KR101491994B1 - Porous support, method for manufacturing the same and membrane for gas or liquid filter comprising the same - Google Patents

Abstract

The present invention relates to a porous support, a method for producing the same, and a membrane for a gas or liquid filter comprising the porous support, wherein the porous support is bonded in the form of a nonwoven fabric including a plurality of pores, and the pores are elliptical.
The porous membrane can be used as a membrane for a gas or liquid filter which is excellent in air permeability and water permeability, is excellent in heat resistance and chemical resistance, and is required to have heat resistance and chemical resistance.

Description

TECHNICAL FIELD [0001] The present invention relates to a porous support, a method for producing the porous support, and a membrane for a gas or liquid filter including the porous support,

The present invention relates to a porous support, a method for producing the same, and a membrane for a gas or liquid filter comprising the porous support. More particularly, the present invention relates to a porous support having excellent heat resistance and chemical resistance, To a membrane for a gas or liquid filter comprising the porous support, a method for producing the same, and a membrane for a gas or liquid filter comprising the porous support.

BACKGROUND ART [0002] Membrane technology has been widely used in the field of liquid processing such as removal of contaminants in a liquid or separation, concentration, and recovery of useful substances as a recent membrane manufacturing technology and application technology are developed remarkably.

Membrane technology is replacing existing technologies due to constant performance and stability due to membrane pore size, convenience due to automation, and simple system.

Conventionally, membranes used in liquid filters include porous membranes and calendered nonwovens.

The porous membrane is a membrane that forms a membrane by using a polymer material such as PTFE, nylon, or polysulfone, and then forms pores by a chemical or physical method. Since the pore structure at this time is a closed pore structure having a two-dimensional shape, the filter efficiency is low.

In the past, when a hydrophobic polymer such as PTFE is used, since the pore structure has a closed pore structure having a two-dimensional shape, since the liquid does not pass therethrough, it is used as a filter requiring pressure, , And low volume is pointed out as a problem.

Furthermore, the thickness of the porous membrane is thicker because the thickness of the porous material is 100 μm depending on the material. Therefore, there is a problem that it is difficult to bend the porous membrane filter material and to introduce a large amount of arsenic into the filter.

On the other hand, the calendered nonwoven fabric is made of a polymer material such as polypropylene, which is formed by melt-blown spinning. However, since the size of the nonwoven fabric is in the order of micrometers, it has no micropores and fibers are not uniformly distributed The pores are uneven, and the pollutants are concentrated through the large pores and the filter efficiency is low.

Also, the calendered nonwoven fabric has an average pore size of 5 to 20 탆, and excessive calendering must be performed in order to reduce the average pore size of the filter to 3 탆 or less. However, excessive calendering prevents porosity by blocking pores. Therefore, if a calendered nonwoven fabric is used as a liquid treatment filter, the filter pressure is high and the pores are blocked quickly, which causes a problem in filter life.

Therefore, even if a liquid processing module is manufactured using existing membrane technology, there is a problem that fluid flow is reduced due to membrane clogging and operation pressure is increased.

This clogging phenomenon is particularly serious in high concentration fluids, and it is impossible to apply the membrane technology to high concentration and high turbidity fluids, and the pores are gradually widened, resulting in poor durability.

Accordingly, it is urgently required to develop a membrane having a high filtration efficiency and a high filtration efficiency depending on the pore size as a thin membrane having a micropore structure so that it can be used for liquid treatment.

Meanwhile, Korean Patent Laid-Open Publication No. 2008-60263 discloses a nonwoven fabric comprising at least one nano fiber layer of polymer nanofibers having an average fiber diameter of less than about 1 탆, an average flow pore size of about 0.5 탆 to about 5.0 탆, The solidity is from about 15 vol% to about 90 vol% and a flow rate of water through the medium at differential pressures of 10 psi (69 kPa) is greater than about 0.055 L / min / cm ² .

