JP2007090231A - Metal fiber filter with pleat for molten polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal fiber filter with pleats using metal fiber nonwoven fabric suppressing cracks on the filter medium surface due to pleat formation, having superior filtering characteristics. <P>SOLUTION: This metal fiber filter has molded pleats in the metallic porous filter medium, and is formed in a cylindrical body with the pleats axially set. The porous filter medium has at least two or more sintered media sheet-likely formed by molding and sintering a single layer or composite layer of the metal fiber nonwoven fabric in sheet-like state, and laminated structure formed by separably superposing the media with gaps therebetween. The sintered medium is the metal fiber filter with pleats for molten polymer wherein an integrated value A of the fiber diameter d (μm), basis weight w (g/m<SP>2</SP>) of the metal fiber layer composing the media, and an average density τ of the media are adjusted to satisfy the relation of following equation (1): A=Σ(di×wi)×τ=800-2,000 (1)(In equation, i is respective values in an optional metal fiber layer). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement of a pleated filter that can increase the filtration area by creases formed on a filtration surface and is suitably used for filtration treatment of molten polymer.

  Metal fiber filters have high strength, heat resistance and corrosion resistance, and can be machined such as rolling and welding, and can be manufactured into porous bodies of various shapes and structures. It is widely used as a member for filtration, and is formed into a leaf shape, a cylindrical shape, a disk shape, or the like according to the equipment and product to be used.

  Disk-shaped and leaf-shaped metal fiber filters are mainly used in the case of molten polymers that melt-spin filaments because the filtration surface is flat and capable of high-pressure filtration, while cylindrical metal fiber filters have a simple structure. Since it can be implemented relatively inexpensively, it is used as a filtration member for filtering, for example, a molten polymer for a resin film that is low-pressure filtered with low viscosity, a fluid to be treated for other aqueous solutions, and the like. However, in order to improve the filtration efficiency, it is desired to increase the filtration area.

  By the way, in the metal fiber filter, metal fibers of corrosion resistant metal such as stainless steel and nickel alloy are selected according to required characteristics such as heat resistance, pressure strength, corrosion resistance, etc., and have predetermined pore characteristics. Specifications such as fiber diameter, basis weight, and molding thickness are set. In particular, when a sheet-shaped filter medium having a thickness of about 5 mm or less is used, each metal fiber is oriented in a direction perpendicular to the flow of the fluid to be treated, and each fiber is strongly sintered at the contact portion. Therefore, for example, there is an advantage that a gel-like material can be finely divided due to segregation or the like generated in the fluid to be treated. A metal fiber filter is employed as one of the reasons for such an advantage.

  Metal fiber filters require a balance between the filtration performance, such as filtration accuracy and efficiency, and the above-mentioned advantages, and a plurality of different types of filter media with specifications such as metal fiber configuration (type, thickness), basis weight, molding thickness, etc. The use of laminated filter media as a laminate is also under consideration.

  On the other hand, in the metal fiber filter, it is desired to increase the filtration area as described above. For this reason, when providing a crease to increase the filtration area, the metal filter is made strong by sintering each metal fiber as described above. Since the shape is maintained only by the joint portion, when excessive deformation occurs, for example, as shown in FIGS. 6 (A) and (B), the metal fiber filter medium itself is cracked and cracked. As a result, it cannot be used as a metal fiber filter. In addition, when cracking the both ends of the creased metal fiber filter together with the barrel portion a as illustrated in FIG. 7, such a crack is a cone-shaped portion c including a bent portion b, particularly a small diameter on the distal end side. It tends to occur in the part d.

  Moreover, the thing which performed the excessive process may generate | occur | produce the crack and crack which concern with progress of time during the use which is filtering the high pressure molten polymer, for example. Therefore, in order to form a pleated metal fiber filter using a metal fiber filter medium, it is important to determine a processing limit that can withstand deformation or to have a structure that can withstand processing.

  For this reason, in a cylindrical pleated metal fiber filter using a metal fiber filter medium, as a means for preventing cracks at the outer top of the filter medium caused by repeated filtration and backwash processes, the pleated porous filter medium There is a proposal that wedge-shaped spacers having different thicknesses are disposed on the outer surface side, and shim-shaped spacers having the same thickness are disposed between the folds on the inner surface side (for example, Patent Document 1).

