JP2010234284A - Composite semipermeable membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite semipermeable membrane usable for selective separation of a liquid mixture and having high acid resistance. <P>SOLUTION: The composite semipermeable membrane is manufactured by forming a polyamide separation-functional layer formed by polycondensing a multiple functional amine with a polyfunctional oxyhalide on a microporous supporting film, and thereafter carrying out processing for allowing the composite semipermeable membrane to contact a cyclic sulfuric ester. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a composite semipermeable membrane useful for the selective separation of liquid mixtures. The composite semipermeable membrane obtained by the present invention can be suitably used for desalination of seawater and brine, for example.

  Regarding the separation of mixtures, there are various techniques for removing substances (eg, salts) dissolved in a solvent (eg, water), but in recent years, the use of membrane separation methods has expanded as a process for saving energy and resources. is doing. Membranes used in membrane separation methods include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes. These membranes can be used for beverages such as seawater, brine, and water containing harmful substances. It is used to obtain water, to manufacture industrial ultrapure water, to treat wastewater, to recover valuable materials.

  The majority of currently marketed reverse osmosis membranes and nanofiltration membranes are composite semipermeable membranes, which have an active layer in which a gel layer and a polymer are crosslinked on a porous support membrane, and monomers on the porous support membrane. There are two types, one having an active layer obtained by polycondensation. Especially, the composite semipermeable membrane obtained by coat | covering the isolation | separation functional layer which consists of crosslinked polyamide obtained by the polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide on a porous support membrane (patent documents 1-4) Is widely used as a separation membrane with high permeability and selective separation.

  However, if the composite semipermeable membrane continues to be used, dirt adheres to the membrane surface with the elapsed time of use, and the amount of water produced in the membrane decreases. Therefore, it is necessary to perform backwashing or chemical cleaning with acid after a certain period of operation. Therefore, in order to continue stable operation over a long period of time, a composite semipermeable membrane with little change in membrane performance before and after cleaning with a chemical solution such as acid is desired.

JP-A-55-147106 JP 62-121603 A JP-A-63-218208 JP 2001-79372 A

  An object of this invention is to provide the composite semipermeable membrane which has high acid resistance.

To achieve the above object, the present invention has the following configuration.
(1) After producing a composite semipermeable membrane by forming a polyamide separation functional layer obtained by polycondensation of a polyfunctional amine and a polyfunctional acid halide on a microporous support membrane, A composite semipermeable membrane obtained by performing a treatment in contact with a cyclic sulfate.
(2) The composite semipermeable membrane according to (1), wherein the cyclic sulfate is ethylene glycol cyclic sulfate and / or 1,3-propanediol cyclic sulfate.

  According to the present invention, a composite semipermeable membrane having high acid resistance can be obtained.

  The present invention relates to a composite semipermeable membrane having a polyamide separation functional layer, a step of forming a polyamide separation functional layer on a microporous support membrane by interfacial polycondensation of a polyfunctional amine and a polyfunctional acid halide, and the polyamide A step of bringing the cyclic sulfate solution into contact with the separation functional layer.

  In the present invention, the microporous support membrane is intended to give strength to a separation functional layer that substantially does not have separation performance of ions or the like and has substantial separation performance. The size and distribution of the pores are not particularly limited. For example, the pores have uniform and fine pores or gradually have large pores from the surface on the side where the separation functional layer is formed to the other surface, and the separation functional layer has A support film having a micropore size of 0.1 nm or more and 100 nm or less on the surface to be formed is preferable.

  The material used for the microporous support membrane and the shape thereof are not particularly limited. For example, a porous support reinforced with a base material that is a fabric mainly composed of at least one selected from polyester or aromatic polyamide is used. . As the material for the porous support, polysulfone, cellulose acetate, polyvinyl chloride, or a mixture thereof is preferably used, and it is particularly preferable to use polysulfone having high chemical, mechanical and thermal stability. .

  Specifically, it is preferable to use polysulfone composed of repeating units represented by the following chemical formula because the pore diameter is easy to control and the dimensional stability is high.

  For example, an N, N-dimethylformamide (hereinafter referred to as DMF) solution of the above polysulfone is cast on a densely woven polyester cloth or nonwoven fabric to a certain thickness, and wet coagulated in water. A microporous support membrane having most of the surface with fine pores having a diameter of several tens of nm or less can be obtained.

