Spiral membrane element

Abstract

To provide a spiral membrane element that can improve reliability of a sealing structure around the inner peripheral end of a separation membrane.SOLUTION: A spiral membrane element comprises: a hollow central tube 5; wound bodies wound around the central tube 5 and each including a separation membrane 1 bent at an inner peripheral end so that supply-side surfaces face each other and a supply-side flow path material 2 interposed between the surfaces of the separation membrane 1; and sealing portions 13 that each prevent mixing of a supply-side flow path and a permeation-side flow path. The supply-side flow path material 2 has a thickness adjusting portion 2a that is thinner, at least at the inner peripheral end, than at a center.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a spiral membrane element (hereinafter, may be abbreviated as "membrane element") including a separation membrane bent at an inner peripheral side end and a supply side channel member interposed between the separation membranes.

Background Art

[0002] Conventional spiral membrane elements generally include, for example, as shown in FIG. 1, a plurality of membrane leaves L in which a permeate side channel member 3 is interposed between opposing separation membranes 1, a supply side channel member 2 interposed between the membrane leaves L, a perforated central tube 5 around which the membrane leaves L and the supply side channel member 2 are wound, and sealing portions 11, 12, 13 for preventing mixing of the supply side channel and the permeate side channel.

[0003] Such a membrane element is manufactured, for example, as shown in FIGS. 2A to 2B, by stacking a supply side channel member 2 and a permeate side channel member 3 while bending the separation membrane 1 to face the supply side surface, and preparing a separation membrane unit U in which adhesives 4, 6 for forming both end sealing portions 11 and an outer peripheral side sealing portion 12 are applied to both end portions in the axial direction A1 of the permeate side channel member 3 and the outer peripheral side end portion of winding. Then, as shown in FIG. 2C, after stacking the separation membrane units U, the central tube 5 is rotated in the direction of the arrow to wind the plurality of separation membrane units U around the central tube 5.

[0004] Further, as described in Patent Document 1, when bending the separation membrane 1, for the purpose of protecting the bent portion, a protective tape may be attached to the supply side surface of the separation membrane 1 along the inner peripheral side end portion.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, as shown in Figure 6, when winding the laminate of the separation membrane unit U around the central tube 5, the bending thickness (e.g., radius of curvature) of the inner circumferential end of the separation membrane 1 increases depending on the thickness of the supply-side flow channel material 2, and this tends to create a triangular step S. As a result, gaps tend to form in the central sealing portion 13 around the central tube 5, which is formed by the adhesive applied to the permeate-side flow channel material 3, raising concerns that the reliability of the sealing structure around the inner circumferential end of the separation membrane 1 will decrease. In particular, when protective tape or the like is provided on the inner circumferential end of the supply side of the separation membrane 1, the bending thickness of the inner circumferential end of the separation membrane 1 increases further due to the protective tape or the like, making the reliability of the sealing structure as described above more likely to become a problem.

[0007] Therefore, the object of the present invention is to provide a spiral membrane element that can improve the reliability of the sealing structure around the inner circumferential end of the separation membrane. [Means for solving the problem]

[0008] The above objective can be achieved by the present invention as described below.

[0009] In other words, the spiral membrane element of the present invention comprises a perforated central tube, a wound body including a separation membrane wound around the central tube and bent at its inner circumferential end to face the supply side, and a supply-side flow channel material interposed between the separation membrane, and a sealing portion for preventing mixing of the supply-side flow channel and the permeate-side flow channel, wherein the supply-side flow channel material has a thickness adjustment portion at least at its inner circumferential end that is thinner than the central portion.

[0010] According to the spiral membrane element of the present invention, the thickness adjustment portion of the supply-side flow channel material, which is thinner, is interposed at the inner circumferential end where the separation membrane bends. This reduces the bending thickness (e.g., radius of curvature) of the inner circumferential end of the separation membrane, thereby reducing the step difference at the inner circumferential ends of the multiple separation membranes arranged around the central tube, and improving the reliability of the sealing structure around the inner circumferential ends. Furthermore, by interposing the thickness adjustment portion of the supply-side flow channel material at the inner circumferential end where the separation membrane bends, the tip of the thickness adjustment portion can more easily and stably enter the inner circumferential end where the separation membrane bends, compared to the case where a supply-side flow channel material of constant thickness is interposed. As a result, the tip of the supply-side flow channel material is more easily positioned uniformly, reducing variations in the sealing structure and improving the reliability of the sealing structure.

[0011] In the above configuration, it is preferable that the thickness adjustment portion has a shape in which the thickness decreases towards the tip. This configuration further reduces the bending thickness (e.g., radius of curvature) of the inner circumferential end of the separation membrane, thereby reducing the step difference at the inner circumferential ends of the multiple separation membranes arranged around the central tube, and further improving the reliability of the sealing structure around the inner circumferential ends.

