JP2014064989A - Composite semipermeable membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite semipermeable membrane having both high removal performance of materials other than water and high water permeable performance even under a condition in which starting and stopping operations are repeated frequently to fluctuate a pressure.SOLUTION: The composite semipermeable membrane includes a support film having a substrate and a porous support layer, and a polyamide separation function layer provided by a polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide. In the composite semipermeable membrane, a polyamide compound is contained in a hollow of the surface and/or the inside of the porous support layer.

Description

  The present invention relates to a composite semipermeable membrane useful for the selective separation of liquid mixtures. The composite semipermeable membrane obtained by the present invention can be suitably used for desalination of seawater and brine, for example.

  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 crosslinked on a porous support membrane, and monomers on the porous support membrane. There are two types, one having an active layer obtained by polycondensation. Among them, the composite semipermeable membrane obtained by coating a porous support membrane with a separation functional layer made of a crosslinked polyamide obtained by polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide has water permeability and salt removal. Widely used as a high-performance separation membrane.

  In water production plants using reverse osmosis membranes, higher water permeability is required in order to further reduce running costs. In addition, when used as a reverse osmosis membrane, it is required that the above membrane performance can be maintained even under long-time operation at high pressure or in operating conditions where the pressure fluctuates due to frequent operation / stop.

  Factors affecting the performance of the composite semipermeable membrane include the form of the separation functional layer, particularly the pleat structure formed on the surface of the polyamide functional layer. As for the relationship between the membrane performance and the pleat structure, it has been proposed that the substantial membrane area can be increased by extending the pleats to improve the water permeability (Patent Documents 1 to 3). Moreover, in order to suppress the performance change at the time of drive | operating a composite semipermeable membrane, the method of suppressing consolidation of a porous support membrane is proposed (patent documents 4-5).

Japanese Patent Laid-Open No. 9-19630 JP-A-9-85068 JP 2001-179061 A Japanese Patent No. 3385824 JP 2000-153137 A

  However, in the conventional composite semipermeable membrane, the water permeation performance or the salt removal performance may be deteriorated under a situation where the pressure applied to the membrane fluctuates, such as when the operation and the stop are frequently repeated.

  An object of the present invention is to provide a composite semipermeable membrane that can achieve both high salt removal performance and water permeation performance even under pressure fluctuation conditions.

In order to achieve the above object, the composite semipermeable membrane of the present invention is obtained by a polycondensation reaction of a base material, a porous support layer disposed on the base material, a polyfunctional amine and a polyfunctional acid halide. And a separation functional layer provided on the porous support tank, the polyamide compound being contained in the porous support layer.
That is, the present invention relates to the following.
(1) (i) a substrate;
(Ii) a porous support layer having a polymer compound as a main component and disposed on the substrate;
(Iii) a separation functional layer containing a polyamide compound produced by a polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide as a main component, and provided on the porous support layer; A composite semipermeable membrane comprising a polyamide compound in a support layer.
(2) The composite semipermeable material according to (1), wherein at least a part of the polyamide compound contained in the porous support layer is disposed so as to interact with the separation functional layer. film.
(3) The composite semipermeable membrane according to (1) or (2), wherein the polyamide compound contained in the porous support layer is contained in a depression on the surface of the porous support layer. .
(4) In at least a part of the porous support layer, the polymer compound, which is a main component of the porous support layer, and the polyamide compound are mixed, (1) to (1) above (3) The composite semipermeable membrane according to any one of (3).
(5) The porous support layer has a multilayer structure of a first layer on the substrate side and a second layer formed on the first layer, and the first layer is formed on the substrate. (1) to (4), wherein the molecular solution A and the polymer solution B forming the second layer are simultaneously applied and then contacted with a coagulation bath and phase-separated. The composite semipermeable membrane according to any one of the above.
(6) The composite semipermeable membrane according to (5), wherein the polymer solution B contains at least one polyamide compound.
(7) The composite semipermeable membrane according to any one of (1) to (6), wherein the base material is a long fiber nonwoven fabric containing polyester as a main component.
(8) The amount of water produced when an aqueous solution having a NaCl concentration of 3.5% by weight, a temperature of 25 ° C., and a pH of 6.5 was permeated at an operating pressure of 4.0 MPa was 1.00 m ³ / m ^2. The composite semipermeable membrane according to any one of the above (1) to (7), wherein the desalting rate is 99.80% or more.

  According to the present invention, a composite semipermeable membrane that achieves both high salt removal performance and water permeability performance is realized even under conditions where the operation is frequently stopped and stopped and the pressure varies.

FIG. 1 is a cross-sectional view illustrating an example of a separation functional layer. FIG. 2 is a cross-sectional view showing an example of the separation functional layer and the porous support layer. FIG. 3 is a cross-sectional view showing an example of the separation functional layer and the porous support layer.

1. Composite Semipermeable Membrane The composite semipermeable membrane includes a support membrane including a base material and a porous support layer, and a separation functional layer provided on the porous support layer.

(1-1) Separation Functional Layer The separation functional layer is a layer that bears a solute separation function in the composite semipermeable membrane. The composition and thickness of the separation functional layer are set according to the intended use of the composite semipermeable membrane.

  The separation functional layer is preferably composed mainly of polyamide. 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.

  In this document, “X contains Y as a main component” means that Y occupies 60% by weight, 80% by weight, or 90% by weight of X, and X is substantially The structure containing only Y is included.

  The thickness of the polyamide separation functional layer is usually preferably in the range of 1 nm to 1 μm and more preferably in the range of 10 nm to 0.5 μm in order to obtain sufficient separation performance and permeated water amount.

  Here, the polyfunctional amine has at least two amino groups in one molecule, at least one of the amino groups is a primary amino group, and further a secondary amino group in one molecule. Refers to an amine that may have For example, as a polyfunctional amine, phenylenediamine, xylylenediamine, 1,3,5-triaminobenzene in which two amino groups are bonded to a benzene ring in any of the ortho-position, meta-position, and para-position, Aromatic polyfunctional amines such as 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine and 4-aminobenzylamine; aliphatic amines such as ethylenediamine and propylenediamine; -An alicyclic polyfunctional amine such as diaminocyclohexane, 1,4-diaminocyclohexane, 4-aminopiperidine, 4-aminoethylpiperazine and the like can be mentioned. Among them, considering the selective separation property, permeability, and heat resistance of the membrane, the polyfunctional amine is an aromatic polyfunctional having 2 to 4 primary amino groups and / or secondary amino groups in one molecule. An amine is preferred. As such a polyfunctional aromatic amine, m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene are preferably used. Among these, m-phenylenediamine (hereinafter referred to as m-PDA) is preferably used 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. For example, examples of the trifunctional acid halide include trimesic acid chloride, 1,3,5-cyclohexanetricarboxylic acid trichloride, 1,2,4-cyclobutanetricarboxylic acid trichloride, and the like. Examples of the bifunctional acid halide include aromatic bifunctional acid halides such as biphenyl dicarboxylic acid dichloride, azobenzene dicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, and naphthalene dicarboxylic acid chloride; adipoyl chloride, sebacoyl chloride, and the like. Aliphatic bifunctional acid halides; cycloaliphatic difunctional acid halides such as cyclopentane dicarboxylic acid dichloride, cyclohexane dicarboxylic acid dichloride, and tetrahydrofuran dicarboxylic acid dichloride can be exemplified. In consideration of the reactivity with the polyfunctional amine, the polyfunctional acid halide is preferably a polyfunctional acid chloride. In view of selective separation of the membrane and heat resistance, the polyfunctional acid chloride is more preferably a polyfunctional aromatic acid chloride having 2 to 4 carbonyl chloride groups in one molecule. Of these, trimesic acid chloride is preferable from the viewpoint of availability and ease of handling. These polyfunctional acid halides may be used alone or in combination of two or more.

