Spiral-type separation membrane element, production method for same, operation method for same, and fluid separation device

Abstract

Provided is a spiral-type separation membrane element with which a transmitted fluid is obtained from a supplied fluid, wherein: wrapped around a central pipe is either one laminate including a separation membrane, a supply-side flow path member, and a transmission-side flow path member, or a plurality of such laminates which are stacked; the separation membrane includes a substrate, a separation function layer, and a porous supporting layer between the substrate and separation function layer, and forms a rectangular envelope-shaped film, a transmission-side surface of which faces inward; the envelope-shaped film has a peripheral part at the four sides thereof; a sealing part is provided to only three sides of the peripheral part excluding the one side in contact with the central pipe; the substrate has a uniform thickness at the sealing part of at least one side; and, at the sealing part of at least one side, the porous supporting layer is provided with a prescribed thickness part which has a prescribed thickness and a thin part which is thinner than the prescribed thickness part.

Description

Spiral-wound separation membrane element, its manufacturing method and operation method, and fluid separation device

[0001] The present invention relates to a separation membrane element used for separating components contained in a fluid such as a liquid or gas, a method for producing the same, and a method for operating the same, and also to a fluid separation device including the separation membrane element.

[0002] There are various methods for separating components contained in fluids such as liquids and gases. For example, in the case of technology for removing ionic substances contained in seawater, brine, etc., separation methods using separation membrane elements have been increasingly used in recent years as a process for saving energy and resources. Separation membranes used in separation methods using separation membrane elements include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, and forward osmosis membranes, depending on their pore size and separation function. These membranes are used, for example, to obtain drinking water from seawater, brine, water containing harmful substances, etc., to produce industrial ultrapure water, to treat wastewater, and to recover valuable resources, and are used according to the target components to be separated and their separation performance.

[0003] Separation membrane elements have in common that a feed fluid is supplied to one side of the separation membrane and a permeate fluid is obtained from the other side. Separation membrane elements are constructed by bundling many separation membrane elements of various shapes to increase the membrane area and enable a large amount of permeate fluid to be obtained per unit element. Various elements are manufactured depending on the application and purpose, such as spiral type, hollow fiber type, plate and frame type, rotating flat membrane type, and flat membrane integrated type.

[0004] For example, spiral-wound separation membrane elements are widely used in reverse osmosis filtration. Spiral-wound separation membrane elements are generally formed by wrapping a single or multiple units, each consisting of a separation membrane for separating components contained in a feed fluid, a feed-side channel material for supplying the feed fluid to the separation membrane surface, and a permeate-side channel material for directing the permeate that has permeated the separation membrane and been separated from the feed fluid to a central pipe, around a central pipe having holes on its surface. In this case, the separation membrane forms a rectangular envelope-like membrane with the permeate side facing inward. The envelope-like membrane must be sealed on only three sides of its periphery, excluding the side that contacts the central pipe, to separate the feed fluid from the permeate. If this sealing is not complete, high separation performance cannot be achieved, and leakage is particularly likely to occur in spiral-wound separation membrane elements used under high pressure. If the envelope-like membrane is not sealed on the one side of its periphery that contacts the central pipe, the permeate will flow into the central pipe. In this specification, the edge of the envelope-shaped membrane on which no sealing portion is provided may be referred to as an "opening," and the state in which the envelope-shaped membrane's edge is not sealed may be referred to as "open."

[0005] When the permeate fluid is the product, even a small amount of leakage of the feed fluid from the seals can cause a serious deterioration in quality. For this reason, improvements to the seals have been proposed to improve the performance of separation membrane elements.

[0006] Specifically, Patent Documents 1 and 2 propose methods of subjecting the sealing portion of a separation membrane to a heat treatment or pressure bonding treatment. Patent Document 3 also proposes a method of manufacturing a fluid separation device that uses a high-fluidity adhesive that easily penetrates into the separation membrane and a low-fluidity adhesive that does not allow the adhesive to flow outside the application area.

[0007] Japanese Unexamined Patent Publication No. 1-288303 Japanese Unexamined Patent Publication No. 1983-136103 Japanese Unexamined Patent Application No. 73008 / 1988

[0008] However, separation membrane elements obtained using the methods described in the above-mentioned patent documents could not be said to sufficiently suppress leakage of the feed fluid from the sealed portions. In particular, when the separation membrane element was operated at high pressure, leakage of the feed fluid from the sealed portions increased, resulting in a significant decrease in salt rejection. Furthermore, an impulse sealer for heating and pressurizing the sealed portions and a device for accurately applying two different types of adhesives were separately required, making the manufacturing process of the separation membrane element complicated. Therefore, an object of the present invention is to provide a spiral separation membrane element that suppresses leakage of the feed fluid from the sealed portions and is less likely to result in a decrease in salt rejection, even when the spiral separation membrane element is operated at high pressure, without complicating the manufacturing process of the spiral separation membrane element.

[0009] In order to achieve the above object, the present invention is characterized by the following configurations (1) to (7): (1) A spiral separation membrane element for obtaining a permeate fluid from a feed fluid, wherein a single or multiple stacked laminates each including a separation membrane, a feed-side channel material provided on the feed-side surface of the separation membrane, and a permeate-side channel material provided on the permeate-side surface of the separation membrane are wound around a central pipe, the separation membrane includes a substrate, a separation functional layer, and a porous support layer present between the substrate and the separation functional layer, and forms a rectangular envelope-shaped membrane with the permeate-side surface facing inward, the envelope-shaped membrane has a peripheral edge on each of its four sides, and plugs for separating the feed fluid from the permeate fluid are provided on only three sides of the peripheral edge, excluding the side that contacts the central pipe, so that the permeate fluid flows into the central pipe, the substrate has a uniform thickness at the plug on at least one side, (2) A spiral separation membrane element in which the porous support layer has, in the plugged portions on at least one side, a predetermined thickness portion having a predetermined thickness and a thinner portion having a thickness thinner than the predetermined thickness portion. (3) A spiral separation membrane element in which the thickness of the thinner portion of the porous support layer is 5 μm or more and 40 μm or less and the thickness of the thinner portion is 20% or more and 70% or less of the thickness of the predetermined thickness portion. (4) A spiral separation membrane element in which the porous support layer has the thinner portion only in the plugged portions on two sides corresponding to both ends of the spiral separation membrane element.(5) A method for producing a spiral separation membrane element according to any one of (1) to (4), comprising the steps of: producing a separation membrane body including the substrate, the separation functional layer, and the porous support layer present between the substrate and the separation functional layer; stacking the separation membrane body, the feed-side channel material, and the permeate-side channel material so that the supply-side surface of the separation membrane body faces the feed-side channel material and the permeate-side surface of the separation membrane body faces the permeate-side channel material, respectively, to form a pre-sealed laminate having a laminate structure in which the separation membrane bodies face each other at the permeate-side surfaces with the permeate-side channel material sandwiched therebetween; and sealing three sides of the four peripheral edges of the laminate structure to form the envelope-shaped membrane. and a step of superposing one or more stacks of the obtained envelope-shaped membranes, each stack including the permeate-side channel material and the feed-side channel material sandwiched therein, and winding the stack around the central pipe so that the side of the envelope-shaped membrane not provided with the sealed portion is in contact with the central pipe to obtain a wound body, wherein in the step of producing the separation membrane main body, the porous support layer is provided with the predetermined thickness portion and the thin thickness portion in a region corresponding to the sealed portion on at least one side. (6) The method for producing a spiral-wound separation membrane element according to (5), wherein, in the step of producing the separation membrane body, exposed substrate portions where the separation functional layer and the porous support layer are not laminated on the substrate are formed at both end portions of two sides of the separation membrane body corresponding to both ends of the spiral-wound separation membrane element, and the thin-thickness portions of the porous support layer are provided in regions inside each of the exposed substrate portions and corresponding to the sealing portions, and the step of forming the envelope-shaped membrane further includes a step of applying the adhesive so as to cover at least the region of the sealing portion where the thin-thickness portion is located, after the step of obtaining the wound body, and a step of curing the adhesive, after the step of curing the adhesive, and a step of trimming both end portions of the wound body to remove the exposed substrate portions. (7) A method for operating a spiral-wound separation membrane element, comprising producing water at a feed fluid pressure of 4.0 MPa or more using the spiral-wound separation membrane element according to any one of (1) to (4).(8) A fluid separation device comprising the spiral separation membrane element according to any one of (1) to (4) above.