[0012] Furthermore, it is preferable that the supply-side flow channel material has the thickness adjustment portion at both the inner and outer circumferential ends. By providing a thickness adjustment portion with a smaller thickness at the outer circumferential end, the effective membrane area of ​​the separation membrane packed into the spiral-type membrane element having a constant outer diameter can be increased. In this case, since the area near the outer circumferential end of the supply-side flow channel material does not contribute much to the separation function, providing a thickness adjustment portion with a smaller thickness has little disadvantage. In addition, the step difference on the outer surface of the wound body can also be reduced.

[0013] Furthermore, in any of the above cases, it is preferable to provide a protective layer along the inner circumferential end of the supply side of the separation membrane. Providing a protective layer prevents damage to the inner circumferential end of the separation membrane and maintains the sealing structure well. However, the protective layer tends to increase the bending thickness (e.g., radius of curvature) of the inner circumferential end of the separation membrane. By providing a thickness adjustment part as in the present invention, the bending thickness can be reduced, further improving the reliability of the sealing structure.

[0014] In the above case, it is preferable that the width of the thickness adjustment portion provided at the inner circumferential end is 0.2 to 2 times the length of half the width of the protective layer. When the width of the thickness adjustment portion is in this ratio, it is possible to improve the reliability of the sealing structure around the inner circumferential end of the separation membrane while sufficiently maintaining the separation function of the separation membrane. [Effects of the Invention]

[0015] According to the present invention, a spiral-type membrane element can be provided that can improve the reliability of the sealing structure around the inner peripheral end of the separation membrane. [Brief explanation of the drawing]

[0016] [Figure 1] This is a partially cutaway perspective view showing an example of a wound body in which membrane leaves and supply channel material are wound around a central tube. [Figure 2A] This is a plan view showing an example of a separation membrane unit used in the spiral membrane element of the present invention. [Figure 2B] This is a front view showing an example of a separation membrane unit used in the spiral membrane element of the present invention. [Figure 2C] This is a front view showing an example of the state before the separation membrane units used in the spiral membrane element of the present invention are stacked and wound. [Figure 3] This is a front cross-sectional view showing an example of the main part of the spiral-type membrane element of the present invention. [Figure 4A] This is a front cross-sectional view showing an example of a supply-side flow channel material that can be used in the present invention. [Figure 4B] It is a front view cross-sectional view showing an example of a supply-side channel member that can be used in the present invention. [Figure 4C] It is a front view cross-sectional view showing an example of a supply-side channel member that can be used in the present invention. [Figure 4D] It is a front view cross-sectional view showing an example of a supply-side channel member that can be used in the present invention. [Figure 5] It is a photograph showing an example of a thickness adjustment part of a supply-side channel member obtained by changing the conditions of hot pressing. [Figure 6] It is a front view cross-sectional view showing an example of a main part of a conventional spiral type membrane element.

Mode for Carrying Out the Invention

[0017] (Spiral type membrane element) The spiral type membrane element of the present invention includes, for example, as shown in FIG. 1, a perforated central tube 5, a separation membrane 1 wound around the central tube 5 and bent at the inner peripheral side end to oppose the supply side surface, and a supply-side channel member 2 interposed between the separation membranes 1. It also includes a winding body R and sealing parts 11, 12, 13 for preventing mixing of the supply-side channel and the permeation-side channel.

[0018] The spiral type membrane element of the present invention, for example, as shown in FIG. 3, has a thickness adjustment part 2a in which the supply-side channel member 2 has a smaller thickness at least at the inner peripheral side end compared to the central part. Regarding other points than the supply-side channel member 2, any of the configurations of the conventional spiral type membrane element can be adopted.

[0019] In FIGS. 1 and 3, an example is shown in which a permeation-side channel member 3 is interposed between the opposing separation membranes 1 in the membrane leaf L. However, it is also possible to form the permeation-side channel on the permeation-side surface of the separation membrane 1 by providing irregularities or grooves etc. In that case, it is possible to omit the permeation-side channel member 3.

[0020] In this embodiment, an example is shown in which the sealing portion includes both end sealing portions 11 and the outer peripheral sealing portion 12. Of the sealing portion, the both end sealing portions 11 are formed by sealing the two end surfaces on both sides of the membrane leaf L in the axial direction A1 with adhesive. The outer peripheral sealing portion 12 is formed by sealing the end surface of the outer peripheral tip of the membrane leaf L with adhesive.

