JP5027554B2 - Method and apparatus for producing uniaxial or multiaxially oriented nanofiber assembly - Google Patents

Description

  The present invention relates to a method and apparatus for producing a uniaxially or multiaxially oriented nanofiber assembly by an electrospinning method, an assembly comprising uniaxially or multiaxially oriented nanofibers produced by the method. And a filter using the integrated body.

  The electrospinning method is a widely known method for producing nanofibers having a single-fiber diameter of nano-order (see, for example, Patent Document 1 and Patent Document 2). The production of nanofibers by electrospinning will be briefly described with reference to FIG. First, a syringe 11 is filled with various biopolymers or polymers (hereinafter, simply referred to as “polymer”) dissolved or melted with a solvent. Then, a DC high voltage of several kV to several tens of kV is applied from a high-voltage DC power supply 13 between a needle-type electrode (not shown) attached to the syringe 11 and a collector electrode 12 for depositing nanofibers. Thus, a strong electric field is generated between the needle-type electrode and the collector electrode. In this environment, when the spinning solution 14 is discharged from the needle-type electrode toward the collector electrode 12, the solvent or the like that has dissolved the polymer is instantaneously evaporated in the electric field, and the polymer is coagulated while coagulating. A nano-order fiber is formed under the gentle conditions of room temperature and atmospheric pressure. At this time, in the case of the polymer solution, there are a portion called a straight jet where the spray goes straight from the nozzle and a portion called a break point where the spray spreads. The longer the straight jet, the easier the fiber structure is formed. It has been reported that when the fiber structure is formed, the droplets are not spread from the break point but are deposited on the substrate so as to draw a spiral. The nanofibers thus formed are deposited on the collector electrode in a state where the fibers are randomly interlaced to obtain a non-woven web. By changing the spraying conditions during electrospraying, nano-micron scale fibers can be formed, and in addition to the fibers, nanoparticles and thin films can be formed. Furthermore, the spinning solution is not limited to the polymer carrier solution, and a polymer / polymer or polymer / inorganic blend solution can also be used. Thus, it is possible to control the laminated structure of the thin film.

  Nanofibers can be expected to exhibit unique functions due to nanostructures. For example, since nanofibers have a much larger surface area than ordinary fibers, in addition to the inherent properties of polymers that conventional fibers have, new functions such as adsorption properties and adhesive properties have emerged. The development of new materials that are not possible can be expected. In addition, it is transparent to visible light, the pore size can be controlled in the nano order, advanced molecular organization is possible, and the living body does not feel nanofiber as a foreign substance and has good biocompatibility. It is done.

  When producing nanofibers by electrospinning, the orientation of the deposited nanofibers cannot be controlled by the conventional method. For this reason, the obtained web can only produce a web in which fibers are randomly interlaced to form a network. For this reason, attempts have been made to control the orientation of the fibers formed in the electrospinning method. For example, in order to obtain uniaxially oriented nanofibers, a method using a collector electrode in which a plurality of conductors having the same potential and a plurality of non-conductors are alternately arranged in a lattice shape (see Patent Document 3) A method in which two plate-like conductive silicon or gold having the same potential by grounding are provided separately (see Non-Patent Document 1), a method using two ring-shaped disks (see Non-Patent Document 2) Etc. have been reported. As a method for orienting nanofibers in a plurality of axes, a method of providing a plurality of electrodes extending radially on an insulating substrate as a collector electrode (see Non-Patent Document 3) has been reported. In addition, Non-Patent Document 1 describes that already formed uniaxially oriented fibers can be layered on each other like a 3D lattice, but multiaxial including direct biaxial orientation by electrospinning. There is no description about the formation of an aligned nanofiber assembly.

JP2002-249966 JP 2004-68161 A JP 2006-283241 A Nano Letters 3, 1677-1171 (2003) Polymer 46, 611-614 (2005) Adv. Mater, 16, No. 4,361-366 (2004)

  As described above, several techniques for orienting nanofibers uniaxially or multiaxially have been reported. However, in the method using a grid-like collector electrode made of a conductor and a nonconductor described in Patent Document 3, The nanofibers are oriented along the conductor on the conductor, and there is a problem that randomly oriented nanofibers are deposited on the non-conductor and the web surface is not uniformly uniaxially oriented. Further, in the method described in Non-Patent Document 1, as a collector electrode, two plate-like conductive silicon or gold having the same potential by grounding are provided apart from each other, the nanofibers are arranged in a direction perpendicular to the electrodes. Although it can be uniaxially oriented, there is a problem that it cannot be said that the orientation state is sufficiently performed. Furthermore, in the method of providing a plurality of radially extending electrodes on an insulating substrate as a collector electrode, a web of nanofibers oriented in a plurality of directions is formed, but the nanofibers are oriented in different directions for each layer. There is a problem that the thickness direction cannot be controlled.

