WO2014104241A1

WO2014104241A1 - Composite semipermeable membrane

Info

Publication number: WO2014104241A1
Application number: PCT/JP2013/084984
Authority: WO
Inventors: 清彦高谷; 雅和小岩; 由恵丸谷; 将弘木村; 佐々木　崇夫
Original assignee: 東レ株式会社
Priority date: 2012-12-27
Filing date: 2013-12-26
Publication date: 2014-07-03
Also published as: JPWO2014104241A1; JP6269474B2

Abstract

The present invention provides a composite semipermeable membrane which is capable of selectively and sufficiently removing a scale component and is also capable of stably obtaining fresh water with high recovery rate. A composite semipermeable membrane of the present invention comprises: a supporting film which comprises a base and a porous supporting layer that is provided on the base; and a polyamide separation function layer that is formed on the porous supporting layer. The polyamide separation function layer is formed of a polyamide that is obtained from an aliphatic polyfunctional amine and a polyfunctional acid halide, and the abundance ratio (molar ratio) thereof satisfies the following relation. 1.2 ≤ number of moles of aliphatic polyfunctional amine/number of moles of polyfunctional acid halide ≤ 1.8

Description

Composite semipermeable membrane

The present invention relates to a composite semipermeable membrane for selectively separating divalent ions from a mixed solution of monovalent ions and divalent ions.

It is necessary or desirable in many technical fields to selectively remove either ion from a mixed solution of monovalent ions and divalent ions.

For example, in a multistage distillation method that desalinates seawater, ions (scale components) such as HCO ₃ ⁻ , SO ₄ ²⁻ , Mg ²⁺ , and Ca ²⁺ contained in seawater are concentrated by heating, It is deposited as a scale of CaCO ₃ , Mg (OH) ₂ , CaSO ₄ or the like. Since the scale adheres to the heat exchanger tube of the heat exchanger, the operating efficiency of desalination is greatly reduced. In order to solve this problem, that is, as a measure against scale and a method for improving operation efficiency, a pretreatment process using a film is performed. Moreover, in the technique of recovering crude oil from a subsea oil field, a water injection method is used in which seawater is injected into the oil field and the crude oil is pushed out with the pressure for the purpose of improving the recovery rate.

However, the water injection method has a problem that a scale is generated by sulfate ions contained in seawater and Ba ²⁺ and Sr ²⁺ contained in crude oil, and the scale ^clogs a pipe for recovering crude oil. . Furthermore, the water injection method also has a problem that the quality of crude oil is reduced due to the generation of hydrogen sulfide by sulfate ion-reducing bacteria present in the crude oil. Therefore, in the recovery of crude oil by the water injection method, removal of sulfate ions from seawater by a membrane is required as a pretreatment step as a measure against scale and improvement of crude oil quality. In these pretreatments, if only divalent ions (particularly sulfate ions) can be selectively removed from the mixed solution of monovalent ions and divalent ions, the difference in osmotic pressure before and after the pretreatment step is reduced. The energy required for removing sulfate ions from seawater can be greatly reduced.

As a membrane for selectively removing scale components from seawater, for example, in Patent Documents 1 and 2, a polyfunctional aromatic carboxylic acid chloride is added to a diamine component of piperazine or a diamine component of piperazine and 4,4′-bipiperidine. There is disclosed a composite nanofiltration membrane made of polyamide obtained by reacting.

Patent Document 3 discloses separation of monovalent ions and divalent ions using a composite reverse osmosis membrane obtained by reacting piperazine and trimesic acid chloride.

In Patent Documents 4 and 5, in the composite semipermeable membrane and the composite nanofiltration membrane obtained by reacting piperazine and trimesic acid chloride, a detailed examination is made on the composition and concentration at the time of film formation.

Japanese Unexamined Patent Publication No. 2005-262078 Japanese Unexamined Patent Publication No. 2007-277298 Japanese Patent Publication No. 1-38522 Japanese Unexamined Patent Publication No. Sho 62-201606 Japanese Unexamined Patent Publication No. 2010-137192

However, the nanofiltration membrane described in Patent Literature 1 and Patent Literature 2 and the reverse osmosis membrane described in Patent Literature 3 have insufficient divalent ion removal performance or selectivity.
Moreover, although the semipermeable membrane and the nanofiltration membrane described in Patent Literature 4 and Patent Literature 5 have sufficient divalent ion removal performance, there is room for improvement in selectivity.

An object of the present invention is to provide a composite semipermeable membrane capable of selectively and sufficiently removing scale components.

As a result of intensive studies to achieve the above object, the present inventors have found the following composite semipermeable membrane capable of selectively and sufficiently removing scale components from raw water such as seawater, and completed the present invention. It came to do.
That is, the present invention has the following configurations (1) to (13).
(1) A composite semipermeable membrane comprising a substrate and a support membrane comprising a porous support layer provided on the substrate, and a polyamide separation functional layer formed on the porous support layer, The polyamide separation functional layer is formed of a polyamide obtained from an aliphatic polyfunctional amine and a polyfunctional acid halide, and the abundance ratio (molar ratio) of the aliphatic polyfunctional amine and the polyfunctional acid halide is represented by the following formula: A composite semipermeable membrane.
1.2 ≦ number of moles of aliphatic polyfunctional amine / number of moles of polyfunctional acid halide ≦ 1.8
(2) The composite semipermeable membrane according to (1), wherein the abundance ratio is 1.3 or more and 1.7 or less.
(3) The composite semipermeable membrane according to (2), wherein the abundance ratio is 1.35 or more and 1.65 or less.
(4) The composite semipermeable membrane according to (3), wherein the abundance ratio is 1.4 or more and 1.6 or less.
(5) In any one of (1) to (4), the polyamide separation functional layer contains a secondary amine, and the polyamide separation functional layer has a zeta potential difference of 12 mV or more at pH 6 and pH 9. The composite semipermeable membrane described.
(6) The composite semipermeable membrane according to any one of (1) to (5), wherein the polyamide is obtained by interfacial polycondensation.
(7) The composite semipermeable membrane according to any one of (1) to (6), wherein the aliphatic polyfunctional amine is bifunctional.
(8) The composite semipermeable membrane according to any one of (1) to (7), wherein the polyfunctional acid halide is a bifunctional or trifunctional acid halide, or a mixture thereof.
(9) The composite semipermeable membrane according to any one of (1) to (8), wherein the aliphatic polyfunctional amine is piperazine and the polyfunctional acid halide is trimesic acid chloride.
(10) The composite half according to any one of (1) to (9), wherein a protective layer containing a polymer component is provided directly on the polyamide separation functional layer or via another layer. Permeable membrane.
(11) The composite semipermeable membrane according to (10), wherein the polymer component is a crosslinked polymer of a hydrophilic polymer.
(12) The composite semipermeable membrane according to (11), wherein the crosslinked body contains a polyvalent aldehyde.
(13) The composite semipermeable membrane according to (12), wherein the crosslinked body contains a reaction product of polyvinyl alcohol and glutaraldehyde.

