KR20200051106A - Polymer film for air purification filter and preparation method thereof - Google Patents

Abstract

The present invention is to provide a polymer film for an air filter and a manufacturing method thereof. The polymer film can realize excellent durability due to excellent adhesion to a nonwoven fabric layer by including a polytetrafluoroethylene film layer having specific crystallinity.

Description

Polymer film for air filter and manufacturing method therefor {POLYMER FILM FOR AIR PURIFICATION FILTER AND PREPARATION METHOD THEREOF}

The present invention is to provide a polymer film for air filters and a method for manufacturing the same, which can realize excellent durability.

A porous body made of polytetrafluoroethylene (hereinafter referred to as "PTFE") is excellent in chemical resistance, heat resistance, weather resistance, and non-flammability, and has properties such as non-adhesiveness and low friction coefficient. Moreover, because of its porous structure, it is also excellent in permeability, flexibility, flexibility, and collection and filtration of fine particles. For this reason, materials made of PTFE are used in a wide range of fields, such as filters for purifying air for life, filtration of fine chemicals, and filters for waste water treatment.

Typically, a filter is manufactured by bonding a porous film to a support such as a non-woven fabric, but there is a problem in that filtration efficiency is significantly lowered when a separate adhesive is used in the bonding process. Also, when the filter is placed under conditions of high temperature and high humidity, Problems such as deterioration of the adhesive strength and separation of the porous film layer or deformation of the filter itself occurred.

Accordingly, it is necessary to develop a material capable of securing the durability of the filter while realizing the desired filtration efficiency.

The present invention is to provide a polymer film for an air filter having improved durability with excellent adhesion to a nonwoven fabric layer, including a polytetrafluoroethylene film layer having a specific crystallinity, and a method for manufacturing the same.

According to the present invention, a polytetrafluoroethylene film layer having a crystallinity of 85% or more measured at 330 ± 3 ° C according to differential scanning calorimetry (DSC) and one side of the polytetrafluoroethylene film layer It provides a polymer film for an air filter, comprising a non-woven layer, the adhesive strength according to Finat FTM 1 measured between the interface of the two layers is 100 gf / inch to 150 gf / inch.

In addition, according to the present invention, there is provided a method for producing a polymer film for the air filter described above.

Hereinafter, a polymer film for an air filter according to embodiments of the present invention will be described in detail.

Prior to that, the terminology is only for referring to a specific embodiment, and is not intended to limit the present invention, unless expressly stated in the specification.

Singular forms used herein include plural forms unless the phrases clearly indicate the opposite.

As used herein, the meaning of 'include' embodies a specific characteristic, region, integer, step, action, element, and / or component, and other specific characteristic, region, integer, step, action, element, component, and / or group. It does not exclude the existence or addition of.

In addition, in this specification, terms including an ordinal number such as 'first' and 'second' are used for the purpose of distinguishing one component from other components, and are not limited by the ordinal number. For example, within the scope of the present invention, the first component may also be referred to as the second component, and similarly, the second component may be referred to as the first component.

In addition, in the present specification, an arbitrary configuration is formed on the “upper (or lower)” or “upper (or lower)” of the substrate, that any configuration is formed in contact with the upper surface (or lower surface) of the substrate. It does not mean that it does not include another structure between the said substrate and any structure formed on (or under) the substrate.

Typically, the polymer film for air filters is manufactured by bonding a porous film to a support such as a non-woven fabric, but when a separate adhesive is used in the bonding process, there is a problem in that filtration efficiency is significantly reduced. In addition, when the filter is placed under conditions of high temperature and high humidity, there is a problem in that the adhesive strength of the adhesive is lowered to separate the film layer or the filter itself is deformed.

When the present inventor uses a polytetrafluoroethylene film layer having a specific crystallinity value, it is confirmed that a lower nonwoven fabric layer and an excellent adhesive force can be realized without using a separate adhesive, and excellent durability is improved while implementing excellent filtration efficiency. A polymer film for air filters was developed.

Ⅰ. For air filter  Polymer film

The polymer film for an air filter according to an embodiment of the present invention includes a polytetrafluoroethylene film layer (hereinafter referred to as "PTFE film layer") and a nonwoven layer, wherein the nonwoven layer is the polytetrafluoro It is bonded to one side of the ethylene film layer.

