Porous film, air-permeable member, and member supply sheet

Abstract

A porous film contains a thermoplastic resin not containing fluorine as a main component, and the thermoplastic resin has a weight average molecular weight of 700,000 or more. A gas-permeable member has a porous film and a bonding layer combined with the porous film. A member supply sheet has a gas-permeable member disposed on a surface of an object having a surface with openings, and a base sheet having the gas-permeable member disposed on a surface, the gas-permeable member having a porous film having a shape that covers the openings when disposed on the surface, and a bonding layer joined with the porous film.

Description

Technical Field

[0001] This invention relates to porous membranes, breathable components, and sheet for supplying components. Background Technology

[0002] Fluorinated resin porous membranes are used in various applications such as filters, sound-permeable membranes, air-permeable membranes, and diaphragms. Fluorine-free porous membranes have also been proposed for these applications.

[0003] For example, Patent Document 1 discloses an olefin resin microporous biaxial stretching membrane, which is a microporous biaxial stretching membrane for a separator used in lithium-ion secondary batteries. It has micropores and contains olefin resin, has a puncture strength of 0.7N or more, and an air permeability of 75s / 100mL to 400s / 100mL.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-095576 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] For porous membranes used to ensure breathability through openings in the casing of smartwatches or similar devices while preventing foreign objects from passing through, high water resistance is required in addition to breathability. However, according to the inventors' research, improving the water resistance of fluorine-free porous membranes is the opposite of ensuring breathability; therefore, when practical water resistance is imparted to fluorine-free porous membranes, a problem of reduced breathability arises.

[0009] Therefore, the object of the present invention is to provide a fluorine-free porous membrane, a breathable component, and a component supply sheet suitable for improving water resistance while maintaining excellent breathability.

[0010] means for solving problems

[0011] The present invention provides a porous membrane, wherein the porous membrane comprises a fluorine-free thermoplastic resin as the main component, and the weight average molecular weight of the thermoplastic resin is above 700,000.

[0012] In another aspect, the present invention provides a porous membrane comprising a fluorine-free thermoplastic resin as the main component, wherein, when the surface of the porous membrane is observed with a scanning electron microscope, multiple island-like regions and multiple fibrils connecting the multiple island-like regions are observed, and the proportion of pores with an equivalent circle diameter of less than 0.7 μm is more than 10%.

[0013] In addition, the present invention also provides a breathable component, wherein the breathable component has the porous membrane of the present invention described above and an adhesive layer bonded to the porous membrane.

[0014] In another aspect, the present invention provides a component supply sheet comprising: a breathable member disposed on the surface of an object having an opening; and a substrate sheet having the breathable member disposed on its surface, wherein the breathable member comprises: a porous membrane having a shape that covers the opening when disposed on the surface; and an adhesive layer bonded to the porous membrane, the porous membrane being the porous membrane of the present invention.

[0015] Invention Effects

[0016] According to the present invention, it is possible to provide a fluorine-free porous membrane, a breathable component, and a component supply sheet that are suitable for improving water resistance while maintaining excellent breathability. Attached Figure Description

[0017] Figure 1 A cross-sectional view illustrating an example of the porous membrane of the present invention.

[0018] Figure 2 A cross-sectional view illustrating an example of the membrane component of the present invention.

[0019] Figure 3 To illustrate Figure 2 A cross-sectional view of a deformed membrane component, Example 1.

[0020] Figure 4 To illustrate Figure 2 A cross-sectional view of a modified example 2 (wound body) of a membrane component.

[0021] Figure 5 A cross-sectional view illustrating an example of the breathable component of the present invention.

[0022] Figure 6 To illustrate Figure 5 A cross-sectional view of a modified example 1 of a breathable component.

[0023] Figure 7 To illustrate Figure 5 A cross-sectional view of a modified example 2 of the ventilated component.

[0024] Figure 8 To illustrate Figure 5 A cross-sectional view of a modified example 3 of the ventilated component.

[0025] Figure 9 To illustrate Figure 5 A cross-sectional view of a modified example 4 of the ventilated component.

[0026] Figure 10 To illustrate Figure 5 A cross-sectional view of a modified example 5 of a breathable component.

[0027] Figure 11 A cross-sectional view illustrating an example of the component supply sheet of the present invention.

[0028] Figure 12 To illustrate Figure 11 A cross-sectional view of a modified example 1 of the component supply sheet.

[0029] Figure 13 To illustrate Figure 11 A cross-sectional view of a modified example 2 of the component supply sheet.

[0030] Figure 14A A figure (5000x magnification) showing the results of observing the surface of the porous membrane of Example 1 using a scanning electron microscope (SEM).

[0031] Figure 14B A graph (5000x magnification) showing the results of SEM observation of the cross-section of the porous membrane of Example 1.

[0032] Figure 15A A figure (5000x magnification) showing the results of SEM observation of the surface of the porous membrane in Example 2.

[0033] Figure 15B A graph (5000x magnification) showing the results of SEM observation of the cross-section of the porous membrane of Example 2.

[0034] Figure 16A A figure (5000x magnification) showing the results of SEM observation of the surface of the porous membrane in Example 3.

[0035] Figure 16B A graph (5000x magnification) showing the results of SEM observation of the cross-section of the porous membrane of Example 3.

[0036] Figure 17A A figure (5000x magnification) showing the results of SEM observation of the surface of the porous membrane of Comparative Example 1.

[0037] Figure 17B A graph (5000x magnification) showing the results of SEM observation of the cross-section of the porous membrane of Comparative Example 1.

[0038] Figure 18 A figure (5000x magnification) showing the results of SEM observation of the surface of the porous membrane in Comparative Example 4.

[0039] Figure 19AA figure (5000x magnification) showing the results of SEM observation of the surface of the porous membrane in Comparative Example 5.

[0040] Figure 19B A graph (5000x magnification) showing the results of SEM observation of the cross-section of the porous membrane in Comparative Example 5. Detailed Implementation

[0041] The porous membrane of the first embodiment of the present invention comprises a fluorine-free thermoplastic resin as the main component, wherein the weight-average molecular weight of the thermoplastic resin is 700,000 or more.

[0042] In a second aspect of the invention, for example, in the porous membrane of the first aspect, the thermoplastic resin is a polyolefin resin.

[0043] In the third aspect of the present invention, for example, the porous membrane of the first or second aspect has a water pressure resistance of 500 kPa or more, and the air permeability of the porous membrane, expressed as a Gurley number, is 60 seconds / 100 mL or less.

[0044] In a fourth aspect of the invention, for example, in a third-party porous membrane, when the value obtained by dividing the air permeability by the water pressure resistance is defined as the ratio R, R ≤ 0.09 is satisfied.

[0045] In the fifth aspect of the present invention, for example, in the porous membrane of any of the first to fourth aspects, when the cross-section of the porous membrane is observed with a scanning electron microscope, the proportion of pores with an equivalent circular diameter of 0.7 μm or less is 10% or more.

[0046] In a sixth aspect of the present invention, for example, in a porous membrane of any of the first to fifth aspects, the porosity is less than 40% when the surface of the porous membrane is observed with a scanning electron microscope.

[0047] In the seventh aspect of the present invention, for example, in the porous membrane of any of the first to sixth aspects, the porosity is 30% or more when the cross-section of the porous membrane is observed with a scanning electron microscope.

[0048] In the eighth aspect of the present invention, for example, the thickness of the porous membrane in any of the first to seventh aspects is 70 μm or less.

[0049] In the ninth aspect of the present invention, for example, the porous membrane of any one of the first to eighth aspects is a stretched membrane.

