KR20160077566A - Porous support having good chemical resistance and thermal stability, method for manufacturing the same, and reinforced membrane comprising the same - Google Patents

Abstract

The present invention relates to a porous support comprising a nanoweb in which nanofibers are integrated in the form of a non-woven fabric including a plurality of pores, the nanoweb having 40 to 85 of a yellowness index measured in accordance with an ASTM E-313 method, a method for preparing the porous support, and a reinforced membrane comprising the porous support. A porous support according to the present invention is very advantageous when the porous support is applied to fuel cells since the porous support has very excellent heat resistance and hydrophilicity as well as excellent air permeability and water permeability.

Description

TECHNICAL FIELD [0001] The present invention relates to a porous support having excellent chemical resistance and thermal stability, a method for producing the porous support, and a reinforced membrane including the porous support,

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.

On the other hand, in order to solve such a problem, research on a reinforced composite membrane produced by impregnating an ion conductor on a porous support is actively studied. However, in the process of preparing a porous support suitable for the reinforced composite membrane as described above, a curing process may be involved. If the curing process does not proceed completely, the amine compound will remain on the porous support, Is oxidized to make the support brown, and in this case, the chemical resistance of the reinforced composite membrane is deteriorated.

The present invention provides a porous support comprising a nano-web having a yellowness index measured according to ASTM E-313, which satisfies a specific value range, a method for producing the same, and a reinforcing membrane comprising the same. I want to.

In one aspect, the present invention is directed to a nanocomposite nanofiber comprising nanofibers integrated into a nonwoven fabric comprising nanofibers comprising a plurality of pores, wherein the nanofiber has a yellowness index of 40 < RTI ID = 0.0 >Lt; RTI ID = 0.0 > 85. ≪ / RTI >

In another aspect, the present invention provides a method of manufacturing a nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite material, And curing the nano-web precursor to produce a nano-web, wherein the nano-web has a yellowness index of from 40 to 85 measured according to the ASTM E-313 method.

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.

Since the porous support according to the present invention includes a nanoweb having a Yellowness index of 40 to 85 as measured according to the ASTM E-313 method, the chemical resistance can be remarkably improved.

In addition, the porous support according to the present invention is very advantageous in application to a fuel cell because it has excellent air permeability and water permeability, and is also excellent in durability, heat resistance and hydrophilicity.

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.

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 studies to produce a porous support having excellent chemical resistance, and as a result, they have found that when a porous support is manufactured using a nano-web having a yellowness index measured according to ASTM E-313, The present invention has been accomplished based on the finding that the above object can be achieved.

More specifically, the porous support according to the present invention comprises nanofibers in which nanofibers are integrated in the form of a nonwoven fabric including a plurality of pores, and the nanofibers have a yellowness index measured according to ASTM E-313 of 40 To 85% by weight.

As the yellowness index of the nano-web satisfies the above range, the residual amount of the amine compound on the porous support is reduced, so that it can have excellent chemical resistance. From such a viewpoint, when the yellowness index is less than 40, complete curing may not be performed and physical properties may be deteriorated. When the yellowness index is more than 85, the nano-web may be carbonized to deteriorate physical properties such as elongation, strength and elastic modulus.

The yellowness index was measured according to ASTM E-313 (Measuring Color Coordinates) method and was measured using a Datacolor 600 model of Datacolor as a CCM (Computer Color Matching) apparatus . The measurement of the yellowness degree using the CCM equipment was performed under conditions including mirror reflection and UV, and the used light source was D65 (relative luminous intensity distribution 300nm-0.03 to 830nm-60.31, daylight having a light temperature of 6504K ) 10 Degree.

In addition, the difference in yellowness index between one surface and the other surface of the nano web may be 10 or less, and preferably 0.16 to 3.36. When the difference in yellowness index between one side of the nano web and the other side of the nano web is more than 10, the difference in physical properties between one side and the other side may occur and the chemical resistance may be deteriorated or the physical properties may be deteriorated.

The nano-web may have an L * value of 70 to 95, an a * value of -10 to 15, and a b * value of 30 to 60 according to a CIE color specification. Where L * denotes brightness. 100 is white and 0 is black. a * means red if positive, green if negative. b * means yellow when positive and blue when negative. When the L * value, the a * value and the b * value according to the above CIE table marking method are out of the above ranges, it is impossible to grasp the chemical resistance and physical properties using the yellow brightness of the polyimide, A porous support may not be usable.

