KR20140074751A - PTFE membrane having porosity and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a porous PTFE separation membrane and a manufacturing method thereof and, more specifically, to a porous PTFE separation membrane which is drastically improved of strength; capable of performing at high pressures while maintaining a stable form; capable of preventing a blockage of pores or air porosity by preventing the strain of a supporting body during a process; capable of drastically enhancing the penetration flux by preventing a decrease in valid membrane area; capable of increasing the lifespan of a PTFE separation membrane at the same time satisfying an excellent particle removal rate; and capable of reducing the production costs by replacing the supporting bodies applied on both surfaces of a PTFE elongation sheet.

Description

TECHNICAL FIELD [0001] The present invention relates to a porous PTFE separator,

 The present invention relates to a porous PTFE separation membrane and a method for producing the same, and more particularly, to a porous PTFE separation membrane capable of improving the permeation flow rate and securing an excellent particle removal rate while improving the strength of the PTFE separation membrane.

Conventionally, a porous body made of polytetrafluoroethylene (hereinafter referred to as "PTFE ") not only has excellent chemical resistance, heat resistance, weather resistance, and nonflammability but also has properties such as non-stickiness and low friction coefficient. Moreover, since it is a porous structure, it is also excellent in transparency, flexibility, flexibility, trapping and filtering of fine particles, and the like. Therefore, the material made of PTFE is used in a wide range of fields such as filtration of fine chemicals and filters for wastewater treatment.

 Among them, the PTFE filter medium mainly consists of a paste composed of a mixture of PTFE fine powder and a lubricant, which is rolled through a rolling process between the two rollers, formed into a sheet state, and after the lubricant is removed, Technology, that is, a method for producing a PTFE flat membrane, is well known.

Specifically, the PTFE porous body produced by stretching PTFE has a fine structure composed of a plurality of fine fibrils (fine fibers) and a plurality of nodes (nodules) connected to each other by the fibrils, and this fine structure is continuous Thereby forming a porous porous structure. At this time, the porous PTFE porous body can arbitrarily set the porous structure such as the pore diameter and porosity by controlling the stretching conditions.

On the other hand, the PTFE porous body exhibits high tensile strength. However, since it is manufactured by stretching to adjust the pore diameter and porosity, it is manufactured from several nanometers to several tens of nanometers in thickness. Should be.

Accordingly, conventionally, as shown in FIG. 1, the supports 20 and 30 are laminated on both sides of the PTFE stretched sheet 10 to secure strength and maintain the shape. However, when the supports 20 and 30 are applied to the both surfaces of the PTFE stretched sheet 10 in order to secure strength and maintain the shape, the tilting phenomenon of the supports 20 and 30 due to a momentary high- And is pressed onto the surface of the PTFE stretched sheet 10 to reduce the effective membrane area, thereby significantly reducing the permeate flow rate and significantly reducing the life of the membrane.

SUMMARY OF THE INVENTION The present invention has been conceived to solve the problems as described above. It is an object of the present invention to improve the strength of a PTFE separator to exhibit stable performance even under high pressure conditions, It is possible to prevent the degradation of porosity and thereby significantly improve the permeation flow rate, to prolong the lifetime of the PTFE separation membrane, to satisfy the excellent particle removal rate at the same time, to replace the support applied to both surfaces of the PTFE stretched sheet, And to provide a porous PTFE separation membrane.

In order to solve the above-described problems,

A porous PTFE separation membrane comprising at least two porous PTFE stretched sheets laminated in a PTFE separation membrane, and at least one fluorinated mesh layer between the porous PTFE stretched sheets laminated do.

 According to a preferred embodiment of the present invention, the fluorine-based mesh layer may have a melting point lower than the melting point of PTFE by 30 ° C or more.