The scale component can be selectively and sufficiently removed from seawater by the composite semipermeable membrane of the present invention. Therefore, generation of scale can be effectively prevented when raw water such as seawater is desalinated by an evaporation method, and fresh water can be stably obtained with a high recovery rate. In addition, when recovering crude oil efficiently from the seabed oil field by water injection method, the injection water that can effectively prevent the generation of scale and deterioration of crude oil quality is stably supplied from seawater. be able to.

1. Composite semipermeable membrane The composite semipermeable membrane of the present invention comprises a substrate and a support membrane comprising a porous support layer provided on the substrate, and a polyamide separation functional layer formed on the porous support layer.

(1-1) Polyamide Separation Functional Layer The separation functional layer is a layer responsible for the solute separation function in the composite semipermeable membrane. In this invention, it forms from the polyamide obtained by reaction of an aliphatic polyfunctional amine and polyfunctional acid halide.

The selective separation of monovalent ions and divalent ions in the composite semipermeable membrane requires control of both surface charge and pore size. As the surface charge is closer to neutrality, monovalent ions are more easily transmitted. At this time, since the pore size of the separation functional layer is controlled to a size that can remove divalent ions, divalent ions can be removed reliably, and the selective removal of divalent ions is enhanced. . Here, since the magnitude of the surface charge depends on the amount of functional groups (amino group, carboxy group) in the polyamide, in order to make the surface charge neutral, the amount of amino group and the amount of carboxy group should be made equal. It is preferable that an aliphatic polyfunctional amine and a polyfunctional acid halide are present in an amount in which both are equal.

The present inventors have intensively studied, and by precisely controlling the abundance ratio of the aliphatic polyfunctional amine and the polyfunctional acid halide in the separation functional layer, improvement of the divalent ion removability of the composite semipermeable membrane, and It has been found that the selective removal of monovalent ions and divalent ions can be improved. At this time, the surface charge is considered to be a value close to neutrality. At this time, the amounts of amino groups and carboxy groups in the polyamide are almost equal, and the network structure of the polyamide is considered to be uniform. Therefore, it is considered that the pore size distribution is also controlled.

The abundance ratio of the aliphatic polyfunctional amine and the polyfunctional acid halide in the polyamide separation functional layer is determined by ¹³ C-NMR measurement of the separation functional layer peeled from the support film, or the strong separation of the separation functional layer peeled from the support film. The components of the aliphatic polyfunctional amine and the polyfunctional acid halide were analyzed by ¹ H-NMR measurement using a sample hydrolyzed with an aqueous solution, and the aliphatic polyfunctional amine component was analyzed for the polyfunctional acid halide. It can be determined by dividing by the component.

The abundance ratio of the aliphatic polyfunctional amine to the polyfunctional acid halide (aliphatic polyfunctional amine / polyfunctional acid halide) in the polyamide separation functional layer is 1.2 or more, preferably 1.3. Or more, more preferably 1.35 or more, and even more preferably 1.4 or more. The abundance ratio is 1.8 or less, preferably 1.7 or less, more preferably 1.65 or less, and even more preferably 1.6 or less in terms of molar ratio. When the abundance ratio is 1.2 or more, the negative charge amount of the membrane can be controlled so as not to become too large, so that high monovalent ion permeability can be obtained. Further, when the abundance ratio is 1.8 or less, the positive charge amount of the membrane can be controlled so as not to become too large, so that sufficient divalent ion removal property can be obtained.

To control the ratio of polyfunctional aliphatic amine and polyfunctional acid halide in the polyamide separation functional layer, adjust the ratio of polyfunctional aliphatic amine concentration to polyfunctional acid halide concentration during interfacial polycondensation. Methods, methods of changing the solvent in which the polyfunctional acid halide is dissolved, methods of disturbing the interfacial polycondensation field with surfactants, methods of stopping the reaction during interfacial polycondensation, additives that inhibit the reaction during interfacial polycondensation And a method of activating the reaction by applying heat from the outside during interfacial polycondensation.

The polyamide separation functional layer of the present invention preferably has a zeta potential difference (absolute value) at pH 6 and pH 9 of 12 mV or more. The zeta potential difference (absolute value) at pH 6 and pH 9 of the separation functional layer is related to divalent ion removal performance and divalent ion selectivity. When the zeta potential difference is 12 mV or more, the divalent ion of the composite semipermeable membrane Removal performance and divalent ion selectivity are increased. This is because the degree of dissociation of the amino group and carboxy group varies greatly between pH 6 and pH 9, and it is considered that the amount of amino group and carboxy group is large when the potential difference is large. When the amount of amino group and carboxy group is large, electrostatic repulsion increases, so that it is considered that the divalent ion removal performance and the divalent ion selectivity are increased. *

The zeta potential can be measured with an electrophoretic light scattering photometer. For example, the measurement is performed by setting in a flat sample cell so that the separation functional layer surface of the composite semipermeable membrane is in contact with the monitor particle solution. The monitor particles are obtained by coating polystyrene latex with hydroxypropylcellulose, and are dispersed in a 10 mM NaCl solution to form a monitor particle solution. By adjusting the pH of the monitor particle solution, the zeta potential at a predetermined pH can be measured. As the electrophoretic light scattering photometer, ELS-8000 manufactured by Otsuka Electronics Co., Ltd. can be used.

The aliphatic polyfunctional amine is an aliphatic amine having two or more amino groups in one molecule. For example, ethylenediamine, N-methylethylenediamine, N, N′-dimethylethylenediamine, diethylenetriamine, 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, hexahydro-1,3,5-triazine, 1,3,5-trimethylhexahydro-1,3,5-triazine, 1,3,5-triethylhexahydro-1,3 , 5-triazine, 1,3,5-tri-n-butylhexahydro-1,3,5-triazine There are exemplified. In view of the stability of performance, it is preferable to use piperazine-based amines and derivatives thereof, and among them, piperazine (hereinafter sometimes referred to as “Pip”) is more preferable. These aliphatic polyfunctional amines may be used alone or in combination of two or more.

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.

Considering the reactivity with the aliphatic polyfunctional amine, the polyfunctional acid halide is preferably a polyfunctional acid chloride. In view of the selective separation and heat resistance of the membrane, the polyfunctional acid chloride is more preferably a polyfunctional aromatic acid chloride having 2 to 4 carbonyl chloride groups in one molecule. Among these, from the viewpoint of easy availability and ease of handling, it is more preferable to use trimesic acid chloride (hereinafter sometimes referred to as “TMC”). These polyfunctional acid halides may be used alone or in combination of two or more.

The polyamide constituting the separation functional layer is preferably a crosslinked polyamide obtained by interfacial polycondensation with the above-mentioned aliphatic polyfunctional amine and polyfunctional acid halide from the viewpoint of ease of production.

