JP2008259983A - Manufacturing method of dry composite semi-permeable membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a dry composite semi-permeable membrane having high resistance against alkaline washing liquid, small variation in permeation flow bundle and salt preventive ratio before and after the membrane washing, and to provide the dry composite semi-permeable membrane obtained by the manufacturing method. <P>SOLUTION: The manufacturing method of a dry composite semi-permeable membrane comprises processes of: forming an undried skin layer containing polyamide-based resin formed by reacting a multi-functional amine component with a multi-functional acid halide component, on the surface of a porous support body; spraying gas multi-stagedly onto the undried skin layer and removing surplus solution; and drying the undried skin layer at 90-140°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a composite semipermeable membrane comprising a skin layer containing a polyamide-based resin and a porous support for supporting the skin layer. Such a composite semipermeable membrane is suitable for production of ultrapure water, desalination of brine or seawater, etc., and it is also a source of contamination contained in it due to contamination that causes pollution such as dye wastewater and electrodeposition paint wastewater. Alternatively, effective substances can be removed and recovered, contributing to the closure of wastewater. Moreover, it can be used for advanced treatments such as concentration of active ingredients in food applications and removal of harmful components in water purification and sewage applications.

  Conventionally, a composite semipermeable membrane formed by forming a thin film having substantially selective separation on a porous support is known. As such a composite semipermeable membrane, a skin layer made of a polyamide obtained by interfacial polymerization of a polyfunctional aromatic amine and a polyfunctional aromatic acid halide is formed on a support. Patent Documents 1 to 4). The composite semipermeable membrane has high desalting performance and water permeation performance, and has high blocking performance against ionic substances, but the permeate flow rate is low and higher permeation flux is desired. It was rare.

  A technique for adding an amine salt to a thin film for the purpose of achieving a high permeation flux is disclosed (Patent Document 5). The produced composite semipermeable membrane is desired to be a dry composite semipermeable membrane from the viewpoint of subsequent processability and storage stability. However, in the method described in Patent Document 5, when the thin film is dried, the amine that forms the amine salt evaporates, and the salt-blocking performance and permeation flux decrease compared to before drying, and the durability against chemical cleaning agents. There was a problem that decreased.

  In addition, for the purpose of obtaining a composite semipermeable membrane having high reverse osmosis performance, the temperature is lower than the flash point of the hydrocarbon solvent used on the surface of the crosslinked polyamide-based ultrathin film in the range of 10 to 80 ° C. And a method of spraying a gas having a moisture content of 1 g or more per kg of dry gas and evaporating the remaining hydrocarbon solvent is disclosed (Patent Document 6).

  Moreover, the technique of carrying out the hot water process of the composite semipermeable membrane after a drying process is disclosed for the purpose of the boron performance improvement (patent document 7). Also, a technique for bringing the composite semipermeable membrane after the drying treatment into contact with an alkaline aqueous solution such as sodium carbonate, hot water, or a chlorine-containing aqueous solution for the purpose of improving the solute exclusion performance of the membrane and improving the water permeability is disclosed. (Patent Document 8).

  Further, if the composite semipermeable membrane is continuously used, the membrane is gradually contaminated. Therefore, it is necessary to clean the membrane with an alkaline aqueous solution. However, the conventional composite semipermeable membrane has a problem that the permeation flux gradually increases or the salt blocking performance decreases when the membrane cleaning is repeated. If the permeation flux increases significantly, it is necessary to lower the pressure in the actual water production operation, so that the operation becomes complicated and the salt rejection rate tends to decrease. Therefore, a composite semipermeable membrane with little change in permeation flux and salt rejection before and after membrane cleaning has been desired.

JP-A-55-147106 JP 62-121603 A JP-A-63-218208 JP 2001-79372 A Japanese Patent Publication No. 6-73617 Japanese Patent Laid-Open No. 5-76740 JP-A-11-19493 JP 2002-177750 A

  An object of the present invention is to provide a method for producing a dry composite semipermeable membrane having high resistance to an alkaline cleaning solution and little change in permeation flux and salt rejection before and after membrane cleaning. Moreover, it is providing the dry composite semipermeable membrane obtained by this manufacturing method.

