Composite semipermeable membrane and production thereof

Abstract

A composite semipermeable membrane including: a substrate; a porous supporting layer formed on the substrate; and a separation functional layer formed on the porous supporting layer, in which the separation functional layer contains crosslinked wholly aromatic polyamide as a main component and contains a carboxy group, a ratio of (molar equivalent of the carboxy group)/(molar equivalent of an amide group) in functional groups contained in the separation functional layer is 0.40 or more, and an average ratio of oxygen atoms/nitrogen atoms in front and rear sides of the separation functional layer is 0.95 or less.

Claims

1. A composite semipermeable membrane comprising: a substrate; a porous supporting layer formed on the substrate; and a separation functional layer formed on the porous supporting layer, the separation functional layer having a rear surface facing the porous supporting layer and a front surface on an opposite side, wherein the separation functional layer contains crosslinked wholly aromatic polyamide as a main component and contains carboxy groups, a ratio of (molar equivalent of the carboxy groups)/(molar equivalent of amide groups) in functional groups contained in the separation functional layer crosslinked wholly aromatic polyamide is 0.40 or more and 0.60 or less, wherein the ratio is obtained using .sup.13C solid-state NMR measurement according to the CP/MAS method and the DD/MAS method, wherein from the obtained spectra, for each peak derived from a carbon atom to which each functional group is bonded, peak division is performed and the amount of the functional group is quantified from the area of the divided peak, an average ratio of oxygen atoms/nitrogen atoms in front and rear surfaces of the separation functional layer is 0.80 or more and 0.95 or less, wherein the average ratio is obtained by using X-ray photoelectron spectroscopy analysis, the separation functional layer is coated with a hydrophilic polymer, and the separation functional layer contains phenolic hydroxyl groups such that a ratio of (molar equivalent of the phenolic hydroxyl groups)/(molar equivalent of the amide groups) is 0.10 or less, wherein the ratio is obtained using .sup.13C solid-state NMR measurement according to the CP/MAS method and the DD/MAS method, wherein from the obtained spectra, for each peak derived from a carbon atom to which each functional group is bonded, peak division is performed and the amount of the functional group is quantified from the area of the divided peak.

2. The composite semipermeable membrane according to claim 1, wherein the hydrophilic polymer has an average molecular weight of 8,000 or more.

3. The composite semipermeable membrane according to claim 1, wherein the hydrophilic polymer is polyethylene glycol or a copolymer containing polyethylene glycol.

4. The composite semipermeable membrane according to claim 1, wherein a weight of the porous supporting layer per unit volume, after passing pure water at a temperature of 25 C. and a pressure of 5.5 MPa for 24 hours or more, is 0.50 g/cm.sup.3 to 0.65 g/cm.sup.3.

5. The composite semipermeable membrane according to claim 1, wherein an average impregnation amount of the porous supporting layer into the substrate per unit area is 1.0 g/m.sup.2 to 5.0 g/m.sup.2, and 20% or more of the substrate sites have an impregnation amount which is 1.2 times or more of the average impregnation amount.

6. The composite semipermeable membrane according to claim 1, wherein the substrate is a long-fiber nonwoven fabric, and an air flow rate of the substrate is 0.5 mL/cm.sup.2/sec to 5.0 mL/cm.sup.2/sec.

7. The composite semipermeable membrane according to claim 1, wherein the substrate is a long-fiber nonwoven fabric, and a difference in a degree of fiber orientation between fibers in a surface of the substrate facing the porous supporting layer and fibers in a surface of the substrate opposite to the porous supporting layer is 10 to 90.

8. The composite semipermeable membrane according to claim 1, wherein, when feed water having conditions of a TDS concentration of 3.5%, a boron concentration of 5 ppm, a pH of 6.5, and a temperature of 25 C. permeates the composite semipermeable membrane at an operation pressure of 5.5 MPa, a membrane permeation flux thereof is 0.9 m.sup.3/m.sup.2/day or more, and a boron removal ratio thereof satisfies the following formula:
(boron removal ratio (%))10310(membrane permeation flux(m.sup.3/m.sup.2/day)).

Description

EXAMPLES

(1) Hereinafter, the present invention will be described in more detail with reference to the following Examples, but the scope of the present invention is not limited to these Examples.

