KR20050098861A - Porous fiber, porous fiber structure and method for production thereof - Google Patents

Abstract

A method for producing a fiber structure which comprises a step of preparing a solution containing a hydrophobic solvent and a polymer soluble in a hydrophobic solvent and an organic compound having a plurality of hydroxyl groups, a step of subjecting the solution to electrostatic spinning and a step of obtaining a fiber structure accumulated on a base material for capturing. The method allows the production of a porous fiber and a fiber structure comprising the porous fiber which is suitable as a substrate for cell culture in the field of regenerative medicine, and has a great surface area and a great interstice and can be controlled with respect to the degree of hydrophilic property.

Description

Porous fiber, porous fiber structure and manufacturing method thereof {POROUS FIBER, POROUS FIBER STRUCTURE AND METHOD FOR PRODUCTION THEREOF}

The present invention relates to a porous fiber formed without the need for a coagulating liquid, a fiber structure comprising the same, and a method for producing the same.

More specifically, the present invention relates to a porous fiber, a fibrous structure, and a manufacturing method thereof, which are mainly composed of a polymer soluble in a hydrophobic solvent and an organic compound containing a plurality of hydroxyl groups.

In the field of regenerative medicine, a porous body may be used as a substrate (stool) when culturing cells. As a porous body, the freeze-dried material of a water absorbing organic substance, a foam, and a fiber structure are known (for example, refer nonpatent literature 1). These porous bodies require cell affinity, biodegradability, and safety. Polyglycolic acid, which is used for surgical sutures, has excellent biocompatibility, biodegradability, and safety. The use for description is examined (for example, refer nonpatent literature 1).

However, since the fiber structures obtained by these conventional methods are too large in fiber diameter, the surface area to which cells can adhere is insufficient, and in order to increase the surface area, a fiber structure having a smaller fiber diameter is desired.

On the other hand, as a method of manufacturing a fiber structure with a small fiber diameter, the electrostatic spinning method is known (for example, refer patent documents 1 and 2). The electrospinning method includes a step of introducing a liquid, for example, a solution containing a fibrous material, or the like into the electric field, thereby attracting the liquid toward the electrode to form a fibrous material.

Typically, the fibrous material is cured while being drawn out of solution. Curing is performed, for example, by cooling (for example, when the spinning liquid is a solid at room temperature), chemical curing (for example, treatment with curing steam), or evaporation of a solvent.

In addition, the fibrous substance obtained can be collected on an appropriately arranged container, and if necessary, can be peeled off there. In addition, since the electrospinning method can directly obtain a nonwoven fabric-like fibrous material, it is not necessary to form a fibrous structure further after weaving the fibers once, so that the operation is easy.

It is known to use the fiber structure obtained by the electrospinning method for the base material which cultures a cell. For example, it has been studied to form a fiber structure made of polylactic acid by electrospinning and to reproduce blood vessels by culturing smooth muscle cells thereon (see Non-Patent Document 2, for example).

However, since the fiber structure obtained by using these electrospinning methods has a narrow fiber diameter, it is easy to take a dense structure having a short distance between the fibers. When this is used as a substrate for cell culture, as the culture proceeds, the cultured cells are deposited on the fiber surface forming the fiber structure, and the fiber structure surface is thickly covered with the cells. As a result, it is difficult for the solution containing nutrients and the like to sufficiently move to the inside of the fiber structure, and there is a problem that cell culture can be performed only in the vicinity of the surface of the fiber structure.

As a method for allowing the solution containing nutrients and the like to easily move to the extreme surface of the fiber forming the fiber structure during cell culture, a method in which the fiber itself forming the fiber structure is made of porous fibers is considered.

For example, a method of forming a fiber structure having regular holes on the fiber surface by an electrospinning method using a solution containing a volatile solvent has been reported (see Non-Patent Document 3 and Patent Document 3). However, in this method, the fiber surface only has pores, and it is difficult to make it porous to the inside of the fiber.

Moreover, the method of forming a fiber structure by the electrospinning method from the solution containing a hydrophilic polymer and a hydrophobic polymer, extracting a hydrophilic polymer by immersing the obtained fiber structure in water, and forming a porous fiber is also reported. 4 and Patent Document 3).

In this method, however, an immersion treatment with water is required and the operation is complicated. In addition, the finally obtained porous fibers consist of substantially hydrophobic polymers, and have a problem in that the hydrophilicity of the fiber structure cannot be controlled.

