JP2014240045A - Method for forming tubular membrane filter, and tubular membrane filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and accurately form a tubular membrane filter from a porous sheet.SOLUTION: A laminated porous sheet obtained by making a PTFE porous membrane overlap a nonwoven fabric and heat-sealing and integrating them together is wound by one round like a sushi roll. An inner surface of a winding terminal part overlaps an inner surface of a winding starting part. A space between overlapping parts is fixed with a pressure sensitive adhesive double coated tape or an adhesive to temporarily retain a tubular shape. Subsequently, the temporarily-retained overlapping parts are fixed by heat seal.

Description

  The present invention relates to a method for forming a tubular filtration membrane and a tubular filtration membrane, and more specifically, a tubular filtration membrane is wound around a sheet-like porous sheet, the tubular filtration membrane being an environmental conservation field, It is used for a filtration apparatus that performs solid-liquid separation processing in the fields of medicine and food.

  Conventionally, porous membranes comprising hollow fiber membranes and flat membranes have been provided as this type of filtration membrane. In Japanese Patent No. 3,851,864, the present applicant provides a filtration module in which hollow fiber membranes made of PTFE are converged. In addition, those using a porous film made of a flat film made of polyolefin resin or polyvinylidene fluoride are also provided.

  Since the hollow fiber membrane module has a narrow gap between adjacent hollow fiber membranes, there is a problem that when the suspended component is deposited between the membrane surfaces or between the membranes, the flow of the treatment liquid becomes poor and the treatment speed tends to decrease. is there. Further, the flat membrane module has a problem that the strength of the filtration membrane is not sufficient, and membrane damage is likely to occur when a load due to air diffusion is applied for a long period of time.

  In order to solve the problems of the conventional hollow fiber membrane and the flat membrane, the present applicant has disclosed in JP-A-2009-101131 that a porous sheet made of a PTFE porous membrane having chemical resistance and strength is formed into a cylindrical shape. A cylindrical filtration membrane that is formed and has a hollow portion surrounded by the porous sheet as a treated liquid channel, and a hollow part that supports the inner side of the cylindrical filtration membrane with a support material and becomes the treated liquid channel The filter membrane element which hold | maintains is provided.

  The filtration membrane element provided in Patent Document 1 is superior in filtration performance, chemical resistance and mechanical strength to the conventional hollow fiber membrane type and flat membrane type filtration membrane elements. There is an advantage that a stable permeation flow rate can be obtained.

Japanese Patent No. 3851864 JP 2009-101311 A

  The cylindrical filtration membrane provided in Patent Document 2 has a diameter of 3 mm to 50 mm and a length of 500 mm to 4000 mm. When the diameter is 3 mm, the circumference is 9.4 mm and the overlapping dimension at both ends is also shortened. However, since the length is 10 to 100 times, the operation of joining the overlapping portions with a uniform width in the length direction It becomes difficult. Therefore, the overlapping dimension is increased and, as shown in FIG. 7, both ends are projected outwardly by about 7 to 10 mm, and the butted portions are heat-sealed with a heat sealer. Therefore, a heat seal portion having a width of 7 to 10 mm protrudes as an ear 101 from the outer peripheral surface of the cylindrical filtration membrane 100.

When the filtration membrane 100 having the ears 101 is immersed in a liquid to be treated (sewage) containing suspension components of the filtration device, the suspension components (S) are likely to accumulate in the ear 101 portions. In addition, the ear 101 inhibits the flow of the liquid to be treated and the flow of aeration, and the suspended components are more likely to accumulate in the ear 101 portion.
In addition, if the suspended components accumulate in the ear 101 portion, the effective filtration area decreases when the diameter of the filtration membrane is small. Furthermore, there is a problem that stress concentrates on the interface 101a from which the ear 101 protrudes from the outer peripheral surface of the cylindrical filtration membrane 100, and damage is likely to occur in the stress concentration portion.

  The present invention has been made in view of the above problems, and enables a simple and accurate coupling without causing the above-mentioned ears in a filtration membrane which is formed by winding a porous sheet and coupling both ends to form a cylindrical shape. It is an issue.