  The thickness of the microporous support membrane affects the strength of the composite semipermeable membrane and the packing density when it is used as an element. In order to obtain sufficient mechanical strength and packing density, it is preferably in the range of 50 to 300 μm, more preferably in the range of 100 to 250 μm. Moreover, it is preferable that the thickness of a porous support body exists in the range of 10-200 micrometers, More preferably, it exists in the range of 30-100 micrometers.

  The form of the microporous support membrane can be observed with a scanning electron microscope, a transmission electron microscope, or an atomic microscope. For example, when observing with a scanning electron microscope, after peeling off the microporous support from the base material, it is cut by a freeze cleaving method to obtain a sample for cross-sectional observation. The sample is thinly coated with platinum, 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 6 kV. A Hitachi S-900 electron microscope or the like can be used as the high-resolution field emission scanning electron microscope. The film thickness and surface pore diameter of the porous support are determined from the obtained electron micrograph. In addition, the thickness and the hole diameter in this invention mean an average value.

  In the present invention, the polyamide constituting the separation functional layer can be formed by interfacial polycondensation of a polyfunctional amine and a polyfunctional acid halide. Here, it is preferable that at least one of the polyfunctional amine or the polyfunctional acid halide contains a trifunctional or higher functional compound.

  The thickness of the separation functional layer is usually in the range of 0.01 to 1 μm, preferably in the range of 0.1 to 0.5 μm, in order to obtain sufficient separation performance and permeated water amount.

  Here, the polyfunctional amine refers to an amine having at least two primary and / or secondary amino groups in one molecule. For example, two amino groups are any of ortho, meta, and para positions. Aromatic polyfunctional amines such as phenylenediamine, xylylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, etc. Aliphatic amines such as ethylenediamine, propylenediamine, alicyclic polyfunctional amines such as 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, piperazine, 1,3-bispiperidylpropane, 4-aminomethylpiperazine, etc. Can be mentioned. Among them, in view of selective separation, permeability, and heat resistance of the membrane, it is preferably an aromatic polyfunctional amine having 2 to 4 primary and / or secondary amino groups in one molecule. As the polyfunctional aromatic amine, m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene are preferably used. Among these, it is more preferable to use m-phenylenediamine (hereinafter referred to as m-PDA) from the standpoint of availability and ease of handling. These polyfunctional amines may be used alone or in combination of two or more.

  The polyfunctional acid halide refers to an acid halide having at least two carbonyl halide groups in one molecule. Examples of trifunctional acid halides include trimesic acid chloride, 1,3,5-cyclohexanetricarboxylic acid trichloride, 1,2,4-cyclobutanetricarboxylic acid trichloride, and bifunctional acid halides include biphenyl dicarboxylic acid. Aromatic difunctional acid halides such as acid dichloride, azobenzene dicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, naphthalene dicarboxylic acid chloride, aliphatic difunctional acid halides such as adipoyl chloride, sebacoyl chloride, cyclopentane Examples thereof include alicyclic difunctional acid halides such as dicarboxylic acid dichloride, cyclohexane dicarboxylic acid dichloride, and tetrahydrofuran dicarboxylic acid dichloride. Considering the reactivity with the polyfunctional amine, the polyfunctional acid halide is preferably a polyfunctional acid chloride, and considering the selective separation property and heat resistance of the membrane, 2 to 4 per molecule. The polyfunctional aromatic acid chloride having a carbonyl chloride group is preferred. Among them, it is more preferable to use trimesic acid chloride from the viewpoint of easy availability and easy handling. These polyfunctional acid halides may be used alone or in combination of two or more.

  Next, the manufacturing method of the composite semipermeable membrane of this invention is demonstrated.

  The separation functional layer in the composite semipermeable membrane uses, for example, an aqueous solution containing the aforementioned polyfunctional amine and a water-immiscible organic solvent solution containing a polyfunctional acid halide, and a microporous support membrane. The skeleton can be formed by interfacial polycondensation on the surface.