[0050] The porous membrane of the tenth aspect of the present invention is a porous membrane containing a fluorine-free thermoplastic resin as the main component, wherein, when the surface of the porous membrane is observed with a scanning electron microscope, multiple island-shaped regions and multiple fibrils connecting the multiple island-shaped regions are observed, and the proportion of pores with an equivalent circle diameter of 0.7 μm or less is 10% or more.

[0051] In the eleventh aspect of the present invention, for example, in the porous membrane of the tenth aspect, the thermoplastic resin is a polyolefin resin.

[0052] The breathable member according to the twelfth aspect of the present invention, for example, has: a porous membrane according to any one of the first to eleventh aspects; and an adhesive layer bonded to the porous membrane.

[0053] The component supply sheet of the thirteenth embodiment of the present invention comprises: a breathable member disposed on the surface of an object having an opening; and a substrate sheet on which the breathable member is disposed, wherein the breathable member comprises: a porous membrane having a shape that covers the opening when disposed on the surface; and an adhesive layer bonded to the porous membrane, the porous membrane being, for example, a porous membrane of any one of the first to eleventh embodiments.

[0054] In the fourteenth aspect of the present invention, for example, in the component supply sheet of the thirteenth aspect, a plurality of the breathable components are disposed on the surface of the substrate sheet.

[0055] The method for manufacturing a porous membrane according to the fifteenth aspect of the present invention includes: a step of mixing a composition comprising a fluorine-free thermoplastic resin and a plasticizer to obtain a compound; a step of performing a pressing or extrusion process; a step of performing a cooling process; a step of performing a stretching process; and a step of performing a plasticizer extraction process, wherein the thermoplastic resin has a weight-average molecular weight of 700,000 or more.

[0056] In the sixteenth aspect of the present invention, such as the method for manufacturing a porous membrane in the fifteenth aspect, the step of performing an annealing treatment is further included.

[0057] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The present invention is not limited to the following embodiments.

[0058] [Porous membrane]

[0059] Figure 1 This illustrates an example of a porous membrane of the present invention. Figure 1The porous membrane 1 contains a fluorine-free thermoplastic resin as its main component. "Main component" refers to the component with the highest content by weight in the porous membrane 1. With this configuration, the porous membrane 1 can, for example, be bonded to objects such as the casing of a smartwatch using a hot-melt adhesive without the need for an adhesive layer.

[0060] The fluorine-free thermoplastic resin (hereinafter sometimes simply referred to as thermoplastic resin) has a weight-average molecular weight of 700,000 or more. The inventors have discovered that by using a thermoplastic resin with a weight-average molecular weight of 700,000 or more, it is possible to maintain excellent air permeability while simultaneously improving water resistance in the porous membrane 1.

[0061] The lower limit of the weight-average molecular weight of thermoplastic resins can be above 750,000. The upper limit of the weight-average molecular weight of thermoplastic resins is, for example, below 1,000,000.

[0062] The porous membrane 1 can be composed of a resin composition containing a thermoplastic resin. The weight percentage of the thermoplastic resin in the resin composition is preferably greater than or equal to 20% by weight and less than 50% by weight. With such a composition, the characteristic cross-sectional structure and surface structure described later can be easily formed during the manufacturing process, especially during stretching.

[0063] The lower limit of the weight percentage of thermoplastic resin in the resin composition is more preferably 25% by weight or more. The upper limit of the weight percentage of thermoplastic resin in the resin composition is more preferably 45% by weight or less.

[0064] The weight ratio of thermoplastic resin in the resin composition can be determined, for example, by the amount of material fed.

[0065] In addition to thermoplastic resin, the resin composition may also contain additives such as plasticizers and antioxidants.

[0066] The water pressure resistance of the porous membrane 1 is evaluated by the water resistance test method B (high water pressure method) specified in JIS L1092:2009, preferably 500 kPa or higher. The porous membrane 1 that meets the above numerical range has high water resistance.

[0067] The lower limit of the water pressure resistance of the porous membrane 1 can be above 600 kPa, above 700 kPa, above 800 kPa, above 900 kPa, and further above 1000 kPa. The upper limit of the water pressure resistance of the porous membrane 1 is, for example, below 2000 kPa. The water pressure resistance of the porous membrane 1 can be above 600 kPa and below 2000 kPa, above 700 kPa and below 2000 kPa, above 800 kPa and below 2000 kPa, above 900 kPa and below 2000 kPa, and further above 1000 kPa and below 2000 kPa.

[0068] The water pressure resistance of the porous membrane 1 can be measured using a testing fixture, according to the water resistance test method described above, as follows. One example of the testing fixture is a 47mm diameter stainless steel (SUS) circular plate with a centrally located through-hole (having a circular cross-section) and a diameter of 1.0mm. This circular plate has a thickness that will not deform under the applied water pressure during the water pressure resistance test. The water pressure resistance test using this fixture can be performed as follows.

[0069] The porous membrane 1, which is the object of evaluation, is fixed to one side of the measuring fixture by covering the opening of the through hole. The fixing is performed in a manner that prevents water leakage from the fixed portion of the membrane during the water pressure resistance test. The porous membrane 1 can be fixed using double-sided adhesive tape with a perforation (1.6 mm in diameter) punched out at the center, matching the shape of the opening. The double-sided adhesive tape is positioned between the measuring fixture and the porous membrane 1, with the perforation surrounding it aligned with the opening. Next, the measuring fixture with the porous membrane 1 fixed is placed in the test apparatus with the side of the porous membrane 1 opposite to the fixed surface as the water pressure application surface during the test. The water pressure resistance is measured according to Method B (high water pressure method) of water resistance test as specified in JIS L1092:2009. The water pressure resistance is measured based on the water pressure when water exits from a point on the membrane surface of the porous membrane 1. The measured water pressure resistance can be taken as the water pressure resistance of the porous membrane 1. The test apparatus can be a device with the same configuration as the water resistance test apparatus illustrated in JIS L1092:2009, and with a test piece mounting structure capable of setting the aforementioned measuring fixture.

[0070] The thickness-direction air permeability of the porous membrane 1 is preferably 60 seconds / 100 mL or less, expressed as a Gurley number. A porous membrane 1 meeting the above numerical range exhibits high air permeability. In this specification, "Gurley number" refers to the air permeability resistance (Gurley permeability) measured according to the Wang Yan test machine method specified in JIS P8117:2009.

[0071] The upper limit of the air permeability of the porous membrane 1 can be expressed as a Graeme number of less than 50 seconds / 100 mL or less than 40 seconds / 100 mL. The lower limit of the air permeability of the porous membrane 1, expressed as a Graeme number, is, for example, greater than 0.1 seconds / 100 mL. The lower limit of the air permeability of the porous membrane 1, expressed as a Graeme number, can be greater than 1 second / 100 mL or greater than 5 seconds / 100 mL. The air permeability of the porous membrane 1 can be greater than 0.1 seconds / 100 mL and less than 50 seconds / 100 mL, or greater than 0.1 seconds / 100 mL and less than 40 seconds / 100 mL.

[0072] It should be noted that even if the size of the porous membrane 1 does not meet the recommended size (50mm×50mm) of the test piece for the Wang Yan test machine method, the air permeability resistance (Gerley air permeability) can still be evaluated based on the Wang Yan test machine method by using a measuring fixture.

