Porous membrane, filter component, and component supply assembly

Abstract

This invention provides a porous membrane suitable for attachment to device housings and the like. [Solution] The porous membrane mainly contains a thermoplastic resin with a melting point of 180°C to 300°C, and has a density of 2.5 N / mm². 2 The compressibility of the porous membrane in the thickness direction when pressure is applied is 20% or less. The thermoplastic resin includes, for example, polymethylpentene resin. When the cross-section of the porous membrane is observed, for example, multiple nodes are included along the thickness direction.

Description

Technical Field

[0001] The present invention relates to a porous film, a filter member, and a member supply assembly.

Background Art

[0002] Porous films of fluororesins are used in various applications such as filters, sound-permeable films, air-permeable films, diaphragms, liquid absorbers, etc. In order to be used for these applications, porous films containing no fluorine have also been proposed.

[0003] For example, Patent Document 1 discloses an olefin resin microporous biaxially stretched film having micropores and containing an olefin resin, characterized in that the puncture strength is 0.7 N or more and the air permeability is 75 to 400 s / 100 mL.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Even a porous film excellent in mechanical strength such as puncture strength may not be able to secure an appropriate mounting pressure when mounted on a housing of a device or the like.

[0006] Therefore, an object of the present invention is to provide a porous film suitable for mounting on a housing of a device or the like.

Means for Solving the Problems

[0007] The present invention is a porous film containing, as a main component, a thermoplastic resin having a melting point of 180°C or higher and 300°C or lower, The porous membrane has a tortoise shell-like structure formed by a plurality of nodes and a plurality of fibrils. A porous membrane is provided.

[0008] From another aspect, the present invention is a porous membrane containing a thermoplastic resin having a melting point of 180°C or higher and 300°C or lower as a main component, 2.5 N / mm 2 where the compression rate in the thickness direction of the porous membrane when a pressure of is applied is 20% or less. A porous membrane is provided.

[0009] From yet another aspect, the present invention includes the porous membrane of the present invention described above, and an adhesive layer joined to the porous membrane, A filter member is provided.

[0010] Furthermore, from still another aspect, the present invention is a member supply assembly including a filter member disposed on the surface of an object having a surface with an opening, and a base material sheet on which the filter member is disposed, where the filter member has a porous membrane having a shape that covers the opening when disposed on the surface, and an adhesive layer joined to the porous membrane, where the porous membrane is the porous membrane of the present invention. A member supply assembly is provided.

Advantages of the Invention

[0011] ]>According to the present invention, a porous membrane suitable for attachment to a housing of a device or the like can be provided.

Brief Description of the Drawings

[0012] [Figure 1A] FIG. 1A is a cross-sectional view schematically showing an example of the porous membrane of the present invention. [Figure 1B] Figure 1B is a schematic diagram showing an example of the surface of the porous membrane of the present invention. [Figure 2] Figure 2 is a schematic cross-sectional view showing an example of the ventilation member of the present invention. [Figure 3] Figure 3 is a schematic cross-sectional view showing a modified example 1 of the ventilation member shown in Figure 2. [Figure 4] Figure 4 is a schematic cross-sectional view showing a modified example (winding body) of the ventilation member shown in Figure 2. [Figure 5] Figure 5 is a schematic cross-sectional view showing an example of a filter member of the present invention. [Figure 6] Figure 6 is a schematic cross-sectional view showing a modified example 1 of the filter member 4 in Figure 5. [Figure 7] Figure 7 is a schematic cross-sectional view showing a modified example 2 of the filter member 4 in Figure 5. [Figure 8] Figure 8 is a schematic cross-sectional view showing a modified example 3 of the filter member 4 in Figure 5. [Figure 9] Figure 9 is a schematic cross-sectional view showing an example of a component supply assembly of the present invention. [Figure 10] Figure 10 shows the results of observing the surface of the porous membrane of Example 1 with a scanning electron microscope (SEM) (2500x magnification). [Figure 11] Figure 11 shows the results of observing the surface of the porous membrane of Example 2 using SEM (2500x magnification). [Figure 12A] Figure 12A shows the results of observing the surface of the porous membrane of Example 3 using SEM (2500x magnification). [Figure 12B] Figure 12B is a magnified view (10,000x) of a portion of Figure 12A. [Figure 12C] Figure 12C shows the results of observing the cross-section of the porous membrane of Example 3 using SEM (1500x magnification). [Figure 13] Figure 13 shows the results of observing the surface of the porous membrane of Example 4 using SEM (2500x magnification). [Figure 14A]Figure 14A shows the results of observing the surface of the porous membrane of Example 5 using SEM (2500x magnification). [Figure 14B] Figure 14B is a magnified view (10,000x) of a portion of Figure 14A. [Figure 15A] Figure 15A shows the results of observing the surface of the film of Comparative Example 1 using SEM (2500x magnification). [Figure 15B] Figure 15B is a magnified view (10,000x) of a portion of Figure 15A. [Figure 15C] Figure 15C shows the results of observing a cross-section of the film of Comparative Example 1 using SEM (2000x magnification). [Figure 16] Figure 16 shows the results of observing the surface of the film of Comparative Example 2 using SEM (2500x magnification). [Figure 17] Figure 17 shows the results of observing the surface of the film of Comparative Example 3 using SEM (2500x magnification). [Figure 18A] Figure 18A shows the results of observing the surface of the film in Reference Example 2 using SEM (2500x magnification). [Figure 18B] Figure 18B is a magnified view (20,000x) of a portion of Figure 18A. [Figure 19] Figure 19 is a graph showing the results of measuring the actual film temperature from hot pressing to cooling using a thermocouple at 100 ms intervals for Example 1, Examples 6-7, and Comparative Example 4. [Figure 20] Figure 20 is a schematic diagram illustrating how to determine the distance between island-like regions of the porous membrane shown in Figure 1. [Figure 21] Figure 21 is a schematic cross-sectional view illustrating the compression test. [Modes for carrying out the invention]

[0013] A porous membrane according to the first aspect of the present invention is A porous film mainly composed of a thermoplastic resin having a melting point of 180°C or higher and 300°C or lower, The porous membrane has a tortoise-shell-like structure formed by multiple nodes and multiple fibrils.

[0014] In a second embodiment of the present invention, for example, in the porous membrane according to the first embodiment, 2.5 N / mm 2 The compressibility of the porous membrane in the thickness direction when pressure is applied is 20% or less.

[0015] A porous membrane according to a third aspect of the present invention is A porous film mainly composed of a thermoplastic resin having a melting point of 180°C or higher and 300°C or lower, 2.5 N / mm 2 The compressibility of the porous membrane in the thickness direction when pressure is applied is 20% or less.

[0016] In a fourth embodiment of the present invention, for example, in a porous membrane according to any one of the first to third embodiments, the thermoplastic resin includes a polymethylpentene resin.

[0017] In a fifth embodiment of the present invention, for example, in a porous membrane according to any one of the first to fourth embodiments, when a cross-section of the porous membrane is observed, a plurality of the nodes are included along the thickness direction.

[0018] In a sixth aspect of the present invention, for example, in a porous membrane according to any one of the first to fifth aspects, the air permeability is 1000 seconds / 100 mL or less, expressed in Gurley numbers.

[0019] In the seventh aspect of the present invention, for example, in a porous membrane according to any one of the first to sixth aspects, the porosity of the porous membrane is 25% or more.

