JP2008190055A - Electrospinning apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrospinning apparatus capable of remarkably improving the production efficiency of fibers and significantly improving the weight distribution of a resultant web, to provide an electrospinning method and to provide an aggregate of nano-fibers obtained therefrom. <P>SOLUTION: The electrospinning apparatus 1 is designed to spin a charged spinning solution into an atmosphere in which an intense electric field is formed by applying a large potential difference between a spinning head 2 for carrying out spinning of the fibers and a collector 4 for collecting the fibers spun therefrom and form the aggregate composed of the ultra-fine fibers on the collector. The electrospinning apparatus is equipped with an injection hole 21 for extending the width of the spinning solution and injecting the spinning solution into the form of a thin film, a tilted surface 22 for making the spinning solution injected from the injection hole flow down in the form of the thin film and the collector 4 provided parallel to and opposite to the tilted surface in the direction vertically extended from the tilted surface. Furthermore, in the electrospinning apparatus, the ultra-fine fibers are spun from the spinning solution flowing down on the tilted surface and collected on the collector. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrospinning apparatus for producing a fiber assembly made of ultrafine fibers (particularly, so-called “nanofibers”) by electrospinning.

  Recently, a spinning technique called electrospinning for obtaining a web composed of an assembly of ultrafine fibers has attracted attention. This spinning technology spins a charged spinning solution into an atmosphere where an electrostatic field is formed and collects it as a fiber assembly, thereby creating a web with a fiber diameter of submicron order or micron order. In recent years, it has become possible to obtain a fiber assembly having a fiber diameter of nanometer order.

  Here, the electrospinning will be briefly described. As described in Non-Patent Document 1 and the like, in electrospinning, spinning is performed using a high voltage. For this reason, charges are induced and accumulated on the surface of the spinning solution by a high voltage. The charges repel each other, and the repulsive force opposes the surface tension of the spinning solution. When the electric field force exceeds the critical value of the surface tension, the repulsive force of the electric charge overcomes the surface tension, and a jet of charged spinning solution is ejected.

  Since the jet composed of the spinning solution thus ejected has a large surface area compared to its volume, the solvent is efficiently evaporated. Further, since the charge density is increased by decreasing the volume, the repulsive force of the charged spinning solution is increased, and the jet liquid is further divided into thinner jets. Through such a process, a fiber assembly made of uniform filaments (so-called “nanofibers”) having a single fiber diameter (filament diameter) of several tens to several hundreds of nanometers is collected as a web collector (collecting means). ) Finally collected on top.

  It is said that this electrospinning first appeared in US Pat. No. 1975504 (Patent Document 1). In addition, this electrospinning is a spinning method that has been used for a long time and has been called by various names such as “electrostatic field spinning”, “electrostatic spinning”, or “charge-induced spinning”. Therefore, in Japan, for example, the following Patent Documents 2 to 9 propose various application techniques.

  Thus, although the history of electrospinning is old, it has the big problem that the production speed of the obtained web is slow. For this reason, since a web cannot be manufactured on an industrial scale, it has not been used as an industrial scale spinning method until recently.

  However, electrospinning using this principle has attracted a great deal of attention recently because various types of polymers such as polymer melts and polymer solutions can be applied. This is because it has been reported that it is also possible to produce webs made of fibers having a diameter of nm (nanometers).

  For example, webs manufactured by electrospinning have been found to be applicable as materials for artificial blood vessels, artificial organs and the like because of their characteristics, and their application to medical and biotechnology has begun to be studied energetically. Also, in the United States in the early 1990s, it was taken up as military research for producing gas filters for biological weapons, and it has been put into practical use as a special air filter for gas turbines and automobiles.

  As explained above, the production of webs by electrospinning has great potential in various fields, but the poor production efficiency due to the slow production speed still remains a big problem. Yes. However, in order to solve this problem, an attempt was made to improve productivity by providing a number of nozzles for forming fibers from the spinning solution in the spinning head and spinning the fibers simultaneously from these nozzles. Has also been made.

  However, in a spinning technique using an electrostatic field such as electrospinning, when a large number of nozzles are provided, there is a problem that electric field interference occurs between the nozzles. Therefore, as an attempt to overcome this drawback, as seen in Patent Document 16 and Patent Document 17, etc., a flat plate electrode is provided between the spinning head and the collector that collects the spun fibers, or scanning is performed. It has been proposed to provide an electrode or an electrostatic quadrupole lens. It has also been proposed to improve the processing speed by using a charge distribution plate in the middle of a large number of arranged nozzles. Certainly, according to these conventional techniques, it is possible to prevent a situation in which fibers (filaments) having the same charge repel each other due to their repulsive force and spread.

  However, in the center where a large number of nozzles are arranged side by side, the influence of the electric fields of adjacent nozzles interfering with each other increases, the amount of fibers to be spun decreases, and in some cases, no fibers are spun at all. Also occurs. On the other hand, at the end portion where the number of nozzles is small, the influence of the electric field received from the adjacent nozzle is reduced, causing a situation where a large amount of fiber is spun on the contrary to the central portion. . Then, as a matter of course, in terms of the weight distribution in the width direction of the obtained web, the weight per unit area becomes small, and the weight per unit area increases toward the end part.

  However, in the prior art, in order to improve the productivity of the web, more nozzles are inevitably provided, and therefore the apparatus size becomes extremely large. In addition, with such a technique, the above-described deterioration of the spot weight on the obtained web becomes more remarkable. Therefore, the conventional electrospinning does not eliminate the uneven spots that occur when trying to improve the production speed, and as a result, the goal of establishing a web production method with high production efficiency has still reached a satisfactory level. There is no current situation.

U.S. Pat. No. 1975504 Japanese Examined Patent Publication No. 44-21817 Japanese Patent Publication No.53-28548 Japanese Patent Publication No.59-12781 Japanese Patent Publication No.62-118661 Japanese Patent Publication No. 63-543 JP-A-47-1943 JP-T 56-501325 JP 59-204957 A U.S. Pat.No. 4,044,404 U.S. Pat. No. 4,323,525 U.S. Pat. No. 4,552,707 U.S. Pat. No. 4,842,505 U.S. Pat. No. 4,904,272 US Pat. No. 5,866,217 Special Table 2002-201559 JP 2005-534828 gazette Fong et al., Polymer 1999, 40, 4585.

