JP2015071159A - Separation membrane element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separation membrane capable of stabilizing separation removal performance when a separation membrane element is operated by applying particularly-high pressure, and the separation membrane element.SOLUTION: A separation membrane element includes a separation membrane body that has at least a base material and a separation function layer, and a plurality of protrusions that are fixed to a permeation-side surface of the separation membrane body. The adjacent protrusions and a channel serving as a flow channel are formed. The representative length of each channel is in the range of 0.12-0.3 mm.

Description

  The present invention relates to a separation membrane used for separating components contained in a fluid such as liquid or 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 membrane consists of a separation functional layer made of a crosslinked polymer such as polyamide, a porous resin layer made of a polymer such as polysulfone, and a nonwoven fabric made of a polymer such as polyethylene terephthalate, which are laminated from the supply side to the permeation side. Is a separation membrane. 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, high performance of membrane elements has been demanded due to increasing demands for reducing water production costs. 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, in Patent Document 1, a flow path material composed of an elastomer called a vane is disposed in a separation membrane, so that a supply-side flow path material such as a net or a permeation-side flow path material such as a tricot is used. Elements that are not required have been proposed. Patent Document 2 proposes an element in which the amount of water produced by the element is increased by disposing a resin having a high elastic modulus on the permeation side of the separation membrane.

Japanese Unexamined Patent Publication No. 2012-518528 International Patent Publication No. 2013-047746

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

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

The present invention provides the following techniques.
(1) a separation membrane body having a supply side surface and a permeation side surface, and a plurality of protrusions fixed to the permeation side surface of the separation membrane body; A separation membrane element comprising:
The protrusion forms a flow path between adjacent protrusions,
A separation membrane element having a representative length of the flow path of 0.12 mm or more and 0.30 mm or less.
(2) It has a water collection pipe, a supply-side surface and a permeation-side surface, and is disposed so as to face the separation membrane that is wound around the water collection tube and the permeation-side surface of the separation membrane. A separation membrane element comprising a sheet and a permeate-side flow path member comprising a plurality of protrusions fixed to the sheet,
The separation membrane element, wherein the projection forms a channel between adjacent projections, and the representative length of the channel is 0.12 mm or more and 0.30 mm or less.

  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 disassembled perspective view which shows one form of a separation membrane leaf. It is a top view which shows a separation membrane provided with the protrusion continuously provided in the length direction (2nd direction) of the separation membrane. It is a top view which shows a separation membrane provided with the protrusion provided discontinuously in the length direction (2nd direction) of a separation membrane. 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 a horizontal surface schematic diagram of a separation membrane. It is sectional drawing which shows schematic structure of a separation membrane main body. 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 an expansion | deployment perspective view which shows a part of separation membrane element of many forms.

  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 includes a separation membrane main body and a protrusion disposed on the separation membrane main body.

  As an example of such a separation membrane, an exploded perspective view of a separation membrane leaf including an example of an embodiment of the separation membrane of the present invention is shown in FIG. In FIG. 1, the separation membrane leaf 4 includes the separation membrane 1 and the separation membrane 7, and is arranged so that the supply side surface 21 of the separation membrane 1 and the supply side surface 71 of the separation membrane 7 face each other. The separation membrane 1 includes a separation membrane body 2 and a projection 31 on the permeate side. The protrusion 31 is provided on the transmission side surface 22 so as to form a flow path. Details of each part of the separation membrane 1 will be described later. The separation membrane body 2 includes a supply-side surface 21 and a permeation-side surface 22. The separation membrane 7 includes a supply-side surface 71 and a permeation-side surface 72.

  In this document, the “supply side surface” of the separation membrane main body means a surface on the side to which raw water is supplied out of the two surfaces of the separation membrane main body. The “transmission side surface” means the opposite side surface. As will be described later, when the separation membrane main body includes the base material 201 and the separation functional layer 203 as shown in FIG. 7, generally, the surface on the separation functional layer side is the surface 21 on the supply side, The surface on the side is the surface 22 on the transmission side.

  In FIG. 7, the separation membrane body 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.

  The x-axis, y-axis, and z-axis direction axes are shown in the figure. 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 and the like, the separation membrane main body 2 is rectangular, and the first direction and the second direction are parallel to the outer edge of the separation membrane main body 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 body <Overview>
As the separation membrane body, a membrane having separation performance according to the method of use, purpose and the like is used. The separation membrane body may be formed of a single layer or a composite membrane including a separation functional layer and a substrate. As shown in FIG. 7, 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 to 300 nm.

  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 document, “X contains Y as a main component” means that the Y content in X is 50% by mass, 70% by mass, 80% by mass, 90% by mass, or 95% by mass. It means that it is more than%. 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 the compound (A) and the compound (B), the compound (A) may be condensed through 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 separation performance like a separation membrane 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. 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 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 pore diameter of the porous support layer are average values, and the thickness of the porous support layer is measured at intervals of 20 μm in a direction perpendicular to the thickness direction by cross-sectional observation, and is an average value of 20 points. 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. Can be obtained.

<Base material>
From the viewpoints of strength, dimensional stability, etc. of the separation membrane body, the separation membrane body 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 non-woven fabric composed of thermoplastic continuous filaments, compared to short-fiber non-woven fabrics, it suppresses the occurrence of non-uniformity and film defects caused by fiber fluffing during casting of a polymer solution. be able to. 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. It is preferable that the degree of orientation difference with respect to the degree is 10 ° to 90 °.

  The separation membrane manufacturing process and the element manufacturing process include a heating process, 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 the figure. The CD direction in the figure 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.

  As for the thickness of the substrate, the total thickness of the substrate and the porous support layer is preferably in the range of 30 μm to 300 μm, or in the range of 50 μm to 250 μm.

(1-3) Protrusion (permeation side channel material)
<Overview>
On the permeate side surface of the separation membrane main body, the protrusion is fixed to the base material so as to form a permeation side flow path (groove) between adjacent protrusions. “Provided so as to form a permeate-side flow path” means that when the separation membrane is incorporated into a separation membrane element described later, the permeated fluid that has permeated the separation membrane main body can reach the water collecting pipe. It means that an object is formed. The details of the configuration of the protrusion are as follows.

(Representative length of permeate side channel)
As shown in the Fanning equation, it is known that the flow resistance is inversely proportional to the representative length of the flow path. That is, the flow resistance decreases as the representative length increases. The representative length is obtained by 4 × cross-sectional area / immersion side length.

  On the other hand, the smaller the distance between the fulcrums of the membrane (that is, the channel width), the more the membrane can be prevented from dropping into the channel, and the increase in flow resistance during operation can be suppressed.

  For these reasons, the representative length of each flow path is preferably 0.12 mm or more and 0.30 mm or less, and more preferably 0.15 mm or more and 0.25 mm or less.

  The representative length is the distance between the midpoint of the height of the protrusion and the midpoint of the height of another protrusion adjacent to the protrusion in the width direction (flow path width: b in the figure). ) And the height of the protrusion (the difference in height between the protrusion 31 and the permeation-side surface 22 of the separation membrane body 2: indicated as c in the figure), the cross-sectional area is (c × b) By calculating the immersion side length as (2 (c + b)), it can be obtained with high accuracy and simplicity.

(Subdivision of flow path)
The more the channels are subdivided, that is, the total cross-sectional area of the channels in the width direction of the separation membrane is constant, the larger the number of channels, the smaller the channel width or the lower the channel height. Become. Therefore, the film can be prevented from falling into the flow path, or the number of films that can be filled in one element is increased. On the other hand, if the total cross-sectional area of the flow paths is constant, the smaller the number of flow paths, the smaller the area where the permeate comes into contact with the flow path walls, so the friction is reduced and the flow resistance is reduced.

Therefore, the ratio {A11 / A1} of the cross-sectional area A11 of each flow path and the sum A1 of the cross-sectional areas of the flow paths existing per 10 mm width of the separation membrane in a plane parallel to the longitudinal direction of the water collecting pipe Is preferably 0.025 or more and 0.075 or less, more preferably 0.03 or more and 0.055 or less. <Compressive Elastic Modulus>
The compression elastic modulus of the protrusion is preferably 0.5 GPa or more and 5.0 GPa or less. In seawater desalination applications, high-pressure operation is performed. Under high pressure, the projections are consolidated and the permeate-side flow path is narrowed, so that the flow resistance increases and the amount of water produced tends to decrease. When the compression elastic modulus of the protrusion is 0.5 GPa or more, such a decrease in the amount of water can be suppressed. Further, if the compression elastic modulus of the protrusion is extremely high, the protrusion is likely to be destroyed when surrounding the separation membrane. On the other hand, when the compression elastic modulus is 5.0 GPa or less, it is possible to suppress protrusion deformation during pressure filtration and stably form the flow path.

