Filter medium with improved filtrate permeability and method for improving filtrate permeability

Abstract

To provide a filtration object passability improving filter material which reduces passage resistance of a filtration object by randomly forming innumerable minute irregularities on a surface of a filter material, and a processing method for improvement in filtration object passability.SOLUTION: A filtration object passability improving filter material reduces a filter material resistance to improve passability of a filtration object by randomly forming innumerable minute irregularities on at least a part of a surface contacting the filtration object. Further, a processing method for improvement in filtration object passability reduces a filter material resistance to improve passability of a filtration object by performing processing for randomly forming innumerable minute irregularities on at least a part of a surface contacting the filtration object.SELECTED DRAWING: Figure 14

Description

[Technical field]

[0001] The present invention relates to a filter medium (or a sieve) used for filtering a liquid or paste-like object to be filtered, and to a technique for reducing the resistance to passage (filter medium resistance) when the object to be filtered passes through. [Background technology]

[0002] To date, the present applicants have proposed a technology capable of suppressing the adhesion of powder by performing a fine particle projection process (e.g., fine particle peening process), which is a type of shot material projection process in which shot material is projected, thereby forming countless irregular (random) tiny projections and recesses on the surface of a member that comes into contact with powder (hereinafter also referred to as a powder contact member), as proposed in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6416151 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, in order to explore the possibility of applying surface modification technology by randomly forming countless micro-convexities to various fields, the applicants have taken various approaches to confirm new effects in various fields that can be obtained by forming countless micro-convexities on the surface of a component, and in the process, the inventors have obtained new knowledge that was not previously known.

[0005] Incidentally, effects that have been known to be obtained up until now by forming multiple (infinite) micro recesses include suppressing the adhesion of powder and sticky substances, and forming infinitely many micro irregularities on the sliding surface to function as oil reservoirs, thereby reducing sliding resistance and suppressing wear; however, the effect discovered this time is a completely different effect that could not have been predicted from these.

[0006] The findings are that by randomly forming countless (multiple) micro-depressions on the surface of a filter material, the resistance of the filter material is reduced, and the filter object passing through it is (Especially the filtrate) The idea is to reduce the resistance to passage.

[0007] The present invention has been made in consideration of such circumstances, and aims to provide a filter medium having a surface with a large number of randomly formed minute irregularities. filtrate Reduced the resistance to passage filtrate Filter media for improved permeability and filtrate The object of the present invention is to provide a processing method for improving passability. [Means for solving the problem]

[0008] For this reason, the present invention filtrate The filter media with improved permeability is filtrate and forming an infinite number of minute projections and recesses at random on at least a portion of the surface that comes into contact with the substrate by shot projection processing, the minute projections and recesses having a minimum projection pitch of 0.5 μm or more and a maximum projection pitch of 40 μm or less, and a minimum recess depth of 0.03 μm or more and a maximum projection depth of 2.0 μm or less. The kurtosis value (Pku) of the surface is greater than 3, and It is characterized by reduced resistance of the filter material to the filtrate.

[0010] The present invention filtrate The filter media with improved permeability is filtrate and forming an infinite number of minute projections and recesses at random on at least a portion of the surface that comes into contact with the substrate by shot projection processing, the minute projections and recesses having a minimum projection pitch of 0.5 μm or more and a maximum projection pitch of 10 μm or less, and a minimum recess depth of 0.3 μm or more and a maximum projection depth of 2.0 μm or less. The kurtosis value (Pku) of the surface is greater than 3, and It is characterized by reduced resistance of the filter material to the filtrate.

[0011] In the present invention, the surface on which the minute projections and recesses are formed may have a water contact angle of 65° or less.

[0014] In the present invention, filtrate can be characterized as being a liquid or paste-like substance for food containing water, oil and other raw materials in any proportion, a liquid or paste-like substance for pharmaceutical use containing water, oil and other raw materials in any proportion, or a liquid or paste-like substance for cosmetics containing water, oil and other raw materials in any proportion.

[0015] The present invention filtrate The process for improving the passability is as follows: filtrate a shot projection process is used to randomly form an infinite number of minute projections and recesses on at least a portion of the surface that comes into contact with the substrate, the minute projections and recesses having a minimum projection pitch of 0.5 μm or more and a maximum projection pitch of 40 μm or less, and a minimum recess depth of 0.03 μm or more and a maximum projection depth of 2.0 μm or less; The kurtosis value (Pku) of the surface is greater than 3, and It is characterized by reducing the resistance of the filter material to the filtrate.

[0017] The present invention filtrate The process for improving the passability is as follows: filtrate a shot projection process is used to randomly form an infinite number of minute projections and recesses on at least a portion of the surface that comes into contact with the substrate, the minute projections and recesses having a minimum projection pitch of 0.5 μm or more and a maximum projection pitch of 10 μm or less, and a minimum recess depth of 0.3 μm or more and a maximum projection depth of 2.0 μm or less; The kurtosis value (Pku) of the surface is greater than 3, and It is characterized by reducing the resistance of the filter material to the filtrate.

[0018] In the present invention, the surface on which the minute projections and recesses are formed may have a water contact angle of 65° or less.

