JP2006233355A - Nonwoven fabric and method for producing nonwoven fabric - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonwoven fabric having a high ionic exchanging rate and a method for producing the nonwoven fabric. <P>SOLUTION: This nonwoven fabric consists of a proton-conductive polymer, has ≤3 μm mean fiber diameter of the constituting fiber, doesn't substantially contain fibers having ≥10 μm fiber diameter and doesn't substantially contain the fibers having ≤60 μm fiber length. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a nonwoven fabric and a method for producing the nonwoven fabric.

  Ion exchange resins are widely used for water treatment, recovery of valuable materials, and purification. As the shape of the ion exchange resin, a particulate form is generally used, and it is known that the ion exchange rate can be increased by reducing the particle size (see, for example, Non-Patent Document 1).

  As a method for immobilizing the ion exchange resin when using the ion exchange resin, a method of forming into a fiber shape is known (for example, see Patent Document 1). However, since the fibrous ion exchange resins produced by these usual methods have a large fiber diameter, a fibrous ion exchange resin having a smaller fiber diameter has been desired in order to obtain a sufficient ion exchange rate.

  On the other hand, an electrostatic spinning method is known as a method for producing a fiber structure having a small fiber diameter (see, for example, Patent Documents 2 and 3). The electrospinning method includes a step of introducing a liquid, for example, a solution containing a fiber-forming substance into an electric field, thereby causing the liquid to move toward an electrode and forming a fibrous substance. Usually, the fiber forming material is cured while it is squeezed out of solution. Curing is performed, for example, by cooling (for example, when the spinning liquid is solid at room temperature), chemical curing (for example, treatment with curing steam), or evaporation of the solvent. Moreover, the obtained fibrous substance is collected on a suitably arranged receptor, and can be peeled from there if necessary.

“Encyclopedia of Plastics and Functional Polymers” Industry Research Association Encyclopedia Publishing Center, February 20, 2004, page 701 JP 2001-181965 A JP-A 63-145465 JP 2002-249966 A

  An object of the present invention is to solve the problems of the prior art and provide a nonwoven fabric having a high ion exchange rate and a method for producing the nonwoven fabric.

As a result of intensive studies in view of the above prior art, the present inventors have completed the present invention.
That is, the object of the present invention is to
Non-woven fabric made of a proton-conductive polymer and having an average fiber diameter of 3 μm or less, a fiber having a fiber diameter of 10 μm or more and substantially no fiber having a fiber length of 60 μm or less Achieved by:

Furthermore, another object of the present invention is to
Adding a fiber-forming organic polymer to a solution containing a proton-conducting polymer, spinning the solution containing the fiber-forming organic polymer by an electrostatic spinning method, and collecting by the spinning. This can be achieved by a method for producing a nonwoven fabric, comprising the steps of obtaining a fiber structure accumulated on a substrate and removing a fiber-forming organic polymer contained in the fiber structure.

  The nonwoven fabric obtained by the present invention is effective as ion exchange resin molding because the fiber diameter of the constituent fibers is small and the ion exchange rate is excellent. Moreover, the obtained nonwoven fabric can also be used as it is, and can also be used in combination with another member according to handling property and other requirements.

Hereinafter, the present invention will be described in detail.
The nonwoven fabric of the present invention is composed of a proton conductive polymer, the average fiber diameter of the constituent fibers is 3 μm or less, there is substantially no fiber having a fiber diameter of 10 μm or more, and the fiber length is substantially 60 μm or less. It is necessary that no fibers are present.

（ｍ、ｎは１以上の整数）

（ｍ、ｎは１以上の整数） Here, an ionomer is preferably used as the proton conductive polymer. Here, the ionomer is a general term for a polymer having a molecular chain to which an inorganic salt group is bonded. A typical structure of an ionomer includes a structure represented by the following formula:

(M and n are integers of 1 or more)

(M and n are integers of 1 or more)

（ｍ、ｎは１以上の整数） More preferably, a fluorine-containing resin having high chemical stability is preferable, and “Nafion” represented by the following formula is more preferable.

