Pressure relief valve and container equipped with pressure relief valve

Abstract

A pressure relief valve according to the present disclosure relieves pressure acting on the reverse surface of a thin film part by rupturing the thin film part. The pressure relief valve comprises a housing including the thin film part on an upper surface thereof, and a vent filter member attached to the housing. The housing has an elastomer as a main component thereof. The vent filter member has a cylindrical holding body, and a porous film held so as to close one end of the holding bod. The thin film part is disposed on the obverse surface of the porous film. The porous film is impermeable to liquid and permeable to gas. The thin film part has a groove on the obverse surface thereof, and has a distal-end part at the depth-direction distal end of the groove. The average thickness of the distal-end part is 0.02 mm or greater. The porous film has an Oken air permeability of 400 seconds or less and a porosity of 30% or greater. The burst pressure of the porous film is higher than the burst pressure of the thin film part.

Description

Pressure relief valves and containers with pressure relief valves

[0001] This disclosure relates to a pressure relief valve and a container with a pressure relief valve. This application claims priority to Japanese Application No. 2024-106226, filed July 1, 2024, and incorporates by reference all of the contents of said Japanese application.

[0002] In the case of a sealed container, an increase in internal pressure can cause the container to swell and potentially burst. Therefore, devices capable of releasing pressure generated inside the container have been developed. For example, in the prior art, a flat prismatic battery has been proposed in which a plate assembly is housed in a main case with a weld margin around the periphery. When a cover plate is placed over the weld margin and welded at the weld margin, the weld strength of the flat prismatic battery is partially reduced along the weld line, forming a fragile portion. The flat prismatic battery is equipped with a safety valve structure that breaks the weld at the fragile portion to release the internal pressure to the outside when the internal pressure increases excessively (see Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2004-103369

[0004] The pressure release valve of the present disclosure is a pressure release valve that releases pressure applied to the back surface of a thin film portion by rupturing the thin film portion, and comprises: a housing including the thin film portion on an upper surface; and a vent filter member attached to the housing, wherein the housing is mainly composed of an elastomer, the vent filter member has a cylindrical holder and a porous membrane held so as to close one end of the holder, the thin film portion is disposed on the surface of the porous membrane, the porous membrane is impermeable to liquids but permeable to gases, the thin film portion has grooves on the surface and a tip portion at the tip end of the groove in the depth direction, the tip portion has an average thickness of 0.02 mm or more, the Oken air permeability of the porous membrane is 400 seconds or less and a porosity of 30% or more, and the burst pressure of the porous membrane is higher than the burst pressure of the thin film portion.

[0005] FIG. 1 is a schematic perspective view showing a pressure relief valve according to an embodiment of the present disclosure. FIG. 2 is a cross-sectional view of the pressure relief valve of FIG. 1 taken along line II-II. FIG. 3 is a schematic partial cross-sectional view showing a housing of a pressure relief valve according to an embodiment of the present disclosure. FIG. 4 is a schematic cross-sectional view showing a housing of a pressure relief valve according to an embodiment of the present disclosure. FIG. 5 is a schematic cross-sectional view showing a vent filter member of a pressure relief valve according to an embodiment of the present disclosure. FIG. 6 is a schematic partial cross-sectional view showing a container with a pressure relief valve according to an embodiment of the present disclosure. FIG. 7 is a schematic cross-sectional view showing a pressure-released state of a container with a pressure relief valve according to an embodiment of the present disclosure. FIG. 8 is a schematic perspective view showing a pressure relief valve according to another embodiment of the present disclosure. FIG. 9 is a cross-sectional view of the pressure relief valve of FIG. 8 taken along line IX-IX.

[0006] In the above-mentioned conventional technology, it is possible to release pressure when the internal pressure rises excessively. However, since the pressure resistance of each container varies, it is not easy to release pressure when the internal pressure suddenly rises above a predetermined value. From a safety perspective, there is a risk that the liquid sealed in the container may leak out of the container through the pressure release valve when the pressure is released. It is desirable that pressure release valves provided in pressure vessels and the like have a simple structure and are compact.

