Metal filters and filter modules

Abstract

To provide a metal filter including a metal support and a porous sintered body of metal particles, where bond strength to the metal support of the porous sintered body is increased.SOLUTION: A metal filter 1 is provided with a metal support 2 having a slit 22 and a porous sintered body 3 of metal particles functioning as a filter element. The slit 22 is defined by the first inclined surface 201 and the second inclined surface 202 of the support 2 and has a tapered cross section. The porous sintered body 3 is made in the slit 22 and bonded to the first inclined surface 201 and the second inclined surface 202.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a metal filter including a metal support and a porous sintered body of metal particles supported on the support as a filter element, and also to a filter module including the metal filter. [Background technology]

[0002] This type of metal filter is widely known, as disclosed in, for example, Patent Document 1. The metal filter of Patent Document 1 includes a metal support having a plurality of openings and a porous sintered body of metal particles that functions as a filter element. The support is, for example, a wire mesh screen, an expanded sheet, or a slit sheet. The porous sintered body of metal particles is disposed within the openings of the support and is bonded to the support. Due to its porous structure, the porous sintered body functions as a filter element that filters fluid. Such a metal filter can achieve a finer separation performance than the size of the openings in the support.

[0003] Such metal filters are typically manufactured by applying a paste containing metal particles and a dispersion medium to disperse the metal particles to the openings of a metallic support, and then heating the support to which the paste has been applied. This heating volatilizes the dispersion medium in the paste, and the metal particles in the paste sinter together, forming a porous sintered body in the openings. Furthermore, during the sintering of the metal particles, the sintered body is bonded to the support.

[0004] The porous sintered body should be firmly bonded to the metal support so as not to come off the metal support, and further improvement in the bonding strength of the porous sintered body to the metal support is desired. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 18403 / 1983 [Patent Document 2] Japanese Patent Application Publication No. Hei 1-194915 [Patent Document 3] Japanese Patent Application Publication No. 194914 / 1999 [Patent Document 4] Japanese Patent Application Publication No. 7-68114 [Patent Document 5] Japanese Patent Application Publication No. 47-23306 [Patent Document 6] Japanese Patent Application Laid-Open No. 2014-83472 [Non-patent literature]

[0006] [Non-Patent Document 1] Chen Chuantou and Suganuma Katsuaki, "New Developments in Power Module Structures by Joining Dissimilar Materials Using Ag Sintering," Chemical Engineering, Kagaku Kogyosha, August 2020, pp. 475-483 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to improve the bonding strength of a porous sintered body to a metal support in a metal filter including a metal support and a porous sintered body of metal particles, and also to provide a filter module including the metal filter. [Means for solving the problem]

[0008] The present invention relates to a metal filter comprising a metal support having slits and a porous sintered body of metal particles that functions as a filter element, the slit is defined by a first inclined surface and a second inclined surface of the support and has a tapered cross section; The porous sintered body is provided in the slit and is joined to the first inclined surface and the second inclined surface.

[0009] For example, the support may be a wedge wire screen, which may comprise at least one wire having a wedge-shaped cross section, the wire having the first inclined surface and the second inclined surface.

[0010] For example, the wedge wire screen may further comprise rods for fixing and supporting the wires.

[0011] For example, the support may be made of stainless steel and the porous sintered body may be made of silver.

[0012] For example, the slit width of the slit may be 5 μm to 100 μm.

[0013] For example, the metal filter may be cylindrical in shape.