The polymer film for an air filter according to an embodiment of the present invention includes a PTFE film layer having a crystallinity of 85% or higher measured at 330 ± 3 ° C according to differential scanning calorimetry (DSC), while satisfactory excellent filtration efficiency. The durability of the filter can be remarkably improved by adhering to the adjacent nonwoven layer and excellent adhesion.

In the present invention, the crystallinity of the PTFE film layer can be specifically measured according to the following method.

Preparation of the film layer of the present invention Using the same PTFE powder (sample 1: reference sample for calculating crystallinity) as a reference material, while heating at a rate of 10 ° C / min from 30 ° C to 400 ° C at a rate of 10 ° C / min, the unit of sample 1 The rate of energy change per mass was measured. The peak of the graph was derived based on the measurement results. As a result of examining the graph of Sample 1, two peaks were derived at about 330 ± 3 ℃ and about 340 ± 3 ℃.

Next, for the film specimen according to the present invention (Sample 2: This is a film that has been heat-set at a specific temperature to be described later), the area of the peak of the graph was calculated in the same manner as in Sample 1. Thereafter, the area ratios of the peaks of 330 ± 3 ° C and 340 ± 3 ° C of Sample 2 were calculated. Crystallinity (%) was derived with an area of 330 ± 3 ° C.

In the case of Sample 1, it is a reference material and has a crystallinity of less than 85%.

Perkinelmer, DSC 6000 may be used as the equipment used to measure the crystallinity.

The crystallinity of the PTFE film layer may be 85% to 98%, or 90% to 98%. When the crystallinity of the PTFE film layer satisfies 85% or more, the strength of the film layer may be improved, and the nonwoven fabric and adhesive strength may be improved. Accordingly, the manufacturing process of the air filter furnace is easy, and when applied as an air filter, it can have higher filtration efficiency and durability. On the other hand, when the crystallinity of the PTFE film layer is less than 85%, shrinkage easily occurs and the bonding process is not easy, and it is easily peeled off from the nonwoven fabric layer due to external impact, and the adhesive strength decreases, so that a lift-off phenomenon may occur during filter production. .

In the present invention, the PTFE film layer has pores with an average diameter of 0.3 µm to 2 µm, and a material larger than the pore size can be physically filtered. By including pores having an average diameter in the above range, it is possible to simultaneously realize excellent collection efficiency, pressure loss reduction, and pinhole generation reduction effect.

In this specification, the "average diameter" of pores refers to pores having a diameter of about 10 nm to about 300 µm contained in the film layer as a population, and their average diameters are measured. Specifically, air or nitrogen is passed through a porous PTFE film layer using a capillary flow porometer, and the pressure passing through the pores is measured to measure the pore size distribution, of which a size of about 10 nm to about 300 μm is measured. The branch pores are used as a population, and the average value of the pores having a diameter in the above range is measured. In addition, the diameter of each individual pore means the longest length of the diameter of the pores identified in the cross section.

As described above, since the polytetrafluoroethylene film layer includes pores of 0.3 μm to 2 μm, the polytetrafluoroethylene film layer may be a porous film layer. More specifically, the polytetrafluoroethylene film layer may be a polytetrafluoroethylene porous film layer having a porosity of 90% to 95%.

Meanwhile, the polytetrafluoroethylene film layer may have an elongation ratio (TD / MD) of 120 to 420, preferably 180 to 300. The TD and MD of the film mean a machine direction (MD) and a transverse direction (TD) of the film, respectively.

Since the polytetrafluoroethylene film layer has the above-described stretching ratio, it can be applied as an air filter, so that it can satisfy appropriate pore characteristics, and is also desirable to realize the desired degree of crystallinity.

The thickness of the PTFE film layer may be 5㎛ to 20㎛, preferably 10㎛ to 15㎛. By satisfying the thickness in the above range, while maintaining proper durability, it is possible to simultaneously realize an excellent collection efficiency, pressure loss reduction, and pinhole generation reduction effect.

In the present invention, two or more PTFE film layers may be included, and two or more PTFE film layers may be stacked continuously, and may be stacked alternately with the nonwoven fabric layer. When the PTFE film layer is included in a multi-layer, each film layer may satisfy the aforementioned thickness.

The polymer film for an air filter according to an embodiment of the present invention includes a nonwoven layer bonded to one surface of the PTFE film layer having the specific crystallinity described above.

