Porous breather

Abstract

To provide a new porous breather capable of making waterproofness and air permeability compatible.SOLUTION: Provided is a porous breather having air permeability and water permeability. In the porous breather, a value of V×C defined below is 100 or more and 520 or less. V=W×Sp / (S100 / Sall), C=h-0.379×2.5614.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a porous breather that is waterproof and breathable. [Background technology]

[0002] Porous membranes made of resins such as PTFE are known as breathers that are waterproof and breathable, but because they require expensive equipment, sintered alloys have been considered as an alternative. For example, Patent Document 1 discloses a sintered alloy in which a sintered alloy body having air vents is subjected to a water-repellent treatment to improve water repellency. Furthermore, Patent Document 2 discloses a method for manufacturing a sintered metal filter having a first filter layer with a relatively large pore size and a second filter layer with a pore size smaller than that of the first filter layer. Furthermore, Patent Document 3 discloses a filter including a porous sintered body obtained by sintering a compression-molded body, and a fluorine-based compound coating film formed on the surface of the sintered body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-105324 [Patent Document 2] Japanese Patent Application Publication No. 7-68114 [Patent Document 3] Japanese Patent Publication No. 2023-046383 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventions disclosed in the above patent documents state that they can achieve both waterproofness and breathability, but do not provide detailed consideration of the level at which they achieve both waterproofness and breathability. On the other hand, breathers for venting battery cases are required to vent gas generated inside the battery to suppress pressure buildup inside the battery pack, and also to prevent the intrusion and leakage of water, oil, etc., so they must be highly waterproof and breathable at the same time. An object of the present invention is to provide a new porous breather that is both waterproof and breathable. [Means for solving the problem]

[0005] The present inventors have conducted studies to solve the above problems and have found that a new porous breather that can achieve both waterproofness and breathability can be provided by satisfying the following specific parameters.

[0006] One aspect of the present invention is a porous breather having air and water permeability, in which the value of V×C, as defined below, is 100 or more and 520 or less. V=W×Sp / (S 100 / S all ) C=h -0.379 ×2.5614 however, When the breather is impregnated with water using the vacuum impregnation method, the water density calculated using the following formula is defined as W. Wet density W = (mass after water impregnation - mass before water impregnation) / breather volume The cross-sectional area of ​​the breather in the thickness direction is 10 μm 2 The total of the above void areas is S all Let's say. The cross-sectional area of ​​the breather in the thickness direction is 10 μm 2 More than 100μm 2 The total void area less than S 100 Let's say. The planar area of ​​the breather is defined as Sp. The thickness of the breather is h.

[0007] Another aspect of the present invention is a porous breather having air and water permeability, When the breather is impregnated with water by the vacuum impregnation method, the water density W calculated by the following formula is 0.2 g / cm 3 That's all, Wet density W = (mass after water impregnation - mass before water impregnation) / breather volume The cross-sectional area of ​​the breather in the thickness direction is 500 μm 2 The total of the above void areas is S 500 When this is done, S for the entire measurement area 500 A porous breather in which the proportion of is 5% or more and 20% or less.

[0008] The cross-sectional area of ​​the breather in the thickness direction is 500 μm 2 The average area of ​​the above voids is Sa 500 When Sa 500 is 1000 μm 2 More than 3500μm 2 Preferably, the cross-sectional area is 10 μm or less. 2 More than 100μm 2 The total void area less than S 100 The cross-sectional area of ​​the breather in the thickness direction is 10 μm 2 The total of the above void areas is S all Then, S 100 / S all It is preferable that the value of S is 7% or more and 35% or less. 500 The ratio of Sr 500 When W 2 ×Sr 500 The value of ×C is preferably 0.005 or more and 0.025 or less.

[0009] Furthermore, when a 10 μL droplet of water is dropped onto the surface of the porous breather, it is preferable that the penetration time for the water droplet to penetrate into the breather is 32 seconds or more and 44 seconds or less, and it is preferable that the porous breather is made of a sintered alloy. [Effects of the Invention]