The L * value, a * value and b * value according to the CIE table marking method were measured using a Datacolor 600 model CCM equipment. The L * value, the a * value and the b * value of the CCM instrument were measured by the CIE table colorimetry using mirror reflection and UV. The light source used was D65 (relative spectral distribution 300 nm-0.03 To 830 nm-60.31, and a light temperature near 6504K).

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.

The porous support of the present invention includes a collection of nanofibers in which the nanofibers produced by electrospinning are randomly arranged, that is, nanobubbles. In consideration of the porosity and thickness of the nanofibers, the nanofibers were measured for 50 fiber diameters using a scanning electron microscope (JSM6700F, JEOL) It is preferable to have an average diameter. If the average diameter of the nanofibers is less than 40 nm, the mechanical strength of the porous support may be lowered. If the average diameter of the nanofibers exceeds 5,000 nm, the porosity may be significantly decreased and the thickness may be increased.

The nano-web is made of the nanofiber as described above, and thus can have a porosity of 50% or more. 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. On the other hand, the nano-web preferably has a porosity of 90% or less. If the porosity of the nano-web exceeds 90%, the morphology of the nano-web 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

On the other hand, the nanoweb may have an average thickness of 5 to 50 μm. If the thickness of the nano-web is less than 5 탆, the mechanical strength and dimensional stability of the separator may be significantly deteriorated. On the other hand, when the thickness of the nano-web exceeds 50 탆, resistance loss increases, have. More preferably, the thickness of the nano-web is in the range of 10 to 30 占 퐉.

In addition, in order to exhibit excellent tensile strength after impregnation with an electrolyte, the nano-web has nanoporous fibers having excellent porosity and optimized diameter and thickness, and the polymers constituting the nano- It is preferable to have a weight average molecular weight. If the weight average molecular weight of the polymer constituting the nano-web is less than 30,000 g / mol, porosity and thickness of the nano-web can be easily controlled, but tensile strength after porosity and wet treatment may be lowered. On the other hand, if the weight average molecular weight of the polymer constituting the nano-web exceeds 500,000 g / mol, the heat resistance may be somewhat improved, but the manufacturing process may not proceed smoothly and the porosity may be lowered.

The nano-web may have a weight average molecular weight in the range described above, and may have a heat resistance of 180 ° C or higher, preferably 300 ° C or higher, as the polymer precursor is converted into a polymer under optimal curing conditions. 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.

Furthermore, the nano-web may be insoluble in an organic solvent at a temperature ranging from room temperature to 100 ° C, and may have chemical stability. The organic solvent may be an organic solvent such as NMP, DMF, DMAc, DMSO, THF or the like.

On the other hand, the nano-web included in the porous support of the present invention may have a strain of 10% or less, 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.

In addition, when the nano-web is made of polyimide, 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.

In the present invention, the nano-web may have an air permeability of 50 to 250 lpm, and preferably 100 to 150 lpm. The air permeability can be measured by the ISO 9237 method. When the air permeability is less than 50 lpm, absorption of the electrolyte may become difficult, and when the air permeability exceeds 250 lpm, the electrolyte may not be sufficiently contained.

On the other hand, the nanoweb included in the porous support of the present invention is excellent in hydrophilicity and can reach saturation humidity for 1 second to 5 minutes, preferably 1 second to 3 minutes, 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 ion-exchange polymer may be impregnated into the nano-web to uniformly impregnate the ion-exchange polymer uniformly throughout the pores of the nano-web. Also, when the hydrophilic property of the nano-web 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 nano-web may have an electrolyte absorption rate of 10 to 60 wt%, and preferably 30 to 40 wt%. 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 nano-web may have a moisture regain of 3.0% or more, preferably 3.0 to 5.0%, 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 nano-web may have a wettability of 2 to 15 cm, preferably 2.1 to 15 cm, and more preferably 3 to 15 cm by a wicking test. 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.

Next, the nano-web 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%. The distilled water was charged into a syringe, water droplets having a diameter of 3 mm were dropped on the nanoweb, and the 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.

