JP2013223861A - Composite diaphragm - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite diaphragm with high boron filter performance and high chemical resistance.SOLUTION: A composite diaphragm includes a polyamide separation functional layer formed on a microporous supporting film comprising a base material and a porous support. The irreversible endotherm of the polyamide separation functional layer within the range of -20 to 150°C in the process of an initial heat-up measured by a temperature modulation DSC method, is not less than 275 J/g. The yellowness of the polyamide separation functional layer is not less than 10 and not more than 40.

Description

  The present invention relates to a composite semipermeable membrane useful for selective separation of a liquid mixture, and more particularly to a composite semipermeable membrane having high boron blocking performance and high chemical resistance.

  Regarding the separation of mixtures, there are various techniques for removing substances (eg, salts) dissolved in a solvent (eg, water), but in recent years, the use of membrane separation methods has expanded as a process for saving energy and resources. doing. Membranes used in membrane separation methods include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes. These membranes can be used for beverages such as seawater, brine, and water containing harmful substances. It is used to obtain water, to manufacture industrial ultrapure water, to treat wastewater, to recover valuable materials.

  The majority of currently marketed reverse osmosis membranes and nanofiltration membranes are composite semipermeable membranes, which have an active layer in which a gel layer and a polymer are cross-linked on a microporous support membrane, and on a microporous support membrane. And having an active layer in which monomers are polycondensed. Among them, the composite semipermeable membrane obtained by coating a separation function layer made of a crosslinked polyamide obtained by polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide on a microporous support membrane is permeable and selective. It is widely used as a separation membrane with high separability.

  However, if the composite semipermeable membrane continues to be used, dirt adheres to the membrane surface with the elapsed time of use, and the membrane permeation flux of the membrane decreases. For this reason, chemical cleaning with alkali or acid is required after a certain period of operation. Therefore, in order to continue stable operation over a long period of time, development of a composite semipermeable membrane with little change in membrane performance before and after cleaning with chemicals such as alkali and acid is desired.

  In order to improve the alkali resistance of the composite semipermeable membrane, a method (Patent Document 1) is disclosed in which a hydrogen ion concentration aqueous solution having a pH of 9 to 13 is brought into contact with the composite semipermeable membrane. Moreover, in order to improve the acid resistance of a composite semipermeable membrane, a method (Patent Document 2) in which a cyclic sulfate is brought into contact with the composite semipermeable membrane is disclosed.

  Boron has toxicity such as causing onset of neuropathy and growth inhibition to human bodies and animals and plants, but since it is contained in seawater, boron removal is important in seawater desalination. Thus, various means for improving the boron removal performance of the composite semipermeable membrane have been proposed (Patent Documents 3 and 4). Patent Document 3 discloses a method of improving the performance by heat-treating a composite semipermeable membrane formed by interfacial polymerization. Patent Document 4 discloses a method of bringing a composite semipermeable membrane formed by interfacial polymerization into contact with a bromine-containing free chlorine aqueous solution.

JP 2006-102624 A JP 2010-234284 A JP-A-11-19493 JP 2001-259388 A

However, even in these composite semipermeable membranes, when the seawater having a temperature of 25 ° C., a pH of 6.5, a boron concentration of 5 ppm, and a TDS concentration of 3.5% by weight is permeated at an operating pressure of 5.5 MPa, the membrane permeation flux is 0.00. The boron removal rate is at most about 91 to 92% at 5 m ³ / m ² · day or less, and the development of a composite semipermeable membrane having higher boron blocking performance has been desired.

  An object of the present invention is to provide a high-performance composite semipermeable membrane having high boron blocking performance and little change in membrane performance before and after chemical cleaning.

In order to achieve the above object, the composite semipermeable membrane of the present invention has one of the following configurations.
(1) A composite semipermeable membrane in which a polyamide separation functional layer is formed on a microporous support membrane comprising a base material and a porous support, and in an initial heating process measured using a temperature modulation DSC method An irreversible endothermic amount of the polyamide separation functional layer in the range of −20 to 150 ° C. is 275 J / g or more, and the yellowness of the polyamide separation functional layer is 10 or more and 40 or less. film.
(2) The composite semipermeable membrane according to (1), wherein the substrate is a long-fiber nonwoven fabric.
(3) The base material is a laminated nonwoven fabric in which 2 to 5 layers of nonwoven fabric are laminated, and has a basis weight of 30 to 150 g / m ^{2. The} composite semipermeable material according to (1) or (2) film.

  The composite semipermeable membrane of the present invention is a high performance composite semipermeable membrane having a high boron removal rate and little change in membrane performance before and after chemical cleaning. By using this membrane, stable operation is expected over a long period of time when desalination of brine or seawater.

1. Composite Semipermeable Membrane The composite semipermeable membrane of the present invention comprises a polyamide separation functional layer formed on a microporous support membrane, and has a temperature of -20 to 150 ° C. in an initial temperature rising process measured using a temperature modulation DSC method. The irreversible endothermic amount of the polyamide separation functional layer in the range is 275 J / g or more, and the yellowness of the polyamide separation functional layer is 10 or more and 40 or less. This composite semipermeable membrane forms a polyamide separation functional layer formed by polycondensation of a polyfunctional amine and a polyfunctional acid halide on a microporous support membrane comprising a base material and a porous support. The separation functional layer is washed with an aqueous solution of 60 ° C. or less, and the polyamide separation functional layer is held with a compound having a primary amino group, and further reacted with the primary amino group to produce a diazonium salt or a derivative thereof. It can be produced by bringing a reagent into contact.

(1-1) Microporous support membrane In the present invention, the microporous support membrane has substantially no separation performance for ions or the like, and gives strength to the separation functional layer having separation performance substantially. It is.

  The thickness of the microporous support membrane described above affects the strength of the composite semipermeable membrane and the packing density when it is used as a membrane element. In order to obtain sufficient mechanical strength and packing density, the thickness of the microporous support membrane is preferably in the range of 30 to 300 μm, more preferably in the range of 50 to 250 μm. The size and distribution of pores of the microporous support membrane are not particularly limited.For example, uniform and fine pores, or gradually having large pores from the surface on the side where the separation functional layer is formed to the other surface, In addition, a microporous support membrane having a micropore size of 0.1 nm to 100 nm on the surface on the side where the separation functional layer is formed is preferable.

