a flange portion 62 that extends in the horizontal direction from the opening peripheral edge on the bottom side of the hollow convex portion 61. The flange portion 62 covers the periphery of the opening end portion 31 in the direction in which the nozzle 21 extends in the electrode 3. In a state where the covering 6 is fitted to the surface (concave surface) 3f facing the nozzle 21 of the electrode 3, it is preferable to fix the electrode 3 and the covering 6 using, for example, an adhesive. Thus, when fixing the electrode 3 and the covering body 6, when viewed from the opening end portion on the bottom side of the hollow convex portion 61, in other words, from the direction in which the nozzle 21 extends in the covering body 6. From the viewpoint of not impairing the insulating properties, it is preferable that no fixing hole penetrating the covering 6 is disposed. The flange portion 62 of the covering 6 preferably extends from the opening periphery of the convex portion 61 in the horizontal direction by 1 mm or more and 15 mm or less, particularly 10 mm or more and 12 mm or less.

  As an adhesive that fixes the electrode 3 and the covering 6, for example, an epoxy resin adhesive or an external tape can be used. In particular, by using a removable adhesive such as a denture stabilizer, the covering 6 can be easily detached from the electrode 3 and the maintainability of the manufacturing apparatus 1A is improved.

  As described above, the inventors significantly increase the charge amount of the raw material liquid sprayed from the nozzle 21 by covering the surface (concave surface) 3f of the electrode 3 facing the nozzle 21 with the covering 6. I found out that The mechanism is expected as follows. In the manufacturing apparatus 1A, the cation in the raw material liquid is attracted to the electrode 3 (cathode) side by the electric field formed between the electrode 3 and the nozzle 21, and the anion in the raw material liquid is the tip of the nozzle 21 (anode). It is pulled toward the 21d side. The raw material liquid to be injected contains a large amount of cations, and the raw material liquid is positively charged. At the same time, electrons are emitted from the electrode 3 (cathode) to the atmosphere by the voltage applied between the electrode 3 and the nozzle 21, and the electrons fly toward the nozzle 21 (anode). The flying (negatively charged) electrons collide with the jetted (positively charged) raw material liquid, neutralizing the charging of the raw material liquid and reducing the charge amount. On the other hand, if the surface of the electrode 3 that is a cathode is covered with a covering 6 with a dielectric exposed, the emission of electrons from the electrode 3 can be suppressed. As a result, it is considered that neutralization of the raw material liquid by flying electrons, that is, a decrease in the charge amount can be suppressed, and the charge amount of the raw material liquid is increased. Furthermore, since the number of electrons flying from the electrode 3 to the nozzle 21 is reduced, the discharge between the electrode 3 and the nozzle 21 is suppressed, and the applied voltage between the electrode 3 and the nozzle 21 can be increased. Thereby, the electric field between the electrode 3 and the nozzle 21 is strengthened, and the charge amount of the raw material liquid can be increased. In addition, when the number of electrons flying from the electrode 3 to the nozzle 21 decreases, the current (leakage current) flowing between the electrode 3 and the nozzle 21 decreases, and the effect of reducing power consumption during nanofiber production can be expected. In order to effectively exhibit the effect, it is preferable to cover the entire surface (90% or more area) of the surface (concave surface) 3f facing the nozzle 21 with the covering body 6, and particularly the surface facing the nozzle 21. It is preferable to cover the entire surface (100% area) with the covering 6.

  Further, in the manufacturing apparatus 1A, as shown in FIG. 2, since the electrode 3 has a concave spherical shape having a concave curved surface, the increase in the charge amount of the raw material liquid becomes more remarkable. That is, in the manufacturing apparatus 1 </ b> A, there is an electrode surface that is far wider than the area of the nozzle 21 at a position approximately equidistant from the tip 21 a of the nozzle 21. Since the total amount of charge accumulated in the cathode 3 and the anode nozzle 21 is equal, the charge is distributed on the surface of the nozzle 21 at a much higher density than the electrode 3, and as a result, the nozzle 21. The electric field in the vicinity becomes stronger. This strong electric field further increases the charge amount of the raw material liquid. From this viewpoint, the area of the nozzle 21 is preferably small, and in particular, the length of the nozzle 21 (the distance between the front end 21a and the rear end 21b of the nozzle 21) is preferably short. Specifically, the length of the nozzle 21 is preferably 50 mm or less, more preferably 10 mm or less, and even more preferably 5 mm or less. Further, by making the electrode 3 concave spherical as in the present embodiment, the volume of the electrode can be reduced as compared with the case where a planar electrode is used, and thus the manufacturing apparatus 1A can be reduced in size.

