JP5486754B2 - Electrospinning method and electrospinning apparatus - Google Patents

Description

  The present invention relates to a novel electrospinning method. The present invention also relates to an electrospinning apparatus to which this novel electrospinning method can be applied.

  The electrospinning method, which is a spinning technique using an electric field, can easily form fibers with nano- to micro-scale diameters at room temperature and atmospheric pressure, and is effective for continuous production of nanofibers. Means. There have been reports on the preparation of polymer weak electrolyte fibers having charged groups such as amino groups and carboxyl groups, but it is difficult to fabricate strong electrolyte polymers having charged groups such as sulfonic acid groups and quaternary ammonium groups. It has been said. This is because a polymer electrolyte solution having a strong electrolyte as a charge group has a high electric conductivity, so that a current is generated in the solution when a voltage is applied, and the solution is prevented from being charged due to electric field concentration on the nozzle surface. It is thought that. In order to avoid such a problem, in the method described in Patent Document 1, a polymer having a strong electrolyte as a charged group is introduced by introducing a sulfonic acid group or a quaternary base into a polymer fiber produced by an electrospinning method. Manufactures fibers. Regarding the one-step fiber formation of the polymer electrolyte using the electrospinning method, Patent Document 2 describes the suppression of the charge relaxation phenomenon by adding a neutral polymer or a sol-gel reaction precursor to the spinning solution. Proposed.

JP 2006-334469 A JP 2007-327148 A

  However, the method described in Patent Document 1 requires a reaction step as a post-treatment for introducing a charged group, leading to an increase in manufacturing cost. Further, in the method described in Patent Document 2, even when spinning can be performed using such a method, the fiber containing the electrolyte is affected by the lines of electric force between the nozzle and the counter electrode that is the collecting portion. Since nanofibers grow vertically from the counter electrode substrate, it has been difficult to produce a sheet in one step even though twisting can be performed.

  The present invention has been made in view of such problems, and an object thereof is to provide a novel electrospinning method.

  Another object of the present invention is to provide an electrospinning apparatus to which this novel electrospinning method can be applied.

  In order to solve the above problems and achieve the object of the present invention, an electrospinning method in which an electric field is formed between a nozzle and a main electrode and a spinning solution is sprayed from the nozzle toward the main electrode to perform spinning. The auxiliary electrode is disposed on the nozzle side with respect to the main electrode and electrically connected to the main electrode, and the spinning solution is sprayed from the nozzle toward the auxiliary electrode to perform spinning. Yes.

  In order to solve the above problems and achieve the object of the present invention, in an electrospinning apparatus for spinning by spinning a spinning solution in an electric field, an electric field is applied between the nozzle for spraying the spinning solution and the nozzle. A main electrode to be formed, and an auxiliary electrode which is disposed on the nozzle side with respect to the main electrode and is electrically connected to the main electrode.

  The auxiliary electrode includes an annular main body that is spaced apart from the main electrode on the nozzle side, and extends from the main body toward the main electrode to be electrically connected to the main electrode. And a leg portion to be connected.

  The present invention relates to the manufacture of a sheet-like material in which fibers having a diameter of nano to micro scale containing an electrolyte are accumulated. An object of this invention is to provide the novel manufacturing method of the sheet-like material which consists of an ultrafine fiber containing electrolyte. Specifically, an object of the present invention is to provide a method for efficiently producing a sheet-like material obtained by accumulating ultrafine fibers containing an electrolyte having a diameter of nano to micro scale using an electrospinning method. In the production of a polymer fiber including an electrolyte using a conventional electrospinning method, there is a drawback that even if the fiber can be produced, a sheet cannot be produced in one step by collecting the fibers. In the present invention, by installing an auxiliary electrode on the main electrode of the electrospinning apparatus, the electrolyte nanofiber was successfully formed into a sheet in one step.

  According to the present invention, it is possible to produce a sheet made of accumulated fibers by installing an auxiliary electrode having an opening for collecting fibers on the main electrode side of the electrospinning method. The thickness of the sheet can be controlled according to the electrospinning time. Further, in the electrospinning method, the fiber diameter can be controlled, and thereby the pore diameter, porosity, basis weight (fiber density), and specific surface area of the sheet can also be controlled.

