KR102641991B1 - Method of preparing fluorine-based resin porous membrane and fluorine-based resin porous membrane prepared thereby - Google Patents

Abstract

A method for producing a fluorine-based resin porous membrane and a fluorine-based resin porous membrane produced by the method are disclosed. The disclosed method of manufacturing a fluorine-based resin porous membrane includes the steps of mixing a fluorine-based resin and a lubricant to produce a paste (S10), extruding the paste to produce a preform (S20), and rolling the preform to produce a rolled sheet. Step (S30), stretching the rolled sheet in the MD direction (S40), stretching the sheet stretched in the MD direction in the TD direction (S50), and performing plasma treatment on the sheet stretched in the TD direction. It includes a step (S60).

Description

Method of preparing fluorine-based resin porous membrane and fluorine-based resin porous membrane prepared by the method {Method of preparing fluorine-based resin porous membrane and fluorine-based resin porous membrane prepared thereby}

A method for producing a fluorine-based resin porous membrane and a fluorine-based resin porous membrane produced by the method are disclosed. More specifically, a method for manufacturing a fluorine-based resin porous membrane capable of producing a fluorine-based resin porous membrane with excellent mechanical strength and large pore size, and a fluorine-based resin porous membrane manufactured by the method are disclosed.

Fluorine resin porous membranes are generally produced by mixing fluorine resin powder and lubricant and sequentially going through molding, extrusion, rolling, and stretching processes. During the manufacturing process of this fluorine resin porous membrane, a porous microstructure consisting of fibrils and nodes is created, and the number of nodes and fibrils is determined depending on the shear stress and pressure received during the process.

Fluorine resin porous membranes are used in a variety of fields, and various pore sizes suitable for various uses are required. For example, a hydrogen ion permeable membrane is manufactured by impregnating a fluorine resin porous membrane with an electrolyte membrane coating solution that allows hydrogen ions to pass through. If the pores of the fluorine resin porous membrane are too small, the electrolyte membrane coating solution cannot be impregnated well, creating a uniform composite membrane. There are problems in manufacturing, and in the case of process filters, filters with various pore sizes suitable for filtering out impurities of various sizes are required.

However, the pore size is determined to some extent by the stretching process, and since the stretching process is generally operated with an emphasis on mechanical strength and thickness, it is not easy to separately control the pore size while fixing other excellent physical properties. For example, a fluorine resin porous membrane with large pore size must be manufactured with a small amount of lubricant and a small degree of stretching, but in this case, the problem of lowering the strength of the membrane occurs.

One embodiment of the present invention provides a method for manufacturing a fluorine-based resin porous membrane capable of producing a fluorine-based resin porous membrane with excellent mechanical strength and large pore size.

Another embodiment of the present invention provides a fluorine-based resin porous membrane manufactured by the above method for producing a fluorine-based resin porous membrane.

One aspect of the present invention is,

Preparing a paste by mixing a fluorine resin and a lubricant (S10);

Extruding the paste to produce a preform (S20);

Manufacturing a rolled sheet by rolling the preform (S30);

Stretching the rolled sheet in the MD direction (S40);

stretching the sheet stretched in the MD direction in the TD direction (S50); and

A method for manufacturing a fluorine resin porous membrane is provided, including the step (S60) of performing plasma treatment on the sheet stretched in the TD direction.

The method of manufacturing the fluorine resin porous membrane further includes a step (S15) of compressing the paste to produce a preformed block between the step (S10) and the step (S20), and in this case, the step (S20) may be changed to a step of manufacturing a preform by extruding the preform block instead of the paste.

The method of manufacturing the fluorine resin porous membrane may further include a step (S35) of drying the rolled sheet to remove the lubricant between the steps (S30) and (S40).

The step (S40) may include stretching in the MD direction at least once, stretching in the TD direction at least once, or a combination thereof.

The plasma treatment in step S60 may be performed under temperature conditions of 300 to 450°C.

The plasma reaction gas used in the plasma treatment in step S60 may include CF ₄ , C ₂ F ₆ , C ₄ F ₈ , NF ₃ , SF _{3 ,} or a combination thereof.

The plasma treatment in the step (S60) may be performed under the conditions that the flow rate of the plasma reaction gas is 10 to 50 sccm, the voltage is 2 to 10 kV, and the power is 200 to 500 W.

Another aspect of the present invention is,

Provided is a fluorine-based resin porous membrane manufactured by the method for producing the fluorine-based resin porous membrane.