[0020] A filter member according to the eighth aspect of the present invention is: A porous membrane according to any one of the first to seventh embodiments, The device comprises an adhesive layer bonded to the porous membrane.

[0021] A component supply assembly according to the ninth aspect of the present invention is: A component supply assembly comprising a filter member disposed on the surface of an object having an opening, and a base sheet on which the filter member is disposed, The aforementioned filter member is A porous membrane having a shape that covers the opening when placed on the surface, The porous membrane comprises an adhesive layer bonded to it, The porous membrane is a porous membrane according to any one of the first to seventh embodiments.

[0022] Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the following embodiments.

[0023] [Porous membrane] An example of the porous membrane of the present invention is shown in Figure 1A. The porous membrane 1 in Figure 1A mainly contains a thermoplastic resin having a melting point of 180°C to 300°C. "Main component" means the component that is present in the most abundant amount by weight in the porous membrane. With this configuration, the porous membrane 1 can be adhered to device housings and the like not only by the use of an adhesive layer, but also by heat fusion.

[0024] Figure 1B is a schematic diagram showing an example of the surface of the porous membrane 1. The porous membrane 1 has a tortoise-shell-like structure formed by a plurality of nodes 1a and a plurality of fibrils 1b. As shown in Figure 1B, the tortoise-shell-like structure is present throughout the porous membrane 1. This structure can suppress the reduction in the thickness of the porous membrane 1 due to compression when it is attached to a device housing or the like. Therefore, an appropriate attachment pressure can be ensured. The tortoise-shell-like structure can be confirmed, for example, by observing the main surface of the porous membrane 1 from a vertical direction. In this disclosure, "main surface" means the surface having the largest area of ​​a sheet-like or film-like member. Also, in this disclosure, "main surface" and "surface" of the porous membrane 1 are used interchangeably.

[0025] In this disclosure, "a tortoise-shell-like structure formed by a plurality of nodes 1a and a plurality of fibrils 1b" refers to a structure that can be confirmed by observing the surface of the porous membrane 1 with a scanning electron microscope (SEM), and means a structure in which island-like regions 1c formed by a plurality of nodes 1a are irregularly connected, and these island-like regions 1c are connected to each other by a plurality of fibrils 1b. Examples of island-like regions 1c include polygonal regions. Note that the polygonal region does not necessarily have to be composed only of straight lines, and also includes substantially polygonal regions in which some of the sides are curves such as circular arcs. The polygon is, for example, a hexagon, but is not limited to this, and may be a pentagon or a quadrilateral, for example. The tortoise-shell-like structure may include a plurality of island-like regions 1c and a plurality of fibrils 1b extending in multiple directions from each of the island-like regions 1c. The island-like regions 1c may be connected to each other or overlap without the use of a plurality of fibrils 1b (see part I in Figure 1B). In other words, multiple fibrils 1b do not necessarily exist between adjacent island-like regions 1c. Island-like regions 1c, which are aggregates of multiple nodes 1a, and nodes 1a may be mixed together (see part II of Figure 1B). Planar regions 1d may exist, formed by the dense concentration of multiple fibrils 1b extending in multiple directions from each of the island-like regions 1c (see part III of Figure 1B). When the surface of the porous membrane 1 is observed with an SEM, the distinction between the planar regions 1d formed by the dense concentration of multiple fibrils 1b and the island-like regions 1c formed by multiple nodes 1a may not be clear at first glance. However, even in such cases, it is possible to distinguish between the island-like regions 1c and the planar regions 1d by magnifying the observation image to, for example, about 10,000 times. The island-like regions 1c may have a more raised shape than the planar regions 1d. When the surface of the porous membrane 1 is observed with an SEM, the longest diameter of the island-like regions 1c may be 0.5 μm or more, 1 μm or more, or even 2 μm or more.

[0026] In the present disclosure, the term "turtle shell-like" is a name given by focusing on the island-shaped region 1c, which represents the state where the island-shaped regions 1c are irregularly arranged like a turtle shell, and does not necessarily mean that the island-shaped regions 1c are densely arranged like a turtle shell.

[0027] The average distance between adjacent island-shaped regions 1c and island-shaped regions 1c is, for example, 0.1 μm or more and 30 μm or less. The lower limit of the average distance of the island-shaped regions 1c may be 0.5 μm or more, 1 μm or more, 2 μm or more, or even 4 μm or more. The upper limit of the average distance of the island-shaped regions 1c may be 20 μm or less, 15 μm or less, 10 μm or less, or even 8 μm or less.

[0028] The average area of the island-shaped region 1c is, for example, 0.1 μm 2 or more and 100 μm 2 or less. The lower limit of the average area of the island-shaped region 1c may be 0.5 μm 2 or more, 1 μm 2 or more, 5 μm 2 or more, 10 μm 2 or more, or even 14 μm 2 or more. The upper limit of the average area of the island-shaped region 1c may be 75 μm 2 or less, 65 μm 2 or less, 55 μm 2 or less, or even 50 μm 2 or less. 2

[0029] The average distance between island-like regions of the porous membrane 1 can be determined by the method described below. Figure 20 is a schematic diagram illustrating how to determine the distance between island-like regions of the porous membrane 1 shown in Figure 1A. First, the surface of the porous membrane 1 is observed using a scanning electron microscope (SEM) (see, for example, Figure 1B). Next, the obtained SEM observation image (or a part thereof) is binarized using image analysis software. Island-like regions are identified from the obtained binarized image, and the area of ​​each island-like region included in the image is calculated. For each island-like region, the equivalent diameter of a circle is calculated from the calculated area. The equivalent diameter of a circle is the diameter of a perfect circle having the same area as the island-like region being measured. As shown in Figure 20, the distance L between island-like regions A and island-like region B is calculated. AB This can be calculated by subtracting the equivalent diameter of the circle of island region A × 1 / 2 and the equivalent diameter of the circle of island region B × 1 / 2 from the distance between the centroid c of island region A and the centroid c of island region B. In this way, for the three island regions (island region B, island region C, and island region D) that are the 1st to 3rd closest in distance from island region A, the distance between the island regions (L AB , L AC and L AD ) is calculated. That is, the distance from island region A to the 4th and subsequent island regions (island region E) is the distance between the island regions (L AE ) will not be used. However, island regions that overlap with island region A in the image (island region F) will be excluded from the three island regions that are closest to island region A (1st to 3rd closest). The average of the distances between island regions and the three island regions closest to island region A, determined in this way, will be considered as the distance between island regions of island region A. The distance between island regions will be determined similarly for each island region included in the image. The average value of the determined distances between island regions can be considered as the average spacing between island regions of porous membrane 1. When identifying island regions, island regions that fall at the edge of the image will be excluded from the analysis. For example, imageJ can be used as image analysis software.

[0030] The average area of ​​the island-like regions of the porous membrane 1 can be determined by the method described below. First, a binarized image is obtained using the same method as described for determining the distance between island-like regions of the porous membrane 1, and nodes are identified from the binarized image. Island-like regions are identified from the obtained binarized image, and the area of ​​each island-like region included in the image is calculated. The average value of the calculated island-like region areas can be considered as the average area of ​​the island-like regions of the porous membrane 1. However, the average area of ​​the island-like regions of the porous membrane 1 should be determined by measuring 30 or more island-like regions, for example, 50 to 200 island-like regions.