[0021] Furthermore, in the present invention, as shown in Figure 1, it is preferable to have a central sealing portion 13 in which both sides of the axial direction A1 of the base end of the central tube 5 and the membrane leaf L are sealed with adhesive. The membrane element of this embodiment has a wound body R in which the membrane leaf L and the supply side flow channel material 2 are wound around the central tube 5 via such a central sealing portion 13.

[0022] A membrane element having the wound body R as described above can be manufactured, for example, by the process shown in Figures 2A to 2C. Figure 2A is a plan view of the separation membrane unit U, Figure 2B is a front view of the separation membrane unit U, and Figure 2C is a front view showing the state before the separation membrane units U are stacked and wound.

[0023] First, as shown in Figures 2A and 2B, the separation membrane 1 is folded in half and bent so that the supply sides face each other, and the supply-side flow channel material 2 is placed between them, and the permeate-side flow channel material 3 is stacked on top of it. Next, adhesives 4 and 6 for forming the sealing portions 11 at both ends and the outer circumference sealing portion 12 are applied to both ends in the axial direction A1 of the permeate-side flow channel material 3 and to the winding end to prepare the separation membrane unit U. At this time, a protective layer may be provided by attaching protective tape to the folded portion of the separation membrane 1.

[0024] The adhesives 4 and 6 are not particularly limited, and conventionally known adhesives can be used. Specifically, any conventionally known adhesive, such as urethane-based adhesives or epoxy-based adhesives, can be used.

[0025] Next, as shown in Figure 2C, a laminate of separation membrane units U is prepared by stacking the same number of separation membrane units U as the membrane leaves L on the permeable channel material 3 which has an extended portion compared to the others. At this time, by applying adhesive to both ends in the axial direction A1 of the extended portion of the lowest permeable channel material 3, a central sealing portion 13 can be formed.

[0026] Next, as shown in Figure 2C, the perforated central tube 5 is rotated in the direction of the arrow to wind multiple separation membrane units U around the central tube 5. At this time, the adhesives 4 and 6 bond the opposing separation membranes 1 and the permeable channel material 3, thereby forming a membrane leaf L having sealing portions 11 at both ends and a sealing portion 12 on the outer circumference.

[0027] As a result, as shown in Figure 1, a wound body R is formed in which the membrane leaf L and the supply-side flow channel material 2 are wound around the central tube 5. After sealing, the wound body R may be trimmed at both ends to adjust the length in the axial direction A1.

[0028] If necessary, an upstream end member such as a seal carrier is provided on the upstream side of the wound body R of the membrane element, and a downstream end member such as an anti-telescopic material is provided on the downstream side. Furthermore, an outer covering material may be provided for purposes such as improving pressure resistance.

[0029] The exterior material is not particularly limited and can include various sheets, films, tapes, etc., and fiber-reinforced plastic (FRP) may be used for reinforcement as needed. A preferred method for forming the fiber-reinforced plastic is to use roving, which is made by impregnating fibers with a curable resin, and wrap this around the outer circumference of the wound body R.

[0030] In a typical 8-inch diameter spiral membrane element, approximately 15 to 30 membrane leaves L are wound around the element. However, in this invention, the supply-side flow channel material 2 is used, which has a thickness adjustment section 2a at least at the inner circumference end compared to the central part. This allows for an increase in the effective membrane area per unit volume. In particular, using a supply-side flow channel material 2 with thickness adjustment sections 2a at both the inner and outer circumference ends further increases the effective membrane area.

[0031] When using the membrane element, it is housed in a pressure vessel, and the feed liquid is supplied from one end face of the membrane element. The supplied feed liquid flows along the supply-side flow channel material 2 in a direction parallel to the axial direction A1 of the central tube 5, and is discharged as a concentrated liquid from the other end face of the membrane element. In addition, the permeate that has permeated the separation membrane 1 as the feed liquid flows along the supply-side flow channel material 2 flows along the permeate-side flow channel material 3, then flows into the interior of the central tube 5 through the opening 5a, and is discharged from the end of the central tube 5.

[0032] (Supply side channel material) The supply-side channel material 2 is no different from conventional materials except for the provision of a thickness adjustment section 2a, and any conventional material can be used. The supply-side channel material 2 generally serves to secure gaps for evenly supplying fluid to the membrane surface. Such a supply-side channel material 2 can be made of, for example, a net, knitted fabric, or a textured sheet, and one with an appropriate thickness can be used as appropriate. Furthermore, it is preferable to install channel materials on both sides of the separation membrane 1, but it is common to use different channel materials for the supply-side channel material 2 installed on the supply liquid side and the permeate-side channel material 3 installed on the permeate liquid side. It is preferable to use a coarse, thick net-like channel material for the supply-side channel material 2, while it is preferable to use a fine-mesh woven or knitted channel material for the permeate-side channel material 3.