  In view of the problems related to the conventional electrospinning technique described above, the problem to be solved by the present invention is that the production efficiency of spinning a large number of fibers by standing a large number of nozzles as in the prior art is poor. Instead of technology, it is an object of the present invention to provide an electrospinning apparatus that can drastically improve the production efficiency of fibers and that can greatly improve the distribution of the weight of the resulting fiber aggregate.

  As the present invention for achieving the above object, an electrospinning apparatus according to the following (1) to (8) is provided.

(1) Extra fine fibers are produced by spinning a charged spinning solution in an atmosphere in which a strong electric field is formed by applying a large potential difference between a spinning head for spinning fibers and a collector for collecting the spun fibers. In an electrospinning apparatus for forming an assembly comprising:
A discharge hole for widening and discharging the spinning solution in a thin film shape, an inclined surface for allowing the spinning solution discharged from the discharge hole to flow down in a thin film shape, and the inclination in a direction extending perpendicularly to the inclined surface An electrospinning apparatus comprising: a collector provided in parallel to and opposite to the surface, wherein ultrafine fibers are spun from a spinning solution flowing down the inclined surface and collected on the collector.
(2) The electrospinning device according to (1), wherein a number of tapered protrusions that are tapered in a direction in which the collector extends are formed on the inclined surface.
(3) The electrospinning device according to (2), wherein the electrospinning device according to (2) has a large number of depressions formed on the inclined surface, and the tapered protrusions are provided in the depressions.
(4) The electrospinning device according to any one of (1) to (3), wherein a tip portion of the tapered protrusion has a needle shape.
(5) The electrospinning device according to any one of (1) to (4), further comprising a high-voltage power supply for applying a charge to the spinning solution before being supplied to the inclined surface.
(6) The electrospinning device according to any one of (1) to (5), wherein a high voltage power source for imparting electric charge to a spinning solution is connected to the tapered protrusions.
(7) The discharge hole stores a spinning chamber in which the spinning solution is stored, a slit channel that flows the spinning solution flowing out from the storage chamber in a thin film shape while being laterally widened, and the spinning solution stored in the storage chamber The electrospinning device according to any one of (1) to (6), further including a back pressure generating member and a pressure equalizing member provided on the slit channel.
(8) The electrospinning device according to any one of (1) to (7), wherein the discharge holes are formed of a group of pores arranged in a horizontal row in a horizontal direction along the width direction of the inclined surface.

  According to the present invention described above, the spinning solution can be discharged from the discharge holes and supplied uniformly to the inclined surface, and the fibers can be spun simultaneously from the inclined surface. Moreover, unlike the prior art, since there are not many tapered nozzles that form a strong electric field, mutual interference between the strong electric fields of the nozzles can be suppressed.

  Therefore, compared with the production of a web (fiber assembly) by a conventional electrospinning apparatus, the production efficiency of nanofiber aggregates having a form such as a nonwoven web obtained by the electrospinning apparatus of the present invention is dramatically improved. be able to.

  Moreover, in the electrospinning apparatus of the present invention, it is possible to suppress mutual interference of strong electric fields between the nozzles as in the prior art. For this reason, the basis weight distribution of the aggregate composed of the obtained nanofibers can be greatly improved.

  The “polymeric substance” that can be used for electrospinning of the present invention includes polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyacrylonitrile-methacrylate copolymer, polymethyl methacrylate, polychlorinated chloride. Vinyl, polyvinylidene chloride-acrylate copolymer, nylon, such as polyethylene, polypropylene, nylon 12, nylon-4, 6, aramid, polybenzimidazole, polyvinyl alcohol, cellulose, cellulose acetate, cellulose acetate butyrate, polyvinylpyrrolidone- Vinyl acetate, poly (bis- (2- (2-methoxy-ethoxyethoxy)) phosphazene), polypropylene oxide, polyethyleneimide, polysuccinic acid ethylene, polyaniline, poly Tylene sulfide, polyoxymethylene-oligo-oxyethylene, SBS copolymer, polyhydroxybutyric acid, polyvinyl acetate, polyethylene terephthalate, polyethylene oxide, collagen, polylactic acid, polyglycolic acid, poly D, L-lactic acid-glycolic acid co Polymers, polyarylate, polypropylene fumarate, biodegradable polymers such as polycaprolactone, biopolymers such as polypeptides and proteins, various types that can be dissolved in melts or suitable solvents such as pitch systems such as coal tar pitch and petroleum pitch New polymers are applicable. In addition, it is also possible to mix and use an emulsion, organic or inorganic powder in the polymer.

  Further, a “spinning solution” is produced using a “volatile solvent” as a solvent for dissolving the “polymer substance”, and the “volatile solvent” is selected from the following group (a) having high volatility. It is preferable to use a mixed solvent of at least one of the above solvents and at least one solvent selected from the following group (b), which is relatively low in volatility.

  Here, as the solvent of the group (a) having high volatility, acetone, chloroform, ethanol, isopropanol, methanol, toluene, tetrahydrofuran, water, benzene, benzyl alcohol, 1,4-dioxane, propanol, carbon tetrachloride, Examples include cyclohexane, cyclohexanone, methylene chloride, phenol, pyridine, trichloroethane, and acetic acid.

  Further, as the solvent of the group (b) having relatively low volatility, N, N-dimethylformamide, dimethyl sulfoxide, N, N-dimethylacetamide, 1-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, Dimethyl carbonate, acetonitrile, N-methylmorpholine-N-oxide, butylene carbonate, 1,4-butyrolactone, diethyl carbonate, diethyl ether, 1,2-dimethoxyethane, 1,3-dimethyl-2-imidazolidinone, 1, Examples include 3-dioxolane, ethyl methyl carbonate, methyl formate, 3-methyl oxazolidine-2-one, methyl propionate, 2-methyl tetrahydrofuran, and sulfolane.

