Spiral separation membrane element and operation method thereof

Abstract

The present invention addresses the problem of providing, without complicating a manufacturing process, a separation membrane element in which leakage of a supplied fluid from a sealing part is suppressed and a desalination rate is unlikely to decrease even when the separation membrane element is repeatedly operated at high pressure for a long period of time.　This spiral separation membrane element is formed by spirally winding, around a center pipe, a laminate consisting of alternating layers of separation membrane units and permeate-side flow channel materials. In the separation membrane unit, separation membranes, each having a porous support layer and a separation functional layer on a substrate, are formed so as to sandwich a supply-side flow channel material with the surfaces of the separation membranes on the separation functional layer side facing inward. In the laminate, a sealing part is provided at the peripheral edges between adjacent separation membrane units sandwiching the permeate-side flow channel material, so that the permeate fluid flows into the central pipe. The spiral-type separation membrane element is characterized in that, on at least one side of the sealing part, the Y value of the sealing part in an XYZ color system based on C-light two-degree visual field transmission measurement is 0.15-2.0%.

Description

Spiral-type separation membrane element and its operating method

[0001] The present invention relates to a spiral-type separation membrane element used for separating components contained in fluids such as liquids and gases, and to a method for operating the same.

[0002] There are various methods for separating components contained in fluids such as liquids and gases. For example, taking the technology for removing ionic substances contained in seawater and brine as an example, the use of separation methods using separation membrane elements has been expanding in recent years as an energy-saving and resource-saving process. Separation membranes used in separation methods using separation membrane elements include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, and forward osmosis membranes, in terms of their pore size and separation function. These membranes are used, for example, in the production of drinking water from seawater, brine, and water containing harmful substances, the production of industrial ultrapure water, wastewater treatment, and the recovery of valuable materials, and are selected according to the target separation components and separation performance.

[0003] Separation membrane elements share the common characteristic of supplying a supply fluid to one side of the separation membrane and obtaining a permeate fluid from the other side. Separation membrane elements are constructed by bundling many separation membrane elements of various shapes to increase the membrane area, allowing a large amount of permeate fluid to be obtained per unit element. Various types of elements are manufactured according to 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-type separation membrane elements are widely used in reverse osmosis filtration. Generally, a spiral-type separation membrane element is formed by winding a single or double set of units around a central pipe having pores on its surface. Each unit consists of a separation membrane for separating components contained in the supply fluid, a supply-side channel material for forming a supply-side channel that supplies the supply fluid to the separation membrane surface, and a permeate-side channel material for forming a permeate-side channel that guides the permeate fluid, separated from the supply fluid and permeated through the separation membrane, to the central pipe. In this case, the separation membrane forms a rectangular envelope-shaped membrane with the permeate-side surface facing inward. The envelope-shaped membrane must be open on only one side in the direction of the central pipe so that the permeate fluid flows into the central pipe, and the peripheral edges of the other three sides must be sealed to isolate the supply fluid from the permeate fluid. If this sealed portion is not completely sealed, high separation performance cannot be obtained, and leakage is particularly likely to occur in spiral-type separation membrane elements used under high pressure. Alternatively, an envelope-shaped membrane can be made by folding a long membrane in a zigzag pattern and sealing two sides.

[0005] When the permeate fluid is the product, even a very small amount of leakage of the supply fluid from the sealing section can cause a degradation in quality and become a significant problem. Therefore, improvements to the sealing section to enhance the performance of the separation membrane element have been proposed.

[0006] Specifically, Patent Documents 1 and 2 propose methods for heat-treating or compressing the separation membrane of the sealing portion. Furthermore, Patent Documents 3 and 4 describe a method for manufacturing a separation membrane element using a sealing resin that is easily impregnated into the separation membrane.

[0007] JP-A-1-288303 JP-A-59-136103 JP-A-59-73008 Patent No. 4484635

[0008] However, the separation membrane elements described above do not fully solve the problems of conventional systems. In particular, when the separation membrane elements are operated under high pressure, leakage of the supply fluid from the sealing section increases, sometimes resulting in a significant decrease in the desalination rate. Furthermore, the manufacturing process of the separation membrane elements becomes complicated due to the need for an impulse sealer to heat and pressurize the sealing section, and equipment to accurately apply two different types of sealing resins. In addition, when the sealing resin is impregnated into the separation functional layer of the reverse osmosis membrane, the difference in hardness between the sealing resin sealing section and the effective membrane section becomes large. This can lead to cracks forming on the membrane surface at the boundary between the sealing resin sealing section and the effective membrane section during long-term or repeated operation, resulting in a decrease in desalination performance.

[0009] Therefore, the present invention aims to provide a separation membrane element that suppresses leakage of the supply fluid from the sealing portion and prevents a decrease in the desalination rate, even when the separation membrane element is operated repeatedly under high pressure for a long period of time, without complicating the manufacturing process of the separation membrane element.

[0010] [1] A spiral-type separation membrane element comprising a substrate, a porous support layer formed on the substrate, and a separation function layer formed on the porous support layer, wherein separation membrane units formed so as to sandwich a supply-side flow channel material with the separation function layer side facing inward, and a permeate-side flow channel material are alternately stacked, and sealing portions are provided at the periphery between adjacent separation membrane units on either side of the permeate-side flow channel material to prevent mixing of the supply fluid and the permeate fluid while allowing the permeate fluid to flow into the central pipe, wherein the stack is wound spirally around the central pipe, characterized in that at least one side of the sealing portion has a Y value of 0.15% or more and 2.0% or less in the XYZ color system based on C-light 2-degree field transmission measurement. [2] The spiral-type separation membrane element according to [1], characterized in that at least one side of the sealing portion has a Y value of 0.15% or more and 1.5% or less in the sealing portion. [3] The spiral-type separation membrane element according to [1] or [2], characterized in that the difference in C hardness between the C hardness of the sealing portion and the C hardness of the effective membrane portion is -1.0 or more and 1.5 or less. [4] The spiral-type separation membrane element according to [1] or [2], characterized in that at least one side of the sealing portion, the difference in Y value between the Y value of the sealing portion and the Y value of the effective membrane portion is 0.1% or more and 1.5% or less. [5] The fractional molecular weight of the porous support layer is 10 kDa to 60 kDa, and the specific surface area S is 20 to 50 m². ２ A spiral-type separation membrane element according to [1] or [2], characterized in that it is / g. [6] A method for operating a spiral-type separation membrane element, using the spiral-type separation membrane element according to [1] or [2], to produce water at a supply water pressure of 4.0 MPa or higher. [7] A fluid separation apparatus using the spiral-type separation membrane element according to [1] or [2].

[0011] The present invention makes it possible to obtain a separation membrane element that suppresses leakage of the supply fluid from the sealing portion and prevents a decrease in desalination rate, even when the separation membrane element is operated repeatedly under high pressure for a long period of time, without complicating the manufacturing process of the separation membrane element.

[0012] This is a partially unfolded perspective view showing an example of a separation membrane element. This is a plan view showing an example of a supply-side flow channel material of the present invention. This is a partially unfolded perspective view showing an example of a separation membrane element of the present invention. This is a cross-sectional view taken along line I-I in Figure 3 showing the cross-sectional structure of the sealing portion and the effective membrane portion of the present invention. This is a cross-sectional view taken along line I-I in Figure 3 showing a conventional cross-sectional structure of the sealing portion and the effective membrane portion. This is a cross-sectional view taken along line I-I in Figure 3 showing another conventional cross-sectional structure of the sealing portion and the effective membrane portion.

[0013] Embodiments of the present invention will be described in detail below. In this specification, "~" means that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0014] 1. Separation Membrane Element In the spiral-type separation membrane element 1a shown in Figure 1, a polymer net is used as the supply-side channel material 2 that forms the supply-side channel. Furthermore, a permeate-side channel material 4 with finer spacing than the supply-side channel material is used as the permeate-side channel material to prevent the separation membrane 3a from falling and to form the permeate-side channel. An envelope-shaped membrane 5a is formed by the separation membrane 3a being bonded to both sides of the permeate-side channel material in an envelope shape. The inside of the envelope-shaped membrane 5a constitutes the permeate fluid channel, and the envelope-shaped membrane 5a, which is alternately layered with the supply-side channel material 2, is bonded to the outer surface of the central pipe at a predetermined portion on the opening side and wound in a spiral shape. The x-axis direction in Figure 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-type separation membrane element, the supply fluid 7 is usually supplied from one side and flows parallel to the central pipe, gradually separating into a permeate fluid 8 and a concentrated fluid 9. The permeate fluid 8 exits the separation element from the side opposite to the side from which the supply fluid 7 is supplied. In this method, since the supply fluid 7 flows from one side to the other of the separation membrane element, there is inevitably a sufficient distance in contact with the membrane, and as a result the supply fluid 7 is sufficiently separated into the permeate fluid 8 and the concentrated fluid 9. The supply fluid to the separation membrane element in this embodiment is not particularly limited and may be pre-treated tap water, liquids containing impurities in the solution such as seawater or brine, or various mixed gases or gases containing impurities, and can be selected according to the purpose of various separation operations such as filtration, concentration, and purification.

[0015] 2. Supply-side flow channel material The supply-side flow channel material is provided on the supply-side surface of the separation membrane and forms a flow channel that supplies the supply fluid to the separation membrane. It plays a role in increasing the flow velocity of the supply fluid and disrupting its flow to suppress concentration polarization of the supply fluid.

[0016] Examples of supply-side flow path materials include continuous-shaped members such as knitted, woven, or netted fabrics made of polyethylene or polypropylene, but a net is preferred from the viewpoint of ensuring sufficient flow path for the supply fluid and effectively suppressing concentration polarization. Here, "net" refers to a structure having a mesh shape in which multiple intersecting constituent fibers are heat-fused together, as shown in Figure 2. For example, it can be manufactured by bonding the resins of the warp threads 21 and weft threads 22 extruded from holes provided in an extrusion die in a molten state, and then cooling and solidifying them.