  Here, the concentration of the polyfunctional amine in the polyfunctional amine aqueous solution is preferably in the range of 0.1 to 20% by weight, more preferably in the range of 0.5 to 15% by weight. In this range, sufficient salt removal performance and water permeability can be obtained. As long as the polyfunctional amine aqueous solution does not interfere with the reaction between the polyfunctional amine and the polyfunctional acid halide, a surfactant, an organic solvent, an alkaline compound, an antioxidant, or the like may be contained. The surfactant has the effect of improving the wettability of the microporous support membrane surface and reducing the interfacial tension between the aqueous amine solution and the nonpolar solvent. The organic solvent may act as a catalyst for the interfacial polycondensation reaction, and when added, the interfacial polycondensation reaction may be efficiently performed.

  In order to perform interfacial polycondensation on the microporous support membrane, first, the above-mentioned polyfunctional amine aqueous solution is brought into contact with the microporous support membrane. The contact is preferably performed uniformly and continuously on the surface of the microporous support membrane. Specific examples include a method of coating a polyfunctional amine aqueous solution on a microporous support membrane and a method of immersing the microporous support membrane in a polyfunctional amine aqueous solution. The contact time between the microporous support membrane and the polyfunctional amine aqueous solution is preferably within a range of 1 to 10 minutes, and more preferably within a range of 1 to 3 minutes.

  After bringing the polyfunctional amine aqueous solution into contact with the microporous support membrane, the solution is sufficiently drained so that no droplets remain on the membrane. By sufficiently draining the liquid, it is possible to prevent the remaining portion of the liquid droplet from becoming a film defect after the film is formed and deteriorating the film performance. As a method for draining, for example, as described in JP-A-2-78428, the microporous support membrane after contacting with the polyfunctional amine aqueous solution is vertically gripped to allow the excess aqueous solution to flow down naturally. A method or a method of forcibly draining an air stream such as nitrogen from an air nozzle can be used. In addition, after draining, the membrane surface can be dried to partially remove water from the aqueous solution.

  Next, an organic solvent solution containing a polyfunctional acid halide is brought into contact with the microporous support membrane after contact with the polyfunctional amine aqueous solution, and a skeleton of the crosslinked polyamide separation functional layer is formed by interfacial polycondensation.

  The concentration of the polyfunctional acid halide in the organic solvent solution is preferably in the range of 0.01 to 10% by weight, and more preferably in the range of 0.02 to 2.0% by weight. This is because a sufficient reaction rate can be obtained when the content is 0.01% by weight or more, and the occurrence of side reactions can be suppressed when the content is 10% by weight or less. Further, it is more preferable to include an acylation catalyst such as DMF in the organic solvent solution, since interfacial polycondensation is promoted.

  The organic solvent is preferably immiscible with water and dissolves the polyfunctional acid halide and does not break the microporous support membrane, and is inert to the polyfunctional amine compound and the polyfunctional acid halide. If there is something. Preferred examples include hydrocarbon compounds such as n-hexane, n-octane, and n-decane.

  The method for contacting the polyfunctional acid halide organic solvent solution with the polyfunctional amine compound aqueous solution phase may be the same as the method for coating the polyfunctional amine aqueous solution on the microporous support membrane.

  As described above, after interfacial polycondensation is performed by contacting an organic solvent solution of a polyfunctional acid halide to form a separation functional layer containing a crosslinked polyamide on a microporous support membrane, excess solvent is drained off. Good. As a method for draining, for example, a method in which a film is held in a vertical direction and excess organic solvent is allowed to flow down and removed can be used. In this case, the time for gripping in the vertical direction is preferably 1 to 5 minutes, more preferably 1 to 3 minutes. If it is too short, the separation functional layer will not be completely formed, and if it is too long, the organic solvent will be overdried and defects will easily occur and performance will be deteriorated.

  The composite semipermeable membrane obtained by the above method is subjected to a hydrothermal treatment step in the range of 40 to 100 ° C., preferably in the range of 60 to 100 ° C. for 1 to 10 minutes, more preferably 2 to 8 minutes. By adding, the solute blocking performance and water permeability of the composite semipermeable membrane can be further improved.

  Next, in this invention, cyclic sulfate is made to contact the composite semipermeable membrane after manufacture. The method of contacting is not particularly limited. For example, the entire composite semipermeable membrane may be immersed in a cyclic sulfate solution, or the solution may be sprayed on the surface of the composite semipermeable membrane. The method is not limited as long as it contacts the cyclic sulfate.

