JP2001038175A - Composite semipermeable membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide composite semipermeable membrane which is produced by coating one surface of polysulfone-based semipermeable membrane with a polyamide-based polymer thin film and is excellent in permeation performance, separation performance and in particular performance with respect to the removal of organic matter. SOLUTION: This composite semipermeable membrane consists of polysulfone- based semipermeable membrane and a polyamide-based polymer thin coating film formed on one surface of the polysulfone-based semipermeable membrane, wherein in a surface infrared absorption spectrum of the surface on the polyamide coating film side of the composite membrane, the ratio T (Aa/As) of the absorption intensity (Aa) of an absorption peak being at 1,600 to 1,700 cm-1, due to C=O of the polyamide, to the absorption intensity (As) of an absorption peak being at about 1,586 cm-1, due to the polysulfone, is 0.05 to 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a composite semipermeable membrane useful as a reverse osmosis membrane or a nanofiltration membrane. More specifically, the present invention relates to a composite semipermeable membrane obtained by forming a thin film polymer having selective permeability on one surface of a porous membrane. The composite semipermeable membrane thus obtained enables desalination of seawater and desalination of can water, recovery of valuables in an aqueous solution, and wastewater treatment, particularly removal of impurities in water, such as organic substances.

[0002]

2. Description of the Related Art A composite hollow fiber membrane having a polyamide polymer thin film on the outer surface of a polysulfone porous hollow fiber membrane is disclosed in U.S. Pat.
No. 95105, PB Report 81-167215,
JP-A-2-2842 discloses a composite hollow fiber membrane.

[0003]

However, U.S. Pat. No. 4,986,0061, Japanese Unexamined Patent Application Publication No. 62-95105.
The conventional composite hollow fiber membrane disclosed in Japanese Patent Laid-Open Publication No. H11-157572 has low water permeability, so high-pressure operation is required, and there is no description on the performance of removing organic substances.

On the other hand, the PB report 81-16721
The composite hollow fiber membrane shown in No. 5 has a large variation in data, is presumed to have a defect in the polymer thin film, has a low separation performance, and does not describe the performance of removing organic substances.

Similarly, the composite hollow fiber membrane disclosed in Japanese Patent Application Laid-Open No. 2-2842 is described with respect to the performance of removing organic substances, but those having high water permeability have a low removal performance, and conversely have a high removal performance. Only those having low water permeability are shown. An object of the present invention is to provide a composite hollow fiber membrane excellent in water permeability and separation performance, particularly, organic substance removal performance by using a composite hollow fiber membrane in which a polyamide-based polymer thin film is optimized. It is intended for.

[0006]

Means for Solving the Problems As a result of intensive studies in view of the above-mentioned objects, the present inventors have found that a composite hollow fiber membrane having a polyamide polymer thin film on the outer surface of a polysulfone porous hollow fiber membrane has an infrared ray. 1600-1 in absorption spectrum
If the ratio T between the absorption intensity Aa of the absorption peak derived from C = O of the polyamide at 700 cm ^-1 and the absorption intensity As of the absorption peak near 1586 cm ^-1 is within a certain range, high separation performance, particularly organic substance removal performance And found that high water-permeability can be exhibited, and the above object has been achieved.

That is, the present invention provides a composite semipermeable membrane comprising a polysulfone-based porous membrane and a polyamide-based polymer thin film covering one surface thereof, wherein the polyamide-based polymer thin film of the composite semipermeable membrane is coated. The absorption intensity Aa of the absorption peak derived from C = O of the polyamide at 1600 to 1700 cm ^-1 in the surface infrared absorption spectrum of
A composite semipermeable membrane characterized in that a ratio T (= Aa / As) of an absorption intensity As of an absorption peak derived from polysulfone near 586 cm ⁻¹ is 0.05 or more and 3 or less. In the present invention, the polyamide-based polymer thin film includes a cross-linked polyamide-based polymer, and further includes a cross-linked polypiperazine amide. In a preferred embodiment, the operating pressure is 0.3 MPa, the temperature is 25 MPa.
The sucrose removal rate with respect to a 0.1% by weight aqueous sucrose solution at pH 6.5 and pH 6.5 is 92% or more, and the water permeability is 0.2 m ³ / m ² /
It is possible to have performance over a day or more. The present invention also includes that the composite semipermeable membrane takes the form of a hollow fiber membrane,
This includes that the polyamide-based polymer thin film is formed on the outer surface side of the hollow fiber membrane.

