WO2021085600A1

WO2021085600A1 - Composite semipermeable membrane and manufacturing method therefor

Info

Publication number: WO2021085600A1
Application number: PCT/JP2020/040810
Authority: WO
Inventors: 吉崎友哉; 征矢恭典; 小岩雅和; 花田茂久
Original assignee: 東レ株式会社
Priority date: 2019-10-31
Filing date: 2020-10-30
Publication date: 2021-05-06
Also published as: JPWO2021085600A1

Abstract

A composite semipermeable membrane according to the present invention comprises a separation functional layer, wherein the separation functional layer contains, as a main component, a semi-aromatic crosslinked polyamide, which is a condensate of a polyfunctional aliphatic amine and a polyfunctional aromatic acid halide, has hollow pleats, has a surface of which the specific surface area is 1.2-5.0, and has a ratio (C/(N+O)) of carbon atoms to the sum of nitrogen atoms and oxygen atoms in an element, of 2.3-4.0, as measured through X-ray photoelectron spectroscopy measurement.

Description

Composite semipermeable membrane and its manufacturing method

INDUSTRIAL APPLICABILITY The present invention is a composite semipermeable membrane which selectively removes polyvalent ions, pesticides, etc. and allows monovalent ions having a small ionic radius to permeate, and has high acid resistance and alkali resistance. Regarding the method. With this film, it is possible to remove salts and minerals from brackish water and seawater, remove salts and minerals in the food field, recover acids and alkalis from industrial applications such as plating and refining, and recover valuable metals of rare metals. It becomes.

Regarding the separation of mixtures, there are various techniques for removing substances (for example, salts) dissolved in a solvent (for example, water), but in recent years, the use of the membrane separation method has expanded as a process for energy saving and resource saving. doing. Membranes used in the membrane separation method include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, etc., and these membranes are, for example, from seawater, drinking water, water containing harmful substances, etc. It is used for the production of drinking water, softening of drinking water, food use, production of industrial ultrapure water, wastewater treatment, recovery of valuable resources, etc.

Most of the reverse osmosis membranes and nanofiltration membranes currently on the market are composite semipermeable membranes, which have an active layer in which a gel layer and a polymer are crosslinked on a support membrane, and a monomer is polycondensed on the support membrane. There are two types, one having an active layer. Among them, the composite semipermeable membrane obtained by coating a separation functional layer made of a crosslinked polyamide obtained by a polycondensation reaction between a polyfunctional amine and a polyfunctional acid halide on a support membrane is permeable and selectively separable. Widely used as a high separation membrane.

Nanofiltration membranes are widely used to separate specific substances from mixed solutions of monovalent ions, divalent ions, and organic substances, and nanofiltration membranes composed of aliphatic amines and acid halides have been proposed.

For example, a nanofiltration membrane made of polyamide obtained by reacting piperazine with a polyfunctional aromatic carboxyl chloride product is disclosed (Patent Document 1). On the other hand, one of the problems that occurs in membrane separation plants that use nanofiltration membranes is fouling due to inorganic or organic substances. The water permeability of the nanofiltration membrane is significantly reduced due to fouling. As a method for improving this, a method of recovering the water permeability by cleaning with a chemical such as an acid or an alkali has been proposed, and a nanofiltration membrane having high chemical resistance (Patent Documents 2 and 3) is also known. Has been done.

JP-A-2007-277298 Japanese Patent Application Laid-Open No. 2003-534422 Special Table 2009-504883A

As described above, the performance required for the nanofiltration membrane includes not only water permeability and selective separation performance but also chemical resistance, but the membrane described in Patent Document 1 has low chemical resistance, while the patent The films described in Document 2 and Patent Document 3 can have high chemical resistance, but have a problem of low selective separability.

An object of the present invention is to provide a composite semipermeable membrane having high monovalent ion / divalent ion selective separation performance and high acid resistance and alkalinity.

In order to achieve the above object, the present invention has the following configuration.
[1] A composite having a support membrane and a separation functional layer containing a semi-aromatic crosslinked polyamide which is a condensate of a polyfunctional aliphatic amine formed on the support membrane and a polyfunctional aromatic acid halide. It is a semipermeable membrane
The specific surface area of the surface of the separation functional layer is 1.2 or more and 5.0 or less.
Composite semipermeable membrane in which the ratio C / (N + O) of the sum of the number of nitrogen atoms and the number of oxygen atoms to the number of carbon atoms measured by X-ray photoelectron spectroscopy on the surface of the separation functional layer is 2.3 or more and 4.0 or less. film.
[2] The composite semipermeable membrane according to the above [1], wherein the separation functional layer has a fold-shaped thin film having a (fold height / thickness) of 1.2 or more.
[3] derived by the composite semipermeable membrane in the separation functional layer surface is measured by the total reflection infrared absorption spectrum method, the support film to the absorption peak intensity derived from the amide group of semi-aromatic polyamide (I _A) the composite semipermeable membrane according to [1] or [2] the ratio of the absorption peak intensity _{_{(I S) (I a /}} I S) is 0.15 to 0.50 to.
[4] Ra / Rb is 0.40 or more and 1.0 or less.
The composite semipermeable membrane according to any one of the above [1] to [3].
R1: The composite semipermeable membrane before immersion in the sulfuric acid aqueous solution in the measurement of Rb below is derived from the amide group of the semi-aromatic polyamide measured by the total internal reflection infrared absorption spectroscopy on the surface on the separation function layer side. absorption peak intensity (I _a) and the absorption peak intensity derived from the support film (I _S) and the ratio of (I _a / I _S)
R2: An amide group of a semi-aromatic polyamide measured by total internal reflection infrared absorption spectroscopy on the surface of the separation function layer side after immersing the composite semipermeable membrane in a 1 mol / L sulfuric acid aqueous solution at 40 ° C. for 21 days. from absorption peak intensity (I _A2) and the absorption peak intensity derived from the support film the ratio between _{_{(I S2) (I A2 /}} I S2)
[5] The composite according to any one of the above [1] to [4], wherein the difference in contact angle before and after immersing the composite semipermeable membrane in a 1 mol / L sulfuric acid aqueous solution at 40 ° C. for 21 days is 15 ° or less. Semipermeable membrane.
[6] Among the polyfunctional aliphatic amine components constituting the separation functional layer, 80 mol% or more of a piperazine derivative having a melting point of 100 ° C. or higher is contained, and the piperazine derivative contains an alkyl group having two or more carbons of the piperazine ring. The composite translucent film according to any one of the above [1] to [5], which is a piperazine substituted with either a fluoroalkyl group or a thioether group.
[7] The molar ratio (amide group ratio) of the total amount of the polyfunctional aliphatic amine and the polyfunctional aromatic acid halide to the amount of the amide group (mol) in the semi-aromatic crosslinked polyamide. The composite translucent film according to any one of the above [1] to [6], wherein is 0.80 or more and 1.20 or less.

Amide group ratio (molar ratio) = amide group amount / (polyfunctional aliphatic amine amount + polyfunctional aromatic acid halide amount)
[8] Any of the above [1] to [7] in which the abundance ratio (molar ratio) of the polyfunctional aliphatic amine and the polyfunctional aromatic acid halide in the semiaromatic polyamide has the following relationship. The composite semipermeable membrane according to.
1.25 ≤ number of moles of polyfunctional aliphatic amine / number of moles of polyfunctional acid aromatic halide ≤ 1.65
[9] The composite semipermeable membrane according to any one of the above [1] to [8], wherein the polyfunctional acid halide is an aromatic polyfunctional carboxylic acid halide or an aromatic polyfunctional sulfonic acid halide.
[10] The magnesium sulfate removal rate and magnesium chloride removal rate are lower when a 2000 ppm magnesium sulfate aqueous solution at 25 ° C and pH 6.5 and a 2000 ppm magnesium chloride aqueous solution at 25 ° C and pH 6.5 are permeated at an operating pressure of 0.5 MPa, respectively. The composite translucent film according to any one of the above [1] to [9], which simultaneously satisfies the formulas (I) and (II).
Magnesium sulfate removal rate ≧ 97% ・・・ (I)
Magnesium Sulfate Removal Rate-Magnesium Chloride Removal Rate ≤ 20% ... (II)
[11] A composite having a support membrane and a separation functional layer containing a semi-aromatic crosslinked polyamide which is a condensate of a polyfunctional aliphatic amine formed on the support membrane and a polyfunctional aromatic acid halide. It is a method for manufacturing a semipermeable membrane.
It has a step of forming a separation functional layer on the support membrane by interfacial polycondensation of a polyfunctional aliphatic amine aqueous solution and a polyfunctional acid halide-containing solution.
The above process
(A) A step of impregnating the support membrane with an aqueous solution of a polyfunctional aliphatic amine,
(B) A method for producing a composite semipermeable membrane, which comprises a step of contacting the support membrane with a polyfunctional acid halide-containing solution at 10 to 38 ° C.
[12] The composite semipermeable membrane according to the above [11], wherein the step (a) is a step of applying a polyfunctional aliphatic amine aqueous solution 5 to 15 ° C. higher than the temperature of the support membrane surface to the support membrane surface. Manufacturing method.

The composite semipermeable membrane of the present invention has a separation functional layer containing a semi-aromatic cross-linked polyamide which is a condensate of a polyfunctional aliphatic amine and a polyfunctional aromatic acid halide as a main component, and has the separation function. The specific surface area of the layer surface is 1.2 or more and 5.0 or less, and in the X-ray photoelectron spectroscopy measurement, the ratio of the sum of nitrogen and oxygen atoms to the carbon atom in the measured element, C / (N + O) is 2. By providing a separation functional layer having a concentration of 0.3 or more and 4.0 or less, a composite semipermeable membrane having high acid resistance and alkalinity in addition to high selective separation performance can be obtained.

FIG. 1A is a cross-sectional view of a composite semipermeable membrane according to an embodiment of the present invention, and FIG. 1B is an enlarged view of a separation functional layer. FIG. 2 is a diagram showing a cross section of the fold structure of the separation function layer.