The manufacturing method of the filtration medium proposed in the above-mentioned Patent Publication No. 2008-60263 includes a radiation beam including at least one radiation beam including a radiation nozzle, a blowing gas injection nozzle and a collector, Blown together with a blowing gas discharged from a gas injection nozzle while compressing and discharging a polymer solution from a spinning nozzle to form a fibrous web of nanofibers using a fine fiber spinning apparatus in which a high voltage electric field is maintained, And is collected on the moving collecting device by a single pass under the radiation beam.

In addition, in JP-A-2008-60263, there is illustrated an example of forming a web by spinning nanofibers using a solution containing 24% by weight of nylon in formic acid as a polymer solution by an electroblow spinning or an electric blowing method .

However, the method of forming the fibrous web of nanofibers in the above-mentioned Patent Publication No. 2008-60263 can not be said to be a manufacturing technique using a multi-hole spinning pack. Further, in order to increase the productivity, an air-spraying electrospinning device using a multi-hole spinning pack having a plurality of spinning nozzles in a plurality of rows and columns and air- , The spinning solution containing 24% by weight of the polymer has a viscosity increased to solidify on the surface of the solution, making it difficult to spin for a long time, and the fiber diameter is increased, There is no problem.

Moreover, ultrafine fiber webs obtained by electrospinning have a problem in that when the pretreatment process for appropriately adjusting the amounts of the solvent and moisture remaining on the web surface is not performed before calendering, the strength of the web is weakened Or if the volatilization of the solvent is made too slow, the phenomenon of melting of the web may occur.

Korean Patent Publication No. 2008-0060263 (published on July 1, 2008)

It is an object of the present invention to provide a porous support which can be used as a membrane for a gas or liquid filter which is excellent in air permeability and water permeability, is excellent in heat resistance and chemical resistance, and is required to have heat resistance and chemical resistance.

Another object of the present invention is to provide a method for producing the porous support.

It is still another object of the present invention to provide a filter membrane comprising the porous support.

According to one embodiment of the present invention, there is provided a porous support in which nanofibers having different average diameters are bonded in the form of a nonwoven fabric including a plurality of pores.

The porous support may include first nanofibers having an average diameter of 1 탆 or more and second nanofibers having an average diameter of less than 1 탆.

The ratio of the average diameter of the first nanofiber and the second nanofiber may be 1.2: 1 to 10: 1.

The porous support may include 20 to 40% by number of the first nanofibers and 60 to 80% by number of the second nanofibers with respect to the whole porous support.

The nanofiber may be a polyimide nanofiber.

The nanofibers on the surface of the porous support may be thermally fused together.

According to another embodiment of the present invention, a nanofiber precursor is formed by discharging a nanofibre precursor solution through the nozzle while an electric field is applied between a nozzle and a collector spaced from each other, and the nanofiber precursor is injected into the collector To produce precursor nanofibers of the porous support, and curing the precursor nanofibers of the porous support. The ratio of the distance between the tip of the nozzle to the center of the nozzle is 1.01 to 1.1.

The porous support may be formed by combining nanofibers having different average diameters into a nonwoven fabric including a plurality of pores.

The porous support may include first nanofibers having an average diameter of 1 탆 or more and second nanofibers having an average diameter of less than 1 탆.

The ratio of the average diameter of the first nanofiber and the second nanofiber may be 1.2: 1 to 10: 1.

The porous support may include 20 to 40% by number of the first nanofibers and 60 to 80% by number of the second nanofibers with respect to the whole porous support.

The nanofiber may be a polyimide nanofiber.

The curing process may be carried out at 80 to 650 ° C.

During the curing process, the nanofibers on the surface of the porous support may be thermally fused together.

According to another embodiment of the present invention, there is provided a membrane for a filter, wherein the polyimide nanofibers include a porous support bonded in the form of a nonwoven fabric including a plurality of pores.

The porous support may comprise nanofibers having different average diameters.

The porous support may include first nanofibers having an average diameter of 1 탆 or more and second nanofibers having an average diameter of less than 1 탆.

The ratio of the average diameter of the first nanofiber and the second nanofiber may be 1.2: 1 to 10: 1.

The porous support may include 20 to 40% by number of the first nanofibers and 60 to 80% by number of the second nanofibers with respect to the whole porous support.