The fluorine resin porous membrane may have an average flow pore size of 0.06 to 1.5 ㎛, a tensile strength in the MD direction measured according to ASTM D638 of 50 MPa or more, and a tensile strength in the TD direction measured according to ASTM D638 may be 50 MPa or more.

The fluorine resin porous membrane may have a thickness of 3 to 100 ㎛, and the electrolyte impregnation time may be 5 minutes or less.

When a fluorine-based resin porous membrane is manufactured according to the method for manufacturing a fluorine-based resin porous membrane according to an embodiment of the present invention, a fluorine-based resin porous membrane with excellent mechanical strength and large pore size can be obtained.

1 is a diagram for explaining a method of manufacturing a fluorine resin porous membrane according to an embodiment of the present invention.
Figure 2 is a diagram for explaining the relationship between the pore size of a fluorine resin porous membrane and the impregnability of an electrolyte membrane coating solution.
Figure 3 is a diagram for explaining a method of measuring the average flow pore size of a fluorine resin porous membrane.
Figure 4 is a diagram for explaining a method of measuring the electrolyte impregnation time of a fluorine resin porous membrane.

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

As used herein, “machine direction” means a direction referred to as machine direction, longitudinal or machine direction.

Also, in this specification, “TD direction (transverse direction)” means a direction perpendicular to the MD direction, referred to as the transverse direction or transverse direction.

The method for manufacturing a fluorine-based resin porous membrane according to an embodiment of the present invention includes the steps of mixing a fluorine-based resin and a lubricant to produce a paste (S10), extruding the paste to produce a preform (S20), and manufacturing the preform by extruding the paste (S20). Manufacturing a rolled sheet by rolling (S30), stretching the rolled sheet in the MD direction (S40), stretching the sheet stretched in the MD direction in the TD direction (S50), and stretching the sheet stretched in the TD direction It includes a step (S60) of performing plasma treatment on the sheet.

In step S10, the fluorine-based resin may be used in the form of powder, small pieces, or a mixture thereof.

In addition, the fluorine-based resin is polytetrafluoroethylene (fluorine-based resin porous membrane), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene- It may include tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-chlorotrifluoroethylene copolymer (TFE/CTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), or combinations thereof.

Additionally, the fluorine-based resin may have a number average molecular weight of 5,000,000 to 15,000,000 g/mol.

In addition, in the step (S10), the lubricant wets the surface of the fluoropolymer and serves to smoothly perform compression, extrusion, and sheet processing.

Additionally, the lubricant may include liquid paraffin, naphtha, white oil, toluene, xylene, or a combination thereof. In addition, as the lubricant, compounds well known as lubricants in the technical field to which the present invention pertains, such as various alcohol-based compounds, ketone-based compounds, and ester-based compounds, may be used.

The content of the lubricant may be 5 to 50 parts by weight, for example, 10 to 50 parts by weight, for example, 10 to 40 parts by weight, based on 100 parts by weight of the fluorine resin. However, the present invention is not limited to this, and the content of the lubricant may vary depending on the type of lubricant, molding conditions, etc.

In the step (S20), the preform is an intermediate for manufacturing a fluorine resin porous membrane, and its form is not particularly limited.

In addition, the method of manufacturing the fluorine-based resin porous membrane may further include a step (S15) of compressing the paste to produce a preform block between the step (S10) and the step (S20). For example, a preformed block can be manufactured by applying a pressure of 1 to 6 MPa to the paste. In this way, if the method of manufacturing the fluorine resin porous membrane further includes a preform block manufacturing step (S15), the step (S20) may be changed to a step of manufacturing a preform by extruding the preform block instead of the paste. You can. For example, in step S20, a sheet may be manufactured by extruding the preformed block at a temperature of 25 to 70°C. At this time, the extrusion speed can be adjusted to a speed of 30 to 70 mm/min. The extruded sheet may have a thickness of 1,000 to 5,000 μm, for example, 2,000 to 4,000 μm, for example, 2,500 to 3,500 μm.

In the step (S30), the rolling (calendering) may be performed in a multi-stage method of one stage or two stages or more. For example, in the step (S30), the rolled sheet is supplied between two rolling rollers, and the fine structure and thickness of the sheet are adjusted by applying appropriate pressure to the two rolling rollers to adjust the gap between the two rolling rollers. It can change. The temperature during the rolling process is not particularly limited, but may be adjusted to, for example, 20 to 100°C. Additionally, the pressure applied to the two rolling rollers is not particularly limited, but may be adjusted to, for example, 10 to 30 MPa. Additionally, the final thickness of the rolled sheet may be 100 to 2,000 μm.