  The viscosity of the spinning solution in which the “polymeric substance” used in the present invention is dissolved in the “solvent” affects the fiber diameter of the obtained fiber. In general, the fiber diameter becomes smaller if the viscosity is low, and thicker if the viscosity is high. . Therefore, the viscosity of the spinning solution is preferably 1 cps to 10000 cps, and more preferably 10 cps to 1000 cps. If the viscosity is higher than this, it will be difficult to obtain fibers efficiently by electrospinning, and the productivity will be extremely reduced, and it will be difficult to obtain fine fibers. Conversely, if the viscosity is too low, the spinning solution Flow control becomes difficult.

  In electrospinning, the repulsive force of electric charges overcomes the surface tension of the spinning solution, so the surface tension of the spinning solution affects the fiber diameter of the resulting fiber, and generally the fiber diameter becomes smaller if the surface tension is low. If it is high, it will be thick. In addition, if the surface tension of the spinning solution is too large, the electrospin phenomenon is difficult to occur and the fiber diameter is increased, and liquid balls are scattered. Similarly, it is preferably 60 dynes or less, and most preferably 50 dynes or less.

In the present invention, electrospinning is performed using the spinning solution described above. Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic apparatus configuration diagram schematically showing one embodiment of the electrospinning apparatus of the present invention.

  In FIG. 1, reference numeral 1 is an electrospinning apparatus. The electrospinning apparatus 1 includes a spinning head denoted by reference numeral 2, a high-voltage power source denoted by reference numeral 3, a collector denoted by reference numeral 4, a storage container denoted by reference numeral 5, a metering supply apparatus denoted by reference numeral 6, and a spinning chamber denoted by reference numeral 7. , An exhaust device of reference numeral 8, an intake device of reference numeral 9, a ground terminal of reference numeral 10, a recovery liquid recovery container of reference numeral 11, a recovery liquid recovery pipe of reference numeral 12, and a supply of spinning liquid of reference numeral 13 It includes a pipe, a base material unwinding device indicated by reference numeral 15, a winding device indicated by reference numeral 16, and the like. Reference symbol B indicates a base material, reference symbol F indicates a spun fiber, and reference symbol P indicates a spinning solution.

  In this case, the high-voltage power source 3 includes a first high-voltage power source 31 and a second high-voltage power source 32. At this time, the first high-voltage power supply 31 is used to form a strong electrostatic field in the spinning region between the spinning head 2 and the collector 4, and the second high-voltage power supply 32 is applied to the spinning solution P in a predetermined amount. It is used to give the electric charge.

  The first high-voltage power supply 31 and the second high-voltage power supply 32 may be shared by branching electrodes from one high-voltage power supply 3. However, even if the common high-voltage power supply 3 is used, it is not necessary to make the applied potential difference the same between the first high-voltage power supply 31 and the second high-voltage power supply 32, and it goes without saying that the applied potential difference can be made different. Yes.

  1 includes an exhaust hood indicated by reference numeral 81, an exhaust pipe indicated by reference numeral 82, a flow rate adjusting device indicated by reference numeral 83, a gas suction means indicated by reference numeral 84, and a solvent removing apparatus indicated by reference numeral 85. Consists of including. Further, the intake device 9 includes a filter denoted by reference numeral 91, an intake hole denoted by reference numeral 92, and the like.

  The electrospinning apparatus 1 according to the present invention configured as described above has a spinning head 2 formed with an inclined surface 22 as shown in the figure. The stored spinning solution P is supplied while being continuously metered by the metering device 6. Examples of the metering device 6 used at this time include devices having a metering function such as a gear pump, a syringe pump, and a tube pump.

  In FIG. 1, one storage container 5 and one metering supply device 6 are shown, but a plurality of storage containers 5 and metering supply devices 6 can also be used. For example, different polymer substances are stored in a plurality of storage containers 5 and mixed by using a stationary kneader or the like in a flow path in the middle of transfer, or a plurality of spinning heads 2 are provided to each spinning. It is also possible to manufacture a fiber assembly by supplying different polymer substances for each head 2.

  At this time, a positive electrode from the DC high-voltage power supply 3 is connected to the inclined surface 22 of the spinning head 2, whereby a positive high potential is applied to the inclined surface 22. On the other hand, the collector 4 on the side for collecting the fibers F spun from the inclined surface 22 of the spinning head 2 is grounded (grounded) via the grounding terminal 10. Therefore, as a matter of course, the potential of the collector 4 is the same as that of the ground terminal 10 due to grounding, that is, 0V.

  In this way, a large potential difference is generated between the inclined surface 22 of the spinning head 2 and the collector 4, thereby forming a strong electrostatic field in the spinning region of the fiber F. In the embodiment illustrated in FIG. 1, the collector 4 is grounded in order to apply a large potential difference between the inclined surface 22 of the spinning head 2 and the collector 4. Alternatively, a voltage having a negative cathodicity (−) may be applied to the collector 4 with respect to the inclined surface 22 having.

  In the electrostatic field described above, the spinning solution P supplied to the spinning head 2 while being continuously metered by the metering and feeding device 6 is an electrode provided in the discharge hole 21 portion in advance from the second high-voltage power source 32, Naturally, positive charges are applied to the surface by the positive voltage applied by the electrode (not shown) provided in the spinning solution P and / or the electrode provided on the inclined surface 22 from the first high-voltage power supply 31. Is induced and accumulated.

  In this way, the positive charges on the spinning solution P repel each other due to repulsive force acting between the same type of charges, and the repulsive force reaches a level until it counters the surface tension of the spinning solution P. When the repulsive force exceeds the critical value of the surface tension, the repulsive force of the spinning liquid P overcomes the surface tension, and the charged spinning liquid P is jetted from the surface of the spinning liquid P.

  Thus, even if the initial jet ejected from the spinning solution P has a large diameter in the initial stage, the solvent that dissolves the polymer substance volatilizes abruptly, so the diameter also decreases abruptly. Then, the jetted jet has a surface area that is geometrically larger than its volume, and the solvent in which the polymer substance is dissolved evaporates very efficiently. At the same time, the charge density carried by the jet itself becomes higher due to the rapid decrease in the volume of the jet.