(1-1-1) Substrate The material used for the microporous support membrane and its shape are not particularly limited. Examples of the substrate of the microporous support membrane include a fabric mainly composed of at least one selected from polyester or aromatic polyamide. Among them, a polyester fabric having high mechanical and thermal stability is particularly preferable. As the form of the fabric, a long fiber nonwoven fabric, a short fiber nonwoven fabric, or a woven or knitted fabric can be preferably used. The polyester forming the fabric is a polyester polymer comprising an acid component and an alcohol component.

  As the acid component, an aromatic carboxylic acid such as terephthalic acid, isophthalic acid or phthalic acid, an aliphatic dicarboxylic acid such as adipic acid or sebacic acid, or an alicyclic dicarboxylic acid such as cyclohexanecarboxylic acid can be used.

  As the alcohol component, ethylene glycol, diethylene glycol, polyethylene glycol, or the like can be used.

  Examples of the polyester polymer include polyethylene terephthalate resin, polybutylene terephthalate resin, polytrimethylene terephthalate resin, polyethylene naphthalate resin, polylactic acid resin, and polybutylene succinate resin. Examples include coalescence.

  It is preferable to use a fibrous base material for the fabric used for the base material. Examples of the fibrous base material include nonwoven fabrics such as long fiber nonwoven fabrics and short fiber nonwoven fabrics. In particular, since the base material is made of a long-fiber non-woven fabric composed of thermoplastic continuous filaments, it suppresses non-uniformity and membrane defects when casting a polymer solution caused by fuzz, which occurs when a short-fiber non-woven fabric is used. be able to. Here, the long fiber nonwoven fabric is a nonwoven fabric having an average fiber length of 30 cm or more and an average fiber diameter of 1 to 100 μm.

  In the case of continuous film formation, since a tension is applied in the film forming direction, it is preferable to use a long-fiber nonwoven fabric that is more excellent in dimensional stability for the substrate. In addition to maintaining high strength, it not only achieves a high effect of preventing membrane breakage, but also improves formability as a laminate including a porous support and a substrate when imparting irregularities to the separation membrane. In addition, the uneven shape on the surface of the separation membrane is stable, which is preferable.

  In addition, a long fiber nonwoven fabric is preferable because the base material can be sufficiently impregnated with a polymer solution containing polysulfone or the like serving as a porous support. By sufficiently impregnating the base material with the polymer solution, the adhesion between the porous support and the base material is improved, and the physical stability of the microporous support film can be enhanced. In addition, when the base material is impregnated with the polymer solution, the rate of substitution of the solvent with the non-solvent is increased during the phase separation for forming the porous support, compared to when the base material is not impregnated with the base material . As a result, generation of macro voids can be suppressed.

  The nonwoven fabric constituting the base material of the present invention may be a single layer, but is preferably a laminated nonwoven fabric obtained by laminating and integrating two or more layers of nonwoven fabric. By using laminated non-woven fabrics, the basis weight of the micro area becomes uniform, and by forming a laminated interface, over-penetration is suppressed by suppressing polymer solution casting. It can be suitably used as a material. The number of laminated nonwoven fabrics is preferably 2 to 5 layers. If the number of laminated nonwoven fabrics is 2 or more, the basis weight uniformity of the micro area is improved and sufficient uniformity is obtained as compared with the case of a single layer. Moreover, if the number of laminated layers is 5 or less, wrinkles can be formed during lamination, and peeling between layers can be suppressed.

  In particular, the fibers disposed on the surface opposite to the porous support (lower surface) are vertically oriented with respect to the film forming direction, so that the strength can be maintained and film breakage and the like can be prevented.

The basis weight of the laminated nonwoven fabric constituting the substrate of the present invention is preferably 30 to 150 g / m ² , more preferably 40 to 120 g / m ² , and still more preferably 50 to 90 g / m 2. ² . If the basis weight of the laminated non-woven fabric is 30 g / m ² or more, a microporous support membrane having a uniform thickness can be obtained with a good film forming property with little over-penetration during casting of the polymer solution. Can be obtained. On the other hand, when the basis weight of the laminated nonwoven fabric exceeds 150 g / m ² , the amount of the polymer solution impregnated into the base material is decreased, so that macro voids may be generated. When the nonwoven fabric is laminated in two or more layers, the basis weight of the minute region becomes uniform and can be controlled within the above range.

  In particular, by improving the basis weight uniformity of the base material in which the long-fiber nonwoven fabric is laminated in two or more layers, the mechanical properties due to partial deterioration of the base material when the composite semipermeable membrane comes into contact with chemicals such as acid and alkali. It is possible to suppress a decrease in membrane performance caused by a decrease in the thickness. When the composite semipermeable membrane comes into contact with alkali, the substrate is hydrolyzed by the catalytic action of carboxylic acid end groups. If the basis weight of the base material is non-uniform, when the composite semipermeable membrane comes into contact with a chemical such as acid or alkali, the mechanical properties are lowered due to partial deterioration of the base material, and the membrane performance is lowered.

  In order to obtain high membrane performance, it is important to control the concentration of the compound having a primary amino group in the mixture of the polyamide separation functional layer and the microporous support membrane as described later. By making the substrate into a long-fiber nonwoven fabric, the macrovoids of the porous support are reduced, so the concentration of compounds having primary amino groups present in the microporous support membrane can be precisely controlled, and the distribution of compounds Becomes uniform. As a result, the reaction occurs uniformly, and the film performance and chemical resistance can be improved.

  In addition, since the long-fiber non-woven fabric is laminated in two or more layers, the basis weight uniformity of the base material is improved, and the over-penetration is suppressed by suppressing excessive permeation during casting of the polymer solution. A microporous support membrane having the following can be obtained. As a result, the concentration of the compound having primary amino groups present in the substrate and the porous support can be precisely controlled, and the distribution of the compound concentration can be made uniform, resulting in uniform reaction and improved membrane performance and chemical resistance. Can be improved.