  Further, in the manufacturing apparatus 1A, the thickness (T3) of the opening end 31 in the direction in which the nozzle 21 extends in the electrode 3 is equal to the thickness of the covering 6 positioned at the opening end 31 (see FIG. 1 and FIG. 2). It is formed thinner than T6). Here, the thickness of the covering 6 positioned at the opening end 31 means the thickness at the position of the opening end 31 of the electrode 3 in the covering 6 covering substantially the entire concave surface of the electrode 3. Specifically, it means the thickness at the open end of the hollow convex portion 61, and does not mean the thickness of the flange portion 62. In the manufacturing apparatus 1A, since the thickness of the opening end 31 of the electrode 3 is formed to be thinner than the thickness of the covering 6 positioned at the opening end 31, the spinning voltage is increased when adjusting the spinning voltage. Even so, the range covered by the electric field generated at the opening end 31 of the electrode 3 is likely to be narrow, hardly affects the raw material liquid having an increased charge amount, and the electrospinning tension is not disturbed. As a result, the productivity of nanofibers can be increased more than ever.

  From the viewpoint of narrowing the range of the electric field generated at the opening end 31 of the electrode 3, the ratio (T6 / T3) of the thickness (T6) of the covering 6 to the thickness (T3) of the opening end 31 of the electrode 3 is: It is preferably greater than 1, more preferably greater than 5, and preferably less than 40000, more preferably less than 5000, specifically greater than 1 and less than 40000. It is more preferable that it is larger than 5 and smaller than 5000. Specifically, from the same viewpoint, the thickness (T3) of the open end 31 of the electrode 3 is preferably 0.5 μm or more, more preferably 1 μm or more, and preferably 2 mm or less. More preferably, it is 1 mm or less, specifically 0.5 μm or more and 2 mm or less, and more preferably 1 μm or more and 1 mm or less. From the same viewpoint, the thickness (T6) of the covering 6 is preferably 1 mm or more, more preferably 2 mm or more, and preferably 20 mm or less, more preferably 10 mm or less, Specifically, it is preferably 1 mm or more and 20 mm or less, and more preferably 2 mm or more and 10 mm or less.

  From the viewpoint of keeping the electrospinning tension stably and constant, the electrode 3 is preferably formed of a conductive sheet. 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. Is mentioned. As the metal sheet, aluminum tape, household aluminum foil, and the like are preferably used from the viewpoints of cost and lightness and thickness uniformity.

  Further, from the viewpoint of keeping the electrospinning tension stably and constant, the electrode 3 is preferably formed of a conductive thin film obtained by plating or vapor-depositing the covering 6. Examples of the metal that forms the conductive film include silver, gold, palladium, platinum, copper, zinc, and the like, and copper is preferably used from the viewpoint of ease of film formation or cost.

  Further, from the viewpoint of keeping the electrospinning tension stable and constant, the electrode 3 is preferably formed of a sheet metal having a substantially uniform thickness. Examples of the sheet metal material include silver, gold, palladium, platinum, copper, nickel, and aluminum.

  Further, from the viewpoint of stably keeping the electrospinning tension constant, the electrode 3 is preferably formed by applying a conductive material to the covering 6. As a conductive material to be applied, materials containing metal powder such as silver powder, gold powder, palladium powder, platinum powder, copper powder, nickel powder, aluminum powder, brass powder, or carbon-based materials such as carbon black and graphite powder. Examples include materials containing conductive powder such as filler.

  Further, from the viewpoint of keeping the electrospinning tension stably and constant, the distance (shortest distance) between the tip 21a of the nozzle 21 and the covering 6 with respect to the absolute value (v (kV)) of the voltage applied to the electrode 3 ( The ratio (d / v) of d (mm)) is preferably 20 or less, more preferably 5 or less, and preferably 0.7 or more, and more preferably 1 or more. Specifically, it is preferably 0.7 or more and 20 or less, more preferably 1 or more and 5 or less. Specifically, from the same viewpoint, the voltage applied to the electrode 3 is preferably 5 kV or more and 100 kV or less, and more preferably 10 kV or more and 50 kV or less. From the same viewpoint, the distance (shortest distance) (d (mm)) between the tip 21a of the nozzle 21 and the covering 6 is preferably 10 mm or more and 100 mm or less, and more preferably 20 mm or more and 50 mm or less. preferable.

