JP2005279579A - Manufacturing method of flat membrane element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a flat membrane element capable of performing efficient laser welding for which a welding area is minimized and of manufacturing the flat membrane element with the performance of being equal to or lower than an SS detection limit and not detecting a colon bacillus. <P>SOLUTION: In a laser irradiation device 26, after piling up a membrane sheet 22 and a support plate 24, in the state that a part of an intermediate material 28 applied to the joining part of the support plate 24 is infiltrated in a part of the membrane sheet 22, a laser beam 26a is emitted from the above of the membrane sheet 22. The intermediate material 28 which absorbs the laser beam 26a generates heat and melts the joining part of the support plate 24 and the joining part of the membrane sheet 22 in which the intermediate material 28 is infiltrated. The melted resins of the membrane sheet and the support plate are mixed and vertically infiltrated to the skin layer 22a of the membrane sheet 22. When irradiation with the laser beam 26a is stopped, the melted resins are hardened in a mixed state. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a flat membrane element, and in particular, a flat membrane element for producing filtered water that is less than the SS detection limit and that does not detect Escherichia coli can be obtained by filtering water to be treated in an immersed state. The present invention relates to a method for manufacturing a membrane element.

  Conventionally, flat membrane elements that are immersed in the liquid to be treated in the vertical direction are formed by joining the peripheral edge of the membrane sheet onto a support plate, and filtered water is filtered by filtering the water to be treated into the membrane sheet. Can be obtained. The filtration performance of a flat membrane element used for wastewater treatment requires that the SS concentration is 0.4 mg / L or less (hereinafter referred to as SS detection limit or less), and filtered water that is not detected by E. coli is required. Is done. In addition to the filtration performance of the membrane sheet itself, the filtration performance of the flat membrane element is greatly influenced by the adhesion at the joint between the membrane sheet and the support plate.

  Conventionally, in the production of a flat membrane element, as a method for joining a membrane sheet to a support plate, as disclosed in Patent Document 1, a method using an adhesive is often employed. Thereby, a membrane sheet can be joined to a support plate cheaply and easily.

Further, as disclosed in Patent Document 2, a method is also proposed in which the interface between the membrane sheet and the support plate is melted and welded by performing ultrasonic irradiation or local heating on each joint. . Thereby, a membrane sheet can be joined to a support plate in a short time.
JP-A-10-128080 Japanese Patent Laid-Open No. 7-24271

  However, in the method using an adhesive as in Patent Document 1, since the membrane sheet is made of a porous material, the adhesive penetrates the membrane sheet over a wider area than the adhesive surface, and the flat membrane element Is soaked in water, the adhesive is likely to deteriorate. For this reason, the bonding with the adhesive has a problem that the area of the membrane sheet subjected to the filtration treatment is reduced and the bonded portion is easily peeled off.

  In addition, as in Patent Document 2, in the welding method using local heating or ultrasonic waves, the film sheet other than the part to be welded is easily damaged, and the film sheet and the support plate are different in structure and density, and thus stable. There was a problem that it was difficult to join.

  In order to cope with this problem, the applicant superimposes a laser-permeable film sheet and a laser-absorbing support plate, and irradiates the film from the film sheet side, thereby applying the film sheet to the support plate. Laser welding methods for welding have been studied. However, since it is difficult to infiltrate the resin melted by laser irradiation to the upper surface of the film sheet from the structure of the film sheet, there is a possibility that leakage occurs at the welding location. Therefore, since it is necessary to repeatedly perform laser irradiation on the welded part in order to prevent leaks, the labor and time required for the welding operation are increased, and the area required for welding is increased and the welded part is deteriorated due to heat. Problems arise.

  The present invention has been made in view of such circumstances, and is capable of performing efficient laser welding while minimizing the area to be welded, as well as a flat surface having SS detection limit or less and E. coli non-detection performance. It aims at providing the manufacturing method of the flat membrane element which can manufacture a membrane element.

  In order to achieve the above-mentioned object, the invention according to claim 1 is configured such that a membrane sheet for performing solid-liquid separation and a support plate for supporting the membrane sheet are overlapped with each other, and a laser is irradiated to each joint portion. In the flat membrane element manufacturing method for manufacturing the flat membrane element by welding the membrane sheet on the support plate, a material having laser absorption between the joint portion of the membrane sheet and the joint portion of the support plate The laser irradiation is performed on the joint portion with an intermediate material formed of

  In the present invention, an intermediate material made of a material having laser absorptivity is interposed between the joint portion of the sheet and the joint portion of the support plate, and the laser irradiation is performed on the joint portion. As a result, the intermediate material generates heat and enters a molten state when it hits the laser, enters the porous portion of the porous membrane sheet, and the porous portion is embedded with the intermediate material. Further, the interface between the membrane sheet and the support plate, which are members having different melting temperatures, is efficiently melted by the heat of the generated intermediate material, and penetrates into the membrane sheet in a state of being intertwined with and fused with the melted intermediate material. Therefore, after cooling, the bonding between the membrane sheet and the support plate becomes strong, the adhesion and bonding strength can be greatly increased, and the occurrence of leakage from the lateral direction can be prevented. Further, since the laser beam is excellent in straightness and only the irradiated intermediate material can be locally heated, the thermal influence on the film sheet can be minimized.