(2) The various characteristics of the composite semipermeable membrane were obtained by measuring the quality of permeate and feed water after supplying seawater (TDS concentration: 3.5%, boron concentration: about 5 ppm), adjusted to a temperature of 25 C. and a pH of 6.5, to the composite semipermeable membrane at an operation pressure of 5.5 MPa and then performing membrane filtration treatment for 24 hours.

(3) (Solute Removal Ratio (TDS Removal Ratio))
TDS removal ratio (%)=100{1(TDS concentration in permeate/TDS concentration in feed water)}

(4) (Membrane Permeation Flux)

(5) The membrane permeation rate of feed water (seawater) is represented by a membrane permeation flux (m.sup.3/m.sup.2/day) which is expressed by a permeate amount (cubic meter) per a membrane surface of square meter and per day.

(6) (Boron Removal Ratio)

(7) The boron removal ratio of the composite semipermeable membrane was determined by the following equation after analyzing the concentration of boron in the feed water and permeate using an ICP emission spectrometer (P-4010, manufactured by Hitachi. Ltd.).
Boron removal ratio (%)=100{1(boron concentration in permeate/boron concentration in feed water)}

(8) (Degree of Fiber Orientation of Substrate)

(9) The degree of fiber orientation of the substrate was obtained by the following steps of: randomly extracting ten small-piece samples from a nonwoven fabric, observing each of the samples with a scanning electron microscope at a magnification of 100 to 1,000 times; respectively measuring angles when setting the longitudinal direction (machine direction) of the nonwoven fabric to 0 and setting the lateral direction (cross direction) of the nonwoven fabric to 90, for ten fibers of each of samples, namely a total of 100 fibers; and rounding off the average value of the measured angles to one decimal point.

(10) (Weight of Porous Supporting Layer Per Unit Volume)

(11) The composite semipermeable membrane was cut to an area of 44.2 cm.sup.2, pure water passed through the composite semipermeable membrane at a temperature of 25 C. and a pressure of 5.5 MPa for 24 hours, and then the composite semipermeable membrane was dried under vacuum. Thereafter, the weight and thickness of the composite semipermeable membrane were measured, and the substrate was separated from the composite semipermeable membrane. The weight and thickness of the substrate was measured, and the weight of the supporting layer per unit volume was calculated by the following equation.
Weight of supporting layer per unit volume (g/cm.sup.3)=(weight of composite semipermeable membraneweight of substrate)/(area of composite semipermeable membrane(thickness of composite semipermeable membranethickness of substrate))

(12) (Average Impregnation Amount of Porous Supporting Layer into Substrate Per Unit Area)

(13) A composite semipermeable membrane having arbitrary 50 points in an area of 5 cm5 cm was dried under vacuum, and then a substrate was separated from the composite semipermeable membrane. The substrate was immersed in a DMF solution for 24 hours, cleaned, and then dried under vacuum to calculate the average impregnation amount of a porous supporting layer into the substrate per unit area from the following equation.
Average impregnation amount=weight of substrate before DMF immersionweight of substrate after DMF immersion

(14) In addition, among the arbitrary 50 points, the percentage of sites having an impregnation amount which is 1.2 times or more of the calculated average impregnation amount was calculated by the following equation.
Percentage of sites having impregnation amount which is 1.2 times or more of average impregnation amount (%)=(number of sites having impregnation amount which is 1.2 times or more of average impregnation amount/50)100

(15) (Air Flow Rate (mL/cm.sup.2/sec))

(16) The air flow rates of a nonwoven fabric having a size of 30 cm50 cm at arbitrary 45 points therein at a barometer pressure of 125 Pa were measured based on JIS L 1906: 2000 4.8 (1) Frazier method. However, the average value thereof was rounded to second decimal point.