(1-1-2) Porous support As the material of the porous support formed on the substrate, polysulfone, cellulose acetate, polyvinyl chloride, or a mixture thereof is preferably used. It is particularly preferable to use polysulfone having high mechanical and thermal stability.

Specifically, it is preferable to use polysulfone composed of repeating units represented by the following chemical formula because the pore diameter of the porous support can be easily controlled and the dimensional stability is high.

  For example, an N, N-dimethylformamide (hereinafter referred to as DMF) solution of the above polysulfone is cast to a certain thickness on the above-mentioned base material, and is wet-coagulated in water, thereby increasing the size of the surface. It is possible to obtain a microporous support membrane having fine pores having a diameter of several tens of nm or less.

  The thickness of the microporous support membrane affects the strength of the composite semipermeable membrane and the packing density when it is used as an element. In order to obtain sufficient mechanical strength and packing density, the thickness of the microporous support membrane is preferably in the range of 30 to 300 μm, more preferably in the range of 50 to 250 μm. Moreover, it is preferable that the thickness of a porous support body exists in the range of 10-200 micrometers, More preferably, it exists in the range of 20-100 micrometers.

  The form of the microporous support membrane can be observed with a scanning electron microscope, a transmission electron microscope, or an atomic microscope. For example, when observing a porous support constituting a microporous support membrane with a scanning electron microscope, the porous support is peeled off from the substrate, and then the porous support is cut by a freeze cleaving method. 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 and surface pore diameter of the porous support constituting the microporous support film are determined from the obtained electron micrograph. In addition, the thickness and the hole diameter in this invention mean an average value.

  The microporous support membrane used in the present invention may be selected from various commercially available materials such as “Millipore Filter VSWP” (trade name) manufactured by Millipore and “Ultra Filter UK10” (trade name) manufactured by Toyo Roshi Kaisha. Although it is possible, “Office of Saleen Water Research and Development Progress Report” No. 359 (1968).

(1-2) Polyamide separation functional layer In the present invention, the polyamide constituting the separation functional layer 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.

  The thickness of the polyamide separation functional layer is usually in the range of 0.01 to 1 μm, preferably in the range of 0.1 to 0.5 μm, in order to obtain sufficient separation performance and permeated water amount.

  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 a 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 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.

  The polyamide separation functional layer constituting the composite semipermeable membrane of the present invention has an irreversible endothermic amount of 275 J / g or more in the range of −20 to 150 ° C. in the initial temperature rising process measured using the temperature modulation DSC method. It is characterized by being.

  Since polyamide is a hydrophilic polymer, it retains a lot of water of hydration, and the endotherm in this temperature range is due to the elimination of water of hydration. The amount of hydration water in the polyamide separation functional layer is related to the higher-order structure of the polyamide, and a polyamide having more hydration water forms a structure with larger intermolecular voids. The smaller the intermolecular gap of the polyamide separation functional layer, the higher the solute removal performance of the composite semipermeable membrane. On the other hand, if the intermolecular gap is too small, the chemical resistance is lowered. This is because the polyamide has an ionic functional group such as an amino group or a carboxy group, and its higher-order structure is destabilized by the interaction between charged sites caused by contact with chemicals such as acid and alkali. is there. That is, the polyamide separation functional layer of the composite semipermeable membrane having excellent chemical resistance according to the present invention forms a structure that retains a large amount of hydration water.

  The hydration state in the polyamide separation functional layer can be analyzed by a temperature modulation DSC method. The temperature-modulated DSC method is a thermal analysis method in which heating and cooling are repeated with a constant period and amplitude, and the average temperature is raised and measured. The signal observed as the total heat flow is a reversible component derived from the glass transition and the like. It can be separated into irreversible components derived from dehydration and the like. After the substrate is physically peeled and removed from the composite semipermeable membrane, the polyamide separation functional layer obtained by extracting and removing the porous support with a solvent such as dichloromethane is measured as an analytical sample. The endothermic amount of the irreversible component in the range of −20 to 150 ° C. is analyzed. The endothermic value is obtained as an average of three measurements. As a result of intensive studies, the inventors have found that a composite semipermeable membrane having an irreversible endothermic amount of a polyamide separation functional layer of 275 J / g or more is excellent in chemical resistance, leading to the present invention. The upper limit of the endothermic amount of the irreversible component of the polyamide separation functional layer is not particularly limited, but can be 2000 J / g, preferably 500 J / g.

  In the present invention, the temperature modulation DSC method is measured with an average temperature increase rate of 2 ° C./min, a temperature modulation period of 60 seconds, a temperature modulation amplitude of ± 1 ° C., and an irreversible in the initial temperature increase process in the range of −20 to 150 ° C. The endothermic amount of the component is measured.

  Further, as a result of intensive studies, the present inventors have found that there is a close relationship between the yellowness of the polyamide separation functional layer, the water permeability of the composite semipermeable membrane, and the boron removal rate.

  Yellowness is the degree to which the hue deviates from the colorless or white color of the polymer specified in Japanese Industrial Standard JIS K7373 in the yellow direction, and is expressed as a positive amount.

  The yellowness of the separation functional layer can be measured with a color meter. Place the composite semipermeable membrane on the glass plate with the separation functional layer side down, and then dissolve and remove the microporous support membrane with a solvent that dissolves only the microporous support membrane, leaving the separation on the glass plate It can be measured by transmission measurement of the functional layer sample. In addition, when putting a composite semipermeable membrane on a glass plate, it is preferable to peel beforehand the fabric for reinforcing the below-mentioned microporous support membrane. As the color meter, SM color computer SM-7 manufactured by Suga Test Instruments Co., Ltd. can be used.

