Filter

Abstract

To provide a filter which achieves small deterioration of a filtration performance compared with filter paper alone to achieve the number of reuses which significantly exceeds those of conventional filters.SOLUTION: A filter 10 is formed by laminating a reinforcement layer 12 on a surface of a filter frame 11 and winding the lamination in a roll form, is continuously reeled out and stretched to dam a flow passage of processed liquid, and causes the processed liquid to flow through mesh holes to capture solid impurities in the processed liquid in a continuously moving state. The filter frame 11 is made of a mesh web wound into a roll shape, and the reinforcement layer 12 is a cellulose nanofiber layer which is made of a cellulose nanofiber, which is fixed to one or both of the filter frame 11, provided in a net structure having a thin film form of a predetermined thickness, enhances strength of the filter frame 11, and provides a high and stable capturing performance.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a reusable filter that allows aqueous liquids to pass through it while trapping solid impurities in the aqueous liquid. [Background technology]

[0002] Coolant liquid is supplied to the surface of metal workpieces being processed in grinding processes and other processes, and after it has been used for lubrication, cooling, washing, etc., it contains solid matter such as metal chips and abrasive grains, as well as impure oils such as lubricating oil and rust-preventive oil. For this reason, continued use of circulated coolant liquid can lead to a decrease in grinding accuracy, and ultimately to a decrease in the quality of the workpiece.

[0003] Therefore, the filter is unwound from a roll and set in a state where it blocks the flow of the aqueous liquid containing solid impurities, and the filter is continuously moved in the planar direction, and the aqueous liquid is passed through the filter while the solid impurities are captured (see Patent Documents 1 and 2).

[0004] The symbols used in the following description of Patent Document 1 are the same as those used in each patent document.

[0005] In the continuous filtration device shown in Patent Document 1, a filtration filter 4 pulled out from a roll body 3 is wound around the outer peripheral surface of a filtration drum 10 via a supply roller 20, and is then led to the outside of a pollution tank 2 via a discharge roller 30. As the filtration drum 10 and the discharge roller 30 rotate, the filtration filter 4 is continuously wound around the filtration drum 10 and moved, while the negative pressure of a vacuum pump 5 separates the solids in the pollution liquid 1 and the purified liquid at the boundary surface of the filtration filter 4, and the solids adhering to the filtration filter 4 can be collected together with the filtration filter 4 into a collection container 70 via a guide roller 60.

[0006] Thus, according to the continuous filtration device disclosed in Patent Document 1, a technology is provided in which the used filtration filter 4 is collected from the collection container 70 and incinerated with solid matter attached thereto, thereby preventing reuse.

[0007] If the filtration filter 4 must be discarded after a single use due to clogging, this will result in increased costs and increased environmental impact. In order to reuse a used filtration filter 4, it is necessary to separate and remove the solid matter adhering to the filter by brushing the adhering surface, then unclog the filter by forcefully spraying cleaning water from a nozzle from the side opposite the adhering surface, and then separate and remove the impure oil adhering to the filter from the filter.

[0008] In the cutting fluid filtration device shown in Patent Document 2, coarse cutting chips in the treated liquid that settle as the liquid rises between the baffle plates 12 are received on the baffle plates 12 and allowed to slide down, received on a discharge conveyor 14 running along the bottom of the filtration tank 1, transported to the return section 14a, scraped off by a scraper 15, and collected in a sludge box 16, and the treated liquid that has passed upward between the baffle plates 12 is allowed to pass upward through the lower running portion of a screen belt filter material 27, during which time fine cutting chips are captured by the screen belt filter material 27.

[0009] When the screen belt filter medium 27 is used repeatedly, the mesh holes of the screen belt filter medium 27 become clogged with fine cutting chips, reducing the filter accuracy. Therefore, in order to remove the cutting chips, the screen belt filter medium 27 is brushed with a brush roller 40 during non-filtration, and a cleaning liquid is sprayed onto the back surface of the screen belt filter medium 27 with a backwash nozzle 39. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2006-305430 A [Patent Document 2] Japanese Patent Application Publication No. 58-170511 Summary of the Invention [Problem to be solved by the invention]

[0011] The cutting fluid filtration device disclosed in Patent Document 2 provides a technique for reusing the screen belt filter material 27. However, there have been no examples of reusing the screen belt filter material 27 described in this technique. The inventors therefore conducted experiments to examine the reuse of filters and found the following problems.

