JP7061908B2 - Composite nanofiber non-woven fabric and its manufacturing method - Google Patents

Description

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

The nanofiber non-woven fabric is a non-woven fabric composed of ultrafine fibers (nanofibers) having a fiber diameter of several tens to several hundreds of nm. Compared to conventional non-woven fabrics with fiber diameters on the order of μm, nanofiber non-woven fabrics have features such as high specific surface area, fine pore size, and unique functional expression derived from microstructures on the order of nm. It has been applied to applications such as membrane reinforcing materials, separators for batteries and capacitors, filter media, and cell culture substrates.

Since polyazole-based compounds have features such as high heat resistance, high mechanical strength, and high chemical stability, nanofiber non-woven fabrics containing polyazole-based compounds are attracting attention as high-performance, high-performance non-woven fabrics.

For example, in Patent Document 1, a composite polyelectrolyte film having a composite layer in which a nanofiber non-woven fabric composed of nanofibers of a polyazole compound and an ionic group-containing polyelectrolyte is composite is provided under low humidification and low temperature conditions. It is described that it has excellent proton conductivity, a small dimensional change rate, and excellent mechanical strength and chemical stability.

Further, Patent Document 2 includes a polytetrafluoroethylene porous membrane in which a high elasticity material such as polybenzimidazole is composited on the inner surface of the small pores, and an electrolyte membrane for a fuel cell containing a polymer electrolyte. It is disclosed that the electrolyte membrane has low resistance, high mechanical strength, and high durability.

Further, Patent Document 3 describes a composite porous film in which a porous base material and a polymer are composited, and the porous base material is a woven fabric of fibers, a non-woven fabric of fibers, a porous metal body, and the like. It is composed of any one of the inorganic material porous bodies, and the polymer contains a condensed ring compound of a 6-membered ring and a 5-membered heterocyclic ring as a repeating unit, and has a three-dimensional network in the pores of the porous substrate. Described is a composite porous membrane forming a porous structure in the form of a shape.

International release 2017/141878 International Release 2016/056430 Japanese Patent Application Laid-Open No. 2008-214462

However, since the polyazole-based compound is a highly heat-resistant polymer having an extremely high softening temperature, the nanofiber non-woven fabric composed of the nanofibers of the polyazole-based compound as in Cited Document 1 is bonded by heat treatment, calendar treatment, pressing, or the like. It is difficult to process. Therefore, it is difficult to obtain a high-quality self-supporting non-woven fabric that does not cause the fibers to loosen or fall off. In the present specification, "self-sustaining" means that the fiber does not self-destruct or collapse under various handling conditions, and "self-destruction / disintegration" means that the fiber does not unravel or fall off, and that it breaks or perpetuates due to stress. It means that there is no deformation. In fact, the polyazole-based nanofiber non-woven fabric has a problem that it is easily broken when exposed to an external stress such as tension, and the fibers are easily loosened and fall off due to friction during handling. These problems often occur when the nanofiber non-woven fabric is continuously wound into a roll or unwound from the roll, which causes a deterioration in the quality of the nanofiber non-woven fabric.

Further, the polytetrafluoroethylene porous membrane of Reference 2 also generally has low rigidity and lacks independence, so that it is liable to undergo permanent deformation due to tension applied during processing and handling, and wrinkles and breakage occur. It is easy to cause problems such as. Further, the polytetrafluoroethylene porous membrane tends to have a smaller pore diameter than the nanofiber non-woven fabric, and tends to cause problems such as pore clogging due to compounding with a high elastic modulus material. Therefore, from the viewpoint of the manufacturing method, it is difficult to maintain the porous structure and the porosity before and after the compounding.

Further, Patent Document 3 improves the rigidity of the porous substrate and reduces the average pore size by combining the porous substrate and the three-dimensional network structure of the polymer. There is no disclosure about the use of non-woven fabric.

The present invention has been made in view of the above circumstances, and although it has characteristics such as low chargeability derived from a polyazole compound, it breaks in a harsh usage environment where stress is applied or in a manufacturing / processing process. It is an object of the present invention to provide a composite nanofiber non-woven fabric which is less likely to cause problems such as fiber unraveling and falling off, and a method for producing the same.

The present inventors have conducted diligent studies to solve the above problems. As a result, it has been found that the above-mentioned problems can be solved by covering at least a part of the fiber surface of the base material nanofiber non-woven fabric with a polyazole-based compound, and the present invention has been completed.

That is, the present invention is as follows.
[1]
Substrate nanofiber non-woven fabric and
It has a polyazole-based compound that covers at least a part of the fiber surface constituting the base material nanofiber nonwoven fabric, and has.
The ratio Y / X of the mass percent concentration X (%) of the polyazole compound in the entire composite nanofiber nonwoven fabric to the mass percent concentration Y (%) of the polyazole compound on the fiber surface of the composite nanofiber nonwoven fabric is 2 That's it ,
Composite nanofiber non-woven fabric for composite electrolyte membranes .
[2]
The mass percent concentration X (%) of the polyazole compound in the entire composite nanofiber nonwoven fabric is 0.5% or more and 10% or less.
The composite nanofiber non-woven fabric according to [1] .
[3]
The polyazole-based compound contains a polybenzimidazole-based compound.
The composite nanofiber non-woven fabric according to [1] or [2] .
[4]
One or more of the fibers constituting the base material nanofiber non-woven fabric selected from the group consisting of polyethersulfone (PES), polyvinylidene fluoride (PVDF), polysulfone (PSU), polyimide (PI), and polyacrylonitrile (PAN). Containing the compound of
The composite nanofiber non-woven fabric according to any one of [1] to [3] .
[5]
The average fiber diameter of the fibers constituting the composite nanofiber non-woven fabric is 100 nm or more and 500 nm or less.
The composite nanofiber non-woven fabric according to any one of [1] to [4] .
[6]
The composite nanofiber nonwoven fabric according to any one of [1] to [5] and
With a proton conductive polymer,
Composite electrolyte membrane.
[7]
The method for producing a composite nanofiber nonwoven fabric according to any one of [1] to [5] .
The step comprising immersing the base material nanofiber non-woven fabric in a polyazole solution in which a polyazole compound and an alkali metal hydroxide are dissolved in a protonic solvent
A method for manufacturing a composite nanofiber non-woven fabric.

According to the present invention, although it has characteristics such as low chargeability derived from a polyazole compound, it causes problems such as breakage, fiber unraveling and falling off in a harsh usage environment where stress is applied and in a manufacturing / processing process. It is possible to provide a difficult composite nanofiber non-woven fabric and a method for producing the same.

It is a schematic diagram for demonstrating the structure of the composite electrolyte membrane of this embodiment. It is a schematic diagram for demonstrating an example of the use mode of the composite electrolyte membrane of this embodiment.

Hereinafter, embodiments for carrying out the present invention (hereinafter, simply referred to as “the present embodiment”) will be described in detail with reference to the drawings as necessary, but the present invention is limited to the following embodiments. It's not a thing. The present invention can be modified in various ways without departing from the gist thereof.

<Composite nanofiber non-woven fabric>
In the composite nanofiber nonwoven fabric of the present embodiment, at least a part of the fiber surface constituting the base material nanofiber nonwoven fabric is coated with a polyazole-based compound. As a result, the composite nanofiber non-woven fabric of the present embodiment solves the problem of fiber unraveling and falling off, which has been conventionally a problem in nanofiber non-woven fabrics composed of nanofibers of polyazole-based compounds, and is derived from polyazole-based compounds. It has both excellent characteristics such as low chargeability and high heat resistance, excellent break elongation derived from the base material nanofiber non-woven fabric, and reduction of fiber unraveling and falling off. Further, since the chargeability is low, the adsorption of foreign substances is suppressed, and wrinkles due to static electricity and troubles of wrapping around the roll are reduced. Therefore, for example, it is possible to reduce the decrease in yield when the composite nanofiber nonwoven fabric of the present embodiment is composited with another resin. In addition, even in harsh usage environments where stress is applied, and in manufacturing and processing processes that include high-speed winding and feeding of long rolls, nanofiber non-woven fabrics and processed products such as breakage and fiber unraveling and falling off. Deterioration of quality is suppressed. Hereinafter, the configuration of the composite nanofiber non-woven fabric will be described in detail.