  The sulfate ester must be cyclic, and examples of the alcohol to be condensed include ethylene glycol, 1,3-propanediol, 1,4-butanediol, diethylene glycol, cyclohexane-1,2-diol, and the like. Among these, ethylene glycol or 1,3-propanediol is preferable. That is, among the cyclic sulfates, ethylene glycol cyclic sulfate and / or 1,3-propanediol cyclic sulfate are preferable.

  It is known that an aromatic amino group is alkylated by a reaction between a sulfate ester and an aromatic amine. Therefore, in the present invention, it is presumed that the cyclic sulfate ester reacts with the unreacted amino terminus in the polyamide separation functional layer, and the unreacted amino terminus in the polyamide separation functional layer is crosslinked by the cyclic sulfate. It is speculated that it can.

  As a result of the reaction between the cyclic sulfate ester and the unreacted amino terminal in the polyamide separation functional layer, sulfuric acid is generated, so that the reaction is continued and the sulfuric acid generated by the reaction is increased in order to increase the reaction rate of the reaction. Is preferably neutralized. Therefore, the pH in the system is adjusted to basic by, for example, containing a base of 2 equivalents or more of the cyclic sulfate in the reaction system between the cyclic sulfate and the unreacted amino terminal in the polyamide separation functional layer. It is desirable to keep it. The base used here is not particularly limited as long as it can neutralize sulfuric acid generated by the reaction, and is sodium carbonate, sodium hydrogen carbonate, sodium acetate, tripotassium phosphate, disodium hydrogen phosphate, triethylamine, Diisopropylethylamine and the like can be used. Further, from the viewpoint of efficiently performing the reaction, in the present invention, an unreacted amino terminus is formed in the polyamide separation functional layer using a solution in which a cyclic sulfate and a base are dissolved in a solvent and the pH is adjusted to basic. The method of making it contact with the composite semipermeable membrane which has is employ | adopted preferably.

  The solvent that can be used here is preferably one that does not destroy the composite semipermeable membrane, and examples thereof include water and organic solvents, and may be a mixed solvent thereof. Of these, water is preferable.

  Furthermore, the composite semipermeable membrane obtained by the above-mentioned method is hydrothermally treated in the range of 40 to 100 ° C., preferably in the range of 60 to 100 ° C. for 1 to 10 minutes, more preferably 2 to 8 minutes. Thus, the solute blocking performance and water permeability of the composite semipermeable membrane can be further improved.

  The composite semipermeable membrane of the present invention formed in this way has a large number of pores together with a raw water channel material such as a plastic net, a permeate channel material such as tricot, and a film for increasing pressure resistance if necessary. Is wound around a cylindrical water collecting pipe and is suitably used as a spiral composite semipermeable membrane element. Furthermore, a composite semipermeable membrane module in which these elements are connected in series or in parallel and accommodated in a pressure vessel can be obtained.

  In addition, the above-described composite semipermeable membrane, its elements, and modules can be combined with a pump that supplies raw water to them, a device that pretreats 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 through the membrane, and water suitable for the purpose can be obtained.

  The higher the operating pressure of the fluid separator, the higher the salt removal rate, but the energy required for operation also increases, and considering the durability of the composite semipermeable membrane, water to be treated is added to the composite semipermeable membrane. The operating pressure at the time of permeation is preferably 1.0 MPa or more and 10 MPa or less. As the feed water temperature rises, the salt removal rate decreases, but as the feed water temperature decreases, the membrane permeation flux also decreases. In addition, when the pH of the feed water becomes high, scales such as magnesium may be generated in the case of feed water with a high salt concentration such as seawater, and there is a concern about deterioration of the membrane due to high pH operation. Is preferred.

  Examples of raw water to be treated by the composite semipermeable membrane according to the present invention include liquid mixtures containing TDS (Total Dissolved Solids) of 500 mg / L to 100 g / L such as seawater, brine, and drainage. . In general, TDS refers to the total dissolved solid content, and is expressed as “mass ÷ volume” or “weight ratio”. According to the definition, the solution filtered through a 0.45 micron filter can be calculated from the weight of the residue by evaporating at a temperature of 39.5 to 40.5 ° C., but more simply converted from practical salt (S) To do.