  In addition, the compression elastic modulus of a protrusion can be calculated | required from the inclination of the linear part of the stress-strain curve in the stress range which a protrusion elastically deforms. More specifically, the result measured by the measuring method in the examples described later only needs to satisfy the above-described range.

  In addition to measuring the compressive elastic modulus, it is sufficient that the amount of deformation of the projections is actually within the range described later by actually performing pressure filtration, the temperature of the raw water is 25 ° C. or less, and the pressure is 5.5 MPa or less. If the deformation rate of the height of the projections is 40% or less when operated under certain conditions, it is suitable for application to seawater desalination.

<Constituent components of protrusion>
The protrusion 31 is preferably formed of a material different from that of the separation membrane body 2. The different material means a material having a composition different from that of the material used in the separation membrane body 2. In particular, the composition of the protrusion 31 is preferably different from the composition of the surface of the separation membrane body 2 on which the protrusion 31 is formed, and may be different from the composition of any layer forming the separation membrane body 2. preferable.

  The material constituting the protrusion 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. Moreover, as a material of the protrusion, urethane resin, epoxy resin, polyethersulfone, polyacrylonitrile, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polystyrene, styrene-acrylonitrile copolymer, styrene -Butadiene-acrylonitrile copolymer, polyacetal, polymethyl methacrylate, methacryl-styrene copolymer, cellulose acetate, polycarbonate, polyethylene terephthalate, polybutadiene terephthalate and fluororesin (ethylene trifluoride chloride, polyvinylidene fluoride, tetrafluoroethylene, (Tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkoxyethylene copolymer, tetrafluoroethylene-ethylene copolymer, etc.) Polymer such as a thermoplastic elastomer resin can be selected. These materials are used alone or as a mixture of two or more. In particular, since a thermoplastic resin is easy to mold, a projection having a uniform shape can be formed.

  Examples of the thermoplastic elastomer-based resin include a polyamide-based thermoplastic elastomer generated by a rubber component such as a polyol and a polyamide, for example, a polyurethane-based thermoplastic elastomer generated by a rubber component such as a polyol and an isocyanate compound, for example, a polyol. Polyester thermoplastic elastomer produced by rubber component and polyester, for example, polystyrene thermoplastic elastomer, for example, polyolefins, composed of rubber component composed of block copolymer composed of one or more of ethylene, propylene, butylene and the like Examples include polyolefin thermoplastic elastomers in which components such as ethylene, propylene, and diene rubber are finely dispersed. These can be used alone or in combination of two or more. . Of these, styrene-based elastomers that have a great effect of imparting flexibility to protrusions and have good compatibility with polyolefin-based resins are preferred.

  Typical polymers of styrene elastomers include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), and styrene-ethylene-butylene-styrene obtained by hydrogenation of each polymer. Although a copolymer (SEBS), a styrene-ethylene-propylene-styrene copolymer (SEPS), etc. can be illustrated, it is not limited to these.

  A composite material is also applicable as the material of the protrusion. Examples of the composite material include a material containing the above-described resin as a base material and further containing a filler. The compression elastic modulus of the protrusion can be increased by adding a filler such as a porous inorganic material to the base material. Specifically, alkaline earth metal silicates such as sodium silicate, calcium silicate and magnesium silicate, metal oxides such as silica, alumina and titanium oxide, and alkaline earth metals such as calcium carbonate and magnesium carbonate. Carbonate, pure meteorite, meteorite powder, caustic clay, wollastonite, sepiolite, attapulgite, kaolin, clay, bentonite, gypsum, talc, etc. can be used as fillers. In addition, the addition amount of a filler will not be specifically limited if it is a range which does not impair the effect of this invention.

  In the present invention, the composition of the protrusions fixed on the permeate side surface of the separation membrane main body has an antioxidant (phenolic compound, phosphite compound, hindered amine compound, Sulfur compounds, etc.) and thickeners (low molecular weight polyolefins, low molecular weight polyolefins modified with carboxylic acids such as maleic acid, liquid paraffin, paraffin wax, microwax, etc.), lubricants (fatty acid amide compounds (eg stearamide, oleic acid) Amide, erucic acid amide, ethylenebisstearic acid amide, etc.), metal soap (eg, calcium stearate, zinc stearate, magnesium stearate, zinc stearate, etc.), fatty acid ester compounds, etc., filler (calcium carbonate, talc, Alumina, silica, mica, clay ) Additives such as may comprise one or two or more kinds.

<Shape and arrangement of protrusions>
<< Overview >>
A tricot that has been widely used in the past is a knitted fabric, and is composed of three-dimensionally intersecting yarns. That is, the tricot has a two-dimensionally continuous structure. When such a tricot is applied as a channel material, the height of the channel is smaller than the thickness of the tricot. That is, the entire thickness of the tricot cannot be used as the height of the flow path.

  On the other hand, as an example of the configuration of the present invention, the protrusions 31 shown in FIG. 1 and the like are arranged so as not to overlap each other. Therefore, all the heights (that is, thicknesses) of the protrusions 31 of the present embodiment are utilized as the heights of the flow paths. Therefore, when the protrusion 31 of this embodiment is applied, a flow path becomes high rather than the case where the tricot which has the same thickness as the height of the protrusion 31 is applied. That is, since the cross-sectional area of the flow path becomes larger, the flow resistance becomes smaller.

  In the form shown in each figure, a plurality of discontinuous protrusions 31 are fixed on one separation membrane body 2. “Discontinuous” is a state in which a plurality of protrusions are provided at intervals. That is, when the protrusions 31 in one separation membrane are peeled from the separation membrane body 2, a plurality of protrusions 31 separated from each other are obtained. On the other hand, members such as nets, tricots, and films exhibit a continuous and integral shape even when separated from the separation membrane body 2.

  By providing a plurality of discontinuous protrusions 31, when the separation membrane 1 is incorporated in the separation membrane element 100 described later, pressure loss can be kept low. As an example of such a configuration, in FIG. 2, the protrusions 31 are formed discontinuously only in the first direction (length direction of the separation membrane), and in FIG. 3, the first direction (length direction of the separation membrane). And in the second direction (width direction of the separation membrane).

  2 and 3, the permeate-side flow path 5 is formed in the space between the adjacent protrusions 31.

  The separation membrane is preferably arranged in the separation membrane element so that the second direction coincides with the winding direction. That is, in the separation membrane element, in the separation membrane, the first direction (width direction of the separation membrane) is parallel to the longitudinal direction of the water collection pipe 6, and the second direction (length direction of the separation membrane) is the longitudinal direction of the water collection pipe 6. It is preferable to be arranged so as to be orthogonal to the direction.

  The protrusions 31 are provided discontinuously in the first direction, and in the form shown in FIGS. 2 and 5, the protrusions 31 are provided so as to be continuous from one end to the other end of the separation membrane body 2 in the second direction. When the separation membrane is incorporated into the separation membrane element as in 5, the protrusion 31 is arranged so as to continue from the inner end to the outer end of the separation membrane 1 in the winding direction. The inner side in the winding direction is the side close to the water collecting pipe in the separation membrane, and the outer side in the winding direction is the side far from the water collecting pipe in the separation membrane.

  FIG. 5 is an explanatory view schematically showing a separation membrane element 100 in which the separation membrane 1 is wound around the water collecting pipe 6. In FIG. 5, the separation membrane 1 is described as one surface of the separation membrane leaf. In the figure, an arrow indicated by CD indicates the longitudinal direction of the water collecting pipe 6 and the width direction of the separation membrane. An arrow indicated by MD indicates the length direction of the separation membrane and the direction of winding around the water collecting pipe 6.

  The protrusions are “continuous in the second direction” when the protrusions are provided without interruption as shown in FIG. 2 and when the protrusions are interrupted as shown in FIG. Includes both substantially continuous cases. The “substantially continuous” form preferably satisfies that the distance e between the protrusions in the second direction (that is, the length of the discontinuous portion in the protrusion) is 5 mm or less. In particular, the distance e is more preferably 1 mm or less, and further preferably 0.5 mm or less. In addition, the total value of the intervals e included from the beginning to the end of the row of protrusions arranged in the second direction is preferably 100 mm or less, more preferably 30 mm or less, and further preferably 3 mm or less. preferable. In the form of FIG. 2, the interval e is 0 (zero).

  When the protrusion 31 is provided without interruption as shown in FIG. 2, membrane dropping is suppressed during pressure filtration. Membrane sagging is that the membrane falls into the channel and narrows the channel.