[0031] Figures 10 to 12B and 13 to 14B show the results of SEM observation of the surface of the porous membranes of Examples 1 to 5, which will be described later. As shown in these observation images, the surface of the porous membranes of Examples 1 to 5 has a tortoise-shell-like structure formed by multiple nodes and multiple fibrils. Specifically, island-like regions 1c formed by multiple nodes 1a are irregularly connected, and these island-like regions 1c are connected to each other by multiple fibrils 1b.

[0032] When observing a cross-section of the porous membrane 1, multiple nodes may be present along the thickness direction. These multiple nodes may extend throughout the entire thickness direction of the porous membrane 1. This structure can suppress the reduction in membrane thickness caused by compression during mounting to a device housing or the like.

[0033] Nodes present in the thickness direction may be lumpy. That is, when observing a cross-section of the porous membrane 1, multiple lumpy nodes may be present along the thickness direction. Lumpy nodes present in the thickness direction correspond to island-like regions when the surface of the porous membrane 1 is observed with a scanning electron microscope (SEM).

[0034] Multiple clump-like nodes may be uniformly distributed across the thickness direction of the porous membrane 1. Adjacent clump-like nodes may be connected by multiple fibrils, or adjacent clump-like nodes may be directly connected to each other without being connected by multiple fibrils.

[0035] Figure 12C shows the results of observing a cross-section of the porous membrane of Example 3, which will be described later, using SEM. As shown in Figure 12C, when observing the cross-section of the porous membrane of Example 3, multiple clump-like nodes are found along the thickness direction. These multiple clump-like nodes are present throughout the entire thickness direction of the porous membrane.

[0036] Porous membrane 1 has a density of 2.5 N / mm². 2 The compressibility Rc in the thickness direction of the porous membrane 1 when pressure is applied is 20% or less. The compressibility Rc is a value per unit amount of resin. In this way, the porous membrane 1 suppresses the reduction in membrane thickness caused by compression when attached to the device housing, etc., so that an appropriate attachment pressure can be ensured.

[0037] The compressibility Rc can be determined by a compression test using a thermomechanical measuring device (TMA). Figure 21 is a schematic cross-sectional view illustrating the compression test. First, the porous membrane 1 is cut into strips 10 mm wide and 10 mm long to form a sample piece S. Next, in an environment of 25°C, a cylindrical indenter 90 with a tip diameter of 1 mm of the TMA is used to gradually apply a load from an initial load P1 (gf) (see (A) in Figure 21) to a maximum load P max While compressing the sample piece S at a loading rate of 50 gf / min until (gf) (see Figure 21 (B)), load P n The function F1 is obtained between (gf) and the deformation rate in the compression direction (%). Note that the load P n The deformation rate (%) at (gf) is given by the load P1(gf) relative to the thickness T1(μm) of the sample piece S at the initial load P1(gf). n Thickness T of sample piece S in (gf) n (μm), and 100 × T n This is calculated using / T1. Next, the function F1 is calculated using the area of ​​the indenter 90 (0.785 mm²). 2 Using ), the load per unit area Pa (gf / mm²) 2 Convert the load Pa (gf / mm²) into a function F2 of deformation rate (%). 2 ) = load P n (gf) / 102 / area of ​​indenter 90 (mm2 Furthermore, considering the pores present in the porous membrane 1, the function F2 is converted to a unit amount of resin, and the load Pb(gf / mm) applied per unit amount of resin is calculated. 2 Obtain the function F3 of the deformation rate (%) at load Pb(gf / mm 2 ) = Load Pa (gf / mm 2 ) / {(100-porosity) / 100}). In function F3, the load Pb is 2.5 gf / mm 2 The rate of deformation (%) at point R is the rate of change. 2.5 When defined as, 100-R 2.5 The value obtained is considered to be the compressibility ratio Rc(%). The measurement conditions for the above compression test are shown below. <Measurement conditions> Initial load P1: 2gf Maximum load P max :500gf Loading speed: 50 gf / min

[0038] The compression ratio Rc may be 19.5% or less, or 19% or less. The lower limit of the compression ratio Rc is, for example, 5%.

[0039] As described above, the melting point of the thermoplastic resin contained in the porous membrane 1 is between 180°C and 300°C. The melting point of the thermoplastic resin being above 180°C ensures sufficient heat resistance in the porous membrane 1. The melting point of the thermoplastic resin being below 300°C allows the porous membrane 1 to be manufactured, for example, by melt molding.

[0040] The melting point of the thermoplastic resin may be between 200°C and 280°C, and may also be between 220°C and 260°C.

[0041] Thermoplastic resins having a melting point between 180°C and 300°C may be fluorine-free thermoplastic resins. Fluorine-free thermoplastic resins may be polyolefin resins. Polyolefin resins include polyethylene (PE) resin, polypropylene (PP) resin, and polymethylpentene (PMP) resin.

[0042] Examples of thermoplastic resins include polymethylpentene resins such as poly(4-methylpentene-1) resin (polymethylpentene resin) and poly(3-methylbutene-1) resin; polyethylene terephthalate resin; polybutylene terephthalate resin; polyethylene naphthalate resin; polyacetal resin; polyphenylene sulfide resin; polyether ether ketone resin; syndiotactic polystyrene resin; ethylene-carbon monoxide copolymer resin; polyamide resins such as nylon 6 resin and nylon 66 resin; cycloolefin polymer (COP) resin; polyphenylene ether (PPE) resin; polyetherimide (PEI) resin; and polyphenylene oxide (PPO) resin.

[0043] The thermoplastic resin may be polymethylpentene resin. Polymethylpentene resin is a homopolymer or copolymer of poly(4-methylpentene-1) resin and poly(3-methylpentene-1) resin, etc. Copolymers include random copolymers and block copolymers. From the viewpoint of heat resistance and moldability, a homopolymer of poly(4-methylpentene-1) resin is preferred. Polymethylpentene resin has a melting point of 230°C to 240°C. Therefore, with such a configuration, a porous film suitable for suppressing thickness reduction due to compression when attached to a device housing, etc., is easily obtained.

[0044] The thermoplastic resin may be poly(4-methylpentene-1) resin. Poly(4-methylpentene-1) resin means a homopolymer of 4-methylpentene-1, or a copolymer of 4-methylpentene-1 and at least one type of α-olefin. The composition ratio of 4-methylpentene-1 to α-olefin contained in the copolymer can be adjusted within a range of melting points of 180°C or higher.

[0045] The porous membrane 1 may contain additives other than thermoplastic resin, such as plasticizers and antioxidants.

[0046] The air permeability in the thickness direction of the porous membrane 1 may be expressed in Gurley numbers as 0.1 / 100mL or more and 10,000 seconds / 100mL or less. In this specification, "Gurley number" is the air permeability resistance (Gurley air permeability) measured in accordance with the Ogane testing machine method specified in JIS P8117:2009. The lower limit of the air permeability of the porous membrane 1 may be expressed in Gurley numbers as 10 seconds / 100mL or more, 30 seconds / 100mL or more, 50 seconds / 100mL or more, and even 70 seconds / 100mL or more. The upper limit of the air permeability of the porous membrane 1 may be expressed in Gurley numbers as 5,000 seconds / 100mL or less, 1,000 seconds / 100mL or less, and even 500 seconds / 100mL or less.