  There is also a proposal to prevent cracks and cracks that occur when bent, by reinforcing the bent top part by heat treatment or resin treatment, etc., for a pleated filter device folded in zigzag (for example, patents) Reference 2).

Japanese Patent Publication No. 63-51049 JP-A-50-128868

  However, in Patent Document 1, the wedge-shaped and shim-shaped spacers are arranged between the folds, that is, the diaphragm-like motion applied to the filter medium is prevented by the spacers, and cracks at the top edge are prevented. However, the combined use of such a spacer not only prevents the flow of the fluid to be treated from blocking the smooth flow of the fluid to be treated by the surface contact with the spacer, but also causes an increase in pressure loss. , Increase in weight as a filter product, and increase in assembly manufacturing man-hours.

  In addition, in the filtering device according to Patent Document 2, the strength is improved by crushing the micropores in advance by heat treatment, resin treatment, or solvent at each bending top of the filter medium. Such sealing treatment is effective filtration area. In addition, for example, in the case of heat treatment, only the heated portion of the filter medium changes systematically, and accordingly, the corrosion resistance and heat resistance of the changed portion of the filter medium are reduced. Therefore, this technique cannot be employed for a molten polymer that is viscous and requires high-temperature filtration as the subject of the present invention.

  In view of the problems in the prior art, the present invention provides a pleated metal fiber filter that uses a metal fiber nonwoven fabric, suppresses cracking and cracking of the filter medium surface due to crease formation, and has excellent filtration characteristics. Make it the purpose.

The invention according to claim 1 is a metal fiber filter with a pleat having a metallic porous filter medium having a cylindrical shape formed by bending a molding fold extending in the axial direction on the entire surrounding surface,
One layer of a metal fiber layer made of a metal fiber non-woven fabric or a plurality of stacked metal fiber layers are sintered and integrated to sinter the metal fiber layer, or a sintered sheet layer of a plurality of layers Comprising two or more sintered media having
And the porous filter medium has a laminated structure in which the sintered media are overlapped with a space layer interposed therebetween,
And the fiber diameter d (micrometer) of the metal fiber of each sintering sheet layer which comprises each sintering media, the fabric weight w (g / m < ² >) of a sintering sheet layer, and density ratio (tau) of this sintering media It is a metal fiber filter with a pleat for molten polymer, wherein the calculated value (A) according to the following formula (1) is adjusted so as to satisfy 800 to 2000.
A = Σ (di × wi) × τ (1)
(I shows the number which numbered each sintered sheet layer).

In the invention according to claim 2, the metal fiber before sintering of the sintered sheet layer is stainless steel having an equivalent diameter of 30 μm or less, and the basis weight of the sintered sheet layer is 100 to 1000 g / m ^2. The invention according to claim 3 is characterized in that the sintered medium includes a first sintered sheet layer that ensures filtration accuracy, and the first sintered sheet that is integrated with the first sintered sheet and has coarse pores. The porous filter medium is composed of two sintered sheet layers, and the first or second sintered sheet layer is bonded to each other. The invention according to claim 4, wherein the porous filter medium is further formed on the outer surface of the porous filter medium so as to protect the porous filter medium. It is characterized by having each.

  As described above, in the present invention, since the porous filter medium is formed by laminating the sintered media through the space layer, the thickness is small unlike the conventional porous filter medium having the entire thickness. In addition, by enabling relative sliding in the space layer, each sintered media can reduce the distance from the bending neutral line to the inner and outer surfaces, and reduce tensile stress and compressive stress. Even in the case of crease processing, each sintered media has sufficient shape-retaining strength and can be set to a large degree of freedom for deformation such as bending, so the conventional laminated filter media in which the entire filter media are sintered together As compared with this, it is possible to prevent the occurrence of defects such as cracks and cracks.

In addition, when the fluid layer is filtered, particularly when a high-viscosity polymer solution is filtered, the fluid to be treated filtered by the fine upstream filtration layer flows in the plane direction in the space layer. It can also be filtered through the downstream filtration layer, and the fluid to be treated will be processed at a rapid, slow, and rapid flow rate, reducing the retention and reducing the occurrence of gelled materials, and cutting the gelled materials. Can help to increase filtration efficiency.
In addition, the filtering characteristics can be further improved by the inventions according to the second to fourth aspects.