[0073] The measuring fixture has a shape and size suitable for mounting on the air permeability measuring section of a pressure testing machine, and is designed with a thickness and material that will not deform due to the pressure difference applied to the test piece during air permeability resistance measurement. An example of the measuring fixture is a SUS circular plate with a thickness of 2 mm and a diameter of 47 mm. A through-hole with an opening smaller than the size of the membrane being evaluated is pre-formed at the center of the surface of the measuring fixture. The cross-section of the through-hole is typically circular, and its diameter is set such that the opening of the through-hole is completely covered by the membrane being evaluated. For example, a diameter of 1 mm or 2 mm can be used for the through-hole. Next, the porous membrane 1 being evaluated is fixed to one surface of the measuring fixture in a manner that covers the opening. The fixing is performed in such a way that, during the air permeability resistance measurement, air only passes through the effective test section of the porous membrane 1 (the portion overlapping the opening when viewed from a direction perpendicular to the main surface of the fixed porous membrane 1), and the fixed portion does not obstruct the passage of air in the effective test section of the porous membrane 1. The porous membrane 1 can be fixed using double-sided adhesive tape with a vent cut out at the center, the shape of which matches the opening. The double-sided adhesive tape is positioned between the measuring fixture and the porous membrane 1, with the vent surrounding it aligned with the opening. Next, the measuring fixture with the porous membrane 1 fixed is placed in the air permeability measuring section of the Wang Yan type testing machine, with the fixed surface of the porous membrane 1 facing downstream of the airflow during measurement. The test is performed using the Wang Yan type testing machine method, and the air permeability resistance indication value t shown on the testing machine is recorded. Then, the formula t can be used... K ={t×(area of ​​the effective test section of porous membrane 1 [cm²])} 2 ]) / 6.452[cm 2 The recorded air permeability resistance indicated value t is converted into the 6.452 cm value specified in the Wang Yan-style testing machine method. 2 The effective test area value t K and the obtained conversion value t K The air permeability resistance (Gerley air permeability) of the porous membrane 1 was determined according to the Wang Yan-style testing machine method. It should be noted that the air permeability resistance measured without the use of a measuring fixture for the porous membrane 1 with the recommended test piece size (50mm×50mm) that meets the Wang Yan-style testing machine method was confirmed to be highly consistent with the air permeability resistance measured using a measuring fixture after the porous membrane 1 was made into a small piece. That is, the use of the measuring fixture has no substantial effect on the measured value of the air permeability resistance.

[0074] The ratio R is defined as the value obtained by dividing the air permeability (seconds / 100mL) of the porous membrane 1 by the water pressure resistance (kPa). The ratio R tends to be smaller as the water resistance and air permeability of the porous membrane 1 increase. Therefore, the ratio R can serve as an indicator for comprehensively evaluating the water resistance and air permeability of the porous membrane 1. The ratio R is preferably 0.09 or less (R≤0.09). A porous membrane 1 that meets the above numerical range can exhibit excellent water resistance and air permeability.

[0075] The upper limit of the ratio R can be below 0.07, below 0.06, below 0.05, and further below 0.04. The lower limit of the ratio R is, for example, above 0.01.

[0076] As described above, the porous membrane 1 contains a fluorine-free thermoplastic resin as its main component. The fluorine-free thermoplastic resin can be a polyolefin resin. By using a polyolefin resin as the thermoplastic resin, it is easy to obtain a porous membrane 1 that is suitable for improving water resistance while maintaining excellent air permeability.

[0077] Polyolefin resins include polyethylene (PE) resin, polypropylene (PP) resin, and polymethylpentene (PMP) resin.

[0078] Polyolefin resins can be polymethylpentene resins. Polymethylpentene resins refer to homopolymers or copolymers of poly(4-methyl-1-pentene) resins, poly(3-methyl-1-pentene) resins, etc. As copolymers, there are random copolymers and block copolymers, etc. From the viewpoint of heat resistance and processability, homopolymers of poly(4-methyl-1-pentene) resins are preferred.

[0079] Polyolefin resins can be poly(4-methyl-1-pentene) resins. Poly(4-methyl-1-pentene) resins refer to homopolymers of 4-methyl-1-pentene, or copolymers of 4-methyl-1-pentene with at least one α-olefin. The ratio of 4-methyl-1-pentene to α-olefin in the copolymer can be adjusted within a range above 180°C.

[0080] The fluorine-free thermoplastic resin can be a thermoplastic resin with a melting point above 180°C and below 300°C. When the melting point of the thermoplastic resin is above 180°C, sufficient heat resistance can be ensured in the porous membrane 1. When the melting point of the thermoplastic resin is below 300°C, the porous membrane 1 can be formed, for example, by melt molding.

[0081] The melting point of thermoplastic resins can be above 200°C and below 280°C, and more specifically, above 220°C and below 260°C.

[0082] The porous membrane 1 is in the form of a membrane or a sheet. The thickness of the porous membrane 1 is preferably 70 μm or less. When the thickness is within the above-mentioned range, it is easy to achieve water pressure resistance and air permeability that meet the above-mentioned range.

[0083] The thickness of the porous membrane 1 can be determined, for example, by measuring the thickness at any 5 points on the porous membrane 1 using a dial indicator and averaging these measurements. Alternatively, the thickness of the porous membrane 1 can be measured at any 5 points in a cross-sectional SEM image of the porous membrane 1 and averaged as the result.

[0084] The upper limit of the thickness of the porous membrane 1 can be less than 60 μm, less than 50 μm, less than 40 μm, and further less than 30 μm. The lower limit of the thickness of the porous membrane 1 is, for example, more than 20 μm.

[0085] The porous membrane 1 may have multiple nodes and multiple fibrils. The porous membrane 1 may have multiple island-like regions and multiple fibrils connecting the multiple island-like regions. Each island-like region may contain multiple nodes. A porous membrane 1 with such a structure is suitable for balancing water resistance and air permeability. The above structure can be confirmed, for example, by observing the main surface of the porous membrane 1 from a vertical direction using a scanning electron microscope (SEM). In this disclosure, "main surface" refers to the surface with the widest area of ​​the membrane-like or sheet-like component. It should be noted that in this disclosure, "main surface," "surface," and "surface" are used with the same meaning for the porous membrane 1.

[0086] When observing the surface of the porous membrane 1 using SEM, the boundaries between the multiple island-like regions and the multiple fibrils connecting them may not be clearly defined. The shape of the island-like regions is not particularly limited. For example, the island-like regions can have polygonal shapes. However, the shape of the polygonal region does not necessarily have to be composed only of straight lines; it also includes roughly polygonal regions with some edges that are curved, such as arcs. Furthermore, the polygonal shape is not limited to a hexagonal shape.

[0087] When the surface of the porous membrane 1 is observed using SEM, cracks can be found on the surface of the island-like regions. These cracks can be formed, for example, by the cracking of blocky nodes during stretching.

[0088] When the surface of the porous membrane 1 is observed using SEM, it is preferable that multiple fine pores are formed in the island-like regions. The porous membrane 1 with such a surface structure is particularly suitable for improving water resistance while maintaining excellent air permeability.

[0089] For example, Figure 14A A figure (5000x magnification) showing the results of SEM observation of the surface of the porous membrane of Example 1 described later. Figure 14AAs shown, in the porous membrane of Example 1, multiple island-shaped regions and multiple fibrils connecting the multiple island-shaped regions were observed. Furthermore, in the porous membrane of Example 1, cracks were present on the surface of the island-shaped regions, and multiple micropores were formed in the island-shaped regions.

[0090] When observing the cross-section of the porous membrane 1 using SEM, multiple nodes can be observed along the thickness direction. These multiple nodes can exist throughout the entire thickness direction of the porous membrane 1. They can also exist uniformly along the thickness direction of the porous membrane 1. Adjacent block nodes can be connected to each other via multiple fibrils, or they can be directly connected without multiple fibrils.

[0091] When observing the cross-section of the porous membrane 1 using SEM, it is preferable that the nodes or block nodes are densely packed together, and that fine gaps (pores) are formed between the nodes or block nodes. The porous membrane 1 with such a cross-sectional structure is particularly suitable for improving water resistance while maintaining excellent air permeability.