[0007] The present disclosure aims to provide a pressure relief valve that has a simple structure, reliably releases pressure when there is a sudden increase in internal pressure, and is highly effective in preventing the liquid sealed in the container from splashing.

[0008] According to the present disclosure, it is possible to provide a pressure relief valve with a simple structure that reliably releases pressure when there is a sudden increase in internal pressure and that is highly effective in preventing the liquid sealed in the container from splashing.

[0009] First, embodiments of the present disclosure will be listed and described.

[0010] (1) A pressure release valve of the present disclosure is a pressure release valve that releases pressure applied to the back surface of a thin film portion by rupturing the thin film portion, and comprises a housing including the thin film portion on its upper surface, and a vent filter member attached to the housing, the housing being mainly composed of an elastomer, the vent filter member having a cylindrical holder and a porous membrane held so as to close one end of the holder, the thin film portion being disposed on the surface of the porous membrane, the porous membrane being impermeable to liquids but permeable to gases, the thin film portion having grooves on its surface and tip portions at the tips of the grooves in the depth direction, the tip portions having an average thickness of 0.02 mm or more, the Oken air permeability of the porous membrane being 400 seconds or less and having a porosity of 30% or more, and the porous membrane having a burst pressure higher than the burst pressure of the thin film portion.

[0011] The pressure release valve has a thin film portion on the top surface of the housing. The thin film portion has a groove on its surface. Because the groove is fragile, when the pressure on the back surface of the thin film portion suddenly rises above a predetermined value, the thin film portion ruptures to release the pressure. This prevents the container from being destroyed by an increase in internal pressure. The thin film portion is disposed on the surface of a porous membrane. The porous membrane is impermeable to liquids but permeable to gases. This prevents the liquid sealed in the container from leaking out of the container through the pressure release valve upon pressure release. The thin film portion has a tip portion at the tip of the groove in the depth direction. The average thickness of the tip portion is 0.02 mm or more. This increases the strength of the thin film portion. The Oken air permeability of the porous membrane is 400 seconds or less, thereby providing a good pressure release effect by the porous membrane. The porosity of the porous membrane is 30% or more, improving gas permeability and providing good pressure release performance of the porous membrane. Furthermore, the burst pressure of the porous membrane is higher than the burst pressure of the thin film portion. This reduces the risk of the porous membrane being damaged before the thin membrane portion bursts, thereby more reliably preventing the liquid sealed in the container from scattering. Therefore, the pressure relief valve reliably releases pressure when the internal pressure rises, and is excellent in preventing the liquid sealed in the container from scattering.

[0012] Here, the term "main component" refers to the component with the largest content ratio in terms of mass, for example, a component with a content ratio of 60 mass % or more.

[0013] "Oken air permeability" is a value measured using an Oken air permeability tester in accordance with JIS-P8117: 2009. A higher air permeability value indicates lower breathability, i.e., higher barrier properties.

[0014] "Porosity" refers to the ratio of the total volume of pores to the total volume of a porous film, and can be calculated from the volume, mass, and true specific gravity of a sample.

[0015] (2) In the above (1), the porous film may be made of polytetrafluoroethylene. By making the porous film of polytetrafluoroethylene, chemical resistance and water repellency can be improved.

[0016] (3) In the above (1) or (2), the housing may have a recess on the bottom surface, the vent filter member may be attached to the recess, and the inner peripheral surface of the vent filter member may form a pressure release flow path. In the pressure release valve, since the housing and the vent filter member have the above configurations, the pressure release valve can reliably release pressure when the internal pressure rises suddenly, with a simpler structure, and is excellent in preventing the liquid sealed in the container from splashing.

[0017] (4) In any of (1) to (3) above, the top surface of the housing may have a depression in the center in a plan view, and the thin film portion may be formed on the bottom surface of the depression. By arranging the thin film portion on the bottom surface of the depression, the thin film portion having the groove may be easily ruptured by pressure applied to its back surface.

[0018] (5) In any one of (1) to (3) above, the top surface of the housing and the top surface of the thin film portion may be formed without any step.