<Polyazole compound>
The polyazole-based compound refers to a polymer containing a repeating unit having a complex five-membered ring (azole ring) containing one or more nitrogen atoms, or a polymer composed of the repeating unit. Such polyazole-based compounds are not particularly limited, but are, for example, polyimidazole-based compounds, polybenzimidazole-based compounds, polybenzbisimidazole-based compounds, polybenzoxazole-based compounds, polyoxazole-based compounds, and polythiazole-based compounds. , Polybenzthiazole-based compounds, Polythiazol-based compounds, Polybenzthiazol-based compounds, Polytriazole-based compounds, Polybenztriazole-based compounds, Polypyrazole-based compounds, Polybenzpyrazole-based compounds, Polyflazan-based compounds, Polybenzfrazan-based compounds. , Polypyrrole compounds can be mentioned.

Further, the repeating unit having an azole ring may have a structure in which the azole ring is bonded to a divalent aromatic group. The divalent aromatic group is not particularly limited, but for example, a p-phenylene group, an m-phenylene group, a naphthalene group, a diphenylene ether group, a diphenylene sulfonyl group, a biphenylene group, a terphenyl group, 2,2-. Examples thereof include a bis (4-carboxyphenylene) hexafluoropropane group. The low chargeability, heat resistance, and mechanical strength of the composite nanofiber non-woven fabric obtained by using a polymer containing a repeating unit having an azole ring and a divalent aromatic group, or a polymer composed of the repeating unit. Chemical stability tends to be improved. Among these, polyimidazole-based compounds, polybenzimidazole-based compounds, and polybenzbenzimidazole-based compounds are preferable, polybenzimidazole is more preferable, and poly [2,2'-(m-phenylene) -5,5'-bis Benzimidazole] is more preferred. The azole ring may contain an oxygen atom or a sulfur atom in addition to the nitrogen atom. Further, in addition to the above divalent aromatic group, a divalent linking group such as an imide group, an amide group, an ester group, an ether group, a sulfonyl group and a carbonyl group may be contained in the repeating unit.

The weight average molecular weight of the polyazole compound is preferably 300 to 500,000, more preferably 1,000 to 100,000, and further preferably 5,000 to 50,000. The weight average molecular weight of the polyazole compound can be measured by the GPC method.

The polyazole compound may be used alone or in combination of two or more.

<Base material nanofiber non-woven fabric>
The base material nanofiber non-woven fabric in the present embodiment is a fiber aggregate formed by bonding nanofibers (ultrafine fibers) having a fiber diameter of nano-order with an adhesive or heat, or by mechanically entwining them. The average fiber diameter of the nanofibers is preferably 750 nm or less, more preferably 500 nm or less, still more preferably 400 nm or less, and particularly preferably 350 nm or less. When the average fiber diameter is 750 nm or less, a unique function derived from a high specific surface area, a fine pore size, and a microstructure on the order of nm is exhibited. The average fiber diameter of the nanofibers is preferably 10 nm or more, more preferably 50 nm or more, and further preferably 100 nm or more. When the average fiber diameter is 10 nm or more, the productivity and processability of the nonwoven fabric are further improved, the uniformity of the basis weight and the porosity is further improved, and the independence tends to be more easily secured.

The method for adjusting the average fiber diameter of the nanofibers can be performed by a conventional method. For example, when spinning nanofibers by the electrostatic spinning method, the applied voltage of the device, the distance between electrodes, the temperature, the humidity, and the spinning solution. Nanofibers having a desired fiber diameter can be obtained by adjusting the solvent type, the concentration of the spinning solution, and the like.

The average fiber diameter of the base material nanofiber non-woven fabric can be determined by a scanning electron microscope. Specifically, the arithmetic average of the fiber diameters of 50 fibers is taken as the average fiber diameter of the base material nanofiber non-woven fabric based on a 5000 times scanning electron micrograph of the surface of the base material nanofiber non-woven fabric. Here, the fiber diameter refers to the length in the direction orthogonal to the length direction of the fiber.

The material constituting the nanofiber is not particularly limited, but is, for example, a polyolefin resin (for example, polyethylene, polypropylene, polymethylpentene, etc.), a styrene resin (for example, polystyrene, etc.), a polyester resin (for example, polyethylene terephthalate, polytry). Methylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polycarbonate, polyarylate, total aromatic polyester resin, etc.), acrylic resins (eg polyacrylonitrile (PAN), polymethacrylic acid, polyacrylic acid, polymethacryl) Methyl acid acid, etc.), polyamide resins (eg 6 nylon, 66 nylon, aromatic polyamide resins, etc.), polyether resins (eg polyetheretherketone, polyacetal, polyphenylene ether, modified polyphenylene ether, aromatic polyetherketone, etc.) ), Urethane-based resin, chlorine-based resin (for example, polyvinyl chloride, polyvinylidene chloride, etc.), fluororesin (for example, polytetrafluoroethylene, polyvinylidene fluoride (PVDF), etc.), polyphenylene sulfide, polyamideimide-based resin, polyimide-based. From the group consisting of resin (PI), polyetherimide-based resin, aromatic polyetheramide-based resin, polysulfone-based resin (for example, polysulfone (PSU), polyethersulfone (PES), etc.), cellulose-based resin, and polyvinyl alcohol-based resin. One or more types to be selected can be mentioned.

Among these, nanofibers composed of one or more kinds of resins selected from the group consisting of polyethersulfone, polyvinylidene fluoride, polysulfone, polyimide and polyacrylonitrile are preferable, and selected from the group consisting of polyethersulfone and polyvinylidene fluoride. Nanofibers composed of one or more compounds are more preferred. The base material nanofiber nonwoven fabric having such nanofibers tends to be excellent in processability and also excellent in chemical stability when coated with a polyazole-based compound using a polyazole solution in a dipping step described later.

Further, as the nanofiber, a fiber in which a functional group is introduced into the above resin can also be used. The functional group to be introduced is not particularly limited, and examples thereof include acidic functional groups such as a sulfonic acid group, a carboxy group, and a phosphoric acid group. Nanofibers having such an acidic functional group have excellent affinity with polyazole compounds due to acid-base interaction. Therefore, by using nanofibers having an acidic functional group, coating tends to proceed more efficiently in the dipping step described later.

The nanofiber may be a fiber made of one of these resins or a fiber made of two or more kinds of resins. Further, the nonwoven fabric may be composed of only one kind of nanofibers having the same resin composition, or may be composed of two or more kinds of nanofibers having different resin compositions.

Even if the material constituting the nanofiber lacks chemical stability such as chemical resistance and solvent resistance in a specific application, the fiber surface is coated with a polyazole compound to provide chemical resistance. , Solvent resistance can be improved. This makes it possible to apply it to specific applications that could not be used with the base material nanofiber non-woven fabric alone.

The base material nanofiber non-woven fabric can be spun and manufactured by, for example, an electrostatic spinning method (electrospinning method), a melt blow method, a spunbond method, or the like. Among these, the electrostatic spinning method has a small average fiber diameter, is composed of substantially continuous fibers, and can continuously produce a wide nanofiber non-woven fabric having a large porosity of more than 1 m. It is preferably used. As a mass production device for spinning and manufacturing nanofiber non-woven fabrics, for example, NS8S1600U (model name, wire electrode method) of "Nanospider" (trade name) manufactured by El Marco Co., Ltd. and EDEN (NF-1001S) of MEC Co., Ltd. ) (Product name, nozzle discharge electrode method), Fuence Co., Ltd.'s Esper mass production machine (nozzle discharge electrode method) can be preferably used.

In order to obtain a high-quality self-supporting non-woven fabric that is less likely to break or unravel and fall off, the base material nanofiber non-woven fabric of the present embodiment is subjected to a bonding process after the spinning process, and the contact points between the nanofibers are partially formed. It is preferable that it is adhered to. Here, "partial" means that some of the many contacts between nanofibers are bonded together. There is a suitable range for the ratio of adhered contacts among the contacts between nanofibers, and the larger the range, the better the independence of the nanofiber non-woven fabric, and the tendency is to suppress the breakage of the non-woven fabric and the unraveling and falling off of the fibers. be. On the other hand, the smaller the number, the less likely it is that residual stress and residual strain will be accumulated in the non-woven fabric at the bonded contacts. For example, when the composite nanofiber non-woven fabric of the present embodiment is composited with a proton conductive polymer to prepare a composite electrolyte membrane, wrinkles are generated by relaxing stress and strain, which leads to deterioration of the quality of the composite electrolyte membrane. , Such deterioration of quality can be suppressed. Examples of the bonding processing method include heat treatment using infrared rays and hot air, heat pressing, and calendar processing.

