KR101972082B1 - Porous support having complex structure, method for manufacturing the same, and reinforced membrane comprising the same - Google Patents

Abstract

The present invention relates to a nanocomposite comprising a first nanobeb, a second nanobeb and a third nanobeb, wherein the nanofibers are integrated into a nonwoven fabric comprising a plurality of pores, wherein the second nanobeb is formed on one surface of the first nanobeb Wherein the third nano-web is formed on the other surface of the surface on which the second nano-web is formed, and the average of the pore of the first nano-web is smaller than the pore of the first nano- Porous pores having a small diameter, a method for producing the porous support, and a reinforcing membrane comprising the porous support.

Description

Technical Field [0001] The present invention relates to a porous support having a composite structure, a method for producing the porous support, and a reinforced membrane including the same. BACKGROUND OF THE INVENTION 1. Field of the Invention [0002]

The present invention relates to a porous support, a method for producing the same, and a reinforcing membrane comprising the porous support.

Since nanofibers have a wide surface area and excellent porosity, they are used in various applications such as water purification filters, air purification filters, composite materials, and separators for batteries. Especially, they can be effectively applied to reinforced composite membranes used in fuel cells for automobiles.

On the other hand, the fuel cell is an electrochemical device operated with hydrogen and oxygen as a fuel, and is being regarded as a next generation energy source because of its high energy efficiency and environment-friendly characteristics with less pollutant discharge.

Such a fuel cell can be classified into an alkali electrolyte fuel cell, a direct oxidation fuel cell, a polymer electrolyte membrane fuel cell (PEMFC), and the like, depending on the type of the electrolyte membrane. The principle that the ion (H ⁺ ) is generated from the anode to the cathode and generates electricity is advantageous in that it can operate at room temperature and the activation time is very short compared to other fuel cells Have.

The polymer electrolyte membrane fuel cell includes a membrane electrode assembly (MEA) and a separator (also referred to as a bipolar plate) in which an oxide electrode and a reducing electrode are formed with a polymer electrolyte membrane interposed therebetween. A fuel supply unit for supplying fuel to the electricity generation unit, and an oxidant supply unit for supplying an oxidant such as oxygen or air to the electricity generation unit.

At this time, as the polymer electrolyte membrane, a single membrane made of a polymer resin such as a fluorine resin, more specifically, a single membrane made of a perfluorosulfonic acid resin is mainly used. However, a single membrane made of DuPont Nafion (TM) resin commercially available as the perfluorosulfonic acid resin has a problem in that the mechanical strength is low and pinholes are formed when used for a long time, resulting in a low energy conversion efficiency . In addition, there is an attempt to increase the thickness of a single film made of Nafion resin in order to reinforce the weak mechanical strength. However, in this case, there is a problem that the resistance loss increases, and the problem that the cost is low due to the use of expensive materials have.

Therefore, in order to solve such a problem, there has been proposed a technique of applying a reinforced composite membrane prepared by impregnating a porous fluorinated ion conductor to a porous polytetrafluoroethylene resin, which is a fluorine resin, as a polymer electrolyte membrane.

However, the Teflon resin commercialized as a polytetrafluoroethylene resin has a very low adhesiveness, so ion conductor selection is limited. In the case of a product to which a fluorine-based ion conductor is applied, a crossover phenomenon of a fuel is larger than that of a hydrocarbon system . In addition, since not only fluorine-based ion conductors but also porous teflon resins are expensive, development of new materials that are still inexpensive for mass production is required.

Therefore, it is urgent to develop a reinforced composite membrane having excellent price competitiveness and improved mechanical strength and dimensional stability.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a method for manufacturing a nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite A third nano-web, and a reinforcing membrane comprising the same.

In one aspect, the present invention provides a nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposer comprising Wherein the first nano-web is formed on one surface of the nano-web and has pores having an average diameter smaller than that of the first nano-web, the third nano-web being formed on the other surface of the surface on which the second nano- Wherein the porous support comprises pores having a smaller average diameter than pores of the web.

In another aspect, the present invention provides a method for producing a porous support comprising electrospinning an electrospinning composition to produce a nanofiber in which nanofibers are integrated into a nonwoven fabric comprising a plurality of pores, The step of making comprises: fabricating a first nanoweb through a first chamber; Preparing a second nano-web including pores having a smaller average diameter than pores of the first nano-web through a second chamber on one surface of the first nano-web; And forming a third nano-web including pores having an average diameter smaller than the pores of the first nano-web through the third chamber on the other surface of the second nano-web. to provide.

In another aspect, the present invention provides a reinforced membrane comprising a porous support according to the present invention and an ion exchange polymer filling the pores of the porous support.

The porous support according to the present invention is characterized in that the second nanoweb and the third nanoweb including pores with an average diameter smaller than the pores formed on the first nanoweb are formed on both surfaces of the first nanoweb having a relatively large average diameter of the pores, The inner porosity of the porous support can be increased, so that the amount of impregnation of the ion conductor in the pores can be increased, which can dramatically improve the dimensional stability of the porous support.

In addition, since the porous support of the present invention has a smaller average diameter of the pores contained in the second nanoweb and the third nanoweb than the pores included in the first nanoweb, as described above, Can be formed more densely, and it is very advantageous to have an excellent mechanical strength while increasing the amount of impregnation.

First, terms used in this specification are defined.

(1) The term " nano " as used herein means nanoscale and includes a size of 1 μm or less.

