KR101416614B1 - Polyimide nanofiber filter with excellent heat-resisting property and its method - Google Patents

Abstract

A polyimide nanofiber filter with improved heat resistance according to the present invention is manufactured via an electrospinning method and an imidization method to solve the problem of low thermal stability of an existing nanofiber filter. The manufactured polyimde nanofiber filter gives fiber thickness gradient to a polyimide nanofiber nonwoven fabric in a manufacturing process thereof. The functional filter has ensured process efficiency by a continuous electrospinning process, high efficiency with price competitiveness and heat resistance.

Description

TECHNICAL FIELD [0001] The present invention relates to a polyimide nanofiber filter having improved heat resistance and a method for manufacturing the same,

The present invention relates to a polyimide nanofiber filter having improved heat resistance and a method for producing the polyimide nanofiber filter. The present invention relates to a polyimide nanofiber filter obtained by electrospinning a polyamic acid (PAA) solution on a cellulose substrate, To a polyimide (PI) nanofiber filter having improved heat resistance, which can be manufactured by a polyimide nanofiber filter, and a method for manufacturing the same.

Generally, a filter is a filtration device for filtering foreign matters in a fluid, and is divided into a liquid filter and an air filter. Among them, the air filter is used to prevent the defect of high-tech products as well as the development of high-tech industries. The air filter is used in a clean room where the biologically harmful substances such as dust, fine particles, biological particles such as bacteria and mold, bacteria, The installation of the room is spreading day by day. Cleanroom applications are widely used in semiconductor manufacturing, computer equipment assembly, tape manufacturing, printing painting, hospitals, pharmaceutical manufacturing, food processing plants, agriculture, forestry and fisheries.

The air filter forms a porous layer having a microporous structure on the surface of the filter medium, thereby performing a function of preventing the dust from penetrating into the filter medium and performing filtration. However, particles having a large particle size are formed by a filter cake on the surface of the filter medium, and fine particles pass through the primary surface layer and gradually accumulate in the filter medium, thereby blocking the pores of the filter. As a result, it is difficult to filter fine particles of nano-sized particles of 1 micron or less in the conventional filter media as well as to increase the pressure loss of the filter and reduce the life of the filter. .

On the other hand, the efficiency of the conventional air filter is measured by the principle that the static electricity is given to the fibrous aggregate constituting the filter filter material and the particles are collected by the electrostatic force. However, the recent European air filter classification standard EN779 has been revised to exclude the filter efficiency due to the static effect in 2012, so that the actual efficiency of the conventional filter is lowered by more than 20%.

In addition, due to the adverse effect of glass fiber, which has been used as a material of conventional heat resistant filter, on the environment, in Europe and the United States, the use of glass fiber is regulated for environmental stability.

In order to solve the above problems, various methods of fabricating nano-sized fibers and applying them to filters have been developed. When nanofibers are implemented in a filter, they have a large specific surface area compared to conventional filter media having a large diameter, good flexibility for surface functional groups, and nanoparticle pore size, so that harmful fine particles and gas can be efficiently removed It was.

However, the implementation of the filter using the nanofibers raises the production cost, and it is not easy to control various conditions for production, and since it is difficult to mass-produce the filter, the filter using the nanofibers has a relatively low unit price It is a fact that production can not be spread. Furthermore, currently, filters used in gas turbines, furnaces, and the like are required to have heat resistance.

In addition, since the technology for spinning conventional nano-nonwoven fabrics is limited to a small-scale working line focused on a laboratory, there is no concept of dividing the spinning block into units or blocks. In this case, only nano-nonwoven fabrics having a constant fiber thickness are emitted. This has a problem in that the air permeability and life time limit are used when the filter is used as a filter.

In order to solve the above problems, the present invention provides a polyimide nanofiber nonwoven fabric laminated on a cellulose substrate by electrospinning a polyamic acid to form two kinds of polyamic acid nanofiber nonwoven fabrics having different thicknesses, To improve the thermal stability and to provide a filter excellent in efficiency of the filter and a method of manufacturing the filter manufactured thereby.