According to another preferred embodiment of the present invention, the fluorine-based mesh layer is formed of at least one selected from the group consisting of perfluoroalkoxy (PFA), florinate ethylene propylene (FEP), and ethyltetrafluoroethylene (ETFE) . ≪ / RTI >

According to another preferred embodiment of the present invention, the fluorine-based mesh layer may be 50 to 500 mesh.

According to another preferred embodiment of the present invention, the porous PTFE stretched sheet to be laminated may have an average pore size of 0.05 to 5.0 탆.

According to another preferred embodiment of the present invention, the average thickness of the porous PTFE stretched sheet to be laminated may be 20 to 60 占 퐉.

 According to another preferred embodiment of the present invention, the porous PTFE separation membrane comprises: a first porous PTFE stretched sheet; A fluorine-based mesh layer laminated on the first porous PTFE stretched sheet; And a second porous PTFE stretched sheet laminated on the fluorine-based mesh layer, wherein the first porous PTFE stretched sheet and the second porous PTFE stretched sheet have a symmetric shape with a difference in average pore size of 0 to 0.05 占 퐉 have.

According to another preferred embodiment of the present invention, the porous PTFE separation membrane comprises: a first porous PTFE stretched sheet; A fluorine-based mesh layer laminated on the first porous PTFE stretched sheet; And a second porous PTFE stretched sheet laminated on the fluorine-based mesh layer, wherein the first porous PTFE stretched sheet and the second porous PTFE stretched sheet have an asymmetric shape with an average pore size difference of 0.1 to 5.0 占 퐉 have.

According to another preferred embodiment of the present invention, the total thickness of the porous PTFE stretched sheet to be laminated may be 50 to 140 탆.

According to another preferred embodiment of the present invention, the thickness of the fluorine-based mesh layer may be 100 to 500 mu m.

According to another preferred embodiment of the present invention, the porous PTFE separator may have a strength of 180 MPa or more.

According to another preferred embodiment of the present invention, the porous PTFE separator may have an IPA permeability of 22,000 LMH (25 ° C, 1 bar) or more and a removal rate of 90% or more for particles having a particle diameter of 0.2 μm or more.

The present invention also provides a filter assembly comprising the porous PTFE separation membrane described above.

The present invention also provides a method for producing a porous PTFE stretched sheet, comprising the steps of: (1) preparing a porous PTFE stretched sheet; (2) a step of laminating the prepared porous PTFE stretched sheet in at least two or more layers and inserting at least one fluorine mesh between the porous PTFE stretched sheets laminated; And (3) thermally adhering and laminating the laminated porous PTFE stretched sheet and the fluorine mesh together.

According to a preferred embodiment of the present invention, the fluorine-based mesh may have a melting point lower than the melting point of PTFE by 30 ° C or more.

According to another preferred embodiment of the present invention, the fluorine-based mesh layer is formed of at least one selected from the group consisting of perfluoroalkoxy (PFA), florinate ethylene propylene (FEP), and ethyltetrafluoroethylene (ETFE) . ≪ / RTI >

According to another preferred embodiment of the present invention, the thermal bonding may satisfy the following relational expression (1).

[Relation 1]

Fluorine Mesh Melting Point (占 폚) <Thermal Adhesion Temperature (占 폚) <PTFE Melting Point (占 폚)

According to another preferred embodiment of the present invention, the thermal bonding temperature may be 260 to 290 ° C.

 The porous PTFE separation membrane of the present invention is remarkably improved in strength, can stably maintain its shape under high pressure conditions and can exhibit stable performance, prevents the pores of the support from leaking during processing, The membrane area can be prevented from being reduced, the permeation flow rate can be remarkably improved, the life of the PTFE separation membrane can be increased, and at the same time, the excellent particle removal rate can be satisfied. In addition, it is possible to replace the support applied to both surfaces of the PTFE stretched sheet, thereby reducing manufacturing cost.