(M and n are integers of 1 or more)

Next, it will be described that the average fiber diameter of the constituent fibers is 3 μm or less.
When the average diameter of the fibers forming the nonwoven fabric of the present invention exceeds 3 μm, the specific surface area of the fibers becomes small and the ion exchange efficiency becomes low. Moreover, if the average diameter of the fiber is 0.1 μm or more, the strength of the obtained nonwoven fabric is sufficient. The average diameter of the fibers constituting the nonwoven fabric is preferably in the range of 0.1 to 1 μm.

Next, the fact that there is substantially no fiber having a fiber diameter of 10 μm or more will be described.
The term “substantially absent” means that fibers having a fiber diameter in the above range are not observed at any point in an electron microscope. In addition, if the fiber forming the nonwoven fabric of the present invention contains a fiber having a fiber diameter exceeding 10 μm, the specific surface area of the fiber is reduced and ion exchange efficiency is lowered, which is not preferable, and the flexibility of the nonwoven fabric is impaired. This is also not preferable. Moreover, in order to exhibit the performance of this nonwoven fabric, it is more preferable that the fiber which has a fiber diameter of 5 micrometers or more does not exist.

  Next, it will be described that there is substantially no fiber having a fiber length of 60 μm or less. Here, “substantially absent” means that both ends of the fiber are not observed in an electron microscope observation at a magnification of 2000 centered on an arbitrary point. Moreover, when the fiber which forms the nonwoven fabric of this invention contains the fiber whose fiber length is 60 micrometers or less, since the entanglement of fibers will become weak and the intensity | strength of a nonwoven fabric will fall, it is unpreferable.

  In order to produce the nonwoven fabric of the present invention, any technique can be used as long as it can obtain a nonwoven fabric that satisfies the above-mentioned requirements at the same time. Adding a molecule, spinning a solution added with the fiber-forming organic polymer by an electrostatic spinning method, obtaining a fiber structure accumulated on a collection substrate by the spinning, and A preferred embodiment of the production method is to remove the fiber-forming organic polymer contained in the fiber structure.

First, the electrostatic spinning method will be described.
Electrospinning is a method in which a solution in which a fiber-forming substrate is dissolved is discharged into an electrostatic field formed between electrodes, the solution is spun toward the electrodes, and the fibrous material formed is collected It is a method of obtaining a fiber structure by accumulating on the fibrous material, and the fibrous substance is not only a state in which the solvent in which the fiber-forming substrate is dissolved is distilled off to form a fiber laminate, The state in which the solvent is contained in the fibrous material is also shown.

Next, an apparatus used in the electrostatic spinning method will be described.
The above-described electrode can be used as long as it has conductivity, and any metal, inorganic, or organic material has a thin film of conductive metal, inorganic, or organic material on an insulator. May be.

  The electrostatic field is formed between a pair or a plurality of electrodes, and a high voltage may be applied to any of the electrodes. This includes, for example, using two high-voltage electrodes with different voltage values (for example, 15 kV and 10 kV) and a total of three electrodes connected to the ground, or when using more than three electrodes. Shall also be included.

Next, the manufacturing method of the fiber structure which comprises the nonwoven fabric of this invention by an electrospinning method is demonstrated later on.
First, a fiber-forming organic polymer is added to a solution containing a proton conductive polymer, and the concentration of the proton conductive polymer with respect to the solvent in the solution in the production method of the present invention is 0.5 to 30% by weight. Is preferred. If the concentration of the proton-conductive polymer substrate is less than 0.5% by weight, it is not preferable because the concentration is too low to form fibers. On the other hand, if it is larger than 30% by weight, the fiber diameter of the obtained fiber is undesirably large. The concentration of the proton conductive polymer with respect to the solvent in the solution is more preferably 2 to 20% by weight, and more preferably 3 to 10% by weight.

