Composite semipermeable membrane and separation membrane element comprising a composite semipermeable membrane

Abstract

To provide a composite semipermeable membrane that exhibits high water production volume and solute removal capabilities even under high-pressure operating conditions, and furthermore, excellent adhesion between the substrate and the porous layer even after chemical washing. [Solution] A composite semipermeable membrane comprising a substrate, a porous layer provided on one surface of the substrate, and a separation functional layer provided on the porous layer, wherein the main component of the porous layer is a polysulfone polymer, the substrate contains fibers having polyphenylene sulfide on at least its surface, and the root mean square height Rq of the surface of the substrate on the side where the porous layer is provided is 1.0 μm or more and 10 μm or less.

Description

Technical Field

[0001] The present invention relates to a composite semipermeable membrane useful for the selective separation of liquid mixtures and a separation membrane element provided with the composite semipermeable membrane.

Background Art

[0002] In general, a composite semipermeable membrane obtained by coating a porous layer with a separation functional layer made of polyamide obtained by a polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide has high water permeability and solute removal properties, and is used for reverse osmosis treatment for removing solutes from raw water, such as seawater desalination.

[0003] In reverse osmosis treatment, a pressure higher than the difference between the osmotic pressure on the feed water side and the osmotic pressure on the permeate water side is applied to the feed water side of the composite semipermeable membrane. In recent years, reverse osmosis treatment has been used for zero liquid discharge (ZLD) to achieve zero discharge of wastewater and for concentration in the valuable substance recovery process. Depending on the solute concentration, there are also an increasing number of cases where the operation is carried out at a higher pressure than before.

[0004] In such high-pressure operation of reverse osmosis treatment, the water permeability of the composite semipermeable membrane may decrease, that is, the water production rate may decrease. When there is no pressure history, since the water permeability of the porous layer is about 100 times or more that of the separation functional layer, the water permeability of the composite semipermeable membrane is dominated by the separation functional layer. However, it has been pointed out in Patent Documents 1 and 2 that the water production rate of the composite semipermeable membrane decreases due to the densification of the porous layer caused by high-pressure operation.

[0005] Patent Documents 1 and 2 disclose a method of suppressing the decrease in the water production rate of the composite semipermeable membrane and improving the water treatment efficiency of brine with a high salt concentration by thinning the base material and the porous layer constituting the composite semipermeable membrane and reducing the permeation resistance of the composite body of the base material and the porous layer. Furthermore, in the methods described in Patent Documents 1 and 2, since more composite semipermeable membranes can be incorporated into the separation membrane element to increase the effective membrane area per unit volume of the separation membrane element, the water treatment efficiency can be improved without changing the size of the spiral type separation membrane element.

[0006] Conventionally, as the base material constituting the composite semipermeable membrane, a large number of non-woven fabrics using polyester fibers have been proposed from the viewpoints of required characteristics and cost. For example, Patent Document 3 discloses a separation membrane support made of a non-woven fabric having excellent mechanical strength that does not deform or break under pressure or the like when used as a separation membrane or a fluid separation element.

[0007] Also, Patent Document 4 discloses that a non-woven fabric using fibers mainly composed of polyphenylene sulfide having smoothness and chemical resistance is used as a separation membrane support such as a composite semipermeable membrane.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, the configurations of Patent Documents 1 to 4 have the problem that when the operating pressure is increased to treat salt water with a high seawater concentration, the solute removal performance is significantly reduced. In addition, there is a problem that after repeatedly performing chemical liquid washing with chemicals contained in drainage or cleaning liquid, such as acidic or alkaline, the base material and the porous layer are peeled off, and the solute removal performance is reduced.

[0010] An object of the present invention is to provide a composite semipermeable membrane having a high water production rate and solute removal performance even under high-pressure operating conditions, and further having excellent adhesion between the base material and the porous layer even after chemical liquid washing.

Means for Solving the Problems

[0011] To solve the above problems, the present invention includes the following configurations [1] to [8]. [1] A composite semipermeable membrane comprising a substrate, a porous layer provided on one surface of the substrate, and a separation functional layer provided on the porous layer, wherein the main component of the porous layer is a polysulfone polymer, the substrate contains fibers having polyphenylene sulfide on at least its surface, and the root mean square height Rq of the surface of the substrate on the side where the porous layer is provided is 1.0 μm or more and 10 μm or less. [2] The mass of the porous layer is 2 g / m 2 More than 10g / m 2 The composite semipermeable membrane described in [1] above is as follows: [3] The composite semipermeable membrane according to [1] or [2] above, wherein the root mean square height Rq of the surface of the substrate on the side where the porous layer is provided is 2.0 μm or more and 6.0 μm or less. [4] The polymer impregnation amount of the above substrate is 0.5 g / m 2 More than 3.0g / m 2 The composite semipermeable membrane described in any one of the above items [1] to [3], which is as follows: [5] The surface of the substrate on the side where the porous layer is provided has an uneven shape, with an average area of ​​500 μm². 2 More than 2000μm 2 The composite semipermeable membrane described in any one of the above items [1] to [4], which is as follows: [6] The surface of the substrate on which the porous layer is provided has a depth of 10 μm or more and an area of ​​500 μm relative to the number of recesses with a depth of 10 μm or more. 2 The composite semipermeable membrane described in [5] above, wherein the proportion of the above-mentioned recesses is 20% or less. [7] A composite semipermeable membrane according to any one of the above [1] to [6], wherein the polysulfone polymer is polysulfone or polyethersulfone. [8] A separation membrane element comprising a composite semipermeable membrane as described in any one of the above items [1] to [7]. [Effects of the Invention]

[0012] According to the present invention, a composite semipermeable membrane can be obtained that has high water production volume and solute removal capabilities even under high-pressure operating conditions, and further exhibits excellent adhesion between the substrate and the porous layer, thereby improving water treatment efficiency. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is an unfolded view of a composite semipermeable film according to one embodiment of the present invention. [Figure 2] Figure 2 is an exploded view of a separation membrane element according to one embodiment of the present invention. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described in detail below, but the present invention is not limited thereto.

[0015] 1.Composite semipermeable membrane As an embodiment of the present invention, a composite semipermeable membrane 1 having a substrate 2, a porous layer 3 provided on the substrate 2, and a separation functional layer 4 provided on the porous layer 3 will be described below, as shown in Figure 1. The composite in which the porous layer 3 is provided on the substrate 2 will also be referred to as a porous support.

[0016] 1.1 Base material The substrate provides physical strength to the composite semipermeable membrane. The substrate in the composite semipermeable membrane of the present invention contains fibers having polyphenylene sulfide (hereinafter referred to as "PPS") on at least its surface.

[0017] The base material only needs to contain fibers having PPS on its surface, may consist solely of fibers having PPS on its surface, or may be a blended fiber type in which fibers having PPS on its surface are mixed with fibers made of other components. In particular, from the viewpoint of improving the peel strength with respect to the porous layer made of polysulfone polymer, it is preferable to use a base material consisting solely of fibers having PPS on its surface.

[0018] The fiber having PPS on its surface may be either a fiber composed solely of PPS or a composite fiber composed of PPS and other components. In particular, a composite fiber in which a low-melting-point polymer having a lower melting point than the high-melting-point polymer is arranged around a high-melting-point polymer is preferred. Furthermore, the fiber having PPS on its surface is a composite fiber having a core-sheath structure, preferably with a structure containing a PPS component in the sheath, and more preferably a core-sheath type composite fiber in which PPS is arranged in the core and copolymerized PPS in the sheath. In the case of a core-sheath type composite fiber, the PPS in the core acts as the skeleton, resulting in excellent mechanical strength, and the copolymerized PPS in the sheath acts as the heat-bonding part, resulting in a PPS composite fiber with high adhesive properties.

[0019] By using composite fibers, the fibers in the nonwoven fabric are strongly bonded to each other by heat-sealing. Therefore, when using a nonwoven fabric as a base material, it is possible to suppress non-uniformity during casting of the polysulfone polymer solution (hereinafter also simply referred to as "polymer solution") used for forming the porous layer due to fluffing, and to suppress film defects. Furthermore, when using the above-mentioned composite fibers, the number of bonding points is increased compared to a blended fiber type which mixes fibers made only of high-melting-point polymers and fibers made only of low-melting-point polymers. As a result, the number of recessed areas in the base material is reduced, and a composite semipermeable film that can withstand high-pressure operation can be produced even when the strength of the porous layer is low.