In the present invention, when the nanofiber is made of a hydrophobic polymer such as polyimide, it has an advantage of excellent heat resistance, chemical resistance, and shape stability. However, since the hydrophilic property is insufficient, It is not possible to impregnate a large amount uniformly over the entire surface of the substrate, and ion conductivity may be lowered due to insufficient formation of the hydrophilic channel. Therefore, in order to satisfy the saturated wetting time, water content, wettability or contact angle by the wicking test, the hydrophobic polymer nanofibers need to be hydrophilized. The hydrophilization treatment can be applied to any conventional method for improving the hydrophilicity of the nano-web, and is not particularly limited in the present invention.

At this time, as an example of the hydrophilic treatment method of the nano-web, the nano-web may include a hydrophilic additive. That is, the nanofiber itself may include the hydrophilic additive, the hydrophilic additive may be impregnated into the pores of the nanoweb, and the hydrophilic additive may be coated on one or both surfaces of the nanoweb Lt; / RTI >

Specifically, when the nanofiber includes the hydrophilic additive, the nanofiber may include 0.1 to 20 parts by weight, preferably 0.5 to 20 parts by weight, more preferably 1 to 20 parts by weight of a hydrophilizing additive per 100 parts by weight of the nanofiber polymer, 2 parts by weight. If the content of the hydrophilic additive is less than 0.1 parts by weight based on 100 parts by weight of the nanofiber polymer, the hydrophilic property may be insufficient and the wettability may be deteriorated to deteriorate the performance of the electrochemical device. If the amount exceeds 20 parts by weight, It is possible to increase the instability of nanofiber jets and cause uneven fiber concentration, which may cause problems when applied to a separator of an electrochemical device.

When the hydrophilic additive is impregnated into the pores of the nano-web or the hydrophilic additive is coated on one surface or both surfaces of the nano-web, the nano-web may be coated with the hydrophilic additive In an amount of 0.1 to 20 parts by weight, preferably 3 to 20 parts by weight, more preferably 5 to 20 parts by weight. If the content of the hydrophilic additive is less than 0.1 parts by weight based on 100 parts by weight of the nanoweb, the hydrophilic property may be insufficient and the wettability may be deteriorated to deteriorate the performance of the electrochemical device. If the amount exceeds 20 parts by weight, It is possible to increase the instability of the fiber jet and cause uneven fiber concentration, which may cause problems in application to the separator of the electrochemical device.

At this time, since the nanofiber includes the hydrophilic additive, the nanofiber has excellent wettability, and when used as a separator for an electrochemical device, the nanofiber has excellent wettability with respect to an electrolyte, thereby improving the efficiency of the cell. In addition, the porous support has excellent durability, heat resistance, and chemical resistance, so that the performance of the electrochemical device can be maintained even under harsh operating conditions.

Next, the hydrophilic additive may be an inorganic or organic hydrophilic additive. The inorganic hydrophilic additive may be subjected to an oxidation and / or reduction reaction, that is, an electrochemical reaction, with an anode or an anode current collector at an operating voltage range of the electrochemical device (for example, 0 to 5 V based on Li / Li ⁺ And is not particularly limited as long as it can withstand the manufacturing process when manufacturing the nanofibers including the nanofibers.

For example, the inorganic hydrophilic additive may be selected from the group consisting of anatase type TiO ₂ anatase, rutile type TiO ₂ rutile, brookite type TiO ₂ brookite, tin dioxide (SnO 2), zirconium dioxide ZrO ₂ ), aluminum oxide (Al ₂ O ₃ ), oxidized single wall carbon nanotube, oxidized multiwall carbon nanotube, oxidized graphite oxide, oxidized graphene, and combinations thereof. preferably TiO may be _two days.

Further, the organic hydrophilic additive may also be oxidized and / or reduced with an anode or an anode current collector in an operating voltage range of the electrochemical device (for example, 0 to 5 V based on Li / Li ^{+ in} the case of a lithium secondary battery) There is no particular limitation so long as it does not cause a reaction, does not impair the conductivity, and can withstand the manufacturing process when manufacturing nanofibers containing the same.

For example, the organic hydrophilic additive may be selected from the group consisting of polyhydroxyethyl methacrylate polyvinyl acetate, polyurethane, polydimethylsiloxane, polyimide, polyamide, polyethylene terephthalate, polymethyl methacrylate, epoxy and combinations thereof Lt; / RTI > group.