[0019] (6) A container with a pressure release valve according to the present disclosure includes the pressure release valve described above in any one of (1) to (5). Because the container with a pressure release valve includes the pressure release valve described above, it reliably releases pressure when the internal pressure rises and is excellent in preventing the liquid sealed in the container from splashing.

[0020] [Details of the Embodiments of the Present Disclosure] The embodiments of the present disclosure will be described below with reference to the drawings.

[0021] <Pressure Release Valve> The pressure release valve is provided, for example, on the sealing plate of a container in an electric or electronic component such as a battery (including a primary battery and a secondary battery), a fuel cell, a condenser, or a capacitor, or on the sealing plate of a container in a general device. The pressure release valve includes a housing. The housing has a thin film portion on the top surface. The thin film portion ruptures when the internal pressure suddenly rises above a predetermined value. In this way, by releasing the pressure on the back surface of the thin film portion, it is possible to prevent the container from bursting.

[0022] FIG. 1 is a schematic perspective view showing a pressure relief valve 50 according to an embodiment of the present disclosure. FIG. 2 is a cross-sectional view of the pressure relief valve 50 taken along line II-II. FIG. 3 is a schematic partial cross-sectional view showing the housing 1 of the pressure relief valve 50, and FIG. 4 is a schematic cross-sectional view showing the entire housing 1. FIG. 5 is a schematic cross-sectional view showing a vent filter member 20 of the pressure relief valve 50. As shown in FIGS. 1 to 5 , the pressure relief valve 50 includes a housing 1 made primarily of elastomer and a vent filter member 20 provided inside the housing 1. The housing 1 has a thin film portion 10 on its top surface 3. More specifically, the housing 1 has a main body 2 and the thin film portion 10 provided in a recess 5 on the top surface 3 of the main body 2. That is, the top surface 3 of the housing 1 is also the top surface 3 of the main body 2. The thin film portion 10 has a groove 15 on its surface. The groove 15 has a tip 12 at its tip in the depth direction. The tip 12 is the thinnest portion, which is a vulnerable location. The rupture of the thin film portion 10 releases the pressure on the back surface of the thin film portion 10. The back surface of the thin film portion 10 is the surface on which the grooves 15 are not formed and is the surface facing the porous membrane described below. In this embodiment, the housing 1 has a recess 9 on its bottom surface. The vent filter member 20 is attached to the recess 9. Methods for attaching the vent filter member 20 to the housing 1 include, for example, insert molding, and bonding using an adhesive, heat welding, ultrasonic welding, etc.

[0023] [Housing] The housing 1 , which is mainly made of elastomer, has a main body portion 2 and a thin film portion 10 .

[0024] The material of the housing 1 is not particularly limited as long as it is an elastomer, and may be a thermoplastic elastomer or a thermosetting elastomer. Examples of thermoplastic elastomers include polystyrene-based thermoplastic elastomers, polyolefin-based thermoplastic elastomers, polyvinyl chloride-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, polybutadiene-based thermoplastic elastomers, and polyisoprene-based thermoplastic elastomers. Examples of thermosetting elastomers include diene-based synthetic rubbers such as silicone rubber, urethane rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber (acrylonitrile-butadiene rubber; NBR), and ethylene-propylene rubber; non-diene-based synthetic rubbers such as butyl rubber, acrylic rubber, fluororubber, and epichlorohydrin rubber; and natural rubber.

[0025] The lower limit of the elastomer content in the housing 1 may be 60 mass%, 80 mass%, 90 mass%, 95 mass%, 98 mass%, or 100 mass%. When the elastomer content in the housing 1 is 90 mass% or more, good elasticity and strength can be achieved.

[0026] In addition to the elastomer, other components may be added to the housing 1 as long as they do not impair the objectives of the present disclosure. Examples of such other components include ultraviolet absorbers, weather stabilizers, copper inhibitors, flame retardants, and colorants.