[0021] In the present invention, filtratecan be characterized as being a liquid or paste-like substance for food containing water, oil and other raw materials in any proportion, a liquid or paste-like substance for pharmaceutical use containing water, oil and other raw materials in any proportion, or a liquid or paste-like substance for cosmetics containing water, oil and other raw materials in any proportion. Effect of the Invention

[0022] According to the present invention, by forming a countless number of minute irregularities randomly on the surface of the filter medium, filtrate Reduced the resistance to passage filtrate Filter media for improved permeability and filtrate It is possible to provide a process for improving passability. [Brief description of the drawings]

[0023] [Figure 1] 1 is a table showing the measurement results of the contact angle of water of each test piece according to one embodiment of the present invention. [Diagram 2] 13 is an image showing the contact angle of water measured for each test piece according to the embodiment of the present invention. [Diagram 3] 2 is a table showing the measurement results of the contact angle of each test piece with oil (salad oil) according to the embodiment of the present invention, and an image showing the contact angle measurement. [Figure 4] FIG. 2 is a diagram showing an example of surface properties (concave and recess pitch and recess depth) of a projection-treated surface of a test piece (sample A) according to the embodiment. [Diagram 5] FIG. 13 is a diagram showing an example of the surface properties (concave-convex pitch and concave depth) of the projection-treated surface of the test piece (sample B) according to the embodiment. [Figure 6] 1 is an enlarged image of the surface of a test piece (Reference) according to the embodiment of the present invention. [Figure 7] 1 is an enlarged image of the surface of a test piece (sample B) according to the embodiment of the present invention. [Figure 8] 13 is an image showing the results of network passability verification of a medium-thick sauce according to the embodiment of the present invention. [Figure 9] 13 is an image showing the results of verification of the mesh-penetrability of chocolate syrup according to the embodiment of the present invention. [Figure 10] FIG. 13 is a diagram showing the size of the mesh of the filter medium used in each actual production line and the size of the minute projections and recesses formed on the filter medium by the projection treatment. [Figure 11] FIG. 2 is a diagram showing an example of the surface texture (pitches and depths of recesses) formed by a projection treatment performed on a filter medium used in a production line for food sauce 1. [Figure 12] FIG. 13 is a diagram showing an example of the surface texture (pitches and depths of recesses) formed by a projection treatment performed on a filter medium used in a production line for food sauce 2. [Figure 13] FIG. 1 is a diagram showing an example of surface properties (pitched and concave portions and depth of concave portions) formed by a projection treatment performed on a filter medium used in a milk production line. [Figure 14] (A) is a graph showing the time reduction (time difference) of the projection treatment (sample B) compared to the untreated (reference), and (B) is a photograph of the exterior of the liquid passage experimental device (experimental method 1). [Figure 15] (A) is a graph showing the time reduction (time difference) of the projection treatment (sample B) compared to the untreated (reference), and (B) is a photograph of the exterior of the liquid passage experimental device (experimental method 2). [Figure 16] 1 is a graph showing the kurtosis value (Pku) on the horizontal axis and the water contact angle (°) on the vertical axis for the projection treatment performed on each test piece according to the embodiment of the present invention. [Figure 17] FIG. 2A is a diagram for explaining the contact angle of water on a surface, and FIG. 2B is a diagram for explaining the kurtosis value (Pku). [Figure 18] FIG. 4 is a diagram showing measurement conditions for the kurtosis value according to the embodiment of the present invention. [Figure 19] 11 is a cross-sectional SEM image of a single minute recess formed experimentally by one-shotting the media used in the fine particle peening process according to the embodiment of the present invention. [Figure 20] This is an SEM image of a cross section of a recess created by laser processing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the present invention is not limited to the embodiment described below.

[0025] Here, the inventors have found that "when a large number (multiple) of minute recesses are randomly formed on the surface of a filter medium, the resistance of the filter medium is reduced, and the amount of the filter medium passing through the recesses is reduced." (Especially the filtrate) The finding that "the passage resistance of the suction pipe can be reduced" will be explained in detail.

[0026] Liquid raw materials, which are an example of a material to be filtered, are used in various situations such as food, pharmaceutical, and cosmetic manufacturing sites. These liquid raw materials are filtered using filter media such as nets and mesh to prevent contamination by foreign matter.

[0027] Among these, there were many voices calling for a reduction in the time required for filtration work in order to improve work efficiency.When performing liquid filtration, the liquid to be filtered is generally poured into the top of the screen (the upstream side of the liquid flow), and the liquid that passes through the screen is collected in a container installed below the screen (the downstream side of the liquid flow) (or sent to the next process downstream).

[0028] When trying to shorten the time required for such filtration operations, for example, the filtration device itself can be made larger, thereby increasing the filtration capacity and shortening the time. However, this raises issues such as securing work space, and there is a demand for shortening the time by using existing equipment.

[0029] Increasing the openings of the net or mesh used in the filter medium will improve the liquid permeability, but this will reduce the filtering capacity, making it meaningless as a measure to prevent foreign matter from getting mixed in. Factors that determine the permeability of liquid filtration, or in other words, the filtering speed, include filtering pressure, filter medium resistance (the resistance of the filter medium itself), and filter medium clogging resistance.

[0030] For these reasons, the inventors have considered that in order to improve the permeability of liquids while maintaining filtering capacity, it is beneficial to reduce the resistance of the filter medium to the flowing object to be filtered, and that a surface modification technique that randomly forms countless minute irregularities may be able to contribute to this.

[0031] Furthermore, the inventors considered that in order to improve the permeability of the liquid (e.g., water), which is one of the objects to be filtered, imparting hydrophilicity to the filter medium would improve the affinity between the filter medium and the object to be filtered (filtrate, e.g., water in this case), and therefore hydrophilicity would be related to reducing the resistance of the filter medium. Therefore, a test was conducted to confirm whether hydrophilicity is improved by randomly forming an innumerable (plural) minute irregularities on the surface of a member.

[0032] Tables 1 and 2 in Fig. 1 show the results of measuring the contact angle of water (purified water) 1 hour and 50 hours after a test piece (here, a flat plate) was washed with water, dried by air blowing, and exposed to the atmosphere. Note that when the contact angle of water is simply mentioned without indicating the drying time, it refers to the value after 50 hours (or the value when sufficient drying time is allowed).

[0033] Figure 2 shows actual images of contact angles measured with water placed on each test piece. The contact angle of water is one of the indices that express "wettability" and "hydrophilicity". The smaller the contact angle of water, the higher the "wettability" and "hydrophilicity", and the larger the contact angle of water, the lower the "wettability" and "hydrophilicity" (see Figure 17(A)). In this embodiment, the water contact angle of the surface of the test piece was obtained (measured) using a portable contact angle meter PCA-11 manufactured by Kyowa Interface Science Co., Ltd.