The hydrophilic additive may be a nano-hydrophilic additive, and accordingly, the average particle diameter of the hydrophilic additive may be 0.005 to 1 탆, preferably 0.005 to 0.8 탆, more preferably 0.005 to 0.5 탆. If the average particle diameter of the nano-hydrophilic additive is less than 0.005 탆, the hydrophilization effect of the nano-hydrophilic particles may be impaired or the handling may be difficult. If the average particle diameter exceeds 1 탆, the physical tensile strength of the support may be lowered, Can be reduced.

As described above, when the nanofiber is made of polyimide, which is a hydrophobic polymer, the main chain of the polyimide has an amine group, a carboxyl group, a hydroxyl group, a hydroxyl group, And a combination of any of these.

That is, the polyimide may be prepared by preparing polyamic acid (PAA), followed by an imidization reaction in a subsequent curing process. The polyamic acid can be prepared according to a conventional production method. Specifically, the polyamic acid can be prepared by mixing a diamine in a solvent, adding dianhydride thereto, and then polymerizing the diamine. As the dianhydride, a wholly aromatic polyimide using an aromatic dianhydride can be preferably used.

At this time, in order that the main chain of the polyimide contains any one substituent selected from the group consisting of an amine group, a carboxyl group, a hydroxyl group, and a combination thereof, the polyimide or the polyamic acid is prepared, Alternatively, the hydrophilic substituent may be substituted for the main chain of the polyamic acid, or the polyimide may be prepared by using the diamine and / or the dianhydride containing the hydrophilic substituent, Can be prepared by polymerizing a comonomer containing a hydroxyl group together. The comonomer containing a hydroxy group may be selected from the group consisting of dianiline including a hydroxy group, diphenylurea including a hydroxy group, diamine including a hydroxy group, and combinations thereof.

When the main chain of the polyimide includes the hydrophilic substituent, the hydrophilic substituent may be 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 entire polyimide . 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 of the hydrophilic substituent is more than 0.1 mol%, generation of side reaction and physical strength may be problematic.

As described above, when the nanofiber is made of a hydrophobic polymer such as polyimide or the like, in order to satisfy the saturated wetting time, water content, wettability by a wicking test, or contact angle, the surface of one or both surfaces of the nano- . When the nano-web is subjected to plasma treatment, a functional group having any hydrophilic property selected from the group consisting of a carboxyl group, a hydroxyl group, an amine group, and a combination thereof may be substituted on the surface of the nano-web.

Specifically, the plasma treatment may be performed using a gas capable of imparting a hydrophilic group to one or both sides of the nanoweb by using a low temperature plasma or a radio frequency (RF) plasma. The gas capable of imparting the hydrophilic group may be any one selected from the group consisting of ammonia gas, argon gas, oxygen gas, and combinations thereof. The flow rate of the gas capable of imparting the hydrophilic group may be 10-200 sccm , The power of the plasma may be 50 to 200 W, and the plasma treatment time may be 10 seconds to 5 minutes.

As described above, when the nanofiber is made of a hydrophobic polymer such as polyimide or the like, in order to satisfy the saturated wetting time, water content, wettability or contact angle by wicking test, the surface of one or both surfaces of the nano- Can be deposited. The inorganic material may be selected from the group consisting of anatase type titanium dioxide (TiO ₂ anatase), rutile type titanium dioxide (TiO ₂ rutile), brookite type titanium dioxide (TiO ₂ brookite), tin dioxide (SnO), zirconium dioxide (ZrO ₂ ) Al ₂ O ₃ , oxidized single wall carbon nanotubes, oxidized multiwall carbon nanotubes, oxidized graphite oxide, oxidized graphene, and combinations thereof.

The porous support is excellent in gas permeability and water permeability, and is excellent in heat resistance and chemical resistance, and is required to have heat resistance and chemical resistance, and is used as a filter medium for gas or liquid filters, a filter medium for dustproof masks, , Materials for filters such as ventilation for printers, materials for high-grade clothes such as moisture-proof tarpaulins, electro-chemical materials such as polymer electrolyte for fuel cell, secondary battery, separator of electrolytic device or capacitor, wound dressing, artificial blood vessel And can be used as a medical material such as a support, a bandage, a mask for cosmetics, and the like.