[0010] The present invention can provide a new porous breather that is both waterproof and breathable. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a schematic diagram of a breather produced in the example. [Figure 2] FIG. 1 is a conceptual diagram of an apparatus for measuring wet density by a vacuum impregnation method. [Figure 3] Schematic diagram of an apparatus for measuring air / water permeability. [Figure 4] 1 is a graph in which the V×C value is plotted on the horizontal axis and the airflow rate is plotted on the vertical axis for the breathers of the examples and comparative examples. [Figure 5] 1 is a graph in which the V×C value is plotted on the horizontal axis and the water permeation amount is plotted on the vertical axis for the breathers of Examples and Comparative Examples. [Figure 6] 1 is a graph in which the value of W2×Sr500×C is plotted on the horizontal axis and the airflow rate is plotted on the vertical axis for the breathers of the examples and comparative examples. [Figure 7] 1 is a graph in which the value of W2×Sr500×C is plotted on the horizontal axis and the amount of water permeation is plotted on the vertical axis for the breathers of Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0012] One embodiment of the present invention is a porous breather having air and water permeability. The porous breather can be obtained by placing a desired powder in a mold made of die steel, ceramics, or the like, and then compression-molding and sintering the powder.

[0013] The material of the powder is not particularly limited, but may be stainless steel, copper, an alloy such as an aluminum alloy or a titanium alloy, or a combination of these. An example of the raw metal powder may be 100% stainless steel (excluding inevitable impurities).

[0014] When resin powder is used, examples include thermosetting resins such as phenol, epoxy, polyurethane, etc., thermoplastic resins such as general-purpose PE, PP, PS, ABS, PMMA, etc., general-purpose engineering plastics such as PC, POM, PA, PET, etc., and super engineering plastics such as PPS, PSU, PEEK, etc. In addition to metals and resins, glass, silica, ceramics, etc. can also be selected.

[0015] The particle size of the powder is not particularly limited, and powders having a particle size of 10 μm or more and 1000 μm or less can be used in appropriate combination. However, in order to achieve both waterproofness and breathability suitable for the breather, it is necessary to control the water repellency / hydrophilicity of the voids in the breather and the surface and interior of the breather. In this embodiment, the particle size of the powder needs to be appropriately controlled to satisfy the parameters described below.

[0016] For example, to increase the water density W, it is necessary to increase the voids, so the amount of powder with a small particle size is reduced; the cross-sectional area in the thickness direction of the breather is 10 μm 2 More than 100μm 2 To increase the area below 500 μm, increase the amount of powder with a small particle size. 2 In order to increase the above area, the amount of powder with a large particle size is increased; etc. In addition, reducing the molding pressure is effective in increasing the void area, but reducing the molding pressure may result in a loss of breather moldability and strength. The inventors have discovered that controlling the powder shape, for example, using water-atomized stainless steel powder, in addition to examining the particle size, can ensure breather moldability and strength even when the molding pressure is reduced. Furthermore, in the production of sintered products, a solid lubricant is typically added to improve moldability, and a release agent is typically added to improve mold releasability. However, even with sufficient mixing, controlling the void area can be difficult. The inventors have discovered that by optimizing the molding pressure according to the powder particle size, moldability and release ability can be ensured without the use of a solid lubricant or release agent. Eliminating the use of a solid lubricant or release agent makes it possible to omit the mixing process, thereby facilitating control of the void area.

[0017] One example of controlling the particle size of a powder is to prepare multiple sieves, such as 60 mesh, 100 mesh, 150 mesh, and 200 mesh, classify the powder using each sieve, and combine powders of the desired particle size. It is also possible to control the parameters described below by bonding powders in a state where metal particles having a specific particle size are unevenly distributed in the mold.

[0018] The conditions for bonding the powders are not particularly limited. A binder may be used, sintering may be used when using metal or alloy powders, or heating may be used to bond the powders together when using thermoplastic resins. When using an alloy whose main component is a metal, the sintering temperature is, for example, between 600°C and 1400°C for 10 minutes to 6 hours, depending on the type and particle size of the metal particles. For example, stainless steel (SUS316) particles are sintered at a temperature between 1100°C and 1400°C for 1 to 2 hours. The sintering atmosphere is preferably selected according to the characteristics of the powder, such as a reducing atmosphere of hydrogen gas after evacuation. Furthermore, the conditions for compression molding before sintering are not particularly limited. For example, if the porosity in the breather is to be reduced, the molding pressure may be increased in the compression molding before the powder is bonded.

[0019] When sintering is performed using SUS316 as the powder, a solid lubricant, a mold release agent, etc. may be contained in the mold as long as the effect of the present invention is not impaired.

[0020] The breather of this embodiment has a V×C ​​value defined below of 100 or more and 520 or less. . V=W×Sp / (S 100 / S all ) C=h -0.379 ×2.5614 however, When the breather is impregnated with water using the vacuum impregnation method, the water density calculated using the following formula is defined as W. Wet density W = (mass after water impregnation - mass before water impregnation) / breather volume The cross-sectional area of ​​the breather in the thickness direction is 10 μm 2 The total of the above void areas is S all Let's say. The cross-sectional area of ​​the breather in the thickness direction is 10 μm 2 More than 100μm 2 The total void area less than S 100 Let's say. The planar area of ​​the breather is defined as Sp. The thickness of the breather is h.