[0047] Furthermore, even if the size of the porous membrane 1 is less than the recommended dimensions (50 mm x 50 mm) for the test specimen of the Wang Ken testing machine method, it is still possible to evaluate the air permeability resistance (Gurley air permeability) in accordance with the Wang Ken testing machine method by using a measuring jig.

[0048] The measuring jig has a shape and size that can be placed in the air permeability measuring section of the Wangyan type testing machine, and has a thickness and material that does not deform due to the differential pressure applied to the test piece when measuring air permeability resistance. An example of a measuring jig is a SUS disc with a thickness of 2 mm and a diameter of 47 mm. A through hole with an opening smaller in size than the membrane to be evaluated is provided at the center of the surface of the measuring jig. The cross-section of the through hole is typically circular, and its diameter is such that the opening of the through hole is completely covered by the membrane to be evaluated. For example, the diameter of the through hole can be 1 mm or 2 mm. Next, the porous membrane 1 to be evaluated is fixed to one side of the measuring jig so as to cover the above opening. The fixing is done so that during the measurement of air permeability resistance, air passes only through the opening and the effective test portion of the porous membrane 1 to be evaluated (the portion that overlaps with the opening when viewed from a direction perpendicular to the main surface of the fixed porous membrane 1), and so as not to obstruct the passage of air in the effective test portion of the porous membrane 1. To fix the porous membrane 1, double-sided adhesive tape with a vent punched out in the center that matches the shape of the opening can be used. The double-sided adhesive tape should be placed between the measuring jig and the porous membrane 1 so that the circumference of the vent coincides with the circumference of the opening. Next, the measuring jig with the porous membrane 1 fixed to it is set in the air permeability measurement section of the Wang-Lan testing machine so that the fixed surface of the porous membrane 1 is on the downstream side of the airflow during measurement, and the test is performed according to the Wang-Lan testing machine method, and the air permeability resistance indicator value t shown by the testing machine is recorded. Next, the recorded air permeability resistance indicator value t is set to the effective test area of ​​6.452 [cm²] specified in the Wang-Lan testing machine method. 2 ] Value per t K In the formula t K = {t × (area of ​​the effective test portion of porous membrane 1 [cm²] 2 ]) / 6.452[cm 2 Converted using ]}, the obtained converted value t K This can be considered the air permeability resistance (Gurley air permeability) of the porous membrane 1 measured in accordance with the Wang-Len testing machine method. It has been confirmed that the air permeability resistance measured without using a measuring jig for a porous membrane 1 that meets the recommended dimensions (50 mm x 50 mm) of the Wang-Len testing machine method agrees well with the air permeability resistance measured using a measuring jig after the porous membrane 1 has been cut into pieces, meaning that the use of a measuring jig does not substantially affect the measured value of air permeability resistance.

[0049] The water pressure resistance of the porous membrane 1 may be 10 kPa or higher, as evaluated by the water pressure resistance test method B (high water pressure method) specified in JIS L1092:2009. The lower limit of the water pressure resistance of the porous membrane 1 may be 100 kPa or higher, 130 kPa or higher, or even 150 kPa or higher. The upper limit of the water pressure resistance of the porous membrane 1 is, for example, 2000 kPa or lower.

[0050] The water pressure resistance of the porous membrane 1 can be measured using a measuring jig in accordance with the water pressure resistance test method described above, as follows. An example of a measuring jig is a 47 mm diameter stainless steel (SUS) disc with a 2.0 mm diameter through-hole (having a circular cross-section) in the center. This disc has a thickness that does not deform under the water pressure applied when measuring water pressure resistance. The water pressure resistance measurement using this measuring jig can be carried out as follows.

[0051] The porous membrane 1 to be evaluated is fixed to one side of the measuring jig so as to cover the opening of the through-hole in the measuring jig. The fixing is done in a way that prevents water from leaking from the fixed part of the membrane during water pressure resistance measurement. For fixing the porous membrane 1, double-sided adhesive tape with a water inlet punched out in the center that matches the shape of the opening can be used. The double-sided adhesive tape should be placed between the measuring jig and the porous membrane 1 so that the circumference of the water inlet matches the circumference of the opening. Next, the measuring jig with the porous membrane 1 fixed is set in the test apparatus so that the side opposite to the fixing surface of the porous membrane 1 becomes the water pressure application surface during measurement, and the water pressure resistance is measured according to the water resistance test method B (high water pressure method) specified in JIS L1092:2009. However, the water pressure resistance is measured based on the water pressure when water is released from one point on the membrane surface of the porous membrane 1. The measured water pressure resistance can be used as the water pressure resistance of the porous membrane 1. The test apparatus can be one that has a configuration similar to the water resistance test apparatus exemplified in JIS L1092:2009, and also has a specimen mounting structure that allows the above-mentioned measuring jig to be set.

[0052] The porosity of the porous membrane 1 is, for example, 25% or more. The porosity of the porous membrane 1 may be 20% or more, or 35% or more. The porosity can be calculated by substituting the mass, thickness, area (area of ​​the main surface), and true density of the porous membrane 1 into the following formula (1).

[0053] Porosity (%) = {1 - (mass [g] / (thickness [cm] × area [cm] 2 ] × true density [g / cm 3 ]))}×100...Equation (1)

[0054] The upper limit of the porosity of the porous membrane 1 is, for example, 95%. The upper limit of the porosity of the porous membrane 1 may also be 90%.

[0055] The porous membrane 1 may be in the form of a sheet or a film. The thickness of the porous membrane 1 is, for example, 1 μm or more and 100 μm or less. This structure makes it easier to suppress the reduction in the thickness of the membrane due to compression when it is attached to a device housing or the like. The thickness of the porous membrane 1 may be 5 μm or more and 80 μm or less, or 10 μm or more and 70 μm or less.

[0056] The thickness of the porous membrane 1 can be determined by measuring the thickness at any five points on the porous membrane 1 using, for example, a dial gauge, and taking the average of these measurements. Alternatively, the thickness of the porous membrane 1 can be determined by measuring the thickness at any five points in the SEM image of the cross-section of the porous membrane 1 and taking the average of these measurements.

[0057] At least one main surface of the porous film 1 may be subjected to a surface modification treatment. Examples of surface modification treatments include chemical treatment, sputter etching, liquid repellency treatment, and plasma treatment. In the region where the surface modification treatment has been applied, the bonding properties of the porous film 1 are improved.

[0058] [Method for manufacturing porous membranes] The porous membrane 1 described above can be manufactured, for example, by the following method.

[0059] The method for producing the porous membrane 1 includes kneading a composition containing a thermoplastic resin having a melting point of 180°C or more and a plasticizer to obtain a kneaded product (step S1), hot-pressing the kneaded product to obtain a pressed product (step S2), cooling the pressed product to obtain a molded product (step S3), stretching the molded product to obtain a sheet (step S4), and extracting and removing the plasticizer from the sheet (step S5).

[0060] Steps S1 to S3 correspond to the process of fabricating a precursor for the porous membrane 1. Steps S4 to S5 correspond to the process of growing the porous structure.

[0061] Step S1 is carried out, for example, at a temperature of 230°C to 260°C for 5 to 30 minutes.

[0062] Polymethylpentene resin can be used as a thermoplastic resin with a melting point between 180°C and 300°C.