In order to solve the above problems, as a first invention, a method for forming a cylindrical filtration membrane is provided. The forming method includes laminating a porous porous sheet obtained by laminating a PTFE porous membrane and a nonwoven fabric, and then winding the round porous sheet around the outer surface of the winding start portion.
Adhering between the overlapping parts with a double-sided pressure-sensitive adhesive tape or adhesive to temporarily hold the cylindrical shape,
The method comprises a method of forming a cylindrical filtration membrane in which the temporarily held portion is heat-sealed and fixed.

  Adhesion with the double-sided adhesive tape is to stick the adhesive tape along the winding start edge, and leave the other side of the adhesive tape with release paper attached, roll it with sushi roll, When the inner peripheral surface is overlapped with the outer peripheral surface of the winding start portion, it is preferable to peel off the release paper and adhere. In the case of using an adhesive, it is preferable that the adhesive is temporarily held while being applied from one end in the length direction to the other end while applying the adhesive.

Further, instead of the above method, it is abutted against the upper surface of a belt-like substrate having a length equivalent to the length of the cylindrical filtration membrane to be formed and having a width corresponding to ½ of the circumferential length of the cylindrical filtration membrane. Provide a jig with protruding parts,
One end in the width direction of the laminated porous sheet obtained by laminating a PTFE porous membrane and a non-woven fabric and fusing them together is abutted against the abutting portion of the jig, while maintaining the abutting state. Wrap the sheet from one end of the jig through the lower surface side to the upper surface side from the other end, pass the upper surface of the abutting portion on the upper surface side, and overlap the upper surface of the one end,
In order to maintain the above state, at least both ends in the length direction are wrapped with a rubber band and held temporarily,
The present invention provides a method for forming a cylindrical filtration membrane in which the temporarily held overlapped portion is thermally fused and fixed.

In any of the above methods, in the heat-sealing step, the cylindrical shape is formed into a flat bag shape, and a shielding band material made of a non-adhesive heat-resistant material is inserted into the hollow portion of the bag,
Pressing the overlapping part with a heat sealer and heat-sealing,
It is preferable that the thickness of the overlapped portion is reduced by the heat fusion, and the end surface at the end of winding is inclined so as to be continuous with the outer peripheral surface of the winding without a step.

As the strip-shaped non-adhesive heat-resistant material inserted into the hollow portion, for example, a PTFE thick sheet or a tape in which a fluororesin adhesive tape is attached to a glass cloth is preferably used.
As described above, when heat-sealing while pressing the overlapping portion with a heat sealer, the thickness of the overlapping portion can be reduced, the thickness of the overlapping portion can be reduced, and the end surface of the winding end portion is crushed and wound. It can be continued without causing a step on the outer peripheral surface on the start side.

  As described above, according to the forming method of the present invention, it is possible to easily and accurately form a cylindrical filtration membrane whose ears do not protrude from the outer peripheral surface. Therefore, it is possible to prevent the suspended components from accumulating in the ear portion and to prevent stress concentration from occurring at the boundary with the outer peripheral surface from which the ear protrudes. As a result, the cylindrical filtration membrane can be prevented from being damaged, and the durability can be enhanced.

  As a second invention, a laminated porous sheet in which a PTFE porous membrane and a nonwoven fabric are laminated and heat-sealed and integrated is wound once so that the inner surface of the winding end portion is overlapped with the inner surface of the winding start portion. A cylindrical shape that is fixed by heat fusion to form a cylindrical shape, a hollow portion surrounded by the laminated porous sheet is a treated liquid flow path, and the circumferential dimension to be overlapped is 3 to 5 mm. A filtration membrane is provided.

  The cylindrical filtration membrane is suitably used when the circumferential length is 10 mm to 150 mm and the length in the axial direction is 500 mm to 4000 mm.

  The cylindrical filtration membrane of the second invention is preferably formed by the formation method of the first invention, but is not limited to the above method, and the winding start and the winding end are overlapped, and a double-sided adhesive tape or adhesive is used. The step of temporarily fixing with an agent may be omitted and the overlapping portion may be directly fixed.

