KR102285993B1 - Porous fluorine resin sheet and method for prepararing the same - Google Patents

Abstract

The present invention relates to a fluororesin porous membrane and a method for manufacturing the same. More specifically, to provide a fluorine-based resin porous membrane having excellent air permeability and strength, and a method for manufacturing the same.

Description

Fluorine-based resin porous membrane and manufacturing method thereof

The present invention relates to a fluororesin porous membrane and a method for manufacturing the same. More specifically, to provide a fluorine-based resin porous membrane having excellent air permeability and strength, and a method for manufacturing the same.

Porous membranes used in various fields are required to have both 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 controlling the pore diameter distribution inside the porous membrane is known.

The fluororesin-based porous membrane may have characteristics such as high heat resistance, chemical stability, weatherability, non-flammability, strength, non-tackiness, low friction coefficient, and low dielectric constant resulting from the fluororesin itself, and in addition, as a porous body It may have properties such as flexibility, liquid permeability, particle collection efficiency, and the like.

Among these fluorine-based resins, a porous membrane manufactured using polytetrafluoroethylene (PTFE), in particular, has high stability to various compounds, and thus gas and liquid in semiconductor-related fields, liquid crystal-related fields, food and medical fields, etc. It is widely used as a microfiltration filter (membrane filter) for a mixture of the form.

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

As described above, the PTFE porous membrane produced 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, and by this microstructure A continuous porous porous structure is formed.

However, due to the nature of the porous membrane, the strength is weak, so that when an external force is applied, the pore structure is easily deformed and the durability is weak. If the strength of the membrane is weakened, the membrane can be destroyed in a harsh environment, so it loses its role as a vent filter.

In order to improve this, there is a method for increasing durability by increasing the extrusion pressure during extrusion of the preform. However, in this case, the porosity may decrease, which is insufficient to ensure sufficient strength while maintaining the breathability, and continuous research on this is still required.

An object of the present invention is to provide a fluororesin porous membrane having excellent air permeability and strength, and a method for manufacturing the same.

In this specification

manufacturing a green body by extruding a paste containing a fluorine-based resin and a lubricant;

first rolling and drying the green body;

first stretching the dried green body;

manufacturing a rolled sheet by second rolling the first stretched preform; and

second stretching the rolled sheet;

There is provided a method for producing a fluorine-based resin porous membrane comprising a.

Also, in this specification,

a maximum compressive load of 2000 to 9000 gf,

A fluorine-based resin porous membrane having a breaking elongation of 5 to 20% is provided.

Hereinafter, a dicing film and a dicing die-bonding film according to specific embodiments of the present invention will be described in more detail.

The terminology used herein is used to describe exemplary embodiments only, and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present specification, terms such as "comprise", "comprising" or "have" are intended to designate the presence of an embodied feature, number, step, element, or a combination thereof, but one or more other features or It should be understood that it does not preclude the possibility of the presence or addition of numbers, steps, elements, or combinations thereof.

Since the present invention may have various changes and may have various forms, specific embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

According to one embodiment of the invention,

manufacturing a green body by extruding a paste containing a fluorine-based resin and a lubricant;

first rolling and drying the green body;

first stretching the dried green body;

manufacturing a rolled sheet by second rolling the first stretched preform; and

A method of manufacturing a fluororesin porous membrane comprising a; second stretching the rolled sheet may be provided.

A method of forming a porous membrane by manufacturing a green body using a resin composition including a fluorine-based resin, rolling, and elongating (stretching) the same has been previously known. However, the fluorine-based resin porous membrane obtained by this process has a weak strength due to the characteristic of porosity, and thus there is a problem in that the membrane or the pore structure is easily deformed when a strong external force is applied.

Accordingly, as a result of the continuous research of the present inventors, when the second stretching process is additionally performed after the first rolling, drying, first stretching and second rolling of the green body, a certain level of node differentiation is achieved through the first stretching. It is possible to provide a fluorine-based resin porous membrane having excellent air permeability and strength by increasing the density of the sheet and thereby increasing the node stiffness by generating node aggregation with physical force through the second rolling. Confirmed through and completed the 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 may be manufactured by extruding a paste including a fluorine-based resin and a lubricant.

The fluorine-based resin is not particularly limited as long as it can be used in the porous membrane, and for example, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), tetrafluoroethylene-hexa Fluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-chlorotrifluoroethylene copolymer (TFE/CTFE), and ethylene-chlorotrifluoroethylene copolymer (ECTFE) ) 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. In addition, in order to control the micropore characteristics of the porous membrane, one or more fluorine-based resins having different number average molecular weights may be mixed and used.