(2) The term " diameter " as used herein means the length of the minor axis passing through the center of the fiber, and " length " means the length of the major axis passing through the center of the fiber.

(3) In the present specification, the average diameter of the pores means an average value obtained by measuring the diameters of 50 pores included in the nanoweb by using a scanning electron microscope (JSM6700F, JEOL).

(4) In the present specification, the average diameter of the nanofibers means an average value obtained by measuring diameters of 50 nanofibers constituting the nanofibers using a scanning electron microscope (JSM6700F, JEOL).

Hereinafter, preferred embodiments of the present invention will be described. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. Further, the embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art.

The inventors of the present invention have conducted extensive research to produce a porous support having excellent mechanical properties and dimensional stability. As a result, it has been found that the average diameter of pores of the first nanoweb is larger than that of the first nanoweb, When the porous support is manufactured by forming the second nano-web and the third nano-web including the small pores, the amount of impregnation of the ion conductor is increased by increasing the porosity of the porous support, The present inventors have found that a porous support excellent in mechanical strength can be obtained by a method of densely forming the surface, thereby completing the present invention.

More specifically, the porous support according to the present invention comprises a first nanobeb, a second nanobeb and a third nanobeb, wherein the nanofibers are integrated in the form of a nonwoven fabric comprising a plurality of pores, And a pore having an average diameter smaller than that of the pores of the first nano-web, wherein the third nano-web is formed on the other surface of the surface on which the second nano-web is formed, And pores having an average diameter smaller than that of the first nanoballs.

At this time, it is preferable that the nanofiber exhibits excellent chemical resistance and is hydrophobic, so that it is not limited to a hydrocarbon-based polymer which is free from the possibility of morphological change due to moisture in a high humidity environment. More specifically, examples of the hydrocarbon-based polymer include nylon, polyimide, polyaramid, polyetherimide, polyacrylonitrile, polyaniline, polyethylene oxide, polyethylene naphthalate, polybutylene terephthalate, styrene butadiene rubber , Polystyrene, polyvinyl chloride, polyvinyl alcohol, polyvinylidene fluoride, polyvinyl butylene, polyurethane, polybenzoxazole, polybenzimidazole, polyamideimide, polyethylene terephthalate, polyethylene, polypropylene A copolymer thereof, and a mixture thereof.

In particular, in the present invention, the nanofiber is more preferably a polyimide nanofiber in view of improving heat resistance, chemical resistance, and shape stability of the porous support.

Here, the nano-web composed of the polyimide nanofiber is prepared by preparing a polyamic acid nanoweb using polyamic acid (PAA) as a polyimide precursor which is well soluble in an organic solvent, . ≪ / RTI > At this time, the polyamic acid nano-web can be manufactured using a method well known in the art, and is not particularly limited. For example, the polyamic acid can be prepared by mixing a diamine in a solvent, adding dianhydride thereto, and electrospinning it.

Meanwhile, the diamine can be used without limitation as well known in the art, and examples thereof include 4,4'-oxydianiline (ODA), 1,3-bis (4-amino Benzene, RODA, p-phenylene diamine, p-PDA, o-phenylene diamine, o-PDA, ), And mixtures thereof, but the present invention is not limited thereto.

The dianhydride may be any of those well known in the art without limitation, for example, pyromellitic dianhydride (PMDA), 3,3 ', 4,4'-benzophenonetetracarboxylic acid (3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, BTDA), 4,4'-oxydiphthalic anhydride (ODPA), 3,4,3' Biphenyltetracarboxylic dianhydride (BPDA), bis (3,4-dicarboxyphenyl) dimethylsilane dianhydride, bis (3,4-dicarboxyphenyldimethylsilane dianhydride) SiDA), and mixtures thereof, but is not limited thereto.

Further, the solvent for dissolving the polyamic acid may be any of those well-known in the art, and examples thereof include m-cresol, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF) (DMSO), acetone, diethyl acetate, tetrahydrofuran (THF), chloroform, gamma -butyrolactone, and mixtures thereof may be used in combination with at least one selected from the group consisting of dimethyl acetamide (DMAc), dimethyl sulfoxide But is not limited thereto.

Meanwhile, as described above, when the nanofiber is polyimide, the main chain of the polyimide may include at least one substituent selected from the group consisting of an amine group, a carboxyl group, a hydroxyl group, and a combination thereof. Since the polyimide is a hydrophobic polymer, it is preferable that the polyimide includes a hydrophilic substituent as described above in order to satisfy physical properties such as a saturation hindrance time, a water content, a wettability or a contact angle by a wicking test of a porous support described later.

In this case, in order for the main chain of the polyimide to contain at least one substituent selected from the group consisting of an amine group, a carboxyl group, a hydroxyl group and a combination thereof, for example, after the polyimide or polyamic acid is prepared The hydrophilic substituent may be substituted for the main chain of the polyimide or polyamic acid, or the polyimide may be prepared by using the diamine and / or the dianhydride containing the hydrophilic substituent, The diamine and the dianhydride may be polymerized together with a comonomer containing the hydroxy group. The comonomer containing a hydroxy group may be selected from the group consisting of, for example, dianiline including a hydroxy group, diphenylurea including a hydroxy group, diamine including a hydroxy group, and combinations thereof One or more of them may be used, but the present invention is not limited thereto.