[Patent Document 1] Japanese Unexamined Patent Publication No. 63-145465

[Patent Document 2] Japanese Unexamined Patent Publication No. 2002-249966

[Patent Document 3] International Publication No. 02/16680 Pamphlet

[Non-Patent Literature 1] Onoriya, Representative of the Southeastern Azawa Masuo Regenerative Medicine, N · T · S, Jan. 31, 2002, p. 258

[Non-Patent Document 2] Joel D. Stitzel, Kristin J. Pawlowski, Gary E. Wnek, David G. Simpson, Gary L. Bowlin, Journal of Biomaterials Applications 2001, 16, (US), 22- Page 33

[Non-Patent Document 3] Michael Bognitzki, Wolfgang Czado, Thomas Frese, Andreas Schaper, Michael Hellwig, Martin Steinhart, Andreas Greiner, by Joachim H. Wendroff, Journal of Advanced Materials 2001, 13, (US), 70. -72 pages

[Non-Patent Document 4] Michael Bognitzki, Thomas Frese, Martin Steinhart, Andreas Greiner, by Joachim H. Wendroff, Polymer Engineering and Science 2001, Vol. 41, USA, pp. 982-989.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram of the manufacturing apparatus for demonstrating one aspect of the manufacturing method of this invention.

2 is a schematic diagram of a manufacturing apparatus for explaining one embodiment of the manufacturing method of the present invention.

FIG. 3 is an electron micrograph (photographing magnification 2000 times) of the surface of the fiber structure obtained by the operation of Example 1. FIG.

4 is an electron micrograph (photographing magnification 10000 times) which photographed the cross section of the fiber obtained by the operation of Example 1. FIG.

FIG. 5 is an electron micrograph (photographing magnification 2000 times) of the surface of the fiber structure obtained by the operation of Example 2. FIG.

FIG. 6 is an electron micrograph (photographing magnification 10000 times) which photographed the cross section of the fiber obtained by the operation of Example 2. FIG.

FIG. 7 is an electron micrograph (photographing magnification 2000 times) of the surface of the fiber structure obtained by the operation of Example 3. FIG.

8 is an electron micrograph (photographing magnification 10000 times) which photographed the cross section of the fiber obtained by the operation of Example 3. FIG.

9 is an electron micrograph (photographing magnification 2000 times) which photographs the surface of the fiber structure obtained by the operation of Example 4. FIG.

10 is an electron micrograph (photographing magnification 10000 times) which photographed the cross section of the fiber obtained by the operation of Example 4. FIG.

FIG. 11 is an electron micrograph (photographing magnification 2000 times) of the surface of the fiber structure obtained by the operation of Example 5. FIG.

FIG. 12 is an electron micrograph (photographing magnification 10000 times) which photographed the cross section of the fiber obtained by the operation of Example 5. FIG.

FIG. 13 is an electron micrograph (photographing magnification 2000 times) of the surface of the fiber structure obtained by the operation of Example 6. FIG.

14 is an electron micrograph (photographing magnification 10000 times) which photographed the cross section of the fiber obtained by the operation of Example 6. FIG.

FIG. 15 is an electron micrograph (photographing magnification 2000 times) of the surface of the fiber structure obtained by the operation of Example 7. FIG.

16 is an electron micrograph (photographing magnification 10000 times) which photographed the cross section of the fiber obtained by the operation of Example 7. FIG.

17 is an electron micrograph (photographing magnification 2000 times) of the surface of the fiber structure obtained by the operation of Example 8. FIG.

18 is an electron micrograph (photographing magnification 10000 times) which photographed the cross section of the fiber obtained by the operation of Example 8. FIG.

FIG. 19 is an electron micrograph (photographing magnification 2000 times) of the surface of the fiber structure obtained by the operation of Example 9. FIG.

20 is an electron micrograph (photographing magnification 10000 times) which photographed the cross section of the fiber obtained by the operation of Example 9. FIG.

FIG. 21 is an electron micrograph (photographing magnification 2000 times) of the surface of the fiber structure obtained by the operation of Comparative Example 1. FIG.

22 is an electron micrograph (photographing magnification 10000 times) which photographed the cross section of the fiber obtained by the operation of the comparative example 1. FIG.

