JP2017013055A - Separation membrane element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separation membrane element capable of stabilizing separation removal performance when operating the separation membrane element while applying a high pressure.SOLUTION: A separation membrane element includes: a separation membrane which has a face of the supply side and a face of the permeation side and forms a separation membrane pair by arranging faces themselves of the permeation side so as to face each other; and a permeation side channel material disposed so as to be opposed to the face of the permeation side of the separation membrane, the permeation side channel material is a porous sheet which is ruggedly molded so as to have protruded parts and recessed parts, a difference of elevation caused by ruggedness is 0.05 to 0.50 mm and the ratio of cross-sectional area of the protruded part to the product of width and height of the protruded part is 0.4 to 0.8.SELECTED DRAWING: Figure 10

Description

  The present invention relates to a separation membrane element used for separating components contained in a fluid such as liquid and gas.

  In the technology for removing ionic substances contained in seawater, brine, and the like, in recent years, the use of separation methods using separation membrane elements is expanding as a process for saving energy and resources. Separation membranes used in separation methods using separation membrane elements are classified into microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, and forward osmosis membranes in terms of their pore sizes and separation functions. These membranes are used, for example, in the production of drinking water from seawater, brackish water and water containing harmful substances, industrial ultrapure water, wastewater treatment and recovery of valuable materials. It is properly used depending on the separation component and separation performance.

  Although there are various forms as the separation membrane element, they are common in that raw water is supplied to one surface of the separation membrane and a permeated fluid is obtained from the other surface. The separation membrane element includes a large number of bundled separation membranes so that the membrane area per one separation membrane element is increased, that is, the amount of permeate fluid obtained per one separation membrane element is large. It is formed to become. As the separation membrane element, various shapes such as a spiral type, a hollow fiber type, a plate-and-frame type, a rotating flat membrane type, and a flat membrane integrated type have been proposed according to applications and purposes.

  For example, spiral separation membrane elements are widely used for reverse osmosis filtration. The spiral separation membrane element includes a center tube and a laminate wound around the center tube. The laminated body includes a supply-side channel material that supplies raw water (that is, water to be treated) to the separation membrane surface, a separation membrane that separates components contained in the raw water, and a permeation side that is separated from the supply-side fluid through the separation membrane. It is formed by laminating a permeate-side channel material for guiding fluid to the central tube. The spiral separation membrane element is preferably used in that a large amount of permeated fluid can be taken out because pressure can be applied to the raw water.

  In the spiral type separation membrane element, in general, a polymer net is mainly used as a supply-side channel material in order to form a supply-side fluid channel. In addition, a stacked type separation membrane is used as the separation membrane. Laminate type separation membranes are laminated from the supply side to the permeate side, a separation functional layer made of a crosslinked polymer such as polyamide, a porous resin layer (porous support layer) made of a polymer such as polysulfone, polyethylene terephthalate, etc. A non-woven substrate made of the above polymer is provided. Further, as the permeation side channel material, a knitted member called a tricot having a smaller interval than the supply side channel material is used for the purpose of preventing the separation membrane from dropping and forming the permeation side channel.

  In recent years, due to the increasing demand for reducing the fresh water generation cost, there has been a demand for higher performance of the separation membrane element. For example, in order to improve the separation performance of the separation membrane element and increase the amount of permeated fluid per unit time, it has been proposed to improve the performance of the separation membrane element member such as each flow path member.

  Specifically, Patent Document 1 proposes a separation membrane element including a porous sheet with irregularities formed as a permeate-side channel material. In Patent Document 2, a separation membrane that does not require a supply-side channel material such as a net or a permeation-side channel material such as a tricot by a channel material composed of an elastomer called a vane disposed on the separation membrane. Elements have been proposed. Patent Document 3 proposes a separation membrane element provided with a flow path material in which yarns are arranged on a nonwoven fabric.

JP 2006-247453 A Special table 2012-518538 gazette US Patent Application Publication No. 2012-0261333

  However, the separation membrane element described above is not sufficient in terms of separation performance, particularly stability performance when operated for a long period of time.

  Accordingly, an object of the present invention is to provide a separation membrane element that can stabilize the separation and removal performance when the separation membrane element is operated under a particularly high pressure.

  In order to achieve the above object, according to the present invention, a separation membrane having a supply side surface and a permeation side surface and forming a separation membrane pair by arranging the permeation side surfaces to face each other, A permeation-side flow path material provided so as to face the permeation-side surface of the separation membrane, and the permeation-side flow path material is a porous sheet that is unevenly shaped to have a convex part and a concave part. The height difference due to the unevenness is 0.05 mm or more and 0.50 mm or less, and the ratio of the cross-sectional area of the protrusion to the product of the width and height of the protrusion is 0.4 or more and 0.8 or less. It is a separation membrane element.

  According to the present invention, a high-efficiency and stable permeation-side flow path can be formed, and a high-performance, high-efficiency separation membrane element having separation component removal performance and high permeation performance can be obtained.

It is a schematic block diagram which shows one form of a membrane leaf. It is a top view which shows the permeation | transmission side flow path material provided with the convex part provided continuously in the length direction (2nd direction) of the porous sheet. It is a top view which shows the permeation | transmission side channel material provided with the convex part discontinuously provided in the length direction (2nd direction) of the porous sheet. It is sectional drawing of the separation membrane of FIG. 2 and FIG. It is a development perspective view showing one form of a separation membrane element. It is sectional drawing which shows schematic structure of a separation membrane. It is a partially expanded perspective view which shows the 1st form of a separation membrane element. It is a partially expanded perspective view which shows the 2nd form of a separation membrane element. It is a partially expanded perspective view which shows the 3rd form of a separation membrane element. It is a figure which shows an example of the method of arrange | positioning the permeation | transmission side channel material to a membrane leaf. It is an example of the cross-sectional view of the convex part in the permeation | transmission side channel material.

  Hereinafter, an embodiment of the present invention will be described in detail.

[1. Separation membrane)
(1-1) Overview of Separation Membrane A separation membrane is a membrane that can separate components in a fluid supplied to the surface of the separation membrane and obtain a permeated fluid that has permeated the separation membrane. The separation membrane can also include a membrane in which embossing or resin is arranged so as to form a flow path. In addition, the separation membrane may be one that cannot form a flow path and expresses only a separation function.

  As an example of such a separation membrane, an exploded perspective view of a membrane leaf including an example of an embodiment of the separation membrane of the present invention is shown in FIG. In FIG. 1, the membrane leaf 4 includes a plurality of separation membranes 2a and 2b. The separation membrane 2a has a supply-side surface 21a and a transmission-side surface 22a, and the separation membrane 2b has a supply-side surface 21b and a transmission-side surface 22b. The two separated separation membranes 2a and 2b are arranged so that the supply-side surface 21a of one separation membrane 2a and the supply-side surface 21b of the other separation membrane 2b face each other. Further, the other separation membrane 2c superimposed thereon is arranged so that the permeation side surface 22c of the separation membrane faces the permeation side surface 22b of the separation membrane 2b below it. 21c is a surface on the supply side of the separation membrane 2c. In this document, the “supply side surface” of the separation membrane means the surface on the side of the separation membrane where raw water is supplied. The “permeate side surface” means the surface on the opposite side from which the permeated fluid that has passed through the separation membrane is discharged. As will be described later, when the separation membrane 2 includes a base material 201, a porous support layer 202, and a separation functional layer 203 as shown in FIG. 6, generally, the surface on the separation functional layer 203 side is on the supply side. The surface 21 and the surface on the base material 201 side are the surface 22 on the transmission side.

  In FIG. 6, the separation membrane 2 is described as a laminate of a base material 201, a porous support layer 202 and a separation functional layer 203. As described above, the surface opened outside the separation functional layer 203 is the supply-side surface 21, and the surface opened outside the base material 201 is the transmission-side surface 22.

  1, 2, 3, 4, and 5 show x-axis, y-axis, and z-axis direction axes. The x-axis may be referred to as a first direction and the y-axis may be referred to as a second direction. As shown in FIG. 1, the separation membrane 2 is rectangular, and the first direction and the second direction are parallel to the outer edge of the separation membrane 2. The first direction may be referred to as the width direction, and the second direction may be referred to as the length direction. In FIG. 1, the first direction (width direction) is represented by a CD arrow, and the second direction (length direction) is represented by an MD arrow.

(1-2) Separation membrane <Overview>
As the separation membrane, a membrane having separation performance according to the method of use, purpose and the like is used. The separation membrane may be formed of a single layer or a composite membrane including a separation functional layer and a substrate. As shown in FIG. 6, in the composite membrane, a porous support layer 202 may be formed between the separation functional layer 203 and the base material 201.