[0027] (Main body portion) As shown in Figure 4, the main body portion 2 has a recess 9 on its bottom surface. The main body portion 2 further has flanges 7 and 8 on its side surfaces for fitting into a container. A depression 5 having an inclined surface 4 formed around its entire periphery is integrally molded in the center of the top surface 3 of the main body portion 2. A thin film portion 10 is disposed on the bottom surface of the depression 5. The inclined surface 4 is formed on the inner peripheral surface of the depression 5 (the inner peripheral surface of the top surface adjacent to the peripheral edge of the thin film portion 10). By disposing the thin film portion 10 on the bottom surface of the depression 5, the thin film portion 10 having the groove 15 becomes more likely to rupture due to pressure applied to the back surface.

[0028] (Thin film portion) The thin film portion 10 has a groove 15 on its surface. As will be described later, the pressure release valve 50 has a simple structure in which the thin film portion 10 is disposed on the surface of the porous membrane 25 of the vent filter member 20. That is, the thin film portion 10, when disposed on the surface of the porous membrane 25, closes one end of the opening of the pressure release flow path 29 formed by the vent filter member 20.

[0029] The width of the groove 15 decreases from the front surface to the back surface in a cross-sectional view. The groove 15 is a cross-shaped groove in a plan view. The pointed end of the thin film portion 10, which is the intersection of the inclined surfaces of the groove 15, is particularly fragile, and will burst due to excessive pressure applied to the back surface of the disk-shaped thin film portion 10, which is mainly composed of elastomer. In Figure 3, the tip of the groove 15 in the depth direction is the thinnest part, and this is the weak point.

[0030] As shown in FIG. 3 , the thin film portion 10 has a tip portion 12 at the tip of the groove 15 in the depth direction. The average thickness T of the tip portion 12 can be set according to the burst pressure of the thin film portion 10. The average thickness T is calculated by taking a cross-sectional photograph with a microscope and measuring three individual pieces. The lower limit of the average thickness T of the tip portion 12 is 0.02 mm, but may also be 0.03 mm or 0.04 mm. By setting the average thickness of the tip portion 12 to 0.02 mm or more, the strength of the thin film portion 10 can be increased. On the other hand, the upper limit of the average thickness T of the tip portion 12 is not particularly limited, but can be, for example, 1.00 mm. In this way, by adjusting the depth of the groove 15 of the thin film portion 10, pressure can be released when the internal pressure suddenly rises above a predetermined value, depending on the pressure resistance that varies from container to container. The burst pressure of the thin film portion 10 can be set arbitrarily depending on the inner diameter, wall thickness, cross-sectional shape, etc. of the container. Therefore, the burst pressure of the thin film portion 10 is set appropriately, taking into consideration the value of the gas pressure caused by heat generated in normal use.

[0031] In this embodiment, the shape of the groove 15 is cross-shaped in plan view and V-shaped in cross section, but the shape of the groove 15 is not particularly limited. In addition to a cross-shaped shape, examples of the shape of the groove 15 in plan view include a linear shape, a radial shape, and a spiral shape. In addition to a V-shaped shape, examples of the shape of the groove 15 in cross section include a U-shaped shape.

[0032] [Vent filter member] The vent filter member 20 is a filter member that is breathable and waterproofs a sealed container or structure while maintaining a pressure adjustment function. The vent filter member 20 has a structure in which a breathable sheet-like porous membrane 25 is attached to a holder 27. The porous membrane 25 of the vent filter member 20 is breathable. When the pressure release valve 50 is provided with the vent filter member 20, the breathable porous membrane 25 allows the pressure release valve 50 to maintain its pressure adjustment function.

[0033] As shown in Figure 5, the vent filter element 20 has a cylindrical holder 27 and a porous membrane 25 held so as to close one end of the holder 27. In addition, the vent filter element 20 has a pressure release flow path 29 formed by the inner circumferential surface of the cylindrical holder 27. The opening of the pressure release flow path 29 is circular in plan view. The porous membrane 25 is held so as to close one end of the holder 27, thereby closing one end of the opening of the pressure release flow path 29.

[0034] (Porous Membrane) As the filter of the vent filter member 20, a porous membrane 25 having a large number of fine through-holes that allow gas to pass through but not liquid to pass through is used.