[0017] The fiber diameter of the constituent fibers that make up the above net can be measured by observation using a commercially available microscope or the like. From the viewpoint of achieving a suitable balance between the flow velocity of the supplied fluid and the pressure loss, the constituent fiber diameter is preferably 0.05 to 0.80 mm, and more preferably 0.10 to 0.50 mm.

[0018] The net, which is the supply-side flow channel material, is composed of multiple intersecting constituent fibers, and the thickness of the net is greatest at the intersections of the constituent fibers.

[0019] The thickness of the supply-side channel material, the net, is the average of the thicknesses at 10 or more randomly selected intersections, and can be calculated by dividing the sum of the measured values ​​by the number of measurement points. The thickness at the intersections can be measured directly using a commercially available thickness measuring instrument, or it can be measured by analyzing images of the supply-side channel material cross-section taken using a microscope.

[0020] The thickness of the net, which is the supply-side flow channel material, is preferably 0.20 to 1.00 mm, and more preferably 0.30 to 0.80 mm, in order to improve the amount of fluid permeating through the separation membrane element while avoiding blockage of the flow channel by foulant in the supply fluid.

[0021] From the viewpoint of achieving a suitable balance between the flow velocity of the supplied fluid and the pressure loss, the intersection spacing of the constituent fibers that make up the net, which is the supply-side flow channel material, is preferably 0.5 to 10.0 mm, and more preferably 1.0 to 6.0 mm.

[0022] Here, "intersection spacing of constituent fibers" refers to the distance between the centers of the intersections of constituent fibers, as shown in Figure 2. Two types of intersection spacings, a and b, can be obtained for one void in the net. The longer of these, b, can be measured at 30 randomly selected voids, and the average value of these measurements can be used as the intersection spacing of the constituent fibers.

[0023] 3. Permeation channel material A permeation channel is formed between the separation membranes that sandwich the permeation channel material by the permeation channel material 4. The form of the permeation channel material is not limited, and tricot, nonwoven fabric, porous sheet with protrusions attached, film with uneven surface molding and perforation processing, or uneven nonwoven fabric can be used. In addition, protrusions that function as permeation channel material may be attached to the permeation side of the separation membrane.

[0024] In particular, using tricot manufactured by a circular knitting machine is preferable because it allows the width of the needle loop and the sinker loop to be made almost the same, enabling both loops to be used as flow channels. Furthermore, it allows for the uniform production of an optimal flow channel width that takes into account membrane drop during operation of the separation membrane element, and it is possible to produce a permeate-side flow channel material that has sufficient pressure resistance and flow characteristics even when thin, thus improving the amount of fluid permeating the separation membrane element.

[0025] While there are no particular limitations on the material of the permeable channel material, polyolefins such as polyethylene and polypolypropylene, copolymerized polyolefins, and polyesters such as polyethylene terephthalate and polybutylene terephthalate, copolymerized polyesters are preferred in terms of chemical resistance and processability. Thermosetting polymers can be used as well as thermoplastic polymers.

[0026] 4. Central Pipe The central pipe is provided for the purpose of collecting the permeate fluid that has passed through the separation membrane. It has a hollow shape and a large number of holes that communicate with the hollow part are opened on the pipe surface. For its material, various materials such as hard plastics like PVC and ABS, and metals like stainless steel are used. Basically, the number of central pipes is one per element.

[0027] 5. Separation Membrane 5-1 Overview As the separation membrane, a separation membrane (composite membrane) having a base material, a porous support layer formed on the base material, and a separation functional layer formed on the porous support layer is used. In the above separation membrane, it is preferable that the base material and the porous support layer form a porous support, and the separation functional layer is provided on the porous support.

[0028] 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 "separation functional layer" refers to a layer having at least a separation function.

[0029] When the separation functional layer has both a separation function and a support function, as the separation functional layer, a layer containing a polymer selected from cellulose, polyvinylidene fluoride, polyethersulfone, and polysulfone as the main component is preferably applied.

[0030] On the other hand, as the separation functional layer, a crosslinked polymer is preferably used in terms of easy control of pore size and excellent durability. In particular, in terms of excellent separation performance of the components in the feed fluid, a polyamide separation functional layer obtained by polycondensing a polyfunctional amine and a polyfunctional acid halide, an organic-inorganic hybrid functional layer, etc. are preferably used. These separation functional layers can be formed by polycondensing monomers on a porous support.

[0031] For example, the separation functional layer can contain polyamide as the 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, an aqueous solution of a polyfunctional amine is applied onto a porous support, and the excess aqueous solution of the polyfunctional amine is removed by an air knife or the like, and then an organic solvent solution containing a polyfunctional acid halide is applied, whereby polycondensation occurs and a polyamide separation functional layer is obtained.

[0032] 5-3 Porous support layer 5-3-1 General overview The porous support layer is a layer that supports the separation functional layer, and when the material is a resin, it can also be referred to as a porous resin layer.

[0033] The material used for the porous support layer and its shape are not particularly limited. For example, it may be formed on a substrate by a porous resin. As the porous support layer, polysulfone (hereinafter, "PSf"), cellulose acetate, polyvinyl chloride, epoxy resin, or a mixture or laminate thereof is used. It is preferable to use PSf, which has high chemical, mechanical, and thermal stability and is easy to control the pore diameter.

[0034] The porous support layer can be produced, for example, by casting a solution of the above PSf in N,N-dimethylformamide (hereinafter, "DMF") to a certain thickness on a substrate (for example, a densely woven polyester non-woven fabric) described later and wet-coagulating it in water.

[0035] 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). In addition, the polymer concentration, the temperature of the solvent, and the poor solvent can be adjusted to obtain a desired form. The porous support layer can control the fractional molecular weight and the specific surface area S as described in "7-2-1 Formation process of porous support layer" described later.

[0036] 5-3-2 Morphology of Porous Support Layer and Porous Supporter As shown in Figure 3 as an example, the separation membrane 3b forms a rectangular envelope-shaped membrane 5b with the substrate-side surface (permeation-side surface) facing inward. The envelope-shaped membrane 5b is open on only one side so that the permeate fluid flows into the central pipe, and sealing portions 10 are provided at the periphery of the other three sides to isolate the supply fluid from the permeate fluid. That is, as shown in Figure 3, the periphery of the three sides consists of sealing portions on the two ends of the separation membrane element and a sealing portion on the side parallel to the central pipe, and the permeate fluid is isolated from the supply fluid by these sealing portions. Alternatively, an envelope-shaped membrane can also be made by folding a long membrane in a zigzag pattern and sealing two sides. In this case, the sealing is on the two ends.

[0037] Although not shown in the diagram, the supply-side flow channel material is positioned between each envelope-shaped membrane 5b, that is, between adjacent envelope-shaped membranes 5b arranged so that their supply-side surfaces face each other. The supply-side flow channel material and the multiple envelope-shaped membranes 5b are wrapped around the central pipe 6 in an overlapping state.

[0038] Figure 4 is a cross-sectional view of the boundary between the sealing portion 10 and the effective membrane portion 11. From top to bottom, the components are arranged in the following order: supply-side channel material 2, separation function layer 303, porous support layer 302, substrate 301, permeable-side channel material 4, substrate 301, porous support layer 302, and separation function layer 303. The sealing portion is filled with sealing resin 12. Typically, the porous support layer 302 has an asymmetrical shape in which the pore diameter gradually increases from the separation function layer 303 towards the substrate 301.

[0039] In the spiral-type separation membrane element of the present invention, the molecular weight cutoff of the porous support layer is 10 kDa to 60 kDa, and the specific surface area S is 20 to 50 m². ２ It is preferable that the value is / g. In this specification, the fractional molecular weight and specific surface area S of the porous support layer may be measured using either the separation membrane before use or after use.

[0040] The specific surface area S represents the degree of the three-dimensional network structure in the porous support layer. A large value for the specific surface area S indicates a dense three-dimensional network structure with many small voids. When the three-dimensional network structure is dense, the capillary force of the porous support layer increases, and the rise in the liquid level shown in equation (1), i.e., the impregnation height of the sealing resin, increases, making it possible to efficiently impregnate the sealing resin into the interior of the porous support layer.

[0041]

[0042] Specific surface area S is 20 m² ２ When the density is 50 m² or higher, the porous support layer can efficiently impregnate the sealing resin into the interior of the porous support layer through its three-dimensional network structure, thereby suppressing leakage of the supplied fluid from the sealing portion. On the other hand, when the specific surface area S is 50 m² or higher, ２ If the value is less than / g, the proportion of the three-dimensional network structure that acts as resistance to the water permeability pathway can be suppressed, and sufficient water permeability can be ensured.

[0043] From the perspective of improving sealing performance in areas where leakage from the porous support layer is significant, and from the perspective of ensuring water permeability, the specific surface area S is 20 to 40 m². ２ / g is preferred, and 22 to 40 m ２ / g is more preferable.

[0044] One method for controlling the specific surface area S within the above range is to bring a porous support, which has been immersed in a first solidification solution to form a porous support layer, into contact with a second solidification solution containing a good solvent for the resin forming the porous support layer. This can be controlled by the contact time between the first and second solidification solutions and the temperature of each solidification solution.

[0045] Furthermore, maintaining salt removal performance is a challenge for long-term and repeated operation. Maintaining salt removal performance is mainly due to structural changes at the interface between the cross-linked polyamide and the porous support layer, or the cross-linked polyamide itself, and the structure of the porous support layer surface that forms the cross-linked polyamide is important. However, when attempting to control the specific surface area S within the above range, the structure of the porous support layer surface also changes, making it difficult to obtain the desired salt removal performance.