Hereinafter, the present invention will be described in detail. In the present invention, a polysulfone-based porous membrane is a reverse osmosis membrane, which does not substantially exhibit separation performance with respect to an object to be separated in a nanofiltration membrane region, and is a support membrane for supporting the polyamide-based polymer thin film. There is no particular limitation. On the surface on which the polyamide-based polymer thin film is to be formed, preferably 0.001 μm
m or more and 0.05 μm or less, more preferably 0.00
It has fine pores of 5 μm or more and 0.03 μm or less, and the structure up to the back surface is preferably composed of fine pores larger than the fine pores on the front surface so as not to unnecessarily increase fluid permeation resistance. It may be either a void or a mixed structure thereof. Further, a reinforcing material such as a woven fabric or a nonwoven fabric made of a material such as polyester may be included. In addition, the characteristics of the polysulfone-based porous membrane were determined by dextran T7.
In terms of the separation characteristics of 0 aqueous solution, the supply pressure is 0.1MP
a, 25 ° C., recovery rate less than 30%, average membrane surface flow velocity 40 cm
/ S, the removal rate is desirably 50% or more.

Examples of the polysulfone resin in the present invention include a polymer composed of a repeating unit represented by the chemical formula 1 (Chemical Formula 1) and a polymer composed of a repeating unit represented by the following chemical formula 2 (Chemical Formula 2). And more preferably a polymer comprising a repeating unit represented by Chemical Formula 1.

[0010]

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[0011]

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The thickness of the polysulfone porous membrane in the present invention is not particularly limited. For example, when taking the form of a hollow fiber membrane, the outer diameter is preferably 100 μm to 2000 μm, and the inner diameter is preferably 30 μm to 1800 μm in consideration of the operability during film formation, the membrane area of the module, and the pressure resistance. 150 μm to 500 μm, inner diameter 50 μm to 300
μm is more preferred. Furthermore, the polysulfone-based porous membrane in the present invention must be able to withstand at least the operating pressure of the composite membrane. Such a polysulfone porous membrane can be selected from various commercially available products, but can usually be produced by a known dry-wet membrane forming method or the like. Further, if necessary, the porous hollow fiber membrane after film formation may be subjected to a wet heat treatment at 50 ° C. as disclosed in JP-A-58-199007, or may be subjected to JP-A-60-19020.
As disclosed in Japanese Patent Publication No. 4 (1999) -1994, a hot water treatment at 90 ° C. or higher may be used.

The polyamide polymer thin film in the present invention is not particularly limited as long as it is composed of a polyamide polymer. A crosslinked polyamide polymer thin film obtained by an interfacial polycondensation reaction between a polyfunctional amine and a polyfunctional acid halide is preferable, and examples thereof include crosslinked polypiperazineamide and wholly aromatic crosslinked polyamide. In particular, crosslinked polypiperazineamide is preferred. The thickness is preferably as thin as possible without pinholes. In consideration of film forming stability, permeation performance and the like, the thickness is preferably 1.0 μm or less, more preferably 0.5 μm or less. A protective layer may be formed on the surface of the separation active layer as needed.