  As a result of intensive studies to achieve the above object, the present inventors have obtained a dry composite semipermeable membrane that has high resistance to an alkaline cleaning solution by the following method and has little change in permeation flux and salt rejection before and after membrane cleaning. Has been found to be able to be produced, and the present invention has been completed.

  That is, the present invention provides a process for forming an undried skin layer containing a polyamide-based resin obtained by reacting a polyfunctional amine component and a polyfunctional acid halide component on the surface of the porous support, a gas on the undried skin layer. The method of manufacturing a dry composite semipermeable membrane including a spraying step of spraying a plurality of steps to remove excess solution and a drying step of drying an undried skin layer at 90 to 140 ° C.

  The method for producing a dry composite semipermeable membrane according to the present invention is characterized in that before the undried skin layer is dried, gas is blown onto the undried skin layer in a multistage manner to gradually remove excess solution. . By gradually removing the excess solution on the undried skin layer, the subsequent interfacial polymerization reaction can be easily controlled. As a result, an excessive reaction between the unreacted polyfunctional acid halide component and the polyfunctional amine component can be suppressed, so that the resistance to the alkaline cleaning liquid is increased, and an increase in permeation flux and a decrease in the salt rejection rate are suppressed. It is done.

  In the drying process of the undried skin layer, the drying temperature needs to be 90 to 140 ° C. When the drying temperature is less than 90 ° C., the evaporation time of the solvent becomes long, so that the polymerization reaction proceeds excessively and the permeation flux of the dry composite semipermeable membrane is lowered. On the other hand, when the temperature exceeds 140 ° C., the film performance deteriorates due to the structural change of the film due to heat.

  In the spraying step, the wind speed of the gas to be sprayed is preferably higher in the second and subsequent stages than in the first stage. It is easy to control the interfacial polymerization reaction by spraying loosely in the first stage of the reaction and spraying more strongly in the second and subsequent stages where the reaction has progressed to some extent.

  In the spraying step, the gas temperature is preferably 10 to 50 ° C. If the temperature is less than 10 ° C, the water vapor becomes a liquid and deactivates the polyfunctional acid halide to hinder the progress of the polymerization reaction. If the temperature exceeds 50 ° C, the solvent is too volatile and the polymerization reaction is insufficient. Tend to be.

  In the spraying step, the gas wind speed is preferably 1 to 30 m / sec. When the wind speed is less than 1 m / sec, the surplus solution cannot be sufficiently removed, so that the effect of the present invention cannot be sufficiently obtained. When the wind speed exceeds 30 m / sec, the surplus solution is almost removed by the first-stage spraying. Therefore, the skin layer is not sufficiently formed, and defects such as pinholes are likely to occur in the skin layer, and the salt blocking performance tends to be lowered.

  In the spraying step, it is preferable that the time for blowing the gas is 0.1 to 10 seconds at each stage. If the spraying time is less than 0.1 seconds, the excess solution cannot be removed sufficiently, so that the effect of the present invention cannot be obtained sufficiently. The rate and permeation flux tend to decrease significantly.

  In the drying step, the drying time is preferably 10 to 300 seconds. When the drying time is less than 10 seconds, the solvent is difficult to evaporate, so that the polymerization reaction proceeds excessively and the permeation flux of the dry composite semipermeable membrane tends to decrease. On the other hand, when the time exceeds 300 seconds, the film performance tends to deteriorate due to the structural change of the film due to heat.

  Moreover, this invention relates to the dry composite semipermeable membrane obtained by the said manufacturing method.

  Embodiments of the present invention will be described below. The method for producing a dry composite semipermeable membrane of the present invention includes a step of forming an undried skin layer containing a polyamide-based resin obtained by reacting a polyfunctional amine component and a polyfunctional acid halide component on the surface of a porous support, It includes a spraying step of spraying gas on the undried skin layer in a multistage manner to remove excess solution, and a drying step of drying the undried skin layer at 90 to 140 ° C.

  The polyfunctional amine component is a polyfunctional amine having two or more reactive amino groups, and examples thereof include aromatic, aliphatic and alicyclic polyfunctional amines.

