KR102177292B1 - Porous fluorine resin sheet and method for prepararing0 the same - Google Patents

Abstract

The present invention relates to a fluorine-based resin porous membrane and a method for producing the same. In more detail, it provides a fluorine-based resin porous membrane excellent in breathability and tensile strength, and a method of manufacturing the same.

Description

Fluorine-based resin porous membrane and its manufacturing method TECHNICAL FIELD [POROUS FLUORINE RESIN SHEET AND METHOD FOR PREPARARING0 THE SAME}

The present invention relates to a fluorine-based resin porous membrane and a method for producing the same. In more detail, it provides a fluorine-based resin porous membrane excellent in breathability and tensile strength, and a method of manufacturing the same.

Porous membranes used in various fields are required to have high filtration efficiency and gas and liquid permeability. Accordingly, a method of increasing the amount of fluid passing through the pores under a specific pressure by uniformly adjusting the pore diameter distribution inside the porous membrane is known.

The fluororesin-based porous membrane may have properties such as high heat resistance, chemical stability, weatherability, non-combustibility, strength, non-adhesiveness, low friction coefficient, and low dielectric constant resulting from the fluorine-based resin itself. It may have properties such as flexibility, liquid permeability, and particle collection efficiency.

Among these fluorine-based resins, porous membranes made using polytetrafluoroethylene (PTFE), in particular, have high stability against various compounds, so gas and liquid are used in semiconductor-related fields, liquid crystal-related fields, and food and medical-related fields. It is widely used as a microfiltration filter (membrane filter) for a mixture of forms.

For such a PTFE porous membrane, a preform is generally made using a paste composed of a mixture of PTFE powder and a lubricant, and the preform is formed into a sheet form by a rolling or extrusion process, and then heat treated to remove the lubricant. It is manufactured by a paste compression method in which pores and fibrils are formed by stretching in the direction of the TD, and the thickness and pores suitable for use are formed by stretching in the TD direction.

As described above, the PTFE porous membrane manufactured by extruding and stretching a PTFE preform has a microstructure consisting of a plurality of microfibrils and a plurality of nodes connected to each other by the fibrils. It forms a porous structure of continuous porosity.

However, due to the characteristics of the porous membrane, the strength is weak, so that when an external force is applied, the pore structure is easily deformed, and thus durability is weak. In order to improve this, there is a method of increasing the durability by increasing the extrusion pressure during extrusion of the preform. However, in this case, since the porosity may decrease, it is insufficient to secure sufficient strength while maintaining breathability, and continuous research on this is still required.

In order to solve the above problems, the present invention provides a fluorine-based resin porous membrane having excellent breathability and strength, and a method of manufacturing the same.

In order to solve the above problem, according to an embodiment of the present invention,

Extruding a paste containing a fluorine-based resin and a lubricant to prepare a preform;

First rolling the preform to manufacture a first rolled sheet;

Drying the first rolled sheet;

Producing a second rolled sheet by second rolling the first rolled sheet; And

Stretching the second rolled sheet;

It provides a method for producing a fluorine-based resin porous membrane comprising a.

Also according to another embodiment of the present invention,

The air permeability is 1 to 50 seconds/100 mL,

Provides a fluorine-based resin porous membrane in which the ratio (MD/TD) of the tensile strength in the machine direction (MD) (unit: MPa) in the machine direction (MD) to the tensile strength in the transverse direction (TD) (unit: MPa) satisfies 1 to 2 do.

The fluorine-based resin porous membrane according to the present invention exhibits excellent breathability and excellent strength, in particular, strength in the TD direction, and exhibits characteristics with little difference in strength in the MD direction and the strength in the TD direction, so that it is resistant to degeneration, and is strong in both TD and MD directions. It can show even stiffness. Therefore, even when an external force is applied, it is not easily deformed and excellent air permeability can be maintained.