In the present invention, as an example of the determination as to whether or not the polyamide-based polymer thin film is a crosslinked product, there is a determination based on the solubility of the polyamide polymer thin film in a solvent. An example is shown below. A polyamide polymer obtained by a reaction between piperazine and isophthalic acid chloride is a non-crosslinked linear polymer, and is known to be soluble in chloroform or the like. Further, a polyamide polymer obtained by a reaction between m-phenylenediamine and isophthalic acid chloride is also a non-crosslinked linear polymer,
It is known to dissolve in N-methyl-2-pyrrolidone, N, N-dimethylacetamide and the like. In contrast,
If the polyamide-based polymer is a crosslinked product, undissolved components remain even if an attempt is made to dissolve in these solvents at a low concentration. By utilizing this property, 1 g of the dried composite semipermeable membrane (including the polysulfone-based porous membrane) can be mixed with chloroform, m-cresol, dichloromethane, N-methyl-2-pyrrolidone or N, N
-Add 100 mL of each of dimethylacetamide and stir at room temperature, and in any case, if any undissolved matter remains, judge this as a crosslinked polyamide. If the polysulfone-based porous membrane does not dissolve in the above-mentioned five types of solvents, it is dissolved and removed in advance with an appropriate solvent, and then the polyamide-based polymer thin film is separated. In addition, the composite semi-permeable membrane, in addition to the composition, a nonwoven fabric
When a reinforcing material such as a woven fabric is included as a component, the above operation is performed after removing the material by a method such as peeling or dissolving in advance. Further, when the composite semipermeable membrane has been used and stains or the like have adhered to the membrane surface, the composite semipermeable membrane is removed by an appropriate cleaning method according to the adhesion state of the stain or the like, and then the above determination is made.

As the surface infrared absorption spectrum in the present invention, an infrared absorption spectrum obtained by ATR infrared spectroscopy is preferably used. The ATR method infrared spectroscopy is an infrared spectroscopy that measures the total reflection infrared light on the surface of the object to be measured.
Information on the surface of the measurement object can be captured sharply. A
In the TR method infrared spectroscopy, it is important to sufficiently press the sample and the internal reflection element to obtain a reproducible spectrum. Increasing the degree of crimping generally increases the absorption intensity on the high wavenumber side due to the improvement in the adhesion between the internal reflection element and the object to be measured, and therefore the absorption intensity ratio T defined in the present invention increases. It is thought that. However, the ATR of the composite semipermeable membrane in the present invention
In the measurement of the infrared absorption spectrum, the porous polysulfone membrane is compressed and densified in the process of compressing the internal reflection element to the sample, and the absorption intensity derived from polysulfone increases. The intensity ratio T decreases. Therefore, measurement was performed at several points while increasing the degree of pressure bonding of the internal reflection element, and when the ratio of the absorption intensity derived from the polyamide polymer and the absorption intensity derived from polysulfone became constant, it was determined that the surface red of the composite film was red. It is assumed to be an external absorption spectrum.

FIG. 1 shows a porous hollow fiber membrane made of polysulfone.
FIG. 2 shows the ATR of the outer surface of a composite hollow fiber membrane in which a polyamide polymer thin film is formed on the outer surface of a polysulfone porous membrane.
An example of a method infrared absorption spectrum is shown. FIG. 3 shows an example of an ATR method infrared absorption spectrum of a membrane obtained by treating the membrane of FIG. 2 with chloroform, dissolving and removing the polysulfone porous membrane, and separating only the polyamide polymer. 1 and 2 show infrared absorption spectra of the hollow fiber membranes of Comparative Example 1 and Example 1 described later. From the comparison of FIG. 1 to FIG.
The absorption peak near m ^-1 is derived from polysulfone and 163
It is clear that the absorption peak near 0 cm ^-1 is derived from polyamide. The absorption peak near 1586 cm ^-1 was due to the C = C expansion and contraction of the aromatic ring of polysulfone at 1630 c.
It is known that the absorption peak near m ^-1 is attributed to the C ＝ O stretching of the polyamide.

[0017] The ratio of the absorption intensity As of the absorption peak around absorption intensity Aa and 1586 cm ^-1 of the absorption peak derived from C = O of polyamide 1600～1700Cm ^-1 in the infrared absorption spectrum of the composite semipermeable membrane T (= Aa / As)
It is considered that the thickness mainly reflects the thickness of the polyamide polymer thin film. That is, those having a large absorption intensity ratio T have a large thickness of the polyamide polymer thin film, and those having a small absorption intensity ratio T have a small thickness of the polyamide polymer thin film. In order to obtain a composite hollow fiber membrane having high organic matter removal performance and high water permeability, the absorption intensity ratio T is preferably 0.05 or more and 3 or less, more preferably 0.1 or more and 1 or less.
5 or less is preferred. If the absorption intensity ratio T is greater than 3,
Although high organic matter removal performance can be obtained, the thickness of the polyamide polymer thin film becomes excessively large, so that the permeation resistance becomes excessively large and the water permeation performance becomes low, which is not preferable. On the other hand, when the ratio is less than 0.05, the water permeability becomes large, but it becomes difficult for the polyamide-based polymer thin film to completely cover the entire support film, which causes a leak and a decrease in organic matter removal properties. Also, since the thickness of the polyamide-based polymer thin film is too small, problems such as a decrease in physical and chemical durability occur,
Not preferred.