  Examples of the aromatic polyfunctional amine include m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, and 3,5-diamino. Examples include benzoic acid, 2,4-diaminotoluene, 2,6-diaminotoluene, N, N′-dimethyl-m-phenylenediamine, 2,4-diaminoanisole, amidole, xylylenediamine and the like.

  Examples of the aliphatic polyfunctional amine include ethylenediamine, propylenediamine, tris (2-aminoethyl) amine, N-phenyl-ethylenediamine, and the like.

  Examples of the alicyclic polyfunctional amine include 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, piperazine, 2,5-dimethylpiperazine, 4-aminomethylpiperazine, and the like. .

  These polyfunctional amines may be used alone or in combination of two or more. In order to obtain a skin layer having a high salt inhibition performance, it is preferable to use an aromatic polyfunctional amine.

  The polyfunctional acid halide component is a polyfunctional acid halide having two or more reactive carbonyl groups.

  Examples of the polyfunctional acid halide include aromatic, aliphatic and alicyclic polyfunctional acid halides.

  Examples of the aromatic polyfunctional acid halide include trimesic acid trichloride, terephthalic acid dichloride, isophthalic acid dichloride, biphenyldicarboxylic acid dichloride, naphthalene dicarboxylic acid dichloride, benzenetrisulfonic acid trichloride, benzenedisulfonic acid dichloride, chlorosulfonylbenzene dicarboxylic acid. An acid dichloride etc. are mentioned.

  Examples of the aliphatic polyfunctional acid halide include propanedicarboxylic acid dichloride, butanedicarboxylic acid dichloride, pentanedicarboxylic acid dichloride, propanetricarboxylic acid trichloride, butanetricarboxylic acid trichloride, pentanetricarboxylic acid trichloride, glutaryl halide, adipoid Examples include luhalides.

  Examples of the alicyclic polyfunctional acid halide include cyclopropane tricarboxylic acid trichloride, cyclobutane tetracarboxylic acid tetrachloride, cyclopentane tricarboxylic acid trichloride, cyclopentane tetracarboxylic acid tetrachloride, cyclohexane tricarboxylic acid trichloride, and tetrahydrofuran. Examples thereof include tetracarboxylic acid tetrachloride, cyclopentane dicarboxylic acid dichloride, cyclobutane dicarboxylic acid dichloride, cyclohexane dicarboxylic acid dichloride, and tetrahydrofurandicarboxylic acid dichloride.

  These polyfunctional acid halides may be used alone or in combination of two or more. In order to obtain a skin layer having a high salt inhibition performance, it is preferable to use an aromatic polyfunctional acid halide. Moreover, it is preferable to form a crosslinked structure by using a trifunctional or higher polyfunctional acid halide as at least a part of the polyfunctional acid halide component.

  In order to improve the performance of the skin layer containing a polyamide-based resin, a polymer such as polyvinyl alcohol, polyvinyl pyrrolidone, or polyacrylic acid, a polyhydric alcohol such as sorbitol, glycerin, or the like may be copolymerized.

  The porous support is formed by forming a microporous layer having a substantially separating function on the surface of a substrate. The microporous layer usually has micropores having an average pore diameter of about 10 to 500 mm.

Examples of the substrate include woven fabrics, nonwoven fabrics, mesh nets, and foamed sintered sheets made of polyester, polypropylene, polyethylene, polyamide, and the like. Among these, non-woven fabrics are preferably used from the viewpoint of film forming properties and cost. As the nonwoven fabric, those having a thickness of 0.08 to 0.15 mm and a density of 0.5 to 0.8 g / cm ³ are preferable. When the thickness is less than 0.08 mm or the density is less than 0.5 g / cm ³ , the strength as the reinforcing sheet cannot be obtained, and it tends to be difficult to maintain the back pressure strength of 2 g / cm ² or more. It is in. On the other hand, when the thickness exceeds 0.15 mm or when the density exceeds 0.8 g / cm ³ , the filtration resistance increases, and the anchoring effect of the microporous layer on the nonwoven fabric decreases. Peeling tends to occur easily at the interface with the porous layer.