According to a preferred embodiment of the present invention, a cellulose substrate; A polyamic acid nanofiber nonwoven fabric having a fiber diameter of 250 to 500 nm laminated on a cellulose substrate by electrospinning and a polyamic acid nanofiber filter having a fiber diameter of 250 to 500 nm, Wherein the polyimide nanofiber nonwoven fabric laminated on the cellulose substrate includes a polyamic acid nanofiber nonwoven fabric having a thickness of 250 nm, and the polyimic acid nanofiber nonwoven fabric laminated on the cellulose substrate is heat treated to provide a polyimide nanofiber filter having improved heat resistance.

According to another preferred embodiment of the present invention, each of the polyamic acid nanofiber nonwoven fabrics is heat-treated at a temperature of 150 to 350 ° C.

According to another preferred embodiment of the present invention, there is provided a method for producing polyamic acid, comprising: supplying a polyamic acid solution in which polyamic acid is dissolved in an organic solvent to each nozzle of each block; Forming a polyamic acid nanofiber nonwoven fabric layer having a fiber diameter of 250 to 500 nm on the polyimic acid nanofiber nonwoven fabric layer having a fiber diameter of 250 to 500 nm; A step of forming a polyamic acid nanofiber nonwoven fabric having a fiber diameter of 50 to 250 nm on the polyimide nanofiber nonwoven fabric, and a step of heat-treating the laminated polyamic acid nanofiber nonwoven fabric by heat treatment to imidize the polyimide nanofiber nonwoven fabric, And a manufacturing method thereof.

According to another preferred embodiment of the present invention, the step of imidizing is performed by calcining at a temperature of 150 to 350 ° C.

According to another preferred embodiment of the present invention, by adjusting the intensity of the voltage applied to each block, adjusting the concentration of the spinning liquid, adjusting the gap between the nozzle and the collector, or adjusting the feeding speed of the long sheet, And polyamic acid nanofiber nonwoven fabrics having different thicknesses are laminated.

According to another preferred embodiment of the present invention, the electrospinning is a bottom-up electrospinning.

The present invention uses a polyamic acid which is a heat-resistant polymer and has excellent heat resistance. Since the continuous electrospinning method is used, not only the manufacturing process is efficient and cost-competitive, but also the nanofiber nonwoven fabric is used.

In addition, since the non-woven fabric comprising two polyamic acid nanofibers having different thicknesses is provided, there is an advantage in that the durability of the filter is good because the pressure loss is small.

1 is a schematic view of a polyimide nanofiber filter having improved heat resistance according to the present invention.
Fig. 2 is a process schematic diagram of the electrospinning apparatus used in the present invention.
3 is a schematic process diagram of a block of an electrospinning device used in the present invention.
4 is a schematic view of an apparatus for measuring thickness of an electrospinning apparatus used in the present invention.
5 is a schematic view of a nozzle block and a nozzle of an electrospinning apparatus used in the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the scope of the present invention, but is merely an example, and various modifications can be made without departing from the technical spirit of the present invention.

First, the production of the polyimide nanofiber filter having improved heat resistance provided by the present invention is largely composed of the following three. First, a step of synthesizing polyamic acid (PAA), a step of preparing a polyamic acid solution by dissolving it in an organic solvent, electrospinning on a cellulose substrate, and a step of polyimide PI) nanofiber nonwoven fabric.

First, polyimide is a polymer containing an imide group in the repeating unit. The polyimide is characterized in that its physical properties do not change even in a temperature range from -273 DEG C to 400 DEG C, and has excellent mechanical strength and heat resistance. However, most of the polyimides are insoluble and have poor physical properties and are difficult to process by conventional techniques, so it is common to process them in the form of its precursor poly (amic acid) (PAA). Therefore, the polyimide is prepared by first polymerizing a polyamic acid and then carrying out an imidation process.

Generally, polyimides are prepared by a two-step reaction.