[0020] The fibers of the substrate used in the composite semipermeable membrane of the present invention are composed of fibers having PPS on at least their surface. By having PPS on the surface of the fibers, when a polysulfone polymer described later is used as the porous layer, the chemical affinity between the porous layer and the substrate is improved, and the peel strength can be increased. Therefore, even when a smooth substrate with a small contact area is used, peeling between the substrate and the porous layer does not occur, and a high removal rate and water production volume can be maintained even during high-pressure operation.

[0021] As the fabric used as the base material, it is preferable to use a nonwoven fabric from the viewpoint of strength, ability to form irregularities, and fluid permeability. As the nonwoven fabric, both long-fiber nonwoven fabrics and short-fiber nonwoven fabrics can be preferably used.

[0022] The base material in the composite semipermeable membrane according to this embodiment is preferably a laminate in which a plurality of non-woven fabrics or the like are overlapped by applying heat and pressure in order to obtain sufficient strength and smoothness, and it is more preferable to apply heat and pressure multiple times. If the number of laminations is two or more, the texture is improved compared to the single layer, and sufficient uniformity can be obtained. Further, if the number of laminations is five or less, it is possible to suppress the formation of wrinkles during lamination and to suppress delamination between layers.

[0023] 1.1.1 Basis weight of the base material The basis weight of the base material in the composite semipermeable membrane according to this embodiment is preferably 30 g / m 2 or more and 100 g / m 2 or less, and more preferably 60 g / m 2 or more and 80 g / m 2 or less. When the basis weight of the base material is 30 g / m 2 or more, there is less over-permeation during polymer solution casting, etc., and good film-forming properties can be obtained. On the other hand, when the basis weight of the base material is 100 g / m 2 or less, the thickness of the composite semipermeable membrane is reduced, and the membrane area per composite semipermeable membrane element can be increased.

[0024] 1.1.2 Density of the base material The density of the base material in the composite semipermeable membrane according to this embodiment is preferably 0.70 g / cm 3 or more and 0.95 g / cm 3 or less. When the density of the base material is 0.70 g / cm 3 or more, there is less over-permeation during polymer solution casting, etc., and good film-forming properties can be obtained, and a composite semipermeable membrane having high mechanical strength and excellent durability can be obtained. On the other hand, when the density of the base material is 0.95 g / cm 3 or less, the polymer solution quickly penetrates into the non-woven fabric during the formation of the porous layer, so that the base material and the porous layer are firmly adhered, and a semipermeable membrane having excellent peel strength can be obtained.

[0025] 1.1.3 Thickness of the base material In the composite semipermeable membrane according to this embodiment, the thickness of the substrate is preferably 50 μm to 120 μm, more preferably 50 μm to 100 μm, and even more preferably 60 μm to 100 μm. When the thickness of the substrate is within the above range, sufficient strength for pressure resistance can be maintained, and the effective membrane area when used as a separation membrane element can be increased.

[0026] 1.1.4 Root mean square height of the substrate Rq The composite semipermeable membrane of the present invention has a root mean square height Rq (hereinafter also simply referred to as "substrate Rq") of the surface of the substrate on the side where the porous layer is provided, which is 1.0 μm or more and 10.0 μm or less. More preferably, the substrate Rq is 1.0 μm or more and 6.0 μm or less, and even more preferably 2.0 μm or more and 6.0 μm or less. When the substrate Rq is 10.0 μm or less, it is possible to prevent the formation of defects and deformation of the porous layer and separation functional layer caused by irregularities in the substrate when the composite semipermeable membrane is operated under high pressure. Therefore, a composite semipermeable membrane with high solute removal performance can be obtained regardless of the strength of the porous layer. Furthermore, when the substrate Rq is 1.0 μm or more, the contact area between the substrate and the porous layer is increased, and a composite semipermeable membrane with excellent peel strength between the substrate and the porous layer can be obtained.

[0027] The Rq of the substrate can be calculated by observing the surface of the substrate on the side where the porous layer is provided using a laser microscope. Specifically, it is calculated using the method described later in "Root Mean Square Height Rq of Substrate". If the substrate already has a porous layer, the Rq of the substrate can be measured by immersing it in a suitable solvent that can dissolve the porous layer and removing the porous layer.

[0028] The Rq of the substrate can be controlled, for example, by the number of times, temperature, and linear pressure of the thermocompression bonding using a flat roll as described in "2.1 Substrate Formation Process" below.

[0029] 1.1.6 Average area of ​​recesses in the substrate In this embodiment, the surface of the substrate on the side where the porous layer is provided in the composite semipermeable membrane has an uneven shape, with an average area of ​​500 μm². 2 More than 2000μm 2Preferably, the following, 500 μm 2 More than 1500μm 2 It is more preferable that the average area of ​​the recesses is 2000 μm². 2 The following conditions prevent the formation of defects and deformation of the porous layer and separation functional layer caused by irregularities in the substrate when the composite semipermeable membrane is operated under high pressure. Furthermore, the average area of ​​the recesses is 500 μm². 2 With these conditions, the peel strength between the substrate and the porous layer is increased, and the performance degradation of the separation membrane element due to peeling near the interface between the substrate and the porous layer is less likely to occur. Furthermore, it is preferable that the number of recesses on the surface of the substrate be between 200 and 600 for a substrate measuring 1224 μm square.

[0030] The average area of ​​the recesses in the substrate can be calculated by observing the surface of the substrate on the side where the porous layer is provided using a laser microscope. Specifically, it is calculated using the method described later in "Average Area of ​​Recesses in Substrate". If the substrate already has a porous layer, it can be observed by immersing it in a suitable solvent that can dissolve the porous layer, leaving only the substrate.

[0031] The average area of ​​the recesses in the base material can be controlled, for example, by making the fibers of the base material a composite fiber in which a low-melting-point polymer having a lower melting point than the high-melting-point polymer is arranged around the high-melting-point polymer, or by the number of times, temperature, and linear pressure of the heat-compression bonding with a flat roll as described in "2.1 Base Material Formation Process" below.

[0032] 1.1.7 Percentage of recesses in the substrate In the composite semipermeable membrane according to this embodiment, the surface of the substrate on the side where the porous layer is provided has an uneven shape, with a depth of 10 μm or more relative to the number of recesses with a depth of 10 μm or more and an area of ​​500 μm. 2 The proportion of the number of recesses (hereinafter also referred to as the "proportion of 10 μm recesses") is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less. Depth 10 μm or more and area 500 μm 2If the above-mentioned recesses are present in the substrate, when the composite semipermeable membrane is operated under high pressure, defects and deformation of the porous layer and separation functional layer due to the recesses in the substrate tend to occur, and the solute removal performance tends to decrease. Therefore, if the proportion of 10 μm recesses is within the above range, high solute removal performance can be obtained even when the composite semipermeable membrane is operated under high pressure.

[0033] The ratio of recesses in the substrate can be calculated by observing the surface of the substrate on the side where the porous layer is provided using a laser microscope. Specifically, it is calculated using the method described later in "Ratio of Recesses in Substrate". If the substrate already has a porous layer, it can be observed by immersing it in a suitable solvent that can dissolve the porous layer, leaving only the substrate.

[0034] The ratio of recesses in the base material can be controlled, for example, by making the base material fibers into composite fibers in which a low-melting-point polymer having a lower melting point than the high-melting-point polymer is arranged around the high-melting-point polymer, or by the number of times, temperature, and linear pressure of heat-compression bonding with a flat roll as described in "2.1 Base Material Formation Process" below.