The nanofibers on the surface of the porous support may be thermally fused together.

Other details of the embodiments of the present invention are included in the following detailed description.

The porous membrane according to the present invention can be used as a membrane for a gas or liquid filter which is required to have heat resistance and chemical resistance because it has excellent air permeability and water permeability as well as excellent heat resistance and chemical resistance.

1 is a schematic view of a nozzle-type electrospinning device.
2 is a scanning electron microscope (SEM) photograph of the porous support prepared in Example 1. Fig.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

The term " nano, " as used herein, refers to nanoscale and includes a size of 1 μm or less.

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.

The porous support according to an embodiment of the present invention is bonded to nanofibers having different average diameters in the form of a nonwoven fabric including a plurality of pores.

Since the porous support includes nanofibers having different average diameters, the air permeability and the passage capacity are improved, so that an excellent filter effect can be obtained when the porous support is used as a filter membrane.

The nanofibers having different average diameters may have two or more distributions based on an average diameter of 1 mu m. For example, the porous support may include first nanofibers having an average diameter of 1 탆 or more and second nanofibers having an average diameter of less than 1 탆. Preferably, the first nanofibers may have an average diameter of 0.1 to 0.9 mu m, and the second nanofibers may have an average diameter of 1.5 to 3 mu m. If the nanofibers having different average diameters have two or more distributions with an average diameter of 1 mu m, the air permeability and the passage capacity can be further improved.

The average diameter of the nanofibers having a diameter of 1 占 퐉 or more is calculated and the average diameter of the first nanofibers is calculated. The average diameter of the nanofibers having a diameter of less than 1 mu m is calculated to be the average diameter of the second nanofibers. The average diameter of the first nanofibers and the second nanofibers is preferably an average diameter of all of the nanofibers present in one entire cross-section of the porous support, but a part of one end surface of the porous support, The average diameter of the nanofibers present in an area of 1 cm ² may be calculated.

In this case, the ratio of the average diameter of the first nanofiber and the second nanofiber may be 1.2: 1 to 10: 1, and preferably 2: 1 to 6: 1. If the ratio of the average diameters of the first nanofibers is less than 1.2, the pore size becomes large and sufficient filter efficiency can not be obtained. When the ratio is more than 10, the pore size becomes small, and sufficient air permeability and passage capacity can not be obtained.

The porous support may include 20 to 40% by number of the first nanofiber and 60 to 80% by number of the second nanofiber with respect to the whole porous support. Preferably, the first nanofiber is 30 To 35% by number of the first nanofibers and 65% to 70% by number of the second nanofibers. When the content of the first nanofiber is less than 20% or the content of the second nanofiber is more than 80% by number, the filter efficiency is good, but the life of the filter may be shortened and the filter differential pressure may be increased. If the content of the first nanofibers exceeds 40% by number or the content of the second nanofibers is less than 60% by number, the filter efficiency may be lowered.

The nanofiber may be a hydrocarbon-based polymer nanofiber that exhibits excellent chemical resistance and is hydrophobic and has no fear of morphological change due to moisture in a high-humidity environment. Specifically, the hydrocarbon-based polymer may include nylon, polyimide (PI), polybenzoxazole (PBO), polybenzimidazole (PBI), polyamideimide (PAI), polyethylene terephthalate polyethyleneterephtalate, polyethylene (PE), polypropylene (PP), copolymers thereof, and mixtures thereof. Among them, heat resistance, chemical resistance, and shape stability A polyimide having a higher molecular weight can be preferably used.

In addition, the nanofibers on the surface of the porous support may be thermally fused together. The thermal fusion means that the surfaces of the nanofibers melt by thermal contact and then adhere to other nanofibers when solidified again. As the nanofibers on the surface of the porous support are thermally fused to each other, the bonding strength of the nanofibers is improved, and the porous support can further improve heat resistance and chemical resistance.