In addition, the method of manufacturing the fluorine-based resin porous membrane may further include a step (S35) of drying the rolled sheet to remove the lubricant between the steps (S30) and (S40).

The drying temperature in step (S35) may be 200 to 250°C. However, the drying temperature is not particularly limited as long as it is a temperature at which the lubricant can be removed, and similarly, the drying time is not particularly limited as long as it is a time at which the lubricant can be completely removed.

The steps (S40) and (S50) may overall include one or more stretching in the MD direction, one or more stretching in the TD direction, or a combination thereof. Specifically, the steps (S40) and (S50) may be performed by performing at least one stretching in the MD direction and then stretching in the TD direction at least one time (m stretching in the MD direction followed by n stretching in the TD). direction stretching), stretching in the MD direction and stretching in the TD direction are performed alternately, but stretching in the MD direction and stretching in the TD direction can be carried out two or more times each (m1 stretching in the MD direction, followed by n1 stretching in the TD direction). Stretching is performed, followed by m2 stretching in the MD direction, followed by n2 stretching in the TD direction). In this case, m, n, m1, n1, m2, and n2 are each independently integers of 1 or more.

Stretching in each direction in steps S40 and S50 may be performed by supplying the rolled sheet to rollers that rotate independently at different speeds. As another example, stretching in the MD direction and stretching in the TD direction in steps S40 and S50 may be performed independently of each other in an oven using a tenter.

In the step (S40), stretching in the MD direction may be performed at a stretching ratio of 3 to 20 times. Additionally, the stretching in the MD direction may be performed at a temperature of 200 to 350°C.

Meanwhile, in step S50, stretching in the TD direction may be performed at a stretching ratio of 10 to 40 times. Additionally, the stretching in the TD direction may be performed at a temperature of 200 to 400°C.

The pores of the fluorine resin porous membrane are created by fibrils that occur between nodes. When a sheet for forming a fluorine resin porous membrane is stretched, the length of the fibrils increases and the number of fibrils increases, which tends to reduce the pore size. If the sheet is stretched strongly to the point where the fibrils break, the pore size increases again. Conversely, if the pore size is increased by weak stretching, the mechanical strength of the membrane weakens, and if the stretching is strong enough to break the fibrils to increase the pore size, the number of fibrils decreases, which also weakens the mechanical strength of the membrane. The method for manufacturing a fluorine-based resin porous membrane according to an embodiment of the present invention expands the pores by adding plasma surface treatment to the heat treatment process essential for the manufacturing process of the fluorine-based resin porous membrane instead of controlling the pore size by controlling the intensity of stretching. It is characterized by:

1 is a diagram for explaining a method of manufacturing a fluorine resin porous membrane according to an embodiment of the present invention.

Referring to FIG. 1, during plasma surface treatment of the sheet 10' stretched in the TD direction, activated species (ATS) penetrate into fine pores (POR) such as between the fibrils 12 connected to the nodes 11. is possible, and the degree of activity of activated species (ATS) can be adjusted by voltage, frequency, gas flow rate, etc. Therefore, the plasma surface treatment can expand the pores of the membrane more effectively because it allows more precise energy control than hot air, which generally generates energy deviation by PID control (Proportional-Integral-Differential control). In addition, when expanding the pores of the membrane through plasma surface treatment, if a fluorine-based gas is used as the plasma reaction gas, surface modification occurs inside the pores, resulting in a significant improvement in the impregnation speed when impregnated with a fluorine-based electrolyte solution.

As described above, the plasma treatment in step S60 serves to expand the pore size of the fluorine resin porous membrane without deteriorating its mechanical properties.

Specifically, referring to FIG. 1, when the sheet 10' stretched in the TD direction as shown in (a) of FIG. 1 is subjected to plasma treatment at a temperature of 300 to 450° C., (b) of FIG. 1 As shown, activated species (ATS) derived from the plasma reaction gas passes through the pores (POR) between the fibrils 12 and expands the pores by pushing the fibrils 12 with greater energy than hot air. After the pores (POR) are expanded in this way, the fibrils 12 are fixed by heat sintering at a temperature of 300 to 450°C.