[0046] As a result of diligent research into the above-mentioned problems, the inventors have found that the molecular weight cutoff of the porous support layer is 10 kDa to 60 kDa, and the specific surface area S is 20 to 50 m². ２ We found that by using a separation membrane with a value of / g, it is easier to control the Y value (brightness) in the XYZ color system based on C-light 2-degree field transmission measurement at the sealing portion of the spiral-type separation membrane element to a desirable range, and that it is possible to achieve both water permeability, maintenance of salt removal properties, and high salt removal performance during long-term and repeated operation.

[0047] In other words, by achieving both the aforementioned fractionation properties and specific surface area S, a superior spiral-type separation membrane element is created that suppresses leakage of the supply fluid from the sealing portion during long-term or repeated operation, and prevents a decrease in water permeability and salt removal performance. Such a separation membrane that achieves both fractionation properties and specific surface area S has not been obtained with conventional technology.

[0048] "Fractional molecular weight" refers to the molecular weight of dextran at which the removal rate of linear dextran is 90%, and can be measured by the method of "measurement of fractional molecular weight of porous support layer" described in the examples below. The fractional molecular weight of the porous support layer is more preferably 30 kDa to 50 kDa, and even more preferably 30 kDa to 45 kDa.

[0049] By setting the fractional molecular weight of the porous support layer within the above range, a separation membrane capable of maintaining salt removal performance during long-term operation or repeated operation can be obtained. When the fractional molecular weight of the porous support layer is 60 kDa or less, deformation of the separation functional layer caused by the separation functional layer falling onto the surface of the porous support layer during long-term operation or repeated operation under high pressure is less likely to occur, and a decrease in salt removal performance is suppressed. Further, when the fractional molecular weight of the porous support layer is 10 kDa or more, an amine aqueous solution is sufficiently supplied from the porous support layer to the interface during the formation of the polyamide functional layer by interfacial polymerization, suppressing a decrease in the water permeability of the separation membrane, forming a polyamide with a preferable strength, and enabling the salt removal performance to be maintained during high-pressure operation. Examples of methods for controlling the fractional molecular weight of the porous support layer within the above range include, for example, a method of adjusting the coagulation liquid temperature when forming the porous support layer, and a method of adjusting the resin concentration of the resin solution for forming the porous support layer. Note that the long-term operation or repeated operation under high pressure as described above is exemplified by the supply pressure during seawater desalination or water production operation in the zero liquid discharge (ZLD) region, and includes, for example, water production operation at 4 MPa or more.

[0050] The mass of the porous support layer according to the present embodiment is preferably 10 to 17 g / m ２ more preferably 10 to 15 g / m ２ still more preferably 11 to 15 g / m ２ By controlling the mass of the porous support layer within the above range, both the strength and the connectivity of the porous support layer can be achieved. The mass of the porous support layer can be controlled, for example, by the resin concentration in the resin solution, the coating thickness of the resin solution on the substrate, the temperature of the coagulation liquid, and the like.

[0051] The thickness of the porous support layer is preferably 15 μm or more and 55 μm or less, and more preferably 20 μm or more and 45 μm. By setting the thickness of the porous support layer within the above range, while ensuring the winding property of the separation membrane element, ensuring appropriate impregnation property of the sealing resin in the sealing portion, suppressing leakage of the supply fluid from the sealing portion, and improving long-term repeated operation performance can be achieved simultaneously.

[0052] The thickness of the porous support layer is the average value obtained by measuring the thickness of the porous support layer in the effective film portion, excluding the sealing portion, over its width. This can be determined by measuring the effective film portion crosswise using a microscope, summing the values ​​for each predetermined thickness, and dividing the sum by the total number of measurement points.

[0053] 5-4 Substrate 5-4-1 Overview From the viewpoint of 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 the base material Long fiber nonwoven fabrics and short fiber nonwoven fabrics can be preferably used as the base material. In particular, long fiber nonwoven fabrics have excellent film-forming properties, so when a polymer solution is cast, it can suppress the leakage of the solution due to over-penetration, the peeling of the porous support layer, the non-uniformity of the film due to fuzzing of the base material, and the occurrence of defects such as pinholes. Furthermore, since the base material is made of a long fiber nonwoven fabric composed of thermoplastic continuous filaments, it can suppress the non-uniformity caused by fiber fuzzing and the occurrence of film defects that occur when polymer solutions are cast, compared to short fiber nonwoven fabrics. In addition, since tension is applied in the film-forming direction when the separation membrane is continuously formed, it is preferable to use a long fiber nonwoven fabric with excellent dimensional stability as the base material.

[0055] In long-fiber nonwoven fabrics, it is preferable that the fibers in the surface layer opposite the porous support layer are more longitudinally oriented than the fibers in the surface layer on the porous support layer side, in terms of moldability and strength. Such a structure provides a high effect in preventing film tearing and the like by maintaining strength. More specifically, the degree of fiber orientation in the surface layer opposite the porous support layer of the long-fiber nonwoven fabric is preferably 0° to 25°, and the difference in the degree of orientation between this and the fiber orientation in the surface layer on the porous support layer side is preferably 10° to 90°.

[0056] The manufacturing process for separation membranes and elements involves heating, which causes the porous support layer or separation functional layer to shrink. This shrinkage is particularly pronounced in the width direction where tension is not applied during continuous film formation. Because this shrinkage can cause problems with dimensional stability, a substrate with a low thermal dimensional change rate is desirable. In nonwoven fabrics, it is preferable that the difference in fiber orientation between the surface layer opposite the porous support layer and the surface layer on the porous support layer side is between 10° and 90°, as this can suppress changes in the width direction due to heat.

[0057] Here, fiber orientation is an index that indicates the orientation of the fibers in the nonwoven fabric substrate that constitutes the porous support layer. Specifically, fiber orientation is the average value of the angle between the film formation direction during continuous film formation, that is, the longitudinal direction of the nonwoven fabric substrate, and the fibers that constitute the nonwoven fabric substrate. In other words, if the longitudinal direction of the fibers is parallel to the film formation direction, the fiber orientation is 0°. Also, if the longitudinal direction of the fibers is perpendicular to the film formation direction, that is, parallel to the width direction of the nonwoven fabric substrate, the fiber orientation is 90°. Therefore, the closer the fiber orientation is to 0°, the more longitudinally oriented the fibers are, and the closer it is to 90°, the more transversely oriented the fibers are.

[0058] The degree of fiber orientation is measured as follows: First, ten small sample pieces are randomly taken from the nonwoven fabric. Next, the surface of these samples is photographed with a scanning electron microscope at 100 to 1000x magnification. From the captured image, ten fibers are selected from each sample, and the angle is measured with the longitudinal direction (vertical direction, film formation direction) of the nonwoven fabric set to 0°. In other words, the angle is measured for a total of 100 fibers per nonwoven fabric. The average value is calculated from the angles of these 100 fibers. The value obtained by rounding the resulting average value to the first decimal place is the degree of fiber orientation.

[0059] While a thicker substrate is preferable to increase the separation membrane strength, if it is too thick, the impregnation of the sealing resin decreases and the packing membrane area per element becomes smaller. Therefore, a substrate thickness of 60 μm to 150 μm is preferable, and a thickness of 70 μm to 110 μm is more preferable.

[0060] Furthermore, the thickness of the separation membrane body, which consists of a separation functional layer, a porous support layer, and a substrate, is preferably 90 μm to 200 μm, and more preferably 100 μm to 140 μm, in order to ensure winding around the central pipe.

[0061] The thickness of the substrate and the separation membrane body is the average value obtained by measuring the thickness of any substrate across its width. This can be done directly using a commercially available thickness measuring instrument, or by analyzing cross-sectional images taken with a microscope.

[0062] 6. Sealing Section 6-1 Overview The sealing section is formed by joining opposing separation membranes via a permeable flow channel material in order to isolate the supply fluid from the permeable fluid.

[0063] 6-2 Morphology of the Sealing Section The sealing section can be formed by bonding with an adhesive or hot melt, or by heat or laser fusion, but sealing with an adhesive is preferred in terms of ensuring the winding of the element and suppressing cost increases. Specifically, it is formed by applying an adhesive to the edge of the opposing separation membrane via the permeable flow channel material and curing it.

[0064] In the present invention, it is required that at least one side of the sealing portion has a Y value of 0.15% or more and 2.0% or less in the XYZ color system based on C-light 2-degree field transmission measurement.

[0065] Here, the XYZ color system is a color system that converts the tristimulus values ​​of color X (red), Y (green), and Z (blue) into x, y, and Y chromaticity coordinates (CIE chromatosity diagram) and represents them as a color solid space. The chromaticity is shown at points on the diagram from x and y obtained by equations (1) and (2), where Y is brightness, and perfect black (lower limit) is represented by 0% and perfect white (upper limit) by 100%.

[0066]

[0067]

[0068] As a result of diligent research, the inventors have found that measuring the Y value of the sealed portion in the XYZ color system based on C-light 2-degree field-of-view transmission measurement is a method for identifying the morphology of the sealed portion. When the void between the separation membrane forming the sealed portion and the permeable channel material is filled by sealing, the light transmittance in that portion increases. Therefore, by measuring the above Y value, the sealing state of the sealed portion can be identified with high accuracy.