[0092] For example, Figure 14B A graph (5000x magnification) showing the results of SEM observation of the cross-section of the porous membrane of Example 1 described later. Figure 14B As shown, in the cross-section of the porous membrane in Example 1, the nodes or block nodes are densely packed together, and fine gaps (pores) are formed between the nodes or block nodes.

[0093] As described above, the porous membrane 1 has multiple gaps (pores). When observing the cross-section of the porous membrane 1 using SEM, the proportion Rc of pores with an equivalent circle diameter of 0.7 μm or less is preferably 10% or more. According to the inventors' research, the water pressure resistance of the porous membrane 1 is related to the presence of pores with an equivalent circle diameter of 0.7 μm or less in the cross-section, showing the following tendency: the larger the proportion Rc, the higher the water pressure resistance of the porous membrane 1. When the proportion Rc meets the above-mentioned numerical range, the porous membrane 1 has excellent water resistance.

[0094] The upper limit of the ratio Rc is, for example, below 40%. The upper limit of the ratio Rc can be below 35%, below 30%, or below 25%.

[0095] The proportion Rc of pores with an equivalent circle diameter of 0.7 μm or less in the cross-section of porous membrane 1 can be determined by the method described below. First, observe the cross-section of porous membrane 1 using SEM (e.g., refer to...). Figure 14BNext, the SEM observation image (or a portion thereof) obtained using image analysis software is binarized. Pores are identified from the binarized image, and the area of ​​each pore in the image is calculated. For each pore, the equivalent circle diameter is calculated based on the calculated area. The equivalent circle diameter is the diameter of a circle with an area equal to the area of ​​the pore being measured. The average calculated equivalent circle diameter can be considered as the equivalent circle diameter of the pores in the cross-section of the porous membrane 1. The ratio Rc can be determined by calculating the ratio of the total area of ​​pores with an equivalent circle diameter of 0.7 μm or less to the area of ​​the aforementioned image. The ratio Rc is determined by measuring 300 or more pores, for example, 300 to 5000 pores. It should be noted that pores located at the image edges are omitted during pore identification. ImageJ can be used as an image analysis software, for example.

[0096] When the surface of porous membrane 1 is observed using SEM, the proportion of pores with an equivalent circular diameter of less than 0.7 μm, Rs, can be less than 20%.

[0097] The lower limit of the ratio Rs is, for example, 5% or higher. The lower limit of the ratio Rs can also be 8% or higher.

[0098] The proportion Rs of pores with an equivalent circular diameter of 0.7 μm or less on the surface of porous membrane 1 can be determined using the same method as described above for determining the proportion Rc in the cross-section of porous membrane 1. However, observing the surface of porous membrane 1 using SEM (e.g., referring to...) Figure 14A The ratio Rs is determined by measuring more than 500, for example, 500 to 26,000 pores.

[0099] When the surface of the porous membrane 1 is observed using SEM, the porosity Ps of the porous membrane 1 is preferably 40% or less. When the surface porosity Ps meets the above-mentioned value range, it is easy to achieve water pressure resistance and air permeability that meet the above-mentioned value range.

[0100] The upper limit of the porosity Ps of the porous membrane 1 can be less than 40%, less than 35%, less than 30%, and further less than 25%. The lower limit of the porosity Ps of the porous membrane 1 is, for example, more than 10%. The lower limit of the porosity Ps of the porous membrane 1 can be more than 15%.

[0101] The porosity Ps of the surface of porous membrane 1 can be determined by the method described below. First, the surface of porous membrane 1 is observed using SEM (e.g., referring to...). Figure 14ANext, the SEM observation image (or a portion thereof) obtained using image analysis software is binarized. Pores are identified from the resulting binarized image, and the area of ​​each pore in the image is calculated. By calculating the ratio of the total pore area to the area of ​​the image, the porosity Ps of the porous membrane 1 can be determined. The porosity Ps is determined by measuring more than 700 pores, for example, 700 to 26,000 pores. It should be noted that pores located at the image edges are omitted from the analysis when identifying pores. ImageJ can be used as an image analysis software, for example.

[0102] When the cross-section of the porous membrane 1 is observed using SEM, the porosity Pc of the porous membrane 1 is preferably 30% or higher. When the porosity Pc of the cross-section meets the above-mentioned value range, it is easy to achieve water pressure resistance and air permeability that meet the above-mentioned value range.

[0103] The upper limit of the porosity Pc of the porous membrane 1 is, for example, 60% or less. The upper limit of the porosity Pc of the porous membrane 1 can be 55% or less. The porosity Pc of the porous membrane 1 can be 30% or more and 60% or less, or 30% or more and 55% or less.

[0104] The porosity Pc in the cross-section of the porous membrane 1 can be determined using the same method as described above for determining the porosity Ps of the surface of the porous membrane 1. However, the cross-section of the porous membrane 1 can be observed using SEM (e.g., referring to...). Figure 14B Porosity Pc is determined by measuring more than 600 pores, for example, 600 to 5000 pores.

[0105] The porous membrane 1 can be a stretched membrane. When the porous membrane 1 is a stretched membrane, it is easy to control water pressure resistance and air permeability. The stretched membrane can be a biaxial stretched membrane or a uniaxial stretched membrane.

[0106] At least one main surface of the porous membrane 1 can be subjected to a surface modification treatment. Examples of surface modification treatments include: oil-repellent treatment, chemical treatment, sputtering etching treatment, plasma treatment, etc. In the area where the surface modification treatment has been performed, the adhesion of the porous membrane 1 is improved.

[0107] Liquid-repellent treatment can be applied to at least one main surface of the porous membrane 1. The liquid-repellent treatment is typically performed by coating the surface of the porous membrane 1 with a liquid-repellent agent or by immersing the porous membrane 1 in a liquid-repellent agent. There are no particular limitations on the liquid-repellent agent; it can be a fluorinated liquid-repellent agent, an organosilicon liquid-repellent agent, or an acrylic liquid-repellent agent. Fluorinated liquid-repellent agents, for example, have a structure with a fluorine-saturated hydrocarbon side chain (perfluoroalkyl) on the main chain of an acrylic resin.

[0108] [Methods for manufacturing porous membranes]

[0109] The porous membrane 1 described above can be manufactured, for example, by the following method.

[0110] The method for manufacturing the porous membrane 1 includes, for example,: mixing a composition comprising a fluorine-free thermoplastic resin and a plasticizer to obtain a compound (step S1); pressing the compound to obtain a pressed body (step S2); cooling the pressed body to obtain a molded body (step S3); stretching the molded body to obtain a sheet (step S4); and extracting the plasticizer from the sheet (step S5).

[0111] Alternatively, as another method, the method for manufacturing the porous membrane 1 includes, for example,: mixing a composition comprising a fluorine-free thermoplastic resin and a plasticizer to obtain a compound (step S1); extruding the compound using a twin-screw extruder (step ST2); cooling the extruded compound to obtain a molded body (step ST3); stretching the molded body to obtain a sheet (step S4); and extracting the plasticizer from the sheet (step S5).

[0112] Steps S1 to S3 correspond to the process of fabricating the precursor of porous membrane 1. Steps S4 to S5 correspond to the process of growing the porous structure. It should be noted that step S5 can also be performed before step S4.

[0113] Step S1 is performed, for example, at a temperature of 230°C to 260°C for 5 to 30 minutes.

[0114] As a fluorine-free thermoplastic resin, polymethylpentene resin can be used, for example.

[0115] In the composition comprising a thermoplastic resin and a plasticizer, resins such as polyethylene, polypropylene, poly-1-butene, and cyclic polyolefins may be mixed within a range that does not affect the properties of the porous membrane 1.