  Hereinafter, the pleated metal fiber filter 1 of the present invention will be described with reference to the drawings. FIG. 1 is a front view illustrating an embodiment of a metal fiber filter with folds according to the present invention, FIG. 2 is a longitudinal sectional view thereof, and FIG. 3 is an enlarged view showing a part of the folds in the AA section of FIG. It is sectional drawing. The number of folds is formed over the entire circumference, and can be appropriately selected according to the purpose of use of the creased metal fiber filter 1. In this embodiment, the pleated metal fiber filter 1 includes a cylindrical porous filter medium 2, a reinforcing cylinder 4 that reinforces the porous filter medium 2 inside, a cap member 10A for fluid circulation fixed to one end, and the like. An end fitting 10 including a sealing member 10B provided at the end is provided. Further, in this embodiment, the porous filter medium 2 is formed by bending a pleat 3 composed of a ridge 3A and a valley 3B that is parallel to the direction of the axis X and is circumferentially spaced at regular intervals. is doing. Further, in this embodiment, the porous filter medium 2 is formed with narrow portions 2B formed by crushing the folds 3 by drawing at both ends of the body portion 2A via the cone portion 2C.

  The reinforcing cylinder 4 has a pressure resistance capable of maintaining a predetermined cylindrical shape even when the porous filter medium 2 is pressurized, and is formed on the inner peripheral surface of the porous filter medium 2 at the one end of the porous filter medium 2. The holding part 4a that keeps inward from the end face is inserted into the porous filter medium 2 almost continuously with the protruding part 4b protruding slightly from the end face of the porous filter medium 2 at the other end. In this embodiment, the reinforcing cylinder 4 is a perforated body formed by using a punching plate. If a perforated body can be formed, for example, a wire mesh can be used.

  In addition, in this embodiment, the base member 10A has a rear end portion that fits into the holding portion 4a, and forms a hexagonal portion 10Aa and an external screw portion 10Ab in series. Further, a through hole having substantially the same shape as the inner hole of the reinforcing cylinder 4 is formed, and the base member 10A is welded to one end of the porous filter medium 2 with a sealing effect. The sealing member 10B has an insertion portion inserted into the protruding portion 4b, for example, in the reinforcing cylinder 4, and is sealed by sealing the other end of the porous filter medium 2. The welding is structured to withstand a predetermined filtration pressure using, for example, TIG welding.

  The pleats 3 of the porous filter medium 2 can be set in consideration of the overall configuration such as thickness, pore accuracy, shape, and dimensions according to the purpose of use of the porous filter medium 2. Usually, for example, the crease formation pitch P (linear distance between the apexes of the adjacent ridges 3A) is 5 to 20 mm, and the fold height H (radial direction between the apex of the ridge 1A and the bottom point of the valley 1B). The distance) is about 3 to 30 mm. Such folds 3 are formed by bending the porous filter medium 2 into a wave shape. In addition, the porous filter medium 2 can also form the outer peripheral surface which joins the inner peripheral surface or the front-end | tip of the pleat 3 in non-circle, such as a cross-sectional circle shape or a square shape.

  FIG. 3 is an enlarged view of a part of the fold 3 in the section AA of the trunk portion 2A of the porous filter medium 2, and the fluid to be treated is the porous filter medium as indicated by an arrow Y in FIG. After being filtered at 2, it passes through the hole 4 </ b> A of the reinforcing cylinder 4 and is taken out through the end fitting 10 of the cap member 10 </ b> A.