  The present invention has the following effects.

  In the electrospinning method and the electrospinning apparatus of the present invention, an auxiliary electrode is placed on the counter electrode that is a collecting part of the electrospinning apparatus, thereby making it possible to form the electrolyte nanofiber into a sheet in one step.

1 is an electrospinning apparatus according to an embodiment of the present invention. It is another example of the auxiliary electrode of the electrospinning apparatus of FIG. It is a photograph which shows the spinning state with the auxiliary electrode of the electrospinning apparatus of FIG. It is a SEM photograph of the secondary electron image of the produced electrolyte nanofiber sheet. It is a photograph of the state of collection with only the main electrode. It is a photograph of the state of collection only with an auxiliary electrode.

  Hereinafter, embodiments for carrying out the invention according to an electrospinning method and an electrospinning apparatus will be described.

  In the electrospinning method, an auxiliary electrode is disposed on the nozzle side with respect to the main electrode, electrically connected to the main electrode, and spinning is performed by spraying a spinning solution from the nozzle toward the auxiliary electrode.

  The electrospinning apparatus includes a nozzle for spraying the spinning solution, a main electrode (target electrode) that forms an electric field between the nozzle, and a main electrode that is disposed apart from the main electrode on the nozzle side. An auxiliary electrode (fiber collecting electrode) that is electrically connected, and the auxiliary electrode is disposed in a ring-shaped body part spaced apart from the main electrode on the nozzle side, and the body part And a leg portion extending from the main electrode toward the main electrode and electrically connected to the main electrode.

The nozzle material is preferably a conductive material or a semiconductor material such as stainless steel, aluminum, platinum, gold, indium tin oxide, carbon, or silicon. Further, even if the nozzle material is an insulating material, electrospinning can be performed by installing an electrode in the nozzle.
Moreover, it is preferable that the diameter of a nozzle exists in the range of 10 micrometers-2 mm. If the nozzle diameter is larger than 2 mm, a low-viscosity spinning solution cannot be retained, which is not preferable. If the diameter of the nozzle is smaller than 10 μm, the spinning solution with high viscosity is clogged, which is not preferable.
Further, the discharge port is not limited to the hole shape, and includes, for example, a slit shape, a triangular shape, a double nozzle shape, and the like.

Moreover, as a material of a main electrode, an auxiliary electrode, and a leg part, it is preferable that they are electroconductive materials or semiconductor materials, such as stainless steel, aluminum, platinum, gold | metal | money, indium tin oxide, carbon, and silicon.
Further, the shape of the main electrode is preferably a rectangular plate, but is not limited thereto. The shape of the auxiliary electrode is preferably an annular shape, but may be an elliptical ring shape, a triangular shape, a square shape, a polygonal shape such as a pentagonal shape, or a shape in which two or more ladders or rods are arranged in parallel. Also good. The shape of the leg is preferably a rod, but is not limited to this. Moreover, the leg part should just be at least 1 piece, and multiple may be sufficient as it.

  When the auxiliary electrode is annular, the inner diameter of the ring is preferably in the range of 1 mm to 20 cm. If the inner diameter of the ring is larger than 20 cm, a sheet is not formed in the auxiliary electrode (ring), which is not preferable. If the inner diameter of the ring is smaller than 1 mm, it becomes difficult to handle the sheet, which is not preferable.

  The distance between the main electrode and the auxiliary electrode is preferably in the range of 0.5 to 40 cm. If the distance between the main electrode and the auxiliary electrode is larger than 40 cm, it is not preferable because sufficient electric field strength for the main electrode to be a fiber target cannot be obtained. If the distance between the main electrode and the auxiliary electrode is smaller than 0.5 cm, a part of the spun fiber adheres to the main electrode, which is not preferable.

The distance between the nozzle and the auxiliary electrode is preferably in the range of 10 to 500 mm. If the distance between the nozzle and the auxiliary electrode is larger than 500 mm, it is not preferable because the electric field strength necessary for electrospinning may not be obtained. If the distance between the nozzle and the auxiliary electrode is less than 10 mm, it is not preferable because corona discharge occurs between the nozzle and the auxiliary electrode.
The spinning voltage is preferably in the range of 2 to 160 kV. A spinning voltage greater than 160 kV is not preferable because the spinning state of the spinning solution becomes unstable due to the influence of corona discharge. If the spinning voltage is less than 2 kV, the electric field strength necessary for electrospinning cannot be obtained.