[0034] For the untreated test piece (SUS304 #700 flat plate: Reference), the contact angle was around 70° both after 1 hour and after 50 hours, and there was no difference in the contact angle over time. The untreated test piece (SUS304 #700 flat plate: Reference: Comparison) was made of SUS304 stainless steel plate whose surface was polished with a P700 buff.

[0035] On the other hand, for sample A, the contact angle after 1 hour was 31.2 to 35.3°, and after 50 hours it was 56.1 to 59.7°. This indicates that the sample was more hydrophilic than the untreated test piece, and that the contact angle varied over time. Sample A was prepared by subjecting an untreated test piece (a flat plate of SUS304 #700: Reference) to Ni blasting treatment to form countless minute projections and recesses randomly on the surface.

[0036] The projection treatment (Ni) performed on sample A is a type of surface treatment (also referred to as shot projection treatment, micro-dimple treatment, fine particle projection treatment, etc.; the same applies below) that forms countless tiny irregularities. It is a surface modification treatment in which a plate material (Reference: comparison reference) made of SUS304 stainless steel plate material has its surface polished with a P700 buff, and media (abrasive material (product name "Nickel (Ni) Powder", particle number #200-350) from Fukuda Metal Foil and Powder Co., Ltd.) is sprayed from a spray nozzle together with compressed air of about 1 / several (e.g., 0.3) MPa onto the surface to be processed (surface of a sample, surface of a component) to perform projection treatment (hereinafter also referred to as projection processing). FIG. 4 shows an example of the surface shape data of sample A.

[0037] The 3D images, surface shapes, and surface shape data in this embodiment, including those described below, were acquired using a shape measuring laser microscope VK-X1000 manufactured by KEYENCE Corporation.

[0038] FIG. 4 shows an example of the surface shape and surface shape data of sample A. Figure 4 shows a portion of the surface of Sample A, which has countless minute irregularities randomly formed on its surface, with an irregularity pitch (diameter of the recess entrance) of approximately 20 to 60 μm and a recess depth of approximately 1.5 μm. The unevenness pitch can be expressed as the distance between protrusions, the width of the entrance of a recess, the width of an opening, or the diameter of an opening.

[0039] For sample B, the contact angle after 1 hour was 15.0 to 18.3°, and after 50 hours the contact angle was 37.1 to 39.2°. Thus, sample B was more hydrophilic than the untreated test piece and sample A, and like sample A, the contact angle varied over time. Sample B was prepared by subjecting an untreated test piece (a flat plate of SUS304 #700: Reference) to projection treatment (C400) to randomly form countless minute projections and recesses on the surface.

[0040] The projection treatment (C400) applied to sample B is one of the surface treatments that form countless minute irregularities, and is a surface modification treatment in which media (SiC (silicon carbide) with particle number #400 (maximum particle diameter 75 μm or less, particle diameter at 50% of cumulative height 30.0 ± 2.0 μm) of "Fuji Random (Carborundum) C" manufactured by Fuji Manufacturing Co., Ltd.)) is sprayed from a spray nozzle along with compressed air of about 1 / several (e.g. 0.3) MPa onto the surface to be processed (surface of the sample, surface of the component) which has been polished with a P700 buff (control).

[0041] FIG. 5 shows an example of the surface shape and surface shape data of sample B. 5 shows a portion of the surface of Sample B, in which countless minute irregularities are randomly formed with an irregularity pitch (diameter of the recess entrance) size in the range of about 4.0 to 20.0 μm and a recess depth in the range of about 0.4 to 2.0 μm. The minute irregularities formed on the surface of Sample B have a smaller irregularity pitch size than those formed on the surface of Sample B. In addition, when indicating a range for the size of the unevenness pitch (spacing between convex parts, entrance width of the concave part, opening width, opening diameter) and the depth of the concave part, the range between the minimum and maximum values ​​of the unevenness pitch and the depth of the concave part is indicated.

[0042] Here, the reason why the contact angle differed over time for Samples A and B is that even though the test pieces appear dry at first glance, trace amounts of moisture (water molecules) are physically adsorbed on their surfaces immediately after washing with water, and due to the influence of this residual moisture, the test pieces exhibited hydrophilic properties with a smaller contact angle immediately after washing. It is believed that the contact angle then increased when the test pieces were exposed to air for 50 hours, as the trace amounts of moisture (water molecules) on the test piece surface were desorbed.

[0043] This phenomenon is believed to be due to the fact that minute (fine) irregularities are formed on the surface of the test piece by the projection process of projecting the shot material, and trace amounts of moisture (water molecules) are temporarily retained in these minute recesses. This is supported by the fact that no difference in contact angle over time was confirmed in the untreated test piece. Furthermore, the fact that there was no difference in the untreated test piece also supports the fact that there was no influence of contamination due to exposure to the atmosphere during this verification experiment.

[0044] From the above, the inventors of the present invention have considered that when the liquid to be filtered is passed through a filter medium having a surface with a countless number of randomly formed micro-irregularities, the liquid components are retained in the micro-irregularities. When the same liquid passes through the filter medium, the compatibility between the liquid and the filter medium improves, so that the filter medium resistance is reduced and the liquid permeability is improved.

[0045] Similarly, the contact angle of salad oil was also measured (see Table 3 and the contact angle measurement image in Figure 3). As with the contact angle measurement of water, the contact angle was in the following order: untreated test piece > sample A > sample B.

[0046] Many of the liquids used in the food, pharmaceutical, and cosmetic markets contain a mixture of water and oil. Sample B, which had a large hydrophilic and lipophilic effect for both components, was treated in the same way on a screen (or filter material, sieve, etc.) and the liquid permeability was compared with that of an untreated screen.