1. 1. Composite Semipermeable Membrane The composite semipermeable membrane of the present invention comprises a support membrane and a semi-aromatic cross-linked polyamide which is a condensate of a polyfunctional aliphatic amine formed on the support membrane and a polyfunctional aromatic acid halide. It has a separating functional layer containing it. Generally, factors that affect the acid resistance and alkali resistance of the separation membrane include the thickness of the separation functional layer and the chemical bond mode (ester bond, amide bond, etc.). We focused on the specific surface area and chemical composition of the layers.

In the present specification, the "specific surface area" is the ratio of the surface area of the separating functional layer to the surface area of the porous support layer. The larger the specific surface area, the greater the water permeability. Conventionally, a separation membrane composed of a separation functional layer containing a polymer of a polyfunctional aliphatic amine and a polyfunctional acid halide has excellent divalent ion selective removal property, but it is difficult to increase the specific surface area. , Acid resistance and alkali resistance improvement could not be achieved.

As a result of diligent studies, the present inventors have found that the separation functional layer having a specific surface area of 1.2 or more, which contains a polymer of a polyfunctional aliphatic amine and a polyfunctional acid halide, has acid resistance, alkali resistance and It has been found that a separation membrane having excellent divalent ion selective removal property can be obtained.

Further, in the present specification, the "chemical composition" of the separation functional layer indicates the ratio of the elements present in the separation functional layer. As a result of diligent studies, the present inventors have calculated the ratio of the sum of the ratio of nitrogen atoms (N) and the ratio of oxygen atoms (O) to the ratio of carbon atoms (C) in the separation functional layer, C / (N + O). It was found that a separation membrane having excellent acid resistance, alkali resistance and divalent ion selective removal property can be obtained when the ratio is 2.3 or more and 4.0 or less.

(1-1) Support Membrane The support membrane is for giving strength to the composite semipermeable membrane by supporting the separation functional layer. The support membrane itself has substantially no separation performance for low molecular weight organic substances, ions and the like. The support film includes a base material and a porous support layer.

The size and distribution of the pores in the support membrane are not particularly limited, but for example, uniform and fine pores, or fine pores gradually increasing from the surface on the side where the separation functional layer is formed to the other surface, that is, the surface on the base material side. It is preferable that the pores have a size of 0.1 nm or more and 100 nm or less on the surface on the side where the separation functional layer is formed.

As shown in FIG. 1A, the support film includes a base material 2 and a porous support layer 3 arranged on the base material.

Examples of the base material 2 include a cloth made of at least one selected from polyester and aromatic polyamide. It is particularly preferred to use polyester, which is mechanically and thermally stable.

As the fabric used for the base material 2, a long fiber non-woven fabric or a short fiber non-woven fabric can be preferably used. When a solution of a polymer polymer is cast on a base material, it strikes through due to over-penetration, the base material and the porous support layer are peeled off, and the film is non-uniform due to fluffing of the base material. Long-fiber non-woven fabrics can be more preferably used because excellent film-forming properties are required so as not to cause defects such as formation and pinholes. Examples of the long-fiber non-woven fabric include long-fiber non-woven fabrics composed of thermoplastic continuous filaments. Since the base material is made of a long-fiber non-woven fabric, it is possible to suppress the non-uniformity at the time of spreading the polymer solution caused by fluffing and the film defects that occur when the short-fiber non-woven fabric is used. Further, in the step of continuously forming a composite semipermeable membrane, tension is applied in the film forming direction of the base material, so that it is preferable to use a long fiber non-woven fabric having excellent dimensional stability as the base material.

In particular, in the base material 2, the orientation of the fibers on the surface opposite to the surface in contact with the porous support layer 3 is longitudinally oriented with respect to the film forming direction, so that the strength of the base material is maintained, the film is torn, and the like. It is preferable because it can prevent. Here, the longitudinal orientation means that the orientation direction of the fibers is parallel to the film forming direction. On the contrary, when the orientation direction of the fibers is perpendicular to the film formation direction, it is called lateral orientation.

The fiber orientation of the fiber is preferably in the range of 0 ° to 25 °. Here, the fiber orientation is an index indicating the orientation of the fibers of the non-woven fabric, and the film-forming direction when continuous film-forming is performed is 0 °, and the direction perpendicular to the film-forming direction, that is, the width direction of the non-woven fabric is 90 °. It refers to the average angle of the fibers that make up the non-woven fabric. Therefore, the closer the fiber orientation is to 0 °, the longer the vertical orientation, and the closer the fiber orientation is to 90 °, the more the horizontal orientation.

The manufacturing process of the composite semipermeable membrane and the manufacturing process of the element include a heating step, but a phenomenon occurs in which the support membrane or the composite semipermeable membrane shrinks due to heating. Especially in continuous film formation, since tension is not applied in the width direction, it tends to shrink in the width direction. Since the shrinkage of the support membrane or the composite semipermeable membrane causes problems in dimensional stability and the like, a base material having a small thermal dimensional change rate is desired.

In the non-woven fabric base material, when the difference in orientation between the fibers on the side opposite to the porous support layer and the fibers on the side of the porous support layer is 10 ° to 90 °, the change in the width direction due to heat can be suppressed. preferable.

The air permeability of the base material ^{is preferably 2.0 cc / cm 2} / sec or more. When the air permeability is in this range, the water permeability of the composite semipermeable membrane becomes high. This is a step of forming a support film, when a polymer polymer is cast on a base material and immersed in a coagulation bath, the non-solvent replacement rate from the base material side is increased, so that the porous support layer is formed. It is considered that this is because the internal structure of the polymer changes, which 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 was attached to the Frazier type tester, the suction fan and air holes were adjusted so that the inclined barometer had a pressure of 125 Pa, and the pressure indicated by the vertical barometer at this time and the type of air holes used were used as the basis. The amount of air passing through the material, that is, the air permeability, can be calculated. As the Frazier type testing machine, KES-F8-AP1 manufactured by Kato Tech Co., Ltd. can be used.

Further, the thickness of the base material is preferably in the range of 10 μm or more and 200 μm or less, and more preferably in the range of 30 μm or more and 120 μm or less.

The porous support layer is, for example, polysulfone, polyethersulfone, cellulose acetate, polyvinyl chloride, or a mixture thereof. Polysulfone and polyethersulfone, which are chemically, mechanically and thermally stable, are particularly preferable.

The thickness of the above-mentioned porous support layer affects the strength of the obtained composite semipermeable membrane and the packing density when it is used as an element. The thickness of the porous support layer is preferably in the range of 50 μm or more and 300 μm or less, and more preferably in the range of 100 μm or more and 250 μm or less in order to obtain sufficient mechanical strength and packing density.

The morphology of the porous support layer can be observed with a scanning electron microscope, a transmission electron microscope, and an atomic force microscope. For example, when observing with a scanning electron microscope, the porous support layer is peeled off from the base material and then cut by a freeze-cutting method to prepare a sample for cross-sectional observation. This sample is lightly 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, a Hitachi S-900 type electron microscope or the like can be used.

The support film 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 Filter Paper Co., Ltd., or "Office of the Office of Saline Water Research and Development Progress Report "No. It can also be produced according to the method described in 359 (1968) and the like.

The thickness of the base material 2 and the thickness of the composite semipermeable membrane 1 can be measured by a digital thickness gauge. Further, since the thickness of the separation functional layer is very thin as compared with the support membrane, the thickness of the composite semipermeable membrane can be regarded as the thickness of the support membrane. That is, the thickness of the composite semipermeable membrane can be measured with a digital thickness gauge, and this can be regarded as the thickness of the support membrane. Further, the thickness of the porous support layer can be easily calculated by subtracting the thickness of the base material from the thickness of the composite semipermeable membrane. As the digital thickness gauge, PEACOCK of Ozaki Seisakusho Co., Ltd. can be used. When using a digital thickness gauge, the thickness is measured at 20 points and the average value is calculated.

If it is difficult to measure the thickness of the base material 2 or the thickness of the composite semipermeable membrane 1 with a thickness gauge, it may be measured with a scanning electron microscope. The thickness of one sample is obtained by measuring the thickness from electron micrographs of cross-sectional observations at arbitrary five points and calculating the average value.

(1-2) Separation Function Layer The Separation Function Layer 4 is a layer that is arranged on the porous support layer 3 as shown in FIG. 1 (a) and has a solute separation function in the composite semipermeable membrane. The separation functional layer contains a polyamide which is a polymer of an aliphatic polyfunctional amine and a polyfunctional aromatic acid halide.

The composite semipermeable membrane of the present invention is a membrane in a region having fractionation characteristics positioned between a reverse osmosis membrane and an ultrafiltration membrane, which is generally defined as a nanofiltration membrane. Membranes commonly known as reverse osmosis membranes actually tend to remove most of the organic matter, ions, while ultrafiltration membranes usually do not remove most of the ionic species, but high. Removes molecular weight organic matter.

The separating functional layer in the composite semipermeable membrane of the present invention is a semi-aromatic cross-linked polyamide obtained by interfacial polymerization of a divalent or higher polyfunctional aliphatic amine compound and a divalent or higher polyfunctional aromatic acid halide. Contains% by weight or more. Preferably, the separation functional layer contains 80% by weight or more, more preferably 90% by weight or more of the semi-aromatic crosslinked polyamide, and more preferably only the semi-aromatic crosslinked polyamide. Since the semi-aromatic crosslinked polyamide is the main component of the separation functional layer, excessive densification due to π-π interaction derived from the aromatic ring in the polyamide is suppressed, and excellent divalent ion selective removal property can be obtained. ..

The polyfunctional aliphatic amine is preferably an alicyclic diamine, more preferably a piperazine derivative.

Further, the polyfunctional aliphatic amine preferably has a ClogP of -1.0 or more and 2.0 or less, and more preferably -0.5 or more and 1.5 or less. Here, ClogP is a value obtained by calculating the octanol-water partition coefficient of a compound from the octanol-water partition coefficient of each functional group contained in the compound (Reference Environ. Sci. Pollute. Res., 2, 153-160 (Reference). 1995)), and can be calculated with structural formula drawing software such as ChemDraw.