FIG. 23 is an electron micrograph (photographing magnification 2000 times) of the surface of the fiber structure obtained by the operation of Comparative Example 2. FIG.

24 is an electron micrograph (photographing magnification 10000 times) which photographed the cross section of the fiber obtained by the operation of the comparative example 2. FIG.

FIG. 25 is an electron micrograph (photographing magnification 2000 times) of the surface of the fiber structure obtained by the operation of Comparative Example 3. FIG.

FIG. 26 is an electron micrograph (photographing magnification 10000 times) which photographed the cross section of the fiber obtained by the operation of the comparative example 3. FIG.

To practice the invention  Best form for

Hereinafter, the present invention will be described in detail.

In the present invention, the fiber structure refers to a three-dimensional structure in which one or a plurality of porous fibers obtained are laminated, woven, woven, or formed by other techniques. As a form of a specific fiber structure, a nonwoven fabric is mentioned, for example, The tube, mesh, etc. which were processed based on it can also be used suitably in the field of regenerative medicine.

The porous fibers and fiber structures of the present invention contain a polymer soluble in a hydrophobic solvent.

The hydrophobic solvent of the present invention is an organic substance that is not liquid and can not dissolve 5% or more of water at normal temperature (for example, 27 ° C). As the hydrophobic solvent of the present invention, a halogen element-containing hydrocarbon is preferable because of good solubility of the polymer. More preferable hydrophobic solvents include methylene chloride, chloroform, dichloroethane, tetrachloroethane, trichloroethane, dibromomethane, bromoform and the like, and methylene chloride is particularly preferable.

Among them, it is preferable to use a volatile solvent. The volatile solvent here is an organic substance whose boiling point at normal pressure is 200 degrees C or less, and is liquid at normal temperature (for example, 27 degreeC).

In the present invention, "dissolvable" means that a solution containing 1% by weight of a polymer at room temperature (for example, 27 ° C) is stably present without causing precipitation. Examples of the polymer which can be dissolved in this hydrophobic solvent include aliphatic polyesters such as polylactic acid, polylactic acid-polyglycolic acid copolymer, and polycaprolactone, polycarbonate, polystyrene, polyallylate, polymethyl methacrylate, and polyethyl methacrylate. Acrylate, cellulose diacetate, cellulose triacetate, polyvinylacetate, polyvinyl methyl ether, poly (N-vinylpyrrolidone), polybutylene succinate, and polyethylene succinate and copolymers thereof. .

Of these, polylactic acid, polycaprolactone, polycarbonate, polystyrene and polyallylate are preferable.

The porous fiber and the fiber structure of the present invention may contain only one kind of polymer soluble in this hydrophobic solvent or two or more kinds.

The porous fiber and the fiber structure of the present invention contain an organic compound having a plurality of hydroxyl groups. When the organic compound which does not have a some hydroxyl group is used, the target porous fiber cannot be obtained, the fiber structure which consists of this porous fiber can not be obtained stably, and cell culture may become difficult further, and it is unpreferable. .

It is preferable that the number average molecular weights of the organic compound which has a hydroxyl group are 62 or more and 300 or less. When the number average molecular weight is greater than 300, it is difficult to form porous fibers, which is not preferable.

Examples of the organic compound having a molecular weight of 62 and having a plurality of hydroxyl groups include ethylene glycol as an example, but an organic compound having a molecular weight of less than 62 and having a plurality of hydroxyl groups is substantially absent. More preferable number average molecular weights of this organic compound are 62 or more and 250 or less.

Examples of the organic compound having a plurality of hydroxyl groups include ethylene glycol, propylene glycol (1,2-propanediol), 1,3-propanediol, diethylene glycol, triethylene glycol, glycerin, pentaerythritol, polyethylene glycol, poly Propylene glycol, polyethyleneglycol polypropylene glycol block polymer, etc. are mentioned.

In the present invention, a polymer which is soluble in a hydrophobic solvent and a polymer or other compound other than an organic compound having a plurality of hydroxyl groups may be used in combination (for example, polymer copolymerization, polymer blend, and compound mixing) within a range that does not impair the object. )

The porous fibers and the fiber structure of the present invention are formed of porous fibers having an average fiber diameter of 0.1 to 20 mu m. If the average fiber diameter is smaller than 0.1 mu m, it is not preferable because the biodegradability is too fast for use as a regenerative medical cell culture substrate. In addition, when the average fiber diameter is larger than 20 µm, the area to which cells can adhere is small, which is not preferable. More preferable average fiber diameter is 0.2-15 micrometers, and especially preferable average fiber diameter is 0.2-10 micrometers. In addition, a fiber diameter shows the diameter when a fiber cross section is circular. However, sometimes the shape of the fiber cross section may be elliptical. The fiber diameter in this case calculates the average of the length of the elliptical long axis direction and the length of the short axis direction as the fiber diameter. In addition, when the fiber cross section is neither circular nor elliptical, the fiber diameter is calculated to approximate a circle or an ellipse.