[0033] In the present invention, the supply-side flow channel material 2 is characterized by having a thickness adjustment portion 2a at least at the inner circumferential end compared to the central portion, as shown in Figure 3. For example, as shown in Figure 3, the thickness adjustment portion 2a of the supply-side flow channel material 2 is interposed at the inner circumferential end where the separation membrane 1 bends, thereby reducing the bending thickness (e.g., radius of curvature) of the inner circumferential end of the separation membrane 1. As a result, the step difference S at the inner circumferential ends of the multiple separation membranes 1 arranged around the central pipe 5 becomes smaller, making it less likely for voids (gaps) such as adhesive to occur, and thus improving the reliability of the sealing structure (central sealing portion 13) around the inner circumferential end.

[0034] Furthermore, after forming the central sealing portion 13 with adhesive applied before winding, the reliability of the sealing structure can be further improved by applying adhesive to the end face of the wound body R. In this case as well, the reliability of the sealing structure can be further improved by having a thickness adjustment portion 2a at the inner circumference end.

[0035] Here, the thickness adjustment section 2a only needs to have a portion with a thickness Ta smaller than the thickness T of the central part of the supply-side flow channel material 2, as shown in Figure 4D, for example. In the present invention, the "central part" of the supply-side flow channel material 2 refers to the midpoint between the inner circumference end and the outer circumference end of the supply-side flow channel material 2, and the midpoint in the axial direction A1. The area of ​​the supply-side flow channel material 2 other than the thickness adjustment section 2a, including the central part of the supply-side flow channel material 2, usually has the same thickness T. However, in the present invention, it is sufficient to have the thickness adjustment section 2a at least at the inner circumference end, and the thickness T of the supply-side flow channel material 2 may vary in areas other than the thickness adjustment section 2a.

[0036] Furthermore, depending on the structure of the supply-side flow channel material 2, the measured thickness T may differ depending on which part is measured. For example, if the intersection of the wires constituting the supply-side flow channel material 2 is the maximum thickness of the supply-side flow channel material 2, the thickness tends to be smaller in parts other than the intersection. Therefore, in this invention, the thickness is determined by comparing identical components within the repeating structure of the supply-side flow channel material 2. For example, if the part with the maximum thickness of the supply-side flow channel material 2 within the repeating structure is the intersection, the thickness of the intersection in the part that may correspond to the thickness adjustment part 2a is measured to determine if there is a part with a smaller thickness.

[0037] Therefore, in the case of the supply-side flow channel material 2 having the intersection portion described above, the portion of the wire having the intersection portion that has a thickness smaller than the thickness of the intersection portion in the central part corresponds to the thickness adjustment portion 2a. Also, if the wires constituting the supply-side flow channel material 2 themselves have wires that have a thickness smaller than the wires in the central part, the portion of the wire with the smaller thickness corresponds to the thickness adjustment portion 2a. In other words, in the present invention, if there is a portion with a smaller thickness in any component of the repeating structure of the supply-side flow channel material 2, this corresponds to the thickness adjustment portion 2a.

[0038] In the present invention, it is sufficient to have such a thickness adjustment portion 2a at least at the inner circumference end, and the shape of its front cross-section and the repeating structure of the supply-side flow channel material 2 may be any. For example, as shown in Figure 4D, the thickness Ta of the thickness adjustment portion 2a may be constant, but as shown in Figures 4A to 4C, for the reasons mentioned above, it is preferable that the thickness becomes thinner towards the tip A2.

[0039] Furthermore, as shown in Figure 4A, the tip of the supply-side flow channel material 2 may be pointed, and as shown in Figure 4B, the tip of the supply-side flow channel material 2 may be curved. Comparing these two, from the viewpoint of arranging the tip of the supply-side flow channel material 2 at a uniform position, it is more preferable for the tip of the supply-side flow channel material 2 to be curved.

[0040] Furthermore, the shape of the thickness adjustment section 2a may be asymmetrical vertically, as shown in Figure 4C, but from the viewpoint of process control in the manufacturing process, it is preferable that the shape of the thickness adjustment section 2a be symmetrical vertically.

[0041] The supply-side flow channel material 2 only needs to have a thickness adjustment portion 2a at at least its inner circumference end, and may have it only at the inner circumference end, at both the inner circumference end and the outer circumference end, or at one or both of the inner circumference end, the outer circumference end and both ends in the axial direction A1. In particular, for the reasons mentioned above, it is preferable to have a thickness adjustment portion 2a at both the inner circumference end and the outer circumference end.