It has long been known that the interfacial polymerization of polyamide proceeds by partitioning and diffusing amines in the organic phase and reacting with polyfunctional acid halides in the organic phase (References PW Morgan, S.A. L. Kwalk, J. Polym. Sci., 299-327 (1959)), ClogP of -1.0 or more and 2.0 or less means that the polyfunctional aliphatic amine to the organic solvent at the time of interfacial polycondensation Distributing and diffusion are optimized, and pleated separation functional layers are easily formed.

Examples of the piperazine derivative having a ClogP of -1.0 or more and 2.0 or less include substituted piperazines in which the piperazine ring is substituted with an alkyl group having 1 to 3 carbon atoms (for example, 2-methylpiperazine, 2-ethylpiperazine, etc.). 2-Normal propyl piperazine, 2,2-dimethyl piperazine, 2,2-diethyl piperazine, 2,2-normal propyl piperazine, 2,3-dimethyl piperazine, 2,3-diethyl piperazine, 2,3-normal propyl piperazine, 2,5-Dimethylpiperazine, 2,5-diethylpiperazine, 2,5-normalpropylpiperazine, 2,6-dimethylpiperazine, 2,6-diethylpiperazine, 2,6-normalpropylpiperazine, 2,3,5 6-Tetramethylpiperazine, etc.).

In the present invention, among the polyfunctional aliphatic amine components constituting the separation functional layer, it is preferable that the piperazine derivative having a melting point of 100 ° C. or higher is contained in an amount of 80 mol% or more, more preferably 90 mol% or more, and the piperazine derivative is piperazine. It is preferably piperazine in which two or more carbons of the ring are substituted with any of an alkyl group, a fluoroalkyl group and a thioether group (hereinafter, also simply referred to as "substituted piperazine").

As a result of diligent studies, the inventors have found that the polyfunctional aliphatic amine constituting the separation functional layer is a piperazine derivative having a melting point of 100 ° C. or higher, and the piperazine derivative has an alkyl group having two or more carbons of the piperazine ring. It has been found that excellent acid resistance and alkali resistance can be obtained by using piperazine (substituted piperazine) substituted with either a fluoroalkyl group or a thioether group.

Examples of the substituted piperazine having a melting point of 100 ° C. or higher and having an alkyl group, a fluoroalkyl group, and a thioether group on two or more carbons of the piperazine ring include 2,2-dimethylpiperazine and 2,2-diethylpiperazine. 2,2-Normalpropyl Piperazine, 2,2-Isopropyl Piperazine, 2,3-Dimethyl Piperazine, 2,3-Diethyl Piperazine, 2,3-Normalpropyl Piperazine, 2,3-Isopropyl Piperazine, 2,5-Dimethyl Piperazine , 2,5-diethylpiperazine, 2,5-normalpropylpiperazine, 2,5-isopropylpiperazine, 2,6-dimethylpiperazine, 2,6-diethylpiperazine, 2,6-normalpropylpiperazine, 2,6-isopropyl Piperazine, 2,3,5,6-tetramethylpiperazine, 2,2-bis (trifluoromethyl) piperazine, 2,3-bis (trifluoromethyl) piperazine, 2,5-bis (trifluoromethyl) piperazine, 2,6-bis (trifluoromethyl) piperazine, 2,2-bis (difluoromethyl) piperazine, 2,3-bis (difluoromethyl) piperazine, 2,5-bis (difluoromethyl) piperazine, 2,6-bis (Difluoromethyl) piperazine, 2,2-bis (methylthio) piperazine, 2,3-bis (methylthio) piperazine, 2,5-bis (methylthio) piperazine, 2,6-bis (methylthio) piperazine, 2,2- Examples thereof include bis (ethylthio) piperazine, 2,3-bis (ethylthio) piperazine, 2,5-bis (ethylthio) piperazine, and 2,6-bis (ethylthio) piperazine.

The melting point of the substituted piperazine is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, and preferably 200 ° C. or lower.

When the melting point of the substituted piperazine is 100 ° C. or higher, the molecular motility around the amide group in the separation functional layer is lowered, and the conformational change of the polyamide at the time of contact with an acid or an alkali is less likely to occur. Is expected to improve. Further, since the melting point is 200 ° C. or lower, the molecular motility of the polyamide is not excessively lowered, so that the permeation of monovalent ions having a small hydrated ionic radius is not hindered, and excellent divalent ion selective removal property can be obtained. ..

Further, by providing a substituent on two or more carbons of the piperazine ring, a steric disorder occurs in the vicinity of the amide group, hydrolysis of the amide group by an acid or an alkali is suppressed, and durability is improved. Furthermore, since the substituent is any of a hydrophobic alkyl group, fluoroalkyl group, and thioether group, the substituent makes the periphery of the amide group hydrophobic, which is a main factor in the hydrolysis of polyamide when it comes into contact with an acid or an alkali. It is considered that the acid resistance and alkali resistance are remarkably improved by suppressing the addition of the water molecule to the amide group.

The number of carbon atoms per substituent of the piperazine ring is preferably 1 to 3. By introducing a substituent having 1 to 3 carbon atoms into the piperazine structure, steric hindrance near the amide group and the pore size distribution (molecular gap) of the polyamide crosslinked structure can be suitably controlled, and water permeability and selective separability are maintained. As it is, it is possible to improve the durability against acids and alkalis. When the number of carbon atoms of the substituent is larger than 4, the cross-linking reaction of the polyamide is difficult to proceed due to steric hindrance, and the selective separability and durability against acids and alkalis are lowered.

Among the substituted piperazines in which substituents are provided on the two carbons of the piperazine ring, there are two types of 2,3-substituted products, 2,5-substituted products, and 2,6-substituted products, cis and trans isomers. Although a steric isomer is present, the trans isomer is more preferable from the viewpoint of improving the acid resistance and alkali resistance of the polyamide. Since the trans isomer has a high steric symmetry of amine, the steric hindrance effect in the vicinity of the amide group when forming the polyamide is larger than that of the cis isomer, and the effect of improving the durability against acids and alkalis is also enhanced.

The substituted piperazine may be used alone or in combination of two or more.

Among the polyfunctional aliphatic amine components constituting the separation functional layer, the acid resistance and alkali resistance of the entire separation functional layer are improved by containing 80 mol% or more of the above substituted piperazine.

The polyfunctional aromatic acid halide is an aromatic acid halide having two or more carbonyl halide groups in one molecule, and gives a semi-aromatic polyamide by reaction with the polyfunctional aliphatic amine. If there is, it is not particularly limited. Examples of the polyfunctional aromatic acid halide include 1,3,5-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,3-benzenedicarboxylic acid, 1,4-benzenedicarboxylic acid, 1, Halogen compounds such as 3,5-benzenetrisulfonic acid and 1,3,6-naphthalenetrisulfonic acid can be used. Among aromatic acid halides, acid halides are preferable, and acid halides of 1,3,5-benzenetricarboxylic acid are particularly preferable from the viewpoints of economy, availability, handling, and reactivity. Trimesinic acid chloride, isophthalic acid chloride which is an acid halide of 1,3-benzenedicarboxylic acid, terephthalic acid chloride which is an acid halide of 1,4-benzenedicarboxylic acid, 1,3,5-benzenetrisulfonic acid. 1,3,5-Benzene trisulfonic acid chloride, which is an acid halide of, and 1,3,6-naphthalene trisulfonic acid chloride, which is an acid halide of 1,3,6-naphthalene trisulfonic acid, are preferable. The polyfunctional aromatic acid halide may be used alone or in combination of two or more, but trifunctional trimesic acid chloride, 1,3,5-benzenetrisulfonic acid chloride, 1,3. By mixing either bifunctional isophthalic acid chloride or terephthalic acid chloride with 6-naphthalene trisulfonic acid chloride, the molecular gap of the polyamide crosslinked structure is expanded, and a film having a uniform pore size distribution is widely spread. Can be controlled to. The mixed molar ratio of the trifunctional acid chloride and the difunctional acid chloride is preferably 1:20 to 50: 1, more preferably 1: 1 to 20: 1.

In the separation membrane of the present invention, the specific surface area of the separation functional layer is 1.2 or more and 5.0 or less, preferably 1.3 or more and 4.0 or less, and more preferably 1.5 or more and 3.0 or less. is there.

When the specific surface area of the separation functional layer is 1.2 or more, a separation membrane having excellent divalent ion selective removal property can be obtained. In addition, as a result of diligent studies, the inventors have found that acid resistance and alkali resistance are improved when the specific surface area of the separation functional layer is 1.2 or more. It is considered that the increase in the specific surface area reduces the effective contact concentration of the acid or alkali per unit area and suppresses the hydrolysis of the polyamide. Since the specific surface area of the separation function layer is 5.0 or less, the following fold structure is not crushed even when the separation membrane is operated at high pressure, and the specific surface area of the separation function layer is 4.0 or less. Therefore, it is possible to obtain film performance with little variation. Further, when the specific surface area of the separation functional layer is 3.0 or less, stable film performance can be maintained for a long time.

The "specific surface area of the separation function layer" is the ratio of the "surface area of the separation function layer" to the "surface area of the porous support membrane". The above-mentioned "surface area of the separation function layer" represents the surface area of the surface of the separation function layer on the side in contact with the feed liquid. Further, the above-mentioned "surface area of the porous support membrane" represents the surface area of the surface in contact with the separation functional layer. The method for obtaining the surface area and the specific surface area can be obtained according to a general method for obtaining the surface area and the specific surface area, and the method is not particularly limited.

Examples of the measuring device that can be used include a surface area measuring device, a specific surface area measuring device (AFM), a scanning electron microscope (SEM, FE-SEM), a transmission electron microscope (TEM), and the like. An example of a specific measurement method is shown in the examples.

In the X-ray photoelectron spectroscopy (hereinafter referred to as XPS) measurement performed by irradiating the composite translucent film of the present invention with X-rays from the separation functional layer side, the nitrogen atom and the oxygen atom with respect to the carbon atom in the measured element The sum ratio, C / (N + O), is 2.3 or more, preferably 2.4 or more, and more preferably 2.5 or more. Further, C / (N + O) is 4.0 or less, preferably 3.5 or less, and more preferably 3.0 or less.