  Accordingly, the present invention provides a method for manufacturing a more strongly uniaxially oriented nanofiber assembly in which the problems in the conventional electrospinning method are improved, and directing and deposition in different directions for each layer by electrospinning. For producing multiaxially oriented nanofiber assemblies comprising laminated nanofibers, devices used to implement these methods, and uniaxially or multiaxially oriented nanofiber assemblies and the assemblies It is to provide a body filter.

  The inventors of the present invention conducted intensive research to solve these problems. As a collector, an insulating plate was used, and two collector electrodes were provided in parallel at both ends thereof, and a potential difference was provided between the two collector electrodes. Specifically, the inventors have found that by providing a voltage difference, it is possible to form a nanofiber assembly having excellent orientation controllability and a multiaxially oriented nanofiber directly and easily by an electrospinning method. Is.

  That is, the present invention relates to a method for accumulating orientation-controlled nanofibers on a collector surface or an assembly to be arranged on a collector by an electrospinning method. The present invention relates to a method for accumulating orientation-controlled nanofibers, wherein two collector electrodes are provided and a potential difference is formed between the two collector electrodes.

  Further, according to the present invention, in the method of accumulating multiaxially oriented nanofibers by the electrospinning method, two collector electrodes are provided in parallel and spaced apart with an insulator interposed therebetween, and a potential difference is generated between the collector electrodes. A multi-axis oriented nanostructure characterized by placing an object to be collected on a given collector and performing electrospinning, then rotating the object to be accumulated at a predetermined angle, and performing electrospinning again. The present invention relates to a method for integrating fibers.

  The present invention also relates to a syringe, a needle-type electrode attached to the syringe, a collector electrode provided so as to be opposed to the needle-type electrode, and a high-voltage DC power source that applies a DC high-voltage between the needle-type electrode and the collector electrode. In the electrospinning apparatus, the collector electrode is provided in parallel with the insulator sandwiched therebetween, and a potential difference applying means for applying a potential difference between one electrode of the electrode and the other electrode is provided. The present invention relates to an electrospinning apparatus.

  The present invention also relates to a monoaxial or multiaxially oriented nanofiber assembly formed by the above methods.

  The present invention also relates to a filter comprising a multiaxially oriented nanofiber assembly deposited on an assembly by the above method.

  In the present invention, in the method of forming a monoaxially oriented nanofiber assembly using an electrospinning method, a collector provided with two collector electrodes in parallel and spaced apart with an insulator interposed therebetween, and By performing electrospinning with a potential difference formed on the collector electrode, it is possible to form a nanofiber assembly that is precisely uniaxially oriented, and the fiber gap of this assembly controls the deposition time. Can be easily adjusted. The fiber diameter can also be easily controlled by appropriately controlling the electrospinning conditions such as the degree of polymerization of the polymer used for spinning, the applied voltage, the polymer concentration of the spinning solution, the solvent used, and the flow rate.

Further, in the electrospinning apparatus of the present invention, since the potential difference is provided between the two collector electrodes, it is possible to produce a nanofiber assembly that is precisely uniaxially oriented.
In addition, the filter formed from the multi-axis nanofiber assembly of the present invention is a filter formed with an appropriate fine pore diameter by controlling the nanofiber deposition time, the number of times of deposition, etc. Useful as a suitable filter.

Hereinafter, the present invention will be described in more detail with reference to the drawings.
FIG. 1 is a schematic diagram illustrating one embodiment of an apparatus used to produce a uniaxially or multiaxially oriented nanofiber assembly of the present invention. In FIG. 1, an electrospinning apparatus includes a syringe 1 having a needle-type electrode attached to the tip, a collector 2 having an electrically conductive aluminum tape 4 attached to both ends of a glass plate 3, and a space between the needle-type electrode and the aluminum tape. It consists of a high-voltage DC power source 5 for applying a voltage to. The needle-type electrode is connected to the positive electrode of the high-voltage DC power source 5, and the discharged solution is charged to the positive electrode. The negative electrode of the high-voltage DC power supply 5 is grounded. On the other hand, a voltage of 1 kV is applied to one of the collector electrodes by a DC power source 7, and the other collector electrode is grounded. The syringe 1 is filled with a polymer solution (spinning solution 6) that is a raw material of the nanofiber, and a certain amount is released from the syringe. A certain amount of release can be performed by pushing the plunger in the syringe constituting the capillary at a constant speed. In the above apparatus, the negative electrode of the high pressure flow power source 5 is grounded, but the method of applying a potential difference between the collector electrodes is not limited to such a method, and the negative electrode of the high pressure flow power source 5 is directly connected to the collector electrode. The collector electrode is directly connected, and the other collector electrode is connected by providing another potential supply means such as another power source or a resistor. May be taken.