The paste including 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 so that compression, extrusion, and sheet processing can be smoothly performed.

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 and extraction by heat after sheet processing. For example, a liquid compound such as liquid paraffin, naphtha, white oil, toluene, or hydrocarbon oil such as xylene may be preferably used as the lubricant. In addition, as the lubricant, various alcohol compounds, ketone compounds, ester compounds, etc., compounds well known as lubricants in the art to which the present invention pertains 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, molding conditions, and the like. For example, the lubricant may be used in an amount of 5 to 50 parts by weight, or 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.

A preform is formed by extruding the paste including the fluororesin and the lubricant.

The green body is an intermediate for manufacturing the fluororesin porous membrane, and its shape is not particularly limited. For example, the green body may be prepared by compressing the paste including the fluorine-based resin and the 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 at a temperature of about 20 to about 80 °C.

After the step of preparing the green body by extruding the paste including the fluorine-based resin and the lubricant, a step of first rolling and drying the green body may be performed.

The first rolling is a step of first rolling the previously prepared preform into a thin sheet. The thickness of the first rolled sheet obtained by the first rolling may be rolled to 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 rolling to a desired thickness by adjusting.

In addition, the temperature range of the first rolling is not particularly limited as long as the rolling is possible, for example, it may be carried out at a temperature of about 20 to about 70 ℃.

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

After the first rolling and drying of the green body, a first stretching step of the dried green body may be performed.

The first stretching may be performed by feeding the green body to rollers rotating at different speeds. Also, the first stretching may be performed using a tenter in an oven.

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

At this time, the draw ratio of the first stretch may be determined according to the use of the porous membrane. For example, the first stretching may be performed by biaxial stretching of 2 to 10 times longitudinal stretching and 2 to 50 times transverse stretching of the green body, but the present invention is not limited thereto.

Here, it may be preferable for the first stretching to be performed near or below the melting point of the green body in order to secure workability. For example, the first stretching may be performed under a temperature of 150 to 330 ℃.

If the temperature of the first stretching is less than 150 ℃, there is a fear that sufficient stretching uniformity may not be secured, and if it exceeds 330 ℃, the fibrils melt during the first stretching by stretching at a temperature higher than the melting point of PTFE may appear.

On the other hand, the first stretching may be performed at a speed of 3 to 20 m/min. When performed at a speed in the above range, stretching uniformity can be secured and uniform pores can be prepared over the entire area, which is optimal may have an effect. When the speed of the first stretching is less than 3 m/min, there is a risk that node differentiation occurs slowly due to the low stretching speed, resulting in non-uniformity in the distribution of stretching pore sizes, and when it exceeds 20 m/min, during stretching Breakage may occur due to stretching without sufficient preheating due to high-speed stretching.

After the first stretching of the dried green body, a second rolling step of the first stretched green body to prepare a rolled sheet may be performed.

The second rolling is a step of rolling the previously prepared first stretched preform into a thin sheet.

The second rolling may be performed by means used in a conventional rolling process, such as a method of rolling to a desired thickness by controlling a gap between the two rolls in the rolling roll. For example, it may be rolled so that the thickness of the rolled sheet obtained by the second rolling is 100㎛ to 2mm.

For example, an initial thickness of the first stretched preform may be 200 μm to 3 mm, and a thickness after the second rolling may be 100 μm to 2 mm.

In addition, the temperature range of the second rolling is not particularly limited as long as the rolling is possible, for example, it may be carried out at a temperature of about 20 to about 70 ℃.

Meanwhile, the second rolling may be performed such that the thickness of the first stretched preform is reduced to 5 to 50% of the initial thickness.

That is, the thickness reduction ratio before and after the second rolling 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 more. % or less.

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, not only the node stiffness increases, but also the formed fibrils are pressed, so that the first stretching effect cannot be implemented. .

In addition, additional fibrils are well generated during the second stretching, so that the second stretching does not proceed properly, so that sufficient fibrils are not secured. It is preferable to perform

In addition, the second rolling is not particularly limited as long as the temperature is possible, for example, may be carried out at a temperature of about 20 to about 70 ℃.

After the second rolling of the first stretched preform to prepare a rolled sheet, the second stretching of the rolled sheet may be performed.

Like the first stretching, the second stretching may be performed by feeding the rolled sheet to rollers rotating at different speeds. In addition, the second stretching may be performed using a tenter in an oven.