[0014] The present invention also relates to a filter module, comprising: The cylindrical metal filter described above; a housing that accommodates the metal filter; ring members provided on both ends of the metal filter; an attachment having a communication hole for fluidly communicating the outside of the filter module with the inside of the metal filter, the attachment being inserted through the housing and attached to the ring member; [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1A is a schematic partial plan view of an exemplary support of a metal filter, FIG. 1B is a cross-sectional view taken along line PP in FIG. 1A, and FIG. 1C is a cross-sectional view taken along line QQ in FIG. 1A. [Figure 2] FIG. 2A shows a schematic and partial view of yet another exemplary support, FIG. 2B shows a cross-section of the wire in the position of the rod, and FIG. 2C shows a cross-section of the wire in the position without the rod. [Figure 3]FIG. 3A is a schematic cross-sectional view of an exemplary metal filter, and FIGS. 3B and 3C show examples of use of the metal filter. [Figure 4] FIG. 4A shows a metal filter according to the embodiment and a metal filter according to a comparative example, and FIG. 4B shows the angle of the inclined surface of the support. [Figure 5] FIG. 5 is a schematic diagram illustrating an example filter module including a metal filter. [Figure 6] FIG. 6 illustrates the steps for manufacturing a metal filter. DETAILED DESCRIPTION OF THE INVENTION

[0016] Metal filters and filter modules according to embodiments will be described below with reference to the drawings. The same or similar components in each embodiment are designated by the same reference numerals. As described below, the metal filter of each embodiment includes a support body having slits and a porous sintered body of metal particles as a filter element.

[0017] 1A is a schematic partial plan view of an exemplary support 2 used in a metal filter. In this embodiment, a flat wedge wire screen is used as the support 2. Therefore, as shown in FIGS. 1B and 1C, the support 2 includes a plurality of wires 20 each having a wedge-shaped (triangular) cross section, and a plurality of rods 21 for fixing and supporting the wires 20.

[0018] The wires 20 are arranged parallel to one another at predetermined intervals and extend linearly. The rods 21 are arranged parallel to one another at predetermined intervals and extend in a direction perpendicular to the wires 20. As shown in Fig. 1B, the rods 21 are joined to the wires 20 at their tips by means of, for example, welding.

[0019] As shown in FIGS. 1B and 1C, the wire 20 has a flat horizontal surface 200, a flat first inclined surface 201, and a flat second inclined surface 202. The wires 20 are spaced apart, so that a slit 22 is defined by the first inclined surface 201 of one wire 20 and the second inclined surface 202 of another wire 20 adjacent to the wire 20. Therefore, the slit 22 extends linearly parallel to the wire 20 as shown in FIG. 1A, penetrates the support 2 in the thickness direction (the vertical direction in FIGS. 1B and 1C), and has a tapered cross section that narrows in the thickness direction. The slit width 22w is determined by the spacing between the wires 20. Here, as shown in FIGS. 1B and 1C, the slit width 22w of the slit 22 refers to the width of the narrowest portion of the slit 22 (the same applies below).

[0020] Fig. 2A shows a schematic and partial view of yet another exemplary support 2. The support 2 in Fig. 2A is also a wedge wire screen, but has a cylindrical shape instead of a flat plate shape. The support 2 is configured by winding a single wire 20 spirally at a predetermined pitch around a plurality of rods 21 (only one rod is shown in Fig. 2B) arranged in the circumferential direction around an axis AX and joining the rods 21.

[0021] Therefore, in one wire, the slit 22 is defined by a first inclined surface 201 of a certain wire portion 20 and a second inclined surface 202 of the wire portion 20 adjacent to the certain wire portion 20. In this exemplary support 2, the slit 22 extends spirally in parallel to the wire 20.

[0022] Although not shown, yet another exemplary cylindrical support 2 is a wedge wire screen configured by a plurality of wires 20 extending parallel to an axis AX and arranged at predetermined intervals from one another in the circumferential direction around the axis AX. In this wedge wire screen, a plurality of slits 22 are positioned at predetermined intervals in the circumferential direction around the axis AX, and each extends parallel to the axis AX.

[0023] The metal support 2 (wire 20) is made of, for example, iron (Fe), copper (Cu), aluminum (Al), titanium (Ti), or an alloy containing one or more of these metals (for example, stainless steel, titanium alloy), etc. As an example, the support 2 (wire 20) is stainless steel (SUS), specifically SUS304, SUS316, SUS316L, SUS310S, etc., or a titanium alloy, specifically Ti-5Al-2.5Sn, Ti-6Al-4V, Ti-15V-3Cr-3Sn-3Al, etc.