The plasma treatment in step S60 may be performed at a temperature of 300 to 450°C. If the plasma treatment in the step (S60) is performed under the above temperature conditions, a fluorine resin porous membrane with a large mean flow pore size and excellent MD tensile strength and TD tensile strength can be manufactured.

Additionally, the gas for plasma reaction used in the plasma treatment in step S60 may include CF ₄ , C ₂ F ₆ , C ₄ F ₈ , NF ₃ , SF _{3 ,} or a combination thereof.

In addition, the plasma treatment in the step (S60) can be performed under the conditions that the flow rate of the plasma reaction gas is 10 to 50 sccm (Standard Cubic Centimeter per Minute), the voltage is 2 to 10 kV, and the power is 200 to 500 W. . If the plasma treatment in the step (S60) is performed under the flow rate, voltage, and power conditions of the plasma reaction gas, a fluorine resin porous membrane with a large average flow pore size and excellent MD tensile strength and TD tensile strength can be manufactured. .

Figure 2 is a diagram for explaining the relationship between the pore size of the fluorine resin porous membrane 10 and the impregnability of the electrolyte membrane coating liquid 20.

Referring to FIG. 2, when the electrolyte membrane coating solution 20 is placed at the bottom end of the pores (POR) of the fluorine resin porous membrane 10, a meniscus is formed, and at this time, the pillar of the electrolyte membrane coating solution 20 The heights (h1, h2) are determined by Equation 1 below. When the surface tension is T, T is inclined from the pore wall by the contact angle (θ) and acts on the circumference of the top of the pillar of the electrolyte membrane coating solution 20.

[Equation 1]

In Equation 1, R is the radius of the pore (POR), and γ is the specific weight of the electrolyte membrane coating solution 20.

Specifically, when coating the electrolyte membrane coating solution 20 on the fluorine resin porous membrane 10, a capillary phenomenon as shown in FIG. 2 occurs. Small pores (POR) have small R1 and large h1, and large pores (POR) have large R2 and small h2. If R is small, the impregnation speed takes a long time and needs to be adjusted to an appropriate value. When a separator with a small pore size is difficult to impregnate and it is desired to increase the pore size, the pore size can be increased through the method of manufacturing a fluorine resin porous membrane according to an embodiment of the present invention, thereby maintaining only the impregnation properties while preserving the required mechanical properties. can be improved.

Also, as described above, the plasma treatment in step S60 serves to improve the impregnation rate of the electrolyte solution (specifically, the fluorine-based electrolyte solution) by modifying the surface of the fluorine-based resin porous membrane. Specifically, in step S60, the active species chemically reacts with the surface of the fluorine-based resin porous membrane, and fluorine atoms are chemically bonded to the surface of the fluorine-based resin porous membrane. Accordingly, the rate at which the fluorine-based electrolyte solution is impregnated into the pores of the surface-modified fluorine-based resin porous membrane increases. It is generally known that a fluorine-based electrolyte with high viscosity is difficult to impregnate into a fluorine-based resin porous membrane. However, the fluorine-based resin porous membrane manufactured by the method for manufacturing a fluorine-based resin porous membrane according to an embodiment of the present invention has large pore sizes and a modified surface. Therefore, the fluorine-based resin porous membrane can be easily impregnated with a fluorine-based electrolyte solution with high viscosity.

Hereinafter, a fluorine resin porous membrane according to an embodiment of the present invention will be described in detail.

The fluorine resin porous membrane may have an average flow pore size of 0.06 to 1.5 ㎛, a tensile strength in the MD direction measured according to ASTM D638 of 50 MPa or more, and a tensile strength in the TD direction measured according to ASTM D638 may be 50 MPa or more.

Additionally, the fluorine resin porous membrane may have a thickness of 3 to 100 μm, and the electrolyte impregnation time may be 5 minutes or less.

As an example, the fluorine resin porous membrane may have a thickness of 3 to 20 μm, and the electrolyte impregnation time may be 50 seconds or less.

As another example, the fluorine resin porous membrane may have a thickness of more than 20 μm and less than 100 μm, and the electrolyte impregnation time may be less than 5 minutes.

The fluorine-based resin porous membrane may be manufactured by the method for manufacturing the fluorine-based resin porous membrane described above.

Hereinafter, the present invention will be described with reference to the following examples, but the present invention is not limited to the following examples.