  The invention according to claim 2 is characterized in that the intermediate material according to claim 1 is interposed in a state of being applied to a joint portion of the membrane sheet or the support plate. Thereby, a welding location can be formed in a free shape. Moreover, since the applied intermediate material can be permeated into the film sheet, it can be melted by generating heat by laser irradiation from the inner surface of the film sheet. Thereby, laser welding can be performed efficiently and adhesion between the membrane sheet and the support plate can be improved.

  The invention according to claim 3 is characterized in that the intermediate material according to claim 1 has a sheet shape. Thereby, since an intermediate material can be stably interposed in the welding part of a membrane sheet and a support plate, stable laser welding can be performed. In addition, when the intermediate material is liquid, smearing is likely to occur, and the intermediate material may not be fully effective. However, the intermediate material is formed into a sheet shape, and the joint portion or support plate of the membrane sheet is formed in advance. The effect of the intermediate material can be further exerted by sticking to the joint portion.

  As described above, according to the flat membrane element according to the present invention, when the membrane sheet and the support plate are joined by laser welding, an intermediate material having a laser absorption property is interposed between the membrane sheet and the support plate. Therefore, the film sheet and the support plate, which are members having different melting temperatures, can be welded in a strong and stable state.

  Hereinafter, preferred embodiments of a method for producing a flat membrane element according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing a flat membrane element manufacturing line 10 which is an embodiment suitably using the flat membrane element manufacturing method of the present invention. FIG. 2 is a sectional view for explaining laser welding at the time of producing a flat membrane element and explaining the configuration of the flat membrane element and the intermediate material.

  As shown in FIGS. 1 and 2, the flat membrane element production line 10 produces a membrane sheet production step 12 for producing a membrane sheet 22, a support plate production step 14 for producing a support plate 24, and an intermediate material 28. Intermediate material manufacturing process 16, coating process 18 for applying intermediate material 28 to support plate 24, and laser welding process for irradiating laser with film sheet 22 and support plate 24 superimposed with intermediate material 28 interposed. 20.

  In the membrane sheet manufacturing process 12, as shown in FIG. 2, the membrane sheet 22 is formed by cutting a sheet composed of a skin layer 22a, an impregnation layer 22b, and a support layer 22c in order from the top into a predetermined size. Manufactured. The skin layer 22a is made of a material having high solid-liquid separation ability and high durability and strength. For example, an organic polymer such as polyolefin is used. The support layer 22c is preferably made of a material having a strength capable of supporting the entire membrane sheet 22, and for example, polyethylene or the like is used. The impregnation layer 22b is formed in a state in which the material constituting the skin layer 22a enters the support layer 22c. The film sheet 22 has been described as being composed of three layers of the skin layer 22a, the impregnation layer 22b, and the support layer 22c. However, the film sheet 22 is not particularly limited, and includes two layers of the skin layer 22a and the impregnation layer 22b. You may use what was comprised. Moreover, it is preferable that the material used for the membrane sheet 22 has laser transparency.

  In the support plate manufacturing step 14, the support plate 24 is manufactured by molding a rectangular plate material that easily collects filtered water permeated from the membrane sheet 22 over the entire surface. The material used for the support plate 24 is preferably a lightweight and high-strength thermoplastic resin, such as ABS resin. Therefore, as a manufacturing method of the support plate 24, it is preferable to adopt an injection molding method with little variation in product accuracy and excellent productivity.

  In the intermediate material manufacturing process 16, an intermediate material 28 that is excellent in laser absorbability and generates heat and melts by absorbing the laser is manufactured. As the intermediate material 28, for example, a resin containing a laser-absorbing pigment adjusted to a predetermined viscosity with a solvent is used. As the resin to be added, for example, a polycarbonate resin, an ABS resin, polyethylene terephthalate (PET), polyethylene (PE), polypropylene, or the like is used. Further, the pigment to be added is preferably a substance having high absorbability, and for example, carbon black is used. The amount of the solvent added is adjusted so that the viscosity of the intermediate material 28 can be applied to the support plate 24 and can penetrate the membrane sheet 22 in the vertical direction. Moreover, as a solvent, it is preferable that it is a substance which does not change the membrane sheet 22, for example, a water-soluble solvent is used. In addition, although what melt | dissolved resin in the solvent was mentioned as an example as the intermediate material 28, it is not specifically limited. A material obtained by dissolving a laser-absorbing pigment directly in a solvent such as a water-soluble solvent may be used as the intermediate material 28.