  At this time, electrospinning occurs as follows. When a high voltage of about several thousand volts, for example, is applied to the needle-type electrode, charged particles having a charge opposite to that of the substrate electrode are collected on the surface of the droplet at the tip of the capillary having a syringe, needle-type electrode, and the like. Due to the interaction between the electric charge accumulated on the liquid surface and the electric field, the meniscus rises in a semispherical shape at the tip of the capillary. Under a higher electric field, a strong electric field is generated at the tip of the capillary due to the effect of electric field concentration, and charged ions are collected on the liquid surface to form a conical meniscus called a Taylor cone. When the electric field is further increased and the sum of gravity and electrical repulsion exceeds the surface tension, a part of the liquid jumps out of the Taylor cone and begins to eject as a droplet or jet. The ejected droplet or jet is strongly charged and is attracted to the conductive substrate by the electric field. At that time, the jet becomes a spray due to the repulsion of electrostatic force (Coulomb explosion). In some cases, it is further decomposed by electrostatic force repulsion inside the droplet to form fine droplets or jets. The size of the droplets formed is very small and the surface area is much smaller than the volume, so that the solvent evaporates in a very short time. Usually, the solvent evaporates during ejection, so that dried solute molecules are deposited on the collector. In the present invention, the nanofibers are positively charged and are deposited in a state of being uniaxially oriented in a direction perpendicular to the two collector electrodes. The diameter of the fiber formed by the electrospinning method depends on the viscosity of the solution, the type of polymer used, the degree of polymerization, the composition of the solution, the applied voltage, the flow rate, etc. When the degree of polymerization is large, when the applied voltage is low, or when the flow rate is large, the fiber diameter is usually thick.

  As described above, in the present invention, a potential difference is provided between the two electrodes on the collector, so that the nanofibers are attracted to the collector electrode as compared with the case where the potentials of both electrodes are the same. The effect of increasing the force and increasing the degree of orientation of the nanofibers is obtained. This potential difference is usually in the range of more than 0V to about 10 kV, but is preferably about 100 v to 10 kV.

  The glass plate 3 described as a member constituting the collector in the apparatus of FIG. 1 is exemplified as an example of a collector material, and can form an insulating region between two collector electrodes provided in parallel. Any material may be used as long as it is present. As a material capable of forming an insulating region between the two collector electrodes, any material such as an insulating substrate made of an inorganic material such as a polymer plate, a silicon wafer, a quartz plate, a ceramic plate or the like can be used. . The collector may be formed of a block body or the like, and is not limited to a plate shape.

  Further, although the aluminum tape is used as the collector electrode in the apparatus of FIG. 1, any material other than aluminum, such as gold, platinum, conductive silicon, conductive carbon, etc., may be used. The collector electrode may be provided integrally on the insulating plate, or may be provided as a separate plate from the insulating plate. Moreover, the formation method may also be a method in which a conductive foil or a conductive plate is attached to an insulating member, or may be another method such as vapor deposition. When the insulating member is a silicon substrate, it may be made conductive by implantation of impurities such as ion plating.

  In electrospinning, since evaporation of the solvent is required, it is generally preferable that the humidity is low, and it is usually performed at 50% RH or less. However, the electrospinning method of the present invention is not limited to this. Although the temperature is not particularly limited, it is not necessary to elevate or cool the spinning atmosphere in general because the evaporation of the solvent occurs rapidly even at room temperature. However, depending on the spinning conditions, the temperature may be lower than room temperature. Alternatively, it may be performed at a temperature higher than room temperature.

  In the present invention, the polymer used for spinning may be any of those conventionally known to be spinnable by electrospinning. Examples of such a polymer include polyimide, polyvinyl pyrrolidone, polyethylene oxide, polystyrene, polyacrylonitrile, acrylonitrile-methacrylate copolymer, poly (meth) acrylate, polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polyethylene, Polypropylene, nylon 66, nylon 4,6, polycaprolactam, aramid, polyether urethane, polyvinyl alcohol, cellulose, cellulose acetate, cellulose acetate butyrate, polyvinyl acetate, polyethylene terephthalate, polypeptide, protein, coal tar pitch, petroleum pitch And various polymers that are soluble in a solvent, such as a conductive polymer.