Example 1: Preparation of polytetrafluoroethylene resin porous membrane

A paste was prepared by mixing 100 parts by weight of polytetrafluoroethylene resin (Chemours, 650J) with 22 parts by weight of a liquid lubricant (ISOPAR™ L FLUID; ExxonMobil Chemical Company) and then aged at room temperature for 24 hours. Thereafter, the paste was compressed at a pressure of 4 MPa to produce a preformed block. Thereafter, the preformed block was extruded to produce a preformed body. Thereafter, the preform was rolled at a temperature of 50°C at a speed of 50 mm/min to produce a rolled sheet with a thickness of 500 μm. Thereafter, the rolled sheet was heat treated in a roll-to-roll process in a heating oven at 200° C. to completely remove the lubricant. Thereafter, the heat-treated sheet was stretched 6 times in the MD direction at 300°C using a difference in roll speed. Thereafter, the MD direction stretched sheet was stretched 15 times in the TD direction using a tenter at 300°C. Thereafter, plasma treatment was performed on the TD direction stretched sheet at a temperature of 375°C. During the plasma treatment, PlasmaJet ^® (Raantec GmbH & Co., KG, Borgholzhausen, Germany) was used as the plasma generator, NF ₃ was used as the plasma reaction gas, and the flow rate of the plasma reaction gas was set to 45 sccm. The voltage was set to 6kV, and the power was set to 350W.

Example 2: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as in Example 1, except that the temperature condition was changed to 300°C.

Example 3: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as in Example 1, except that the temperature condition was changed to 450°C.

Example 4: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as Example 1, except that the flow rate of the plasma reaction gas was changed to 10 sccm.

Example 5: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as in Example 1, except that the flow rate of the plasma reaction gas was changed to 50 sccm.

Example 6: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as in Example 1, except that the voltage was changed to 2 kV.

Example 7: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as in Example 1, except that the voltage was changed to 10 kV.

Example 8: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as Example 1, except that the power was changed to 200W.

Example 9: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as in Example 1, except that the power was changed to 500W.

Example 10: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as Example 1, except that CF ₄ was used instead of NF ₃ as the plasma reaction gas.

Example 11: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as Example 1, except that C ₂ F ₆ was used instead of NF ₃ as the plasma reaction gas.

Example 12: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as Example 1, except that C ₄ F ₈ was used instead of NF ₃ as the plasma reaction gas.

Example 13: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as Example 1, except that SF ₃ was used instead of NF ₃ as the plasma reaction gas.

Reference Example 1: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as in Example 1, except that the temperature condition was changed to 250°C.

Reference Example 2: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as in Example 1, except that the temperature condition was changed to 500°C.

Reference Example 3: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as in Example 1, except that the flow rate of the plasma reaction gas was changed to 5 sccm.

Reference Example 4: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as in Example 1, except that the flow rate of the plasma reaction gas was changed to 60 sccm.

Reference Example 5: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as in Example 1, except that the voltage was changed to 1 kV.

Reference Example 6: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as in Example 1, except that the voltage was changed to 11 kV.

Reference Example 7: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as in Example 1, except that the power was changed to 100W.

Reference Example 8: Preparation of polytetrafluoroethylene resin porous membrane

During the plasma treatment, a polytetrafluoroethylene resin porous membrane was manufactured in the same manner as in Example 1, except that the power was changed to 600W.

Comparative Example 1: Preparation of polytetrafluoroethylene resin porous membrane

A polytetrafluoroethylene resin porous membrane was manufactured in the same manner as Example 1, except that the TD direction stretched sheet was heat-treated at 375°C without plasma treatment.

The manufacturing conditions of the polytetrafluoroethylene resin porous membrane (PTFE porous membrane) prepared in Examples 1 to 13, Reference Examples 1 to 8, and Comparative Example 1 are summarized in Table 1 below.

Plasma processing conditions Gas for plasma reaction Temperature conditions (℃) Gas flow rate for plasma reaction (sccm) Voltage (kV) Power (W) Example 1 NF ₃ 375 45 6 350 Example 2 NF ₃ 300 45 6 350 Example 3 NF ₃ 450 45 6 350 Example 4 NF ₃ 375 10 6 350 Example 5 NF ₃ 375 50 6 350 Example 6 NF ₃ 375 45 2 350 Example 7 NF ₃ 375 45 10 350 Example 8 NF ₃ 375 45 6 200 Example 9 NF ₃ 375 45 6 500 Example 10 C F ₄ 375 45 6 350 Example 11 C ₂ F ₆ 375 45 6 350 Example 12 C ₄ F ₈ 375 45 6 350 Example 13 SF ₃ 375 45 6 350 Reference example 1 NF ₃ 250 45 6 350 Reference example 2 NF ₃ 500 45 6 350 Reference example 3 NF ₃ 375 5 6 350 Reference example 4 NF ₃ 375 60 6 350 Reference example 5 NF ₃ 375 45 One 350 Reference example 6 NF ₃ 375 45 11 350 Reference example 7 NF ₃ 375 45 6 100 Reference example 8 NF ₃ 375 45 6 600 Comparative Example 1 NF ₃ 375 - - -