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

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

Here, it may be preferable for the second stretching to be performed near or above the melting point of the rolled sheet to secure workability. For example, the second stretching may be performed at a temperature of 300 to 380 °C.

When the temperature of the second stretching is less than 300° C., there is a risk that the fibrils formed in the first stretching are not further stretched and fracture occurs. breakage may occur.

The second stretching may be performed at a speed of 3 to 20 m/min. When performed at a speed in the above range, stretching uniformity can be ensured and uniform pores can be prepared over the entire area, thereby providing an optimal effect. can have When the speed of the second stretching is less than 3 m/min, there is a risk that node differentiation occurs slowly due to the low stretching speed, resulting in non-uniformity in the distribution of stretching pore sizes, and when it exceeds 20 m/min, during stretching Breakage may occur due to stretching without sufficient preheating due to high-speed stretching.

According to the method for manufacturing the fluororesin porous membrane described above, after the second rolling of the first stretched preform as described above to prepare a rolled sheet, the second stretching of the rolled sheet is additionally carried out, so that fibril increases in the number of , and the node density increases. Accordingly, the strength of the porous membrane may be remarkably improved as compared to a case in which the porous membrane is manufactured without the second stretching or the first stretching and the second stretching are continuously performed.

According to an embodiment to be described later, in the porous membrane additionally subjected to the second stretching as described above, the average pore size and the maximum pore size inside the porous membrane are increased compared to the case in which the second stretching is not performed, but the actual strength is nevertheless increased. The maximum compressive load and elongation at break, which are the evaluation indicators, showed rather improved effects.

This is because, according to the manufacturing method of the above embodiment, the rigidity of the initially formed node is increased while the differentiation of the node is suppressed, and the number of nodes is also increased by the fibrils generated during the second elongation, thereby increasing the rigidity and the number of fibrils of the node. Accordingly, it is possible to maintain the porosity of the interior and exhibit the effect of improving the strength while having excellent ventilation.

The manufacturing method of the fluorine-based resin porous membrane of the embodiment comprises the steps of: extruding a paste containing a fluorine-based resin and a lubricant to prepare a preform; first rolling and drying the green body; first stretching the dried green body; manufacturing a rolled sheet by second rolling the first stretched preform; And it may further include a detailed manufacturing step according to commonly known conditions or methods before and after each of the steps of stretching the rolled sheet or between individual steps.

On the other hand, in the method for manufacturing the fluororesin porous membrane of the embodiment, after the second rolling of the first stretched preform to prepare a rolled sheet and before the second stretching of the rolled sheet, the rolled sheet is dried Additional steps may be included.

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

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

According to another embodiment of the present invention, a fluororesin porous membrane having a maximum compressive load of 2000 to 9000 gf and a breaking elongation of 5 to 20% may be provided.

The maximum compressive load was measured at a rate of 3mm/sec using TA.XT.PLUS equipment of Stable Micro System (Tip: using a 6mm spherical type tip), and the elongation at break was the final 200㎛ PET of the product. It is the result of attaching to the film and applying a load to the non-attached part. The elongation at break was described with respect to the elongation in the MD direction of the unattached part with a size of 30mm in the MD direction X 9.5mm in the TD direction.

The fluorine-based resin porous membrane of the other embodiment exhibits high maximum compressive load and elongation at break despite the increase in average pore size and maximum pore size compared to the conventional porous membrane, and maintains porosity by securing high node density and large number of fibrils However, it can exhibit sufficient strength.

The maximum compressive load means the maximum pressure load value that the porous membrane according to the present invention is not destroyed and can be restored back to its original characteristics by the elasticity of the membrane, through which the objective strength of the porous membrane can be known. At this time, if the value of the maximum compressive load is less than 2000 gf, there is a risk that the membrane may be deformed even with a small impact because it does not have a sufficient pressure load. If the elongation at break is low, the film of the product is easy to break, which can easily cause the membrane to tear.

In addition, the elongation at break means the ratio of the length at which the product breaks, and when the value of the elongation at break is less than 5%, the film of the product is easy to break, which can easily cause the membrane to tear, etc., 20% If it is exceeded, there may be a problem in that the product is greatly denatured and the fibrils of the membrane are broken.

On the other hand, 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 adjusted in a suitable range depending on the use of the porous membrane. can be

In addition, the fluororesin porous membrane may have a maximum pore size of 150 to 5000 nm, and an average pore size of 70 to 3000 nm. By having the maximum and average pore sizes, it is possible to ensure sufficient air permeability and porosity of the porous membrane.