[0042] The width W of the thickness adjustment section 2a and the shape of the cross-section when viewed from the front may vary slightly, but from the viewpoint of reducing variations in the sealing structure, it is preferable that they be constant or approximately constant.

[0043] The width W of the thickness adjustment portion 2a at the inner circumference end is preferably 3 mm or more, and more preferably 5 mm or more, from the viewpoint of reducing bending thickness and ensuring the stability of the sealing structure. Furthermore, the width W of the thickness adjustment portion 2a is preferably 30 mm or less, and more preferably 20 mm or less, from the viewpoint of maintaining good separation function.

[0044] When a thickness adjustment section 2a is provided at the outer peripheral end, the width W is preferably 3 mm or more, and more preferably 5 mm or more, from the viewpoint of reducing the step difference on the outer peripheral surface. Furthermore, the width W of the thickness adjustment section 2a at the outer peripheral end is preferably 30 mm or less, and more preferably 20 mm or less, from the viewpoint of maintaining good separation function. Note that the width W of the thickness adjustment section 2a at the outer peripheral end and the width W of the thickness adjustment section 2a at the inner peripheral end may be the same or different.

[0045] For example, in applications such as seawater desalination and wastewater treatment using RO membranes or NF membranes, a mesh structure in which linear objects are arranged in a grid can be preferably used as the supply-side flow channel material 2.

[0046] The constituent materials are not particularly limited, but polyethylene and polypropylene are commonly used. These resins may contain disinfectants or antibacterial agents. The thickness of the supply-side flow channel material 2 is generally 0.3 to 3.0 mm, with 0.5 to 1.0 mm being preferable. If the thickness is too high, the effective membrane area of ​​the membrane that can be contained in the membrane element and the amount of permeation will decrease, while if it is too low, contaminants will adhere more easily, leading to a deterioration in permeation performance.

[0047] From the viewpoint of further improving the reliability of the sealing structure, the thickness adjustment portion 2a of the supply-side flow channel material 2 preferably has a thickness of 50% or less in at least a portion, more preferably has a thickness of 30% or less in at least a portion, and even more preferably has a thickness of 20% or less in at least a portion.

[0048] One method for forming the thickness adjustment section 2a in the supply-side flow channel material 2 is to form the thickness adjustment section 2a when manufacturing the supply-side flow channel material 2 of a fixed width. However, from the viewpoint of manufacturing efficiency, it is preferable to form the thickness adjustment section 2a on one or more ends after cutting the supply-side flow channel material 2, which has a fixed thickness, to a fixed width or a predetermined shape. It is also possible to form the thickness adjustment section 2a on one or both ends of the supply-side flow channel material 2 by continuous processing after cutting it to a fixed width.

[0049] Any method for forming the thickness adjustment portion 2a may be heating and pressing, heating and deformation, grinding, polishing, or ultrasonic treatment, but heating and pressing such as a heating press or heating roll press, or ultrasonic treatment such as an ultrasonic applied press is preferred.

[0050] Specifically, as shown in Figure 5, for example, by applying heat and press to a mesh structure net under various conditions, thickness adjustment sections 2a of different thicknesses can be formed. The example shown in Figure 5 uses a diamond-shaped net made of polypropylene (PP) (intersection thickness 0.86 mm), and the heat and press conditions were 80 kgf press load, 15 mm press width, and varying temperature and time.

[0051] As shown in Figure 5, it can be seen that the intersection is crushed and the thickness is reduced, and it can be confirmed that the thickness decreases as the temperature and time increase. In other words, by changing the heating and pressing conditions according to the material and structure of the supply-side flow channel material 2, a thickness adjustment section 2a of the desired thickness can be formed. For example, the thermal deformation onset temperature for polypropylene is 60-65°C, but for polyethylene it is 30-50°C, so the thickness adjustment section 2a can be formed by heating and pressing at a lower temperature.

[0052] Furthermore, it is also possible to trim the edges after heating and pressing so that the edges become straight, or to adjust the length of the tip of the thickness adjustment section 2a to create a supply-side flow channel material 2 with a desired width.

[0053] (central canal) The central tube 5 can be any type having openings 5a around its circumference, and any conventional type can be used. Generally, when used in seawater desalination or wastewater treatment, the permeate water that has passed through the separation membrane 1 enters the central tube 5 through the holes in the wall, forming a permeate channel. The length of the central tube 5 is generally longer than the axial length of the wound body R, but a central tube 5 with a connected structure, such as being divided into multiple sections, may also be used. The material that constitutes the central tube 5 is not particularly limited, but thermosetting resins or thermoplastic resins are used.