The absorption wavelength of infrared absorption derived from polyamide varies depending on its chemical composition. For example, in the case of polyamide formed by the reaction between metaphenylenediamine and trimesic acid chloride, the absorption wavelength due to the above-mentioned C 伸縮 O expansion and contraction occurs. Absorption derived from polyamide attributed to
Shift to around cm ^-1 . Therefore, in this case, 166
The absorption intensity near 0 cm ^{-1 was set to} 1600 in the present invention.
It is to be regarded as the absorption intensity of the absorption peak derived from C ＝ O of the polyamide of １1700 cm ⁻¹ .

Next, an example of the method for producing a composite semipermeable membrane of the present invention will be described. By performing an interfacial polycondensation reaction between a polyfunctional amine and a polyfunctional acid halide on the outer surface of the polysulfone-based porous membrane, the composite semipermeable membrane of the present invention can be formed. That is, the polysulfone-based porous membrane is brought into contact with a concentration-adjusted amine solution, and after the excess amine solution is drained, it is brought into contact with a concentration-adjusted polyfunctional acid halide solution to cause an interfacial polycondensation reaction. Yields a composite semipermeable membrane.

Examples of the polyfunctional amine include an aromatic amine and an aliphatic amine, and any of these may be used.

The aromatic amine is an aromatic amine having two or more amino groups in one molecule. Examples of the difunctional or higher functional amine include m-phenylenediamine and p-amine.
Phenylenediamine, 4,4'-diaminodiphenylamine, 4,4'-diaminodiphenylether, 3,
4′-diaminodiphenyl ether, 3,3′-diaminodiphenylamine, 3,5-diaminobenzoate,
4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 1,3,5-triaminobenzene and the like may be mentioned, and a mixture thereof may be used. Above all, m
-Phenylenediamine is most preferred.

The aliphatic amine may be any bifunctional or higher amine, and specific examples thereof include piperazine, 2-methylpiperazine, 2-ethylpiperazine,
5-dimethylpiperazine, homopiperazine, t-2,5
-Piperazine derivatives such as -dimethylpiperazine, bis (4-piperidyl) methane, 1,2-bis (4-piperidyl) ethane, 1,3-bis (4-piperidyl) propane, N, N'-dimethylethylenediamine, ethylenediamine , Propylene diamine, propylene triamine,
N, N'-dimethylpropanediamine, 4- (aminomethyl) piperidine, cyclohexanediamine, and the like may be mentioned, and a mixture thereof, or an amide prepolymer composed of these may be used. Of these, piperazine is most preferred.

Examples of polyfunctional acid halides include polyfunctional acyl halides, which may be aromatic or aliphatic, and which can react with the polyfunctional amine to form a polymer. What is necessary is just functional or more. Aromatic or aliphatic bifunctional or trifunctional acid halides are preferred,
For example, trimesic acid halide, trimellitic acid halide, pyromellitic acid halide, benzophenone tetracarboxylic acid halide, isophthalic acid halide, terephthalic acid halide, diphenyldicarboxylic acid halide, naphthalenedicarboxylic acid halide, benzenedisulfonic acid halide, chlorosulfonylisophthalic acid halide Pyridinedicarboxylic acid halide, 1,3,5-cyclohexanetricarboxylic acid halide, and the like. Considering the water permeability, the organic matter removal performance, and the like, trimesic acid chloride, isophthalic acid chloride, terephthalic acid chloride, and a mixture thereof are preferable.