  The composite semipermeable membrane of the present invention is characterized by having a high acid resistance. As an index of acid resistance, it is appropriate to use resistance to an aqueous sulfuric acid solution at pH 1 as an index. The pH 1 condition is an acidic condition stronger than the pH at the time of acid cleaning in the membrane filtration operation. Therefore, if resistance to a sulfuric acid aqueous solution at pH 1 is exhibited, it is ensured that the membrane is not easily deteriorated even if acid cleaning is performed multiple times. Because.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples.

  Various characteristics of the composite separation membranes in Comparative Examples and Examples are as follows. Seawater (TDS concentration of about 3.5%) adjusted to a temperature of 25 ° C. and pH 6.5 was supplied to the composite semipermeable membrane at an operating pressure of 5.5 MPa. Membrane filtration was performed, and the water quality of the permeated water and the feed water was measured.

(Desalination rate (TDS removal rate))
TDS removal rate (%) = 100 × {1- (TDS concentration in permeated water / TDS concentration in feed water)}
(Membrane permeation flux)
Membrane permeation flux (m ³ / m ² / day) was expressed in terms of the permeation amount of the feed water (seawater) per square meter of the membrane surface with the permeation amount per day (cubic meter).

(Boron removal rate)
The boron concentration in the feed water and the permeated water was analyzed with an ICP emission analyzer (P-4010 manufactured by Hitachi, Ltd.), and obtained from the following formula.
Boron removal rate (%) = 100 × {1− (boron concentration in permeated water / boron concentration in feed water)}
(Acid resistance)
The characteristic ratio of the membrane before and after immersion in the sulfuric acid aqueous solution at pH 1 was determined by the following equation.
TDS SP ratio = (100−TDS removal rate after immersion) / (100−TDS removal rate before immersion)
Membrane permeation flux ratio = membrane permeation flux after immersion / membrane permeation flux boron before immersion SP ratio = (100−boron removal rate after immersion) / (100−boron removal rate before immersion)
Note that SP is an abbreviation for substance permeation.

(Comparative Example 1)
A 15.7 wt% DMF solution of polysulfone was cast on a polyester nonwoven fabric (air permeability 0.5 to 1 cc / cm ² / sec) at a room temperature (25 ° C.) with a thickness of 200 μm, and immediately immersed in pure water 5 A microporous support membrane was prepared by leaving for a minute.

  The microporous support membrane (thickness 210 to 215 μm) thus obtained was immersed in a 3.8% by weight aqueous solution of m-PDA for 2 minutes, the support membrane was slowly pulled up in the vertical direction, and air Nitrogen was blown from the nozzle to remove excess aqueous solution from the surface of the support membrane, and then an n-decane solution containing 0.175% by weight of trimesic acid chloride was applied so that the surface was completely wetted and allowed to stand for 1 minute. Next, in order to remove excess solution from the membrane, the membrane was held vertically for 1 minute and drained. Then, it wash | cleaned for 2 minutes with 90 degreeC hot water, and obtained the composite semipermeable membrane. The composite semipermeable membrane thus obtained was evaluated, and the membrane permeation flux, TDS removal rate, and boron removal rate were the values shown in Table 1, respectively.

  Furthermore, in order to evaluate the acid resistance of the composite semipermeable membrane, the obtained composite semipermeable membrane was immersed in an aqueous sulfuric acid solution adjusted to pH 1 for 13 days. After immersion, the composite semipermeable membrane was washed with RO water. When the composite semipermeable membrane after immersion was evaluated, the membrane permeation flux, TDS removal rate, and boron removal rate after immersion in the sulfuric acid aqueous solution were the values shown in Table 1, respectively. The membrane permeation flux ratio, TDS SP ratio, and boron SP ratio are also shown in Table 1.

(Comparative Example 2)
As in Comparative Example 1, after preparing a composite semipermeable membrane, the composite semipermeable membrane was immersed in an aqueous solution of 20 mM dimethyl sulfate and 40 mM sodium acetate for 24 hours. The membrane was washed with RO water and then with hot water at 95 ° C. for 2 minutes.

  When the obtained composite semipermeable membrane was evaluated, the membrane permeation flux, TDS removal rate, and boron removal rate were the values shown in Table 1, respectively.