[0054] (Permeate side channel material) Any conventional permeate channel material 3 can be used. The permeate channel material 3 is installed between opposing separation membranes 1 in the membrane reef L, as shown in Figure 1, when using RO membranes or NF membranes in applications such as seawater desalination and wastewater treatment. This permeate channel material 3 is required to support the pressure on the membrane from the back of the membrane and to ensure a flow path for the permeate.

[0055] To ensure such functionality, it is preferable that the permeable channel material 3 is formed from a tricot knitted fabric, and more preferably that the tricot knitted fabric is reinforced with resin or fused after knitting.

[0056] Examples of constituent yarns for the permeable channel material 3 include polyesters such as polyethylene terephthalate and polyethylene naphthalate, and polyolefins such as polyethylene and polypropylene. Among these, polyethylene terephthalate is particularly preferred from the viewpoint of processability and productivity.

[0057] When resin reinforcement is performed after knitting is complete, methods include impregnating the fibers with resin and allowing it to harden, or coating the fiber surface with resin and allowing it to harden. Examples of resins used for reinforcement include melamine resin and epoxy resin.

[0058] The constituent yarns of the permeable channel material 3 may be monofilament or multifilament, but a tricot knit fabric is formed by constituent yarns of a certain thickness. Among tricot knit fabrics, half knit or double denby knit, which have a clearly defined structure of linearly continuous grooves, are preferred.

[0059] The thickness of the permeate-side channel material 3 is preferably 0.10 to 0.40 mm, more preferably 0.15 to 0.35 mm, and even more preferably 0.20 to 0.30 mm. A thickness of 0.10 mm or more ensures sufficient channel space and reduces pressure loss of the permeate. A thickness of 0.40 mm or less increases the effective membrane area of ​​the separation membrane in the membrane element, making it easier to increase the flow rate of the permeate. The constituent yarn of the permeate-side channel material 3 is preferably 0.1 to 0.15 mm in thickness when forming a tricot knitted fabric of the above thickness.

[0060] In the membrane element, the direction in which the permeable flow channel material 3 is arranged may be any direction, but it is preferable that the direction of the linearly continuous grooves is along the circumferential direction.

[0061] (separation membrane) Any conventional membrane can be used as the separation membrane 1. For example, various porous membranes can be used, but a composite semipermeable membrane having a separation functional layer on the surface of a porous support is preferred. As for the porous support, one having a polymer porous layer on one side of a nonwoven fabric layer is preferred. The thickness of the separation membrane, especially the composite semipermeable membrane, is preferably about 70 to 160 μm, and more preferably 85 to 130 μm.

[0062] These composite semipermeable membranes are called RO (reverse osmosis) membranes, NF (nanofiltration) membranes, or FO (forward osmosis) membranes depending on their filtration performance and treatment method, and can be used for ultrapure water production, seawater desalination, brine desalination, and wastewater reuse.

[0063] Examples of separation functional layers include polyamide-based, cellulose-based, polyether-based, and silicon-based separation functional layers, but those having a polyamide-based separation functional layer are preferred. Generally, a polyamide-based separation functional layer is a homogeneous film without visible pores and has the desired ion separation ability. This separation functional layer is not particularly limited as long as it is a polyamide-based thin film that does not easily peel off from the polymer porous layer, but for example, a polyamide-based separation functional layer obtained by interfacial polymerization of a polyfunctional amine component and a polyfunctional acid halide component on a porous support film is well known.

[0064] The method for forming the polyamide-based separation functional layer on the surface of the polymer porous layer is not particularly limited, and any known method can be used. For example, methods such as interfacial polymerization, phase separation, and thin-film coating can be used, but in the present invention, interfacial polymerization is particularly preferred. Interfacial polymerization is a method in which, for example, the polymer porous layer is coated with an amine aqueous solution containing a polyfunctional amine component, and then an organic solution containing a polyfunctional acid halide component is brought into contact with this amine aqueous solution coated surface to cause interfacial polymerization and form a skin layer.

[0065] The polyfunctional amine component contained in the amine aqueous solution is a polyfunctional amine having two or more reactive amino groups, and examples include aromatic, aliphatic, and alicyclic polyfunctional amines. Examples of aromatic polyfunctional amines include m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 2,4-diaminotoluene, 2,6-diaminotoluene, N,N'-dimethyl-m-phenylenediamine, 2,4-diaminoanisole, amidol, xylylenediamine, and the like. Examples of aliphatic polyfunctional amines include ethylenediamine, propylenediamine, tris(2-aminoethyl)amine, and n-phenylethylenediamine. Examples of the alicyclic polyfunctional amines include 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, piperazine, 2,5-dimethylpiperazine, and 4-aminomethylpiperazine. These polyfunctional amines may be used individually or in combination of two or more. In particular, in the present invention, when a high rejection rate is desired in reverse osmosis membrane performance, it is preferable to use m-phenylenediamine as the main component, which provides a highly dense separation functional layer, and when a high flux retention rate is desired in NF membrane performance, it is preferable to use piperazine as the main component.