The tubular filtration membrane of the present invention is composed of a laminated porous sheet in which a PTFE porous membrane and a nonwoven fabric are integrated, and has a higher strength than a filtration membrane made of a single PTFE porous membrane. Also, the PTFE porous membrane itself is extremely excellent in durability, and the suspended matter adhering to the membrane surface can be almost completely decomposed and cleaned using a high concentration oxidizing agent or alkali that could not be used conventionally. In particular, since the strength is increased by laminating with a non-woven fabric, a strong mechanical load can be applied in the air diffusion treatment, and the filtration function can be restored to near the initial state. As described above, the strength of the filtration membrane is increased and the chemical resistance is also excellent. As a result, the lifetime can be greatly extended, and a stable permeated water amount can be obtained over a long period of time. Very useful in high turbidity wastewater treatment.
Therefore, the cylindrical filtration membrane of the present invention having the above-described configuration is suitably used as a filtration membrane element that performs solid-liquid separation treatment by immersing in a liquid to be treated containing a large amount of suspended components, particularly in wastewater containing activated sludge. It is done.

The PTFE porous membrane of the filtration membrane is composed of a stretched PTFE porous membrane, the average pore diameter is 0.01 μm to 5.0 μm, the average maximum length of the fibrous skeleton surrounding the pores is 30 μm or less, and the average film thickness is 200 μm. The following is preferable.
The PTFE porous membrane may be composed of a single expanded PTFE porous membrane, or may be a laminate of PTFE porous membranes having different specifications such as pore diameter.
Since the expanded PTFE porous membrane is manufactured not only by extrusion but also through rolling and a high-magnification stretching process, the film thickness is thin, it has high strength due to advanced molecular orientation, and can exhibit high porosity. Since it is possible to form a fibrous skeleton that is porous and hardly clogged, it is possible to provide a membrane material with low flow resistance and excellent filtration performance.

Therefore, even if many fine holes are provided with an average pore diameter of 0.01 μm to 5.0 μm, a high-performance filtration membrane with a large amount of permeated water can be obtained. The average pore diameter is measured by a palm porometer (model number CFP-1200A) manufactured by PMI.
Furthermore, when the average maximum length of the fibrous skeleton surrounding the pores in the outermost layer of the expanded PTFE porous membrane is 30 μm or less, particularly when wastewater containing activated sludge or wastewater containing fine particles is used as the liquid to be treated. The average maximum length of the fibrous skeleton surrounding the pores is more preferably 5 μm or less. The average maximum length of the fibrous skeleton surrounding the pores in the outermost layer on the membrane surface is the maximum value of the distance connecting the two points on the outer periphery of the pores composed of the resin portion and the fibers connected thereto on the SEM image. Determined by measuring with.
And it is preferable that the average film thickness of the said expanded PTFE porous membrane is 200 micrometers or less.
In addition, although a minimum is not specifically limited, It is preferable that it is 50 micrometers or more. The average film thickness is measured by a dial gauge, and the porosity is measured by the method described in ASTM D792. The porosity is preferably 40% to 90%.

The expanded porous PTFE membrane preferably has a tensile strength defined in JIS K 7113 of 10 N / mm ² or more.
Furthermore, the amount of permeated water does not decrease even when immersed in 3 mass% sulfuric acid, 4 mass% sodium hydroxide aqueous solution, and 10% effective chlorine concentration sodium hypochlorite aqueous solution at a temperature of 50 ° C. for 10 days. It is preferable to have excellent chemical resistance.

The nonwoven fabric laminated and integrated with the PTFE porous membrane is made of a polyolefin-based resin or a polyester-based resin, and has a basis weight of 40 g / m ^{2 to} 120 g / m ² , a thickness of 0.3 mm to 0.9 mm, JIS L 1096A. It is preferable that the burst strength based on 199 kPa to 600 kPa, the puncture strength based on JIS T 8115 is 8N to 24N, and the porosity is 65% to 90%.

Further, as a third invention, a resin-made net support held in a cylindrical shape is disposed on the inner peripheral side of the cylindrical filtration membrane of the second invention,
A cylindrical filtration membrane element is provided in which sealing portions are provided at both ends in the axial direction of the cylindrical filtration membrane and the net support, and a treated liquid outlet is opened at least at one end of the sealing portion.
The inner peripheral surface of the nonwoven fabric of the cylindrical filtration membrane and the outer peripheral surface of the net support may be partially or fully fixed, or the net support is provided along the inner peripheral surface of the cylindrical filtration membrane without fixing. You may place your body.