The first step is a step of synthesizing polyamic acid. The polyamic acid is polymerized by adding a dianhydride to a reaction solution in which diamine is dissolved. In order to increase the degree of polymerization, the reaction temperature, the water content of the solvent, Purity control is required. Organic polar solvents such as dimethylacetamide (DMAc), dimethylformamide (DMF) and en-methyl-2-pyrrolidone (NMP) are mainly used as the solvent used in this step. Examples of the diamine include 4,4'-oxydianiline (ODA), para-phenylene diamine (p-PDA), and o-phenylene diamine diamine, o-PDA) may be used. Examples of the anhydride include pyromellitic dianhydride (PMDA), benzophenonetetracarboxylic dianhydride (BTDA), 4-4'-oxydiphthalic anhydride (4-4 ' bisdiphthalic anhydride (ODPA), biphenyl-tetracarboxylic acid dianhydride (BPDA), and bis (3,4'-dicarboxyphenyl) dimethylsilanediamine hydride (bis (3,4-dicarboxyphenyl) dimethylsilane dianhydride, SIDA).

The weight average molecular weight (Mw) of the polyamic acid prepared by the above method is preferably 10,000 to 500,000. If the molecular weight of the polyamic acid is less than 10,000, sufficient physical properties for forming the nanofiber nonwoven fabric can not be obtained. If the molecular weight exceeds 500,000, the handling of the solution is not easy and the processability is degraded.

The second step is the dehydration and ring-closing reaction step of producing the polyimide from polyamic acid as the following four methods.

In the re-impregnation method, a polyamic acid solution is added to an excess amount of a poor solvent to obtain a solid polyamic acid. As the re-precipitation solvent, water is mainly used, but toluene or ether is used as a co-solvent.

The chemical imidization method is a method in which a imidization reaction is chemically performed using a dehydration catalyst such as acetic anhydride / pyridine, and is useful for producing a polyimide film.

The thermal imidization method is a method in which the polyamic acid solution is heated to 150 to 350 ° C to thermally imidize it. In the simplest process and the crystallization degree is high, the amine exchange reaction occurs when the amine type solvent is used. have.

Finally, in the isocyanate method, diisocyanate is used instead of diamine as a monomer, and a monomer mixture is heated to a temperature of 120 ° C or higher to produce polyimide while CO ₂ gas is generated.

(Scheme 1) Mechanism of production of polyimide

Hereinafter, an electrospinning apparatus for producing a filter by electrospinning a spinning solution on a substrate will be described with reference to the drawings.

FIG. 1 is a schematic view of a polyimide nanofiber filter having improved heat resistance according to the present invention, FIG. 2 is a schematic view of the process of the electrospinning device used in the present invention, and FIG. 3 is a block diagram of the electrospinning device Fig. 5 is a schematic view of a nozzle block and a nozzle of an electrospinning device used in the present invention. Fig. 5 is a schematic view of a nozzle for measuring the thickness of the electrospinning device used in the present invention.

As shown in the drawing, the electrospinning apparatus 10 of the present invention includes a spinning liquid main tank (not shown) in which a spinning liquid is filled and a weighing device for supplying a fixed amount of the polymer spinning solution filled in the spinning liquid main tank (3) in which a plurality of nozzles (2) in the form of a pin are arranged for discharging the polymer solution for use in the spinning liquid main tank and a pump (not shown), and a nozzle block (20) for accommodating a collector (4) spaced apart from the nozzle (2) by a predetermined distance and a voltage generating device (1a, 1b) for generating a voltage to the collector (4) And a case 8 made of a conductor or a negative conductor in the block 20.

In the present invention, one spinning liquid main tank (not shown) is provided. However, in the case where the spinning liquid is composed of two or more spinning liquids, two or more main spinning liquid main tanks may be provided, or one spinning liquid main tanks It is also possible to divide into two or more spaces and supply two or more polymer spinning solution filled in each divided space.

With the above structure, the electrospinning apparatus 10 is configured such that the spinning liquid filled in the spinning liquid main tank in the block 20 continuously flows into the plurality of nozzles 2 to which a high voltage is applied through the metering pump And the spinning liquid of the polymer supplied to the nozzle 2 is radiated and focused on the collector 4 having a high voltage applied thereto through the nozzle 2 to form a nanofiber nonwoven fabric (not shown) The nanofiber nonwoven fabric is laminated to produce a filter.

A feeding roller 11 is provided at the front end of the electrospinning device 10 for feeding a long sheet (not shown) in which a polymer spinning solution is injected from the block 20 to laminate nanofibers, Up rollers 12 for winding up a long sheet on which fibers are stacked.