[0010] According to the present invention, it is possible to obtain a spiral separation membrane element that suppresses leakage of the supply fluid from the sealed portion and is less likely to decrease in salt rejection rate, even when the spiral separation membrane element is operated at high pressure, without complicating the manufacturing process of the spiral separation membrane element.

[0011] Fig. 1 is a partially developed perspective view showing an example of a spiral-wound separation membrane element. Fig. 2 is a plan view showing an example of a feed-side channel material of the present invention. Fig. 3 is a partially developed perspective view showing an example of a spiral-wound separation membrane element of the present invention. Fig. 4 is a cross-sectional view taken along line II of Fig. 3, showing the cross-sectional structure of an envelope-shaped membrane of the present invention.

[0012] Hereinafter, embodiments of the present invention will be described in detail.

[0013] 1. Spiral-Wound Separation Membrane Element In the spiral-wound separation membrane element 1a shown in FIG. 1, a polymer net is used as the feed-side channel material 2, which forms the feed-side channel. Furthermore, a permeation-side channel material 4, which has finer gaps than the feed-side channel material, is used as the permeation-side channel material to prevent the separation membrane 3a from sagging and to form the permeation-side channel. Separation membranes 3a are superimposed on both sides of the permeation-side channel material 4 and bonded in an envelope-like manner to form an envelope-like membrane 5a. The inside of the envelope-like membrane 5a forms the permeate fluid channel. The envelope-like membrane 5a, which is alternately stacked with the feed-side channel material 2, is spirally wound with a predetermined portion of the opening side bonded to the outer circumferential surface of the central pipe. The x-axis direction in FIG. 1 is the longitudinal direction of the central pipe. The y-axis direction is perpendicular to the longitudinal direction of the central pipe. In the spiral-wound separation membrane element 1a, a feed fluid 7 is typically supplied from one end face. As the feed fluid 7 flows parallel to the central pipe, it is gradually separated into a permeate fluid 8 and a concentrated fluid 9. The permeate fluid 8 exits the spiral-wound separation membrane element 1a from the end face opposite to the end face to which the feed fluid 7 is supplied. This system is characterized in that the feed fluid 7 flows from one end face to the other of the spiral-wound separation membrane element 1a, thereby inevitably contacting the membrane for a sufficient distance, thereby allowing the feed fluid 7 to be sufficiently separated into a permeate fluid 8 and a concentrated fluid 9. The feed fluid to the spiral-wound separation membrane element of this embodiment is not particularly limited and may be pretreated tap water, a liquid containing impurities in solution such as seawater or brine, or various mixed gases or gases containing impurities. It can be selected according to the purpose of various separation operations, such as filtration, concentration, and purification.

[0014] 2. Feed-side channel material The feed-side channel material is provided on the feed-side surface of the separation membrane, forms a channel for supplying a feed fluid to the separation membrane, and plays a role in increasing the flow rate of the feed fluid and disturbing the flow, thereby suppressing concentration polarization of the feed fluid.

[0015] Examples of the feed-side channel material include continuous members such as knitted fabrics, woven fabrics, or nets made of polyethylene or polypropylene, among others. Nets are preferred from the viewpoint of ensuring sufficient flow paths for the feed fluid and effectively suppressing concentration polarization. Here, "net" refers to a mesh-like structure formed by heat-sealing multiple intersecting fibers, as shown in FIG. 2 . Such a net can be manufactured, for example, by adhering the resins of warp threads 21 and weft threads 22 extruded from holes in an extrusion die in a molten state, followed by cooling and solidifying the resins.

[0016] The fiber diameter of the constituent fibers constituting the net can be measured by observation using a commercially available microscope, etc. From the viewpoint of achieving a favorable balance between the flow rate of the supply fluid and the pressure loss, the constituent fiber diameter is preferably 0.05 to 0.80 mm, more preferably 0.10 to 0.50 mm.

[0017] The net, which is the feed-side channel material, is composed of a plurality of constituent fibers that intersect with each other, and the thickness of the net is greatest at the intersections of the constituent fibers.

[0018] The thickness of the net, which is the feed-side channel material, is the average value of the thicknesses at 10 or more randomly selected intersections, and can be calculated by dividing the total measured values ​​by the number of measurement points. The thickness at the intersections may be measured directly using a commercially available thickness measuring device, or may be measured by analyzing an image of the cross section of the feed-side channel material photographed using a microscope.

[0019] The thickness of the net serving as the feed-side flow path material is preferably 0.20 to 1.00 mm, more preferably 0.30 to 0.80 mm, in order to increase the amount of fluid permeating the separation membrane element while avoiding blockage of the flow path due to foulants in the feed fluid.

[0020] The intersection interval of the constituent fibers constituting the net, which is the supply side flow path material, is preferably 0.5 to 10.0 mm, more preferably 1.0 to 6.0 mm, from the viewpoint of achieving a good balance between the flow rate of the supply fluid and the pressure loss.

[0021] Here, "intersection spacing of constituent fibers" refers to the distance between the centers of intersections of constituent fibers, as shown in Figure 2. Two types of intersection spacing, a and b, are obtained for one gap in the net, and the longer of these, b, is measured at 30 randomly selected gaps, and the average value of these measurements can be used as the intersection spacing of the constituent fibers.

[0022] 3. Permeate Side Channel Material A permeate side channel is formed between the separation membranes sandwiching the permeate side channel material by the permeate side channel material 4. The material of the permeate side channel material is not limited, and tricot, nonwoven fabric, a porous sheet with protrusions attached, a film with a concave-convex shape and perforations, or a concave-convex nonwoven fabric can be used. Furthermore, protrusions that function as the permeate side channel material may be attached to the permeate side of the separation membrane.