[0069] As shown in Figure 6, the more voids there are inside the porous support layer in the sealing portion, that is, the larger the leakage path 14 of the supplied fluid in the planar direction of the porous support layer, the smaller the Y value becomes. On the other hand, as shown in Figure 5, the fewer voids there are inside the substrate and the porous support layer, that is, the smaller the leakage path 14 of the supplied fluid in the planar direction of the porous support layer, the larger the Y value becomes. However, if the Y value becomes too large, the hardness difference between the sealing portion and the effective membrane portion becomes large, and during long-term or repeated operation, cracks may occur on the membrane surface near the boundary, forming a leakage path 13 of the supplied fluid and leading to a decrease in desalination performance. For this reason, in the spiral-type separation membrane element of the present invention, the Y value needs to be between 0.15% and 2.0%. If the Y value is less than 0.15%, the mixing of the supplied fluid into the permeate fluid cannot be sufficiently prevented, and if the Y value is greater than 2.0%, cracks will occur on the membrane surface near the boundary during long-term or repeated operation, and the element performance will decrease. From the viewpoint of achieving both efficient sealing of leakage paths of the supply fluid in the planar direction of the porous support layer and long-term operational stability, it is preferable that the concentration is 0.3% to 1.5%, and more preferably 1.0% to 1.5%.

[0070] Furthermore, since the Y value varies depending on the structure, thickness, and material of the porous support layer and substrate, it is preferable that the Y value difference, expressed as the difference between the Y value of the sealed portion and the Y value of the effective film portion, be 0.1% or more and 1.5%, and more preferably 0.2% or more and 1.3%, in terms of achieving both efficient sealing of the leakage path of the supply fluid in the planar direction of the porous support layer and long-term operational stability.

[0071] Since the Y value is affected by residual moisture in the separation membrane, the measurement is performed by removing the tape fixing the end plates and outer surface of the spiral-type separation membrane element, disassembling and unfolding it to remove the envelope-shaped membrane, drying it in a vacuum oven set to 40°C until there is no change in the weight of the sample, and then randomly taking small pieces of the sealed part and measuring them to obtain the average value. This can be measured using a commercially available optical measuring instrument such as a colorimeter, with the following conditions: colorimetric conditions: C light 2-degree field of view, photometric method: left and right (45°) two-way illumination method, measurement hole diameter: φ12 mm, optical conditions: transmission measurement with 0° illumination and 0° reception in accordance with JIS Z 8722 condition e.

[0072] To bring the Y value within the above range, methods such as changing the degree or thickness of the three-dimensional network structure of the porous support layer, changing the shape or thickness of the substrate, changing the moisture content of the film in the adhesive-coated area, controlling the viscosity of the adhesive and its affinity with the support layer material, controlling the pressure during winding, or a combination of these methods can be used.

[0073] Another preferred means for achieving the above Y value is to set the impregnation rate of the adhesive to 25% or more and 90% or less. In terms of achieving both efficient sealing of leakage paths of the supply fluid in the planar direction of the porous support layer and long-term operational stability, the impregnation rate of the adhesive is more preferably 45% or more and 80% or less, and even more preferably 60% or more and 80% or less.

[0074] The measurement of adhesive impregnation is affected by residual moisture in the separation membrane. Therefore, after removing the tape fixing the end plates and outer surface of the spiral-type separation membrane element, the element is disassembled and unfolded to extract the envelope-shaped membrane. After drying it in a vacuum oven set to 40°C until there is no change in the weight of the sample, small pieces of the sealed area are randomly taken and measured, and the average value obtained is the result. This can be measured by observing and analyzing the cross-section of the adhesive area using a broad ion beam (BIB) and scanning electron microscope (SEM).

[0075] To keep the adhesive impregnation rate within the above range, methods such as changing the degree and thickness of the three-dimensional network structure of the porous support layer, changing the shape and thickness of the substrate, changing the water content in the film of the adhesive-coated area, controlling the viscosity of the adhesive and its affinity with the support layer material, controlling the pressure during winding, or a combination of these methods can be used.

[0076] The adhesive impregnation rate of the sealing area can be measured by observing and analyzing the cross-section of the adhesive area using a broad ion beam (BIB) and a scanning electron microscope (SEM). BIB is a method in which a shielding plate is placed in close contact with the sample, and the portion protruding from the shielding plate is scraped off with a broad ion beam to create a smooth observation surface. Normally, cross-sectional observation of a film is performed by freeze-fracture using liquid nitrogen, but this method results in irregularities on the observation surface, making it difficult to determine the adhesive impregnation rate. Using BIB makes it possible to create a smooth cross-section, and it is possible to visualize how far the adhesive has impregnated into the support layer.

[0077] The impregnation rate of the adhesive is determined by analyzing the support layer region within the cross-section of the sealed area. The thickness of the support layer in the unsealed area where adhesive is not applied is measured, and the region corresponding to the support layer thickness is determined from the functional layer side surface of the sealed area cross-section. For example, if the average thickness of the support layer in the unsealed area is 0.040 mm, the range of 0.040 mm from the functional layer side surface of the sealed area cross-section is analyzed. The analysis method involves binarizing the adhesive region and the rest of the sealed area cross-section, and then analyzing it using imageJ.

[0078] The spiral-type separation membrane element of the present invention can prevent cracks from forming on the membrane surface near the boundary between the sealing portion and the effective membrane portion during long-term or repeated operation, thereby suppressing the formation of a leakage path 13 for the supplied fluid. The difference in hardness between the sealing portion and the effective membrane portion is expressed as the difference between the C hardness of the sealing portion and the C hardness of the effective membrane portion (hereinafter referred to as the C hardness difference), and this C hardness difference is preferably between -1.0 and 1.5, and more preferably between -1.0 and 1.0. By reducing the C hardness difference in this way, a spiral-type separation membrane element more suitable for long-term and repeated operation can be made.

[0079] In the present invention, the width of the sealing portion is preferably 5 mm or more, and more preferably 10 mm or more, in order to suppress leakage of the supplied fluid. On the other hand, from the viewpoint of effective film area, it is preferably 50 mm or less, and more preferably 30 mm or less. In other words, from the viewpoint of achieving both sealing performance and productivity, the width of the sealing portion is preferably 5 mm or more and 50 mm or less, and more preferably 10 mm or more and 30 mm or less.

[0080] Here, the width of the sealed portion refers to the width of the part sealed by bonding with adhesive or hot melt, or by heat or laser fusion. The measurement can be taken by measuring from a plane at any location where a sealed portion exists, and then dividing the sum of the values ​​for each sealed portion by the total number of measurement locations.

[0081] In the spiral-type separation membrane element of the present invention, it is preferable that regions where the Y value in the XYZ color system, based on C-light 2-degree field transmission measurement of the sealing portion, is 0.15% or more and 2.0% or less, are provided on at least two sides of the separation membrane element, as this simplifies the assembly process of the separation membrane element and improves the sealing performance in areas where leakage contributes significantly.

[0082] 7. Method for Manufacturing Separation Membrane Elements 7-1 Overview Conventional element manufacturing equipment can be used to manufacture separation membrane elements. In addition, the methods described in the references (Japanese Patent Publication No. 44-14216, Japanese Patent Publication No. 4-11928, Japanese Patent Application Publication No. 11-226366) can be used as the element manufacturing method. Details are as follows.

[0083] 7-2 Method for Manufacturing Separation Membrane 7-2-1 Step for Forming Porous Support Layer The step for forming a porous support layer in the method for manufacturing a separation membrane of the present invention includes the following steps (a) to (c). Step (a) A step of placing a resin solution obtained by dissolving a thermoplastic resin in a good solvent onto a substrate. Step (b) Immersing the resin solution placed on the substrate into a first coagulation solution containing a non-solvent and a good solvent of the thermoplastic resin to form a porous support layer on the substrate, wherein the amount of good solvent in the porous support consisting of the substrate and the porous support layer is 10 to 60 g / m² ２Step (c) A step of obtaining a porous support. Step (c) A step of immersing the porous support in a second coagulation solution.

[0084] In step (a) above, the resin solution is applied to the substrate. Then, in step (b) above, the resin solution is brought into contact with a first coagulation solution containing the non-solvent of the resin and a good solvent, thereby initiating phase separation from the surface of the resin solution and forming a porous support layer.

[0085] In conventional methods for forming porous support layers, the surface of the resin solution comes into large contact with the solidifying liquid, which is the non-solvent of the resin, causing it to solidify immediately and form a dense three-dimensional network structure. On the other hand, the interior of the resin solution solidifies relatively slowly compared to the surface because the dense three-dimensional network structure formed on the surface of the resin solution suppresses the inflow of the solidifying liquid and the outflow of good solvents from the resin solution. Therefore, in conventional methods for forming porous support layers, phase separation progresses inside the resin solution, and the interior of the porous support layer forms a network structure with larger voids compared to the surface. A network structure with large voids has weak capillary forces, which is unfavorable for improving the impregnation of the sealing resin into the porous support layer, resulting in a low Y value.

[0086] As a result of diligent research, the inventors have determined that in step (b), the amount of good solvent in the porous support is 10 to 60 g / m². ２ By setting the porous support obtained in step (b) to a second solidification solution in step (c), the interior of the porous support layer is completely solidified, forming a dense three-dimensional network structure inside the porous support layer, and a separation membrane with small pore sizes on the surface of the porous support layer can be obtained. In step (c), by bringing the inner layer of the porous support into contact with the second solidification solution while the porous support contains a certain amount of good solvent, the inner layer of the porous support layer dissolves, forming a dense three-dimensional network structure with high communication in the inner layer, and improving the impregnation of the sealing resin. In other words, it becomes possible to control the fractional molecular weight and specific surface area S within an appropriate range.

[0087] "Resin" refers to the thermoplastic resin that forms the main component of the porous support layer, specifically as described above.

[0088] "Good solvent" refers to a solvent that dissolves the resin. By selecting a good solvent, the rate at which the good solvent flows out of the resin solution in step (b) can be adjusted. As a result, the pore size on the back surface of the porous support layer and the flow path on the substrate surface of the porous support layer can be controlled. As a good solvent, at least one solvent selected from the group consisting of amides such as N-methyl-2-pyrrolidone, tetrahydrofuran, dimethyl sulfoxide, tetramethylurea, N,N-dimethylacetamide, DMF, N,N-dimethylisobutylamide, N,N-diisopropylisobutylamide, and N,N-bis(2-ethylhexyl)isobutylamide, acetone, lower alkyl ketones such as methyl ethyl ketone, esters such as trimethyl phosphate, and lactones such as γ-butyrolactone is preferably used. Among these, the use of DMF as the good solvent is more preferable.