The texture (g / m ² ) of the base material nanofiber non-woven fabric can be appropriately adjusted according to the intended use, but is preferably 0.5 g / m ² or more and 50 g / m ² or less, preferably 1.0 g / m ² . It is more preferably 20 g / m ² or more, and further preferably 1.0 g / m ² or more and 10 g / m ² or less. When the basis weight is 0.5 g / m ² or more, the independence of the base material nanofiber non-woven fabric is further improved, the handling when producing the composite nanofiber non-woven fabric becomes easy, and the manufacturing process tends to be stabilized. .. Further, the mechanical properties of the obtained composite nanofiber non-woven fabric tend to be further improved. Further, when the basis weight is 50 g / m ² or less, the productivity of the base material nanofiber non-woven fabric is improved, and the composite nanofiber non-woven fabric tends to be thinner.

Further, in a wide range of applications of the composite nanofiber non-woven fabric, for example, when it is used as an electrolyte membrane reinforcing material, the texture is preferably 0.5 g / m ² or more and 7.5 g / m ² or less, preferably 1.0 g / m. It is more preferably m ² or more and 5.0 g / m ² or less, and further preferably 1.5 g / m ² or more and 3.5 g / m ² or less. When the texture is 0.5 g / m ² or more, in addition to the above, the reinforcing effect of the electrolyte membrane of the obtained composite nanofiber non-woven fabric is further improved, and when the texture is 7.5 g / m ² or less. , The resistance of the composite electrolyte membrane reinforced with the composite nanofiber non-woven fabric can be kept low.

The basis weight (g / m ² ) of the base material nanofiber non-woven fabric is obtained as follows. The weight of the base material nanofiber non-woven fabric cut out to 200 mm × 150 mm is measured with a precision balance and converted into the weight per 1 m ² to obtain the texture (g / m ² ) of the base material nanofiber non-woven fabric.

The thickness of the base material nanofiber non-woven fabric can be appropriately adjusted depending on the intended use, but is preferably 3 μm or more and 200 μm or less, more preferably 3 μm or more and 100 μm or less, and further preferably 5 μm or more and 50 μm or less. By setting the thickness in such a range, the self-supporting property of the film is further improved, the handling when producing the composite nanofiber non-woven fabric becomes easy, and the production process tends to be stabilized. Further, the mechanical properties of the obtained composite nanofiber non-woven fabric tend to be further improved.

Further, when the composite nanofiber non-woven fabric is used as the electrolyte membrane reinforcing material, the thickness is preferably 5 μm or more and 30 μm or less, and further preferably 5 μm or more and 25 μm or less. When the thickness is within the above range, it is possible to achieve both the mechanical strength and the proton conductivity of the obtained composite nanofiber non-woven fabric and the composite electrolyte membrane provided with the proton conductive polymer.

The thickness of the base material nanofibers is determined as follows using a contact-type film thickness meter (manufactured by Mitutoyo, product name "ABS Digimatic Indicator ID-F125"). The thickness of the base material nanofiber non-woven fabric cut into 100 mm × 100 mm is measured at any five points, and the arithmetic mean thereof is taken as the thickness of the base material nanofiber non-woven fabric.

The porosity of the base material nanofiber non-woven fabric is not particularly limited, but is preferably 50% or more and 98% or less, more preferably 70% or more and 98% or less, and further preferably 80% or more and 95% or less. When the porosity is 50% or more, the permeability of gas or liquid tends to be further improved, and it is more suitable when used as a filter medium, a separator or the like. Further, when used as a resin reinforcing material, defective impregnation of the resin tends to be further suppressed. On the other hand, when the porosity is 98% or less, the independence of the base material nanofiber non-woven fabric is improved, and the handleability tends to be further improved.

The porosity of the base material nanofiber non-woven fabric is obtained as follows. First, the weight of the base material nanofiber non-woven fabric cut into 40 mm × 30 mm is measured with a precision balance, and the film density ρ (g / cm ³ ) is calculated from the measured weight and the thickness of the base material nanofiber non-woven fabric according to the following formula (A). Calculated by
Film density ρ (g / cm ³ ) = m / (4.0 × 3.0 × t) (A)
m: Weight (g) of the base material nanofiber non-woven fabric cut out to 40 mm × 30 mm
t: Thickness of base material nanofiber non-woven fabric (cm)

Then, from the obtained film density ρ and the true density ρ ₀ (g / cm ³ ) of the material constituting the base material nanofiber non-woven fabric, the void ratio (%) can be obtained by the following formula (B).
Porosity (%) = (1- (ρ / ρ ₀ )) x 100 (B)

<Covering state>
The mass percent concentration X (%) of the polyazole compound in the entire composite nanofiber non-woven fabric is preferably 0.3% or more and 15% or less, and more preferably 0.5% or more and 10% or less. When the mass percent concentration X (%) of the polyazole compound is 0.3% or more, the antistatic performance and the mechanical strength tend to be further improved. Further, when the mass percent concentration X (%) of the polyazole-based compound is 15% or less, it tends to be possible to suppress the excess polyazole-based compound from closing the voids of the base material nanofiber non-woven fabric. As a result, it is possible to obtain a composite nanofiber nonwoven fabric that maintains the fine and high porosity porous structure of the substrate nanofiber nonwoven fabric, so that the functions derived from the substrate nanofiber nonwoven fabric tend to be more effectively expressed. be.

The mass percent concentration X (%) of the polyazole compound in the entire composite nanofiber nonwoven fabric can be determined by, for example, the following method using nuclear magnetic resonance spectroscopy (NMR). First, the composite nanofiber nonwoven fabric is completely dissolved in a deuterated solvent for NMR measurement. ¹ H-NMR measurement is performed on this measurement solution, and an NMR spectrum is obtained. From the multiple peaks of the obtained NMR spectrum, the material constituting the base material nanofiber non-woven fabric, the polyazole compound, and the peaks derived from each are selected one by one, and their integral values, _{IN F and I AZOLE ,} are obtained. do. It is preferable that the peak selected here does not overlap with other peaks as much as possible. Further, from the molecular weights M _NF and M _AZOLE of the repeating unit of the material constituting the base material nanofiber non-woven fabric and the polyazole compound, and the number of hydrogen atoms (protons) giving these peaks in the repeating unit n _NF and n _AZOLE . The mass percent concentration X (%) of the polyazole compound in the entire composite nanofiber nonwoven fabric can be calculated by the following formula (C).
Mass percent concentration X (%) of the polyazole compound in the entire non-woven fabric
= 100 x (M _AZOLE x I _AZOLE / n _AZOLE ) / ((M _AZOLE x I _AZOLE / n _AZOLE ) + (M _NF x I _NF / n _NF )) (C)
I _NF : Integrated value of NMR peak A of the material constituting the base material nanofiber non-woven fabric I _AZOLE : Integrated value of NMR peak B of polyazole-based compound M _NF : Molecular weight of repeating unit A having a hydrogen atom to which NMR peak A belongs M _AZOLE : Molecular weight of repeating unit B having hydrogen atom to which NMR peak B belongs n _NF : Number of hydrogen atoms giving NMR peak A in repeating unit A n _AZOLE : Hydrogen atom giving NMR peak B in repeating unit B Number of

The mass percent concentration X (%) of the polyazole compound is controlled by adjusting the concentration of the polyazole compound in the polyazole solution used in the production method described later, adjusting the drying rate by changing the solvent of the polyazole solution, and the like. can do.

The mass percent concentration Y (%) of the polyazole compound on the fiber surface of the composite nanofiber non-woven fabric is preferably 2% or more, more preferably 5% or more, still more preferably 10% or more. The upper limit of the mass percent concentration Y (%) is not particularly limited, but may be 100% or less, 80% or less, 50% or less, or 30% or less. When the mass percent concentration Y (%) of the polyazole-based compound is 2% or more, the effects of the polyazole-based compound covering the surface of the base material nanofibers, such as antistatic and high mechanical strength, tend to be easily obtained. Further, since the mass percent concentration Y (%) of the polyazole-based compound is 100% or less, it is difficult for the excess polyazole-based compound to block the voids of the base material nanofiber non-woven fabric, and the fine and high content of the base material nanofiber non-woven fabric is obtained. Functions derived from a porous structure with a porosity tend to be easily exhibited.