<Separation function layer>
The thickness of the separation functional layer is not limited to a specific numerical value, but is preferably 5 nm or more and 3000 nm or less in terms of separation performance and transmission performance. In particular, in the case of a reverse osmosis membrane, a forward osmosis membrane, and a nanofiltration membrane, the thickness is preferably 5 nm or more and 300 nm or less.

  The thickness of the separation functional layer can be based on a normal method for measuring the thickness of the separation membrane. For example, the separation membrane is embedded with resin, and an ultrathin section is prepared by cutting the separation membrane, and the obtained section is subjected to processing such as staining. Thereafter, the thickness can be measured by observing with a transmission electron microscope. Further, when the separation functional layer has a pleat structure, measurement can be made at intervals of 50 nm in the cross-sectional length direction of the pleat structure located above the porous support layer, the number of pleats can be measured, and the average can be obtained. it can.

  The separation function layer may be a layer having both a separation function and a support function, or may have only a separation function. The “separation function layer” refers to a layer having at least a separation function.

  When the separation functional layer has both a separation function and a support function, a layer containing cellulose, polyvinylidene fluoride, polyether sulfone, or polysulfone as a main component is preferably applied as the separation functional layer.

  In this specification, “X contains Y as a main component” means that the Y content in X is 50 mass% or more, 70 mass% or more, 80 mass% or more, 90 mass% or more, or It means a case of 95% by mass or more. In addition, when there are a plurality of components corresponding to Y, the total amount of these components only needs to satisfy the above range.

  On the other hand, as the separation functional layer supported by the porous support layer, a crosslinked polymer is preferably used in terms of easy control of the pore diameter and excellent durability. In particular, a polyamide separation functional layer obtained by polycondensation of a polyfunctional amine and a polyfunctional acid halide, an organic-inorganic hybrid functional layer, and the like are preferably used in terms of excellent separation performance of components in raw water. These separation functional layers can be formed by polycondensation of monomers on the porous support layer.

  For example, the separation functional layer can contain polyamide as a main component. Such a film is formed by interfacial polycondensation of a polyfunctional amine and a polyfunctional acid halide by a known method. For example, by applying a polyfunctional amine aqueous solution to the porous support layer, removing the excess amine aqueous solution with an air knife or the like, and then applying an organic solvent solution containing a polyfunctional acid halide, the polyamide separation functional layer Is obtained.

Further, the separation functional layer may have an organic-inorganic hybrid structure containing Si element or the like. The separation functional layer having an organic-inorganic hybrid structure can contain, for example, the following compounds (A) and (B):
(A) a silicon compound in which a reactive group and a hydrolyzable group having an ethylenically unsaturated group are directly bonded to a silicon atom, and (B) a compound other than the compound (A) and having an ethylenically unsaturated group Compound.

Specifically, the separation functional layer may contain a condensate of the hydrolyzable group of the compound (A) and a polymer of the ethylenically unsaturated group of the compounds (A) and / or (B). That is, the separation functional layer is
A polymer formed by condensation and / or polymerization of only the compound (A),
-The polymer formed by superposing | polymerizing only a compound (B), and-At least 1 sort (s) of polymer of the copolymer of a compound (A) and a compound (B) can be contained. The polymer includes a condensate. In the copolymer of compound (A) and compound (B), compound (A) may be condensed via a hydrolyzable group.

  The hybrid structure can be formed by a known method. An example of a method for forming a hybrid structure is as follows. A reaction solution containing the compound (A) and the compound (B) is applied to the porous support layer. In order to condense the hydrolyzable group after removing the excess reaction solution, heat treatment may be performed. As a polymerization method of the ethylenically unsaturated groups of the compound (A) and the compound (B), heat treatment, electromagnetic wave irradiation, electron beam irradiation, and plasma irradiation may be performed. For the purpose of increasing the polymerization rate, a polymerization initiator, a polymerization accelerator and the like can be added during the formation of the separation functional layer.

  For any separation functional layer, the surface of the membrane may be hydrophilized with an alcohol-containing aqueous solution or an alkaline aqueous solution, for example, before use.

<Porous support layer>
The porous support layer is a layer that supports the separation functional layer, and is also referred to as a porous resin layer.

  Although the material used for a porous support layer and its shape are not specifically limited, For example, you may form on a board | substrate with porous resin. As the porous support layer, polysulfone, cellulose acetate, polyvinyl chloride, epoxy resin or a mixture and laminate of them is used, and polysulfone with high chemical, mechanical and thermal stability and easy to control pore size. Is preferably used.

  The porous support layer gives mechanical strength to the separation membrane and does not have a separation performance like a separation functional layer for components having a small molecular size such as ions. The pore size and pore distribution of the porous support layer are not particularly limited. For example, the porous support layer may have uniform and fine pores, or the side on which the separation functional layer is formed. It may have a pore size distribution such that the diameter gradually increases from the surface to the other surface (base material side). In any case, the projected area equivalent circle diameter of the pores measured using an atomic force microscope or an electron microscope on the surface on the side where the separation functional layer is formed is 1 nm or more and 100 nm or less. preferable. Particularly in terms of interfacial polymerization reactivity and retention of the separation functional layer, the pores on the surface on the side where the separation functional layer is formed in the porous support layer preferably have a projected area equivalent circle diameter of 3 nm to 50 nm. .

  The thickness of the porous support layer is not particularly limited, but is preferably in the range of 20 μm to 500 μm, more preferably 30 μm to 300 μm, for reasons such as giving strength to the separation membrane.

  The form of the porous support layer can be observed with a scanning electron microscope, a transmission electron microscope, or an atomic force microscope. For example, when observing with a scanning electron microscope, after peeling off the porous support layer from the substrate, it is cut by the freeze cleaving method to obtain a sample for cross-sectional observation. The sample is thinly coated with platinum, platinum-palladium, or ruthenium tetrachloride, preferably ruthenium tetrachloride, and observed with a high-resolution field emission scanning electron microscope (UHR-FE-SEM) at an acceleration voltage of 3 kV to 6 kV. A Hitachi S-900 electron microscope or the like can be used as the high-resolution field emission scanning electron microscope. Based on the obtained electron micrograph, the film thickness of the porous support layer and the projected area equivalent circle diameter of the surface can be measured.

  The thickness and the pore diameter of the porous support layer are average values, and the thickness of the porous support layer is an average value of 20 points measured at intervals of 20 μm in a direction orthogonal to the thickness direction by cross-sectional observation. Moreover, a hole diameter is an average value of each projected area circle equivalent diameter measured about 200 holes.

  Next, a method for forming the porous support layer will be described. The porous support layer is formed by casting a solution of polysulfone in N, N-dimethylformamide (hereinafter referred to as DMF), for example, on a substrate to be described later, for example, a densely woven polyester cloth or non-woven cloth, to a certain thickness. And can be produced by wet coagulation in water.

  The porous support layer is “Office of Saleen Water Research and Development Progress Report” no. 359 (1968). In addition, in order to obtain a desired form, the polymer concentration, the temperature of the solvent, and the poor solvent can be adjusted.

  For example, a predetermined amount of polysulfone is dissolved in DMF to prepare a polysulfone resin solution having a predetermined concentration. Next, this polysulfone resin solution is applied to a substrate made of polyester cloth or nonwoven fabric to a substantially constant thickness, and after removing the surface solvent in the air for a certain period of time, the polysulfone is coagulated in the coagulation liquid. A porous support layer can be obtained.

<Base material>
From the viewpoint of the strength and dimensional stability of the separation membrane, the separation membrane can have a substrate. As the base material, it is preferable to use a fibrous base material in terms of strength, unevenness forming ability and fluid permeability.

  As a base material, both a long fiber nonwoven fabric and a short fiber nonwoven fabric can be used preferably. In particular, since the long fiber nonwoven fabric has excellent film-forming properties, when the polymer solution is cast, the solution penetrates through the permeation, the porous support layer peels off, and Can suppress the film from becoming non-uniform due to fluffing of the substrate and the like, and the occurrence of defects such as pinholes. In addition, since the base material is made of a long-fiber nonwoven fabric composed of thermoplastic continuous filaments, compared to a short-fiber nonwoven fabric, non-uniform film formation and film defects caused by fiber fluffing during polymer solution casting can be prevented. Can be suppressed. Furthermore, since the separation membrane is tensioned in the film-forming direction when continuously formed, it is preferable to use a long-fiber nonwoven fabric excellent in dimensional stability as a base material.

  In the long-fiber nonwoven fabric, in terms of moldability and strength, it is preferable that the fibers in the surface layer on the side opposite to the porous support layer have a longitudinal orientation than the fibers in the surface layer on the porous support layer side. According to such a structure, not only a high effect of preventing membrane breakage by maintaining strength is realized, but also a laminate comprising a porous support layer and a substrate when imparting irregularities to the separation membrane The moldability is improved, and the uneven shape on the surface of the separation membrane is stabilized, which is preferable.