[0047] An untreated net made of SUS304 (Reference: comparison control) and a net of the same specifications that had been subjected to the same projection treatment as Sample B were prepared, and a comparative experiment was conducted in which food sauce was poured onto these nets. The meshes used in the experiment were an untreated SUS304 mesh (Reference) with a mesh size of approximately 500 μm and a wire diameter of approximately 180 μm, which is a kitchen sieve sold at general home improvement stores, and a mesh that had been subjected to the same projection treatment as Sample B. Verification tests were conducted using these meshes.

[0048] FIG. 6 shows an enlarged image of an untreated SUS304 mesh (Reference), and FIG. 7 shows an enlarged image of a mesh that was subjected to the same projection treatment (C400) as sample B. These enlarged images were taken using a KEYENCE VHK-7000 digital microscope.

[0049] On the surface of the wire of the net that was subjected to the same projection treatment as sample B (Fig. 7), it can be seen that countless minute irregularities were formed by the projection treatment, giving it a matte appearance. On the other hand, on the surface of the wire of the untreated SUS304 net (Reference) (Fig. 6), although there are some parts that resemble contact scratches, overall it is seen that the surface has a shine similar to a mirror, with streak-like processing marks from the drawing process, etc.

[0050] Figure 8 shows images taken from the back of the net (the side through which the sauce passes and comes out) after food sauce was poured onto each of the two nets mentioned above, in order to confirm the difference in the permeability (degree of passage) of the food sauce due to the differences in these nets. The food sauce used was a medium-thick sauce made by Company K, which is easily available in supermarkets and other outlets, and the amount dispensed was 5 ml each.

[0051] Looking at the image in Figure 8, it can be seen that the untreated sauce on the mesh in Figure 8(A) has multiple areas over a wide area where it has not passed through to the back side, while the sauce on the mesh that has been treated in the same way as sample B in Figure 8(B) has the entire sauce dripped onto the front side passing through the mesh to the back side.

[0052] As mentioned above, it is believed that a mesh (filter material) with countless randomly formed minute projections and recesses on the surface of the wire material that makes up the mesh (filter material) has better compatibility with the object to be filtered, resulting in improved permeability compared to an untreated mesh (or filter material).

[0053] Similarly, a comparative experiment was conducted by preparing a SUS304 #700 mesh (Reference) and a mesh of the same specifications that was subjected to the same projection treatment as Sample B, and dripping chocolate syrup onto these meshes. Chocolate syrup has a higher viscosity than food sauces, and can be used as an example of a paste-like material to be filtered. In addition, the term "paste-like" refers to a soft, viscous, glue-like or kneaded material, or may refer to a material that has been ground up and processed into a semi-solid material with fluidity.

[0054] Figure 9 shows images taken from the back of the screen (the side where the syrup passes through and comes out) after chocolate syrup was poured onto each of the two screens mentioned above, in order to confirm the difference in how the chocolate syrup passes through each of the screens. The chocolate syrup used was manufactured by Company M and is easily available in supermarkets, etc., and the amount dispensed was 7 ml each.

[0055] Looking at Figure 9, the chocolate syrup on the untreated wire mesh in Figure 9(A) does not pass through the wire over the entire surface, but remains entirely on the top (front side) of the wire. On the other hand, the chocolate syrup on the wire mesh that was treated in the same way as sample B in Figure 9(B) has some areas that pass through to the back side of the wire, and the chocolate syrup has also permeated the inside of the wire mesh (the gaps between the wires).

[0056] As mentioned above, a mesh (filter material) having countless randomly formed minute projections and recesses on the surface of the wire that makes up the mesh (filter material) is thought to have better compatibility with the object to be filtered, and therefore better permeability than an untreated mesh (or filter material).

[0057] In addition, SUS304 filter media used in the production lines of Food Sauce 1 (food manufacturer A), Food Sauce 2 (food manufacturer B), Liquid Chocolate 1 (food manufacturer C), Liquid Chocolate 2 (food manufacturer D), and Milk Lotion (cosmetics manufacturer E) were subjected to projection treatment (C3000, B400, C400, C400, C1000) and the filter media was used in the production lines. It was confirmed that the filtration time could be shortened by about 30 to 50% compared to conventional untreated filter media, and that there was an improvement in permeability (reduction in filter media resistance).

[0058] Figure 10 shows the size of the mesh of the filter media used in each actual production line and the size of the minute irregularities formed by the projection treatment on the filter media. In the experiment for food sauce 1, a filter medium (mesh size of about 63μm) that had been subjected to projection treatment (C3000) was used, and on the surface of the filter medium that had been subjected to this treatment, countless minute irregularities were randomly formed with an irregularity pitch (diameter of the inlet of the recess) size in the range of about 0.05 to 2.0μm and a recess depth in the range of about 0.03 to 0.1μm. An example of the surface shape of a test piece (flat plate) of SUS304 that had been subjected to projection treatment (C3000) is shown in Figure 11.

[0059] In the experiment for food sauce 2, a filter medium (mesh size of about 10,000 μm) that had been subjected to projection treatment (B400) was used, and on the surface of the filter medium that had been subjected to this treatment, countless minute irregularities were randomly formed with an irregularity pitch (diameter of the inlet of the irregularities) in the range of about 20 to 40 μm and an irregularity depth in the range of about 1.0 to 2.0 μm. An example of the surface shape of a test piece (flat plate) of SUS304 that had been subjected to projection treatment (B400) is shown in Figure 12.

[0060] In the experiments with Liquid Chocolate (liquid chocolate used in chocolate products, etc.) 1 and Liquid Chocolate 2, a filter medium (mesh size of about 259μm) that had been subjected to projection treatment (C400) was used, and on the surface of the filter medium that had been subjected to this treatment, countless minute irregularities were randomly formed with an irregularity pitch (diameter of the inlet of the irregularities) size of about 4.0 to 20μm and an irregularity depth of about 0.4 to 2.0μm. An example of the surface shape of a SUS304 test piece (flat plate) that had been subjected to projection treatment (C400) is similar to that shown in Figure 5.