[0023] Among these, when a tricot manufactured by a circular knitting machine is used, it is possible to make the width of the needle loop and the width of the sinker loop almost the same, and to use either loop as a flow path, and it is also possible to manufacture a uniform flow path with an optimal width that takes into account membrane sagging during operation of the separation membrane element, and it is also possible to manufacture a permeation-side flow path material that is thin but has both sufficient pressure resistance and flow characteristics.For these reasons, the above tricot is preferred in terms of improving the amount of permeating fluid through the separation membrane element.

[0024] When the permeate-side channel material is a tricot, the fiber diameter of the fibers constituting the tricot is preferably 30 μm or more and 300 μm or less in order to ensure the rigidity and pressure resistance of the tricot body.

[0025] The thickness of the permeate-side channel material is preferably 50 μm or more and 800 μm or less, more preferably 100 μm or more and 500 μm or less. When the thickness of the permeate-side channel material is 800 μm or less, the number of membrane leaves that can be packed in one vessel can be increased. Furthermore, when the thickness of the permeate-side channel material is 50 μm or more, the flow resistance can be relatively small, thereby obtaining good separation characteristics and permeation performance.

[0026] 4. Central Pipe The central pipe is provided to collect the permeate fluid that has permeated the separation membrane. It is hollow and has many holes on the surface of the pipe that connect to the hollow part. Various materials are used for the central pipe, such as hard plastics such as PVC and ABS, and metals such as stainless steel. Basically, there is one central pipe per element.

[0027] The size and number of holes provided in the central pipe are not particularly limited as long as they can efficiently collect the permeate that has permeated the separation membrane, and can be designed depending on the size of the spiral separation membrane element, the water permeability of the separation membrane used, the operating pressure, etc. The holes may be arranged at equal intervals, or the intervals between holes may increase or decrease from the upstream side to the downstream side of the separation membrane element.

[0028] 5. Separation Membrane 5-1 Overview A composite membrane having a porous support layer and a separation functional layer provided on a substrate is used as the separation membrane depending on the method of use, purpose, etc. The separation membrane preferably has a structure including a porous support layer between the substrate and the separation functional layer.

[0029] 5-2 Separation Functional Layer The separation functional layer may be a layer having both a separation function and a support function, or may have only a separation function. Note that the term "separation functional layer" refers to a layer having at least a separation function.

[0030] When the separation functional layer has both a separation function and a support function, a layer containing one polymer selected from cellulose, polyvinylidene fluoride, polyethersulfone, and polysulfone as a main component is preferably used as the separation functional layer. In this specification, the term "main component" means the component that has the highest content by mass among all components.

[0031] On the other hand, crosslinked polymers are preferably used as the separation functional layer because they allow for easy control of pore size and have excellent durability. In particular, polyamide separation functional layers obtained by polycondensation of polyfunctional amines and polyfunctional acid halides, and organic-inorganic hybrid functional layers are preferably used because they have excellent separation performance for components in the feed fluid 7. These separation functional layers can be formed by polycondensation of monomers on a porous support layer, which will be described later.

[0032] For example, the separation functional layer can contain polyamide as a main component. Such a membrane can be formed by interfacial polycondensation of a polyfunctional amine and a polyfunctional acid halide by a known method. For example, a polyfunctional amine aqueous solution is applied to a porous support layer, excess polyfunctional amine aqueous solution is removed with an air knife, and then an organic solvent solution containing a polyfunctional acid halide is applied, resulting in polycondensation and the formation of a polyamide separation functional layer.

[0033] The thickness of the separation functional layer is preferably 25 nm or more and 50 nm or less, more preferably 30 nm or more and 45 nm or less. When the thickness of the separation functional layer is 25 nm or more, a separation membrane with excellent oxidation resistance can be obtained. Furthermore, when the thickness of the separation functional layer is 50 nm or less, sufficient membrane permeation flux can be provided, and stable membrane performance can be obtained. The thickness of the separation functional layer can be analyzed using observation techniques such as transmission electron microscopy (TEM), TEM tomography, and focused ion beam / scanning electron microscopy (FIB / SEM).

[0034] 5-3 Porous Support Layer 5-3-1 Overview The porous support layer is a layer that supports the separation function layer, and when made of resin, it can also be called a porous resin layer.

[0035] The material and shape of the porous support layer are not particularly limited, but for example, the porous support layer may be formed on a substrate using a porous resin. Examples of the porous support layer include polysulfone, cellulose acetate, polyvinyl chloride, epoxy resin, or a mixture or laminate of these. It is preferable to use polysulfone, which has high chemical, mechanical, and thermal stability and whose pore size is easy to control.

[0036] The porous support layer can be produced, for example, by casting a solution of the polysulfone in N,N-dimethylformamide (hereinafter referred to as DMF) onto a substrate (e.g., a tightly woven polyester nonwoven fabric) described below to a certain thickness, and then wet-coagulating the resulting mixture in water.

[0037] The porous support layer can be formed according to the method described in Office of Saline Water Research and Development Progress Report No. 359 (1968), where the polymer concentration, solvent temperature, and antisolvent can be adjusted to obtain the desired morphology.

[0038] 5-3-2 Shape of Porous Support Layer As shown in Fig. 3, the separation membrane 3b in this embodiment forms a rectangular envelope-shaped membrane 5b with the permeate side facing inward. The envelope-shaped membrane 5b has peripheral edges on all four sides, and seals 10 for isolating the feed fluid from the permeate fluid are provided on only three sides of the peripheral edge, excluding the edge that contacts the central pipe, so that the permeate fluid flows into the central pipe 6. That is, as shown in Fig. 3, the seals on the three sides consist of seals on two sides corresponding to both ends of the spiral separation membrane element and a seal on one side parallel to the central pipe 6.

[0039] In this embodiment, the porous support layer has a predetermined thickness portion P having a predetermined thickness on two sides corresponding to both ends of the spiral separation membrane element, as shown in FIG. １ and a thin portion P having a thickness thinner than the predetermined thickness portion. ２ Similarly, the sealing portion 10 on one side parallel to the central pipe 6 has a predetermined thickness portion P １ and thin part P ２ will be established.

[0040] Thickness T of the specified thickness part １ is the thickness obtained by measuring the thickness of the porous support layer 302 of the effective membrane portion excluding the sealing portion 10, and the thickness T ２ The thickness T of the predetermined thickness part １ The thickness is obtained by measuring a portion of the porous support layer 302 that is 10% or more thinner than the thickness of the porous support layer 302 .

[0041] In this embodiment, the thin portion P ２ The thin portion P ２ It is more preferable that the thin portion P is provided at least in the plugged portions 10 on two sides corresponding to both ends of the spiral separation membrane element, and it is even more preferable that the thin portion P is provided only in the plugged portions 10 on two sides corresponding to both ends of the spiral separation membrane element, as will be described later. ２ The predetermined thickness portion P １ and thin part P ２ The contour line of the sealing portion 10 is a single-step staircase shape, but the contour line may be made up of multiple steps, or may be a line segment made up of a continuous straight line or curve. ２ The presence of ２ This can promote adhesive impregnation into the spiral-wound separation membrane element, thereby improving the sealing performance of the spiral-wound separation membrane element.