[0035] Examples of materials that can be used for the porous membrane 25 include polytetrafluoroethylene (PTFE), polyamide, polyolefin, polyester, and polyamide. The porous membrane 25 may be made of polytetrafluoroethylene. By making the porous membrane 25 of polytetrafluoroethylene, chemical resistance and water repellency can be improved. Here, "may be made of polytetrafluoroethylene" means that the porous membrane 25 may contain only polytetrafluoroethylene, or may contain polytetrafluoroethylene as a main component. "Containing as a main component" means that the porous membrane 25 contains more than 50% by mass.

[0036] A laminated membrane made up of a combination of multiple resin membranes may be used as the porous membrane 25. The use of a laminated membrane can improve the strength of the porous membrane 25. Examples of the form of the laminated membrane include nonwoven fabric and mesh.

[0037] The porous membrane 25 may contain additives other than the above-mentioned materials, as long as they do not impair the desired effects of the present disclosure. Examples of such additives include inorganic fillers, metal powders, metal oxide powders, and metal sulfide powders for improving wear resistance, preventing low-temperature flow, and facilitating pore generation.

[0038] The lower limit of the water-resistant pressure of the porous membrane 25 is not particularly limited and can be set appropriately depending on the application, but may be, for example, 15 kPa. The upper limit of the water-resistant pressure of the porous membrane 25 may be, for example, 800 kPa, from the viewpoint of favorably adjusting the porosity of the porous membrane 25. The "water-resistant pressure" refers to the pressure at which water begins to leak from one side of a membrane when water pressure is applied to the other side, and is also called the water leakage pressure. Generally, the larger the pore size of the through-holes, the more likely water is to leak and the lower the water-resistant pressure, while the smaller the pore size, the higher the water-resistant pressure. Specifically, the water-resistant pressure is measured in accordance with JIS-L1092 (2009).

[0039] The upper limit of the Oken air permeability of the porous membrane 25 is 400 seconds, and may be 40 seconds, 30 seconds, or 20 seconds. When the upper limit of the Oken air permeability of the porous membrane 25 is 400 seconds, the pressure release effect of the porous membrane 25 is good. On the other hand, the lower limit of the Oken air permeability of the porous membrane 25 is not particularly limited, but may be 0.5 seconds from the viewpoint of maintaining good water pressure resistance of the porous membrane 25.

[0040] The lower limit of the porosity of the porous membrane 25 is 30%, but may be 40%, or 50%. On the other hand, the upper limit of the porosity of the porous membrane 25 is not particularly limited, but may be 85% or 80%. When the porosity of the porous membrane 25 is 30% or more, the gas permeability is improved and the pressure release performance of the porous membrane 25 is good. When the porosity of the porous membrane 25 is 85% or less, the mechanical strength and durability of the porous membrane 25 can be maintained and damage such as bursting due to internal pressure can be prevented.

[0041] The burst pressure in this disclosure is an index of pressure resistance. The burst pressure can be evaluated by measuring the pressure at which the material bursts when pressure is applied at a pressure increase rate of 98 kPa / min. In the pressure release valve 50, the burst pressure of the porous membrane 25 is higher than the burst pressure of the thin film portion 10, which reduces the risk of the porous membrane 25 being damaged before the thin film portion 10 bursts, thereby more reliably preventing the liquid sealed in the container from splashing.

[0042] Next, an example of a method for manufacturing the porous membrane 25 will be described. The method for manufacturing the porous membrane 25 may include, for example, a step of forming a sheet using a raw material for forming the porous membrane, a step of heating the sheet-shaped molded product to a temperature above the melting point of the raw material for forming the porous membrane, a step of cooling the molten resin, and a step of stretching the non-porous sheet-shaped molded product to make it porous. In this way, by stretching the porous membrane 25 after molding, it is possible to form a porous membrane 25 while reducing the diameter of the pores in the porous membrane 25.

[0043] (Holding Body) The holding body 27 is cylindrical as shown in Fig. 5, and the inner peripheral surface of the holding body 27 becomes the inner peripheral surface of the vent filter member 20. The inner peripheral surface of the cylindrical holding body 27 forms a pressure release flow path 29 of a container equipped with a pressure release valve. In other words, the inner peripheral surface of the cylindrical holding body 27 defines a flow path for releasing pressure.