  For example, when polyimide is used, the polyimide is not particularly limited as long as it can be dissolved in a solvent. As an example of such a polyimide, the polyimide described by the following structural formula is mentioned, for example. These are all known polymers. A fluorine-containing polyimide containing a fluorine group and a sulfonated polyimide containing a sulfonic acid group can be preferably used in the present invention. Examples of the fluorine-containing polyimide containing a fluorine group include 6FDA type polyimide, and examples of the sulfonated polyimide containing a sulfonic acid group include NTDA type polyimide. The 6FDA-based polyimide is a polyimide using 2,2-bis (3,4-carboxyphenyl) hexafluoropropane as a polyimide synthesis raw material, and the NTDA-based polyimide is 1,4,5,5 as a synthetic raw material. It is a polyimide using 8-naphthotetracarboxylic acid.

  The above example is merely an example of a polymer used in practicing the present invention, and the polymer used in the present invention is not limited to the specific polyimide. Furthermore, the polymer is not limited to polyimide.

  Solvents used to dissolve these polymers (solutes) to form a spinning solution include acetone, chloroform, ethanol, isopropanol, methanol, toluene, tetrahydrofuran, water, benzene, toluene, xylene, benzyl alcohol, 1, Those having relatively high volatility such as 4-dioxane, propanol, carbon tetrachloride, cyclohexane, cyclohexanone, methylene chloride, phenol, pyridine, trichloroethane, acetic acid, N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) N, N-dimethylacetamide (DMAc), 1-methyl-2-pyrrolidone (NMP), ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), acetonitrile (A ), N-methylmorpholine-N-oxide, butylene carbonate (BC), 1,4-butyrolactone (BL), diethyl carbonate (DEC), diethyl ether (DEE), 1,2-dimethoxyethane (DME), 1, 3-dimethyl-2-imidazolidinone (DMI), 1,3-dioxolane (DOL), ethyl methyl carbonate (EMC), methyl formate (MF), 3-methyl oxazolidine-2-one (MO), methyl pro Examples include relatively low volatility such as pionate (MP), 2-methyltetrahydrofuran (MeTHF), sulfolane (SL). These solvents can be selected and used in consideration of the solubility of the polymer used. These solvents may be used alone or in combination of two or more as necessary. Furthermore, an electrolyte such as water, sodium hydroxide solution, or lithium chloride solution may be added to improve the electrical properties of the spinning solution.

  In the spinning solution, the polymer may be used alone, or two or more polymers may be used in combination, and organic or inorganic powder other than the polymer may be added. The polymer may also be in the form of an emulsion. The spinning solution is not limited to the above-described polymer, and a sol or gel containing an inorganic substance such as metal or ceramic as a main component may be used. When an integrated body made of nanofibers, such as a web, is formed using a sol or gel containing an inorganic substance such as metal or ceramic as a main component, a web made of inorganic fibers can be formed by sintering.

  In addition, when forming a multiaxially aligned nanofiber assembly such as biaxial alignment, the uniaxially aligned nanofiber assembly is manufactured, and the assembly on which the nanofibers are deposited is rotated by, for example, 90 ° C. Then, the nanofibers may be continuously deposited. By repeating this operation if necessary, a multi-layered integrated body such as two layers as shown in FIG. 2 can be obtained. By changing the rotation angle, a biaxially oriented nanofiber assembly having an arbitrary crossing angle can be formed, and if necessary, the angle is not changed only in one direction, but two or more types are sequentially applied. By changing it, it is possible to produce a multiaxially aligned nanofiber assembly having three or more axes. Further, after changing the integration angle, it can be returned to the initial angle again, and if necessary, the integration angle can be changed again to obtain a multilayered assembly of three or more layers.

  Any material can be used as long as it has an accumulation surface such as a film, plate, or cloth. Moreover, when using an integrated body with a to-be-assembled body, what is necessary is just to select and use a suitable to-be-assembled body according to the use for which this is used. For example, when the nanofiber assembly is used as a filter together with the assembly, materials such as cloth, filter paper, and porous membrane that are conventionally used as filter materials are preferably used.

EXAMPLES Hereinafter, although a synthesis example and an Example are given and this invention is demonstrated concretely, this invention is not limited at all by this.
In addition, the physical property of the compound in a synthesis example was measured using the following apparatus.

[Nuclear magnetic resonance (NMR) measurement]
In order to confirm that the imidation reaction proceeded reliably, the obtained polyimide was dissolved in d-DMSO and measured by ¹ HNMR. Integration was 32 times. The apparatus used for the measurement is AL400 manufactured by JEOL Ltd.