[0024] The slit width 22w is, for example, 5 μm or more, 5 μm to 100 μm, and more specifically, 5 μm to 10 μm. Here, the symbol "to" includes the numerical values ​​before and after it as the lower and upper limits (the same applies hereinafter).

[0025] Although each of the exemplified supports 2 is a wedge wire screen, it may be, for example, a wire screen including non-wedge-shaped wires having a first inclined surface and a second inclined surface. For example, a wire screen made of non-wedge-shaped wires having a first inclined surface and a second inclined surface, as disclosed in Patent Document 6, may be used.

[0026] FIG. 3 is a cross-sectional view partially illustrating an exemplary metal filter 1. The metal filter 1 includes, in addition to one of the metal supports 2 having slits 22 exemplified above, a porous sintered body 3 (hereinafter simply referred to as a sintered body) of metal particles (metal powder) that functions as a filter element. It is well known that the sintered body 3 functions as a filter element for filtering fluids due to its porous structure, as disclosed in Patent Documents 1-5. Note that the sintered body 3 in FIG. 3 is shown schematically and differs from the actual structure of the sintered body.

[0027] The sintered body 3 is located inside the slit 22, extends in the extension direction of the slit 22, and is provided in the form of a film so as to close the slit 22. The sintered body 3 is joined to the first inclined surface 201 and the second inclined surface 202 of the support body 2, and is thereby supported by the support body 2.

[0028] According to this configuration, as shown in Figures 3B and 3C, when a fluid (gas or liquid) passes through the slit 22, it also passes through the sintered body 3. Therefore, the fluid is filtered by the sintered body 3, and solids contained in the fluid are captured by the sintered body 3. As shown in Figures 3B and 3C, the direction in which the fluid passes through the slit 22 does not matter. In this way, a fractionation performance finer than the slit width 22w can be obtained.

[0029] Examples of the material for the sintered body 3, and therefore the material for the metal particles used to form the sintered body 3, include metals such as aluminum (Al), titanium (Ti), iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), chromium (Cr), cobalt (Co), palladium (Pd), silver (Ag), platinum (Pt), and gold (Au), as well as alloys containing one or more of these metals (e.g., stainless steel and bronze), as disclosed in Patent Document 1. As the material for the sintered body 3, a mixture of two or more types of particles of the above-mentioned metals or metal alloys may be used.

[0030] The particle size of the metal particles used to form the sintered body 3 is appropriately selected depending on the size of the slit width 22w, etc. For example, metal submicro / micro particles (0.1 μm<particle size≦100 μm) and nanoparticles (20 nm≦particle size≦100 nm) may be used. As an example, metal particles with an average particle size of 0.2 μm to 10 μm may be used.

[0031] 3A, the thickness 3t of the sintered body 3 is smaller than the thickness of the slit 22, and the sintered body 3 partially fills the slit 22. Alternatively, the sintered body 3 may have the same thickness as the slit 22 and fill the entire slit 22. Furthermore, alternatively, the sintered body 3 may have a thickness larger than the thickness of the slit 22 and not only fill the entire slit 22 but also exist outside the slit 22 and be layered on the support 2. In short, as long as the sintered body 3 functions as a filter element and is bonded to the inclined surfaces 201 and 202, its thickness 3t can be appropriately selected depending on the application of the metal filter 1.

[0032] The combination of the metal material of the support 2, the metal material of the sintered body 3, the slit width 22w, the average particle size of the metal particles, and the thickness 3t of the sintered body 3 can be selected as appropriate depending on the application of the metal filter 1 and the properties of the fluid to be filtered. For example, a support 2 (wire 20) made of stainless steel is used, a sintered body 3 made of silver is used, a slit width 22w of 5-50 μm is selected, and silver particles with an average particle size of 0.2 μm to 10 μm are selected.

[0033] If the support 2 has a flat plate shape as shown in FIG. 1, the metal filter 1 will have a flat plate shape, and if the support 2 has a cylindrical shape as shown in FIG. 2, the metal filter 1 will have a cylindrical shape.