  More specifically, the fiber orientation degree in the surface layer on the side opposite to the porous support layer of the long-fiber nonwoven fabric is preferably 0 ° or more and 25 ° or less, and the fiber orientation in the surface layer on the porous support layer side. The degree of orientation difference with respect to the degree is preferably 10 ° or more and 90 ° or less.

  The process for producing the separation membrane and the process for producing the separation membrane element include a heating step, but a phenomenon occurs in which the porous support layer or the separation functional layer contracts due to the heating. In particular, the shrinkage is remarkable in the width direction where no tension is applied in continuous film formation. Since shrinkage causes problems in dimensional stability and the like, a substrate having a small rate of thermal dimensional change is desired. In the nonwoven fabric, when the difference between the fiber orientation degree on the surface layer opposite to the porous support layer and the fiber orientation degree on the porous support layer side surface layer is 10 ° or more and 90 ° or less, the change in the width direction due to heat is suppressed. Can also be preferred.

  Here, the fiber orientation degree is an index indicating the direction of the fibers of the nonwoven fabric substrate constituting the porous support layer. Specifically, the fiber orientation degree is an average value of angles between the film forming direction when continuous film forming is performed, that is, the longitudinal direction of the nonwoven fabric base material and the longitudinal direction of the fibers constituting the nonwoven fabric base material. is there. That is, if the longitudinal direction of the fiber is parallel to the film forming direction, the fiber orientation degree is 0 °. If the longitudinal direction of the fiber is perpendicular to the film forming direction, that is, if it is parallel to the width direction of the nonwoven fabric substrate, the degree of orientation of the fiber is 90 °. Accordingly, the closer to 0 ° the fiber orientation, the longer the orientation, and the closer to 90 °, the lateral orientation.

  The degree of fiber orientation is measured as follows. First, 10 small piece samples are randomly collected from the nonwoven fabric. Next, the surface of the sample is photographed at 100 to 1000 times with a scanning electron microscope. In the photographed image, 10 fibers are selected for each sample, and the angle of the fibers in the longitudinal direction when the longitudinal direction of the nonwoven fabric is 0 ° is measured. Here, the longitudinal direction of the nonwoven fabric refers to “Machine direction” at the time of manufacturing the nonwoven fabric. The longitudinal direction of the nonwoven fabric coincides with the film forming direction of the porous support layer and the MD direction in FIGS. The CD direction in FIGS. 1 and 5 corresponds to “Cross direction” at the time of manufacturing the nonwoven fabric.

  In this way, the angle is measured for a total of 100 fibers per nonwoven fabric. For the 100 fibers thus measured, an average value is calculated from the angle in the longitudinal direction. The value obtained by rounding off the first decimal place of the obtained average value is the fiber orientation degree.

  It is preferable that the thickness of the substrate is selected so that the total thickness of the substrate and the porous support layer is in the range of 30 μm to 300 μm, or in the range of 50 μm to 250 μm.

(1-3) Permeation side channel material <Overview>
In the separation membrane element, the porous sheet 302 constituting the permeate-side flow path member is preferably arranged so that the second direction coincides with the winding direction as shown in FIG. That is, in the separation membrane element of FIGS. 7, 8, and 9, the porous sheet 302 has the first direction (width direction of the separation membrane) parallel to the longitudinal direction of the water collection pipe 6 and the second direction (separation membrane). Is preferably arranged so that the longitudinal direction of the water collecting pipe 6 is orthogonal to the longitudinal direction of the water collecting pipe 6.

  Further, the porous sheet constituting the permeation side flow path member is present in a region where the permeation side surfaces of the separation membrane are bonded to each other. That is, the two separation membranes are bonded to each other with the porous sheet constituting the permeate-side flow path member interposed therebetween, and the porous sheet exists between the separation membranes in at least a part of the bonded portion. It is preferable. In FIG. 10, the size of the porous sheet 302 constituting the permeate-side channel material is the same as the size of the separation membrane, but actually the porous sheet may be larger or the separation membrane May be large. When the separation membrane is larger, since the porous sheet becomes a wall, the spread of the adhesive can be suppressed.

(Porous sheet)
The porous sheet is preferably a nonwoven fabric from the viewpoint of handleability. The porous sheet densely welded portion, rough welded portion, and non-welded portion of the present invention are present, and the ratio of the area of each region to the area of the nonwoven fabric, as will be described later, the dense weld rate, the coarse weld rate, the non-weld rate Called.

  The porous sheet is disposed so as to be sandwiched between the separation membranes. In other words, the unevenness of the porous sheet is in contact with the separation membrane at both the convex and concave portions. In this application, a convex part calls the unevenness | corrugation of one side which contacts a separation membrane, and the unevenness | corrugation of the other side is called a recessed part.

  The close welding rate is the ratio of the area occupied by the close welded portion to the area of the nonwoven fabric.

  The close welded portion is a region where a plurality of fibers are heat-sealed, and the size of the close welded portion is different from the fiber diameter constituting the nonwoven fabric. For example, the surface of the nonwoven fabric is observed with an electron microscope or the like, and a portion having a width larger than the average diameter of the fibers constituting the nonwoven fabric becomes a welded portion. Eight times or more becomes a dense welded part. In addition, an average fiber diameter is an average value of the diameter measured about arbitrary 50 fibers which comprise a nonwoven fabric and are not welded with the other fiber.

  The ratio of the minor axis to the major axis in the densely welded portion (referred to as aspect ratio) is 0.1 or more and 1.0 or less, more preferably 0.3 or more and 0.8, in order to maintain the uniformity of rigidity of the nonwoven fabric. It is as follows.

  The non-welded portion is a region where the nonwoven fabric fibers are not welded.

<Cross-sectional shape of convex part>
FIG. 11 is a cross-sectional view of a convex portion (a plane perpendicular to the sheet plane). This cross section is perpendicular to the longitudinal direction of the convex portion and passes through the center of the convex portion in the longitudinal direction. In this cross section, the ratio of the cross sectional area S of the convex portion to the product of the width d and the height H1 of the convex portion (cross sectional area ratio A) is preferably 0.4 or more and 0.8 or less. That is, the cross-sectional area ratio A is
A = S / (d × H1)
And 0.4 ≦ A ≦ 0.8
Preferably satisfying
0.6 ≦ A ≦ 0.7
It is particularly preferable to satisfy The width W is the maximum width in the cross section, and the height H1 is the maximum height in the cross section.

  That the cross-sectional area ratio A is 0.8 or less indicates that at least one of the width and the height is not constant in one cross-sectional shape of the convex portion. That is, in the cross section of the flow path material satisfying this equation, there is a portion recessed inward from the rectangular outer edge.

  In a rectangular channel material with side lengths W and H1, A is “1”. In this case, since the angle of the convex portion is close to a right angle, the right angle portion of the convex portion breaks the separation membrane during the pressurizing operation, and the separation characteristics are lost.

On the other hand, when the convex portion that satisfies the above-described requirements is provided, the separation membrane can be stably supported during the pressurization operation, and the stress applied to the convex portion becomes uniform over the entire convex portion, so that the same Even under operating pressure, the deformation of the convex portion tends to be small. For this reason, in the cross section of the convex portion, the ratio of the cross sectional area S of the convex portion to the product of the width W and the height H1 of the convex portion (cross sectional area ratio A) is 0.4 or more and 0.8 or less. It is preferable that In particular, in the convex portion, the width at an arbitrary height is preferably equal to or greater than the width at a higher position. That is, the width may be constant in part from the upper part of the convex part to the lower part (part fixed to the sheet), but it is preferably formed so that the width increases at least in part. Furthermore, it is preferable that the width gradually increases from the upper part to the lower part. (Dense welding rate on convex surface)
The convex portion of the porous sheet needs to have a high strength in order to stably support the separation membrane, particularly during a pressure operation. A convex surface refers to the area | region which contacts a separation membrane in a convex part. The higher the tight welding rate, the stronger the fibers of the porous sheet are welded together and the higher the strength. Therefore, the tight welding rate on the surface is preferably 80% to 100%, more preferably 90% to 100%.

(Non-welding rate on concave surface)
The concave portion of the porous sheet guides the water that has permeated through the membrane to the flow path due to the unevenness, and can improve the fluidity of the water in the permeate side flow path by itself becoming a flow path due to the gap between the fibers in the recess. As a result, the water production capacity of the separation membrane element is improved. The concave surface refers to a region in contact with the separation membrane in the concave portion.

  Therefore, the non-welding rate is preferably 30% or more and 85% or less, more preferably 55% or more and 85% or less, and the gap between fibers is preferably maintained. In addition, a non-welding rate is 85% or less, and can hold | maintain the aggregate | assembly of a fiber in a porous sheet form.

