JP2012055817A - Separation membrane element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separation membrane element which is effective for improvement of separation/removal performance in the separation membrane element omitting a passage material, improvement of separation membrane element performance, such as an increase in the amount of permeated fluid per unit of time, and stability performance.SOLUTION: In the separation membrane element, a first separation membrane having a surface height difference of 50 μm or less and a second separation membrane having a surface height difference of 100 μm or more and 2,000 μm or less are disposed alternately.

Description

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

  There are various methods for separating components contained in fluid such as liquid and gas. For example, taking a technique for removing ionic substances contained in seawater, brine, and the like as an example, in recent years, the use of a separation method using a separation membrane element is expanding as a process for saving energy and resources. Separation membranes used in separation methods using separation membrane elements include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, and forward osmosis membranes in terms of their pore size and separation function. Membranes are used, for example, when drinking water is obtained from seawater, brackish water, water containing harmful substances, etc., or for production of industrial ultrapure water, wastewater treatment, recovery of valuable materials, etc. Depending on the separation performance.

  The separation membrane element is common in that the raw fluid is supplied to one surface of the separation membrane and the permeated fluid is obtained from the other surface. The separation membrane element is configured to bundle many separation membrane elements of various shapes to increase the membrane area and to obtain a large amount of permeated fluid per unit element. Various elements such as molds, hollow fiber types, plate-and-frame types, rotating flat membrane types, and flat membrane integrated types are manufactured.

  For example, taking a fluid separation membrane element used for reverse osmosis filtration as an example, the separation membrane element member is a supply-side flow path material that supplies the raw fluid to the separation membrane surface, and a separation that separates components contained in the raw fluid A spiral separation membrane element in which a member made of a permeate-side flow path material for guiding a permeate-side fluid that has permeated the separation membrane and separated from the supply-side fluid to the central tube is wound around the central tube. It is widely used in that pressure is applied to the fluid and a large amount of permeated fluid is taken out.

  As a member of the spiral type reverse osmosis separation membrane element, the supply side flow path material mainly uses a polymer net to form a flow path of the supply side fluid, and the separation membrane has a high cross-linkage such as polyamide. A separation function layer consisting of molecules, a porous support membrane made of a polymer such as polysulfone, and a composite semipermeable membrane in which nonwoven fabrics made of a polymer such as polyethylene terephthalate are laminated from the supply side to the permeation side are used. In the road material, a fabric member called a tricot having a smaller interval than the supply side flow path material is used for the purpose of preventing the film from dropping and forming a flow path on the permeate side.

  In recent years, the need for higher performance of membrane elements has been demanded due to the increase in water production cost of separation membrane elements. From the viewpoint of increasing the separation performance of the separation membrane element and the amount of permeated fluid per unit time, it has been proposed to improve the performance of each flow path member, separation membrane, and element member. For example, in Patent Document 1, a method of using a sheet-like material formed with unevenness as a permeate-side flow path material, and in Patent Document 2, without using a base material, unevenness is formed on the supply side surface, and a hollow passage is formed inside In Patent Documents 3 and 4, a sheet-shaped composite semipermeable membrane comprising a porous support having irregularities and a separation active layer is used, and a supply-side channel material such as a net or a tricot is used. A method that does not use the permeate-side channel material has been proposed.

JP 2006-247453 A JP-A-11-114381 JP 2010-99590 A JP 2010-125418 A

  However, the separation membrane element described above is not sufficient in terms of performance improvement, particularly stable performance when operated for a long period of time. The method of using an object as a permeate-side channel material only reduces the flow resistance on the permeate side and has a resistance on the sheet surface, so that it cannot be said that the effect of reducing the flow resistance is sufficient.

  In the method described in Patent Document 2, in which a substrate is not used, irregularities are formed on the supply side surface, and a flat membrane having a hollow passage is used, a hollow passage extending in a direction parallel to the membrane surface is flattened. Since it is in the film, it is difficult to increase the height of the unevenness on the surface, and the uneven shape is limited (in the example, a groove with a step of 0.15 mm), and the shape of the permeation side flow path is also limited, so supply The flow resistance reduction effect on the side and permeate side is not sufficient.

  Patent Documents 3 and 4 use a sheet-like composite semipermeable membrane comprising a porous support having irregularities and a separation active layer, and supply side channel materials such as nets and permeation side channel materials such as tricots In the method using no membrane, although only the membrane performance when the cell for flat membrane evaluation is used is described in the examples, the performance when the separation membrane element is actually configured is not disclosed, and the performance is also disclosed. It is insufficient. When the separation membrane element is actually operated with pressure applied, the cross-sectional area of the supply-side channel and permeation-side channel is likely to change, and the performance tends to change when the operation is performed for a long period of time as well as the initial stage. is there. Furthermore, in order to avoid the problems of increased flow resistance and flow path shrinkage due to the unevenness of the membranes placed facing each other and the cross-sectional area of the flow path becoming slight, the shape, size, arrangement, etc. of the unevenness are limited, It cannot be said that the flow resistance reduction effect and the turbulent flow improvement effect (stirring effect) on the supply side and the permeation side are sufficient.

  Therefore, the present invention provides a separation membrane element that is effective for improving separation performance in a separation membrane element that omits a flow path material, improving separation membrane element performance such as an increase in the amount of permeated fluid per unit time, and stability performance. With the goal.

  In order to achieve the above object, the present invention is characterized in that the first separation membrane having a surface height difference of 50 μm or less and the second separation membrane having a surface height difference of 100 μm or more and 2000 μm or less are alternately arranged. A separation membrane element.

  According to the present invention, the separation membrane having a smooth surface and the separation membrane having a height difference on the surface are alternately arranged, so that the unevenness of the film surface is not pinched or the protrusions are not overlapped, and the flow path material The supply-side and permeate-side flow paths can be formed with high efficiency and stability while omitting. Furthermore, by optimizing the shape, size, and arrangement of the unevenness, a sufficient flow resistance reduction effect and turbulent flow improvement effect can be obtained. As a result, it is possible to obtain a high-performance, high-efficiency separation membrane element that can reduce the raw material cost of the separation membrane element, simplify the manufacturing process, and reduce the environmental load.