[Gel permeation chromatography (GPC) measurement]
Gel permeation chromatography (GPC) was used to determine the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the polymer. Polystyrene was used as a standard substance. The measuring device is RI-101 manufactured by Shodex, and the column is KF-805L manufactured by Schodex.

[Synthesis Example 1]
(Synthesis of fluorine-containing polyimide)
<Synthesis of polyamic acid>
In a 1000 mL three-necked flask, 35.00064 g (0.10472 mol) of 2,2-diaminodiphenylhexafluoropropane (6FAP) was added, and 230 cc of distilled N, N-dimethylacetamide (DMAc) was added and completely dissolved. Thereafter, 4,6.5190 g (0.10472 mol) of 2,2-bis (3,4-carboxyphenyl) hexafluoropropane (6FDA) and 405 cc of DMAc were further added and dissolved to obtain a solution. This solution was stirred overnight at room temperature to obtain a polyamic acid.

<Imidization>
To the polyamic acid solution obtained above, 54.10 g (0.5299 mol) of acetic anhydride was added dropwise, and then triethylamine was added dropwise, followed by stirring for 24 hours. The obtained polymer solution was slowly dropped into methanol to obtain a granular polyimide (6FDA-p-6FAP) represented by the following formula. A ¹ H-NMR spectrum of the resulting polyimide is shown in FIG. The weight average molecular weight (Mw) was 4.2 × 10 ⁵ and Mw / Mn was 2.0.

[Synthesis Example 2]
In Synthesis Example 1, 11.79241 g (0.03528 mol) of 2,2-diaminodiphenylhexafluoropropane (6FAP) and 15.2-bis (3,4-carboxyphenyl) hexafluoropropane (6FDA) of 15.79241 g (0.03528 mol). A polyimide was synthesized in the same manner as in Synthesis Example 1 except that 67396 g (0.03528 mol), 90.89 g (0.8903 mol) of acetic anhydride, and 212 cc of DMAc were used. The obtained polyimide (6FDA-p-6FAP) had a polystyrene-reduced weight average molecular weight (Mw) by GPC of 3.2 × 10 ⁵ and Mw / Mn was 2.0.

[Synthesis Example 3]
A polyimide was synthesized in the same manner as in Synthesis Example 1 except that 628 cc of DMAc and 53.46 g (0.5236 mol) of acetic anhydride were used in Synthesis Example 1. The obtained polyimide (6FDA-6FAP) had a weight average molecular weight (Mw) of 1.2 × 10 ⁵ and Mw / Mn of 2.0.

[Example 1]
A uniaxially oriented polyimide (6FDA-p-6FAP) nanofiber assembly was manufactured using the apparatus of FIG. The distance between the needle electrode and the collector is 10 cm, the size of the glass substrate of the collector is 100 × 70 mm, the distance between the aluminum electrodes is 30 mm, the width of the aluminum electrodes is 10 mm, the applied voltage is 15 kV, and one of the aluminum electrodes Applied a positive voltage of 1 kV from the power source 7, the other electrode was grounded, the spinning solution flow rate was 0.12 mL / h, a filter paper was placed in the center of the collector, and electrospinning was performed. As the spinning solution, the N, N-dimethylacetamide (DMAc) 14 wt% solution of polyimide (6FDA-6FAP) having a weight average molecular weight (Mw) of 420,000 obtained in Synthesis Example 1 was used. The nanofibers were deposited on the filter paper by changing the electrospinning time to 1, 3, 5, 10, 15, and 30 minutes.

  The produced nanofibers were vacuum-dried at 150 ° C. for 10 hours, and then the sample was coated with platinum and observed with a scanning electron microscope (SEM). An SEM photograph is shown in FIG. As is clear from FIG. 4, the obtained nanofiber assembly was strongly oriented in the uniaxial direction. The magnification of the SEM photograph is 1000 times for 1 minute deposition, 3000 times for 3 minute deposition, 7000 times for 5 minute deposition, 10,000 times for 10 minute deposition, 20,000 times for 15 minute and 30 minute deposition. . When the diameter of the nanofiber and the fiber gap were calculated from the SEM image, the average diameter of the nanofiber was 468 nm. The average fiber gap was as shown in Table 1 (see FIG. 5). In FIG. 5, the line indicating the range in the figure indicates the measured size range of the gap.

[Example 2]
Using the same apparatus as in Example 1, nanofibers were deposited on the filter paper for 1 minute using the same spinning solution and the same electrospinning conditions. After 1 minute deposition time, the filter paper was rotated 90 °, and nanofiber deposition was continued for 1 minute. Similar deposition operations were performed at different times of 3 minutes, 5 minutes, 10 minutes, 15 minutes, and 30 minutes, respectively, to form six types of biaxially oriented nanofiber assemblies.