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

The method for preparing a porous support according to the present invention comprises the steps of: spinning a spinning solution to produce a nanobubbelite precursor in which nanofibers are integrated into a nonwoven fabric including a plurality of pores; And curing the nano-web precursor to produce a nano-web, wherein the nano-web has a yellowness index of 40 to 85 as measured according to the ASTM E-313 method.

First, the step of spinning a spinning solution to produce a nanofibrous precursor integrated with nanofibers in the form of a nonwoven fabric including a plurality of pores may be performed by a method well known in the art, and is not particularly limited.

In addition, in the manufacturing method of the present invention, the spinning solution includes monomers for forming the nanofibers, and the monomers for forming the nanofibers are preferably hydrocarbon-based polymers, same.

At this time, it is preferable that the monomers for forming the nanofibers are included in an amount of 5 to 20% by weight based on the total weight of the spinning 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.

Next, in the production method of the present invention, the above-mentioned spinning is not particularly limited, but may be performed by electrospinning, electro-blown spinning, centrifugal spinning or melt blowing And preferably electrospinning can be used.

Next, a step of curing the nanobubbles precursor to prepare a nanobeb is performed.

The step of curing the nano-web precursor to prepare a nano-web may include, for example, a method of converting a nano-fiber precursor prepared through electrospinning into a polyimide by imidization during a curing process . In particular, in order to satisfy the yellowness index of the present invention, the curing temperature should be appropriately controlled during the curing process. For example, the curing temperature may be 1 to 50 minutes at 80 to 650 ° C, It is preferable that the curing process is performed for 30 minutes. When the curing temperature is lower than 80 ° C, the conversion rate is lowered. As a result, the heat resistance and chemical resistance of the nanoweb may be deteriorated. When the curing temperature is higher than 650 ° C, There is a possibility that the physical properties of the resin are deteriorated.

When the curing time is within the above range, a nano web having a yellowness index of 40 to 85 as measured according to the ASTM E-313 method can be prepared.

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, 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.

Example  One

100 parts by weight of PMDA and ODA monomer were dissolved in 650 g of 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 then fed through a metering gear pump to a spinning chamber having 20 nozzles and a high voltage of 46 kV to spin the nanoweb precursor. At this time, the supply amount of the solution was 1.5 ml / min, and the ratio of the distance between the tip of the nozzle to the center of the nozzle was 1.02.

Next, the nanobubbles were thermally cured for 10 minutes in a continuous curing furnace maintained at a temperature of 420 ° C. while transferring the nanobubbles precursor by a roll-to-roll method to prepare a porous support.

Example  2

A porous support was prepared in the same manner as in Example 1 except that 50 parts by weight of PMDA, 10 parts by weight of ODA and 40 parts by weight of PDA monomer were used.

Example  3

A porous support was prepared in the same manner as in Example 1, except that 45 parts by weight of PMDA, 5 parts by weight of BPDA, 10 parts by weight of ODA and 40 parts by weight of PDA monomer were used.

Example  4

A porous support was prepared in the same manner as in Example 1 except that 50 parts by weight of PMDA, 10 parts by weight of ODA and 40 parts by weight of PDA monomer were used.

Comparative Example  One

50 parts by weight of PMDA, 10 parts by weight of ODA and 40 parts by weight of PDA monomer were dissolved in 650 g of 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 then fed through a metering gear pump to a spinning chamber having 20 nozzles and a high voltage of 46 kV to spin the nanoweb precursor. At this time, the supply amount of the solution was 1.5 ml / min, and the ratio of the distance between the tip of the nozzle to the center of the nozzle was 1.02.

Next, the nanobubbles were thermally cured for 50 seconds in a continuous curing furnace maintained at a temperature of 420 ° C. while transferring the nanobubbles precursor by a roll-to-roll method to prepare a porous support.

Comparative Example  2

A porous support was prepared in the same manner as in Comparative Example 1, except that it was thermally cured for 60 minutes in a continuous curing furnace maintained at a temperature of 420 占 폚.

Test Example  1: Chemical resistance measurement

The L * value, a * value and b * value of the surface and back surface of the porous support prepared in Examples 1 to 4 and Comparative Examples 1 and 2 were measured by the yellowness index and the CIE table marking method.