  In FIG. 3, the protrusions 31 are discontinuously provided not only in the first direction but also in the second direction. That is, the protrusions 31 are provided at intervals in the length direction. However, as described above, the protrusion 31 is substantially continuous in the second direction, so that the film sagging is suppressed. In addition, by providing the discontinuous protrusions 31 in the two directions as described above, the contact area between the protrusions and the fluid is reduced, so that the pressure loss is reduced. In other words, this form is a configuration in which the flow path 5 includes a branch point. That is, in the configuration of FIG. 3, the permeating fluid is divided by the protrusions 31 while flowing through the flow path 5, and can further merge downstream.

  As described above, in FIG. 2, the protrusions 31 are provided so as to be continuous from one end to the other end of the separation membrane body 2 in the second direction. In FIG. 3, the protrusion 31 is divided into a plurality of portions in the second direction, but the plurality of portions are provided so as to be lined up from one end to the other end of the separation membrane body 2.

  The projection is “provided from one end of the separation membrane body to the other end” means that the projection is provided up to the edge of the separation membrane body 2 and the region where the projection is not provided in the vicinity of the edge. Includes both certain forms. That is, the protrusions only need to be distributed in the second direction to such an extent that the permeate-side flow path can be formed, and there may be a portion where the protrusions are not provided in the separation membrane body. For example, on the permeate side surface, a protrusion need not be provided in a portion (in other words, a contact portion) bonded to another separation membrane. Moreover, the area | region where a protrusion is not arrange | positioned may be provided in some places, such as the edge part of a separation membrane, for the reason on the other specification or manufacture.

  Also in the first direction, the protrusions 31 can be distributed substantially evenly over the entire separation membrane main body. However, similar to the distribution in the second direction, it is not necessary to provide a protrusion on the portion of the permeate-side surface that is bonded to another separation membrane. Moreover, the area | region where a protrusion is not arrange | positioned may be provided in some places, such as the edge part of a separation membrane, for the reason on the other specification or manufacture.

<< Dimensions of separation membrane body and protrusions >>
2 to 4, a to f indicate the following values.

a: Length of the separation membrane body 2 b: Spacing of the projections 31 in the width direction of the separation membrane body 2 c: Height of the projections d: Width of the projections e: Above in the length direction of the separation membrane body 2 Projection interval f: Length of the projection 31 For measurement of the values a, b, c, d, e, and f, for example, a commercially available shape measurement system or a microscope can be used. 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.

(Length of separation membrane body a)
The length a is a distance from one end of the separation membrane body 2 to the other end in the second direction (length direction of the separation membrane). When this distance is not constant, the length a can be obtained by measuring this distance at 30 or more positions in one separation membrane body 2 and obtaining an average value.

(Flow path width b in the first direction)
The interval b between the adjacent protrusions 31 in the first direction (the width direction of the separation membrane) corresponds to the width of the flow path 5. When the width of one flow path 5 is not constant in one cross section, that is, when the side surfaces of two adjacent protrusions 31 are not parallel, the maximum value and the minimum width of one flow path 5 are within one cross section. The average value is measured and the average value is calculated. As shown in FIG. 4, in the cross section perpendicular to the second direction, when the protrusion 31 has a trapezoidal shape with a thin top and a thick bottom, first, the distance between the upper portions of the two adjacent protrusions 31 and the lower portion The distance is measured and the average value is calculated. The interval between the protrusions 31 is measured in any 30 or more cross sections, and an average value is calculated in 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. In particular, when operating at a high pressure exceeding 1.5 MPa, the salt concentration of the supplied water is high and the concentration polarization is large on the membrane surface, and the permeation resistance may increase. In such a case, if the flow channel on the permeate side is simply enlarged and the pressure loss is reduced to increase the permeation efficiency too much, concentration polarization tends to be accelerated, and the membrane falls into the permeate side flow channel, causing the permeate side flow. The road shrinks. For this reason, the interval b is preferably 0.2 mm or more and 5 mm or less. 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.

(Projection height c)
The height c is a difference in height between the protrusion and the surface of the separation membrane main body. As shown in FIG. 4, the height c is a difference in height between the highest portion of the protrusion 31 and the permeation side surface of the separation membrane main body in a cross section perpendicular to the second direction. That is, in the height, the thickness of the portion impregnated in the base material is not considered. The height c is a value obtained by measuring the heights of 30 or more protrusions 31 and averaging them. The height c of the protrusion may be obtained by observing the cross section of the protrusion in the same plane, or may be obtained by observing the cross section of the protrusion in a plurality of planes.

  The height c can be appropriately selected according to the use condition and purpose of the element, but may be set as follows, for example.

  The larger the height c, the smaller the flow resistance. Therefore, the height c is preferably 0.03 mm or more, 0.05 mm or more, or 0.1 mm or more. On the other hand, the smaller the height c, the larger the number of films filled per element. Therefore, the height c is preferably 0.5 mm or less, 0.4 mm or less, or 0.3 mm or less. These upper and lower limits can be combined. For example, the height c is preferably 0.03 mm or more and 0.5 mm or less, preferably 0.05 mm or more and 0.4 mm or less, and 0.1 mm or more. More preferably, it is 0.3 mm or less.

  Moreover, it is preferable that the difference in height between two adjacent protrusions is small. If the difference in height is large, the separation membrane is distorted during pressure filtration, so that defects may occur in the separation membrane. The difference in height between two adjacent protrusions is preferably 0.1 mm or less (100 μm or less), more preferably 0.06 mm or less, and further preferably 0.04 mm or less.

  For the same reason, the maximum height difference of all the protrusions provided on the separation membrane is preferably 0.25 mm or less, particularly preferably 0.1 mm or less, and further preferably 0.03 mm or less.

(Projection width d)
The width d of the protrusion 31 is measured as follows. First, the average value of the maximum width and the minimum width of one protrusion 31 is calculated in one cross section perpendicular to the first direction (the width direction of the separation membrane). That is, in the protrusion 31 with a thin upper part and a thick lower part as shown in FIG. 4, the width of the lower part and the upper part of the protrusion 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 protrusion 31 is preferably 0.1 mm or more, more preferably 0.13 mm or more. When the width d is 0.13 mm or more, the shape of the protrusion can be maintained even when pressure is applied to the protrusion 31 during operation of the separation membrane element, and the permeate-side flow path is stably formed. The width d is preferably 0.7 mm or less, and more preferably 0.5 mm or less. When the width d is 0.7 mm or less, a sufficient flow path on the transmission side can be secured.

  When the width of the protrusion is wider than the flow path width b in the second direction, the pressure applied to the protrusion can be dispersed.

  The protrusion 31 is formed such that its length is larger than its width. Such a long protrusion 31 is also referred to as a “wall-like object”.

(Distance e between protrusions in the second direction)
The interval e between the protrusions 31 in the second direction is the shortest distance between the adjacent protrusions 31 in the second direction (the length direction of the separation membrane). As shown in FIG. 2, the protrusion 31 is continuously provided in the second direction from one end of the separation membrane body 2 to the other end (in the separation membrane element, from the inner end to the outer end in the winding direction). The distance e is 0 mm. Moreover, as shown in FIG. 3, when the protrusion 31 is interrupted in the second direction, the interval e is preferably 5 mm or less, more preferably 1 mm or less, and further preferably 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. In addition, the minimum of the space | interval e is 0 mm.

(Projection length f)
The length f of the protrusion 31 is the length of the protrusion 31 in the length direction (that is, the second direction) of the separation membrane body 2. The length f is obtained by measuring the length of 30 or more protrusions 31 in one separation membrane 1 and calculating the average value thereof. The length f of the protrusion may be equal to or less than the length a of the separation membrane body. When the length f of the protrusion is equal to the length a of the separation membrane body, it means that the protrusion 31 is continuously provided from the inner end to the outer end in the winding direction of the separation membrane 1. The length f is preferably 10 mm or more, more preferably 20 mm or more. Since the length f is 10 mm or more, the flow path is secured even under pressure.

(shape)
The shape of the protrusion 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 protrusion may be a straight column shape, a trapezoidal shape, a curved column shape, or a combination thereof.

  When the cross-sectional shape of the protrusion is trapezoidal, 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 in contact with the smaller one. For example, when the upper base of the protrusion is shorter than the lower base, the upper width is wider than the lower width in the flow path therebetween. 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 projection is preferably 0.6 or more and 1.4 or less, and more preferably 0.8 or more and 1.2 or less. preferable.

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

  However, the upper side may be rounded in the cross section of the protrusion as long as the protrusion is not significantly crushed during pressure filtration.

  The protrusion can be formed of a thermoplastic resin. If the protrusion is a thermoplastic resin, the shape of the protrusion can be adjusted freely so that the required separation characteristics and permeation performance conditions can be satisfied by changing the processing temperature and the type of thermoplastic resin selected. be able to.