[0066] The polyfunctional acid halide component contained in the organic solution is a polyfunctional acid halide having two or more reactive carbonyl groups, and includes aromatic, aliphatic, and alicyclic polyfunctional acid halides. Examples of aromatic polyfunctional acid halides include trimesic acid trichloride, terephthalic acid dichloride, isophthalic acid dichloride, biphenyl dicarboxylic acid dichloride, naphthalenedicarboxylic acid dichloride, benzenetrisulfonic acid trichloride, benzenedisulfonic acid dichloride, and chlorosulfonylbenzenedicarboxylic acid dichloride. Examples of aliphatic polyfunctional acid halides include propanedicarboxylic acid dichloride, butanedicarboxylic acid dichloride, pentanedicarboxylic acid dichloride, propanetricarboxylic acid trichloride, butanetricarboxylic acid trichloride, pentanetricarboxylic acid trichloride, glutaryl halide, and adipoyl halide. Examples of the alicyclic polyfunctional acid halides include cyclopropanetricarboxylic acid trichloride, cyclobutanetetracarboxylic acid tetrachloride, cyclopentanetricarboxylic acid trichloride, cyclopentanetetracarboxylic acid tetrachloride, cyclohexanetricarboxylic acid trichloride, tetrahydrofurantetracarboxylic acid tetrachloride, cyclopentanedicarboxylic acid dichloride, cyclobutanedicarboxylic acid dichloride, cyclohexanedicarboxylic acid dichloride, and tetrahydrofrancolamine carboxylic acid dichloride. These polyfunctional acid halides may be used individually or in combination of two or more. To obtain a skin layer with high salt-blocking performance, it is preferable to use aromatic polyfunctional acid halides. Furthermore, it is preferable to use a polyfunctional acid halide with a valent or higher valency in at least a portion of the polyfunctional acid halide component to form a crosslinked structure.

[0067] The organic solvent containing the polyfunctional acid halide is not particularly limited as long as it has low solubility in water and dissolves the polyfunctional acid halide component without degrading the porous support film. Examples include saturated hydrocarbons such as cyclohexane, heptane, octane, and nonane, and halogen-substituted hydrocarbons such as 1,1,2-trichlorotrifluoroethane. Preferably, it is a saturated hydrocarbon with a boiling point of 300°C or lower, and more preferably with a boiling point of 200°C or lower.

[0068] The aforementioned amine aqueous solution or organic solution may contain additives to improve various properties and handling characteristics. Examples of such additives include polymers such as polyvinyl alcohol, polyvinylpyrrolidone, and polyacrylic acid; polyhydric alcohols such as sorbitol and glycerin; surfactants such as sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and sodium lauryl sulfate; basic compounds such as sodium hydroxide, trisodium phosphate, and triethylamine to remove hydrogen halides generated by polymerization; acylation catalysts; and solubility parameters of 8 to 14 (cal / cm³) as described in Japanese Patent Publication No. 8-224452. 3 ) 1 / 2 Examples include the following compounds.

[0069] A coating layer made of various polymer components may be provided on the exposed surface of the separation functional layer. The polymer component is not particularly limited as long as it does not dissolve the separation functional layer and the porous support membrane and does not leach during water treatment operations. Examples include polyvinyl alcohol, polyvinylpyrrolidone, hydroxypropyl cellulose, polyethylene glycol, and saponified polyethylene-vinyl acetate copolymer. Of these, polyvinyl alcohol is preferred, and it is particularly preferable to use polyvinyl alcohol with a degree of saponification of 99% or more, or to crosslink polyvinyl alcohol with a degree of saponification of 90% or more with the polyamide resin of the skin layer to create a structure that is less likely to leach during water treatment. By providing such a coating layer, the charge state of the membrane surface is adjusted and hydrophilicity is imparted, so the adhesion of contaminants can be suppressed, and the Flux retention effect can be further enhanced through a synergistic effect with the present invention.

[0070] The nonwoven fabric layer used in the present invention is not particularly limited as long as it provides appropriate mechanical strength while maintaining the separation and permeability performance of the composite semipermeable membrane, and commercially available nonwoven fabrics can be used. Examples of such materials include those made of polyolefin, polyester, cellulose, etc., and mixtures of multiple materials can also be used. Polyester is particularly preferable in terms of moldability. Long-fiber nonwoven fabrics and short-fiber nonwoven fabrics can be used as appropriate, but long-fiber nonwoven fabrics are preferable in terms of preventing fine fuzzing that can cause pinhole defects and maintaining uniformity of the membrane surface.