[0034] 4A shows a metal filter 1 according to the embodiment and a metal filter 1' according to a comparative example. In the metal filter 1' according to the comparative example, a sintered body 3' is bonded to the vertical surfaces 201', 202' (not the inclined surfaces) that define the slit 22' of the support body 2'. In FIG. 4A, the sintered bodies 3, 3' are shown in a further simplified form to facilitate comparison.

[0035] 4A , assuming that the sintered bodies 3, 3' have the same thickness 3t, the contact area, and therefore the bonding area, of the sintered body 3 in the metal filter 1 according to the embodiment with the inclined surfaces 201, 202 is larger than the bonding area of ​​the sintered body 3' in the metal filter 1' according to the comparative example with the vertical surfaces 201', 202'. Therefore, when sintered bodies 3, 3' of the same thickness are formed under the same sintering conditions and bonded to the supports 2, 2' within the slits 22, 22', the bonding strength of the sintered body 3 in the metal filter 1 according to the embodiment to the support 2 is higher than the bonding strength of the sintered body 3' in the metal filter 1' according to the comparative example to the support 2'.

[0036] In this way, in the metal filter 1 of the present application, the sintered body 3 is bonded to two inclined surfaces 201, 202 that define the slit 22 having a tapered cross section, thereby improving the bonding strength of the sintered body 3 to the support body 2.

[0037] FIG. 4B shows the angle θ (where 0<θ<90°) between the inclined surface 201 / 202 and the straight line L in the penetration direction of the slit 22 in the embodiment of FIG. 4A (the sintered body 3 is not shown). θ=0° is a comparative example. In this embodiment, as θ becomes larger, a larger bonding area can be secured, and therefore the bonding strength can be further improved. θ may be, for example, 1°≦θ<90°, and considering that the inclined surface 201 / 202 is realized by the wire 20, θ may be, for example, 1°≦θ≦20°.

[0038] 5 illustrates a filter module 4 (hereinafter simply referred to as a module) including a cylindrical metal filter 1. The module 4 includes a housing 40 that houses the metal filter 1. The housing 40 is, for example, cylindrical, but may have other shapes.

[0039] The module 4 further includes ring members 41 attached to both ends of the metal filter 1. The ring members 41 may be made of, for example, metal, and are joined to both ends of the metal filter 1 by means of, for example, welding, brazing, adhesive, or the like. The ring members 41 are used to reinforce the ends of the metal filter 1, respectively.

[0040] The module 4 further includes attachments 42 that are inserted through the housing 40 and attached to each of the ring members 41. The attachments 42 may be made of, for example, metal. The attachments 42 are airtightly inserted through the housing 40, inserted into the ring members 41, and joined to the ring members 41 by means of, for example, welding. The attachments 42 have a tubular shape. Therefore, the attachments 42 have communication holes 420 that fluidly connect the outside of the module 4 and the inside of the metal filter 1.

[0041] This allows fluid to flow from the outside of module 4 to the inside of metal filter 1 via communication hole 420, and also allows fluid to flow from the inside of metal filter 1 to the outside of module 4 via communication hole 420.

[0042] The above-described module 4 is an example of the use of the metal filter 1, and it goes without saying that the metal filter 1 may be used in other ways.

[0043] The steps of the method for manufacturing the metal filter 1 will be exemplified below.

[0044] A preparation step is carried out to prepare a metal support 2 having slits 22 and a paste 5 (see FIG. 6) containing metal particles and a dispersion medium for dispersing the metal particles.

[0045] Next, as shown in Figure 6, an application step is carried out in which paste 5 is applied to the inside of slit 22 of support 2. At this time, paste 5 is applied in the form of a film inside slit 22 so as to seal the inside of slit 22, and is brought into contact with first inclined surface 201 and second inclined surface 202. As described above, slit 22 having a tapered cross section is formed by first inclined surface 201 and second inclined surface 202 of support 2, so that paste 5 (and therefore metal particles) can easily be introduced into slit 22. In this way, the metal filter 1 of the present application has an advantageous structure from the viewpoint of manufacturing.