  Generally, when the height of the convex portion on the separation functional layer (that is, the height of the folds) is increased, the water permeability is improved, but the salt permeability is also increased. In addition, the presence of excessively enlarged pleats is likely to be deformed during pressurization, and this causes a decrease in membrane surface area and partial destruction during pressurization, thereby reducing water permeability and salt removal performance. In particular, in the case of a membrane for seawater desalination operated at a relatively high pressure, this tendency tends to appear in performance.

  Therefore, the present inventors have made extensive studies by paying attention to the chemical structures of the separation functional layer and the porous support layer. As a result, it was found that high salt removal performance and water permeation performance can both be achieved by including the polyamide compound constituting the separation functional layer in the porous support layer. Moreover, it has been found that the change in salt removal performance due to pressure is smaller as the proportion of the polyamide compound is larger. Furthermore, high salt removal performance and water permeation performance can both be achieved by precisely controlling the number density and height of the convex portions. In systems where pressure fluctuates, such as frequent operation and shutdown, the number density of protrusions is higher and the number of protrusions is smaller than that of films with a higher number density of protrusions. Is preferable in that the change in water permeability is small.

  The average height of the convex portions of the separation functional layer is preferably less than 100 nm, more preferably less than 90 nm. When the height of the convex portion is less than 100 nm, stable film performance can be obtained without causing fold deformation or crushing even under conditions where the pressure fluctuates due to frequent repetition of operation and stoppage. it can.

  Further, the average number density of the convex portions of the separation functional layer is preferably 10.0 pieces / μm or more, and more preferably 13.0 pieces / μm or more. When the average number density is 10.0 pieces / μm or more, the surface area of the composite semipermeable membrane is increased and sufficient water permeability can be obtained, and further, deformation of the convex portion during pressurization can be suppressed, Stable membrane performance can be obtained. Further, the average number density of the convex portions of the separation functional layer is preferably 30.0 pieces / μm or less. When the average number density is 30.0 pieces / μm or less, the effective surface area can be suppressed from decreasing due to the protrusions contacting each other.

  The height and number density of the protrusions are values measured for the protrusions having a height of 1/5 or more of the 10-point average surface roughness.

The 10-point average surface roughness is a value obtained by the following calculation method. First, a cross section perpendicular to the film surface is observed with an electron microscope at the following magnification. In the obtained cross-sectional image, the surface of the separation functional layer (indicated by reference numeral “1” in FIG. 1) appears as a curve of a pleated structure in which convex portions and concave portions are continuously repeated. About this curve, the roughness curve defined based on ISO4287: 1997 is calculated | required. Thereafter, a cross-sectional image is extracted with a width of 2.0 μm in the direction of the average line of the roughness curve (FIG. 1). In the extracted image having a width of 2.0 μm, the height of the ridges of the folds and the depth of the recesses in the separation functional layer are measured using the average line as a reference line (indicated by reference numeral “2” in FIG. 1). A convex part is selected in order of decreasing height from the highest convex part, an average value is calculated for the absolute values of the heights H1 to H5 of the five convex parts up to the fifth, and the depth is determined from the deepest concave part. The concave portions are selected in order of decreasing depth, and the average value is calculated for the absolute values of the depths D1 to D5 of the five concave portions up to the fifth. Further, the sum of absolute values of the two obtained average values (the average value of the height of the convex portion and the depth of the concave portion) is calculated. The sum thus obtained is the 10-point average surface roughness.
The average line is a straight line defined based on ISO 4287: 1997. In the measurement length, the total area of the regions surrounded by the average line and the roughness curve is equal above and below the average line. It is a straight line drawn.

  The cross section of the separation functional layer can be observed with a scanning electron microscope or a transmission electron microscope. For example, for observation with a scanning electron microscope, a composite semipermeable membrane sample is thinly coated with platinum, platinum-palladium, or ruthenium tetroxide, preferably ruthenium tetroxide, and a high resolution field emission type with an acceleration voltage of 3 to 6 kV. Observation is performed using a scanning electron microscope (UHR-FE-SEM). A Hitachi S-900 electron microscope or the like can be used as the high-resolution field emission scanning electron microscope. The observation magnification is preferably 5,000 to 100,000 times, and preferably 10,000 to 50,000 times for obtaining the height of the convex portion. In the obtained electron micrograph, the height of the convex portion can be directly measured with a scale or the like in consideration of the observation magnification.

  Furthermore, the average number density of the convex portions is measured as follows. In the composite semipermeable membrane, when arbitrary cross sections are observed, the convex portions having a height of 1/5 or more of the above-mentioned 10-point average surface roughness value are counted in each cross section. The average number density is obtained by calculating the number density in each cross section (that is, the number of convex portions per 1 μm), and further calculating the arithmetic average value from the number density in 10 cross sections. Here, each cross section to be observed has a width of 2.0 μm in the direction of the average line of the roughness curve.

  Moreover, the average height of a convex part is measured as follows. In the composite semipermeable membrane, when observing arbitrary 10 cross-sections, in each cross-section, all convex portions having a height of 1/5 or more of the above-mentioned 10-point average surface roughness value are selected. The height of each convex part is measured, and the average height per convex part is calculated. Furthermore, the average height is obtained by calculating the arithmetic average based on the calculation results for the 10 cross sections. Here, each cross section to be observed has a width of 2.0 μm in the direction of the average line of the roughness curve.

  The standard deviation of the height of the convex part is based on the height of the convex part, which is equal to or more than one fifth of the value of the 10-point average surface roughness measured in the cross section of 10 points, similarly to the average height. Calculated.

  The standard deviation of the height of the convex portion of the separation functional layer is preferably 70 nm or less. If the standard deviation is within this range, the height of the projections is uniform, so that stable membrane performance can be obtained even when the composite semipermeable membrane is operated at high pressure.

  The presence or absence of the polyamide can be observed with the electron microscope, and can be used in combination with elemental analysis such as energy dispersive X-ray spectroscopy (EDX) or electron beam energy loss spectroscopy (EELS). The number of hits and depth can be quantified.

(1-2) Support Membrane The support membrane includes a base material and a porous support layer, has substantially no separation performance such as ions, and has a strength to a separation functional layer having separation performance substantially. Can be given.

  The thickness of the support membrane 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, it is preferably in the range of 30 to 300 μm, more preferably in the range of 50 to 250 μm.