[0116] Plasticizers are non-volatile solvents that, when mixed with thermoplastic resins such as polymethylpentene, form a mixture at a temperature above the resin's melting point and exhibit thermally induced phase separation upon cooling. Plasticizers can be liquid or solid at room temperature. They can be used alone or in combination with other plasticizers.

[0117] The mixing ratio of thermoplastic resin to plasticizer is set in a manner that allows for the formation of a homogeneous compound in step S1. Specifically, the weight percentage of thermoplastic resin in the resin composition is preferably greater than or equal to 20% by weight and less than 50% by weight. With this configuration, the aforementioned characteristic cross-sectional and surface structures are more easily formed during stretching (step S4).

[0118] In a composition containing a thermoplastic resin and a plasticizer, additives such as antioxidants, nucleating agents, antistatic agents, flame retardants, lubricants, UV absorbers, colorants, and inorganic fillers for improving strength may be further mixed in, depending on the purpose.

[0119] Step S2 is performed, 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.

[0120] In step S3, for example, the pressed body obtained in step S2 is brought into contact with a heat conductor and cooled to a temperature sufficiently low than the crystallization temperature of the thermoplastic resin to cure it. Examples of heat conductors used for cooling include water, air, metal, and plasticizers.

[0121] The manufacturing method may also include extruding the compound using a twin-screw extruder (step ST2) instead of step S2. In step ST2, the compound can be extruded onto metal rollers with controlled surface temperature. A flat die (coat hanger die) can be used in the extrusion of the compound. By using a flat die, the compound can be extruded in a wide width, thus easily obtaining a sheet-like formed body in step ST2.

[0122] In the case where step ST2 replaces step S2, the manufacturing method may also include cooling the extruded compound to obtain a shaped body (step ST3) instead of step S3. In step ST3, for example, a metal roller with a controlled surface temperature can be used to stretch the compound while cooling it, thereby obtaining a sheet-like shaped body. The surface temperature of the metal roller is controlled, for example, at 120°C. There can be multiple metal rollers. By passing the compound through multiple metal rollers, a sheet-like shaped body can be formed while cooling is being performed.

[0123] Between steps S3 and S4, an annealing process (step S3') may also be performed on the cooled molded body. Step S3' is performed, for example, at a temperature of 180°C to 200°C for 30 to 60 minutes.

[0124] In step S4, the cooled molded body is stretched at least once in at least a uniaxial direction. Stretching in at least a uniaxial direction includes longitudinal uniaxial stretching, transverse uniaxial stretching, simultaneous biaxial stretching, and successive biaxial stretching. The molded body can be stretched sequentially or simultaneously. Through step S4, pores are generated in the molded body. At this time, cracks are generated on the surface of the molded body, for example, on the surface of island-like regions, and multiple fine through-holes are formed in the island-like regions. In the cross-section of the molded body, for example, nodes or block nodes are densely packed together, and fine gaps (pores) are formed between nodes or block nodes.

[0125] The stretching temperature can be 20℃~240℃, 50℃~230℃, or 100℃~220℃ for longitudinal and transverse stretching, respectively.

[0126] The stretch ratio, measured in the longitudinal and / or transverse uniaxial direction, can be 2.0 to 10.0 times, 2.0 to 8.0 times, or 2.0 to 5.0 times.

[0127] The strain rate during tension can be 1% / second to 10% / second, 1% / second to 8% / second, or 1% / second to 5% / second in the longitudinal and / or transverse directions. When the strain rate is within the above range, fracture is less likely to occur during tension, thus improving productivity.

[0128] In step S5, for example, an extraction solvent is used to extract and remove the plasticizer from the sheet. After step S5, the sheet after plasticizer removal can be dried using a dryer or by natural drying. The porous membrane 1 can be obtained through the above operations.

[0129] As the extraction solvent, it is preferable to use 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 porous membrane 1. Examples of such extraction solvents include: hydrocarbons such as n-hexane and cyclohexane; halogenated hydrocarbons such as dichloromethane 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. When safety is a consideration, alcohols and ketones are preferred. Methyl ethyl ketone (MEK) can be used as an extraction solvent.

[0130] Between steps S4 and S5, heat curing can be performed on the sheet. Heat curing can be performed, for example, using a hot air circulating oven. By performing heat curing, the thermal shrinkage of the stretched sheet can be reduced. The heat curing temperature is, for example, 50°C to 240°C. The heat curing temperature can also be 100°C to 230°C, or even 150°C to 220°C.

[0131] Heat setting can be performed after step S4, between steps S4 and S5, or both after steps S4 and S5. Examples of heat setting methods include: using a tenter frame to fix the width direction and continuously passing the product through the heat treatment furnace; applying appropriate tension and continuously passing the product through the heat treatment furnace without fixing the width direction; and winding the product into rolls and feeding them into the heat treatment furnace in batches.

[0132] [Membrane components]

[0133] An example of the membrane component of the present invention is shown in Figure 2 middle. Figure 2 The membrane component 2 (2A) has a porous membrane 1. Figure 3 The middle shows Figure 2 Example 1: Deformation of a membrane component. Figure 3 The membrane component 2 (2B) also has 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 operability (operability) of the membrane component 2.

[0134] The breathable support material 3 typically has higher air permeability in the thickness direction compared to the porous membrane 1. Examples of the breathable support material 3 are woven fabrics, nonwoven fabrics, meshes, and openwork. Examples of materials constituting the breathable support material 3 are polyesters such as polyethylene terephthalate (PET), polyolefins such as polyethylene (PE) and polypropylene (PP), and aromatic polyamide resins. When viewed from a direction perpendicular to the main surface of the membrane member 2, the shape of the breathable support material 3 may be the same as or different from that of the porous membrane 1. When viewed from a direction perpendicular to the main surface of the membrane member 2, the breathable support material 3 may have a peripheral portion corresponding to the peripheral portion of the porous membrane 1.

[0135] Figure 3 The membrane component 2B has a breathable support material 3 disposed on one side of the porous membrane 1. The membrane component 2 may have two or more breathable support materials 3. In the membrane component 2, breathable support materials 3 may be disposed on two sides of the porous membrane 1. The porous membrane 1 and the breathable support materials 3 may be joined by welding such as thermal fusion and ultrasonic welding, or by adhesives or bonding agents.

[0136] The membrane component 2 may also have optional layers and / or components other than those described above.

[0137] The thickness of membrane component 2 is, for example, 1 μm to 300 μm. The thickness of membrane component 2 can also be 50 μm to 200 μm.

[0138] The basis weight of membrane component 2 is, for example, 1.0 g / m³. 2 ~200.0g / m 2 The basis weight of membrane component 2 can be 10.0 g / m³. 2 ~100.0g / m 2 .

[0139] The membrane component 2 may have the same properties as the porous membrane 1, such as air permeability in the thickness direction and / or water pressure resistance.

[0140] Liquid-repellent treatment and / or coloring treatment can also be applied to membrane component 2.

[0141] Membrane component 2 can be used, for example, as a filter component. However, the uses of membrane component 2 are not limited to the examples described above.

[0142] When viewed from a direction perpendicular to the main surface of membrane member 2, the shape of membrane member 2 can be, for example, a polygon including squares and rectangles, a circle, an ellipse, or a strip. The corners of the polygon can be rounded. However, the shape of membrane member 2 is not limited to the above examples. The strip-shaped membrane member 2 can also be wound to form a wound body. In addition, if necessary, it can be wound in a state of being stacked with a release liner.

[0143] Figure 4 The middle shows Figure 2 Example 2 of the deformation of the membrane component (wound body). Figure 4 The coil 10 shown includes Figure 2 The membrane component 2A and the release liner 11 are bonded together by an adhesive layer 12. In the winding body 10, the release surface 13 formed when the release liner 11 is peeled off from the membrane component 2A is located between the membrane component 2A and the adhesive layer 12. That is, in the winding body 10, the adhesive layer 12 is peeled off from the membrane component 2A when the release liner 11 is peeled off, thereby obtaining a membrane component 2A without an adhesive layer 12 formed on its surface.