  Then, the repulsive force in the jet increases more rapidly due to the action of the charge having increased density, and further splits into thinner jets. The polymer substance constituting the jet finally undergoes such a re-fission process of the jet, so that the uniform filament F having a single fiber diameter (filament diameter) of several tens to several hundreds of nanometers (so-called “ A fiber assembly composed of “nanofibers” is formed and collected on the collector 4.

  In the present invention, the above-mentioned “polymeric substance” used for producing a web composed of fiber aggregates is 5 μS / cm to 500 mS / cm (the measurement unit “S” described here represents “Siemens”). ), Preferably having a conductivity of 5 μS / cm to 50 mS / cm. By using a polymer substance having an electric conductivity in such a range, the electric field concentration at the tip of a jet formed by overcoming the surface tension of the spinning liquid P and abruptly spun up is increased, It is possible to obtain nanofibers F split into a good shape, and the production speed is improved.

  This is because, in the electrospinning technique, when the jet of the spinning solution P containing a rapidly spun polymer material is split in the process of forming the fiber F, the conductivity of the jet is less than 5 μS / cm. If there is, the jet tip potential drops. In this case, the concentration of the electric field strength on the jet becomes weak, and there is a possibility that the splitting into the nanofibers F does not occur well.

  On the other hand, if the electrical conductivity exceeds 500 mS / cm, the electrospinning phenomenon tends to become unstable. Moreover, when the conductivity increases, the concentration of charges generated on the surface of the jet is not buffered hydrodynamically, but charges are dispersed in the jet because of its high electrical conductivity. If it does so, the phenomenon which a jet breaks up will become difficult to occur, and the target nanofiber F cannot be obtained.

  In this electrospinning, in the process of forming the fiber F as described above, the solvent that dissolves the polymer substance to be fiberized is rapidly volatilized. For this reason, an air conditioning means for providing a spinning chamber 7 surrounding the spinning region between the spinning head 2 and the collector 4 and air-conditioning the spinning chamber 7 so that the volatilized solvent does not diffuse to the surroundings and deteriorate the working environment. (In the embodiment shown in FIG. 1, the exhaust device 8 and the intake device 9 correspond). Further, such air conditioning is desirably attached to the spinning chamber 7 in order to keep the solvent concentration, temperature, humidity, etc. in the spinning chamber 7 constant, and thus to maintain stable spinning conditions at all times. .

  At this time, it is preferable to remove the solvent volatilized in the spinning chamber 7 by attaching an exhaust device 8 to the spinning chamber 7 and sucking air in the spinning chamber 7. In order to maintain and adjust the material balance with the air containing the solvent to be discharged, it is preferable to provide an intake device 9 including, for example, an intake hole, a blower, and a fan. In the embodiment of FIG. 1, as such an intake device 9, an intake hole 92 provided with a filter 91 is illustrated.

  At this time, the temperature of the air sucked into the spinning chamber 7 through the air intake device 9 is in the range of 5 ° C. to 80 ° C. in consideration of the volatility of the solvent and the accumulation degree of the fiber group (filament group) F to be spun. It is preferable to adjust with. Therefore, the intake device 9 may be provided with a heater (not shown) in the middle of the intake pipe as necessary. In addition, the discharge wind speed of the air containing the solvent can be adjusted in the range of 0.1 m / s to 5 m / s in the spinning region so that the jet of the spinning liquid P to be spun is not adversely affected. desirable.

  As described above, the air sucked into the spinning chamber 7 from the air intake device 9 is the solvent-containing air in which the solvent that dissolves the polymer material spun by spinning from the inclined surface 22 of the spinning head 2 is volatilized. It becomes. The solvent-containing air is exhausted out of the spinning chamber 7 by the exhaust device 8. Needless to say, the exhaust device 8 includes gas suction means 84 including, for example, a blower, a fan, a vacuum suction machine, and an ejector in the middle of the exhaust pipe 82.

  In this way, the air containing the solvent sucked by the exhaust device 8 recovers or separates and removes the solvent via the solvent removal device 85 such as a cold trap or a solvent adsorption device, and then in the direction of the arrow shown in the figure. Only solvent free air is released. At this time, the amount of air containing the solvent sucked by the exhaust device 8 is preferably adjusted, for example, by providing a flow control device 83 such as a damper or a flow control valve in the exhaust pipe 82 of the exhaust device 8. .

  As described above, the fiber assembly composed of the nanofiber F according to the present invention is formed. In forming the fiber assembly composed of the nanofiber F, the characteristic of the spinning head 2 is formed. Structure plays a big role. That is, the electrospinning apparatus 1 of the present invention has a great feature in the structure of the spinning head 2. Therefore, the features of the spinning head 2 of the present invention will be described in more detail below with reference to FIG.

  FIG. 2 is an explanatory view (perspective view) for explaining the structure of the spinning head 2 according to the present invention. In FIG. 2, the spinning head 2 includes at least a discharge hole denoted by reference numeral 21 and an inclined surface denoted by reference numeral 22. Further, the discharge hole 21 includes an upper plate of reference numeral 21a, a spacer of reference numeral 21b, a storage chamber of reference numeral 21c, a spinning liquid supply hole of reference numeral 21d, and a base of reference numeral 21e. The In FIG. 2, reference numeral 22 indicates an inclined surface on which the spinning liquid P discharged from the discharge hole 21 flows down. In the present invention, such an inclined surface 22 is formed on the spinning head 2. This is a major feature.

  In FIG. 2, FIG. 2A illustrates an example in which the flow path shape of the discharge portion of the discharge hole 21 through which the spinning solution P is discharged has a slit that extends in the horizontal direction (horizontal direction). In addition, FIG. 2 (b) is provided with a large number of pore groups arranged in parallel in a horizontal row in place of the slit-like channel shape of the discharge hole 21 illustrated in FIG. 2 (a). This is an embodiment of the discharge hole 21 ′. In the present invention, instead of the discharge hole 21, a discharge hole 21 ′ composed of such a hole group can also be used.