  Moreover, a solvent may be used individually by 1 type and may combine several solvent. The solvent is not particularly limited as long as it can dissolve the proton-conducting polymer and the fiber-forming organic polymer and evaporates at the stage of spinning by an electrostatic spinning method to form a fiber. For example, acetone, chloroform, ethanol, isopropanol, methanol, toluene, tetrahydrofuran, water, benzene, benzyl alcohol, 1,4-dioxane, propanol, methylene chloride, carbon tetrachloride, cyclohexane, cyclohexanone, phenol, pyridine, trichloroethane, acetic acid, Examples include formic acid, hexafluoroisopropanol, hexafluoroacetone, N, N-dimethylformamide, acetonitrile, N-methylmorpholine-N-oxide, 1,3-dioxolane, methyl ethyl ketone, and a mixed solvent of the above solvents.

  Among these, from the viewpoint of handling properties and physical properties, it is preferable to use aliphatic alcohol, water, methylene chloride, chloroform and a mixed solvent thereof, more preferably a mixed solvent of aliphatic alcohol and water. .

  The fiber-forming organic polymer is not limited as long as it is an organic polymer that can be added to a solution containing a proton conductive polymer and gives a viscosity necessary for electrostatic spinning. The molecular weight of is preferably 1,000,000 or more. When the molecular weight is 1,000,000 or less, in order to give the viscosity necessary for electrospinning, the fiber diameter increases as the amount added is increased, and the fiber-forming property of the proton-conductive polymer increases. Since the ratio of the organic polymer is increased, the ionic conductivity of the nonwoven fabric is lowered, which is not preferable. More preferably, the molecular weight is 2,000,000 or more.

  Further, since the smaller the ratio of the fiber-forming organic polymer to the proton-conducting polymer, the better. Therefore, the concentration of the fiber-forming organic polymer is preferably 1% by weight or less, more preferably 0.8%. 5% by weight or less.

The fiber-forming organic polymer is not limited as long as it is an organic polymer that can be added to a solution containing a proton conductive polymer and gives a viscosity necessary for electrostatic spinning. Is preferably dissolved in a mixed solvent of an aliphatic alcohol and water, and examples thereof include polyethylene oxide, polyvinyl alcohol, polyvinyl ester, polyvinyl ether, polyvinyl pyridine, polyacrylamide, ether cellulose, and pectin.
Among these, polyethylene oxide is more preferable from the viewpoint of handling.

Next, a step of obtaining a fiber structure accumulated on the collection substrate will be described.
In the production method of the present invention, since the spinning is performed by the electrostatic spinning method, the fiber structure is laminated on the electrode that is the collection substrate. If a flat surface is used for the collection substrate, a planar nonwoven fabric can be obtained. However, by changing the shape of the collection substrate, a structure having a desired shape can be produced.
In addition, when the uniformity is low, such as when the fiber structure is concentrated and laminated at one place on the substrate, the substrate can be swung or rotated.

  Next, the step of removing the fiber-forming organic polymer contained in the fiber structure will be described. Any method can be applied as long as it removes the fiber-forming organic polymer contained in the fiber structure. However, as a preferred method, the fiber-forming organic polymer is dissolved, but the proton-conducting polymer is dissolved. The method of immersing the said fiber structure in the solvent which does not do is mentioned. The solvent is preferably water, and an inorganic salt can be added or the pH can be adjusted as necessary.

  Moreover, it is also possible to heat-treat the fiber structure containing the fiber-forming organic polymer or the fiber structure from which the fiber-forming organic polymer has been removed. By heat treatment, the crystallinity of the proton conductive polymer can be increased, or the proton conductive polymer can be thermally denatured.

  Moreover, the use of the nonwoven fabric obtained by this invention is not limited to the member for ion exchange resins, It can use for various uses, such as various filters, a catalyst support base material, and a battery separator member.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. The evaluation items in the following examples and comparative examples were carried out by the following methods.
Moreover, each value in an Example was calculated | required with the following method.
Average fiber diameter:
The surface of the obtained fiber structure was photographed with a scanning electron microscope (S-2400, manufactured by Hitachi, Ltd.) (magnification: 2000 times), and randomly selected 20 locations from the photograph, and the fiber diameter was measured. The average value of all the fiber diameters (n = 20) was determined and used as the average fiber diameter.