The elongated sheet is provided for preventing and transporting the nanofibers. One end and the other end of the elongated sheet are wound around a feeding roller 11 provided at the front end of the electrospinning device 10 and a winding roller 12 provided at the rear end.

On the other hand, the electrospinning apparatus 10 of each of the blocks 20a and 20b is installed in the advancing direction (a) of the long sheet with respect to the collector 4. An auxiliary belt 6 is provided between the collector 4 and the long sheet and a long sheet in which nanofibers are stacked and formed on the respective collectors 4 through the auxiliary belts 6 is formed in a horizontal direction Lt; / RTI > That is, the auxiliary belt 6 rotates in synchronization with the conveyance speed of the long sheet, and has the auxiliary belt roller 7 for driving the auxiliary belt 6. The auxiliary belt roller 7 is an automatic roller having at least two frictional forces. Since the auxiliary belt 6 is provided between the collector 4 and the long sheet, the long sheet is smoothly conveyed without being attracted to the collector 4 to which the high voltage is applied.

With the structure as described above, the spinning solution filled in the spinning liquid main tank in the block 20 of the electrospinning device 10 is sprayed onto the elongate sheet placed on the collector 4 through the nozzle 2 , The spinning liquid sprayed on the long sheet is accumulated, and the nanofiber nonwoven fabric is laminated. The auxiliary belt 6 is driven by the rotation of the auxiliary belt roller 7 provided on both sides of the collector 4 and the elongated sheet is conveyed to be positioned in the block 20b at the rear end of the electrospinning device 10 And the above-described process is repeatedly performed.

5, the nozzle block 3 includes a plurality of nozzles 2 arranged upward from the discharge port, a tube 43 formed of a row of nozzles 2, a spinning solution storage tank 44, And a spinning liquid circulating pipe (45).

First, the spinning liquid storage tank 44 connected to the spinning liquid main tank to receive and store the spinning solution is connected to the nozzle 2 through the spinning liquid circulating pipe 45 by the metering pump (not shown) And the spinning solution is supplied to the spinning solution. Here, the tube 43 having a plurality of nozzles 2 in a row is supplied with the same spinning solution from the spinning solution storage tank 44, but a plurality of spinning solution main tanks are provided, It is also possible to supply a spinning liquid of different kinds to each of the tubes 43 and radiate them.

When radiated from the discharge port of the plurality of nozzles 2, the overflowed solution is moved to the overflow solution storage tank 41. The overflow solution storage tank 41 is connected to the spinning solution main tank so that the overflow solution can be reused for spinning.

The main controller 30 of the present invention controls the spinning conditions in the course of the spinning and controls the amount of the spinning solution supplied to the nozzle block 3, 1), and controls the conveying speed of each block in accordance with the thickness of the nano-fiber nonwoven fabric and the two-component substrate measured by the thickness measuring device 9.

The thickness measuring device 9 of the present invention is disposed so as to face the long sheets located at the front end and the rear end of the block 20 and having the laminated nanofiber nonwoven fabric therebetween. The thickness measuring device 9 is connected to the main controller 30 for controlling the radiation conditions of the electrospinning device 10 so that the thickness measuring device 9 measures the thickness of the non- The main controller 30 controls the conveying speed of each block 20 based on the received signal. For example, in the case of electrospinning, when the thickness of the nanofibers discharged to the block 20a located at the front end portion is measured thinly, the conveyance speed of the block 20b located at the rear end portion is reduced, The thickness of the film is controlled to be constant. In addition, the main controller 30 increases the discharge amount of the nozzle block 3 and controls the voltage intensity of the voltage generators 1a and 1b to increase the discharge amount of the nanofibers per unit area, It is possible to control it uniformly.