[0044] The holder 27 has an opening at one end. The holder 27 holds the porous membrane 25 so as to close the opening. The porous membrane 25 can be held in place by, for example, applying an adhesive to the opening at one end of the holder 27 and adhering it so as to close the pressure release flow path 29.

[0045] Examples of materials for the holder 27 include polytetrafluoroethylene and polyamide, which are materials for the porous membrane 25, and silicone rubber, urethane rubber, polystyrene-based thermoplastic elastomer, polyolefin-based thermoplastic elastomer, polyvinyl chloride-based thermoplastic elastomer, and polyester-based thermoplastic elastomer, which are materials for the housing 1. Among these, the material for the holder 27 may be silicone rubber, from the viewpoint of improving the elasticity, heat resistance, and chemical resistance of the holder 27.

[0046] In addition to the resin components described above, other components may be added to the holder 27 as long as they do not impair the objectives of the present disclosure. Examples of such other components include ultraviolet absorbers, weather stabilizers, copper inhibitors, flame retardants, and colorants.

[0047] [Method for Manufacturing Pressure Relief Valve] The pressure relief valve can be manufactured by, for example, attaching a vent filter member having a porous film containing polytetrafluoroethylene to a recess in a housing having a thin film portion.

[0048] The pressure release valve 50 has a simple structure, reliably releases pressure when the internal pressure rises suddenly, and is excellent in preventing the liquid sealed in the container from scattering.

[0049] <Container with Pressure Release Valve> The container with a pressure release valve includes the above-described pressure release valve. Fig. 6 is a schematic partial cross-sectional view showing a container with a pressure release valve according to one embodiment of the present disclosure. As shown in Fig. 6, the container with a pressure release valve 90 includes a pressure release valve 50. In the container with a pressure release valve 90, the flanges 7 and 8 of the housing 1 of the pressure release valve 50 are fitted into the upper surface of the container 40, thereby attaching the pressure release valve 50. As described above, the inner circumferential surface of the cylindrical holder 27 of the pressure release valve 50 forms the pressure release flow path 29 of the container with a pressure release valve 90.

[0050] The container 40 in the container 90 with a pressure release valve is not particularly limited, and a known sealed pressure container or the like can be used. Examples of such containers 40 include pressure containers for electric or electronic components such as primary batteries, secondary batteries, fuel cells, condensers, and capacitors, pressure containers for general equipment, and pressure containers for storing chemical solutions, etc. The container 90 with a pressure release valve is equipped with a pressure release valve 50, which reliably releases pressure when the internal pressure rises and is excellent in preventing the liquid sealed in the container 40 from splashing.

[0051] As shown in Figure 7, when the internal pressure of the sealed container 90 with a pressure release valve increases and exceeds a predetermined internal pressure, the excess pressure exerts stress on the back surface of the thin film portion 10 through the porous membrane 25. The grooves 15 of the thin film portion 10 are then forced apart, and stress is concentrated at the apex of the thin film portion 10, which is the intersection of the cross-shaped grooves 15 and is particularly vulnerable. As a result, the thin film portion 10 is unable to withstand the internal excess pressure and bursts. This causes the pressure release valve 50 to release the excess pressure indicated by arrow F to the outside. Therefore, even if the internal pressure of the container 90 with a pressure release valve becomes excessively high for some reason, the container 90 with a pressure release valve can be prevented from bursting.

[0052] In the above embodiment, a recess having an inclined surface formed around its entire periphery is integrally formed in the center of the upper surface of the main body of the housing, and a thin film portion is disposed on the bottom surface of the recess. However, in the present disclosure, the arrangement of the thin film portion is not limited to this. For example, the main body of the housing may not have an inclined surface, and the thin film portion may be disposed flush with the upper surface of the main body in the center of the upper surface of the main body.