[0089] Step (a) can be carried out by applying a resin solution to the substrate or by immersing the substrate in a resin solution.

[0090] The resin solution can be applied to the substrate by various coating methods. Among these, pre-metering coating methods such as die coating, slide coating, and curtain coating, which can supply an accurate amount of resin solution, are preferred. In particular, the slit die method for applying the resin solution is preferred for forming the porous support layer. The coating thickness of the resin solution on the substrate is preferably 50 to 150 μm, and more preferably 80 to 120 μm. By setting the coating thickness within the above range, the thickness of the porous support layer and the pore diameter on the back surface of the porous support layer can be controlled to a suitable range.

[0091] For example, if the resin solution contains PSf, the PSf concentration (i.e., the solid content concentration) is preferably 17 to 24% by mass.

[0092] By setting the PSf concentration within the above range, a certain amount of good solvent can be included in step (c), and as a result, the specific surface area S can be controlled to a desirable range.

[0093] When applying a resin solution, if PSf is used as the resin, it is preferable to apply the solution within the range of 10 to 40°C. Within this range, the resin can be applied without precipitation. The preferred temperature range of the resin solution can be adjusted as appropriate depending on the viscosity of the resin solution used.

[0094] The thermoplastic resin contained in the resin solution may be changed as appropriate, taking into consideration various properties such as the strength characteristics, permeability characteristics, and surface characteristics of the porous support layer.

[0095] The solvent contained in the resin solution may be a single good solvent for the resin, or a mixture of several good solvents may be used. The solvent can be adjusted as appropriate, taking into account the strength characteristics of the porous support layer to be manufactured and the impregnation of the resin solution into the substrate.

[0096] In step (b), the resin solution placed on the substrate is brought into contact with a first coagulation solution mainly composed of a non-solvent, which has a lower solubility of the resin compared to the good solvent in the resin solution. By coagulating the resin, a porous support layer having a dense three-dimensional network structure can be formed.

[0097] The first coagulation solution is a mixed solution of a resin non-solvent and a good solvent, with the non-solvent being the main component. The concentration of the good solvent in the first coagulation solution is preferably 10 to 40% by mass.

[0098] Furthermore, the contact time between the resin solution and the first coagulation solution is preferably 3 to 60 seconds, and more preferably 3 to 30 seconds. When the contact time between the resin solution and the first coagulation solution is within the above range, the substitution of good solvents in the resin solution with the coagulation solution can be controlled.

[0099] Furthermore, the temperature of the first coagulation solution is preferably 10 to 45°C. If the temperature of the first coagulation solution is 45°C or lower, the vibration of the coagulation solution surface due to thermal motion does not intensify, and the surface smoothness of the porous support layer is improved. Also, if the temperature of the first coagulation solution is 10°C or higher, a sufficient coagulation rate can be obtained, and film-forming properties are good. When the temperature of the coagulation solution is within the above range, the molecular weight cutoff of the porous support layer can be controlled to the range of 10 kDa to 60 kDa, and a separation functional layer with excellent salt removal properties can be formed.

[0100] Examples of non-solvents used in the first coagulation solution include water, hexane, pentane, benzene, toluene, methanol, ethanol, trichloroethylene, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, pentanediol, hexanediol, low molecular weight polyethylene glycol, aliphatic hydrocarbons, aromatic hydrocarbons, aliphatic alcohols, or mixtures thereof.

[0101] In step (c), the porous support obtained in step (b) is brought into contact with the inner layer of the porous support layer with a second coagulation solution while containing a good solvent. By dissolving the inner layer of the porous support layer, a dense three-dimensional network structure is formed in the inner layer of the porous support layer, and the specific surface area S can be controlled.

[0102] In the method for producing the separation membrane according to this embodiment, an important control factor is the amount of good solvent in the porous support. The amount of good solvent in the porous support when immersed in the second coagulation solution is 10 to 60 g / m². ２ Preferably, 20 to 50 g / m ２ More preferably, 30-40 g / m ２ A more preferable amount of good solvent in the porous support is 10 g / m². ２ If the amount is above this, the amount of good solvent is sufficient to dissolve the resin. On the other hand, the amount of good solvent in the porous support is 60 g / m². ２ The following conditions can suppress structural changes in the surface layer of the porous support. The amount of good solvent in the porous support when immersed in the second solidification solution can be controlled, for example, by the concentration of the good solvent in the first solidification solution used in step (b), the temperature, and the contact time between the resin solution and the first solidification solution.

[0103] The temperature of the second coagulation solution used in step (c) is preferably 20 to 90°C, and more preferably 50 to 85°C. If the temperature of the coagulation solution is 20°C or higher, the inner layer of the porous support layer can be sufficiently dissolved and the connectivity can be controlled, and if it is 90°C or lower, changes in the surface structure of the porous support layer due to thermal shrinkage can be suppressed.

[0104] The second coagulation solution used in step (c) only needs to contain a non-solvent of the resin, and is preferably a mixed solution of the non-solvent of the resin and a good solvent. The concentration of the good solvent in the second coagulation solution is preferably 0.1 to 10% by mass, and more preferably 1 to 10% by mass. If the concentration of the good solvent in the second coagulation solution is 0.1% by mass or more, the inner layer of the porous support layer can be sufficiently dissolved, and if it is 10% by mass or less, changes in the surface structure of the porous support layer can be suppressed.

[0105] Furthermore, since phase separation progresses moment by moment, it is preferable that the time between step (b) and step (c) be as short as possible. The interval between obtaining the porous support in step (b) and carrying out step (c) is preferably 10 seconds or less, more preferably 7 seconds or less, and even more preferably 5 seconds or less.

[0106] Next, it is preferable to wash the obtained porous support with hot water or the like to remove any remaining solvent in the porous support. The temperature of the hot water used for washing is preferably 50 to 100°C, and more preferably 60 to 95°C. If the hot water temperature is 100°C or lower, the degree of shrinkage of the porous support can be kept to a minimum. Also, if the hot water temperature is 50°C or higher, a high cleaning effect can be obtained.

[0107] 7-2-2 Formation Process of the Separation Functional Layer Next, the method for forming the separation functional layer will be described.

[0108] The separation functional layer can be obtained, for example, by forming a crosslinked polyamide by chemically reacting a polyfunctional amine with a polyfunctional acid halide, as described above. Interfacial polymerization is the most preferred method of chemical reaction from the viewpoint of productivity and performance. Specifically, the separation functional layer is preferably formed by performing interfacial polycondensation on the surface of a porous support layer using an aqueous solution containing a polyfunctional amine and an organic solvent containing a polyfunctional acid halide. This process forms a crosslinked polyamide. The following describes a specific process for forming a crosslinked aromatic polyamide using a polyfunctional aromatic amine as the polyfunctional amine and a polyfunctional acid chloride as the polyfunctional acid halide, but the present invention is not limited thereto.

[0109] Interfacial polymerization includes the following steps (d) and (e): Step (d) A step of contacting an aqueous solution containing a polyfunctional aromatic amine with a porous support layer. Step (e) After step (d), a step of contacting a solution in which a polyfunctional aromatic acid chloride is dissolved with the porous support layer.

[0110] In step (d), the concentration of the polyfunctional aromatic amine in the aqueous solution of the polyfunctional aromatic amine is preferably 0.1 to 20% by mass, and more preferably 0.5 to 15% by mass. When the concentration of the polyfunctional aromatic amine is within this range, sufficient solute removal performance and water permeability can be obtained.

[0111] It is preferable that the contact with the polyfunctional aromatic amine aqueous solution be carried out uniformly and continuously on the porous support layer. Specifically, examples include coating the porous support layer with the polyfunctional aromatic amine aqueous solution, or immersing the porous support layer in the polyfunctional aromatic amine aqueous solution. The contact time between the porous support layer and the polyfunctional aromatic amine aqueous solution is preferably 1 second to 10 minutes, and more preferably 10 seconds to 3 minutes.

[0112] After contacting the porous support layer with the polyfunctional aromatic amine aqueous solution, it is preferable to remove any remaining liquid droplets from the surface of the porous support. Removing the liquid can suppress the occurrence of defects in the separation functional layer. Methods for removing the liquid include, for example, holding the porous support vertically after contact with the polyfunctional aromatic amine aqueous solution to allow excess solution to flow naturally, or forcibly removing the liquid by blowing a stream of air such as nitrogen from an air nozzle. After removing the liquid, the film surface can also be dried to remove some of the water from the aqueous solution.

[0113] The concentration of polyfunctional aromatic acid chloride in the solution is preferably 0.01 to 10% by mass, and more preferably 0.02 to 2.0% by mass. A sufficient reaction rate can be obtained by setting the concentration of polyfunctional aromatic acid chloride in the solution to 0.01% by mass or higher. Furthermore, the occurrence of side reactions can be suppressed by setting the concentration of polyfunctional aromatic acid chloride in the solution to 10% by mass or lower.

[0114] The solvent used in the solution for dissolving the polyfunctional aromatic acid chloride is preferably an organic solvent that is immiscible with water, dissolves the polyfunctional aromatic acid chloride without destroying the porous support, and is inert to the polyfunctional aromatic amine and the polyfunctional aromatic acid chloride. Preferred examples of organic solvents include hydrocarbon compounds such as n-nonane, n-decane, n-undecane, n-dodecane, isooctane, isodecane, and isododecane, or mixtures thereof.

[0115] The method for contacting the porous support layer with an organic solvent solution of polyfunctional aromatic acid chloride and an aqueous solution of polyfunctional aromatic amine can be the same as the method for coating the porous support layer with the aqueous solution of polyfunctional aromatic amine.