As described above, when the main chain of the polyimide includes a hydrophilic substituent, the hydrophilic substituent is contained in an amount of 0.01 to 0.1 mol%, preferably 0.01 to 0.08 mol%, more preferably 0.02 to 0.08 mol% based on the total amount of the polyimide can do. If the content of the hydrophilic substituent is less than 0.01 mol%, hydrophilization may be insufficient due to the reduction of the hydrophilic group of the main chain of the polyimide. If the content exceeds 0.1 mol%, generation of a side reaction and physical strength reduction may be a problem.

Meanwhile, in the present invention, when the nanofibers forming the first nano-web, the second nano-web and the third nano-web are made of a hydrophobic polymer such as polyimide and the like, the saturated saturation reaching time, moisture content , The wettability due to the wicking test or the contact angle is adjusted to a desired range by performing plasma treatment on the surface of the second nanoweb or the third nanoweb located on the surface of the porous support according to the present invention, Can be deposited.

First, when the surface of the porous support is subjected to the plasma treatment, the surface of the porous support can be replaced with a functional group having at least one hydrophilic property selected from the group consisting of a carboxyl group, a hydroxyl group, an amine group, and a combination thereof.

More specifically, the plasma treatment may be performed by, for example, a method of treating a gas capable of imparting a hydrophilic group to one or both surfaces of the porous support using a low-temperature plasma or a radio frequency (RF) plasma. At this time, the gas capable of imparting the hydrophilic group may be at least one selected from the group consisting of, for example, ammonia gas, argon gas, oxygen gas, and combinations thereof, but is not limited thereto. Also, the flow rate of the gas capable of imparting the hydrophilic group may be 10 to 200 sccm, the power of the plasma may be 50 to 200 W, and the plasma treatment time may be 10 seconds to 5 minutes.

Next, the inorganic layer may include, but is not limited to, anatase-type titanium dioxide (TiO ₂ anatase), rutile-type titanium dioxide (TiO ₂ rutile), brookite-type titanium dioxide (TiO ₂ brookite), tin dioxide , Zirconium dioxide (ZrO ₂ ), aluminum oxide (Al ₂ O ₃ ), oxidized single-walled carbon nanotubes, oxidized multi-walled carbon nanotubes, oxidized graphite oxide, oxidized graphene, The above precursors can be deposited using chemical vapor deposition (CVD) or physical vapor deposition (PVD) methods including sputtering. The deposition may be performed by, for example, placing a cartridge capable of imparting a hydrophilic group to the surface by using an RF sputtering or evaporator, and then performing the treatment at a temperature of 50 to 300 ° C for 1 minute to 60 minutes. However, It is not.

On the other hand, the porous support of the present invention includes a collection of nanofibers, i.e., nanoballs, in which nanofibers as described above produced by electrospinning are randomly arranged. That is, the nanofibers are integrated into a nonwoven fabric including a plurality of pores. In the present invention, the nanofibers are divided into a first nanofiber, a second nanofiber, and a third nanofiber for convenience. The constituent materials and formation methods are all the same.

First, the first nano-web includes pores having an average diameter of 5 탆 to 6 탆 and refers to a nano-web located inside the porous support.

Next, the second nano-web is formed on one surface of the first nano-web and includes pores having an average diameter smaller than pores of the first nano-web, and refers to a nano-web located on the surface of the porous support . More specifically, the average diameter of the second nano web pores and the average diameter ratio of the first nano web pores may be 1: 3 to 1:10, preferably 1: 3 to 1: 8, 3 to 1: 5.

The third nano-web may be formed on the other surface of the surface on which the second nano-web is formed. The third nano-web may include pores having an average diameter smaller than that of the first nano- Quot; More specifically, the average diameter of the third nano web pores and the average diameter ratio of the first nano web pores may be from 1: 3 to 1:10, and preferably from 1: 3 to 1: 8, 3 to 1: 5.

In the present invention, the average diameters of pores included in the second nanoweb and the third nanoweb may be the same or different, and are not particularly limited. More specifically, the average pore size of the second nanoweb and / or the third nanoweb may be 1.5 탆 or less.

In the present invention, the total thickness of the porous support may be from 5 탆 to 50 탆, more preferably from 5 탆 to 35 탆, and most preferably from 5 탆 to 20 탆. If the thickness of the porous support is less than 5 탆, the mechanical strength and dimensional stability of the separator may be significantly reduced. If the thickness exceeds 50 탆, the resistance loss may increase during application to the separator, .

The thickness ratio of the first nano-web to the second nano-web or the third nano-web is preferably 1: 0.2 to less than 1. If the thickness ratio of the second nano-web or the third nano-web is less than 0.2, the physical properties of the porous support may be deteriorated. If the thickness ratio of the second nano-web or the third nano- You may lose your sex. At this time, the thickness of the second nanoweb or the third nanoweb may be substantially the same. If the thicknesses of the second nanoweb and the third nanoweb are not substantially equal to each other, the impregnation amount of the ion conductor may be changed to increase the asymmetry A film can be obtained.

As described above in the present invention, the average diameters of the pores included in the first nanoweb, the second nanoweb, and the third nanoweb are different from each other in the case where the diameters of the nanofibers forming the respective nanofibers are different or the diameters of the nanofibers are the same It can be controlled by adjusting the lamination density of the nano-web.

More specifically, the ratio of the diameter of the nanofibers forming the first nanobubbles to the diameter of the nanofibers forming the second nanobubbles may be from 1: 1 to 10: 1, and the ratio of 1: 1 to 5: 1 Is more preferable. The ratio of the diameter of the nanofibers forming the first nanobubbles to the diameter of the nanofibers forming the third nanobubbles may be from 10: 1 to 1: 1, more preferably from 5: 1 to 1: 1 More preferable.