[0012] First, the strength of filter paper decreases as the number of times it is reused increases. In particular, in order to reuse filter paper, a process is required in which the solid matter adhering to the filter paper is brushed to remove the solid matter, and the filter paper runs in a meandering manner, which causes the strength of the filter paper to decrease significantly. In addition, when the strength of the filter paper decreases significantly, the mesh holes become larger and the filtration performance decreases.

[0013] Furthermore, if the strength of the filter paper decreases, cracks will appear on the side edges of the filter during filtration, and once a crack appears, there is a risk that the tension will change significantly when the filter paper is not wound smoothly, causing stress concentration at the crack, which will rapidly grow into a large crack and cause the filter paper to burst. If the filter paper bursts during filtration, not only will it be time-consuming to replace the filter paper, but it will also cause the previously filtered liquid to mix with unfiltered liquid, posing a major problem in that the filtration must be restarted from the beginning.

[0014] For this reason, from the perspective of safety, there is a need to limit the number of times that filter paper can be reused to a minimum, so that there is no risk of the filter paper bursting.One method of solving this problem is to collect data through experiments on the number of times that each type of filter can be reused before small cracks appear on the side edges, and then limit the number of times that the filter paper can be reused to a number less than the minimum number of times that can be reused.

[0015] On the other hand, another solution to the problem is to improve the cost performance of filter materials by increasing the number of times that commercially available filter paper and filter cloth can be reused. In the above situation, there have been no proposals to improve the number of times that filter paper can be reused.

[0016] The present invention has been made to solve these problems, and has an object to provide a filter that, by laminating a reinforcing layer based on filter paper or the like, increases the strength of the entire filter with little deterioration in strength, and is less likely to cause the mesh holes to become larger, resulting in little deterioration in filtration performance, and thus allowing for a significantly greater number of reuses than filter paper alone. [Means for solving the problem]

[0017] In order to achieve the above-mentioned object, the filter of the first aspect of the present invention is a filter that comprises a filter body having mesh holes and a reinforcing layer laminated on the surface of the filter body, wound into a roll, and in a state in which the flow passage of the liquid to be treated containing fine particle solid impurities is blocked and the liquid to be treated moves continuously, the filter allows the liquid to pass through the mesh holes and captures the solid impurities in the liquid to be treated without allowing them to flow downstream.

[0018] The filter of the present invention is particularly characterized in that the filter body is made of a mesh web wound into a roll, and the reinforcing layer is a cellulose nanofiber layer that is fixed to one or both surfaces of the filter body and is provided in a mesh structure in the form of a thin film of a required thickness, reinforcing the strength of the filter body and imparting a higher and more stable capture performance than the capture performance of the mesh holes in the filter body.

[0019] The filter according to the present invention is characterized in that the cellulose nanofibers are impregnated into the filter body.

[0020] The filter of the second aspect of the present invention is characterized in that, in addition to the configuration of the first aspect, the cellulose nanofiber layer penetrates and is engaged with the filter body, and the fibers of the cellulose nanofiber are entangled with each other among the fibers of the filter body.

[0021] The filter of the third aspect of the present invention has the same configuration as the first or second aspect, and in addition, the size of the mesh holes in the filter body is larger than the aperture diameter at which the desired capture performance is obtained, and the mesh structure of the cellulose nanofiber layer covers the mesh holes, so that the desired capture performance is obtained according to the thickness of the mesh structure.

[0022] A filter according to a fourth aspect of the present invention has the same configuration as any of the first to third aspects, and furthermore, the filter body is any one of filter paper, filter cloth, nonwoven fabric, and single-layer mesh film. Effect of the Invention

[0023] According to the present invention, by laminating a reinforcing layer on a base such as filter paper, the strength of the filter as a whole is increased with little deterioration in strength, and the mesh holes are less likely to become large, so that deterioration in filtration performance is small, and thus a filter can be provided which can be reused a significantly greater number of times than filter paper alone. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a block diagram showing an impurity removal apparatus to which a filter according to the present embodiment is applied, arranged in the order of processing steps. [Diagram 2] FIG. 2(A) shows an oblique view of a filter in accordance with the present embodiment, FIG. 2(B) shows a partially enlarged cross-sectional view of the filter body, FIG. 2(C) shows a partially enlarged cross-sectional view of a filter having a reinforcing layer adhered to one side of the filter body, and FIG. 2(D) shows a partially enlarged cross-sectional view of a filter having reinforcing layers adhered to both sides of the filter body. [Diagram 3] FIG. 3 is a schematic diagram showing the steps of producing a filter in which a reinforcing layer is laminated on one surface of a filter body. [Figure 4] FIG. 4 is a schematic diagram showing the manufacturing process of a filter in which reinforcing layers are laminated on both sides of a filter body. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A filter according to an embodiment of the present invention will now be described with reference to the drawings.