[0116] After the reaction, the organic solvent is removed from the film surface. Methods for removing the organic solvent include, for example, vertically gripping the porous support and allowing excess organic solvent to drain naturally; drying the organic solvent by blowing air with a fan; or removing excess organic solvent with a water-air mixture.

[0117] Furthermore, depending on the desired performance of the separation membrane, aliphatic amines or alicyclic polyfunctional amines may be used instead of polyfunctional aromatic amines, and aliphatic difunctional acid halides or alicyclic difunctional acid halides may be used instead of polyfunctional aromatic acid chlorides to form crosslinked aliphatic polyamides or crosslinked alicyclic polyamides. In addition, chemical treatments such as chlorine, acid, alkali, and nitrite may be applied as needed to improve separation and permeability, and monomers may be washed to produce a continuous sheet of separation membrane.

[0118] 7-3 In an example of a method for laminating separation membranes and winding separation membranes, a separation membrane unit is formed by folding the separation membrane in half with the separation functional layer side facing inward and sandwiching the supply-side flow channel material. The separation membrane units and the permeate-side flow channel material are then alternately laminated, and a laminate is formed by sealing three sides of the separation membrane unit, excluding the folded side. Between adjacent separation membrane units with the permeate-side flow channel material in between, the peripheral edges of three sides of the separation membrane unit, excluding the folded side, are sealed to form a sealed portion. In the above laminate, an envelope-shaped membrane is formed between separation membrane units whose three sides are sealed, with an opening only on one side in the direction of the central pipe.

[0119] Another method for laminating the separation membranes involves folding and bonding one separation membrane so that its permeable side faces inward, or overlapping and bonding two separation membranes so that their permeable sides face inward, to form an envelope-shaped membrane, with a sealed portion formed at the sealed periphery. Sealing can be achieved by bonding with adhesive or hot melt, or by heat or laser fusion.

[0120] The adhesive used to form the envelope-shaped membrane preferably has a viscosity 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 separation membrane element, but an adhesive viscosity of 15 Pa·sec or less makes it less likely for wrinkles to occur when winding the separation membrane around the central pipe. Also, when the adhesive viscosity is 4 Pa·sec or higher, the outflow of adhesive from between the separation membranes is suppressed, reducing the risk of adhesive adhering to unwanted parts. In the range of 4 to 15 Pa·sec, the lower the viscosity of the adhesive, the easier it is to impregnate the separation membrane, and the higher the Y value. If the adhesive viscosity falls below 4 Pa·sec, the amount of adhesive that flows out increases, and the amount of adhesive used for impregnation decreases, so the Y value becomes lower.

[0121] The amount of adhesive applied is preferably such that, after the separation membrane is wound around the central pipe, the width of the adhesive-applied portion is between 10 mm and 100 mm. This ensures that the separation membrane is securely bonded, thereby suppressing the inflow of the supply fluid to the permeate side. Furthermore, a relatively large effective membrane area can be secured.

[0122] Urethane-based adhesives are preferred as adhesives, and to achieve a viscosity in the range of 4 to 15 Pa·sec, it is preferable that the main component isocyanate and the curing agent polyol are mixed in a ratio of isocyanate:polyol = 1:1 to 1:5. The viscosity of the adhesive is measured in advance using a B-type viscometer (JIS K 6833) to determine the viscosity of the main component, curing agent individually, and the mixture with specified mixing ratios.

[0123] The separation membrane, to which the adhesive has been applied, is positioned so that the closed portion of the envelope-shaped membrane is located on the inside in the winding direction, and the separation membrane is wrapped around the central pipe. In this way, the separation membrane is wound in a spiral shape.

[0124] The water content of the separation membrane in the area where the adhesive is applied (hereinafter referred to as the membrane water content of the adhesive-coated area) is preferably 10% or less, and more preferably 7.5% or less, in order to suppress foaming of the adhesive. Lowering the membrane water content makes it easier for the adhesive to penetrate, and the Y value increases. The water content of the separation membrane can be determined by formula (4).

[0125]

[0126] 7-4 Other Processes The manufacturing method of the separation membrane element may include further winding of a film and filament on the outside of the winding body of the separation membrane formed as described above, or it may include further steps such as edge cutting to trim the ends of the separation membrane in the longitudinal direction of the central pipe and attaching end plates.

[0127] 8. Use of Separation Membrane Elements Separation membrane elements may be connected in series or parallel and housed in a pressure vessel to be used as a separation membrane module.

[0128] Furthermore, the separation membrane elements and separation membrane modules described above can be combined with pumps to supply fluid to them, and devices to pre-treat the fluid to constitute a fluid separation apparatus. By using this separation apparatus, for example, feedwater can be separated into permeate water such as drinking water and concentrated water that did not permeate the membrane, thereby obtaining water suitable for the purpose.

[0129] While a higher operating pressure for the fluid separation device improves the removal rate, it also increases the energy required for operation. Considering the maintenance of the supply and permeation channels of the separation membrane element, the operating pressure when the supply fluid permeates through the membrane module is preferably between 0.2 MPa and 8 MPa.

[0130] Generally, leakage of supply water from the sealing portion increases with higher supply water pressure, leading to deterioration of permeate water quality. However, the separation membrane element of this embodiment has high adhesive impregnation properties into the substrate and porous support layer, and excellent sealing properties. Therefore, it is particularly preferable to operate it in a water production method that uses a supply water pressure of 4.0 MPa or higher, as this ensures a stable water production volume and desalination rate even during long-term operation.

[0131] As the supply water temperature increases, the salt removal rate decreases, but as it decreases, the membrane permeation flux also decreases, so a temperature between 5°C and 45°C is preferable. Furthermore, when the pH of the supply water is in the neutral range, even if the supply water is a highly saline liquid such as seawater, the formation of scale such as magnesium is suppressed, and membrane deterioration is also suppressed.

[0132] The feedwater treated by the separation membrane element is not particularly limited, but when used for water treatment, examples of feedwater include liquid mixtures containing TDS (Total Dissolved Solids) of 500 mg / L to 100 g / L, such as seawater, brine, and wastewater. Generally, TDS refers to the total amount of dissolved solids and is expressed as "mass ÷ volume," but it is sometimes expressed as a "weight ratio" with 1 L considered as 1 kg. According to the definition, it can be calculated from the weight of the residue after evaporating a solution filtered through a 0.45 μm filter at a temperature of 39.5 to 40.5°C, but a simpler method is to convert it from the practical salinity (S).

[0133] 9. Leak Detection Method For detecting leaks of the supply fluid in the planar direction of the porous support layer in the sealing portion of the separation membrane element, or leaks from cracks in the membrane surface at the boundary between the sealing resin sealing portion and the effective membrane portion, it is acceptable to measure the monovalent ion concentration in the permeate water. However, it is preferable to measure the divalent ion concentration in the permeate water because it allows for higher detection sensitivity. When the separation membrane is a reverse osmosis membrane, the removal rate of the separation membrane body varies depending on the operating conditions, but if there are no major defects such as cracks or abrasions on the membrane surface, the removal rate of monovalent ions is in the range of 99.00 to 99.90%, while the removal rate of divalent ions is higher than that of monovalent ions, at 99.990% or more.

[0134] Therefore, if the removal rate of divalent ions in the separation membrane element falls below the removal rate of divalent ions in the separation membrane body during operation, it can be determined that the supply fluid has mixed into the permeable side due to a structural defect in the element, such as leakage of the supply fluid in the planar direction of the porous support layer in the sealing portion, or due to a large defect in the membrane surface.

[0135] While there are no particular restrictions on the type of divalent ions used, Ca ions and Mg ions are preferably used due to their availability and safety. As a method for detecting leaks, for example, a permeate sampling tube is inserted into the central pipe of the element from the permeate sampling line, permeate is sampled at arbitrary locations, and the concentration of divalent ions in the sampled permeate is measured and compared with the removal rate of the separation membrane body to detect the location of the leak. For example, if the concentration of divalent ions is high near the sealing part on the supply water side, it indicates that there is leakage of the supply fluid in the planar direction of the porous support layer or leakage due to a crack in the membrane surface, while if the concentration of divalent ions is high in other locations, it indicates that a major defect has occurred in the separation membrane body. As for the analysis method of divalent ion concentration, known methods can be used, such as ion chromatography, ICP emission spectrometry, and colorimetric quantitative analysis.

[0136] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples.

[0137] (Separation membrane preparation) On a long-fiber polyester nonwoven fabric (average thickness 90 μm, longitudinal substrate strength 420 N / 5 cm), a 20% by mass DMF solution of PSf was prepared as a resin solution under conditions of 25°C, resulting in a porous support layer mass of 20 g / m² in the composite semipermeable membrane. ２ The substrate was coated in this manner. Subsequently, the substrate coated with the resin solution was immersed for 15 seconds in a first solidification solution consisting of a DMF aqueous solution at 20°C to create a porous support with a porous support layer formed on the substrate. The amount of good solvent in the obtained porous support was 44 g / m². ２ Next, the porous support layer was immersed in a second coagulation solution consisting of an aqueous solution of DMF, left for 5 minutes, and then washed with 90°C hot water for 2 minutes. The washed porous support was then immersed in a 3% by mass aqueous solution of m-PDA for 2 minutes. The porous support was slowly lifted vertically, and excess aqueous solution was removed from the surface of the porous support by blowing nitrogen with an air nozzle. After that, a decane solution containing 0.165% by mass of TMC was applied to the surface until it was completely wet, and then left to stand for 1 minute. The membrane was then held vertically to drain and remove excess solution, washed with pure water, and a separation membrane roll having a cross-linked polyamide separation functional layer was obtained.