(17) (Stability Under High Solute Concentration)

(18) The composite semipermeable membrane was immersed in concentrated seawater, adjusted to a TDS concentration of 7.0%, a temperature of 25 C. and a pH of 8, for 100 hours, and the permeation flux ratio and boron SP ratio before and after the immersion were obtained. Here, SP refers to the abbreviation of substance permeation.
Permeation flux ratio=permeation flux after passing water/permeation flux before passing water
Born SP ratio=(100boron removal ratio after passing water)/(100boron removal ratio before passing water)

(19) (Pressure Resistance)

(20) A permeated liquid channel member (tricot (thickness: 300 m, groove width: 200 m, row width: 300 m, groove depth: 105 m)) was provided to a permeation side, and seawater (TDS concentration: 3.5%), adjusted to a temperature of 25 C. and a pH of 6.5, was passed for 1 min200 times at a pressure of 7.0 MPa, and the change in membrane thickness before and after passing water was measured. In addition, the permeation flux ratio and boron SP ratio before and after passing water were measured.

(21) (Functional Group Analysis of Separation Functional Layer by .sup.13C Solid-State NMR Method)

(22) The measurement of a separation functional layer by a .sup.13C solid-state NMR method is as follows. First, after a composite semipermeable membrane having a separation functional layer on a supporting membrane was formed using the manufacturing method of the present invention, a substrate was physically separated from the composite semipermeable membrane to collect a porous supporting layer and a separation functional layer. The collected porous supporting layer and separation functional layer were dried by leaving them at 25 C. for 24 hours, and then were added to dichloromethane contained in a beaker little by little and stirred to dissolve the polymer constituting the porous supporting layer. The insoluble matter in the beaker was collected with a filtration paper, and was cleaned with dichloromethane several times. The collected separation functional layer was dried by a vacuum dryer to remove the remained dichloromethane. The obtained separation functional layer was made into a powdered sample by frost shattering, and the powder sample was hermetically charged in a sample tube used in the solid-state NMR method, so as to perform .sup.13C solid-state NMR measurement according to the CP/MAS method and the DD/MAS method. In the .sup.13C solid-state NMR measurement, CMX-300, manufactured by Chemagnetics Inc., can be used. From the obtained spectra, for each peak derived from a carbon atom to which each functional group is bonded, peak division was performed, and the amount of the function group was quantified from the area of the divided peak.

(23) (Elemental Analysis of Surface of Separation Functional Layer by XPS Measurement)

(24) The composition information of the elements constituting the separation functional layer can be obtained by XPS. Samples used for the XPS measurement were prepared as follows. First, the composite semipermeable membrane fabricated based on the method disclosed in the present invention was dried at 25 C. for 24 hours. The elemental analysis of the surface of the separating functional layer opposite to the supporting membrane was carried out without further processing. On the other hand, since it is required to remove the supporting membrane in the measurement of the surface of the separation functional layer faced to the supporting membrane, first, only the substrate in the supporting membrane was peeled off. The remained composite semipermeable membrane was fixed on a silicon wafer such that the porous supporting layer becomes a surface, and the porous supporting layer was dissolved by dichloromethane, so as to obtain the surface of only the separation functional layer. The XPS measurement of this sample was carried out in the same manner as above, and the elemental analysis of the surface of the separation functional layer faced to the supporting membrane was carried out. In the XPS measurement, for example, ESCALAB220iXL, manufactured by VG Scientific Co., Ltd., can be used. Transverse axis correction was carried out by matching the neutral carbon (CHx) of C1s peak of the obtained spectrum data to 284.6 eV, and then the peak area of each element was calculated.

(25) (TOF-SIMS Measurement)

(26) The composite semipermeable membrane was immersed in ultrapure water for 1 day to be cleaned. This membrane was dried by a vacuum dryer, and TOF-SIMS measurement was carried out. This measurement was carried out using the TOF.SIMS.sup.5, manufactured by ION-TOF Inc. The secondary ions, generated by applying a primary accelerating voltage of 30 kV to Bi.sub.3.sup.++ as primary ion species, were measured by a time-of-flight mass spectrometer, so as to obtain mass spectra.

Example 1

(27) A DMF solution containing 18.0 wt % of polysulfone (PSf) was cast onto a long fiber-made polyester nonwoven fabric (air flow rate: 2.0 mL/cm.sup.2/sec) to a thickness of 200 m under a condition of 25 C., immediately immersed in pure water, and left for 5 minutes, thereby forming a porous supporting layer.