It is a cross-sectional schematic diagram which shows the example of the separation membrane element of this invention.

  Hereinafter, the present invention will be described in more detail.

  The present invention is a separation membrane element characterized in that the first separation membrane 1 having a surface height difference of 50 μm or less and the second separation membrane 2 having a surface height difference of 100 μm or more and 2000 μm or less are alternately arranged. is there.

  Here, the separation membrane is not limited as long as it separates components in the fluid supplied to the surface of the separation membrane and obtains a permeated fluid that has permeated through the separation membrane. However, the separation functional layer, porous support membrane, Those made of materials are preferably used. As the separation functional layer, a crosslinked polymer is preferably used in terms of pore size control and durability, and polyfunctional amine and polyfunctional acid halide are polycondensed on the porous support membrane in terms of component separation performance. A polyamide separation functional layer, an organic / inorganic hybrid functional layer, and the like can be suitably used. A membrane having a separation function and a support function such as a cellulose membrane, a PVDF membrane, a PES membrane, or a polysulfone membrane can also be used.

  In this invention, the case where the polyamide which comprises a separation function layer is used is explained in full detail. The polyamide film can be formed by interfacial polycondensation of a polyfunctional amine and a polyfunctional acid halide. Here, it is preferable that at least one of the polyfunctional amine or the polyfunctional acid halide contains a trifunctional or higher functional compound.

  Here, the polyfunctional amine has at least two primary amino groups and / or secondary amino groups in one molecule, and at least one of the amino groups is a primary amino group. An amine, for example, phenylenediamine, xylylenediamine, 1,3,5-triaminobenzene, in which two amino groups are bonded to the benzene ring in any of the ortho, meta, and para positions. , 2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, aromatic polyfunctional amines such as 4-aminobenzylamine, aliphatic amines such as ethylenediamine and propylenediamine, 1,2- Examples include alicyclic polyfunctional amines such as diaminocyclohexane, 1,4-diaminocyclohexane, 4-aminopiperidine, and 4-aminoethylpiperazine. It is possible. Among them, considering the selective separation property, permeability, and heat resistance of the membrane, it may be an aromatic polyfunctional amine having 2 to 4 primary amino groups and / or secondary amino groups in one molecule. Preferably, as such a polyfunctional aromatic amine, m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene are preferably used. Among these, it is more preferable to use m-phenylenediamine (hereinafter referred to as m-PDA) from the standpoint of availability and ease of handling. These polyfunctional amines may be used alone or in combination of two or more. When using 2 or more types simultaneously, the said amines may be combined and the said amine and the amine which has at least 2 secondary amino group in 1 molecule may be combined. Examples of the amine having at least two secondary amino groups in one molecule include piperazine and 1,3-bispiperidylpropane.

  The polyfunctional acid halide refers to an acid halide having at least two carbonyl halide groups in one molecule. Examples of trifunctional acid halides include trimesic acid chloride, 1,3,5-cyclohexanetricarboxylic acid trichloride, 1,2,4-cyclobutanetricarboxylic acid trichloride, and bifunctional acid halides include biphenyl dicarboxylic acid. Aromatic difunctional acid halides such as acid dichloride, azobenzene dicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, naphthalene dicarboxylic acid chloride, aliphatic difunctional acid halides such as adipoyl chloride, sebacoyl chloride, cyclopentane Examples thereof include alicyclic difunctional acid halides such as dicarboxylic acid dichloride, cyclohexane dicarboxylic acid dichloride, and tetrahydrofuran dicarboxylic acid dichloride. Considering the reactivity with the polyfunctional amine, the polyfunctional acid halide is preferably a polyfunctional acid chloride, and considering the selective separation property and heat resistance of the membrane, 2 to 4 per molecule. The polyfunctional aromatic acid chloride having a carbonyl chloride group is preferred. Among them, it is more preferable to use trimesic acid chloride from the viewpoint of easy availability and easy handling. These polyfunctional acid halides may be used alone or in combination of two or more.

  In terms of maintaining the surface separation by molding and maintaining the subsequent separation performance, the ratio of the bifunctional halogen compound to the trifunctional halogen compound is the molar ratio (mole of the bifunctional halogen compound / mol of the trifunctional halogen compound). Mol) is preferably 0.05 to 1.5, more preferably 0.1 to 1.0.

  Furthermore, a separation membrane having an organic / inorganic hybrid structure containing Si element in terms of moldability and chemical resistance can also be used. The organic-inorganic hybrid film is not particularly limited. For example, (A) a silicon compound in which a reactive group having an ethylenically unsaturated group and a hydrolyzable group are directly bonded to a silicon atom, and (B) other than the silicon compound Condensation of the hydrolyzable group of the silicon compound (A) with the compound having an ethylenically unsaturated group of (A) and the ethylenic unsaturated of the compound (A) and the compound (B) having an ethylenically unsaturated group. Saturated polymer can be used.

  First, the silicon compound (A) in which a reactive group having an ethylenically unsaturated group and a hydrolyzable group are directly bonded to a silicon atom will be described.

  The reactive group having an ethylenically unsaturated group is directly bonded to the silicon atom. Examples of such reactive groups include vinyl groups, allyl groups, methacryloxyethyl groups, methacryloxypropyl groups, acryloxyethyl groups, acryloxypropyl groups, and styryl groups. From the viewpoint of polymerizability, a methacryloxypropyl group, an acryloxypropyl group, and a styryl group are preferable.