In addition, the fluorine-based resin porous membrane, air permeability of 5 to 50 seconds / 100mL, and may have a water pressure of 20 to 160 kPa. As it has the air permeability and water pressure resistance value, it can be used as an excellent microfiltration filter for a mixture of gas and liquid in various fields such as semiconductor-related fields, liquid crystal-related fields, food and medical related fields.

The fluororesin 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. can be adjusted.

The present invention provides a fluorine-based resin porous membrane with improved strength while maintaining excellent air permeability by maintaining internal porosity, and a method for manufacturing the same.

According to the method for manufacturing a fluororesin porous membrane of the present invention, it is possible to efficiently produce a fluororesin porous membrane satisfying these characteristics without adding additional components to raw materials or significantly changing equipment.

1 is a scanning electron microscope (SEM) photograph showing the node distribution on the surface of a fluorine-based resin porous membrane according to Examples and Comparative Examples of the present invention.

The invention is described in more detail in the following examples. However, the following examples only illustrate the present invention, and the content of the present invention is not limited by the following examples.

<Example>

Example 1

To 100 parts by weight of polytetrafluoroethylene resin CD145E (manufactured by AGC), 20 parts by weight of a liquid lubricant (product name: (ISOPARTM H FLUID; ExxonMobil Chemical Company) was mixed to prepare a paste. The paste was extruded to a thickness A 1 mm preform was prepared. The preform was first rolled at a temperature of 50° C. at a speed of 25 m/min (first rolling) to prepare a sheet with a thickness of about 350 μm. The prepared sheet was prepared at about 250° C. The liquid lubricant was completely dried and removed by heating at a temperature of

The dried sheet was stretched 1.5 times in the longitudinal direction (MD) at a speed of 5 m/min at a temperature of 300° C. (first stretching) to prepare a preform having a thickness of about 300 μm.

The first stretched green body was rolled at a speed of 25 m/min at a temperature of 50° C. (second rolling) to form a rolled sheet having a thickness of about 250 μm.

Then, the rolled sheet was stretched twice in the longitudinal direction (MD) at a rate of 5 m/min at a temperature of 380° C. (second stretching), and closely adhered for about 30 s through a 380° C. Roll to obtain a porous membrane having a thickness of 200 μm.

Example 2

Polytetrafluoroethylene resin 6J (manufactured by MDF) was mixed with 22 parts by weight of a liquid lubricant (product name: (ISOPARTM H FLUID; ExxonMobil Chemical Company) with respect to 100 parts by weight to prepare a paste. Extrude the paste A 1 mm preform was prepared. The preform was first rolled at a temperature of 50° C. at a speed of 25 m/min (first rolling) to prepare a sheet with a thickness of about 350 μm. The liquid lubricant was completely dried and removed by heating at a temperature

The dried sheet was stretched twice in the longitudinal direction (MD) at a speed of 5 m/min at a temperature of 300° C. (first stretching) to prepare a preform having a thickness of about 300 μm.

The first stretched green body was rolled at a speed of 25 m/min at a temperature of 50° C. (second rolling) to form a rolled sheet having a thickness of about 250 μm.

Then, the rolled sheet was stretched twice in the longitudinal direction (MD) at a rate of 5 m/min at a temperature of 360° C. (second stretching), and closely adhered for about 30 s through a 360° C. Roll to obtain a porous membrane having a thickness of 200 μm.

Comparative Example 1

To 100 parts by weight of polytetrafluoroethylene resin CD145E (manufactured by AGC), 20 parts by weight of a liquid lubricant (product name: (ISOPARTM H FLUID; ExxonMobil Chemical Company) was mixed to prepare a paste. The paste was extruded to a thickness A preform of 1 mm was prepared.The preform was rolled at a temperature of 50° C. at a speed of 25 m/min (first rolling) to prepare a sheet with a thickness of about 300 μm. The prepared sheet was subjected to a temperature of about 250° C. The liquid lubricant was completely dried and removed by heating in. The dry sheet was stretched three times in the longitudinal direction (MD) at a speed of 5 m/min at a temperature of 380° C. (first stretching), and a preform with a thickness of about 200 μm was prepared.

The first stretched preform sheet was brought into close contact for about 30 s through a 380° C. roll to obtain a porous membrane having a thickness of 200 μm.