(28) The obtained supporting membrane was immersed in an aqueous solution containing 5.5 wt % of m-phenylenediamine (m-PDA) for 2 minutes, this supporting membrane was slowly lifted in the vertical direction, the remained aqueous solution was removed from the surface of the supporting membrane by blowing nitrogen from an air nozzle, and then an n-decane solution containing 0.165 wt % of trimesic acid chloride (TMC) at 25 C. was applied such that the surface of the supporting membrane is completely wetted, and left for 1 minute. Subsequently, in order to remove the remained solution from the membrane, this membrane was vertically maintained for liquid removal for 1 minute, and was then cleaned with hot water at 50 C. for 2 minutes to obtain a composite semipermeable membrane.

(29) The obtained composite semipermeable membrane was immersed in an aqueous solution containing 0.2 wt % of sodium nitrite, adjusted to a pH of 3.35 at 35 C., for 1 minute. The adjustment of pH of sodium nitrite was performed by sulfuric acid. Subsequently, the composite semipermeable membrane was immersed in an aqueous solution containing 0.3 wt % of aniline at 35 C. for 1 minute to perform a diazo coupling reaction. Finally, the composite semipermeable membrane was immersed in an aqueous solution containing 0.1 wt % of sodium sulfite at 35 C. for 2 minutes.

(30) As the result of evaluating the membrane performance of the composite semipermeable membrane obtained in this way, membrane permeation flux, solute removal ratio, and boron removal ratio are the values shown in Table 2, respectively. Further, as the result of evaluating the stability and pressure resistance of the composite semipermeable membrane under a high solute concentration condition, permeation flux ratio and boron SP ratio are shown in Table 2. The functional group ratio of the separation functional layer, elemental composition, the weight of the porous supporting layer per unit volume, average impregnation amount, the air flow rate of the substrate, and the difference in fiber orientation degree of the substrate are shown in Table 1, respectively.

Examples 2 to 12

(31) Each composite semipermeable membrane was fabricated in the same manner as in Example 1, except for the conditions given in Table 1 and Table 2. As the result of evaluating the obtained composite semipermeable membrane, the performances thereof are given in Table 1 and Table 2.

Example 13

(32) The composite semipermeable membrane obtained in Example 6 was immersed in an aqueous solution containing 0.1 ppm of polyethylene glycol (number average molecular weight: 8,000, manufactured by Wako Pure Chemical Industries, Ltd.) for 1 hour to obtain a composite semipermeable membrane of Example 13. As the result of evaluating the obtained composite semipermeable membrane, the performances thereof are given in Table 1 and Table 2.

Example 14

(33) The composite semipermeable membrane obtained in Example 6 was immersed in an aqueous solution containing 1 ppm of polyethylene glycol (number average molecular weight: 8,000, manufactured by Wako Pure Chemical Industries, Ltd.) for 1 hour to obtain a composite semipermeable membrane of Example 14. As the result of evaluating the obtained composite semipermeable membrane, the performances thereof are given in Table 1 and Table 2. As the result of measuring the stability of the composite semipermeable membrane under a high solute concentration condition and then performing the analysis of the surface of the separation functional layer according to TOF-SIMS, a polyethylene glycol-derived peak (.sup.45C.sub.2H.sub.5O.sup.+) was detected in addition to a crosslinked wholly aromatic polyamide-derived benzene ring peak (.sup.75C.sub.6H.sub.3.sup.+.

Example 15

(34) The composite semipermeable membrane obtained in Example 6 was immersed in an aqueous solution containing 1,000 ppm of polyethylene glycol (number average molecular weight: 8,000, manufactured by Wako Pure Chemical Industries, Ltd.) for 1 hour to obtain a composite semipermeable membrane of Example 15. As the result of evaluating the obtained composite semipermeable membrane, the performances thereof are given in Table 1 and Table 2. As the result of measuring the stability of the composite semipermeable membrane under a high solute concentration condition and then performing the analysis of the surface of the separation functional layer according to TOF-SIMS, a polyethylene glycol-derived peak (.sup.45C.sub.2H.sub.5O.sup.+) was detected in addition to a crosslinked wholly aromatic polyamide-derived benzene ring peak (.sup.75C.sub.5H.sub.3.sup.+).