  As in Example 1, the produced nanofiber assembly was vacuum-dried at 150 ° C. for 10 hours, and then the sample was coated with platinum and observed by SEM. An SEM photograph is shown in FIG. From the SEM photograph in FIG. 6, it can be seen that the obtained biaxially oriented nanofiber assembly is strongly oriented in the biaxial direction. The diameter of the nanofiber in FIG. 6 was the same as in Example 1. From the SEM photograph, the average length of one side of the hole, the average area of the hole, and the porosity were calculated. The results are shown in Table 2 (see FIG. 7 for the length of one side of the hole).

[Example 3]
Using the same apparatus as in Example 1, nanofibers were deposited on filter paper for 30 minutes with the same spinning solution and the same electrospinning conditions. The filter paper was rotated 90 ° and subsequently deposited for 30 minutes. This operation was repeated to prepare a structure in which four layers were stacked for 30 minutes per layer. An SEM photograph is shown in FIG. From the SEM photograph of FIG. 8 (a), it can be seen that the obtained biaxially aligned assembly comprising four layers is strongly aligned in the biaxial direction.

[Example 4]
Using the same apparatus as in Example 1, nanofibers were deposited on the filter paper for 15 minutes with the same spinning solution and the same electrospinning conditions. The filter paper was rotated 90 ° and subsequently deposited for 15 minutes. This operation was repeated to prepare a structure in which eight layers laminated for 15 minutes per layer were stacked. An SEM photograph is shown in FIG. From the SEM photograph of FIG. 8 (b), it can be seen that the biaxially oriented assembly comprising the eight layers obtained is strongly oriented in the biaxial direction.

[Comparative Example 1]
The electrospinning was performed for 120 minutes in the same manner as in Example 1 except that a conductive substrate using an aluminum foil was used instead of the collector 2 in which the conductive aluminum tape was bonded to both ends of the glass plate as the collector. went. An SEM photograph is shown in FIG. From the SEM photograph of FIG. 8C, it can be seen that the nanofiber assembly obtained by the conventional method is not oriented at all.

[Example 5 and Comparative Example 2]
(Permeation performance evaluation by pure water permeation experiment)
The nanofiber assembly produced in Examples 3 and 4 and Comparative Example 1 was immersed in a 70% aqueous methanol solution overnight. The apparatus shown in FIG. 9 was used for the permeability evaluation. When the permeation performance is evaluated using the apparatus shown in FIG. 9, Millipore water is put into the reservoir 8 so that the temperature of the thermostatic bath is 25 ° C., and the sample 10 that has been applied with the methanol aqueous solution is placed on the lower surface of the cell 9. Then, nitrogen gas was introduced and the pressure was kept constant at 0.02 MPa. The weight of pure water that permeated the sample was weighed every 30 seconds, and the value when the flow rate became constant was recorded. The pure water permeability coefficient Lp was calculated from the obtained permeation flow rate. The unit of the pure water permeability coefficient at this time was ml / h / mmHg / m ² .

  The pure water permeation coefficient Lp obtained from the result of the pure water permeation experiment is shown in FIG. Compared with the non-woven nanofiber assembly of Comparative Example 1 in which the structure was not controlled, the values of Lp decreased in the structures of Examples 3 and 4 in which the structure was controlled. From FIG. 8, it is considered that this is mainly due to a decrease in the apparent pore diameter.

(Evaluation of pore size by dextran permeation experiment)
<Preparation of dextran aqueous solution>
Dextran having nominal molecular weights of 8500-11500, 35000-45000, 64000-76000, 100000-200000 is mixed at an equal weight ratio and adjusted with Millipore water to a total of 1.0 g / L. And used as a stock solution.

<Dextran transmission experiment>
Following the pure water permeation experiment, using the sample where the pure water permeation experiment was performed, the millipore water in the reservoir was discarded, the dextran aqueous solution was added, the temperature of the thermostatic bath was 25 ° C., nitrogen gas was introduced, and the pressure was 0.02 MPa. Constant. When the flow rate became constant, a solution that permeated the sample was collected.

<Gel filtration chromatography (GFC) measurement>
The inhibition rate of dextran was determined using GFC. The detector of the GFC is a suggestive refractometer, and the concentration of the solution cannot be directly determined. However, the intensity ratio between the stock solution and the solution that has permeated the sample is the same as the concentration ratio by making the amount of solution injected into the column constant. Assuming that there was, the blocking rate was calculated.