  Dielectric materials used for the covering 6 include ceramic materials such as mica, alumina, zirconia, and barium titanate as insulating materials, bakelite (phenol resin), nylon (polyamide), vinyl chloride resin, polystyrene, polyester, and polypropylene. And resin materials such as 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 the nylon, various polyamides such as 6 nylon and 66 nylon can be used. Moreover, a commercial item can also be used as nylon. As such a commercial item, MC nylon (trademark) is mentioned, for example. The dielectric used for the covering 6 can contain an antistatic agent. By containing an antistatic agent, when the charged raw material liquid, nanofiber, or the like adheres to the covering 6, charging of the covering 6 can be reduced. As the antistatic agent, known commercial products can be used. For example, Peletron (Sanyo Chemical Industry Co., Ltd.), Electro Stripper (Kao Corporation), Electro Master (Kao Corporation), Riquemar (RIKEN Vitamin ( Co., Ltd.), Riquet Master (RIKEN Vitamin Co., Ltd.) and the like.

  In the manufacturing apparatus 1A, it is preferable that the covering 6 covers the electrode 3 with a uniform thickness. The thickness of the dielectric exposed on the surface constituting the covering 6 is preferably 0.8 mm or more, particularly 2 mm or more, particularly 8 mm or more. By doing so, it is possible to sufficiently suppress the emission of electrons from the electrode and to increase the charge amount of the raw material liquid. If it is thinner than this, the emission of electrons from the electrode 3 may not be sufficiently suppressed, and the charge amount of the raw material liquid may not be increased. In addition, the said thickness points out the thickness of the coating body 6 (equal to the thickness of the coating body 6), when the coating body 6 is comprised from the single type or multiple types of dielectric material. Also, when the covering 6 is a composite containing metal or air particles or layers in the interior (portion not exposed on the surface), it indicates the thickness of the dielectric existing between the surface and the metal or air And The upper limit value of the thickness of the covering 6 is preferably 25 mm or less, particularly 20 mm or less, especially 15 mm or less. By doing so, it is possible to prevent the raw material liquid sprayed from the tip 21a of the nozzle 21 and becoming a fiber from being attracted to and attached to the dielectric. Further, since the raw material liquid is less likely to adhere to the electrode, a higher voltage can be applied, thereby increasing the charge amount of the raw material liquid. If it is thicker than this, the raw material liquid sprayed from the tip of the nozzle 21 and in the form of a fiber tends to adhere to the covering 6. When the covering 6 is composed of a single kind or a plurality of kinds of dielectrics, for example, the thickness of the covering 6 is preferably 0.8 mm to 25 mm, particularly 2 mm to 20 mm, particularly 8 mm to 15 mm.

  In 1 A of manufacturing apparatuses, a collection part (not shown) collects nanofibers, and is arrange | positioned in the position facing the airflow injection part 5. FIG. In particular, a collecting electrode (not shown) can be arranged as a part of the collecting part. The collection electrode can be a flat plate made of a conductive material such as metal. The plate surface of the collection electrode and the air flow injection direction by the air flow injection unit 5 are substantially orthogonal to each other. Further, as will be described later, the collecting electrode can be coated on the substantially entire surface with a covering with a dielectric exposed, more preferably on the entire surface. 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 nanofiber to the collecting electrode, a lower (negative) potential is applied to the collecting electrode 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. The lower limit of the distance (shortest distance) between the collection electrode (electrode surface) and the tip 21a of the nozzle 21 is preferably 100 mm or more, and more preferably 500 mm or more. If it is narrower than this, the nanofiber may not be sufficiently solidified before reaching the collecting electrode. The upper limit is preferably 3000 mm or less, more preferably 1000 mm or less. If it is wider than this range, the electric attraction force by the collecting electrode is weakened, and the collection rate of the nanofiber is lowered. For example, it is preferably 100 mm or more and 3000 mm or less, and more preferably 500 mm or more and 1000 mm or less.

  In the manufacturing apparatus 1A, a collector (not shown) in which nanofibers are collected is further collected between the collection electrode and the nozzle 21 so as to be adjacent to the collection electrode. Can also be arranged. As a collector, insulators, such as a film, a mesh, a nonwoven fabric, and paper, can be used, for example.

  In the manufacturing apparatus 1 </ b> A, an air exhaust unit (not shown) that exhausts the injected air flow may be disposed so as to face the air flow injection unit 5. The air exhaust part is preferably arranged on the side farther from the nozzle 21 than the collection electrode described above. For example, a known device such as a suction box can be used as the air exhaust unit.