  The porous filter medium 2 is formed by using a plurality of sintered media 12, 12... In this embodiment. In the case shown in FIG. 4 (A), the sintered media 12 is made of two metal fiber layers 17A and 17B made of a web-like metal fiber nonwoven fabric in which metal fibers 15 are entangled with each other and superimposed. By sintering and integrating and reducing the thickness, as shown in FIG. 4B, the first sintered sheet layer 18A in which the metal fiber layer 17A is sintered and the other metal fiber layer 17B are formed. The sintered media 12 which is an integral multilayer body including the sintered second sintered sheet layer 18B is formed. The first sintered sheet layer 18A is densely provided with fine pores so as to ensure substantial filtration accuracy, and therefore the metal fiber layer 17A can also form the first sintered sheet layer 18A. A web of specifications is used. The second sintered sheet layer 18B has relatively coarse pores as compared to the first sintered sheet layer 18A, and the metal fiber layer 17B is also formed in accordance with the specifications. As described above, the first sintered sheet layer 18A and the second sintered sheet layer 18B are integrally bonded and sintered in advance, whereby the sintered media 12 is formed as a composite sheet. The sintered media 12 can also be formed as a sintered sheet layer 18 using one metal fiber layer 17 as shown in FIGS. At that time, the sintered sheet layer 18 is compared with the first sintered sheet layer 18A as the first sintered sheet layer 18A having fine pores so as to ensure substantial filtration accuracy. It can also be configured as the second sintered sheet layer 18 </ b> B having coarse pores.

  In this embodiment, as shown in FIG. 4 (E), the porous filter medium 2 is composed of the sintered media 12 and 12 composed of two composite sheets in the present embodiment, and the dense first sintered sheet layer. A laminated structure in which 18A faces each other, that is, the coarse second sintered sheet 18B is disposed outside, and the space layer 20 is interposed therebetween to be mirror-imaged, that is, symmetrical to each other. In this embodiment, protective meshes 22 and 23 are attached to the inner and outer surfaces of the porous filter medium 2.

  In addition, the porous filter medium 2 is disposed in a separated state, that is, in a non-bonded state, as the sintered media 12 and 12 separate the space layer 20 as described above. The space layer 20 does not necessarily have a constant uniform width, and can be changed by the adjacent sintered media 12 at about 0.5 mm or less. It can also include having a constant part, having a changing part, and contacting the partially overlapping sintered media 12.

  As in this example, the second sintered sheet is formed by using the two sintered media 12 having a composite structure and directing the second sintered sheet layer 18B having coarse pores outward. Regardless of the direction of the flow of the fluid to be treated, the layer 18B functions as a prefilter when the second sintered sheet layer 18B is filtered, and captures coarse particles in advance as the porous filter medium 2. The filter life can be extended. Various composite structures such as adding a layer having an intermediate pore diameter to the sintered media 12 can be adopted.

The sintered media 12 includes a fiber diameter d (μm) of the metal fibers 15 in each metal fiber layer 17 of the sintered sheet layer 18 constituting the sintered media 12 and a basis weight (g / m ² ) of each sintered sheet layer 18. , And the relationship with the density ratio τ of all metal fibers in the sintered media 12, the following equation is satisfied.
A = Σ (di × wi) × τ = 800 to 2000 (1)

  Here, “i” indicates a number for each of the sintered sheet layers 18 in the sintered media 12, and the sintered media 12 has different types of sintered sheets as shown in FIG. 4B, for example. For the A value in the case of a layered structure composed of layers 17, multiply the total value of the values obtained by multiplying the fiber diameter d of the metal fibers 15 and the basis weight W of each layer by the density ratio of the metal fibers. In the present invention, this value is expressed as an anonymous number.

In addition, the fiber diameter d of a metal fiber means the diameter (micrometer) in the arbitrary cross sections of the metal fiber which comprises the layer, and the cross-sectional shape of the metal fiber is square shape, indefinite shape, etc. In the case of the non-circular shape, an equivalent diameter which is an average value of the longest dimension and the shortest dimension when an arbitrary cross section of, for example, about 20 metal fibers arbitrarily extracted from each layer is measured is used. The basis weight w is indicated as a mass (g) per 1 m ² for each metal fiber layer 17, that is, g / m ² . In the present invention, the basis weight of the metal fiber layer 17 before sintering and the basis weight of the sintered sheet layer after sintering are treated as the same. Further, regarding the density ratio τ, as defined in JIS Z2500, assuming that the mass of the predetermined volume when the sintered media is dense is 100, all the metal fibers present in the volume are all present. It shall be shown by the ratio with mass.