In addition, the porous fiber of the present invention preferably has a fiber length of 20 µm or more, and if the fiber length is 20 µm or less, the mechanical strength of the resulting fiber structure is insufficient. The fiber length is preferably 40 µm or more, more preferably 1 mm or more.

The porous fiber in the present invention refers to a fiber having independent holes and / or communication holes in the fiber surface and inside of the fiber, and the independent holes and / or communication holes in the fiber form hollow portions, and the hollow fiber as the whole fiber. It may be.

The fiber structure of the present invention consists of porous fibers having a porosity of at least 5%. Here, the porosity refers to an independent hole and a communication hole reaching a fiber surface in a randomly cut fiber cross section, and an independent hole and a communication hole inside a fiber, that is, a fiber-forming substance (a polymer soluble in a hydrophobic solvent, a plurality of hydroxyl groups). It means that the sum of the areas of the spaces free of organic compounds having and other required polymers or other compounds) occupies at least 5% of the total area of the fiber cross section including these spaces. If the porosity is less than 5%, a solution containing nutrients or the like does not sufficiently penetrate into the base material at the time of cell culture, which is not preferable. As for this porosity, 10% or more is preferable.

That is, as a preferable aspect of this invention, it consists of the polymer which can melt | dissolve in a hydrophobic solvent, and the organic compound which has a some hydroxyl group, The porous fiber which has an average fiber diameter of 0.1-20 micrometers and a porosity of at least 5%, and it It is preferable to use aliphatic polyester, polycarbonate, polystyrene, polyallylate as a polymer which is a fibrous structure and can be dissolved in a hydrophobic solvent.

The method for producing the fiber structure of the present invention is not particularly limited as long as the fiber and the like having the aforementioned fiber diameter are obtained, but electrostatic spinning is preferable.

Hereinafter, the method of producing by the electrospinning method will be described in detail.

In the electrospinning method used in the present invention, a solution in which a polymer soluble in a hydrophobic solvent and an organic compound having a plurality of hydroxyl groups is dissolved in a hydrophobic solvent is discharged into an electrostatic field formed between the electrodes, and the solution is sprayed toward the electrode. The fibrous structure can be obtained by accumulating the formed fibrous material on the collecting substrate. In addition, when the fibrous material is accumulated, the porous fibers of the present invention are already formed. Here, the fibrous substance indicates not only a state in which the solvent in the solution is already distilled off to form a porous fiber and a fiber structure, but also a state in which the solvent of the solution is still contained.

First, the apparatus used by the electrostatic radiation method is demonstrated. The electrode used in the present invention only needs to exhibit conductivity of any of metals, inorganics and organics. Moreover, you may have a thin film of the metal, inorganic substance, or organic substance which shows electroconductivity on an insulator. The electrostatic field in the present invention is formed between a pair or a plurality of electrodes, and a high voltage may be applied to any electrode. This includes, for example, the case where two high voltage electrodes having different voltage values (for example, 15 kV and 10 kV) use three electrodes in total, and three or more electrodes connected to the earth. It shall also be included when the electrode of.

Next, the manufacturing method of the present invention by the electrospinning method will be described in more detail. First, there is a step of preparing a solution in which a polymer soluble in a hydrophobic solvent and an organic compound having a plurality of hydroxyl groups are dissolved in a hydrophobic solvent. It is preferable that the density | concentration of the polymer which can melt | dissolve in the hydrophobic solvent in the solution in the manufacturing method of this invention is 1-30 weight%. If the concentration of the polymer soluble in the hydrophobic solvent is less than 1% by weight, the concentration is too low, which makes it difficult to form the fiber structure, which is not preferable. Moreover, when larger than 30 weight%, the fiber diameter of the obtained fiber structure becomes large and it is unpreferable. The concentration of the polymer that can be dissolved in a more preferable hydrophobic solvent is 2 to 20% by weight.