(Non-welding rate on the convex side)
The side surface of the convex portion of the porous sheet needs to have appropriate rigidity in order to support the separation membrane during the pressurizing operation. The convex side surface is a region extending from the surface opposite to the concave surface to the convex surface. On the other hand, if the convex side surface has an air gap, the permeated water can pass through the convex side surface, and as a result, the fluidity of water is increased and the freshness of the separation membrane element is improved. Therefore, it is preferable that the non-welding rate of the convex portion side surface of the porous sheet is 20% or more and 90%.

(Measuring method of close welding rate and surface open area rate)
An example of the measuring method is a microscope method.
In the microscope method, for example, a high-precision shape measurement system KS-1100 manufactured by Keyence Corporation is used, the surface is photographed at a magnification of 100 times, and the image is converted to black and white by setting the texture value to zero. Subsequently, the obtained digital image is analyzed by image analysis software (ImageJ) and calculated as a close welding rate or a surface opening ratio (%) = 100 × (area of the close welding portion or opening portion / cutting area). By repeating this, the average value can be set as the close deposition rate or the surface open area rate.

(Welding method)
As a method for welding the nonwoven fabric, a conventionally known method such as laser irradiation, heat roll, or calendering can be employed. In the case of welding with a hot roll, embossing is preferable because a dense weld portion can be stably formed during production.

  Embossing is a process in which a nonwoven fabric is hot-pressed using an embossing roll, and is usually pressed by two rolls, a roll having a smooth surface and a hot roll having an embossed pattern.

  Embossing may be applied to either one or both sides of the nonwoven fabric, but in the case of one side, the surface side where the height difference exists tends to have a lower adhesion rate than the other side. In addition, since the densely welded portion exists in the thickness direction in contrast to the two sides, the rigidity is increased, and the method is excellent in that it can be stably conveyed.

(Elevation difference of non-woven fabric by embossing)
When a difference in height is imparted to the nonwoven fabric by embossing, it can be freely adjusted by changing the pressure heat treatment conditions so that the separation characteristics and water permeation performance of the separation membrane element are satisfied. . However, if the height difference is too deep, the number of membrane leaves that can be filled in the vessel when the element is formed decreases. Therefore, the fresh water generation capacity of the element is reduced, and the operation cost for increasing the fresh water generation amount is increased.

  Therefore, in consideration of the balance between the above-described performances and operating costs, the height difference is preferably 0.05 mm or more and 0.50 mm or less, preferably mm or less, and more preferably 0.15 mm or more and 0.35 mm or less.

  Such a height difference is analyzed by, for example, an average height difference using a film thickness measuring instrument (manufactured by Anritsu Co., Ltd., KG601A), 30 points having a height difference of 5 μm or more are measured, and the values of the respective heights are summed Can be obtained by dividing the measured value by the total number of points.

(Thickness H1 of the porous sheet constituting the permeate-side channel material)
It is preferable that the thickness of the porous sheet which comprises a permeation | transmission side channel material is 0.2 mm or less. This is because the porous sheet is preferably impregnated with an adhesive in order to seal between the permeation side surfaces of the two separation membranes. Moreover, the convex part mentioned later becomes high, so that a porous sheet is made thin, the flow resistance as a permeation | transmission side channel material falls, and it exists in the tendency for element performance to improve.

<Constituent component of porous sheet>
The component constituting the porous sheet is not limited to a specific substance, but a resin is preferably used. Specifically, in view of chemical resistance, ethylene vinyl acetate copolymer resin, polyolefin such as polyethylene and polypropylene, and polyolefin copolymer are preferable. In addition, the material of the permeate side channel material is urethane resin, epoxy resin, polyethersulfone, polyacrylonitrile, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polystyrene, styrene-acrylonitrile copolymer Polymer, styrene-butadiene-acrylonitrile copolymer, polyacetal, polymethyl methacrylate, methacryl-styrene copolymer, cellulose acetate, polycarbonate, polyethylene terephthalate, polybutadiene terephthalate and fluororesin (ethylene trifluoride chloride, polyvinylidene fluoride, tetrafluoride) Ethylene, ethylene tetrafluoride-hexafluoropropylene copolymer, ethylene tetrafluoride-perfluoroalkoxyethylene copolymer, ethylene tetrafluoride-ethylene copolymer Etc.) can also be selected polymers such as. These materials are used alone or as a mixture of two or more.

<Shape and arrangement of convex parts>
<< Overview >>
Also in the first direction, the convex portions 301 can be distributed almost uniformly over the entire porous sheet 302. However, similarly to the distribution in the second direction, it is not necessary to provide the convex portion 301 at the adhesion portion with the separation membrane on the transmission side surface. Moreover, the area | region where the convex part 301 is not arrange | positioned may be provided in some places, such as an edge part of the porous sheet 302, for reasons of other specifications or manufacturing.

<< Projection size >>
2 to 4, b to e indicate the following values.

b: Interval between the convex portions 301 in the width direction of the separation membrane 2 c: Height of the convex portion (height difference between the convex portion 301 and the concave portion 303)
d: Width of the convex portion 301 e: Interval of the convex portion 301 in the length direction of the separation membrane 2 For measurement of the values b, c, d, e, for example, a commercially available shape measuring system or a microscope is used. it can. Each value is obtained by performing measurement at 30 or more locations on one separation membrane, and calculating an average value by dividing the sum of these values by the number of measurement total locations. Thus, each value obtained as a result of the measurement at at least 30 locations should satisfy the range described below.

(Spacing b of convex portions 301 in the width direction of the separation membrane)
An interval b between adjacent convex portions 301 in the first direction (the width direction of the separation membrane) corresponds to the width of the permeation side flow path 5. When the width of one permeation side flow path 5 is not constant in one cross section, that is, when the side surfaces of two adjacent convex portions 301 are not parallel, the width of one permeation side flow path 5 is within one cross section. Measure the average value of the maximum and minimum values and calculate the average value. As shown in FIG. 4, in the cross section perpendicular to the second direction, when the convex portion 301 has a trapezoidal shape with a thin top and a thick bottom, first, the distance between the upper portions of the two adjacent convex portions 301 and the lower portion The distance is measured and the average value is calculated. In any 30 or more cross sections, the interval between two adjacent convex portions 301 is measured, and an average value is calculated for each cross section. And the space | interval b is calculated by calculating further the arithmetic mean value of the average value obtained in this way.

  As the distance b increases, the pressure loss decreases, but the film falls easily. Conversely, the smaller the distance b, the less likely the film will drop, but the greater the pressure loss. Considering the pressure loss, the interval b is preferably 0.05 mm or more, 0.2 mm or more, or 0.3 mm or more. Further, in terms of suppressing film sagging, the interval b is preferably 5 mm or less, 3 mm or less, 2 mm or less, or 0.8 mm or less.

  These upper and lower limits can be combined arbitrarily. For example, the interval b is preferably 0.05 mm or more and 5 mm or less, and within this range, the pressure loss can be reduced while suppressing the film sagging. The distance b is more preferably 0.05 mm or more and 3 mm or less, 0.2 mm or more and 2 mm or less, and further preferably 0.3 mm or more and 0.8 mm or less.

(Convex width d)
The width d of the convex portion 301 is measured as follows. First, in one cross section perpendicular to the first direction (the width direction of the separation membrane), an average value of the maximum width and the minimum width of one convex portion 301 is calculated. That is, in the convex part 301 whose upper part is thin and whose lower part is thick as shown in FIG. 4, the width of the lower part and the upper part of the channel material are measured, and the average value is calculated. By calculating such an average value in at least 30 cross-sections and calculating the arithmetic average thereof, the width d per film can be calculated.

  The width d of the convex portion 301 is preferably 0.2 mm or more, and more preferably 0.3 mm or more. When the width d is 0.2 mm or more, the shape of the flow channel material can be maintained even when pressure is applied to the convex portion 301 or the porous sheet 302 during operation of the separation membrane element, and the permeation side flow channel is stable. Formed. The width d is preferably 2 mm or less, and more preferably 1.5 mm or less. When the width d is 2 mm or less, a sufficient flow path on the permeate side can be secured.

  When the width d of the convex portion 301 is wider than the interval b between the convex portions 301 in the second direction, the pressure applied to the flow path material can be dispersed.