[0046] Next, a sintering step is carried out in which the support 2 coated with the paste 5 is heated. This heating volatilizes the dispersion medium in the paste 5, and the metal particles in the paste 5 are sintered together to form a sintered body 3 that functions as a filter element. Then, during the sintering of the metal particles, the sintered body 3 is bonded to the first inclined surface 201 and the second inclined surface 202.

[0047] Through the above steps, the metal filter 1 of the present invention is manufactured.

[0048] Regarding the step of preparing the support 2, the support 2 may be a wedge wire screen or a wire screen, as exemplified above.

[0049] The conditions for the paste 5 and the sintering conditions for the metal particles are based on well-known techniques such as those disclosed in Patent Documents 1 to 5, and are common technical knowledge, so a description thereof will be omitted here.

[0050] As described above, the dispersion medium is selected so that it volatilizes at a temperature lower than the sintering temperature during sintering. The dispersion medium may contain, for example, an organic solvent such as an alcohol or ester, and the content of metal particles in the paste may be determined in accordance with well-known conditions disclosed in Patent Documents 1-5.

[0051] Sintering is carried out by heating at a temperature lower than the melting point of the metal particles for a period of several tens of minutes to several hours. Therefore, the sintering temperature and sintering time vary depending on the metal particles used. Regarding other conditions, the sintering process may be carried out in a high-temperature furnace or on a hot plate, or may be carried out under pressure or without pressure, in air, oxygen, or vacuum. These conditions are selected appropriately depending on the metal material used.

[0052] For example, as disclosed in Patent Document 3, in the case of nickel particles, the sintering process may be carried out at a temperature of about 600°C to 1000°C for about 10 to 60 minutes in an atmosphere of nitrogen or argon to which 10 to 50% hydrogen has been added. As disclosed in Patent Document 1, in the case of stainless steel particles, the sintering process may be carried out at a temperature of about 870°C to 1370°C, and in the case of bronze particles, the sintering process may be carried out at a temperature in the range of about 760°C to about 1040°C for about 30 minutes to 2 hours under pure hydrogen or other reduced pressure or vacuum. Known sintering conditions may be applied to other metal particles, and therefore a description thereof will be omitted.

[0053] In addition, as disclosed in Non-Patent Document 1, a method for producing a silver nanoparticle by dispersing micro / submicro silver particles with an organic solvent ("CELTOL TM By using a silver paste consisting of "Agnesium-Iron-Based Polymer ...

[0054] Here, it is preferable to select a metal material for the support 2 whose melting point is higher than that of the metal particles so that the slit structure of the support 2 is not significantly affected by heat during the sintering process. For example, when low-temperature sintering of silver particles is carried out as described above, it is recommended to use a support 2 made of stainless steel.

[0055] Optionally, before the coating step, a step of surface treating the first inclined surface 201 and the second inclined surface 202 may be carried out in order to improve the bonding strength between the sintered body 3 and the support body 2. The surface treatment of the inclined surfaces 201 and 202 may be a plating treatment, application of flux, oxide film reduction treatment, electrolytic polishing, shot peening, or the like.

[0056] The following describes an example of manufacturing a metal filter including a wedge wire screen made of stainless steel with slits of 5 μm to 100 μm and a porous sintered body made of silver particles arranged in the slits of the wedge wire screen in the form of a film.

[0057] Such a wedge wire screen is available, for example, from Toyo Screen Kogyo Co., Ltd. under the trade name "Fine Wedge" (registered trademark).

[0058] To form the sintered body, silver particles with an average particle size of 2µm to 10µm are prepared. Then, a paste containing these silver particles and a dispersion medium such as ethylene glycol, diethyl glycol methyl ether acetate, or terpineol is created. The silver particles in the paste are 60wt% to 90wt%.

[0059] The paste thus obtained is applied to the inside of the slits of a wedge wire screen.

[0060] The paste-coated wedge wire screen is heated in an air atmosphere at a sintering temperature of 180°C to 350°C for 0.5 to 2 hours to carry out the sintering process. This volatilizes the organic solvent, and the necks of each silver particle grow, sintering the silver particles together to produce a porous sintered silver body with a neck structure. This sintering also bonds the porous sintered silver body to the first and second inclined surfaces of the wires of the wedge wire screen.