The porous support includes a web of nanofibers, i.e., a collection of nanofibers in which the nanofibers are arranged in a certain direction or randomly. In consideration of the porosity and thickness of the nanofiber web, the nanofiber was measured for 50 fiber diameters using a scanning electron microscope (JSM6700F, JEOL), and the fiber diameter was measured to be 40 to 5000 nm 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 5000 nm, the porosity may be significantly decreased and the thickness may be increased.

The porous support 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, the efficiency of application to the filter membrane can be improved. On the other hand, the porous support preferably has a porosity of 90% or less. If the porosity of the porous support exceeds 90%, the morphology of the porous support may be deteriorated and the post-treatment 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 (2). 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.

&Quot; (2) "

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

In addition, the porous support may have an average thickness of 5 to 50 탆. If the thickness of the porous support is less than 5 탆, mechanical strength and dimensional stability may be significantly deteriorated. On the other hand, if the thickness exceeds 50 탆, resistance loss may increase, and weight reduction and integration may be deteriorated. The thickness of the porous support is more preferably in the range of 10 to 30 占 퐉.

In order to exhibit excellent tensile strength even after wetting, the polymer constituting the porous support has a weight average of 30,000 to 500,000 g / mol. It is preferable to have a molecular weight. If the weight average molecular weight of the polymer constituting the porous support is less than 30,000 g / mol, porosity and thickness of the porous support can be easily controlled, but tensile strength after porosity and wet treatment may be lowered. On the other hand, when the weight average molecular weight of the polymer constituting the porous support exceeds 500,000 g / mol, the heat resistance may be improved somewhat, but the production process may not proceed smoothly and the porosity may be lowered.

The porous support may have a weight average molecular weight in the range as 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 porous support is less than 180 ° C, the heat resistance of the porous support may be lowered at a high temperature due to its low heat resistance, and thus the performance of the filter manufactured using the porous support may deteriorate. In addition, when the heat resistance of the porous support is lowered, the shape is deformed due to abnormal heat generation, thereby deteriorating the performance, and in the worst case, it may rupture and explode.

The porous support is insoluble in an organic solvent at a temperature of from room temperature to 100 캜 and may have chemical stability. The organic solvent may be an organic solvent such as NMP, DMF, DMAc, DMSO, THF or the like.

A method of manufacturing a porous support according to another embodiment of the present invention includes the steps of discharging a nanofibre precursor solution through the nozzle while applying an electric field between a nozzle and a collector spaced from each other to form a nanofiber precursor, Concentrating the fiber precursor on the collector to produce precursor nanofibers of the porous support; and curing the precursor nanofibers of the porous support. The ratio of the distance between the tip of the nozzle to the center of the nozzle is 1.01 to 1.1.

In step 1, the precursor nanofibers of the porous support are prepared by electrospinning the nanofiber precursor solution.

The nanofiber precursor solution is a solution containing a precursor for forming the nanofiber (hereinafter referred to as a nanofiber precursor). The nanofiber precursor exhibits excellent chemical resistance and is hydrophobic. Therefore, in a high humidity environment, A hydrocarbon-based polymer free from the risk of deformation due to the presence of the polymer.

Specifically, the hydrocarbon-based polymer may be selected from the group consisting of nylon, polyimide, polybenzoxazole, polybenzimidazole, polyamideimide, polyethylene terephthalate, polyethylene, polypropylene, copolymers thereof, . Among them, it is preferable to use polyimide having superior heat resistance, chemical resistance, and shape stability.

However, since the hydrocarbon-based polymer is not soluble in an organic solvent, the porous nanofiber can not be directly produced through a spinning process. That is, it is difficult to prepare a spinning solution because the hydrocarbon-based polymer which is not costly to the organic solvent does not dissolve in the organic solvent. Therefore, when preparing a porous support containing a hydrocarbon-based polymer having insolubility in an organic solvent, the polymer precursor may be prepared without dissolving it in an organic solvent, or may be formed by forming a polymer precursor nanofiber using a polymer precursor that is well- Can be produced through a predetermined reaction.