The mass percent concentration Y (%) of the polyazole compound on the fiber surface of the composite nanofiber non-woven fabric is based on the quantitative information (relative element concentration) of the element at several nm on the fiber surface obtained by X-ray photoelectron spectroscopy (XPS). It is calculated to. Select the materials that make up the base material nanofiber non-woven fabric and the polyazole compounds, and the elements that can be detected only in each of them, and combine their relative element concentrations C _NF (atomic%) and _{CA AZOLE} (atomic%) in the composite nanofiber non-woven fabric. Obtained by XPS measurement. Further, from the molecular weights M _NF and M _AZOLE of the material constituting the base material nanofiber non-woven fabric and the polyazole compound and the number of selected elements in the repeating unit N _NF and N _AZOLE , the following formula (D) is used. The mass percent concentration Y (%) of the polyazole compound on the fiber surface of the composite nanofiber non-woven fabric can be calculated.
Mass percent concentration Y (%) on the fiber surface of the polyazole compound
= 100 x (M _AZOLE x C _AZOLE / N _AZOLE ) / ((M _AZOLE x C _AZOLE / N _AZOLE ) + (M _NF x C _NF / N _NF )) (D)
C _NF : Relative element concentration of element A detected only in the material constituting the base material nanofiber non-woven fabric C _AZOLE : Relative element concentration of element B detected only in polyazole-based compounds M _NF : Repeating unit A having element A Molecular weight of M _AZOLE : Molecular weight of repeating unit B having element B N _NF : Number of element A in repeating unit A N _AZOLE : Number of element B in repeating unit B

The mass percent concentration Y (%) of the polyazole compound is controlled by adjusting the concentration of the polyazole compound in the polyazole solution used in the production method described later, adjusting the drying rate by changing the solvent of the polyazole solution, and the like. can do.

The ratio Y / X of the mass percent concentration X (%) of the polyazole compound in the entire composite nanofiber nonwoven fabric to the mass percent concentration Y (%) of the polyazole compound on the fiber surface of the composite nanofiber nonwoven fabric exceeds 1. It is preferable, and it is more preferable that it is 2 or more. The upper limit of the ratio Y / X is not particularly limited, but may be 100 or less, 50 or less, 30 or less, or 20 or less. The ratio Y / X is an index indicating the amount of the polyazole-based compound unevenly distributed on the fiber surface of the composite nanofiber non-woven fabric, and the fact that the ratio Y / X exceeds 1 means that the polyazole-based compound is the base material nanofiber non-woven fabric. It means that it is compounded so as to cover the fiber surface of the fiber and is unevenly distributed on the fiber surface. As a result, the polyazole-based compound that coats the surface of the base material nanofibers tends to provide effects such as antistatic and high mechanical strength.

The texture (g / m ² ) of the base material nanofiber non-woven fabric can be appropriately adjusted according to the intended use, but is preferably 0.5 g / m ² or more and 50 g / m ² or less, preferably 1.0 g / m ² . It is more preferably 20 g / m ² or more, and further preferably 1.0 g / m ² or more and 10 g / m ² or less. When the basis weight is 0.5 g / m ² or more, the independence of the composite nanofiber non-woven fabric is further improved, the handling when manufacturing a product using the composite nanofiber non-woven fabric becomes easy, and the manufacturing process is stabilized. There is a tendency. In addition, the mechanical properties of the obtained product tend to be further improved. Further, when the basis weight is 50 g / m ² or less, the obtained product tends to be thinner.

Further, when the composite nanofiber non-woven fabric is used as an electrolyte membrane reinforcing material, the texture is preferably 0.5 g / m ² or more and 7.5 g / m ² or less, and 1.0 g / m ² or more and 5.0 g / g / or more. It is more preferably m ² or less, and further preferably 1.5 g / m ² or more and 3.5 g / m ² or less. When the basis weight is 0.5 g / m ² or more, in addition to the above, it is easy to handle when forming a composite electrolyte membrane by combining with a proton conductive polymer, the process is stabilized, and the reinforcing effect of the electrolyte membrane is obtained. Will improve even more. Further, when the basis weight is 7.5 g / m ² or less, the resistance of the composite electrolyte membrane can be kept low.

The basis weight (g / m ² ) of the composite nanofiber non-woven fabric is obtained as follows. The weight of the composite nanofiber non-woven fabric cut out to 200 mm × 150 mm is measured with a precision balance, and converted into the weight per 1 m ² to obtain the texture (g / m ² ) of the composite nanofiber non-woven fabric.

The fiber diameter of the composite nanofiber nonwoven fabric can be controlled by the fiber diameter of the base material nanofiber nonwoven fabric and the coating amount of the polyazole-based compound on the fiber surface. The average fiber diameter of the fibers constituting the composite nanofiber nonwoven fabric of the present embodiment is preferably 750 nm or less, more preferably 500 nm or less, still more preferably 400 nm or less, and particularly preferably 350 nm or less. When the average fiber diameter is 750 nm or less, a unique function derived from a high specific surface area, a fine pore size, and a microstructure on the order of nm is exhibited. In particular, the reinforcing effect as a resin reinforcing material tends to be improved, and the separation performance as a filter medium tends to be improved. The average fiber diameter is preferably 10 nm or more, more preferably 50 nm or more, and further preferably 100 nm or more. When the average fiber diameter is 100 nm or more, the productivity and processability of the nonwoven fabric are further improved, the uniformity of the basis weight and the porosity is further improved, and the independence tends to be more easily secured.

The average fiber diameter of the composite nanofiber non-woven fabric can be determined by a scanning electron microscope. Specifically, the arithmetic average of the fiber diameters of 50 fibers is taken as the average fiber diameter of the composite nanofiber non-woven fabric based on a 5000 times scanning electron micrograph of the surface of the composite nanofiber non-woven fabric. Here, the fiber diameter refers to the length in the direction orthogonal to the length direction of the fiber.

The thickness of the composite nanofiber non-woven fabric can be appropriately adjusted depending on the intended use, but is preferably 3 μm or more and 200 μm or less, more preferably 3 μm or more and 100 μm or less, and further preferably 5 μm or more and 50 μm or less. By setting the thickness in such a range, the self-supporting property of the film is further improved, the handling when manufacturing a product using the composite nanofiber non-woven fabric becomes easy, and the manufacturing process tends to be stabilized. In addition, the mechanical properties of the obtained product tend to be further improved.

Further, when the composite nanofiber non-woven fabric is used as the electrolyte membrane reinforcing material, the thickness is preferably 3 μm or more and 30 μm or less, and further preferably 3 μm or more and 25 μm or less. When the thickness is within the above range, it is possible to achieve both the mechanical strength and the proton conductivity of the composite electrolyte membrane provided with the composite nanofiber non-woven fabric and the proton conductive polymer.

The thickness of the composite nanofiber is determined as follows using a contact type film thickness meter (manufactured by Mitutoyo, product name "ABS Digimatic Indicator ID-F125"). The thickness of the composite nanofiber nonwoven fabric cut out to 100 mm × 100 mm is measured at any five points, and the arithmetic average thereof is taken as the thickness of the composite nanofiber nonwoven fabric.

The porosity of the composite nanofiber non-woven fabric can be controlled according to the porosity of the base material nanofiber non-woven fabric. The porosity of the composite nanofiber non-woven fabric is not particularly limited, but is preferably 50% or more and 98% or less, more preferably 70% or more and 98% or less, and further preferably 75% or more and 95% or less. When the porosity is 50% or more, the permeability of gas or liquid tends to be further improved, and it is more suitable when used as a filter medium, a separator or the like. Further, when used as a resin reinforcing material, poor resin impregnation tends to be further suppressed, while the porosity of 98% or less improves the independence of the composite nanofiber non-woven fabric and makes it easy to handle. Tends to improve.

The porosity of the composite nanofiber non-woven fabric is obtained as follows. First, the weight of the composite nanofiber non-woven fabric cut into 40 mm × 30 mm is measured with a precision balance, and the film density ρ (g / cm ³ ) is calculated from the measured weight and the thickness of the composite nanofiber non-woven fabric by the following formula (A). do.
Film density ρ (g / cm ³ ) = m / (4.0 × 3.0 × t) (A)
m: Weight (g) of the composite nanofiber non-woven fabric cut into 40 mm × 30 mm
t: Thickness of composite nanofiber non-woven fabric (cm)

Then, from the obtained film density ρ and the true density ρ ₀ (g / cm ³ ) of the material constituting the composite nanofiber non-woven fabric, the void ratio (%) can be obtained by the following formula (B). The true density ρ ₀ of the material constituting the composite nanofiber non-woven fabric is the true density ρ _NF (g / cm ³ ) of the material constituting the base material nanofiber non-woven fabric, and the true density ρ _AZOLE (g / cm ³ ) of the polyazole-based compound. , Calculated by the following formula (E) using the mass percent concentration X (%) of the polyazole-based compound in the entire composite nanofiber non-woven fabric.
Porosity (%) = (1- (ρ / ρ ₀ )) x 100 (B)
True density ρ ₀ (g / cm ³ ) = 100 × ρ _NF × ρ _AZOLE / (X × ρ _NF + (100-X) × ρ _AZOLE ) (E)

<Manufacturing method of composite nanofiber non-woven fabric>
The method for producing the composite nanofiber nonwoven fabric in the present embodiment will be described. The method for producing a composite nanofiber nonwoven fabric includes a step of immersing the substrate nanofiber nonwoven fabric in a polyazole solution in which a polyazole compound and an alkali metal hydroxide are dissolved in a protonic solvent. This makes it possible to obtain a composite nanofiber nonwoven fabric in which at least a part of the fiber surface is coated with a polyazole-based compound. The dipping step may be a batch type or a continuous type.

