POROUS SUPPORT HAVING EXCELLENT FILLING CHARACTERISTICS OF ION CONDUCTOR, METHOD FOR MANUFACTURING THE SAME, AND REINFORCED MEMBRANE INCLUDING THE SAME

Abstract

Disclosed is a porous support including fine porous structures formed between nanofibers, wherein the fine porous structures have a porosity of 50% to 90%, a pore size of 0.01 μm to 10 μm and an air permeability of 0.01 to 7 sec/100 cc.Math.air, and the porous support has a thickness of 5 μm to 50 μm, a method of manufacturing the same and a reinforced membrane including the same.

Claims

1. A porous support comprising fine porous structures formed between nanofibers, wherein the fine porous structures have a porosity of 50% to 90%, a pore size of 0.01 μm to 10 μm and an air permeability of 0.01 to 7 sec/100cc.Math.air, and the porous support has a thickness of 5 μm to 50 μm.

2. The porous support according to claim 1, wherein the air permeability of the porous support is increased by 5 sec/100cc.Math.air or more after impregnating with an ion conductor solution having a high viscosity of about 10,000 cps or more.

3. The porous support according to claim 1, wherein the porosity of the porous support is less than 10% after impregnating with an ion conductor solution having a high viscosity of about 10,000 cps or more.

4. The porous support according to claim 1, wherein the nanofibers comprise 0.1 to 20 parts by weight of a hydrophilic additive, with respect to 100 parts by weight of the nanofiber polymer.

5. The porous support according to claim 1, wherein the nanofibers are polyimide nanofibers.

6. The porous support according to claim 5, wherein the main chain of polyimide comprises any one substituent group selected from the group consisting of an amine group, a carboxylic group, a hydroxyl group and a combination thereof.

7. The porous support according to claim 6, wherein the polyimide is prepared by polymerizing diamine, dianhydride and a comonomer containing a hydroxyl group to prepare polyamic acid and then imidizing the polyamic acid.

8. The porous support according to claim 7, wherein the comonomer containing a hydroxyl group is any one selected from the group consisting of dianiline containing a hydroxyl group, diphenyl urea containing a hydroxyl group, diamine containing a hydroxyl group and a combination thereof.

9. A method of manufacturing a porous support comprising: preparing an electrospinning solution; and electrospinning the prepared electrospinning solution to form, between nanofibers, fine porous structures having a porosity of 50% to 90%, a pore size of 0.01 μm to 10 μm, and an air permeability of 0.01 to 7 sec/100cc.Math.air, wherein the produced porous support has a thickness of 5 μm to 50 μm.

10. The method according to claim 9, wherein the preparing the electrospinning solution comprises adding diamine and dianhydride to a solvent.

11. The method according to claim 9, wherein the forming the fine porous structures comprises: producing polyamic acid nanofibers including fine porous structures; and imidizing the polyamic acid nanofibers to produce polyimide nanofibers.

12. A reinforced membrane comprising: the porous support according to claim 1; and an ion exchange polymer filling pores of the porous support.

Description

EXAMPLE 1-1

[0067] 100 parts by weight of pyromellitic dianhydride (PMDA), oxydianiline (ODA) and phenylenediamine (PDA) monomers, and 5 parts by weight of nano TiO.sub.2 anatase as a hydrophilic additive were dissolved in a dimethylformamide solution to prepare a 5 L spinning solution having a solid content of 12.5% by weight and a viscosity of 620 poise. The prepared spinning solution was transferred to a solution tank and then spun to produce polyamic acid nanofibers, and the polyamic acid nanofibers were transferred by a roll-to-roll method and heat-cured in a continuous curing furnace maintained at a temperature of 420° C. for 10 minutes to produce a porous support including the polyimide nanofibers. At this time, properties of the produced porous support are as follows.

EXAMPLES 1-2 TO 1-4 AND COMPARATIVE EXAMPLE 1

[0068] Porous supports having properties shown in Table 1 were produced in the same manner as in Example 1.