  In the spinning head 2 of the electrospinning apparatus 1 of the present invention configured as described above, the present inventors have set the spinning solution P from the discharge hole 21 in a spinning atmosphere in which a strong electrostatic field is formed. The slanted surface 22 was made to flow down as a thin film flow with a positive charge. Then, surprisingly, in the process in which the positively charged spinning solution P flows down the inclined surface 22, a part of the spinning solution P overcomes the surface tension and enters the spinning atmosphere by the action of strong Coulomb force. It has been found that the fiber F is spun. In addition, when the fibers F start to be spun from the spinning solution P flowing down the inclined surface 22, an extremely large number of fibers F are spun one after another from many portions of the spinning solution P flowing down the inclined surface 22 in a thin film shape. I found.

  Such a phenomenon has not been reported in the prior art, and in the prior art, as described in the “Background Art” section of this specification, a large number of nozzle groups are provided in parallel, and the spinning solution is respectively supplied from the tip of each nozzle. A method of discharging P was adopted. However, such a method has a number of disadvantages as described above. Therefore, in the present invention, the inclined surface 22 as described above is used in the present invention in place of the tapered nozzle used as a means for discharging the spinning solution P to the electrostatic field.

  In the embodiment of the spinning head 2 of the present invention illustrated in FIG. 2, the spinning head 2 according to the present invention has a discharge hole 21 having a slit-shaped spinning liquid channel. The “discharge hole” referred to in the present invention is not used for spinning the fiber F from its tip as in the prior art, but simply serves to discharge the spinning solution uniformly.

  As illustrated in FIG. 2, the discharge hole 21 has a slit-like spinning liquid flow path. The spinning liquid flow path includes, for example, an upper plate 21 a and a spacer 21 b for defining a slit gap between the discharge holes 21. The storage chamber 21c stores the spinning solution P, the supply hole 21d for the spinning solution P, and the like. The storage chamber 21c that constitutes a part of the slit-shaped discharge hole 21 is formed by a horizontally long groove-shaped chamber that is provided horizontally across the width direction of the flow surface of the inclined surface 22 through which the spinning solution P flows down. In the bottom, a single or a plurality of supply holes 21d for the spinning solution P are provided.

  In the spinning head 2 configured as described above, the discharge hole 21 is configured so that the spinning solution P can be supplied uniformly in the width direction of the inclined surface 22 and the formation of the liquid film can be made uniform. P is discharged. For this purpose, as the structure of the discharge hole 21, a storage chamber 21c for temporarily storing the spinning liquid P is provided, and a supply hole 21d for the spinning liquid P is opened at the bottom. If it does so, about the flow of the spinning liquid P discharged from the discharge hole 21, the flow in the width direction of the inclined surface 22 can be made uniform. This also makes it possible to make the liquid film of the spinning solution P flowing through both ends and the center of the inclined surface 22 uniform, thereby preventing the liquid film from being formed unevenly. Can also be suppressed.

  In the spinning head 2 of the present invention, as illustrated in the embodiment of FIG. 2, a spacer 21b is provided between the base 21e of the spinning head 2 and the upper plate 21a, so that the spinning liquid P passes therethrough. A slit-like flow path is formed. Therefore, the spinning solution P supplied from the metering supply device 6 (see FIG. 1) such as a gear pump to the spinning head 2 is quantitatively supplied to the supply hole 21d opened at the bottom of the storage chamber 21c while being continuously measured. .

  Subsequently, the spinning solution P thus supplied to the supply hole 21d is discharged from the bottom of the storage chamber 21c through the supply hole 21d, and the width of the storage chamber 21c engraved in the base portion 21e of the spinning head 2 in a groove shape. It stays until it is fully filled in the direction (groove width direction). Then, the spinning solution P filling the storage chamber 21c passes through the slit-like flow path, and is discharged from the discharge port of the discharge hole 21, and finally forms a uniform liquid film over the entire width of the inclined surface 22. It flows down while forming.

  At this time, the slit-like flow path having a narrow gap formed between the base portion 21e of the spinning head 2 and the upper plate 21a widens the flow of the spinning solution P by its capillary action and flows out in the lateral direction uniformly. Thereby, the flow of the spinning liquid P flowing out from the storage chamber 21c is played down uniformly over the entire width of the inclined surface 22. The inclined surface 22 that is the flow lower surface of the spinning solution P may be provided with a fine groove or a fine mesh groove in which the spinning solution P is formed in the flow-down direction as necessary.

  In addition, the slit-shaped flow path having a narrow gap formed between the base 21e of the spinning head 2 and the upper plate 21a may be a flow path having a tapered shape with respect to the discharging direction of the spinning liquid P. Such a tapered shape can be easily formed by giving a taper to the spacer 21b shown in the embodiment of FIG.

  Furthermore, in order to uniformly discharge the flow of the spinning solution P in the width direction of the inclined surface 22, a non-woven fabric filter made of a fine metal wire, a wire mesh filter, or a porous sintered metal is uniformly placed on the slit-like channel portion. It may be provided as a pressure member (not shown). By doing so, a back pressure is generated in the storage chamber 21c, and the spinning liquid P is pushed out from the discharge hole 21 so as to push out the spinning solution P through the pressure equalizing member (not shown). The spinning solution P can be discharged more uniformly from the entire width.

  Here, regarding the slit gap t and slit width W of the discharge hole 21, the viscosity of the spinning liquid P to be used, the discharge amount and discharge pressure, the properties of the spinning liquid P such as the electrical conductivity, or the production amount of the fiber F The optimum range is determined by conditions such as production efficiency. Therefore, it is only necessary to appropriately select and use an optimum value in conformity with these conditions, and it is not necessary to specifically limit the value. However, under normal conditions, the slit gap t is preferably in the range of 0.05 mm to 10 mm, and the slit width W is preferably 1 cm to 100 cm.

  The remaining spinning solution P discharged from the discharge hole 21 and spun from the inclined surface 22 and passed through the inclined surface 22 without being fiberized is recovered. It flows into the container 11. Then, the spinning solution P that has flowed into the recovery container 11 is returned to the storage container that stores the spinning solution P via the recovery pipe 12, and the refluxed spinning liquid P is supplied to the metering supply device 6 via the supply pipe 13. Is supplied again to the spinning head 2.