  Further, the shape of the projections in the planar direction of the separation membrane may be linear as a whole as shown in FIGS. 2 and 3, and other shapes are, for example, curved, sawtooth, and wavy. May be. Further, in these shapes, the protrusions may be broken lines or dots. From the viewpoint of reducing the flow resistance, a dot shape or a broken line shape is preferable. However, since the protrusions are interrupted, the number of places where film sagging occurs during pressure filtration increases.

  Moreover, when the shape of the separation film in the planar direction of the separation membrane is a straight line, the adjacent protrusions may be arranged substantially parallel to each other. “Arranged substantially parallel” means, for example, that the projections do not intersect on the separation membrane, the angle formed by the longitudinal direction of two adjacent projections is 0 ° or more and 30 ° or less, and the angle is It includes that it is 0 ° or more and 15 ° or less, and that the angle is 0 ° or more and 5 ° or less.

  Further, the angle formed by the longitudinal direction of the projection and the longitudinal direction of the water collecting pipe is preferably 60 ° or more and 120 ° or less, more preferably 75 ° or more and 105 ° or less, and 85 ° or more and 95 ° or less. More preferably. When the angle formed between the longitudinal direction of the protrusion 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 body can be prevented from dropping when the separation membrane body is pressurized in the separation membrane element. For this purpose, it is preferable that the contact area between the separation membrane main body and the projection is large, that is, the area of the projection relative to the area of the separation membrane main body (projected area on the membrane surface of the separation membrane main body) 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. The cross section of the flow path is the cross section of the flow path in order to ensure a large contact area between the separation membrane body perpendicular to the longitudinal direction of the flow path and the projections and to ensure a wide cross sectional area of the flow path. The shape is preferably a concave lens. Further, the protrusion 31 may have a straight column shape with no change in width in a cross-sectional shape in a direction perpendicular to the winding direction. Moreover, as long as the separation membrane performance is not affected, the cross-sectional shape in the direction perpendicular to the winding direction has a trapezoidal wall-like object having a change in width, an elliptic cylinder, an elliptic cone, four A shape like a pyramid or a hemisphere may be sufficient.

  The shape of the protrusion is not limited to the shape shown in FIGS. When placing protrusions on the permeate side surface of the separation membrane body by fixing a molten material, for example, as in the hot melt method, the processing temperature and the type of hot melt resin to be selected can be changed. The shape of the protrusion can be freely adjusted so that the required separation characteristics and permeation performance conditions can be satisfied.

  In FIG. 1 to FIG. 3, the planar shape of the protrusion 31 is linear in the length direction. However, the protrusion 31 can be changed to another shape as long as it is convex with respect to the surface of the separation membrane body 2 and does not impair the desired effect as the separation membrane element. That is, the shape of the protrusion in the planar direction may be a curved line, a wavy line, or the like. A plurality of protrusions included in one separation membrane may be formed so that at least one of the width and the length is different from each other.

(Projected area ratio)
The projected area ratio of the projections to the permeation side surface of the separation membrane may be 0.03 or more and 0.85 or less, particularly in terms of reducing the flow resistance of the permeation side flow path and forming the flow path stably. Preferably, it is 0.15 or more and 0.85 or less, more preferably 0.2 or more and 0.75 or less, and further preferably 0.3 or more and 0.6 or less. The projected area ratio is a value obtained by dividing the projected area of the protrusion obtained when the separation membrane is cut out at 5 cm × 5 cm and projected onto a plane parallel to the surface direction of the separation membrane by the cut-out area (25 cm ² ). is there. This value can also be expressed by df / (b + d) (e + f) described in the above equation v).

(Defect rate)
The water that has permeated through the separation membrane passes through the permeation side flow path 5 and is collected in the water collecting pipe 6. In the separation membrane, water that has passed through a region far from the water collecting pipe, that is, a region in the vicinity of the outer end in the winding direction (region near the right end in FIG. 5) It merges with the water that has passed through the inner area and heads for the water collecting pipe 6. Therefore, in the permeate side flow path, the amount of water present is smaller in the direction far from the water collecting pipe 6.

  Therefore, there is no protrusion in the region near the end on the outer side in the winding direction, and even if the flow resistance in that region increases, the influence on the amount of water produced by the entire element is slight. For the same reason, in the region in the vicinity of the outer end in the winding direction, the formation accuracy of the protrusions is low, and the resin forming the protrusions is continuously applied in the first direction (the width direction of the separation membrane). However, the effect on the amount of water produced as an element is small. In this region, the same applies to the case where the separation membrane body is applied without a gap in the surface direction (xy plane).

  Therefore, the distance from the outer end in the winding direction of the separation membrane body 2 to the outer end in the winding direction of the transmission-side projection 31, that is, the region provided at the outer end in the winding direction of the separation membrane main body 2. The length L3 in the second direction (length direction of the separation membrane) of the region R3, which is a region where the permeation-side flow path is not formed, is the length L1 in the second direction of the entire separation membrane (described above). The ratio of the occupying ratio to "a") is preferably 0% to 30%, more preferably 0% to 10%, and particularly preferably 0% to 3%. This ratio is called a defect ratio.

  The defect rate is represented by (L3 / L1) × 100 in FIG.

  For convenience of explanation, FIG. 6 shows a form in which no protrusion is provided in the region R3. However, the region 3 may be a region provided with continuous protrusions in the width direction.

  FIG. 6 is a cross-sectional view of the separation membrane body 2 and the end portions on the outer side in the winding direction of the permeation-side protrusions 31 cut in the length direction of the permeation-side protrusions 31. In FIG. 6, the permeation-side protrusion 31 is fixed to the separation membrane main body 2 and extends to the front of the outer end of the separation membrane main body 2 in the winding direction. For convenience of explanation, FIG. 6 shows a mode in which the transmission-side protrusions 31 are continuously provided in the length direction, but the various forms described above are applied as the transmission-side protrusions 31. As already mentioned.

  In the drawing, a region where the projection is provided is indicated by R2, and a region where the transmission side projection 31 is not provided is indicated by R3. Further, the length of the separation membrane body 2 in the MD direction is L1, the length of the transmission-side projection 31 in the MD direction (that is, the length of the region R2) is L2, and the length of the separation-side projection 31 in the MD direction of the region R3 where the transmission-side projection 31 is not present. The length is indicated by L3. Here, the MD direction represents the length direction of the separation membrane and the winding direction of the separation membrane.

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

(2-2) Separation membrane <Overview>
The separation membrane 1 is wound around the water collecting pipe 6 and is arranged so that the width direction of the separation membrane is along the longitudinal direction of the water collecting pipe 6. As a result, the separation membrane 1 is disposed such that the length direction is along the winding direction.

  Therefore, the protrusions 31 that are wall-like objects are discontinuously arranged at least in the longitudinal direction of the water collecting pipe 6 on the permeation-side surface 22 of the separation membrane 1. That is, the flow path 5 is formed 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 pipe, that is, the flow resistance is reduced, so that a large amount of fresh water is obtained.

  “Inside in winding direction” and “Outside in winding direction” are as shown in FIG. That is, the “inner end portion in the winding direction” and the “outer end portion in the winding direction” correspond to the end portion closer to the water collecting pipe 6 and the far end portion in the separation membrane 1, respectively.

  As described above, since the protrusion does not need to reach the edge of the separation membrane, for example, at the outer end portion of the envelope-like membrane in the winding direction and the end portion of the envelope-like membrane in the longitudinal direction of the water collecting tube The thing does not need to 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 1 is arranged so that the supply-side surface 21 faces the supply-side surface 71 of another separation membrane 7 with a supply-side flow path material (not shown) interposed therebetween. In the separation membrane leaf 4, a supply-side flow path is formed between the supply-side surfaces of the separation membranes facing each other.

  Further, the two membrane leaves 4 are overlapped, so that the separation membrane 1 and the separation membrane 7 of the other membrane leaf facing the permeation side surface 22 of the separation membrane 1 form an envelope-like membrane. In the envelope-like membrane, between the opposite permeate side surfaces, in the rectangular shape of the separation membrane, only one side inside the winding direction is opened, and the other three sides are sealed so that the permeate flows into the water collecting pipe 6. Stopped. 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 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-like 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 permeate side of the separation membrane. 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 separation 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 separation membrane leaf and the envelope membrane, the separation membranes facing each other (separation membranes 1 and 7 in FIG. 1) may have the same configuration or different configurations. That is, in the separation membrane element, it is only necessary to provide the above-described protrusion on at least one of the two permeate-side surfaces facing each other. 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 flow path material (for example, a membrane that has the same configuration as the separation membrane main body).