The cylindrical filtration membrane element of the present invention uses a resin-made net support retained in a cylindrical shape as a support material for the cylindrical filtration membrane. In the net support, the warp and weft crossing made of a fiber net or the like are bent, and the entire net is easily deformed to block the hollow portion. The net support of the present invention does not bend each warp and weft, and does not generate a bend such that the hollow portion is closed as a whole, thereby increasing the support strength of the tubular filtration membrane.
Thus, while increasing the strength of the cylindrical filtration membrane itself and increasing the strength with the net support, the filtration membrane has a strength that does not break while being loaded with a transmembrane differential pressure of 50 kPa or less, and The net support has a strength that does not deform.

The net support is preferably formed as a net by heat-sealing the intersection of an outer wire and an inner wire made of polyolefin resin, polyester resin, or fluorine resin. It is preferable that one or both of the outer wire and the inner wire of the net support are inclined with respect to the central axis of the cylinder, and the hole surrounded by the outer wire and the inner wire has a rhombus shape. The net support each diameter of the outer wire and an inner wire 1 mm to 3 mm, with the magnitude of the hole surrounded by the outer wire and the inner wire is 0.1 mm ² to 10 mm ^2, the length of the diagonal line of the hole Is preferably 7 mm or less, and the net support preferably has a crushing strength with a radial load of 0.5 kg / cm or more.

  In the separation membrane element for filtration of the present invention, the diameter of the filtration membrane and the net support can be set as described above, and the treated liquid channel can be made larger than the hollow portion of the hollow fiber membrane. Even if the resistance with respect to is small and the effective length of the cylindrical filtration membrane is large, the pressure loss is small and the decrease in flow rate can be suppressed. Therefore, it is advantageous for increasing the size of the membrane module. In particular, in the membrane separation activated sludge method, it is considered promising from the viewpoint of space saving to increase the size by deepening the immersion tank, but in that case, it is particularly suitable. In addition, since the ears do not protrude from the cylindrical filtration membrane, it is possible to prevent the suspended components from accumulating in the ears.

  As a fourth invention, there is provided a membrane module for filtration for external pressure filtration or immersion type external pressure suction filtration comprising a plurality of the filtration membrane elements and connecting the filtration membrane elements with a space.

In the membrane module for filtration according to the present invention, for example, the filtration membrane elements are arranged side by side, a common treated liquid water collecting pipe is disposed above the filtration membrane elements, and provided on the upper surface of the juxtaposed separation membrane elements for filtration. A tip of a branch pipe branched from the common treated liquid collecting pipe may be connected to the treated liquid outlet, and the separation membrane element for filtration may be suspended and supported. With this configuration, a large number of filtration membrane elements can be installed, and a large effective membrane area can be secured, so that a large processing capacity can be obtained. Further, it is easy to configure a filtration device in which an air diffuser is installed between the filtration membrane elements, and the membrane surface can be washed uniformly.
The separation membrane elements for filtration do not necessarily need to be arranged in parallel, and any configuration may be used as long as a plurality of separation membrane elements are arranged with a space therebetween.
Since the membrane module for filtration of the present invention is extremely excellent in chemical resistance and mechanical strength, it can be suitably used for a liquid to be treated consisting of waste water containing activated sludge.

  As described above, according to the method for forming a tubular filtration membrane of the present invention, when a porous sheet is used as a tubular shape, the outer peripheral surface of the winding start portion is overlapped with the inner peripheral surface of the winding end portion and heat-sealed. Can be performed easily and accurately. Therefore, there is an advantage that a cylindrical filtration membrane having a small diameter and a large length can be easily produced.

  In addition, since the tubular filtration membrane of the present invention does not protrude the ear from the outer peripheral surface, it is possible to prevent the suspended component from accumulating in the ear portion, and stress concentration occurs in the interface from which the ear portion protrudes, and the filtration membrane Damage can be prevented and the durability of the filtration membrane can be increased.