  In the nanofiber manufacturing method using the manufacturing apparatus 1A of the first embodiment described above, the raw material liquid is injected from the tip 21a of the nozzle 21 in a state where an electric field is generated between the electrode 3 and the nozzle 21. To do. 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. As described above, the charge amount per unit mass of the raw material liquid becomes extremely high due to the electrode 3 being covered with the covering 6. Then, the raw material liquid is directed toward the collector (not shown) by injecting an air flow from the air flow 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 placed on the airflow ejected from the airflow ejecting unit 5 and attracted to the electric field created by the collecting electrode (not shown), so as to face the airflow ejecting unit 5. Deposited on the surface of the collected collector. In order to attract positively charged nanofibers to the collector, a lower (negative) potential is applied to the collector electrode 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 nanofiber manufacturing method using the manufacturing apparatus 1 </ b> A of the first embodiment, the thickness of the opening end 31 of the electrode 3 is thinner than the thickness of the covering 6 positioned at the opening end 31. Therefore, even if the spinning voltage is increased when adjusting the spinning voltage, the range covered by the electric field generated at the opening end 31 of the electrode 3 tends to be narrowed. Therefore, even if the charge amount of the raw material liquid sprayed from the tip of the nozzle 21 is extremely high, the electric field spinning is not affected by the electric field generated at the opening end 31 and the balance of the electrospinning tension is not lost. The tension can be made stable and constant. Further, since the amount of charge of the raw material liquid sprayed from the tip of the nozzle 21 is extremely high, the force for attracting the raw material liquid in the direction of the electrode 3 becomes large. Therefore, even when a larger amount of raw material liquid (per unit time) than before is ejected from the nozzle 21, it is possible to produce nanofibers that are as thin as the conventional one. In addition, defects or the like are hardly generated in the obtained nanofiber, and the productivity of the nanofiber can be increased as compared with the conventional one. The defect referred to here is, for example, a material liquid droplet solidified as it is or a bead-like material formed by solidifying a raw material liquid droplet without being sufficiently stretched.

  Next, the nanofiber manufacturing apparatus 1B which is 2nd Embodiment of the electrospinning apparatus of this invention is demonstrated. FIG. 3 shows a manufacturing apparatus 1B of the second embodiment. FIG. 3B shows a top view of the manufacturing apparatus 1B. FIG. 3A is a side view of the A-A ′ cross section in FIG. In addition, regarding the manufacturing apparatus 1B of the second embodiment, the description regarding the manufacturing apparatus 1A of the first embodiment is appropriately applied to points that are not particularly described. In FIG. 3, the same members as those in FIGS. 1 and 2 are denoted by the same reference numerals.

  The manufacturing apparatus 1B includes a raw material injection unit 2 that injects a raw material liquid for producing nanofibers. The raw material injection unit 2 includes a liquid feeding unit 23 and a nozzle 21. A concave spherical electrode 3 having a concave curved surface 3f is disposed at a position immediately above the opening of the nozzle 21 with its inner surface facing downward. The nozzle 21 is made of metal or the like and has conductivity. A direct current voltage is applied between the nozzle 21 and the electrode 3 by a direct current high voltage power source 41 which is a voltage generation unit via a ground 42 and a metal conductor 43. The nozzle 21 is grounded as shown in FIG. 3A and becomes an anode. On the other hand, a negative voltage is applied to the electrode 3 to become a cathode.

  In the manufacturing apparatus 1B, as shown in FIG. 3A, the electrode 3 has a concave spherical shape as a whole, and particularly has a substantially bowl shape. And the concave surface 3f is provided in the inner surface. Further, as shown in FIG. 3 (b), the electrode 3 includes an opening 32 for disposing the air flow injection unit 5 at the positions of two opposing side surfaces, an air flow injected from the air flow injection unit 5, and It has an opening 33 through which the raw material liquid sprayed from the nozzle 21 is formed into a fiber shape. In addition, as long as the inner surface becomes the concave curved surface 3f, the shape of the outer surface of the electrode 3 does not need to be a substantially bowl shape, and may be another shape.

  In the manufacturing apparatus 1 </ b> B, the air flow injection unit 5 injects an air flow between the nozzle 21 and the electrode 3 through the opening 32 provided in the electrode 3 as shown in FIGS. 3A and 3B. It is arranged at a position where it can be done. The generated fiber is positively charged and extends from the nozzle 21 serving as the anode toward the electrode 3 serving as the cathode. However, the airflow ejected from the airflow ejecting unit 5 changes the traveling direction of the fiber. It is converted and transported through the opening 33 in a direction with a collection part (not shown) (downward direction in FIG. 3B) and contributes to stretching the nanofiber.