  Further, through a process in which a hydrolyzable group directly bonded to a silicon atom is changed to a hydroxyl group, a condensation reaction occurs in which silicon compounds are bonded together by a siloxane bond, resulting in a polymer. Examples of hydrolyzable groups include functional groups such as alkoxy groups, alkenyloxy groups, carboxy groups, ketoxime groups, aminohydroxy groups, halogen atoms and isocyanate groups. As an alkoxy group, a C1-C10 thing is preferable, More preferably, it is a C1-C2 thing. The alkenyloxy group preferably has 2 to 10 carbon atoms, more preferably 2 to 4 carbon atoms, and further 3 carbon atoms. As the carboxy group, those having 2 to 10 carbon atoms are preferable, and further, those having 2 carbon atoms, that is, an acetoxy group. Examples of the ketoxime group include a methyl ethyl ketoxime group, a dimethyl ketoxime group, and a diethyl ketoxime group. The aminohydroxy group is one in which an amino group is bonded to a silicon atom via an oxygen atom via oxygen. Examples of such include dimethylaminohydroxy group, diethylaminohydroxy group, and methylethylaminohydroxy group. As the halogen atom, a chlorine atom is preferably used.

  In forming the separation functional layer, a silicon compound in which a part of the hydrolyzable group is hydrolyzed and has a silanol structure can be used. In addition, two or more silicon compounds having a high molecular weight such that a part of the hydrolyzable group is not hydrolyzed, condensed, or crosslinked can be used.

The silicon compound (A) is preferably represented by the following general formula (a).
Si (R ¹ ) _m (R ² ) _n (R ³ ) _4-mn (a)
(R ¹ represents a reactive group containing an ethylenically unsaturated group. R ² represents an alkoxy group, an alkenyloxy group, a carboxy group, a ketoxime group, a halogen atom or an isocyanate group. R ³ represents H or alkyl. M and n are integers satisfying m + n ≦ 4 and satisfy m ≧ 1 and n ≧ 1 In each of R ¹ , R ² and R ³ , two or more functional groups are bonded to a silicon atom. They may be the same or different.)
R ¹ is a reactive group containing an ethylenically unsaturated group, and is as described above.

R ² is a hydrolyzable group, and these are as described above. The number of carbon atoms of the alkyl group to be R ³ is preferably 1-10, and more preferably 1-2.

  As the hydrolyzable group, an alkoxy group is preferably used in forming the separation functional layer because the reaction solution has viscosity.

  Such silicon compounds include vinyltrimethoxysilane, vinyltriethoxysilane, styryltrimethoxysilane, methacryloxypropylmethyldimethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropyltriethoxy. Examples include silane and acryloxypropyltrimethoxysilane.

  In addition to the silicon compound of (A), a silicon compound having no hydrolyzable group can also be used in combination with no reactive group having an ethylenically unsaturated group. Such a silicon compound is defined as “m ≧ 1” in the general formula (a), and examples thereof include compounds in which m is zero in the general formula (a). Examples of such include tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, and methyltriethoxysilane.

  Next, the compound (B) having an ethylenically unsaturated group other than the silicon compound (A) will be described.

  The ethylenically unsaturated group has addition polymerizability. Examples of such compounds include ethylene, propylene, methacrylic acid, acrylic acid, styrene, and derivatives thereof.

  In addition, this compound may be an alkali-soluble compound having an acid group in order to increase the selective permeability of water and increase the salt rejection when a composite semipermeable membrane is used for separation of an aqueous solution. preferable.

  Preferred acid structures are carboxylic acid, phosphonic acid, phosphoric acid, and sulfonic acid, and these acid structures may exist in any form of acid form, ester compound, and metal salt. These compounds having one or more ethylenically unsaturated groups may contain two or more acids, but among them, compounds containing 1 to 2 acid groups are preferred.

  Examples of the compound having a carboxylic acid group among the compounds having one or more ethylenically unsaturated groups include the following. Maleic acid, maleic anhydride, acrylic acid, methacrylic acid, 2- (hydroxymethyl) acrylic acid, 4- (meth) acryloyloxyethyl trimellitic acid and the corresponding anhydride, 10-methacryloyloxydecylmalonic acid, N- ( 2-hydroxy-3-methacryloyloxypropyl) -N-phenylglycine and 4-vinylbenzoic acid.

  Among the compounds having at least one ethylenically unsaturated group, compounds having a phosphonic acid group include vinylphosphonic acid, 4-vinylphenylphosphonic acid, 4-vinylbenzylphosphonic acid, 2-methacryloyloxyethylphosphonic acid. 2-methacrylamidoethylphosphonic acid, 4-methacrylamido-4-methyl-phenyl-phosphonic acid, 2- [4- (dihydroxyphosphoryl) -2-oxa-butyl] -acrylic acid and 2- [2-dihydroxyphosphoryl] ) -Ethoxymethyl] -acrylic acid-2,4,6-trimethyl-phenyl ester.

  Among the compounds having one or more ethylenically unsaturated groups, the phosphate ester compounds include 2-methacryloyloxypropyl monohydrogen phosphate, 2-methacryloyloxypropyl dihydrogen phosphate, and 2-methacryloyloxyethyl monoester. Hydrogen phosphate and 2-methacryloyloxyethyl dihydrogen phosphate, 2-methacryloyloxyethyl-phenyl-hydrogen phosphate, dipentaerythritol-pentamethacryloyloxyphosphate, 10-methacryloyloxydecyl-dihydrogen phosphate, dipentaerythritol penta Methacryloyloxyphosphate, phosphoric acid mono- (1-acryloyl-piperidin-4-yl) -ester, 6- (methacrylamide) hexyl dihydrogen phosphate and 1,3-bis- (N-acryloyl-N-pro Le - amino) - propan-2-yl - dihydrogen phosphate are exemplified.

  Among the compounds having one or more ethylenically unsaturated groups, examples of the compound having a sulfonic acid group include vinylsulfonic acid, 4-vinylphenylsulfonic acid, and 3- (methacrylamide) propylsulfonic acid.