  In this document, unless otherwise specified, the thickness of each layer and film means an average value. Here, the average value represents an arithmetic average value. That is, the thickness of each layer and film is obtained by calculating the average value of the thicknesses of 20 points measured at intervals of 20 μm in the direction orthogonal to the thickness direction (direction of the film surface) in cross-sectional observation.

[Porous support layer]
The porous support layer preferably contains the following materials as main components. The material of the porous support layer is not particularly limited, but a homopolymer or copolymer such as polysulfone, polyethersulfone, polyamide, polyester, cellulosic polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, or polyphenylene oxide is used. It can be used alone or blended. Here, cellulose acetate, cellulose nitrate and the like are used as the cellulose polymer; polyethylene, polypropylene, polyvinyl chloride, polyacrylonitrile and the like are used as the vinyl polymer. Among them, homopolymers or copolymers such as polysulfone, polyamide, polyester, cellulose acetate, cellulose nitrate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, and polyphenylene sulfide sulfone are preferable. More preferred is cellulose acetate, polysulfone, polyphenylene sulfide sulfone, or polyphenylene sulfone. Among these materials, polysulfone can be particularly preferably used because of its high chemical, mechanical and thermal stability and easy molding.

Specifically, as the material for the porous support layer, polysulfone composed of repeating units represented by the following chemical formula (I) is preferable because the pore diameter can be easily controlled and the dimensional stability is high.

  Polysulfone preferably has a weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) using N-methylpyrrolidone as a solvent and polystyrene as a standard substance, preferably 10,000 to 200,000, or 15, It is in the range of 000-100,000. When the Mw is 10,000 or more, preferable mechanical strength and heat resistance can be obtained as the porous support layer. Moreover, when Mw is 200,000 or less, the viscosity of the solution falls within an appropriate range, and good moldability can be realized.

  The porous support layer can be obtained, for example, by casting an N, N-dimethylformamide (hereinafter referred to as DMF) solution of the above polysulfone to a constant thickness on a substrate and wet coagulating it in water. . By this method, a porous support layer in which most of the surface has fine pores having a diameter of several nm to 30 nm can be obtained.

  It is preferable to contain a polyamide compound in the porous support layer. The inventors pay attention to the chemical structure of the separation functional layer and the porous support layer, and by conducting intensive studies, by incorporating polyamide molecules inside the porous support layer, the salt removal performance by pressure is improved. We found that the change was smaller. The reason for this is that the porous support layer contains physical or chemical adsorption between the porous support layer and the separation functional layer by including the same type of material as the separation functional layer at the interface with the separation functional layer. As a result, it is considered that the adhesion between the porous support layer and the separation functional layer is improved, and the salt removal performance is improved.

  Here, “containing a polyamide compound in the porous support layer” means that the polyamide compound is present in a depression on the surface of the porous support layer, and a polymer compound that is a main component in the porous support layer. It is sufficient to satisfy at least one of the mixed states.

  Moreover, in order to obtain sufficient mechanical strength and packing density, the thickness of the porous support layer is preferably in the range of 10 to 200 μm, and more preferably in the range of 20 to 100 μm. In order to obtain sufficient mechanical strength and packing density, the thickness of the substrate is preferably in the range of 10 to 250 μm, more preferably in the range of 20 to 200 μm.

  The surface of the porous support layer (that is, the surface facing the separation functional layer) has a structure in which minute protrusions are dispersed. That is, as shown in FIG. 2, the portion where the porous support layer 4 is joined to the concave portion of the separation function layer 5 having a pleated structure has a form of a microprojection 3. The higher the density of the microprotrusions 3 on the surface of the porous support layer 4, the higher the number density of convex portions in the separation functional layer. This is considered to be due to the following reason.

  In the formation of the separation functional layer, the polyfunctional amine aqueous solution is in contact with the support membrane, and the polyfunctional amine aqueous solution is transferred from the inside of the porous support layer to the surface during polycondensation. The surface of the porous support layer functions as a reaction field for polycondensation, and the pleated protrusions of the separation functional layer grow by supplying the polyfunctional amine aqueous solution from the porous support layer to the reaction field. Moreover, it is thought that the said microprotrusion on the porous support layer surface becomes a main reaction field. Therefore, if the number density of microprojections on the surface of the porous support layer, which is a reaction field, is large, the number of growth points of the protrusions increases, and as a result, the number density of the protrusions increases. In general, a porous support layer having a high number density of microprojections on the surface is dense and has a small porosity and a small pore diameter.

  On the other hand, if the porosity of the porous support layer is high, the pore diameter is large, and the continuity is high, the monomer supply rate increases, so that the ridges of the pleats are easy to grow.

  Thus, the height of the convex portion and the thickness of the separation functional layer are determined by the polyfunctional amine aqueous solution holding capacity, the release rate and the supply amount of the porous support layer, and the number density of the convex portions can be controlled by the surface structure. . Specifically, in the porous support layer, in order to achieve both the height and the number density of the above-described protrusions, it is preferable that the part on the substrate side has a high porosity, a large pore diameter, and high continuity. The separation functional layer side portion preferably has a high number density of microprotrusions. As an example of such a structure, the porous support layer is positioned closer to the separation functional layer than the first layer for efficiently transferring the polyfunctional amine aqueous solution, and controls the number density of the convex portions. It is preferable to provide a second layer. In particular, the first layer is preferably in contact with the substrate, and the second layer is preferably located on the outermost layer of the porous support layer so as to be in contact with the separation functional layer.

  The first layer plays a role of transferring an aqueous polyfunctional amine solution necessary for forming the separation functional layer to the polymerization field. In order to efficiently transfer the monomer, it is preferable to have continuous pores. In particular, the pore diameter is preferably 0.1 μm or more and 1 μm or less.

  As described above, the second layer serves as a polymerization field and serves to supply and supply the monomer to the separation functional layer to be formed by holding and releasing the monomer, and also serves as a starting point for the convex growth. Fulfill.

  Here, the porous support layer having a high number density of microprotrusions on the surface can form convex portions having a high number density. However, since the porous support layer is dense, the transfer rate of the monomer to the polymerization field is low, and the formed convex portions have a high density. There is a problem that becomes small and non-uniform. At this time, the above-mentioned first layer, which is a layer having continuous pores, is thinly laminated on the first layer as the second layer on the substrate side, thereby forming a porous support layer. Since the transfer rate of the monomer can be compensated, a uniform convex part having a large height can be formed. Thus, in order to simultaneously control the height, uniformity and number density of the convex portions, it is preferable that the porous support layer includes a first layer and a second layer formed thereon.

  Furthermore, it is preferable that the interface of the layer contained in the porous support layer has a continuous structure. A continuous structure refers to a structure in which no skin layer is formed between layers. The skin layer here means a portion having a high density. Specifically, the diameter of the surface pores of the skin layer is in the range of 1 nm to 50 nm. When a skin layer is formed between the layers, the permeation flux decreases dramatically because of the high resistance in the porous support layer.