  For the metal fibers, various alloys based on nickel, titanium, and cobalt are selected in addition to stainless steel, Inconel (registered trademark), and Hastelloy (registered trademark). In particular, by using a so-called focused fiber manufacturing method in which a large number of wires are bundled into a bundle to reduce the diameter and then each wire is separated to reduce the diameter of the wire, a fine fiber with the equivalent diameter is possible, and flexibility For example, a fiber having a fiber length of about 10 to 100 mm is used. Further, the metal fiber nonwoven fabric is formed into a web shape by opening with a card machine or an air raid method, and the metal fiber layer 17 is formed using the metal fiber nonwoven fabric. As described above, the sintered sheet layer 18 is formed by sintering the metal fiber layer 17 to have a predetermined porosity (reciprocal of density).

  In the present invention, as described above, the relation between the fiber diameter d of each medium 12 and the basis weight w and the density is set to 800 to 2000 in relational expression (1). The sheet-like media itself is thin like a film, and no matter how many the layers are laminated, sufficient rigidity cannot be obtained as a whole. For this reason, for example, it is difficult to maintain the shape at the folds. For example, a shape change is caused by the filtration pressure, and the filtration performance is lowered. That is, in order to properly maintain a predetermined filter medium shape or pleat shape, each medium needs to have a sufficient shape retention strength. However, if the media is below the lower limit of the range, it cannot be achieved.

  On the other hand, when the value is increased to exceed 2000, the total thickness cannot be increased and the curvature diameter cannot be reduced. Defects such as cracks are generated in the film, making it difficult to achieve the present invention. For these reasons, more preferably 1000 to 1600.

  The protective mesh 6 is not necessarily required in the present invention. However, when the mesh 6 is provided, the shape of the fold shape is improved and the flow path of the fluid to be processed is provided even when the folds are in close contact with each other. For example, a mesh of about 30-100 # made of stainless steel wire can be easily applied. However, the present invention is not limited to this, and various configurations of mesh can be employed.

  In this way, the present invention forms the porous filter medium 2 by forming a laminated structure in which two or more sintered media are interposed with a space layer between them, and sets the sintered media in a specific condition range. It can be formed into a shape and can prevent the occurrence of cracks and the like in the pleated metal fiber filter. If necessary, it may be a composite composed of three layers of sintered media in which a space layer and a sintered media are arranged. Further, as shown in FIG. 1, it is also possible to have a narrow-diameter portion whose end is pressed by drawing.

  For the purpose of a filter product having a filtration accuracy of 3 μm, Example Product 1 and Comparative Product 1.2 shown in Table 1 by a metal fiber layer using a metal fiber nonwoven fabric made of fine stainless steel having a fiber diameter of 10 μm or less shown in Table 1 Each of the three types of sintered media was prepared.

  In Example Product 1, each of the sintered media has two types of fiber diameters, and each of the sintered media is laminated and sintered by adjusting the basis weight. In the production, the stainless steel fiber web laminated for each medium is pressure-sintered to a thickness (t) of 0.24 mm, and the sintering condition is heated to 1000 ° C. in a non-oxidizing atmosphere. At the time of the sintering, the medium is simultaneously provided with a stainless steel protective mesh (wire diameter: 0.19 mm × 30 #) disposed on both sides of the medium in the state of a porous filter medium. Are stacked.

  Comparative example product 1.2 is also pressure-sintered in the same manner as described above, but its configuration is set to have a predetermined basis weight of stainless steel fibers of three different fiber diameters, and is integrally molded, The single thicknesses are 0.41 mm and 0.52 mm, which are more than twice the single thicknesses of the examples. Note that the porosity ε in the table is a ratio indicating the pore portion per total volume of the sintered media, and means that the larger the ratio is, the more porous it is in this example. The characteristic is 63 to 66%.

  Each sintered sheet having a width of 1000 mm thus formed (for example product 1, a laminate of the first medium and the second medium) is passed between two crease rolls having gear-like irregularities. Thus, the three types of porous filter media having a continuous pleat height of 8 mm were obtained. Each filter medium is formed on the surface of a reinforcing cylinder made of a punching plate having a thickness of 2 mm and an outer diameter of 50 mm, and each filter is formed, and the fold pitch is set to 10 mm. In addition, each value of Table 1 is an average value of what formed two pieces each.