1 is a cross-sectional view of a porous PTFE separation membrane according to the prior art.
2 is a cross-sectional view of a porous PTFE separation membrane according to a preferred embodiment of the present invention.
3 is a schematic diagram of a compressor that can be used in the present invention.
4 is a schematic diagram of an extruder which can be used in the present invention.
5 is a schematic diagram of a calender roll that can be used in the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in more detail with reference to the accompanying drawings.

As described above, in the conventional porous PTFE separation membrane, the supporting members 20 and 30 are applied to both sides of the PTFE stretched sheet 10 in order to secure strength and maintain the shape, , 30, and is pressed onto the surface of the PTFE stretched sheet 10 to reduce the effective membrane area, thereby significantly reducing the permeate flow rate and significantly reducing the life of the membrane.

Accordingly, the present invention provides a PTFE separator having a multi-layer structure in which at least two porous PTFE stretched sheets are laminated, and at least one fluorine mesh layer is interposed between the porous PTFE stretched sheets. PTFE separator is provided to solve the above-mentioned problem. This makes it possible to improve the strength of the PTFE separator and to secure the excellent shape stability while preventing the clogging of the pores or the porosity due to the sagging phenomenon of the support during the process, thereby significantly improving the permeate flow rate and extending the life of the PTFE separator It is possible to replace the support applied to both surfaces of the PTFE stretched sheet at the same time and to reduce the manufacturing cost.

 2 is a cross-sectional view of a porous PTFE separation membrane according to an embodiment of the present invention. Referring to FIG. 2, the porous PTFE separation membrane according to an embodiment of the present invention includes porous PTFE stretch sheets 60 and 70, And a fluorine-based mesh layer 50 interposed therebetween. The porous PTFE stretched sheet is not limited to a two-layer structure as shown in FIG. 2. The porous PTFE stretched sheet may be a multilayer structure stacked in two or more layers, and at least one fluorine-based mesh layer is included between the multi- And serves to ensure excellent strength and shape stability.

 More preferably, as shown in FIG. 2, a first porous PTFE stretched sheet 70, a fluorinated mesh layer 50 laminated on the first porous PTFE stretched sheet 70, a fluorinated mesh layer And a second porous PTFE stretched sheet 60 laminated on the second porous PTFE sheet 50.

The porous PTFE stretched sheets 60 and 70 may have an average pore size of 0.05 to 5.0 μm, more preferably 0.1 to 1.0 μm.

Further, the thickness of each of the porous PTFE stretched sheets 60 and 70 may be 20 to 60 占 퐉, and the total thickness of the porous PTFE stretched sheets to be laminated is preferably 50 to 140 占 퐉. When the total thickness of the laminated porous PTFE stretched sheet is less than 50 탆, there is a disadvantage in that the particle collecting efficiency is low or roughness occurs on the surface of the joint separator due to the impregnation of the mesh to easily cause contamination of the membrane. There is a problem that the pressure difference is large and the flow rate is small.

 The first porous PTFE stretched sheet 70 and the second porous PTFE stretched sheet 60 which are laminated with the fluorine mesh layer 50 sandwiched therebetween may be symmetrical or asymmetric and the use of the porous PTFE separator used As shown in FIG.

When the first porous PTFE stretched sheet 70 and the second porous PTFE stretched sheet 60 stacked with the fluorine mesh layer 50 therebetween are symmetrical with respect to the average pore size difference of 0 to 0.05 占 퐉, It is suitable for pharmaceuticals, pharmaceuticals, biotechnology and the like. When the asymmetric type having an average pore difference of 0.1 to 5.0 μm is used, the flow rate is large and the service life is long. Lt; / RTI &gt;

The fluorine-based mesh layer 50 contained between the porous PTFE stretched sheets 60 and 70 which are laminated in multiple layers serves to improve the strength and ensure excellent form stability, and the porous PTFE stretch sheets 60 and 70 It is possible to prevent the pores from clogging and the porosity from being lowered, thereby significantly improving the permeate flow rate and increasing the lifetime of the PTFE membrane. In addition, the fluorine-based mesh layer 50 serves as a support as well as serves as a binder, and can be lapped through thermal fusion without using an adhesive. Accordingly, the fluorine-based mesh layer 50 preferably has a melting point lower than the melting point of PTFE by 30 ° C or more.