If the diameter ratio of the nanofibers is more than 10: 1, the thickness variation of the porous support may be excessive. On the other hand, when the ratio of the diameters of the nanofibers is less than 1: 1, the physical properties of the porous support may deteriorate.

When the ratio of the fiber diameters of the first nanoweb and the second nanoweb or the fiber diameters of the first nanoweb and the third nanoweb is 1: 1, the density of the nanoweb should be different. To this end, the spinning nozzle density for manufacturing the first nanoweb should be reduced to less than half the spinning nozzle density for manufacturing the second nanoweb or the third nanoweb.

More specifically, the density of the first nanoweb may be in the range of 0.01 to 0.5 g / cm < ³ >, and the density ratio of the first nanoweb and the second nanoweb or the third nanoweb may be greater than 1: 1 To 10, more preferably greater than 1: 1 to 5.

Meanwhile, the first nano-web, the second nano-web, and the third nano-web of the present invention may have a porosity of 50% or more because they are made of the nanofibers described above. Since the porous support has a specific surface area of 50% or more as described above, it is easy to impregnate the electrolyte when applied as a separation membrane, and as a result, the efficiency of the battery can be improved. The first nano-web, the second nano-web, and the third nano-web preferably have a porosity of 90% or less. If the porosity of the nano-web exceeds 90%, the morphology stability may be deteriorated and the post-process may not proceed smoothly. The porosity can be calculated according to the ratio of the volume of air to the total volume of the porous support according to Equation (1). In this case, a rectangular volume sample is prepared and measured by measuring the width, length, and thickness, and the air volume can be obtained by subtracting the volume of the polymer inversely calculated from the density after measuring the mass of the sample from the total volume.

[Equation 1]

Porosity (%) = (air volume in nano web / total volume of porous support) x 100

Also, in the present invention, the porous support has a thickness of nanofibers having excellent porosity and optimized diameter, and is easy to manufacture. In order to exhibit excellent tensile strength after electrolyte impregnation, the first nanofiber, The second nanoweb and the third nanoweb preferably have a weight average molecular weight of 30,000 to 500,000 g / mol. When the weight average molecular weight of the polymer is less than 30,000 g / mol, the porosity and thickness of the nanoweb can be easily controlled, but tensile strength after porosity and wet treatment may be lowered. If the weight average molecular weight of the polymer is more than 500,000 g / mol, the heat resistance may be somewhat improved, but the manufacturing process is not smooth and the porosity is lowered.

The first nanoweb, the second nanoweb, and the third nanoweb have a weight average molecular weight in the range described above, and the polymer precursor is converted into a polymer under optimal curing conditions, so that the heat resistance is preferably 180 ° C or higher Lt; 0 > C or higher. If the heat resistance of the nano-web is less than 180 ° C, the nano-web may be easily deformed at a high temperature as heat resistance deteriorates, and thus the performance of the electrochemical device manufactured using the nano-web may deteriorate. Also, when the heat resistance of the nano web is deteriorated, the shape of the nano web may be deformed due to abnormal heat generation, and the performance may be deteriorated.

On the other hand, the porous support of the present invention is insoluble in an organic solvent at a temperature of from room temperature to 100 ° C, and can be chemically stable. The organic solvent may be an organic solvent such as NMP, DMF, DMAc, DMSO, THF or the like.

In addition, the porous support of the present invention may have a strain rate of 10% or less and preferably 5% or less. The strain rate can be measured as an average of the transverse and longitudinal strains before and after leaving the nano-web at 100 ° C for 100 mm and 200 ° C for 24 hours. If the strain exceeds 10% by length, the dimensional stability of the support and morphological deformation can be achieved under high temperature environment.

If the first nano-web, the second nano-web, and the third nano-web are made of polyimide nanofibers, the imide conversion may be 90% or more, preferably 99% or more. The imide conversion rate was measured by the infrared spectrum with respect to the nano web, it can be determined by calculating the ratio of the p- substituted CH absorbance already de CN absorbance versus 1500㎝ ^-1 in 1375㎝ ^-1. If the imide conversion is less than 90%, the physical properties and shape stability can not be secured due to unreacted materials.

The porous support of the present invention is excellent in hydrophilicity and can reach the saturation humidity for 1 second to 5 minutes, preferably 1 second to 3 minutes, and more preferably 1 second to 60 seconds. The saturation humidification arrival time is determined by KS K ISO 9073-6, Textile - Nonwoven Fabric Test Methods - Part 6: Water Absorption Time in Absorption Measurement Standard, . When the saturation humidification time is within the above range, the porous support of the present invention may be impregnated with an ion-exchange polymer to uniformly impregnate the ion-exchange polymer uniformly throughout the entire pores in the porous support during the preparation of the reinforced membrane. Also, when the hydrophilic property of the porous support is increased, a hydrophilic channel is further formed when the reinforced membrane is used as a membrane for a fuel cell, so that ion conductivity can be improved.

In addition, the porous support may have an electrolyte absorption rate of 10 to 60% by weight, and preferably 30 to 40% by weight. The electrolyte absorptivity was measured according to KS K ISO 9073-6, Textile-Nonwoven Fabric Test Method, Part 6: Absorption Measurement Standard, liquid humidification time method, 70/30 (v / v) ratio of ethyl methyl carbonate and ethylene carbonate, v) The mixture can be dropped at a height of 25 mm to measure the time the specimen is completely wet. If the electrolyte absorptivity is less than 10 wt%, the electrolyte absorption may decrease and the battery performance may not be sufficiently exhibited. If the electrolyte absorptivity is more than 60 wt%, the physical properties of the support may deteriorate.