(Test 1: Appearance)
Since the cracking state of each filter medium accompanying the pleating process and the occurrence of cracks were confirmed with a microscope, the values in the above formula (1) of each layer in the example products are all as small as 1400 to 1600, The above-mentioned defect generation was not observed in the fold portion or the drawn thin wall portion, and it was satisfactory. This state can be seen in the cross-sectional photograph of FIG. 5, and the space layer has a thickness of about 0.5 mm. On the other hand, in the comparative product, all of the values were 2200 or more, and cracks as seen in FIG.

(Test 2: Bubble test)
About each obtained filter, the bubble point pressure of the initial stage and intersection based on a JIS-B8356 filtration particle size test was measured. The test is based on a method in which pressure is gradually applied while flowing air from the inside of the filter under a predetermined condition. The pressure when bubbles are first generated is set as an initial bubble point pressure (PAS), and further pressure is applied. The pressure at which the tangent lines intersect in the region where the rate of change gradually decreases in the relationship curve between the air pressure and the air flow rate when the test is performed is the intersection bubble point pressure (PES).

  That is, the higher the PAS value, the smaller the pore diameter, and the smaller the PES / PAS, the more uniform the pore diameter. Show.

It is a front view which illustrates one form of a creased metal fiber filter concerning the present invention. (A) is the longitudinal cross-sectional view which deleted the part. It is an expansion partial cross-sectional view which expands and shows a part of cross section. (A) is sectional drawing which shows the state which accumulated the metal fiber layer, (B) is sectional drawing which illustrates the sintering media which sintered the metal fiber layer of (A), (C) is 1 layer of metal fiber 2D is a cross-sectional view illustrating a sintered medium formed by sintering the metal fiber layer of (C), and FIG. 2E is a cross-sectional view illustrating an enlarged porous filter medium. . It is sectional drawing which shows an Example goods by a thin diameter part. 6A and 6B are diagrams showing a crack state of a conventional product, in which FIG. 6A is a front view illustrated with a protective mesh attached, and FIG. 6B is an enlarged front view of 250 times with the protective mesh removed. It is a front view which illustrates the conventional metal fiber filter with a pleat.

Explanation of symbols

2 Porous filter medium 3 Fold 12 Sintered media 17, 17A, 17B Metal fiber layer 18, 18A, 18B Sintered sheet layer

Claims (4)

A pleated metal fiber filter having a metallic porous filter medium in the form of a tube formed by bending a molded fold extending in the axial direction on the entire surrounding surface,
One layer of a metal fiber layer made of a metal fiber non-woven fabric or a plurality of stacked metal fiber layers are sintered and integrated to sinter the metal fiber layer, or a sintered sheet layer of a plurality of layers Comprising two or more sintered media having
And the porous filter medium has a laminated structure in which the sintered media are overlapped with a space layer interposed therebetween,
And the fiber diameter d (micrometer) of the metal fiber of each sintering sheet layer which comprises each sintering media, the fabric weight w (g / m < ² >) of a sintering sheet layer, and density ratio (tau) of this sintering media A pleated metal fiber filter for a molten polymer, wherein the calculated value (A) according to the following formula (1) is adjusted to satisfy 800 to 2000.
A = Σ (di × wi) × τ (1)
(I shows the number which numbered each sintered sheet layer). The metal fiber before sintering of the sintered sheet layer is stainless steel having an equivalent diameter of 30 μm or less, and the basis weight of each metal fiber layer constituting the sintered sheet is 100 to 1000 g / m ² . The pleated metal fiber filter according to claim 1.   The sintered medium includes a first sintered sheet layer that ensures filtration accuracy, and a multilayered body that is integrated with the first sintered sheet and includes a second sintered sheet layer having coarse pores. And the porous filter medium is formed by wire-bonding the sintered medium composed of the two multilayers with the first or second sintered sheet layer facing each other and a space layer therebetween. 3. The pleated metal fiber filter according to claim 1, wherein the metal fiber filter is formed by symmetrically superimposing.   The pleated metal fiber filter according to any one of claims 1 to 3, wherein the porous filter medium further has protective meshes for protecting the porous filter medium on both outer surfaces thereof.