In addition, it is possible to efficiently produce a fluorine-based resin porous membrane that satisfies these characteristics without adding additional components to raw materials or greatly changing equipment.

Unless expressly stated in the specification, terminology is only intended to refer to specific embodiments and is not intended to limit the invention.

The singular forms used in the present specification also include plural forms unless the phrases clearly indicate the opposite.

The meaning of'comprising' as used herein specifies a specific characteristic, region, integer, step, action, element or component, and excludes the addition of another specific characteristic, region, integer, step, action, element, or component. It is not.

Hereinafter, a preferred embodiment is presented to aid the understanding of the present invention. However, the following examples are provided for easier understanding of the present invention, and the content of the present invention is not limited thereby.

A method of producing a green body using a resin composition containing a fluorine-based resin, rolling it, and stretching (stretching) it to form a porous film has been known previously. However, the fluorine-based resin porous membrane obtained by this process has poor strength due to its porosity, and thus there is a problem in that the membrane or pore structure is easily deformed even when a strong external force is applied.

Accordingly, as a result of continuous research by the present inventors, when the fluorine-based resin is extruded, rolled, and stretched after drying, if the rolling process is additionally performed and stretched, the density of the sheet increases and the node stiffness increases accordingly. As a result, it was confirmed that it was possible to provide a fluorine-based resin porous membrane having excellent breathability and strength, resulting in the present invention.

Hereinafter, a method of manufacturing a fluorine-based resin porous membrane according to an embodiment of the present invention will be described in detail for each step.

First, a preform is manufactured by extruding a paste containing a fluorine-based resin and a lubricant.

The fluorine-based resin is not particularly limited as long as it can be used for the porous membrane, and examples include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), and tetrafluoroethylene-hexa Fluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-chlorotrifluoroethylene copolymer (TFE/CTFE), and ethylene-chlorotrifluoroethylene copolymer (ECTFE) ) It may be one or more fluorine-based compounds selected from the group consisting of. Preferably, it may be polytetrafluoroethylene (PTFE).

In order to secure basic physical properties of the porous membrane, the fluorine-based resin may preferably have a number average molecular weight of 5,000,000 to 15,000,000 g/mol. And, in order to control the microporous properties of the porous membrane, one or more fluorine-based resins having different number average molecular weights may be mixed and used.

The paste containing the fluorine-based resin may include a lubricant together with the fluorine-based resin.

The lubricant is added to wet the surface of the fluorine-based resin and to smoothly perform compression, extrusion, and sheet processing.

The type of the lubricant is not particularly limited as long as it is a material that can be removed by means such as evaporation extraction by heat after sheet processing. For example, as the lubricant, liquid compounds such as liquid paraffin, naphtha, white oil, hydrocarbon oils such as toluene and xylene may be preferably used. In addition, as the lubricant, compounds well known as lubricants in the art, such as various alcohol compounds, ketone compounds, and ester compounds, may be used.

The content of the lubricant included in the paste is not particularly limited, and may vary depending on the type of lubricant and molding conditions. For example, the lubricant may be used in an amount of 5 to 50 parts by weight, 10 to 50 parts by weight, or 10 to 40 parts by weight based on 100 parts by weight of the heat-treated fluorine-based resin powder.

The paste containing the fluorine-based resin and lubricant is extruded to form a preform.

The preform is an intermediate for producing a fluorine-based resin porous membrane, and its shape is not particularly limited. For example, the preform may be prepared by compressing a paste including the fluorine-based resin and a lubricant by a conventional method such as a rolling method, and the thickness may be adjusted to be about 0.15 to about 2.5 mm.

In addition, in order to allow the extrusion process to proceed smoothly, the extrusion may be performed under a temperature of about 20 to about 80°C.

Next, the preform is first rolled to produce a first rolled sheet.