As a result of diligent studies, the inventors have determined that the C / (N + O) of the separation functional layer is 2.3 or more and 4.0 or less, thereby achieving both high acid resistance and alkali resistance and excellent divalent ion selective removal property. I found that I could do it.

When the C / (N + O) of the separation functional layer is 2.3 or more, it means that the chemical composition of the polyamide is hydrophobic. Therefore, water, which is a main factor in the hydrolysis of the polyamide when it comes into contact with an acid or an alkali. It is considered that the acid resistance and alkali resistance were greatly improved by suppressing the addition of the molecule to the amide group. Further, when the C / (N + O) of the separation functional layer is 4.0 or less, the polyamide is not excessively hydrophobic, and the hydrophobic interaction acting between the polyamides is appropriate, so that the pores are excessively dense. It is considered that the permeability of the monovalent ion does not decrease due to the conversion, and excellent divalent ion removal selectivity can be obtained.

As shown in FIG. 1 (b), the separation function layer 4 has a fold-shaped thin film 41. The folds have a structure in which convex portions 42 and concave portions 43 are alternately arranged.

Figure 2 shows an enlarged view of the fold structure. In FIG. 2, the “fold height H / thin film thickness T” is preferably 1.2 or more. The height H and the thickness T are average values as described later, but are simply referred to as "height" and "thickness" for convenience of explanation. If the H / T is in this range, it can be said that there is a gap in the convex portion 42 (between the thin film 41 and the porous support layer 3). That is, in this case, the separating functional layer has a hollow pleated structure. By having a hollow fold structure, it is possible to secure a space between the separation function layer and the support membrane that can hold the permeated liquid, and the acid and alkali components that have permeated from the surface side of the separation function layer to the support membrane side can be removed. The contained water can be efficiently diffused into the hollow space, and the decomposition of the polyamide due to the contact with a local acid or alkali can be suppressed. The H / T is preferably 2.0 or more, and more preferably 3.0 or more.

The measurement method of height H and thickness T is as follows. The composite semipermeable membrane is cut into 3 cm × 3 cm squares and washed with distilled water. The washed composite semipermeable membrane is embedded with an epoxy resin and further stained with osmium tetroxide. In the sample thus obtained, an image of the cross section of the thin film 41 of the separation function layer 4 at a magnification of 1 million is obtained with a scanning transmission electron microscope. Ten convex portions 42 are randomly selected, and the shortest distance between the outer surface and the inner surface of the convex portions 42 is measured at five points for each convex portion 42. The average value of the 50 values thus obtained is calculated, and this average value is defined as the fold thickness T. Further, for 50 randomly selected convex portions 42, the maximum distance from the outer surface of each convex portion 42 to the surface of the porous support layer (distance from the apex of the fold to the surface of the support film) is measured. The average value of the obtained 50 values is taken as the average value of the fold height H. These values T and H are used to calculate H / T.

The thin film thickness T of the separation functional layer is preferably 10 nm or more, more preferably 15 nm or more. When the thin film thickness is 10 nm or more, a composite semipermeable membrane having sufficient water permeability can be easily obtained, and when the thin film thickness T is 15 nm or more, the removability due to the occurrence of defects is achieved. A composite semipermeable membrane having sufficient water permeability can be stably obtained without causing a decrease.

The thin film thickness T of the separation functional layer is preferably 100 nm or less, more preferably 50 nm or less, and further preferably 30 nm or less. When the thin film thickness is 100 nm or less, stable film performance can be obtained, and when the thin film thickness is 80 nm or less, sufficient water permeability and stable film performance can be obtained. Further, when the thin film thickness is 30 nm or less, more sufficient water permeability can be provided and stable film performance can be maintained.

The fold height H is preferably 20 nm or more, more preferably 50 nm or more. When the fold height is 20 nm or more, a composite semipermeable membrane having sufficient acid resistance and alkali resistance can be easily obtained.

The fold height H is preferably 1000 nm or less, more preferably 800 nm or less, and further preferably 300 nm or less. The fold height of 1000 nm or less prevents the folds from collapsing even when the composite semipermeable membrane is operated at high pressure, and the fold height of 800 nm or less provides stable membrane performance. Obtainable. Further, when the fold height is 300 nm or less, stable film performance can be maintained for a long time.

Of the two surfaces F1 and F2 of the composite semipermeable membrane shown in FIG. 1A, the semiaromatics measured by total reflection infrared absorption spectroscopy (hereinafter, ATR-IR) on the surface F1 on the separation function layer side. the absorption peak intensity derived from the absorption peak intensity derived from the amide group of the polyamide and the support film (I _a) is defined as I _S. The ratio of the respective peak intensities, I _A / I _S is 0.15 or more, preferably 0.20 or more, and more preferably 0.35 to 0.50. By I _A / I _S is 0.15 or more, interaction such as hydrogen bonding between intramolecular or molecules of the amide groups in the separating functional layer is increased, the contact to the amide groups of the acid or alkali inhibition And performance stability is improved. Further, by I _A / I _S is 0.50 or less, it is possible to achieve both high acid, alkali resistance and high divalent ion selective removability.
I _A is specifically as follows, I _S is the composite semipermeable membrane substrate, the porous support layer has a separation function layer, if the porous support layer is polysulfone or polyether sulfone Is defined as follows.

I _A: 1600 ~ 1650cm absorption maximum peak present in the range of ^-1 I _S: absorption peak corresponding to the porous support layer of 1242Cm ^-1 In the present invention, the composite semipermeable membrane of 40 ° C. 1 mol The absorption peak intensity derived from the amide group of the semi-aromatic polyamide when measured by ATR-IR after being immersed in the / L sulfuric acid aqueous solution for 21 days _{is defined as after I A2,} and the absorption peak derived from the porous support layer. Intensity is defined as _IS2. Further, the ratios R1 and R2 are defined as follows.
R1: Absorption derived from the amide group of the semi-aromatic polyamide measured by total internal reflection infrared absorption spectroscopy on the surface of the separation functional layer for the composite semipermeable membrane before immersion in the sulfuric acid aqueous solution in the measurement of Rb below. peak intensity (I _a) and the absorption peak intensity derived from the support film (I _S) and the ratio of (I _a / I _S)
R2: Derived from the amide group of semi-aromatic polyamide measured by total internal reflection infrared absorption spectroscopy on the surface of the separation functional layer after immersing the composite semipermeable membrane in a 1 mol / L sulfuric acid aqueous solution at 40 ° C. for 21 days. Ratio of absorption peak intensity (I _A2 ) to absorption peak intensity derived from the support membrane (I _S2 _{) (IA2} / _IS2 )
R2 / R1 is 0.40 or more, preferably 0.60 or more, more preferably 0.80 or more, and preferably 1.0 or less.

The peak intensity ratio R2 / R1 can be used as an index of the strength of the separation functional layer. It is the ratio of the absorption peak value to the porous support layer and the absorption peak value corresponding to the separation function layer. The closer the peak intensity ratio before and after acid immersion is to 1.0, the more the polyamide constituting the separation function layer is eluted. It shows that decomposition does not occur and the state before acid contact is maintained.

The peak intensity ratios R1 and R2 can be measured as follows. First, the membrane to be measured is sufficiently dried. Next, the surface of the membrane (that is, the surface of the separation function layer) is irradiated with infrared rays, and the reflected light is detected to obtain a spectrum. More specific measurement methods are described in Examples. The peak intensity ratios R1 and R2 described in this document are specifically calculated from the values measured by the method described in the examples.

The difference in contact angle with the surface of the separation functional layer before and after immersing the composite semipermeable membrane in a 1 mol / L sulfuric acid aqueous solution at 40 ° C. for 21 days is preferably 15 ° C. or less, more preferably 10 ° C. or less. .. The contact angle here refers to a static contact angle, and means a high degree of hydrophilicity on the surface of the separation functional layer.

As a result of diligent studies, the inventors have found that the smaller the difference in contact angle between the surfaces of the separation functional layer before and after being immersed in a sulfuric acid aqueous solution for a long period of time, the higher the acid resistance and alkali resistance.

When pure water is dropped on the surface of the separation functional layer, the formula (1) called "Young's formula" is established.

γ _S = γ _L cos θ + γ _SL (1)
Here, γ _S is the surface tension of the separation function layer, γ _L is the surface tension of pure water, and γ _SL is the interfacial tension between the separation function layer and pure water. The angle θ formed by the tangent of pure water and the surface of the separation function layer when this equation is satisfied is called the contact angle. The small difference in contact angle between the surfaces of the separation functional layer before and after being immersed in a sulfuric acid aqueous solution for a long period of time means that the change in hydrophilicity of the surface due to hydrolysis of polyamide or partial exposure of the support layer is small. Therefore, since decomposition and peeling of the separation functional layer are unlikely to occur, it is considered that a decrease in divalent selective removability due to contact with a strong acid can be suppressed.

The separation functional layer in the present invention contains an amide group derived from a polymer of a polyfunctional aliphatic amine and a polyfunctional aromatic acid halide, and an amino group and a carboxy group derived from an unreacted functional group. As a result of diligent studies by the present inventors, 7 represented by the following formula has an amide group ratio of 0.80 or more and 1.20 or less, so that in addition to high water permeability and selective separability, it is resistant to acids and alkalis. We have found that high durability can be obtained. The amide group ratio is more preferably 0.90 or more and 1.10 or less. If it is less than 0.80, the crosslinked structure of the polyamide is not sufficiently formed, so that the durability against acids and alkalis is low. On the contrary, if it is larger than 1.20, the durability against acids and alkalis is further increased, but the density is excessive. As the temperature increases, the water permeability and selective separability are greatly reduced.

(Amid group ratio) = (Amid group molar amount ratio) / {(Polyfunctional aliphatic amine molar amount ratio) + (Polyfunctional aromatic acid halide molar amount ratio)}
Here, the molar ratio of amide groups, the molar ratio of polyfunctional aliphatic amines, and the ratio of polyfunctional aromatic acid halides in the formula ^{can be obtained from the 13} C solid-state NMR measurement of the above-mentioned separation functional layer.