  In the manufacturing apparatus 1B of the second embodiment, the entire surface of the surface (concave surface) 3f facing the nozzle 21 of the surface of the electrode 3 that is a cathode is coated with the covering 6 with a dielectric exposed on the surface. Yes. Since the tip of the nozzle 21 is located outside the concave curved surface 3 f, the concave curved surface 3 f faces the nozzle 21. The thickness of the covering 6 is substantially constant, and the electrode 3 and the covering 6 are in direct contact. A surface (concave surface) 3f in contact with the covering 6 in the electrode 3 and a surface 6f in contact with the electrode 3 in the covering 6 have the same shape. In the manufacturing apparatus 1B, the thickness (T3) of the opening end 31 in the direction in which the nozzle 21 extends in the electrode 3 is equal to the thickness (T6) of the covering 6 positioned at the opening end 31 as shown in FIG. It is formed thinner than. The electrode 3 and the covering 6 are fixed with an adhesive.

  As the dielectric constituting the covering 6 used in the manufacturing apparatus 1B, the same dielectric as that constituting the covering 6 of the manufacturing apparatus 1A of the first embodiment can be used. And it is easy to use a molded body obtained by melt-molding various thermoplastic resins. The dielectric can contain the same antistatic agent as used in the covering 6 of the manufacturing apparatus 1A. The thickness of the covering 6 that covers the electrode 3 can be the same as the thickness of the covering 6 that covers the electrode 3 in the manufacturing apparatus 1A.

  Even when the manufacturing apparatus 1B of the second embodiment is used, the charge amount of the raw material liquid can be increased by the action of the covering 6 as in the manufacturing apparatus 1A of the first embodiment. In addition, in the manufacturing apparatus 1B, since the electrode 3 has a concave spherical shape as in the manufacturing apparatus 1A, the increase in the charge amount of the raw material liquid becomes more remarkable, and the manufacturing apparatus can be downsized. And since the thickness of the opening end part 31 of the electrode 3 is formed thinner than the thickness of the covering 6 located in the opening end part 31, even if the spinning voltage is increased when adjusting the spinning voltage, the electrode 3 The range of the electric field generated at the open end 31 of the electrode is likely to be narrowed, hardly affects the raw material liquid with an increased charge amount, and the electrospinning tension is not lost, and the electrospinning tension is stable. Can be constant. The length of the nozzle 21 is preferably 50 mm or less, more preferably 10 mm or less, and even more preferably 5 mm or less.

  In the manufacturing apparatus 1B, the distance (shortest distance) between the tip 21a of the nozzle 21 and the surface (concave surface) 3f facing the nozzle 21 of the electrode 3 is the distance between the tip 21a of the nozzle 21 and the electrode 3 in the manufacturing apparatus 1A. It can be made to be the same as the distance (shortest distance) between the concave curved surface 3f. The position of the tip 21a of the nozzle 21 is preferably located at the center of the concave surface 3f of the electrode 3 or in the vicinity of the center. Specifically, it is preferable to arrange at a position within 10 mm from the center of the concave curved surface 3f. As a result, the electric field at the tip 21a of the nozzle 21 becomes stronger, and the amount of charge of the raw material liquid increases. From this viewpoint, it is particularly preferable that the concave curved surface 3f of the electrode 3 has a substantially hemispherical shape of a true spherical shell. In the manufacturing apparatus 1B of the second embodiment, as shown in FIG. 3A, the plane including the circle defined by the opening end 31 of the concave curved surface 3f of the electrode 3 is substantially orthogonal to the direction in which the nozzle 21 extends. However, as shown in FIG. 4, the electrodes 3 may be arranged so as to be inclined so that the plane and the direction in which the nozzle 21 extends intersect at an angle other than 90 degrees.

  In the manufacturing apparatus 1B, the electrode 3 may cover a part or all of the surface that does not face the nozzle 21 with a covering with a dielectric exposed. Specifically, in FIG. 3A, the outer surface of the electrode 3 (the surface opposite to the concave curved surface 3 f) may be covered with the covering body 6. Moreover, you may coat | cover almost the whole surface of the collection electrode which is a part of collection part (not shown) with the coating body which exposed the dielectric material on the surface.