Example 16

(35) The composite semipermeable membrane obtained in Example 6 was immersed in an aqueous solution containing 10,000 ppm of polyethylene glycol (number average molecular weight: 8,000, manufactured by Wako Pure Chemical Industries, Ltd.) for 1 hour to obtain a composite semipermeable membrane of Example 16. As the result of evaluating the obtained composite semipermeable membrane, the performances thereof are given in Table 1 and Table 2. As the result of measuring the stability of the composite semipermeable membrane under a high solute concentration condition and then performing the analysis of the surface of the separation functional layer according to TOF-SIMS, a polyethylene glycol-derived peak (.sup.45C.sub.2H.sub.5O.sup.+) was detected in addition to a crosslinked wholly aromatic polyamide-derived benzene ring peak (.sup.75C.sub.6H.sub.3.sup.+).

Example 17

(36) The composite semipermeable membrane obtained in Example 6 was immersed in an aqueous solution containing 1 ppm of polyethylene glycol (number average molecular weight: 2,000, manufactured by Wako Pure Chemical Industries, Ltd.) for 1 hour to obtain a composite semipermeable membrane of Example 17. As the result of evaluating the obtained composite semipermeable membrane, the performances thereof are given in Table 1 and Table 2. As the result of measuring the stability of the composite semipermeable membrane under a high solute concentration condition and then performing the analysis of the surface of the separation functional layer according to TOF-SIMS, a polyethylene glycol-derived peak (.sup.45C.sub.2H.sub.5O.sup.+) was detected in addition to a crosslinked wholly aromatic polyamide-derived benzene ring peak (.sup.75C.sub.6H.sub.3.sup.+).

Example 18

(37) The composite semipermeable membrane obtained in Example 6 was immersed in an aqueous solution containing 1 ppm of polyethylene glycol (number average molecular weight: 400, manufactured by Wako Pure Chemical Industries, Ltd.) for 1 hour to obtain a composite semipermeable membrane of Example 18. As the result of evaluating the obtained composite semipermeable membrane, the performances thereof are given in Table 1 and Table 2.

Example 19

(38) The composite semipermeable membrane obtained in Example 6 was immersed in an aqueous solution containing 1 ppm of Pluronic F-127 (manufactured by Sigma-Aldrich Co., Ltd.) for 1 hour to obtain a composite semipermeable membrane of Example 19. As the result of evaluating the obtained composite semipermeable membrane, the performances thereof are given in Table 1 and Table 2. As the result of measuring the stability of the composite semipermeable membrane under a high solute concentration condition and then performing the analysis of the surface of the separation functional layer according to TOF-SIMS, a polyethylene glycol-derived peak (.sup.45C.sub.2H.sub.5O.sup.+) was detected in addition to a crosslinked wholly aromatic polyamide-derived benzene ring peak (.sup.75C.sub.6H.sub.3.sup.+).

Example 20

(39) The composite semipermeable membrane obtained in Example 6 was immersed in an aqueous solution containing 1 ppm of polyacrylic acid (number average molecular weight: 25,000, manufactured by Wako Pure Chemical Industries. Ltd.) for 1 hour to obtain a composite semipermeable membrane of Example 20. As the result of evaluating the obtained composite semipermeable membrane, the performances thereof are given in Table 1 and Table 2.

Comparative Examples 1 to 3

(40) Each composite semipermeable membrane was fabricated in the same manner as in Example 1, except that the conditions given in Tables 1 and 2 were changed.

(41) In Comparative Example 1, treatment with an aqueous solution of sodium nitrite and a diazo coupling reaction were not carried out. As the result of evaluating the obtained composite semipermeable membrane, the performances thereof are given in Table 1 and Table 2.

Comparative Example 4

(42) A composite semipermeable membrane was fabricated in the same manner as in Example 1, except that diazo coupling reaction conditions were changed. That is, a composite semipermeable membrane was previously immersed in an aqueous solution containing 0.3% of m-PDA at 35 C. for 1 minute, and then was immersed in an aqueous solution containing 0.2 wt % of sodium nitrite, adjusted to a pH of 3.35 at 35 C., for 1 minute. As the result of evaluating the obtained composite semipermeable membrane, the performances thereof are given in Table 1 and Table 2.