[Example 1]
“Nafion” solution (“Nafion” perfluorinated ion-exchange resin, 5 wt% solution in a mixture of lower aliphatic alcohols and water, d0.874, Sigma Aldrich average, 4 parts by weight, polyethylene oxide, and total weight of polyethylene oxide (Shimaru Aldrich) 1,000,000) parts by weight were mixed at room temperature (25 ° C.) to prepare a solution. Spinning was performed using the apparatus shown in FIG. 1 to obtain a fiber structure. The inner diameter of the ejection nozzle 1 was 0.6 mm, the voltage was 15 kV, and the distance from the ejection nozzle 1 to the electrode 4 was 15 cm. The average diameter of the fibers constituting the obtained fiber structure was 1.2 μm. An electron micrograph of the fiber structure is shown in FIG.

[Example 2]
“Nafion” solution (“Nafion” perfluorinated ion-exchange resin, 5 wt% solution in a mixture of lower aliphatic alcohols and water, d0.874, Sigma Aldrich average, 4 parts by weight, polyethylene oxide, and total weight of polyethylene oxide (Shimaru Aldrich) (000,000) 0.05 parts by weight were mixed at room temperature (25 ° C.) to prepare a solution. Spinning was performed using the apparatus shown in FIG. 1 to obtain a fiber structure. The inner diameter of the ejection nozzle 1 was 0.6 mm, the voltage was 15 kV, and the distance from the ejection nozzle 1 to the electrode 4 was 15 cm. The average diameter of the fibers constituting the obtained fiber structure was 0.9 μm. An electron micrograph of the fiber structure is shown in FIG.

[Example 3]
“Nafion” solution (“Nafion” perfluorinated ion-exchange resin, 5 wt% solution in a mixture of lower aliphatic alcohols and water, d0.874, Sigma Aldrich average, 4 parts by weight, polyethylene oxide, and total weight of polyethylene oxide (Shimaru Aldrich) 1,000,000) was mixed at room temperature (25 ° C.) to prepare a solution. Spinning was performed using the apparatus shown in FIG. 1 to obtain a fiber structure. The inner diameter of the ejection nozzle 1 was 0.6 mm, the voltage was 15 kV, and the distance from the ejection nozzle 1 to the electrode 4 was 15 cm. The average diameter of the fibers constituting the obtained fiber structure was 1.1 μm. An electron micrograph of the fiber structure is shown in FIG.

[Example 4]
“Nafion” solution (“Nafion” perfluorinated ion-exchange resin, 5 wt% solution in a mixture of lower aliphatic alcohols and water, d0.874, Sigma Aldrich average, 4 parts by weight, polyethylene oxide, and total weight of polyethylene oxide (Shimaru Aldrich) (000,000) 0.2 part by weight was mixed at room temperature (25 ° C.) to prepare a solution. Spinning was performed using the apparatus shown in FIG. 1 to obtain a fiber structure. The inner diameter of the ejection nozzle 1 was 0.6 mm, the voltage was 15 kV, and the distance from the ejection nozzle 1 to the electrode 4 was 15 cm. The average diameter of the fibers constituting the obtained fiber structure was 2.0 μm. An electron micrograph of the fiber structure is shown in FIG.

[Example 5]
“Nafion” solution (“Nafion” perfluorinated ion-exchange resin, 5 wt% solution in a mixture of lower aliphatic alcohols and water, d0.874, Sigma-Aldrich) 000) 0.15 parts by weight was mixed at room temperature (25 ° C.) to prepare a solution. Spinning was performed using the apparatus shown in FIG. 1 to obtain a fiber structure. The inner diameter of the ejection nozzle 1 was 0.6 mm, the voltage was 15 kV, and the distance from the ejection nozzle 1 to the electrode 4 was 15 cm. The average diameter of the fibers constituting the obtained fiber structure was 3.8 μm. An electron micrograph of the fiber structure is shown in FIG.