[0021] The water density W represents the weight of water contained in the breather divided by the volume of the breather when the breather is impregnated with water by the vacuum impregnation method. The vacuum impregnation method is performed under the following conditions using the device shown in Figure 2. ·Water (specific gravity 1.0g / cm 3 ) Vacuum level: 0.08MPa The water density W is 0.2 g / cm 3 It is preferable that the concentration is 0.25 g / cm or more. 3The upper limit is not particularly limited, but is usually 0.45 g / cm 3 The following is the result.

[0022] The voids in the breather are measured by observing the cross section of the breather in the thickness direction. The cross section of the breather in the thickness direction is observed at 200x magnification using, for example, a microscope (Keyence: VHX8000), and the void area is measured. More specifically, the cross section is cut using a cutting machine manufactured by Refine Tech, and then resin-filled with Bakelite using a resin-filling machine manufactured by Refine Tech. In order to remove the plastic flow layer from the cut surface, the surface is polished with waterproof abrasive paper, and then buffed with 0.3 μm alumina using a buffing machine manufactured by Refine Tech. The surface is then observed using a microscope. The cross section of the breather may be observed in the thickness direction of the breather, or a portion of it may be observed. When observing a portion of it, the observation area is 1.5 mm. 2 It is preferable that this is equal to or greater than this. The void area was measured by observing the cross section of the breather, and the cross section area was 10 μm 2 The total of the above void areas is S all and the cross-sectional area is 10 μm 2 More than 100μm 2 The total void area less than S 100 The cross-sectional area is 500 μm 2 The total of the above void areas is S 500 The cross-sectional area is 500 μm 2 The average area of ​​the above voids is Sa 500 Let's say.

[0023] In this embodiment, S 500 The ratio of S is preferably 5% or more and 20% or less. 500 If the ratio is less than 5%, the breathability tends to be insufficient, and if it exceeds 20%, the water permeability tends to be high and the waterproofness tends to be insufficient. Also, S 500 is 90,000 μm 2 More than 330,000μm 2 It is preferable that S 500 is 90,000 μm 2Below 330,000 μm, the breathability tends to be insufficient. 2 If the temperature exceeds this, the water permeability will increase and the waterproofing will tend to be insufficient. In addition, the cross-sectional area is 500 μm 2 The average void area of ​​the above, Sa 500 is 1000 μm 2 More than 3500μm 2 It is preferable that the value is less than or equal to Sa 500 is 1000 μm 2 Below 3500 μm, the breathability tends to be insufficient. 2 If the temperature exceeds this, the water permeability will increase and the waterproofing will tend to be insufficient. Also, the cross-sectional area is 10 μm 2 The total void area S all Cross-sectional area of ​​10 μm 2 More than 100μm 2 The total void area is less than S 100 The ratio (S 100 / S all It is preferable that the value of S is 7% or more and 35% or less. 100 / S all If the value is below 7%, the permeability If the content is too high, the waterproofing tends to be insufficient, and if it exceeds 35%, the breathability tends to be insufficient. Also, the cross-sectional area is 10 μm 2 Porosity Sr all is preferably 15% or more and 30% or less.

[0024] A breather typically has a cylindrical shape with a thickness and a front and back main surfaces. A simple schematic diagram is shown in FIG. 1. The main surface may be circular, rectangular, or irregular, and can be appropriately set depending on the application to which the breather is applied. In this specification, the planar area of ​​the breather, i.e., the area of ​​the main surface, is defined as Sp, and the thickness of the breather is defined as h. The main surface of the breather may also include uneven portions. In this case, h is the value obtained by dividing the volume of the breather by the area of ​​the main surface Sp. If the cross section of the breather parallel to the main surface is not uniform, the value obtained by dividing the volume of the breather by the thickness h of the breather is defined as the area of ​​the main surface Sp. In this specification, the thickness direction of the breather is as shown in FIG. 1, and is the direction in which air and water pass through when the breather is installed.

[0025] In this specification, the thickness correction coefficient C is defined as follows: C=h -0.379 ×2.5614 In porous breathers, the thicker the breather, the lower the air permeability and water permeability tend to be, but thickness is not inversely proportional to air permeability and water permeability. The inventors have focused on this relationship and found the following correlation for the thickness correction coefficient C. In other words, air permeability and water permeability can be controlled by changing the thickness of the breather.