It is preferable that the density | concentration of the organic compound which has some hydroxyl group in the solution in this invention is 2-50 weight%. When the density | concentration of the organic compound which has some hydroxyl group is less than 2 weight%, the total area of the recessed part and the void part in a fiber cross section will become small, and it is unpreferable. Moreover, when larger than 50 weight%, formation of a fiber structure becomes difficult and it is unpreferable. The density | concentration of the organic compound which has more preferable several hydroxyl groups is 4-30 weight%.

When the boiling point of the organic compound which has a some hydroxyl group used for this invention is low, it may evaporate partly with a solvent at the time of spinning by an electrospinning method. In this invention, it is preferable that 1 weight% or more of the organic compound which has a hydroxyl group supplied at least remains. 5 to 60 weight%, more preferable content is 10 to 60 weight%.

In the manufacturing method of the fiber structure by the electrospinning method of this invention, this hydrophobic solvent may be used independently and may combine several hydrophobic solvent. Moreover, you may use another solvent together in the range which does not impair the objective of this invention. Specific examples of the hydrophobic solvent are as described above.

Next, the step of spinning the solution by the electrospinning method will be described. Any method can be used to discharge this solution in the electrostatic field.

Hereinafter, a preferred embodiment for producing the fiber structure of the present invention using Fig. 1 will be described in more detail.

By supplying the solution (2 in FIG. 1) to the nozzle, the solution is placed at an appropriate position in the electrostatic field, and the solution is spun by an electric field to form fibers. For this purpose, a suitable device may be used, for example a needle shape in which a voltage is applied to the tip of the cylindrical solution holder (3 in FIG. 1) of the syringe by a suitable means, for example a high voltage generator (6 in FIG. 1). Solution injection nozzle (1 in FIG. 1) is installed, and a solution is guided to the front-end | tip.

The tip of this jet nozzle (1 in Fig. 1) is disposed at an appropriate distance from the grounded fibrous material collecting electrode (5 in Fig. 1), and the solution (2 in Fig. 1) is connected to the jet nozzle (1 in Fig. 1). When exiting the tip, a fibrous material is formed between the tip and the fibrous material collecting electrode (5 in FIG. 1).

In addition, fine droplets of this solution may be introduced into the electrostatic field by a method apparent to those skilled in the art, and as one preferred embodiment thereof, the following description will be given using FIG. The only requirement at that time is to keep the water droplets in the electrostatic field and keep them separate from the fibrous material collecting electrode (5 in FIG. 2) at a distance where fibrosis can occur. For example, an electrode (4 in FIG. 2) opposed to a fibrous material collecting electrode is inserted directly into a solution (2 in FIG. 2) in a solution holding tank (3 in FIG. 2) having a nozzle (1 in FIG. 2). You may also

When the solution is fed from the nozzle into the electrostatic field, several nozzles may be used to speed up the production of fibrous material. The distance between the electrodes depends on the charging amount, the nozzle size, the spinning liquid flow rate, the spinning liquid concentration, and the like. When the distance is about 10 kPa, a distance of 5 to 20 cm was appropriate.

The electrostatic potential applied is generally 3 to 100 kV, preferably 5 to 50 kV, more preferably 5 to 30 kV. The desired electrostatic potential may be made by any suitable method in the prior art.

In the above description, when the electrode also serves as a collecting substrate, the collecting substrate may be additionally formed between the electrodes separately from the electrodes, and the fiber structure may be collected therein. In this case, it is also possible to continuously produce a fiber structure by providing a belt-like substance between electrodes and making it a collection substrate, for example.

Finally, the steps for obtaining the fiber structure accumulated on the collecting substrate will be described. In the present invention, the solvent is evaporated depending on the conditions to form a fibrous material while the solution is oriented toward the collecting substrate.

At ordinary room temperature and atmospheric pressure, the solvent evaporates completely until it is collected on the collecting substrate, but if the solvent evaporation is insufficient, it may be carried out under reduced pressure. The porous fiber of this invention is formed at the latest at the time of collection on this collecting substrate. In addition, although the temperature to cut depends on the evaporation behavior of a solvent and the viscosity of a spinning liquid, it is 0-50 degreeC normally. Porous fibers are further accumulated on the collecting substrate to produce the fiber structure of the present invention.