The non-woven fabric layer may be formed in a multi-layer as a material that functions as a support so that a filter is applied to a product to implement proper durability, and may be bonded to the upper and lower surfaces of the PTFE film layer, respectively.

The non-woven fabric layer may include one or more polymers selected from the group consisting of polyethylene terephthalate and polyethylene, preferably a core-shell particle type polymer composed of the polyethylene terephthalate core and polyethylene shell structure. It can contain. By including the polymer, it is suitable to implement a desired degree of adhesion to the adjacent PTFE layer.

The thickness of the nonwoven layer may be 100 μm to 200 μm, and preferably 130 μm to 170 μm. By satisfying the thickness in the above range, proper durability can be maintained. When the non-woven fabric layer is formed in a multi-layer, the thickness may mean the total sum of each non-woven fabric layer.

The polymer film for an air filter according to an embodiment of the present invention satisfies the adhesive strength according to the Finat FTM 1 standard measured between the above-described PTFE film layer and the nonwoven fabric layer, 100gf / inch to 150gf / inch, and accordingly The durability of the filter is further improved.

The adhesive force measured according to the Finat FTM 1 criterion was specifically evaluated for the adhesive strength by peeling the nonwoven layer at an angle of 180 ° at a rate of 300 mm / min with respect to the polymer film specimen (width 1 inch * length 20 cm). The adhesive force was calculated by measuring the average length of 100 mm. The time adhesion during peeling is continuously measured for 100 mm, and the average value of these values is calculated as the adhesion.

When the adhesive force between the PTFE film layer and the nonwoven fabric layer is less than 100 gf / inch, the problem of separating the two layers occurs when manufacturing with a filter, and when it exceeds 150 gf / inch, the pores are deformed and the appearance may be uneven. , This may result in non-uniform collection efficiency and pressure loss. The adhesive strength may preferably be 110 gf / inch to 140 gf / inch, and further improve the durability of the filter within the range.

Hereinafter, the structure of the polymer film 10 for an air filter according to embodiments of the present invention will be described in detail with reference to the drawings.

1 schematically shows a cross-sectional structure of a polymer film 10 for an air filter according to an embodiment of the present invention.

According to Figure 1, the air filter polymer film 10 includes two non-woven fabric layer, the first non-woven fabric layer 210, the PTFE film layer 100 and the second non-woven fabric layer 220 is sequentially stacked structure to be.

Ⅱ. For air filter  Manufacturing method of polymer film

According to the present invention, there is provided a method for manufacturing a multi-layer film for an air filter described above.

The method of manufacturing a polymer film for an air filter according to an embodiment of the present invention is performed by forming a PTFE unsealed sheet, stretching and heat-setting it to form a film layer, and then bonding the nonwoven fabric layer.

First, the step of mixing the polytetrafluoroethylene powder with a lubricant.

In the present invention, in order to form the PTFE layer, a composition in which polytetrafluoroethylene powder and a lubricant are mixed may be used, and a mixed solvent and other additives may be included as necessary.

The polytetrafluoroethylene powder, the material used in the porous filter field can be used without particular limitation. As commercially available products, 650J from MCF, CD145E from AGC, and the like can be used.

The lubricant may be a material used in the porous filter field without particular limitation. Preferably as a liquid lubricant, for example, Isoparaffinic Hydrocarbon Solvent can be used. As a commercially available product, Isopar H, Isopar L, Isopar G, Isopar M, and the like can be used, and preferably Isopar H can be used. Preferably, the polytetrafluoroethylene powder has a specific gravity of 2.15 or more and 2.25 or less.

The composition for forming the PTFE layer may be mixed with 20 to 30 parts by weight of a lubricant, preferably 24 to 28 parts by weight with respect to 100 parts by weight of polytetrafluoroethylene powder. By using a composition for forming a PTFE film layer that satisfies the above content range, it is possible to exhibit specific properties desired by the present invention through extrusion, rolling, drying, and heat fixing steps described later.

A method of manufacturing a polymer film for an air filter according to an embodiment of the present invention includes extruding the mixture to form a green sheet.

The extrusion and rolling steps can be applied without particular limitations to the method applied in the art. For example, the extrusion step is a step of manufacturing a preformed PTFE block in a sheet form, and may be performed by extruding under conditions of 30 ° C to 70 ° C, preferably 40 ° C to 60 ° C. In addition, it may be carried out under the conditions of extrusion pressure 200Mpa to 350Mpa.