  In the coating step 18, the intermediate material 28 is coated on the surface of the support plate 24. The intermediate material is applied by, for example, immersing a convex plate having the same range as the joint portion in the intermediate material 28 and pressing the convex plate against the joint portion of the support plate 24. The method is not particularly limited.

  In the laser welding process 20, the manufactured film sheet 22 and the support plate 24 are overlapped, and the applied intermediate material 28 is irradiated with laser light 26 a from above the film sheet 22. The output of the laser beam 26a is preferably an output that passes through the membrane sheet 22 and is absorbed by the support plate 24. For example, in the case of a laser irradiation device 26 for semiconductors, the output is set to 25W. Further, the irradiation speed is preferably a speed that allows the intermediate material 28 to efficiently absorb the laser light 26a and does not affect other portions than the irradiated portion, and is set to 30 mm / s, for example. If laser irradiation is performed while traveling, laser irradiation can be efficiently performed in a short space and in a short time.

  Next, the operation of the flat membrane element manufacturing method of the present invention will be described using the flat membrane element manufacturing line 10 configured as described above.

  The laser welding method has characteristics that it is possible to perform welding with high strength and adhesiveness over a relatively small area, and to reduce melting and deformation other than at the welding location. Therefore, when the flat membrane element 20 is manufactured, when the membrane sheet 22 is joined to the support plate 24, the joining area and the adhesiveness are excellent while minimizing the area of the joining portion, and damage in the joining process. Therefore, it can be said that the laser welding method is an appropriate method.

  However, since the membrane sheet 22 has water permeability, most of the membrane sheet 22 is made of low-density porous resin, while the support plate 24 is made of high-density resin because of its high strength. . Laser welding is performed when a resin having laser absorptivity absorbs the laser beam 26a and generates heat, so it is difficult to firmly weld resins having extremely different structures and densities.

  Therefore, in the present invention, the intermediate portion 28 made of a material having laser absorbability is interposed between the joint portion of the membrane sheet 22 and the joint portion of the support plate 24, and laser irradiation is performed on the joint portion. I did it.

  2A shows a state in which the film sheet 22 is superposed on the support plate 24 and the laser beam 26a is irradiated without the intermediate material 28, and FIG. 2B shows the film sheet 22, the support plate 24, and the like. A state in which the laser beam 26a is irradiated with the intermediate member 28 interposed therebetween is shown.

  As shown in FIG. 2A, in the laser welding step 20 of FIG. 1, after the film sheet 22 and the support plate 24 are overlapped, the laser beam 26a is irradiated from above the film sheet 22 by the laser irradiation device 26. . The irradiated laser light 26a passes through the film sheet 22 having laser permeability and is absorbed on the interface of the support plate 24 having laser absorption.

  At this time, the support layer 22c of the membrane sheet 22 can be melted by the heat of the resin melted on the interface of the support plate 24, but the porous impregnation layer 22b disperses the heat of the melted resin. In addition, the impregnation layer 22b cannot be completely melted, and it is difficult to penetrate the melted resin into the impregnation layer 22b and reach the skin layer 22a.

  The membrane sheet 22 and the support plate 24 are cured by mixing the molten resin on the interface of the support plate 24 with the molten support layer 22c of the membrane sheet 22 by laser welding. The skin layer 22a and the impregnated layer 22b constituting the structure are fixed in an extremely unstable state due to their structures, and the lateral direction of the impregnated layer 22b is not shielded at the location where the membrane sheet 22 is welded. For this reason, when a commercialized flat membrane element is immersed and subjected to suction filtration, there is a possibility that a leak may occur from the lateral direction at the welding position of the membrane sheet 22.

  In the present invention, as shown in FIG. 1, the intermediate material is manufactured in the intermediate material manufacturing process 16, and the intermediate material 28 is applied to the surface of the support plate 24 in the application process 18. For this reason, in the laser welding step 20 of FIG. 1, as shown in FIG. 2B, the laser beam 26a is irradiated in a state where the intermediate material 28 applied to the support plate 24 has penetrated into a part of the film sheet 22. Is done. When the intermediate material 28 absorbs the laser beam 26a, the interface of the support plate 24 that generates heat and comes into contact with the intermediate material 28 and the portion where the intermediate material 28 penetrates into the film sheet 22 are melted and mixed. The molten and mixed resin penetrates vertically to the skin layer 22a of the membrane sheet 22, so that the porous portion of the porous membrane sheet 22 is filled with the penetrated resin. Thereby, the membrane sheet 22 can be stably and reliably welded to the surface of the support plate 24 within the range of the joint portion of the intermediate member 28, and leakage from the lateral direction at the joint portion can be prevented.