The thickness measuring device 9 includes a thickness measurement unit configured to measure a distance between the nanofiber nonwoven fabric in which the nanofiber nonwoven fabric is laminated and the elongated sheet by ultrasonic measurement, and a pair of ultrasonic longitudinal waves and a transverse wave, The thickness of the nanofiber nonwoven fabric and the long sheet is calculated on the basis of the distance measured by the pair of ultrasonic measuring devices, as shown in FIG. More particularly, the present invention relates to a method and a device for measuring the propagation time of longitudinal waves and transverse waves of longitudinal waves and transverse waves, respectively, by projecting ultrasound waves and transverse waves to longitudinal sheets laminated with nanofibers, Measuring the time, measuring a propagation time of the longitudinal wave and the transverse wave and a temperature coefficient of propagation velocity and propagation velocity of the longitudinal wave and the transverse wave at a reference temperature of the long sheet in which the nanofibers are stacked, Is a thickness measuring apparatus for calculating a thickness

The electrospinning apparatus 10 used in the present invention does not change the conveying speed from the initial value when the thickness deviation amount of the nanofiber nonwoven fabric is less than the predetermined value and sets the conveying speed to the initial value It is possible to simplify the control of the conveyance speed by the conveyance speed control apparatus. Further, in addition to the control of the conveying speed, the discharge amount and the voltage intensity of the nozzle block 3 can be adjusted. When the thickness deviation amount is less than the predetermined value, the discharge amount of the nozzle block 3 and the voltage intensity are not changed from the initial value , It is possible to control the amount of discharge of the nozzle block 3 and the intensity of the voltage to be changed from the initial value when the amount of deviation of the nozzle block 3 is equal to or larger than the predetermined value. .

The block 20 of the electrospinning device 10 is divided into a front end block 20a located at the front end portion and a rear end block 20b located at the rear end portion according to the radiation position. In the embodiment of the present invention, the number of blocks is limited to two, but it is also possible to have two or more blocks.

In the present invention, the same polymer spinning solution is radiated in each of the blocks 20a and 20b, but it is also possible to spin different kinds of polymer spinning solution for each block 20a and 20b, It is also possible to emit two or more different kinds of polymer solution. When at least two different types of spinning solutions are supplied and radiated for each of the blocks 20a and 20b, polymer nanofiber nonwoven fabrics of different kinds can be successively laminated.

On the other hand, a laminating device 19 is provided at the rear end of the electrospinning device 10 of the present invention. The laminating device 19 applies heat and pressure through which the elongated sheet and the nanofiber nonwoven fabric are adhered to each other, and then wound on the winding roller 12 to produce a filter.

The electrospinning device 10 can increase the collecting area to uniform the density of the nanofibers and effectively prevent the droplet phenomenon, thereby improving the quality of the nanofibers, The nanofibers and nanofibers thereof can be mass-produced. In addition, since the material and the electrospinning condition can be controlled in the electrospinning in the block 20 having the nozzle 2 having a plurality of pins, the width and thickness of the nonwoven fabric and the filament can be freely changed and adjusted.

In addition, when the polymer is spun as described above, it is most preferable to spin the polymer under environmental conditions of 30 to 40 DEG C and 40 to 70% of the temperature depending on the polymer material.

In the present invention, the diameter of the nanofiber is preferably 30 to 1000 nm, more preferably 50 to 500 nm.

Hereinafter, a method for producing a polyimide nanofiber filter having improved heat resistance according to the present invention will be described.

First, in the present invention, polyamic acid is used as a spinning solution, and a cellulose substrate 100 is used as a long sheet.

The polyamic acid solution obtained by dissolving the polyamic acid in an organic solvent is supplied to the spinning liquid main tank of the electrospinning device 10. The polyamic acid solution supplied to the spinning liquid main tank is continuously supplied in a constant amount into the plurality of nozzles 2 of the nozzle block 3 to which a high voltage is applied through the metering pump. The polyamic acid solution supplied to each of the nozzles 2 is sprayed onto the cellulose substrate 100 positioned on the collector 4 with a high voltage applied thereto through the nozzle 2 to form a polyamic acid nanofiber nonwoven fabric.

In the present invention, a polyamic acid solution is used as the spinning solution, but the present invention is not limited thereto.

The cellulose base material 100 in which the polyamic acid nanofibers are laminated in the front end block 20a of the electrospinning device 10 includes a feed roller 11 operated by driving of a motor Is transferred from the front end block 20a into the rear end block 20b by the rotation of the auxiliary belt 6 driven by the rotation of the roller 11 and the above process is repeated while the polyamic acid A nanofiber nonwoven fabric is formed.