In general, polyazole compounds have low solubility due to their rigid molecular skeleton, and are only soluble in highly soluble solvents such as aprotic polar solvents. Therefore, when the base material nanofiber non-woven fabric is immersed in a solution in which the polyazole compound alone is dissolved in an aprotonic polar solvent, there arises a problem that the base material nanofiber non-woven fabric is dissolved. However, by coexisting with an alkali metal hydroxide, this production method using a polyazole solution in which a polyazole compound is dissolved in a protonic solvent does not cause the problem that the base nanofiber non-woven fabric is dissolved in the polyazole solution. In addition, the polyazole-based compound and the base material nanofiber non-woven fabric can be composited so as to cover the fiber surface more uniformly.

In the present embodiment, the protonic solvent refers to a solvent that dissociates and releases protons, such as water, alcohols, and fatty acids. Examples of the protonic solvent are shown below, but the solvent is not limited to this as long as it is a solvent that dissociates and releases protons. Of the protonic solvents, other than water is used as a protonic organic solvent. Examples of protonic solvents are water; as aliphatic alcohols, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2 -Pentanol, 3-pentanol, 2-methyl-1-butanol, isopentyl alcohol, tert-pentyl alcohol, 3-methyl-2-butanol, neopentyl alcohol, 1-hexanol, 2-methyl-1-pentanol , 4-Methyl-2-pentanol, 2-ethyl-1-butanol, 1-heptanol, 2-heptanol, 3-heptanol, 1-octanol, 2-octanol, 2-methyl-1-hexanol, 1-nonanol, 3,5,5-trimethyl-1-hexanol, 1-decanol, 1-undecanol, 1-dodecanol, allyl alcohol, propargyl alcohol, benzyl alcohol, cyclohexanol, 1-methylcyclohexanol, 2-methylcyclohexanol, 3- Methylcyclohexanol, 4-methylcyclohexanol, α-terpineol, avietinol, fusel oil; 2-methoxyethanol, 2-ethoxyethanol, 2- (methoxymethoxy) ethanol, 2-isopropoxy as having multiple functional groups. Ethanol, 2-butoxyethanol, 2- (isopentyloxy) ethanol, 2- (hexyloxy) ethanol, 2-phenoxyethanol, 2- (benzyloxy) ethanol, furfuryl alcohol, tetrahydrofurfuryl alcohol, diethylene glycol, diethylene glycol monomethyl ether , Diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, tetraethylene glycol, polyethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol Monomethyl Ether, Dipropylene Glycol Monoethyl Ether, Tripropylene Glycol Monomethyl Ether, Polypropylene Glycol, Diacetone Alcohol, 2-Chloroethanol, 1-Chloro-2-propanol, 3-Chloro-1,2-Propanediol, 1,3 -Dichloro-2-propanol, 2,2,2-trif Luoloethanol, 3-hydroxypropionitrile, 2-aminoethanol, 2- (diethylamino) ethanol, 2- (diethylamino) ethanol, diethanolamine, N-butyldiethanolamine, triethanolamine, triisopropanolamine, 2,2'- Thiodiethanol; as diols, 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2 , 3-Butandiol, 1,5-Pentanediol, 2-Buten-1,4-diol, 2-Methyl-2,4-Pentanediol, 2-Ethyl-1,3-Hexanediol, Glycerin, 2-Ethyl -2- (Hydroxymethyl) -1,3-propanediol, 1,2,6-hexanetriol; as phenols, phenol, cresol, o-cresol, m-cresol, p-cresol, xylenol; fluorinated alcohol As a kind, the general formula [CF _3- (CF ₂ ) _x- (CH ₂ ) _y -OH] is x = 1 to 20, y = 0 to 19, and x + y is 20 or less, or halogenated with fluorine or the like. Examples thereof include substituted alcohol. These solvents may be used alone or in combination of two or more.

The alkali metal hydroxide is not particularly limited, and examples thereof include monovalent alkali metal hydroxides such as LiOH, NaOH, KOH, RbOH, CsOH, and FrOH. Among these, it is preferable from the viewpoint of solubility of the polyazole compound in which NaOH is mixed at the same time.

The mass percent concentration of the polyazole compound in the polyazole solution is preferably 0.005 to 25% by mass, more preferably 0.005 to 20% by mass, still more preferably 0.005 to 20% by mass, with the total amount of the polyazole solution being 100% by mass. It is 0.01 to 15% by mass, and particularly preferably 0.01 to 5% by mass. When the mass percent concentration of the polyazole compound is 0.005 mass% or more, the fiber surface of the base material nanofiber non-woven fabric tends to be efficiently coated. Further, when the mass percent concentration of the polyazole-based compound is 25% by mass or less, the generation of undissolved substances of the polyazole-based compound tends to be suppressed.

The mass percent concentration of the alkali metal hydroxide in the polyazole solution is preferably 0.001 to 25% by mass, more preferably 0.001 to 20% by mass, with the total amount of the polyazole solution being 100% by mass. , More preferably 0.01 to 15% by mass, and particularly preferably 0.01 to 5% by mass. When the amount of the alkali metal hydroxide is 0.001% by mass or more, the polyazole-based compound is sufficiently dissolved, and the fiber surface of the base material nanofiber non-woven fabric tends to be efficiently coated. Further, when the amount of the alkali metal hydroxide is 25% by mass or less, the precipitation of the alkali metal hydroxide tends to be suppressed.

Further, the mass percent concentration of the polyazole compound and the alkali metal hydroxide in the polyazole solution is 0.005 to 25% by mass of the polyazole compound and 0.001 to 25% by mass of the alkali metal hydroxide, which is more preferable. Is 0.005 to 20% by mass of the polyazole compound and 0.001 to 20% by mass of the alkali metal hydroxide, more preferably 0.01 to 15% by mass of the polyazole compound and the alkali metal hydroxide. It is 0.01 to 15% by mass.

The mass ratio of the alkali metal hydroxide to the polyazole compound in the polyazole solution is preferably 1.5 or less, more preferably 0.2 to 1.5, and further preferably 0.3 to 1. It is 2. When the mass ratio is within the above range, the polyazole-based compound is sufficiently dissolved, and the fiber surface of the base material nanofiber non-woven fabric tends to be efficiently coated.

When dissolving the polyazole compound, a method of adding the polyazole compound and the alkali metal hydroxide to the protonic solvent and heating the compound is preferable in order to improve the solubility. The temperature at this time is preferably 10 to 160 ° C, more preferably 10 to 150 ° C, and even more preferably 10 to 90 ° C. The upper limit of heating may be the boiling point of the protonic solvent.

<Solution removal process>
The method for producing the composite nanofiber nonwoven fabric of the present embodiment may include a solution removing step of removing an excess polyazole solution, if necessary, after the dipping step. The method for removing the solution is not particularly limited, but for example, a method of wiping off the excess polyazole solution with a cloth or paper, a method of blowing off the excess polyazole solution with an air stream, a method of contacting with a mass roll, a method of applying vibration, etc. Can be mentioned. By removing the excess polyazole solution, the porosity and fine structure of the base material nanofiber non-woven fabric are maintained, and a high-quality composite nanofiber non-woven fabric having excellent flatness tends to be obtained.

<Drying process>
The method for producing the composite nanofiber nonwoven fabric of the present embodiment may include a drying step of drying the attached polyazole solution, if necessary, after the dipping step. The drying method is not particularly limited, and examples thereof include heat drying treatment using infrared rays and hot air, vacuum drying treatment, natural drying, and combinations thereof.

<Washing process>
The method for producing the composite nanofiber nonwoven fabric of the present embodiment may include a washing step of washing the composite nanofiber nonwoven fabric with acid and / or water, if necessary, after the drying step. By washing, the alkali metal hydroxide in the coating film of the polyazole compound can be removed. The cleaning method is not particularly limited as long as the composite nanofiber non-woven fabric is brought into contact with an acid and / or water to dissolve the alkali metal hydroxide in the acid or water. When water is used for washing, for example, if the pH of the water after washing with water is 6 to 7, it can be considered that the alkali metal hydroxide has been sufficiently removed.