[0063] The composition containing the thermoplastic resin and plasticizer may also contain other resins, such as polyethylene, polypropylene, poly-1-butene, and cyclic polyolefins, to the extent that they do not affect the properties of the porous membrane 1.

[0064] A plasticizer is a non-volatile solvent that, when mixed with a thermoplastic resin such as polymethylpentene resin, forms a mixture above the melting point of the resin, and exhibits thermally induced phase separation when the mixture is cooled. The form of the plasticizer may be liquid or solid at room temperature. The plasticizer may be used alone or in a mixture of two or more plasticizers. For example, such a plasticizer may have a kinematic viscosity of 50 to 150 mmHg at 40°C. 2 The / s option can be used.

[0065] The mixing ratio of the thermoplastic resin and the plasticizer is set so that a uniform kneaded product can be obtained in step S1 and a molded article can be formed in step S3. Specifically, the weight ratio of the thermoplastic resin in the composition containing the thermoplastic resin and the plasticizer is, for example, 20 wt% to 80 wt%, preferably 30 wt% to 70 wt%. A weight ratio of 20 wt% or more of the thermoplastic resin prevents the viscosity of the composition from decreasing too much. A weight ratio of 80 wt% or less of the thermoplastic resin makes it easier to obtain a good porous structure.

[0066] The composition containing the thermoplastic resin and plasticizer may further contain additives such as antioxidants, nucleating agents, antistatic agents, flame retardants, lubricants, ultraviolet absorbers, colorants, and inorganic fillers for strength improvement, depending on the purpose.

[0067] Step S2 is carried out, for example, at a temperature of 230°C to 260°C for 2 to 30 minutes. The thickness of the pressed body obtained by step S2 is, for example, 0.1 mm.

[0068] In step S3, for example, the pressed body obtained in step S2 may be cooled and solidified to a temperature sufficiently lower than the crystallization temperature of the thermoplastic resin by bringing it into contact with a heat conductor. Examples of heat conductors used for cooling include water, air, plasticizers, and metals. Water is preferred as the heat conductor used for cooling.

[0069] In step S4, the molded body is stretched at least once in at least one axial direction. This stretching in at least one axial direction includes longitudinal uniaxial stretching, transverse uniaxial stretching, simultaneous biaxial stretching, and sequential biaxial stretching. The molded body may be sequentially biaxially stretched, or simultaneously biaxially stretched. Step S4 causes pores to form in the molded body.

[0070] The stretching temperature may be 20°C to 240°C, 50°C to 230°C, or even 100°C to 220°C for both longitudinal and transverse stretching.

[0071] The stretching ratio may be 2.0 to 10.0 times, 2.0 to 8.0 times, or even 2.0 to 5.0 times, in the uniaxial direction of the longitudinal and / or transverse direction.

[0072] The strain rate during stretching may be 1% / second to 10% / second, 2% / second to 8% / second, or even 3% / second to 5% / second in the longitudinal and / or transverse directions. When the strain rate is within the above numerical range, fracture is less likely to occur during stretching, and productivity is further improved. When the strain rate is within the above numerical range, 2.5 N / mm 2 Porous membranes with a compressibility ratio Rc in the thickness direction of 20% or less when pressure is applied are easily realized.

[0073] In step S5, for example, the plasticizer is extracted and removed from the sheet using an extraction solvent.

[0074] As the extraction solvent, a solvent that is a poor solvent for thermoplastic resins such as polymethylpentene resin, but a good solvent for plasticizers, and whose boiling point is lower than the melting point of the porous membrane is preferably used. Examples of such extraction solvents include hydrocarbons such as n-hexane and cyclohexane; halogenated hydrocarbons such as methylene chloride and 1,1,1-trichloroethane; alcohols such as ethanol and isopropanol; ethers such as diethyl ether and tetrahydrofuran; and ketones such as acetone and 2-butanone. Considering safety, alcohols and ketones are preferably used. Methyl ethyl ketone (MEK) may also be used as the extraction solvent.

[0075] Between step S4 and step S5, the sheet may be heat-set. Heat setting can be performed, for example, using a hot air circulating oven. By performing heat setting, the thermal shrinkage of the sheet after stretching can be reduced. The heat setting temperature is, for example, 50°C to 240°C. The heat setting temperature may also be 100°C to 230°C, or even 150°C to 220°C.

[0076] Heat setting may be performed after step S4, between steps S4 and S5, or both after step S4 and after S5. Methods for heat setting include fixing the width direction with a tenter and passing it continuously through the heat treatment furnace, applying appropriate tension and passing it continuously through the heat treatment furnace without fixing the width direction, or winding it onto a roll and feeding it into the heat treatment furnace in batches.

[0077] [Ventilation components] An example of the ventilation member of the present invention is shown in Figure 2. The ventilation member 2(2A) in Figure 2 comprises a porous membrane 1. A modified example of the ventilation member of Figure 2 is shown in Figure 3. The ventilation member 2(2B) in Figure 3 further comprises a breathable support material 3. The breathable support material 3 is laminated on the porous membrane 1. The breathable support material 3 improves the strength and handling of the ventilation member 2.

[0078] The breathable support material 3 typically has higher breathability in the thickness direction compared to the porous membrane 1. Examples of breathable support material 3 include woven fabrics, nonwoven fabrics, nets, and meshes. Examples of materials constituting the breathable support material 3 include polyesters such as polyethylene terephthalate (PET), polyolefins such as polyethylene (PE) and polypropylene (PP), and aramid resins. The shape of the breathable support material 3 may be the same as or different from the shape of the porous membrane 1 when viewed perpendicular to the main surface of the ventilation member 2. The breathable support material 3 may have a shape corresponding to the peripheral edge of the porous membrane 1 when viewed perpendicular to the main surface of the ventilation member 2. If the shape of the porous membrane 1 is circular, this shape is ring-shaped. The composition and shape of the breathable support material 3 are not limited to the above examples.

[0079] The ventilation member 2B in Figure 3 comprises one breathable support member 3 positioned on one side of the porous membrane 1. The ventilation member 2 may comprise two or more breathable support members 3. In the ventilation member 2, breathable support members 3 may be positioned on both sides of the porous membrane 1. The porous membrane 1 and the breathable support member 3 may be joined by welding such as heat welding and ultrasonic welding, adhesives, or other adhesives.

[0080] The ventilation member 2 may include any other layers and / or members other than those described above.

[0081] The thickness of the ventilation member 2 is, for example, 1 to 300 μm, and may also be 50 to 200 μm.

[0082] The basis weight of the ventilation member 2 is, for example, 1.0 to 200.0 g / m². 2 Therefore, 10.0~100.0 g / m 2 That's fine.

[0083] The ventilation member 2 may have the same properties as the porous membrane 1, for example, air permeability in the thickness direction and / or water pressure resistance.

[0084] The ventilation member 2 may be treated with a liquid-repellent coating and / or a coloring coating.

[0085] The ventilation member 2 can be used, for example, as a filter member. However, the applications of the ventilation member 2 are not limited to the above examples.

[0086] The shape of the ventilation member 2, when viewed perpendicular to the main surface of the ventilation member 2, may be, for example, a polygon including squares and rectangles, a circle, an ellipse, or a strip. The corners of the polygon may be rounded. However, the shape of the ventilation member 2 is not limited to the above examples. A strip-shaped ventilation member 2 may be wound to form a wound body. Alternatively, it may be wound in a laminated state with a release liner, if necessary.