[Base material]
Examples of the substrate constituting the support film include polyester polymers, polyamide polymers, polyolefin polymers, and mixtures and copolymers thereof, but mechanical strength, heat resistance, water resistance, and the like. A polyester polymer is preferable because an excellent support film can be obtained.

  The polyester polymer is preferably a polyester composed of an acid component and an alcohol component. Examples of the acid component include aromatic carboxylic acids such as terephthalic acid, isophthalic acid and phthalic acid, aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and alicyclic dicarboxylic acids such as cyclohexanecarboxylic acid. Further, as the alcohol component, ethylene glycol, diethylene glycol, polyethylene glycol, or the like can be used.

  Examples of polyester polymers include, but are not particularly limited to, for example, polyethylene terephthalate resin, polybutylene terephthalate resin, polytrimethylene terephthalate resin, polyethylene naphthalate resin, polylactic acid resin, and polybutylene succinate resin. Moreover, the copolymer of these resin is also mentioned.

  As the fabric used for the substrate, it is preferable to use a fibrous substrate in terms of strength, unevenness forming ability, and fluid permeability. As the fibrous base material, either a long fiber nonwoven fabric or a short fiber nonwoven fabric can be preferably used. In particular, long-fiber non-woven fabrics have excellent permeability when casting a polymer solution on a base material, and the porous support layer peels off, and the film becomes non-uniform due to fluffing of the base material. This is preferable because defects such as pinholes can be suppressed. In particular, the base material is preferably made of a long-fiber nonwoven fabric composed of thermoplastic continuous filaments. Moreover, since continuous tension | tensile_strength is applied with respect to the film forming direction when forming a semipermeable membrane continuously, it is preferable to use the long-fiber nonwoven fabric which is more excellent in dimensional stability for a base material.

  In the long-fiber nonwoven fabric, in terms of moldability and strength, it is preferable that the fibers in the surface layer on the side opposite to the porous support layer have a longitudinal orientation than the fibers in the surface layer on the porous support layer side. According to such a structure, not only a high effect of preventing film breakage by maintaining strength is realized, but also a lamination including a porous support layer and a substrate when imparting irregularities to a semipermeable membrane Formability as a body is also improved, and the uneven shape on the surface of the semipermeable membrane is stabilized, which is preferable. More specifically, the fiber orientation degree in the surface layer on the side opposite to the porous support layer of the long fiber nonwoven fabric is preferably 0 ° to 25 °, and the fiber orientation degree in the surface layer on the porous support layer side. And the orientation degree difference is preferably 10 ° to 90 °.

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

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

  The degree of fiber orientation is measured as follows. First, 10 small piece samples are randomly collected from the nonwoven fabric. Next, the surface of the sample is photographed at 100 to 1000 times with a scanning electron microscope. In the photographed image, 10 samples are selected for each sample, and the angle when the longitudinal direction (longitudinal direction, film forming direction) of the nonwoven fabric is 0 ° is measured. That is, the angle is measured for a total of 100 fibers per nonwoven fabric. An average value is calculated from the angles of 100 fibers thus measured. The value obtained by rounding off the first decimal place of the obtained average value is the fiber orientation degree.

(1-3) Water production amount and desalination rate The composite semipermeable membrane was obtained by allowing an aqueous solution of 3.5% by weight NaCl, 25 ° C., pH 6.5 to pass through at an operating pressure of 5.5 MPa for 24 hours. It is preferable that the amount of water produced is 1.00 m ³ / m ² / day or more and the desalination rate is 99.5% or more. In addition, the amount of water produced after permeating an aqueous solution of 3.5 wt% NaCl, 25 ° C., pH 6.5 at an operating pressure of 4.0 MPa for 24 hours is 1.00 m ³ / m ² / day or more, In addition, it is more preferable that the desalination rate is 99.8% or more because it enables more energy-saving operation.

In addition, the composite semipermeable membrane
(i) An aqueous solution having a NaCl concentration of 3.5% by weight, a temperature of 25 ° C., and a pH of 6.5 was supplied to the composite semipermeable membrane at an operating pressure of 5.5 MPa, and filtered for 24 hours. After processing,
(ii) The operation at an operating pressure of 5.5 MPa was performed for 1 minute, the pressure was reduced to 0 MPa in 30 seconds, held for 1 minute, and then increased to 5.5 MPa in 30 seconds, 5000 times,
(iii) Furthermore, it is preferable that the amount of water produced when permeated at an operating pressure of 5.5 MPa is 0.85 m ³ / m ² / day or more and the desalting rate is 99.5% or more.

In (iii) above, when the operating pressure is 4.0 MPa, the amount of water produced is 1.00 m ³ / m ² / day or more, and the desalination rate is 99.8% or more, resulting in more energy saving. Since driving | operation becomes possible, it is more preferable.

2. Next, a method for manufacturing the composite semipermeable membrane will be described. The manufacturing method includes a support film forming step and a separation functional layer forming step.

(2-1) Support film forming step The support film forming step includes a step of applying a polymer solution to the porous substrate, a step of impregnating the porous substrate with the polymer solution, and the step of impregnating the solution. A step of immersing the porous substrate in a coagulation bath in which the solubility of the polymer is lower than that of a good solvent for the polymer to coagulate the polymer to form a three-dimensional network structure may be included. In addition, the step of forming the support film may further include a step of preparing a polymer solution by dissolving a polymer that is a component of the porous support layer in a good solvent for the polymer.

  By controlling the impregnation of the polymer solution into the substrate, a support film having a predetermined structure can be obtained. In order to control the impregnation of the polymer solution into the substrate, for example, a method of controlling the time until the polymer solution is immersed on the non-solvent after the polymer solution is applied on the substrate, or the temperature of the polymer solution or The method of adjusting a viscosity by controlling a density | concentration is mentioned, These methods are also combinable.

  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. 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. In addition, what is necessary is just to prepare the preferable range of time until it immerses in a coagulation bath suitably with the viscosity of the polymer solution to be used.

  As a result of intensive studies by the present inventors, the higher the polymer concentration (that is, the solid content concentration) in the polymer solution, the more porous support layer having a higher number density of microprojections on the surface is obtained. It turned out that the number density of a convex part also becomes high. Further, in order to realize a pleat structure that can withstand pressure fluctuations, the porous support layer includes a polyamide molecule having the same functional group as that of the separation functional layer at least in a portion close to the surface layer on the separation functional layer side. It is preferably formed using a polymer solution having a solid content concentration to form a layer.

  As described above, when the porous support layer has a multilayer structure including the first layer and the second layer, the composition of the polymer solution A forming the first layer and the polymer solution B forming the second layer are , May be different from each other. “Different composition” means that at least one of the types of the polymer to be contained and its solid content concentration, the additive and its concentration, and the solvent are different.

  The solid content concentration a of the polymer solution A is preferably 12% by weight or more, and more preferably 13% by weight or more. When the solid content concentration a is 12% by weight or more, the communication hole is formed to be relatively small, so that a desired hole diameter is easily obtained.

  The solid content concentration a is preferably 18% by weight or less, and more preferably 15% by weight or less. When the solid content concentration a is 18% by weight or less, the phase separation sufficiently proceeds before solidification of the polymer, so that a porous structure is easily obtained.