The washed composite nanofiber non-woven fabric may be dried again if necessary. The drying treatment method is not particularly limited, and examples thereof include heat drying treatment using infrared rays and hot air, vacuum drying treatment, natural drying, and combinations thereof.

<Use>
The use of the composite nanofiber non-woven fabric of the present embodiment is not particularly limited, and is suitably used for, for example, a resin reinforcing material, an electrolyte membrane reinforcing material, a separator for a battery or a capacitor, a filter medium, a cell culture substrate, and the like. Above all, it is suitably used as a reinforcing material for an electrolyte membrane, particularly as a reinforcing material for an electrolyte membrane for a polymer electrolyte fuel cell. By using the composite nanofiber non-woven fabric as the electrolyte membrane reinforcing material, the mechanical strength and durability of the electrolyte membrane can be improved. Hereinafter, the composite electrolyte membrane including the composite nanofiber nonwoven fabric and the proton conductive polymer will be described.

FIG. 1 shows a schematic cross-sectional view when a composite nanofiber non-woven fabric and a proton conductive polymer are composited. As shown in FIG. 1, the composite nanofiber nonwoven fabric 1 is composited with the proton conductive polymer 2, and the voids thereof are at least partially filled with the proton conductive polymer 2 to form the composite layer 3. Proton conductive polymer layers 2 are formed on both sides of the composite layer 3. FIG. 2 shows a schematic diagram for explaining an example of the usage mode of the composite electrolyte membrane of the present embodiment. As shown in FIG. 2, the composite nanofiber non-woven fabric 1 of the present embodiment includes an electrode catalyst layer 4, a proton conductive polymer layer 2 which is an electrolyte, and a composite layer 3 of a composite nanofiber non-woven fabric 1 and a proton conductive polymer 2. The membrane electrode composite can be configured and used in the order of the proton conductive polymer layer 2 and the electrode catalyst layer 4.

The thickness of the composite electrolyte membrane is preferably 1 μm or more and 300 μm or less, more preferably 2 μm or more and 100 μm or less, still more preferably 5 μm or more and 50 μm or less, and particularly preferably 5 μm or more and 25 μm or less. By adjusting the thickness of the composite electrolyte membrane within the above range, inconveniences such as the direct reaction between hydrogen and oxygen can be reduced, and even if differential pressure or strain occurs during fuel cell manufacturing or fuel cell operation, the membrane There is a tendency that damage to the fuel cell is less likely to occur. Further, from the viewpoint of maintaining the ion permeability of the composite electrolyte membrane better and maintaining the performance as the electrolyte membrane more effectively and surely, it is preferable to adjust the thickness within the above range.

The thickness of the composite electrolyte membrane is determined as follows using a contact-type film thickness meter (manufactured by Mitutoyo, product name "ABS Digimatic Indicator ID-F125"). The thickness of the composite electrolyte membrane cut out to 100 mm × 100 mm is measured at any five points, and the arithmetic mean thereof is taken as the thickness of the composite electrolyte membrane.

The proton conductive polymer is not particularly limited, and examples thereof include a perfluorocarbon polymer compound having an ion exchange group and a hydrocarbon polymer compound having an aromatic ring in the molecule in which an ion exchange group is introduced. .. These may be used alone or in combination of two or more. Among these, a perfluorocarbon polymer compound having an ion exchange group is preferable from the viewpoint of further excellent chemical stability.

The ion exchange capacity (milli equivalent / g) of the proton conductive polymer is preferably 0.5 mm equivalent / g or more and 3.0 mm equivalent / g or less, and 0.65 mm equivalent / g or more and 2.0 mm equivalent. It is more preferably less than / g, and even more preferably 0.8 mm equivalent / g or more and 1.5 mm equivalent / g or less. When the ion exchange capacity is 3.0 mm equivalent / g or less, when used as an electrolyte membrane, the swelling of the electrolyte membrane under high temperature and high humidification during fuel cell operation tends to be further reduced. By reducing the swelling in this way, there is a tendency to reduce problems such as a decrease in the strength of the electrolyte membrane, wrinkles generated and peeling from the electrode, and a problem in which the gas barrier property is deteriorated. Further, when the ion exchange capacity is 0.5 mm equivalent / g or more, the power generation capacity of the fuel cell provided with the obtained electrolyte membrane tends to be further improved.

The ion exchange capacity can be determined by the following method. An electrolyte membrane (sheet area of about 2 cm ² or more and 20 cm ² or less) in which the counter ion of the ion exchange group is in a proton state is immersed in 30 mL of a saturated NaCl aqueous solution at 25 ° C. and left for 30 minutes with stirring. Next, the protons in the saturated NaCl aqueous solution are neutralized and titrated using a 0.01 N NaOH aqueous solution using phenolphthalein as an indicator. The electrolyte membrane obtained after neutralization, in which the counterion of the ion exchange group is in the state of sodium ions, is rinsed with pure water, vacuum dried, and then weighed. The amount of substance of NaOH required for neutralization is M (mmol), the weight of the electrolyte membrane in which the counter ion of the ion exchange group is sodium ion is W (mg), and the equivalent weight EW (g / eq) is given by the following formula (F). ).
EW (g / eq) = (W / M) -22 (F)
Further, the ion exchange capacity (milli equivalent / g) is calculated by taking the reciprocal of the obtained EW value and multiplying it by 1000.

The ion exchange group is not particularly limited, and examples thereof include a sulfonic acid group, a sulfonimide group, a sulfonamide group, a carboxy group and a phosphoric acid group, and a sulfonic acid group is preferable. The ion exchange group may be used alone or in combination of two or more.

The hydrocarbon-based polymer compound having an aromatic ring in the molecule is not particularly limited, and for example, polyphenylene sulfide, polyphenylene ether, polysulfone, polyether sulfone, polyether ether sulfone, polyether ketone, polyether ether ketone, poly. Thioether Sulfone, Polythioether Sulfone, Polythioether Ketone, Polybenzimidazole, Polybenzoxazole, Polyoxadiazole, Polybenzoxadinone, Polyxylylene, Polyphenylene, Polythiophene, Polypyrrole, Polyaniline, Polyacene, Polycyanogen, Polynaphthylidine, Polyphenylene Sulfide Examples thereof include sulfone, polyphenylene sulfone, polyimide, polyetherimide, polyesterimide, polyamideimide, polyarylate, aromatic polyamide, polystyrene, polyester, and polycarbonate. These may be used alone or in combination of two or more.

The perfluorocarbon polymer compound having an ion exchange group is not particularly limited, and is, for example, a perfluorocarbon sulfonic acid resin, a perfluorocarbon carboxylic acid resin, a perfluorocarbon sulfonic acid resin, a perfluorocarbon sulfonamide resin, and a perfluorocarbon phosphorus. Acid resins and amine and metal salts of these resins can be mentioned. These may be used alone or in combination of two or more.

The perfluorocarbon polymer compound is not particularly limited, but more specifically, a polymer represented by the following formula [1] can be mentioned.
-[CF ₂ CX ¹ X ² ] _a- [CF ₂ -CF (-O- (CF ₂ -CF (CF ₂ X ³ )) _b -O _c- (CFR ¹ ) _d- (CFR ² ) _e- ( CF ₂ ) _f -X ⁴ )] _g- [1]
Here, in the formula, X ¹ , X ² and X ³ each independently represent a halogen atom or a perfluoroalkyl group having 1 or more and 3 or less carbon atoms. a and g satisfy 0 ≦ a <1, 0 <g ≦ 1, and a + g = 1. b is an integer of 0 or more and 8 or less. c is 0 or 1. d and e are integers of 0 or more and 6 or less independently of each other. f is an integer of 0 or more and 10 or less. However, d + e + f is not equal to 0. R ¹ and R ² independently represent a halogen atom, a perfluoroalkyl group having 1 or more carbon atoms and 10 or less carbon atoms, or a fluorochloroalkyl group. X ⁴ indicates COOZ, SO ₃ Z, PO ₃ Z ₂ or PO ₃ HZ. Here, Z is a hydrogen atom, an alkali metal atom, an alkaline earth metal atom or an amine (NH ₄ , NH ₃ R ³ , NH ₂ R ³ R ⁴ , NHR ³ R ⁴ R ⁵ or NR ³ R ⁴ R ⁵ ). R ⁶ ) is shown. Further, R ³ , R ⁴ , R ⁵ and R ⁶ each independently indicate an alkyl group or an arene group.