The concentration of these polyfunctional compounds differs depending on the kind of the polyfunctional compound and the partition coefficient with respect to the solvent. For example, when piperazine is the polyfunctional amine, the solvent is water, trimesic acid chloride is the polyfunctional acid halide, and the solvent is n-hexane, the concentration of piperazine is about 0. .1 to 10
%, Preferably about 0.5 to 5% by weight, and the concentration of trimesic acid chloride is about 0.1 to 10%.
%, Preferably about 0.1 to 5% by weight. When these concentrations are low, the formation of the interfacial polymer film is incomplete and defects are liable to occur, resulting in a decrease in separation performance. Conversely, when the concentration is too high, the interfacial polymer film becomes too thick, causing a decrease in permeation performance, or in the production film. May increase the amount of unreacted matter remaining, and may adversely affect the film performance. In addition, the concentration ratio between the polyfunctional amine and the polyfunctional acid halide has an important effect on the membrane performance of the resulting composite semipermeable membrane. Obtainable.
The optimal concentration ratio (polyfunctional amine concentration / polyfunctional acid halide concentration) is in the range of 20-0.1.

When an acid is generated by the condensation reaction, an alkali as an acid scavenger may be added to the reaction solution, or a surfactant may be added to improve the wettability of the porous film. A reaction accelerator of another polyfunctional compound may be added as needed. Examples of the acid scavenger include caustic alkali such as sodium hydroxide, sodium phosphate such as trisodium phosphate, tertiary amine such as pyridine, triethylenediamine, and triethylamine. Examples of the surfactant include sodium lauryl sulfonate, sodium lauryl benzene sulfonate, and the like. Examples of the reaction accelerator include dimethylformamide. These can be previously contained in the polyfunctional amine solution and / or the polyfunctional acid halide solution. The concentrations of the surfactant, the acid scavenger and the reaction accelerator also have a significant effect on the membrane performance, but the optimum values can be determined experimentally.

As the solvent for the polyfunctional amine solution and the solvent for the polyfunctional acid halide solution, the polyfunctional amine and the polyfunctional acid halide are dissolved, respectively. Is not particularly limited, as long as it forms a polysulfone-based porous hollow fiber membrane. For example, water is used as the solvent for the polyfunctional amine, and n-hexane, cyclohexane, n-heptane, n-octane, n-nonane, n-hexane is used as the solvent for the polyfunctional acid halide.
Examples thereof include hydrocarbon solvents such as -decane and n-undecane and mixtures thereof.

The temperatures of the polyfunctional amine solution and the polyfunctional acid halide solution are not particularly limited, but any combination of polyfunctional compounds that cause an interfacial reaction at room temperature sufficiently quickly can be used in operation. About room temperature, ie 5-4
A range of 5 ° C is used. If the temperature is too high, the deterioration of the polyfunctional compound is promoted, or there is a problem that the evaporation of the solvent is promoted.On the other hand, if the temperature is too low, the polyfunctional amine solution to the polysulfone-based porous hollow fiber membrane is used. Insufficiency of impregnation, the interface reaction rate becomes too low to form a polymer thin film completely, and the viscosity of the solvent becomes too high, which hinders the film forming process.

In the present invention, bringing each solution into contact with the polysulfone-based porous membrane means applying each solution to the polysulfone-based porous membrane, or dipping and passing through each solution. Further, after the contact with the polyfunctional amine solution, the excess solution on the surface of the polysulfone-based porous membrane may cause peeling of the thin film. Therefore, it is preferable to remove the excess solution. Examples of the removal method include a method in which the polysulfone-based porous membrane is allowed to run in the air and naturally fall and air-dry, and a method in which the polyfunctional amine and the polyfunctional halide are scraped using a third liquid different from the solution. And spraying with air or an inert gas, and drying with a dryer. Further, after contact with the polyfunctional acid halide solution, it may be immersed in an aqueous solution of an acid scavenger for neutralization and termination of the reaction. Examples of acid scavengers include sodium phosphate, such as trisodium phosphate, sodium carbonate, and the like. Further, in order to remove oligomers and unreacted monomers, surfactants, acid scavengers, reaction accelerators, and the like remaining in the film, pure water, hot water, an acid aqueous solution, an alkaline aqueous solution, an organic solvent, an organic solvent aqueous solution, The membrane can be washed with an oxidizing agent aqueous solution, a reducing agent aqueous solution, or the like.