[0042] In this embodiment, the thickness T １ is maintained at a predetermined thickness in order to ensure stable element wrapping, stable formation of a separation functional layer in the effective membrane portion, and membrane performance with little variation. １ is preferably 10 μm or more and 80 μm or less. １ The lower limit of T is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 25 μm or more. １ The upper limit is preferably 80 μm or less, and more preferably 60 μm or less.

[0043] In this embodiment, the thickness T of the thin portion ２ From the viewpoint of the winding property of the spiral separation membrane element, T ２ The lower limit of T is preferably 5 μm or more, and more preferably 15 μm or more. ２The upper limit of the thickness of the thin portion is preferably 40 μm or less, and more preferably 35 μm or less. By setting the thickness of the thin portion within the above range, it is possible to ensure the wrapping property of the separation membrane element and to improve the sealing property by improving the impregnation property of the adhesive in the sealing portion.

[0044] In this embodiment, from the viewpoint of suppressing stress concentration near the boundary portion where the film thickness change is large and preventing damage to the separation functional layer, the ratio of the thickness of the thin portion to the thickness of the predetermined thickness portion is preferably 20% or more, more preferably 30% or more. Furthermore, from the viewpoint of adhesive impregnation, the ratio of the thickness of the thin portion to the thickness of the predetermined thickness portion is preferably 70% or less, more preferably 50% or less.

[0045] By setting the thickness of the thin portion and the ratio of the thickness of the thin portion to the thickness of the specified thickness portion within these ranges, the sealing properties of the sealing portion can be improved while at the same time, performance degradation due to membrane rupture during long-term operation can be suppressed by ensuring the mechanical strength of the porous support layer.

[0046] The thickness of a thin portion is the average value of the values ​​obtained by measuring the thickness of any thin portion across its width, and can be determined by measuring the cross section of the thin portion using a microscope and dividing the sum of the values ​​of each thin portion by the total number of measurement locations.

[0047] The thickness of the specified thickness portion is the average value obtained by measuring the thickness of the porous support layer of the effective membrane portion excluding the sealing portion across its width, and can be determined by measuring the cross section using a microscope at the location where the specified thickness portion exists, and dividing the sum of the values ​​of each specified thickness portion by the total number of measurement locations.

[0048] In this embodiment, the overall width W of the sealing portion １ From the viewpoint of suppressing leakage of the feed fluid, the total width W of the sealed portion is preferably 5 mm or more, more preferably 10 mm or more, and the wider the better. On the other hand, from the viewpoint of ensuring the effective membrane area of ​​the spiral-wound separation membrane element, １ The total width W of the sealing portion is preferably 50 mm or less, and more preferably 30 mm or less. １is preferably 5 mm or more and 50 mm or less, and more preferably 10 mm or more and 30 mm or less.

[0049] In this embodiment, the width W of the thin part of the porous support layer ２ From the viewpoint of suppressing leakage of the supply fluid from the sealed portion, the width W of the thin portion is preferably 1 mm or more, and more preferably 3 mm or more. ２ The width W of the thin portion is preferably 45 mm or less, and more preferably 20 mm or less. ２ is preferably 1 mm or more and 45 mm or less, and more preferably 3 mm or more and 20 mm or less.

[0050] In order to prevent leakage of the supply fluid from the sealing portion, the overall width W １ Width W of the thin part of the porous support layer ２ The ratio of the total width W of the sealing portion is preferably 10% or more, and more preferably 20% or more. １ Width W of the thin part of the porous support layer ２ Although there is no particular upper limit to the ratio, it is usually 95% or less.

[0051] Here, the total width W of the sealing portion １ The total width W of the sealed portion is the width of the portion sealed by adhesion with adhesive or hot melt, or by fusion with heat or laser. １ The width W of the thin part of the porous support layer is measured from a plane at any location where a plug is present, and the sum of the values ​​of each plug is divided by the total number of measurement locations. ２ is the average value of the values ​​obtained by measuring the width of any thin portion, and can be obtained by measuring the locations where thin portions exist using a microscope, adding up the values ​​of each thin portion, and dividing the total number of measurement locations.

[0052] In this embodiment, it is preferable that the thin portions of the porous support layer are provided only on the plugged portions on two of the three sides corresponding to both ends of the spiral-wound separation membrane element, because this simplifies the assembly process of the spiral-wound separation membrane element and improves the sealing performance of areas that contribute significantly to leakage of the feed fluid.

[0053] 5-4 Substrate 5-4-1 Overview From the viewpoint of the strength, dimensional stability, etc. of the separation membrane 3b, the separation membrane has a substrate 301. As the substrate, it is preferable to use a fibrous substrate in terms of strength and fluid permeability.

[0054] 5-4-2 Form of Substrate Both long-fiber nonwoven fabrics and short-fiber nonwoven fabrics can be preferably used as the substrate. Long-fiber nonwoven fabrics, in particular, have excellent membrane-forming properties, and thus can prevent excessive penetration of the polymer solution when it is cast, which can prevent the porous support layer from peeling off, and can also prevent membrane nonuniformity and defects such as pinholes caused by substrate fluffing. Furthermore, by using a long-fiber nonwoven fabric made of thermoplastic continuous filaments as the substrate, it is possible to prevent, compared to short-fiber nonwoven fabrics, the occurrence of membrane defects and nonuniformity caused by fiber fluffing during polymer solution casting. Furthermore, because tension is applied in the membrane-forming direction during continuous membrane production, it is preferable to use a long-fiber nonwoven fabric, which has excellent dimensional stability, as the substrate.

[0055] In terms of moldability and strength, it is preferable that the fibers in the surface layer opposite the porous support layer of the long-fiber nonwoven fabric be more longitudinally oriented than the fibers in the surface layer on the porous support layer side. Such a structure maintains strength, thereby achieving a high effect of preventing membrane rupture and the like. More specifically, the degree of fiber orientation in the surface layer of the long-fiber nonwoven fabric opposite the porous support layer is preferably 0° to 25°, more preferably 5° to 20°. Furthermore, the difference between the degree of fiber orientation in the surface layer of the long-fiber nonwoven fabric opposite the porous support layer and the degree of fiber orientation in the surface layer on the porous support layer side is preferably 10° to 90°, more preferably 30° to 90°.

[0056] The manufacturing process of separation membranes and spiral-wound separation membrane elements includes a heating step, which causes shrinkage of the porous support layer or separation function layer. Shrinkage is particularly pronounced in the width direction, where no tension is applied during continuous membrane production. Since shrinkage can cause problems with dimensional stability, a substrate with a small rate of thermal dimensional change is desirable. In a nonwoven fabric substrate, it is preferable for the difference in fiber orientation between the surface layer on the side opposite the porous support layer and the surface layer on the porous support layer side to be 10° to 90°, as this can also suppress changes in the width direction due to heat.