[0026] [Filter application example] 1 is a block diagram showing an example of an impurity removal device to which the filter according to the present embodiment is applied, in a symbolic diagram and with the processing steps arranged in order. The impurity removal device includes, for example, a filter supply unit 1, a filtration tank unit 2, a brushing unit 3, a mesh hole clogging elimination unit 4, a drying unit 5, and a filter winding unit 6.

[0027] Next, the processing steps of the impurity removal device will be described. The filter 10 according to this embodiment is wound in a roll shape, and is continuously unwound at a constant speed from the state supported by the filter supply unit 1, and is set to a state in which it is led to the filtration tank unit 2 and blocks the flow of the aqueous liquid containing solid impurities, and moves in the surface direction. In the filtration tank unit 2, the filter 10 actively allows the aqueous liquid to flow through the mesh holes by utilizing the pressure difference between the upstream and downstream liquid pressures acting on the blocking surface of the filter (by increasing the upstream liquid pressure or decreasing the downstream liquid pressure), and captures the solid impurities in a state of close contact due to the pressure difference of the liquid pressure without allowing them to flow through the mesh holes. Next, the filter 10 moves from the blocking position to the brushing unit 3, where the solid impurities captured by brushing are swept away. The filter 10 is then moved to a mesh hole clogging elimination unit 4, where fluid pressure is applied to the mesh holes from the side opposite to the capture surface to remove fine solid impurities clogging the mesh holes from the capture surface, thereby eliminating clogging of the mesh holes. The filter 10 is then dried in a drying unit 5 and wound up again into a roll in a filter winding unit 6, making it possible to use it repeatedly.

[0028] In this way, filter 10 is continuously unwound at a constant speed from a rolled-up state, stretched like a film so as to block the flow path of the treated liquid containing fine particle solid impurities, and in a state of continuous movement, a liquid pressure difference (either by increasing the liquid pressure on the upstream side or decreasing the liquid pressure on the downstream side) is actively created between the upstream filter surface and the downstream filter surface at the damming position, causing the treated liquid to flow through the mesh holes, thereby capturing the solid impurities in the treated liquid without allowing them to flow downstream.

[0029] [Outline of filter configuration] Fig. 2(A) shows a perspective view of a roll form of filter 10 according to this embodiment. Fig. 2(B) shows a partially enlarged cross-sectional view of filter body 11 having mesh holes 11a constituting the filter, Fig. 2(C) shows a partially enlarged cross-sectional view of filter 10 formed by fixing reinforcing layer 12 to one surface of filter body 11, and Fig. 2(D) shows a partially enlarged cross-sectional view of filter 10 formed by fixing reinforcing layer 12A to one surface of filter body 11 and fixing reinforcing layer 12B to the other surface. Note that filters 10 shown in Figs. 2(C) and 2(D) are not limited to being manufactured by the manufacturing methods shown in Figs. 3 and 4.

[0030] [Example of the general process for making filters] 3 is a schematic diagram of the manufacturing process of a filter 10 in which a reinforcing layer 12 is laminated on one surface of a filter body 11. A filter manufacturing apparatus 20 includes a filter body supplying unit 21, a reinforcing layer forming unit 22, a drying unit 23, and a filter winding unit 24. The filter body 11 wound in a roll in the filter body supplying unit 21 has a cellulose nanofiber layer 12 applied or adsorbed as a thin layer of a required thickness on one surface (lower surface) in the reinforcing layer forming unit 22, and then the moisture is removed in the drying unit 23, and the filter is then subjected to roll pressure and further dried by a heater roll or the like, and finally wound into a roll in the filter winding unit 24, thereby manufacturing a filter 10 in which the reinforcing layer 12 is laminated and fixed on one surface of the filter body 11.