[0087] A modified example (winding body) of the ventilation member shown in Figure 2 is shown in Figure 4. The winding body 10 shown in Figure 4 includes the ventilation member 2A and the release liner 11 of Figure 2. The ventilation member 2A and the release liner 11 are joined to each other by an adhesive layer 12. In the winding body 10, the peeling surface 13 formed when the release liner 11 is peeled off from the ventilation member 2A is located between the ventilation member 2A and the adhesive layer 12. That is, in the winding body 10, when the release liner 11 is peeled off, the adhesive layer 12 is also peeled off from the ventilation member 2A, resulting in a ventilation member 2A in which the adhesive layer 12 is not formed on the surface.

[0088] The ventilation member 2A, supplied by the wound body 10 and without an adhesive layer 12 formed on its surface, can be joined to the opening of the housing by any joining method. In other words, the ventilation member 2A has a high degree of freedom in terms of how it can be joined to the opening of the housing. Joining methods include, for example, joining by a newly placed adhesive layer on the surface of the ventilation member 2A, joining by heat welding, and joining by ultrasonic welding.

[0089] The ventilation member 2A supplied by the wound body 10 can be processed into any shape as needed. In other words, the ventilation member 2A has a high degree of freedom in shape. However, "shape" includes "size". The above point means that, according to the wound body 10, the ventilation member 2A, which functions as a waterproof membrane, can be supplied with a high degree of freedom in terms of the method of joining to the opening of the housing and / or in terms of shape.

[0090] Furthermore, with the winding body 10, the slippage between the ventilation member 2A and the release liner 11 during winding is suppressed by the adhesive layer 12. The winding body 10 can suppress the occurrence of malfunctions (abnormal shape of the winding body) caused by winding tightness during winding.

[0091] [Filter components] An example of the filter member of the present invention is shown in Figure 5. The filter member 4(4A) in Figure 5 has permeability in the thickness direction and includes the ventilation member 2 described above as a ventilation member that prevents the passage of foreign matter in that direction. The filter member 4A is, for example, placed on the surface of an object having an opening, to ensure ventilation through the opening while preventing the passage of foreign matter through the opening. In this case, the filter member 4A is usually placed such that the ventilation member 2 covers the opening of the object.

[0092] The filter member 4A includes an adhesive layer 5 positioned on one side of the ventilation member 2. The ventilation member 2 and the adhesive layer 5 are directly joined together. The filter member 4A can be positioned on the surface of an object via the adhesive layer 5.

[0093] When handling the filter member 4 and when placing it on an object, strong force may be applied to the member 4 in a specific direction. However, the ventilation member 2 has a tortoise-shell-like structure formed by multiple nodes and multiple fibrils, and is equipped with a porous membrane 1 that can suppress the reduction in membrane thickness due to compression. For this reason, for example, the filter member 4 can be manufactured without limiting the direction in which the ventilation member 2 (or porous membrane 1) is incorporated into the filter member 4.

[0094] Examples of adhesives constituting the adhesive layer 5 include acrylic adhesives, silicone adhesives, urethane adhesives, epoxy adhesives, and rubber adhesives. When it is necessary to consider the use of the filter member 4 at high temperatures, it is preferable to select an acrylic adhesive or a silicone adhesive, particularly a silicone adhesive, which has excellent heat resistance. The adhesive layer 5 may also be a substrate-less double-sided adhesive tape. The adhesive may also be a curable adhesive such as a phenolic resin, epoxy resin, urea resin, polyurethane resin, melamine resin, and polyester resin.

[0095] The outer circumference of the ventilation member 2 and the outer circumference of the adhesive layer 5 coincide when viewed perpendicular to the main surface of the ventilation member 2. Furthermore, the shape of the adhesive layer 5 corresponds to the peripheral edge of the ventilation member 2 when viewed perpendicular to the main surface of the ventilation member 2. The area of ​​the ventilation member 2 not joined to the adhesive layer 5 can be used as the ventilation area of ​​the filter member 4A. However, the shape of the adhesive layer 5 is not limited to the above example.

[0096] The area of ​​the ventilation zone is, for example, 40 mm². 2 The following applies: A filter member 4 whose ventilation area falls within this range is suitable for placement on objects with small diameter openings, for example. The lower limit of the ventilation area is, for example, 0.008 mm. 2 That concludes the explanation. However, the area of ​​the ventilation region may be larger depending on the type of object on which the filter member 4 is placed.

[0097] A modified example of the filter member 4 in Figure 5 is shown in Figure 6. The filter member 4 (4B) in Figure 6 further comprises a base material layer 6 positioned on one side of the ventilation member 2, and the ventilation member 2 and the adhesive layer 5 are joined via the base material layer 6, except that it has the same configuration as the filter member 4A. The base material layer 6 improves the strength and handling of the filter member 4 and suppresses damage to the ventilation member 2 during handling and placement on an object.

[0098] Examples of materials constituting the base layer 6 include polyolefins such as PE and PP, polyesters such as PET, silicone resins, polycarbonates, polyimides, polyamide-imides, polyphenylene sulfide, polyether ether ketone (PEEK), polyvinyl chloride, fluororesins, and metals such as aluminum and stainless steel. Examples of fluororesins include PTFE, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-ethylene copolymer (ETFE). However, the materials constituting the base layer 6 are not limited to the above examples.

[0099] The outer circumference of the ventilation member 2 and the outer circumference of the base material layer 6 coincide when viewed perpendicular to the main surface of the ventilation member 2. Furthermore, the shape of the base material layer 6 corresponds to the peripheral edge of the ventilation member 2 when viewed perpendicular to the main surface of the ventilation member 2. The area of ​​the ventilation member 2 where the base material layer 6 is not joined can be used as the ventilation area of ​​the filter member 4B. However, the shape of the base material layer 6 is not limited to the above example.

[0100] The ventilation member 2 and the base layer 6 may be joined by an adhesive or bonding agent, or by welding such as heat welding and ultrasonic welding. The ventilation member 2 and the base layer 6 may also be joined by an adhesive layer. This adhesive layer may have the same configuration as the adhesive layer 5. The base layer 6 and the adhesive layer 5 may be the base material and adhesive layer of a single-sided adhesive tape or a double-sided adhesive tape, respectively.

[0101] A modified example of the filter member 4 in Figure 5, Part 2, is shown in Figure 7. The filter member 4 (4C) in Figure 7 has the same configuration as the filter member 4B, except that it further comprises a base material layer 6 (6B) positioned on the other side of the ventilation member 2. The ventilation member 2 is sandwiched between the pair of base material layers 6 (6A, 6B). This sandwiching structure further improves the strength and handling of the filter member 4.

[0102] A modified example 3 of the filter member 4 in Figure 5 is shown in Figure 8. The filter member 4 (4D) in Figure 8 has the same configuration as the filter member 4C, except that it further includes a tab film 7 and the tab film 7 is joined to the base material layer 6 (6B) via an adhesive layer 5 (5B). The tab film 7 has tabs that protrude outward from the outer circumference of the base material layer 6B when viewed perpendicular to the main surface of the base material layer 6B. The filter member 4D can be handled and placed on the surface of an object by gripping the tabs. The tab film 7 is usually removed when the filter member 4D is used. The tab film 7 may be made of the same material as the material that constitutes the base material layer 6. The tab film 7 is usually removed by gripping the tabs and lifting it. At this time, a strong force is applied to the ventilation member 2 in the lifting direction.