  The spinning humidity is preferably in the range of 0 to 70 relative%. When the spinning humidity is higher than 70 relative%, there is a possibility that induction of electric charge necessary for electrospinning does not occur at the nozzle tip, which is not preferable.

  The spinning temperature is preferably in the range of 5 to 50 ° C. A spinning temperature higher than 50 ° C. is not preferable because the solvent of the spinning solution may evaporate. If the spinning temperature is lower than 5 ° C., the solvent of the spinning solution may be solidified, which is not preferable.

  The spinning material is preferably a single type or a combination of two or more types of polymer electrolytes. A polyelectrolyte is a polymer compound having many charged groups. As the charged group, a negatively charged group such as a carboxyl group, a phosphoric acid group, and a sulfonic acid group, a positively charged group such as an amino group, a pyridyl group, an imidazole group, a quaternary ammonium group, a quaternary pyridinium base, and a quaternary imidazole group, Any one type selected from amphoteric charged groups such as a betaine group, a phosphatidylcholine group, and an amino acid group, or a combination of any two or more types can be adopted.

  Specific examples of the polymer electrolyte include copolymers of perfluorosulfonic acid and polytetrafluoroethylene (for example, Nafion (registered trademark)), polystyrene sulfonic acid and copolymers thereof, sulfonated polysulfone, and sulfonated polyethersulfone. , Sulfonated polyetheretherketone, cellulose sulfate, carboxymethylcellulose, polyacrylic acid, polyvinylpyridine and its quaternized product, polyvinylbenzyltrimethylammonium, polyallylamine, polyethyleneimine and its quaternized product, 2-methacryloyloxyethyl phosphorylcholine alone Polymers and copolymers, blends of these polymers, and the like can be mentioned, but the invention is not particularly limited thereto.

  Further, the solvent for the spinning material is not particularly limited as long as it dissolves the polymer electrolyte, but protic polar solvents such as water, methanol, ethanol, 1-propyl alcohol, 2-propyl alcohol, butanol, acetic acid, formic acid and the like. , Aprotic polar solvents such as acetone, methyl ethyl ketone, acetonitrile, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, hexane, cyclohexane, cyclohexanone, dichloromethane, dichloroethane, trichloroethane , Chloroform, trichloroethylene, benzene, ethylbenzene, xylene, toluene, diethyl ether, 1,4-dioxane, methyl acetate, ethyl acetate, tetrahydrofuran, methylene chloride, etc. Any one selected from the medium or the like, or it is preferable that any two or more thereof.

  Moreover, it is preferable that the density | concentration of a spinning material exists in the range of 0.1-50 mass%. The concentration of the spinning material is more preferably in the range of 5 to 20% by mass. If the concentration of the spinning material is larger than 50% by mass, it is not preferable because the accumulation of electric charges is hindered due to an increase in solution electrical conductivity and spraying may not occur even when a voltage is applied. When the concentration of the spinning material is lower than 0.1% by mass, it is difficult to form a uniform fiber structure, which is not preferable.

  In addition to the spinning material, the additive is preferably any one selected from polyvinyl alcohol, polyethylene oxide, polyvinyl pyrrolidone, polyhydroxyethyl methacrylate, polyacrylamide and the like, or any combination of two or more.

  The concentration of the additive is preferably in the range of 0.1 to 50% by mass with respect to the spinning material. When the concentration of the additive is 0.1% by mass or more, there is an advantage that the spinnability is improved by the effect of the additive. There exists an advantage that the ratio of the polymer electrolyte contained in the produced fiber can be enlarged as the density | concentration of an additive is 50 mass% or less.

  The supply flow rate of the spinning solution is preferably in the range of 1 to 500 μL / min. When the supply flow rate of the spinning solution is 1 μL / min or more, there is an advantage that a stable spray state can be maintained for a long time without insufficient solution supply at the nozzle tip. If the supply flow rate of the spinning solution is 500 μL / min or less, there is an advantage that a stable spray state without dripping from the nozzle tip can be maintained for a long time.