The first rolling is a step of first rolling the preform prepared above into a thin sheet. The first rolled sheet obtained by the first rolling may be rolled to have a thickness of about 100 μm to about 2 mm, but the present invention is not limited thereto, and the gap between the two rolls in the rolling roll is It can be rolled by means used in a normal rolling process, such as a method of adjusting and rolling to a desired thickness.

In addition, the temperature range of the first rolling is not particularly limited as long as it is a temperature capable of rolling, and may be performed at, for example, about 20 to about 70°C.

Next, the first rolled sheet is dried.

The drying process is a process for removing the lubricant contained in the first rolled sheet.

The drying temperature is not particularly limited as long as it is a temperature at which the lubricant can be removed, and it may be preferably dried at a temperature of about 150 to about 250°C. In addition, the drying time is not particularly limited as long as it is a time in which the lubricant can be completely removed.

Next, the dried first rolled sheet is second rolled to produce a second rolled sheet.

The second rolled sheet may be performed such that the thickness of the first rolled sheet before performing the second rolling process is reduced by about 5% to about 50%.

That is, the thickness reduction rate according to the following equation 1 is about 5% or more, or about 10% or more, or about 15% or more, or about 20% or more, and about 50% or less, about 45% or less, or about 40% or less It can be done if possible.

[Equation 1]

Thickness reduction rate (%) = (thickness of first rolled sheet-thickness of second rolled sheet) / thickness of first rolled sheet * 100

At this time, if the thickness reduction rate is too small, the effect of improving the strength by the second rolling process is insignificant, and if the thickness reduction rate is too large, fibrils are well generated from the node and not stretched, so that sufficient fibrils cannot be secured, and fracture may occur during stretching. In this respect, it is preferable to perform the second rolling process so as to have a thickness reduction rate in the above-described range.

On the other hand, since there is little difference in thickness before and after drying of the first rolled sheet, the thickness of the first rolled sheet in Equation 1 may be either before or after drying.

According to the manufacturing method of the fluorine-based resin porous membrane of the present invention, secondary rolling is performed before the first rolled sheet is dried and then stretched as described above, thereby increasing the sheet and node density. Accordingly, the tensile strength, particularly the tensile strength in the TD direction, is remarkably improved compared to the case of immediately stretching without secondary rolling or the case of continuously performing primary and secondary rolling and then drying and stretching.

On the other hand, in the second rolled sheet subjected to secondary rolling according to the present invention, the porosity of the sheet decreases compared to when the secondary rolling process is not performed, but nevertheless, the air permeability, which is an index to evaluate the actual permeability, is Rather, it showed an improved effect. This seems to be because, according to the manufacturing method of the present invention, the stiffness of the initially formed node is increased while the differentiation of the node is suppressed, and the length of the fibrils is increased, not the node differentiation by stretching. Accordingly, the resulting pore size increases, thereby reducing the porosity but greatly improving the air permeability.

In addition, the second rolling is not particularly limited as long as the rolling is possible, and may be performed at a temperature of, for example, about 20 to about 70°C.

Next, a step of stretching the second rolled sheet is performed.

The stretching may be performed by supplying the second rolled sheet to rollers rotating at different speeds. Further, the stretching may be performed in an oven using a tenter.

The stretching process may include both longitudinal (MD) stretching and transverse (TD) stretching, or may be performed in only one direction. When stretching in both directions, stretching in the longitudinal direction and the transverse direction may be performed sequentially or simultaneously.

The draw ratio at this time may be determined according to the use of the porous membrane. For example, the stretching may be performed by biaxial stretching of 2 to 10 times of longitudinal stretching and 2 to 50 times of transverse stretching of the second rolled sheet, but the present invention is not limited thereto.

Here, it may be preferable to perform the stretching near or below the melting point of the second rolled sheet in order to secure workability. For example, the stretching may be performed under a temperature of about 150 to about 360 °C.

The fluorine-based resin porous membrane obtained through the process of the above embodiment has excellent breathability and strength.