The filtration membrane of embodiment of this invention is shown, (A) is a perspective view, (B) is the BB sectional drawing of (A), (C) is a principal part expanded sectional view. (A)-(D) are drawings which show the process of 1st Embodiment of the filtration membrane formation method. It is a perspective view of the jig | tool used with the formation method of 2nd Embodiment. (A)-(C) are drawings which show the process of the filtration membrane formation method of 2nd Embodiment. The filtration membrane element using the filtration membrane of this invention is shown, (A) is a perspective view, (B) is a disassembled perspective view, (C) is CC sectional drawing of (A). (A) is a perspective view which shows the filtration module using the said filtration membrane element, (B) is drawing which shows the state set to the said filtration module filtration apparatus. (A) (B) is drawing which shows the problem of a prior art example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 and 2 show a method for forming a cylindrical filtration membrane according to the first embodiment of the present invention.
The cylindrical filtration membrane 1 is obtained by winding a laminated porous sheet 5 obtained by laminating an expanded PTFE porous membrane 3 and a nonwoven fabric 4 and heat-sealing them together to make a sushi roll with the nonwoven fabric 4 as an inner peripheral side. The inner surface of the winding end portion 5b is overlapped and fixed on the outer surface of the winding start portion 5a to form a cylindrical shape.

  The cylindrical filtration membrane 1 has a circumferential length of 10 mm to 150 mm, an overlapped circumferential dimension of 3 mm to 5 mm, and a length of 500 mm to 4000 mm. In the present embodiment, the cylindrical filtration membrane 1 has an outer diameter of 15 mm (circumferential length is 47 mm), a dimension L of the overlapping portion is 5 mm, and a length is 1000 mm.

The expanded PTFE porous membrane 3 constituting the cylindrical filtration membrane 1 has an average pore diameter of 0.01 μm to 5.0 μm, an average maximum length of a fibrous skeleton surrounding the pores of 30 μm or less, and an average film thickness of 200 μm or less. The porosity is 40% to 90%. The expanded porous PTFE membrane 3 has a tensile strength specified in JIS K 7113 of 10 N / mm ² or more, 3 mass% sulfuric acid, 4 mass% sodium hydroxide aqueous solution, effective chlorine concentration 10%. Even when immersed in each of the sodium hypochlorite aqueous solutions at a temperature of 50 ° C. for 10 days, the permeated water amount does not decrease and has excellent chemical resistance that is not damaged.

The nonwoven fabric 4 laminated and integrated on the inner surface (inner peripheral surface in a cylindrical shape) of the expanded porous PTFE membrane 3 is made of a polyolefin resin or a polyester resin. In this embodiment, the nonwoven fabric 4 has chemical resistance and is low in cost. Made of available polypropylene.
The basis weight is 40 g / m 2 to 120 g / m 2, 60 g / m 2 in this embodiment, and the thickness is 0.3 mm to 0.9 mm. The burst strength is 199 kPa to 600 kPa as measured in accordance with JIS L 10096A, and 265 kPa in this embodiment. The puncture strength is 8N to 24N as measured in accordance with JIS T 8115, and is 13N in this embodiment. The porosity of the nonwoven fabric 4 is set to 65% to 90%.

  In the step shown in FIG. 2, the laminated porous sheet 5 is used as the cylindrical filtration membrane 1 shown in FIG. The laminated porous sheet 5 has a rectangular shape having a width X that is a size of the circumferential length of the tubular filtration membrane 1 +5 mm (overlay allowance) and a length Y that is equivalent to the length of the tubular filtration membrane 1.

  First, as shown in FIG. 2 (A), the length of one side of the double-sided pressure-sensitive adhesive tape 10 is 3 mm wide along one end side in the width direction of the outer surface of the PTFE porous membrane 3 of the flat laminated porous sheet 5. Sticks over the entire length of the direction. At that time, it is preferable that the double-sided pressure-sensitive adhesive tape 10 is pulled in and adhered for about 1 mm so as not to protrude from the edge.

Next, as shown in FIG. 2 (B), one end in the width direction is set as the winding start end P1 and the other end is set as the winding end end P2 so that the nonwoven fabric 4 of the laminated porous sheet 5 becomes the inner peripheral surface. Wind once in a roll. Since the double-sided pressure-sensitive adhesive tape 10 is previously adhered to the outer peripheral surface of the winding start portion, when the inner peripheral surface of the winding end portion is overlaid, the double-sided adhesive tape 10 is adhered while peeling the release paper on the surface.
As described above, the space between the overlapped winding start portion and winding end portion is adhered with a double-sided adhesive tape and temporarily held in a cylindrical shape.