  Furthermore, in order to evaluate the acid resistance of the composite semipermeable membrane, the obtained composite semipermeable membrane was immersed in an aqueous sulfuric acid solution adjusted to pH 1 for 13 days. After immersion, the substrate was washed with RO water. When the composite semipermeable membrane after immersion was evaluated, the membrane permeation flux, TDS removal rate, and boron removal rate after immersion in the sulfuric acid aqueous solution were the values shown in Table 1, respectively. The membrane permeation flux ratio, TDSSP ratio, and boron SP ratio are also shown in Table 1.

(Comparative Example 3)
A membrane was prepared by the same process as in Comparative Example 2, except that diethyl sulfate was used instead of dimethyl sulfate.

  When the obtained composite semipermeable membrane was evaluated, the membrane permeation flux, TDS removal rate, and boron removal rate were the values shown in Table 1, respectively.

  Furthermore, in order to evaluate the acid resistance of the composite semipermeable membrane, the obtained composite semipermeable membrane was immersed in an aqueous sulfuric acid solution adjusted to pH 1 for 13 days. After immersion, the substrate was washed with RO water. When the composite semipermeable membrane after immersion was evaluated, the membrane permeation flux, TDS removal rate, and boron removal rate after immersion in the sulfuric acid aqueous solution were the values shown in Table 1, respectively. The membrane permeation flux ratio, TDS SP ratio, and boron SP ratio are also shown in Table 1.

Example 1
A membrane was produced in the same manner as in Comparative Example 2 except that ethylene glycol cyclic sulfate was used instead of dimethyl sulfate.

  When the obtained composite semipermeable membrane was evaluated, the membrane permeation flux, TDS removal rate, and boron removal rate were the values shown in Table 1, respectively.

  Furthermore, in order to evaluate the acid resistance of the composite semipermeable membrane, the obtained composite semipermeable membrane was immersed in an aqueous sulfuric acid solution adjusted to pH 1 for 13 days. After immersion, the substrate was washed with RO water. When the composite semipermeable membrane after immersion was evaluated, the membrane permeation flux, TDS removal rate, and boron removal rate after immersion in the sulfuric acid aqueous solution were the values shown in Table 1, respectively. The membrane permeation flux ratio, TDS SP ratio, and boron SP ratio are also shown in Table 1.

(Example 2)
A membrane was prepared by the same process as in Comparative Example 2, except that 1,3-propanediol cyclic sulfate was used instead of dimethyl sulfate.

  When the obtained composite semipermeable membrane was evaluated, the membrane permeation flux, TDS removal rate, and boron removal rate were the values shown in Table 1, respectively.

  Furthermore, in order to evaluate the acid resistance of the composite semipermeable membrane, the obtained composite semipermeable membrane was immersed in an aqueous sulfuric acid solution adjusted to pH 1 for 13 days. After immersion, the substrate was washed with RO water. When the composite semipermeable membrane after immersion was evaluated, the membrane permeation flux, TDS removal rate, and boron removal rate after immersion in the sulfuric acid aqueous solution were the values shown in Table 1, respectively. The membrane permeation flux ratio, TDS SP ratio, and boron SP ratio are also shown in Table 1.

  As described above, the composite semipermeable membrane obtained by the present invention has smaller membrane permeation flow rate ratio, TDS SP ratio, and boron SP ratio than the cyclic sulfate ester untreated membrane before and after being immersed in the sulfuric acid solution at pH 1. Small change in membrane performance. Further, the membrane permeation flow rate ratio, the TDS SP ratio, and the boron SP ratio are smaller than those of the non-cyclic sulfate-treated membrane, and the change in membrane performance is small. Therefore, the composite semipermeable membrane obtained by the present invention has high acid resistance.

  The composite semipermeable membrane of the present invention can be particularly suitably used for brine or seawater desalination.

Claims (2)

  A composite semipermeable membrane is produced by forming a polyamide separation functional layer formed by polycondensation of a polyfunctional amine and a polyfunctional acid halide on a microporous support membrane, and then the composite semipermeable membrane is converted to a cyclic sulfate. The composite semipermeable membrane obtained by performing the process made to contact.   The composite semipermeable membrane according to claim 1, wherein the cyclic sulfate is ethylene glycol cyclic sulfate and / or 1,3-propanediol cyclic sulfate.