[0057] Here, the fiber orientation degree is an index indicating the direction of the fibers of the nonwoven fabric substrate. Specifically, the fiber orientation degree is the average value of the angle between the film-forming direction during continuous film production, i.e., the longitudinal direction of the nonwoven fabric substrate, and the fibers constituting the nonwoven fabric substrate. In other words, if the longitudinal direction of the fibers is parallel to the film-forming direction, the fiber orientation degree is 0°. Also, if the longitudinal direction of the fibers is perpendicular to the film-forming direction, i.e., parallel to the width direction of the nonwoven fabric substrate, the fiber orientation degree is 90°. Therefore, the closer the fiber orientation degree is to 0°, the more longitudinally oriented the fiber is, and the closer it is to 90°, the more transversely oriented the fiber is.

[0058] The degree of fiber orientation is measured as follows. First, 10 small samples are randomly taken from the nonwoven fabric. Next, the surface of each sample is photographed at 100 to 1000 magnifications using a scanning electron microscope. In the photographed image, 10 fibers are selected for each sample, and the angle is measured when the longitudinal direction of the nonwoven fabric (longitudinal direction, film-forming direction) is set to 0°. In other words, the angle is measured for a total of 100 fibers per nonwoven fabric. The average value of the angles measured for the 100 fibers is calculated. The value obtained by rounding the obtained average value to one decimal place is the degree of fiber orientation.

[0059] Examples of the thermoplastic continuous filaments that make up the long-fiber nonwoven fabric include polyethylene terephthalate fibers, polypropylene fibers, and nylon fibers.

[0060] In this embodiment, the substrate 301 is configured to have a predetermined thickness in the plugged portion 10 on at least one side, i.e., the substrate is not thinned by partial compaction or the like and has a uniform thickness. Since the substrate is not thinned by partial compaction or the like, the impregnation of the adhesive that penetrates into the porous support layer through the substrate can be improved, thereby improving the sealing performance of the spiral-wound separation membrane element. When multiple plugged portions 10 are provided, the substrate is preferably configured to have a predetermined thickness, i.e., has a uniform thickness, in all of them, and it is more preferable that the substrate have a uniform thickness across its entire surface.

[0061] The thickness of the substrate is preferably 20 μm or more and 200 μm or less, and more preferably 50 μm or more and 150 μm or less. From the viewpoint of increasing the strength of the separation membrane, the thickness of the substrate is preferably 20 μm or more and more preferably 50 μm or more. On the other hand, from the viewpoint of adhesive impregnation and windability around a pipe, the thickness of the substrate is preferably 200 μm or less and more preferably 150 μm or less. The thickness of the substrate is the average value of the values ​​obtained by measuring the thickness of any substrate across its width, and may be measured directly using a commercially available thickness measuring device, or may be measured by analyzing an image of the cross section of the substrate photographed using a microscope.

[0062] 6. Manufacturing Method of Spiral-Wound Separation Membrane Element 6-1 Overview Conventional element manufacturing equipment can be used to manufacture spiral-wound separation membrane elements. Furthermore, methods described in reference documents (Japanese Patent Publication No. 44-14216, Japanese Patent Application Laid-Open No. 4-11928, and Japanese Patent Application Laid-Open No. 11-226366) can be used to manufacture spiral-wound separation membrane elements. Details are as follows.

[0063] 6-2 Manufacturing of Separation Membrane Body The manufacturing method of the separation membrane before forming the separation membrane body, i.e., the envelope-shaped membrane, can be briefly summarized as follows. A resin is dissolved in a good solvent, and the resulting resin solution is cast onto a substrate and immersed in pure water to combine the porous support layer and the substrate. The porous support layer has a predetermined thickness portion and a thinner thickness portion, thinner than the predetermined thickness portion, in a region corresponding to the above-mentioned sealed portion on at least one side. The method for forming the thinner thickness portion in the porous support layer is not particularly limited. For example, a coating bar having a stepped surface with convex portions (thicker diameter portions) on both ends is used to apply the resin solution to the substrate surface so that a predetermined thickness portion is formed, and the convex portions (thicker diameter portions) of the coating bar are used to form thinner thickness portions on two sides of the peripheral edge corresponding to the left and right ends in the width direction of the coating bar. Another method is to apply the resin solution to the substrate surface in two stages using coaters with different application widths, forming a thinner thickness portion in the first stage and a predetermined thickness portion in the second stage. Another method is to first apply a resin solution to the substrate surface to a predetermined thickness, and then scrape off the resin from the areas where the thin sections are desired. Other methods may be used to reduce the amount of resin solution applied only to the areas where the thin sections are to be formed. Then, as described above, a separation function layer is formed on the porous support layer. Furthermore, if necessary, chemical treatment with chlorine, acid, alkali, nitrous acid, or the like is performed to improve separation and permeation performance, and then monomers and the like are washed away to produce a continuous sheet of separation membrane.

[0064] In the manufacturing process of the separation membrane body in this embodiment, it is preferable that exposed substrate portions, where the separation functional layer and the porous support layer are not laminated on the substrate, are formed at both ends of two sides of the separation membrane body corresponding to both ends of the spiral-wound separation membrane element, and that thin-thickness portions of the porous support layer are provided inside each of the exposed substrate portions in regions corresponding to the above-mentioned sealing portions. By providing exposed substrate portions at both ends of the above-mentioned two sides of the separation membrane body, it is possible to suppress the phenomenon of curling of both ends of the substrate in the width direction due to differences in the thermal shrinkage rates between the substrate and the porous support layer and separation functional layer. This significantly improves the workability of the manufacturing process of the separation membrane body and the subsequent winding process of the envelope-shaped membrane.

[0065] The method for forming the exposed substrate portion is not particularly limited, but may be, for example, a method in which the area onto which the resin solution for forming the porous support layer is applied is made smaller than the size of the substrate.

[0066] 6-3 Lamination and Winding of Separation Membranes The separation membrane bodies, the feed-side channel material, and the permeate-side channel material are laminated to form a pre-sealed laminate, with the feed-side surface of the separation membrane body obtained by the above method facing the feed-side channel material and the permeate-side surface of the separation membrane body facing the permeate-side channel material, respectively. The obtained pre-sealed laminate includes a laminate structure in which the separation membrane bodies face each other at the permeate-side surfaces, sandwiching the permeate-side channel material. An envelope-shaped membrane is formed by sealing three of the four peripheral edges of the laminate structure. The envelope-shaped membrane obtained in this way has a rectangular shape with the permeate-side surface of the separation membrane facing inward, and sealing portions are provided on only three of the peripheral edges of the envelope-shaped membrane. The sealing can be performed by adhesion using an adhesive or hot melt, or by heat or laser fusion, etc.

[0067] As a method for producing the pre-sealed laminate, for example, a method in which one separation membrane body is folded with a feed-side channel material sandwiched therebetween so that the feed-side surface faces inward, and multiple sets of these are laminated together with a permeate-side channel material may be mentioned. Alternatively, another method may be a method in which two separation membrane bodies are stacked together with a permeate-side channel material sandwiched therebetween so that the permeate-side surfaces of the separation membrane bodies face inward, and then further laminated with a feed-side channel material.