  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 1 includes the permeation-side protrusion 31. The permeate-side protrusion 31 forms a permeate-side channel between the inside of the envelope-shaped membrane, that is, between the permeate-side surfaces of the facing separation membranes.

(2-4) Supply side channel (channel material)
The separation membrane element 100 includes a channel material (not shown) having a projected area ratio with respect to the separation membrane 1 exceeding 0 and less than 1 between the surfaces on the supply side of the facing separation membrane. 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 refers to the projected area 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. Divided value.

  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. 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.

(Unevenness processing)
Further, instead of disposing the supply-side channel material on the supply-side surface of the separation membrane, a difference in height can be imparted to the supply side of the separation membrane by a method such as embossing, hydraulic forming, or calendering.

  Examples of the embossing method include roll embossing, and the pressure and processing temperature for carrying out this can be appropriately determined according to the melting point of the separation membrane. For example, when the separation membrane has a porous support layer containing an epoxy resin, the linear pressure is preferably 10 kg / cm or more and 60 kg / cm or less, and the heating temperature is preferably 40 ° C. or more and 150 ° C. or less. Moreover, when it has a porous support layer containing heat resistant resins, such as polysulfone, it is preferable that it is 10 to 70 kg / cm of linear pressure, and roll heating temperature 70 to 160 degreeC is preferable. In any case of roll embossing, a winding speed of 1 m / min to 20 m / min is preferable.

  When embossing is performed, the shape of the roll handle is not particularly limited, but it is important to reduce the flow resistance of the flow path and stabilize the flow path when supplying and permeating fluid to the separation membrane element. is there. In these respects, there are ellipses, circles, ellipses, trapezoids, triangles, rectangles, squares, parallelograms, rhombuses, and irregular shapes in the shape observed from the upper surface. Those formed in the surface direction, those formed in a widened form, and those formed in a narrowed form are used.

  The difference in height on the supply-side surface of the separation membrane that can be imparted by embossing can be freely adjusted by changing the pressure heat treatment conditions so as to satisfy the conditions that require separation characteristics and water permeation performance. However, if the difference in height on the supply side surface of the separation membrane is too deep, the flow resistance is reduced, but the number of membrane leaves that can be filled in the vessel when the element is formed is reduced. If the height difference is small, the flow resistance of the flow path increases, and the separation characteristics and water permeation performance deteriorate. 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 of each performance and the operating cost described above, in the separation membrane, the difference in height of the supply side surface of the separation membrane is preferably more than 0.5 mm and preferably 2.0 mm or less, and 0.6 mm or more. 1.0 mm or less is more preferable.

  The difference in height on the supply side surface of the separation membrane can be obtained by the same method as in the case of the above-described difference in height on the permeation side of the separation membrane.

  The channel width is preferably 0.2 mm or more and 10 mm or less, and more preferably 0.5 mm or more and 3 mm or less.

  The pitch may be appropriately designed between 1/10 and 50 times the channel width. The flow path width is the part that sinks on the surface where the height difference exists, and the pitch is the highest point on the surface where the height difference exists to the highest point on the adjacent high part. It is the horizontal distance.

  The projected area ratio of the portion that becomes convex by embossing is preferably 0.03 or more and 0.5 or less, more preferably 0.10 or more and 0.40, for the same reason as in the case of the supply-side channel material. Hereinafter, it is particularly preferably 0.15 or more and 0.35 or less.

  The “height difference” in the surface of the separation membrane is the difference in height between the surface of the separation membrane body and the apex of the flow channel material (that is, the height of the flow channel material). Is the difference in height between the concave and convex portions.

(2-5) Water Collection Pipe The water collection pipe 6 is not particularly limited as long as it is configured so that permeated water flows 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 Form As a more specific form, FIGS. 8 to 10 show separation membrane elements 100A, 100B, and 100C of the first to third forms. FIG. 8 is an explanatory view showing the separation membrane element 100 </ b> A of the first embodiment partially disassembled, and a plurality of separation membranes 1 are wound around the water collecting 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 1 forms an envelope-like membrane 11, and the permeation-side protrusion 31 is arranged inside the envelope-like separation membrane 11 as described above. A supply-side protrusion 32 is disposed between the envelope films 11.

  For convenience, in FIG. 8 to FIG. 10, the transmission side protrusion 31 is shown as a dot shape, but as described above, the shape of the protrusion 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 1 is separated into the permeated water 102 and the concentrated water 103 by the separation membrane 1. 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. 9, 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 1.

  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 the present embodiment, raw water is supplied from the outer peripheral surface of the separation membrane element 100B (the outer peripheral surface of the wound body). 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 1 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 1 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. 10, 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 100C is the same as the element of the second embodiment except that the separation membrane element 100C is disposed at each of the first end and the second end and includes an end plate 92 having a hole. 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 raw water is supplied to the envelope 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, deformation of the envelope 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]
The manufacturing method of a separation membrane element includes the process of manufacturing a separation membrane. In addition, the step of producing the separation membrane includes at least the following steps:
Preparing a separation membrane body having a base material and a separation functional layer;
A step of softening a material having a composition different from that of the separation membrane body by heat,
The softened material is disposed on the base material side surface of the separation membrane main body to form a permeation-side flow path material, and the material is solidified so that the protrusions are formed on the separation membrane main body. Including a step of fixing.

  Each process in the manufacturing method of a separation membrane element is demonstrated below.

(3-1) Manufacture of separation membrane body The manufacturing method of the separation membrane body has been described above, but it is 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, chemical treatment such as chlorine, acid, alkali, nitrous acid, etc. is performed to enhance separation performance and permeation performance as necessary, and the monomer is washed to produce a continuous sheet of the separation membrane body.

  In addition, before or after the chemical treatment, unevenness may be formed on the separation membrane main body by embossing or the like.

(3-2) Arrangement of Protrusions (Permeation-side Channel Material) The separation membrane manufacturing method includes a step of providing discontinuous protrusions on the permeation-side surface of the separation membrane body. This step may be performed at any time during the manufacture of the separation membrane. For example, the protrusion may be provided before the porous support layer is formed on the base material, or after the porous support layer is provided and before the separation functional layer is formed. Alternatively, after the separation functional layer is formed, it may be performed before or after the above-described chemical treatment is performed.

  The method for arranging the protrusions includes, for example, a step of placing 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 protrusions. 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 protrusions 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.

(3-3) Formation of supply-side flow path When the supply-side flow path material is a discontinuous member formed of a material different from that of the separation membrane main body, formation of a protrusion is used for forming the supply-side flow path material. The same method and timing can be applied.

  Further, a difference in height can be imparted to the supply side of the separation membrane by a method such as embossing, hydraulic forming, or calendering.

  Examples of the embossing method include roll embossing, and the pressure and processing temperature for carrying out this can be appropriately determined according to the melting point of the separation membrane. For example, when the separation membrane has a porous support layer containing an epoxy resin, the linear pressure is preferably 10 kg / cm or more and 60 kg / cm or less, and the heating temperature is preferably 40 ° C. or more and 150 ° C. or less. Moreover, when it has a porous support layer containing heat resistant resins, such as polysulfone, it is preferable that it is 10 to 70 kg / cm of linear pressure, and roll heating temperature 70 to 160 degreeC is preferable. In any case of roll embossing, a winding speed of 1 m / min to 20 m / min is preferable.

  When embossing is performed, the shape of the roll handle is not particularly limited, but it is important to reduce the pressure loss of the flow path and stabilize the flow path when supplying and permeating fluid to the separation membrane element. is there. In these respects, an ellipse, a circle, an ellipse, a trapezoid, a triangle, a rectangle, a square, a parallelogram, a rhombus, an indefinite shape, and the like are adopted as the shape observed from the upper surface. In addition, three-dimensionally, it may be formed so that the width becomes smaller as the height is higher, or conversely, it may be formed so that the width becomes wider as the height is higher, regardless of the height. They may be formed with the same width.

  The difference in height on the supply-side surface of the separation membrane that can be imparted by embossing can be freely adjusted by changing the pressure heat treatment conditions so as to satisfy the conditions that require separation characteristics and water permeation performance.

  As described above, when the supply-side flow path is formed by fixing the supply-side flow path material to the separation membrane main body, or when the supply-side flow path material is formed by roughening the membrane, these supplies are supplied. The step of forming the side channel may be regarded as one step in the separation membrane manufacturing method.

  When the supply-side flow path is a continuously formed member such as a net, after the separation membrane is manufactured by arranging protrusions on the separation membrane body, the separation membrane and the supply-side flow path material Can be superimposed.