[0035] 1.1.8 Amount of polymer impregnation into the substrate The amount of polymer impregnation in the substrate of the composite semipermeable film according to this embodiment is 0.5 g / m². 2 More than 3.0g / m 2 The following is preferable: 0.5 g / m 2 More than 2.0g / m 2 The following is more preferable: 0.5 g / m 2 More than 1.0g / m 2 The following is even more preferable. Polymer impregnation amount refers to the amount of polymer that forms the porous layer contained in the substrate after the porous layer has been peeled off, and can be measured by the method described in "polymer impregnation amount of substrate" below. By setting the polymer impregnation amount of the substrate within the above range, the sealing agent of the separation membrane element can be well impregnated into the substrate and the porous layer, and the separation membrane element can exhibit good removal performance. Furthermore, when the polymer impregnation amount is within the above range, the amount of polyfunctional amine adsorbed on the polymer portion in the substrate during the formation of the separation functional layer is within an appropriate range, and a separation functional layer with excellent salt removal performance can be formed.

[0036] The amount of polymer impregnation into the substrate can be controlled, for example, by conditions such as the thickness of the polymer solution applied to the substrate, the temperature of the polymer solution, and the time from when the polymer solution is applied to the substrate until it is immersed in the solidification solution (solidification bath) in the "2.2 Porous Layer Formation Process" described later, or by the number of times, temperature, and linear pressure of the heat-compression bonding with a flat roll as described in "2.1 Substrate Formation Process".

[0037] 1.2 Porous layer The main component of the porous layer in the composite semipermeable membrane of the present invention is a polysulfone polymer. As described above, by using a polysulfone polymer as the porous layer, the chemical affinity between the porous layer and the substrate composed of fibers having PPS on at least its surface is improved, and the peel strength can be increased. "Main component" means a component that accounts for 50% by mass or more. The proportion of polysulfone polymer in the porous layer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably consists only of polysulfone polymer.

[0038] "Polysulfone polymer" refers to a polymer having an aromatic ring, a sulfonyl group, and an ether group in its main chain. For example, polysulfone polymers represented by the chemical formulas (I), (II), and (III) below are preferably used, but the present invention is not limited to these. In the formulas below, n is an integer of 1 or more, for example, an integer such as 50 to 80. Furthermore, copolymers with other monomers are also possible, and functional groups may be introduced or substituted, as long as they do not hinder the effects of the present invention.

[0039] [ka]

[0040] Specific examples of polysulfone polymers include polysulfone (hereinafter referred to as "Psf"), polyethersulfone, polyphenylsulfone homopolymers, and copolymers thereof. One type may be used alone, or two or more types may be used in combination. Among these, polysulfone or polyethersulfone is preferred, and polysulfone is more preferred, due to its high chemical, mechanical, and thermal stability and ease of molding.

[0041] The mass-average molecular weight (hereinafter referred to as "Mw") of Psf, measured by gel permeation chromatography (GPC) with N-methylpyrrolidone as the solvent and polystyrene as the standard substance, is preferably between 10,000 and 200,000, and more preferably between 15,000 and 100,000. When the Mw of Psf is 10,000 or higher, desirable mechanical strength and heat resistance can be obtained as a porous layer. Furthermore, when the Mw is 200,000 or lower, the viscosity of the solution is within an appropriate range, and good moldability can be achieved.

[0042] 1.2.1 Mass of the porous layer The mass of the porous layer in the composite semipermeable membrane according to this embodiment is 2 g / m². 2 More than 10g / m 2 The following is preferable: 2 g / m 2 More than 8g / m 2 The following is more preferable: 4 g / m 2 More than 8g / m 2 The following is even more preferable: The mass of the porous layer is 2 g / m 2 The above conditions ensure that the necessary strength and surface morphology for a porous layer are obtained, and performance does not deteriorate easily even during high-pressure operation. Furthermore, the mass of the porous layer is 10 g / m². 2 Under the following conditions, the permeation resistance caused by the thickness of the porous layer is suppressed, resulting in a composite semipermeable membrane with a high water production capacity retention rate. Furthermore, the effective membrane area of ​​the separation membrane element can also be increased.

[0043] The mass of the porous layer can be controlled by, for example, the polymer concentration in the polymer solution, the thickness of the polymer solution applied to the substrate, and the temperature of the coagulation solution.

[0044] 1.2.2 Thickness of the porous layer In the composite semipermeable membrane according to this embodiment, the thickness of the porous layer is preferably 4 μm to 30 μm, more preferably 4 μm to 12 μm, and even more preferably 4 μm to 10 μm. When the thickness of the porous layer is 4 μm or more, it can be applied without generating surface defects. Furthermore, when the thickness of the porous layer is 30 μm or less, a composite semipermeable membrane with a high water production capacity can be obtained.

[0045] The thickness of the porous layer can be controlled, for example, by the thickness of the polymer solution applied to the substrate, the temperature of the coagulation solution, and the amount of impregnation controlled by the substrate weight.

[0046] 1.3 Separation functional layer The separation functional layer of the composite semipermeable membrane according to this embodiment preferably contains polyamide, and more preferably contains polyamide as a main component. "Contained as a main component" means that the polyamide accounts for 50% by mass or more of the components of the separation functional layer. Furthermore, the polyamide contained in the separation functional layer is preferably a crosslinked polyamide, and more preferably a crosslinked aromatic polyamide.

[0047] "Polyamide" refers to a polycondensate formed by polycondensing a polyfunctional amine and a polyfunctional acid halide.

[0048] "Cross-linked polyamide" refers to a polyamide having a cross-linked structure. Examples include a form in which a cross-linked structure is formed via a cross-linking agent, and a form in which at least one of a polyfunctional amine and a polyfunctional acid halide is trifunctional or more, and the polyamide forms a network-like cross-linked structure.

[0049] "Cross-linked aromatic polyamide" refers to a cross-linked polyamide formed by polycondensation of a polyfunctional aromatic amine and a polyfunctional aromatic acid halide.

[0050] "Cross-linked aliphatic polyamide" refers to a cross-linked polyamide formed by polycondensation of a polyfunctional aliphatic amine and a polyfunctional aromatic acid halide.

[0051] The presence of polyamide in the separation functional layer can be confirmed, for example, by ATR-FTIR (total internal reflection-Fourier transform infrared spectroscopy).

[0052] In particular, the separation functional layer preferably contains 50% by mass or more of cross-linked polyamide, more preferably 80% by mass or more, and even more preferably 90% by mass or more, from the viewpoint of exhibiting high solute removal performance.

[0053] From the viewpoint of obtaining rigid molecular chains and forming a pore structure suitable for the removal of fine solutes such as hydrated ions and boron, it is preferable that the crosslinked polyamide contains at least one of a polyfunctional amine and a polyfunctional acid halide that is trifunctional or more. In particular, it is preferable that the separation functional layer contains a crosslinked aromatic polyamide obtained by polycondensation of a polyfunctional aromatic amine and a polyfunctional aromatic acid halide.

[0054] A "polyfunctional amine" refers to an amine having at least two primary and / or secondary amino groups in one molecule. Examples of polyfunctional amines include polyfunctional aromatic amines in which two amino groups are bonded to the aromatic ring in an ortho, meta, or para position, such as o-phenylenediamine, m-phenylenediamine (hereinafter referred to as "m-PDA"), p-phenylenediamine, o-xylylenediamine, m-xylylenediamine, p-xylylenediamine, o-diaminopyridine, m-diaminopyridine, and p-diaminopyridine; and polyfunctional aromatic amines such as 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, and 4-aminobenzylamine. Furthermore, examples of polyfunctional amines include aliphatic amines such as ethylenediamine and propylenediamine, and alicyclic polyfunctional amines such as 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, piperazine, 2,5-dimethylpiperazine, 2-methylpiperazine, 2,6-dimethylpiperazine, 2,3,5-trimethylpiperazine, 2,5-diethylpiperazine, 2,3,5-triethylpiperazine, 2-n-propylpiperazine, 2,5-di-n-butylpiperazine, 1,3-bispiperidylpropane, and 4-aminomethylpiperazine. These polyfunctional amines may be used individually or in combination.

[0055] In particular, from the viewpoint of solute removal, water permeability, and heat resistance of the composite semipermeable membrane, it is preferable to use m-PDA, p-phenylenediamine, and 1,3,5-triaminobenzene as the polyfunctional amine. Among these, it is more preferable to use m-PDA due to its availability and ease of handling. These polyfunctional aromatic amines may be used individually or in combination of two or more.