  As described above, it is ideal to use the spinning solution P that has not been fiberized from the spinning head 2 in a circulating manner. However, if the spinning solution P is repeatedly used, the solvent in the spinning solution P in which the polymer substance is dissolved evaporates and becomes insufficient. Then, due to this influence, the ratio of the component composition of the spinning solution P may change. Therefore, although not shown in FIG. 1, it is preferable that the spinning solution P once supplied to the spinning head 2 and recovered without being fiberized is recovered in a container different from the storage container 6. The component composition of the collected spinning solution P is preferably prepared again and returned to the storage container 6.

  The inclined surface 22 formed on the spinning head 2 of the present invention plays a role of allowing the spinning solution P supplied thereon to flow down in the form of a thin film. Therefore, as long as the spinning solution P has a function of flowing down, the surface shape may be a flat surface having a zero curvature or a curved surface having a certain degree of curvature. In short, the electrospinning apparatus 1 of the present invention is characterized by utilizing the fact that the fiber spinning phenomenon occurs when the charged spinning solution P is exposed to a strong electrostatic field in the form of a thin film.

  In this way, the spinning head 2 of the present invention forms jets composed of a large number of spinning fluids P by utilizing the entire surface of the spinning fluid P that substantially spreads and flows down on the inclined surface 22 as a thin film. Can be fiberized. In addition, the inclined surface 22 which concerns on this invention has played the role for enabling supply of the spinning liquid P continuously using the inclination.

  As described above, in the electrospinning apparatus 1 of the present invention, a fiber assembly made of nanofibers can be obtained by flowing the spinning solution P charged on the inclined surface 22 in a thin film shape. However, in addition to the embodiment of the electrospinning apparatus 1 that uses such a simple inclined surface 22, an embodiment as described below can be adopted.

  Therefore, other embodiments will be described. The jet of the spinning liquid P formed from the inclined surface 22 of the electrospinning apparatus 1 of the present invention must overcome the surface tension of the spinning liquid P. For this purpose, it is also effective to cause a large charge accumulation (concentration) in a part of the spinning solution P flowing down the inclined surface 22 or to locally reduce the surface tension of the spinning solution P.

Hereinafter, another embodiment using such an action will be described in detail with reference to FIG.
FIG. 4 is an explanatory diagram for explaining an embodiment of the inclined surface 22 according to the present invention. FIG. 4A shows only the inclined surface 22 illustrated in FIG. 1 and FIG. FIG. 4B and FIG. 4C are schematic front sectional views showing other embodiments of the inclined surface 22. In FIG. 4, reference numeral 22a indicates an electrically insulating member, reference numeral 22b indicates a highly conductive member, reference numeral 22c indicates a tapered protrusion, and reference numeral 22d indicates a minute recess (recess).

  In the inclined surface 22 of the present invention configured as in the embodiment shown in FIG. 4, the inclined surface 22 conducts electricity well with an electric insulating member 22a whose portion that contacts the spinning solution P exhibits electric insulation. A sandwich structure with the good conductive member 22b is adopted. In the above-described embodiment, the sandwich structure of the electrically insulating member 22a and the highly conductive member 22b is adopted. However, the present invention is not limited to such a structure, and the electrically insulating member 22a is semiconductive. It may be a member, or a good electrical conductive member.

  At this time, as shown in the figure, the tapered protrusion 22c is implanted in the highly conductive member 22b through a minute recess (recess) 22d provided in the electrical insulating member 22a. At this time, the shape of the tip of the tapered protrusion 22c is not particularly limited as long as it is tapered, but a needle-like shape is particularly preferable. This is because the needle-shaped tip tends to concentrate the electric charge most easily and is suitable for restricting the jet direction of the jet jetted along the tapered protrusion 22c in one direction. Note that the positive high voltage (high potential) applied to the inclined surface 22 is applied via the good conductive member 22b in the embodiment of FIG.

  In the embodiment of the present invention shown in FIG. 4 described above, a large number of tapered protrusions 22c are formed on the surface of the inclined surface 22 provided on the spinning head 2 so as to taper in the direction in which the collector 4 extends. . Therefore, utilizing the property that charges are concentrated at the sharp tip of the tapered protrusion 22c, a strong charge can be locally applied from the tapered protrusion 22c to the spinning solution P existing around the tapered protrusion 22c. As shown in FIG. 4B, the tip of the tapered protrusion 22c may slightly protrude from the upper end surface level of the inclined surface 22, or the upper end surface level of the inclined surface 22 as shown in FIG. 4C. You may make it dent.

  In the present invention, the spinning solution P that stays for a short time in the minute recess 22d provided as needed while flowing down the inclined surface 22 and wets the tapered protrusion 22c by its surface tension is formed on the tapered protrusion 22c. Then, the wetting angle is inevitably increased as compared with the case of being located on a flat plate. As a result, the surface tension is relatively lowered, the surface tension of the spinning liquid P is overcome, and the spinning liquid P is easily detached from the spinning liquid P. As described above, the locally strong charge wets the tapered protrusion 22c. When applied to the liquid P, the spinning liquid P that has become a jet along the tip direction of the tapered protrusion 22c is spun out vigorously.

  At this time, in the present invention, a predetermined amount of charge is applied to the spinning solution P from the second high-voltage power source 32 in advance, in addition to applying the charge to the spinning solution P from the tapered protrusion 22c as described above. Is preferred. In this way, it is not necessary to apply an amount of charge that can overcome the surface tension of the spinning solution P only from the tapered protrusion 22c. That is, if a predetermined amount of charge is applied to the spinning solution P from the second high-voltage power source 32 in advance, the amount of charge applied from the tapered protrusion 22c can be reduced by that amount, and the load on the tapered protrusion 22c can be reduced. Can do.

  In addition, as illustrated in FIGS. 4B and 4C, the micro-indented portion plays a role in favorably wetting the tapered protrusion 22c with the spinning solution P and stagnates around the tapered protrusion 22c for a short time. Thus, it plays a role of accumulating a stronger charge than the other spinning solution P. Therefore, as illustrated in FIGS. 4A and 4B, the inclined surface 22 with which the spinning solution P contacts is preferably a well-known ceramic electrical insulating material commonly used for insulators, On the other hand, the tapered protrusion 22c that imparts an electric charge to the spinning solution P is preferably formed of a metal material having good electrical conductivity.