  The polyamide separation functional layer having a yellowness of 10 or more is a polyamide separation functional layer having a structure having an electron donating group and an electron withdrawing group in an aromatic ring and / or a structure extending conjugation in the polyamide separation functional layer. Examples of the electron donating group include a hydroxyl group, an amino group, and an alkoxy group. Examples of the electron withdrawing group include a carboxyl group, a sulfonic acid group, an aldehyde group, an acyl group, an aminocarbonyl group, an aminosulfonyl group, a cyano group, a nitro group, and a nitroso group. Examples of the structure extending the conjugation include polycyclic aromatic rings, polycyclic heterocycles, ethenylene groups, ethynylene groups, azo groups, imino groups, arylene groups, heteroarylene groups, and combinations of these structures. By having these structures, the polyamide separation functional layer exhibits a yellowness of 10 or more. However, when the amount of these structures is increased, the yellowness is greater than 40. Moreover, when these structures are combined in multiple, the structure part becomes large, it exhibits red, and yellowness becomes larger than 40. When the yellowness is larger than 40, when the amount of the structure is increased and the structure portion is enlarged, pores on the surface and inside of the polyamide separation functional layer are blocked and the boron removal rate is increased, but the water permeability is greatly decreased. If the yellowness is 10 or more and 40 or less, the boron removal rate can be increased without excessively reducing the water permeability.

  In order to impart the structure to the polyamide separation functional layer, there are a method of supporting the compound having the structure on the polyamide separation functional layer and / or a method of chemically treating the polyamide separation functional layer to impart the structure. Can be mentioned. In order to maintain the structure for a long time, a method of chemically treating the polyamide separation functional layer to impart the structure is preferable.

As a method for chemically treating a polyamide separation functional layer, a reagent that forms a diazonium salt or a derivative thereof by reacting a composite semipermeable membrane having a primary amino group in a polyamide separation functional layer with a primary amino group The method of making it contact is mentioned. The formed diazonium salt or derivative thereof reacts with an aromatic compound to form an azo group. Conjugation is extended by this azo group, and the polyamide separation functional layer is colored yellow to orange, and has a yellowness of 10 or more. Furthermore, in order for the yellowness to be 10 or more and 40 or less, as will be described later, the polyamide separation functional layer is brought into contact with a compound having a primary amino group, and the contact-treated polyamide separation functional layer and the microporous support are formed. compound concentrations having a primary amino group in the mixture of the membrane may in the range of from 0.01~0.4g / m ^2. The molecular weight of the carbon skeleton excluding the functional group of the compound having a primary amino group is preferably 500 or less.

  The primary amino group possessed by the polyamide separation functional layer is the partial structure or terminal functional group of the polyamide that forms the separation functional layer, or the partial structure or terminal function of the polyamide that forms the separation functional layer. A primary amino group obtained by further retaining a compound having a primary amino group in the separation functional layer having a primary amino group as a group may be used. In order to obtain a higher boron removal rate, it is preferable to retain a compound having a primary amino group in the separation functional layer.

  Examples of the compound having a primary amino group include aliphatic amines, cycloaliphatic amines, aromatic amines, and heteroaromatic amines. From the viewpoint of the stability of the diazonium salt or derivative thereof produced, aromatic amines and heteroaromatic amines are preferred.

  Examples of the reagent that reacts with a primary amino group to produce a diazonium salt or a derivative thereof include aqueous solutions of nitrous acid and salts thereof, nitrosyl compounds, and the like. Since an aqueous solution of nitrous acid or a nitrosyl compound easily generates gas and decomposes, it is preferable to sequentially generate nitrous acid by, for example, a reaction between nitrite and an acidic solution.

2. Next, a method for producing a composite semipermeable membrane according to the present invention will be described. The production method includes (2-1) a microporous support membrane forming step and (2-2) a separation functional layer forming step.

(2-1) Microporous support membrane forming step The microporous support membrane forming step is a step of applying a polymer solution, which is a component of the porous support, to the substrate. The step of impregnating the polymer solution as a component, and the base material impregnated with the polymer solution into a solvent (non-solvent) having a low polymer solubility compared to a good solvent for the polymer as a component of the porous support A step of immersing the polymer in a coagulation bath to solidify the polymer to form a three-dimensional network structure.

  The step of forming the microporous support membrane may further include a step of preparing a polymer solution by dissolving a polymer that is a component of the porous support in a good solvent for the polymer.

  The solvent in which the polymer is dissolved may be any good polymer solvent. The good solvent of the present invention dissolves a polymer material.

  As the good solvent, although it varies depending on the polymer, generally, for example, lower alkyl such as N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, methyl ethyl ketone, acetone, tetrahydrofuran, tetramethylurea, trimethyl phosphate, etc. Examples include ketones, esters, amides, and the like, and mixed solvents thereof.

  As the non-solvent, although it varies depending on the polymer, for example, water, hexane, pentane, benzene, toluene, methanol, ethanol, carbon tetrachloride, o-dichlorobenzene, trichloroethylene, ethylene glycol, diethylene glycol, triethylene glycol, Aliphatic hydrocarbons such as propylene glycol, butylene glycol, pentanediol, hexanediol, low molecular weight polyethylene glycol, aromatic hydrocarbons, aliphatic polyhydric alcohols, aromatic polyhydric alcohols, chlorinated hydrocarbons, or other chlorine And organic solvents and mixed solvents thereof.

  The polymer solution may contain an additive for adjusting the pore size, porosity, hydrophilicity, elastic modulus and the like of the microporous support membrane.

  Additives for adjusting the pore size and porosity include water, alcohols, polyethylene glycol, polyvinyl pyrrolidone, polyvinyl alcohol, water-soluble polymers such as polyacrylic acid or salts thereof, lithium chloride, sodium chloride, calcium chloride Inorganic salts such as lithium nitrate, formaldehyde, formamide and the like are exemplified, but not limited thereto. Examples of additives for adjusting hydrophilicity and elastic modulus include various surfactants.

  As the coagulation bath, water is usually used, but any non-solvent that does not dissolve the polymer may be used.

  The membrane form of the microporous support membrane changes depending on the composition of the coagulation bath, and the membrane-forming property of the composite membrane also changes accordingly.

  Further, the temperature of the coagulation bath is preferably -20 ° C to 100 ° C. More preferably, it is 10-30 degreeC. If it is higher than this range, the vibration of the coagulation bath surface becomes intense due to thermal motion, and the smoothness of the film surface after film formation tends to decrease. On the other hand, if it is too low, the coagulation rate will be slow, causing a problem in film forming properties.

  It is also important to control the impregnation of the polymer solution into the substrate. In order to control the impregnation of the polymer solution into the base material, for example, there is a method of controlling the time until the polymer solution is immersed on the base material after being applied on the base material.