Evaluation example: Evaluation of physical properties of polytetrafluoroethylene resin porous membrane

The physical properties of the polytetrafluoroethylene resin porous membranes prepared in Examples 1 to 13, Reference Examples 1 to 8, and Comparative Example 1 were evaluated in the following manner, and the results are shown in Table 2 below.

(1) Thickness (㎛): The thickness of the polytetrafluoroethylene resin porous membrane was measured using a dial thickness gauge from Mitsutoyo.

(2) Mean Flow Pore Size (㎛): The average flow pore size of the polytetrafluoroethylene resin porous membrane was measured using PMI's Capillary Flow Porometer equipment. Specifically, referring to Figure 3, after mounting the polytetrafluoroethylene resin porous membrane on the measuring equipment, it is completely wetted with a surface tension test solution (GALWICK), and nitrogen is applied in a direction perpendicular to the polytetrafluoroethylene resin porous membrane. Injected. The pressure increases steadily, and when it reaches a certain pressure, the droplet of the test solution filling the largest hole in the pore bursts out. The pressure at this time was designated as the bubble point. Subsequently, as the pressure continues to increase, all of the solution filling the remaining small pores that have not burst burst out as droplets. At this time, the Flow Rate (Wet Curve) according to the pressure was recorded to calculate the size of the pore. For porous membranes in a dry state that are not wetted with the test solution, the flow rate increases steadily as the pressure increases (dry curve), and at this time, the pressure at the point where the dry curve is 1/2 and the wet curve intersects Porosity was calculated according to Equation 2 below and defined as the average flow pore size.

[Equation 2]

Pd = 4ycosθ

In Equation 2, P is the pressure, d is the pore diameter, y is the surface tension, and θ is the contact angle.

(3) MD direction tensile strength and TD direction tensile strength (MPa): The MD direction tensile strength and TD direction tensile strength were measured using a Universal Test Machine (Roell Z010, ZWICK) according to the measurement method of ASTM D638.

(4) Electrolyte impregnation time: The impregnation time is defined as follows. That is, the impregnation time was measured by measuring the rate of change in the contact angle between the polytetrafluoroethylene resin porous membrane and the electrolyte for analysis. Specifically, the time for the contact angle to fall below 10°, measured using a contact angle measuring device (Femtobiomed, smartdrop), was measured and recorded as the impregnation time. The electrolyte for the analysis was 3M ionomer solution [mixture of ethanol and water, viscosity 400 cp (TA instruments, DHR-3, 25°C, shear rate 1 sec ^-1 )].

Figure 4 is a diagram for explaining a method of measuring the electrolyte impregnation time of a fluorine resin porous membrane.

Referring to FIG. 4, (a) of FIG. 4 is a diagram showing the contact angle immediately after dropping a drop of the electrolyte solution 30 for analysis on the polytetrafluoroethylene resin porous membrane 10, and (b) of FIG. This is a diagram showing the contact angle after a predetermined time has elapsed after dropping a drop of the electrolyte solution 30 for analysis on the polytetrafluoroethylene resin porous membrane 10 as shown in (a) of Figure 4. Here, the impregnation time is shown in Figure 4. The time elapsed from the time when a drop of the electrolyte solution 30 for analysis was dropped on the polytetrafluoroethylene resin porous membrane 10 as shown in (a) until the time when θ becomes 10° in (b) of FIG. it means.