  In the separation membrane according to the present invention, in order to form the separation functional layer, in addition to the silicon compound of (A), a reaction liquid containing a compound having one or more ethylenically unsaturated groups and a polymerization initiator is used. The In addition to coating the reaction solution on the porous membrane and condensing the hydrolyzable groups, it is necessary to increase the molecular weight of these compounds by polymerization of ethylenically unsaturated groups. When the silicon compound of (A) is condensed alone, the bond of the crosslinking chain concentrates on the silicon atom, and the density difference between the silicon atom periphery and the part away from the silicon atom increases, so the pore size in the separation functional layer Tends to be non-uniform. On the other hand, in addition to the high molecular weight and cross-linking of the silicon compound itself of (A), the cross-linking point due to condensation of hydrolyzable groups and the ethylenically unsaturated group are copolymerized with the compound (B) having an ethylenically unsaturated group. Crosslink points due to polymerization of saturated groups are moderately dispersed. By appropriately dispersing the crosslinking points in this manner, a separation functional layer having a uniform pore diameter is formed, and a composite semipermeable membrane having a balance between water permeability and removal performance can be obtained. At this time, a compound having one or more ethylenically unsaturated groups is required to have a high molecular weight since it may be eluted when using a separation membrane if it has a low molecular weight, causing a decrease in membrane performance.

  In the method for producing a separation membrane according to the present invention, (A) the content of a silicon compound in which a reactive group having an ethylenically unsaturated group and a hydrolyzable group are directly bonded to a silicon atom is the solid content contained in the reaction solution. The amount is preferably 10 parts by weight or more, more preferably 20 parts by weight to 50 parts by weight with respect to 100 parts by weight. Here, the solid content contained in the reaction solution is obtained by the above production method except for all components contained in the reaction solution, excluding the solvent and distilled components such as water and alcohol produced by the condensation reaction. It refers to the component finally contained in the separation membrane as a separation functional layer. When the amount of the silicon compound (A) is small, the degree of crosslinking tends to be insufficient, so that there is a possibility that problems such as elution of the separation functional layer during membrane filtration and deterioration of separation performance may occur.

  The content of the compound (B) having an ethylenically unsaturated group is preferably 90 parts by weight or less, more preferably 50 parts by weight to 80 parts by weight with respect to 100 parts by weight of the solid content contained in the reaction solution. It is. When the content of the compound (B) is in these ranges, the resulting separation functional layer has a high degree of crosslinking, and thus membrane filtration can be performed stably without the separation functional layer eluting.

  Next, a method for forming a separation functional layer on a porous support membrane in the method for producing a separation membrane according to the present invention will be described.

  Examples of methods for forming the separation functional layer include a step of applying a reaction solution containing the silicon compound (A) and a compound (B) having an ethylenically unsaturated group, a step of removing the solvent, ethylene The step of polymerizing the polymerizable unsaturated group and the step of condensing the hydrolyzable group are performed in this order. In the step of polymerizing the ethylenically unsaturated group, the hydrolyzable group may be condensed at the same time.

  First, the reaction liquid containing (A) and (B) is brought into contact with the porous support membrane. Such a reaction solution is usually a solution containing a solvent, but such a solvent does not destroy the porous support membrane and dissolves (A) and (B) and a polymerization initiator added as necessary. If it is, it will not specifically limit. To this reaction solution, 1 to 10 times mol amount, preferably 1 to 5 times mol amount of water with respect to the number of moles of the silicon compound of (A) is added together with inorganic acid or organic acid, and (A) It is preferable to promote hydrolysis of the silicon compound.

  As the solvent for the reaction solution, water, an alcohol-based organic solvent, an ether-based organic solvent, a ketone-based organic solvent, and a mixture thereof are preferable. For example, as an alcohol organic solvent, methanol, ethoxymethanol, ethanol, propanol, butanol, amyl alcohol, cyclohexanol, methylcyclohexanol, ethylene glycol monomethyl ether (2-methoxyethanol), ethylene glycol monoacetate, diethylene glycol monomethyl ether, Examples include diethylene glycol monoacetate, propylene glycol monoethyl ether, propylene glycol monoacetate, dipropylene glycol monoethyl ether, and methoxybutanol. Examples of ether organic solvents include methylal, diethyl ether, dipropyl ether, dibutyl ether, diamyl ether, diethyl acetal, dihexyl ether, trioxane, dioxane and the like. Also, ketone organic solvents include acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl amyl ketone, methyl cyclohexyl ketone, diethyl ketone, ethyl butyl ketone, trimethylnonanone, acetonitrile acetone, dimethyl oxide, phorone, cyclohexanone, dye Acetone alcohol etc. are mentioned. The amount of the solvent added is preferably 50 to 99 parts by weight, more preferably 80 to 99 parts by weight. If the amount of the solvent added is too large, defects tend to occur in the membrane, and if it is too small, the water permeability of the resulting separation membrane tends to be low.

  The contact between the porous support membrane and the reaction solution is preferably performed uniformly and continuously on the surface of the porous support membrane. Specifically, for example, there is a method in which the reaction solution is coated on the porous support film using a coating device such as a spin coater, a wire bar, a flow coater, a die coater, a roll coater, or a spray. Moreover, the method of immersing a porous support membrane in a reaction liquid can be mentioned.

  When immersed, the contact time between the porous support membrane and the reaction solution is preferably in the range of 0.5 to 10 minutes, and more preferably in the range of 1 to 3 minutes. After the reaction solution is brought into contact with the porous support membrane, it is preferable to sufficiently drain the liquid so that no droplets remain on the membrane. By sufficiently draining the liquid, it is possible to prevent the remaining portion of the liquid droplet from becoming a film defect after the film is formed and deteriorating the film performance. As a method for draining liquid, the porous support membrane after contact with the reaction liquid is vertically gripped to allow the excess reaction liquid to flow down naturally, or air such as nitrogen is blown from an air nozzle to forcibly drain the liquid. A method or the like can be used. In addition, after draining, the membrane surface can be dried to remove a part of the solvent in the reaction solution.