[0053] FIG. 8 is a schematic perspective view showing a pressure release valve 80 according to another embodiment. FIG. 9 is a cross-sectional view of the pressure release valve 80 taken along line IX-IX. As shown in FIGS. 8 and 9, the pressure release valve 80 includes a housing 31 made primarily of elastomer and a vent filter member 70 disposed inside the housing 31. The vent filter member 70 has a structure in which a breathable, sheet-like porous membrane 75 is attached to a holder 77. In the vent filter member 70, the inner circumferential surface of the cylindrical holder 77 forms a pressure release flow path 79 for the container to which the pressure release valve is attached. The housing 31 also has a thin film portion 60 on its top surface 33. More specifically, the housing 31 includes a main body portion 32 and a thin film portion 60 disposed in the center of the top surface 33 of the main body portion 32. That is, the top surface 33 of the housing 31 is also the top surface 33 of the main body portion 32. The thin film portion 60 has a tip portion 62 at the tip of the groove 65 in the depth direction. The tip 62 is the thinnest part, which is the weak spot. Rupture of the thin film portion 60 releases pressure on the back surface of the thin film portion 60. In the pressure release valve 80, the housing 31 also has a recess on its bottom surface, and the vent filter member 70 is attached to the recess on the bottom surface of the housing 31. The main body portion 32 has a recess on its bottom surface and flange portions 37 and 38 on its side for fitting into the container. The top surfaces of the thin film portion 60 and the main body portion 32 form the same plane without any steps. By arranging the thin film portion 60 in this manner, the thin film portion 60 having the groove 65 is easily ruptured by pressure on the back surface. In this way, in the pressure release valve 80, rupture of the thin film portion 60 releases pressure on the back surface of the thin film portion 60, preventing bursting due to rupture of the container.

[0054] The porous membrane may be surface-modified to have oil repellency, for example by coating with a perfluoro-based oil repellent.

[0055] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0056] [Containers with Pressure Relief Valves No. 1 to No. 13] (1) Fabrication of Pressure Relief Valves As test products, pressure relief valves No. 1 to No. 13 were fabricated, each equipped with a silicone rubber housing having the shape shown in FIG. 1 and a polytetrafluoroethylene (PTFE) vent filter member. The specific dimensions of each pressure relief valve are shown in Table 1. The thin film portion of the housing was circular in plan view, with a diameter of 6.5 mm and an average thickness (average value of three points) of 0.7 mm. The grooves used were cross-shaped in plan view, approximately V-shaped in cross section, with a top width of 1.4 mm and a bottom width of 0.4 mm. The porous membrane used was a multi-layer stretched porous membrane made of polytetrafluoroethylene and circular in plan view. The porous membrane size was 9 mm in diameter (effective diameter, i.e., the diameter of the pressure relief flow path was 4.5 mm) and had an average thickness (average value of three points) of 0.19 mm. Note that No. In No. 13, a pressure relief valve was used that was only a housing without a vent filter member.

[0057] (2) Preparation of Containers with Pressure Release Valves As the containers, stainless steel pressure vessels having dimensions of 35.5 mm in diameter x 100 mm and an average thickness of 1.25 mm were used, and the above-mentioned pressure release valves No. 1 to No. 13 were installed therein to prepare Containers with Pressure Release Valves No. 1 to No. 13.

[0058] [Evaluation] (Water Pressure Resistance) The water pressure resistance [kPa] was measured in accordance with JIS-L1092 (2009).

[0059] (Porosity) The porosity is calculated by multiplying the volume of the porous film, the mass of the porous film, and the true specific gravity of polytetrafluoroethylene, 2.17 g / cm ３ From this, the ratio of the total volume of pores to the total volume of the porous membrane was calculated.

[0060] (Oken Air Permeability) The Oken air permeability [seconds] was measured in accordance with JIS-P8117:2009 using a digital Oken air permeability smoothness tester (manufactured by Asahi Seiko Co., Ltd., model number "EG01").

[0061] (Burst Pressure) Burst pressure: When pressure was applied at a pressure increase rate of 98 kPa / min, the pressure [kPa] at which the thin film portion and the porous film burst was measured.