  In contrast to the electrospinning apparatus 1 of the present invention described above, in the conventional electrospinning apparatus, the spinning solution is discharged from a small hole formed in the nozzle and supplied. For this reason, it is absolutely necessary to secure a space for installing the nozzles and also ensure an interval between the nozzles. Even if the nozzle shape is made as small as possible, there has been a limit that the nozzle shape must be increased due to its structure in order to obtain optimum spinning conditions. Therefore, mutual interference of electric fields occurs between a large number of nozzles provided independently, and it is extremely difficult to eliminate this.

  However, in the electrospinning apparatus 1 of the present invention, a group of small tapered protrusions is provided in place of the conventional nozzle, and the spinning liquid P is not discharged from the small hole drilled in the nozzle, but on the inclined surface 22. Supply by flowing down. Thus, in the present invention, the structure of the spinning head 2 can be extremely simplified because the spinning liquid is not ejected from the small holes formed in the nozzle as in the conventional nozzle.

  In addition, since a structure in which a large number of nozzle groups having a certain size are protruded is not employed, the installation interval s of the tapered protrusions 22c can be further reduced. For example, the installation interval s of the tapered protrusions can be reduced to about 0.1 mm, although it depends on properties such as the viscosity of the spinning liquid P. For this reason, the jet of the spinning solution P can be generated from a very large number of tapered protrusions 22c. Therefore, as a matter of course, the production efficiency of the fiber assembly is also dramatically improved as compared with the conventional electrospinning apparatus.

  As described above, the spinning head 2 of the present invention has an extremely large number of small tapered protrusions 22c formed on the inclined surface 22 without providing a nozzle group having a complicated structure. Since each of the tapered projections 22c has a small shape, the charge capacity of each of the tapered projections 22c itself is much smaller than that of a conventional nozzle. 4C, the tapered protrusion 22c exists at a position retracted from the plane level of the inclined surface 22, so that the interference of the electric field is further reduced. Of course, since the tapered protrusion 22c according to the present invention has a tapered shape, the advantage that a large charge can be concentrated on the tip can be maintained as it is.

  Therefore, a large charge can be locally accumulated in the spinning solution P to be spun as a jet while eliminating the adverse effect of electric field interference caused by the tapered protrusions 22c. Therefore, on the inclined surface 22 according to the present invention, it can be considered that a number of conventional nozzles are in the same state as being arranged in the inclined surface 22 in a form that is extremely small in size. This is not possible with the prior art.

  That is, it can be said that the electrospinning apparatus 1 according to the present invention realizes minimization of the nozzle, which is impossible with the prior art, in consideration of optimum spinning conditions and the like. Thus, the electrospinning apparatus 1 according to the present invention can strongly suppress the mutual interference of the electrostatic field. Therefore, the fiber assembly (web) composed of nanofibers spun from the spinning head 2 of the present invention and collected by the collector 4 is compared with the fiber assembly obtained by the conventional method with many nozzles. Even so, the weight distribution in the width direction is greatly improved, and the productivity is also greatly improved.

  At that time, the inclination angle θ of the inclined surface 22 formed in the spinning head 2 of the present invention includes spinning, such as the viscosity of the spinning liquid P, the flow rate, the strength of the electrostatic field, and the thickness of the spinning liquid P flowing on the surface. What is necessary is just to adjust suitably according to conditions, Therefore, it is not necessary to specifically limit. However, the inclination angle θ is preferably 5 ° to 65 °, more preferably 10 ° to 35 °.

  In general, when the inclination angle θ is less than 5 °, the inclined surface 22 approaches the horizontal plane as much, so that a large number of fibers are produced in the process of flowing down the spinning solution P having a viscosity suitable for electrospinning from the inclined surface 22. The effect of the inclined surface 22 of the present invention that the F is stably spun is eliminated. Conversely, when the inclination angle θ is larger than 65 °, most of the spinning solution P is not spun from the inclined surface 22, and most of the spinning solution P simply flows down the inclined surface 22. . Furthermore, since the inclination angle θ becomes too steep, it becomes difficult to control the film thickness to form a liquid film having a stable thickness on the inclined surface 22, and even to perform electrospinning itself. There is a case.

  As the material of the spinning head 2 of the present invention, the use of a metal material that does not corrode on the contact surface with the spinning solution P and has good conductivity gives the spinning solution P a desirable charge amount. This is preferable. However, the material of the spinning head 2 is not limited to a metal material, and it is possible to use a semi-insulator or an insulator if the electrical conductivity of the spinning liquid P used is high.

  However, in the spinning solution P having a high electrical conductivity, electric charges are difficult to accumulate inside due to the high electrical conductivity, and therefore the concentration of the electric field is alleviated. For this reason, in general, when a spinning solution P having high electrical conductivity is used, it becomes difficult to perform electrospinning. In consideration of this point, in order to widen the range in which the electrical conductivity of the spinning solution P can be adjusted, Those having good conductivity are preferable. For example, as such a material having appropriate conductivity, a material obtained by coating or lining an insulating material such as glass or plastic with a conductive material to give appropriate conductivity can be exemplified.

  Next, the collector 4 on the side for collecting the fibers F spun from the inclined surface 22 of the spinning head 2 described above will be described. As illustrated in FIG. 1, the collector 4 is provided in parallel and opposite to the inclined surface 22 in a direction extending perpendicularly to the inclined surface 22 provided in the spinning head 2. At that time, the voltage difference (potential difference) formed between the spinning head 2 (inclined surface 22) and the collector 4 is preferably 1 kV to 500 kV, more preferably 2 kV to 200 kV, and still more preferably 5 kV to 100 kV. The fiber F obtained by electrospinning generally has a smaller fiber diameter as the applied voltage is higher.