  The step of condensing the hydrolyzable group of silicon is performed by performing a heat treatment after bringing the reaction solution into contact with the porous support membrane. The heating temperature at this time is required to be lower than the temperature at which the porous support membrane melts and the performance as a separation membrane decreases. In order to allow the condensation reaction to proceed rapidly, it is usually preferred to heat at 0 ° C. or higher, more preferably 20 ° C. or higher. Further, the reaction temperature is preferably 150 ° C. or lower, and more preferably 100 ° C. or lower. If the reaction temperature is 0 ° C. or higher, the hydrolysis and condensation reaction proceed rapidly, and if it is 150 ° C. or lower, the hydrolysis and condensation reaction are easily controlled. Further, by adding a catalyst that promotes hydrolysis or condensation, the reaction can proceed even at a lower temperature. Furthermore, in the present invention, the heating condition and the humidity condition are selected so that the separation functional layer has pores, and the condensation reaction is appropriately performed.

  As a polymerization method of the ethylenically unsaturated group of the compound (A) having a silicon compound and the compound (B) having an ethylenically unsaturated group, heat treatment, electromagnetic wave irradiation, electron beam irradiation, and plasma irradiation can be performed. Here, the electromagnetic wave includes infrared rays, ultraviolet rays, X-rays, γ rays and the like. The polymerization method may be appropriately selected as appropriate, but polymerization by electromagnetic wave irradiation is preferred from the viewpoint of running cost, productivity and the like. Among electromagnetic waves, infrared irradiation and ultraviolet irradiation are more preferable from the viewpoint of simplicity. When the polymerization is actually performed using infrared rays or ultraviolet rays, these light sources do not need to selectively generate only light in this wavelength range, and any light source containing electromagnetic waves in these wavelength ranges may be used. However, from the viewpoint of ease of shortening the polymerization time and controlling the polymerization conditions, it is preferable that the intensity of these electromagnetic waves is higher than electromagnetic waves in other wavelength regions.

  Electromagnetic waves can be generated from halogen lamps, xenon lamps, UV lamps, excimer lamps, metal halide lamps, rare gas fluorescent lamps, mercury lamps, and the like. The energy of the electromagnetic wave is not particularly limited as long as it can be polymerized, but in particular, high-efficiency, low-wavelength ultraviolet rays have high film-forming properties. Such ultraviolet rays can be generated by a low-pressure mercury lamp or an excimer laser lamp. The thickness and form of the separation functional layer according to the present invention may vary greatly depending on the respective polymerization conditions. If polymerization is performed using electromagnetic waves, the thickness and shape of the separation functional layers vary greatly depending on the wavelength of electromagnetic waves, the intensity, the distance to the irradiated object, and the processing time. Sometimes. Therefore, these conditions need to be optimized as appropriate.

  For the purpose of increasing the polymerization rate, it is preferable to add a polymerization initiator, a polymerization accelerator or the like during the formation of the separation functional layer. Here, the polymerization initiator and the polymerization accelerator are not particularly limited, and are appropriately selected according to the structure of the compound to be used, the polymerization technique, and the like.

  The polymerization initiator is exemplified below. As an initiator for polymerization by electromagnetic waves, benzoin ether, dialkylbenzyl ketal, dialkoxyacetophenone, acylphosphine oxide or bisacylphosphine oxide, α-diketone (for example, 9,10-phenanthrenequinone), diacetylquinone, furylquinone, anisylquinone, 4,4′-dichlorobenzylquinone and 4,4′-dialkoxybenzylquinone, and camphorquinone are exemplified. Initiators for thermal polymerization include azo compounds (eg, 2,2′-azobis (isobutyronitrile) (AIBN) or azobis- (4-cyanovaleric acid)), or peroxides (eg, peroxidation). Dibenzoyl, dilauroyl peroxide, tert-butyl peroctanoate, tert-butyl perbenzoate or di- (tert-butyl) peroxide), aromatic diazonium salts, bissulfonium salts, aromatic iodonium salts, aromatic sulfonium salts, Examples include potassium persulfate, ammonium persulfate, alkyl lithium, cumyl potassium, sodium naphthalene, and distyryl dianion. Of these, benzopinacol and 2,2'-dialkylbenzopinacol are particularly preferred as initiators for radical polymerization.

  Peroxides and α-diketones are preferably used in combination with aromatic amines to accelerate initiation. This combination is also called a redox system. Examples of such systems include benzoyl peroxide or camphorquinone and amines (eg, N, N-dimethyl-p-toluidine, N, N-dihydroxyethyl-p-toluidine, ethyl p-dimethyl-aminobenzoate). Ester or a derivative thereof). Furthermore, a system containing a peroxide in combination with ascorbic acid, barbiturate or sulfinic acid as a reducing agent is also preferred.

  Subsequently, when this is heat-processed at about 100-200 degreeC, a polycondensation reaction will occur and the separation membrane which concerns on this invention in which the separation functional layer derived from a silane coupling agent was formed in the porous support membrane surface can be obtained. Although the heating temperature depends on the material of the porous support membrane, if it is too high, dissolution occurs and the pores of the porous support membrane are blocked, resulting in a decrease in the amount of water produced in the composite semipermeable membrane. On the other hand, if it is too low, the polycondensation reaction becomes insufficient, and the removal rate decreases due to elution of the functional layer.

  In the above production method, the step of increasing the molecular weight of the silane coupling agent and the compound having one or more ethylenically unsaturated groups may be performed before the polycondensation step of the silane coupling agent, or after You can go. Moreover, you may carry out simultaneously.

  The composite semipermeable membrane thus obtained can be used as it is, but before use, it is preferable to hydrophilize the surface of the membrane with, for example, an alcohol-containing aqueous solution or an alkaline aqueous solution.

  When the difference in height of the separation membrane is given, embossing, water pressure, calendering, or the like can be performed at any step before, during, or after the heat treatment. Also. Processing may be performed before, during or after UV treatment.