[Example 6]
“Nafion” solution (“Nafion” perfluorinated ion-exchange resin, 20 wt% solution in a mixture of lower aliphatic alcohols and water, d0.976, Sigma-Aldrich) 1,000,000) parts by weight were mixed at room temperature (25 ° C.) to prepare a solution. Spinning was performed using the apparatus shown in FIG. 1 to obtain a fiber structure. The inner diameter of the ejection nozzle 1 was 0.6 mm, the voltage was 15 kV, and the distance from the ejection nozzle 1 to the electrode 4 was 15 cm. The average diameter of the fibers constituting the obtained fiber structure was 1.6 μm. An electron micrograph of the fiber structure is shown in FIG.

[Comparative Example 1]
“Nafion” solution (“Nafion” perfluorinated ion-change resin, 5 wt% solution in a mixture of lower aliphatic alcohols and water, d0.874, Sigma Aldrich average, weight of polyethylene oxide, molecular weight of polyethylene oxide (000) , 000) 0.005 parts by weight were mixed at room temperature (25 ° C.) to prepare a solution. Spinning was performed using the apparatus shown in FIG. The inner diameter of the ejection nozzle 1 was 0.6 mm, the voltage was 15 kV, and the distance from the ejection nozzle 1 to the electrode 4 was 15 cm. When the obtained structure was observed with an electron microscope, a fiber structure was not confirmed. An electron micrograph is shown in FIG.

[Comparative Example 2]
“Nafion” solution (“Nafion” perfluorinated ion-exchange resin, 5 wt% solution in a mixture of lower aliphatic alcohols and water, d0.874, Sigma Aldrich average, 4 parts by weight, polyethylene oxide, and total weight of polyethylene oxide (Shimaru Aldrich) When 0.25 parts by weight of (000,000) were mixed at room temperature (25 ° C.), polyethylene oxide was not completely dissolved, and a uniform solution could not be produced.

[Comparative Example 3]
“Nafion” solution (“Nafion” perfluorinated ion-exchange resin, 5 wt% solution in a mixture of lower aliphatic alcohols and water, d0.874, sigma aldrich) ) 0.015 parts by weight were mixed at room temperature (25 ° C.) to prepare a solution. Spinning was performed using the apparatus shown in FIG. The inner diameter of the ejection nozzle 1 was 0.6 mm, the voltage was 15 kV, and the distance from the ejection nozzle 1 to the electrode 4 was 15 cm. When the obtained structure was observed with an electron microscope, a fiber structure was not confirmed. An electron micrograph is shown in FIG.

[Comparative Example 4]
“Nafion” solution (“Nafion” perfluorinated ion-exchange resin, 5 wt% solution in a mixture of lower aliphatic alcohols and water, d0.874, Sigma-Aldrich) ) 0.1 part by weight was mixed at room temperature (25 ° C.) to prepare a solution. Spinning was performed using the apparatus shown in FIG. The inner diameter of the ejection nozzle 1 was 0.6 mm, the voltage was 15 kV, and the distance from the ejection nozzle 1 to the electrode 4 was 15 cm. When the obtained structure was observed with an electron microscope, a fiber structure was not confirmed. An electron micrograph is shown in FIG.

[Comparative Example 5]
A device using a “Nafion” solution (“Nafion” perfluorinated ion-exchange resin, 5 wt% solution in a mixture of lower aliphatic alcohols and water, d0.874, sigma aldritch) as a solution is shown in FIG. . The inner diameter of the ejection nozzle 1 was 0.6 mm, the voltage was 15 kV, and the distance from the ejection nozzle 1 to the electrode 4 was 15 cm. When the obtained structure was observed with an electron microscope, a fiber structure was not confirmed. An electron micrograph is shown in FIG.