[0029]

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples. The case where the composite semipermeable membrane in the present invention is a hollow fiber membrane will be described in detail. However, even if the form of the membrane is a flat membrane or a tubular membrane, only the shape of the polysulfone-based porous membrane is different. Can obtain a composite semipermeable membrane excellent in water permeability and separation performance by the same technique. The performance and infrared absorption spectrum shown in Examples and Comparative Examples were measured by the following methods and conditions.

(1) Preparation of Mini Module for Evaluation of Membrane Performance A loop was formed with 54 (18 in Comparative Example 1) hollow fiber membranes, and one end of the loop was inserted into a holder and sealed with epoxy resin. At this time, sealing was performed in a state where the hollow fiber membrane protruded from the opposite end of the holder by several cm, and after the epoxy resin was cured, the projection was cut to form an opening of the hollow fiber membrane. . The effective length of the hollow fiber membrane is 38.5
cm, and the effective area is 457 cm based on the outer diameter of the hollow fiber membrane.
² (152 cm ^{2 in} Comparative Example 1). (2) Separation performance of sucrose aqueous solution of composite hollow fiber membrane 80 g of sucrose was dissolved in 80 L of RO water, and 1000 mg /
An L aqueous solution was obtained. Water was supplied to the outer surface of the hollow fiber membrane at a temperature of 25 ° C., a pressure of 0.30 MPa, an average membrane surface flow rate of 13 cm / sec, and a recovery of less than 1%. Recovery RC is defined by the following equation. RC (%) = Qp / Qf × 100 Qp: Flow rate of permeate Qf: Flow rate of feed solution One hour later, the flow rate of permeate flowing out of the hollow portion and the sucrose concentration were measured. The water permeability was represented by the permeated liquid amount per unit membrane area (m ² ) and unit time (day). The removal rate Rj, which is an index of the removal performance, is defined by the following equation. In addition, the measurement of the sucrose concentration was performed by the anthrone sulfate method colorimetric analysis. Rj (%) = (1−Cp / Cf) × 100 Cp: sucrose concentration of permeate Cf: sucrose concentration of feed solution

(3) ATR method infrared absorption spectrum The composite hollow fiber membrane was heated and dried at 80 ° C. overnight under reduced pressure.
Measure the ATR infrared absorption spectrum of the outer surface of the hollow fiber membrane
Was. Hollow fiber membrane is divided into two parts by a plane almost parallel to the fiber axis
And used as a measurement sample. Measurement is SPECTRA TECH
Internal reflection element using IR μs / SIRM
Using diamond 45 ° as the resolution 8cm^-1,
The measurement was carried out at a cumulative number of 64 times. Also, at the time of Fourier transform
Apodization of Happ-Genzel
Made in function. Measurement of 12 outer surfaces of hollow fiber membrane
And the absorption intensity ratio T defined by the following equation:_(i)The average of
The value was defined as the absorption intensity ratio T of the composite hollow fiber membrane. In addition,
Character_(i)Is the value at the i-th measurement position.
Taste, i is an integer of 1 to 12. T_(i)= Aa_(i)/ As_(i) Aa_(i): 1600 to 170 at i-th measurement position
0cm^-1Of the absorption peak derived from C = O of the polyamide
Absorption intensity As_(i): 1586 cm at the i-th measurement position^-1Attached
Absorption intensity of absorption peak derived from nearby polysulfone
And the above T_(i)Values fluctuate, and as crimping increases
And become smaller. In the present invention, the pressure is measured at each measurement position.
Perform several measurements while increasing the degree of
T _(i)Is the value at which ceases to decrease_(i)
Adopted as. Also, a base for calculating the absorption intensity
Slines were determined by the following procedure. 1600-170
0cm^-1Of the absorption peak derived from C ＝ O of the polyamide
Regarding the absorption intensity, the skirt on the high wavenumber side of this absorption and 1
586cm^-1Absorption peak derived from nearby polysulfone
The valley on the low wavenumber side was connected to be the baseline. 1586
cm^-1Absorption peak near polysulfone
For strength, connect the valleys on both sides of this absorption to the baseline.
In. Note that these baselines are
Pulled so as not to intersect with Le.