[0068] When the sealing is performed by adhesive bonding, the viscosity of the adhesive is preferably in the range of 4 to 15 Pa·sec, and more preferably 5 to 12 Pa·sec. Wrinkles in the separation membrane can reduce the performance of the spiral-wound separation membrane element, but an adhesive viscosity of 15 Pa·sec or less makes it less likely for wrinkles to form when the separation membrane is wound around the central pipe. Furthermore, an adhesive viscosity of 4 Pa·sec or more prevents the adhesive from leaking out from between the separation membranes, reducing the likelihood of the adhesive adhering to unwanted areas.

[0069] The adhesive is cured after the step of obtaining the wound body, which will be described later.

[0070] When an adhesive is used in the process of forming the envelope-shaped membrane, and when at least thin portions are provided in the sealing portions of two of the three sides formed on the peripheral edge of the envelope-shaped membrane, which correspond to both ends of the spiral separation membrane element, it is preferable to apply the adhesive so that the adhesive covers at least the area corresponding to the thin portions, as this can improve the sealing ability of the spiral separation membrane element.

[0071] The amount of adhesive applied is preferably such that the width of the adhesive-coated portion after the separation membrane is wound around the central pipe is 10 mm to 100 mm. This ensures reliable adhesion of the separation membrane, suppressing the inflow of the feed fluid to the permeate side. It also ensures a relatively large effective membrane area. The width is preferably 10 mm to 100 mm, more preferably 20 mm to 80 mm.

[0072] The adhesive is preferably a urethane adhesive, and to achieve a viscosity in the range of 4 to 15 Pa·sec, it is preferable to use a mixture of isocyanate as the base agent and polyol as the curing agent in a ratio of isocyanate:polyol = 1:1 to 1:5. The viscosity of the adhesive is measured using a B-type viscometer (JIS K 6833) for the base agent, the curing agent alone, and a mixture with a specified blending ratio.

[0073] The resulting laminate, including the envelope-shaped membrane and the permeate-side channel material and feed-side channel material sandwiched therein, is wound around the central pipe so that one side of the envelope-shaped membrane's peripheral edge that is not provided with a sealed portion is in contact with the central pipe, i.e., so that the opening is positioned on the inside in the winding direction. In this way, the separation membrane is spirally wound to form a wound body. Here, the laminate, including the envelope-shaped membrane and the permeate-side channel material and feed-side channel material sandwiched therein, may be wound around the central pipe as a single set, or multiple sets may be superimposed and wound around the central pipe, depending on the membrane area of ​​the separation membrane element to be produced.

[0074] If the above-mentioned exposed substrate portions are provided in the process for manufacturing the separation membrane body, the exposed substrate portions provided in the regions corresponding to both ends of the spiral-wound separation membrane element for the purpose of suppressing curling of the separation membrane are no longer necessary after the separation membrane is spirally wound. Therefore, by trimming both ends of the wound body to remove the exposed substrate portions after winding the separation membrane and after the adhesive has cured, a wound body can be obtained in which the ends of the separation membrane in the longitudinal direction of the center pipe are trimmed evenly.

[0075] 6-4 Other Steps The manufacturing method for a spiral-wound separation membrane element may include further winding a film, filaments, etc. around the outside of the separation membrane wound body formed as described above, or may include further steps such as attaching end plates.

[0076] 7. Use of Spiral-Wound Separation Membrane Elements Spiral-wound separation membrane elements may be connected in series or in parallel and housed in a pressure vessel to be used as a separation membrane module.

[0077] Furthermore, the spiral-wound separation membrane element and separation membrane module can be combined with a pump for supplying fluids to them, a device for pretreating the fluids, etc. to form a fluid separation device. By using this separation device, for example, feed water can be separated into permeated water such as drinking water and concentrated water that has not permeated the membrane, thereby obtaining permeated water suitable for the purpose.

[0078] The higher the operating pressure of the fluid separation device, the more improved the removal rate of components contained in the feed fluid. On the other hand, taking into consideration the energy required for operation and the retention of the feed and permeation channels of the spiral separation membrane element, the operating pressure when the feed fluid is permeated through the membrane module is preferably 0.2 MPa or more and 8 MPa or less.

[0079] Generally, the higher the feed fluid pressure, the more the leakage of the feed fluid from the sealing portions increases, leading to a deterioration in the quality of the permeated fluid, but the spiral-wound separation membrane element of this embodiment has excellent sealing properties due to high adhesive impregnation into the thin portions of the substrate and the porous support layer. Therefore, it is particularly preferable to operate the spiral-wound separation membrane element of this embodiment using an operating method for producing water at a feed fluid pressure of 4.0 MPa or more, as this ensures a stable water production volume and salt rejection even during long-term operation.

[0080] As the feed fluid temperature increases, the removal rate of components contained in the feed fluid decreases, but as the temperature decreases, the membrane permeation flux also decreases. Therefore, the feed fluid temperature is preferably 5°C or higher and 45°C or lower, and more preferably 15°C or higher and 40°C or lower. Furthermore, when the feed fluid is a liquid, if the pH of the feed water is in the neutral range, even if the feed water is a liquid with a high salt concentration such as seawater, the generation of scale such as magnesium is suppressed and membrane deterioration is also suppressed. Therefore, the pH of the feed water is preferably 5 to 9.5, and more preferably 6 to 9.

[0081] The feed fluid to be treated by the spiral-wound separation membrane element is not particularly limited. When used for water treatment, the feed water may be a liquid mixture containing 500 mg / L to 100 g / L of TDS (Total Dissolved Solids), such as seawater, brine, or wastewater. Generally, TDS refers to the amount of total dissolved solids and is expressed as "mass / volume," but it can also be expressed as a "weight ratio" assuming 1 L is equal to 1 kg. By definition, TDS can be calculated from the weight of the residue obtained by evaporating a solution filtered through a 0.45 μm filter at a temperature of 39.5 to 40.5°C, or more simply, it can be calculated from the practical salinity (S).

[0082] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0083] (Preparation of Separation Membrane Body) As a substrate, a nonwoven fabric made of polyethylene terephthalate fiber (fineness: 1 dtex, thickness: approximately 90 μm, air permeability: 1 cc / cm ２ / sec, density: 0.80g / cm ３) was used. The fiber orientation degree in the surface layer of the nonwoven fabric opposite the porous support layer was 15°, and the difference between the fiber orientation degree in the surface layer opposite the porous support layer and the fiber orientation degree in the surface layer on the porous support layer side was 30°. A 16.0 mass% DMF solution of polysulfone at 20°C was used as the material for forming the porous support layer. This resin solution was applied to the front side of the nonwoven fabric so that thin portions of a constant width were formed on both the left and right ends. At this time, a bar coater equipped with a coating bar having a stepped surface with convex portions (thick diameter portions) 70 μm high and 10 mm wide on both ends was placed on the surface of the nonwoven fabric to be coated with the resin solution, and the resin solution was applied to the surface of the nonwoven fabric so as to form a predetermined thickness portion, and the convex portions (thick diameter portions) of the coating bar were used to form thin portions on both the left and right ends in the width direction. In addition, between the outer widthwise edges of the thinner portion and both widthwise edges of the nonwoven fabric, there were provided substrate exposed portions with a width of 25 mm on each side, where only the nonwoven fabric was present and neither the separating functional layer nor the porous support layer was present. The back surface of the nonwoven fabric was supported over its entire width by a backup roll.