[0056] "Polyfunctional acid halides" refer to acid halides or polyfunctional acid anhydride halides having at least two halogenated carbonyl groups in one molecule, and are not particularly limited as long as they form a separation functional layer of polyamide through polycondensation with the above-mentioned polyfunctional amines. Examples of trifunctional acid halides include trimesic acid chloride (hereinafter referred to as "TMC"), 1,3,5-cyclohexanetricarboxylic acid trichloride, and 1,2,4-cyclobutanetricarboxylic acid trichloride. Examples of difunctional acid halides include aromatic difunctional acid halides such as biphenyldicarboxylic acid dichloride, biphenylenecarboxylic acid dichloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, and naphthalenedicarboxylic acid chloride; aliphatic difunctional acid halides such as adipoyl chloride and sebacoyl chloride; and alicyclic difunctional acid halides such as cyclopentanedicarboxylic acid dichloride, cyclohexanedicarboxylic acid dichloride, and tetrahydrofrancicarboxylic acid dichloride. These polyfunctional acid halides may be used individually or in combination.

[0057] From the viewpoint of solute removal and heat resistance of the composite semipermeable membrane, the polyfunctional acid halide is more preferably a polyfunctional aromatic acid chloride having 2 to 4 carbonyl chloride groups in one molecule.

[0058] 1.4 Separation membrane element An example of the configuration of a separation membrane element equipped with a composite semipermeable membrane according to this embodiment will be described with reference to Figure 2. As shown in Figure 2, the separation membrane element 5 comprises a composite semipermeable membrane 1, a supply-side flow channel material 8, a permeable-side flow channel material 9, a water collection pipe 10, and end plates 6 and 7.

[0059] The supply-side channel material 8 is positioned opposite the supply side of the composite semipermeable membrane 1 and is wrapped around the water collection pipe 10 together with the composite semipermeable membrane 1. A net is preferred as the supply-side channel material 8. By using a supply-side channel material 8 with a thickness of 0.3 mm to 1.0 mm, the water treatment efficiency of the separation membrane element using the composite semipermeable membrane according to this embodiment can be further improved.

[0060] The permeable channel material 9 is positioned opposite the permeable side of the composite semipermeable membrane 1 and is spirally wound around the water collection pipe 10 together with the composite semipermeable membrane 1. When using the composite semipermeable membrane according to this embodiment, it can withstand the winding pressure, thereby suppressing deformation of the porous layer and the separation functional layer, and improving the initial processing efficiency of the separation membrane element.

[0061] For example, tricot or a protrusion-adhering sheet can be used as the permeable channel material 9. By using a permeable channel material 9 with a thickness of 0.1 mm to 0.5 mm, the processing efficiency of the separation membrane element using the composite semipermeable membrane according to this embodiment can be further improved.

[0062] The water collection pipe 10 is a hollow cylindrical member having multiple holes on its side.

[0063] The end plates 6 and 7 are disc-shaped members equipped with multiple supply ports (or discharge ports).

[0064] The separation of fluids by the separation membrane element 5 will now be explained. The supply water 11 is supplied to the separation membrane element 5 from multiple supply ports on the end plate 6. The supply water 11 moves within the supply-side channel formed by the supply-side channel material 8 on the supply side of the composite semipermeable membrane 1. The fluid that permeates through the composite semipermeable membrane 1 (shown as permeate water 12 in the figure) moves within the permeate-side channel formed by the permeate-side channel material 9. The permeate water 12 that reaches the collection pipe 10 enters the inside of the collection pipe 10 through the holes in the collection pipe 10. The permeate water 12 that has flowed inside the collection pipe 10 is discharged to the outside from the end plate 7. On the other hand, the fluid that did not permeate through the composite semipermeable membrane 1 (shown as concentrated water 13 in the figure) moves within the supply-side channel and is discharged to the outside from the end plate 7. In this way, the supply water 11 is separated into permeate water 12 and concentrated water 13.

[0065] 2. Method for manufacturing composite semipermeable membranes 2.1 Substrate Formation Process This section provides an example of the substrate formation process when a laminate of nonwoven fabrics is used as the substrate for a composite semipermeable membrane.

[0066] The base material is obtained by heat-pressing a laminate of nonwoven fabrics using, for example, a two-roll x two-set system, a two-roll x three-set system, or a three-roll system such as elastic / metal / elastic, elastic / metal / metal, or metal / elastic / metal, using two or more sets of metal / metal or metal / elastic flat rolls continuously or discontinuously during the manufacturing process.

[0067] A "flat roll" refers to a roll with no irregularities on its surface. For example, by using a combination of a flat metal roll and an elastic roll, it is possible to suppress the fusion of fibers on the surface of the nonwoven fabric and maintain its shape.

[0068] Examples of elastic rolls include so-called paper rolls such as paper, cotton, and aramid paper, and resin rolls such as urethane resin, epoxy resin, silicone resin, polyester resin, and hard rubber.

[0069] The surface temperature of the metal roll is preferably 20 to 90°C lower than the melting point of the polymer constituting at least the surface of the fibers constituting the base material, and more preferably 30 to 70°C lower. If the surface temperature of the metal roll is 20°C or more lower than the melting point of the polymer constituting at least the surface of the fibers constituting the base material, excessive fusion of the surface fibers of the base material can be suppressed, the polysulfone polymer solution for forming the porous layer can penetrate more easily, and a porous support with excellent peel strength can be obtained. On the other hand, if the difference between the surface temperature of the metal roll and the melting point of the polymer constituting at least the surface of the fibers constituting the nonwoven fabric is 90°C or less, the fibers constituting the base material can be firmly bonded to each other, and the unevenness and recess area of ​​the base material can be controlled.

[0070] Furthermore, it is also preferable to create a temperature difference between the metal roll and the elastic roll, so that the surface temperature of the elastic roll is 10 to 120°C lower than the surface temperature of the metal roll.

[0071] Furthermore, the linear pressure of the flat roll is preferably 196 N / cm or more and 4900 N / cm or less, more preferably 490 N / cm or more and 4900 N / cm or less, and even more preferably 980 N / cm or more and 4900 N / cm or less. When the linear pressure of the flat roll is 196 N / cm or more, the fibers constituting the substrate are firmly bonded to each other, and the unevenness and recess area of ​​the substrate can be controlled. Also, when the linear pressure of the flat roll is 4900 N / cm or less, excessive fusion of the surface fibers of the substrate can be suppressed, and a porous support with excellent peel strength can be obtained without hindering the penetration of the polymer solution into the substrate.

[0072] The Rq of the substrate can be controlled by adjusting the surface temperature and linear pressure of the flat rolls mentioned above. For example, the Rq of the substrate can be reduced by increasing the surface temperature of the metal rolls, increasing the linear pressure of the flat rolls, or extending the thermocompression bonding time.

[0073] 2.2 Process for forming a porous layer The process for forming the porous layer in the composite semipermeable membrane according to this embodiment comprises the following steps (a) and (b). Step (a) A step of forming a flat film from a polymer solution for forming a porous layer, which is obtained by dissolving a polysulfone polymer in a good solvent. Step (b) A step of obtaining a porous layer by solidifying the polysulfone polymer in a solidification solution containing a non-solvent and a good solvent for the polysulfone polymer.

[0074] The process for forming a porous layer may further include a step of preparing a polysulfone polymer solution by dissolving a polysulfone polymer, which is a component for forming the porous layer, in a good solvent for the polysulfone polymer.

[0075] The details of the polysulfone polymer that forms the main component of the porous layer are as described above. The following conditions are particularly preferred when the polysulfone polymer is Psf.

[0076] A "good solvent" is one that dissolves polysulfone polymers. By selecting a good solvent, the rate at which the good solvent flows out of the polymer solution in step (b) above can be adjusted. As a result, the surface properties of the porous layer, the density layer thickness, and the surface roughness can be controlled. As a good solvent, at least one solvent selected from the group consisting of amides such as N-methylpyrrolidone, tetrahydrofuran, dimethyl sulfoxide, tetramethylurea, N,N-dimethylacetamide, N,N-dimethylformamide (hereinafter referred to as "DMF"), N,N-dimethylisobutylamide, N,N-diisopropylisobutylamide, and N,N-bis(2-ethylhexyl)isobutylamide, lower alkyl ketones such as acetone and methyl ethyl ketone, esters such as trimethyl phosphate, and lactones such as γ-butyrolactone is preferably used. Among these, dimethyl sulfoxide and DMF are preferably used as good solvents.