  The thickness of the separation functional layer is not limited, but is preferably 5 to 3000 nm in terms of separation performance and transmission performance. In particular, it is preferably 5 to 300 nm for reverse osmosis, forward osmosis, and nanofiltration membranes.

  The thickness of the separation functional layer can be based on the conventional method for measuring the thickness of the separation membrane. For example, after embedding the separation membrane with a resin, an ultrathin section is prepared, and after treatment such as staining, It can be measured by observing with a scanning electron microscope. As the main measurement method, when the separation functional layer has a pleat structure, measurement is performed at intervals of 50 nm in the cross-sectional length direction of the pleat structure located above the porous support membrane, and the number of pleats is measured at 20 pieces. It can be obtained from the average.

  When a porous support membrane is used in the present invention, it can be used as a membrane that supports the separation functional layer while maintaining the performance as a separation membrane.

  Although the material used for a porous support membrane and its shape are not specifically limited, For example, the film | membrane which formed the porous support body in the base material can be illustrated. As the material for the porous support, polysulfone, cellulose acetate, polyvinyl chloride, epoxy resin or a mixture and lamination of these materials is used, and the chemical, mechanical and thermal stability is high, and the pore size is controlled. It is preferable to use easy polysulfone.

  For example, a solution of the above polysulfone in N, N-dimethylformamide (hereinafter referred to as DMF) is cast on a substrate described later, for example, a densely woven polyester cloth or non-woven fabric, to a certain thickness, It can be manufactured by wet coagulation with.

  The porous support membrane used in the present invention is “Office of Saleen Water Research and Development Progress Report” No. 359 (1968), the polymer concentration, the solvent temperature, and the poor solvent can be adjusted to produce the above-described form. 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. At this time, DMF as a solvent is rapidly volatilized on the surface portion that comes into contact with the coagulation liquid, and polysulfone coagulates rapidly, and fine communication holes having the portion where DMF is present as a core are generated.

  Further, in the interior from the surface portion toward the base material, the volatilization of DMF and the solidification of polysulfone proceed more slowly than the surface, so that the DMF tends to aggregate and form large nuclei, and thus generate. The communication hole becomes larger in diameter. Of course, the above nucleation conditions gradually change depending on the distance from the film surface, so that a support film having a smooth pore size distribution without a clear boundary is formed. The present invention relates to the polysulfone resin solution used in this forming step, the temperature of the polysulfone resin solution, the concentration of polysulfone, the relative humidity of the atmosphere in which it is applied, the time from application to immersion in the coagulation liquid, the temperature and composition of the coagulation liquid, etc. By adjusting the ratio, it is possible to obtain a polysulfone membrane in which the average porosity and the average pore diameter are controlled.

  Furthermore, you may use a base material at the point of the intensity | strength of a separation membrane, dimensional stability, and uneven | corrugated formation ability. As the base material, it is preferable to use a fibrous base material in terms of strength, unevenness-forming ability, and fluid permeability.

  As long as the porous support membrane is one that 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 distribution are particularly Although it is not limited, for example, on the surface on the side where the separation functional layer is formed, which has uniform and fine holes, or gradually has a large fine hole from the surface on the side where the separation functional layer is formed to the other surface. A porous support membrane in which the projected area equivalent circle diameter of the pores measured from the surface using an atomic force microscope, an electron microscope or the like is 1 nm or more and 100 nm or less is preferably used. In particular, it preferably has a projected area equivalent circle diameter of 3 to 50 nm in terms of interfacial polymerization reactivity and retention of the separation functional membrane.

  The thickness of the porous support membrane is not particularly limited, but it should be in the range of 20 to 500 μm in terms of the strength of the separation membrane, the difference in height of the separation membrane, and the morphological stability of the supply side and permeate side channels. Is more preferable, and it is 30-300 micrometers.

  The form of the porous support membrane 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, the porous support is peeled off from the substrate, and then cut by a 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 to 6 kV. A Hitachi S-900 electron microscope or the like can be used as the high-resolution field emission scanning electron microscope. The film thickness of the porous support membrane and the projected area equivalent circle diameter are determined from the obtained electron micrograph. The thickness of the support membrane and the pore diameter are average values, and the thickness of the support membrane is an average value of 20 points measured by cross-sectional observation in a direction perpendicular to the thickness direction at intervals of 20 μm. The hole diameter is an average value of the diameters corresponding to the projected area circles by counting 200 holes.

  Although it does not specifically limit as a base material, A fibrous base material is used preferably at the point which gives moderate mechanical strength, maintaining the separation and permeation | permeation performance of a separation membrane, and controlling the height difference of the surface of a separation membrane.

  As the fibrous base material, polyolefin, polyester, cellulose and the like are used, and polyolefin and polyester are preferable from the viewpoint of forming a difference in height of the separation membrane and from the viewpoint of shape retention. Moreover, what mixed several raw materials can also be used as a base material.

  The separation membrane element of the present invention has a difference in surface height between the first separation membrane 1 having a surface height difference of 50 μm or less in order to stably form the supply side and permeation side flow paths and to obtain high separation / permeation performance. However, it is essential that the second separation membranes 2 of 100 μm or more and 2000 μm or less are alternately arranged. Here, the first separation membrane 1 may or may not be processed to give a height difference. The height difference H0 of the surface of the first separation membrane 1 is preferably 35 μm or less, more preferably 20 μm. It is as follows.

  On the other hand, the second separation membrane 2 is preferably provided with a height difference of 200 μm or more and 1500 μm or less, particularly preferably 300 μm to 500 μm in order to stabilize the element supply side and permeation side flow paths and improve separation and permeation performance. 1000 μm. In the example shown in FIG. 1, the height difference H0 of the surface of the second separation membrane 2 is the sum of the height H1 of the convex portion on the supply fluid side and the height H2 of the convex portion on the permeate fluid side. The height H1 of the convex portion on the supply fluid side is preferably 150 μm to 500 μm. Moreover, it is preferable that the height H2 of the convex part on the permeating fluid side is 150 μm to 500 μm.