[0084] The nonwoven fabric coated with the resin solution was immediately immersed in pure water at 20°C and left for 5 minutes, and then immersed in warm water at 80°C for 1 minute to produce a porous support layer roll consisting of a fiber-reinforced polysulfone support membrane with a thickness of 50 μm in the specified thickness portion and a thickness of 25 μm in the thinner thickness portion.

[0085] The surface of the polysulfone layer of the porous support layer was then immersed in an aqueous solution containing 3.8% by mass of m-PDA and 0.8% by weight of ε-caprolactam for 2 minutes, and then slowly pulled up vertically. Excess aqueous solution was then removed from the surface of the porous support layer by blowing nitrogen from an air nozzle.

[0086] Next, an n-decane solution containing 0.18% by mass of trimesoyl chloride was applied to the surface of the polysulfone porous support layer so that it was completely wet, and then the layer was left to stand for 1 minute. After that, excess solution was removed from the membrane with an air blower, and the membrane was washed with hot water at 90°C for 1 minute to obtain a composite separation membrane roll.

[0087] (Fabrication of a spiral-type separation membrane element) The obtained composite separation membrane roll was unwound, and the effective area of ​​the spiral-type separation membrane element was 8.5 m ２ A polypropylene net (thickness: 0.6 mm, length: 840 mm) was sandwiched between the sheets as a feed channel material to prepare a leaf.

[0088] A tricot (thickness: 0.26 mm) was laminated on the permeate side of the obtained leaf as a permeate-side channel material. The resulting pre-sealed laminate had a laminate structure in which the separation membrane bodies faced each other on the permeate side, sandwiching the permeate-side channel material. An envelope-shaped membrane with a sealed portion was formed by opening only one side of the laminate structure so that the permeating fluid could flow into the central pipe, and applying a urethane adhesive to the peripheral portions of the other three sides to isolate the feed fluid from the permeating fluid. Of the sealed portions formed on the three sides of the peripheral portion of the envelope-shaped membrane, the adhesive was applied to the sealed portions on the two sides corresponding to both ends of the spiral-wound separation membrane element so that the adhesive spread to the area corresponding to the thin portion. Eight sets of these envelope-shaped membranes were prepared and then spirally wound around a PVC (polyvinyl chloride) central pipe (width: 1016 mm, diameter: 19 mm, number of holes: 23 x 1 linear row), and the outer periphery of the resulting wound body was fixed with tape. Thereafter, both ends of the wound body were trimmed to remove the exposed substrate portions, and end plates were attached, thereby producing a spiral-wound separation membrane element with a diameter of 4 inches and eight leaves, in which a feed fluid was supplied from one end face and a concentrate fluid and a permeate fluid were discharged from the other end face.

[0089] (Measurement of Substrate Thickness) The thickness of the substrate was measured at 20 locations across the width using a Mitutoyo digital thickness gauge (Model ID-C112X), and the average value was calculated.

[0090] (Measurement of thickness of predetermined thickness portion of porous support layer) The thickness of the predetermined thickness portion of the porous support layer was measured at 20 locations at a magnification of 1000x using a digital microscope VHX-1000 manufactured by Keyence Corporation, to measure the thickness of the porous support layer in the effective membrane portion excluding the sealing portion, and the average value was calculated.

[0091] (Measurement of thickness of thin portion of porous support layer) The thickness of the thin portion of the porous support layer was measured at 20 locations at a magnification of 1000 times using a Keyence VHX-1000 digital microscope, and the average value was calculated. The ratio of the thickness of the thin portion to the thickness of the predetermined thickness portion measured above was also calculated.

[0092] (Measurement of overall width of plugged portion) The width of the plugged portion was measured by disassembling and unfolding the spiral separation membrane element, taking out the envelope-like membrane, measuring 30 points from a plane where any plugged portion was present, and calculating the average value.

[0093] (Measurement of width of thin portion of porous support layer) The width of the thin portion of the porous support layer was measured at 20 locations at a magnification of 100 times using a Keyence VHX-1000 digital microscope, and the average value was calculated. In addition, the ratio of the width of the thin portion to the total width of the sealed portion measured above was also calculated.

[0094] (Water production rate) The spiral separation membrane element was placed in a pressure vessel, and an aqueous NaCl solution with a concentration of 32,000 ppm and a pH of 6.5 was used as feed water. After 30 minutes of operation under conditions of an operating pressure of 5.5 MPa and a temperature of 25°C, 1-minute sampling was carried out, and the water permeation rate per day was measured as the water production rate (m ３ The recovery rate was 8%.

[0095] (Removal Rate (TDS Removal Rate)) The TDS concentrations of the feed water used in the 1-minute operation for measuring the amount of water produced and the sampled permeated water were determined by conductivity measurement, and the TDS removal rate was calculated using the following formula: TDS removal rate (%) = 100 × {1 - (TDS concentration in permeated water / TDS concentration in feed water)}

[0096] Example 1 The spiral separation membrane element produced by the above method was placed in a pressure vessel and evaluated under the above conditions. The results are shown in Table 1.

[0097]

[0098] Examples 2 to 6 Spiral-wound separation membrane elements were produced in the same manner as in Example 1, except that the diameter of the convex portion (large diameter portion) of the coating bar was changed and the thickness of the thin portion in the sealed portion was set as shown in Table 1. The spiral-wound separation membrane element was placed in a pressure vessel, and the performance of each element was evaluated under the same conditions as in Example 1. The results are shown in Table 1.

[0099] Examples 7 to 10 Spiral-wound separation membrane elements were produced in the same manner as in Example 1, except that the width of the convex portion (large diameter portion) of the coating bar was changed to make the width of the thin portion in the sealing portion as shown in Table 1. The spiral-wound separation membrane elements were placed in a pressure vessel, and the performance of each element was evaluated under the same conditions as in Example 1. The results were as shown in Table 1.

[0100] Example 11 A spiral-wound separation membrane element was produced in the same manner as in Example 1, except that after forming a porous support layer roll with thin sections formed on both left and right ends in the width direction, the porous support layer in the sealing section of the remaining side where adhesive was applied other than the left and right ends was ground by blasting from the surface side of the porous support layer so as to provide thin sections with the same thickness and width as the left and right ends. The spiral-wound separation membrane element was placed in a pressure vessel, and the performance of each element was evaluated under the same conditions as in Example 1. The results are shown in Table 2.

[0101]

[0102] Examples 12 to 14 The spiral-wound separation membrane element was placed in a pressure vessel, and the performance was evaluated in the same manner as in Example 1 except that the operating pressure was set to the conditions shown in Table 2. The results are shown in Table 2.