[0103] [Component supply assembly] The filter member 4 can be supplied, for example, by a member supply sheet. An example of a member supply assembly, which is a method of supplying the filter member 4, is shown in Figure 9. The member supply assembly 20 in Figure 9 comprises a filter member 4 that is placed on the surface of an object having an opening, and a base sheet 9 on which the filter member 4 is placed. The member supply assembly 20 shown in Figure 9 includes a filter member 4D as the filter member 4.

[0104] The filter member 4(4D) is placed on the base sheet 9 via an adhesive layer 5. The member supply assembly 20 allows for efficient supply of the filter member 4, for example, to a step of placing it on the surface of an object.

[0105] The filter member 4 may be placed on the base sheet 9 via an adhesive layer provided on the surface on which the filter member 4 is placed. The adhesive layer on the placement surface is preferably weakly tacky.

[0106] Although not shown in the diagram, multiple filter members 4 may be arranged on the surface of the base sheet 9.

[0107] Examples of materials constituting the base sheet 9 include paper, metal, resin, and composite materials thereof. Examples of metals include stainless steel and aluminum. Examples of resins include polyester such as PET, and polyolefins such as PE and PP. However, the materials constituting the base sheet 9 are not limited to the above examples. The base sheet 9 may be in the form of a single sheet or a strip. If the sheet 9 is in the form of a strip, the component supply assembly 20 may be wound to form a wound body.

[0108] Examples of objects on which the filter member 4 is placed include the housings of electronic devices and the housings of vehicle electrical components. The filter member 4 can be placed on the outer and / or inner surfaces of the housing. In this case, the opening may be a vent and / or sound vent provided in the housing. Examples of electronic devices include wearable devices such as smartwatches and wristbands; various cameras including action cameras and security cameras; information and communication devices such as mobile phones, smartphones and tablets; virtual reality (VR) devices; augmented reality (AR) devices; and sensor devices. Examples of vehicle electrical components include lamps and ECUs. However, the objects are not limited to the above examples.

[0109] The foreign matter that is prevented from passing through by the arrangement of the filter element 4 is, for example, particles such as dust, or liquid water such as water droplets. [Examples]

[0110] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the examples shown below.

[0111] [Example 1] As the thermoplastic resin, poly(4-methylpentene-1) resin (manufactured by Mitsui Chemicals, RT18, melting point: 232°C) was prepared. As the plasticizer, a resin with a kinematic viscosity of 110 mm at 40°C was used. 2 Liquid paraffin (MORESCO) with a concentration of 1 / s was prepared. Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (BASF Japan) was prepared as an antioxidant. 50.0 wt% of thermoplastic resin, 49.8 wt% of plasticizer, and 0.2 wt% of antioxidant were mixed to obtain a mixture. The mixture was kneaded using a Laboplast Mill (Toyo Seiki Seisakusho) at 260°C for 30 minutes to obtain a homogeneous knead. The knead was hot-pressed using a compression molding machine heated to 260°C to obtain a pressed body. The pressed body was cooled by contacting it with 18°C ​​water while sandwiched between a pair of polyimide plates to obtain a molded body.

[0112] Next, the molded body was simultaneously biaxially stretched using a biaxial stretcher under the conditions of a stretching temperature of 150°C and a stretching ratio of 2.5 times (longitudinal direction) × 2.5 times (transverse direction). The strain rate during stretching was 4% / second (2.6 mm / second) in both the longitudinal and transverse directions. This yielded a sheet. Finally, using methyl ethyl ketone (MEK) as the extraction solvent, the sheet was immersed in MEK at room temperature for 2 minutes to perform an extraction operation. This extracted and removed the plasticizer from the sheet. The extraction operation was carried out with the sheet fixed to a stainless steel frame to suppress shrinkage. In this way, the porous film of Example 1 was obtained.

[0113] Figure 10 shows the results of observing the surface of the porous membrane of Example 1 using SEM (2500x magnification).

[0114] [Example 2] As a plasticizer, its kinematic viscosity at 40°C is 68 mmHg. 2 Liquid paraffin (MORESCO) with a concentration of 1 / s was prepared. A mixture was obtained by mixing 70.0 wt% thermoplastic resin, 29.8 wt% plasticizer, and 0.2 wt% antioxidant. The mixture was kneaded using a laboplast mill at 230°C for 30 minutes to obtain a homogeneous knead. The porous membrane of Example 2 was obtained by the same method as in Example 1, except for these steps.

[0115] Figure 11 shows the results of observing the surface of the porous membrane of Example 2 using SEM (2500x magnification).

[0116] [Example 3] As a plasticizer, its kinematic viscosity at 40°C is 92 mmHg. 2 Liquid paraffin (MORESCO) with a concentration of / s was prepared. Apart from these, the porous membrane of Example 3 was obtained using the same method as in Example 1.

[0117] Figure 12A shows the results of SEM observation of the surface of the porous membrane of Example 3 (2500x magnification). Figure 12B is a magnified view of a portion of Figure 12A (10000x magnification). Figure 12C shows the results of SEM observation of the cross-section of the porous membrane of Example 3 (1500x magnification).

[0118] [Example 4] As a plasticizer, its kinematic viscosity at 40°C is 68 mmHg. 2 Liquid paraffin (MORESCO) with a viscosity of 1 / s was prepared. A mixture was obtained by mixing 30.0 wt% thermoplastic resin, 69.8 wt% plasticizer, and 0.2 wt% antioxidant. The mixture was kneaded using a laboplast mill at 230°C for 30 minutes to obtain a homogeneous knead. Simultaneous biaxial stretching was performed using a biaxial stretcher at a stretching temperature of 150°C and a stretching ratio of 2.0 times (longitudinal) × 2.0 times (transverse). The porous membrane of Example 4 was obtained by the same method as in Example 1, except for these steps.

[0119] Figure 13 shows the results of observing the surface of the porous membrane of Example 4 using SEM (2500x magnification).

[0120] [Example 5] Simultaneous biaxial stretching was performed using a biaxial stretcher under the conditions of a stretching temperature of 150°C and a stretching ratio of 2.0 times (longitudinal direction) x 2.0 times (transverse direction). Apart from this, the porous membrane of Example 5 was obtained using the same method as in Example 1.

[0121] Figure 14A shows the results of observing the surface of the porous membrane of Example 5 using SEM (2500x magnification). Figure 14B is a magnified view of a portion of Figure 14A (10000x magnification).

[0122] [Comparative Example 1] As the thermoplastic resin, poly(4-methylpentene-1) resin (manufactured by Mitsui Chemicals, MX002, melting point: 224°C) was prepared. As a plasticizer, it had a kinematic viscosity of 68 mm at 40°C. 2 Liquid paraffin (MORESCO) with a concentration of 1 / s was prepared. A mixture was obtained by mixing 30.0 wt% thermoplastic resin, 69.8 wt% plasticizer, and 0.2 wt% antioxidant. The mixture was kneaded using a laboplast mill at 230°C for 30 minutes to obtain a homogeneous knead. The film of Comparative Example 1 was obtained by the same method as in Example 1, except for these steps.

[0123] Figure 15A shows the results of SEM observation of the surface of the film of Comparative Example 1 (2500x magnification). Figure 15B is a magnified view of a portion of Figure 15A (10000x magnification). Figure 15C shows the results of SEM observation of the cross-section of the film of Comparative Example 1 (2000x magnification).