The polymer precursor can be used without particular limitation as long as it can form the hydrocarbon polymer. For example, a porous support containing polyimide is prepared by preparing a PAA nanofiber precursor using polyamic acid (PAA) as a polyimide precursor which is well soluble in an organic solvent, and then carrying out an imidization reaction in a subsequent curing process ≪ / RTI >

The polyamic acid may be prepared according to a conventional method. Specifically, the polyamic acid may be prepared by mixing a diamine in a solvent and adding dianhydride thereto followed by polymerization.

Examples of the dianhydride include pyromellitic dianhydride (PMDA), 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride (3,3', 4,4'-benzophenonetetracarboxylic dianhydride, BTDA ), 4,4'-oxydiphthalic anhydride (ODPA), 3,4,3 ', 4'-biphenyltetracarboxylic acid anhydride (3,4,3', 4 ' -biphenyltetracarboxylic dianhydride (BPDA), bis (3,4-dicarboxyphenyl) dimethylsilane dianhydride (SiDA), and mixtures thereof. Examples of the diamine include 4,4'-oxydianiline (ODA), p-phenylene diamine (p-PDA), o-phenylene diamine diamine, o-PDA, and mixtures thereof. The solvent for dissolving the polyamic acid may include m-cresol, N-methyl-2-pyrrolidone (NMP), di The solvent is selected from the group consisting of methylformamide (DMF), dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), acetone, diethyl acetate, tetrahydrofuran (THF), chloroform, gamma -butyrolactone, Can be used.

The precursor solution containing the nanofiber precursor may be prepared by dissolving the nanofiber precursor in a conventional organic solvent such as NMP, DMF, DMAc, DMSO, or THF.

At this time, it is preferable that the nanofiber precursor is included in a concentration of 5 to 20% by weight based on the total weight of the precursor solution. If the concentration of the precursor solution is less than 5% by weight, the spinning does not proceed smoothly. Therefore, the fiber can not be formed or fibers having a uniform diameter can not be produced, whereas when the concentration of the polymer precursor solution is less than 20% , The discharge pressure may increase sharply so that the radiation may not be produced or the fairness may be lowered.

Then, the prepared precursor solution is electrospun using a conventional spinning apparatus to produce a nanofiber precursor.

1 is a schematic view of a nozzle-type electrospinning device. 1, the electrospinning is performed by supplying a predetermined amount of the precursor solution to a plurality of nozzles 3 using a metering pump 2 in a solution tank 1 in which the nanofibrous precursor solution is stored, The nanofiber precursor solution is discharged through a plurality of nozzles 3, and then a nanofiber precursor is formed at the same time as the particles are scattered. Further, the coagulated nanofiber precursor is collected by the collector 4 to collect precursor nanofibers of the porous support, Can be produced.

At this time, the intensity of the electric field between the nozzle 3 and the collector 4 applied by the high voltage generating portion 6 and the voltage transmitting rod 5 is preferably 850 to 3,500 V / cm. If the electric field intensity is less than 850 V / cm, the precursor solution is not continuously discharged, so that it is difficult to produce nanofibers having uniform thickness, and the nanofibers formed after being radiated are smoothly focused on the collector 4 The production of a porous support may be difficult. On the other hand, when the electric field strength exceeds 3,500 V / cm, the nanofiber can not be accurately placed on the collector 4, so that a porous support having a normal shape can not be obtained.

In addition, the plurality of nozzles are provided such that the ratio of the distance between the nearest positioned nozzle to the tip and the distance between the centers is 1.01 to 1.1. When the ratio of the distance between the tip of the nozzle and the distance between the centers of the nozzles is within the above range, the porous support comprising nanofibers having different average diameters can be manufactured.

The distance between the tips of the nozzles means the distance from the tip of the first nozzle to the tip of the second nozzle. In this case, the second nozzle is a nozzle closest to the first nozzle, and the tip of the nozzle means the end of the nozzle through which the nanofibrous precursor solution is discharged. The distance between the centers of the nozzles means a distance from the center of the first nozzle to the center of the second nozzle. The center of the nozzle means a position for bisecting the length of the nozzle.