  The time until the polymer solution is applied on the substrate and then immersed in the coagulation bath is preferably in the range of usually 0.1 to 5 seconds, more preferably in the range of 0.1 to 4 seconds. is there.

  If the time until dipping in the coagulation bath is within this range, the organic solvent solution containing the polymer is sufficiently impregnated between the fibers of the base material and then solidified. As a result, the microporous support membrane is firmly bonded to the substrate by the anchor effect, and the microporous support membrane of the present invention can be obtained.

  Moreover, since the impregnation property to the base material of a polymer solution improves by using a long-fiber nonwoven fabric as a base material, time until it is immersed in a coagulation bath can be shortened. When the time until immersion is long, the separation functional layer side surface (upper surface) becomes dense and the filtration resistance increases, so that the membrane permeation flux of the composite semipermeable membrane decreases. In addition, what is necessary is just to adjust the preferable range of time until it immerses in a coagulation bath suitably with the viscosity etc. of the polymer solution to be used.

  Next, the microporous support membrane obtained under such preferable conditions is washed with hot water in order to remove the membrane-forming solvent remaining in the membrane. The temperature of the hot water at this time is preferably 50 to 100 ° C, more preferably 60 to 95 ° C. When the temperature of the hot water is 100 ° C. or lower, the degree of shrinkage of the microporous support membrane is reduced, and a decrease in water permeability is suppressed. Moreover, a big cleaning effect is acquired because the temperature of hot water is 50 degreeC or more.

(2-2) Separation functional layer forming step The separation functional layer constituting the composite semipermeable membrane of the present invention comprises an aqueous solution containing the aforementioned polyfunctional amine and an organic solvent solution containing the polyfunctional acid halide. The skeleton can be formed by interfacial polycondensation on the surface of the microporous support membrane. The organic solvent solution containing the polyfunctional acid halide is immiscible with water.

The composite semipermeable membrane of the present invention comprises a step of forming a polyamide separation functional layer by contacting a polyfunctional amine aqueous solution and a polyfunctional acid halide solution on a microporous support membrane, and the formed polyamide separation functional layer. A step of washing with an aqueous solution of 60 ° C. or less, a step of bringing the obtained polyamide separation functional layer into contact with a compound having a primary amino group, and a reagent that reacts with the primary amino group to produce a diazonium salt or a derivative thereof. It can be obtained by a method for producing a composite semipermeable membrane comprising a contacting step and a contacting step with a reagent that reacts with a diazonium salt or a derivative thereof. At this time, the concentration of the compound having primary amino groups in the mixture of the polyamide separation functional layer and the microporous support membrane after contacting the compound having primary amino groups with the polyamide separation functional layer is 0.01 to 0. It is better to be within the range of 4 g / m ² . Hereinafter, each manufacturing process for manufacturing the composite semipermeable membrane of the present invention will be described in detail.

  The separation functional layer in the composite semipermeable membrane uses, for example, an aqueous solution containing the aforementioned polyfunctional amine and a water-immiscible organic solvent solution containing a polyfunctional acid halide, and a microporous support membrane. The skeleton can be formed by interfacial polycondensation on the surface.

  Here, the concentration of the polyfunctional amine in the polyfunctional amine aqueous solution is preferably in the range of 0.1 to 20% by weight, more preferably in the range of 0.5 to 15% by weight. When the concentration of the polyfunctional amine is within this range, sufficient salt removal performance and water permeability can be obtained. As long as the polyfunctional amine aqueous solution does not interfere with the reaction between the polyfunctional amine and the polyfunctional acid halide, a surfactant, an organic solvent, an alkaline compound, an antioxidant, or the like may be contained. The surfactant has the effect of improving the wettability of the microporous support membrane surface and reducing the interfacial tension between the aqueous amine solution and the nonpolar solvent. The organic solvent may act as a catalyst for the interfacial polycondensation reaction, and when added, the interfacial polycondensation reaction may be efficiently performed.

  In order to perform interfacial polycondensation on the microporous support membrane, first, the above-mentioned polyfunctional amine aqueous solution is brought into contact with the microporous support membrane. The contact is preferably performed uniformly and continuously on the surface of the microporous support membrane. Specific examples include a method of coating a polyfunctional amine aqueous solution on a microporous support membrane and a method of immersing the microporous support membrane in a polyfunctional amine aqueous solution. The contact time between the microporous support membrane and the polyfunctional amine aqueous solution is preferably in the range of 1 second to 10 minutes, and more preferably in the range of 10 seconds to 3 minutes.

  After bringing the polyfunctional amine aqueous solution into contact with the microporous support membrane, the solution is sufficiently drained 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, for example, as described in JP-A-2-78428, the microporous support membrane after contacting with the polyfunctional amine aqueous solution is vertically gripped to allow the excess aqueous solution to flow down naturally. A method or a method of forcibly draining an air stream such as nitrogen from an air nozzle can be used. In addition, after draining, the membrane surface can be dried to partially remove water from the aqueous solution.

  Next, an organic solvent solution containing a polyfunctional acid halide is brought into contact with the microporous support membrane after contact with the polyfunctional amine aqueous solution, and a skeleton of the crosslinked polyamide separation functional layer is formed by interfacial polycondensation.

  The concentration of the polyfunctional acid halide in the organic solvent solution is preferably in the range of 0.01 to 10% by weight, and more preferably in the range of 0.02 to 2.0% by weight. This is because a sufficient reaction rate can be obtained when the content is 0.01% by weight or more, and the occurrence of side reactions can be suppressed when the content is 10% by weight or less. Further, it is more preferable to include an acylation catalyst such as DMF in the organic solvent solution, since interfacial polycondensation is promoted.

  The organic solvent is preferably immiscible with water and dissolves the polyfunctional acid halide and does not break the microporous support membrane, and is inert to the polyfunctional amine compound and the polyfunctional acid halide. If there is something. Preferred examples include hydrocarbon compounds such as n-hexane, n-octane, and n-decane.