  As a raw material liquid used in the manufacturing apparatuses 1A to 1B of the above embodiments, 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 is used. it can. 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 the natural polymer include pullulan, hyaluronic acid, chondroitin sulfate, poly-γ-glutamic acid, modified corn starch, β-glucan, glucooligosaccharide, 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 , High molecular compounds such as polystyrene resin, polyvinyl butyral resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyurethane resin, polyamide resin, polyimide resin, and polyamideimide resin are also used. Door can be. These polymer compounds can be used alone or in combination of two or more.

  The nanofibers manufactured by the manufacturing apparatuses 1A to 1B of the above embodiments are 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 nanofiber manufacturing 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 manufacturing apparatus 1A-1B of the said embodiment.
For example, in the manufacturing apparatuses 1 </ b> A to 1 </ b> B, the covering 6 is disposed on substantially the entire surface (concave surface) 3 f facing the nozzle 21 in the surface of the electrode 3. You may coat | cover almost the whole outer surface with the coating body which exposed the dielectric material on the surface. Preferably, as shown in FIG. 5, the outer surface of the nozzle 21 may be covered with a covering body 7. The covering body 7 extends beyond the tip 21 a of the nozzle 21. The extending portion 7 a of the covering body 7 has a cylindrical shape surrounding the nozzle 21 and has a hollow portion. This hollow portion communicates with the inside of the nozzle 21. The covering 7 is composed of a single type of dielectric. By covering substantially the entire outer surface of the nozzle 21 with the covering 7, the number of electrons flying from the electrode 3 and flowing into the nozzle 21 can be suppressed. As a result, the discharge between the electrode 3 and the nozzle 21 is less likely to occur, and the applied voltage between the electrode 3 and the nozzle 21 can be increased and the distance can be reduced. Thereby, the electric field between the electrode 3 and the nozzle 21 is strengthened, and the charge amount of the raw material liquid can be increased. In order to effectively exhibit the above-described effect, it is preferable to cover substantially the entire outer surface (90% or more area) of the nozzle 21 with the covering 7, and in particular, cover the entire outer surface (100% area) of the nozzle 21. It is preferable to cover with the covering body 7. Further, by extending the covering 7 beyond the tip 21 a of the nozzle 21, it is possible to suppress electrons from flying to the tip 21 a of the nozzle 21, and the charge amount of the raw material liquid can be further increased.

  The length of the extended portion 7a of the covering 7 is preferably 1 mm or more, and more preferably 10 mm or more. If it is shorter than this, the effect of extending the covering 7 is reduced. The upper limit value is preferably 15 mm or less, and more preferably 12 mm or less. If it is longer than this, the raw material liquid sprayed from the tip of the covering body 7 and in the form of a fiber tends to adhere to the electrode 3 or the covering body 6. For example, the length of the extended portion 7a is preferably 1 mm or more and 15 mm or less, and particularly preferably 10 mm or more and 12 mm or less. By forming the extended portion 7a of this length, it is possible to effectively increase the charge amount of the raw material liquid by suppressing the discharge between the electrode 3 and the nozzle 21.

As the dielectric constituting the covering 7 that covers the nozzle 21, the same dielectric as that constituting the covering 6 that covers the electrode 3 can be used. The dielectric can contain the same antistatic agent as used in the covering 6. In addition, the thickness of the covering 7 that covers the nozzle 21 can be the same as the thickness of the covering 6 that covers the electrode 3.
As described above, in the manufacturing apparatuses 1 </ b> A to 1 </ b> B, in addition to the covering of the electrode 3 with the covering 6, the covering of the collecting electrode with the covering and / or the covering of the nozzle 21 with the covering 7 can be combined. .

  Further, in the manufacturing apparatuses 1A to 1B, as shown in FIGS. 2, 4 and 5, the electrode 3 has a concave spherical shape as a whole, but faces the nozzle 21 which is an inner surface of the concave spherical shape. As long as the surface 3f is formed in the concave curved surface 3f, the shape of the outer surface on the back surface side does not need to be a substantially bowl shape, and may be another shape. Specifically, it may have a shape as shown in FIG. In the electrode 3 having the concave curved surface 3 f shown in FIG. 6, the surface (concave curved surface) 3 f in contact with the covering 6 and the surface 6 f in contact with the electrode 3 in the covering 6 have the same shape, and the opening of the electrode 3. The thickness of the end 31 is formed thinner than the thickness of the covering 6 positioned at the opening end 31, but the shape of the electrode 3 having the opposing surface (concave surface) 3 f is in contact with the electrode in the covering 6. The shape of the part is not similar. That is, the thickness of the open end 31 of the electrode 3 is thinner than the thickness of the covering 6 positioned at the open end 31, but the thickness of the electrode 3 is covered except for the open end 31 of the electrode 3. It is formed thicker than the thickness of the body 6.