 The fluorine-based mesh layer 50 is not particularly limited as long as it is a fluorine-based one having excellent chemical resistance. More preferably, the fluorine-based mesh layer 50 is composed of a perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP), ethyltetrafluoroethylene Or mixed form.

Further, the fluorine-based mesh layer 50 may be 50 to 500 mesh. If the fluorine-based mesh layer 50 is less than 50mesh, the strength and shape stability of the fluorine-based mesh layer 50 are inferior. If the fluorine-based mesh layer 50 is more than 500mesh, the flow of the PTFE filter may be disturbed in the joint separator. The thickness of the fluorine-based mesh layer 50 is preferably 100 to 500 μm.

 The porous PTFE separator according to a preferred embodiment of the present invention satisfies the mechanical strength of 180 MPa or more and has an IPA permeability of 22,000 LMH (25 ° C, 1 bar) or more and a particle diameter of 0.2 μm or more It is possible to exhibit excellent filtration efficiency with a removal rate of 90% or more for the particles.

In addition, the porous PTFE separation membrane according to one preferred embodiment of the present invention can be used as a separation membrane of a filter assembly composed of a PTFE membrane, a mesh support, a housing, etc., and can be used for purification of semiconductor chemicals or other industrial wastewater treatment .

 Next, a method of manufacturing the porous PTFE separation membrane of the present invention will be described.

(1) preparing a porous PTFE stretched sheet; (2) a step of laminating the prepared porous PTFE stretched sheet in at least two or more layers and inserting at least one fluorine mesh between the porous PTFE stretched sheets laminated; And (3) thermally adhering and laminating the laminated porous PTFE stretched sheet and the fluorine mesh together.

 First, step (1) produces a porous PTFE stretched sheet. The porous PTFE stretched sheet can be usually produced by a method of producing a porous PTFE stretched sheet, and is not particularly limited.

However, more preferably, a paste can be prepared by first mixing a polytetrafluoroethylene (PTFE) powder and a liquid lubricant. The PTFE powder contained in the paste can be used without limitation as long as it is conventionally used in the PTFE separation membrane. Preferably, the average particle diameter of the PTFE powder is 300 to 500 탆, but is not limited thereto. The molecular weight and the like are not particularly limited, and commercially available products may be used. Examples thereof include Polyflon F-104 (Daikin Industries) and Fluon CD-123 (Asahi ICI Fluoropolymers Co., Ltd.).

The liquid lubricant contained in the paste is for performing smooth extrusion, calendering and preform formation while wetting the surface of the PTFE fine powder. The material is not particularly limited as long as it can be removed by means such as evaporation extraction by heat after forming into a sheet Do not. For example, as the liquid lubricant, various alcohols, ketones, esters, and the like may be used in addition to hydrocarbon oils such as liquid paraffin, naphtha, white oil, toluene, and xylene.

The paste may comprise 10 to 50 parts by weight of a liquid lubricant based on 100 parts by weight of polytetrafluoroethylene (PTFE) powder.

Next, the paste can be compressed and preformed in a compressor. The compressor can be used without limitation as long as it is usually used for compressing a polymer membrane. FIG. 3 is a schematic view of a compressor that can be used in the present invention. When the paste is introduced into the compressor for manufacturing a separation membrane 200, pressure is applied to form a paste into the preform 210. In this case, a preform having various cross sections can be manufactured according to the shape of the compressor, and the size of the preform can also be set according to conditions.

On the other hand, the temperature and the pressure inside the compressor can be set according to the condition of the compressor applied in the production of the conventional PTFE separator, and preferably the pressure can be performed at 18 to 25 ° C and 1 to 3 MPa.