  The solid content concentration b of the polymer solution B is preferably 14% by weight or more, more preferably 15% by weight or more, still more preferably 20% by weight or more, and may be 25% by weight or more. When the polysulfone concentration of the polymer solution B is 14% by weight or more, deformation of the porous structure is suppressed even when the operating pressure largely fluctuates. Since the second layer directly supports the separation functional layer, deformation of the second layer can cause damage to the separation functional layer.

  Further, the solid content concentration b is preferably 35% by weight or less, and more preferably 30% by weight or less. When the polysulfone concentration in the polymer solution B is 35% by weight or less, the surface pore diameter of the porous support layer is adjusted to such an extent that the monomer supply rate during formation of the separation functional layer does not become too small. Therefore, a convex portion having an appropriate height is formed when the separation functional layer is formed.

  The solid content concentration a and the solid content concentration b preferably satisfy the relational expression (a / b) ≦ 1.0. Further, it is more preferable that the solid content concentration a and the solid content concentration b satisfy the above-mentioned relational expressions while satisfying the respective preferable numerical ranges described above.

  The “solid content concentration” described above can be replaced with “polymer concentration”. When the polymer forming the porous support layer is polysulfone and / or polyamide, the above-mentioned “solid content concentration” can be replaced with “polysulfone and / or polyamide concentration”. The temperature of the polymer solution during application of the polymer solution is preferably within the range of 10 to 60 ° C., for example, if it is polysulfone. Within this range, the polymer solution does not precipitate and is solidified after sufficiently impregnating the organic solvent solution containing the polymer between the fibers of the substrate. As a result, the support film is firmly bonded to the substrate by the anchor effect, and the support film of the present invention can be obtained. The temperature range of the polymer solution may be appropriately adjusted depending on the viscosity of the polymer solution to be used, and the range that can be examined by those having ordinary knowledge in the art is within the scope of the present invention.

  In the formation of the support film, it is preferable to apply the polymer solution A forming the second layer at the same time as applying the polymer solution A forming the first layer on the substrate. When a curing time is provided after the application of the polymer solution A, a high-density skin layer is formed on the surface of the first layer by the phase separation of the polymer solution A, and the permeation flux is greatly reduced. Therefore, it is preferable to apply the polymer solutions A and B at the same time so that the polymer solution A does not form a high-density skin layer by phase separation. For example, “applied simultaneously” means that the polymer solution A is in contact with the polymer solution B before reaching the substrate, that is, when the polymer solution A is applied to the substrate. In this state, the polymer solution B is coated on the polymer solution A.

  After the polymer solution A and the polymer solution B are simultaneously coated on the substrate as described above, the polymer is phased by bringing the substrate coated with the polymer solution A and the polymer solution B into contact with the coagulation bath. They may be separated to form the porous support layer of the present invention. By forming the porous support layer in this way, a high permeation flux can be realized.

  Application of the polymer solution onto the substrate can be carried out by various coating methods, but pre-metering coating methods such as die coating, slide coating, curtain coating and the like that can supply an accurate amount of the coating solution are preferably applied. Furthermore, in the formation of the porous support layer having a multilayer structure of the present invention, there is further provided a double slit die method in which the polymer solution forming the first layer and the polymer solution forming the second layer are simultaneously applied. Preferably used.

  The polymers contained in the polymer solution A and the polymer solution B may be the same or different from each other. As appropriate, various characteristics such as strength characteristics, permeability characteristics, and surface characteristics of the support membrane to be manufactured can be prepared in a wider range.

  The solvent contained in the polymer solution A and the polymer solution B may be the same solvent or different solvents as long as they are good polymers. As appropriate, it can be prepared in a wider range in consideration of the strength characteristics of the support membrane to be produced and the impregnation of the polymer solution into the substrate.

  The good solvent is not particularly limited as long as it dissolves the polymer that forms the porous support layer. Examples of good solvents include N-methyl-2-pyrrolidone (NMP); tetrahydrofuran; dimethyl sulfoxide; amides such as tetramethylurea, dimethylacetamide, and dimethylformamide; lower alkyl ketones such as acetone and methylethylketone; trimethyl phosphate, γ- And esters such as butyrolactone and lactones; and mixed solvents thereof.

  The non-solvent for the polymer is not particularly limited. For example, water, hexane, pentane, benzene, toluene, methanol, ethanol, trichloroethylene, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, pentanediol, Examples thereof include aliphatic hydrocarbons such as hexanediol and low molecular weight polyethylene glycol, aromatic hydrocarbons, aliphatic alcohols, or mixed solvents thereof.

  The polymer solution may contain an additive for adjusting the pore size, porosity, hydrophilicity, elastic modulus, etc. of the support membrane. Additives for adjusting the pore size and porosity include water; alcohols; water-soluble polymers such as polyethylene glycol, polyvinyl pyrrolidone, polyvinyl alcohol and 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.

  A polyamide compound may be added to the polymer solution. Further, when two or more polymer solutions are applied in layers, it is preferable to add a polyamide compound to the polymer solution B located on the separation function layer side. In this way, the polymer compound and the polyamide compound which are the main components can be mixed in the porous support layer.

  When a polyamide compound is added to the polymer solution to form a porous support layer, the polyamide compound can also be present in the porous support layer. The presence of the polyamide compound in the porous support layer improves the adhesion between the porous support layer and the separation functional layer, and can realize a pleat structure that can withstand pressure fluctuations. “The polyamide compound is present in the porous support layer” refers to (1) the polyamide compound faces a recess between the microprotrusions 3 and 3 of the porous support layer 4 as shown in FIG. Either the state where the polyamide compound is present in the portion indicated by the number 6 or (2) the state where the polyamide compound is mixed without being phase-separated with the polymer compound which is the main component of the porous support layer may be satisfied. .

  The reason why the adhesion between the porous support layer and the separation functional layer is improved by the presence of the polyamide compound in the porous support layer is that the polyamide compound in the porous support layer and the polyamide in the separation functional layer are It is considered that the effect is exhibited by chemically bonding or showing an interaction such as physical adsorption or chemical adsorption. Therefore, the polyamide compound in the porous support layer only needs to be present in a place where the above-described interaction with the polyamide constituting the separation functional layer is allowed, and may be intermittently dispersed on the surface of the porous support layer. Or may be continuously present so as to cover the surface of the porous support layer, and is not particularly limited. The effect of the present invention can be obtained if at least a part of the polyamide compound present in the porous support layer is arranged so as to interact with the separation functional layer.

  As the coagulation bath used in the present invention, water is usually used, but it is not particularly limited as long as it does not dissolve the polymer. Further, the temperature of the coagulation bath is preferably -20 ° C to 100 ° C. More preferably, it is 10-30 degreeC. When the temperature is 100 ° C. or lower, the magnitude of vibration of the coagulation bath surface due to thermal motion can be suppressed, and the film surface can be formed smoothly. Further, when the temperature is −20 ° C. or higher, the solidification rate can be kept relatively high, and good film forming properties are realized.