[0144] The membrane member 2A, supplied by the winding 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. That is, the membrane member 2A has a high degree of freedom in the joining method with the opening of the housing. Joining methods include, for example, joining by a newly configured adhesive layer on the surface of the membrane member 2A, joining by thermal fusion, and joining by ultrasonic fusion.

[0145] The membrane component 2A supplied by the winding body 10 can be processed into any shape as needed. That is, the membrane component 2A has a high degree of freedom in shape. Here, "shape" includes "size". The above points mean that, according to the winding body 10, the membrane component 2A, which functions as a waterproof membrane, can be supplied in a state with a high degree of freedom in the method of joining with the opening of the shell and / or in shape.

[0146] Furthermore, according to the winding body 10, the misalignment between the film member 2A and the release liner 11 during winding is suppressed by the adhesive layer 12. In the winding body 10, the occurrence of faults (abnormal shape of the winding body) caused by winding tightness, etc., can be suppressed.

[0147] [Breathable components]

[0148] Figure 5 An example of the breathable component of the present invention is shown in the figure. Figure 5The breathable member 4 (4A) has the porous membrane 1 or membrane member 2 described above as a member that has air permeability in the thickness direction and prevents foreign objects from passing through in that direction. The breathable member 4 is, for example, disposed on the surface of an object having an opening, ensuring air permeability through the opening while preventing foreign objects from passing through it. In this case, the breathable member 4 is typically disposed such that the porous membrane 1 or membrane member 2 covers the opening of the object. Figure 5 The breathable member 4A has a porous membrane 1. Hereinafter, the breathable member 4 with a porous membrane 1 will be described as an example of a member that has breathability in the thickness direction and prevents foreign objects from passing through in that direction.

[0149] The breathable member 4 (4A) has an adhesive layer 5 disposed on one side of the porous membrane 1. The porous membrane 1 and the adhesive layer 5 are directly bonded. The breathable member 4A can be disposed on the aforementioned surface of the object via the adhesive layer 5.

[0150] Examples of adhesives constituting adhesive layer 5 include acrylic adhesives, silicone adhesives, urethane adhesives, epoxy adhesives, and rubber adhesives. When considering the use of the breathable component 4 at high temperatures, acrylic or silicone adhesives with excellent heat resistance, especially silicone adhesives, are preferred. Adhesive layer 5 can be a substrate-free double-sided adhesive tape. The adhesive can also be a curable adhesive such as phenolic resin, epoxy resin, urea-formaldehyde resin, polyurethane resin, melamine resin, and polyester resin.

[0151] When viewed from a direction perpendicular to the main surface of the porous membrane 1, the outer periphery of the porous membrane 1 coincides with the outer periphery of the adhesive layer 5. Furthermore, when viewed from a direction perpendicular to the main surface of the porous membrane 1, the shape of the adhesive layer 5 corresponds to the shape of the peripheral portion of the porous membrane 1. The area in the porous membrane 1 that is not bonded to the adhesive layer 5 can be considered as the air-permeable area of ​​the air-permeable member 4A. However, the shape of the adhesive layer 5 is not limited to the example described above.

[0152] The area of ​​the breathable zone is, for example, 40mm. 2 The following describes a breathable component 4 whose breathable area falls within this range, suitable for placement on objects with small-diameter openings. The lower limit of the breathable area is, for example, 0.008 mm². 2 That's all. However, the area of ​​the ventilated region can also be larger depending on the type of object to which the ventilated component 4 is to be installed.

[0153] Figure 6 The middle shows Figure 5 Example 1: Deformation of the breathable component. Figure 6 In addition to having an adhesive layer 5 (5B) disposed on the other side of the porous membrane 1, the breathable component 4 (4B) also has a connection with... Figure 5The porous membrane 1 has the same structure as the breathable component 4A. The porous membrane 1 is sandwiched between a pair of adhesive layers 5 (5A, 5B).

[0154] like Figure 6 As shown, the adhesive layer 5 may include a first adhesive layer 5A bonded to one side (first main surface 1a) of the porous membrane 1 and a second adhesive layer 5B bonded to the other side (second main surface 1b) of the porous membrane 1.

[0155] Figure 7 The middle shows Figure 5 Example 2: Deformation of the breathable component. Figure 7 The breathable member 4 (4C) not only has a substrate layer 6 disposed on one side of the porous membrane 1, and the porous membrane 1 and the adhesive layer 5 are bonded through the substrate layer 6, but also has the following characteristics: Figure 5 The structure is the same as that of the breathable component 4A. The strength and operability of the breathable component 4 can be improved by the substrate layer 6, and the damage of the porous membrane 1 during operation or when placed on an object can be suppressed.

[0156] Examples of materials constituting the substrate layer 6 include polyolefins such as PE and PP, polyesters such as PET, silicone resins, polycarbonate, polyimide, polyamide-imide, polyphenylene sulfide, polyether ether ketone (PEEK), polyvinyl chloride, fluorinated resins, and metals such as aluminum and stainless steel. Examples of fluorinated resins include PTFE, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-ethylene copolymer (ETFE). However, the materials constituting the substrate layer 6 are not limited to the examples mentioned above.

[0157] When viewed from a direction perpendicular to the main surface of the porous membrane 1, the outer periphery of the porous membrane 1 coincides with the outer periphery of the substrate layer 6. Furthermore, when viewed from a direction perpendicular to the main surface of the porous membrane 1, the shape of the substrate layer 6 corresponds to the shape of the peripheral portion of the porous membrane 1. The area in the porous membrane 1 that is not bonded to the substrate layer 6 can be considered as the air-permeable area of ​​the air-permeable member 4C. However, the shape of the substrate layer 6 is not limited to the example described above.

[0158] The porous membrane 1 and the substrate layer 6 can be bonded by adhesives or glues, or by welding such as thermal fusion and ultrasonic welding. The porous membrane 1 and the substrate layer 6 can also be bonded by an adhesive layer. This adhesive layer can have the same structure as adhesive layer 5. The substrate layer 6 can be a single-sided or double-sided adhesive tape.

[0159] Figure 8 The middle shows Figure 5 Example 3: Deformation of the breathable component. Figure 8 In addition to having a substrate layer 6 (6B) disposed on the other side of the porous membrane 1, the breathable component 4 (4D) also has a similar structure to... Figure 5The porous membrane 1 has the same structure as the breathable component 4C. The porous membrane 1 is sandwiched between a pair of substrate layers 6 (6A, 6B). This clamping structure further improves the strength and operability of the breathable component 4.

[0160] like Figure 8 As shown, the substrate layer 6 may include a first substrate layer 6A bonded to one side (first main surface 1a) of the porous membrane 1 and a second substrate layer 6B bonded to the other side (second main surface 1b) of the porous membrane 1.

[0161] Figure 9 China indicates Figure 5 Example 4: Deformation of the breathable component. Figure 9 The breathable component 4 (4E) also has a release liner 7, and the porous membrane 1 is bonded to the release liner 7 by an adhesive layer 5 (5B). In addition, it has a... Figure 6 The breathable component 4B has the same structure.

[0162] like Figure 9 As shown, the breathable member 4 (4E) may also have a release liner 7, with a second adhesive layer 5B disposed between the release liner 7 and the porous membrane 1, and the second adhesive layer 5B bonded to the release liner 7.