Example 1 20% by weight of polysulfone resin (Teijin Amoco Engineering Plastics, Udel P-3500), 4% by weight of triethylene glycol, 0.5% by weight of sodium laurylbenzenesulfonate, and 75.5% by weight of dimethylacetamide % Of the spinning solution is discharged from an outer peripheral portion of a nozzle for producing a hollow fiber having a double-tube structure, and an aqueous solution composed of 30% by weight of dimethylacetamide and 70% by weight of water is discharged from a central portion. After that, the mixture was taken into a coagulation bath containing water as a main component at a rate of 15 m / min to obtain a polysulfone porous hollow fiber membrane. Thereafter, the residual solvent was removed in a water washing step, and a hot water treatment at 70 ° C. was performed. Subsequently, this porous hollow fiber membrane was treated with piperazine 2.0
% By weight, 1.0% by weight of triethylenediamine and 0.065% by weight of sodium laurylbenzenesulfonate in RO
An amine aqueous solution obtained by dissolving in water was prepared, and a continuous porous hollow fiber membrane was immersed and passed through this solution. The concentration composition of the aqueous amine solution is controlled to be constant. Subsequently, after removing the excess amine solution on the surface of the porous hollow fiber membrane, trimesic acid chloride was 0.96% by weight.
N-hexane solution, Fluorinert FC-70, 1
It was sequentially contacted with an aqueous solution of acetic acid by weight and subjected to a dry heat treatment in a drying tower. Further, the composite hollow fiber membrane was washed with water in a washing tank to obtain a composite hollow fiber membrane having a thin film made of crosslinked polypiperazinamide on the outer surface. The absorption intensity ratio T in the ATR infrared absorption spectrum of the obtained composite hollow fiber membrane was 0.54. The sucrose removal rate measured under the above-mentioned conditions was 95.6%, and the water permeability was 272 L / m ² / day.

Example 2 A composite hollow fiber membrane was produced in the same manner as in Example 1 except that the concentration of the n-hexane solution of trimesic acid chloride was changed to 0.85% by weight. The absorption intensity ratio T, sucrose removal rate, and water permeability were 1.02, 95.8%, and 21 respectively.
It was 1 L / m ² / day.

Example 3 Composite hollow fiber was prepared in the same manner as in Example 1, except that the concentration of triethylenediamine in the aqueous amine solution was changed to 2.0% by weight and the concentration of the n-hexane solution of trimesic acid chloride was changed to 0.75% by weight. A film was prepared. The absorption intensity ratio T, sucrose removal rate, and water permeability were 0.16, 95.2%, and 38, respectively.
It was 4 L / m ² / day.

Comparative Example 1 In Example 1, the hollow fiber membrane was taken out before the impregnation with the aqueous amine solution. The absorption intensity ratio T, sucrose removal rate, and water permeability were 0.00, 0.0%, and 12,000 L /, respectively.
m ² / day.

Comparative Example 2 A composite hollow fiber membrane was prepared in the same manner as in Example 1 except that the contact time with an n-hexane solution containing 0.96% by weight of trimesic acid chloride was 10 times that in Example 1. Obtained. The absorption intensity ratio T, the sucrose removal rate, and the water permeability were each 3.
5, 97.2%, 73 L / m ² / day.