  Next, the support membrane obtained under such preferable conditions is preferably 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. If it is higher than this range, the shrinkage of the support membrane will increase and the water permeability will deteriorate. Conversely, if it is low, the cleaning effect is small.

(2-2) Formation of Separation Function Layer Next, as an example of the formation process of the separation function layer constituting the composite semipermeable membrane, description will be given by forming a layer containing polyamide as a main component (that is, a polyamide separation function layer). To do. The formation process of the polyamide separation functional layer uses an aqueous solution containing the above-mentioned polyfunctional amine and an organic solvent solution containing polyfunctional acid halide (immiscible with water), and the interfacial weight on the surface of the support membrane. It includes forming a polyamide skeleton by performing condensation.

  The concentration of the polyfunctional amine in the polyfunctional amine aqueous solution is preferably in the range of 0.1 wt% to 20 wt%, and more preferably in the range of 0.5 wt% to 15 wt%. . Within this range, sufficient water permeability and salt and boron removal performance can be obtained.

  The polyfunctional amine aqueous solution may contain a surfactant, an organic solvent, an alkaline compound, an antioxidant, or the like as long as it does not interfere with the reaction between the polyfunctional amine and the polyfunctional acid halide. The surfactant has the effect of improving the wettability of the support membrane surface and reducing the interfacial tension between the aqueous amine solution and the nonpolar solvent. Since the organic solvent may act as a catalyst for the interfacial polycondensation reaction, the interfacial polycondensation reaction may be efficiently performed by adding the organic solvent.

  The polyfunctional amine aqueous solution preferably contains at least one compound among isopropyl alcohol, glycerin, triethanolamine, and triethanolamine-N-oxide, which are organic compounds having a hydroxyl group. By containing glycerin, polyamide is formed in the depression on the surface of the porous support layer when the separation functional layer is formed by interfacial polymerization.

  In order to perform the interfacial polycondensation on the support membrane, first, the polyfunctional amine aqueous solution is brought into contact with the support membrane. The contact is preferably performed uniformly and continuously on the support membrane surface. Specifically, a method of coating a support membrane with a polyfunctional amine aqueous solution and a method of immersing the support membrane in a polyfunctional amine aqueous solution can be exemplified. The contact time between the support membrane and the polyfunctional amine aqueous solution is preferably in the range of 5 seconds to 10 minutes, and more preferably in the range of 10 seconds to 3 minutes. By setting the contact time within this range, a polyfunctional amine aqueous solution in an amount suitable for forming a preferable separation functional layer can be held on the support membrane.

  After bringing the polyfunctional amine aqueous solution into contact with the support membrane, it is preferable to sufficiently drain the liquid so that no droplets remain on the membrane. The portion where the droplets remain may become a defect after the formation of the composite semipermeable membrane, and this defect deteriorates the removal performance of the composite semipermeable membrane. By sufficiently draining the liquid, generation of defects can be suppressed. The method of draining is not particularly limited. For example, as described in JP-A-2-78428, the support film after contacting with the polyfunctional amine aqueous solution is vertically gripped to allow the excess aqueous solution to flow down naturally. And a method of forcibly draining an air stream such as nitrogen from an air nozzle. In addition, after draining, the membrane surface can be dried to partially remove water from the aqueous solution.

  Next, an organic solvent solution containing polyfunctional acid halide (immiscible with water) is brought into contact with the support membrane after contact with the polyfunctional amine aqueous solution to form a crosslinked polyamide separation functional layer by interfacial polycondensation.

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

  The water-immiscible organic solvent is preferably one that dissolves the polyfunctional acid halide and does not destroy the support membrane, and may be any one that is inert to the polyfunctional amine compound and polyfunctional acid halide. . Preferred examples include hydrocarbon compounds such as hexane, heptane, octane, nonane and decane, but are not limited thereto.

  The method of bringing the organic solvent solution containing the polyfunctional acid halide into contact with the support membrane can be performed in the same manner as the method of coating the support membrane with the polyfunctional amine aqueous solution.

  In the interfacial polycondensation step of the present invention, the support membrane is sufficiently covered with a crosslinked polyamide thin film, and a water-immiscible organic solvent solution containing a polyfunctional acid halide in contact with the support membrane is left on the support membrane. It is important to keep it. For this reason, the time for performing the interfacial polycondensation is preferably from 0.1 second to 3 minutes, and more preferably from 0.1 second to 1 minute. When the interfacial polycondensation time is 0.1 seconds or more and 3 minutes or less, the support membrane can be sufficiently covered with a crosslinked polyamide thin film, and an organic solvent solution containing a polyfunctional acid halide is supported on the support membrane. Can be held on.

  After the polyamide separation functional layer is formed on the support membrane by interfacial polycondensation, excess solvent is drained. As a liquid draining method, for example, a method of removing the excess organic solvent by flowing down naturally by holding the film in the vertical direction can be used. In this case, the time for gripping in the vertical direction is preferably 1 minute or more and 5 minutes or less, and more preferably 1 minute or more and 3 minutes or less. 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 a defective part will occur in the polyamide separation functional layer, resulting in poor membrane performance.

3. Utilization of composite semipermeable membrane The composite semipermeable membrane manufactured in this way is combined with raw water flow path materials such as plastic nets, permeate flow path materials such as tricot, and a film for enhancing pressure resistance as required. The spiral semi-permeable membrane element can be formed by being wound around a cylindrical water collecting pipe having a large number of holes. Further, this element can be connected in series or in parallel and housed in a pressure vessel to constitute a composite semipermeable membrane module.

  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 better the salt removal performance, 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 1.0 MPa or more and 10.0 MPa or less. The operation pressure is a so-called transmembrane pressure. As the feed water temperature increases, the salt removal performance decreases, but the membrane permeation flux decreases as the supply water temperature decreases, so 5 ° C. or higher and 45 ° C. or lower is preferable. 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 include liquid mixtures containing TDS (Total Dissolved Solids) of 500 mg / L to 100 g / L such as seawater, brine, and drainage. Generally, TDS refers to the total amount of dissolved solids and is expressed as “mass / volume”, or expressed as “weight ratio” by regarding 1 L as 1 kg. According to the definition, the solution filtered with 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 content.

  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, and many modifications can be made within the technical idea of the present invention. It is possible by those who have.

<Creation of semipermeable membrane>
In the following examples, polysulfone UDEL p-3500 manufactured by Solvay Advanced Polymers Co., Ltd. was used as the polysulfone.

Example 1
A 15% by weight polysulfone DMF solution (polymer solution A) and a 25% by weight polysulfone DMF solution (polymer solution B) were prepared by heating and maintaining a mixture of each solvent and solute at 90 ° C. for 2 hours. did.

Each of the prepared polymer solutions was cooled to room temperature, supplied to a separate extruder, and filtered with high precision. Thereafter, the filtered polymer solution is passed through a double slit die and is high on a long-fiber nonwoven fabric made of polyethylene terephthalate fibers (thread diameter: 1 dtex, thickness: about 90 μm, air permeability: 1.3 cc / cm ² / sec). The molecular solution A was cast at a thickness of 110 μm and the polymer solution B at a thickness of 50 μm at the same time, and immediately immersed in pure water at 25 ° C. and washed for 5 minutes to obtain a support membrane.