Thickness (㎛) Average flow pore size (㎛) MD direction tensile strength
(MPa) Tensile strength in TD direction
(MPa) Impregnation time
(candle) Example 1 48 0.156 69 66 128 Example 2 29 0.108 52 55 112 Example 3 87 0.133 60 87 240 Example 4 61 0.099 77 80 179 Example 5 70 0.387 53 50 33 Example 6 57 0.065 89 69 264 Example 7 72 1.211 52 61 15 Example 8 79 0.083 59 67 255 Example 9 45 0.314 72 61 68 Example 10 62 0.130 70 65 141 Example 11 41 0.138 58 63 150 Example 12 55 0.166 74 55 232 Example 13 51 0.146 59 70 121 Reference example 1 11 0.109 30 22 117 Reference example 2 sample fracture - - - - Reference example 3 72 0.077 58 70 427 Reference example 4 67 0.443 21 34 110 Reference example 5 59 0.054 55 70 351 Reference example 6 75 1.537 30 19 85 Reference example 7 66 0.123 64 59 338 Reference example 8 43 0.399 27 22 158 Comparative Example 1 49 0.045 51 69 > 600 seconds (no impregnation)

Referring to Table 1, the polytetrafluoroethylene resin porous membranes prepared in Examples 1 to 13 have an average flow pore size of 0.06 ㎛ or more, and both MD and TD tensile strengths are high at 50 MPa or more, It was found that the electrolyte impregnation time was short.

However, the polytetrafluoroethylene resin porous membranes prepared in Reference Example 1, Reference Examples 3 to 8, and Comparative Example 1 have an average flow pore size of less than 0.06㎛, a tensile strength in the MD direction as low as less than 50MPa, or a TD It was found that the directional tensile strength was low, less than 50 MPa, and/or the electrolyte impregnation time was long.

In addition, the polytetrafluoroethylene resin porous membrane prepared in Reference Example 1 was found to be unusable due to fracture.

In the above, preferred embodiments according to the present invention have been described with reference to the drawings and examples, but this is merely illustrative, and various modifications and other equivalent embodiments can be made by those skilled in the art. You will be able to understand. Therefore, the scope of protection of the present invention should be determined by the appended patent claims.

10, 10': fluorine resin porous membrane 11: node
12: Fibril 20: Electrolyte membrane coating solution
30: electrolyte POR: pore
ATS: active species R, R1, R2, r: pore radius
h, h1, h2: Height of electrolyte membrane coating liquid θ: Contact angle

Claims (10)

Preparing a paste by mixing a fluorine resin and a lubricant (S10);
Extruding the paste to produce a preform (S20);
Manufacturing a rolled sheet by rolling the preform (S30);
Stretching the rolled sheet in the MD direction (S40);
stretching the sheet stretched in the MD direction in the TD direction (S50); and
Comprising a step (S60) of performing plasma treatment on the sheet stretched in the TD direction,
The plasma treatment in the step (S60) is a method of manufacturing a fluorine resin porous membrane wherein the plasma treatment is performed under temperature conditions of 300 to 450 ° C. According to paragraph 1,
Between the step (S10) and the step (S20), a step (S15) of compressing the paste to produce a preformed block is further included, in which case the step (S20) is performed on the preformed block instead of the paste. A method for producing a fluorine resin porous membrane that changes to the step of producing a preform by extruding. According to paragraph 1,
Between the step (S30) and the step (S40), the method of producing a fluorine resin porous membrane further includes a step (S35) of drying the rolled sheet to remove the lubricant. According to paragraph 1,
The step (S40) is a method of producing a fluorine resin porous membrane comprising stretching in the MD direction at least once, stretching in the TD direction at least once, or a combination thereof. delete According to paragraph 1,
The plasma reaction gas used in the plasma treatment in the step (S60) is CF ₄ , C ₂ F ₆ , C ₄ F ₈ , NF ₃ , SF ₃ or a combination thereof. Method for producing a fluorine-based resin porous membrane. According to paragraph 1,
The plasma treatment in the step (S60) is performed under the conditions that the flow rate of the plasma reaction gas is 10 to 50 sccm, the voltage is 2 to 10 kV, and the power is 200 to 500 W. A method of manufacturing a fluorine resin porous membrane. A fluorine-based resin porous membrane manufactured by the method for producing a fluorine-based resin porous membrane according to any one of claims 1 to 4, 6, and 7,
The fluorine resin porous membrane has an average flow pore size of 0.06 to 1.5 ㎛, a tensile strength in the MD direction measured according to ASTM D638 of 50 MPa or more, and a tensile strength in the TD direction measured according to ASTM D638 of 50 MPa or more,
The fluorine-based resin porous membrane has a thickness of 3 to 100㎛ and an electrolyte impregnation time of 5 minutes or less. delete delete

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