[0138] (Fabrication of separation membrane element) The obtained separation membrane roll is unwound, and the effective area of ​​the separation membrane element is 0.35 m². ２ The polypropylene net shown in Table 1 (thickness: 0.8 mm, length: 550 mm) was folded and cut in this manner, and a separation membrane unit was fabricated by sandwiching it as a flow channel material on the water supply side.

[0139] Next, the sealing portion of the separation membrane unit was dried with a press heater to a membrane moisture content of 7.5%. The obtained separation membrane unit was laminated with tricot (thickness: 0.26 mm) shown in Table 1 as the permeate channel material, and urethane adhesive was applied to the periphery of the three sides other than the side through which the permeate fluid flows to form an envelope-shaped membrane, so that the permeate fluid flows into the central pipe. Two sets of these envelope-shaped membranes were prepared and then spirally wound around a PVC (polyvinyl chloride) central pipe (width: 300 mm, outer diameter: 19 mm, inner diameter: 14 mm, number of holes: 8 x straight row). After fixing the outer surface of the wound body with tape, the edges at both ends were cut and end plates were attached to create a separation membrane element with a diameter of 2.5 inches and a 2-leaf configuration, through which supply water is supplied and concentrated water is discharged from one side.

[0140] (Measurement of adhesive impregnation rate of the sealing portion) The spiral-type separation membrane element was disassembled and unfolded, and the envelope-shaped membrane was removed. In a direction perpendicular to the longitudinal direction of the water collection tube, the sealing portion was cut out from the end face in 3 mm x 3 mm sizes at the 20%, 50%, and 80% positions relative to the total length of the envelope-shaped membrane, to obtain samples A to C. In a direction perpendicular to the longitudinal direction of the water collection tube, the samples were scraped off with a broad ion beam at a position 1 mm toward the effective membrane side from the end face of samples A to C to form a smooth end face of the sealing portion. Conductive treatment (Pt coating) was applied to the observation surface, and the upper and lower support layers were observed at 1500x magnification under the condition of an acceleration voltage of 1.5 kV using a Hitachi High-Tech cold cathode field emission scanning electron microscope Regulus 8220.

[0141] Binarization was performed using imageJ. Background processing was performed by setting the Rolling Ball Radius of Substruct Background to 50 pixels. Then, binarization was performed using Make Binary, and the image was inverted to black and white. After that, particle analysis was performed using Analyze Particle with Size (pixel2) set to 100-Infinity. The total Area obtained from the particle analysis was taken as the adhesive impregnation area. The image threshold was set to 0-255, and the Area of ​​the entire image was obtained using Analyze Particle and taken as the total area. The adhesive impregnation area was divided by the total area and multiplied by 100 to obtain the adhesive impregnation rate. The adhesive impregnation rate was analyzed for the upper and lower support layers, and the average value was taken as the adhesive impregnation rate for that sample. The same procedure was performed on the opposite side from where samples A to C were sampled, and the adhesive impregnation rate was obtained for samples D to F. In addition, samples were taken at 20%, 50%, and 80% positions along the width of the envelope-shaped membrane, parallel to the longitudinal direction of the water collection pipe, and the adhesive impregnation rate was obtained for samples G to I. The average value of the adhesive impregnation rate for samples A to I was calculated and defined as the average adhesive impregnation rate.

[0142] (Measurement of substrate thickness) The thickness of the substrate was measured at 10 points across its width using a Mitutoyo digital thickness gauge (Model ID-C112X), and the average value was calculated.

[0143] (Thickness measurement of the supply-side channel material) The supply-side channel material was cut into 10 x 10 cm pieces, and a Keyence VR-3000 one-shot 3D shape measuring machine was used to observe the longitudinal cross-section parallel to the fibrous rows of the supply-side channel material at a magnification of 20x. The thickness of 30 arbitrary intersection points was extracted and measured, and the average value was calculated.

[0144] (Measurement of the thickness of the permeable channel material) The thickness of the permeable channel material was measured at 10 points across its width using a Mitutoyo digital thickness gauge (Model ID-C112X), and the average value was calculated.

[0145] (Measurement of specific surface area S of the porous support layer) The specific surface area S of the porous support layer was measured from the porous support by nitrogen adsorption measurement. The porous support layer was peeled off from the porous support with tape, and the peeled porous support layer was cut into 5 mm squares with a single blade to obtain 0.1 to 0.3 g of measurement sample. The measurement sample was dried in a vacuum at 45°C for 4 hours. The dried sample was measured using a nitrogen adsorption analyzer (Microtrac Bell; BELSORP-miniII) with an adsorption temperature of 77 K and adsorbate N ２ The specific surface area S was measured by the BET method under the condition that the gaseous material had a second virial coefficient of -4.264 × 10⁻⁷ Pa⁻¹.

[0146] (Measurement of molecular weight cutoff of porous support layer) Aldrich dextran Mw1500 (product number: 31394), Mw6000 (product number: 31388), Mw15000-20000 (product number: 31387), Mw-40000 (product number: 31389), Mw-60000 (product number: 31397), and Mw-200000 (product number: 31398) were each dissolved in distilled water to a concentration of 500 ppm to prepare dextran aqueous solutions, which were used as the raw water.

[0147] The porous support was cut into a circle with a diameter of 4.3 cm, and the cut-out sample was placed in a stirring-type ultra-holder (UHP-43K, manufactured by Advantec Toyo Co., Ltd.) (effective filtration area: 10.9 cm²). ２ ). A 25°C dextran solution was placed in the cell of the Ultra Holder and the cap was attached. While stirring at 1000 rpm, the water production volume was 0.2 to 0.8 [m³]. ３ / m ２ The pressure was increased to [ / day] and filtration was started. The first 5g of the permeate was discarded as preliminary permeate, and the next 5g was taken as the filtration sample. The dextran concentration of the raw water and the filtration sample was measured by GPC.

[0148] Concentration measurements using GPC were performed as follows: The sampled solution was filtered through a 0.45 micron pore size filter, and the resulting filtrate was subjected to a GPC column (Tosoh TSK-gel-G4000PWXL). The column temperature was 40°C, the mobile phase was 1 mL / min of distilled water for liquid chromatography, and the sample input volume was 100 μl. Measurements were taken using a suggestive refractive index system (Tosoh RI-8020) with a slice time of 0.02 min and a base-line range of 4.5–11.0 min.

[0149] The calibration curve showing the relationship between retention time and the molecular weight of dextran in GPC was calculated as follows: A monodisperse dextran solution was analyzed using GPC, and the retention time for each solution was measured. The retention time at the peak top of each solution was plotted against the measured molecular weight of monodisperse dextran, and the calibration curve between retention time and molecular weight was obtained from the exponential approximation curve. In addition, the retention time at which the dextran removal rate reached 90% was calculated from the difference in the suggested refractive index of the raw water and the filtered sample, and the fractional molecular weight at which the dextran removal rate reached 90% was determined from the calibration curve. Note that since the substrate does not exhibit fractionation performance for any of the above-mentioned dextran aqueous solutions, the fractional molecular weight of the porous support layer can be measured by measuring the fractional molecular weight of the porous support.

[0150] (Measurement of the Mass of the Porous Support Layer) A rectangle measuring 0.11 m x 0.19 m was cut from the porous support, dried at 120°C for 2 hours, and the mass of the porous support was measured. The porous support layer was then peeled off from the porous support with tape, and the mass of the substrate was measured. The mass of the porous support layer was calculated using equation (5).

[0151]

[0152] (Measurement of the amount of good solvent in the porous support) In the process of fabricating the composite semipermeable membrane, the porous support, on which a porous support layer was formed by immersing the substrate in the first coagulation solution of step (b), was cut into a 0.11 m × 0.19 m rectangle while wet, and immersed in a polytetrafluoroethylene container containing 500 g of 90°C hot water for 1 hour. After immersion, 10 mL of the hot water in which the porous support was immersed was collected. GC-MS measurement was performed on the collected solution. The good solvent concentration [ppm] of the collected solution was calculated from a calibration curve of peak area and good solvent concentration of resin solution prepared in advance. From the calculated good solvent concentration, the amount of good solvent in the porous support was determined using equation (6).

[0153]

[0154] (Removal rate) A spiral-type separation membrane element is placed in a pressure vessel, and the feedwater is NaCl concentration 32,000 mg / L, MgSO4. ４ An aqueous solution adjusted to a concentration of 2,000 mg / L and pH 6.5 was used, and the system was operated for 30 minutes under conditions of an operating pressure of 5.5 MPa, a concentrated water flow rate of 10 L / min, and a temperature of 25°C. After sampling, the Mg ion concentration was determined from the feedwater and the sampled permeate by ion chromatography, and the removal rate was calculated using the following formula.

[0155] Removal rate (%) = 100 × {1 - (Mg ion concentration in permeate water / Mg ion concentration in feed water)} (Mg ion concentration of permeate water measured near the sealing part and in the central part) A spiral-type separation membrane element was placed in a pressure vessel, and the feed water was 32,000 mg / L NaCl and MgSO4. ４ Using an aqueous solution adjusted to a concentration of 2,000 mg / L and pH 6.5, and operating under conditions of an operating pressure of 5.5 MPa, a concentrated water flow rate of 10 L / min, and a temperature of 25°C, a permeate sampling tube (SUS pipe with an outer diameter of 3.18 mm and an inner diameter of 0.71 mm) was inserted into the central pipe of the element from the permeate sampling line. Permeate samples were taken near the sealing part on the supply water side (5 cm from the element end) and in the central part (15 cm from the element end), and the Mg ion concentration of the sampled permeate was determined by ion chromatography.

[0156] (Durability) A spiral-type 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 the feedwater. The system was operated for 1 minute under operating pressure of 5.5 MPa and temperature of 25°C, after which the operation was terminated. This cycle (start and stop) was repeated 3000 times, and the subsequent MgSO4 test was performed. ４ The removal rate was measured.