[0163] When viewed from a direction perpendicular to the main surface of the porous membrane 1, the release liner 7 has tabs that protrude further outward than the outer periphery of the porous membrane 1. By grasping the tabs, the air-permeable member 4E can be manipulated or placed onto the surface of an object. The release liner 7 is typically removed when using the air-permeable member 4E. The release liner 7 can, for example, be made of the same material as the material constituting the substrate layer 6.

[0164] Figure 10 The middle shows Figure 5 Example 5: Deformation of the breathable component. Figure 10 The breathable member 4 (4F) not only has a release liner 7, but also has a bonding layer 5 (5B) that bonds the substrate layer 6 (6B) to the release liner 7, in addition to having a release liner 7. Figure 8 The breathable components have the same 4D structure.

[0165] [Component supply sheet]

[0166] The breathable component 4 can be supplied, for example, by means of a component supply sheet. Figure 11 The image shows an example of a component supply sheet used as a method for supplying the ventilating component 4. Figure 11The component supply sheet 20 (20A) includes: a breathable member 4 (4A) disposed on the surface of an object having an opening, and a substrate sheet 9 on which the breathable member 4 (4A) is disposed. The component supply sheet 20A has the breathable member 4A as the breathable member 4. The breathable member 4A includes: a porous membrane 1 having a shape that covers the opening when disposed on the surface of the object, and an adhesive layer 5 bonded to the porous membrane 1.

[0167] The breathable component 4 (4A) is disposed on the substrate sheet 9 via the adhesive layer 5. According to the component supply sheet 20 (20A), for example, the breathable component 4 can be efficiently supplied to the process of disposing of the breathable component 4 on the surface of the object.

[0168] The breathable member 4 can be disposed on the substrate sheet 9 via an adhesive layer on the disposed surface of the breathable member 4 disposed in the substrate sheet 9. The adhesive layer on the disposed surface is preferably weakly adhesive.

[0169] Although the illustration is omitted, multiple breathable components 4 can also be configured on the surface of the substrate sheet 9.

[0170] Examples of materials constituting the substrate sheet 9 include paper, metal, resin, and composites thereof. Metals include, for example, stainless steel and aluminum. Resins include, for example, polyesters such as PET, and polyolefins such as PE and PP. However, the materials constituting the substrate sheet 9 are not limited to the examples mentioned above. The substrate sheet 9 can be in the form of a single sheet or a strip. When the substrate sheet 9 is in the form of a strip, the component supply sheet 20 can be wound to form a wound body.

[0171] Examples of objects to which the venting member 4 is configured include the housing of electronic devices and the housing of electrical components for vehicles. The venting member 4 can be configured on the outer and / or inner surface of the housing. In this case, the opening can be a vent and / or a sound-transmitting opening provided in the housing. Examples of electronic devices include wearable devices such as smartwatches and wristbands; various cameras including action cameras and security monitoring 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 electrical components for vehicles include lights and ECUs. However, the objects are not limited to the above examples.

[0172] Foreign objects such as dust particles and water droplets are prevented from passing through by the configuration of the breathable component 4.

[0173] Figure 12 The middle shows Figure 11 Example 1: A variation of the component supply sheet. Figure 12 The component supply piece 20 (20B) has, in addition to having Figure 9 In addition to being a breathable component 4, the breathable component 4E has the same characteristics as... Figure 11 The components supplied are of the same composition as sheet 20A.

[0174] Figure 13 The middle shows Figure 11 Example 2: A variation of the component supply sheet. Figure 13 The component supply sheet 20 (20C) has, in addition to having Figure 10 In addition to being a breathable component 4, the breathable component 4F has the same characteristics as... Figure 11 The components supplied are of the same composition as sheet 20A.

[0175] Example

[0176] The present invention will be further described in detail below through embodiments. The present invention is not limited to the embodiments shown below.

[0177] [Example 1]

[0178] Poly(4-methyl-1-pentene) resin (manufactured by Mitsui Chemicals, DX845, weight-average molecular weight: 776,000) was used as the thermoplastic resin. A plasticizer with a kinematic viscosity of 110 mmHg at 40°C was prepared. 2 / s of liquid paraffin (manufactured by MORESCO). Pentaerythritol tetra(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (manufactured by BASF Japan) was used as an antioxidant. A mixture of 30.0 wt% thermoplastic resin, 69.8 wt% plasticizer, and 0.2 wt% antioxidant was obtained. The mixture was kneaded at 260°C for 30 minutes using a LABO PLASTOMILL (manufactured by Toyo Seiki Co., Ltd.) to obtain a homogeneous compound. 1.6 g of the compound particles were sandwiched between two polyimide plates (150 μm thick), further sandwiched between stainless steel plates (3.0 mm thick). The particles were then hot-pressed at 1.0 kN for 5 minutes using a compression molding machine heated to 260°C to obtain a pressed body. The pressed body, sandwiched between the polyimide plates, was contacted with water at 18°C ​​to cool it, thus obtaining a molded body. Next, the molded body was subjected to simultaneous biaxial stretching using a biaxial stretching machine at a stretching temperature of 100°C and a stretching ratio of 2 times (longitudinal) × 2 times (transverse). The strain rate during stretching was 1% / s (0.655 mm / s) in both the longitudinal and transverse directions. This yielded a sheet. The stretching was performed 5 minutes after the molded body was placed in an oven set to the stretching temperature. Finally, the sheet was extracted by immersing it in methyl ethyl ketone (MEK) at room temperature for 2 minutes using MEK as the extraction solvent. This removed the plasticizer from the sheet. To suppress sheet shrinkage, the extraction was performed while the sheet was fixed in a stainless steel frame. Through the above operations, the porous membrane of Example 1 was obtained.

[0179] Figure 14A A figure (5000x magnification) showing the results of SEM observation of the surface of the porous membrane of Example 1. Figure 14B A graph (5000x magnification) showing the results of SEM observation of the cross-section of the porous membrane of Example 1.

[0180] [Example 2]

[0181] The plasticizer was extracted from the cooled molded body. After the plasticizer was removed, simultaneous biaxial stretching was performed. Otherwise, the porous membrane of Example 2 was obtained by the same method as in Example 1.

[0182] Figure 15A A figure (5000x magnification) showing the results of SEM observation of the surface of the porous membrane in Example 2. Figure 15B A graph (5000x magnification) showing the results of SEM observation of the cross-section of the porous membrane of Example 2.

[0183] [Example 3]

[0184] The cooled molded body was annealed at 180°C for 30 minutes. Plasticizer extraction was performed on the annealed molded body. Simultaneous biaxial stretching was then performed after annealing. Otherwise, the porous membrane of Example 3 was obtained using the same method as in Example 1.

[0185] Figure 16A A figure (5000x magnification) showing the results of SEM observation of the surface of the porous membrane in Example 3. Figure 16B A graph (5000x magnification) showing the results of SEM observation of the cross-section of the porous membrane of Example 3.

[0186] [Comparative Example 1]

[0187] Poly(4-methyl-1-pentene) resin (manufactured by Mitsui Chemicals, RT18, weight-average molecular weight: 499,000) was used as the thermoplastic resin. A plasticizer with a kinematic viscosity of 110 mmHg at 40°C was used as the plasticizer. 2 / s of liquid paraffin (manufactured by MORESCO). Pentaerythritol tetra(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (manufactured by BASF Japan) was used as an antioxidant. A mixture was obtained by mixing 50.0% by weight of thermoplastic resin, 49.8% by weight of plasticizer, and 0.2% by weight of antioxidant. Otherwise, the porous membrane of Comparative Example 1 was obtained by the same method as in Example 1.

[0188] Figure 17A A figure (5000x magnification) showing the results of SEM observation of the surface of the porous membrane of Comparative Example 1. Figure 17B A figure (5000x magnification) showing the results of SEM observation of the cross-section of the porous membrane of Comparative Example 1.