[0071] The polymer porous layer is not particularly limited as long as it can form the polyamide-based separation functional layer, but is usually a microporous layer having a pore size of about 0.01 to 0.4 μm. Examples of materials for forming the microporous layer include polysulfone, polyaryl ethersulfone (exemplified by polyethersulfone), polyimide, and polyvinylidene fluoride. It is particularly preferable to form the polymer porous layer using polysulfone or polyaryl ethersulfone because they are chemically, mechanically, and thermally stable.

[0072] (protective layer) It is preferable that the supply side of the separation membrane 1 be provided with a protective layer along the inner circumference end (bent portion). Such a protective layer makes the separation membrane 1 less susceptible to damage compared to when the separation membrane 1 at the bent portion is exposed to the supply side.

[0073] The protective layer is preferably formed such that both ends of the protective layer are parallel to the center line of the bent portion on the supply side of the separation membrane 1, and it is more preferable that the center line of the bent portion is located in the center of the protective layer.

[0074] The width of the protective layer is, for example, 25 to 50 mm. In this invention, the width W of the thickness adjustment portion 2a provided at the inner circumference end is preferably 0.2 to 2 times, more preferably 0.3 to 1.5 times, and even more preferably 0.5 to 1 time, relative to half the length of the width of the protective layer. When the width W of the thickness adjustment portion 2a is in this ratio, the reliability of the sealing structure around the inner circumference end of the separation membrane 1 can be improved while sufficiently maintaining the separation function of the separation membrane 1.

[0075] Examples of such protective layers include adhesive tape, film bonding, and resin coating, but from the viewpoint of simplicity of the formation process and material leaching, it is preferable to use adhesive tape.

[0076] The thickness of the protective layer is, for example, 25 to 100 μm, but the thicker the protective layer, the more effective the thickness adjustment portion 2a provided at the inner circumference end is at reducing the bending thickness (e.g., radius of curvature).

[0077] (Another embodiment of a spiral membrane element) In the above description, the most preferred embodiment of the present invention has been described. However, the present invention is not limited to this embodiment, and various modifications are possible within substantially the same scope as the technical idea described in the claims of the present invention.

[0078] In other words, in the above embodiment, as shown in Figures 2A to 2C, the separation membrane 1 was folded in half so as to sandwich the supply-side flow channel material 2, the permeate-side flow channel material 3 was placed on top of it, and adhesives 4 and 6 were applied. However, in the present invention, it is also possible to place the separation membrane 1 folded in half on top of the permeate-side flow channel material 3 and apply adhesives 4 and 6 on top of that. Furthermore, a continuous separation membrane 1 may be used, making the outer peripheral sealing portion 12 unnecessary. [Industrial applicability]

[0079] According to the present invention, a spiral membrane element can be provided that can improve the reliability of the sealing structure around the inner circumferential end of the separation membrane. For this reason, the spiral membrane element of the present invention can be suitably used in various applications such as ultrapure water production, seawater desalination, brine desalination, and wastewater reuse treatment. [Explanation of Symbols]

[0080] 1: Separation membrane 2: Supply side channel material 2a: Thickness adjustment section 3: Permeate side channel material 5: Central tube 13: Center side sealing part (sealing part) A1: Axial direction R: Coiled body T: Thickness of the supply-side flow channel material Ta: Thickness of the thickness adjustment section W: Width of the thickness adjustment section S: Step

Claims

1. A spiral membrane element comprising a perforated central tube, a wound body including a separation membrane wound around the central tube and bent at its inner circumferential end to face the supply side, and a supply-side flow channel material interposed between the separation membrane, and a sealing portion to prevent mixing of the supply-side flow channel and the permeate-side flow channel, The tip of the inner circumferential end of the separation membrane is positioned around the central tube. The supply-side flow channel material has a thickness adjustment portion at least at the inner circumferential end that is thinner than the central portion. The thickness adjustment portion is interposed at the inner circumferential end of the separation membrane and is provided in a range of 3 mm to 30 mm in width from the tip. Spiral-type membrane element.

2. The spiral film element according to claim 1, wherein the thickness adjustment portion has a shape in which the thickness decreases towards the tip.

3. The spiral membrane element according to claim 1, wherein the supply-side flow channel material has the thickness adjustment portion at the inner circumferential end and the outer circumferential end.

4. The spiral membrane element according to any one of claims 1 to 3, wherein the supply side of the separation membrane is provided with a protective layer along the inner circumferential end.

5. The spiral film element according to claim 4, wherein the width of the thickness adjustment portion provided at the inner circumference end is 0.2 to 2 times the length of half the width of the protective layer.

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