Next, the preform may be extruded from an extruder. Specifically, the extruder which can be used in the present invention can be used without limitation as long as it is usually used for the production of a polymer membrane, and can be preferably a ram extruder. FIG. 4 is a schematic view of an extruder that can be used in the present invention. The preform is introduced into the extruder, and the extrudate is extruded through the interior of the extruder 300. In this case, the extrudate 310 having various cross sections may be manufactured according to the shape of the extruder 300, and may have a rod shape. The size of the extrudate can also be set according to the conditions. The extrusion conditions may be carried out under the conditions of a conventional PTFE separation membrane extrusion process, preferably at 35 to 75 DEG C and at a pressure of 1 to 25 MPa.

Next, a step of calendering the extruded extrudate into a sheet shape can be performed. 5 is a schematic view of a calender roll that can be used in the present invention, and when the extruded extrudate passes through a calender roll 400, it expands into a sheet shape 410. In this case, preferably, the sheet may have a thickness of 500 to 1000 mu m.

The calendered sheet can then be heated to remove the liquid lubricant. Specifically, the heating temperature of the sheet may be in the range of the temperature at which the liquid lubricant is removed, preferably 120 to 200 ° C.

Next, the sheet from which the liquid lubricant is removed can be stretched. It can be stretched by a conventional stretching method, more preferably 0.5 to 3 times, and can be biaxially stretched to 2 to 5 times after uniaxial stretching. More specifically, a conventional PTFE sheet is conveyed through a roller. In this case, the biaxial stretching can be performed using the speed difference between the rollers.

After the elongation process, pores generated by the blowing agent form nodes and fibrils, and additional pores are formed. Specifically, in the PTFE separation membrane, pores composed of a node and a fibril are formed through a stretching process, and the pores formed through the foaming agent are also extended in the heating step, so that a considerable number of nodes and fibrils can be generated.

The stretching temperature may also be 150 to 320 DEG C, but is not limited thereto.

Finally, the stretched PTFE separation membrane may be fired to prevent heat shrinkage. The firing temperature may be performed at 300 to 400 ° C for 10 seconds to 10 minutes.

In the step (2), the porous PTFE stretched sheet is laminated in at least two or more layers, and at least one fluorine mesh is inserted between the porous PTFE stretched sheets.

At least one or more fluorine-based meshes are inserted between the porous PTFE stretched sheets to improve the strength of the porous PTFE separator and to ensure excellent shape stability, and the fluorine mesh is inserted between the porous PTFE stretched sheets Accordingly, it is possible to prevent the pores from being clogged or the porosity from being lowered under the high pressure condition, thereby significantly improving the permeation flow rate and increasing the life of the PTFE membrane.

In addition, the inserted fluorine mesh can be used as a support as well as to secure strength, and can be lapped through heat fusion without using an adhesive separately. The fluorine-based mesh preferably has a melting point lower than the melting point of PTFE by 30 ° C or more. Considering that the melting point of PTFE is approximately 320 ° C, the melting point of the fluorine-based mesh may be 250 to 290 ° C have.

More preferably, the fluorine-based mesh layer is preferably prepared in the form of perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP), ethyltetrafluoroethylene (ETFE), or the like.

 In the step (3), the laminated porous PTFE stretched sheet and the fluorine mesh are thermally bonded together to form a laminate.

 The fluoric mesh serves as a support as well as a binder, and can be lapped through heat fusion without using an adhesive. Since the porous PTFE stretched sheet is required to be partially melted and laminated with a fluorine mesh while maintaining its shape, the heat bonding can proceed according to the condition of the following relational expression (1).

[Relation 1]

Fluorine Mesh Melting Point (占 폚) <Thermal Adhesion Temperature (占 폚) <PTFE Melting Point (占 폚)

In this case, the preferable heat bonding temperature may be 260 to 290 ° C.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples should not be construed as limiting the scope of the present invention, and should be construed to facilitate understanding of the present invention.