Accordingly, according to another embodiment of the present invention, the air permeability is 1 to 50 seconds/100 mL, and the tensile strength in the machine direction (MD) direction relative to the tensile strength (unit: MPa) in the transverse direction (TD) (unit: MPa) A ratio of) (MD/TD) to satisfy 1 to 2, provides a fluorine-based resin porous membrane.

The air permeability was measured using Toyoseiki's Gurley type Densometer (No. 158) according to the Japanese industrial standard JIS Gurley, and the tensile strength in the MD direction and the tensile strength in the TD direction were based on ASTM D638. It is measured by.

The fluorine-based resin porous membrane of the present invention may exhibit very excellent air permeability with air permeability of about 50 seconds/100 mL or less, or 45 seconds/100 mL or less, or about 40 seconds/100 mL or less, or about 30 seconds/100 mL or less. Since the air permeability is advantageous as the value is lower, the lower limit value is not particularly limited, but may be, for example, about 1 second/100 mL or more, or about 3 seconds/100 mL or more, or about 5 seconds/100 mL or more. Particularly, the fluorine-based resin porous membrane of the present invention can exhibit high air permeability even though it exhibits lower porosity than the conventional porous membrane.

In addition, the fluorine-based resin porous membrane of the present invention may have a maximum pore size of 150 to 5000 nm and an average pore size of 70 to 3000 nm.

In addition, the fluorine-based resin porous membrane of the present invention has a ratio of tensile strength in MD direction to tensile strength in TD direction (MD/TD) of about 1 or more, or about 1.05 or more, or about 1.1 or more, and about 2 or less, or about 1.8 or less, or about 1.5 or less, or about 1.4 or less, the difference between the tensile strength in the MD direction and the tensile strength in the TD direction is smaller than that of the conventional fluorine-based resin porous membrane. Therefore, as the ratio of tensile strength approaches isotropic, it is strong in deformation and can exhibit even stiffness in both the TD and MD directions.

According to an embodiment of the present invention, the fluorine-based resin porous membrane has a tensile strength in the MD direction measured by ASTM D638 of 50 to 200 MPa, or 70 within a range that satisfies the above-described air permeability and MD/TD tensile strength ratio. To 200 MPa, or 100 to 180 MPa, but the present invention is not limited thereto, and the tensile strength in the MD direction may be adjusted within a suitable range according to the use of the porous membrane.

In addition, The fluorine-based resin porous membrane may have a tensile strength in the TD direction of 30 to 200 MPa, or 50 to 180 MPa, or 70 to 170 MPa as measured by ASTM D638, but the present invention is not limited thereto, and the TD direction The tensile strength can be adjusted within a suitable range according to the use of the porous membrane.

According to an embodiment of the present invention, the fluorine-based resin porous membrane may have a porosity of 50 to 90%, or 50 to 80%, or 55 to 75%, but the present invention is not limited thereto, and the porosity is the use of the porous membrane. It can be adjusted in a suitable range according to.

According to an embodiment of the present invention, the fluorine-based resin porous membrane may have a thickness of 10 to 350 μm and a density of 0.1 to 1.5 g/cm 3, but the present invention is not limited thereto, and the thickness and density of the fluorine-based resin porous membrane are It can be adjusted within a suitable range according to the use of the porous membrane.

<Example>

Example 1

A paste was prepared by mixing 22 parts by weight of a liquid lubricant (product name: (ISOPARTM H FLUID; ExxonMobil Chemical Company)) with respect to 100 parts by weight of polytetrafluoroethylene resin CD145E (manufactured by AGC). A molded body was prepared.

The preform was rolled at a rate of 50 mm/min under a temperature of 50° C. to form a first rolled sheet having a thickness of about 300 μm. The manufactured first rolled sheet was heated and dried under a temperature of 200° C. to remove the lubricant.

Subsequently, the first rolled sheet from which the lubricant was removed was rolled at a rate of 50 mm/min at a temperature of 30° C. to form a second rolled sheet having a thickness of 270 μm.