The thickness of the polyamide separation functional layer is preferably 40 nm or less. If the thickness is 40 nm or less, sufficient water permeability can be obtained while enhancing divalent ion removal performance. *

The thickness of the polyamide separation functional layer can be analyzed using an observation technique such as a transmission electron microscope, TEM tomography, or a focused ion beam / scanning electron microscope (FIB / SEM). For example, when observing by TEM tomography, the composite nanofiltration membrane is treated with a water-soluble polymer to maintain the shape of the polyamide separation functional layer, and then stained with osmium tetroxide or the like for observation. *

In the present specification, unless otherwise specified, the thickness of a layer or film means an average value. Here, the average value represents an arithmetic average value.
The thickness of the layer or 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 in the cross-sectional observation of the layer or film (the surface direction of the layer or film or the horizontal direction). It is done.

(1-2) Support membrane The support membrane includes a base material and a porous support layer provided on the base material, and has substantially no separation performance of ions or the like, and has a strength in the separation functional layer. Can be given.

The thickness of the support membrane affects the strength of the composite semipermeable membrane and the packing density when the composite semipermeable membrane is used as a membrane element. In order to obtain sufficient mechanical strength and packing density, the thickness of the support membrane is preferably in the range of 50 to 300 μm, more preferably in the range of 100 to 250 μm.

(1-2-1) Porous Support Layer The porous support layer in the present invention preferably contains the following materials as main components. As a material for the porous support layer, polysulfone, polyethersulfone, polyamide, polyester, cellulosic polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, homopolymer or copolymer such as polyphenylene oxide, alone or in a blend Can be used.

Here, cellulose acetate, cellulose nitrate and the like are used as the cellulose polymer, and polyethylene, polypropylene, polyvinyl chloride, polyacrylonitrile and the like can be used as the vinyl polymer.
Among them, homopolymers such as polysulfone, polyamide, polyester, cellulose acetate, cellulose nitrate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, and copolymers thereof are preferable.
More preferred is cellulose acetate, polysulfone, polyphenylene sulfide sulfone, or polyphenylene sulfone.

Among these materials, polysulfone is particularly preferably used because of its high chemical, mechanical and thermal stability and easy molding.
Specifically, it is preferable to use polysulfone composed of repeating units represented by the following chemical formula as the main component of the porous support layer because the pore diameter can be easily controlled and the dimensional stability is high.

The polysulfone used in the present invention preferably has a weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) using N-methylpyrrolidone as a developing solvent and polystyrene as a standard substance. Those within the range of 200,000, more preferably 15,000 to 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 size and distribution of the pores in the porous support layer are not particularly limited. For example, the pore size is gradually increased from the surface on the side where the uniform and fine pores or the separation functional layer is formed to the other surface, that is, the surface on the substrate side. A hole that is a micropore and that has a size of 0.1 to 100 nm on the surface on the side where the separation functional layer is formed is preferable.

The porous support layer is prepared by, for example, casting an N, N-dimethylformamide (hereinafter also referred to as “DMF”) solution in which the above polysulfone is dissolved to a certain thickness on a substrate. Can be obtained by wet coagulation in water. Most of the surface of the support membrane obtained by this method can have fine pores having a diameter of 1 to 30 nm.

Also, the thickness of the porous support layer affects the strength of the resulting composite semipermeable membrane and the packing density when it is used as an element. In order to obtain sufficient mechanical strength and packing density, the thickness is preferably in the range of 10 to 200 μm, more preferably in the range of 20 to 150 μm.

The morphology of the porous support layer can be observed with a scanning electron microscope, a transmission electron microscope, or an atomic microscope. For example, when observing with a scanning electron microscope, after peeling off the porous support layer from the substrate, it is cut by the freeze cleaving method to obtain a sample for cross-sectional observation. The sample is thinly coated with platinum or platinum-palladium or ruthenium tetrachloride, preferably ruthenium tetrachloride, and observed with a high resolution field emission scanning electron microscope (UHR-FE-SEM) at an acceleration voltage of 3 to 15 kV. As the high-resolution field emission scanning electron microscope, Hitachi S-900 electron microscope can be used.

(1-2-2) Substrate Examples of the substrate constituting the support membrane include a polyester polymer, a polyamide polymer, a polyolefin polymer, or a mixture or copolymer thereof. Among these, a polyester polymer is preferable because an excellent support film can be obtained due to mechanical strength, heat resistance, water resistance, and the like.

The polyester polymer used in the present invention is a polyester composed of an acid component and an alcohol component, and is preferably the main component of the substrate in the present invention. In addition, a main component means 70 weight% or more in the polymer which comprises a base material, Preferably it contains 90 weight% or more.

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 the polyester polymer include polyethylene terephthalate resin, polybutylene terephthalate resin, polytrimethylene terephthalate resin, polyethylene naphthalate resin, polylactic acid resin, and polybutylene succinate resin. Examples include coalescence. Among them, a polyethylene terephthalate homopolymer or a copolymer thereof is preferably used because it is particularly excellent in production cost.

The base material in the present invention is a cloth-like material made of the polymer or the like. It is preferable to use a fibrous base material for the fabric in terms of strength, unevenness forming ability, and fluid permeability.
As a base material, both a long fiber nonwoven fabric and a short fiber nonwoven fabric can be used preferably.
In the long-fiber non-woven fabric or the short-fiber non-woven fabric, the fibers in the surface layer on the side opposite to the porous support layer are preferably longitudinally oriented as compared with the fibers in the surface layer on the porous support layer side in terms of moldability and strength. The longitudinal alignment will be described later.

By taking such a structure, not only a high effect of preventing the membrane breakage of the composite semipermeable membrane by maintaining the strength is realized, but also the porous support layer when imparting irregularities to the separation functional layer, Formability as a laminate including a substrate is also improved, and the uneven shape on the surface of the separation functional layer is stabilized, which is preferable.

More specifically, the fiber orientation degree in the surface layer of the long fiber nonwoven fabric or short fiber nonwoven fabric opposite to the porous support layer is preferably 0 ° to 25 °. Further, it is preferable that the difference in the degree of orientation between the fiber orientation degree on the surface layer opposite to the porous support layer and the fiber orientation degree on the surface layer on the porous support layer side is 10 ° to 90 °.

In the manufacturing process of the composite semipermeable membrane and the manufacturing process of the element, a heating process is included, but a phenomenon occurs in which the porous support layer or the separation functional layer contracts due to the heating. This is particularly noticeable 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 low thermal dimensional change rate 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.

In the present specification, the “fiber orientation degree” is an index indicating the fiber orientation of the nonwoven fabric base material constituting the porous support layer. A nonwoven fabric base material when the film forming direction for continuous film formation, that is, the longitudinal direction of the nonwoven fabric base material is 0 °, and the direction perpendicular to the film forming direction, that is, the width direction of the nonwoven fabric base material is 90 °. This refers to the average angle of the constituent fibers. Accordingly, the closer to 0 ° the fiber orientation, the longer the orientation, and the closer to 90 °, the lateral orientation.