The abundance ratio of the polyfunctional aliphatic amine and the polyfunctional aromatic acid halide in the separation functional layer (polyfunctional aliphatic amine / polyfunctional aromatic acid halide) is preferably 1.25 or more in terms of molar ratio, which is more preferable. Is 1.3 or more, more preferably 1.35 or more. The abundance ratio is preferably 1.65 or less, more preferably 1.60 or less, and further preferably 1.55 or less in terms of molar ratio. When the abundance ratio is 1.25 or more and 1.65 or less, it is considered that the amounts of amino groups and carboxy groups in the polyamide are substantially equal, and the network structure of the polyamide is uniform. Therefore, it is considered that the pore size distribution is also controlled.

The abundance ratio of the polyfunctional aliphatic amine and the polyfunctional aromatic acid halide in the separation functional layer can ^{be determined by measuring 13} C-NMR of the separation functional layer peeled from the support film or by measuring the separation functional layer peeled from the support film at a high temperature. ^{By 1} H-NMR measurement using a sample hydrolyzed with a strong alkaline aqueous solution of the above, the components of the aliphatic polyfunctional amine and the polyfunctional aromatic acid halide are analyzed, and the components of the aliphatic polyfunctional amine are polymorphized. It can be obtained by dividing by the component of the functional aromatic acid halide.

As a method of controlling the abundance ratio of the polyfunctional aliphatic amine and the polyfunctional aromatic acid halide in the separation functional layer, the ratio of the polyfunctional aliphatic amine concentration and the polyfunctional aromatic acid halide concentration at the time of intercondensation is used. Method, method of changing the solvent that dissolves the polyfunctional acid halide, method of disturbing the intercondensation field with a surfactant, method of stopping the reaction during intercondensation, method of inhibiting the reaction during intercondensation. There are a method of adding an additive and a method of activating the reaction by applying heat from the outside at the time of intercondensation.

The composite translucent film of the present invention has a magnesium sulfate removal rate when permeated with a 2000 ppm magnesium sulfate aqueous solution at 25 ° C and pH 6.5 and a 2000 ppm magnesium chloride aqueous solution at 25 ° C and pH 6.5 at an operating pressure of 0.5 MPa. 97% or more, preferably 98% or more, more preferably 99% or more, and the difference between the magnesium sulfate removal rate and the magnesium chloride removal rate is 20% or less, preferably 15% or less, still more preferably 10% or less. Therefore, in addition to high selective separation performance, high acid resistance and alkalinity can be achieved.

(1-3) In addition, a protective layer containing a polymer component provided directly or via another layer is provided on a separation functional layer composed of a polyfunctional aliphatic amine and a polyfunctional aromatic acid halide. May be good. The protective layer can improve the divalent ion (particularly sulfate ion) removing performance of the composite semipermeable membrane and can improve the selective separability between the monovalent ion and the divalent ion.

The polymer component is not particularly limited as long as it is a polymer that does not dissolve the separation functional layer and the support film and does not elute during the water treatment operation. For example, polyvinyl alcohol, polyvinylpyrrolid, polyvinylpyrrolidone, hydroxypropyl cellulose, polyethylene glycol, chitosan. , And a saponified polyethylene-vinyl acetate copolymer and the like.
Of these, polyvinyl alcohol is preferable from the viewpoint of economy, availability, and handling. In particular, the saponification degree of polyvinyl alcohol is preferably 85% or more, and more preferably 90% or more. When the saponification degree is 85% or more, it is soluble in hot water (about 80 ° C) due to the influence of hydrogen bonds between molecular chains, but becomes water-insoluble near room temperature (about 25 ° C), and water treatment operation It is possible to prevent the elution of polyvinyl alcohol at the time. 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 is lowered, and the elution of polyvinyl alcohol during the water treatment operation can be prevented. On the other hand, when the degree of polymerization is 50,000 or less, the viscosity of the polyvinyl alcohol aqueous solution can be preferably maintained, and the coating thickness of the polyvinyl alcohol aqueous solution can be reduced. As a result, both the above-mentioned function as a protective layer and the water permeability of the film can be achieved.

Further, by cross-linking the polymer in the protective layer to the separation functional layer, the removability of divalent ions can be enhanced as compared with the non-cross-linked layer, and the elution of the polymer in the protective layer during water treatment operation is highly advanced. Can be prevented. As the polymer to be crosslinked, a hydrophilic polymer is preferable from the viewpoint of ease of handling and suppression of deterioration of water permeability, and polyvinyl alcohol is particularly preferable, and polyvinyl alcohol having 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 cross-linking is enhanced when the degree of saponification is 85% or more.
As a method for cross-linking polyvinyl alcohol, it is preferable to use an organic cross-linking agent such as polyvalent aldehyde, epoxy compound, polyvalent carboxylic acid, organic titanium compound, organic zirconium compound, and inorganic cross-linking agent such as boron compound, which is economical. Polyvalent aldehyde is more preferable from the viewpoint of easy availability and handling, 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 elute during the water treatment operation, and the film performance tends to deteriorate. The thickness of the protective layer is usually 5 μm or less, preferably 3 μm or less, and more preferably 2 μm or less. On the other hand, if the protective layer is too thick, the permeation flux tends to decrease.

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

(2-1) Support film forming step The support film forming step can be rephrased as the forming of the porous support layer. This step includes a step of applying a polymer solution to a base material and a step of immersing the base material to which the solution is applied in a coagulation bath to coagulate the polymer.

In the step of applying the polymer solution to the base material, the polymer solution is prepared by dissolving the polymer, which is a component of the porous support layer, in a good solvent of the polymer.

When polysulfone is used as the polymer, the temperature of the polymer solution when the polymer solution is applied is preferably in the range of 10 ° C to 60 ° C. When 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, a porous support layer firmly bonded to the base material can be obtained by the anchor effect. The preferable temperature range of the polymer solution can be appropriately adjusted depending on the type of polymer used, the desired solution viscosity, and the like.

As the solvent of the polymer solution, N, N-dimethylformamide (DMF) is preferable.

The time from applying the polymer solution on the substrate to immersing it in the coagulation bath is preferably in the range of 0.1 to 5 seconds. If the time until immersion 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. The preferable range of the time until immersion in the coagulation bath can be appropriately adjusted depending on the type of the polymer solution to be used, the desired solution viscosity, and the like.

Water is usually used as the coagulation bath, but it may be any one that does not dissolve the polymer that is a component of the porous support layer. The temperature of the coagulation bath is preferably −20 ° C. to 100 ° C. The temperature of the coagulation bath is more preferably 10 ° C to 50 ° C. When the temperature of the coagulation bath is 100 ° C. or lower, 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, when the temperature is −20 ° C. or higher, the solidification rate can be maintained, so that the film forming property can be improved.

Next, the support film thus obtained may be washed with hot water in order to remove the solvent remaining in the film. The temperature of the hot water at this time is preferably 40 ° C. to 100 ° C., more preferably 60 ° C. to 95 ° C. When the cleaning temperature is not more than the upper limit, the shrinkage of the support membrane does not become too large, and the deterioration of the water permeability can be suppressed. Further, if the cleaning temperature is 40 ° C. or higher, a high cleaning effect can be obtained.

(2-2) Separation Function Layer Formation Step Next, a separation function layer forming step constituting the composite semipermeable membrane will be described. In the step of forming the separation functional layer, an aqueous solution containing a polyfunctional aliphatic amine compound and an organic solvent solution containing a polyfunctional aromatic acid halide are used to generate a polyamide by interfacial polycondensation on the surface of a support film. ..

Specifically, the step of forming the separation functional layer is
(A) A step of impregnating the support membrane with an aqueous solution of a polyfunctional aliphatic amine,
(B) After the (a), there is a step of contacting the support membrane with a polyfunctional acid halide-containing solution at 10 to 38 ° C.

In order to form a fold-shaped polyamide thin film and obtain a film having both excellent divalent ion selective removal property, acid resistance, and alkali resistance, as described above, a polyfunctional aliphatic amine to an organic solvent during interfacial polymerization is required. It is important to optimize the distribution and diffusion of For this optimization, it is preferable to bring the support membrane impregnated with the polyfunctional aliphatic amine into contact with the organic solvent solution containing the polyfunctional acid halide at 10 ° C. to 38 ° C. When this technique is carried out, a separation functional layer is formed in a pleated shape, and a film having both selective removal of divalent ions, acid resistance, and alkali resistance can be obtained.

Further, in the step (a), the film performance is further improved by applying a polyfunctional aliphatic amine aqueous solution having a temperature of 5 to 15 ° C. higher than the temperature of the support film surface to the support film surface.

The solvent in the polyfunctional aromatic acid halide-containing solution is an organic solvent. The organic solvent is immiscible with water, does not destroy the support film, and does not inhibit the reaction of forming the crosslinked polyamide, and has a solubility parameter (SP value) of 15.2 (MPa). ^Use an organic solvent having a log P of 1/2 or more and a log P of 3.2 or more. When the SP value is 15.2 (MPa) ^1/2 or more and the logP is 3.2 or more, the partition and diffusion of the polyfunctional aliphatic amine during interfacial polycondensation are optimized, and the amount of functional groups can be increased. Can be increased. As a representative example, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, heptadecane, hexadecane and the like, cyclooctane, ethylcyclohexane, 1-octene, 1-decene and the like alone or a mixture thereof are preferably used.

The aqueous solution containing the polyfunctional aliphatic amine may contain a surfactant. For example, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium dodecyldiphenyl ether disulfonate, styrene bis (sodium naphthalene sulfonate), sodium polyoxyethylene alkyl ether sulfate and the like can be mentioned. Since the surface of the porous support layer can be uniformly coated with an aqueous solution of a piperazine compound by containing a surfactant, the separation functional layer is uniformly formed, the effect of stabilizing the membrane performance, and the porosity with the separation functional layer. The effect of enhancing the adhesiveness with the sex support layer can be obtained.

The aqueous solution containing the polyfunctional aliphatic amine may contain alcohol. For example, ethanol, 1-propanol, 2-propanol, butanol and the like can be mentioned. By containing alcohol, the same effect as that of the above-mentioned surfactant can be obtained.