  The membrane sheet 22 and the support plate 24 are made of materials having different melting points. Therefore, if a material that generates heat to a temperature at which the membrane sheet 22 and the support plate 24 are melted is used as the intermediate material 28, the interface between the membrane sheet 22 and the support plate 24 can be efficiently melted by laser irradiation. 22 can be firmly welded to the support plate 24 at each joint.

  Furthermore, if the intermediate material 28 is used as a laser absorber, it is not necessary to provide the film sheet 20 or the support plate 24 with laser absorbability in advance. Therefore, when the membrane sheet 22 or the support plate 24 is manufactured, it is not necessary to add a laser-absorbing pigment or the like. Thereby, the time, material cost, and equipment cost which the membrane sheet manufacturing process 12 and the support plate manufacturing process 14 require can be reduced significantly.

  Further, in the membrane sheet 22 or the support plate 24, the addition amount of a pigment or the like having a laser absorptivity is limited in terms of function and strength in the flat membrane element after the product. However, since the intermediate material 28 is used in the present invention, such a problem does not occur. For this reason, the pigment etc. which have laser absorptivity can be added to the intermediate material 28 to the maximum extent. Thereby, laser welding can be performed efficiently and the total amount of pigments and the like used in the flat membrane element can be reduced.

  In the flat membrane element manufacturing line 10 described above, the number, shape, material, and the like of each member and device are not particularly limited.

  In the flat membrane element manufacturing line 10, an application process for applying the viscous intermediate material 28 to the support plate 24 is provided, but it is not particularly limited. The intermediate material 28 may be applied to the film sheet 22. In addition, when a sheet shape is adopted as the intermediate material 28, the intermediate material 28 can be stably interposed between the membrane sheet 22 and the support plate 24, so that stable laser welding can be performed. Further, in the support plate manufacturing step 14, if the support plate 24 in which the bead of the same material as the intermediate material 28 is provided at the joint portion of the support plate 24 is manufactured, the intermediate between the membrane sheet 22 and the support plate 24. The step of interposing the material 28 can be omitted.

  Further, in the laser welding step 20, if laser irradiation is performed while pressing the upper surface of the film sheet 22 at a predetermined pressure, the laser welding is performed in a state where the impregnated layer of the film sheet 22 is compressed. The membrane sheet 22 can be stably welded to the support plate 24.

  Furthermore, even when manufacturing the flat membrane element 20 in which the spacer comprised by the nonwoven fabric which has water permeability between the membrane sheet 22 and the support plate 24 is manufactured, the manufacturing method of the flat membrane element of this invention is used suitably. be able to. Thereby, the flat membrane element which can prevent the close_contact | adherence with the membrane sheet 22 and the support plate 24 at the time of a filtration process, and can form the flow path through which filtered water flows efficiently can be manufactured.

  The flat membrane element 20 manufactured in the flat membrane element manufacturing line 10 is not particularly limited with respect to the filtration method. When manufacturing a flat membrane element that filters by suctioning the support plate 24 with a suction pump, a flat membrane element that performs suction filtration in a siphon type, or a flat membrane element that pressurizes and filters the membrane surface of the flat membrane element by gravity Moreover, the manufacturing method of the flat membrane element of this invention can be used suitably.

The block diagram which showed the flat membrane element manufacturing line which used the manufacturing method of the flat membrane element of this invention suitably Sectional view showing laser welding of membrane sheet and support with and without intermediate material

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Flat membrane element manufacturing line, 12 ... Membrane sheet manufacturing process, 14 ... Support plate manufacturing process, 16 ... Intermediate material manufacturing process, 18 ... Coating process, 20 ... Laser welding process, 22 ... Membrane sheet, 22a ... Skin layer, 22b ... impregnation layer, 22c ... support layer, 24 ... support plate, 26 ... laser irradiation device, 26a ... laser light, 28 ... intermediate material

Claims (3)

A membrane element that performs solid-liquid separation and a support plate that supports the membrane sheet are overlapped, and a laser is applied to each joint portion to weld the membrane sheet onto the support plate, thereby forming a flat membrane element. In the method for producing a flat membrane element for producing
The intermediate portion made of a material having a laser absorptivity is interposed between the joint portion of the film sheet and the joint portion of the support plate, and the laser irradiation is performed on the joint portion. Manufacturing method of flat membrane element.   The method for manufacturing a flat membrane element according to claim 1, wherein the intermediate material is interposed in a state of being applied to a joint portion of the membrane sheet or the support plate.   The method for manufacturing a flat membrane element according to claim 1, wherein the intermediate material has a sheet shape.

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