The density of the second rolled sheet was 1.79 g/cm 3, and the porosity was 18.9%.

Subsequently, the second rolled sheet was stretched three times in the longitudinal direction (MD) at a temperature of 200° C. and adhered for about 30 s through a 360° C. Roll to obtain a 200 μm-thick porous membrane.

Example 2

Until the lubricant removal (drying) process was performed in the same manner as in Example 1.

Subsequently, the first rolled sheet from which the lubricant was removed was rolled at a rate of 50 mm/min at a temperature of 30° C. to form a second rolled sheet having a thickness of 240 μm.

The density of the second rolled sheet was 1.91 g/cm 3, and the porosity was 14.2%.

Subsequently, the second rolled sheet was stretched three times in the longitudinal direction (MD) at a temperature of 200° C. and adhered for about 30 s through a 360° C. Roll to prepare a 190 μm-thick porous membrane.

Example 3

Until the lubricant removal (drying) process was performed in the same manner as in Example 1.

Subsequently, the first rolled sheet from which the lubricant was removed was rolled at a rate of 50 mm/min at a temperature of 30° C. to form a second rolled sheet having a thickness of 180 μm.

The second rolled sheet had a density of 2.15 g/cm 3 and a porosity of 2.2%.

Subsequently, the second rolled sheet was stretched three times in the longitudinal direction (MD) at a temperature of 200° C. and closely adhered for about 30 s through a 360° C. Roll to prepare a 150 μm-thick porous membrane.

Example 4

In Example 2, a porous membrane was manufactured by performing the same process as in Example 2, except that the amount of the liquid lubricant was 26 parts by weight.

At this time, the density of the second rolled sheet was 1.71 g/cm 3, and the porosity was 16%.

Example 5

A paste was prepared by mixing 22 parts by weight of a liquid lubricant (product name: (ISOPARTM H FLUID; ExxonMobil Chemical Company)) based on 100 parts by weight of polytetrafluoroethylene resin 6J (manufactured by MDF). A molded body was prepared.

The preform was rolled at a rate of 50 mm/min under a temperature of 50° C. to form a first rolled sheet having a thickness of about 300 μm. The manufactured first rolled sheet was heated and dried under a temperature of 200° C. to remove the lubricant.

Subsequently, the first rolled sheet from which the lubricant was removed was rolled at a rate of 50 mm/min at a temperature of 30° C. to form a second rolled sheet having a thickness of 240 μm.

The density of the second rolled sheet was 1.61 g/cm 3, and the porosity was 22%.

Subsequently, the second rolled sheet was stretched three times in the longitudinal direction (MD) at a temperature of 300° C. and adhered for about 30 s through a 360° C. Roll to prepare a 200 μm thick porous membrane.

Comparative Example 1

A paste was prepared by mixing 22 parts by weight of a liquid lubricant (product name: (ISOPARTM H FLUID; ExxonMobil Chemical Company)) with respect to 100 parts by weight of polytetrafluoroethylene resin CD145E (manufactured by AGC). A molded body was prepared.

The preform was rolled at a rate of 50 mm/min under a temperature of 50° C. to form a first rolled sheet having a thickness of about 270 μm. The prepared first rolled sheet was heated and dried at a temperature of 50° C. to remove the lubricant.

The density of the first rolled sheet was 1.56 g/cm 3, and the porosity was 30%.

Subsequently, the first rolled sheet was stretched three times in the longitudinal direction (MD) at a temperature of 200° C. and adhered for about 30 s through a 360° C. Roll to prepare a 200 μm thick porous membrane.

Comparative Example 2

In Comparative Example 1, a porous membrane was manufactured by performing the same process as in Comparative Example 1, except that the amount of the liquid lubricant was 26 parts by weight.

At this time, the density of the first rolled sheet was 1.52 g/cm 3, and the porosity was 33%.