EXAMPLE 2-1

[0069] PMDA, ODA and PDA monomers were dissolved in a dimethylformamide solution to prepare a 5 L spinning solution having a solid content of 12.5% by weight and a viscosity of 620 poise. The prepared spinning solution was transferred to a solution tank, fed by a volumetric gear pump to a spinning chamber having 26 nozzles and to which a high voltage of 49 kV was applied and then spun to produce a polyamic acid nanoweb. At this time, the amount of the supplied solution was 1.0 ml/min.

[0070] Subsequently, the polyamic acid nanoweb was heat-cured in a continuous curing furnace maintained at a temperature of 420° C. for 10 minutes to produce a polyimide nanoweb.

[0071] Meanwhile, nano TiO.sub.2 anatase as a hydrophilic additive was added to dimethylformamide, followed by stirring to prepare a hydrophilic additive solution. The produced nanoweb was dipped in the prepared hydrophilic additive solution at room temperature (20° C.) for 10 minutes and then dried in a hot air oven at 80° C. for 3 hours or longer. The dipping and drying processes were repeated 2 to 5 times to impregnate the nanoweb with the hydrophilic additive.

[0072] At this time, properties of the produced porous support are the same as in Example 1-1.

EXAMPLE 2-2

[0073] PMDA, ODA and PDA monomers were dissolved in a dimethylformamide solution to prepare a 5 L spinning solution having a solid content of 12.5% by weight and a viscosity of 620 poise. The prepared spinning solution was transferred to a solution tank, fed by a volumetric gear pump to a spinning chamber having 26 nozzles and to which a high voltage of 49 kV was applied and then spun to produce a polyamic acid nanoweb. At this time, the amount of the supplied solution was 1.0 ml/min.

[0074] Subsequently, the polyamic acid nanoweb was heat-cured in a continuous curing furnace maintained at a temperature of 420° C. for 10 minutes to produce a polyimide nanoweb. Both surfaces of the produced polyimide nanoweb were treated with plasma at 20 W for 5 minutes using low-temperature plasma by feeding oxygen gas at a flow rate of 150 sccm to a plasma treatment chamber.

[0075] At this time, properties of the produced porous support are the same as in Example 1-1.

EXAMPLE 2-3

[0076] PMDA, ODA and PDA monomers were dissolved in a dimethylformamide solution to prepare a 5 L spinning solution having a solid content of 12.5% by weight and a viscosity of 620 poise. The prepared spinning solution was transferred to a solution tank, fed by a volumetric gear pump to a spinning chamber having 26 nozzles and to which a high voltage of 49 kV was applied and then spun to produce a polyamic acid nanoweb. At this time, the amount of the supplied solution was 1.0 ml/min.

[0077] Subsequently, the polyamic acid nanoweb was heat-cured in a continuous curing furnace maintained at a temperature of 420° C. for 10 minutes to produce a polyimide nanoweb. Both surfaces of the produced polyimide nanoweb were sputtered using an RF sputter at a constant deposition power of 150 W and at a constant sample temperature of 200° C. for 10 minutes to form a TiO.sub.2 inorganic layer.

[0078] At this time, properties of the produced porous support are the same as in Example 1-1.

EXAMPLE 2-4

[0079] PMDA, ODA and PDA, and a diphenyl urea monomer containing a hydroxyl group were dissolved in a weight ratio of 50:45:5 in a dimethylformamide solution to prepare a 5 L spinning solution having a solid content of 12.5% by weight and a viscosity of 620 poise.

[0080] The prepared spinning solution was transferred to a solution tank, fed by a volumetric gear pump to a spinning chamber having 26 nozzles and to which a high voltage of 49 kV was applied and then spun to produce a polyamic acid nanoweb. At this time, the amount of the supplied solution was 1.0 ml/min.

[0081] Subsequently, the polyamic acid nanoweb was heat-cured in a continuous curing furnace maintained at a temperature of 420° C. for 10 minutes to produce a polyimide nanoweb.

[0082] At this time, properties of the produced porous support are the same as in Example 1-1.