In addition, the rolling step is a step of pressing the sheet with a roller (including an upper roller and a lower roller) in order to make the sheet produced in the extrusion step to an appropriate thickness, 30 ° C to 70 ° C, preferably 40 ° C to 60 ° C It can be carried out under ℃ conditions.

In the method of manufacturing a multi-layer film for an air filter according to an embodiment of the present invention, after the extrusion and rolling steps, may further include a step of drying.

In the drying step, a method applied in the art may be applied without particular limitation. For example, the drying step may be performed for 30 seconds to 60 seconds under conditions of 170 ° C to 250 ° C.

When two or more PTFE layers according to the present invention are included and they are successively stacked, the extrusion and rolling steps are performed several times according to the number of layers, and they are formed through the steps of laminating and stretching them, or preformed into a multi-layer It may be formed and formed through extrusion, rolling, and stretching.

In the method of manufacturing a multi-layer film for air filters according to an embodiment of the present invention, the step of stretching the dried sheet is performed.

The stretching step may be performed at an appropriate stretching ratio in consideration of the final porosity, final thickness of the desired PTFE film layer, and durability of the film. For example, it may be performed by stretching 20 to 35 times at 280 ° C to 320 ° C in the TD direction. Preferably it can be carried out by stretching 25 to 30 times at 300 ℃ to 310 ℃. Further, it may be performed by stretching 5 to 15 times at 280 ° C to 320 ° C in the MD direction. It may be preferably performed by stretching at 300 ° C to 310 ° C at 6 to 12 times or 8 to 10 times.

Further, within the stretching ratio, the stretching ratio (TD / MD) of the PTFE film layer may be stretched to have 120 to 420. Preferably it may be stretched to have a draw ratio (TD / MD) of 180 to 300.

Since the polytetrafluoroethylene film layer has the above-described stretching ratio, it can be applied as an air filter, so that it can satisfy appropriate pore characteristics, and is also desirable to realize the desired degree of crystallinity.

In the method of manufacturing a multi-layer film for an air filter according to an embodiment of the present invention, a step of heat-setting the film that has undergone the stretching process may be performed. Through the heat setting step, the green sheet is sintered, so that the crystallinity desired by the present invention can satisfy the above-described average pore size and thickness range, and in particular, it is possible to realize excellent adhesion with an adjacent lower nonwoven layer.

The heat setting step is performed at 370 ° C to 420 ° C, and preferably can be performed at 380 ° C to 410 ° C or 380 ° C to 400 ° C, and is performed under the above temperature conditions, to differential scanning calorimetry (DSC). Accordingly, a polytetrafluoroethylene film layer having a crystallinity measured at 330 ± 3 ° C of 85% or more may be formed.

When the heat setting step is carried out at a temperature of less than 370 ℃, it is difficult to implement the degree of crystallinity of the PTFE layer desired by the present invention, and accordingly, the adhesive force between the PTFE layer and the nonwoven fabric layer in the polymer film for air filters that is finally manufactured will be reduced. Can be. In addition, when it exceeds 420 ° C, film appearance may be uneven due to an excessive temperature difference from a subsequent step (for example, wrinkles may be generated in the film due to a temperature difference when the heat-set film exits the outlet). Yes), the film may melt and break.

The heat setting step may be performed for 5 seconds to 20 seconds, preferably 10 seconds to 15 seconds.

The PTFE film layer that has undergone the heat setting step may include pores having an average diameter of 0.3 μm to 2 μm. By including pores having an average diameter in the above range, it is possible to simultaneously realize excellent collection efficiency, pressure loss reduction, and pinhole generation reduction effect. In addition, the PTFE film layer subjected to the heat setting step may be a polytetrafluoroethylene porous film layer having a porosity of 90% to 95%.

Finally, the step of bonding the nonwoven fabric layer to any one side of the PTFE film layer prepared through the heat setting. The non-woven fabric layer may be used without limitation as previously described in the air filter polymer film.

In the bonding step, a method applied in the art may be applied without particular limitation. For example, it may be carried out at 150 ℃ to 200 ℃, preferably 170 ℃ to 185 ℃. It is bonded within the temperature range to enable proper adhesion.

When the polymer film for an air filter according to the present invention includes two or more nonwoven layers, it can be produced by repeatedly performing the above-mentioned bonding step.