(3-4) Formation of separation membrane leaf As described above, the separation membrane leaf may be formed by folding the separation membrane so that the surface on the supply side faces inward, or two separate sheets The separation membrane 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.

  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 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.

(3-5) Formation of Envelope-shaped Membrane One separation membrane is folded and bonded so that the transmission side faces inward, or two separation membranes are stacked and bonded so that the transmission side faces inward. Thus, 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.

  The adhesive used for forming the envelope film preferably has a viscosity in the range of 40P to 150P, and more preferably 50P to 120P. 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 the adhesive applied is preferably such that the width of the portion to which the adhesive is applied after the leaf is wrapped around the water collecting pipe 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 or more and 150 P or less, the isocyanate of the main agent and the polyol of the curing agent have an isocyanate / polyol weight ratio of 1/5 or more and 1 or less. Such a mixture is preferred. The viscosity of the adhesive is obtained by measuring the viscosity of a mixture in which the main agent, the curing agent alone, and the mixture ratio are defined in advance with a B-type viscometer (JIS K 6833).

(3-6) Winding of separation membrane A conventional element manufacturing apparatus can be used for manufacturing a separation membrane element. In addition, as an element production method, a method described in a reference document (Japanese Patent Publication No. 44-14216, Japanese Patent Publication No. 4-11928, Japanese Unexamined Patent Publication No. 11-226366) is used. it can. 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 element is wrapped, leading to suppression of leakage, and the flow path around the water collection pipe is stable. Secured. The spacer may be wound longer than the circumference of the water collecting pipe.

(3-7) Other steps The method for producing 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 to obtain water that meets the purpose.

  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.

[5. Other forms of separation membrane element]
<Configuration of separation membrane element>
Another embodiment of the separation membrane element will be described. In addition, the above-mentioned matter is applied about the structure which is not mentioned below, a manufacturing process, and utilization.

  In the present embodiment, as shown in FIG. 11, the protrusion 3 is fixed to a sheet different from the separation membrane. That is, as shown in FIG. 11, the separation membrane element includes a separation membrane 20 </ b> A; and a permeate-side flow path member 14 including a sheet 13 and a protrusion 3 fixed on the sheet 13.

  The separation membrane element of the present embodiment is manufactured by the same method as the separation membrane element including the leaf shown in FIG. 1 except that the separation membrane element includes a step of sandwiching the permeation side channel material between the separation membranes.

<Separation membrane>
Unlike the separation membrane 1 in FIG. 1, the separation membrane 20 </ b> A does not include the protrusion 3. That is, as the separation membrane 20A, the same configuration as that of the separation membrane main body 2 of the embodiment of FIG. 1 is adopted. The separation membrane 20A is arranged so that the surfaces on the permeate side and the surfaces on the supply side face each other.

<Permeate channel material>
The permeate-side channel material 14 is disposed between the permeate-side surfaces 122 of the two separation membranes 20A. The surface on the supply side of the separation membrane is indicated by reference numeral “121”. More specifically, the two separation membranes 20A are bonded (sealed) in the same manner as the separation membrane 2 and the separation membrane 7 in FIG. It is preferable that the sheet 13 of the permeation-side flow path material 14 exists between the separation membranes in at least a part of the adhesion portion. In FIG. 11, the size of the sheet 13 and the size of the separation membrane 20 </ b> A are shown to be the same, but actually, the sheet may be larger or the separation membrane may be larger.

  The case where the protrusion is fixed to the separation membrane and the case where the protrusion is fixed to a sheet different from the separation membrane are common in that the protrusion is fixed to the sheet-like member. . In this document, for convenience of explanation, a sheet-like member provided as a member different from the separation membrane is referred to as a “sheet”.

<Sheet>
The porosity of the sheet 13 is preferably 20% or more and 90% or less, and particularly preferably 45% or more and 80% or less.

  If the accuracy of the arrangement of the protrusions is insufficient, the groove between the protrusions may be blocked. However, when the porosity of the sheet is 20% or more, the permeated water can move to another groove through the gap of the sheet 13, and the amount of water produced by the separation membrane element increases. Furthermore, since the resin constituting the protrusion 3 can be appropriately impregnated into the sheet 13, peeling of the protrusion 3 from the sheet 13 can be suppressed. Moreover, since the sheet 13 can be appropriately impregnated with the adhesive that seals between the separation membranes, the supply water can be prevented from flowing into the permeate-side flow path.

  Moreover, it can suppress that resin which comprises the protrusion 3 impregnates to the back of the sheet | seat 13 because a porosity is 90% or less. When the resin is impregnated to the back of the sheet 13, the thickness of the sheet 13 becomes uneven at the resin-impregnated portion and the surrounding portion. Moreover, the breadth of the adhesive agent which adhere | attaches leaves can be moderately suppressed because the porosity is 90% or less. As a result, it is possible to secure a region where the adhesive is not applied after the separation membrane element is formed, that is, a region (effective membrane area) where pressure filtration functions effectively. Thereby, the fall of the amount of fresh water of a separation membrane element can be suppressed.

  Here, the porosity means the ratio of voids per unit volume of the substrate. The porosity is obtained by dividing the value obtained by subtracting the dry weight of the base material from the weight of the pure water contained in the base material by the apparent volume of the base material at the time of drying. Calculated.

  The thickness of the sheet 13 is preferably 0.2 mm or less. In order to seal between the permeation side surfaces of the two separation membranes, it is preferable that the sheet 13 sandwiched between the separation membranes at the sealing location is impregnated with an adhesive. When the thickness of the sheet 13 is 0.2 mm or less, the adhesive is impregnated throughout in the thickness direction of the sheet 13, so that it is possible to prevent the supply water from being mixed into the permeated water. However, even if the thickness of the sheet 13 exceeds 0.2 mm, the separation membrane can be sealed with an adhesive if the porosity of the sheet 13 is 80% or more. Moreover, since the intensity | strength of the sheet | seat 13 is securable because the thickness of the sheet | seat 13 is 0.02 mm or more, damage to the sheet | seat 13 can be suppressed.

  In particular, if the thickness of the sheet 13 is 0.02 mm or more and 0.2 mm or less, the porosity is preferably 20% or more and 80% or less, and the thickness of the sheet 13 is more than 0.02 mm and 0.4 mm or less. If present, the porosity is more preferably 30% or more and 90% or less.

  Specifically, a nonwoven fabric is preferably used as the sheet 13. As the sheet 13, for example, the same material and structure as the base material of the separation membrane described above are applied.

<Protrusions>
For the protrusions fixed to the sheet, the configuration (that is, the shape, dimensions, arrangement, material, etc.) described for the protrusions fixed to the base material of the separation membrane with reference to FIG. In addition, the permeation side channel material of the present embodiment is manufactured by providing protrusions on the sheet by the same method as that for providing protrusions on the separation membrane.

  The protrusions may be provided on either side of the sheet or may be provided on both sides. In any case, the permeation-side channel material is arranged so as to be sandwiched between the permeation-side surfaces of the two separation membranes, and the surface on which the projections of the permeation-side channel material are provided is on the permeation side of the separation membrane. Opposite the surface.

  The relationship between the height c of the projection and the thickness H1 of the sheet will be described. The ratio (c / H0) of the height c of the protrusions to the sum H0 of the sheet thickness H1 and the height c of the protrusions is preferably 0.05 or more. This is because a wide flow path can be secured. On the other hand, when the ratio (c / H0) is 0.7 or less, the sheet can be prevented from being broken or damaged by the protrusions when the sheet is wound while tension is applied. This is because the larger the ratio (c / H0), the greater the load on the sheet of protrusions and the lower the physical durability of the sheet.

  When the ratio (c / H0) is 0.13 or less, the porosity of the sheet is preferably 30% or more and 90% or less. When the ratio (c / H0) exceeds 0.13 (or 0.15 or more) and is 0.7 or less, the porosity of the sheet is 20% or more and 80% or less. Is preferred.

  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.

(Preparation of medium pressure evaluation 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 ), a 17.0 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.

(Preparation of high-pressure evaluation film)
It was prepared in the same manner as the medium pressure evaluation membrane except that the m-PDA concentration was 3.9% by weight and the trimesic acid chloride concentration in the n-decane solution was 0.12% by weight.

(Pitch, spacing and height of protrusions)
Using a scanning electron microscope (S-800) (manufactured by Hitachi, Ltd.), 30 sections of any separation membrane were photographed at 100 times. Fifty permeate side channels were selected from the photograph, and the pitch and channel width were measured. For example, when 5 channels are included in one photograph, a total of 150 channels are photographed, and 50 channels were selected therefrom.