(Space e between protrusions in the length direction of the porous sheet)
The interval e between the convex portions 301 in the second direction (the length direction of the porous sheet) is the shortest distance between the adjacent convex portions 301 in the second direction (the length direction of the separation membrane). As shown in FIG. 2, the convex portion 301 is provided continuously from one end to the other end of the separation membrane 2 in the second direction (in the separation membrane element, from the inner end to the outer end in the winding direction). If there is, the interval e is 0 mm. Moreover, as shown in FIG. 3, when the convex part 301 has interrupted in the 2nd direction, the space | interval e becomes like this. Preferably it is 5 mm or less, More preferably, it is 1 mm or less, More preferably, it is 0.5 mm or less. . When the distance e is within the above range, the mechanical load on the film is small even when the film is dropped, and the pressure loss due to the blockage of the flow path can be relatively small. For example, when the upper bottom of the flow path material is shorter than the lower bottom, the width of the upper part is wider than the width of the lower part of the flow path therebetween. The lower limit of the interval e is 0 mm.

(Projection shape)
The shape of the convex portion 301 is not particularly limited, but a shape that reduces the flow resistance of the flow path and stabilizes the flow path when permeated can be selected. In these respects, in any cross section perpendicular to the surface direction of the separation membrane, the shape of the convex portion 301 may be a straight column shape, a trapezoidal shape, a curved column shape, or a combination thereof.

  When the cross-sectional shape of the convex portion 301 is a trapezoid, if the difference between the length of the upper base and the length of the lower base is too large, membrane drop during pressure filtration is likely to occur at the membrane contacting the smaller side. Therefore, the upper film tends to drop downward. Therefore, in order to suppress such a drop, the ratio of the length of the upper base to the length of the lower base of the flow path material is preferably 0.6 or more and 1.4 or less, and is 0.8 or more and 1.2 or less. Further preferred.

  From the viewpoint of reducing flow resistance, the shape of the convex portion 301 is preferably a straight column shape perpendicular to the separation membrane surface described later. Further, the convex portion 301 may be formed so that the width becomes smaller at a higher portion, or conversely, the width at a higher portion may be formed wider, or the height from the surface of the separation membrane. Regardless, it may be formed to have the same width.

  However, the upper side may be rounded in the cross section of the convex portion 301 as long as the channel material is not significantly crushed during pressure filtration.

  Further, the shape of the projection 301 in the planar direction of the separation membrane may be linear as a whole as shown in FIGS. 2 and 3, and other shapes such as a curved shape, a sawtooth shape, and a wavy shape may be used. There may be. Moreover, in these shapes, the convex part 301 may be a broken line shape or a dot shape. From the viewpoint of reducing the flow resistance, a dot shape or a broken line shape is preferable. However, since the flow path material is interrupted, the number of places where film sagging occurs during pressure filtration increases.

  Moreover, when the shape in the planar direction of the porous sheet 302 of the convex part 301 is linear, the adjacent flow-path material may be arrange | positioned substantially parallel mutually. “Arranged substantially in parallel” means, for example, that the channel material does not intersect on the separation membrane, the angle formed by the longitudinal direction of two adjacent channel materials is 0 ° or more and 30 ° or less, It includes that the angle is from 0 ° to 15 °, and that the angle is from 0 ° to 5 °.

  Moreover, the angle formed by the longitudinal direction of the convex portion 301 and the longitudinal direction of the water collecting pipe 6 is preferably 60 ° or more and 120 ° or less, more preferably 75 ° or more and 105 ° or less, and 85 ° or more and 95. More preferably, it is not more than 0 °. When the angle formed by the longitudinal direction of the flow path material and the longitudinal direction of the water collecting pipe is within the above range, the permeated water is efficiently collected in the water collecting pipe.

  In order to stably form the flow path, it is preferable that the separation membrane can be prevented from dropping when the separation membrane is pressurized in the separation membrane element. For this purpose, it is preferable that the contact area between the separation membrane and the channel material is large, that is, the area of the channel material relative to the area of the separation membrane (projected area of the channel material with respect to the membrane surface of the separation membrane) is large. On the other hand, in order to reduce pressure loss, it is preferable that the cross-sectional area of a flow path is wide. In order to ensure a large cross-sectional area of the flow path while ensuring a large contact area between the separation membrane and the flow path material perpendicular to the longitudinal direction of the flow path, The shape is preferably a concave lens. Further, the convex portion 301 may be a straight column shape having no change in width in a cross-sectional shape in a direction perpendicular to the winding direction. In addition, if it is within a range that does not affect the performance of the separation membrane, the convex portion 301 is a trapezoidal wall-like object or elliptical column whose width changes in the cross-sectional shape in the direction perpendicular to the winding direction. The shape may be an elliptical cone, a quadrangular pyramid, or a hemisphere.

  In FIG. 2, the planar shape of the convex portion 301 is linear in the length direction. However, the convex part 301 can be changed to another shape as long as it is convex with respect to the surface of the separation membrane 2 and does not impair the desired effect as the separation membrane element.

[2. Separation membrane element)
(2-1) Overview As shown in FIG. 5, the separation membrane element 100 includes the water collection pipe 6 and the separation membrane 2 that is wound around the water collection pipe 6 with any of the configurations described above.

(2-2) Separation membrane <Overview>
As shown in FIG. 5, the separation membrane 2 is wound around the water collecting pipe 6, and is arranged so that the width direction of the separation membrane 2 is along the longitudinal direction of the water collecting pipe 6. As a result, the separation membrane 2 is disposed such that the length direction is along the winding direction.

  Therefore, as shown in FIG. 5, the convex portions 301 are discontinuously arranged on the permeation side surface 22 of the separation membrane 2 at least with respect to the longitudinal direction of the water collecting pipe 6. That is, the permeate-side channel 5 is formed so as to be continuous from the outer end to the inner end of the separation membrane in the winding direction. As a result, the permeated water can easily reach the central water collecting pipe 6, that is, the flow resistance is reduced, so that a large amount of fresh water can be obtained.

  “Inside in winding direction” and “Outside in winding direction” are as shown in FIG. That is, the “inner end in the winding direction” and the “outer end in the winding direction” correspond to the end closer to the water collecting pipe 6 and the far end in the separation membrane 2, respectively.

  As described above, since the flow path material does not have to reach the edge of the separation membrane, for example, in FIG. 5, the outer end of the envelope-shaped membrane (separation membrane 2) in the winding direction and the longitudinal direction of the water collection tube In the end portion of the envelope membrane (separation membrane 2), a flow path material may not be provided.

<Membrane leaf and envelope membrane>
As shown in FIG. 1, the separation membrane forms a membrane leaf 4 (sometimes simply referred to as “leaf” in this document). In the leaf 4, the separation membrane 2 a is arranged so that the supply-side surface 21 a faces the supply-side surface 21 b of another separation membrane 2 b with a supply-side channel material (not shown) interposed therebetween. In the membrane leaf 4, a supply-side flow path is formed between the supply-side surfaces of the separation membranes facing each other.

  Further, as shown in FIG. 1, the two membrane leaves 4 are overlapped so that the permeation side surface 22b of the separation membrane 2b faces the permeation side surface 22c of the separation membrane 2c of the other membrane leaf. The membrane leaf 4 forms an envelope-like film. The envelope membrane is a pair of separation membranes (one consisting of separation membranes 2b and 2c) arranged so that the surfaces on the permeate side facing each other face each other. The envelope-shaped membrane is rectangular, and the permeate side surface is rectangular in the separation membrane so that the permeate flows into the water collecting pipe 6, and is opened only on one side in the winding direction, and on the other three sides. Is sealed. The permeate is isolated from the raw water by this envelope membrane.

  Examples of the sealing include a form bonded by an adhesive or hot melt, a form fused by heating or laser, and a form in which a rubber porous sheet is sandwiched. Sealing by adhesion is particularly preferable because it is the simplest and most effective.

  In addition, on the surface on the supply side of the separation membrane, the inner end in the winding direction is closed by folding or sealing. Since the supply side surface of the separation membrane is sealed rather than folded, bending at the end of the separation membrane hardly occurs. By suppressing the occurrence of bending in the vicinity of the crease, the generation of voids between the separation membranes and the occurrence of leaks due to the voids are suppressed when wound.

  By suppressing the occurrence of leak in this way, the recovery rate of the envelope film is improved. The recovery rate of the envelope film is obtained as follows. That is, an air leak test (air leak test) of the separation membrane element is performed in water, and the number of envelope-shaped membranes in which the leak has occurred is counted. Based on the count result, the ratio of (number of envelope films in which air leak has occurred / number of envelope films used for evaluation) is calculated as the recovery rate of the envelope film.

  A specific air leak test method is as follows. The end of the central pipe of the separation membrane element is sealed, and air is injected from the other end. The injected air passes through the holes of the water collecting pipe and reaches the permeation side of the separation membrane. However, as described above, if the separation membrane is not sufficiently folded and bent near the fold, Will move through the gap. As a result, the air moves to the supply side of the separation membrane, and the air reaches the water from the end (supply side) of the separation membrane element. Thus, air leak can be confirmed as the generation of bubbles.