  However, if the voltage difference exceeds 500 kV, a short circuit is likely to occur between the electrodes (between the inclined surface 22 of the spinning head 2 and the collector 4). Further, if the voltage is too high, electric leakage and discharge phenomenon are likely to occur, but insulation for preventing these becomes difficult. On the other hand, when the voltage is less than 1 kV, the electrospinning phenomenon hardly occurs, and the nanofiber F having the target fiber diameter cannot be obtained.

  In the electrospinning apparatus according to the present invention, by changing the distance between the inclined surface 22 formed on the spinning head 2 and the collector 4, the single fiber diameter or fiber length of the fiber F obtained or collected. The form of the network structure formed by entanglement of the fibers F can be changed. That is, the longer the distance, the smaller the fiber diameter, and the shorter, the larger the fiber diameter.

  Furthermore, the dryness of the fiber F is improved by increasing the distance, increasing the spread of the spun jet, increasing the collection range of the fiber F on the collector 4, and promoting the evaporation of the solvent. Can be made. Conversely, when the distance is shortened, the collection area of the fibers F decreases, but the fibers F are collected in a weak dry state, so that the adhesion between the collected fibers F can be improved.

  As described above, in the electrospinning of the present invention, the distance A between the inclined surface 22 and the collector 4 can be arbitrarily adjusted according to the purpose and the form of the fiber assembly to be manufactured. However, the distance A is preferably in the range of 1 cm to 100 cm, more preferably 5 cm to 30 cm, considering the productivity, operability, safety, etc. of the fiber aggregate to be collected.

  In the above description, it has been described that the fiber F spun from the spinning head 2 is directly collected by the collector 4. However, normally, as illustrated in FIG. 1, a base material B such as a conductive thin metal plate is provided on the collector 4, and the fibers F are collected on the base material B. This is preferable.

  However, as illustrated in FIG. 3A, when the fiber assembly 14 collected on the collector 4 can move while sliding on the surface of the collector 4, the collected fiber assembly 14 is predetermined. It is also possible to wind up the fiber assembly 14 while moving it in the direction of the winding device 16 at a speed of. In this winding, in order to easily separate the wound fiber aggregates 14 from each other, a well-known winding method generally used may be a winding method with a release paper. good.

  In this regard, if further spreading is required, in the case of producing a long nonwoven fabric web (fiber assembly), the base material B is removed from the unwinding device 15 to the collector 4 as illustrated in FIG. The substrate B is unwound at a predetermined speed and brought into contact with the collector 4, whereby the base material B is grounded. If it does so, since the electric potential of the base material B will be 0V, the base material B can be newly used as a collector.

  And the fiber assembly which consists of nanofibers F is continuously formed on the base material B which has been unwound from the unwinding device 15 in this way, and the base material B is wound up by the winding device 16, A “long nonwoven web” composed of an assembly of nanofibers can be produced. At this time, as the base material B to be a new collector, a metal non-woven fabric or woven fabric having good conductivity, a thin metal plate, or the like can be used.

1 is a schematic apparatus configuration diagram schematically showing an embodiment of an electrospinning apparatus according to the present invention. 1 is a schematic apparatus configuration diagram schematically showing an embodiment of a spinning head according to the present invention. It is explanatory drawing which illustrated a mode that the fiber assembly collected on the collector was wound up. FIG. 4 is a schematic front sectional view in which the inclined surface 22 illustrated in FIGS. 1 and 2 is taken out and left on a horizontal plane.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Electrospinning apparatus 2: Spinning head 3: High voltage power supply 4: Collector 5: Storage container 6: Measuring supply apparatus 7: Spinning chamber 8: Exhaust apparatus 9: Intake apparatus 10: Grounding terminal 11: Spinning liquid collection container 12: Spinning liquid recovery pipe 13: Spinning liquid supply pipe 14: Fiber assembly 15: Substrate unwinding device 16: Winding device 21: Discharge hole 21a: Upper plate 21b: Spacer 21c: Reserving chamber 21d: Spinning liquid Supply hole 21e: Base 22: Inclined surface 22a: Electrical insulating member 22b: Conductive member 22c: Tapered protrusion 22d: Micro-dent (recess)
81: Exhaust hood 82: Exhaust pipe 83: Flow rate adjusting device 84: Gas suction means 85: Solvent removal device 91: Filter 92: Intake hole B: Base material F: Spinned fiber P: Spinning liquid

Claims (8)

An assembly consisting of ultrafine fibers by spinning a charged spinning solution in an atmosphere in which a strong electric field is formed by applying a large potential difference between the spinning head for spinning the fibers and the collector for collecting the spun fibers. In an electrospinning apparatus for forming a body on the collector,
A discharge hole for widening and discharging the spinning solution in a thin film shape, an inclined surface for allowing the spinning solution discharged from the discharge hole to flow down in a thin film shape, and the inclination in a direction extending perpendicularly to the inclined surface An electrospinning apparatus comprising: a collector provided in parallel to and opposite to the surface, wherein ultrafine fibers are spun from a spinning solution flowing down the inclined surface and collected on the collector.   The electrospinning device according to claim 1, wherein a plurality of tapered protrusions that are tapered in a direction in which the collector extends are formed on the inclined surface.   The electrospinning device according to claim 2, wherein the electrospinning device has a plurality of depressions formed on the inclined surface, and the tapered protrusions are provided in the depressions.   The electrospinning device according to any one of claims 1 to 3, wherein a tip portion of the tapered protrusion has a needle shape.   The electrospinning device according to any one of claims 1 to 4, further comprising a high-voltage power supply that applies a charge to the spinning solution before being supplied to the inclined surface.   The electrospinning device according to any one of claims 1 to 5, wherein a high voltage power source for applying a charge to a spinning solution is connected to the tapered protrusions.   The discharge hole has a storage chamber for storing the spinning solution, a slit channel for flowing the spinning solution flowing out from the storage chamber in a thin film shape while being laterally widened, and a back pressure on the spinning solution stored in the storage chamber. The electrospinning device according to any one of claims 1 to 6, further comprising a pressure equalizing member provided on the slit flow path.   The electrospinning device according to any one of claims 1 to 7, wherein the discharge holes are formed of a group of pores arranged in a horizontal row in a horizontal direction along a width direction of the inclined surface.

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