  The height difference on the surface of the separation functional layer can be measured using a commercially available shape measurement system or the like. For example, the height difference can be measured from a cross section by a laser microscope, or measured by a high-precision shape measurement system KS-1000 manufactured by Keyence.

  The method for providing the height difference is not particularly limited, and methods such as embossing, hydraulic forming, and calendering can be used for the separation membrane. Furthermore, the moldability of the separation functional layer, the porous support layer, and the substrate is preferably improved by performing a heat treatment at 40 to 150 ° C. at the time of molding of the separation membrane or after the molding, and the structural breakdown of the separation membrane due to molding can be suppressed. In addition, it is possible to improve the uneven shape retainability. The heat treatment temperature can be identified by using a known method by peeling only the base material from the separation membrane and performing DSC measurement on the base material.

  The embossing conditions can be appropriately determined according to the melting point and heat distortion temperature of the porous support membrane. For example, when using a heat-resistant resin such as polysulfone, the heat treatment temperature is preferably 100 to 150 ° C, When using an epoxy resin, 80-130 degreeC is preferable. The molding speed is preferably 0.5 to 20 m / min.

  In the case of hydroforming, a molding member is arranged on the rear surface of the separation membrane (permeate fluid side), and a liquid is pressurized from the separation membrane surface (supply fluid side) to form a height difference in the separation membrane, followed by heat treatment. The pressure at the time of molding is not particularly limited as long as a height difference of 100 μm or more and 2000 μm or less can be formed on the separation membrane, but it is 0.5 to 5 MPa in order to form a stable flow path without causing a decrease in membrane performance. Is preferred. The heat treatment temperature is preferably 50 ° C to 100 ° C.

  The forming step is not particularly limited, but the step of processing the support membrane, the step of processing the base material, the step of processing the support film, the laminate laminated with the base material, the separation membrane A processing step can be preferably used.

  The shape of the height difference is not particularly limited, but it is important to reduce the flow resistance of the flow path and stabilize the flow path when the fluid is supplied to and passed through the separation membrane element. 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 area of the convex portion having a position higher in the upper surface direction than the center line of the height difference is preferably 5% to 80% with respect to the observation area (two-dimensional area) from the upper surface of the film. In view of flow path stability, it is particularly preferably 10% to 60%.

  The structure of the separation membrane element of the present invention is not particularly limited as long as the above sheet-like separation membrane can be used, and examples thereof include a spiral type, a disk type, and a flat membrane type.

  Next, the manufacturing method of the separation membrane element of this invention is demonstrated.

  The method for producing the separation membrane element of the present invention is not limited, but the first separation membrane 1 obtained by laminating the polyamide separation functional layer on the porous support membrane and the substrate and having a surface height difference of 50 μm or less; A typical method for manufacturing an element by alternately arranging the second separation membranes 2 provided with a height difference H0 of 100 μm or more and 2000 μm or less obtained by forming unevenness on the separation membrane 1 will be described. In addition, as described above, the concave-convex forming can be taken before, during or after the separation membrane forming step.

  After combining the porous support membrane and the substrate, the polyfunctional amine aqueous solution is applied to the porous support membrane, the excess amine aqueous solution is removed with an air knife, etc., and then the polyfunctional acid halide-containing solution is applied, and the polyamide is applied. A separation functional layer is formed. Desirably, the organic solvent is immiscible with water, dissolves the polyfunctional acid halide, does not break the porous support membrane, and is inert to the polyfunctional amine compound and polyfunctional acid halide. Anything is acceptable. Preferred examples include hydrocarbon compounds such as n-hexane, n-octane, and n-decane. Furthermore, chemical treatment with chlorine, acid, alkali, nitrous acid or the like is performed to improve separation performance and permeation performance as necessary, and the monomer is washed to obtain a continuous sheet of a smooth separation membrane.

Thereafter, the continuous sheet is cut into an appropriate size and embossed on one half of the obtained sheet-like separation membrane (conical shape: diameter 1 mm, height 0.7 mm, tip R = 0.2 mm) , Spacing 5 mm). Subsequently, a separation membrane preheated to 80 ° C. is passed between calender rolls heated to 95 ° C. at a pressure of 100 kg / cm ² so that one half is a smooth portion and the other half is a portion having an uneven shape. A sheet-like separation membrane is produced. Using a conventional element manufacturing apparatus, the sheet is folded in half so that smooth portions and uneven portions are alternately arranged to produce an 8-inch element having 26 leaves and an effective leaf area of 37 m ² . As an element manufacturing method, a method described in a reference document (Japanese Patent Publication No. 44-14216, Japanese Patent Publication No. 4-11928, Japanese Patent Laid-Open No. 11-226366) can be used.

  The means for alternately arranging the first separation membrane 1 having a surface height difference of 50 μm or less and the second separation membrane 2 having a surface height difference of 100 μm or more and 2000 μm or less is not particularly limited. It can also be produced by alternately stacking separation membrane sheets having a height difference and separation membrane sheets having a height difference of 100 μm or more and 2000 μm or less on the surface.

  The separation membrane element of the present invention manufactured as described above can further be a separation membrane module connected in series or in parallel and housed in a pressure vessel.

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

  The higher the operating pressure of the fluid separator, the higher the removal rate, but the energy required for operation also increases, and considering the retention of the supply flow path and permeation flow path of the membrane element, the membrane module is covered. The operating pressure when passing through the treated water is preferably 0.2 MPa or more and 5 MPa or less. As the feed water temperature rises, the salt removal rate decreases, but as the feed water temperature decreases, the membrane permeation flux also decreases. In addition, when the pH of the feed water becomes high, scales such as magnesium may be generated in the case of feed water with a high salt concentration such as seawater, and there is a concern about deterioration of the membrane due to high pH operation. Is preferred.