  When the membrane leaf is formed by folding, the longer the leaf (that is, the longer the original separation membrane), the longer the time required for folding the separation membrane. However, by sealing the supply side surface of the separation membrane instead of folding, an increase in manufacturing time can be suppressed even if the leaf is long.

  In the membrane leaf and the envelope membrane, the separation membranes facing each other (separation membranes 2b and 2c in FIG. 1) may have the same configuration or different configurations. That is, in the separation membrane element, at least one of the two permeation-side surfaces facing each other only needs to be provided with the above-described permeation-side flow passage material, so that the separation membrane provided with the permeation-side flow passage material and the permeation side Separation membranes that do not include a channel material may be alternately stacked. However, for convenience of explanation, in the separation membrane element and the explanation related thereto, the “separation membrane” includes a separation membrane that does not include the permeate-side channel material (for example, a membrane that has the same configuration as the separation membrane).

  The separation membranes facing each other on the permeate side surface or the supply side surface may be two different separation membranes, or one membrane folded.

(2-3) Permeation-side channel As described above, the separation membrane 2 includes the convex portion 301. By the convex portion 301, a permeate-side flow path is formed inside the envelope-shaped membrane, that is, between the permeate-side surfaces of the facing separation membrane.

(2-4) Supply side channel (channel material)
The separation membrane element 100 has a supply-side flow path material in which the projected area ratio with respect to the separation membrane 2 exceeds 0 and is less than 1 between the surfaces on the supply side of the facing separation membrane (see reference numeral 32 in FIGS. 7 and 8). Is provided. The projected area ratio of the supply-side channel material is preferably 0.03 or more and 0.50 or less, more preferably 0.10 or more and 0.40 or less, and particularly preferably 0.15 or more and 0.35 or less. . When the projected area ratio is 0.03 or more and 0.50 or less, the flow resistance can be suppressed to be relatively small. The projected area ratio is the projected area of the channel material obtained when the separation membrane and the supply-side channel material are cut out at 5 cm × 5 cm and the supply-side channel material is projected onto a plane parallel to the surface direction of the separation membrane. Is divided by the cut-out area (25 cm 2).

  As will be described later, the height of the supply-side channel material is preferably more than 0.5 mm and not more than 2.0 mm, more preferably not less than 0.6 mm and not more than 1.0 mm, in consideration of the balance of each performance and operation cost.

  The shape of the supply-side channel material is not particularly limited, and may have a continuous shape or a discontinuous shape. Examples of the channel material having a continuous shape include members such as a film and a net. Here, the continuous shape means that it is continuous over the entire range of the flow path material. The continuous shape may include a portion where a part of the flow path material is discontinuous to such an extent that a problem such as a decrease in the amount of water produced does not occur. The definition of “discontinuity” is as described for the passage-side channel material (see paragraph 0077). The material of the supply side channel material is not particularly limited, and may be the same material as the separation membrane or a different material.

(2-5) Water Collection Pipe The water collection pipe 6 (see FIGS. 7 to 10) is not particularly limited as long as it is configured to allow permeate to flow therethrough. As the water collecting pipe 6, for example, a cylindrical member having a side surface provided with a plurality of holes is used.

(2-6) First Mode As more specific modes, FIGS. 7 to 9 show separation membrane elements 100A, 100B, and 100C of the first to third modes. FIG. 7 is an explanatory view showing the separation membrane element 100 </ b> A of the first embodiment partially disassembled, and a plurality of separation membranes 2 are wound around the water collection pipe 6. In addition to the above-described configuration, the separation membrane element 100A further includes the following configuration.

  That is, the separation membrane element 100A includes end plates 92 with holes at both ends (that is, the first end and the second end). In the separation membrane element 100A, an outer package 81 is wound around the outer peripheral surface of the wound separation membrane (hereinafter referred to as “wrapping body”).

  The holeless end plate 91 described later does not include a hole through which raw water can pass, whereas the holed end plate 92 includes a plurality of holes through which the raw water can pass.

  Moreover, the separation membrane 2 forms an envelope-like membrane 11, and the convex portion 301 is arranged inside the envelope-like membrane 11 as described above. A supply-side channel material 32 is disposed between the envelope-shaped films 11.

  For convenience, in FIG. 7, FIG. 8, and FIG. 9, the convex portion 301 (permeation-side channel material) is shown as a dot shape, but as described above, the shape of the permeation-side channel material is not limited to this shape. .

  Next, water treatment using the separation membrane element 100A will be described. The raw water 101 supplied from the first end of the separation membrane element 100A flows into the supply-side flow path through the hole of the end plate 92. In this way, the raw water 101 in contact with the supply side surface of the separation membrane 2 is separated into the permeated water 102 and the concentrated water 103 by the separation membrane 2. The permeated water 102 flows into the water collecting pipe 6 through the permeate side flow path. The permeated water 102 that has passed through the water collection pipe 6 flows out of the separation membrane element 100A from the second end of the separation membrane element 100A. The concentrated water 103 flows out of the separation membrane element 100A from the hole of the end plate 92 provided at the second end through the supply side flow path.

(2-7) Second Embodiment With reference to FIG. 8, the separation membrane element 100B of the present embodiment will be described. In addition, about the component already demonstrated, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  The separation membrane element 100B includes an end plate 91 that is disposed at the first end and has no holes, and an end plate 92 that is disposed at the second end and has holes. Further, the separation membrane element 100B includes a porous member 82 that is further wound around the outermost surface of the surrounded separation membrane 2.

  As the porous member 82, a member having a plurality of holes through which raw water can pass is used. These holes provided in the porous member 82 may be referred to as raw water supply ports. As long as the porous member 82 has a plurality of holes, the material, size, thickness, rigidity and the like are not particularly limited. By adopting a member having a relatively small thickness as the porous member 82, the membrane area per unit volume of the separation membrane element can be increased.

  The thickness of the porous member 82 is, for example, 1 mm or less, 0.5 mm or less, or 0.2 mm or less. Further, the porous member 82 may be a member having flexibility or flexibility that can be deformed so as to follow the outer peripheral shape of the wound body. More specifically, as the porous member 82, a net, a porous film, or the like can be applied. The net and the porous film may be formed in a cylindrical shape so that the wound body can be accommodated therein, or may be long and wound around the wound body.

  The porous member 82 is disposed on the outer peripheral surface of the separation membrane element 100B. By providing the porous member 82 in this manner, holes are provided on the outer peripheral surface of the separation membrane element 100B. It can be said that the “outer peripheral surface” is a portion excluding the first end surface and the second end surface in the entire outer peripheral surface of the separation membrane element 100B. In this embodiment, the porous member 82 is disposed so as to cover almost the entire outer peripheral surface of the wound body.

  According to this embodiment, raw water is supplied from the outer peripheral surface of the separation membrane element 100B (the outer peripheral surface of the wound body) via the porous member 82. Therefore, even if the separation membrane element 100B is repeatedly operated or the separation membrane element 100B is operated under a high pressure condition, deformation of the wound body due to the surrounding separation membrane 2 and the like being pushed out in the longitudinal direction ( It is possible to suppress so-called telescopes. Furthermore, in this embodiment, since raw | natural water is supplied from the clearance gap between a pressure vessel (not shown) and a separation membrane element, generation | occurrence | production of the abnormal stagnation of raw | natural water is suppressed.

  In the separation membrane element 100B, since the end plate at the first end is the end plate 91 without holes, the raw water does not flow into the separation membrane element 100B from the surface of the first end. The raw water 101 is supplied to the separation membrane 2 through the porous member 82 from the outer peripheral surface of the separation membrane element 100B. The raw water 101 supplied in this way is divided into permeated water 102 and concentrated water 103 by the separation membrane. The permeated water 102 passes through the water collection pipe 6 and is taken out from the second end of the separation membrane element 100B. The concentrated water 103 flows out of the separation membrane element 100B through the hole of the end plate 92 with a hole at the second end.

(2-8) Third Embodiment With reference to FIG. 9, a separation membrane element 100C of the present embodiment will be described. In addition, about the component already demonstrated, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  The separation membrane element 100 </ b> C is the same as the element of the second embodiment except that the separation membrane element 100 </ b> C is disposed at each of the first end and the second end and includes an end plate 92 having holes. In addition, the separation membrane element 100C includes a porous member 82, like the separation membrane element 100B.

  With this configuration, in this embodiment, the raw water 101 is not only supplied from the outer peripheral surface of the separation membrane element 100C to the envelope through the hole of the porous member 82, but also the end plate 92 with a hole at the first end. The separation membrane element 100 </ b> C is supplied to the winding body through the first hole. The permeated water 102 and the concentrated water 103 are discharged from the second end to the outside of the separation membrane element 100C, similarly to the separation membrane element 100A of the first form.