The aqueous solution containing the polyfunctional aliphatic amine may contain an alkaline compound. For example, sodium hydroxide, trisodium phosphate, triethylamine and the like can be mentioned. By containing the alkaline compound, hydrogen halide generated in the intercondensation reaction can be removed, the decrease in the reactivity of the piperazine compound can be suppressed, the polyamide reaction can be promoted, and in addition to the selective separability, Durability against acids and alkalis can be improved.

The aqueous solution containing a polyfunctional aliphatic amine and the organic solvent solution containing a polyfunctional acid halide each contain compounds such as an acylation catalyst, a polar solvent, an acid trapping agent, and an antioxidant, if necessary. May be.

In order to carry out interfacial polycondensation on the porous support layer, first, the surface of the porous support layer is coated with an aqueous solution containing a polyfunctional aliphatic amine. As a method of coating the surface of the porous support layer with the aqueous solution containing the polyfunctional aliphatic amine, the surface of the porous support layer may be uniformly and continuously coated with this aqueous solution. For example, the aqueous solution is porous. The method may be carried out by a method of applying to the surface of the sex support layer, a method of immersing the support film in an aqueous solution, or the like, but in the present invention, a method of applying the aqueous solution to the surface of the porous support layer is more preferable. By applying an aqueous solution containing a polyfunctional aliphatic amine to the surface of the support layer, the amount of water contained in the support layer is reduced and the heat capacity is reduced as compared with the dipping method. In the interfacial polymerization step after coating, the cross-linking reaction of the polyamide proceeds efficiently, and excellent acid resistance and alkali resistance can be obtained.

Further, it is preferable to apply a polyfunctional aliphatic amine-containing aqueous solution having a temperature of 5 to 15 ° C. higher than the film surface temperature of the support film on the surface of the support film. By raising the temperature of the polyfunctional aliphatic amine-containing aqueous solution higher than the film surface temperature of the support film, the amount of amine retained on the support film surface increases, and the amine diffuses when the later polyfunctional aromatic acid halide is applied. The sex improves. As a result, a highly uniform pleated structure and pore structure are formed, and a separation membrane having both excellent acid resistance, alkali resistance and divalent ion selective removal property can be obtained. When a polyfunctional aliphatic amine-containing aqueous solution having a temperature of 16 ° C. or higher higher than the membrane surface temperature of the support film is used, diffusion is inhibited by improving the reaction rate, so that the fold structure and pore structure become non-uniform, and acid resistance is increased. Alkali resistance is reduced.

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

The concentration of the polyfunctional aliphatic amine is preferably 0.5% by weight or more and 8.0% by weight or less, more preferably 1.0% by weight or more and 6.0% by weight or less, and further preferably. Is 2.0% by weight or more and 4.0% by weight or less. If the concentration is lower than 0.5% by weight, a uniform separation functional layer is not formed, and a film having insufficient selective separability and durability against acids and alkalis can be obtained. Further, when the concentration is higher than 10.0% by weight, the thickness of the separation functional layer becomes too thick, and the water permeability is significantly deteriorated.

Then, the organic solvent solution containing the above-mentioned polyfunctional acid halide is applied to the porous support layer containing the aqueous solution containing the polyfunctional aliphatic amine. The coating temperature needs to be in the range of 10 ° C. to 38 ° C. The contact temperature of the organic solvent solution is more preferably in the temperature range of 20 ° C. to 35 ° C. When the coating temperature is 10 ° C. or lower, the diffusion rate of amine in the organic solvent is not sufficient, and it becomes difficult to form a fold structure and a polyamide having a pore size required for divalent ion selective removal. Further, if the temperature at the time of coating exceeds 39 ° C., diffusion is hindered by improving the reaction rate, so that the pleated structure and the pore structure become non-uniform, and there is a problem that acid resistance and alkali resistance are lowered.

When trimesic acid chloride is contained as a polyfunctional aromatic acid halide, the concentration of trimesic acid chloride in the organic solvent solution is preferably about 0.05% by weight or more and 0.70% by weight or less, more preferably 0. It is .08% by weight or more and 0.3% by weight or less. Within this range, sufficient water permeability, selective separation performance, and durability against acids and alkalis can be obtained. When other trifunctional acid chlorides and difunctional acid chlorides are used, they are used after adjusting the molar concentration of the acid chlorides to be about the same according to the molecular weight ratio of the above-mentioned trimesic acid chlorides.

By contacting the polyfunctional aliphatic amine and the polyfunctional acid halide in this way, both are interfacially polymerized. The interfacial polymerization is preferably carried out under a temperature condition of 50 ° C. or higher, more preferably carried out under a temperature condition of 80 ° C. or higher, and preferably carried out at a melting point or higher of the polyfunctional aliphatic amine. Further, the interfacial polymerization is preferably carried out under a temperature condition of 120 ° C. or lower. By performing the interfacial polymerization at 50 ° C. or higher, it is possible to suppress a decrease in the motility of the monomer or oligomer due to the increase in bulkiness of the polyamide in the interfacial polymerization reaction, and the amide group ratio becomes 0.80 or higher. By performing interfacial polymerization above the melting point of the polyfunctional aliphatic amine, the polyfunctional aliphatic amine can maintain high motility in the reaction system, an efficient cross-linking reaction proceeds, and excellent acid resistance and alkali resistance are obtained. Both valent ion selective removal properties can be achieved. Further, by performing the interfacial polymerization at 120 ° C. or lower, overdrying of the separation functional layer and the porous support layer can be prevented, and practical water permeability and divalent ion selective removal property can be ensured.

The time for carrying out the interfacial polymerization is preferably 0.1 seconds or more and 3 minutes or less, and more preferably 0.1 seconds or more and 1 minute or less.

Next, it is preferable to remove the organic solvent solution after the reaction by a draining step. The organic solvent can be removed by, for example, a method of grasping the membrane in the vertical direction and naturally flowing down the excess organic solvent to remove the organic solvent, a method of drying the organic solvent by blowing wind with a blower, or a mixed fluid of water and air. A method of removing excess organic solvent can be used. In particular, removal with a mixed fluid of water and air is preferable. When a mixed fluid of water and air is used, the separation functional layer contains water, which causes swelling and high water permeability. In the case of natural flow, the time for gripping in the vertical direction is preferably between 1 minute and 5 minutes, and more preferably between 1 minute and 3 minutes. When the gripping time is 1 minute or more, it is easy to obtain a separation functional layer having a desired function, and when it is 3 minutes or less, the occurrence of defects due to overdrying of the organic solvent can be suppressed, so that the deterioration of performance can be suppressed. Can be done.

The composite semipermeable membrane obtained by the above method is further subjected to a step of washing with hot water in the range of 25 ° C. to 90 ° C. for 1 minute to 60 minutes to prevent the solute of the composite semipermeable membrane. And water permeability can be further improved.

3. 3. Utilization of Composite Semipermeable Membrane The composite semipermeable membrane of the present invention can be suitably used as a nanofiltration membrane for separating monovalent ions and divalent ions. This composite translucent film can be used to remove acids and alkalis from industrial applications such as salt removal and mineral adjustment from brackish water and seawater, salt removal and mineral adjustment in the food field, plating, and refining, as well as acid and alkali solutions. It is possible to recover the metal inside.

The composite semipermeable membrane of the present invention has a tubular shape in which a large number of holes are bored together with a raw water flow path material such as a plastic net, a permeation water flow path material such as a tricot, and a film for increasing pressure resistance as needed. It is wound around the water collecting pipe of the above and is suitably used as a spiral type composite semipermeable membrane element. Further, the elements can be connected in series or in parallel to form a composite semipermeable membrane module housed in a pressure vessel.

Further, the above-mentioned 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 form 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 the membrane, and water suitable for the purpose can be obtained.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.
<Measurement of specific surface area of membrane>
The separation membrane sample was embedded in PVA resin, _{stained with OsO 4} to facilitate cross-sectional observation, and cut with an ultramicrotome to prepare 10 ultrathin sections. A cross-sectional photograph of the obtained ultrathin section was taken using a transmission electron microscope. The acceleration voltage at the time of observation was 100 kV, and the observation magnification was 10,000 times. The 10 cross-sectional photographs obtained were analyzed with the image analysis software ImageJ, the length of the separation functional layer and the length of the porous support layer were calculated, and then the average specific surface area of the separation functional layer was calculated from the following formula. I asked.

Specific surface area of separation function layer = (length of separation function layer) ² / (length of porous support layer) ²
<Presence or absence of fold structure>
In the cross-sectional photograph taken by the transmission electron microscope at the time of measuring the specific surface area, "the fold height H of the separation functional layer" and "the thin film thickness T of the separation functional layer" were measured, and "H / T" was calculated. If the H / T is 1.2 or more, the separation function layer has a hollow pleated structure, and if it is less than 1.2, the separation function layer does not have a hollow fold structure. ..

The measurement of the thickness T and the height H will be described with reference to FIG. The composite semipermeable membrane was cut into 3 cm × 3 cm squares and washed with distilled water at 25 ° C. for 24 hours. The washed composite semipermeable membrane was embedded with an epoxy resin and then stained with osmium tetroxide to prepare a measurement sample. In the obtained sample, an image of the cross section of the thin film 41 of the separation function layer 4 was obtained with a scanning transmission electron microscope (manufactured by Hitachi, Ltd .; HD2700) at a magnification of 1 million times.

Ten convex portions 42 were randomly selected, and the shortest distance between the outer surface and the inner surface of the convex portions 42 was measured at five locations for each convex portion 42. The average value of the 50 values thus obtained was calculated and used as the fold thickness T.

In addition, for 50 randomly selected convex portions 42, the maximum distance from the outer surface of each convex portion 42 to the surface of the porous support layer (distance from the apex of the fold to the surface of the support film) was measured. The average value of the obtained 50 values was taken as the average value of the fold height H.