&Lt; Example 1 >

20 parts by weight of liquid paraffin (Exopon Mobil, product name: Isopar-H) as a liquid lubricant was mixed with 100 parts by weight of a PTFE fine powder having an average diameter of 500 탆 (DF-130, Solvay) to form a PTFE paste. The PTFE paste was compressed at a pressure of 3 MPa at 20 캜 to form a preform. The preform was introduced into the ram extruder, and the conditions inside the ram extruder were extrusion molded at a pressure of 2 MPa (20 kg / cm 2) and an extrusion process at 50 캜 to form a rod having an outer diameter of 10 mm. Thereafter, the extruded rod was passed through a calender roll to form a sheet, followed by a continuous process, and then the formed PTFE sheet was heated at 190 DEG C for 5 minutes to remove liquid paraffin. Continuously, the formed PTFE sheet was stretched at 200 占 폚 in the longitudinal direction by 2 times and 5 times in the transverse direction by the speed difference between the rollers to form nodes and fibrils, and then fired at 380 占 폚 to produce a porous PTFE stretched sheet Respectively.

Two sheets of the prepared porous PTFE stretched sheet (average pore size: 0.2 mu m, thickness: 40 mu m) were laminated, and a perfluoroalkoxy (PFA) mesh (400 mesh) having a melting point of 300 DEG C was placed between the porous PTFE stretched sheets. Two porous PTFE stretched sheets and a perfluoroalkoxy (PFA) mesh were laminated and bonded through calender rolls. At this time, the temperature of the calender roll was 250 ° C.

&Lt; Example 2 >

The procedure of Example 1 was repeated except that the perfluoroalkoxy (PFA) mesh located between the porous PTFE stretched sheets was 100mesh.

&Lt; Example 3 >

The same procedure as in Example 1 was carried out except that an ETFE mesh (400 mesh) having a melting point of 270 占 폚 was used as a mesh located between the porous PTFE stretched sheets.

<Example 4>

Except for using a porous PTFE stretched sheet (average pore size 0.45 mu m, thickness 40 mu m) and porous PTFE stretched sheet (average pore size 0.2 mu m, thickness 40 mu m) as a porous PTFE stretched sheet laminated in two layers, .

<Comparative Example>

A porous PTFE stretched sheet (average pore size: 0.2 μm, thickness: 80 μm) was subjected to the same procedure as in Example 1 except that a perfluoroalkoxy (PFA) mesh (400 mesh) .

<Experimental Example>

1. Tensile strength

The maximum stress in the MD direction was measured by using a universal testing machine (USM) for the porous PTFE separator prepared in Examples 1 to 4 and Comparative Example.

2. Measurement of permeability

The cartridge was mounted in a cartridge housing under a constant pressure of 25 ° C and 1 bar, and IPA was filtered, and the treatment flow rate was expressed as LMH.

3. Measurement of particle removal rate

The porous PTFE separation membranes prepared in Examples 1 to 4 and Comparative Examples were mounted on a permeable cell, IPA was filtered and sufficiently wetted, and a solution in which fine dust (ISO Fine Test Dust) was diluted in pure water was pumped through the pump housing Respectively. At this time, the number of particles having a size of 0.2 μm or more before and after passing through the filter was measured, and the change in the number of particles was expressed as a percentage.

division TD Tensile Strength, MPa
(stress at maximum load) IPA Transmittance (LMH)
(25 &lt; 0 &gt; C, 1 bar) Particle removal rate,%
(LPCs > 0.2um) Example 1 212.64 22,085 94.3 Example 2 207.81 22,372 93.1 Example 3 215.09 21,981 94.5 Example 4 214.65 27,338 91.2 Comparative Example 1 37.807 18,381 94.5

 As can be seen from Table 1, Example 1-4, in which the fluorine-based meshes were laminated between the porous PTFE stretched sheets having the multilayer stacked layers, showed significantly improved strength compared to the comparative example in which the fluorine mesh was applied to both surfaces of the porous PTFE stretched sheet So that excellent strength can be secured and the cost can be reduced.