Among these, the perfluorocarbon sulfonic acid resin represented by the following formula [2] or the formula [3] or a metal salt thereof is preferable.
-[CF ₂ CF ₂ ] _a- [CF ₂ -CF (-O- (CF ₂ -CF (CF ₃ )) _b -O- (CF ₂ ) _c -SO ₃ X)] _d- [2]
Here, in the formula, a and d satisfy 0 ≦ a <1, 0 ≦ d <1, and a + d = 1. b is an integer of 1 or more and 8 or less. c is an integer of 0 or more and 10 or less. X represents a hydrogen atom or an alkali metal atom.
-[CF ₂ CF ₂ ] _e- [CF ₂ -CF (-O- (CF ₂ ) _f -SO ₃ Y)] _g- [3]
Here, in the formula, e and g satisfy 0 ≦ e <1, 0 ≦ g <1, and e + g = 1. f is an integer of 0 or more and 10 or less. Y represents a hydrogen atom or an alkali metal atom.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to the following examples.

<Metsuke of base material nanofiber non-woven fabric>
The weight of the base material nanofiber non-woven fabric cut out to 200 mm × 150 mm was measured with a precision balance, and converted into the weight per 1 m ² to obtain the texture (g / m ² ) of the base material nanofiber non-woven fabric.

<Average fiber diameter of base material nanofiber non-woven fabric and composite nanofiber non-woven fabric>
Based on a 5000x scanning electron micrograph of the surface of the base material nanofiber non-woven fabric and the composite nanofiber non-woven fabric, the arithmetic average of the fiber diameters of 50 fibers is the average of the base material nanofiber non-woven fabric and the composite nanofiber non-woven fabric. The fiber diameter was used. Here, as the fiber diameter, the length in the direction orthogonal to the length direction of the fiber was used.

<Thickness of base material nanofiber non-woven fabric and composite nanofiber non-woven fabric>
The thickness of the base material nanofiber non-woven fabric and the composite nanofiber non-woven fabric was measured using a contact type film thickness meter (manufactured by Mitutoyo, product name "ABS Digimatic Indicator ID-F125"). The thicknesses of the base material nanofiber non-woven fabric and the composite nanofiber non-woven fabric cut into 100 mm × 100 mm were measured at arbitrary five points, and the arithmetic average thereof was taken as the thickness of the base material nanofiber non-woven fabric and the composite nanofiber non-woven fabric.

<Porosity of base material nanofiber non-woven fabric and composite nanofiber non-woven fabric>
The weights of the base material nanofiber non-woven fabric and the composite nanofiber non-woven fabric cut out to 40 mm × 30 mm were measured with a precision balance, and the film density ρ (g) was taken from the measured weight and the thickness of the base material nanofiber non-woven fabric and the composite nanofiber non-woven fabric. / Cm ³ ) was calculated by the following formula (A).
Film density ρ (g / cm ³ ) = m / (4.0 × 3.0 × t) (A)
m: Weight (g) of the base material nanofiber non-woven fabric cut out to 40 mm × 30 mm
t: Thickness of nanofiber non-woven fabric (cm)

The void ratio (%) of the base material nanofiber non-woven fabric is calculated from the obtained film density ρ and the true density ρ ₀ (g / cm ³ ) of the material constituting the base material nanofiber non-woven fabric according to the following formula (B). Asked. For the composite nanofiber nonwoven fabric, the void ratio (%) was determined by the following formula (B) from the obtained film density ρ and the true density ρ ₀ of the composite nanofiber nonwoven fabric.
Porosity (%) = (1- (ρ / ρ ₀ )) x 100 (B)

The true density ρ ₀ of the composite nanofiber non-woven fabric is the true density ρ _NF (g / cm ³ ) of the material constituting the base material nanofiber non-woven fabric, the true density ρ _AZOLE (g / cm ³ ) of the polyazole-based compound, and the composite. It was calculated by the following formula (E) using the mass percent concentration X (%) of the polyazole-based compound in the entire nanofiber non-woven fabric.
True density ρ ₀ (g / cm ³ ) = 100 × ρ _NF × ρ _AZOLE / (X × ρ _NF + (100-X) × ρ _AZOLE ) (E)

<Mass percent concentration of polyazole compounds in the entire composite nanofiber non-woven fabric>
The mass percent concentration X (%) of the polyazole compound in the entire composite nanofiber nonwoven fabric was determined by the following method using nuclear magnetic resonance spectroscopy (NMR). ¹ H-NMR measurement was performed using a nuclear magnetic resonance apparatus (manufactured by JEOL Ltd., product name "JNM-ECS400") for a measurement solution in which a composite nanofiber non-woven fabric was completely dissolved in a deuterated solvent for NMR measurement. , NMR spectra were obtained. The material constituting the base material nanofiber non-woven fabric, the polyazole compound, and the peaks derived from each were selected one by one, and their integral values, _{IN F and I AZOLE ,} were obtained. Further, from the molecular weights M _NF and M _AZOLE of the repeating unit of the material constituting the base material nanofiber non-woven fabric and the polyazole compound, and the number of hydrogen atoms (protons) giving these peaks in the repeating unit n _NF and n _AZOLE . The mass percent concentration X (%) of the polyazole compound in the entire composite nanofiber non-woven fabric was calculated by the following formula (C).
Mass percent concentration X (%) of the polyazole compound in the entire non-woven fabric
= 100 x (M _AZOLE x I _AZOLE / n _AZOLE ) / ((M _AZOLE x I _AZOLE / n _AZOLE ) + (M _NF x I _NF / n _NF )) (C)

<Mass percent concentration of polyazole compound on the fiber surface of composite nanofiber non-woven fabric>
The mass percent concentration Y (%) of the polyazole compound on the fiber surface of the composite nanofiber non-woven fabric was determined by the following method using X-ray photoelectron spectroscopy (XPS). The composite nanofiber non-woven fabric was subjected to XPS measurement using an X-ray photoelectron spectrometer (manufactured by Thermo Fisher Scientific, product name "ESCALAB 250"). The measurement sample covered with a 1 mm × 2 mm slot type mask was subjected to XPS measurement, the analysis area was an ellipse having a size of about 1 mm, and the photoelectron capture angle was set to 0 °. Elements constituting the base material nanofiber non-woven fabric and polyazole compounds were selected, and their relative element concentrations C _NF (atomic%) and _{CA AZOLE} (atomic%) were obtained. Further, from the molecular weights M _NF and M _AZOLE of the material constituting the base material nanofiber non-woven fabric and the polyazole compound and the number of selected elements in the repeating unit N _NF and N _AZOLE , the following formula (D) is used. The mass percent concentration Y (%) of the polyazole compound on the fiber surface of the composite nanofiber non-woven fabric was calculated.
Mass percent concentration Y (%) on the fiber surface of the polyazole compound
= 100 x (M _AZOLE x C _AZOLE / N _AZOLE ) / ((M _AZOLE x C _AZOLE / N _AZOLE ) + (M _NF x C _NF / N _NF )) (D)

<Evaluation of fiber unraveling and falling off of base material nanofiber non-woven fabric and composite nanofiber non-woven fabric>
The surface of the base material nanofiber non-woven fabric or the composite nanofiber non-woven fabric cut out to 50 mm × 50 mm was rubbed in the same direction three times with 20 mm × 20 mm clean paper (manufactured by Sakurai Co., Ltd., product name “EX Clean Blue EX72B”). Then, the surface of the base material nanofiber non-woven fabric or the composite nanofiber non-woven fabric was visually observed to confirm the presence or absence of fluffing due to the loosening and falling of the fibers, and the determination was made according to the following criteria.
◯: No unraveling or falling off of the fiber was confirmed.
X: It was confirmed that the fibers were unraveled and dropped off.

<Breaking elongation of base material nanofiber non-woven fabric and composite nanofiber non-woven fabric>
For the base material nanofiber non-woven fabric or composite nanofiber non-woven fabric, distinguish the flow direction (MD) and the direction orthogonal to MD (TD) when processing into a sheet shape, and use the base material nanofiber non-woven fabric or composite nanofiber non-woven fabric in the MD direction. It was cut out to a size of 70 mm and 10 mm in the TD direction. Tensile tests in the MD direction were performed on the five cut-out samples in accordance with JIS K-7127, and the arithmetic average values of the obtained five points of elongation at break (%) were used as the base material nanofiber non-woven fabric and composite nanofiber. The breaking elongation (%) of the non-woven fabric was used. For the measurement, a tensile tester equipped with a 50N load cell (manufactured by A & D Co., Ltd., product name "Tensilon universal material tester RTG-1210") was used. The distance between the chucks was 50 mm, the crosshead speed was 300 mm / min, the temperature was 24 ° C., and the relative humidity was 45%.