Comparative Example 2

To 100 parts by weight of polytetrafluoroethylene resin 6J (manufactured by MDF), 22 parts by weight of a liquid lubricant (product name: (ISOPARTM H FLUID; ExxonMobil Chemical Company) was mixed to prepare a paste. The paste was extruded to a thickness A 1 mm green body was prepared.

The preform was rolled at a temperature of 50° C. at a speed of 25 m/min (first rolling) to prepare a sheet having a thickness of about 300 μm. The prepared sheet was heated at a temperature of about 250° C. to completely dry and remove the liquid lubricant. The dried sheet was stretched 4 times in the longitudinal direction (MD) at a speed of 5 m/min at a temperature of 360° C. (first stretching) to prepare a green body having a thickness of about 200 μm.

The first stretched preform sheet was adhered through a 360° C. roll for about 30 s to obtain a porous membrane having a thickness of 200 μm.

Comparative Example 3

To 100 parts by weight of polytetrafluoroethylene resin CD145E (manufactured by AGC), 20 parts by weight of a liquid lubricant (product name: (ISOPARTM H FLUID; ExxonMobil Chemical Company) was mixed to prepare a paste. The paste was extruded to a thickness A 1 mm preform was prepared. The preform was first rolled at a temperature of 50° C. at a speed of 25 m/min (first rolling) to prepare a sheet with a thickness of about 300 μm. The prepared sheet was prepared at about 250° C. The liquid lubricant was completely dried and removed by heating at a temperature of

The dried sheet was stretched 1.5 times in the longitudinal direction (MD) at a speed of 5 m/min at a temperature of 300° C. (first stretching), and then the first stretched green body was stretched at a speed of 5 m/min under a temperature of 380° C. By stretching twice in the longitudinal direction (MD) (second stretching), a green body having a thickness of about 230 μm was prepared.

The second stretched green body was rolled at a speed of 25 m/min at a temperature of 50° C. (second rolling) to form a rolled sheet having a thickness of about 200 μm. Then, the rolled sheet was closely adhered for about 30 s through a 380° C. Roll to obtain a porous membrane with a thickness of 200 μm.

Comparative Example 4

To 100 parts by weight of polytetrafluoroethylene resin 6J (manufactured by MDF), 22 parts by weight of a liquid lubricant (product name: (ISOPARTM H FLUID; ExxonMobil Chemical Company) was mixed to prepare a paste. The paste was extruded to a thickness A 1 mm preform was prepared. The preform was first rolled at a temperature of 50° C. at a speed of 25 m/min (first rolling) to prepare a sheet with a thickness of about 300 μm. The prepared sheet was prepared at about 250° C. The liquid lubricant was completely dried and removed by heating at a temperature of

The dried sheet was stretched twice in the longitudinal direction (MD) at a rate of 5 m/min at a temperature of 300°C (first stretching), and then the first stretched green body was stretched at a rate of 5 m/min under a temperature of 360°C. By stretching twice in the longitudinal direction (MD) (second stretching), a green body having a thickness of about 230 μm was prepared.

The first stretched green body was rolled at a speed of 25 m/min at a temperature of 50° C. (second rolling) to form a rolled sheet having a thickness of about 200 μm. Then, the rolled sheet was closely adhered for about 30 s through a 360° C. Roll to obtain a porous membrane with a thickness of 200 μm.

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

Fluorine resin type lubricant content
(parts by weight) Whether the second stretch Whether the second rolling 2nd rolling period gun
draw ratio Thickness reduction rate according to the second rolling
(%) Example 1 CD145E 20 O O After the first stretching 2nd rolling X3 16.7 Example 2 6J 22 O O After the first stretching 2nd rolling X4 16.7 Comparative Example 1 CD145E 20 X X - X3 - Comparative Example 2 6J 22 X X - X4 - Comparative Example 3 CD145E 20 O O after the second stretch X3 15 Comparative Example 4 6J 22 O O after the second stretch X4 15

< Experimental example >

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

1) air permeability

The air permeability was measured using a Gurley type Densometer (No. 158) manufactured by Toyoseiki according to the Japanese industrial standard Gurley measurement method.

More specifically, the time it takes for 100 mL of air to pass through a membrane of 1 square inch under a constant air pressure of 4.8 inches (unit: seconds/100 mL) was defined as the air permeability.

2) pore size

The pore size was measured using a Capillary Flow Porometer (Model No.: CFP-1500AE) of Porous Materials Inc. After wetting the porous membrane using Galwick liquid with a surface tension of 15.9, all pores of the porous membrane were replaced with Galwick liquid, and the flow of nitrogen gas obtained when the nitrogen gas was flowed while increasing the pressure was measured to measure the pore size of the porous membrane. .