  FIG. 11 shows the result of the dextran permeation experiment (dextran blocking rate). Similar to the pure water permeation experiment, in the dextran permeation experiment, there was a difference between the non-woven nanofiber assembly of Comparative Example 1 in which the structure was not controlled and the nanofiber assembly of Examples 3 and 4 in which the structure was controlled. It was. In the nanofiber assembly of Comparative Example 1, no dextran was blocked at any molecular weight, whereas in the nanofiber assemblies of Examples 3 and 4, the dextran was slightly but in the molecular weight of 100,000 to 300,000. I was able to stop. This is thought to be mainly due to the fact that the apparent pore diameter decreased due to the structure control, and further the variation in the pore diameter decreased. The diameter of dextran having a molecular weight of 300,000 is calculated to be 218 nm.

  The apparent pore diameters of the nanofiber assemblies of Examples 3 and 4 were calculated from SEM photographs. The results are shown in Table 3. In either case, the pore size is smaller than that of dextran, and it is considered that dextran is normally blocked by molecular sieves. However, the actual dextran rejection rate was very small. This is probably because the nanofibers were spread by the water pressure during the permeation experiment, and the structure of the aggregate was disturbed.

[Example 6]
In Example 1, electrospinning was performed in the same manner as in Example 1 except that the concentration of polyimide was 17% by weight and NMP and DMF were used instead of DMAc as the solvent of the spinning solution.
Further, in Example 1, instead of the polyimide obtained in Synthesis Example 1, the polyimides obtained in Synthesis Examples 2 and 3 were used, the polyimide concentration was 17% by weight, and DMAc as a solvent for each polyimide, Electrospinning was performed in the same manner as in Example 1 using NMP and DMF.
The average diameter of the nanofiber obtained by these is shown in FIG.

[Example 7]
In Example 1, a 17% by weight solution of the polyimide obtained in Synthesis Example 3 was used, DMAc, NMP and DMF were used as the solvent, and the spinning solution flow rate was 0.12, 0.24,. Electrospinning was performed under conditions of 36, 0.60, and 0.96 mL / h. The average diameter of the nanofiber obtained by these is shown in FIG.

[Example 8]
In Example 1, electrospinning was performed using a solution of 17% by weight of the polyimide obtained in Synthesis Example 3, using DMAc, NMP, and DMF as solvents and applying voltages of 10, 15, and 20 kV. The average diameter of the nanofiber obtained by these is shown in FIG.

[Example 9]
In Example 1, electrospinning was performed using the polyimide solution obtained in Synthesis Example 3, using DMAc, NMP, and DMF as solvents, and polymer concentrations of 17, 18, and 19% by weight. The average diameter of the nanofiber obtained by these is shown in FIG.

[Example 10]
Same as Example 1 except that the same apparatus as in Example 1 was used, and a 15% by weight DMF 15 wt% solution of 6FDA-p-APPS previously shown in the structural formula was used as the spinning solution, and the deposition time was 15 minutes each. Thus, a biaxially oriented nanofiber assembly was produced. An SEM photograph of the obtained aggregate is shown in FIG. From FIG. 16, it can be seen that a biaxially oriented nanofiber assembly having good orientation is produced even when 6FDA-p-APPS DMF is used.

[Example 11]
Using the same apparatus as in Example 1, as a spinning solution, a 15% by weight solution of 6FDA-p-APPS in DMF previously shown in the structural formula was used. Under the same electrospinning conditions as in Example 1, 15 nanofibers were formed on the filter paper. Deposited for minutes. Subsequently, the filter paper was rotated by 60 °, and the nanofibers were continuously deposited under the same conditions for 15 minutes. Thereafter, the filter paper was further rotated by 60 ° in the same direction to deposit nanofibers for 15 minutes to produce a triaxially aligned nanofiber assembly. An SEM photograph of the obtained aggregate is shown in FIG. From the SEM photograph of FIG. 17, it can be seen that the obtained aggregate is well oriented in the triaxial direction.

[Example 12]
Using the same apparatus as in Example 1, as the spinning solution, a DMF 15% by weight solution of 6FDA-p-FAP-b-3MPA (n: m = 70: 70) previously shown in the structural formula was used. A biaxially oriented nanofiber assembly was produced in the same manner as in Example 1 except that the time was 15 minutes. An SEM photograph of the obtained aggregate is shown in FIG. From FIG. 18, it can be seen that a biaxially oriented nanofiber assembly having good orientation is produced even when 6FDA-p-APPS DMF is used.

  The uniaxial or multiaxially oriented nanofiber assembly obtained by the present invention can be obtained as separators, electrolyte membranes, filters, medical bandages, medical barrier webs, medical tissue culture supports, sensors for various batteries such as lithium batteries. Further, by carbonizing the accumulated body, it can be used as a wide range of materials such as electrode materials, and can be particularly preferably used as a filter.