  Moreover, it is preferable that the average diameter of a fiber exists in the range of 5 nm-50 micrometers. When the average fiber diameter is 50 μm or less, an effect of increasing the specific surface area of the polymer electrolyte fiber and the polymer electrolyte fiber assembly can be expected. This effect becomes more prominent as the average fiber diameter decreases. When the fiber diameter is nano-order, the mechanical strength of one fiber is not sufficient and handling becomes difficult, so the average fiber diameter is preferably 5 nm or more, and more preferably 50 nm or more.

  The thickness of the fiber accumulation sheet is preferably 1 μm or more, and more preferably 5 μm or more. There exists an advantage that the function derived from a fiber material is expressed as the thickness of a fiber accumulation sheet is 1 micrometer or more. There exists an advantage that the stable self-supporting film | membrane is obtained as the thickness of a fiber integration sheet is 5 micrometers or more.

  In a sheet-like material composed of ultrafine fibers containing an electrolyte, improvement of functions such as ion exchange ability and electric conductivity of the electrolyte is expected depending on the specific surface area of the ultrafine fibers. Such materials are used for ion exchange filters, adsorption filters, and catalyst-carrying sheets. In addition, small molecules and polymer electrolytes are widely used as dispersants for one-dimensional nanomaterials such as nanoparticles, nanotubes, nanorods, and nanowires made of organic, inorganic, and metal materials. It is also possible to uniformly disperse the nanomaterial in the material. Nanofiber sheets obtained by composites of nanomaterials are used for conductive sheets, electromagnetic wave absorbing sheets, flexible electrodes, sensor substrates, and light emitting sheets.

  Further, the present invention is not limited to the embodiment for carrying out the invention described above, and various other configurations can be adopted without departing from the gist of the present invention.

  Next, specific examples of the present invention will be described. However, it goes without saying that the present invention is not limited to these examples.

[Example 1] (Effect of auxiliary electrode)
<Preparation of spinning solution>
Commercially available 20% by mass Nafion (registered trademark) solution (DE2021, manufactured by Wako Pure Chemical Industries, Ltd., solvent: 34% by mass water and 44% by mass 1-propanol) and polyvinyl alcohol (PVA, manufactured by Wako Pure Chemical Industries, average polymerization degree 1500) and ion exchange. A spinning solution was prepared by adding water. In this solution, the electrolyte (Nafion (registered trademark)) concentration is 7 mass%, and the PVA concentration is 3 mass%. Nafion (registered trademark) is a perfluorosulfonic acid and polytetrafluoroethylene copolymer, and is a fluorine-based polymer electrolyte having a sulfonic acid group, which is a strong electrolyte, as a charged group. Since it is a polymer electrolyte excellent in chemical stability and proton conductivity, it is used as an ion exchange membrane, an ion exchange resin, an electrolyte membrane for fuel cells, a sensor material, and a catalyst.

<Production of electrolyte fiber>
An apparatus as shown in FIG. 1 was used for the electrospinning method. The apparatus includes a DC high-voltage stabilized power supply 1 (manufactured by Pulse Electronics Co., Ltd., HDV-20K) and a syringe pump 2 (manufactured by Minato Concept, MCIP-III). The sample solution is placed in a glass syringe 4 having a capacity of 1 mL, to which a stainless steel nozzle 3 having an inner diameter of 0.5 mm is attached, and this syringe 4 is attached to the syringe pump 2. Then, an aluminum ring-shaped auxiliary electrode 6 was placed on an aluminum flat plate-like main electrode 5 via aluminum legs 7. In FIG. 1, the positions of the nozzle 3, the main electrode 5, and the auxiliary electrode 6 are installed in the vertical direction, but the nozzle 3 can also be installed in the lateral direction with respect to the main electrode 5 and the auxiliary electrode 6. . In addition, the auxiliary electrode 6 has a shape of an elliptical ring, a triangle, a quadrangle, a pentagon or the like shown in FIGS. 2A to 2G, and two or more ladders or rods arranged in parallel. It may be a shape or the like. The electrospinning conditions were an applied voltage of 20 kV, a nozzle-main electrode distance of 10 cm, and a syringe solution supply flow rate of 3 μL / min. The distance between the main electrode 5 and the auxiliary electrode 6 is 5 cm, and the inner diameter of the ring of the auxiliary electrode 6 is 6 cm.