On the other hand, the porous support may have a moisture regain of 3.0% or more, preferably 3.0 to 5.0%, and more preferably 3.1 to 5.0%. The moisture content was determined by measuring the weight (O: sample weight) after reaching moisture equilibrium in a fiber laboratory standard state (KS K 0901) for 24 hours in accordance with the method of moisture measurement of KS K 0221 textile: oven balance method , And dried at 105 to 110 ° C for 1 hour and 30 minutes, and then the weight (D: weight of the dried sample) is measured.

&Quot; (2) "

Moisture content (%) = (O-D) / D x 100

(O: weight of specimen, D: weight of dried specimen)

In addition, the porous support of the present invention may have a wettability by wicking test of 2 to 15 cm, preferably 2.1 to 15 cm, and more preferably 3 to 15 cm. The wicking test was conducted according to the AATCC Test Method 197-2011, Vertical Wicking of Textiles (Option B, Measure distance at a given time), 30 minutes after immersing the specimen Can be measured by a method of measuring the maximum wicking distance. If the wettability by the wicking test is less than 2 cm, the ion conductor and the support may be separated from each other in the operating environment of the fuel cell, the operation time may be delayed or the physical form stability may be deteriorated under the low humidity condition, Acceleration of the swelling of the ion conductor in a fuel cell operating environment may result in reduced durability, or the ion conductor and support may desorb.

Furthermore, the porous support of the present invention may have a contact angle of 90 ° or less, preferably 1 to 50 °, and more preferably 5 to 35 °. The contact angle was maintained at 30 ° and RH 40%. Distilled water was charged into a syringe, water droplets having a diameter of 3 mm were dropped on the porous support, and water droplets were spread for 5 minutes. After 5 minutes, The contact angle can be measured. When the contact angle is less than 1 °, the wettability of the nano web is excellent. However, it may be difficult to manufacture the nano-web having an excessively high quality of the additive in the spinning process. It may be difficult to exhibit sufficient performance when used.

Since the porous support of the present invention as described above has excellent productivity, and is excellent in mechanical properties and dimensional stability, it can be used as a filter medium for gas or liquid filters, a filter medium for dustproof masks, automotive venting, Materials for high-grade clothes such as breathable tarpaulins, electrochemical materials such as polymer electrolytes of fuel cells, secondary batteries, separators of electrolytic devices or capacitors, wound dressings, artificial vascular supports, bandages, And a medical material such as a mask for cosmetics.

Next, a method for producing a porous support according to the present invention will be described.

The manufacturing method of the present invention includes a step of electrospinning an electrospinning composition to produce a nano-web in which nanofibers are integrated into a nonwoven fabric including a plurality of pores, Comprising the steps of: preparing a second nanoweb; Preparing a first nano-web including pores having an average diameter larger than pores of the second nano-web on the second nano-web; And producing a third nano-web including pores having an average diameter smaller than that of the first nano-web on the first nano-web.

First, the step of preparing a nano-web in which nanofibers are integrated into a nonwoven fabric including a plurality of pores by electrospinning an electric discharge composition may be performed by a method well known in the art, and is not particularly limited. For example, in the case where the nanofiber is made of polyimide which is a hydrophobic polymer, the production method of the porous support includes a step of preparing an electrospinning solution by adding a diamine and a dianhydride to a solvent, A process for producing a polyamic acid nanoweb in which nanofibers are integrated in the form of a nonwoven fabric including a plurality of pores, and a process for producing a polyimide nanoweb by imidizing the polyamic acid nanoweb.

In the manufacturing method of the present invention, the electrospinning solution contains monomers for forming the nanofibers, and the monomers for forming the nanofibers are preferably hydrocarbon-based polymers, Do.

At this time, the monomers for forming the nanofibers are preferably included in an amount of 5 to 20% by weight based on the total weight of the electrospun solution. If the content of the monomers is less than 5% by weight, the fiber can not be formed or fibers having a uniform diameter can not be produced because the spinning does not proceed smoothly, whereas the content of the monomers exceeds 20% by weight If the discharge pressure increases suddenly, the radiation may not be produced or the fairness may deteriorate.

Wherein the porous support is transferred from the first chamber to the third chamber while forming the second nanoweb in the first chamber and the second nanoweb is formed in the second chamber by transferring the porous support from the first chamber to the third chamber, Forming a first nano-web, and forming a third nano-web in a third chamber. However, the present invention is not limited to this, and the porous support may form the first to third nanowires while replacing the size of the nozzle, the density of the nozzles, etc. in one chamber.

In addition, the average diameter of the pores of the first nanoweb and the third nanoweb can be adjusted by changing the thickness of the electrospun fiber. That is, when the thickness of the electrospun fiber is thick, the average diameter of the pores becomes large, and when the thickness of the electrospun fiber is small, the average diameter of the pores becomes small. In addition, the thickness of the fiber can be controlled by varying the supply amount of the solution during electrospinning, the shape of the nozzle, the voltage, the radial distance, and the viscosity of the solution.