[0031] The lamination of the reinforcing layer 12 onto the filter body 11 is not limited to any particular technique, but for example, a roll coating method can be used. According to the roll coating method, the filter body 11 is passed between a gravure roll immersed in a mixture in which cellulose nanofibers are dispersed at a required concentration and a pressure roll placed on the gravure roll, and the mixture pumped up into the cells of the gravure roll is transferred to the filter body 11.

[0032] 4 is a schematic diagram showing the manufacturing process of filter 10 in which reinforcing layers 12 are laminated on both surfaces of filter body 11. Filter manufacturing apparatus 30 includes filter body supply unit 31, a first reinforcing layer forming unit 32, a first drying unit 33, a second reinforcing layer forming unit 34, a second drying unit 35, and a filter winding unit 36. The filter body 11 wound in a roll in the filter body supply unit 31 has a cellulose nanofiber layer 12A coated or adsorbed as a thin layer of the required thickness on one side (the lower side) in the first reinforcing layer forming unit 32, then the moisture is removed in the first drying unit 33, roll pressure is applied and the filter is dried using a heater roll or the like, and then the cellulose nanofiber layer 12B is coated or adsorbed as a thin layer of the required thickness on the other side (the lower side) in the second reinforcing layer forming unit 34, then the moisture is removed in the second drying unit 35, roll pressure is applied and the filter is dried using a heater roll or the like, and finally the filter is wound up in a roll in the filter winding unit 36, thereby producing a filter 10 in which reinforcing layers 12A, 12B are laminated and fixed to both sides of the filter body 11.

[0033] [Advanced filter configuration] The filter body 11 is prepared as a mesh web wound into a roll before the reinforcing layer 12 is laminated. Specifically, any one of filter paper, filter cloth, nonwoven fabric, and single-layer mesh film can be used for the filter body 11. Several types of filter bodies 11 with different mesh sizes, for example, fixed-quantity filter papers and fixed-quantity filter cloths made of φ1, 2, 4, 6, 8, and 10 μm, are commercially available, and an appropriate one can be selected from these depending on the purpose, such as the size of the object to be filtered and the amount of filtration per unit time.

[0034] Filter paper can generally be made of cotton fibers (cellulose), or it can be made of a biologically inactive mixture of cellulose acetate and cellulose nitrate, glass fiber filter paper, PTFE membrane that has been hydrophilized, or quartz filter paper using high-purity fine silica fibers.

[0035] The filter cloth may be made of yarn made from any one of the following raw materials: polyethylene terephthalate, polypropylene, polyamide, polyester, acrylic, heat-resistant nylon, polyimide, PPS, glass, PTFE, or glass PTFE. The yarn may be either spun yarn (short fiber yarn), multifilament (long fiber yarn), or monofilament (long single fiber yarn), and may be processed into plain weave, twill weave, satin weave, double weave, or needle punched felt, and may also be used as a mesh filter.

[0036] The nonwoven fabric may be a mesh filter made by nonwoven processing of spun yarn (short fiber yarn) made of polyethylene, polypropylene, polyamide, polyester, or the like.

[0037] The single-layer mesh film is a biaxially oriented film of polyethylene, polypropylene, polyamide, polyester, or the like, in which pinholes are provided over the entire surface in a closely spaced relationship by needle punching or laser processing.

[0038] The reinforcing layer 12 is made by dispersing cellulose nanofibers in water, which have a thickness of 1-100 nm, a variety of lengths with no specified orientation, and are intricately entangled. The cellulose nanofibers are laminated, for example by a roll coater, on one or both sides of the filter body 11, and the moisture is removed by a water-absorbing roll or the like and the layer is flattened by applying pressure. During this process, the cellulose nanofibers penetrate the filter body 11 and adhere strongly, providing an adhesion strength that will not easily peel off even if the filter body 11 is bent or brushed.

[0039] [Adhesive strength of reinforcing layer 12] The reason why the cellulose nanofibers impregnate the filter body 11 and pierce it due to the roll pressure is because the cellulose nanofibers are needle-shaped bodies that are about five times stronger than iron. By applying pressure to flatten the cellulose nanofibers after stacking the cellulose nanofibers 12, the cellulose nanofibers impregnate the filter body 11 and the strength of the filter body 11 is increased, and the cellulose nanofibers that have entered obliquely into the walls of the mesh holes of the filter body 11 pierce and become locked into the walls of the mesh holes, and the cellulose nanofibers that are oriented in a direction approximately perpendicular to the surface parts of the filter body 11 other than the mesh holes pierce and become locked, and the fibers of the cellulose nanofibers become entangled with each other between the fibers of the filter body.