[Comparative Example 6]
A solution using a “Nafion” solution (“Nafion” perfluorinated ion-exchange resin, 20 wt% solution in a mixture of lower aliphatic alcohols and water, d0.976, Sigma Aldrich) as a solution. . The inner diameter of the ejection nozzle 1 was 0.6 mm, the voltage was 15 kV, and the distance from the ejection nozzle 1 to the electrode 4 was 15 cm. When the obtained structure was observed with an electron microscope, a fiber structure was not confirmed. An electron micrograph is shown in FIG.

It is the figure which showed typically the manufacturing apparatus for performing the manufacturing method of this invention. It is the photograph figure obtained by imaging | photography (2000 times) the surface of the fiber obtained by operation of Example 1 with a scanning electron microscope. It is the photograph figure obtained by image | photographing (2000 times) the surface of the fiber obtained by operation of Example 2 with a scanning electron microscope. It is the photograph figure obtained by photographing the surface of the fiber obtained by operation of Example 3 with a scanning electron microscope (2000 times). It is the photograph figure obtained by image | photographing (2000 times) the surface of the fiber obtained by operation of Example 4 with a scanning electron microscope. It is the photograph figure obtained by photographing the surface of the fiber obtained by operation of Example 5 with a scanning electron microscope (2000 times). It is the photograph figure obtained by photographing the surface of the fiber obtained by operation of Example 6 with a scanning electron microscope (2000 times). 6 is a photographic view obtained by photographing (2000 times) the structure obtained by the operation of Comparative Example 1 with a scanning electron microscope. FIG. It is the photograph figure obtained by image | photographing (2000 times) the structure obtained by operation of the comparative example 3 with a scanning electron microscope. It is the photograph figure obtained by image | photographing (2000 times) the structure obtained by operation of the comparative example 4 with a scanning electron microscope. It is the photograph figure obtained by image | photographing (2000 times) the structure obtained by operation of the comparative example 5 with a scanning electron microscope. It is the photograph figure obtained by image | photographing (2000 times) the structure obtained by operation of the comparative example 6 with a scanning electron microscope.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solution ejection nozzle 2 Solution 3 Solution holding tank 4 Electrode 5 High voltage generator

Claims (13)

  Non-woven fabric made of a proton-conductive polymer, having an average fiber diameter of 3 μm or less, having no fiber having a fiber diameter of 10 μm or more, and having substantially no fiber length of 60 μm or less .   The nonwoven fabric of claim 1, wherein the proton conducting polymer is an ionomer. The nonwoven fabric according to claim 2, wherein the ionomer has a structure represented by the following general formula (I).

(M and n are integers of 1 or more)   Adding a fiber-forming organic polymer to a solution containing a proton-conducting polymer, spinning the solution containing the fiber-forming organic polymer by an electrostatic spinning method, and collecting by the spinning. A method for producing a nonwoven fabric, comprising: obtaining a fiber structure accumulated on a substrate; and removing a fiber-forming organic polymer contained in the fiber structure.   The production method according to claim 4, wherein the proton conductive polymer is an ionomer. The production method according to claim 5, wherein the ionomer has a structure represented by the following general formula (I).

(M and n are integers of 1 or more)   The manufacturing method of Claim 4 whose solution containing the said proton-conductive polymer is a solution which consists of a volatile organic solvent.   The production method according to claim 7, wherein the volatile organic solvent is a mixed solvent of an aliphatic alcohol and water.   The production method according to claim 4, wherein the fiber-forming organic polymer is a thermoplastic polymer.   The production method according to claim 9, wherein the thermoplastic polymer is polyethylene oxide.   The production method according to claim 4, wherein the fiber-forming organic polymer has a molecular weight of 1,000,000 or more.   The method according to claim 4, wherein the step of removing the fiber-forming organic polymer from the fiber structure is performed by immersing the fiber structure in a solvent capable of dissolving the organic polymer.   The production method according to claim 5, wherein the solvent in which the fiber structure is immersed is water.

Images