[0061] In the emulsion experiment, a filter medium (mesh size of 100μm or more) that had been subjected to projection treatment (C1000) was used, and on the surface of the filter medium that had been subjected to this treatment, countless minute irregularities were randomly formed with an irregularity pitch (diameter of the inlet of the recess) size in the range of about 0.5 to 2.5μm and a recess depth in the range of about 0.3 to 1.0μm. An example of the surface shape of a test piece (flat plate) of SUS304 that had been subjected to projection treatment (B400) is shown in Figure 13.

[0062] From the above, it can be seen that filter media that has been processed to randomly create countless tiny irregularities has the effect of improving permeability (reducing filter media resistance), and can reduce filtration time by approximately 30 to 50% on an actual production line (production site), thereby contributing to increased production efficiency.

[0063] The projection treatment (C3000) applied to the filter media used in the Food Sauce 1 experiment is one of the surface treatments that form countless minute irregularities. The surface of a SUS304 stainless steel plate (control) was polished with a P700 buff and media (product name "Fuji Random C (Carborundum)", SiC (silicon carbide) with particle number #3000 (maximum particle size 13μm or less, particle size at 50% of cumulative height 4.0±0.5μm)) was sprayed from a spray nozzle along with compressed air of about 1 / several (e.g. 0.3) MPa, and the projection treatment (projection processing) was performed on the processed surface. This is equivalent to a surface modification treatment.

[0064] The projection treatment (B400) performed on the filter media used in the Food Sauce 2 experiment is one of the surface treatments that form countless minute irregularities, and is equivalent to a surface modification treatment in which the surface of a stainless steel plate made of SUS304 (control) was polished with a P700 buff, and media (shot material) with particle number 400 (median particle size ≦53 μm) of abrasive FGB (Fuji Glass Beads) made by Fuji Manufacturing Co., Ltd. was sprayed from an injection nozzle along with compressed air of about 1 / several (e.g. 0.3) MPa to perform a projection treatment (projection processing) on ​​the processed surface.

[0065] Here, a food sauce is a liquid or paste-like seasoning used to accompany other foods or in cooking, such as a liquid seasoning made by adding salt, sugar, vinegar, and spices to vegetable or fruit juice or puree, and adjusting and maturing it.

[0066] The projection treatment (C400) applied to the filter media used in the experiments with Liquid Chocolate 1 and 2 was the same as the treatment applied to Sample B described above.

[0067] The projection treatment (C1000) applied to the filter media used in the emulsion experiment is a type of surface treatment that creates countless tiny irregularities, and is equivalent to a surface modification treatment in which media (SiC (silicon carbide) with particle number #1000 (maximum particle size 32 μm or less, particle size at 50% of cumulative height 11.5 ± 1.0 μm) of product name "Fuji Random C (Carborundum)") is sprayed from an injection nozzle along with compressed air of about 1 / several (e.g. 0.3) MPa onto the surface of a plate (control) made of stainless steel made of SUS304, which has been polished with a P700 buff, to perform a projection treatment (projection processing) on ​​the processed surface.

[0068] Furthermore, according to the above experiments, if the unevenness pitch (diameter of the inlet of the recess, distance between adjacent protrusions) of the micro-bumps formed on the surface of the filter material is in the range of 0.5 μm to 40 μm and the depth of the recess is in the range of 0.03 μm to 2.0 μm, there is an effect of reducing the resistance of the filter material (i.e., an effect of improving the passability of the object to be filtered). In particular, filter media that have been subjected to projection processing (C400, C1000) have a relatively large effect in reducing filter material resistance, and if the concave-convex pitch of the micro-convexities (convexity entrance diameter, spacing between adjacent convexities) is in the range of 0.5 to 10 μm and the concave-convexity depth is in the range of 0.3 μm to 2.0 μm, it is possible to further reduce the filter material resistance.

[0069] <Experimental method 1> In addition, using an apparatus as shown in FIG. 14(B), the time (passing time) required for the liquid (filter object) in the cylinder to pass through the net and be discharged by free fall was measured. Specifically, we prepared a mesh made of SUS304 #700 (Reference) and a mesh (filter material) of the same specifications that had been subjected to a projection treatment (C1000). We set these meshes in the mesh installation location of the liquid passage experimental device and confirmed the difference in liquid passage time due to the difference in mesh. As shown in Figure 14(B), the liquid passage experimental device is a cylinder made of acrylic (diameter about 100 mm) arranged almost vertically, with a plug (drain plug) placed below the net installation location closed, and liquid (here, water) is poured (about 5 L) into the cylinder to a specified starting height position, and from that state, the plug (drain plug) placed below the net installation location is opened to start discharging the liquid inside. After that, the time for the height of the liquid (height of the water column) in the cylinder to pass point A (the highest point), the time for it to pass point B (the middle point), and the time for it to pass point C (the lowest point) are measured. Here, the experimental results when water was used as the liquid are shown.

[0070] Here, the difference in water permeability depending on whether or not projection processing is performed is measured by measuring the time difference, and the measurement method is to use a high-speed camera to capture the falling water and measure the time difference in the water passing through each point. The high-speed camera used is "MEMRECAM HX-6 manufactured by NAC Image Technology Co., Ltd." The same applies to Experimental Method 2 described below.

[0071] FIG. 14(A) is a graph showing the difference (YX: time reduction of sample B compared to the reference) between the transit time (X) of the liquid surface at each point when a SUS304 #700 net (Reference) was set and the transit time (Y) of each point on the liquid surface when a net that had been subjected to the same projection treatment as sample B was set.

[0072] From Figure 14(A), it was confirmed that at all points A, B, and C, when a net with a micro-irregularity formed on its surface by projection processing was set, the passage time was faster (faster discharge speed, falling speed, etc.) and, in turn, the filter material resistance was smaller. In this experimental device, the experiment was conducted using approximately 5 L of water. However, since an actual production line handles several tons to tens of tons of liquid, the time required for filtration on the production line can be reduced by several thousand to tens of thousands of times, for example, 1 to 4 ms.