Examples 4 to 6 20% by weight of polysulfone resin (Teijin Amoco Engineering Plastics, Udel P-3500), 4% by weight of triethylene glycol, 0.5% by weight of sodium laurylbenzenesulfonate, and 75% by weight of dimethylacetamide. A spinning stock solution consisting of 5% by weight is discharged from the outer peripheral portion of a hollow fiber manufacturing nozzle having a double-tube structure, and an aqueous solution consisting of 30% by weight of dimethylacetamide and 70% by weight of water is discharged from the central portion. After passing through the running section, it was taken into a coagulation bath containing water as a main component at a rate of 15 m / min to obtain a polysulfone porous hollow fiber membrane. Thereafter, the residual solvent was removed in a water washing step. An aqueous amine solution was prepared by dissolving 2.0% by weight of piperazine, 1.0% by weight of triethylenediamine, and 0.065% by weight of sodium laurylbenzenesulfonate in RO water. The membrane was immersed and passed. The concentration composition of the aqueous amine solution is controlled to be constant. Subsequently, after removing the excess amine solution from the surface of the porous hollow fiber membrane, the porous hollow fiber membrane was successively contacted with an n-hexane solution containing acid chloride having the composition shown in Table 1, Fluorinert FC-70, and a 1% by weight aqueous acetic acid solution. Then, a dry heat treatment was performed in a drying tower. Further, the composite hollow fiber membrane was washed with water in a washing tank to obtain a composite hollow fiber membrane having a thin film made of crosslinked polypiperazinamide on the outer surface. Table 1 shows the absorption intensity ratio T in the ATR infrared absorption spectrum of the obtained composite hollow fiber membrane, the sucrose removal rate measured under the above-described conditions, and the water permeability.

[0038]

[Table 1] (Note) Trimesic acid chloride is abbreviated as TMC, and isophthalic acid chloride is abbreviated as IPC.

[0039]

The composite semipermeable membrane of the present invention is obtained by forming a polyamide-based polymer thin film on one surface of a polysulfone-based porous membrane. The composite semipermeable membrane has excellent permeation performance and separation performance, especially excellent organic substance removal performance. It is a semipermeable membrane. Therefore, the composite semipermeable membrane of the present invention can be used as a reverse osmosis membrane, for producing desalination by desalination of seawater, seawater, etc., for producing ultrapure water used for producing semiconductors, and as a nanofiltration membrane, for producing small pure water. It can be used in various fields such as equipment, water purifier applications, advanced water purifier applications, valuable resource recovery applications, and wastewater treatment applications.

[Brief description of the drawings]

FIG. 1 shows an ATR infrared absorption spectrum of the outer surface of a polysulfone porous hollow fiber membrane used in Example 1.

FIG. 2 shows an ATR infrared absorption spectrum of the outer surface of the composite hollow fiber membrane obtained in Example 1.

FIG. 3 shows an ATR infrared absorption spectrum of only the polyamide polymer on the outer surface of the composite hollow fiber membrane obtained in Example 1, which was separated.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Atsushi Kumano 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd. Research Laboratory

Claims (7)

[Claims] 1. A composite semipermeable membrane comprising a polysulfone-based porous membrane and a polyamide-based polymer thin film covering one surface thereof, the surface of the composite semipermeable membrane on the side on which the polyamide-based polymer thin film is coated. In the infrared absorption spectrum,
1600~1700cm ^-1 polyamide C = absorption of the absorption peak derived from O intensity Aa and 1586cm ratio of absorption intensity As of the absorption peak derived from polysulfone near ^-1 T (= Aa / As) is 0.05 The composite semipermeable membrane, which is at least 3 and at most 3. 2. The composite semipermeable membrane according to claim 1, wherein T (= Aa / As) is 0.1 or more and 1.5 or less. 3. The composite semipermeable membrane according to claim 1, wherein the polyamide polymer is a crosslinked polyamide polymer. 4. The composite semipermeable membrane according to claim 1, wherein the polyamide polymer comprises a crosslinked polypiperazine amide. 5. Operating pressure 0.3 MPa, temperature 25 ° C., p
Removal of sucrose from 0.1 wt% sucrose aqueous solution of H6.5
Deletion rate is more than 92%, water permeability is 0.2m^Three/ M ^Two/ Day or more
The composite according to any one of claims 1 to 4, which has the following performance.
Semi-permeable membrane. 6. The composite semipermeable membrane according to claim 1, wherein the composite semipermeable membrane takes the form of a hollow fiber membrane. 7. The composite semipermeable membrane according to claim 1, wherein the polyamide-based polymer thin film is formed on the outer surface of the hollow fiber membrane.