Comparative Example 3

In Comparative Example 1, the same process as in Comparative Example 1 was performed, except that 6J (manufactured by MDF) was used as a polytetrafluoroethylene resin instead of CD145E (manufactured by AGC), and the stretching temperature was set to 300°C. Thus, a porous membrane was prepared.

At this time, the density of the first rolled sheet was 1.45 g/cm 3, and the porosity was 38%.

Comparative Example 4

A paste was prepared by mixing 22 parts by weight of a liquid lubricant (product name: (ISOPARTM H FLUID; ExxonMobil Chemical Company)) with respect to 100 parts by weight of polytetrafluoroethylene resin CD145E (manufactured by AGC). The paste was extruded to prepare a preform. Was prepared.

The preform was rolled at a rate of 50 mm/min under a temperature of 50° C. to form a first rolled sheet having a thickness of about 300 μm. Subsequently, the first rolled sheet was rolled at a rate of 50 mm/min under a temperature of 30° C. to form a second rolled sheet having a thickness of 240 μm.

Subsequently, the second rolled sheet was heated and dried under a temperature of 200° C. to remove the lubricant.

The density of the second rolled sheet was 1.58 g/cm 3, and the porosity was 29%.

Subsequently, the second rolled sheet was stretched three times in the longitudinal direction (MD) under a temperature of 200° C. and adhered for 30 s through a 360° C. Roll to obtain a porous membrane having a thickness of 190 μm.

The main process conditions of the Examples and Comparative Examples are summarized and shown in Table 1 below.

Type of fluorine resin Lubricant content
(Part by weight) Rolling after drying (second rolling) Sheet thickness reduction rate due to the second rolling* Stretching temperature Example 1 CD145E 22 O 10% 200℃ Example 2 CD145E 22 O 20% 200℃ Example 3 CD145E 22 O 40% 200℃ Example 4 CD145E 26 O 20% 200℃ Example 5 6J 22 O 20% 300℃ Comparative Example 1 CD145E 22 X 0% 200℃ Comparative Example 2 CD145E 26 X 0% 200℃ Comparative Example 3 6J 22 X 0% 300℃ Comparative Example 4 CD145E 22 X
(Dry after second rolling) 20% 200℃

* Thickness reduction rate (%) = (thickness of the first rolled sheet-thickness of the second rolled sheet) / thickness of the first rolled sheet * 100

<Experimental Example>

The properties of the porous membranes prepared in Examples and Comparative Examples were evaluated by the following method.

1) pore size

The pore size was measured using Porous Materials Inc.'s Capillary Flow Porometer (Model No.: CFP-1500AE) equipment. The pore size of the porous membrane was measured by wetting the porous membrane with a Galwick liquid with a surface tension of 15.9, replacing all the pores of the porous membrane with Galwick liquid, and then measuring the flow of nitrogen gas obtained when flowing while increasing the pressure of the nitrogen gas. .

When the pore size of the porous membrane is large, the Galwick liquid filled in the pores is easily removed even by a small pressure nitrogen gas, whereas, when the pore size is small, the Galwick liquid is removed by the large nitrogen pressure. The pore size (average pore size and maximum pore size) was calculated using Equation 1 below.

[Equation 1]

D = 4·γ·cosθ/P

In Equation 1,

D means pore diameter,

γ means surface tension (15.9),

P means nitrogen pressure,

cosθ is 1 (the θ value is 0° due to the low surface tension of Galwick liquid).

2) air permeability

Air permeability was measured using Toyoseiki's Gurley type Densometer (No. 158) according to the Japanese industrial standard JIS Gurley measurement method.

In more detail, the time required for 100 mL of air to pass through a 1 square inch membrane under a constant air pressure of 4.8 inches (unit: second/100 mL) was taken as the air permeability.

3) Tensile strength

According to the measurement method of ASTM D638, tensile strength in the MD direction and the TD direction was measured using a Universal Test Machine (ZWICK's Roell Z010), respectively.