<X-ray photoelectron spectroscopy>
In the XPS measurement, the composite semipermeable membrane is immersed in a hydrochloric acid aqueous solution at 25 ° C. and pH 2 for 30 minutes, then immersed in pure water at 90 ° C. for 30 minutes to wash the membrane surface, and then dried at room temperature and vacuum. It was carried out about the thing. The composition of the elements detected in the range of 0 eV or more and 1400 eV or less was analyzed by wide scan analysis by XPS measurement. Using the X-ray photoelectron spectroscopy measuring device SSX-100 manufactured by SSI of the United States, aluminum Kα1 line and Kα2 line (1486.6 eV) are measured as excitation X-rays, X-ray output is 10 kV, 20 mV, and photoelectron escape angle is 90 °. Then, the measurement at different film positions was repeated 10 times, and the average value was taken as the measured value.

<Total internal reflection infrared spectroscopy>
For ATR-IR measurement, the Avatar 360FT-IR measuring machine manufactured by Nicolet Co., Ltd. is used, and the single reflection type horizontal ATR measuring device (OMNI-Sampler) manufactured by Nicolet Co., Ltd. and the ATR crystal made of germanium are used as accessories for total reflection measurement. Then, the spectrum was obtained by irradiating the surface of the porous body with infrared rays. As the measurement conditions, the resolution ^{was set to 2 cm -1} , the number of scans was set to 256, and the measurement was performed at any 10 points. The thus obtained spectrum, after the automatic baseline ^correction, 900 cm ^-1, 1800 cm -1, and corrected as zero point three points 3800 cm ^-1. From the spectra thus obtained, the ^{peak having the maximum value among 1600 cm -1} and 1650 cm ^-1 was determined as the peak derived from the amide group, and the peak 1242 cm ^-1 was determined as the peak derived from the support film, and the peak intensity ratio I seeking _a / I _S, to calculate the average value of an arbitrary 10-point measurement. Then, the composite semipermeable membrane to be measured is immersed in a 1 mol / L sulfuric acid aqueous solution at 40 ° C. for 21 days, washed with a large amount of pure water, sufficiently dried, and again _{after the} peak intensity ratio IA / under the above conditions. seek _post I S, and calculates the ratio R2 / R1 of the peak intensity ratio to the peak intensity ratio before acid immersion (I _a / I _S).

<Amide group ratio per unit area>
The base material was physically peeled off from the composite semipermeable membrane 5 m ² , and the porous support layer and the separating functional layer were recovered. The recovered porous support layer and separation functional layer were washed with warm water at 95 ° C. for 2 hours. After drying by allowing to stand at 25 ° C. for 24 hours, it was added little by little to a beaker containing dichloromethane and stirred to dissolve the polymer constituting the porous support layer. The insoluble matter in the beaker was collected with filter paper. This insoluble matter was placed in a beaker containing dichloromethane and stirred to recover the insoluble matter in the beaker. This process was repeated until the elution of the polymer forming the porous support layer in the dichloromethane solution could not be detected. The recovered separation functional layer was dried in a vacuum dryer to remove residual dichloromethane.

The obtained separation functional layer was made into a powder sample by freeze-grinding, sealed in a sample tube used for ^{solid-state NMR measurement, and 13} C solid-state NMR measurement was performed by CP / MAS method and DD / MAS method. ^{For 13} C solid-state NMR measurement, for example, CMX-300 manufactured by Chemagnetics can be used. An example of measurement conditions is shown below.

Reference substance: Polydimethylsiloxane (internal standard: 1.56 ppm)
Sample rotation speed: 10.5 kHz
Pulse repetition time: 100s
From the obtained spectrum, peak division was performed for each peak derived from the carbon atom to which each functional group was bonded, and the functional group amount ratio was quantified from the area of the divided peak. Using the quantified value, the amide group ratio was calculated according to the following formula.

(Amid group ratio) = (Amid group molar amount ratio) / {(Aliphatic polyfunctional amine molar amount ratio) + (Polyfunctional acid halide molar amount ratio)}
<Abundance ratio of polyfunctional aliphatic amines and polyfunctional acid chlorides constituting the separation functional layer>
The lyophilized product of the separation functional layer prepared for the above-mentioned measurement of amide group ratio was hydrolyzed by heating with a strong alkaline heavy aqueous solution, and the hydrolyzed heavy aqueous solution was filtered and ^{measured by 1} H-NMR. The data obtained by the measurement was analyzed, and the abundance ratio of the polyfunctional aliphatic amine and the polyfunctional acid chloride was calculated from the area value of the peak.

<sulfonyl ₄ removal rate>
Composite semi-permeable membrane, a temperature 25 ° C., pH 6.5, were subjected to membrane filtration process by supplying the salt water adjusted to MgSO ₄ concentration 2000 mg / L at the operating pressure 0.5 MPa. The electric conductivity of the feed water and permeate water measured by Toa Electronics Ltd. electrical conductivity meter to obtain respective practical salinity, i.e. MgSO ₄ concentration. Based on the silyl ₄ concentration thus obtained and the following formula, the transferase ₄ removal rate was calculated.

MgSO ₄ removal rate (%) = {1- / ( MgSO 4 concentration in the feed solution) (MgSO ₄ concentration in the permeate)} × 100
<MgCl ₂ removal rate>
Evaluation water adjusted to a temperature of 25 ° C., a pH of 6.5, and a MgCl ₂ concentration of 2000 ppm was supplied to the composite semipermeable membrane at an operating pressure of 0.5 MPa to perform a membrane filtration treatment. 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 salt content, that is, the MgCl ₂ concentration. _{The MgCl 2} removal rate was calculated based on the MgCl ₂ concentration thus obtained and the following formula.

MgCl ₂ removal rate (%) = 100 × {1- (MgCl 2 concentration / MgCl ₂ concentration in the feed water of the transmitted water)}
<NaCl removal rate>
Evaluation water adjusted to a temperature of 25 ° C., a pH of 6.5, and a NaCl concentration of 500 ppm was supplied to the composite semipermeable membrane at an operating pressure of 0.5 MPa to perform membrane filtration treatment. 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 salt content, that is, the NaCl concentration. The NaCl removal rate was calculated based on the NaCl concentration thus obtained and the following formula.

NaCl removal rate (%) = 100 × {1- (NaCl concentration in permeated water / NaCl concentration in feed water)}
<Monovalent ion / divalent ion selectivity>
The monovalent ion / divalent ion selectivity was calculated based on the calculated sulfonyl _{4 removal rate, NaCl removal rate and the following formula.}
Monovalent ion / divalent ion selectivity = (100-NaCl removal rate) / (100- Then ₄ removal rate)
<Membrane permeation flux>
In the test of the previous section, the _{amount of water permeated through the membrane of the supplied water (sulfonyl 4} aqueous solution) was measured, and the value converted to the amount of water permeated per day (cubic meter) per square meter of the membrane surface was converted into the membrane permeation flux (m ³ / m ² / Day).

<Acid resistance test>
After immersing the composite semipermeable membrane in a monosulfuric acid aqueous solution at 40 ° C. for 10 days, the _{removal rate of sulfonyl 4} was measured, and the removal performance before and after the immersion was compared.

<Alkali resistance test>
After immersing the composite semipermeable membrane in a 1 M sodium hydroxide aqueous solution at 40 ° C. for 10 days, the _{removal rate of sulfonyl 4} was measured, and the removal performance before and after the immersion was compared.

(Example 1)
<Preparation of composite semipermeable membrane>
An 18 wt% dimethylformamide (DMF) solution of polysulfone was cast on a non-woven fabric (breathability 1.0 cc / cm ^{2 / sec) made of polyester fibers manufactured by the papermaking method at room temperature (25 ° C.) at a coating thickness of 180 μm.} Immediately after that, the porous support layer was formed on the base material by immersing it in pure water for 5 minutes to prepare a support film.

Next, the film surface temperature of the support film was adjusted to 26 ° C while removing excess water by blowing air adjusted to 26 ° C. After immersing in an aqueous solution at 30 ° C. in which 2.0% by weight of 2-normal butyl piperazine, 250 ppm by weight of sodium dodecyldiphenyl ether disulfonate, and 1.0% by weight of trisodium phosphate are dissolved for 15 seconds, nitrogen is blown from an air nozzle to make an excess aqueous solution. Was removed to form a coating layer of an aqueous amine solution on the support film. Further, an n-decane solution at 38 ° C. containing 0.2% by weight of trimesic acid chloride (TMC) was uniformly applied to the entire surface of the porous support layer, and then allowed to stand at 50 ° C. for 1 minute, and two fluids (2 fluids) were applied to the film surface. Pure water and air) were sprayed to remove the surface solution. Then, it was washed with pure water of 80 degreeC, and a composite semipermeable membrane was obtained.

(Example 2)
In Example 1, the composite semipermeable membrane was changed in the same manner as in Example 1 except that the polyfunctional aliphatic amine was changed to cis-2.3-dimethylpiperazine and the solution temperature of the polyfunctional acid chloride was changed to 30 ° C. Was produced.

(Example 3)
In Example 2, the temperature at which air was blown onto the support membrane and the surface temperature of the support membrane were adjusted to 25 ° C., and the polyfunctional aliphatic amine was changed to trans-2,5-dimethylpiperazine. A composite semipermeable membrane was prepared in the same manner as in the above.

(Example 4)
In Example 3, the method of forming the coating layer of the amine aqueous solution on the support film was changed to the method of applying the amine aqueous solution on the support film surface and allowing it to stand for 15 seconds, and a few polyfunctional aliphatic amines were added. A composite semipermeable membrane was prepared in the same manner as in Example 3 except that the mixture was changed to 5,6-tetramethylpiperazine.

(Example 5)
In Example 4, the composite semi-compounded by the same method as in Example 4 except that the atmospheric temperature after applying the polyfunctional aliphatic amine trans-2,5-dinormalpropylpiperazine and the polyfunctional acid chloride solution was changed to 80 ° C. A permeable membrane was prepared.

(Example 6)
In Example 5, the polyfunctional aliphatic amine was changed to trans-2,5-bis (difluoromethyl) piperazine, the amine aqueous solution temperature was changed to 40 ° C., and the TMC concentration was changed from 0.2% by weight to 0.1% by weight. A composite semipermeable membrane was prepared in the same manner as in Example 5 except that it was changed to%.