The nanofibers having different average diameters may have two or more distributions based on an average diameter of 1 mu m. For example, the porous support may include first nanofibers having an average diameter of 1 탆 or more and second nanofibers having an average diameter of less than 1 탆. Preferably, the first nanofibers may have an average diameter of 0.1 to 0.9 mu m, and the second nanofibers may have an average diameter of 1.5 to 3 mu m. If the nanofibers having different average diameters have two or more distributions with an average diameter of 1 mu m, the air permeability and the passage capacity can be further improved.

In this case, the ratio of the average diameter of the first nanofiber and the second nanofiber may be 1.2: 1 to 10: 1, and preferably 2: 1 to 6: 1. If the ratio of the average diameters of the first nanofibers is less than 1.2, the pore size becomes large and sufficient filter efficiency can not be obtained. When the ratio is more than 10, the pore size becomes small, and sufficient air permeability and passage capacity can not be obtained.

The porous support may include 20 to 40% by number of the first nanofiber and 60 to 80% by number of the second nanofiber with respect to the whole porous support. Preferably, the first nanofiber is 30 To 35% by number of the first nanofibers and 65% to 70% by number of the second nanofibers. When the content of the first nanofiber is less than 20% or the content of the second nanofiber is more than 80% by number, the filter efficiency is good, but the life of the filter may be shortened and the filter differential pressure may be increased. If the content of the first nanofibers exceeds 40% by number or the content of the second nanofibers is less than 60% by number, the filter efficiency may decrease.

In order to convert the nanofiber precursor into the nanofiber, a curing process is performed as an additional process for the nanofiber precursor. For example, if the nanofibrous precursor produced through electrospinning is made of polyamic acid, it is converted to polyimide through imidization during the curing process.

Accordingly, it is preferable that the temperature during the curing process is appropriately adjusted in consideration of the conversion rate of the nanofiber precursor. Concretely, it is preferable that the curing process is carried out at 80 to 650 ° C. 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 porous support may deteriorate. When the curing temperature exceeds 650 ° C, There is a possibility that the physical properties of the resin are deteriorated.

Also, as the precursor nanofibers of the porous support are cured, the nanofibers on the surface of the porous support can be thermally fused to each other. As the nanofibers on the surface of the porous support are thermally fused to each other, the bonding strength of the nanofibers is improved, and the porous support can further improve heat resistance and chemical resistance. In order to thermally fuse the nanofibers of the surface of the porous support to each other, the curing temperature may be adjusted to 400 to 650 ° C.

The filter membrane according to another embodiment of the present invention includes a porous support in which polyimide nanofibers are bonded in the form of a nonwoven fabric including a plurality of pores. Since the filter membrane includes a porous support made of polyimide, it can be used as a membrane for a gas or liquid filter which is excellent in heat resistance and chemical resistance and is required to have heat resistance or chemical resistance. Also, the filter membrane can be used in an environment where the flow of the filtration fluid, such as a gas turbine filter, an automobile filter or a bag filter, is strong or can be exposed to an external impact. For example, the liquid filter membrane may have an operation temperature of 100 ° C or higher, and preferably 180 ° C.

In addition, the porous support may include nanofibers having different average diameters, and the nanofibers of the porous support surface may be thermally fused to each other. The description of the porous support including the nanofibers having different average diameters and the porous support on which the nanofibers of the surface are thermally fused to each other has been described above, and thus a detailed description thereof will be omitted.

The filter membrane may have an air permeability of 50 lpm to 250 lpm, and preferably 100 lpm to 150 lpm. The air permeability can be measured by the ISO 9237 method. If the air permeability is less than 50 lpm, the filter efficiency may increase, but the differential pressure may increase, and if it exceeds 250 lpm, the differential pressure may be lowered but the filter efficiency may decrease.

The filter membrane may have a removal efficiency of particles of 0.1 mu m size of 85 wt% or more, and preferably 95 wt% or more. The removal efficiency of the 0.1 탆 sized particles can be measured by the RS K 0004 method. If the particle removal efficiency of the 0.1 탆 size is less than 85%, the filtration function is lost and it can not be used.