  In the manufacturing apparatuses 1A to 1B, the nozzle 21 may be a curved pipe having a curvature. Further, in the manufacturing apparatuses 1A to 1B, the concave curved surface 3f of the electrode 3 is preferably the shape of the inner surface of the hemispherical spherical shell, but instead, for example, the shape of the inner surface of the spherical shell of the spherical crown may be used. . In the manufacturing apparatus 1A, the nozzle 21 is disposed at the bottom of the concave curved surface 3f, but the nozzle 21 may be disposed at other positions.

  Furthermore, the technical elements of one embodiment may be replaced with the technical elements of another embodiment as long as the advantageous effects achieved by the present invention are not impaired.

  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, “%” and “part” mean “% by mass” and “part by mass”, respectively.

[Example 1]
Nanofibers were manufactured using the manufacturing apparatus 1A shown in FIGS. Specifically, a covering 6 having a hollow convex portion 61 and a flange portion 62 extending from the opening periphery of the convex portion 61 is prepared, and an aluminum tape having a thickness of 100 μm is formed on the outer curved surface of the hollow convex portion 61. (Product No. # 433 HD manufactured by 3M Company) was pasted to form an electrode 3 in which the concave curved surface 3f was a hemisphere having a radius of 45 mm. The covering 6 was formed of a dielectric (monomer cast nylon (MC901 cutting plate (blue) made of white copper)) having a thickness of 10 mm, that is, the thickness (T3) of the opening end 31 of the electrode 3 was 100 μm. The thickness (T6) of the covering 6 positioned at the open end 31 is 10 mm, thus, the surface (concave surface) 3f in contact with the covering 6 in the electrode 3 and the surface in contact with the electrode 3 in the covering 6 The tip 21a of the nozzle 21 is placed at the center of the hemisphere, and the tip 21a is positioned in a plane including a circle defined by the open end 31 of the concave curved surface 3f. The extending direction of the nozzle was matched with the rotational symmetry axis of the hemisphere.

  Next, Dermacryl 79 (manufactured by Akzo Nobel Co., Ltd.) 20.1%, 1-butanol (manufactured by Wako Pure Chemical Industries, Ltd.) 71.3%, Sunsoft A-181E-C (manufactured by Taiyo Kagaku Co., Ltd.) A solution formulated at a ratio of 8.6% was used. A fixed amount of the raw material liquid was sent to the nozzle 21 with a syringe pump. The discharge rate of the raw material liquid sprayed from the nozzle 21 was set to 30 mL / h. The inner diameter of the nozzle 21 was 0.3 mm and the length was 20 mm. Further, the flow rate of the air flow injected from the air flow injection unit 5A was set to 100 L / min. The distance (shortest distance) between the tip 21 a of the nozzle 21 and the electrode 3 is 45 mm, the distance (shortest distance) (d (mm)) between the tip 21 a of the nozzle 21 and the covering 6 is 35 mm, and the tip 21 a of the nozzle 21. The distance (shortest distance) between the electrode and the collection electrode (electrode surface) was 850 mm. And the voltage of -25 kV and -35 kV was applied between the nozzle 21 and the electrode 3, and it spun on 2 conditions. FIG. 8 shows a photograph of the obtained nanofiber taken with a scanning electron microscope (SEM), and FIG. 9 shows a fiber diameter distribution chart obtained by measuring the fiber diameter from the SEM image and counting it. In the fiber diameter distribution diagram shown in FIG. 9, the horizontal axis is the fiber diameter [μm], and the vertical axis is the number [number]. The manufacturing environment was a room temperature of 23 ° C. and a humidity of 20% RH.