(Example 7)
In Example 5, a composite semipermeable membrane was prepared in the same manner as in Example 5 except that the polyfunctional aliphatic amine was changed to trans-2,5-bis (dimethylthio) piperazine and the amine aqueous solution temperature was changed to 41 ° C. ..

(Example 8)
In Example 5, a composite semipermeable membrane was prepared in the same manner as in Example 5 except that the polyfunctional aliphatic amine was changed to trans-2,5-dimethylpiperazine and the amine aqueous solution temperature was changed to 35 ° C.

(Example 9)
In Example 8, the polyfunctional aliphatic amine was compounded in the same manner as in Example 8 except that the atmospheric temperature after applying the polyfunctional

aliphatic amine

2,3,5,6-tetramethylpiperazine and the polyfunctional acid chloride solution was changed to 120 ° C. A semipermeable membrane was prepared.

(Example 10)
In Example 9, the polyfunctional aliphatic amine was changed to trans-2,5-dinormalbutylpiperazine, the amine concentration was changed to 4.0% by weight, and the polyfunctional acid chloride was changed to 1,3,5-benzenetrisulfonic acid chloride. A composite semipermeable membrane was prepared in the same manner as in Example 9 except for the above.

(Example 11)
In Example 9, a composite semipermeable membrane was prepared in the same manner as in Example 9 except that the polyfunctional aliphatic amine was changed to trans-2,5-diethylpiperazine.

(Example 12)
In Example 9, a composite semipermeable membrane was prepared in the same manner as in Example 9 except that the polyfunctional aliphatic amine was changed to trans-2,5-dimethylpiperazine.

(Example 13)
In Example 9, a composite semipermeable membrane was prepared in the same manner as in Example 9 except that the polyfunctional aliphatic amine was changed to trans-2,5-bis (difluoromethyl) piperazine.

(Comparative Example 1)
In Example 3, a composite semipermeable membrane was prepared in the same manner as in Example 3 except that the polyfunctional aliphatic amine was piperazine and the amine aqueous solution temperature was changed to 25 ° C.

(Comparative Example 2)
In Comparative Example 1, a composite semipermeable membrane was prepared by the same method as in Comparative Example 1 except that the concentration of the polyfunctional aliphatic amine was changed to 8.0% by weight and the atmospheric temperature after applying the polyfunctional acid chloride solution was changed to 120 ° C. did.

(Comparative Example 3)
The membrane prepared in Comparative Example 2 was set in a cell for evaluation of a flat membrane, and an aqueous solution containing pH 7.5 and sodium hypochlorite 20 ppm was applied to the supply side and the permeation side of the composite semipermeable membrane with a differential pressure of 1.5 MPa. It was given and contacted for 30 minutes to prepare a composite semipermeable membrane in which the polyamide of the separation functional layer was chlorinated.

(Comparative Example 4)
In Comparative Example 1, the polyfunctional acid chloride was combined in the same manner as in Comparative Example 1 except that the atmospheric temperature after applying the 1,3,5-benzenetrisulfonic acid chloride and the polyfunctional acid chloride solution was changed to 120 ° C. A semipermeable membrane was prepared.

(Comparative Example 5)
In Comparative Example 1, a composite semipermeable membrane was prepared in the same manner as in Comparative Example 1 except that the polyfunctional aliphatic amine was changed to 2-methylpiperazine.

(Comparative Example 6)
In Comparative Example 5, a composite semipermeable membrane was prepared in the same manner as in Comparative Example 5 except that the polyfunctional aliphatic amine concentration was 6.0% by weight and the atmospheric temperature after applying the polyfunctional acid chloride solution was changed to 120 ° C. did.

(Comparative Example 7)
In Comparative Example 1, the aliphatic amine piperazine and the aromatic amine m-phenylenediamine are adjusted in a molar ratio of 9: 1 so that the polyfunctional amine concentration is 6.0% by weight. A composite semipermeable membrane was prepared in the same manner as in Comparative Example 1 except that it was changed.

(Comparative Example 8)
In Example 3, a composite semipermeable membrane was prepared in the same manner as in Example 3 except that the solution temperature of the polyfunctional aliphatic amine was 2-normal butylpiperazine and the polyfunctional acid chloride was changed to 10 ° C.

(Comparative Example 9)
In Comparative Example 8, the method of forming the coating layer of the amine aqueous solution on the support film was changed to the method of applying the amine aqueous solution on the support film surface and allowing it to stand for 15 seconds, and the solution temperature of the polyfunctional acid chloride was changed to 40. A composite semipermeable membrane was prepared in the same manner as in Example 3 except that the temperature was changed to ° C.

As shown in the examples, the specific surface area of the surface of the separation functional layer containing a semi-aromatic cross-linked polyamide, which is a condensate of a polyfunctional aliphatic amine and a polyfunctional aromatic acid halide, as a main component is 1.2 or more. A composite semipermeable membrane having a C / (N + O) of 2.3 or more and 4.0 or less of 5.0 or less has high acid resistance and alkalinity in addition to high monovalent ion / divalent ion selective separation performance. ..

Claims

A composite semipermeable membrane having a support membrane and a separation functional layer containing a semi-aromatic crosslinked polyamide formed on the support membrane, which is a condensate of a polyfunctional aliphatic amine and a polyfunctional aromatic acid halide. And
The specific surface area of the surface of the separation functional layer is 1.2 or more and 5.0 or less.
Composite semipermeable membrane in which the ratio C / (N + O) of the sum of the number of nitrogen atoms and the number of oxygen atoms to the number of carbon atoms measured by X-ray photoelectron spectroscopy on the surface of the separation functional layer is 2.3 or more and 4.0 or less. film.
The composite semipermeable membrane according to claim 1, wherein the separating functional layer has a fold-shaped thin film having a (fold height / thickness) of 1.2 or more.
The composite separation functional layer side surface of the semipermeable membrane, as measured by total reflection infrared absorption spectrum method, the absorption peak derived from an a support film the absorption peak intensity derived from the amide group of semi-aromatic polyamide (I A) the composite semipermeable membrane according to claim 1 or 2 intensity (I S) and the ratio of (I a / I S) is 0.15 to 0.50.
Ra / Rb is 0.40 or more and 1.0 or less.
The composite semipermeable membrane according to any one of claims 1 to 3.
R1: The composite semipermeable membrane before immersion in the sulfuric acid aqueous solution in the measurement of Rb below is derived from the amide group of the semi-aromatic polyamide measured by the total internal reflection infrared absorption spectroscopy on the surface on the separation function layer side. absorption peak intensity (I a) and the absorption peak intensity derived from the support film (I S) and the ratio of (I a / I S)
R2: An amide group of a semi-aromatic polyamide measured by total internal reflection infrared absorption spectroscopy on the surface of the separation function layer side after immersing the composite semipermeable membrane in a 1 mol / L sulfuric acid aqueous solution at 40 ° C. for 21 days. from absorption peak intensity (I A2) and the absorption peak intensity derived from the support film the ratio between (I S2) (I A2 / I S2)
The composite semipermeable membrane according to any one of claims 1 to 4, wherein the difference in contact angle before and after immersing the composite semipermeable membrane in a 1 mol / L sulfuric acid aqueous solution at 40 ° C. for 21 days is 15 ° or less.
Among the polyfunctional aliphatic amine components constituting the separation functional layer, 80 mol% or more of a piperazine derivative having a melting point of 100 ° C. or higher is contained, and the piperazine derivative contains two or more carbons of the piperazine ring as an alkyl group or a fluoroalkyl group. , The composite translucent film according to any one of claims 1 to 5, which is a piperazine substituted with any of the thioether groups.
The molar ratio (amide group ratio) of the total amount of the polyfunctional aliphatic amine and the polyfunctional aromatic acid halide to the amount of the amide group (mol) in the semi-aromatic cross-linked polyamide is 0. The composite translucent film according to any one of claims 1 to 6, which is 80 or more and 1.20 or less.
Amide group ratio (molar ratio) = amide group amount / (polyfunctional aliphatic amine amount + polyfunctional aromatic acid halide amount)
The composite semipermeable membrane according to any one of claims 1 to 7, wherein the abundance ratio (molar ratio) of the polyfunctional aliphatic amine and the polyfunctional aromatic acid halide in the semi-aromatic polyamide is as follows. film.
1.25 ≤ number of moles of polyfunctional aliphatic amine / number of moles of polyfunctional acid aromatic halide ≤ 1.65
The composite semipermeable membrane according to any one of claims 1 to 8, wherein the polyfunctional acid halide is an aromatic polyfunctional carboxylic acid halide or an aromatic polyfunctional sulfonic acid halide.
The following formulas show the magnesium sulfate removal rate and magnesium chloride removal rate when a 2000 ppm magnesium sulfate aqueous solution at 25 ° C and pH 6.5 and a 2000 ppm magnesium chloride aqueous solution at 25 ° C and pH 6.5 are permeated at an operating pressure of 0.5 MPa, respectively. ) And (II) at the same time. The composite translucent film according to any one of claims 1 to 9.
Magnesium sulfate removal rate ≧ 97% ・・・ (I)
Magnesium Sulfate Removal Rate-Magnesium Chloride Removal Rate ≤ 20% ... (II)
A composite semipermeable membrane having a support membrane and a separation functional layer containing a semi-aromatic crosslinked polyamide formed on the support membrane, which is a condensate of a polyfunctional aliphatic amine and a polyfunctional aromatic acid halide. It is a manufacturing method of
It has a step of forming a separation functional layer on the support membrane by interfacial polycondensation of a polyfunctional aliphatic amine aqueous solution and a polyfunctional acid halide-containing solution.
The above process
(A) A step of impregnating the support membrane with an aqueous solution of a polyfunctional aliphatic amine,
(B) A method for producing a composite semipermeable membrane, which comprises a step of contacting the support membrane with a polyfunctional acid halide-containing solution at 10 to 38 ° C.
The method for producing a composite semipermeable membrane according to claim 11, wherein step (a) is a step of applying a polyfunctional aliphatic amine aqueous solution having a temperature higher than the temperature of the support membrane surface by 5 to 15 ° C. on the support membrane surface.