[0103] Comparative Example 1 A spiral-wound separation membrane element was produced in the same manner as in Example 1, except that the thickness and width of the thin portion in the sealed portion were set as shown in Table 2, i.e., no thin portion was provided. The spiral-wound separation membrane element was placed in a pressure vessel, and the performance of each element was evaluated under the same conditions as in Example 1. The results are shown in Table 2.

[0104] Comparative Example 2 A spiral-wound separation membrane element was produced in the same manner as in Example 12, except that the thickness and width of the thin portion in the sealed portion were set as shown in Table 2, i.e., no thin portion was provided. The spiral-wound separation membrane element was placed in a pressure vessel, and the performance was evaluated under the same conditions as in Example 12. The results are shown in Table 2.

[0105] Comparative Example 3 A spiral-wound separation membrane element was produced in the same manner as in Example 13, except that the thickness and width of the thin portion in the sealed portion were set as shown in Table 2, i.e., no thin portion was provided. The spiral-wound separation membrane element was placed in a pressure vessel, and the performance was evaluated under the same conditions as in Example 13. The results are shown in Table 2.

[0106] Comparative Example 4 A spiral-wound separation membrane element was produced in the same manner as in Example 14, except that the thickness and width of the thin portion in the sealed portion were set as shown in Table 2, i.e., no thin portion was provided. The spiral-wound separation membrane element was placed in a pressure vessel, and the performance was evaluated under the same conditions as in Example 14. The results are shown in Table 2.

[0107] That is, in Comparative Examples 1 to 4, the thickness of the porous support layer in the plugged portion was uniform and there were no thin portions, so there were areas where the adhesive was insufficiently impregnated, resulting in a decrease in the sealing ability of the spiral-wound separation membrane element and a decrease in the TDS removal rate. The performance degradation was particularly pronounced when the operating pressure was increased. As is clear from the results shown in Tables 1 and 2, the spiral-wound separation membrane elements of Examples 1 to 14 can be said to stably provide excellent separation performance because they can suppress leakage of the feed fluid from the plugged portion even when the spiral-wound separation membrane element is operated at high pressure without complicating the manufacturing process of the spiral-wound separation membrane element.

[0108] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2024-032632) filed on March 5, 2024, the entire contents of which are incorporated by reference.

[0109] The spiral-wound separation membrane element of the present invention is used to separate components contained in fluids such as liquids and gases, and is particularly suitable for use as an RO water purifier or for desalinizing brackish water or seawater.

[0110] 1a, 1b Spiral separation membrane element 2 Feed-side channel material 3a, 3b Separation membrane 4 Permeate-side channel material 5a, 5b Envelope-shaped membrane 6 Center pipe 7 Feed fluid 8 Permeated fluid 9 Concentrated fluid 10 Plug 301 Substrate 302 Porous support layer 303 Separation function layer a Intersection interval of feed-side channel material in a direction perpendicular to the feed fluid flow direction b Intersection interval of feed-side channel material in a direction parallel to the feed fluid flow direction W １ Overall width of the sealing part W ２ Width of the thin part of the porous support layer T １ Thickness of the predetermined thickness portion of the porous support layer T ２ Thickness of the thin part of the porous support layer B １ Substrate thickness P １ Predetermined thickness portion P of the porous support layer ２ Thin part of porous support layer

Claims

1. A spiral separation membrane element for obtaining a permeate fluid from a feed fluid, comprising: a laminate including a separation membrane, a feed-side channel material provided on the feed side surface of the separation membrane, and a permeate-side channel material provided on the permeate side surface of the separation membrane; one or more laminated laminates are superimposed and wound around a central pipe; the separation membrane includes a substrate, a separation functional layer, and a porous support layer present between the substrate and the separation functional layer, and forms a rectangular envelope-shaped membrane with the permeate side surface facing inward; the envelope-shaped membrane has peripheral edges on all four sides, and seals are provided on only three sides of the peripheral edge, excluding the edge that contacts the central pipe, to separate the feed fluid from the permeate fluid so that the permeate fluid flows into the central pipe; the substrate has a uniform thickness at the seal on at least one side; The spiral separation membrane element, wherein the porous support layer has, in the plugged portion on at least one side, a predetermined thickness portion having a predetermined thickness and a thinner thickness portion having a thickness thinner than the predetermined thickness portion.

2. A spiral separation membrane element according to claim 1, wherein the overall width of the plugged portion is 5 mm or more and 50 mm or less, and the ratio of the width of the thin portion of the porous support layer to the overall width of the plugged portion is 10% or more.

3. A spiral separation membrane element according to claim 1, wherein the thickness of the thinner portion of the porous support layer is 5 μm or more and 40 μm or less, and the thickness of the thinner portion is 20% or more and 70% or less of the thickness of the predetermined thickness portion.

4. The spiral-wound separation membrane element according to claim 1, wherein the porous support layer has the thin portions only in the sealed portions on two sides corresponding to both ends of the spiral-wound separation membrane element.

5. A method for producing a spiral separation membrane element according to any one of claims 1 to 4, comprising: a step of producing a separation membrane body including the substrate, the separation functional layer, and the porous support layer present between the substrate and the separation functional layer; a step of laminating the separation membrane body, the supply-side channel material, and the permeate-side channel material so that the supply-side surface of the separation membrane body faces the supply-side channel material and the permeate-side surface of the separation membrane body faces the permeate-side channel material, respectively, to form a pre-sealed laminate having a laminate structure in which the separation membrane bodies face each other on the permeate-side channel material, with the permeate-side channel material sandwiched between them, and sealing three sides of the four peripheral edges of the laminate structure to form the envelope-shaped membrane; and a step of superposing one or more stacks of the obtained envelope-shaped membranes, each stack including the permeate-side channel material and the feed-side channel material sandwiched therein, and winding the stack around the central pipe so that the side of the envelope-shaped membrane not provided with the sealed portion is in contact with the central pipe to obtain a wound body, wherein in the step of producing the separation membrane main body, the porous support layer is provided with the predetermined thickness portion and the thin thickness portion in a region corresponding to the sealed portion on at least one side.

6. A method for producing a spiral separation membrane element according to claim 5, wherein in the process for producing the separation membrane body, exposed substrate portions in which the separation function layer and the porous support layer are not laminated on the substrate are formed at both ends of two sides of the separation membrane body corresponding to both ends of the spiral separation membrane element, and the thin portions of the porous support layer are provided in areas inside each of the exposed substrate portions and corresponding to the sealing portions; in the process for forming the envelope-shaped membrane, the adhesive is applied so that it covers at least the area of ​​the sealing portion where the thin portions are located; after the process for obtaining the wound body, the method further includes a step of hardening the adhesive; and after the process for hardening the adhesive, the method further includes a step of trimming both ends of the wound body to remove the exposed substrate portions.

7. A method for operating a spiral-wound separation membrane element, comprising producing water at a feed fluid pressure of 4.0 MPa or more using the spiral-wound separation membrane element according to any one of claims 1 to 4.

8. A fluid separation device comprising the spiral-wound separation membrane element according to any one of claims 1 to 4.

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