[0077] Step (a) can be carried out by coating a polysulfone polymer solution onto a substrate or by immersing the substrate in a polysulfone polymer solution.

[0078] The application of polymer solutions to substrates can be carried out by various coating methods. Among these, pre-metering coating methods such as die coating, slide coating, and curtain coating, which allow for the application of precise amounts of solution, are preferred. Furthermore, in the formation of porous layers, the slit die method for applying polymer solutions is even more preferably used.

[0079] The concentration of the polysulfone polymer in the polymer solution (i.e., the solid content concentration) is preferably 15% by mass or more and 30% by mass or less, more preferably 16% by mass or more and 25% by mass or less, and even more preferably 17% by mass or more and 20% by mass or less. When the concentration is 15% by mass or more, the mass of the porous layer is 2 g / m 2 More than 10g / m 2 Sufficient porous layer strength can be obtained even under the following conditions. Furthermore, when the concentration is 30% by mass or less, the viscosity of the polymer solution falls within an appropriate range, allowing for the application of a precise amount of solution using various coating methods.

[0080] The temperature of the polymer solution when applied to the substrate is preferably between 10°C and 60°C. When the polymer solution temperature is within this range, the polymer does not precipitate, and the polymer solution is sufficiently impregnated into the spaces between the fibers of the substrate before solidifying. As a result, a porous support can be obtained in which the porous layer is firmly bonded to the substrate by impregnation. The preferred temperature range of the polymer solution can be appropriately adjusted depending on the viscosity of the polysulfone-based polymer solution used.

[0081] Furthermore, the polysulfone polymer can be selected as appropriate, taking into consideration various properties such as the strength characteristics, permeability characteristics, and surface characteristics of the porous layer to be manufactured.

[0082] For example, by pouring a polymer solution onto a substrate to a certain thickness and then wet-solidifying it in a solidification bath, a porous layer can be obtained in which most of the surface has fine pores with a diameter of several 1 to 30 nm.

[0083] The solvent contained in the polymer solution may be the same solvent as the polysulfone polymer, or a different solvent, as long as it is a good solvent for the polysulfone polymer. It can be adjusted as appropriate, taking into account the strength characteristics of the porous layer to be manufactured and the impregnation of the polymer solution into the substrate.

[0084] As described above, applying a polymer solution to a substrate causes the polymer solution to impregnate the substrate. To control the impregnation of the polymer solution into the substrate, methods include controlling the time between applying the polymer solution to the substrate and immersing it in a solidification solution (solidification bath), or adjusting the viscosity by controlling the temperature or concentration of the polymer solution. It is also possible to combine these methods.

[0085] In step (b), the polymer solution placed on the substrate is immersed in a coagulation solution in which the solubility of the polysulfone polymer is lower than that of the good solvent in the polymer solution, thereby solidifying the polysulfone polymer and forming a three-dimensional network structure.

[0086] Furthermore, by including a non-solvent such as water and a good solvent in the coagulation solution, it becomes possible to form a dense layer on the film surface through non-solvent-induced phase separation.

[0087] Examples of non-solvents include water, hexane, pentane, benzene, toluene, methanol, ethanol, trichloroethylene, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, pentanediol, hexanediol, low molecular weight polyethylene glycol, aliphatic hydrocarbons, aromatic hydrocarbons, aliphatic alcohols, or mixtures thereof.

[0088] The temperature of the coagulation solution is preferably between 5°C and 50°C, and more preferably between 5°C and 30°C. When the temperature of the coagulation solution is 50°C or lower, the vibration of the coagulation bath surface due to thermal motion does not become excessive, and the surface smoothness of the porous layer is improved. Furthermore, when the temperature of the coagulation solution is 5°C or higher, a sufficient coagulation rate is obtained, and film formation is good. In addition, when the temperature of the coagulation solution is within the above range, a porous layer with a surface pore size of 3 nm to 10 nm is easily obtained.

[0089] Next, it is preferable to wash the porous support with hot water to remove the solvent used in the polymer solution remaining in the resulting porous support. The temperature of the hot water at this time is preferably 50°C to 100°C, and more preferably 60°C to 95°C. If the temperature of the hot water is 100°C or lower, the degree of shrinkage of the porous support can be kept to a minimum. Also, if the temperature of the hot water is 50°C or higher, a high cleaning effect can be obtained.

[0090] 2.3 Process for forming the separation functional layer The separation functional layer can be obtained, for example, by forming a polyamide by polycondensation of a polyfunctional amine and a polyfunctional acid halide, as described above. Interfacial polymerization is the most preferred method of polycondensation from the viewpoint of productivity and performance. That is, the separation functional layer is preferably formed by performing interfacial polycondensation on the surface of the porous layer using an aqueous solution containing a polyfunctional amine and an organic solvent containing a polyfunctional acid halide. This process forms the polyamide. The following describes a specific process for forming a crosslinked aromatic polyamide using a polyfunctional aromatic amine as the polyfunctional amine and a polyfunctional aromatic acid chloride as the polyfunctional acid halide, but the present invention is not limited thereto.

[0091] Interfacial polymerization comprises the following steps (c) and (d). Step (c) A step of bringing an aqueous solution containing a polyfunctional aromatic amine into contact with a porous layer. Step (d) is a step in which, after step (c), a solution containing a polyfunctional aromatic acid chloride is brought into contact with the porous layer.

[0092] In step (c), the concentration of the polyfunctional aromatic amine in the aqueous solution of the polyfunctional aromatic amine is preferably 0.1% by mass or more and 20% by mass or less, and preferably 0.5% by mass or more and 15% by mass or less. When the concentration of the polyfunctional aromatic amine is within the above range, sufficient solute removal performance and water permeability can be obtained.

[0093] It is preferable to apply the polyfunctional aromatic amine aqueous solution uniformly and continuously to the porous layer. Specifically, examples include coating the porous layer with the polyfunctional aromatic amine aqueous solution or immersing the porous layer in the polyfunctional aromatic amine aqueous solution. The contact time between the porous layer and the polyfunctional aromatic amine aqueous solution is preferably 1 second to 10 minutes, and more preferably 10 seconds to 3 minutes.

[0094] After contacting the porous layer with the polyfunctional aromatic amine aqueous solution, it is preferable to remove any remaining liquid droplets from the surface of the porous support. Removing the liquid can suppress the occurrence of defects in the separation functional layer. Methods for removing the liquid include, for example, holding the porous support vertically after contact with the polyfunctional aromatic amine aqueous solution to allow excess solution to flow naturally, or forcibly removing the liquid by blowing a stream of air such as nitrogen from an air nozzle. After removing the liquid, the film surface can also be dried to remove some of the water from the aqueous solution.

[0095] In step (d), the concentration of polyfunctional aromatic acid chloride in the solution is preferably 0.01% by mass or more and 10% by mass or less, and more preferably 0.02% by mass or more and 2.0% by mass or less. A sufficient reaction rate can be obtained when the concentration of polyfunctional aromatic acid chloride in the solution is 0.01% by mass or more. Furthermore, the occurrence of side reactions can be suppressed when the concentration of polyfunctional aromatic acid chloride in the solution is 10% by mass or less.

[0096] The solvent used in the solution for dissolving the polyfunctional aromatic acid chloride is preferably an organic solvent that is immiscible with water, dissolves the polyfunctional aromatic acid chloride without destroying the porous support, and is inert to the polyfunctional aromatic amine and the polyfunctional aromatic acid chloride. Preferred examples of organic solvents include hydrocarbon compounds such as n-nonane, n-decane, n-undecane, n-dodecane, isooctane, isodecane, and isododecane, or mixtures thereof.

[0097] The method for contacting a porous layer with an organic solvent solution of polyfunctional aromatic acid chloride and an aqueous solution of polyfunctional aromatic amine can be the same as the method for coating the porous layer with the aqueous solution of polyfunctional aromatic amine.

[0098] After the reaction, the organic solvent is removed from the film surface. Methods for removing the organic solvent include, for example, vertically gripping the porous support and allowing excess organic solvent to drain naturally; drying the organic solvent by blowing air with a fan; or removing excess organic solvent with a water-air mixture.