[0189] [Comparative Example 2]

[0190] A mixture was obtained by mixing 30.0% by weight of thermoplastic resin, 69.8% by weight of plasticizer, and 0.2% by weight of antioxidant. Otherwise, a porous membrane of Comparative Example 2 was obtained by the same method as Comparative Example 1. It should be noted that in Comparative Example 2, the membrane fractured upon stretching.

[0191] [Comparative Example 3]

[0192] Poly(4-methyl-1-pentene) resin (manufactured by Mitsui Chemicals, DX 820, weight average molecular weight: 266,000) was used as the thermoplastic resin. Otherwise, the porous membrane of Comparative Example 3 was obtained by the same method as Comparative Example 2. It should be noted that in Comparative Example 3, the membrane fractured upon stretching.

[0193] [Comparative Example 4]

[0194] Poly(4-methyl-1-pentene) resin (manufactured by Mitsui Chemicals, MX 002, weight average molecular weight: 600,000) was used as the thermoplastic resin. Otherwise, the porous membrane of Comparative Example 4 was obtained by the same method as Comparative Example 2.

[0195] Figure 18 A figure (5000x magnification) showing the results of SEM observation of the surface of the porous membrane in Comparative Example 4.

[0196] [Comparative Example 5]

[0197] As the thermoplastic resin, a resin with a weight average molecular weight of 691,100 was used, obtained by mixing poly(4-methyl-1-pentene) resin (manufactured by Mitsui Chemicals, DX 470, weight average molecular weight: 493,000) and poly(4-methyl-1-pentene) resin (manufactured by Mitsui Chemicals, DX 845, weight average molecular weight: 776,000) at a mass ratio of 30:70. A mixture was obtained by mixing 50.0% by weight of the thermoplastic resin, 49.8% by weight of the plasticizer, and 0.2% by weight of the antioxidant. The plasticizer was extracted from the cooled molded article. After the plasticizer was removed, simultaneous biaxial stretching was performed. Otherwise, a porous membrane of Comparative Example 5 was obtained by the same method as in Example 1.

[0198] Figure 19A A figure (5000x magnification) showing the results of SEM observation of the surface of the porous membrane in Comparative Example 5. Figure 19BA graph (5000x magnification) showing the results of SEM observation of the cross-section of the porous membrane in Comparative Example 5.

[0199] The manufacturing conditions of the porous membranes of Examples 1 to 3 and Comparative Examples 1 to 5 are shown in Table 1.

[0200] Table 1

[0201] ※1: Plasticizers are extracted and removed before stretching.

[0202] Using the methods described above for porous membranes, the thickness, air permeability, and water pressure resistance of the porous membranes of Examples 1 to 3 and Comparative Examples 1 to 5 were evaluated. The evaluation results are shown in Table 2.

[0203] Table 2

[0204] ※2: Measurement could not be performed because the membrane broke during stretching.

[0205] Using the method described above for porous membranes, the surface porosity Ps and cross-sectional porosity Pc of the porous membranes of Examples 1 to 3 and Comparative Examples 1 to 5 were determined. The results are shown in Table 3.

[0206] Table 3

[0207] ※3: Measurement could not be performed because the membrane broke during stretching.

[0208] As shown in Table 2, the porous membranes of Examples 1 to 3, which used thermoplastic resins with a weight-average molecular weight of 700,000 or more, had a water pressure resistance of 500 kPa or more and an air permeability of less than 60 seconds / 100 mL, as expressed in Graley number. They improved water resistance while maintaining excellent air permeability.

[0209] Depend on Figure 14A , Figure 15A and Figure 16A and Figure 17A , Figure 18 and Figure 19A A comparison reveals that multiple island-like regions and multiple fibrils connecting these island-like regions were observed in the porous membranes of Examples 1 to 3. According to... Figure 14B , Figure 15B and Figure 16B and Figure 17B and Figure 19BThe comparison shows that in the porous membranes of Examples 1 to 3, the nodes or block nodes are densely packed together, and fine gaps (pores) are observed between the nodes or block nodes. In addition, as shown in Table 3, in the porous membranes of Examples 1 to 3, when the cross-section is observed by SEM, the proportion Rc of pores with an equivalent circle diameter of 0.7 μm or less is more than 10%.

[0210] These results suggest that, in the porous membranes of Examples 1 to 3, the aforementioned characteristic cross-sectional and surface structures are easily formed by using thermoplastic resins with a weight-average molecular weight of 700,000 or more, thereby achieving high water resistance and high air permeability.

[0211] The results above show that the porous membranes of Examples 1 to 3 are suitable for improving water resistance while maintaining excellent air permeability.

[0212] Industrial practicality

[0213] The technology of this invention can be applied, for example, to waterproof and breathable membranes, waterproof and sound-permeable membranes, and separators for energy storage devices.

Claims

1. A porous membrane, wherein, The porous membrane contains a fluorine-free thermoplastic resin as its main component. The thermoplastic resin has a weight-average molecular weight of 700,000 or higher.

2. The porous membrane according to claim 1, wherein, The thermoplastic resin is a polyolefin resin.

3. The porous membrane according to claim 1, wherein, The porous membrane has a water pressure resistance of 500 kPa or higher, and its air permeability, expressed as a Grylls number, is less than 60 seconds / 100 mL.

4. The porous membrane according to claim 3, wherein, When the value obtained by dividing the air permeability by the water pressure resistance is defined as the ratio R, R ≤ 0.09 is satisfied.

5. The porous membrane according to claim 1, wherein, When the cross-section of the porous membrane is observed using a scanning electron microscope, the proportion of pores with an equivalent circular diameter of 0.7 μm or less is more than 10%.

6. The porous membrane according to claim 1, wherein, When the surface of the porous membrane is observed using a scanning electron microscope, the porosity is less than 40%.

7. The porous membrane according to claim 6, wherein, When the cross-section of the porous membrane is observed using a scanning electron microscope, the porosity is greater than 30%.

8. The porous membrane according to claim 1, wherein, The thickness of the porous membrane is less than 70 μm.

9. The porous membrane according to claim 1, wherein, The porous membrane is a stretched membrane.

10. A porous membrane comprising a fluorine-free thermoplastic resin as a main component, wherein, When the surface of the porous membrane is observed using a scanning electron microscope, multiple island-like regions and multiple fibrils connecting the multiple island-like regions are observed, and the proportion of pores with an equivalent circular diameter of less than 0.7 μm is more than 10%.

11. The porous membrane according to claim 10, wherein, The thermoplastic resin is a polyolefin resin.

12. A breathable component, wherein, The breathable component has: The porous membrane according to any one of claims 1 to 11; and An adhesive layer that bonds to the porous membrane.

13. A component supply sheet, the component supply sheet comprising: a breathable member disposed on the surface of an object having an open surface; and a substrate sheet having the breathable member disposed on its surface, wherein, The breathable component has: A porous membrane having a shape that covers the opening when disposed on the surface; and An adhesive layer is bonded to the porous membrane. The porous membrane is the porous membrane according to any one of claims 1 to 11.

14. The component supply sheet according to claim 13, wherein, A plurality of the breathable members are disposed on the surface of the substrate sheet.

15. A method for manufacturing a porous membrane, wherein, The method for manufacturing the porous membrane includes: The process of mixing a composition containing a fluorine-free thermoplastic resin and a plasticizer to obtain a compound; The process of performing compression or extrusion processing; The process of implementing cooling treatment; The process of performing stretching treatment; and The process of extracting and treating plasticizers is implemented. The thermoplastic resin has a weight-average molecular weight of 700,000 or higher.

16. The method for manufacturing a porous membrane according to claim 15, wherein, The method for manufacturing the porous membrane further includes a step of performing an annealing process.

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