(43) TABLE-US-00001 TABLE 1 Substrate Separation functional layer Difference Phenolic Porous supporting layer in fiber Carboxy hydroxyl Oxygen atoms/ Weight Average Sites of 1.2 orientation group/ group/ nitrogen PSf per unit impregnation times or degree of amide group amide group atoms concentration volume amount more kind Air flow rate substrate Table 1 () () () (%) (g/cm.sup.3) (g/cm.sup.3) (%) () (mL/cm.sup.2/sec) (degree) Ex. 1 0.41 0.06 0.93 18.0 0.60 1.9 22 long fiber 2.0 21 Ex. 2 0.46 0.07 0.89 18.0 0.62 1.8 22 long fiber 2.0 23 Ex. 3 0.45 0.09 0.92 15.7 0.78 2.4 16 long fiber 2.0 23 Ex. 4 0.46 0.05 0.81 18.0 0.63 2.0 20 long fiber 2.0 24 Ex. 5 0.41 0.10 0.95 18.0 0.59 2.0 24 long fiber 2.0 21 Ex. 6 0.47 0.07 0.87 18.0 0.62 1.8 22 long fiber 2.0 20 Ex. 7 0.45 0.09 0.88 15.7 0.80 2.4 16 long fiber 2.0 22 Ex. 8 0.42 0.06 0.82 18.0 0.55 2.0 20 long fiber 2.0 24 Ex. 9 0.42 0.09 0.93 18.0 0.72 0.7 10 short fiber 0.4 Ex. 10 0.44 0.10 0.94 15.7 0.84 2.3 16 long fiber 2.0 20 Ex. 11 0.49 0.08 0.90 24.0 0.59 0.9 20 long fiber 2.0 25 Ex. 12 0.49 0.10 0.84 18.0 0.62 1.8 22 long fiber 2.0 20 Ex. 13 0.47 0.07 0.87 18.0 0.62 1.8 22 long fiber 2.0 20 Ex. 14 0.47 0.07 0.87 18.0 0.62 1.8 22 long fiber 2.0 20 Ex. 15 0.47 0.07 0.87 18.0 0.62 1.8 22 long fiber 2.0 20 Ex. 16 0.47 0.07 0.87 18.0 0.62 1.8 22 long fiber 2.0 20 Ex. 17 0.47 0.07 0.87 18.0 0.62 1.8 22 long fiber 2.0 20 Ex. 18 0.47 0.07 0.87 18.0 0.62 1.8 22 long fiber 2.0 20 Ex. 19 0.47 0.07 0.87 18.0 0.62 1.8 22 long fiber 2.0 20 Ex. 20 0.47 0.07 0.87 18.0 0.62 1.8 22 long fiber 2.0 20 Comp. 0.45 0.01 1.02 18.0 0.60 2.0 22 long fiber 2.0 26 Ex. 1 Comp. 0.39 0.15 1.05 18.0 0.60 2.1 22 long fiber 2.0 24 Ex. 2 Comp. 0.39 0.14 1.03 18.0 0.58 2.0 20 long fiber 2.0 23 Ex. 3 Comp. 0.36 0.16 1.12 18.0 0.63 2.0 22 long fiber 2.0 25 Ex. 4