  The obtained support membrane was immersed in a 4.0 wt% m-PDA and 5.0 wt% glycerin aqueous solution for 2 minutes, and then slowly pulled up so that the membrane surface was vertical. Nitrogen was blown from the air nozzle to remove the excess aqueous solution from the surface of the support membrane, and then held in a hot air dryer at 90 ° C. for 2 minutes. Next, an n-decane solution at 25 ° C. containing 0.12% by weight of trimesic acid chloride was applied so that the film surface was completely wetted. After leaving still for 1 minute, in order to remove excess solution from the film, the film surface was held vertically for 1 minute to drain the liquid. Then, the composite semipermeable membrane provided with a base material, a porous support layer, and a polyamide separation functional layer was obtained by washing with water at 45 ° C. for 2 minutes.

(Example 2)
A composite semipermeable membrane in Example 2 was obtained in the same manner as in Example 1 except that a DMF solution containing 18% by weight of polysulfone was used as the polymer solution A.

(Example 3)
In Example 1, except that an NMP solution of 15% by weight of polysulfone was used as the polymer solution A and an NMP solution of 25% by weight of polysulfone was used as the polymer solution B, the same as in Example 1, the same as in Example 3. A composite semipermeable membrane was obtained.

Example 4
In Example 1, the same procedure as in Example 1 was used, except that a polymer solution A was a 18% by weight polysulfone DMF solution and the polymer solution B was a 20% polysulfone DMF solution. A composite semipermeable membrane was obtained.

(Example 5)
In Example 1, the composite in Example 5 was used in the same manner as in Example 1 except that a short fiber nonwoven fabric having a yarn diameter of 1 dtex, a thickness of about 90 μm, and an air permeability of 0.7 cc / cm ² / sec was used as the base material. A semipermeable membrane was obtained.

(Example 6)
((Synthesis of polyamide molecules))
To a 500 mL eggplant-shaped flask, 12.2 g of m-PDA was added and dissolved in 250 mL of methylene chloride. After sufficiently stirring at room temperature, 20 mL of a methylene chloride solution containing 10 g of trimesic acid chloride was dropped into this solution at a rate of 2 mL / min, and the reaction was performed while maintaining the temperature at room temperature. The obtained white solid was washed with methanol and purified by reprecipitation using methylene chloride and methanol in this order. As a result, 18.0 g of polyamide molecules having a distribution between molecular weights 300 and 2000 were obtained. This molecule was dissolved in DMF.

  A DMF solution containing 15% by weight of polysulfone (Polymer solution A) and a DMF solution (Polymer solution B) containing 25% by weight of polysulfone and 0.5% by weight of the above-mentioned polyamide molecules are stirred while the mixture of each solvent and solute is stirred. It was prepared by heating and holding at 90 ° C. for 2 hours.

Each of the prepared polymer solutions was cooled to room temperature, supplied to a separate extruder, and filtered with high precision. Thereafter, the filtered polymer solution is passed through a double slit die and is high on a long-fiber nonwoven fabric made of polyethylene terephthalate fibers (thread diameter: 1 dtex, thickness: about 90 μm, air permeability: 1.3 cc / cm ² / sec). The molecular solution A was cast at a thickness of 110 μm and the polymer solution B at a thickness of 50 μm at the same time, and immediately immersed in pure water at 25 ° C. and washed for 5 minutes to obtain a support membrane.

  The obtained support membrane was immersed in a 4.0 wt% aqueous solution of m-PDA for 2 minutes, and then slowly pulled up so that the membrane surface was vertical. Nitrogen was blown from the air nozzle to remove the excess aqueous solution from the surface of the support membrane, and then held in a hot air dryer at 90 ° C. for 2 minutes. Next, an n-decane solution at 25 ° C. containing 0.12% by weight of trimesic acid chloride was applied so that the film surface was completely wetted. After leaving still for 1 minute, in order to remove excess solution from the film, the film surface was held vertically for 1 minute to drain the liquid. Then, the composite semipermeable membrane provided with a base material, a porous support layer, and a polyamide separation functional layer was obtained by washing with water at 45 ° C. for 2 minutes.

(Example 7)
In Example 6, a DMF solution containing 15% by weight of polysulfone was used as the polymer solution A, and a DMF solution containing 28% by weight of polysulfone and 0.5% by weight of the polyamide molecule was used as the polymer solution B. In the same manner as in Example 6, a composite semipermeable membrane in Example 7 was obtained.

(Comparative Example 1)
The support membrane obtained in Example 1 was immersed in a 4.0 wt% aqueous solution of m-PDA for 2 minutes, and then slowly pulled up so that the membrane surface was vertical. Nitrogen was blown from the air nozzle to remove the excess aqueous solution from the surface of the support membrane, and then held in a hot air dryer at 90 ° C. for 2 minutes. Next, an n-decane solution at 25 ° C. containing 0.12% by weight of trimesic acid chloride was applied so that the film surface was completely wetted. After leaving still for 1 minute, in order to remove excess solution from the film, the film surface was held vertically for 1 minute to drain the liquid. Then, the composite semipermeable membrane provided with a base material, a porous support layer, and a polyamide separation functional layer was obtained by washing with water at 45 ° C. for 2 minutes.

(Comparative Example 2)
A support membrane was obtained by the same procedure as in Example 1, except that only 25% by weight of the polysulfone DMF solution was applied on the nonwoven fabric with a thickness of 160 μm using a single slit die instead of a double slit die. A separation functional layer was formed on the obtained support membrane by the same procedure as in Example 1 to obtain a composite semipermeable membrane in Comparative Example 2.

(Comparative Example 3)
A composite semipermeable membrane in Comparative Example 3 was obtained in the same manner as Comparative Example 1 except that only a 15% by weight polysulfone DMF solution was used as the polymer solution.

(Comparative Example 4)
A composite semipermeable membrane in Comparative Example 4 was obtained in the same manner as Comparative Example 1 except that only a 15% by weight NMP solution of polysulfone was used as the polymer solution.

(Comparative Example 5)
A composite semipermeable membrane in Comparative Example 5 was prepared in the same manner as in Example 1, except that a polymer sulfone 20 wt% polysulfone DMF solution was used as the polymer solution A, and a polysulfone 13 wt% DMF solution was used as the polymer solution B. Obtained.

(Comparative Example 6)
The composite semipermeable membrane in Comparative Example 6 was prepared in the same manner as in Example 1 except that 25% by weight polysulfone DMF solution was used as the polymer solution A and 15% by weight polysulfone DMF solution was used as the polymer solution B. Obtained.

(Comparative Example 7)
The composite semipermeable membrane in Comparative Example 7 was prepared in the same manner as in Example 1 except that a polymer sulfone 20 wt% DMF solution was used as the polymer solution A and a polysulfone 18 wt% DMF solution was used as the polymer solution B. Obtained.