Also, the average diameter of the pores of the first to third nano-webs can be adjusted by changing the density of the nano-webs even if the thickness of the electrospun fibers is the same. That is, even if the thickness of the electrospun fiber is the same, if the number of the fibers laminated per unit area is reduced, the average diameter of the pores becomes larger, and even if the thickness of the electrospun fiber is the same, The average diameter size of the pores becomes smaller. In order to control the number of fibers stacked per unit area even if the thickness of the fibers is the same, the density can be adjusted by changing the density of the spinneret during electrospinning.

Hereinafter, a method of forming the porous support while transferring the porous support from the first chamber to the third chamber will be described in detail.

The step of preparing the second nanoweb in the first chamber is carried out by spinning the electrospinning composition to prepare a nanobubbel precursor and then curing the nanobeb precursor. The radiation may be, for example, but is not limited to, electrospinning, electro-blown spinning, centrifugal spinning or melt blowing radiation, and the like .

In particular, in the manufacturing method of the present invention, it is most preferable to use electrospinning, and the electrospinning method can be performed by a method well known in the art, and is not particularly limited.

In addition, it is preferable that the curing process is appropriately performed in consideration of the conversion rate of the nano-web precursor. For example, the curing temperature can be performed at 80 to 650 ° C. When the curing temperature is lower than 80 캜, the conversion rate is lowered. As a result, the heat resistance and chemical resistance of the nano-web may be deteriorated. When the curing temperature is higher than 650 캜, the nano- There is a risk of degradation.

Next, a first nano-web including pores having an average diameter larger than the pores of the second nano-web is formed on the second nano-web in the second chamber, and the first nano- A third nano-web comprising pores having an average diameter smaller than that of the first nano-web is produced. The manufacturing of the first nanoweb and the third nanoweb proceeds in the same manner as the manufacturing of the first nanoweb except for the diameter of the nanofibers or the density of the spinneret.

More specifically, the ratio of the diameter of the nanofibers forming the first nanobubbles to the diameter of the nanofibers forming the second nanobubbles is 1: 1 to 10: 1, preferably 1: 1 to 5: 1 .

The ratio of the diameter of the nanofibers forming the first nanobubbles to the diameter of the nanofibers forming the third nanobubbles may be 1: 1 to 10: 1, preferably 1: 1 to 5: 1. have.

The supply amount of the electrospinning solution to be supplied to the electric spray nozzle in the first nanoporous web may be 0.1 to 10.0 ml / min, preferably 0.5 to 4.5 ml / min. When the supply amount of the electrospinning solution supplied to the nozzle for electric discharge in the production of the first nano-web is less than 0.1 ml / min, the spinning jet may intermittently occur and fiber formation may be difficult. If the amount is more than 10.0 ml / May not be properly formed and the solution may fall into droplets.

In addition, the supply amount of the electrospinning solution supplied to the nozzle for electric discharge in the production of the second nanoweb or the third nanoweb may be 0.1 to 5.0 ml / min, preferably 0.1 to 2.5 ml / min. When the supply amount of the electrospinning solution supplied to the nozzle for electric discharge is less than 0.1 ml / min during the production of the second nanoporous web, the spinning jet may intermittently occur and fiber formation may be difficult. When the amount of the electrospinning solution is more than 5.0 ml / The dimensional stability of the reinforcing film may be lowered.

The density of the electric spraying nozzle in manufacturing the first nano-web may be 0.1 to 2 / cm, preferably 0.2 to 1 / cm. When the density of the electric discharge nozzle is less than 0.1 / cm, the productivity of the nanofibers may be decreased. When the density of the nozzles is more than 2 / cm, it may be difficult to control the density of the first nanofibers. .

In addition, the density of the electric discharge nozzle in the production of the second nano-web or the third nano-web may be 0.1 to 6 / cm, preferably 0.4 to 4 / cm. If the density of the electric discharge nozzle is less than 0.1 / cm, the productivity of the nanofiber may be deteriorated. If the density of the electric discharge nozzle is more than 6 / cm, the discharge drops of the respective nozzles may be combined with each other, The repulsion may not result in good radiation.

Next, the reinforcing membrane according to the present invention is characterized by comprising the above-mentioned porous support of the present invention and an ion-exchange polymer filling the pores of the porous support.

At this time, the ion exchange polymer may be filled in the pores of the porous support by, for example, impregnation or in-situ polymerization, but the present invention is not limited thereto.

More specifically, the impregnation may be performed by immersing the porous support of the present invention in a solution containing an ion exchange polymer. At this time, the impregnation temperature and time may be affected by various factors. For example, the thickness of the nano-web, the concentration of the ion exchange polymer, the type of the solvent, the concentration of the ion exchange polymer to be impregnated in the porous support, and the like can be influenced. However, the temperature range for performing the impregnation process may be 100 ° C or less, preferably 70 ° C or less at normal temperature. However, the impregnation temperature can not be higher than the melting point of the nanofibers forming the porous support.

In addition, the in-situ polymerization may be carried out by immersing a monomer or low molecular weight oligomer forming an ion-exchange polymer in a porous support, followed by in-situ polymerization in the porous support.

On the other hand, the ion-exchange polymer may be used without limitation in the art, for example, a cation exchange polymer having a cation exchange group such as proton, or a cation exchange polymer such as a hydroxide ion, a carbonate or a bicarbonate And an anion exchange polymer having an anion exchange group.

Since the reinforcing membrane of the present invention as described above has excellent dimensional stability and mechanical strength as described above, it can be used variously as a polymer electrolyte membrane for a fuel cell or a membrane for a reverse osmosis filter.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention.