(44) TABLE-US-00002 TABLE 2 m-PDA TMC Nitrous acid Coupling Coupling concentration concentration concentration compound concentration Table 2 (%) (%) (%) () (%) Ex. 1 5.5 0.165 0.2 aniline 0.3 Ex. 2 5.5 0.165 0.4 aniline 0.3 Ex. 3 5.5 0.165 0.4 aniline 0.3 Ex. 4 5.5 0.165 0.4 aniline 1.0 Ex. 5 5.5 0.165 0.2 m-PDA 0.3 Ex 6 5.5 0.165 0.4 m-PDA 0.3 Ex. 7 5.5 0.165 0.4 m-PDA 0.3 Ex. 8 5.5 0.165 0.4 m-PDA 1.0 Ex. 9 5.5 0.165 0.4 m-PDA 0.3 Ex. 10 5.5 0.165 0.4 m-PDA 0.3 Ex. 11 5.5 0.165 0.4 m-PDA 0.3 Ex. 12 5.5 0.165 0.4 diamino-pyridine 0.3 Ex. 13 5.5 0.165 0.4 m-PDA 0.3 Ex. 14 5.5 0.165 0.4 m-PDA 0.3 Ex. 15 5.5 0.165 0.4 m-PDA 0.3 Ex. 16 5.5 0.165 0.4 m-PDA 0.3 Ex. 17 5.5 0.165 0.4 m-PDA 0.3 Ex. 18 5.5 0.165 0.4 m-PDA 0.3 Ex. 19 5.5 0.165 0.4 m-PDA 0.3 Ex. 20 5.5 0.165 0.4 m-PDA 0.3 Comp. 5.5 0.165 Ex. 1 Comp. 5.5 0.165 0.4 aniline 0.05 Ex. 2 Comp. 5.5 0.165 0.4 m-PDA 0.05 Ex. 3 Comp. 5.5 0.165 0.4 Ex. 4 Stability under high Membrane performance (5.5 MPa) solute concentration Pressure resistance Membrane Solute Boron condition Boron permeation removal removal Permeation Boron SP Permeation SP flux ratio ratio flux ratio ratio flux ratio ratio Table 2 (m.sup.3/m.sup.2/d) (%) (%) () () () () Ex. 1 1.28 99.7 90.4 1.18 1.20 0.86 1.04 Ex. 2 1.21 99.8 91.9 1.08 1.11 0.88 1.01 Ex. 3 1.19 99.8 92.3 1.12 1.18 0.72 1.44 Ex. 4 0.88 99.8 94.5 1.04 1.09 0.89 1.05 Ex. 5 1.14 99.7 92.0 1.19 1.22 0.89 1.01 Ex 6 0.99 99.8 93.7 1.07 1.10 0.87 1.05 Ex. 7 1.02 99.8 93.4 1.13 1.17 0.70 1.42 Ex. 8 0.80 99.8 95.2 1.05 1.07 0.85 1.03 Ex. 9 0.88 99.8 93.9 1.14 1.18 0.70 1.35 Ex. 10 1.05 99.7 91.5 1.10 1.22 0.73 1.40 Ex. 11 0.78 99.8 94.8 1.09 1.15 0.90 1.06 Ex. 12 1.03 99.7 93.2 1.13 1.18 0.88 1.05 Ex. 13 0.97 99.8 93.9 1.05 1.08 0.86 1.07 Ex. 14 0.91 99.8 95.0 1.03 1.05 0.89 1.05 Ex. 15 0.86 99.8 95.2 1.03 1.05 0.88 1.06 Ex. 16 0.80 99.8 95.4 1.02 1.05 0.85 1.09 Ex. 17 0.94 99.8 94.3 1.05 1.09 0.88 1.07 Ex. 18 1.00 99.8 93.7 1.07 1.12 0.86 1.06 Ex. 19 0.90 99.8 95.2 1.03 1.05 0.88 1.07 Ex. 20 1.01 99.8 93.3 1.05 1.09 0.87 1.08 Comp. 0.90 99.7 90.1 1.29 1.33 0.83 1.02 Ex. 1 Comp. 1.25 99.6 88.2 1.30 1.41 0.85 1.06 Ex. 2 Comp. 1.22 99.6 88.7 1.28 1.36 0.86 1.07 Ex. 3 Comp. 0.82 99.8 94.4 1.33 1.44 0.80 1.09 Ex. 4

(45) From Table 1 and Table 2, it has been found that the composite semipermeable membranes of Examples 1 to 20, in each which the functional group ratio of the polyamide separation functional layer and the ratio of oxygen/nitrogen are controlled, have higher membrane performance stability under a high solute concentration condition than the composite semipermeable membranes of Comparative Examples 1 to 4. Further, it has been found that, by using a long-fiber nonwoven fabric having a large fiber orientation degree difference as a substrate and using a porous supporting layer in which the weight thereof per unit volume was controlled, a composite semipermeable membrane having high pressure resistance can be obtained.

(46) While the invention has been described in detail and with reference to specific embodiments thereof it will be apparent to one skilled in the art that various changes and modifications can be made without departing from the spirit and scope thereof. This application is based on Japanese Patent Application filed on Feb. 28, 2013 (Application No. 2013-039649), the content thereof being incorporated herein by reference.

INDUSTRIAL APPLICABILITY

(47) The composite semipermeable membrane according to the present invention can be suitably used for desalination of brackish water or seawater.