The L * value, a * value and b * value according to the yellowness index and the CIE table coloring method were measured according to the ASTM E313 method and measured using a Datacolor 600 model of Datacolor as a CCM (Computer Color Matching) . The measurement of the yellowness degree using the CCM equipment was performed under conditions including mirror reflection and UV, and the used light source was D65 (relative luminous intensity distribution 300nm-0.03 to 830nm-60.31, daylight having a light temperature of 6504K ) 10 Degree.

division Surface / back Yellowness index CIE L * a * b * L * a * b * Example 1 surface 77.87 82.99 2.93 46.02 If 81.23 82.79 3.19 48.68 Example 2 surface 57.50 87.93 -4.95 36.85 If 57.34 88.28 -5.25 37.03 Example 3 surface 50.53 90.51 -6.82 33.49 If 49.52 90.53 -6.79 32.74 Example 4 surface 67.07 79.24 3.65 35.35 If 68.15 79.12 3.59 36.11 Comparative Example 1 surface 36.79 87.62 -5.31 28.72 If 38.13 87.58 -5.38 29.59 Comparative Example 2 surface 90.45 50.35 -10.5 60.31 If 93.27 52.13 -13.78 63.12

Test Example  2: Chemical resistance measurement

The chemical resistance of the porous support prepared in Examples 1 to 4 and Comparative Examples 1 and 2 was tested and is shown in Table 2 below.

The chemical resistance test was carried out according to the following procedure. The organic solvents used were polar solvents NMP, DMF, DMAc and DMSO, and 2 mol of sulfuric acid was used as the acid. In this case, the weight ratio of each organic solvent to the nano-web was 15 parts by weight. After immersing at 80 ° C for 24 hours, the amount of polymer dissolved was calculated by the following formula (3).

&Quot; (3) "

Chemical resistance (%) = (O-D) / D x 100

(O: weight of sample before chemical resistance test, D: weight of dried sample after test)

division Chemical resistance NMP DMF DMAc DMSO Sulfuric acid Example 1 99.3 98.1 98.4 98.7 99.9 Example 2 99.9 99.9 99.9 99.9 99.9 Example 3 99.9 99.9 99.9 99.8 99.9 Example 4 98.7 97.9 98.2 98.6 99.8 Comparative Example 1 0.3 0.1 0.1 0.2 85.3 Comparative Example 2 75.2 65 63 70 90.6

Referring to Table 2, it can be seen that Examples 1 to 4, in which the yellowness index of the porous support satisfies 40 to 85, are excellent in chemical resistance. On the other hand, in Comparative Examples 1 and 2 in which the yellowness index of the porous support is out of the above range, the chemical resistance is remarkably lowered.

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 (14)

Wherein the nanofibers comprise a nanoweb integrated into a nonwoven fabric comprising a plurality of pores,
Wherein the nano-web has a yellowness index of 40 to 85 as measured according to the ASTM E-313 method. The method according to claim 1,
Wherein the difference in yellowness index of one side of the nano web and the other side of the nano web is 10 or less. The method according to claim 1,
Wherein the nano-web has an L * value of 70 to 95 according to the CIE color specification, an a * value of -10 to 15, and a b * value of 30 to 60. The method according to claim 1,
Wherein the saturation hindrance time of the nano-web is from 1 second to 5 minutes. The method according to claim 1,
Wherein the nano-web has a moisture content of 3.0% or more. The method according to claim 1,
The nano-web is a porous support having a wettability of 2 cm to 15 cm by wicking test. The method according to claim 1,
Wherein the nano-web has a contact angle of 90 DEG or less. 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 any one substituent selected from the group consisting of an amine group, a carboxyl group, a hydroxyl group, and combinations thereof. Spinning a spinning solution to produce a nanobeb precursor integrated with nanofibers in the form of a nonwoven fabric including a plurality of pores; And
And curing the nano-web precursor to produce a nano-web,
Wherein the nano-web has a yellowness index of 40 to 85 as measured according to the ASTM E-313 method. 11. The method of claim 10,
Wherein the curing is carried out at 80 to < RTI ID = 0.0 > 650 C < / RTI > for 1 to 50 minutes. 11. The method of claim 10,
Further comprising the step of depositing an inorganic material on one or both surfaces of the nano web. 13. The method of claim 12,
Wherein the step of depositing the inorganic material is carried out by a sputtering method. A porous support according to claim 1; And
And an ion exchange polymer that fills the pores of the porous support.