The fiber orientation degree is measured as follows.
Ten small sample samples are randomly collected from the nonwoven fabric, and the surface of the sample is photographed at 100 to 1000 times with a scanning electron microscope. In the photographed image, 10 fibers are selected from each sample, and for a total of 100 fibers, the longitudinal direction (longitudinal direction, film forming direction) of the nonwoven fabric is 0 °, and the width direction (lateral direction) of the nonwoven fabric is 90 degrees. Measure the angle at °. In the average value of the measured angles, the value obtained by rounding off the first decimal place is the fiber orientation degree.

The air permeability of the substrate is preferably 2.0 cc / cm ² / sec or more. When the air permeability is within this range, the water permeability of the composite semipermeable membrane is enhanced. This is a process of forming a porous support membrane. When a polymer is cast on a base material and immersed in a coagulation bath, the non-solvent replacement rate from the base material side becomes faster. This is presumably because the internal structure of the support layer changes and affects the amount of monomer retained and the diffusion rate in the subsequent step of forming the separation functional layer.

The air permeability can be measured by a Frazier type tester based on JIS L1096 (2010). For example, a base material is cut out to a size of 200 mm × 200 mm and used as a sample. This sample is attached to the Frazier type tester, and the suction fan and air hole are adjusted so that the inclined barometer has a pressure of 125 Pa. Based on the pressure indicated by the vertical barometer at this time and the type of air hole used, The amount of air passing through the material, that is, the air permeability can be calculated. As the Frazier type tester, KES-F8-AP1 manufactured by Kato Tech Co., Ltd. can be used.
The thickness of the substrate is preferably in the range of 10 to 200 μm from the viewpoint of mechanical strength and packing density, and more preferably in the range of 30 to 120 μm.

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

In addition, the thickness of a base material and the thickness of a composite semipermeable membrane can be easily measured with a digital thickness gauge. Moreover, since the thickness of the separation functional layer is very thin compared with the support membrane, the thickness of the composite semipermeable membrane can be regarded as the thickness of the support membrane. Therefore, the thickness of the porous support layer can be calculated by measuring the thickness of the composite semipermeable membrane with a digital thickness gauge and subtracting the thickness of the substrate from the thickness of the composite semipermeable membrane. As the digital thickness gauge, “PEACOCK (registered trademark)” manufactured by Ozaki Mfg. Co., Ltd. can be used. When a digital thickness gauge is used, the average value is calculated by measuring the thickness at 20 locations.
In addition, when it is difficult to measure the thickness of the substrate or the thickness of the composite semipermeable membrane with a thickness gauge, the thickness may be measured with a scanning electron microscope.

(1-3) Protective layer As a result of intensive studies, the inventors of the present application have provided it directly or via another layer on a polyamide separation functional layer composed of a polyfunctional aliphatic amine and a polyfunctional acid halide. It has been found that the protective layer containing the polymer component improves the ability to remove divalent ions (particularly sulfate ions) of the composite semipermeable membrane and improves the selective separation between monovalent ions and divalent ions. It was.

First, since the membrane charge can be neutralized by the protective layer, electrostatic interaction between ions and the membrane can be suppressed. As a result, the removability of monovalent ions in the film can be reduced. Furthermore, the polymer component contained in the protective layer can block pores larger than divalent ions. As a result, it is considered that the removal of divalent ions (particularly sulfate ions) can be sufficiently enhanced.

The polymer component is not particularly limited as long as it does not dissolve the polyamide separation functional layer and the porous support membrane and does not elute during the water treatment operation. For example, polyvinyl alcohol, polyvinyl pyrrole, polyvinyl pyrrolidone, hydroxypropyl cellulose, polyethylene Examples thereof include glycol, chitosan, and saponified polyethylene-vinyl acetate copolymer.

Of these, polyvinyl alcohol is preferable from the viewpoint of economy, availability, and ease of handling. In particular, the saponification degree of polyvinyl alcohol is preferably 85% or more, and more preferably 90% or more. When the degree of saponification is 85% or more, it is soluble in hot water (about 80 ° C) due to the influence of intermolecular chain hydrogen bonding, but becomes water-insoluble near room temperature (about 25 ° C), and water treatment operation The elution of polyvinyl alcohol at the time can be prevented. The degree of polymerization of polyvinyl alcohol is preferably in the range of 50 to 50,000. When the degree of polymerization is 50 or more, the solubility in water decreases, and elution of polyvinyl alcohol during water treatment can be prevented. On the other hand, when the degree of polymerization is 50000 or less, the viscosity of the aqueous polyvinyl alcohol solution can be suitably maintained, and the coating thickness of the aqueous polyvinyl alcohol solution can be reduced. As a result, the above-described function as the protective layer and the water permeability of the membrane can be compatible.

In addition, the polymer in the protective layer can be cross-linked to the polyamide separation functional layer, so that the ability to remove divalent ions can be enhanced compared to uncrosslinked, and the elution of the polymer in the protective layer during water treatment operation can be enhanced. Can be prevented. In addition, as a polymer to bridge | crosslink, a hydrophilic polymer is preferable from the point of the ease of handling and a water-permeable fall suppression, Especially polyvinyl alcohol is preferable and polyvinyl alcohol with a saponification degree of 85% or more is more preferable. Since the reactivity of polyvinyl alcohol changes depending on the degree of saponification, the effect of crosslinking is enhanced when the degree of saponification is 85% or more.

As a method of crosslinking polyvinyl alcohol, it is preferable to use an organic crosslinking agent such as a polyhydric aldehyde, an epoxy compound, a polyvalent carboxylic acid, an organic titanium compound, or an organic zirconium compound, or an inorganic crosslinking agent such as a boron compound. From the viewpoint of easy availability and ease of handling, a polyvalent aldehyde is more preferable, and glutaraldehyde is particularly preferable from the viewpoint of ease of reactivity.

The thickness of the protective layer is not particularly limited, but is usually 0.01 μm or more, preferably 0.05 μm or more. If the thickness of the protective layer is too thin, the polymer component tends to be eluted during the water treatment operation, and the membrane performance tends to deteriorate. Moreover, the thickness of a protective layer is 5 micrometers or less normally, Preferably it is 3 micrometers or less, More preferably, it is 2 micrometers or less. On the other hand, if the thickness of the protective layer is too thick, the permeation flux tends to decrease.

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 a substrate and a step of immersing the substrate coated with the solution in a coagulation bath to coagulate the polymer. .

In the step of applying the polymer solution to the substrate, the polymer solution is prepared by dissolving the polymer that is a component of the porous support layer in a good solvent for the polymer.

The temperature of the polymer solution during application of the polymer solution is preferably in the range of 10 ° C. to 60 ° C. when polysulfone is used as the polymer. If the temperature of the polymer solution is within this range, the polymer does not precipitate, and the polymer solution is sufficiently impregnated between the fibers of the base material and then solidified. As a result, the porous support layer is firmly bonded to the substrate by the anchor effect, and a good support film can be obtained. The preferred temperature range of the polymer solution can be adjusted as appropriate depending on the type of polymer used, the desired solution viscosity, and the like.