  Next, as shown in FIG. 2 (C), the cylindrical shape is formed into a flat bag shape in which the overlapping portion 14 is located at the center of the upper surface, and non-adhesive to the hollow portion of the flat bag from one end opening in the length direction. A shielding strip 12 made of a heat-resistant material is inserted. In this embodiment, the shielding band member 12 is a tape in which a fluororesin adhesive tape is attached to a glass cloth.

  Next, as shown in FIG. 2D, the overlapping portion 14 is heat-sealed while pressing the heat sealer 15 against the overlapping portion 14 from one end to the other end in the length direction of the temporarily holding overlapping portion 14. And fix it. The heat sealer 15 is provided with a heater wire having a width of 5 mm. Since the heat sealer 15 melts while pressing the portion where the double-sided pressure-sensitive adhesive tape 10 is interposed and the end of the winding, the winding end P2 is substantially stepped from the inner peripheral surface. It is fused to the inner peripheral side in a tilted state that does not occur.

  In the above-described process, the laminated porous sheet 5 is wound once in the width direction, the both ends are overlapped in the inner and outer directions, and after temporary holding, heat-sealed and fixed to the tubular shape, and the tubular filtration without the ear shown in FIG. A membrane 1 is created. As described above, when the overlapping portion is temporarily held using the adhesive tape, it is not necessary to heat-seal with the heat sealer while holding the overlapping portion, and attention should be paid to the operation of the heat sealer. Can be fixed easily and accurately.

  Instead of the double-sided adhesive tape 10, both ends in the length direction are partially fixed with an adhesive in a state where the winding end portion is overlapped with the winding start portion. The part may also be partially fixed with an adhesive to temporarily hold the overlapped part. Furthermore, you may adhere | attach the full length of a length direction with an adhesive agent. In this case as well, after being bonded, heat-sealing is performed and fixed.

3 and 4 show a method for forming the tubular filtration membrane 1 of the second embodiment.
In the second embodiment, the double-sided pressure-sensitive adhesive tape uses a jig 20 instead of being held by an adhesive, and in a state where the double-sided adhesive tape is set on the jig 20, the overlapping portion is heat-sealed with a heat sealer and fixed.

  The jig 20 has a length Y equivalent to the length of the cylindrical filtration membrane 1 to be formed, and an upper surface of a strip-shaped substrate 21 having a width S corresponding to ½ of the circumferential length of the cylindrical filtration membrane 1. The abutting portion 22 has a protruding shape. The protruding amount of the abutting portion 22 is a dimension corresponding to the thickness of the laminated porous sheet 1. The abutting portion 22 protrudes from the belt-like substrate 21 at the approximate center in the width direction.

A forming method using the jig 20 is shown in FIG. The laminated porous sheet 5 is obtained by laminating the same PTFE porous membrane 3 and the nonwoven fabric 4 as those in the first embodiment, and heat-sealing and integrating them.
As shown in FIG. 4A, first, one end P <b> 1 in the width direction of the laminated porous sheet 5 is abutted against the abutting portion 22 of the jig 20.
Next, as shown in FIG. 4B, the jig 20 is wound from one end 20a in the width direction to the lower surface 20b and from the other end 20c to the upper surface 20d. On the upper surface side, the upper surface of the abutting portion 21 is passed and overlapped with the upper surface of the one end 20a. Since the laminated porous sheet 5 has a set width and the width of the jig 20 corresponds to a fixed width, the overlapped portion 14 has a set overlap dimension (5 mm).

  Next, as shown in FIG. 3C, the rubber band 25 is wound around both ends of the jig in the length direction. The rubber band 25 is strongly wound so as to be pushed down so that the upper surface of the abutting portion 22 and the overlapping portion of the winding start portion and the winding end portion rise above the other portions. Therefore, the portion where the winding start end is abutted against the abutting portion 22 is positioned, and the overlapped portion is also positioned and held since the winding end portion on the upper surface side does not return beyond the abutting portion 22. Can be temporarily held. Further, when the cylindrical filtration membrane to be created is long, the rubber band 25 is wound around and held at an intermediate portion in the length direction.