TABLE-US-00001 TABLE 1 Items Exam- Exam- Exam- Exam- Compar- ple ple ple ple ative 1-1 1-2 1-3 1-4 Example 1 Thickness of porous 11.97 9.5 30.15 22.33 13.75 support [μm] Mean air 0.31607 1.4187 3.054 6.7128 14.443 permeability [s] Mean pore size [μm] 4.3864 1.6619 1.9779 0.4891 0.3977 Maximum active 5.2197 1.8566 2.2852 1.0065 1.02 pore size [μm]

TEST EXAMPLE 1

[0083] The porous supports according to Examples and Comparative Example 1 were each bar-coated with low-viscosity, medium-viscosity and high-viscosity solutions. At this time, for the low-viscosity solution, the medium-viscosity solution and the high-viscosity solution, bar-coating was performed at a rate of 20-30 mm/s, 20-30 mm/s, and 20-30 mm/s, respectively.

[0084] Next, the air permeability and porosity of the porous support were measured. Air permeability was time (seconds) required for 100 cc of air to pass through a 1 square inch test specimen at a hydraulic pressure of 4.88 inches, which was measured using an air permeation tester (ASTM 0726-58). That is, 1 square inch specimens were produced from the porous supports according to Examples and Comparative Example 1 and then disposed between clamp plates. Then, a cylinder was dropped and a time required for 100 cc of air to pass through the cylinder at a hydraulic pressure of 4.88 inches was measured and results are shown in the following Table 2.

[0085] The assessment method is as follows. A case in which air permeability after coating is increased by 5 sec/100cc.Math.air or more and porosity in the fine porous structures is less than 10% is represented by ‘⊚’, a case in which air permeability after coating is increased by 5 sec/100cc.Math.air or more, or porosity in the fine porous structures is less than 10% is represented by ‘◯’, and a case in which air permeability after coating is increased by less than 5 sec/100cc.Math.air or porosity in the fine porous structures is 10% or more is represented by ‘Δ’, and a case in which there is no variation in air permeability after impregnation is represented by ‘X’.

[0086] In addition, air permeability of the porous support impregnated with the high-viscosity solution was measured and results are shown in the following Table 2.

TABLE-US-00002 TABLE 2 Low-viscosity High-viscosity Variation in air 300 cps, Medium-viscosity 10000 cps, permeability after Nafion dispersion 1000 cps, SPAES high-viscosity (solid content Nafion dispersion (solid content solution 20%, room (solid content 20%, room impregnation Items temperature) 20%, −15° C.) temperature) (sec/100 cc .Math. air) Example 1-1 ⊚ ⊚ ⊚ +4054.6 Example 1-2 ⊚ ⊚ ⊚ +1201.4 Example 1-3 ⊚ ⊚ ⊚ +392.5 Example 1-4 ⊚ ⊚ ⊚ +39.7 Comparative ⊚ ◯ Δ +4.7 Example 1 Example 2-1 ⊚ ⊚ ⊚ +2917.5 Example 2-2 ⊚ ⊚ ⊚ +6011.2 Example 2-3 ⊚ ⊚ ⊚ +699.3 Example 2-4 ⊚ ⊚ ⊚ +178.0

[0087] As can be seen from Table 2, in the case of the porous support according to Example having air permeability satisfying the range defined in the present invention, air permeability is excellent even after coating with low-viscosity, medium-viscosity and high-viscosity solutions and coating is easily conducted. On the other hand, in the case of the porous support according to Comparative Example 1 having air permeability not satisfying the range defined in the present invention, coating of a high-viscosity solution is not easily conducted due to high porosity in the high-viscosity solution.

[0088] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

INDUSTRIAL APPLICABILITY

[0089] The present invention relates to a porous support, a method of manufacturing the same and a reinforced membrane including the same. The porous support includes fine porous structures having low air permeability formed between nanofibers, thereby providing easy coating and/or impregnation of low-viscosity and medium-viscosity solutions as well as high-viscosity solutions, thus increasing the content of electrolytes in the porous support and offering excellent air permeability so that mobility of ions can be improved. As a result, efficiency of the reinforced membrane produced using the porous support can be remarkably improved.

[0090] Owing to wide surface area and excellent porosity, the porous support is useful for a variety of applications such as filters for water purification, filters for air purification, composite materials, membranes for cells and the like, in particular, for reinforced composite membranes for fuel cells for cars.