The time from application of the polymer solution on the substrate to immersion in the coagulation bath is preferably in the range of 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, the preferable range of time until it immerses in a coagulation bath can be suitably adjusted with the kind of polymer solution to be used, desired solution viscosity, etc.

As the coagulation bath, water is usually used, but any solid can be used as long as it does not dissolve the polymer that is a component of the porous support layer. The membrane form of the support membrane obtained by the composition of the coagulation bath changes, and the resulting composite semipermeable membrane also changes. The temperature of the coagulation bath is preferably 5 ° C to 100 ° C. More preferably, it is 10 ° C to 40 ° C. If the temperature of the coagulation bath is lower than the upper limit, vibration of the coagulation bath surface due to thermal motion can be suppressed, and the smoothness of the film surface after film formation can be maintained. Further, if the temperature is equal to or higher than the lower limit, the solidification rate can be maintained, so that the film forming property can be improved.

Next, the support membrane thus obtained is washed with hot water in order to remove the solvent remaining in the membrane. The temperature of the hot water at this time is preferably 40 ° C. to 100 ° C., more preferably 60 ° C. to 95 ° C. If the washing temperature is lower than the upper limit, the shrinkage degree of the support membrane does not become too large, and deterioration of water permeability can be prevented. Moreover, if the cleaning temperature is equal to or higher than the lower limit, the cleaning effect is sufficient.

(2-2) Formation Process of Separation Function Layer Next, as an example of the formation process of the polyamide separation function layer constituting the composite semipermeable membrane, formation of polyamide that performs interfacial polycondensation will be described. In the process of forming the polyamide separation functional layer, polyamide separation is performed by performing interfacial polycondensation on the surface of the support film using an aqueous solution containing an aliphatic polyfunctional amine and an organic solvent solution containing a polyfunctional acid halide. A functional layer is formed.

The concentration of the aliphatic polyfunctional amine in the aliphatic polyfunctional amine aqueous solution is preferably 1.0% by weight or more and 8.0% by weight or less. When the concentration of the aliphatic polyfunctional amine is 1.0% by weight or more, a uniform separation function layer is formed, and sufficient divalent ion removal performance can be obtained. Moreover, if it is 8.0 weight% or less, the thickness of the separation functional layer will not be too thick, and sufficient monovalent ion permeability and water permeability can be obtained.

As an organic solvent for dissolving the polyfunctional acid halide, a solubility parameter (SP value) that is immiscible with water, does not destroy the support membrane, and does not inhibit the formation reaction of the crosslinked polyamide. ) Is 15.2 (MPa) ^1/2 or more, and an organic solvent having a log P of 3.2 or more is used. When the SP value is 15.2 (MPa) ^1/2 or more and the log P is 3.2 or more, the distribution and diffusion of the aliphatic polyfunctional amine at the time of interfacial polycondensation are optimized, and the amount of functional groups is reduced. Can be increased. As typical examples, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, heptadecane, hexadecane, cyclooctane, ethylcyclohexane, 1-octene, 1-decene, or a mixture of these is preferably used. And nonane, decane, undecane, and dodecane are preferable from the viewpoint of stability of performance expression.

The concentration of the polyfunctional acid halide in the water-immiscible organic solvent solution is preferably in the range of 0.01 wt% to 5.0 wt%, preferably 0.1 wt% to 3.0 wt%. It is more preferable that it is in the following range, and it is more preferable that it is in the range of 0.2 wt% or more and 1.0 wt% or less. When the polyfunctional acid halide concentration is 0.01% by weight or more, a sufficient reaction rate can be obtained, and when it is 5.0% by weight or less, the occurrence of side reactions can be suppressed.

When piperazine is contained as the aliphatic polyfunctional amine and trimesic acid chloride is contained as the polyfunctional acid halide, the piperazine concentration / trimesic acid chloride concentration is preferably 5.0 or more and 30.0 or less. More preferably, it is 0 or more and 30.0 or less. Pip / TMC ≧ 1.2 is obtained as the abundance ratio (molar ratio) of piperazine (Pip) and trimesic acid chloride (TMC) in the formed polyamide within the range of 5.0 to 30.0. And high divalent ion selectivity can be obtained.

The aqueous solution containing the aliphatic polyfunctional amine may contain a surfactant. Examples thereof include sodium dodecylbenzenesulfonate, sodium dodecylsulfate, sodium dodecyldiphenyl ether disulfonate, styrene bis (sodium naphthalenesulfonate), sodium polyoxyethylene alkyl ether sulfate, and the like. By including a surfactant, the effect of increasing the adhesion between the separation functional layer and the porous support layer, and the effect of increasing the amount of functional groups in the polyamide, particularly the amount of amino groups, by disturbing the interfacial polycondensation field can get. At this time, when piperazine is contained as the aliphatic polyfunctional amine and trimesic acid chloride is contained as the polyfunctional acid halide, the value of Pip / TMC in the polyamide can be made closer to 1.5. Valent ion selectivity is obtained.

The aqueous solution containing the aliphatic polyfunctional amine may contain alcohol. For example, ethanol, 1-propanol, 2-propanol, butanol and the like can be mentioned. By including alcohol, the interfacial polycondensation field is disturbed, and the effect of increasing the amount of functional groups in the polyamide, particularly the amount of amino groups, can be obtained.

The aqueous solution containing the aliphatic polyfunctional amine may contain an alkaline compound. Examples thereof include sodium hydroxide, trisodium phosphate, triethylamine and the like. By including an alkaline compound, hydrogen halide generated in the interfacial polycondensation reaction can be removed, and a decrease in the reactivity of the aliphatic polyfunctional amine can be suppressed, and high divalent ion selectivity can be obtained.

An aqueous solution containing an aliphatic polyfunctional amine and an organic solvent solution containing a polyfunctional acid halide each contain compounds such as an acylation catalyst, a polar solvent, and an antioxidant as necessary. Also good.

In order to perform interfacial polycondensation on the support membrane, the support membrane surface is first coated with an aqueous solution containing an aliphatic polyfunctional amine. As a method of coating the surface of the support membrane with an aqueous solution containing an aliphatic polyfunctional amine, it is sufficient that the surface of the support membrane is uniformly and continuously coated with this aqueous solution, and a known coating means, for example, an aqueous solution is supported. What is necessary is just to perform by the method of coating on the surface of a membrane, the method of immersing a support membrane in aqueous solution, etc. The contact time between the support membrane and the aqueous solution containing the aliphatic polyfunctional amine is preferably in the range of 5 seconds to 10 minutes, and more preferably in the range of 10 seconds to 2 minutes.

Next, it is preferable to remove the excessively applied aqueous solution by a liquid draining step. As a method of draining, there are, for example, a method of holding the film surface in a vertical direction and letting it flow down naturally, a method of removing it by blowing air, and the like. After draining, the membrane surface may be dried to remove all or part of the water in the aqueous solution.

Thereafter, an organic solvent solution containing the above-mentioned polyfunctional acid halide is applied to a support film coated with an aqueous solution containing an aliphatic polyfunctional amine, and a separation functional layer of crosslinked polyamide is formed by interfacial polycondensation. 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.