[0062] (Evaluation of liquid ejection upon bursting) Evaluation of liquid ejection upon bursting was carried out by applying a pressure of 98 kPa / min to a container filled with water, carrying out a burst test, and videotaping the test to confirm whether or not liquid ejection occurred upon bursting of the thin film portion.

[0063] (Time to Pressure Release) The time to pressure release [seconds] was measured as the time until the pressure was released by the rupture of the thin film portion. A time of 180 seconds or less was considered acceptable.

[0064] The evaluation results of Test No. 1 to Test No. 13 are shown in Table 1.

[0065]

[0066]

[0067] From the results in Table 1, Nos. 1 to 8, which were equipped with vent filter members having a porous membrane that was impermeable to liquids but permeable to gases, in which the average thickness of the tip portions at the tips of the grooves in the depth direction of the thin film portion was 0.02 mm or more, in which the Oken air permeability of the porous membrane was 400 seconds or less, in which the porosity was 30% or more, and in which the burst pressure of the porous membrane was higher than the burst pressure of the thin film portion, did not spray out liquid when the thin film portion burst, and the time until pressure release was also good.

[0068] On the other hand, in No. 9, in which the average thickness of the groove depth direction tip in the thin film portion was less than 0.02 mm, the thin film portion burst when pressure was applied, and liquid spurted out. No. 10, in which the Oken air permeability of the porous membrane exceeded 400 seconds, took a long time to release pressure and failed the test. No. 11, in which the porosity of the porous membrane was less than 30% and the Oken air permeability exceeded 400 seconds, took an extremely long time to release pressure and failed the test. No. 12, in which the burst pressure of the porous membrane was lower than the burst pressure of the thin film portion, burst after water leakage from the thin film portion. No. 13, which was not equipped with a vent filter member, experienced liquid spurting when the thin film portion burst.

[0069] From the above, it can be seen that the pressure relief valve reliably releases pressure when the internal pressure rises, and is excellent in preventing the liquid sealed in the container from scattering.

[0070] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the configurations of the above-described embodiments, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0071] DESCRIPTION OF SYMBOLS 1, 31 Housing 2, 32 Main body 3, 33 Upper surface of housing (main body) 4 Inclined surface 5 Recess 7, 8 Flange 9 Recess 10, 60 Thin film 12, 62 Depth direction tip (thinnest part of thin film) 15, 65 Groove 20, 70 Vent filter member 25, 75 Porous film 27, 77 Holder 29, 79 Pressure release flow path 37, 38 Flange 40 Container 50, 80 Pressure release valve 90 Container with pressure release valve

Claims

1. A pressure relief valve which releases pressure applied to the rear surface of a thin film portion by the rupture of the thin film portion, comprising: a housing containing the thin film portion on its upper surface; and a vent filter member attached to the housing, wherein the housing is primarily made of elastomer, the vent filter member has a cylindrical holder and a porous membrane held so as to close one end of the holder, the thin film portion is disposed on the surface of the porous membrane, the porous membrane is impermeable to liquids but permeable to gases, the thin film portion has grooves on its surface and has tip portions at the tips of the grooves in the depth direction, the tip portions having an average thickness of 0.02 mm or more, the Oken air permeability of the porous membrane is 400 seconds or less and a porosity of 30% or more, and the burst pressure of the porous membrane is higher than the burst pressure of the thin film portion.

2. The pressure relief valve of claim 1, wherein said porous membrane is made of polytetrafluoroethylene.

3. A pressure relief valve as set forth in claim 1 or claim 2, wherein the housing has a recess on its bottom surface, the vent filter member is attached to the recess, and the inner peripheral surface of the vent filter member forms a pressure relief flow path.

4. A pressure relief valve as set forth in any one of claims 1 to 3, wherein the top surface of the housing has a depression in the center when viewed from above, and the thin film portion is formed on the bottom surface of the depression.

5. A pressure relief valve according to any one of claims 1 to 3, wherein the upper surface of the housing and the upper surface of the thin film portion are formed without any step.

6. A container with a pressure relief valve, comprising the pressure relief valve according to any one of claims 1 to 5.

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