[0073] In other words, by using a screen (filter material) that has been subjected to a projection treatment to form micro-irregularities on its surface, it is possible to reduce the resistance of the filter material to the flowing object to be filtered while maintaining the same filtering capacity with the same mesh size (opening size, wire diameter, etc.), thereby improving the pass-through of the object to be filtered. This has been confirmed to enable shortening of filtration time in various situations, such as food, pharmaceutical, and cosmetics manufacturing sites, making filtration more efficient and ultimately contributing to improved production efficiency.

[0074] <Experimental method 2> In addition, using an apparatus as shown in FIG. 15(B), the time (passing time) required for the liquid (filter object) in the cylinder to pass through the net and be discharged by free fall was measured. Specifically, we prepared a mesh made of SUS304 #700 (Reference) and a mesh (filter material) of the same specifications that had been subjected to a projection treatment (C1000). We set these meshes in the mesh installation location of the liquid passage experimental device and confirmed the difference in liquid passage time due to the difference in mesh. As shown in Fig. 15(B), in this liquid passage experimental device, a liquid (here, water) is poured (about 5 L) into an acrylic cylinder (diameter about 100 mm) arranged almost vertically with a plug (drain plug) installed below the net installation location closed. In this state, the top end is plugged and the plug (drain plug) installed below the net installation location is opened. From this state, the plug at the top end is removed and the liquid inside begins to be discharged from the plug (drain plug) installed below the net installation location. After that, the time until the height of the liquid (height of the water column) in the cylinder passes point A (the highest point), the time until it passes point B (the middle point), and the time until it passes point C (the lowest point) are measured. Here, the experimental results when water is used as the liquid are shown.

[0075] FIG. 15(A) is a graph showing the difference (YX: time reduction of sample B compared to the reference) between the transit time (X) of the liquid surface at each point when a SUS304 #700 net (Reference) was set and the transit time (Y) of each point on the liquid surface when a net that had been subjected to the same projection treatment as sample B was set.

[0076] This figure 1 5 (A) It was confirmed that at all points A, B, and C, when a screen with a micro-irregularity formed on its surface by projection processing was set, the passage time was faster (faster discharge speed, falling speed, etc.) and the filter resistance was smaller. In this experimental device, experiments were conducted using approximately 5 L of water. However, since actual production lines handle several tons to tens of tons of liquid, the time required for filtration on the production line can be reduced by several thousand to tens of thousands of times, for example, 1 to 7.5 ms.

[0077] In other words, by using a screen (filter material) that has been subjected to a projection treatment to form micro-irregularities on its surface, it is possible to reduce the resistance of the filter material to the flowing object to be filtered while maintaining the same filtering capacity with the same mesh size (opening size, wire diameter, etc.), thereby improving the pass-through of the object to be filtered. This has been confirmed to enable shortening of filtration time in various situations, such as food, pharmaceutical, and cosmetics manufacturing sites, making filtration more efficient and ultimately contributing to improved production efficiency.

[0078] Furthermore, by forming minute irregularities on at least a portion of the surface that comes into contact with the object to be filtered, the resistance of the filter medium to the object to be filtered can be reduced, thereby improving the passability of the object to be filtered.

[0079] We also investigated the contact angle of water (wettability) of the surface with micro-irregularities and the kurtosis value (value indicating the sharpness of the irregularities), which is closely related to the hydrophilicity of the surface with micro-irregularities. The conditions for measuring the kurtosis value are shown in Figure 18. The kurtosis value (Pku) is one of the indices that indicate the sharpness or peakedness of the height distribution (see FIG. 17(B)). Pku=3: The height distribution is normal. Pku>3: Surface has many sharp peaks and valleys Pku<3: The surface has few sharp peaks and valleys This indicates that. A kurtosis value (Pku) of less than 3 indicates a water-repellent surface, while a value of more than 3 indicates a hydrophilic surface.

[0080] The results are shown in FIG. 16. The contact angle on the surface of the test piece of "hydrophilic treatment 1 (sample A)" (= projection treatment (Ni)) was 57.7°, and the kurtosis value (Pku) was 3.37.

[0081] In addition, the contact angle of the surface of the test piece of "hydrophilic treatment 2 (sample B)" (= projection treatment (C400)) was 38.4°, and the kurtosis value (Pku) was 4.17.

[0082] In addition, the contact angle on the surface of the test piece subjected to "hydrophilic treatment 3" (= projection treatment (C1000)) was 64.9°, and the kurtosis value (Pku) was 4.13.

[0083] From FIG. 16, it is considered that if the water contact angle of the surface on which minute irregularities are formed is 65° or less, there is an effect of reducing the resistance of the filter medium. Also, from Fig. 16, it is considered that there is a reduction effect in filter resistance if the kurtosis value (Pku) of the surface on which the micro-irregularities are formed is greater than 3. Furthermore, from Fig. 16, it is considered that there is a greater reduction effect in filter resistance if the kurtosis value (Pku) is 3.3 or more, or 4.0 or more.

[0084] As described above, a filter medium having countless randomly formed minute projections and recesses on the surface that comes into contact with the liquid or paste-like object to be filtered can reduce the filter medium resistance to the flowing object to be filtered, thereby improving the liquid permeability (reducing filter medium resistance) while maintaining filtering capacity.

[0085] In this way, it has been discovered that forming countless micro-convexities (micro-depressions) randomly on the surface of a filter material (mesh elements, sieve) reduces the filter material resistance and therefore the resistance to passage of the object to be filtered, which can contribute to shortening the filtration time.However, this discovery relates to an effect that was previously unknown for components having countless micro-convexities (micro-depressions) formed on their surface, and is unpredictable from previous knowledge.

[0086] Based on this new knowledge, the present invention relates to a filter medium having a countless number of randomly arranged minute irregularities (minute recesses) on its surface, which is used as a filter medium with improved liquid permeability (filter medium with reduced passage resistance).

[0087] As described above, according to the present invention, by randomly forming countless minute irregularities on the surface through which the liquid or paste-like filtration target passes, it is possible to provide a filter medium that improves liquid permeability (filter medium with reduced passage resistance) that reduces the passage resistance of the filtration target.