  Since the raw water is supplied not only from one end of the separation membrane element 100C (that is, the end plate 92 having a hole) but also from the outer peripheral surface of the separation membrane element 100C through the porous member 82, Deformation can be suppressed. Also in this embodiment, since the raw water is supplied from the gap between the pressure vessel and the separation membrane element, the occurrence of abnormal stagnation is suppressed.

[3. Method for manufacturing separation membrane element]
Each process in the manufacturing method of a separation membrane element is demonstrated below.

(3-1) Manufacture and Post-Processing of Separation Membrane The manufacturing method of the separation membrane has been described above, but it can be summarized as follows.

  The resin is dissolved in a good solvent, and the resulting resin solution is cast on a substrate and immersed in pure water to combine the porous support layer and the substrate. Thereafter, as described above, a separation functional layer is formed on the porous support layer. Furthermore, in order to improve separation performance and permeation performance as necessary, chemical treatment with chlorine, acid, alkali, nitrous acid or the like is performed, and the monomer is washed to produce a continuous porous sheet of separation membrane.

  Before or after the chemical treatment, the separation membrane may be uneven by embossing or the like, or a flow path material may be formed on the permeation side surface and / or the supply side surface of the separation membrane with a resin. Also good.

  When unevenness processing is performed on the separation membrane, a difference in height can be imparted to the supply side of the separation membrane by methods such as embossing, hydraulic forming, and calendering.

  When the supply-side flow path is a continuously formed member such as a net, after the separation membrane is manufactured by arranging the permeation-side flow path material in the separation membrane body, the separation membrane and the supply-side flow are What is necessary is just to overlap with a road material.

  The method of arranging the flow path material includes, for example, a step of arranging a soft material on the separation membrane and a step of curing it. Specifically, ultraviolet curable resin, chemical polymerization, hot melt, drying or the like is used for the arrangement of the flow path material. In particular, hot melt is preferably used. Specifically, a step of softening a material such as resin by heat (that is, heat melting), a step of placing the softened material on the separation membrane, and curing the material by cooling. A step of fixing on the separation membrane.

  Examples of the method for arranging the flow path material include coating, printing, spraying, and the like. Examples of the equipment used include a nozzle type hot melt applicator, a spray type hot melt applicator, a flat nozzle type hot melt applicator, a roll type coater, an extrusion type coater, a printing machine, and a sprayer.

(3-2) Formation of membrane leaf As described above, the membrane leaf may be formed by folding the separation membrane so that the surface on the supply side faces inward, or two separate separation membranes may be formed. It may be formed by bonding so that the surfaces on the supply side face each other.

  The manufacturing method of the separation membrane element preferably includes a step of sealing the inner end portion in the winding direction of the separation membrane on the surface on the supply side. In the sealing step, the two separation membranes are overlapped so that the surfaces on the supply side face each other. Further, the inner end in the winding direction of the stacked separation membranes, that is, the left end in FIG. 5 is sealed so that the permeated water can flow into the water collecting pipe 6.

  Examples of the method of “sealing” include adhesion by an adhesive or hot melt, fusion by heating or laser, and a method of sandwiching a rubber porous sheet. Sealing by adhesion is particularly preferable because it is the simplest and most effective.

  At this time, a supply-side channel material formed separately from the separation membrane may be disposed inside the overlapped separation membrane. As described above, the arrangement of the supply-side flow path material can be omitted by providing a height difference in advance on the supply-side surface of the separation membrane by embossing or resin coating.

  Either the supply-side sealing or the permeation-side sealing (envelope-like membrane formation) may be performed first, or the supply-side sealing is performed while stacking separation membranes. And the sealing of the surface on the transmission side may be performed in parallel. However, in order to suppress the generation of wrinkles in the separation membrane during winding, the adhesive or hot melt at the end in the width direction is allowed to allow the adjacent separation membranes to shift in the length direction due to winding. It is preferable to complete the solidification or the like, that is, the solidification for forming an envelope-like film, after the winding is completed.

(3-3) Formation of an envelope-like membrane A single separation membrane is folded so that the permeation side faces inward, and a porous sheet having the above-mentioned convex portions is sandwiched between opposing separation membranes, and bonded together. Or by stacking two separation membranes so that the permeation side faces inward and sandwiching the porous sheet having the above-mentioned convex part between one separation membrane and the other separation membrane By combining them, an envelope-like film can be formed. In the rectangular envelope film, the other three sides are sealed so that only one end in the length direction is opened. Sealing can be performed by bonding with an adhesive or hot melt, or by fusion with heat or laser.

  At this time, in the sealed part, a porous sheet may exist between the separation membranes, and the porous sheet may be disposed inside the sealing part of the separation membrane.

  The adhesive used for forming the envelope-shaped film preferably has a viscosity in the range of 40 P (poise) to 150 P (poise), more preferably 50 P (poise) to 120 P (poise). If the adhesive viscosity is too high, wrinkles are likely to occur when the laminated leaves are wrapped around the water collection pipe. Wrinkles may impair the performance of the separation membrane element. Conversely, if the adhesive viscosity is too low, the adhesive may flow out of the end of the leaf and soil the device. Moreover, when an adhesive adheres to a portion other than the portion to be bonded, the performance of the separation membrane element is impaired, and the work efficiency is significantly reduced due to the processing operation of the adhesive that has flowed out.

  The amount of adhesive applied is preferably such that the width of the portion where the adhesive is applied after the membrane leaf is wrapped around the water collecting tube is 10 mm or more and 100 mm or less. As a result, the separation membrane is securely bonded, and the inflow of the raw water to the permeate side is suppressed. In addition, the effective membrane area of the separation membrane element can be secured relatively large.

  As the adhesive, a urethane-based adhesive is preferable, and in order to make the viscosity in the range of 40 P (poise) or more and 150 P (poise) or less, the isocyanate of the main agent and the polyol of the curing agent have an isocyanate / polyol weight ratio of 1 / What mixed so that it might become 5 or more and 1 or less is preferable. The viscosity of the adhesive is obtained by measuring the viscosities of a main agent, a curing agent alone, and a mixture in which a blending ratio is previously determined with a B-type viscometer (JIS K 6833).

  When a porous sheet exists in the sealing portion, the separation membranes can be bonded to each other through the porous sheet by an adhesive soaked in the porous sheet. Moreover, when there is no porous sheet in the sealing portion, the separation membrane is directly bonded.

(3-4) Separation membrane winding For manufacturing the separation membrane element, a conventional element manufacturing apparatus can be used. In addition, as an element manufacturing method, methods described in reference documents (Japanese Patent Publication No. 44-14216, Japanese Patent Publication No. 4-11928, Japanese Patent Application Laid-Open No. 11-226366) can be used. Details are as follows.

  When the separation membrane is wound around the water collecting pipe, the separation membrane is arranged so that the closed end of the leaf, that is, the closed portion of the envelope-shaped membrane faces the water collecting pipe. By winding the separation membrane around the water collecting pipe in such an arrangement, the separation membrane is wound in a spiral shape.

  If a spacer such as a tricot or base material is wound around the water collection pipe, the adhesive applied to the water collection pipe will not flow easily when the separation membrane element is wrapped, leading to suppression of leakage, and the flow path around the water collection pipe Is secured stably. The spacer may be wound longer than the circumference of the water collecting pipe.

(3-5) Other steps The method of manufacturing a separation membrane element may include further winding a film, a filament, and the like around the outer periphery of the wound membrane of the separation membrane formed as described above. Further steps such as edge cutting for aligning the end of the separation membrane in the longitudinal direction of the water collecting pipe, attachment of an end plate, and the like may be included.

[4. (Use of separation membrane element)
The separation membrane element may be further used as a separation membrane module by being connected in series or in parallel and housed in a pressure vessel.

  In addition, the separation membrane element and the separation membrane module described above can be combined with a pump that supplies fluid to them, a device that pretreats the fluid, and the like to form a fluid separation device. By using this separation device, for example, raw water can be separated into permeated water such as drinking water and concentrated water that has not permeated through the membrane, and water suitable for the purpose can be obtained.

  The higher the operating pressure of the fluid separator, the higher the removal rate, but the energy required for operation also increases, and considering the retention of the separation membrane element supply channel and permeation channel, the membrane module The operating pressure when passing through the water to be treated is preferably 0.2 MPa or more and 5 MPa or less. As the raw water temperature increases, the salt removal rate decreases, but as the raw water temperature decreases, the membrane permeation flux also decreases. Moreover, when the pH of the raw water is in a neutral region, even if the raw water is a high salt concentration liquid such as seawater, the generation of scales such as magnesium is suppressed, and the deterioration of the membrane is also suppressed.