[ Example : Preparation of porous support]

( Example  One)

(1) Fabrication of the second nanobebe precursor

Polyamic acid was dissolved in a dimethylformamide solvent to prepare 5 L of a spinning solution having a solid content of 13% by weight and a 480 poise. The prepared spinning solution was transferred to a solution tank, which was supplied through a metering gear pump to a first spinning chamber composed of 20 nozzles and applied with a high voltage of 46 kV, and was radiated to form a spinning solution containing pores having an average diameter of 1.2 탆 2 nano-web precursor. At this time, the solution supply amount was 0.9 ml / min.

(2) Production of first nanobeb precursor

The second nanoparticle precursor was transferred to a second spinning chamber to spin the first nanoparticle precursor onto the second nanoparticle precursor at a rate of 2.5 ml / min. A first nano-web precursor containing pores having a diameter of 6 m was prepared.

(3) Production of the third nanoparticle precursor

The first nano-web precursor formed on the second nano-web precursor is transferred to a third spinning chamber, and a third nano-web precursor is poured on the first nano-web precursor in the same manner as in (1) To prepare a third nano-web precursor.

(4) Preparation of Porous Support

Next, the nano-web precursor having the third nanobubbles formed thereon was transferred in a roll-to-roll manner, and thermosetting was performed for 6 minutes in a continuous curing furnace maintained at a temperature of 420 ° C to prepare a porous support.

( Example  2)

(1) Fabrication of the second nanobebe precursor

Polyamic acid was dissolved in a dimethylformamide solvent to prepare 5 L of a spinning solution having a solid content of 13% by weight and a 480 poise. The prepared spinning solution was transferred to a solution tank, which was supplied through a metering gear pump to a first spinning chamber composed of 20 nozzles and applied with a high voltage of 46 kV, and was radiated to form a spinning solution containing pores having an average diameter of 1.2 탆 2 nano-web precursor. At this time, the solution supply amount was 0.9 ml / min and the spinning nozzle density was 0.4 pieces / cm.

(2) Production of first nanobeb precursor

The second nanoparticle precursor was transferred to a second spinning chamber to spin the first nanoparticle precursor onto the second nanoparticle precursor at a solution feed rate of 0.9 ml / min and a spinneret nozzle density of 0.2 particles / cm. A first nano-web precursor including pores having an average diameter of 5 탆 was prepared in the same manner as in (1) above.

(3) Production of the third nanoparticle precursor

The first nano-web precursor formed on the second nano-web precursor is transferred to a third spinning chamber, and a third nano-web precursor is poured on the first nano-web precursor in the same manner as in (1) To prepare a third nano-web precursor.

(4) Preparation of Porous Support

Next, the nano-web precursor having the third nanobubbles formed thereon was transferred in a roll-to-roll manner, and thermosetting was performed for 6 minutes in a continuous curing furnace maintained at a temperature of 420 ° C to prepare a porous support.

( Example  3)

(1) Fabrication of the second nanobebe precursor

Polyamic acid was dissolved in a dimethylformamide solvent to prepare 5 L of a spinning solution having a solid content of 13% by weight and a 480 poise. The prepared spinning solution was transferred to a solution tank, which was supplied through a metering gear pump to a first spinning chamber having 20 nozzles and a high voltage applied at 46 kV to spin the spinning solution, thereby spinning the spinning solution containing pores having an average diameter of 6 μm 2 nano-web precursor. At this time, the solution supply amount was 2.5 ml / min.

(2) Production of first nanobeb precursor

The second nanoparticle precursor was transferred to a second spinning chamber to spin the first nanoparticle precursor onto the second nanoparticle precursor at a rate of 0.9 ml / min. To prepare a first nano-web precursor including pores having a diameter of 1.2 mu m.

(3) Production of the third nanoparticle precursor

The first nano-web precursor formed on the second nano-web precursor is transferred to a third spinning chamber, and the third nano-web precursor is poured on the first nano-web precursor in the same manner as in (1) To prepare a third nano-web precursor.

(4) Preparation of Porous Support

Next, the nano-web precursor having the third nanobubbles formed thereon was transferred in a roll-to-roll manner, and thermosetting was performed for 6 minutes in a continuous curing furnace maintained at a temperature of 420 ° C to prepare a porous support.

( Comparative Example  One)

Polyamic acid was dissolved in a dimethylformamide solvent to prepare 5 L of a spinning solution having a solid content of 13% by weight and a 480 poise. The prepared spinning solution was transferred to a solution tank, which was supplied through a metering gear pump to a first spinning chamber composed of 20 nozzles and applied with a high voltage of 46 kV and spinning to prepare a first nano-web precursor. At this time, the solution supply amount was 0.9 ml / min.

Then, the polyamic acid nanoweb was thermally cured in a continuous curing furnace maintained at a temperature of 420 ° C. for 6 minutes to prepare a porous support composed of a nanoweb having pores having an average diameter of 1.2 μm.

( Comparative Example  2)

A porous support composed of a nanoweb containing pores with an average diameter of 6 m was prepared in the same manner as in Comparative Example 1 except that the solution supply amount was 2.5 ml / min.