[0088] In this embodiment, experiments on the passage resistance were conducted on water, salad oil, food sauce, chocolate syrup, liquid chocolate, and milky lotion, but the present invention can be applied to filter media for filtering liquid or paste-like filtration targets such as liquid or paste-like seasonings (soy sauce, ketchup, mayonnaise, etc.), foods, liquid or paste-like cosmetics, and liquid or paste-like fats and oils such as oil, grease, petroleum, and kerosene.

[0089] Incidentally, in the present embodiment, it has been described that the minute concaves and convexes are formed randomly by shot projection processing, but it is also possible to form the minute concaves and convexes randomly by subjecting the surface of the member to chemical polishing (chemical etching) or plasma processing (e.g. argon bombardment processing), etc. However, the present invention is not limited to this, and the minute recesses according to the present invention can also be formed by at least one of chemical etching, plasma processing, shot projection processing, etc., or by an appropriate combination of these. For chemical polishing (chemical etching), it is assumed that an aqueous solution of, for example, acidic agents such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, or iron (III) chloride in any ratio is prepared and used.

[0090] In addition, forming micro-irregularities (micro-depressions) on the surface of a filter medium also includes the formation of a composite irregular shape (composite dimples) on the surface of a filter medium, for example by transfer, using a mold having micro-irregularities (micro-depressions) on its surface formed based on (utilizing) chemical etching, plasma treatment, shot projection treatment, etc.

[0091] In addition, the effect of improving the passing of the filtration target (the effect of reducing the resistance of the filter material) by forming the minute irregularities according to this embodiment is considered to be equivalent to any non-magnetic austenitic stainless steel (SUS303, 304, 316, etc.) regardless of the surface finish specification such as #700 for the base material before the projection treatment, for example, in the case of stainless steel. In addition, the present invention is also applicable to metal materials other than stainless steel (for example, in the case of iron, for example, steel (SS400, etc.), aluminum, titanium, etc., metals or alloys, etc.).

[0092] In addition, the filter material according to the present invention can be, for example, a reticulated member (mesh member) having a net-like structure, a punched metal member (member with punched openings) having a plurality of openings (including resin), etc., but is not limited to these, and there are no particular limitations on the structure, shape, size, etc., as long as it is a filter material.

[0093] In the present invention, the object to be filtered is not particularly limited as long as it is a substance that can be filtered, but can be, for example, a liquid or paste-like substance for food containing water, oil, and other raw materials in any ratio, a liquid or paste-like substance for pharmaceutical use containing water, oil, and other raw materials in any ratio, a liquid or paste-like substance for cosmetics containing water, oil, and other raw materials in any ratio, etc.

[0094] In the present invention, the subject to be filtered also includes a case where a solid or powder is dispersed in a liquid or a paste-like substance.

[0095] In addition, the micro-roughness formation process (shot material projection process, micro-dimple process) of this embodiment uses a known injection device to inject media (shot material, abrasive particles) having different specifications (material, size, shape, etc.) as described above while adjusting the conditions, and collide them against the surface of the component that is the target of surface treatment processing, thereby obtaining the desired treated product (Ni, B400, C400, C1000, C3000, etc.) with different surface shapes (surface textures).

[0096] For example, a blasting device can be used as the injection device, and an example of the blasting device is "PNEUMA BLASTER" (model: SC series, SG series, etc.) manufactured by Fuji Manufacturing Co., Ltd. In addition, for example, the one described in JP 2019-25584 A can be used.

[0097] More specifically, as an injection device for injecting the injected particles toward the surface of the component, a known blast processing device (blast processing device) that injects abrasives (fine particles) together with compressed gas (air, argon, nitrogen, etc.) can be used.

[0098] Commercially available blast processing equipment (blast processing devices) include suction type blast processing equipment that uses the negative pressure generated by the injection of compressed gas to inject abrasives, gravity type blast processing equipment that injects abrasives that drop from an abrasive tank on the compressed gas, direct pressure type blast processing equipment that introduces compressed gas into a tank containing abrasives and combines the abrasive flow from the abrasive tank with the compressed gas flow from a separately provided compressed gas supply source and injects the abrasive flow, and blower type blast processing equipment that injects the direct pressure compressed gas flow on the gas flow generated by a blower unit, and all of these can be used to inject the aforementioned injection particles. Alternatively, a water jet can be used, which sprays a shot at high pressure with a liquid such as water.

[0099] Here, in the present invention, in order to identify the shape or structure of the uneven surface formed by (or based on) a shot material projection process known as a micro-roughness forming process, micro-dimple process, fine particle projection process, etc., a method of identification is used in which countless dimple-shaped micro-roughnesses (micro-depressions and ridge-like convestibules around the depressions, each with its own shape, pitch and depth) are formed randomly, which is completely different from the geometric and regular uneven shapes formed according to pre-designed drawings using laser processing or the like. In other words, instead of using the expression "micro-depressions are formed on the surface by (or based on) the shot projection process," a specific method (expression) such as "countless micro-convexities (or micro-depressions) are randomly formed on the surface of the filter material" is used. However, in comparison with prior art, it is anticipated that there may be cases in which it will be difficult to adopt the uneven surface formed by the shot projection process as a distinctive identifying method (expression) that distinguishes it from others.

[0100] For this reason, it is conceivable that there will be a situation in which it will be necessary to specify the uneven surface formed by (or based on) the shot material projection process using the specification method (expression) of "forming micro-irregularities on the surface by (or based on) the shot material projection process." Therefore, at the time of filing this application, there existed circumstances in which it was impossible or unrealistic to specify the shape, structure, characteristics, etc. of the micro-irregularities formed by the shot projection process, and there were cases in which it was unavoidable to use the expression "by forming micro-irregularities on the surface by (or based on) the shot projection process (taking into account cases such as transfer)", as will be explained below.