That is, a preferred embodiment of the production method of the present invention comprises the steps of preparing a solution in which a polymer soluble in a hydrophobic solvent and an organic compound having a plurality of hydroxyl groups is dissolved in a hydrophobic solvent, spinning the solution by electrospinning, and A method of obtaining a fiber structure comprising porous fibers having an average fiber diameter of 0.1 to 20 µm and a porosity of at least 5%, comprising obtaining a fiber structure accumulated on a collecting substrate. As a polymer which can be dissolved in this hydrophobic solvent, it is preferable to use aliphatic polyester, polycarbonate, polystyrene, polyallylate, and it is preferable to use a volatile solvent as a hydrophobic solvent.

Although the fiber structure obtained by this invention may be used independently, you may use it in combination with another member according to handleability and other requirements. For example, by using a nonwoven fabric, a woven fabric, a film, or the like which can be a support substrate as a collecting substrate, a fiber structure can be formed thereon, whereby a member combining the support substrate and the fiber structure can also be created.

The use of the fibrous structure obtained by the present invention is not limited to regenerative medical cell culture substrates, and can be used for various applications that can utilize concave portions and hollow holes, which are features of the present invention, such as various filters and catalyst supporting substrates.

Disclosure of the Invention

A first object of the present invention is to provide a material suitable as a substrate for cell culture in the field of regenerative medicine, and specifically, a fiber and a fiber in which a solution containing nutrients and the like necessary for cell culture can be easily moved throughout the cell. To provide a structure.

The 2nd object of this invention is providing the manufacturing method which can obtain the porous fiber structure to which hydrophilicity was provided, without requiring complicated processes, such as an extraction operation.

Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples. In addition, the evaluation item in each following example and the comparative example was implemented with the following method.

Porosity:

Scanning electron micrographs of fiber cross sections in the obtained porous fibers or fiber structures were taken (photographing magnification 10000 times).

From the cross-sectional photograph, the entire portion of the fiber cross section in the photographic surface was cut out and the weight thereof was measured. Next, the void portion of the fiber in the photographic surface was cut out and the weight thereof was measured. The porosity with respect to one fiber was computed from these weights, the operation was repeated 5 times, and the average value was computed.

Average fiber diameter:

From the photograph obtained by taking the surface of the obtained porous fiber or a fiber structure by the scanning electron microscope ("S-2400" by Hitachi, Ltd.), it picked 20 places at random and measured the fiber diameter. The average value (n = 20) of fiber diameter was calculated | required and it was set as average fiber diameter.

Check for the presence of fibers less than 20 μm in fiber length

The photograph obtained by photographing (magnification 8000 times) by the scanning electron microscope ("S-2400" by Hitachi, Ltd.) was observed on the surface of the obtained fiber structure, and it was confirmed whether the fiber of less than 20 micrometers of fiber length exists. .

Method for quantifying organic compounds having hydroxyl groups:

The obtained fibrous structure was measured by ¹ H-NMR (JNM-EX-270, manufactured by Nippon Electronics Co., Ltd.) at 20 ° C using heavy chloroform (CDCl ₃ ) as a solvent. The molar ratio in a fiber structure was calculated | required from the integral ratio of the proton derived from chemical structure, and content (weight%) was calculated based on it.

Example 1

1 part by weight of polylactic acid (manufactured by Shimadzu Corporation, trade name: `` Lacty 9031 ''), 1 part by weight of ethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.), 8 parts by weight of methylene chloride (manufactured by Wako Pure Chemical Industries, Ltd.) The parts were mixed at room temperature (25 ° C) to create a slightly cloudy solution.

This solution was discharged to a fibrous material collecting electrode for 5 minutes using the apparatus shown in FIG. The internal diameter of the jet nozzle was 0.8 mm, the voltage was 12 kV, and the distance from the jet nozzle to the fibrous material collecting electrode was 10 cm. As a result of measuring the obtained fiber structure by the scanning electron microscope ("S-2400" by Hitachi, Ltd.), the average fiber diameter was 3 micrometers and the fiber of 20 micrometers or more was not observed. In addition, no fiber with a fiber length of less than 20 µm was observed.

The porosity was about 40% and the ethylene glycol content in the fiber structure was 18.0% by weight. 3 and 4 show scanning electron micrographs of the surface of the fiber structure and the fiber cross section.