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 of nitrogen gas. Conversely, 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 above,

D means the pore diameter,

γ means the surface tension (15.9),

P means nitrogen pressure,

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

3) Porosity

The densities of the membrane for which the porosity is to be measured and the reference membrane without micropores were respectively measured with an AG scale of METTLER TOLEDO, and then the porosity of the membrane was calculated from Equation 2 below.

[Equation 2]

Porosity (%) = (1 - density of the membrane to be measured / density of the reference membrane) * 100

4) Water pressure resistance

It calculated|required based on the regulation of JIS L1092 water resistance test method B (high water pressure method).

Take 5 specimens of about 40mm(w)X 19.5mm(p) from the sample, laminate the adhesive film except for the 30mm X 9.5mm inner diameter, and install it so that water touches the surface of the water resistance test device, and the cylinder Put water in the , turn the piston handle, apply water pressure at a rate of 100 kPa for 1 minute, measure the water pressure (kPa) when water comes out from 3 places on the back side of the specimen or when the waterproof/moisture-permeable material ruptures, and measure 5 times. The average value was made into the water pressure resistance.

5) Maximum compressive load

The maximum compressive load was measured at a speed of 3mm/sec using the TA.XT.PLUS equipment of Stable Micro System (Tip: using a 6mm spherical type tip).

At this time, the point at which the specimen did not break and the strength did not increase any more was confirmed as the maximum compressive load.

6) Elongation at break

Elongation at break was measured by attaching the porous membranes prepared in Examples and Comparative Examples to 200 μm PET film, and applying a load to the non-attached portion.

The elongation in the MD direction of the non-attached part with a size of 30mm in the MD direction X 9.5mm in the TD direction was described.

breathability
(sec/100mL) Maximum/average pore size (nm) membranous
Porosity (%) water pressure
(kPa) maximum compression
weight
(gf) breakage
location
(mm) break elongation
(%) Example 1 43 810/399 58 145 7855 10.49 13.3 Example 2 6 2402/1105 85 35 3050 12.5 17.5 Comparative Example 1 46 790/380 58 145 5540 8.4 8.5 Comparative Example 2 5 2303/1301 84 35 2050 11.8 12.3 Comparative Example 3 80 587/398 53 170 10025 2.5 1.5 Comparative Example 4 10 1581/981 78 50 3489 6.5 2.5

According to Table 2, the fluorine-based resin porous membrane according to the embodiment of the present invention increases the average pore size and the maximum pore size inside the porous membrane compared to Comparative Examples 1 and 2 in which the second stretching is not performed, but, nevertheless, the maximum compression The load and elongation at break showed rather improved effects.

In addition, the fluororesin porous membrane according to an embodiment of the present invention has an elongation at break value that is about 7 times higher than Comparative Examples 3 and 4 in which the first stretching and the second stretching are continuously performed, despite the increase in the porosity of the membrane. could be confirmed to have

Accordingly, in the present invention in which the second stretching is additionally performed after the second rolling, it was confirmed that the strength of the porous membrane was significantly improved compared to the case of manufacturing the porous membrane without the second stretching or continuously performing the first stretching and the second stretching. .

Claims (10)

manufacturing a green body by extruding a paste including a fluorine-based resin and a lubricant;
first rolling and drying the green body;
first stretching the dried green body;
manufacturing a rolled sheet by second rolling the first stretched preform; and
Including; second stretching the rolled sheet;
The second rolling is performed so that the thickness of the first stretched preform is reduced to 5 to 50% compared to the initial thickness,
The second stretching is performed at a speed of 3 to 20 m/min under a temperature of 300 to 380 ° C.
A method for producing a fluorine-based resin porous membrane.
According to claim 1,
The first stretching is performed at a rate of 3 to 20 m/min under a temperature of 150 to 330 °C, a method for producing a fluorine-based resin porous membrane.
delete delete According to claim 1,
The initial thickness of the first stretched preform is 200㎛ to 3mm,
After the second rolling, the thickness is 100 μm to 2 mm, a method for producing a fluorine-based resin porous membrane.
According to claim 1,
The fluorine-based resin is polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer Copolymer (ETFE), tetrafluoroethylene-chlorotrifluoroethylene copolymer (TFE / CTFE), and ethylene-chlorotrifluoroethylene copolymer (ECTFE) comprising at least one fluorine-based compound selected from the group consisting of, A method for producing a fluorine-based resin porous membrane.
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