[0099] 3. Methods of using composite semipermeable membranes As described above, the composite semipermeable membrane according to this embodiment is suitably used as a spiral-type separation membrane element. Furthermore, these elements can be connected in series or parallel and housed in a pressure vessel to form a separation membrane module.

[0100] Furthermore, the above-mentioned composite semipermeable membranes, separation membrane elements, and separation membrane modules can be combined with pumps that supply water to them, and devices that pre-treat the supply water to constitute a fluid separation system. By using this separation system, for example, gas separation or separation of supply water into permeate water such as drinking water and concentrated water that did not permeate the membrane can be performed to obtain water suitable for the purpose.

[0101] Examples of feedwater treated by the composite semipermeable membrane according to this embodiment include liquid mixtures containing 500 mg / L to 100 g / L of TDS (Total Dissolved Solids), such as seawater, brine, and wastewater. Generally, TDS is expressed as "mass / volume" or "mass ratio". By definition, it can be calculated from the mass of the residue after evaporating a solution filtered through a 0.45 micron filter at a temperature of 39.5 to 40.5°C, but a simpler method is to convert it from the practical salinity (S).

[0102] A higher operating pressure when permeating feedwater through the composite semipermeable membrane improves the solute removal rate. However, considering the increased energy required for operation and the durability of the composite semipermeable membrane, the operating pressure when permeating feedwater through the composite semipermeable membrane is preferably between 0.5 MPa and 12 MPa. Higher feedwater temperatures decrease the solute removal rate, while lower temperatures reduce the amount of water produced. Therefore, a feedwater temperature of 5°C to 55°C is preferable.

[0103] The composite semipermeable membrane according to this embodiment allows for the appropriate modification of the separation functional layer according to the solute to be removed. For example, by providing a separation functional layer containing cross-linked aromatic polyamide in the composite semipermeable membrane, it can be used as a reverse osmosis membrane for treating seawater or brine. Furthermore, the NaCl removal rate of the composite semipermeable membrane, calculated by the method described later in "NaCl removal rate and water production volume of composite semipermeable membrane," is preferably 99.70% or higher, more preferably 99.80% or higher, and even more preferably 99.83% or higher. The water production volume of the composite semipermeable membrane is 0.90 m³. 3 / m 2 / day or more is preferable, 0.93m 3 / m 2 It is more preferable that the water production volume retention rate after the high-pressure test is 75% or higher, more preferably 80% or higher, and even more preferably 85% or higher. It is also preferable that the water production volume retention rate and the NaCl removal rate simultaneously satisfy the above ranges.

[0104] Furthermore, when treating supply water with high solute concentrations, such as seawater, a high pH of the supply water may lead to the formation of magnesium and other scales. Additionally, there is a concern that filtering high-pH supply water may degrade the membrane, so it is preferable that the pH of the supply water be neutral.

[0105] In this embodiment, the composite semipermeable membrane preferably has a peel strength between the porous layer and the substrate measured by the method described later in "Peel Strength After Chemical Treatment" of 30 N / 15 mm or more, more preferably 40 N / 15 mm or more, and even more preferably 50 N / 15 mm or more. If the peel strength is 20 N / 15 mm or more, a composite semipermeable membrane with excellent durability that does not cause practical problems can be obtained. [Examples]

[0106] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited thereto. Unless otherwise specified, the porous support was obtained by immersing a composite semipermeable membrane in a 2% by mass sodium hypochlorite aqueous solution for 48 hours and removing the separation functional layer. The substrate may be measured before the porous layer is formed, or if a porous layer is already provided on the substrate, the porous support may be immersed in a good solvent (DMF) at 60°C for 24 hours to dissolve the porous layer, replaced with pure water, dried at 120°C for 2 hours, and the substrate from which the porous layer has been removed may be measured.

[0107] <Mass of the porous layer> A porous support was cut into a rectangle measuring 0.11 m × 0.19 m, dried at 120°C for 2 hours, and its mass was measured. Additionally, masking tape (P-Cut Tape No. 4140, 100 mm wide, manufactured by Teraoka Seisakusho Co., Ltd.) was applied to the porous layer side of the support, and the tape was peeled off twice in the longitudinal (MD) direction to remove the porous layer from the substrate. The mass of the substrate from which the porous layer had been removed was measured, and the mass of the porous layer was calculated using the following formula (1). The same procedure was performed for five different samples, the arithmetic mean of the obtained values ​​was calculated, and the value rounded to the first decimal place was taken as the mass of the porous layer. Mass of porous layer [g / m 2 ] = (mass of porous support - mass of substrate) / (0.11 × 0.19) ... Equation (1).

[0108] <Thickness of the porous layer> The thickness of the composite semipermeable membrane was measured using a Dial Thickness Gauge G-7C (manufactured by Ozaki Seisakusho Co., Ltd.). At this time, since the separation functional layer was very thin, the thickness of the composite semipermeable membrane was considered to be the sum of the thickness of the substrate and the porous layer. Subsequently, the porous support layer was peeled off from the substrate with tape using the method described in "Mass of the Porous Layer" above, and the thickness of the obtained substrate was measured with a Dial Thickness Gauge G-7C. The difference between the thickness of the composite semipermeable membrane and the thickness of the substrate was taken as the thickness of the porous layer. For each thickness measurement, the arithmetic mean of 20 randomly selected measurement points on the same membrane surface was calculated and the value was rounded to the first decimal place.

[0109] <Root mean square height of the base material Rq> The surface of the substrate forming the porous layer was observed using a laser microscope (Olympus OLS4100) with a standard lens at 20x magnification. The lowest concave point was set as the lower height limit, and the highest convex point as the upper height limit, and the surface shape was measured. The observation size of the substrate was 1224 μm square. Next, the data obtained from the measurements was processed using OLYMPUS analysis software OLS5100LEXT. Noise was removed by automatic noise reduction and tilt correction was performed. Then, "surface roughness" was selected, and "Rq" was calculated under the analysis conditions shown below. The same operation was performed on five different substrates, and the arithmetic mean of the obtained values ​​was calculated and rounded to the second decimal place to obtain the Rq value for each substrate. [Analysis conditions] Measurement range: Entire area (1224 μm square) Filter type: Gaussian Parameters: Height / Composite Histogram class division method: 200 divisions Load area ratio for V-parameters: p=10%, q=80% Load area ratio for Sxp parameters: p=2.5%, q=50% Correlation threshold: s=0.2 Peak / valley discrimination limit: Szx=5% Smoothing settings: Smoothing is performed as a preprocessing step before calculating shape parameters. Missing point interpolation setting: Calculates roughness parameters by storing unmeasured points.

[0110] <Average area of ​​recesses in the substrate> The data observed using the "root mean square height Rq of the substrate" as described above was processed using OLYMPUS's OLS5100LEXT analysis software. Automatic noise reduction and tilt correction were performed as image processing. Then, "Area / Volume" was selected, and the "area of ​​the recesses" and "number of recesses" were calculated under the analysis conditions shown below. The average area of ​​the recesses in the substrate was calculated using equation (2) below. The same operation was performed for five different samples, and the arithmetic mean of the obtained values ​​was calculated and rounded to the first decimal place to obtain the average area of ​​the recesses in the substrate. Average area of ​​concave [μm²] 2] = Total area of ​​recesses / Number of recesses ···Equation (2) [Analysis conditions] Measurement range: Entire area (1224 μm square) Threshold 1: 0 μm Measure the lower limit below threshold 1 (100 μm) 2 (Exclude areas smaller than the following size from calculations.)

[0111] <Percentage of recesses in the substrate> The data observed using the "root mean square height Rq of the substrate" as described above was processed using OLYMPUS's OLS5100LEXT analysis software. Automatic noise reduction and tilt correction were performed. The entire corrected image area was selected. Then, "Area / Volume" was selected, and the following analysis conditions were applied: "Depth 10 μm or more and area 500 μm". 2 The number of recesses above and below, and the number of recesses with a depth of 10 μm or more were calculated. From the obtained data, the area of ​​500 μm was calculated. 2 The number of recesses was calculated, and the percentage of 10 μm recesses in the substrate was calculated using the following formula (3). The same procedure was performed on five different samples, and the arithmetic mean of the obtained values ​​was calculated and rounded to the first decimal place to determine the percentage of 10 μm recesses in the substrate. Percentage of 10μm recesses [%] = (depth of 10μm or more and area of ​​500μm) 2 (Number of recesses above this level / Number of recesses with a depth of 10 μm or more) × 100 ... Equation (3) [Analysis conditions] Measurement range: Entire area (1224 μm square) Threshold 1: -10 μm Measure the lower limit below threshold 1 (100 μm) 2 (Exclude areas smaller than the following size from calculations.)