The results are shown in Table 2 below.

Ventilation
(Sec/100mL) Max/average
Pore size
(nm) Porosity of sheet before stretching (%) After stretching
membranous
Porosity (%) The tensile strength,
MD (MPa) The tensile strength,
TD (MPa) MD/TD Example 1 43 810/450 18.9 65 135 102 1.32 Example 2 38 830/471 14.2 65 168 142 1.18 Example 3 30 880/503 2.2 65 164 155 1.06 Example 4 15 1205/631 16 68 157 142 1.11 Example 5 9 2301/1303 22 72 75 57 1.32 Comparative Example 1 46 790/384 30 65 165 62 2.66 Comparative Example 2 20 1178/550 33 66 142 48 2.96 Comparative Example 3 10 1903/950 38 71 52 17 3.06 Comparative Example 4 41 780/383 29 63 155 43 3.60

Referring to Table 1, the fluorine-based resin porous membrane according to the embodiment of the present invention exhibited better air permeability despite the lower porosity than the comparative example. In addition, it was confirmed that the ratio of tensile strength (MD/TD) was 2 or less, the difference between MD tensile strength and TD tensile strength was small, and high TD tensile strength was shown.

On the other hand, it can be seen that the fluorine-based resin porous membranes of Comparative Examples 1 to 3, in which the second rolling was not performed before stretching, exhibited lower air permeability and tensile strength than the examples under equivalent conditions. In addition, it was found that Comparative Example 4, in which the first rolling and the second rolling were continuously performed and dried, had no effect of increasing the tensile strength. Accordingly, it can be seen that the process sequence of performing the second rolling also has an important effect on the increase in node stiffness and tensile strength.

Claims (11)

Extruding a paste containing a fluorine-based resin and a lubricant to prepare a preform;
First rolling the preform to produce a first rolled sheet;
Drying the first rolled sheet;
Producing a second rolled sheet by second rolling the first rolled sheet; And
Stretching the second rolled sheet;
Including,
The second rolling is performed so that the thickness reduction rate according to the following Equation 1 is 5 to 50%, a method for producing a fluorine-based resin porous membrane:
[Equation 1]
Thickness reduction rate (%) = (thickness of the first rolled sheet-thickness of the second rolled sheet) / thickness of the first rolled sheet * 100
The method of claim 1,
The fluorine-based resin is polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer Containing one or more fluorine-based compounds selected from the group consisting of coalescence (ETFE), tetrafluoroethylene-chlorotrifluoroethylene copolymer (TFE/CTFE), and ethylene-chlorotrifluoroethylene copolymer (ECTFE), Method for producing a fluorine-based resin porous membrane.
The method of claim 1,
The first rolling is performed so that the thickness of the first rolled sheet is 100 μm to 2 mm.
delete The method of claim 1,
The second rolling is performed so that the thickness reduction rate according to Equation 1 is 10 to 40%, a method of manufacturing a fluorine-based resin porous membrane.
The method of claim 1,
The stretching is performed under a temperature of 150 to 360 °C, a method for producing a fluorine-based resin porous membrane.
i) the air permeability is 1 to 50 seconds/100 mL,
ii) Porosity of a fluorine-based resin in which the ratio (MD/TD) of the tensile strength in the machine direction (MD) direction (unit: MPa) to the tensile strength in the transverse direction (TD) direction (unit: MPa) satisfies 1 to 2 membrane.
The method of claim 7,
A fluorine-based resin porous membrane exhibiting a porosity of 50 to 90%.
The method of claim 7,
A fluorinated resin porous membrane having a tensile strength of 50 to 200 MPa in the MD direction as measured by ASTM D638.
The method of claim 7,
A fluororesin porous membrane having a tensile strength of 30 to 200 MPa in the TD direction as measured by ASTM D638.
The method of claim 7,
The air permeability is 1 to 30 seconds / 100 mL, fluorine-based resin porous membrane.