 In addition, the IPA permeability was improved in Example 1-4, and the IPA permeability was further increased in Example 2 and Asymmetric Example 4 in which mesh size was small, compared with the Comparative Example where the effective membrane area was reduced due to the migration of the support.

Claims (18)

In the PTFE separator,
Layer structure in which at least two porous PTFE stretched sheets are laminated,
And at least one fluorine-based mesh layer is disposed between the porous PTFE stretched sheets. The method according to claim 1,
Wherein the fluorine-based mesh layer has a melting point lower than the melting point of PTFE by 30 占 폚 or more.

The method according to claim 1,
Wherein the fluorine-based mesh layer comprises at least one selected from the group consisting of perfluoroalkoxy (PFA), florinate ethylene propylene (FEP), and ethyltetrafluoroethylene (ETFE). The method according to claim 1,
Wherein the fluorine-based mesh layer has a thickness of 50 to 500 mesh. The method according to claim 1,
Wherein said porous PTFE-elongated sheet has an average pore size of 0.05 to 5.0 占 퐉. The method according to claim 1,
Wherein the average thickness of the porous PTFE stretched sheet laminated is 20 to 60 占 퐉. The method according to claim 1,
In the porous PTFE separation membrane,
A first porous PTFE stretched sheet;
A fluorine-based mesh layer laminated on the first porous PTFE stretched sheet; And
And a second porous PTFE stretched sheet laminated on the fluorine-based mesh layer,
Wherein the first porous PTFE stretched sheet and the second porous PTFE stretched sheet have a symmetrical shape with a difference in average pore size of 0 to 0.05 占 퐉. The method according to claim 1,
In the porous PTFE separation membrane,
A first porous PTFE stretched sheet;
A fluorine-based mesh layer laminated on the first porous PTFE stretched sheet; And
And a second porous PTFE stretched sheet laminated on the fluorine-based mesh layer,
Wherein the first porous PTFE stretched sheet and the second porous PTFE stretched sheet are asymmetric with an average pore size difference of 0.1 to 5.0 占 퐉. The method according to claim 1,
Wherein the total thickness of the porous PTFE stretched sheet laminated is 50 to 140 占 퐉. The method according to claim 1,
Wherein the fluorine-based mesh layer has a thickness of 100 to 500 占 퐉. The method according to claim 1,
Wherein the porous PTFE separation membrane has a strength of 180 MPa or more. The method according to claim 1,
Wherein the porous PTFE separation membrane has an IPA permeability of 22,000 LMH (25 DEG C, 1 bar) or more and a removal rate of 90% or more for particles having a diameter of 0.2 m or more. A filter assembly comprising the porous PTFE separation membrane of any one of claims 1 to 12. (1) preparing a porous PTFE stretched sheet;
(2) a step of laminating the prepared porous PTFE stretched sheet in at least two or more layers and inserting at least one fluorine mesh between the porous PTFE stretched sheets laminated; And
(3) a step of thermally bonding and laminating the laminated porous PTFE stretched sheet and the fluorine mesh together. 15. The method of claim 14,
Wherein the fluorine-based mesh has a melting point lower than the melting point of PTFE by 30 ° C or more. 15. The method of claim 14,
Wherein the fluorine-based mesh comprises at least one selected from the group consisting of perfluoroalkoxy (PFA), florinate ethylene propylene (FEP), and ethyltetrafluoroethylene (ETFE). Way. 15. The method of claim 14,
Wherein the thermal bonding satisfies the following relational expression (1): &quot; (1) &quot;
[Relation 1]
Fluorine Mesh Melting Point (占 폚) <Thermal Adhesion Temperature (占 폚) <PTFE Melting Point (占 폚) 15. The method of claim 14,
Wherein the thermal bonding temperature is 260 to 290 ° C.

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