[Reference Example 1]
Nanofibers were manufactured using the manufacturing apparatus 100 shown in FIG. The manufacturing apparatus 100 shown in FIG. 7 differs from the manufacturing apparatus 1A shown in FIGS. 1 and 2 only in the shape of the electrodes. The electrode 103 of the manufacturing apparatus 100 shown in FIG. 7 includes a concave spherical surface portion whose inner surface is formed into a concave curved surface 103f, and a planar flange portion 132 extending from the periphery of the opening end portion 131 of the concave spherical surface portion. Had. The manufacturing apparatus 100 is formed by covering the entire surface of the concave curved surface 103 f of the electrode 103 and a part of the flange portion 132 with the covering body 6. The thickness (T103) of the opening end 131 of the electrode 103 was 10 mm, and the thickness (T6) of the covering 6 located at the opening end 31 was also 10 mm. The other configuration of the manufacturing apparatus 100 is the same as the configuration of the manufacturing apparatus 1A of Example 1, and spinning was performed under the same conditions. FIG. 8 shows a photograph of the obtained nanofiber taken with a scanning electron microscope (SEM), and FIG. 9 shows a fiber diameter distribution chart obtained by measuring the fiber diameter from the SEM image and counting it. In the fiber diameter distribution diagram shown in FIG. 9, the horizontal axis is the fiber diameter [μm], and the vertical axis is the number [number]. The manufacturing environment was a room temperature of 23 ° C. and a humidity of 20% RH.

  From the results shown in FIGS. 8 and 9, the applied voltage −25 kV can be obtained by using any one of the manufacturing apparatus 1A for manufacturing the nanofiber of Example 1 and the manufacturing apparatus 100 for manufacturing the nanofiber of Reference Example 1. Spinning could be stably performed under the above conditions. In addition, a fiber with a nano-sized diameter was obtained. On the other hand, in the experiment in which −35 kV was applied, as shown in Example 1, spinning was possible only with the nanofiber manufacturing apparatus 1A. Furthermore, with respect to the fiber diameter, it was confirmed that a nanofiber with a small diameter could be obtained from the spinning result when -25 kV was applied. This is because the manufacturing apparatus 1 </ b> A that manufactured the nanofiber of Example 1 has the thickness of the opening end 31 of the electrode 3 positioned at the opening end 31 compared to the manufacturing apparatus 100 that manufactured the nanofiber of Reference Example 1. Since it is formed thinner than the thickness of the covering 6, the range covered by the electric field generated at the opening end 31 of the electrode 3 is narrowed, and without affecting the raw material liquid having an increased charge amount, This is considered to be because the tension of electrospinning was stably made constant without breaking the balance of tension.

1A, 1B nanofiber manufacturing equipment (electrospinning equipment)
2 Raw material injection part 20 Nozzle assembly 21 Nozzle 21a Tip 22 Support part 23 Liquid feeding part 3 Electrode 3f Concave surface 31 Open end 32,33 Opening 30 Base 4 Voltage generating part 41 DC high voltage power supply 42 Ground 43 Metal conductor 5 Air flow Injecting portion 51 Through hole 6 Covering body 6f Surface in contact with electrode 3 61 Convex portion 62 Flange portion

Claims (9)

A raw material injection section having a conductive nozzle for injecting the raw material liquid;
An electrode having a concave curved surface disposed electrically insulated from the nozzle;
A voltage generator for generating a voltage between the nozzle and the electrode;
An electrospinning apparatus comprising an airflow injection unit that injects an airflow between the nozzle and the electrode,
The electrode occupies a surface that occupies an area of 90% or more of the total surface area of the surface facing the nozzle, the surface is covered with a cover with an exposed dielectric, and the electrode and the cover are in contact with each other.
The surface of the electrode in contact with the covering and the surface of the covering in contact with the electrode have the same shape,
The electrospinning apparatus, wherein a thickness of an opening end portion of the electrode in a direction in which the nozzle extends is thinner than a thickness of the covering body positioned at the opening end portion.   The electrospinning apparatus according to claim 1, wherein a thickness of the opening end portion of the electrode is 0.5 μm or more and 2 mm or less.   The electrospinning apparatus according to claim 1 or 2, wherein a shape of the electrode and a shape of a portion of the covering that is in contact with the electrode are similar to each other.   The electrospinning apparatus according to any one of claims 1 to 3, wherein the electrode is formed of a conductive sheet.   The electrospinning apparatus according to any one of claims 1 to 3, wherein the electrode is formed of a conductive thin film obtained by performing plating or vapor deposition on the covering. The electrodes, electrospinning apparatus according to any one of claims 1 to 3 which is formed with a thickness GaHitoshi like sheet metal.   The electrospinning apparatus according to claim 1, wherein the electrode is formed by applying a conductive material to the covering.   When fixing the said electrode and the said covering body, the hole for fixing which penetrates this covering body is not arrange | positioned in the location which can be seen from the direction where the said nozzle extends in this covering body. 2. The electrospinning apparatus according to item 1.   The ratio (d / v) of the distance (d) between the tip of the nozzle and the covering to the absolute value (v) of the voltage applied to the electrode is 20 or less. The electrospinning apparatus according to item.