  The fluid to be treated by the separation membrane element is not particularly limited, but when used for water treatment, as raw water, TDS (Total Dissolved Solids: total dissolved solids) of 500 mg / L or more and 100 g / L or less such as seawater, brine, drainage, etc. For example). In general, TDS indicates the total dissolved solid content, and is expressed by “mass / volume”, but 1 L may be expressed as 1 kg and may be expressed by “weight ratio”. According to the definition, the solution filtered through a 0.45 μm filter can be calculated from the weight of the residue by evaporating at a temperature of 39.5 ° C. or higher and 40.5 ° C. or lower. Convert.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples.

(Position difference and thickness of porous sheet)
The porous sheet was cut in the width direction of the separation membrane element using a single blade, and the average height difference was analyzed from the measurement result on the transmission side of 5 cm × 5 cm using Keyence high-precision shape measurement system KS-1100. Thirty points with a height difference of 10 μm or more were measured, and the total value of each height value was divided by the number of total measurement points.

  Moreover, about thickness, the thickness of the nonwoven fabric in a recessed part was measured 30 places, and the value which totaled the value of each height was divided | segmented and calculated | required by the number of the measurement total places.

(Pitch and spacing of unevenness, width)
Using a high-precision shape measurement system KS-1100 manufactured by Keyence Corporation, the horizontal distance from the apex of the channel material on the permeate side of the separation membrane to the apex of the adjacent channel material was measured at 200 points, and the average value was pitched. Calculated as

  Further, the distances b, e, and width d were measured by the above-described method in the photograph in which the pitch was measured (see FIGS. 2 and 3).

(Pitch between tight welds)
Using a high-precision shape measurement system KS-1100 manufactured by Keyence Corporation, the horizontal distance between the center of gravity position of a certain tightly welded portion and the center of gravity of another tightly welded portion adjacent to this tightly welded portion was measured at 50 locations.
(Cross sectional area ratio of convex part)
Using a high-precision shape measurement system KS-1100 manufactured by Keyence Corporation, the cross-sectional area of the protrusions as shown in FIG. Subsequently, the ratio of the cross-sectional area to the product of the width and height of the convex portion measured by the above method was calculated, and the average value of 30 arbitrary convex portions was taken as the cross-sectional area ratio.

(Water production)
For the separation membrane element, a NaCL aqueous solution with a concentration of 200 mg / L and pH 6.5 was used as the feed water, and the sample was run for 10 minutes after operating for 100 hours under conditions of an operating pressure of 0.15 MPa and a temperature of 25 ° C. The amount of water per unit area and per day was expressed as the amount of water produced (L / day).

(Desalination rate (TDS removal rate))
For the raw water and the sampled permeate used in the operation for 10 minutes in measuring the amount of water produced, the TDS concentration was determined by conductivity measurement, and the TDS removal rate was calculated from the following formula.
TDS removal rate (%) = 100 × {1- (TDS concentration in permeated water / TDS concentration in raw water)}
(Preparation of separation membrane)
On a non-woven fabric made of polyethylene terephthalate fiber (yarn diameter: 1 dtex, thickness: about 90 μm, air permeability: 1 cc / cm ² / sec, density: 0.80 g / cm ³ ), 15.0 wt% DMF solution of polysulfone is 180 μm. Cast at room temperature (25 ° C.), immediately immersed in pure water for 5 minutes, and immersed in warm water at 80 ° C. for 1 minute to form a porous support layer comprising a fiber-reinforced polysulfone support membrane ( A thickness of 130 μm) was produced.

  Thereafter, the surface of the polysulfone layer of the porous support membrane was immersed in a 2.2 wt% aqueous solution of m-PDA for 2 minutes, and then slowly pulled up in the vertical direction. Furthermore, the excess aqueous solution was removed from the surface of the support film by blowing nitrogen from the air nozzle.

  Thereafter, an n-decane solution containing 0.08% by weight of trimesic acid chloride was applied so that the surface of the film was completely wetted, and then allowed to stand for 1 minute. Thereafter, excess solution was removed from the membrane by air blowing, and washed with hot water at 80 ° C. for 1 minute.

Example 1
The separation membrane was folded and cut so that the effective area at the separation membrane element was 0.5 m ^2, and the net (thickness: 0.50 mm, pitch: 2.5 mm × 2.5 mm, fiber diameter: 0.25 mm, Was used as a supply-side channel material.

  Further, as the permeate side channel material, embossed non-woven fabric shown in Table 1 is laminated on the permeate side surface of the leaf and the permeate side channel material is laminated, and a water collecting pipe made of ABS (acrylonitrile-butadiene-styrene) (width: 300 mm, diameter: 30 mm, 15 holes × 1 line) was spirally wound, and a film was wound around the outer periphery, and then fixed with tape. The sealing between the leaves was performed by discharging and curing the epoxy adhesive while adjusting the moving speed of the nozzle. The form of the obtained sealing part was as shown in Table 1.

  Thereafter, edge cutting, end plate attachment, and filament winding were performed to produce a 2-inch element having a width of 260 mm and a leaf length of 1,900 mm. Both end plates were perforated end plates.

  When the separation membrane element was placed in a pressure vessel and operated under the conditions described above, the element performance was as shown in Table 1.

(Examples 2 to 8)
A separation membrane element was produced in the same manner as in Example 1 except that the permeation side channel material was changed to the porous sheet shown in Tables 1 and 2.

  When the separation membrane element was put in a pressure vessel and operated under the above-described conditions, the element performance was as shown in Tables 1 and 2.

(Comparative Example 1)
When the embossed biaxially stretched polyester film (Toray Lumirror, thickness 0.03mm) is used as the permeate-side channel material, the cross-sectional area ratio is too large, and the separation membrane is defective, and the entire porous sheet Since the welding rate of the element was too high, the water permeated through the separation membrane could not move to the permeate side flow path, and the amount of water produced by the element was significantly reduced.

(Comparative Example 2)
When the porous sheet was made into a non-woven fabric as shown in Table 3 and the convex portions were arranged in the same manner as in Example 1, the cross-sectional area ratio was small, the porous sheet had no densely welded portion, only the non-welded portion. Therefore, when the nonwoven fabric roll was unwound in the separation membrane element production process, the nonwoven fabric was broken and the separation membrane element could not be produced.

  As is apparent from the results shown in Tables 1 to 3, the separation membrane elements of Examples 1 to 12 of the present invention obtain a sufficient amount of permeated water having a high desalination rate even when operated for a long time. It can be said that it has stable separation performance.

  The separation membrane element of the present invention can be particularly suitably used for brine or seawater desalination.

DESCRIPTION OF SYMBOLS 1 Separation membrane 11 Envelope-shaped membrane 2 Separation membrane 2a Separation membrane 2b Separation membrane 2c Separation membrane 21 Supply side surface 21a Supply side surface 21b Supply side surface 21c Supply side surface 22 Permeation side surface 22a Permeation side surface 22b Permeation side surface 22c Permeation side surface 201 Base material 202 Porous support layer 203 Separation functional layer 31 Permeation side flow path material 32 Supply side flow path material 301 Convex part 302 Porous sheet 303 Concave part 4 Membrane leaf 5 Permeation side flow path 6 Water Collection Pipe 7 Separation Membrane 71 Supply Side Surface 72 Permeation Side Surface 81 Exterior Body 82 Porous Member 91 End Plate (No Hole)
92 End plate (with holes)
100 Separation Membrane Element A Cross-Section Area Ratio b Width in Permeation Side Channel Material c Height Difference of Permeation Side Channel Material d Permeation Side Channel Material Width e Permeation Side Channel Material Length S S Convex Cross-sectional area of 100A separation membrane element (first form)
100B separation membrane element (second form)
100C separation membrane element (third form)
101 Raw water 102 Permeated water 103 Concentrated water

Claims (3)

A separation membrane having a supply-side surface and a permeation-side surface and forming a separation membrane pair by being arranged so that the permeation-side surfaces face each other;
A permeate-side channel material provided to face the permeate-side surface of the separation membrane;
With
The permeate-side flow path material is a porous sheet that has been concavo-convex molded so as to have convex and concave portions,
The height difference due to the unevenness is 0.05 mm or more and 0.50 mm or less,
A separation membrane element, wherein a ratio of a cross-sectional area of the convex portion to a product of a width and a height of the convex portion is 0.4 or more and 0.8 or less. The porous sheet has a tightly welded portion and a non-welded portion,
The proportion of the densely welded portion on the convex surface of the porous sheet is 80% or more and 100 or less,
The separation membrane element according to claim 1, wherein the proportion of the non-welded portion on the surface of the recess is 30% or more and 85% or less.   The separation membrane element according to claim 1 or 2, wherein a proportion of the non-welded portion in the side surface of the convex portion of the porous sheet is 20% or more and 90%.