The coating temperature of the organic solvent solution containing the aforementioned polyfunctional acid halide is preferably 10 ° C. or lower. When the coating temperature is 10 ° C. or lower, the separation functional layer becomes thin and the water permeability becomes high.

Next, it is preferable to remove the organic solvent solution after the reaction by a liquid draining step. The organic solvent can be removed by, for example, a method in which the membrane is held in a vertical direction to remove excess organic solvent by flowing down, a method in which the organic solvent is dried by blowing air with a blower, or a mixed fluid of water and air. A method of removing excess organic solvent with (2 fluids) can be used.

The composite semipermeable membrane obtained by the above-described method is further added with a process of washing with hot water for 1 minute to 60 minutes within the range of 25 ° C to 90 ° C, so that the solute blocking performance of the composite semipermeable membrane is added. And water permeability can be further improved.

(2-3) Protection Layer Formation Step Next, the protection layer formation step will be described. In the protective layer forming step, a protective layer containing a polymer component is formed on the separation functional layer directly or via another layer.

Specifically, the protective layer forming step is a step in which a solution containing a polymer component is applied directly on the polyamide separation functional layer or via another layer (for example, a hydrophilic layer containing a hydrophilic resin). And subsequently drying the solution.

Examples of the coating method include spraying, coating, and showering. As the solvent, in addition to water, an organic solvent that does not deteriorate the performance, such as a polyamide separation functional layer, may be used in combination. Such organic solvents include, for example, aliphatic alcohols such as methanol, ethanol, propanol, and butanol; lower alcohols such as methoxymethanol and methoxyethanol. Of course, these may be used alone or as a mixed solvent of two or more.

The temperature of the solution is not particularly limited as long as the solution exists as a liquid, but is preferably 10 to 90 ° C. from the viewpoint of preventing deterioration of the polyamide separation functional layer and ease of handling. More preferably, the temperature is ˜60 ° C., and more preferably 10 to 45 ° C.

The step of drying the solution after coating the solution on the polyamide separation functional layer is performed, for example, by heating or blowing. The temperature at which the drying treatment is performed is not particularly limited, but is preferably about 20 to 160 ° C, more preferably 40 to 130 ° C, and further preferably 60 to 120 ° C. When the drying temperature is 20 ° C. or higher, the time required for drying can be shortened, and good film performance can be obtained by sufficiently drying the solution. On the other hand, since the structural change of the film due to heat is suppressed when the temperature is 160 ° C. or less, good film performance can be obtained.

As a method for crosslinking the polymer component, a crosslinking method in the case of using polyvinyl alcohol will be given below. As a crosslinking method, for example, a method of immersing in an acidic polyhydric aldehyde solution after drying treatment (Method A), or an acidic solution containing polyvinyl alcohol and a polyhydric aldehyde is applied on the polyamide separation functional layer and dried by heating. Thus, there is a method (Method B) in which polyvinyl alcohol is cross-linked to the polyamide separation functional layer with a polyvalent aldehyde at the same time as forming the protective layer. The acid may be an inorganic acid or an organic acid, and for example, sulfuric acid, hydrochloric acid and the like are used. Furthermore, there is a method (Method C) in which an aqueous solution containing polyvinyl alcohol and an organic titanium compound or an organic zirconium compound is coated on a polyamide separation functional layer and dried by heating to form a protective layer of crosslinked polyvinyl alcohol. It is done. The method B is more preferable from the viewpoints of economy and ease of operation.

When using the method B, the concentration of polyvinyl alcohol in the solution is preferably 0.01 to 1% by weight, more preferably 0.1 to 0.7% by weight. A polyvinyl alcohol concentration in the solution of 0.01% by weight or more is suitable for obtaining the above function as a protective layer. Moreover, it is suitable for the polyvinyl alcohol concentration in a solution to be 1 weight% or less in order to make the above-mentioned function as a protective layer and the water permeability of a film compatible.

When Method B is used, the polyvalent aldehyde concentration is preferably 0.001 to 0.5% by weight, more preferably 0.01 to 0.3% by weight.
When the method B is used, the acid concentration is in the range of 0.01 to 1 mol / liter, more preferably in the range of 0.01 to 0.5 mol / liter, still more preferably 0.01 to 0.3. It may be in the range of mol / liter. When the concentration is 0.01 mol / liter or more, the function of the acid as a catalyst is sufficiently expressed. In addition, if the acid concentration is extremely high, the crosslinking reaction may be inhibited. However, if the acid concentration is 1 mol / liter or less, the crosslinking reaction is hardly hindered.

In addition, various conventionally known treatments may be performed in order to improve the salt blocking property, water permeability, oxidation resistance, and the like of the composite semipermeable membrane.

3. Use of Composite Semipermeable Membrane The composite semipermeable membrane of the present invention can be suitably used for removing divalent ions. For example, the present invention is applicable to salt removal or mineral adjustment from canned water or seawater, and salt removal or mineral adjustment in the food field.

More specifically, the composite semipermeable membrane of the present invention is suitably used for membrane separation treatment before distillation on raw water (for example, seawater, surface water, etc.) in a method for obtaining fresh water by a distillation method. By this membrane separation treatment, it is possible to obtain permeated water that is reduced to such an extent that the scale component does not become a practical problem. Fresh water is obtained by processing the permeated water thus obtained by a distillation method. Thus, by reducing the concentration of the scale component in the water used for distillation, precipitation of scales such as CaCO ₃ , Mg (OH) ₂ , and CaSO ₄ can be effectively suppressed in the distillation step.

Examples of the distillation method in the present invention include a multistage distillation method, a multiple effect method, an evaporation compression method, and the like, and the multistage distillation method is particularly preferable. The multistage distillation method is a preferable method because the thermal energy required to obtain the same amount of fresh water can be greatly reduced as compared with a method in which the entire amount is evaporated in one stage. For details on the conditions of the multistage evaporation method, etc., ““ Freshing Technology Handbook ”, November 25, 2004, edited by the Freshwater Technology Handbook Editorial Planning Committee, issued by the Fresh Water Promotion Center, pages 122-124, etc. These known techniques can be employed as appropriate.

Moreover, this composite semipermeable membrane is suitably used for obtaining water to be injected into the oil field from the subsea oil field for the purpose of improving the recovery rate of the crude oil. That is, by using this composite semipermeable membrane for membrane separation treatment of raw water (for example, seawater, surface water, etc.) containing divalent ions (particularly sulfate ions), the divalent ions (particularly sulfate ions) are used. Permeated water can be obtained in which the concentration of is sufficiently reduced to such an extent that it does not become a practical problem. Furthermore, in the permeated water obtained in this way, the concentration of divalent ions (particularly, sulfate ions) is reduced to such an extent that there is no problem in the subsequent steps. That is, when permeated water is injected into the oil field, (1) scale is generated by Ba ²⁺ or Sr ²⁺ contained in the crude oil and sulfate ions contained in the raw water, and the pipe for crude oil recovery is blocked. And (2) Hydrogen sulfide is generated by sulfate ion-reducing bacteria present in the crude oil and the quality of the crude oil is deteriorated. In addition, since only divalent ions (especially sulfate ions) can be selectively separated from the mixed solution of monovalent ions and divalent ions, the difference in osmotic pressure before and after membrane separation treatment is reduced, and sulfuric acid from seawater is reduced. The energy required for ion removal can be greatly reduced.