  In the next step, the overlapping portion is heat-sealed with a heat sealer as in the first embodiment. In this heat-sealing step, the wound rubber band 25 may be sequentially removed immediately before being heat-sealed.

FIG. 5 shows a filtration membrane element 30 using the cylindrical filtration membrane 1 formed by the above method.
A cylindrical net support 6 is disposed on the inner periphery of the cylindrical filtration membrane 1, and the upper and lower surfaces of the cylindrical filtration membrane 1 and the cylindrical net support 6 are closed with sealing materials 7 and 8. A treated liquid outlet 9 is provided at the center of the upper sealing material 7, and the treated liquid is taken out from the treated liquid channel 31 formed of a hollow portion surrounded by the net support 6 through the outlet 9. . The sealing materials 7 and 8 on the upper and lower surfaces are heat-sealed to the upper and lower surfaces of the cylindrical filtration membrane 1 and the net support 6 which are circular plates made of fluororesin such as PTA.

The net support 6 disposed on the inner periphery of the cylindrical filtration membrane 1 and supporting the cylindrical filtration membrane 1 is made of a polyolefin resin, a polyester resin, or a fluorine resin, and in this embodiment is chemically resistant. And polypropylene which is available at low cost. Rather than knitting these inner and outer wire rods into a cross shape from the polypropylene as the outer wire rod and the inner wire rod, the outer wire rod is crossed on the outer surface of the inner wire rod, and the intersection is heat-sealed. It is on the net.
The outer and inner wires each have a wire diameter of 1 mm to 3 mm. Preferably, the inner wire diameter 6 b is 1.2 mm to 1.6 mm, and the outer wire diameter 6 a is 1.3 mm to 1.7 mm. In the present embodiment, the outer wire and the inner wire are inclined at ± 45 degrees with respect to the axis L when the cylindrical wire is formed. Therefore, the hole surrounded by the outer wire and the inner wire is a rhombus. The size is 0.1 mm ² to 10 mm ² hole, preferably a 0.1 mm ² to 4 mm ^2, the length of a diagonal line ls hole 6h 7 mm or less, preferably a 3 mm to 4 mm, 3.8 mm in the present embodiment It is said.

  The net support 6 formed into a cylindrical shape is inserted into the inner periphery of the cylindrical filtration membrane 1, and the outer peripheral surface of the net support 6 is disposed along the inner peripheral surface of the tubular filtration membrane 1. Although not fixed in this embodiment, the outer peripheral surface of the net support 6 and the inner peripheral surface made of the nonwoven fabric 4 of the filtration membrane 2 may be fixed partially or entirely. The fixing can be performed using a heat welding apparatus.

As shown in FIG. 6A, a plurality of filtration membrane elements 1 having the above-described configuration are used as filtration membrane modules 50 in parallel.
The membrane module for filtration 50 is used for submersion type external pressure suction filtration. The filtration membrane elements 1 are arranged in parallel, and branch pipes 52 branched from a common treated liquid water collection pipe 51 arranged above are provided. The filtration membrane element 1 is suspended in connection with the treated liquid outlet 9.

  As shown in FIG. 6B, the membrane module for filtration 50 is set in a tank 61 of a filtration device 60. A liquid 70 to be treated containing suspended components is introduced into the tank 61. The liquid 70 to be treated is solid-liquid separated by driving the suction pump 63 connected to the water collecting pipe 51 to pass through the cylindrical filtration membrane 2 of each filtration membrane element 1 and connected to the treated liquid outlet 9. The liquid is sucked from the branch pipe 52 to the common processed liquid take-out pipe 51 and collected as a processed liquid.

  Air bubbling is performed in order to peel and remove suspended components deposited on the surface of the filtration membrane element 1. More specifically, the blower 65 is operated to introduce pressurized air into the cleaning pipe 66, and bubbles 67 generated by injecting pressurized air from a gas injection hole (not shown) of the cleaning pipe 66 are filtered. While being brought into contact with the outer surface of the filter membrane 2 of the element 1, it is lifted in the axial direction, and the suspended components adhering and depositing on the surface of the filter membrane element 1 are strongly peeled and removed. Thereby, membrane filtration can be continued stably. Air bubbling may be performed constantly or periodically.