(Comparative Example 8)
A support membrane was obtained by the same procedure as in Example 1 except that only a 18% by weight polysulfone DMF solution was used as the polymer solution.
On the obtained support membrane, an aqueous solution containing 3.0% by weight of m-PDA, 0.15% by weight of sodium lauryl sulfate, 3.0% by weight of triethylamine, and 6.0% by weight of camphorsulfonic acid was applied. After leaving still for 1 minute, in order to remove excess solution from the membrane, the membrane surface was held vertically for 2 minutes to drain the solution, and nitrogen was blown from an air nozzle to remove excess aqueous solution from the surface of the support membrane. Thereafter, a hexane solution at 25 ° C. containing 0.20% by weight of trimesic acid chloride was applied so that the film surface was completely wetted. After leaving still for 1 minute, in order to remove excess solution from the film, the film surface was held vertically for 1 minute to drain the liquid. Thereafter, the separation functional layer was formed by holding in a hot air dryer at 120 ° C. for 3 minutes to obtain a composite semipermeable membrane in Comparative Example 8.

(Comparative Example 9)
A support membrane was obtained by the same procedure as in Example 1 except that only a 17% by weight polysulfone DMF solution was used as the polymer solution.
An aqueous solution containing 3.0% by weight of m-PDA was applied on the obtained support film. After leaving still for 1 minute, in order to remove excess solution from the membrane, the membrane surface was held vertically for 2 minutes to drain the solution, and nitrogen was blown from an air nozzle to remove excess aqueous solution from the surface of the support membrane. Thereafter, an Isopar L (available from ExxonMobil Corp.) solution at 25 ° C. containing 0.13% by weight of trimesic acid chloride was sprayed so that the membrane surface was completely wetted. After leaving still for 1 minute, in order to remove excess solution from the film, the film surface was held vertically for 1 minute to drain the liquid. Thereafter, the composite semipermeable membrane in Comparative Example 9 was obtained through washing with room temperature water.

(Comparative Example 10)
A DMF solution containing 15% by weight of polysulfone was applied to a nonwoven fabric with a thickness of 110 μm, and thereafter, a support membrane provided with a single porous support layer was obtained by the same procedure as in Example 1. On the porous support layer thus obtained, a DMF solution of 25% by weight of polysulfone was applied in a thickness of 50 μm, and a two-layer porous support layer was again formed through the same procedure as in Example 1. That is, the first layer and the second layer included in the porous support layer were applied and solidified sequentially, not simultaneously.
A separation functional layer was formed on the support membrane having the two porous support layers obtained in this manner by the same procedure as in Example 1 to obtain a composite semipermeable membrane in Comparative Example 10.

<Measurement of convex number density, height and standard deviation>
A composite semipermeable membrane sample was embedded with an epoxy resin, stained with OsO ₄ to facilitate cross-sectional observation, and cut with an ultramicrotome to prepare 10 ultrathin sections. A cross-sectional photograph of the obtained ultrathin slice was taken using a transmission electron microscope. The acceleration voltage at the time of observation was 100 kV, and the observation magnification was 10,000 times. About the obtained cross-sectional photograph, the number of the convex part in the distance of 2.0 micrometers in width was measured using the scale, and 10 point average surface roughness was computed as mentioned above. Based on this 10-point average surface roughness, the number of the portions having a height of 1/5 or more of the 10-point average surface roughness was taken as a convex portion, and the number was counted. The average number density of the convex portions of the separation functional layer was determined. Moreover, the height of all the convex parts in a cross-sectional photograph was measured with the scale, and while calculating | requiring the average height of a convex part, the standard deviation was calculated.

<Salt removal performance (TDS removal rate) and start / stop test>
By supplying an aqueous solution having an NaCl concentration of 3.5% by weight, a temperature of 25 ° C. and a pH of 6.5 to the composite semipermeable membrane at an operating pressure of 5.5 MPa, water treatment operation can be performed for 24 hours. After being performed, the salt removal property was measured using the permeated water obtained at an operating pressure of 5.5 MPa. Thereafter, the operation at an operating pressure of 5.5 MPa is performed for 1 minute, the pressure is reduced to 0 MPa in 30 seconds, the pressure is maintained for 1 minute, and the pressure is increased to 5.5 MPa in 30 seconds, and then the salt removal performance is measured. Went.

  The operating pressure when measuring the salt removal performance was 5.5 MPa or 4.0 MPa, and the other conditions were the same as those during cycle operation. The salt removal performance was measured using the obtained permeated water.

Practical salinity was obtained by measuring the electrical conductivity of the supplied water and the permeated water with an electric conductivity meter manufactured by Toa Radio Industry Co., Ltd. From the TDS concentration obtained by converting this practical salt content, the salt removal performance, that is, the TDS removal rate was determined by the following equation.
TDS removal rate (%) = 100 × {1− (TDS concentration in permeated water / TDS concentration in feed water)}

<Membrane permeation flux>
The amount of permeated water obtained by the above filtration treatment for 24 hours was expressed as a membrane permeation flux (m ³ / m ² / day) with a water permeation amount per cubic meter (m ³ ) per day.

The results are shown in Table 1. From Examples 1 to 7, the composite semipermeable membrane of the present invention has high water permeability and salt removal property, and excellent maintainability of these performances under operating conditions in which operation is frequently stopped and repeated and the pressure varies. I understand.

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

1 Separation function layer 2 Average line (reference line)
3 Microprojection 4 Porous support layer 5 Separation function layer 6 Polyamide

Claims (8)

(I) a substrate;
(Ii) a porous support layer having a polymer compound as a main component and disposed on the substrate;
(Iii) comprising as a main component a polyamide compound produced by a polycondensation reaction between a polyfunctional amine and a polyfunctional acid halide, and a separation functional layer provided on the porous support tank,
A composite semipermeable membrane comprising a polyamide compound in the porous support layer.   2. The composite semipermeable membrane according to claim 1, wherein at least part of the polyamide compound contained in the porous support layer is disposed so as to be in contact with the separation functional layer.   The composite semipermeable membrane according to claim 1 or 2, wherein the polyamide compound contained in the porous support layer is contained in a dent on the surface of the porous support layer.   The polymer compound that is a main component of the porous support layer and the polyamide compound are mixed in at least a part of the porous support layer. A composite semipermeable membrane as described in 1.   Polymer solution A in which the porous support layer has a multilayer structure of a first layer on the substrate side and a second layer formed on the first layer, and forms the first layer on the substrate. 5 and the polymer solution B forming the second layer are applied at the same time, and then contacted with a coagulation bath and phase-separated. Composite semipermeable membrane.   The composite semipermeable membrane according to claim 5, wherein the polymer solution B contains at least one polyamide compound.   The composite semipermeable membrane according to any one of claims 1 to 6, wherein the base material is a long-fiber nonwoven fabric containing polyester as a main component. The amount of water produced when an aqueous solution having a NaCl concentration of 3.5% by weight, a temperature of 25 ° C., and a pH of 6.5 is permeated at an operating pressure of 4.0 MPa is 1.00 m ³ / m ² / day or more. And the desalination rate is 99.80% or more, The composite semipermeable membrane in any one of Claims 1-7 characterized by the above-mentioned.