The polymer film for an air filter according to the present invention manufactured through the above-described steps satisfies 100 gf / inch to 150 gf / inch of adhesive strength according to Finat FTM 1 between the PTFE film layer and the interface of the nonwoven fabric layer. It can realize excellent durability even when placed in various environments when used.

The polymer film for an air filter according to the present invention may include a polytetrafluoroethylene film layer having a specific crystallinity and realize excellent durability with excellent adhesion to a nonwoven fabric layer.

In addition, the polymer film for an air filter according to the present invention can exhibit excellent collection efficiency.

1 schematically shows a cross-sectional structure of a polymer film 10 for an air filter according to an embodiment of the present invention.

Hereinafter, preferred embodiments are presented to help understanding of the invention. However, the following examples are only for illustrating the invention, and the invention is not limited thereto.

Example  And Comparative example

Manufacturing example  : PTFE Film layer  Forming composition

(1) Production Example 1

26 parts by weight of Isoparaffinic Hydrocarbon Solvent (Isopar H) was mixed with 100 parts by weight of polytetrafluoroethylene fine powder (MCF, 650J, SSG 2.16) to prepare a composition for forming a PTFE film layer (A-1).

(2) Production Example 2

With respect to 100 parts by weight of polytetrafluoroethylene fine powder (AGC, CD145E, SSG 2.19), 23 parts by weight of Isoparaffinic Hydrocarbon Solvent (Isopar H) was mixed to prepare a composition for forming a PTFE film layer (A-2).

Example  1: Preparation of polymer film

Using the composition for forming a PTFE film layer (A-1) of Preparation Example 1, the resultant was extruded at 50 ° C to prepare a green sheet. The green sheet was rolled at a temperature of 50 ° C. to have a thickness of 10 to 40% with respect to the extruded thickness.

After rolling, a process of drying at 200 ° C. for 10 seconds was performed. Next, a process of stretching at 300 ° C in the MD direction to 9 times and in the TD direction at 300 ° C at 30 times was performed. The step of heat-setting the stretched sheet at 390 ° C. for 20 seconds was performed.

A nonwoven fabric layer was disposed on the upper and lower portions of the heat-fixed PTFE film layer, and bonded to 180 ° C to prepare a polymer film for an air filter.

The multi-layer film 10 for air filters manufactured according to the above method has a structure shown in FIG. 1 (a).

Example  2

In Example 1, a polymer film for an air filter was prepared in the same manner as in Example 1, except that the sheet stretched in the heat setting step was heat-set at 400 ° C. for 20 seconds.

Example  3

In Example 1, the polymer film for air filters was prepared in the same manner as in Example 1, except that the composition for forming the film layer of Preparation Example 2 was used and the sheet stretched in the heat setting step was heat-set at 400 ° C. for 20 seconds. It was prepared.

Comparative example  One

In Example 1, a polymer film for air filters was prepared in the same manner as in Example 1, except that the composition for forming the film layer of Preparation Example 2 was used and the heat setting step was not performed.

Comparative example  2

In Comparative Example 1, a polymer film for an air filter was prepared in the same manner as in Comparative Example 1, except that the sheet stretched in the heat setting step was heat-set at 350 ° C. for 20 seconds.

Comparative example  3

In Comparative Example 1, a polymer film for an air filter was prepared in the same manner as in Comparative Example 1, except that the sheet stretched in the heat setting step was heat-set at 360 ° C. for 20 seconds.

Comparative example  4

In Example 1, a polymer film for an air filter was prepared in the same manner as in Example 1, except that the sheet stretched in the heat setting step was heat-set at 350 ° C for 20 seconds.

Comparative example  5

In Example 1, a polymer film for an air filter was prepared in the same manner as in Example 1, except that the sheet stretched in the heat setting step was heat-set at 365 ° C. for 20 seconds.

Experiment method

(1) Measurement of crystallinity of polytetrafluoroethylene film layer

Preparation of the film layer of the present invention The same PTFE powder as used (Sample 1 (about 5-10 mg), powder used in Preparation Example 1) was used as a reference material, and the rate of 10 ° C./min from about 30 ° C. to 400 ° C. While heating to, the energy change rate per unit mass of Sample 1 was measured. As a result of the measurement, the peak of the graph was derived. For the film specimen according to the present invention (Sample 2, which is a film that has been heat-set at a specific temperature to be described later), areas of about 330 ± 3 ° C and 340 ± 3 ° C peaks were calculated in the same manner as in Sample 1. Thereafter, the crystallinity (%) was derived from the area ratio at 330 ± 3 ° C.