Membranes for the filter may be a differential pressure is 1.5kgf / cm ² to 4.0kgf / cm ^2, may preferably 1.6kgf / cm ² to 2.5kgf / cm ^2. The differential pressure can be measured by the RS K 0004 method. If the differential pressure is less than 1.5 kgf / cm ² , the filtration efficiency may be lowered. If the differential pressure is more than 4.0 kgf / cm ² , the filter life may be shortened.

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. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[ Manufacturing example : Preparation of porous support]

( Example  One)

Polyamic acid was dissolved in a dimethylformamide solution to prepare 5 liters of spinning solution of 480 poise at 13 wt%. The prepared spinning solution was transferred to a solution tank, which was supplied through a metering gear pump to a spinning chamber having 20 nozzles and a high voltage of 46 kV to spin the nanofibers precursor. At this time, the supply amount of the solution was 1.5 ml / min. At this time, the ratio of the distance between the tip of the nozzle to the center of the nozzle was 1.02.

Then, the nanofiber precursor was thermally cured in a continuous curing furnace maintained at a temperature of 420 ° C for 6 minutes while transferring the nanofiber precursor by a roll-to-roll method, thereby preparing a porous support composed of polyimide nanofibers. At this time, the winding tension was 10N.

The prepared porous support had 31% by number of first nanofibers having an average diameter of 2 占 퐉 and 69% by number of second nanofibers having an average diameter of 0.5 占 퐉.

( Example  2)

A polyimide porous support was prepared in the same manner as in Example 1 except that the ratio of the distance between the tip of the nozzle and the distance between the center of the nozzle at the time of spinning the nanofiber precursor was changed to 1.06.

The prepared porous support contained 28% by number of first nanofibers having an average diameter of 1.8 占 퐉 and 72% by number of second nanofibers having an average diameter of 0.5 占 퐉.

( Example  3)

A polyimide porous support was prepared in the same manner as in Example 1 except that the ratio of the distance between the tip of the nozzle and the distance between the center of the nozzle at the time of spinning the nanofiber precursor was changed to 1.08.

The prepared porous support contained 33% by number of first nanofibers having an average diameter of 2.3 占 퐉 and 67% by number of second nanofibers having an average diameter of 0.6 占 퐉.

( Comparative Example  One)

Polyamic acid was dissolved in a dimethylformamide solution to prepare 5 liters of spinning solution of 480 poise at 13 wt%. The prepared spinning solution was transferred to a solution tank, which was supplied through a metering gear pump to a spinning chamber having 20 nozzles and a high voltage of 46 kV to spin the nanofibers precursor. At this time, the supply amount of the solution was 1.5 ml / min. At this time, the ratio of the distance between the tip of the nozzle to the center of the nozzle was 1.00.

Next, the nanofiber precursor 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 polyimide nanofibers.

The prepared porous support contained 100% by number of the first nanofibers having an average diameter of 1.5 탆.

( Comparative Example  2)

A polyimide porous support was prepared in the same manner as in Comparative Example 1, except that the ratio of the distance between the tip of the nozzle and the distance between the center of the nozzle at the time of spinning the nanofiber precursor was changed to 1.2.

The prepared porous support contained 25% by number of first nanofibers having an average diameter of 2.5 占 퐉 and 75% by number of second nanofibers having an average diameter of 0.7 占 퐉.

[ Test Example  1: Characteristic measurement of porous support]

The surface of the porous support prepared in Example 1 was observed with a scanning electron microscope (SEM). The results are shown in Fig.

2, the porous support includes first nanofibers having an average diameter of 2 μm and second nanofibers having an average diameter of 0.5 μm, and the nanofibers on the surface of the porous support are mutually heat- And it can be confirmed that it is fused.

The heat resistance, chemical resistance, water permeability, air permeability, removal efficiency and differential pressure of the porous support prepared in the above Examples and Comparative Examples were measured, and the results are summarized in Table 1 below.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Heat resistance ^{1 )} 468 467 466 469 461 Chemical resistance ^{2 )} No change No change No change No change No change Air permeability ^{3 )} 105 145 120 45 270 Removal efficiency ^{4 )} 95 95 90 50 75 Differential pressure ^{5 )} 2.1 1.7 2.4 4.5 4.2

1) Heat resistance: TGA analysis, the decomposition temperature was measured while raising the temperature to 800 ° C at a rate of 10 ° C / min in a nitrogen atmosphere.