[0124] [Comparative Example 2] A mixture was obtained by mixing 50.0 wt% thermoplastic resin, 49.8 wt% plasticizer, and 0.2 wt% antioxidant. The film of Comparative Example 2 was obtained using the same method as for Comparative Example 1, excluding this mixture.

[0125] Figure 16 shows the results of observing the surface of the film of Comparative Example 2 using SEM (2500x magnification).

[0126] [Comparative Example 3] A mixture was obtained by mixing 70.0 wt% thermoplastic resin, 29.8 wt% plasticizer, and 0.2 wt% antioxidant. The film of Comparative Example 3 was obtained using the same method as for Comparative Example 1, excluding this mixture.

[0127] Figure 17 shows the results of observing the surface of the film of Comparative Example 3 using SEM (2500x magnification).

[0128] Table 1 shows the manufacturing conditions for Examples 1-5 and Comparative Examples 1-3.

[0129] [Table 1]

[0130] Using the method described above for porous membranes, the Gurley permeability, water pressure resistance, etc., of the porous membranes of Examples 1 to 5 and the membranes of Comparative Examples 1 to 3 were evaluated. The evaluation results are shown in Table 2.

[0131] [Table 2]

[0132] [Example 6] The pressed body was cooled by bringing it into contact with 90°C water while sandwiched between polyimide plates to obtain a molded body. The film of Example 6 was obtained by the same method as in Example 1, except for this step.

[0133] [Example 7] The pressed body was cooled by contacting it with 5°C water while sandwiched between polyimide plates to obtain a molded body. The film of Example 7 was obtained by the same method as in Example 1, except for this step.

[0134] [Comparative Example 4] The pressed body was cooled by leaving it at room temperature to obtain a molded body. Apart from this, the film of Comparative Example 4 was obtained using the same method as in Example 1.

[0135] The manufacturing conditions for Examples 6-7 and Comparative Example 4 are shown in Table 3 along with the manufacturing conditions for Example 1. Figure 19 shows the results of measuring the actual film temperature from hot pressing to cooling using thermocouples at 100 ms intervals for Examples 1, Examples 6-7, and Comparative Example 4.

[0136] Figure 18A shows the results of observing the surface of the film of Comparative Example 4 using SEM (2500x magnification). Figure 18B is a magnified view of a portion of Figure 18A (20000x magnification).

[0137] [Table 3]

[0138] As can be seen from the comparison between Figures 10-12B and 13-14B, and Figures 15A-15B and 16-17, the porous membranes of Examples 1-5 had a tortoise-shell-like structure formed by multiple nodes and multiple fibrils. Specifically, in the porous membranes of Examples 1-5, island-like regions formed by multiple nodes were irregularly connected, and these island-like regions were connected to each other by multiple fibrils. In contrast, the membranes of Comparative Examples 1-3 did not have such a tortoise-shell-like structure. Since the membranes of Comparative Examples 1-3 did not have island-like regions, it was not possible to determine the average spacing between island-like regions and the average area of ​​the island-like regions.

[0139] The porous membranes of Examples 1-5 contained multiple island-like regions and multiple fibrils extending in multiple directions from each of these island-like regions. Regions where island-like regions were connected or overlapping without the involvement of multiple fibrils were also observed (see, for example, Figure 14B). Some porous membranes contained a mixture of island-like regions, which are aggregates of multiple nodes, and nodes (see, for example, Figure 12B). Some porous membranes also contained planar regions formed by the dense concentration of multiple fibrils extending in multiple directions from each of the island-like regions (see, for example, Figures 10 and 11).

[0140] On the other hand, the membranes of Comparative Examples 1 to 3 exhibited a structure known as a cellular structure, which lacked distinct nodes and fibrils.

[0141] The reason why a tortoise-shell-like structure was formed in the porous membranes of Examples 1-5, while it was not formed in the membranes of Comparative Examples 1-3, is presumed to be as follows: The thermoplastic resins used in Examples 1-5 (RT18) and Comparative Examples 1-3 (MX002) contain ethylene units as polymer chain units. It is known that MX002 contains more ethylene units than RT18. Due to the difference in ethylene unit content, the compatibility between the thermoplastic resin and the plasticizer, and the temperature range at which the thermoplastic resin precipitates as a solid phase, differed between Examples 1-5 and Comparative Examples 1-3, which is thought to have led to differences in the structure after phase separation. As a result, a tortoise-shell-like structure was ultimately obtained in Examples 1-5, while a cell structure without a tortoise-shell-like structure was obtained in Comparative Examples 1-3.

[0142] Furthermore, in Examples 6-7 and Comparative Example 4, which used the same RT18 thermoplastic resin as in Example 1 but with different cooling conditions, a tortoise-shell-like structure was observed in Examples 6-7, similar to Example 1 (not shown). On the other hand, in Comparative Example 4, where air cooling was performed, a tortoise-shell-like structure could not be observed (see Figures 18A and 18B). As shown in Figure 19, in Comparative Example 4, the relatively slow cooling rate of the thermoplastic resin greatly promoted crystal growth and phase separation, and it is thought that a tortoise-shell-like structure was not formed. From these results, it is considered that the cooling conditions also influence the formation of the tortoise-shell-like structure.

[0143] Furthermore, as can be seen from the comparison between Figure 12C and Figure 15C, the porous membrane of Example 3 had multiple clump-like nodes uniformly present along the thickness direction. In contrast, such a structure could not be observed in the membrane of Comparative Example 1.

[0144] As shown in Table 2, the porous membranes of Examples 1-5 have a density of 2.5 N / mm². 2 The compressibility Rc in the thickness direction when pressure was applied was 20% or less. In contrast, the films of Comparative Examples 1 to 3 showed compressibility Rc values ​​ranging from 21.4% to 42.5%.

[0145] These results indicate that the porous membranes of Examples 1 to 5 can suppress the reduction in membrane thickness caused by compression during attachment to device housings and the like. [Industrial applicability]

[0146] The technology of the present invention can be applied, for example, to waterproof and breathable membranes, waterproof and sound-permeable membranes, separators for energy storage devices, and the like.

Claims

1. A porous membrane mainly composed of a thermoplastic resin having a melting point of 180°C or higher and 300°C or lower, 2.5 N / mm 2 The compressibility in the thickness direction of the porous membrane when pressure is applied is 20% or less. Porous membrane.

2. The thermoplastic resin includes a polymethylpentene resin. The porous membrane according to claim 1.

3. When the cross-section of the porous membrane is observed, it contains multiple nodes along the thickness direction. The porous membrane according to claim 1 or 2.

4. The air permeability is expressed in Gurley numbers as 1000 seconds / 100 mL or less. The porous membrane according to claim 1 or 2.

5. The porosity of the porous membrane is 25% or more. The porous membrane according to claim 1 or 2.

6. A porous membrane according to claim 1 or 2, A porous membrane comprising an adhesive layer bonded to the porous membrane, Filter component.

7. A component supply assembly comprising a filter member disposed on the surface of an object having an opening, and a base sheet on which the filter member is disposed, The aforementioned filter member is A porous membrane having a shape that covers the opening when placed on the surface, The porous membrane comprises an adhesive layer bonded to it, The porous membrane is the porous membrane described in claim 1 or 2. Component supply assembly.

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