Example 2

The same operation as in Example 1 was carried out except that 1 part by weight of diethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd., reagent grade) was used instead of ethylene glycol. The average fiber diameter was 4 mu m, and no fibers with a fiber diameter of 20 mu m or more were observed. In addition, no fiber with a fiber length of less than 20 µm was observed. The porosity was about 15% and the diethylene glycol content in the fiber structure was 47.9 wt%. 5 and 6 show scanning electron micrographs of the surface of the fiber structure and the fiber cross section.

Example 3

In Example 1, the same operation was performed except having used 1 weight part of triethylene glycol (made by Wako Pure Chemical Industries Ltd., reagent grade 1) instead of ethylene glycol. The average fiber diameter was 3 mu m, and no fibers with a fiber diameter of 20 mu m or more were observed. In addition, no fiber with a fiber length of less than 20 µm was observed. The porosity was about 15% and the triethylene glycol content in the fiber structure was 46.2 wt%. 7 and 8 show scanning electron micrographs of the surface of the fiber structure and the fiber cross section.

Example 4

In Example 1, the same operation was performed except having used 1 weight part of polyethyleneglycol (average molecular weight 200, Wako Pure Chemical Industries Ltd., reagent grade 1) instead of ethylene glycol. The average fiber diameter was 2 mu m, and no fibers with a fiber diameter of 20 mu m or more were observed. In addition, no fiber with a fiber length of less than 20 µm was observed. The porosity was about 15% and the polyethylene glycol content in the fiber structure was 50.0 wt%. 9 and 10 show scanning electron micrographs of the surface of the fiber structure and the fiber cross section.

Example 5

In Example 1, the same operation was performed except having used 1 weight part of propylene glycol (1, 2- propanediol) (made by Wako Pure Chemical Industries Ltd., reagent grade) instead of ethylene glycol. The average fiber diameter was 4 mu m, and no fibers with a fiber diameter of 20 mu m or more were observed. In addition, no fiber with a fiber length of less than 20 µm was observed. The porosity was about 15% and the 1,2-propanediol content in the fiber structure was 15.3% by weight. 11 and 12 show scanning electron micrographs of the surface of the fiber structure and the fiber cross section.

Example 6

In Example 1, the same operation was performed except having used 1 weight part of polycaprolactone (average molecular weight about 70000-100000, Wako Pure Chemical Industries, Ltd.) instead of polylactic acid. The average fiber diameter was 4 mu m, and no fibers with a fiber diameter of 20 mu m or more were observed. In addition, no fiber with a fiber length of less than 20 µm was observed. The porosity was about 15% and the ethylene glycol content in the fiber structure was 16.7% by weight. 13 and 14 show scanning electron micrographs of the surface and the fiber cross section of the fiber structure.

Example 7

In Example 1, operation similar to Example 1 was performed except having used 1 weight part of polycarbonates (Teijin Kasei Co., Ltd. make: brand name "Panlite L1250") instead of polylactic acid. The average fiber diameter was 3 mu m, and no fibers with a fiber diameter of 20 mu m or more were observed. In addition, no fiber with a fiber length of less than 20 µm was observed. The porosity was about 35% and the ethylene glycol content in the fiber structure was 12.3% by weight.

15 and 16 show scanning electron micrographs of the surface of the fiber structure and the fiber cross section.

Example 8

In Example 1, the same operation was performed except having used 1 weight part of polystyrene (average molecular weight 250000, Kanto Chemical Co., Ltd.) instead of polylactic acid. The average fiber diameter was 6 mu m, and no fibers with a fiber diameter of 20 mu m or more were observed. In addition, no fiber with a fiber length of less than 20 µm was observed. The porosity was about 35% and the ethylene glycol content in the fiber structure was 11.2% by weight. 17 and 18 show scanning electron micrographs of the surface of the fiber structure and the fiber cross section.

Example 9

In Example 1, operation similar to Example 1 was performed except having used 1 weight part of polyallylate (Unitica Co., Ltd. make: brand name "U-polymer U-100") instead of polylactic acid. The average fiber diameter was 3 mu m, and no fibers with a fiber diameter of 20 mu m or more were observed. In addition, no fiber with a fiber length of less than 20 µm was observed. The porosity was about 35% and the ethylene glycol content in the fiber structure was 12.5% by weight. 19 and 20 show scanning electron micrographs of the surface and the fiber cross section of the fiber structure.