Hereinafter, the cellulose base material 100 will be described. The cellulose base material (100) is characterized by excellent dimensional stability at a high temperature and high heat resistance. The fine cellulosic fibers have a high crystallinity and a high elastic modulus in that they form a fine porous structure, and are essentially excellent in dimensional stability at high temperatures. With this feature, the cellulosic substrate 100 can be used as a high-performance filter, a functional sheet, a living product such as a sheet for cooking or absorbent sheet, a substrate for a semiconductor device or a wiring board, a substrate for a low linear expansion rate material, And the like.

In an embodiment of the present invention, the cellulose base material 100 is used instead of the long sheet, but the present invention is not limited thereto.

On the other hand, the front end voltage supplying device 1a for supplying a voltage to the front end block 20a lowers the radiation voltage to form a polyamic acid nanofiber nonwoven fabric having a fiber diameter of 250 to 500 nm on the cellulose substrate 100 And a rear end voltage supplying device 1b for supplying a voltage to the rear end block 20b is provided with a high radiation voltage so that a polyamic acid nanofiber nonwoven fabric having a fiber diameter of 50 to 250 nm is wound on the back end block 20b with a fiber diameter of 250 to 500 nm And then laminated on the polyamic acid nanofiber nonwoven fabric.

The radiation voltage given by each of the voltage supply devices 1a and 1b is 1 kV or more, preferably 20 kV or more, and the voltage applied by the front-end voltage supply device 1a is supplied to the rear- Voltage.

In the present invention, a polyimic acid nanofiber nonwoven fabric having a fiber diameter of 250 to 500 nm is laminated on a base material by applying a low voltage to the front end block 20a of the electrospinning device 10, The polyimic acid nanofiber nonwoven fabric having a fiber diameter of 50 to 250 nm is laminated on the polyamic acid nanofiber nonwoven fabric having the fiber diameter of 250 to 500 nm to form a polyamic acid nanofiber filter. However, when a polyamic acid nanofiber nonwoven fabric having a fiber diameter of 50 to 250 nm is radiated from the front end block 20a and a polyamic acid nanofiber nonwoven fabric having a fiber diameter of 250 to 500 nm is wound around the rear end block 20b, Or the like.

In addition, the number of blocks of the electrospinning device 10 may be three or more, and three layers of nano-fiber non-woven fabrics having different fiber thicknesses may be formed on the two- It would also be possible to fabricate a fiber filter.

It is also possible that the nanofiber nonwoven fabrics having different fiber thicknesses are continuously laminated by varying the intensity of the voltage applied to each block 20. In a block 20, It is also possible to form a hybrid nanofiber nonwoven fabric in which two or more polymers are electrospun to form a laminated layer

In addition, the nozzle (2) and the collector (4) there is a road width by adjusting the distance between to form a different nano-fiber non-woven fabric, in the case where the spinning liquid identical to the same supply voltage, the closer the room range the fiber diameter is It is also possible that a nanofiber nonwoven fabric having different fiber diameters is formed according to the principle that the diameter becomes thicker and the fiber diameter becomes narrower as the spinning distance becomes longer.

In addition, it is also possible to manufacture hybrid nanofiber nonwoven fabrics by constituting two or more kinds of polymers of the spinning solution to be used.

Thus, a polyamic acid nanofiber nonwoven fabric having a fiber diameter of 250 to 500 nm is laminated on the cellulose substrate 100, and a polyamide nanofiber nonwoven fabric having a fiber diameter of 250 to 500 nm is formed on the cellulose substrate 100, A polyamic acid nanofiber filter in which micamic nanofiber nonwoven fabric is laminated is produced.

As described above, the laminated polyamic acid nanofiber filter is thermally imidized while being passed through the laminating device 19 and is made of a polyimide nanofiber filter. Imidization in the laminating apparatus 19 is carried out at 150 to 350 ° C, and the polyamic acid nanofiber filter is dewatered to produce a polyimide nanofiber filter.