[0101] In the shot projection process, projected particles (media) are collided with the surface to be processed using compressed air at speeds of several tens to over a hundred meters per second, forming irregular, micron-sized, roughly spherical depressions with convex edges over almost the entire surface of the surface to be processed without significant dimensional change. When the media collides to form micro-depressions in the shot projection process, the periphery of the depressions rises in a crater-like manner to form convexities (see Figure 19). These raised convexities are then depressed by collision with other media, resulting in irregular convexity heights.

[0102] In contrast, mechanical processes such as laser processing and cutting create regular concave portions and do not create convex portions because they are removal processes (the convex portions are not raised with the formation of the concave portions).For this reason, the height of the convex portions around the minute concave portions in mechanical processes such as laser processing and cutting matches the height of the surface (original material surface) of the processed material (the component being laser processed) (see Figure 20).

[0103] In addition, since the minute projections and recesses formed by the shot projection process are formed in an countless irregular (random) manner, the surface texture (shape) formed by the shot projection process differs from the surface shape (texture) formed by processes such as polishing and grinding, which scrape the surface and create scratches (grooves such as streaks).However, when measured with a surface roughness meter, the two end up with similar numerical values, so it is not possible to distinguish between the two based on surface roughness, etc.

[0104] However, the effects obtained by the surface texture (shape) formed by the shot projection process (such as improving the passage of the object to be filtered and reducing the resistance of the filter material) are exceptional and cannot be predicted from the surface shape (texture) formed by processes such as polishing and grinding, which scrape and scratch the surface. Furthermore, shot peening, which involves colliding media of the order of a few millimeters to impart residual stress and improve the fatigue limit, makes it impossible to predict that a surface that has been subjected to shot projection treatment would have the effect of improving the passability of the object to be filtered or the effect of reducing the resistance of the filter media.

[0105] In this way, the tiny concaves and convexes formed by the shot material projection process are formed in an countless irregular (random) manner, the shapes of the tiny concaves and the convexities surrounding them are irregular, and in light of this irregularity being the source of the effects achieved by the present invention, it is not possible to specify the surface formed by the shot material projection process other than by using the expression "formed by (or based on) the shot material projection process" as a term for specifying the surface texture (shape) formed by the shot material projection process. As described above, at the time of filing this application, there are circumstances that make it impossible or unrealistic to specify the shape, structure, characteristics, etc. of the minute irregularities formed by the shot projection process.

[0106] The present invention is not limited to the above-described embodiment of the invention, and various modifications can be made without departing from the spirit and scope of the present invention. [Industrial Applicability]

[0107] The present invention provides a filter medium and a processing method for improving the passability of a filtration target, which reduce the resistance to passage of the filtration target by randomly forming countless micro-irregularities on the surface of the filter medium, and is useful and usable in industrial fields involving filtration operations.

Claims

1. A filter medium with improved filtrate permeability, characterized in that at least a portion of the surface that comes into contact with the filtrate has micro-convexities and concaves formed randomly through a shot material projection process, the micro-convexities having a minimum unevenness pitch of 0.5 μm or more and a maximum unevenness pitch of 40 μm or less, and a minimum concave depth of 0.03 μm or more and a maximum concave depth of 2.0 μm or less, thereby making the kurtosis value (Pku) of the surface greater than 3 and reducing the filter medium resistance to the filtrate.

2. A filter medium with improved filtrate permeability, characterized in that at least a portion of the surface that comes into contact with the filtrate has micro-convexities and concaves formed randomly through a shot material projection process, the micro-convexities having a minimum unevenness pitch of 0.5 μm or more and a maximum unevenness pitch of 10 μm or less, and a minimum concave depth of 0.3 μm or more and a maximum concave depth of 2.0 μm or less, thereby making the kurtosis value (Pku) of the surface greater than 3 and reducing the filter medium resistance to the filtrate.

3. 3. The filter medium for improving filtrate permeability according to claim 1, wherein the surface on which the minute projections and recesses are formed has a water contact angle of 65° or less.

4. The filtrate is a liquid or paste-like substance for food containing water, oil and other raw materials in any proportion, a liquid or paste-like substance for pharmaceutical use containing water, oil and other raw materials in any proportion, or a liquid or paste-like substance for cosmetics containing water, oil and other raw materials in any proportion. The filtrate permeability improving filter medium according to any one of claims 1 to 3, characterized in that the filtrate is a liquid or paste-like substance for pharmaceutical use containing water, oil and other raw materials in any proportion.

5. A treatment method for improving filtrate passability, characterized in that by forming, on at least a portion of a surface that comes into contact with the filtrate, countless micro-convexities and concaves randomly based on a shot material projection process, the micro-convexities having a minimum unevenness pitch of 0.5 μm or more and a maximum unevenness pitch of 40 μm or less, and a minimum concave depth of 0.03 μm or more and a maximum concave depth of 2.0 μm or less, the kurtosis value (Pku) of the surface is greater than 3 and the filter material resistance to the filtrate is reduced.

6. A treatment method for improving filtrate passability, characterized in that by forming, on at least a portion of a surface that comes into contact with the filtrate, micro-convexities and concaves randomly based on a shot material projection process, the micro-concave portions having a minimum unevenness pitch of 0.5 μm or more and a maximum unevenness pitch of 10 μm or less, and a minimum concave depth of 0.3 μm or more and a maximum concave depth of 2.0 μm or less, the kurtosis value (Pku) of the surface is greater than 3 and the filter material resistance to the filtrate is reduced.

7. 7. The method for improving filtrate passing property according to claim 5 or 6, wherein the surface on which the minute projections and recesses are formed has a contact angle of water of 65° or less.

8. The method for improving filtrate passability according to any one of claims 5 to 7, characterized in that the filtrate is a liquid or paste-like substance for food containing water, oil, and other raw materials in any proportion, a liquid or paste-like substance for pharmaceutical use containing water, oil, and other raw materials in any proportion, or a liquid or paste-like substance for cosmetics containing water, oil, and other raw materials in any proportion.

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