[0040] The reinforcing layers 12 (12A, 12B) are dried, and thus the reinforcing layers 12 (12A, 12B) have a mesh structure in a thin film of a required thickness, and become a cellulose nanofiber layer that is laminated with high adhesive strength to the filter body 11. The reinforcing layers 12 (12A, 12B) cover the mesh holes 11a of the filter body 11, and can stably achieve meshes finer than the size of the mesh holes 11a for a long period of time.

[0041] The filter 10, in which the reinforcing layers 12 (12A, 12B) are fixed to one or both sides of the filter body 11, is wound up in a roll as a final form so that it can be installed in an impurity removal device for reuse.

[0042] The filter 10 is provided with a mesh structure in the form of a thin film of the required thickness on the filter body 11, and the cellulose nanofiber layer 12 significantly increases the burst strength, and the mesh structure is maintained for a long period of time, thereby maintaining a capture performance that is higher and more stable than the capture performance of the mesh holes in the filter body 11.

[0043] In filter 10, the size of the mesh holes in the filter body 11 is larger than the aperture diameter required to obtain the desired capture performance, and the mesh structure of the cellulose nanofiber layer covers the mesh holes, so that the desired capture performance is obtained according to the thickness of the mesh structure.

[0044] Filter 10 according to this embodiment is unwound from a roll and set in a state in which it blocks the flow of aqueous liquid containing solid impurities, capturing solid impurities as it moves in a planar direction; it is a filter that can remove solid impurities and eliminate clogging of mesh holes, allowing it to be reused repeatedly; in particular, it is possible to control the capture performance of solid impurities, obtain stable capture performance that is significantly superior to that of filter paper alone, and obtain a significantly greater number of repeated uses than that of filter paper alone.

[0045] According to the present invention, the filter comprises a filter body made of a mesh web and a thin-film porous reinforcing layer, and by controlling the thickness of the reinforcing layer, the capture performance of particulate solid impurities can be controlled. In addition, a stable capture performance that is significantly greater than that of conventional filters can be obtained. In addition, the filter can be repeatedly used a number of times that is significantly greater than that of conventional filters (filter paper). This makes it possible to provide a useful filter with improved cost performance. [Explanation of symbols]

[0046] 1...Filter supply unit, 2... Filtration tank unit, 3…Brushing unit, 4...Mesh hole clogging elimination unit, 5…Drying unit, 6...Filter winding unit, 10…Filter, 11...Filter body, 12...Reinforcing layer (cellulose nanofiber layer), 20...Filter manufacturing equipment, 21...Filter body supply unit, 22...reinforcing layer forming unit, 23…Drying unit, 24...Filter winding unit, 30...Filter manufacturing equipment, 31...Filter body supply unit, 32...first reinforcing layer forming unit, 33…first drying unit, 34...second reinforcing layer forming unit, 35…second drying unit, 36...Filter winding unit.

Claims

1. A filter comprising a filter body having mesh holes and a reinforcing layer laminated on a surface of the filter body, the filter body being set in a state of blocking the flow of a liquid to be treated containing particulate solid impurities as the liquid flows through a flow passage, thereby allowing a portion of the liquid to be treated excluding the solid impurities to flow through the mesh holes and capturing the solid impurities in the liquid to be treated without allowing them to flow downstream of the filter body in the flow passage, The filter body is made of a mesh web wound into a roll, The reinforcing layer is a cellulose nanofiber layer having no orientation and fixed to one or both surfaces of the filter body, the cellulose nanofiber layer being provided in a thin film shape having a required thickness and having a mesh structure, The reinforcing layer has a structure in which the non-oriented cellulose nanofibers penetrate into the filter body. A filter characterized by:

2. The cellulose nanofibers are impregnated into the filter body.

2. The filter of claim 1.

3. The fibers of the cellulose nanofibers are entangled with each other among the fibers of the filter body.

3. The filter according to claim 1 or 2.

4. The size of the mesh holes of the filter body is larger than the diameter at which the desired capture performance is obtained, and the network structure of the cellulose nanofiber layer covers the mesh holes. A filter according to any one of claims 1 to 3.

5. The filter body is any one of filter paper, filter cloth, nonwoven fabric, and single-layer mesh film. A filter according to any one of claims 1 to 4.

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