That is, when the polyamic acid nanofiber filter is imidized, a polyimide nanofiber nonwoven fabric 200 having a fiber diameter of 250 to 500 nm is laminated on the cellulose substrate 100, and the polyimide nanofiber filter having a fiber diameter of 250 to 500 nm A polyimide nanofiber nonwoven fabric 300 having a fiber diameter of 50 to 250 nm is laminated on the nanofiber nonwoven fabric 200 to finally produce a polyimide nanofiber filter.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example 1

A polyamic acid solution having a concentration of 20 wt% and a viscosity of 102,000 cps was prepared by dissolving polyamic acid (Sangafronton Tech Co., Ltd.) in a solvent of dimethylacetamide (DMAc), and the polyamic acid solution was added to the spinning liquid main tank . After applying the applied voltage to the front end block at 15 kV, the polyamic acid solution was electrospun onto a cellulose substrate having a basis weight of 30 gsm to form a polyamic acid nanofiber nonwoven fabric having a thickness of 2.5 탆 and a fiber diameter of 350 nm, The applied voltage was 20 kV and the polyamic acid solution was electrospun on the polyamic acid nanofiber nonwoven fabric having a fiber diameter of 350 nm to form a polyamic acid nanofiber nonwoven fabric having a thickness of 2.5 탆 and a fiber diameter of 150 nm. After electrospinning, the polyimide nanofiber filter was prepared by imidizing polyamic acid by heat treatment at 150 ° C in a laminating apparatus. At this time, electrospinning was performed under the conditions of a distance between the electrode and the collector of 40 cm, a spinning solution flow rate of 0.1 mL / h, a temperature of 22 ° C, and a humidity of 20%.

Example 2

In Example 1, electrospinning was carried out under the same conditions except that the imidization temperature was changed to 250 캜.

Example 3

Electrospinning was carried out in the same manner as in Example 1 except that the imidation temperature was changed to 350 캜.

Comparative Example 1

A nylon 6 solution was prepared by dissolving nylon 6 in formic acid, and the nylon 6 solution was added to the spinning liquid main tank. A cellulose substrate having a basis weight of 30 gs on a collector was subjected to electrospinning under the conditions of an applied voltage of 20 kV, a spinning solution flow rate of 0.1 mL / h, a temperature of 22 캜, and a humidity of 20%, and passed through a laminating apparatus to produce a nylon 6 nanofiber filter.

Comparative Example 2

A polyamic acid solution having a concentration of 20 wt% and a viscosity of 102,000 cps was prepared by dissolving polyamic acid (Sangafronton Tech Co., Ltd.) in a solvent of dimethylacetamide (DMAc), and the polyamic acid solution was added to the spinning liquid main tank . After applying the applied voltage to the front end block at 15 kV, the polyamic acid solution was electrospun onto a cellulose substrate having a basis weight of 30 gsm to form a polyamic acid nanofiber nonwoven fabric having a thickness of 5 탆 and a fiber diameter of 350 nm. At this time, electrospinning was performed under the conditions of a distance between the electrode and the collector of 40 cm, a spinning solution flow rate of 0.1 mL / h, a temperature of 22 ° C, and a humidity of 20%. After electrospinning, the polyimide nanofiber filter was prepared by imidizing polyamic acid by heat treatment at 150 ° C in a laminating apparatus.

- Evaluation of heat shrinkage

The filters of Examples and Comparative Examples were cut into 3 cm x 3 cm and stored at 190 ° C for 30 minutes, and the heat shrinkage ratio was evaluated and shown in Table 1.

- Filtration efficiency measurement

The DOP test method was used to measure the efficiency of the fabricated nanofiber filter. The DOP test method measures the dioctyl phthalate (DOP) efficiency with an automated filter analyzer (AFT) of TSI 3160 from TSI Incorporated and measures the permeability, filter efficiency and differential pressure of the filter media material .

The automation analyzer is a device that automatically measures the velocity of air, DOP filtration efficiency, air permeability (permeability), etc. by passing DOP through the filter sheet by making particles of desired size and is a very important device for high efficiency filter.