[0026] In addition, S for the entire measurement area 500 The ratio of Sr 500 When W 2 ×Sr 500 It is preferable that the value of ×C is 0.005 or more and 0.025 or less. 2 ×Sr 500 If the value of ×C is less than 0.005, the breathability tends to be insufficient, and if it exceeds 0.025, the water permeability tends to be high and the waterproofness tends to be insufficient.

[0027] Furthermore, when a 10 μL water droplet is dropped on the surface of the breather, the penetration time t, which is the time it takes for the water droplet to penetrate into the breather, is preferably 32 seconds or more and 44 seconds or less. If the penetration time t is less than 32 seconds, the water permeability tends to be high and waterproofness tends to be insufficient, and if it is more than 44 seconds, breathability tends to be insufficient.

[0028] The breather may have a water-repellent coating on its surface when a highly hydrophilic powder is used, and may not have a water-repellent coating when a highly hydrophobic powder is used. The type of water-repellent coating is not particularly limited as long as it is a film that has water repellency, and a typical example is a water-repellent coating made from a fluorine-based compound, but it may also be a water-repellent coating made from grease or a coating of stearic acid. The water-repellent coating can improve waterproofing.

[0029] For example, when SUS316 powder is used, the density of the porous breather is 4.2 g / cm during compression molding. 3 More than 6.0g / cm 3 Preferably, it is 4.3 g / cm or less. 3 More than 5.9g / cm 3 By setting the density within the above range, the air permeability and water permeability become good.

[0030] The breather of this embodiment has high breathability. The amount of air permeation measured under the following conditions using the device shown in FIG. 3 is preferably 50 mL / min or more, and more preferably 65 mL / min or more. Pressure when measuring breathability: 5kPa Figure 3 shows the main parts of a pressurized air / water permeability tester for porous breathers. The air permeability test is carried out by supplying pressurized air from the upper pipe in Figure 3, allowing the breather to ventilate and measuring the leakage amount using a gas meter at the outlet. For the water permeability test, a water tank was attached to the end of the supply pipe, water was pumped into the breather, and the amount of water permeation was measured using a weight scale in the water receiver on the outlet side.

[0031] Furthermore, the breather of this embodiment has a low water permeability. The water permeability measured under the following conditions using the device shown in Figure 3 is preferably 2.5 mL / min or less, and more preferably 1 mL / min or less. Pressure when measuring permeability: 10 kPa [Example]

[0032] The present invention will be described in detail below with reference to experimental examples, but the present invention is not limited to the results of the following experimental examples. Two types of SUS powder with different classification conditions were used as raw material powder for the porous breather. Powder A (average particle size 70 μm) and Powder B (average particle size 200 μm) were mixed and filled into a mold, and then compression molded by pressing. The density at this time was 4.7 to 5.7 g / cm. 3The obtained green compact was sintered at 1300°C for 1 hour in a reducing atmosphere using hydrogen, to obtain a cylindrical breather made of the sintered alloy of Example 1 having a diameter of about 12 mm and a thickness of about 6 mm. These samples were coated with a water-repellent coating on the surface and inside by immersion.

[0033] The physical properties of the obtained breather were measured by the following methods. <Water density> The wet density W was measured using the apparatus shown in FIG. 2 under the following conditions. ·Water (specific gravity 1.0g / cm 3 ) Vacuum level: 0.08MPa <Porosity> The breather was cut near the center in a direction perpendicular to the plane direction (thickness direction), embedded in resin so that the resulting thickness direction cross section served as the polished surface, and polished with waterproof abrasive paper in the order of #60, #220, #400, #800, and #1200. When cutting the sample, a plastic flow layer may form on the cut surface, so the sample was thoroughly polished with waterproof abrasive paper to remove the plastic flow layer. After that, the sample was buffed with 0.3 μm alumina slurry, and a color image was taken at 200x magnification using a microscope (Keyence: VHX8000). The image was then binarized using image analysis software, and the void area within the observation field was measured. S was calculated from the average of five arbitrary points. all , Sr all , S 100 , S 500 , Sr 500 , Sa 500 were calculated respectively.

[0034] <10μL penetration time> A 10 μL water droplet was dropped onto the surface (main surface) of the breather obtained in the example using a contact angle measuring device, and the penetration time until the water droplet penetrated into the breather was measured. These values ​​are shown in Tables 1 and 2.