[0112] <Amount of polymer impregnation in the substrate> The mass of the substrate from which the porous layer was peeled off with tape was measured in the same manner as the "mass of the porous layer" described above. Then, the substrate was immersed in a good solvent (DMF) at 60°C for 24 hours to dissolve the polymer impregnated in the substrate. After taking the substrate out of the good solvent and replacing it with pure water, it was dried at 120°C for 2 hours, and the mass of the substrate after immersion in the good solvent was measured. The polymer impregnation amount of the substrate was calculated from the following formula (4). The same operation was carried out on five different samples, the arithmetic mean of the obtained values was calculated, and the value rounded to the second decimal place was taken as the polymer impregnation amount of the substrate. Polymer impregnation amount of substrate [g / m 2 = (Mass of substrate - Mass of substrate after immersion in good solvent) / (0.11 × 0.19) ··· Formula (4).

[0113] <NaCl removal rate and water production rate of composite semipermeable membrane> Raw water adjusted to 25°C and pH 6.5 (NaCl concentration 3.2 mass%) was supplied to the composite semipermeable membrane at an operating pressure of 5.5 MPa, and membrane filtration treatment was carried out for 2 hours. Then, the electrical conductivities of the feed water and the permeate water were measured with a multi-water quality meter (MM60R) manufactured by Toa DK Kogyo Co., Ltd. Next, using the calibration curve created in advance, this conductivity was converted to calculate the NaCl concentration. From the obtained NaCl concentration, the NaCl removal rate, which is the solute removal performance, was determined by the following formula (5). NaCl removal rate [%] = 100 × {1 - (NaCl concentration in permeate water / NaCl concentration in feed water)} ··· Formula (5) Also, after carrying out the above membrane filtration treatment for 2 hours, the amount of water permeated through the membrane for 30 minutes was measured, and it was converted to the water production rate (cubic meters) per square meter of the membrane surface per day, and the water production rate [m 3 / m 2 / day] was calculated.

[0114] <NaCl high-pressure test> The composite semipermeable membrane, whose performance was evaluated in the "NaCl removal rate and water production volume of composite semipermeable membranes" described above, was subjected to membrane filtration treatment for 6 hours by supplying raw water (NaCl concentration 3.2 mass%) adjusted to 45°C and pH 6.5 at an operating pressure of 7.0 MPa. Subsequently, the membrane performance was evaluated using the same method as in "NaCl removal rate and water production volume of composite semipermeable membranes," and the NaCl removal rate and water production volume after high-pressure operation were determined. Furthermore, the quality of the membrane performance was judged by the water production volume retention rate calculated by the following formula (6). Water production retention rate [%] = Water production volume after high-pressure operation / Water production volume before high-pressure operation × 100 ... Equation (6).

[0115] <Peel strength after chemical treatment> A composite semipermeable membrane was subjected to chemical treatment by immersion in a 1 mol / L sodium hydroxide aqueous solution adjusted to pH 13 at 25°C for 40 hours. After that, it was thoroughly washed with water and air-dried to obtain the chemically treated composite semipermeable membrane. The obtained chemically treated composite semipermeable membrane was cut into 1.5 cm × 15 cm sections, yielding 10 sections. For each section, a highly adhesive aluminum tape (AT-75, manufactured by Nitto Denko Corporation) was attached to the surface of the separation functional layer, and using a Tensilon test machine (RTG-1210), the aluminum tape was pulled 5 cm at a gripping and moving speed of 10 mm / min and in a peeling direction of 180° at 25°C to peel the interface between the porous layer with the separation functional layer and the substrate, and the maximum peeling force was determined. The same measurement was performed for all 10 sections, and the average value of the obtained values ​​was defined as the peeling strength. In the case of a laminate of a porous layer and a substrate without a separation functional layer, aluminum tape is applied to the surface of the porous layer, and the interface between the porous layer and the substrate is peeled off to determine the peel strength.

[0116] [Reference Example 1] Manufacturing of Polyphenylene Sulfide Nonwoven Fabric A Using polyphenylene sulfide resin (Toray Industries, Ltd., product code: E2280) as the core component and polyphenylene sulfide (PPS) resin (Toray Industries, Ltd., product code: M2588) as the sheath component, the core and sheath components were melted in an extruder, weighed to a mass ratio of 80:20, and a core-sheath composite fiber was spun. The spun core-sheath composite fiber was cooled and solidified in an atmosphere at room temperature of 20°C, passed through a rectangular ejector, the yarn was pulled and stretched, and collected on a moving net to form a nonwoven web. Next, it was temporarily bonded using a pair of upper and lower metal calender rolls, and the basis weight was 36 g / m². 2 A spunbond nonwoven web (a) was obtained in this manner. Two of the obtained spunbond nonwoven webs (a) in a temporarily bonded state were stacked on top of each other, and the laminated nonwoven web was passed between the middle and bottom of a set of three flat rolls: the top being a resin elastic roll, the middle a metal roll, and the bottom a resin elastic roll, and heat-pressed. The laminated nonwoven web was then folded back and passed between the top and middle, and heat-pressed again. Finally, the back side of the obtained laminated composite nonwoven fabric, which had been in contact with the elastic rolls, was brought into contact with a metal cold roll with a surface temperature of 45°C for 1 second, resulting in a basis weight of 72 g / m². 2 A polyphenylene sulfide nonwoven fabric A with a thickness of 90 μm and an Rq of 1.0 μm was manufactured. The surface temperatures of the three flat rolls used were 140°C for the top, 200°C for the middle, and 140°C for the bottom, and the linear pressure was 1715 N / cm.

[0117] [Reference Example 2] Manufacturing of Polyphenylene Sulfide Nonwoven Fabric B In the spinning, nonwoven web formation, and temporary bonding processes, the basis weight is 35 g / m². 2 Using a spunbond nonwoven web (b) that had been temporarily bonded in such a state, the heat-sealing conditions were adjusted so that the Rq of the nonwoven fabric substrate after heat-sealing was 10.0 μm, in the same manner as in Reference Example 1, with a basis weight of 70 g / m². 2 A polyphenylene sulfide nonwoven fabric B with a thickness of 90 μm was manufactured.

[0118] [Reference Example 3] Manufacturing of Polyphenylene Sulfide Nonwoven Fabric C In the spinning, nonwoven web formation, and temporary bonding processes, the basis weight is 37.5 g / m². 2Using a spunbond nonwoven web (c) that had been temporarily bonded in such a state, the procedure was the same as in Reference Example 1, except that the heat-sealing conditions were adjusted so that the Rq of the nonwoven fabric substrate after heat-sealing was 5.8 μm, resulting in a basis weight of 75 g / m². 2 A polyphenylene sulfide nonwoven fabric C with a thickness of 90 μm was manufactured.

[0119] [Reference Example 4] Manufacturing of Polyphenylene Sulfide Nonwoven Fabric D Except for using a spunbond nonwoven web (a) and adjusting the heat-sealing conditions so that the Rq of the nonwoven fabric substrate after heat-sealing was 5.8 μm, the procedure was the same as in Reference Example 1, resulting in a basis weight of 72 g / m². 2 A polyphenylene sulfide nonwoven fabric D with a thickness of 90 μm was manufactured.

[0120] [Reference Example 5] Manufacturing of Polyphenylene Sulfide Nonwoven Fabric E Except for using a spunbond nonwoven web (b) and adjusting the heat-sealing conditions so that the Rq of the nonwoven fabric substrate after heat-sealing was 0.8 μm, the procedure was the same as in Reference Example 1, with a basis weight of 70 g / m². 2 A polyphenylene sulfide nonwoven fabric E with a thickness of 90 μm was manufactured.