  As described above, in the present invention, the cylindrical filtration membrane 1 having a diameter larger than that of the hollow fiber membrane is used, so that it is possible to suppress the pressure loss due to the movement of the treated liquid inside the cylindrical filtration membrane 1. Moreover, since the ear | edge does not protrude from the outer peripheral surface of this cylindrical filtration membrane 1, it can prevent that a suspended component accumulates in an ear | edge part, and can prevent that the flow of to-be-processed liquid stagnates in an ear | edge part. Furthermore, the cylindrical filtration membrane 1 increases the strength as a laminated body of the expanded PTFE porous membrane 3 and the nonwoven fabric 4, and the net support 6 that supports the cylindrical filtration membrane 1 on the inner peripheral side does not bend easily and has a cylindrical shape. Therefore, the processed liquid flow path can be secured since the mechanical strength is increased and the mechanical strength is increased, and even when a large transmembrane pressure difference is applied, the hollow portion is not deformed and collapsed.

DESCRIPTION OF SYMBOLS 1 Cylindrical filtration membrane 3 Stretched PTFE porous membrane 4 Nonwoven fabric 5 Laminated porous sheet 6 Net support 50 Filter membrane module

Claims (7)

A laminated porous sheet obtained by laminating and integrating a PTFE porous membrane and a nonwoven fabric is wound around with a sushi roll, and the inner surface of the winding end portion is overlapped with the inner surface of the winding start portion,
After temporarily holding the cylindrical shape by fixing with a double-sided adhesive tape or an adhesive between the overlapping,
A method of forming a cylindrical filtration membrane in which the temporarily held overlapped portion is fixed by thermal fusion. Provided with a jig having an abutment projecting on the upper surface of a belt-like substrate having a length equivalent to the length of the cylindrical filtration membrane to be formed and having a width corresponding to ½ of the circumferential length of the cylindrical filtration membrane ,
One end in the width direction of the laminated porous sheet obtained by laminating and fixing the PTFE porous membrane and the nonwoven fabric is abutted against the abutting portion projecting from the upper surface of the jig, and the other end is passed through the lower surface side from one end of the jig. Wrapping more on the upper surface side, passing the upper surface of the abutting portion on the upper surface side and overlapping the upper surface of the one end,
In order to maintain the above state, at least both ends in the length direction are wrapped with a rubber band and held temporarily,
A method of forming a cylindrical filtration membrane in which the temporarily held overlapped portion is fixed by thermal fusion. In the heat-sealing step, the cylindrical shape is made into a flat bag shape, and a shielding band made of a non-adhesive heat-resistant material is inserted into the hollow portion of the bag,
Pressing the overlapping part with a heat sealer and heat-sealing,
The method for forming a tubular filtration membrane according to claim 1 or 2, wherein the thickness of the overlapped portion is reduced by the thermal fusion and is inclined so as to be continuous with the outer peripheral surface of the winding end without any step.   A laminated porous sheet obtained by laminating and fixing a PTFE porous membrane and a nonwoven fabric is wound around by sushi roll, and the inner surface of the winding end portion is overlaid on the inner surface of the winding start portion and fixed by heat fusion. A cylindrical filtration membrane having a cylindrical shape, wherein a hollow portion surrounded by the laminated porous sheet is a treated liquid flow path, and the circumferential dimension to be overlapped is 3 to 5 mm.   The cylindrical filtration membrane according to claim 4, wherein the cylindrical filtration membrane has a peripheral length of 10 mm to 150 mm and a length of 500 mm to 4000 mm. A net support body disposed on the inner peripheral side of the tubular filtration membrane according to claim 4 or 5,
The filtration membrane element which provided the sealing part in the both ends of the axial direction of the said cylindrical filtration membrane and a net support body, and opened the processed liquid outlet in the sealing part of at least one end.   A membrane module for filtration for external pressure filtration or submerged external pressure suction filtration comprising a plurality of filtration membrane elements according to claim 6 and connecting the filtration membrane elements with a space therebetween.

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