  The method for bringing the polyfunctional acid halide organic solvent solution into contact with the polyfunctional amine compound aqueous solution phase may be performed in the same manner as the method for contacting the polyfunctional amine aqueous solution with the microporous support membrane. After the polyfunctional acid halide organic solvent solution is brought into contact with the polyfunctional amine compound aqueous solution phase for interfacial polycondensation to form a separation functional layer containing a crosslinked polyamide on the microporous support membrane, an excess solvent is used. The liquid should be drained. As a method for draining, for example, a method in which a film is held in a vertical direction and excess organic solvent is allowed to flow down and removed can be used. In this case, the time for gripping in the vertical direction is preferably 1 to 5 minutes, more preferably 1 to 3 minutes. If it is too short, the separation functional layer will not be completely formed, and if it is too long, the organic solvent will be overdried and defects will easily occur and performance will be deteriorated.

  In the present invention, the composite semipermeable membrane obtained by the above-described method is washed by bringing it into contact with an aqueous solution of 60 ° C. or less, or by washing it with an aqueous solution containing an acid or alcohol, thereby providing high chemical resistance. A composite semipermeable membrane having properties can be obtained.

  When the polyamide separation functional layer is heated to 60 ° C or higher, the higher-order structure changes with the release of hydrated water, the intermolecular voids become smaller as the processing temperature rises, and is unstable to chemicals such as acids and alkalis. Become. Therefore, in the present invention, the temperature of the aqueous solution brought into contact with the composite semipermeable membrane is preferably 60 ° C. or less, and more preferably 50 ° C. or less.

  The time for contacting the polyamide composite membrane with the aqueous solution is 1 minute or more and 10 minutes or less, more preferably 2 minutes or more and 8 minutes or less. When it is 1 minute or longer, a sufficient cleaning effect can be obtained, and when it is 10 minutes or shorter, high production efficiency is obtained.

  The polyamide separation functional layer obtained as described above is brought into contact with a compound having a primary amino group. The primary amino group reacts with a reagent that forms a diazonium salt or a derivative thereof, and further reacts with an aromatic compound to form an azo group, thereby improving the boron removal rate.

  The concentration and time of contact can be adjusted as appropriate to obtain the desired effect.

  Examples of the compound having a primary amino group include aliphatic amines, cycloaliphatic amines, aromatic amines, and heteroaromatic amines. From the viewpoint of the stability of the diazonium salt or derivative thereof produced, aromatic amines and heteroaromatic amines are preferred. However, in order for the yellowness to be 10 or more and 40 or less, the molecular weight of the carbon skeleton excluding the functional group of the compound having a primary amino group needs to be 500 or less. The method for bringing the compound having a primary amino group into contact with the separation functional layer is not particularly limited. Even if a solution of a compound having a primary amino group is applied, the above-described solution is added to the solution of the compound having a primary amino group. The composite semipermeable membrane may be immersed, and it is preferable to carry out uniformly and continuously.

  As the solvent for dissolving the compound having a primary amine, any solvent may be used as long as the compound is dissolved and the composite semipermeable membrane is not eroded. In addition, the solution contains a surfactant, an acidic compound, an alkaline compound, an antioxidant, or the like as long as it does not interfere with the reaction between the primary amino group and the reagent that forms the diazonium salt or derivative thereof. May be.

  The concentration of the compound having a primary amino group in the mixture of the polyamide separation functional layer and the microporous support membrane is a value measured by the method described below. After contacting the compound having a primary amino group with the polyamide separation functional layer, the droplet is removed, the composite semipermeable membrane is cut out, the substrate is peeled off, and the mixture of the polyamide separation functional layer and the microporous support membrane Get. The compound having the primary amino group is dissolved, and the polyamide separation functional layer and the microporous support membrane are immersed in a solvent that does not dissolve, and the compound having the primary amino group is extracted into the solvent. The extracted components are measured with an ultraviolet-visible spectrophotometer, a high performance liquid chromatography, a gas chromatography or the like obtained from a calibration curve in advance, and the weight of the compound in the mixture of the polyamide separation functional layer and the microporous support membrane is calculated.

Next, the concentration of the compound having a primary amino group in the mixture of the polyamide separation functional layer and the microporous support membrane is determined from the following formula.
Compound concentration (g / m ² ) = compound weight / membrane area

However, in order for the yellowness degree of the polyamide separation functional layer to be 10 or more and 40 or less, the polyamide separation functional layer and the microporous support after contacting the compound having a primary amino group with the polyamide separation functional layer compound concentrations having a primary amino group in the mixture of film is required to be within the scope of 0.01~0.4g / m ^2.

It is then contacted with a reagent that reacts with the primary amino group to produce a diazonium salt or derivative thereof. Examples of the reagent that reacts with the primary amino group to be contacted to produce a diazonium salt or a derivative thereof include aqueous solutions of nitrous acid and salts thereof, nitrosyl compounds, and the like. Since an aqueous solution of nitrous acid or a nitrosyl compound easily generates gas and decomposes, it is preferable to sequentially generate nitrous acid by, for example, a reaction between nitrite and an acidic solution. In general, nitrite reacts with hydrogen ions to produce nitrous acid (HNO ₂ ), but it is efficiently produced when the pH of the aqueous solution is 7 or less, preferably 5 or less, more preferably 4 or less. Among these, an aqueous solution of sodium nitrite reacted with hydrochloric acid or sulfuric acid in an aqueous solution is particularly preferable because of easy handling.

  The concentration of nitrous acid or nitrite in the reagent that reacts with the primary amino group to produce a diazonium salt or a derivative thereof is preferably in the range of 0.01 to 1% by weight. When the nitrite concentration and the nitrite concentration are 0.01% by weight or more, a sufficient amount of diazonium salt or a derivative thereof can be obtained to improve the boron removal rate, and the nitrite concentration and the nitrite concentration are When the content is 1% by weight or less, handling of the solution becomes easy.

  The temperature of the nitrous acid aqueous solution is preferably 15 ° C to 45 ° C. If the temperature is lower than this, the reaction takes time, and if it exceeds 45 ° C., decomposition of nitrous acid is quick and difficult to handle.