[0035] In Example 1, cylindrical sintered alloy breathers of Examples 2 to 12 and Comparative Examples 1 to 4 with a diameter of approximately 12 mm and a thickness of approximately 6 mm or 12 mm were obtained in the same manner as in Example 1, except that the classification conditions of the SUS powder, the powder mixing ratio, and the target density were appropriately changed. For Examples 2 to 12 and Comparative Examples 1 to 4, various measurements were carried out in the same manner as in Example 1, and the values ​​obtained are shown in Tables 1 and 2.

[0036] [Table 1]

[0037] [Table 2]

[0038] Also, W×Sp / (S 100 / S all ) and V, which is represented by h -0.379 The results are shown in Figure 4, where the value of V × C multiplied by C, expressed as × 2.5614, is plotted on the horizontal axis and the air permeability on the vertical axis. Also, the results are shown in Figure 5, where the value of V × C is plotted on the horizontal axis and the water permeability on the vertical axis. It can be seen from FIGS. 4 and 5 that when the value of V×C is 100 or more and 520 or less, the breather can be made to be both waterproof and breathable. Furthermore, W 2 ×Sr 500 The results are shown in Figure 6, where the value of ×C is plotted on the horizontal axis and the ventilation volume on the vertical axis. 2 ×Sr 500 The results are shown in Figure 7, where the value of ×C is plotted on the horizontal axis and the water permeability on the vertical axis. From Figures 6 and 7, W 2 ×Sr 500 It can be seen that even when the value of ×C is 0.005 or more and 0.025 or less, the breather can be one that is both waterproof and breathable. [Explanation of symbols]

[0039] 1 container 2 Porous breather 3 Sealing lid 4. Vacuum pump 5. Air and water permeability direction 6 plane (principal surface) 7 Diameter-directed vertical section of a plane 8 Seals

Claims

1. A porous breather having air and water permeability, wherein a value of V×C defined below is 100 or more and 520 or less. V=W×Sp / (S １００ / S ａｌｌ ) C=h －０．３７９ ×2.5614 however, When the breather is impregnated with water by the vacuum impregnation method, the water-containing density calculated by the following formula is defined as W. Wet density W = (mass after water impregnation - mass before water impregnation) / breather volume - Cross-sectional area of ​​the breather in the thickness direction is 10 μm ２ The sum of the above void areas is S ａｌｌ Let's say. - Cross-sectional area of ​​the breather in the thickness direction is 10 μm ２ 100 μm or more ２ The total void area less than S １００ Let's say. The planar area of ​​the breather is defined as Sp. ・Let the thickness of the breather be h.

2. A porous breather having air and water permeability, When the breather is impregnated with water by a vacuum impregnation method, the water density W calculated by the following formula is 0.2 g / cm ３ That's all, Wet density W = (mass after water impregnation - mass before water impregnation) / breather volume The cross-sectional area of ​​the breather in the thickness direction is 500 μm ２ The sum of the above void areas is S ５００ When this is done, S for the entire measurement area ５００ A porous breather in which the ratio of

3. The cross-sectional area of ​​the breather in the thickness direction is 500 μm ２ The average area of ​​the above voids is Sa ５００ When this is done, Sa ５００ is 1000 μm ２ 3500 μm or more ２ 3. The porous breather of claim 1, wherein:

4. The cross-sectional area of ​​the breather in the thickness direction is 10 μm ２ 100 μm or more ２ The total void area less than S １００ The cross-sectional area of ​​the breather in the thickness direction is 10 μm ２ The sum of the above void areas is S ａｌｌ When this is done, S １００ / S ａｌｌ 3. The porous breather according to claim 1, wherein the value of is 7% or more and 35% or less.

5. W defined below ２ ×Sr ５００ 3. The porous breather according to claim 1, wherein the value of ×C is 0.005 or more and 0.025 or less. When the breather is impregnated with water by the vacuum impregnation method, the water-containing density calculated by the following formula is defined as W. Wet density W = (mass after water impregnation - mass before water impregnation) / breather volume - Cross-sectional area of ​​the breather in the thickness direction: 500 μm ２ The sum of the above void areas is S ５００ When this is done, S for the entire measurement area ５００ The ratio of Sr ５００ Let's say. ・C=h －０．３７９ × 2.5614 (where h is the thickness of the breather.)

6. 3. The porous breather according to claim 1, wherein when a 10 μL water droplet is dropped on a surface of the porous breather, the penetration time for the water droplet to penetrate into the breather is 32 seconds or more and 44 seconds or less.

7. 3. The porous breather of claim 1, wherein the porous breather is made of a sintered alloy.

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