[0157] (Measuring the viscosity of the adhesive) The viscosity of the adhesive was measured by mixing the main component and the hardener, and measuring the viscosity of the mixture at 25°C using a Type B viscometer (JIS K 6833) after starting at 20 rpm for 1 minute.

[0158] (Measurement of film moisture content in the adhesive-coated area) A sample of the separation membrane from the sealing area of ​​the spiral-type separation membrane element was cut into a 3 cm x 10 cm strip before adhesive application, and its weight was immediately measured (weight of the separation membrane before drying). Then, the same sample was dried in a vacuum oven set to 40°C until there was no further change in weight, and its weight was measured again (absolutely dry weight of the separation membrane). The film moisture content in the adhesive-coated area was determined using formula (4).

[0159]

[0160] (Measurement of Y value and Y value difference) After removing the tape fixing the end plates and outer surface of the spiral-type separation membrane element, it was disassembled and unfolded to take out the envelope-shaped membrane, and dried in a vacuum oven set to 40°C until there was no change in the weight of the sample to be measured. Any sealed part of the dried sample to be measured, and an effective membrane part separated from the sealed part by 50 mm or more, were used as the effective membrane part for measuring the Y value. For each, transmission measurements were performed at 20 locations from a plane using a Suga Test Instruments Co., Ltd. SM color computer (model: SM-7-CH), with color measurement conditions: C light 2-degree field of view, photometric method: left and right (45°) two-way illumination method, measurement hole diameter: φ12 mm, optical conditions: 0° illumination and 0° reception in accordance with JIS Z 8722 condition e. The average value of the Y value in the XYZ color system was calculated, and the Y value difference was calculated from the following formula.

[0161] Y-value difference = Y-value of the sealing part - Y-value of the effective film part (Measurement of C hardness and C hardness difference) After removing the tape that fixes the end plates and outer surface of the spiral-type separation membrane element, it was disassembled and unfolded to take out the envelope-shaped membrane and dried in a vacuum oven set to 40°C until there was no change in the weight of the sample. Next, the hardness was measured from the plane at 20 locations on the dried envelope-shaped membrane where there was a sealing part and the effective film part using an Asker C hardness tester manufactured by Polymer Instruments Co., Ltd., and the average value was calculated and the C hardness difference was calculated from the following formula.

[0162] C hardness difference = Average C hardness of the sealing portion - Average C hardness of the effective membrane portion (Example 1) The fabricated separation membrane element was placed in a pressure vessel and evaluated under the above conditions, and the results were as shown in Table 1.

[0163]

[0164] (Examples 2 and 3) A 15.7% by mass DMF solution of PSf was used as the resin solution, and the mass of the porous support layer in the composite semipermeable membrane was 25 g / m². ２ A separation membrane element was prepared in the same manner as in Example 1, except that the substrate coated in the specified manner was immersed for 5 minutes in a first coagulation solution consisting of a 30°C DMF aqueous solution.

[0165] The separation membrane element was placed in a pressure vessel, and its performance was evaluated under the same conditions as in Example 1. The results are shown in Table 1.

[0166] (Example 4) An 18% by mass DMF solution of PSf was used as the resin solution, and the mass of the porous support layer in the composite semipermeable membrane was 14 g / m². ２ A separation membrane element was prepared in the same manner as in Example 1, except that the substrate coated in the specified manner was immersed for 15 seconds in a first coagulation solution consisting of a DMF aqueous solution at 25°C.

[0167] The separation membrane element was placed in a pressure vessel, and its performance was evaluated under the same conditions as in Example 1. The results are shown in Table 1.

[0168] (Examples 5-7) Separation membrane elements were prepared in the same manner as in Example 4, except that the moisture content of the film in the adhesive-coated area was changed.

[0169] The separation membrane element was placed in a pressure vessel, and its performance was evaluated under the same conditions as in Example 1. The results are shown in Table 1.

[0170] (Examples 8-10) Separation membrane elements were fabricated in the same manner as in Example 3, except that the viscosity of the urethane adhesive used in the fabrication of the separation membrane elements was changed.

[0171] The separation membrane element was placed in a pressure vessel, and its performance was evaluated under the same conditions as in Example 1. The results are shown in Table 1.

[0172] (Examples 11 and 12) Separation membrane elements were fabricated in the same manner as in Example 4, except that the water content of the adhesive-coated portion of the membrane was changed and the viscosity of the urethane adhesive used in the fabrication of the separation membrane element was changed.

[0173] The separation membrane element was placed in a pressure vessel, and its performance was evaluated under the same conditions as in Example 1. The results are shown in Table 1.

[0174] (Examples 13-15) The separation membrane element was placed in a pressure vessel, and all other conditions were the same as in Example 4 except that the operating pressure was set to the conditions in Table 1. The performance of each element was evaluated, and the results are shown in Table 1.

[0175] (Comparative Example 1) A 15.7% by mass DMF solution of PSf was used as the resin solution, and the mass of the porous support layer in the composite semipermeable membrane was 25 g / m². ２ The substrate coated in this manner was immersed for 5 minutes in a first coagulation solution consisting of a 30°C DMF aqueous solution. Separation membrane elements were also prepared in the same manner as in Example 1, except that the water content of the film in the adhesive-coated area was changed to 20%.

[0176] The separation membrane element was placed in a pressure vessel, and its performance was evaluated under the same conditions as in Example 1. The results are shown in Table 2.

[0177]

[0178] (Comparative Example 2) A 18.3% by mass DMF solution of PSf was used as the resin solution, resulting in a porous support layer mass of 11 g / m² in the composite semipermeable membrane. ２A separation membrane element was prepared in the same manner as in Example 1, except that the substrate was immersed for 2 seconds in a first coagulation solution consisting of a 25°C DMF aqueous solution.

[0179] The separation membrane element was placed in a pressure vessel, and its performance was evaluated under the same conditions as in Example 1. The results are shown in Table 2.

[0180] (Comparative Example 3) A separation membrane element was prepared in the same manner as in Example 3, except that the moisture content of the adhesive-coated portion of the membrane was as shown in Table 2.

[0181] The separation membrane element was placed in a pressure vessel, and its performance was evaluated under the same conditions as in Example 1. The results are shown in Table 2.

[0182] In other words, in Comparative Example 1, the high moisture content of the membrane inhibited the impregnation of the adhesive, resulting in insufficient adhesive impregnation in areas where leakage from the porous support layer in the sealing portion contributed significantly, leading to a decrease in the sealing performance of the separation membrane element and a reduction in the element removal rate. The performance degradation was particularly pronounced when operating at higher pressures. In Comparative Example 2, the increased specific surface area of ​​the porous support layer resulted in a dense three-dimensional network structure with numerous small voids, increasing the capillary force of the porous support layer itself. In Comparative Example 3, the low moisture content of the membrane made it easier for the adhesive to penetrate, and although the impregnation of the adhesive into the porous support layer in the sealing portion improved, the large difference in hardness between the sealing resin sealing portion and the effective membrane boundary led to cracks on the membrane surface during repeated operation, resulting in a performance degradation.

[0183] As is clear from the results shown in Tables 1 and 2, the separation membrane elements of Examples 1 to 10 can be said to have excellent and stable separation performance because, without complicating the manufacturing process of the separation membrane elements, they suppress leakage of the supply fluid from the sealing portion and do not easily decrease in desalination rate, even when the separation membrane elements are operated repeatedly under high pressure for a long period of time.

[0184] The 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 in RO water purifiers and for desalination of brine and seawater.

[0185] 1a, 1b Spiral separation membrane element 2 Supply side flow channel material 3a, 3b Separation membrane 4 Permeate side flow channel material 5a, 5b Envelope-shaped membrane 6 Central pipe 7 Supply fluid 8 Permeate fluid 9 Concentrated fluid 10 Sealing section 11 Effective membrane section 12 Sealing resin 13 Supply fluid leakage path 14 Supply fluid leakage path 21 Warp threads 22 Weft threads 301 Substrate 302 Porous support layer 303 Separation function layer 304 Porous support

Claims

1. A spiral-type separation membrane element comprising a substrate, a porous support layer formed on the substrate, and a separation function layer formed on the porous support layer, wherein separation membrane units formed so as to sandwich a supply-side flow channel material with the separation function layer side facing inward, and a permeate-side flow channel material are alternately stacked, and sealing portions are provided at the periphery between adjacent separation membrane units on either side of the permeate-side flow channel material to prevent mixing of the supply fluid and the permeate fluid while allowing the permeate fluid to flow into the central pipe, the stacked body is wound spirally around the central pipe, characterized in that at least one side of the sealing portion has a Y value of 0.15% or more and 2.0% or less in the XYZ color system based on C-light 2-degree field transmission measurement.

2. The spiral-type separation membrane element according to claim 1, characterized in that the Y value of the sealing portion is 0.15% or more and 1.5% or less on at least one side of the sealing portion.

3. The spiral-type separation membrane element according to claim 1 or 2, characterized in that the difference in C hardness between the C hardness of the sealing portion and the C hardness of the effective membrane portion is -1.0 or more and 1.5 or less.

4. The spiral-type separation membrane element according to claim 1 or 2, characterized in that, at least one side of the sealing portion, the difference in Y values ​​between the Y value of the sealing portion and the Y value of the effective membrane portion is 0.1% or more and 1.5% or less.

5. The molecular weight cutoff of the porous support layer is 10 kDa to 60 kDa, and the specific surface area S is 20 to 50 m². ２ The spiral-type separation membrane element according to claim 1 or 2, characterized in that it is / g.

6. A method for operating a spiral-type separation membrane element, wherein water is produced using the spiral-type separation membrane element described in claim 1 or 2, at a supply water pressure of 4.0 MPa or higher.

7. A fluid separation device using a spiral-type separation membrane element according to claim 1 or 2.

Images