2) Chemical resistance: Measurement of weight change after soaking in DMF at 100 ℃ for 24 hours.

3) Ventilation: Measured according to ISO 9237 method.

4) Removal efficiency: measured by RS K 0004 method.

5) Differential pressure: measured by RS K 0004 method.

Referring to Table 1, it can be seen that the porous membranes prepared in the examples have better air permeability and passage capacity than the membranes prepared in the comparative examples, and are excellent in heat resistance and chemical resistance.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of the right.

1: solution tank
2: metering pump
3: Nozzle
4: Collector
5: Voltage transferring rod
6: High voltage generator

Claims (20)

The nozzle is manufactured by electrospinning through a nozzle having a ratio of the distance between the tip of the nozzle to the distance between the center of the nozzle is 1.01 to 1.1,
A porous support in which nanofibers having different average diameters are bonded in the form of a nonwoven fabric comprising a plurality of pores. The method according to claim 1,
Wherein the porous support comprises first nanofibers having an average diameter of at least 1 탆 and second nanofibers having an average diameter of less than 1 탆. 3. The method of claim 2,
Wherein the ratio of the average diameter of the first nanofiber and the second nanofiber is 1.2: 1 to 10: 1. 3. The method of claim 2,
Wherein the porous support comprises 20 to 40% by number of the first nanofibers and 60 to 80% by number of the second nanofibers with respect to the whole porous support. The method according to claim 1,
Wherein the nanofiber is a polyimide nanofiber. The method according to claim 1,
Wherein the nanofibers on the surface of the porous support are thermally fused to each other. A nanofiber precursor solution is discharged through the nozzle to form a nanofiber precursor, and the nanofiber precursor is collected by the collector to form precursor nanofibers of the porous support, Manufacturing steps, and
And curing the precursor nanofibers of the porous support,
Wherein the ratio of the distance between the tip of the nozzle to the distance between the center of the nozzle is 1.01 to 1.1. 8. The method of claim 7,
Wherein the porous support is formed by combining nanofibers having different average diameters in the form of a nonwoven fabric including a plurality of pores. 9. The method of claim 8,
Wherein the porous support comprises first nanofibers having an average diameter of at least 1 占 퐉 and second nanofibers having an average diameter of less than 1 占 퐉. 10. The method of claim 9,
Wherein the ratio of the average diameter of the first nanofiber and the second nanofiber is 1.2: 1 to 10: 1. 10. The method of claim 9,
Wherein the porous support comprises 20 to 40% by number of the first nanofibers and 60 to 80% by number of the second nanofibers with respect to the whole porous support. 8. The method of claim 7,
Wherein the nanofiber is a polyimide nanofiber. 8. The method of claim 7,
Wherein the curing step is carried out at 80 to < RTI ID = 0.0 > 650 C. < / RTI > 14. The method of claim 13,
Wherein the nanofibers on the surface of the porous support are thermally fused to each other during the curing process. A membrane for a filter comprising a porous support, which is manufactured by electrospinning through a nozzle having a ratio of the distance between the nozzle tip to the center of the nozzle is 1.01 to 1.1 and the polyimide nanofibers are bonded in the form of a nonwoven fabric including a plurality of pores . 16. The method of claim 15,
Wherein the porous support comprises nanofibers having different average diameters. 17. The method of claim 16,
Wherein the porous support comprises first nanofibers having an average diameter of 1 占 퐉 or more and second nanofibers having an average diameter of less than 1 占 퐉. 18. The method of claim 17,
Wherein the ratio of the average diameter of the first nanofiber and the second nanofiber is 1.2: 1 to 10; 1. 18. The method of claim 17,
Wherein the porous support comprises 20 to 40% by number of the first nanofibers and 60 to 80% by number of the second nanofibers with respect to the whole porous support. 16. The method of claim 15,
Wherein the nanofibers on the porous support surface are thermally fused to each other.

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