  The fluid to be treated by the separation membrane element of the present invention is not particularly limited, but when used for water treatment, as raw water, 500 mg / L to 100 g / L TDS (Total Dissolved Solids: total seawater, brine, wastewater, etc.) Liquid mixture containing dissolved solids). In general, TDS refers to the total dissolved solid content, and is expressed as “mass ÷ volume” or “weight ratio”. According to the definition, the solution filtered through a 0.45 micron filter can be calculated from the weight of the residue by evaporating at a temperature of 39.5 to 40.5 ° C., but more simply converted from practical salt (S) To do.

  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.

(Separation membrane surface height difference)
Using a high precision shape measurement system KS-1000 manufactured by Keyence, the average height difference was analyzed from the surface measurement results of 5 cm × 5 cm. A portion having a height difference of 10 μm or more was measured, and a value obtained by summing up the values of the respective heights was divided by the number of the total measurement portions.

(Desalination rate (TDS removal rate))
TDS removal rate (%) = 100 × {1− (TDS concentration in permeated water / TDS concentration in feed water)}.

  In addition, when the measured value after 1 hour and the measured value after 8 hours changed 0.1% or more, the result was added.

(Water production)
The amount of water permeated through the membrane element of the feed water (brine water) was expressed as the amount of water produced per cubic element (cubic meter) per day (m ³ / day). In addition, it added when the measured value after 1 hour and the measured value after 8 hours were 1 m < ³ > / day or more.

(Example 1, Comparative Example 1-2)
A non-woven fabric made of polyester fiber (yarn diameter: 1 dtex, thickness: about 100 μm, air permeability: 1 cc / cm ² / sec), 15.0% by weight of polysulfone and DMF solution with a thickness of 180 μm at room temperature (25 ° C.) A porous support membrane (thickness: 140 μm) roll made of a fiber-reinforced polysulfone support membrane was prepared by casting, immediately immersing in pure water, and allowing to stand for 5 minutes.

  Thereafter, the porous support membrane roll is unwound, and the polysulfone surface is coated with 1.8% by weight of m-PDA and 4.5% by weight of ε-caprolactam in an aqueous solution, and nitrogen is blown from an air nozzle from the support membrane surface. After removing the excess aqueous solution, an n-decane solution at 25 ° C. containing 0.06% by weight of trimesic acid chloride was applied so that the surface was completely wetted. Thereafter, the excess solution was removed from the membrane by air blow and washed with hot water at 80 ° C. to obtain a separation membrane roll having a surface height difference of 50 μm or less (12 μm).

After the roll-shaped continuous sheet is cut into a predetermined size, the surface of the obtained sheet-shaped separation membrane is embossed in the shape shown in Table 1 and given a height difference, so that the half has a surface height difference. A sheet-like separation membrane having a difference of 50 μm or less (12 μm) and the other half having a surface height difference of 100 μm or more and 2000 μm or less (600 μm) was produced. Subsequently, the sheet is heat-treated at 90 ° C. for 1 minute, and then continuously laminated while being folded so that smooth portions and uneven portions are alternately arranged, so that the effective area at the separation membrane element is 37 m ^2. 26 leaf-like materials having a width of 930 mm were prepared. When DSC of the substrate was measured, an endothermic peak was observed in the vicinity of 90 ° C.

  Here, the pitch in the table indicates the horizontal distance from the highest point of the high part on the surface with a difference in height to the highest part of the adjacent high part, and counts for 200, and the average value did.

  After that, a separation membrane element was produced by spirally winding 26 leaf-like objects around a water collection pipe, and a film was wound around the outer periphery, fixed with tape, edge cut, end plate attachment, filament winding, and 8 inches. An element was produced. Table 2 shows the performance when the element was placed in a pressure vessel and operated at a raw water of 500 mg / L sodium chloride, an operating pressure of 0.75 MPa, an operating temperature of 25 ° C., and a pH of 7 (recovery rate of 15%).

  Without molding, net (thickness: 900 μm, pitch: 3 mm × 3 mm) is supplied side flow path material, tricot (thickness: 300 μm, groove width: 200 μm, ridge width: 300 μm, groove depth: 105 μm) permeate side Although both the removal rate and the amount of fresh water were reduced as compared with Comparative Example 1 (conventional separation membrane element) used as the channel material, both the removal rate and the amount of fresh water were increased as compared with Comparative Example 2 composed only of the uneven membrane. . In Comparative Example 2, when rhombus embossing was performed on the entire surface of the separation membrane, the membrane was damaged due to the effect of a partial narrowing of the cross-section of the flow path due to the separation membrane separation within the element, resulting in a large removal rate and water production amount. Seems to have deteriorated.

(Examples 2 to 5)
In Example 2, when the shape of the concavo-convex portion of the second separation membrane was made into a net shape, as shown in Table 2, both the removal rate and the amount of fresh water were excellent.

  In Example 3, when the height difference of the 2nd separation membrane was enlarged with the same shape as Example 2, while the amount of fresh water was improved with respect to Example 2, it resulted in a somewhat reduced removal rate.

  In Example 4, when the height difference, shape, and the like of the second separation membrane of Example 1 were changed, the amount of water produced was slightly increased.

  In Example 5, when the shape and the like of the second separation membrane of Example 1 were changed, both the removal rate and the amount of fresh water increased.

(Comparative Examples 3 and 4)
As a result of making the height difference of the second separation membrane out of the scope of the present invention, the flow path forming ability was inferior and the performance was greatly reduced.

  As described above, the separation membrane element of the present invention has high freshness performance, stable operation, and excellent removal performance in addition to the omission of the flow path material.

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

1: First separation membrane 2: Second separation membrane 3: Supply fluid side 4: Permeate fluid side H0: Difference in surface height (= H1 + H2)
H1: Height of convex part on supply fluid side H2: Height of convex part on permeate fluid side

Claims (1)

  A separation membrane element, wherein a first separation membrane having a surface height difference of 50 μm or less and a second separation membrane having a surface height difference of 100 μm or more and 2000 μm or less are alternately arranged.

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