[ Test Example  1: comprising a porous support Reinforced membrane  Dimensional stability and mechanical strength, elongation measurement]

The porous support prepared in Examples 1, 2 and 3 and Comparative Examples 1 and 2 was impregnated with 0.05% by weight of a 5% by weight Nafion solution per unit area (cm ² ) of the support, and then dried in a 60 ° C vacuum drying oven And dried for 4 hours or more to prepare an ion exchange enhanced membrane. Swelling of the membrane occurs when a charged group of functional groups in the ion exchange enhanced membrane is in the water. The dimensional stability of these ion exchange membranes was evaluated by comparing the volume of wet film (V _wet ) and the volume of dry film (V _dry ). At this time, the wet film was immersed in ultrapure water for 24 hours at room temperature, and then its volume was measured.

&Quot; (3) "

Dimensional stability (%) = 100 - ((V _wet - V _dry ) / V _wet ) x 100)

(V _wet : wet film volume, V _dry : dry film volume)

In addition, the mechanical strength and elongation of the reinforcing membrane including the porous support were evaluated according to KS K ISO 9073-3: 2009.

Average pore size (占 퐉)
(Second / first / third nano web) Reinforced membrane
Dimensional stability (%) Reinforced membrane
Strength (MPa) Reinforced membrane
Shinto (%) Example 1 1.2 / 6 / 1.2 90.6 47 14 Example 2 1.2 / 5 / 1.2 87.3 45 13 Example 3 6 / 1.2 / 6 73.4 36 13 Comparative Example 1 1.2 / 1.2 / 1.2 70.1 26 15 Comparative Example 2 6/6/6 59.5 27 12

Referring to Table 1, it can be seen that the reinforced membrane including the porous support manufactured according to the embodiment has high dimensional stability and is well impregnated even down to the inside of the porous support, thereby providing excellent mechanical strength. On the contrary, the porous support prepared according to Comparative Examples 1 and 2 has poor dimensional stability and low strength of the reinforced membrane.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the disclosed exemplary embodiments, but various modifications and changes may be made without departing from the scope of the invention. To those of ordinary skill in the art.

Claims (15)

Wherein the nanofibers comprise a first nanoweb, a second nanoweb, and a third nanoweb integrated into a nonwoven fabric comprising a plurality of pores,
Wherein the second nano-web is formed on one surface of the first nano-web and includes pores having an average diameter smaller than pores of the first nano-web,
Wherein the third nano-web is formed on the other surface of the surface on which the second nano-web is formed, the porous support including pores having an average diameter smaller than that of the first nano-web; And
And an ion exchange polymer that fills the pores of the first nanoweb, the second nanoweb, and the third nanoweb of the porous support,
Wherein the first nanoweb comprises pores having an average diameter of 5 to 6 m,
Wherein the average diameter of the second nano-web pores, the average diameter of the third nano-web pores, and the average diameter ratio of the first nano-web pores are 1: 3 to 1:10. delete delete The method according to claim 1,
Wherein the ratio of the thickness of the first nano-web to the thickness of the second nano-web or the third nano-web is less than 1: 0.2 to 1. The method according to claim 1,
Wherein the ratio of the diameter of the nanofibers forming the first nanobubbles to the diameter of the nanofibers forming the second nanobubbles is 1: 1 to 10: 1. The method according to claim 1,
Wherein the ratio of the diameter of the nanofibers forming the first nanobubbles to the diameter of the nanofibers forming the third nanobubbles is 1: 1 to 10: 1. The method according to claim 1,
Wherein the density of the first nanoweb is 0.01 to 0.5 g / cm < ³ >, and the density ratio of the first nanoweb and the second nanoweb or the third nanoweb is greater than 1: 1 to 10 membrane. The method according to claim 1,
Wherein the nanofiber is a polyimide nanofiber. 9. The method of claim 8,
Wherein the main chain of the polyimide includes at least one substituent selected from the group consisting of an amine group, a carboxyl group, a hydroxyl group, and a combination thereof. Preparing a porous support comprising a first nano-web, a second nano-web and a third nano-web, wherein the nanofibers are integrated in a non-woven form including a plurality of pores; And
Filling the pores of the first nano web, the second nano web, and the third nano web with an ion exchange polymer,
Wherein the step of preparing the porous support comprises:
Producing a second nanoweb;
Preparing a first nano-web including pores having an average diameter larger than pores of the second nano-web on the second nano-web; And
Preparing a third nano-web including pores having an average diameter smaller than the pores of the first nano-web on the first nano-web,
Wherein the first nanoweb comprises pores having an average diameter of 5 to 6 m,
Wherein the average diameter of the second nano web pores, the average diameter of the third nano web pores, and the average diameter ratio of the first nano web pores are 1: 3 to 1:10. 11. The method of claim 10,
Wherein the ratio of the diameter of the nanofibers forming the first nanobubbles to the diameter of the nanofibers forming the second nanobubbles is 1: 1 to 10: 1. 11. The method of claim 10,
Wherein the ratio of the diameter of the nanofibers forming the first nanobubbles to the diameter of the nanofibers forming the third nanobubbles is 1: 1 to 10: 1. 11. The method of claim 10,
The supply amount of the electrospinning solution to be supplied to the nozzle for electric discharge in the production of the first nano-web is 0.1 to 10.0 ml / min,
Wherein the supplying amount of the electrospinning solution to be supplied to the nozzle for electric discharge in the production of the second nano-web or the third nano-web is 0.1 to 5.0 ml / min. 11. The method of claim 10,
The density of the electric spraying nozzle in manufacturing the first nano-web is 0.1 to 2 / cm,
Wherein the densities of the electric discharge nozzles in the production of the second nano-web or the third nano-web are 0.1 to 6 / cm. delete