The DOP% efficiency is defined as:

DOP% transmittance = 1 - 100 (DOP concentration downstream / DOP concentration upstream)

The filtration efficiencies of Examples and Comparative Examples were measured by the above-mentioned methods and are shown in Table 2.

Examples 1 to 3 Comparative Example 1 Comparative Example 2 Heat shrinkage (%) <3% 10% 5%

Examples 1 to 3 Comparative Example 1 Comparative Example 2 0.35 탆 DOP
Filtration efficiency (%) > 99% 90% 89%

It can be seen that the polyimide nanofiber filter manufactured through the embodiment of the present invention has better heat shrinkage and filtration efficiency than the comparative example.

- pressure drop and filter life measurement

The pressure drop of the fabricated nanofiber filter was measured with ASHRAE 52.1 according to the flow rate of 50 / / m ³ , and the filter life was measured accordingly. The data of Examples 1 to 3 and Comparative Examples 1 to 2 are shown in Table 3.

Examples 1 to 3 Comparative Examples 1 to 2 Pressure drop (in.w.g) <4 > 8 Filter life (month) 6.7 4.1

According to Table 3, the filter manufactured through the embodiment of the present invention has a lower pressure drop due to a lower pressure drop than the comparative example, and has a longer filter life, resulting in superior durability.

Thus, those skilled in the art will appreciate that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the embodiments described above are to be considered in all respects only as illustrative and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

1a, 1b: voltage generating device, 2: nozzle,
3: nozzle block, 4: collector,
6: auxiliary belt, 7: auxiliary belt roller,
8: case, 9: thickness measuring device,
10: electrospinning device, 11: feed roller,
12: take-up roller, 19: laminating apparatus,
20, 20a, 20b: block, 30: main controller,
41: Overflow solution storage tank, 43: Tubular body,
44: spinning liquid storage tank, 45: spinning liquid circulation pipe,
100: cellulose substrate,
200: polyimide nanofiber nonwoven fabric,
300: polyimide nanofiber nonwoven fabric.

Claims (6)

A cellulose substrate;
A polyamic acid nanofiber nonwoven fabric having a fiber diameter of 250 to 500 nm laminated on the cellulose substrate by electrospinning; And
A polyamic acid nanofiber nonwoven fabric having a fiber diameter of 50 to 250 nm laminated by electrospinning on a polyamic acid nanofiber filter having a fiber diameter of 250 to 500 nm;
Wherein the polyimide nanofiber nonwoven fabric laminated on the cellulose substrate is subjected to heat treatment to heat the polyimide nanofiber nonwoven fabric laminated on the cellulose substrate.
The method according to claim 1,
Wherein each of the polyamic acid nanofiber nonwoven fabrics is heat-treated at a temperature of 150 to 350 ° C.
Supplying a polyamic acid solution obtained by dissolving polyamic acid in an organic solvent to a nozzle of each block;
Forming a laminate of a polyamic acid nanofiber nonwoven fabric having a fiber diameter of 250 to 500 nm on a cellulose substrate by electrospinning a polyamic acid solution from a nozzle of a front end block of the block;
Depositing a polyamic acid nanofiber nonwoven fabric having a fiber diameter of 50 to 250 nm on the polyamic acid nanofiber nonwoven fabric having a fiber diameter of 250 to 500 nm by electrospunning a polyamic acid solution from a nozzle of a rear end block of the block; And
Heat-treating each of the laminated polyamic acid nanofiber nonwoven fabrics by imidization;
Wherein the polyimide nanofiber filter has an improved heat resistance.
The method of claim 3,
Wherein the imidizing step is carried out by calcining at a temperature of 150 to 350 DEG C. 5. The method for producing a polyimide nanofiber filter according to claim 1,
The method of claim 3,
A polyamic acid nanofiber nonwoven fabric having different fiber diameters by adjusting the intensity of the voltage applied to each block, adjusting the concentration of the spinning liquid, adjusting the interval between the nozzles and the collector, or adjusting the feeding speed of the long sheet, Wherein the polyimide nanofiber filter is laminated on the polyimide nanofiber filter.
The method of claim 3,
Wherein the electrospinning is bottom-up electrospinning. &Lt; RTI ID = 0.0 &gt; 15. &lt; / RTI &gt;

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