<Charging potential of base material nanofiber non-woven fabric and composite nanofiber non-woven fabric>
A base material nanofiber non-woven fabric or a composite nanofiber non-woven fabric cut out to 100 mm × 100 mm was placed on clean paper (manufactured by Sakurai Co., Ltd., product name “EX Clean Blue EX72B”). Static elimination was performed for 1 minute using 3M's Ionized Air Blower 967. Five minutes after the static electricity removal was stopped, the end of the nanofiber non-woven fabric was grasped by a hand wearing AS ONE's Clean Nole Nitrile Gloves (powder-free) and peeled off from the clean paper. The charging potential (kV) of the above was measured with an electrostatic measuring device (manufactured by Simco, product name "Electrostatic Fieldmeter AD-1684A").

[Example 1]
<Manufacturing of polybenzimidazole (PBI) solution>
1 g of polybenzimidazole (manufactured by Sigma-Aldrich Japan, weight average molecular weight 27000) was sufficiently pulverized, 5 g of a 16 mass% sodium hydroxide aqueous solution and 20 g of ethanol were added, and then the mixture was heated and stirred at 80 ° C. for 1 hour. Polybenzimidazole was dissolved and a reddish brown transparent polybenzimidazole solution was obtained. This solution contains 3.8% by mass of polybenzimidazole, 3.1% by mass of sodium hydroxide (converting sodium in the solution as a hydroxide), 16.1% by mass of water, and 77.0% by mass of ethanol. Met. By adding ethanol to this solution, the concentration of polybenzimidazole was adjusted to 0.05% by mass, and the composite nanofiber non-woven fabric was produced.

<Manufacturing of composite nanofiber non-woven fabric>
The base material nanofiber non-woven fabric shown in Example 1 of Table 1 was immersed in the above PBI solution and immediately pulled up. After wiping off the excess PBI solution adhering to the pulled-up base material nanofiber non-woven fabric with a filter paper and roughly drying it by air drying, it is placed in a dryer (manufactured by Espec Co., Ltd., model "SPH-201M") set at 100 ° C. for 30 minutes. It was dried. The dried composite nanofiber non-woven fabric was washed with water by immersing it in a water bath twice for 30 minutes. Further, it was roughly dried by air drying, and then dried in a dryer (manufactured by Espec Co., Ltd., model "SPH-201M") set at 100 ° C. for 30 minutes to obtain a composite nanofiber non-woven fabric.

With respect to the obtained composite nanofiber non-woven fabric, the mass percent concentration X (%) of the polyazole-based compound in the entire composite nanofiber non-woven fabric, the mass percent concentration Y (%) of the polyazole-based compound on the fiber surface of the composite nanofiber non-woven fabric, Y / X. The values, average fiber diameter (nm), thickness (μm), void ratio (%), presence / absence of fiber unraveling and falling off, elongation at break (%), and charging potential (kV) were evaluated. In calculating the mass percent concentration X (%) of the polyazole compound in the entire composite nanofiber non-woven fabric, dehydrogenated N, N-dimethylformamide (DMF) in which the composite nanofiber non-woven fabric is dissolved so as to have a concentration of 3% by mass is used. -D7) In the ¹ H-NMR spectrum of the solution, a peak around 7.3-7.4 ppm derived from polyether sulfone (PES) and around 9.3-9.4 ppm derived from polybenzimidazole (PBI). The integrated value of the peak of was used. The chemical shift criterion used was a peak of 8.02 ppm derived from DMF. In calculating the mass percent concentration Y (%) of the polyazole compound on the fiber surface of the composite nanofiber non-woven fabric, the relative element concentration (atomic%) of sulfur (S) of PES obtained by XPS measurement and nitrogen (N) of PBI ) Relative element concentration (atomic%) was used. The results are shown in Table 1.

[Example 2]
A composite nanofiber non-woven fabric was prepared and evaluated by the same method as in Example 1 except that the concentration of polybenzimidazole was adjusted to 0.3% by mass. The results are shown in Table 1.

[Example 3]
A composite nanofiber non-woven fabric was prepared and evaluated by the same method as in Example 1 except that the concentration of polybenzimidazole was adjusted to 0.5% by mass. The results are shown in Table 1.

[Example 4]
A composite nanofiber non-woven fabric was prepared and evaluated by the same method as in Example 1 except that the concentration of polybenzimidazole was adjusted to 1.0% by mass. The results are shown in Table 1.

[Example 5]
A composite nanofiber non-woven fabric was prepared and evaluated by the same method as in Example 1 except that the concentration of polybenzimidazole was adjusted to 1.5% by mass. The results are shown in Table 1.

[Example 6]
A composite nanofiber nonwoven fabric was obtained and evaluated by the same method as in Example 5 except that the substrate nanofiber nonwoven fabric described in Example 6 of Table 1 was used. In calculating the mass percent concentration X (%) of the polyazole compound in the entire composite nanofiber non-woven fabric, dehydrogenated N, N-dimethylformamide (DMF) in which the composite nanofiber non-woven fabric is dissolved so as to have a concentration of 3% by mass is used. -D7) In the ¹ H-NMR spectrum of the solution, peaks near 2.2-2.6 ppm and 2.9-3.3 ppm derived from polyvinylidene fluoride (PVDF) and derived from polybenzimidazole (PBI). The integrated value of the peak near 9.3-9.4 ppm was used. The chemical shift criterion used was a peak of 8.02 ppm derived from DMF. In calculating the mass percent concentration Y (%) of the polyazole compound on the fiber surface of the composite nanofiber non-woven fabric, the relative element concentration (atomic%) of fluorine (F) of PVDF obtained by XPS measurement and nitrogen (N) of PBI ) Relative element concentration (atomic%) was used. The results are shown in Table 1.

[Comparative Example 1]
With respect to the base material nanofiber nonwoven fabric shown in Comparative Example 1 of Table 1, the presence or absence of fiber unraveling and falling off, the elongation at break (%), and the charging potential (kV) were evaluated without particularly compounding with a polyazole-based compound. bottom. The results are shown in Table 1.

[Comparative Example 2]
The evaluation was carried out in the same manner as in Comparative Example 1 except that the base material nanofiber non-woven fabric described in Comparative Example 2 in Table 1 was used. The results are shown in Table 1.

[Comparative Example 3]
The evaluation was carried out in the same manner as in Comparative Example 1 except that the base material nanofiber non-woven fabric described in Comparative Example 3 in Table 1 was used. The results are shown in Table 1.

The composite nanofiber non-woven fabric of the present invention has properties derived from polyazole-based compounds such as low chargeability, and is subject to breakage, fiber unraveling and falling off even in harsh usage environments where stress is applied and in manufacturing and processing processes. It is a high-quality nanofiber non-woven fabric that does not cause problems. Therefore, it has industrial applicability as a material for various applications such as a resin reinforcing material, an electrolyte membrane reinforcing material, a separator for a battery or a capacitor, a filter medium, and a cell culture substrate.

Claims (7)

Substrate nanofiber non-woven fabric and
It has a polyazole-based compound that covers at least a part of the fiber surface constituting the base material nanofiber nonwoven fabric, and has.
The ratio Y / X of the mass percent concentration X (%) of the polyazole compound in the entire composite nanofiber nonwoven fabric to the mass percent concentration Y (%) of the polyazole compound on the fiber surface of the composite nanofiber nonwoven fabric is 2 That's it ,
Composite nanofiber non-woven fabric for composite electrolyte membranes . The mass percent concentration X (%) of the polyazole compound in the entire composite nanofiber nonwoven fabric is 0.5% or more and 10% or less.
The composite nanofiber non-woven fabric according to claim 1 . The polyazole-based compound contains a polybenzimidazole-based compound.
The composite nanofiber non-woven fabric according to claim 1 or 2 . One or more of the fibers constituting the base material nanofiber non-woven fabric selected from the group consisting of polyethersulfone (PES), polyvinylidene fluoride (PVDF), polysulfone (PSU), polyimide (PI), and polyacrylonitrile (PAN). Containing the compound of
The composite nanofiber non-woven fabric according to any one of claims 1 to 3 . The average fiber diameter of the fibers constituting the composite nanofiber non-woven fabric is 100 nm or more and 500 nm or less.
The composite nanofiber non-woven fabric according to any one of claims 1 to 4 . The composite nanofiber nonwoven fabric according to any one of claims 1 to 5 .
With a proton conductive polymer,
Composite electrolyte membrane. The method for producing a composite nanofiber nonwoven fabric according to any one of claims 1 to 5 .
The step comprising immersing the base material nanofiber non-woven fabric in a polyazole solution in which a polyazole compound and an alkali metal hydroxide are dissolved in a protonic solvent
A method for manufacturing a composite nanofiber non-woven fabric.

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