[0061] This provides the above-mentioned metal filter.

[0062] [Performance evaluation] A sample (hereinafter simply referred to as "sample") was prepared using the flat wedge wire screen (15 mm long x 15 mm wide: 50 μm slit width) shown in Figure 1 as a support and the metal filter (Figure 3) containing a silver porous sintered body as a filter element. The sample was manufactured using the manufacturing method exemplified above.

[0063] The gas permeation rate and particle capture rate of the sample were measured before and after the pressure test. The evaluation area within the sample was a range with a diameter of φ = 9 mm centered on the center of the sample in the vertical and horizontal directions. The fluid passed through the sample in the direction shown in Figure 3B.

[0064] To measure the gas permeability, air compressed to a maximum of 1 MPa was passed through the sample. The measurement results of the gas permeability before and after the pressure test are shown in Table 1 below.

[0065] The particle collection efficiency was measured using a particle counter (Model 3889, manufactured by Kanomax) to count the number of fine particles contained in the air that passed through the sample. The measurement results of the particle collection efficiency before and after the pressure resistance test are shown in Table 2 below.

[0066] [Table 1]

[0067] [Table 2]

[0068] As can be seen from the comparison of gas permeation rates before and after the pressure test in Table 1, and the comparison of particle capture rates before and after the pressure test in Table 2, it was confirmed that the sample functions normally as a filter even in the actual assumed usage environment. -5It has a gas permeability of the order of 1000μm and reliably captures particles of 0.3μm size, so it can be evaluated as functioning as a submicron filter. The sample's gas permeability and particle capture rate did not change before and after the pressure test, confirming that it has the strength to withstand real-world environments.

[0069] Although the preferred embodiments and examples have been described above, the present invention is not limited to the above. [Explanation of symbols]

[0070] 1 Metal filter 2 Metal support 20 wire 201 1st slope 202 Second slope 21 Rod 22 Slit 22w slit width 3. Porous sintered body of metal particles 4 Filter Module 40 Housing 41 Ring member 42 Attachment 420 Communication hole 5. Paste

Claims

1. A metal filter, a metallic wedge wire screen having slits and serving as a support; a porous sintered body of metal particles that functions as a filter element; The wedge wire screen is A plurality of wires are arranged parallel to each other and spaced apart from each other at predetermined intervals; The wires each have a triangular cross section and have a first inclined surface and a second inclined surface; the slit is defined by the first inclined surface of the wire and the second inclined surface of another wire adjacent to the wire, has a tapered cross section, and extends parallel to the wire; the porous sintered body is provided in the slit and bonded to the first inclined surface and the second inclined surface; A metal filter characterized by:

2. A metal filter, a metallic wedge wire screen having slits and serving as a support; a porous sintered body of metal particles that functions as a filter element; The wedge wire screen is A wire is wound in a spiral shape at a predetermined pitch, the wire has a triangular cross section and has a first sloping surface and a second sloping surface; the slit is defined in the wire between the first inclined surface and the second inclined surface, and has a tapered cross section, and extends spirally parallel to the wire; the porous sintered body is provided in the slit and bonded to the first inclined surface and the second inclined surface; A metal filter characterized by:

3. The wedge wire screen further comprises rods for fixing and supporting the wires. The metal filter according to claim 1 or 2.

4. the wedge wire screen is made of stainless steel, and the porous sintered body is made of silver; The metal filter according to any one of claims 1 to 3.

5. The slit width of the slit is 5 μm to 100 μm. The metal filter according to any one of claims 1 to 4.

6. The metal filter has a cylindrical shape. The metal filter according to any one of claims 1 to 5.

7. A filter module comprising: The metal filter according to claim 6; a housing that accommodates the metal filter; ring members provided on both ends of the metal filter; an attachment having a communication hole for fluidly communicating the outside of the filter module with the inside of the metal filter, the attachment being inserted through the housing and attached to the ring member; A filter module characterized by:

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