[0121] [Reference Example 6] Manufacturing of polyphenylene sulfide nonwoven fabric F Except for using a spunbond nonwoven web (b) and adjusting the heat-sealing conditions so that the Rq of the nonwoven fabric substrate after heat-sealing was 11.0 μm, the procedure was the same as in Reference Example 1, with a basis weight of 70 g / m². 2 A polyphenylene sulfide nonwoven fabric F with a thickness of 90 μm was manufactured.

[0122] [Reference Example 7] Manufacturing of polyethylene terephthalate nonwoven fabric G A polyethylene terephthalate resin with an intrinsic viscosity IV of 0.65, a melting point of 260°C, and a titanium dioxide content of 0.3% by mass was used as the core component, and a copolymerized polyethylene terephthalate resin with an intrinsic viscosity IV of 0.66, an isophthalic acid copolymerization rate of 11 mol%, a melting point of 230°C, and a titanium dioxide content of 0.2% by mass was used as the sheath component. The core component and sheath component were melted in an extruder, and weighed to a mass ratio of 80:20 to produce a core-sheath composite fiber. The spun core-sheath composite fiber was cooled and solidified in an atmosphere at room temperature of 20°C, passed through a rectangular ejector, the yarn was pulled and stretched, and collected on a moving net to form a nonwoven web. Next, it was temporarily bonded using a pair of upper and lower metal calender rolls, and the basis weight was 37.5 g / m². 2 A spunbond nonwoven web (g) was obtained in this manner. Two of the obtained spunbond nonwoven webs (g) in a temporarily bonded state were stacked on top of each other, and the laminated nonwoven web was passed between the middle and bottom of a set of three flat rolls: the top being a resin elastic roll, the middle a metal roll, and the bottom a resin elastic roll, and heat-pressed. The laminated nonwoven web was then folded back and passed between the top and middle, and heat-pressed again. Finally, the back side of the obtained laminated composite nonwoven fabric, which was in contact with the elastic rolls, was brought into contact with a metal cold roll with a surface temperature of 45°C for 1 second, resulting in a basis weight of 75 g / m². 2 A polyethylene terephthalate nonwoven fabric G with a thickness of 90 μm and an Rq of 4.8 μm was manufactured. The surface temperatures of the three flat rolls used were 140°C for the top, 180°C for the middle, and 140°C for the bottom, and the linear pressure was 1715 N / cm.

[0123] [Reference Example 8] Manufacturing of polyethylene terephthalate nonwoven fabric H Except for using a spunbond nonwoven web (b) and adjusting the heat-sealing conditions so that the Rq of the nonwoven fabric substrate after heat-sealing was 1.0 μm, the procedure was the same as in Reference Example 7, with a basis weight of 70 g / m². 2 A polyethylene terephthalate nonwoven fabric H with a thickness of 90 μm was manufactured.

[0124] [Example 1] On the base material, polyphenylene sulfide nonwoven fabric A, an 18% by mass DMF solution of PSf as a polymer solution is laid at 25°C, resulting in a porous layer with a mass of 5 g / m². 2The substrate was coated in such a manner. Subsequently, the substrate coated with the polymer solution was immersed in pure water for 15 seconds to create a porous support with a porous layer formed on the substrate. The porous layer was immersed in pure water and left for 5 minutes, then washed with 90°C hot water for 2 minutes. The washed porous support was immersed in a 3 mass% aqueous solution of m-PDA for 2 minutes. The support was slowly lifted vertically, and excess aqueous solution was removed from the surface of the porous support by blowing nitrogen with an air nozzle. Then, a decane solution containing 0.165 mass% TMC was applied so that the surface of the porous layer was completely wetted, and it was left to stand for 1 minute. Furthermore, the membrane was made vertical to drain and remove excess solution, and it was washed with pure water to obtain a composite semipermeable membrane having a cross-linked polyamide separation functional layer.

[0125] [Example 2] A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained by the same method as in Example 1, except that polyphenylene sulfide nonwoven fabric B was used as the base material.

[0126] [Example 3] A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained by the same method as in Example 1, except that polyphenylene sulfide nonwoven fabric C was used as the base material.

[0127] [Example 4] The mass of the porous layer is 15 g / m 2 A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Example 3, except that the layer was coated in such a way to create a porous support.

[0128] [Example 5] The mass of the porous layer is 1 g / m 2 A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Example 3, except that the layer was coated in such a way to create a porous support.

[0129] [Example 6] A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Example 3, except that a porous support was prepared by coating it with an 18% by mass DMF solution of polyethersulfone as the polymer solution.

[0130] [Example 7] Using polyphenylene sulfide nonwoven fabric D as the base material, the mass of the porous layer is 6 g / m². 2 Apply so that the polymer impregnation amount of the substrate is 0.1 g / m². 2 A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained by the same method as in Example 1, except that a porous support was fabricated to achieve the desired result.

[0131] [Example 8] The mass of the porous layer is 2 g / m 2 Apply so that the polymer impregnation amount of the substrate is 3.2 g / m². 2 A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Example 7, except that a porous support was fabricated to achieve the desired result.

[0132] [Comparative Example 1] A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained by the same method as in Example 1, except that polyphenylene sulfide nonwoven fabric E was used as the base material.

[0133] [Comparative Example 2] A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained by the same method as in Example 1, except that polyphenylene sulfide nonwoven fabric F was used as the base material.

[0134] [Comparative Example 3] A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained by the same method as in Example 1, except that polyethylene terephthalate nonwoven fabric G was used as the base material.

[0135] [Comparative Example 4] A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Example 4, except that a porous support was prepared by coating it with an 18% by mass DMF solution of polyacrylonitrile as the polymer solution.

[0136] [Comparative Example 5] A composite semipermeable membrane having a cross-linked polyamide separation functional layer was obtained by the same method as in Example 1, except that polyethylene terephthalate nonwoven fabric H was used as the base material.

[0137] The results of various measurements of the obtained composite semipermeable membrane are shown in Tables 1 and 2.

[0138] [Table 1]

[0139] [Table 2] [Industrial applicability]

[0140] The composite semipermeable membrane according to this embodiment can be used for seawater desalination, brine desalination, drinking water production, industrial ultrapure water production, wastewater treatment, and recovery of valuable materials. [Explanation of symbols]

[0141] 1 Composite semipermeable membrane 2 Base material 3. Porous layer 4 Separation functional layer 5 Separation membrane element 6 End plate 7 End plate 8 Supply side channel material 9 Permeate side channel material 10 Water collection pipe 11 Supply water 12 Permeated water 13 Concentrated water

Claims

1. A composite semipermeable membrane comprising a substrate, a porous layer provided on one surface of the substrate, and a separation functional layer provided on the porous layer, The main component of the porous layer is a polysulfone polymer. The substrate contains fibers having polyphenylene sulfide on at least its surface, A composite semipermeable membrane in which the root mean square height Rq of the surface of the substrate on the side where the porous layer is provided is 1.0 μm or more and 10 μm or less.

2. The mass of the porous layer is 2 g / m ２ 10g / m or more ２ The composite semipermeable membrane according to claim 1, which is as follows:

3. The composite semipermeable membrane according to claim 1 or 2, wherein the root mean square height Rq of the surface of the substrate on the side where the porous layer is provided is 2.0 μm or more and 6.0 μm or less.

4. The polymer impregnation amount of the aforementioned substrate is 0.5 g / m². ２ 3.0g / m or more ２ The composite semipermeable membrane according to claim 1 or 2, which is as follows:

5. The surface of the substrate on the side where the porous layer is provided has an uneven shape, with an average area of ​​500 μm² for the recesses. ２ 2000 μm or more ２ The composite semipermeable membrane according to claim 1 or 2, which is as follows:

6. The surface of the substrate on which the porous layer is provided has a depth of 10 μm or more relative to the number of recesses with a depth of 10 μm or more and an area of ​​500 μm. ２ The composite semipermeable membrane according to claim 5, wherein the proportion of the number of recesses is 20% or less.

7. The composite semipermeable membrane according to claim 1 or 2, wherein the polysulfone polymer is polysulfone or polyethersulfone.

8. A separation membrane element comprising a composite semipermeable membrane according to claim 1 or 2.

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