Perkinelmer, DSC 6000 was used as the equipment used to measure the crystallinity.

(2) Evaluation of adhesion

With respect to the polymer film for air filters prepared according to Examples and Comparative Examples, the adhesive force between the PTFE layer and the interface of the nonwoven fabric layer was made into a 1 inch wide 20 cm specimen according to Finat FTM 1 method, and then one nonwoven fabric at an angle of 180 °. The force was measured when the PTFE layer was peeled while peeling off at a speed of 300 mm / min. The results are shown in Table 1 below.

(3) Filter durability evaluation

With respect to the polymer film for air filters prepared according to Examples and Comparative Examples, after bending to produce a filter, pressure of 40 mmAq was applied, and interlayer pushing or peeling was confirmed. Table 1 shows the results.

division PFFE layer Adhesion
(gf / inch) Durability evaluation
(Peeling off) Mean pore
(㎛) Crystallinity
(%) Example 1 0.4 ~ 0.5 90 110 X Example 2 0.4 ~ 0.5 98 140 X Example 3 0.5 ~ 0.6 90 110 X Comparative Example 1 0.5 ~ 0.6 0 20 O Comparative Example 2 0.5 ~ 0.6 30 50 O Comparative Example 3 0.5 ~ 0.6 50 70 O Comparative Example 4 0.4 ~ 0.5 30 50 O Comparative Example 5 0.4 ~ 0.5 70 90 O

As can be seen from Table 1, when the crystallinity of the PTFE film layer is outside the range of the present invention, it was confirmed that the peeling was easily performed and the durability was remarkably reduced. Regarding the durability evaluation, when the peeling process easily occurs during the bending process or the interlayer pushing phenomenon occurs, the filter efficiency or the differential pressure characteristic is also significantly reduced, so the application life of the air filter as a comparative example is short.

10: air filter polymer film (10)
100: PTFE film layer
200 (210, 220): non-woven fabric layer

Claims (11)

A polytetrafluoroethylene film layer having a crystallinity of 85% or more measured at 330 ± 3 ° C. according to differential scanning calorimetry (DSC); And
Including; non-woven fabric layer bonded to any one side of the polytetrafluoroethylene film layer;
A polymer film for an air filter having an adhesive strength of 100 gf / inch to 150 gf / inch according to Finat FTM 1 measured between the interfaces of the two layers.
According to claim 1,
The polytetrafluoroethylene film layer has a crystallinity of 85% to 98%, a polymer film for an air filter.
According to claim 1,
The polytetrafluoroethylene film layer includes pores having an average diameter of 0.3 μm to 2 μm, a polymer film for an air filter.
According to claim 1,
The thickness of the polytetrafluoroethylene film layer is 5㎛ to 20㎛, polymer film for air filters.
According to claim 1,
The nonwoven layer comprises at least one member selected from the group consisting of polyethylene terephthalate and polyethylene, a polymer film for an air filter.
According to claim 1,
The thickness of the non-woven fabric layer is 100㎛ to 200㎛, polymer film for air filters.
According to claim 1,
A polymer film for an air filter further comprising a nonwoven layer on the other side of the polytetrafluoroethylene film layer.
Mixing the polytetrafluoroethylene powder with a lubricant;
Extruding the mixture to form a green sheet;
Stretching the sheet;
Heat-setting the stretched sheet at 370 ° C to 420 ° C to form a polytetrafluoroethylene film layer having a crystallinity of 85% or higher measured at 300 ± 3 ° C according to differential scanning calorimetry (DSC); And
A method of manufacturing a polymer film for an air filter comprising a; bonding a nonwoven fabric layer to any one side of the polytetrafluoroethylene film layer.
The method of claim 8,
The mixing step, polytetrafluoroethylene powder is mixed with 20 parts by weight to 30 parts by weight of a lubricant with respect to 100 parts by weight, a method for producing a polymer film for an air filter.
The method of claim 9,
The stretching step is performed at 20 to 35 times at 280 ° C to 380 ° C in the TD direction, a method for producing a polymer film for an air filter.
The method of claim 8,
The stretching step
A method of manufacturing a polymer film for air filters, which is performed 5 to 15 times at 280 ° C to 320 ° C in the MD direction.

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