  The contact time with the nitrous acid aqueous solution may be a time for forming a diazonium salt and / or a derivative thereof, and can be processed in a short time at a high concentration, but a long time is required at a low concentration. Therefore, the solution having the above concentration is preferably within 10 minutes, more preferably within 3 minutes. The contacting method is not particularly limited, and the composite semipermeable membrane may be immersed in the reagent solution or the reagent solution. As the solvent for dissolving the reagent, any solvent may be used as long as the reagent is dissolved and the composite semipermeable membrane is not eroded. The solution may contain a surfactant, an acidic compound, an alkaline compound, or the like as long as it does not interfere with the reaction between the primary amino group and the reagent.

  A part of the diazonium salt produced by contact or a derivative thereof is converted into a phenolic hydroxyl group by reacting with water. Further, it reacts with an aromatic ring having a structure forming a microporous support membrane or a separation functional layer, or an aromatic ring of a compound having a primary amino group held in the separation functional layer to form an azo group. Thereby, improvement of boron removal rate can be expected.

  Next, it is contacted with a reagent that reacts with a diazonium salt or a derivative thereof. Reagents used here are chloride ion, bromide ion, cyanide ion, iodide ion, boron fluoride, hypophosphorous acid, sodium bisulfite, sulfite ion, aromatic amine, phenols, hydrogen sulfide, thiocyanate. An acid etc. are mentioned. When it reacts with sodium hydrogen sulfite and sulfite ions, a substitution reaction occurs instantaneously, and the amino group is substituted with a sulfo group. Moreover, a diazo coupling reaction occurs by making it contact with an aromatic amine and phenols, and it becomes possible to introduce | transduce an aromatic into a film surface. These reagents may be used singly or may be used by mixing a plurality of them, or may be brought into contact with different reagents a plurality of times. The reagent to be contacted is preferably sodium hydrogen sulfite and sulfite ion.

  The concentration and time of contact can be appropriately adjusted so that a sufficient amount of diazonium salt or a derivative thereof can be obtained to improve the boron removal rate.

  The contact temperature is preferably 10 to 90 ° C. Since the reaction proceeds rapidly when the temperature is 10 ° C. or higher, an amount of a diazonium salt or a derivative thereof sufficient to improve the boron removal rate can be obtained. Moreover, since it becomes difficult to shrink | contract a polymer because temperature is 90 degrees C or less, the fall of the permeated water amount is suppressed.

  The composite semipermeable membrane of the present invention has a cylindrical shape in which a large number of holes are perforated together with a raw water channel material such as a plastic net, a permeate channel material such as tricot, and a film for enhancing pressure resistance as required. It is wound around a water collecting pipe and is preferably used as a spiral composite semipermeable membrane element. Furthermore, a composite semipermeable membrane module in which these elements are connected in series or in parallel and accommodated in a pressure vessel can be obtained.

  In addition, the above-described composite semipermeable membrane, its elements, and modules can be combined with a pump that supplies raw water to them, a device that pretreats the raw water, and the like to form a fluid separation device. By using this separation device, the 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 salt removal rate, but the energy required for operation also increases, and considering the durability of the composite semipermeable membrane, water to be treated is added to the composite semipermeable membrane. The operating pressure at the time of permeation is preferably 0.5 MPa or more and 10 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.

  Examples of raw water to be treated by the composite semipermeable membrane according to the present invention include liquid mixtures containing TDS (Total Dissolved Solids) of 500 mg / L or more and 100 g / L or less, such as seawater, brine, and drainage. It is done. 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 ° C. or higher and 40.5 ° C. or lower. Convert from.

  The composite semipermeable membrane of the present invention is characterized by having high chemical resistance, but it is appropriate to use the resistance to each of pH 1 and pH 13 as an index for chemical resistance. is there. Since pH 1 is the strongest condition as pH during acid washing in membrane filtration operation, and pH 13 is the strongest condition as pH during alkali washing, if resistance to each aqueous solution of pH 1 and pH 13 is exhibited, acid or This is because it is ensured that the film is not easily deteriorated even when cleaning with alkali is performed.

  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.

  The basis weight of the base material in the composite semipermeable membranes described in Comparative Examples and Examples was measured as follows.

  Three non-woven fabrics of 30 cm × 50 cm constituting the base material were collected, the weight of each sample was measured, the average value of the obtained values was converted per unit area, and the first decimal place was rounded off. .

  The concentration of the compound having a primary amino group in the mixture of the polyamide separation functional layer and the microporous support membrane in the composite semipermeable membrane described in Comparative Examples and Examples, and the yellowness of the separation functional layer were measured as follows. did.

(Concentration of compound having primary amino group in the mixture of the polyamide separation functional layer and the microporous support membrane)
After contacting the compound having a primary amino group with the polyamide separation functional layer, the droplets are removed, the composite semipermeable membrane is cut out 10 × 10 cm, the substrate is peeled off, and the polyamide separation functional layer and the microporous support are removed. A mixture of membranes was obtained. This was immersed in 50 g of ethanol for 8 hours, and the components extracted in ethanol were measured with an ultraviolet-visible spectrophotometer (UV-2450 manufactured by Shimadzu Corporation) obtained in advance with a calibration curve. The weight of the compound having a primary amino group in the support membrane mixture was calculated. Next, the concentration of the compound having a primary amino group in the mixture of the polyamide separation functional layer and the microporous support membrane was determined from the following formula. Here, the membrane area is the area of the composite semipermeable membrane cut out above.
Compound concentration (g / m ² ) = compound weight / membrane area

(Yellowness)
After drying the composite semipermeable membrane for 8 hours at room temperature, the substrate is peeled off and placed on a glass plate with the separation functional layer side down, and then the microporous support membrane is dissolved and removed with dichloromethane. The separation functional layer remaining on the surface was measured with an SM color computer SM-7 manufactured by Suga Test Instruments Co., Ltd.

  Various characteristics of the composite semipermeable membranes in the comparative examples and the examples are as follows. Seawater (TDS concentration: about 3.5%, boron concentration: about 5 ppm) adjusted to a temperature of 25 ° C. and pH 6.5 is applied to the composite semipermeable membrane at an operating pressure of 5. The membrane filtration treatment was carried out for 24 hours while supplying at 5 MPa, and the water quality was determined by measuring the quality of the permeated water and the supplied water thereafter.