Comparative Example 1

In Example 1, the same operation was performed except having used 9 weight part of methylene chlorides instead of ethylene glycol. The average fiber diameter was 2 mu m, and no fibers with a fiber diameter of 20 mu m or more were observed. In addition, no fiber with a fiber length of less than 20 µm was observed. In the fiber cross section, no concave portions or hollow holes were seen, and the porosity was 0%. Content of the organic compound which has a hydroxyl group in a fiber structure was 0 weight%. 21 and 22 show scanning electron micrographs of the surface and the fiber cross section of the fiber structure.

Comparative Example 2

In Example 1, the same operation was performed except having used 1 weight part of polyethyleneglycol (average molecular weight 400, Wako Pure Chemical Industries Ltd., reagent grade 1) instead of ethylene glycol. The average fiber diameter was 3 mu m, and no fibers with a fiber diameter of 20 mu m or more were observed. In addition, no fiber with a fiber length of less than 20 µm was observed. In the fiber cross section, no concave portions or hollow holes were seen, and the porosity was 0%. The polyethyleneglycol content in the fiber structure was 50.0 wt%. 23 and 24 show scanning electron micrographs of the surface and the fiber cross section of the fiber structure.

Comparative Example 3

In Example 1, the same operation was performed except having used 1 weight part of polyethyleneglycol (average molecular weight 600, Wako Pure Chemical Industries Ltd., reagent grade 1) instead of ethylene glycol. The average fiber diameter was 3 mu m, and no fibers with a fiber diameter of 20 mu m or more were observed. In addition, no fiber with a fiber length of less than 20 µm was observed. In the fiber cross section, no concave portions or hollow holes were seen, and the porosity was 0%. The polyethyleneglycol content in the fiber structure was 50.0 wt%. 25 and 26 show scanning electron micrographs of the surface of the fiber structure and the fiber cross section.

Claims (13)

Porous fiber which consists of a polymer which can melt | dissolve in a hydrophobic solvent, and the organic compound which has a some hydroxyl group, and whose average fiber diameter is 0.1-20 micrometers, and a porosity is at least 5%. The porous fiber according to claim 1, wherein the hydrophobic solvent is a halogen element-containing hydrocarbon. The porous fiber according to claim 2, wherein the halogen-containing carbon is selected from the group consisting of methylene chloride, chloroform, dichloroethane, tetrachloroethane, trichloroethane, dibromomethane, and bromoform. The porous fiber according to claim 1, wherein the polymer soluble in a hydrophobic solvent is selected from the group consisting of polylactic acid, polycaprolactone, polycarbonate, polystyrene, and polyallylate. The porous fiber of Claim 1 whose number average molecular weights of the organic compound which has a some hydroxyl group are 62 or more and 300 or less. A fibrous structure comprising a porous fiber composed of a polymer soluble in a hydrophobic solvent and an organic compound having a plurality of hydroxyl groups, and having an average fiber diameter of 0.1 to 20 µm and a porosity of at least 5%. The fiber structure according to claim 6, wherein the hydrophobic solvent is a halogen element-containing hydrocarbon. The fiber structure according to claim 7, wherein the halogen-containing hydrocarbon is selected from the group consisting of methylene chloride, chloroform, dichloroethane, tetrachloroethane, trichloroethane, dibromomethane and bromoform. The fiber structure according to claim 6, wherein the number average molecular weight of the organic compound having a plurality of hydroxyl groups is 62 or more and 300 or less. The fiber structure according to claim 1, wherein the polymer soluble in a hydrophobic solvent is selected from the group consisting of polylactic acid, polycaprolactone, polycarbonate, polystyrene, and polyallylate. Preparing a solution in which a polymer soluble in a hydrophobic solvent and an organic compound having a plurality of hydroxyl groups are dissolved in a hydrophobic solvent, spinning the solution by electrospinning, and obtaining a fibrous structure accumulated on a collecting substrate. A method for producing a fiber structure comprising porous fibers having an average fiber diameter of 0.1 to 20 µm and a porosity of at least 5%. The method for producing a fibrous structure according to claim 11, wherein the hydrophobic solvent is a halogen element-containing hydrocarbon. The method for producing a fibrous structure according to claim 12, wherein the halogen-containing hydrocarbon is selected from the group consisting of methylene chloride, chloroform, dichloroethane, tetrachloroethane, trichloroethane, dibromomethane and bromoform.