  For the selected 50 channels, measure the horizontal distance from one apex of the adjacent protrusions across the channel to the other apex, and divide the measured value by the number of measurement points (50). Got the value. This average value will be shown later as a pitch.

  For the distance b, in the channel where the pitch was measured, the distance between the midpoint of one height of the adjacent protrusions across the channel and the midpoint of the other height was measured. Further, an average value was calculated. This average value will be shown later as an interval (channel width) b.

  Further, for the height c, in the channel where the pitch was measured, the height was measured for one of the adjacent protrusions across the channel, and an average value was calculated. This average value will be shown later as height c.

(Representative length)
Using the height c and the interval b measured by the above method, the cross-sectional area (c × b) and the immersion side length (2 (c + b)) are calculated, and the representative length (4 × cross-sectional area / infiltration side length) is calculated. )

(Ratio (A11 / A1))
A sample having a width of 10 mm was cut out from an arbitrary portion of the separation membrane. The sample was cut to have at least one cross section parallel to the width direction. Next, the cross-sectional area A of all the flow paths included in one cross section parallel to the width direction of the sample was measured using a high-precision shape measurement system KS-1100 manufactured by Keyence Corporation. The average value of the obtained cross-sectional areas was calculated as the cross-sectional area A11, and the total was calculated as A1. The ratio (A11 / A1) was calculated. In addition, when the flow path was cut at both ends in the width direction when the sample was cut, the flow paths at both ends were excluded from the measurement targets.

(Water production (medium pressure))
The separation membrane or separation membrane element was operated for 105 hours under conditions of 2,000 ppm salt as raw water, an operating pressure of 1.5 MPa, an operating temperature of 25 ° C., and a pH of 6.5 (recovery rate of 15%). Thereafter, permeated water was obtained by operating for 10 minutes under the same conditions. From the volume of permeated water obtained by the operation for 10 minutes, the water permeation amount (cubic meter) per unit area of the separation membrane and per day was expressed as water production amount (high pressure) (m ³ / day).

(Water production (high pressure))
The separation membrane or separation membrane element was operated for 10 hours under conditions of 3.5 wt% salt as raw water, operating pressure 5.5 MPa, operating temperature 25 ° C., pH 6.5 (recovery rate 15%). Thereafter, permeated water was obtained by operating for 10 minutes under the same conditions. From the volume of permeated water obtained by the operation for 10 minutes, the water permeation amount (cubic meter) per unit area of the separation membrane and per day was expressed as water production amount (high pressure) (m ³ / 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)}.

(Compressive modulus)
The protrusion is melt-molded into a cylindrical shape having a diameter of 10 mm and a thickness of 25 mm, and compression stress is applied at 30 ° C. under a compression speed of 7 mm / min using a Tensilon Universal Material Tester (RTF-2430) (manufactured by A & D). The initial slope of the obtained curve was calculated. This initial gradient is the compression modulus.

(Change over time)
It is the rate of change in water production (%) between 2 hours and 100 hours after the start of operation, and can be expressed as 100- (water production after 100 hours / water production after 2 hours) × 100. The closer it is, the smaller the variation in the amount of water produced is.

(Durability (Medium pressure))
After finishing the measurement of the amount of water produced (medium pressure), the operation pressure was changed to 2.5 MPa without ending the operation, and the operation was carried out for 1 hour. Subsequently, the pressure was changed to 1.5 MPa, and after operation for 1 hour, sampling was performed for 10 minutes, and the amount of water produced was measured. From the volume of permeate obtained, per unit area of the separation membrane and per day The water permeability (cubic meter) was defined as the amount of water produced (medium pressure) (m ³ / day). The durability (medium pressure) (%) is expressed by 100− (water production amount (medium pressure) / water production amount (medium pressure)) × 100. The closer the value is to 0, the higher the durability of the separation membrane element. It was used as an index.

(Durability (high pressure))
After the measurement of the amount of fresh water (high pressure) was completed, the operation was not terminated and the operation pressure was changed to 6.5 MPa, and the operation was performed for 1 hour. Subsequently, the pressure was changed to 5.5 MPa, and after 1 hour of operation, sampling was performed for 10 minutes and the amount of water produced was measured. From the permeate volume obtained, the unit area of the separation membrane and per day The water permeability (cubic meter) was defined as the amount of water produced (high pressure) (m ³ / day). Durability (high pressure) (%) is expressed as 100- (water production amount (high pressure) / water production amount (high pressure)) × 100, and the closer the value is to 0, the higher the durability, the index of the separation membrane element. .

(Example 1)
A protrusion was formed over the entire permeation side of the medium pressure evaluation membrane. That is, using a gravure roll while adjusting the temperature of the backup roll to 15 ° C., a saponified ethylene-vinylacetic acid copolymer (6820 manufactured by Tosoh Corporation, compression elastic modulus: 1 GPa) is applied to the permeation side surface of the separation membrane. Applied. The resin temperature was 180 ° C. and the processing speed was 10 m / min.

  The shape of the obtained protrusion was as shown in Table 1.

  Here, the pitch is an average value of the horizontal distances from the vertexes of the convex portions of the separation membrane to the vertexes of the neighboring convex portions, measured at 200 locations on the transmission side surface.

The obtained separation membrane was folded and cut so that the effective area of the separation membrane element was 37.0 m ^2, and the net (thickness: 0.74 mm, pitch: 5 mm × 5 mm, fiber diameter: 370 μm, projected area ratio) : 0.13) was used as a supply-side channel material, and 26 leaves were produced with a width of 900 mm and a leaf length of 800 mm.

  The leaf thus obtained was spirally wound around a water collecting pipe made of ABS (width: 1,020 mm, diameter: 30 mm, number of holes 40 × 1 straight line), and a film was further wound around the outer periphery. After fixing with tape, edge cutting, end plate attachment, and filament winding were performed to produce an 8-inch element. Both end plates were perforated end plates. That is, in this example, the separation membrane element of the first form shown in FIG. 8 was produced.

  When the separation membrane element was placed in a pressure vessel and operated under medium pressure conditions, the amount of permeate produced, the desalting rate, the rate of change with time, and the durability were as shown in Table 1.

(Examples 2-9)
The separation membrane was prepared in the same manner as in Example 1 except that the protrusion width and pitch were changed as shown in Tables 1 to 3 and the representative length and ratio A11 / A1 were changed. did. Subsequently, a separation membrane element was produced in the same manner as in Example 1.

  When the separation membrane element was put in a pressure vessel and operated under medium pressure conditions to obtain permeated water, the amount of water produced, the desalting rate, the rate of change with time, and the durability were as shown in Tables 1 to 3.

(Example 10)
All the conditions for the formation of protrusions were implemented except that the resin was applied linearly to the permeate side surface of the separation membrane body so that it was parallel to the longitudinal direction of the separation membrane body (that is, the longitudinal direction of the nonwoven fabric as the base material) In the same manner as in Example 7, a separation membrane was produced. Subsequently, a separation membrane element was produced in the same manner as in Example 1.

  When the separation membrane element was placed in a pressure vessel and operated under medium pressure conditions to obtain permeated water, the amount of water produced, desalting rate, rate of change with time, and durability were as shown in Table 3.

(Example 11)
All the conditions for the formation of protrusions were implemented except that the resin was applied linearly to the permeate side surface of the separation membrane body so that it was parallel to the longitudinal direction of the separation membrane body (that is, the longitudinal direction of the nonwoven fabric as the base material). In the same manner as in Example 8, a separation membrane was produced. Subsequently, a separation membrane element was produced in the same manner as in Example 1.

When the separation membrane element was placed in a pressure vessel and operated under medium pressure conditions to obtain permeated water, the amount of water produced, the desalting rate, the rate of change with time, and the durability were as shown in Table 3 (Example 12). )
All the conditions for the formation of protrusions were implemented except that the resin was applied linearly to the permeate side surface of the separation membrane body so that it was parallel to the longitudinal direction of the separation membrane body (that is, the longitudinal direction of the nonwoven fabric as the base material). In the same manner as in Example 9, a separation membrane was produced. Subsequently, a separation membrane element was produced in the same manner as in Example 1.

When the separation membrane element was put in a pressure vessel and operated under medium pressure conditions to obtain permeated water, the amount of water production, desalting rate, rate of change with time, and durability were as shown in Table 3 (Example 13). )
When using a high-pressure evaluation membrane and forming projections on the backside of the separation membrane, the resin is polystyrene (compression modulus: 3.5 GPa). A separation membrane was prepared in the same manner as in Example 1 except that the protrusions were formed on Lumirror S type (50 μm) and transferred to the membrane substrate. Subsequently, a separation membrane element was produced in the same manner as in Example 1.