It is a schematic diagram of one mode of a biaxially oriented nanofiber web manufacturing apparatus of the present invention. It is a conceptual diagram which shows biaxially-oriented nanofiber multilayer assembly manufacture of this invention. 2 is a ¹ HNMR spectrum diagram of 6FDA-p-6FAP synthesized in Synthesis Example 1. FIG. It is a drawing-substituting photograph and is an SEM photograph of the uniaxially oriented nanofiber assembly obtained in Example 1 of the present invention. It is a figure which shows the magnitude | size of the fiber gap | interval of a uniaxially oriented nanofiber assembly | attachment in relation to deposition time. It is a drawing substitute photograph and is an SEM photograph of six biaxially oriented nanofiber assemblies of the present invention. It is a figure which shows the length of the one side of the hole of a biaxially oriented nanofiber aggregate | assembly in relation to deposition time. BRIEF DESCRIPTION OF THE DRAWINGS It is a drawing substitute photograph, (a) is a SEM photograph of the biaxially-oriented nanofiber assembly of 4 layer structure of this invention, (b) is the biaxially-oriented nanofiber assembly of 8 layer structure of this invention. (C) is a SEM photograph of an unoriented nanofiber assembly by a conventional method. It is the schematic of the apparatus used in the transmission performance evaluation experiment. It is a figure which shows the value of the pure water permeability coefficient Lp calculated | required from the result of the pure water penetration experiment. It is a figure which shows the dextran blocking rate calculated | required from the result of the dextran permeation | transmission experiment. FIG. 6 is a view showing the average diameter of the uniaxially oriented nanofiber assembly obtained in Example 6. FIG. 6 is a view showing the average diameter of the uniaxially oriented nanofiber assembly obtained in Example 7. FIG. 10 is a diagram showing the average diameter of the uniaxially oriented nanofiber assembly obtained in Example 8. FIG. 10 is a diagram showing the average diameter of the uniaxially oriented nanofiber assembly obtained in Example 9. It is a drawing substitute photograph, and is an SEM photograph of the biaxially oriented nanofiber assembly obtained in Example 10. It is a drawing-substituting photograph, and is an SEM photograph of the triaxially oriented nanofiber assembly obtained in Example 11. It is a drawing substitute photograph, and is an SEM photograph of the biaxially oriented nanofiber assembly obtained in Example 12. It is the schematic of the conventional electrospinning apparatus.

Explanation of symbols

1, 11 Syringe 2 Collector 3 Glass plate 4 Aluminum tape 5, 13 High voltage DC power supply 6, 14 Spinning solution 7 DC power supply 8 Reservoir 9 Cell 10 Sample 12 Collector electrode

Claims (9)

In a method of accumulating orientation-controlled nanofibers on a collector surface or an assembly to be arranged on a collector by an electrospinning method, two collector electrodes are arranged in parallel as a collector with an insulator interposed therebetween And using the two collector electrodes having a potential difference of 100 V to 10 kV formed on the two collector electrodes. In a method of accumulating multi-axis oriented nanofibers by electrospinning, two collector electrodes are provided in parallel with a space between insulators, and a potential difference of 100 V to 10 kV is applied between the collector electrodes. A multi-axis-oriented nanofiber is characterized in that after the object is placed on the collector and electrospun, the object is rotated by a certain angle and then electrospun again. How to accumulate. The method for accumulating orientation-controlled nanofibers according to claim 1 or 2 , wherein the collector electrode is made of aluminum. The method for accumulating orientation-controlled nanofibers according to any one of claims 1 to 3 , wherein the spinning polymer is polyimide. 5. The method for accumulating orientation-controlled nanofibers according to claim 4 , wherein the polyimide is a fluorine-containing polyimide containing a fluorine group or a sulfonated polyimide containing a sulfonic acid group. To collect nanofibers. Electrospinning apparatus comprising a syringe, a needle-type electrode attached to the syringe, a collector electrode provided spaced apart from and opposed to the needle-type electrode, and a high-voltage DC power source for applying a DC high-voltage between the needle-type electrode and the collector electrode The collector electrode is provided in parallel and spaced apart with an insulator interposed therebetween, and a potential difference applying means for applying a potential difference of 100 V to 10 kV between one electrode and the other electrode of the electrode is provided. Electrospinning device characterized by 7. The electrospinning apparatus according to claim 6, wherein the potential difference applying means is a direct current power source. Nanofiber aggregate oriented in uniaxial or multiaxial deposited by the method of any of claims 1-5.   A filter comprising a multiaxially oriented nanofiber assembly formed on an assembly by the method according to claim 2.