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

Also, the above-described composite semipermeable membrane, its elements, and modules can be combined with a pump for supplying raw water to them, a device for pretreating the raw water, and the like to constitute a fluid separation device. By using this separation device, raw water can be separated into permeated water such as drinking water and concentrated water that has not permeated through the membrane, and water suitable for the purpose can be obtained.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<< Characteristic Evaluation 1 >>
<MgSO ₄ removal rate>
The composite semipermeable membrane was subjected to membrane filtration treatment by supplying salt water adjusted to a temperature of 25 ° C., pH 7.5, and MgSO ₄ concentration of 2000 mg / L at an operating pressure of 0.48 MPa. The electric conductivity of the feed water and the permeated water was measured with an electric conductivity meter manufactured by Toa Denpa Kogyo Co., Ltd. to obtain the respective practical salinities, that is, MgSO ₄ concentrations. Based on the MgSO ₄ concentration thus obtained and the following formula, the MgSO ₄ removal rate was calculated.
MgSO ₄ removal rate (%) = {1- / ( MgSO 4 concentration in the feed solution) (MgSO ₄ concentration in the permeate)} × 100

<NaCl removal rate>
The composite semipermeable membrane was subjected to membrane filtration treatment by supplying evaluation water adjusted to a temperature of 25 ° C., pH 7.5, and NaCl concentration of 500 ppm at an operating pressure of 0.48 MPa. The electric conductivity of the supplied water and the permeated water was measured with an electric conductivity meter manufactured by Toa Denpa Kogyo Co., Ltd. to obtain the respective practical salinities, that is, NaCl concentrations. Based on the NaCl concentration thus obtained and the following equation, the NaCl removal rate was calculated.
NaCl removal rate (%) = 100 × {1− (NaCl concentration in permeated water / NaCl concentration in feed water)}

<Membrane permeation flux>
In the test of the preceding paragraph, the amount of the permeated water of the feed water (MgSO ₄ aqueous solution or NaCl aqueous solution) was measured, and the value converted into the daily water permeation amount (cubic meter) per square meter of the membrane surface was measured as the membrane permeation flux (m ³ / m ² / day).

<Divalent ion selectivity>
The divalent ion selectivity was determined based on the following formula using the MgSO ₄ removal rate and the NaCl removal rate obtained in the previous test.
Divalent ion selectivity = (MgSO ₄ removal rate) / (NaCl removal rate)

<Abundance ratio of piperazine and trimesic acid chloride constituting separation functional layer>
After separating the base material from the composite semipermeable membrane to obtain a laminate of the porous support layer and the separation functional layer, the separation layer was obtained by dissolving the porous support layer with dichloromethane. The obtained separation functional layer was hydrolyzed by heating with a strong alkaline heavy aqueous solution, and the hydrolyzed aqueous solution was filtered and subjected to ¹ H-NMR measurement. The data obtained by the measurement was analyzed, and the abundance ratio of piperazine and trimesic acid chloride was calculated from the peak area value.

<Zeta potential>
The composite semipermeable membrane is washed with ultrapure water, set in a flat sample cell so that the separation functional layer surface of the composite semipermeable membrane is in contact with the monitor particle solution, and an electrophoretic light scattering photometer (ELS) manufactured by Otsuka Electronics Co., Ltd. -8000). As the monitor particle solution, a measurement solution in which polystyrene latex monitor particles were dispersed in a 10 mM NaCl aqueous solution adjusted to pH 6 and pH 9 was used.

<Thickness of separation functional layer>
The composite semipermeable membrane was embedded with PVA and then stained with osmium tetroxide to obtain a measurement sample.
The obtained sample was photographed using TEM tomography, and the obtained 3D image was analyzed by analysis software. For TEM tomography analysis, JEOL field emission analytical electron microscope JEM2100F was used. Using the acquired image at a magnification of 300,000 times, the thickness of the separation functional layer was analyzed at 50 points. The above measurement and analysis were performed with an accuracy of 0.1 nanometer or more, and the average thickness was calculated from Formula 1 with two significant digits.
Thickness of separation functional layer = sum of measured thickness / number of samples (Equation 1)

<Production of composite semipermeable membrane>
(Example 1)
A 15% by weight dimethylformamide (DMF) solution of polysulfone was cast at a room temperature (25 ° C.) at a coating thickness of 180 μm on a non-woven fabric (air permeability 1.0 cc / cm ² / sec) made of polyester fiber manufactured by a papermaking method. Thereafter, the substrate was immediately immersed in pure water for 5 minutes to form a porous support layer on the substrate, thereby preparing a support film.
Next, the support membrane was immersed for 10 seconds in an aqueous solution in which piperazine was 1.0 wt%, sodium dodecyl diphenyl ether disulfonate 100 ppm, and trisodium phosphate 1.0 wt%, and then from an air nozzle. A solution in which trimesic acid chloride was dissolved in n-decane (SP value = 15.8, logP = 4.7) so that the content of trimesic acid chloride was 0.20% by weight was removed by blowing nitrogen. It was uniformly applied to the entire surface of the layer (application temperature 20 ° C.). After standing for 1 minute, two fluids (pure water and air) were sprayed onto the film surface to remove the surface solution. Then, it wash | cleaned with the pure water of 80 degreeC, and obtained the composite semipermeable membrane. When the composite semipermeable membrane obtained in this way was evaluated, the membrane performance was the value shown in Table 1.

(Examples 2 to 10, Comparative Examples 1 to 3)
In Example 1, the same method as in Example 1 except that the piperazine concentration, trimesic acid chloride concentration, trisodium phosphate concentration, sodium dodecyl diphenyl ether disulfonate concentration, and the solvent for dissolving trimesic acid chloride were changed to the values shown in Table 1. A composite semipermeable membrane was prepared. Table 1 shows the membrane performance of the obtained composite semipermeable membrane.

(Examples 11 and 12)
A composite semipermeable membrane was produced in the same manner as in Example 1 except that the solution application temperature of trimesic acid chloride was changed to the value shown in Table 2 in Example 1. Table 2 shows the membrane performance of the obtained composite semipermeable membrane.

(Example 13, Comparative Example 4)
In Example 1, after removing the trimesic acid chloride solution with two fluids, it was immersed in an aqueous piperazine solution having the concentration shown in Table 2 for 2 minutes. Then, it wash | cleaned with the pure water of 80 degreeC, and obtained the composite semipermeable membrane. When the composite semipermeable membrane obtained in this way was evaluated, the membrane performance was the value shown in Table 2.