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

(Membrane permeation flux)
Membrane permeation flux (m ³ / m ² / day) was expressed in terms of the permeation amount of the feed water (seawater) per square meter of the membrane surface with the permeation amount per day (cubic meter).

(Boron removal rate)
The boron concentration in the feed water and the permeated water was analyzed with an ICP emission analyzer (P-4010 manufactured by Hitachi, Ltd.), and determined from the following formula.
Boron removal rate (%) = 100 × [1- (boron concentration in permeated water / boron concentration in feed water)]

(chemical resistance)
The operation of immersing the composite semipermeable membrane in a pH 13 sodium hydroxide aqueous solution and a pH 1 sulfuric acid aqueous solution for 1 hour each at room temperature was repeated 15 cycles, and the membrane permeation flux ratio and boron SP ratio before and after that were determined.
Membrane permeation flux ratio = membrane permeation flux after immersion / membrane permeation flux boron SP ratio before immersion = (100−boron removal rate after immersion) / (100−boron removal rate before immersion)
Note that SP is an abbreviation for substance penetration.

(Irreversible heat absorption)
After the substrate was physically peeled and removed from the composite semipermeable membrane, the porous support was extracted and removed with dichloromethane to prepare an analytical sample of the polyamide separation functional layer. The prepared sample was vacuum-dried for 48 hours and stored in a nitrogen atmosphere. About 5 mg of the obtained analytical sample was measured by using a differential scanning calorimeter (Q-100: manufactured by TA instruments) and Universal Analysis manufactured by TA Instruments, by means of a temperature modulation DSC method, an average heating rate of 2 ° C./min, temperature The analysis was performed under the conditions of a modulation period of 60 seconds and a temperature modulation amplitude of ± 1 ° C., and the endothermic amount (J / g) of the irreversible component in the range of −20 to 150 ° C. in the initial temperature rising process was taken as the average value of three measurements. Asked. Note that an automatic cooling system using liquid nitrogen and an electric furnace were used for temperature drop and temperature rise during measurement.

Example 1
A 15.7 wt% DMF solution of polysulfone was cast at room temperature (25 ° C.) with a thickness of 200 μm on a polyester nonwoven fabric (monolayer nonwoven fabric with air permeability of 1 cc / cm ² / sec, basis weight of 83 g / m ² ) composed of short fibers. The microporous support membrane (thickness 210 to 215 μm) was prepared by immediately immersing in pure water and allowing to stand for 5 minutes.

  The obtained microporous support membrane was immersed in a 4.5% by weight aqueous solution of m-phenylenediamine (hereinafter referred to as m-PDA) for 2 minutes, and the support membrane was slowly pulled up in the vertical direction to produce an air nozzle. After removing excess aqueous solution from the surface of the support membrane by applying nitrogen, a 25 ° C. n-decane solution containing 0.175% by weight of trimesic acid chloride was applied so that the surface was completely wetted and allowed to stand for 1 minute. Next, in order to remove excess solution from the membrane, the membrane was held vertically for 1 minute to drain, and then washed with hot water at 50 ° C. for 2 minutes.

  Then, it was immersed in an aqueous solution of 500 ppm of m-PDA for 60 minutes and treated at room temperature (35 ° C.) for 1 minute with a 0.3 wt% aqueous sodium nitrite solution adjusted to pH 3 with sulfuric acid. The composite semipermeable membrane was removed from the aqueous nitrous acid solution, washed with water, and immersed in a 0.1% by weight aqueous sodium sulfite solution for 2 minutes. The composite semipermeable membrane thus obtained was evaluated. The TDS removal rate, the membrane permeation flux, and the boron removal rate were values shown in Table 2, respectively. Further, the yellowness and the endothermic amount of the separation functional layer of this composite semipermeable membrane were the values shown in Table 2. Furthermore, the m-PDA concentration in the mixture of the polyamide separation functional layer and the microporous support membrane after immersion in the m-PDA solution was the value shown in Table 1.

  Moreover, when the chemical resistance of the composite semipermeable membrane was evaluated, the membrane permeation flux ratio and boron SP ratio before and after chemical contact were as shown in Table 2.

(Examples 2-14, Comparative Examples 1-5)
Example 1 except that the substrate used (type, number of layers, basis weight), temperature of washing water after interfacial polycondensation, m-PDA concentration to be immersed, and sodium nitrite concentration were changed to the conditions described in Table 1. Similarly, a composite semipermeable membrane was produced and processed. In the composite semipermeable membranes of Examples 6 to 14, a long fiber nonwoven fabric was used as a base material. Moreover, the composite semipermeable membrane of Examples 7 and 9-14 used the laminated nonwoven fabric which laminated | stacked 2-7 layers of the long-fiber nonwoven fabric as a base material.

  When the obtained composite semipermeable membrane was evaluated, the TDS removal rate, membrane permeation flux, boron removal rate, and chemical resistance were as shown in Table 2. Further, the yellowness and irreversible endothermic amount of the separation functional layer of this composite semipermeable membrane were the values shown in Table 2. Furthermore, the m-PDA concentration in the mixture of the polyamide separation functional layer and the microporous support membrane after immersion in the m-PDA solution was the value shown in Table 1.

  Moreover, when the chemical resistance of the composite semipermeable membrane was evaluated, the membrane permeation flux ratio and boron SP ratio before and after chemical contact were as shown in Table 2.

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

Claims (3)

  A composite semipermeable membrane in which a polyamide separation functional layer is formed on a microporous support membrane comprising a base material and a porous support, and -20 to 20 in the initial temperature rising process measured using a temperature modulation DSC method A composite semipermeable membrane, wherein the polyamide separation functional layer has an irreversible endothermic amount of 275 J / g or more in a range of 150 ° C., and the polyamide separation functional layer has a yellowness of 10 or more and 40 or less.   The composite semipermeable membrane according to claim 1, wherein the base material is a long-fiber nonwoven fabric. 3. The composite semipermeable membrane according to claim 1, wherein the base material is a laminated nonwoven fabric in which 2 to 5 layers of nonwoven fabric are laminated and has a basis weight of 30 to 150 g / m ² .