When the separation membrane element was put in a pressure vessel and operated under high pressure conditions to obtain permeated water, the amount of water produced, desalting rate, rate of change with time, and durability were as shown in Table 4 (Example 14, 15)
Except for using the high-pressure evaluation film, and changing the width and pitch of the protrusions as shown in Table 4 and changing the representative length and the ratio A11 / A1 with respect to the formation conditions of the protrusions, all are the same as in Example 13. Thus, a separation membrane was produced. Subsequently, a separation membrane element was produced in the same manner as in Example 1.

When the separation membrane element was placed in a pressure vessel and operated under high pressure conditions to obtain permeate, the amount of water produced, the desalting rate, the rate of change with time, and the durability were as shown in Table 4.
(Example 16)
When using a high-pressure evaluation membrane and forming projections, the resin is polyethylene terephthalate (compression elastic modulus: 2.9 GPa), and when the projections are formed on the back side of the separation membrane in advance, a biaxially stretched polyester film ( A separation membrane was prepared in the same manner as in Example 6 except that a protrusion was formed on a Toray Lumirror S type 50 μm) and then the transparent protrusion was transferred to a membrane substrate. Subsequently, a separation membrane element was produced in the same manner as in Example 1.

When the separation membrane element was placed in a pressure vessel and operated under high pressure conditions to obtain permeated water, the amount of water produced, the desalting rate, the rate of change with time, and the durability were as shown in Table 4 (Example 17).
Using a high-pressure evaluation film, the resin was changed for the formation conditions of the protrusions, and 50 wt% of magnesium silicate (manufactured by Wako Pure Chemical Industries, Ltd.) was added to polystyrene (compression elastic modulus: 4.1 GPa). When the protrusions were previously formed on the back side of the separation membrane, except that the protrusions were once formed on a biaxially stretched polyester film (Toray Lumirror S type 50 μm) and then transferred to the membrane substrate. A separation membrane was prepared in the same manner as in Example 6. Subsequently, a separation membrane element was produced in the same manner as in Example 1.

When the separation membrane element was placed in a pressure vessel and operated under high pressure conditions to obtain permeated water, the amount of water produced, the desalting rate, the rate of change with time, and the durability were as shown in Table 1 (Example 18).
All the conditions for the formation of protrusions were implemented except that the resin was applied linearly to the permeate side surface of the separation membrane body so that it was parallel to the longitudinal direction of the separation membrane body (that is, the longitudinal direction of the nonwoven fabric as the base material). A separation membrane was prepared in the same manner as in Example 13. Subsequently, a separation membrane element was produced in the same manner as in Example 1.

When the separation membrane element was put in a pressure vessel and operated under high pressure conditions to obtain permeated water, the amount of water production, desalting rate, rate of change with time and durability were as shown in Table 5 (Example 19).
All the conditions for the formation of protrusions were implemented except that the resin was applied linearly to the permeate side surface of the separation membrane body so that it was parallel to the longitudinal direction of the separation membrane body (that is, the longitudinal direction of the nonwoven fabric as the base material). A separation membrane was prepared in the same manner as in Example 14. Subsequently, a separation membrane element was produced in the same manner as in Example 1.

When the separation membrane element was placed in a pressure vessel and operated under high pressure conditions to obtain permeate, the amount of water produced, the desalting rate, the rate of change with time, and the durability were as shown in Table 5 (Example 20).
All the conditions for the formation of protrusions were implemented except that the resin was applied linearly to the permeate side surface of the separation membrane body so that it was parallel to the longitudinal direction of the separation membrane body (that is, the longitudinal direction of the nonwoven fabric as the base material). A separation membrane was produced in the same manner as in Example 15. Subsequently, a separation membrane element was produced in the same manner as in Example 5.

When the separation membrane element was placed in a pressure vessel and operated under high pressure conditions to obtain permeated water, the amount of water produced, the desalting rate, the rate of change with time, and the durability were as shown in Table 5 (Example 21).
By forming the protrusions on the sheet instead of forming on the substrate side of the separation membrane, a sheet-like channel material was produced, and this channel material was disposed between the separation membranes.

  Specifically, the height is 0.23 mm on a sheet which is a papermaking nonwoven fabric (yarn diameter: 1 dtex, thickness: about 0.03 mm, porosity 25%), and as a result, the representative length is 0.18. A projection having the same dimensions as in Example 1 was formed in the same manner as in Example 1 except that.

  Further, a separation membrane element was produced in the same manner as in Example 1 except that the sheet-like separation membrane thus obtained was sandwiched between the permeation side surfaces of the separation membrane.

  When this element was placed in a pressure vessel and operated under the above-mentioned conditions to obtain permeated water, the amount of water produced, the desalting rate, the rate of change with time, and the durability were as shown in Table 6.

(Example 22)
By forming the protrusions on the sheet instead of forming on the substrate side of the separation membrane, a sheet-like channel material was produced, and this channel material was disposed between the separation membranes.

  Specifically, the height is 0.23 mm on a sheet which is a papermaking nonwoven fabric (yarn diameter: 1 dtex, thickness: about 0.03 mm, porosity 25%), and as a result, the representative length is 0.18. A protrusion having the same dimensions as in Example 11 was formed in the same manner as in Example 11 except that.

  Further, a separation membrane element was produced in the same manner as Example 11 except that the sheet-like separation membrane thus obtained was sandwiched between the permeation side surfaces of the separation membrane.

  When this element was placed in a pressure vessel and operated under the above-mentioned conditions to obtain permeated water, the amount of water produced, the desalting rate, the rate of change with time, and the durability were as shown in Table 6.

(Comparative Examples 1 and 2)
Except for using a high-pressure evaluation film and changing the width and pitch of the protrusions as shown in Table 6 and changing the representative length and the ratio A11 / A1 as to the formation conditions of the protrusions, all are the same as in Example 1. Thus, a separation membrane was produced. Subsequently, a separation membrane element was produced in the same manner as in Example 1.

  When the separation membrane element was placed in a pressure vessel and operated under high pressure conditions to obtain permeate, the amount of water produced, the desalting rate, the rate of change with time, and the durability were as shown in Table 6.

  As is clear from the results, the separation membrane and the separation membrane element of the examples have high water production performance, stable operation performance, and excellent removal performance.

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

DESCRIPTION OF SYMBOLS 1 Separation membrane 11 Envelope-shaped membrane 2 Separation membrane main body 21 Supply side surface 22 Permeation side surface 201 Base material 202 Porous support layer 203 Separation functional layer 31 Protrusion (permeation side channel material)
32 Supply side flow path material 4 Separation membrane leaf 5 Permeation side flow path 6 Water collecting pipe 7 Separation membrane 13 Sheet 71 Supply side surface 72 Permeation side surface 82 Porous member 91 End plate (no hole)
92 End plate (with holes)
100 Separation membrane element 100A Separation membrane element (first form)
100B separation membrane element (second form)
100C separation membrane element (third form)
a Separation membrane (leaf) length b Projection width interval c Projection height d Projection width e Projection length interval f Projection length R2 From inside of winding direction in separation membrane A region including from the beginning to the end of the projections arranged outside R3 A region where no projection is provided at the outer end of the separation membrane in the winding direction L1 Length of the entire separation membrane (the length a)
L2 Length of region R2 L3 Length of region R3 101 Raw water 102 Permeated water 103 Concentrated water

Claims (5)

A water collecting pipe, a separation membrane body having a supply side surface and a permeation side surface, and a plurality of protrusions fixed to the permeation side surface of the separation membrane body; A separation membrane element comprising:
The protrusion forms a flow path between adjacent protrusions,
A separation membrane element having a representative length of the flow path of 0.12 mm or more and 0.30 mm or less. A water collecting pipe, a separation membrane having a supply-side surface and a permeation-side surface, wound around the water collection tube, and a sheet and a sheet disposed so as to face the permeation-side surface of the separation membrane A permeation-side flow path member provided with a plurality of protrusions fixed to the separation membrane element,
The protrusion forms a flow path between adjacent protrusions,
A separation membrane element having a representative length of the flow path of 0.12 mm or more and 0.30 mm or less.   The ratio (A11 / A1) between the cross-sectional area A11 of the flow path and the sum A1 of the cross-sectional areas of the flow paths existing around a width of 10 mm of the separation membrane in a plane parallel to the longitudinal direction of the water collecting pipe is 0. The separation membrane element according to claim 1 or 2, which is 0.025 or more and 0.075 or less.   The separation membrane element according to any one of claims 1 to 3, wherein a height of the protrusion is 0.5 mm or less. The separation membrane element according to any one of claims 1 to 4, wherein a compression elastic modulus of the projection is 0.5 GPa or more and 5.0 GPa or less.

Images