(Example 14)
The film obtained in Example 1 contains 0.2% by weight of polyvinyl alcohol (saponification degree 88%, average polymerization degree 500), glutaraldehyde 0.065% by weight, and sulfuric acid 0.04 mol / liter as an acid catalyst. The aqueous solution was applied to the film surface, dried at 65 ° C. for 2 minutes with a hot air dryer, and crosslinked. Thereafter, in order to remove the uncrosslinked product and the acid catalyst, washing is performed with hot water at 70 ° C., and after contact with an aqueous solution containing 10% by weight of isopropyl alcohol for 10 minutes, sufficient washing is performed to obtain a composite semipermeable membrane. It was. The evaluation results of this film are shown in Table 3.

(Example 15)
An aqueous solution (isopropanol: water = 3: 7) containing 0.2% by weight of polyvinyl alcohol (saponification degree 98%, average polymerization degree 1000) was applied to the film surface obtained in Example 1 and then dried with hot air. A protective layer was formed by drying at 90 ° C. for 2 minutes using a machine to obtain a composite semipermeable membrane. The evaluation results of this film are shown in Table 3.

(Example 16)
An aqueous solution containing 0.2% by weight of polyvinyl alcohol (saponification degree 88%, average polymerization degree 500) and 0.04% by weight of an organic titanium compound (titanium lactate) was applied to the surface of the film obtained in Example 1. Then, it dried at 40 degreeC with the hot air dryer for 12 hours, and bridge | crosslinked polyvinyl alcohol. Thereafter, in order to remove the uncrosslinked product and the organotitanium compound, washing is performed with hot water at 70 ° C., and after contact with an aqueous solution containing 10% by weight of isopropyl alcohol for 10 minutes, sufficient washing with water is performed to form a composite semipermeable membrane. Obtained. The evaluation results of this film are shown in Table 3.

(Example 17)
A protective layer was formed on the membrane obtained in Example 4 in the same manner as in Example 14 to obtain a composite semipermeable membrane. The evaluation results of this film are shown in Table 3.

From Examples 1 to 13, when the abundance ratio of piperazine and trimesic acid chloride in the polyamide separation functional layer measured by NMR is in the range of 1.2 to 1.8, the selective removal of divalent ions is 2 It turns out that it is high above. From Examples 11 and 12, the water permeability can be increased by lowering the coating temperature of the trimesic acid chloride solution. Further, from Examples 14 to 17, the divalent ion removal rate can be increased by forming a protective layer on the polyamide separation functional layer.

<< Characteristic Evaluation 2 >>
Seawater (TDS (Total Dissolved Solids concentration: about 3.5%)) adjusted to a temperature of 25 ° C. and pH 7.5 was supplied to the composite semipermeable membrane at an operating pressure of 1.0 MPa to perform membrane filtration treatment, By measuring the water quality of the feed water, the ion removal rate, TDS removal rate, and membrane permeation flux were determined from the following formulas from the following formulas.
In the measurement of the ion removal rate, among the solute concentrations in the raw water and the permeated water, the cation and anion concentrations were measured by ion chromatography. The apparatus used was an ion chromatograph manufactured by Nippon Dionex Co., Ltd. Moreover, in the measurement of the TDS removal rate, the electric conductivity of the permeated water and the supplied water was measured with an electric conductivity meter manufactured by Toa Radio Industry Co., Ltd., and the TDS concentration was determined.
Ion removal rate (%) = 100 × {1- (each ion concentration in permeated water / each ion concentration in feed water)}
TDS removal rate (%) = 100 × {1− (TDS concentration in permeated water / TDS concentration in feed water)}
In addition, the membrane permeation flux (m ³ / m ² / d) was expressed by the amount of water per day (cubic meter) per square meter of membrane surface.

(Example 18)
Table 4 shows the evaluation results in the characteristic evaluation 2 of the composite semipermeable membrane obtained in Example 3.

(Example 19)
Table 4 shows the evaluation results in the characteristic evaluation 2 of the composite semipermeable membrane obtained in Example 4.

(Example 20)
Table 4 shows the evaluation results in the characteristic evaluation 2 of the composite semipermeable membrane obtained in Example 17.

(Comparative Example 5)
Table 4 shows the evaluation results in the characteristic evaluation 2 of the composite semipermeable membrane obtained in Comparative Example 2.

Table 4 shows that the composite semipermeable membrane of the present invention has a high removal rate of divalent ions such as sulfate ions, calcium ions, and magnesium ions. Therefore, the scale component can be sufficiently removed.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. The present application is a Japanese patent application filed on December 27, 2012 (Japanese Patent Application No. 2012-285666), a Japanese patent application filed on May 31, 2013 (Japanese Patent Application No. 2013-115031) and an application filed on May 31, 2013. This is based on a Japanese patent application (Japanese Patent Application No. 2013-115033), the contents of which are incorporated herein by reference.

Claims

A composite semipermeable membrane comprising a base material and a support membrane comprising a porous support layer provided on the base material, and a polyamide separation functional layer formed on the porous support layer, wherein the polyamide separation A functional layer is formed of a polyamide obtained from an aliphatic polyfunctional amine and a polyfunctional acid halide, and the abundance ratio (molar ratio) of the aliphatic polyfunctional amine and the polyfunctional acid halide is in the relationship of the following formula: Semipermeable membrane.
1.2 ≦ number of moles of aliphatic polyfunctional amine / number of moles of polyfunctional acid halide ≦ 1.8
The composite semipermeable membrane according to claim 1, wherein the abundance ratio is 1.3 or more and 1.7 or less.
The composite semipermeable membrane according to claim 2, wherein the abundance ratio is 1.35 or more and 1.65 or less.
The composite semipermeable membrane according to claim 3, wherein the abundance ratio is 1.4 or more and 1.6 or less.
The composite half layer according to any one of claims 1 to 4, wherein the polyamide separation functional layer contains a secondary amine, and the difference in zeta potential between pH 6 and pH 9 of the polyamide separation functional layer is 12 mV or more. Permeable membrane.
The composite semipermeable membrane according to any one of claims 1 to 5, wherein the polyamide is obtained by interfacial polycondensation.
The composite semipermeable membrane according to any one of claims 1 to 6, wherein the aliphatic polyfunctional amine is bifunctional.
The composite semipermeable membrane according to any one of claims 1 to 7, wherein the polyfunctional acid halide is a bifunctional or trifunctional acid halide, or a mixture thereof.
The composite semipermeable membrane according to any one of claims 1 to 8, wherein the aliphatic polyfunctional amine is piperazine and the polyfunctional acid halide is trimesic acid chloride.
The composite semipermeable membrane according to any one of claims 1 to 9, wherein a protective layer containing a polymer component is provided on the polyamide separation functional layer directly or via another layer.
The composite semipermeable membrane according to claim 10, wherein the polymer component is a crosslinked polymer of a hydrophilic polymer.
The composite semipermeable membrane according to claim 11, wherein the crosslinked product contains a polyvalent aldehyde.
The composite semipermeable membrane according to claim 12, wherein the crosslinked product contains a reaction product of polyvinyl alcohol and glutaraldehyde.