<Observation / Measurement Method>
As for the spinning state, the nozzle tip was irradiated with a 250 W metal halide lamp (manufactured by Megilo Proc., LS-M250) and observed using a scattered image. Moreover, the structure of the fiber was observed using a scanning electron microscope (SEM, manufactured by TOPCON, SM-200). Observation was performed under the condition of an acceleration voltage of 10 kV. As an observation sample, a surface of a polymer fiber coated with gold with a thickness of about 5 nm using a fine coater (manufactured by JEOL, JFC-1200) was used. From the obtained secondary electron image, the fiber diameters at arbitrary 200 points on the fiber were measured, and the average fiber diameter was determined.

<Observation and measurement results>
After application of the electric field, continuous spinning of the solution from the tip of the nozzle 3 was confirmed, and the fiber F produced as shown in FIG. 3 was collected in the ring opening of the auxiliary electrode 6. By spinning for several minutes, a sheet with accumulated fibers could be obtained. FIG. 4 shows a secondary electron image of the produced electrolyte nanofiber sheet obtained by SEM observation. The average fiber diameter of the fibers constituting the produced sheet was 131 nm.
By installing an auxiliary electrode having an opening in the counter electrode of the electrospinning apparatus, it was possible to collect the electrolyte nanofibers and to produce a sheet-like material in one step. Here, the formation of an electric field in the vicinity of the ring opening of the auxiliary electrode 6 suppresses the vertical growth of fibers from the counter electrode substrate, and the sheet can be formed by collecting and accumulating fibers in the opening of the auxiliary electrode 6. it is conceivable that.

[Comparative Example 1]
For comparison, electrospinning was performed with the apparatus of FIG. 1 using only the main electrode 5 without using the auxiliary electrode 6. The spinning solution used for the production of the electrolyte fiber and the production conditions are the same as in Example 1. In this case, as shown in the photograph of the state of collection only by the main electrode 5 in FIG. 5, the fibers grow vertically from the main electrode under the influence of the electric lines of force between the nozzle 3 and the main electrode 5. A sheet-like material could not be produced.

[Comparative Example 2]
For comparison, electrospinning was performed with the apparatus of FIG. 1 using only the auxiliary electrode 6 without using the main electrode 5 of FIG. The spinning solution used for the production of the electrolyte fiber and the production conditions are the same as in Example 1. In this case, as shown in the photograph of the state of collection only by the auxiliary electrode 6 in FIG. 6, the fiber is affected by the electric lines of force between the nozzle 3 and the auxiliary electrode 6 and from the auxiliary electrode 6 toward the nozzle 3. The sheet-like material could not be produced because it grew vertically.

1. DC high-voltage stabilized power supply, 2. Syringe pump, 3 ... Nozzle, 4. Syringe, 5. Main electrode, 6. Auxiliary electrode, 7 ... Leg

Claims (3)

An electrospinning method in which an electric field is formed between a nozzle and a main electrode, and a spinning solution is sprayed from the nozzle toward the main electrode to perform spinning.
An auxiliary electrode is disposed on the nozzle side with respect to the main electrode and electrically connected to the main electrode,
The spinning solution is sprayed and spun from the nozzle toward the auxiliary electrode ,
The auxiliary electrode has an opening,
The fiber produced by spinning is collected in the opening,
An electrospinning method characterized by the above. In an electrospinning apparatus for spinning by spinning a spinning solution in an electric field,
A nozzle for spraying the spinning solution;
A main electrode for forming an electric field between the nozzle,
Have a, an auxiliary electrode to which the are spaced to the nozzle side is connected the main electrode and electrically to said main electrodes,
The auxiliary electrode has an opening,
The fiber produced by spinning is collected in the opening,
An electrospinning apparatus characterized by that. The auxiliary electrode has an annular main body that is spaced apart from the main electrode on the nozzle side, and extends from the main body toward the main electrode and is electrically connected to the main electrode. Legs
The electrospinning apparatus according to claim 2, comprising:

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