  Examples of the material for forming the microporous layer include various materials such as polysulfone and polyarylethersulfone such as polyethersulfone, polyimide, and polyvinylidene fluoride, but particularly chemically, mechanically, and thermally. From the viewpoint of stability, polysulfone and polyaryl ether sulfone are preferably used. The thickness of the microporous layer is usually about 25 to 125 μm, preferably about 40 to 75 μm, but is not necessarily limited thereto.

  The method for forming the microporous layer on the substrate surface is not particularly limited, and a conventionally known method can be appropriately employed.

  The method for forming the undried skin layer containing the polyamide-based resin on the surface of the porous support (on the microporous layer) is not particularly limited, and any known method can be used. For example, an interfacial condensation method, a phase separation method, a thin film coating method, and the like can be given. Specifically, the interfacial condensation method comprises forming an undried skin layer by interfacial polymerization by contacting an amine aqueous solution containing a polyfunctional amine component with an organic solution containing a polyfunctional acid halide component, A method of placing a skin layer on a porous support, or a method of directly forming an undried skin layer on the porous support by the interfacial polymerization on the porous support. Details of the conditions of the interfacial condensation method are described in JP-A-58-24303, JP-A-1-180208 and the like, and those known techniques can be appropriately employed.

  In the present invention, an aqueous solution coating layer comprising an aqueous amine solution containing a polyfunctional amine component is formed on a porous support, and then an organic solution containing the polyfunctional acid halide component is contacted with the aqueous solution coating layer to perform interfacial polymerization. The method of forming an undried skin layer by making it preferable is preferable.

  In the interfacial polymerization method, the concentration of the polyfunctional amine component in the aqueous amine solution is not particularly limited, but is preferably 0.1 to 5% by weight, more preferably 0.5 to 2% by weight. When the concentration of the polyfunctional amine component is less than 0.1% by weight, defects such as pinholes are likely to occur in the skin layer, and the salt blocking performance tends to decrease. On the other hand, when the concentration of the polyfunctional amine component exceeds 5% by weight, the polyfunctional amine component is likely to penetrate into the porous support, or the film thickness becomes too thick to increase the permeation resistance and increase the permeation flow. The bundle tends to decrease.

  The concentration of the polyfunctional acid halide component in the organic solution is not particularly limited, but is preferably 0.01 to 5% by weight, and more preferably 0.05 to 3% by weight. If the concentration of the polyfunctional acid halide component is less than 0.01% by weight, the unreacted polyfunctional amine component tends to remain, or defects such as pinholes are likely to occur in the skin layer, resulting in a decrease in salt blocking performance. Tend to. On the other hand, when the concentration of the polyfunctional acid halide component exceeds 5% by weight, the unreacted polyfunctional acid halide component tends to remain, or the film thickness becomes too thick to increase the permeation resistance, thereby increasing the permeation flux. It tends to decrease.

  The organic solvent used in the organic solution is not particularly limited as long as it has low solubility in water, does not deteriorate the porous support, and dissolves the polyfunctional acid halide component. For example, cyclohexane, heptane, octane And saturated hydrocarbons such as nonane, and halogen-substituted hydrocarbons such as 1,1,2-trichlorotrifluoroethane. Preferred is a saturated hydrocarbon having a boiling point of 300 ° C. or lower, more preferably a boiling point of 200 ° C. or lower.

Various additives can be added to the amine aqueous solution and the organic solution for the purpose of facilitating film formation and improving the performance of the resulting composite semipermeable membrane. Examples of the additive include surfactants such as sodium dodecylbenzenesulfonate, sodium dodecylsulfate, and sodium laurylsulfate, sodium hydroxide that removes hydrogen halide generated by polymerization, trisodium phosphate, and triethylamine. And basic compounds, acylation catalysts, compounds having a solubility parameter of 8 to 14 (cal / cm ³ ) ^1/2 described in JP-A-8-224452, and the like.

  In the production method of the present invention, after an undried skin layer is formed on the surface of the porous support by the above method, gas is blown onto the undried skin layer in a multistage manner (in a plurality of times), and surplus It is necessary to gradually remove the solution. In order to fully express the effect of the present invention, it is preferable to blow the gas in two or more stages, more preferably three or more stages. On the other hand, from the viewpoint of the apparatus to be used and the effects, 5 steps or less are preferable.

  The gas to be blown is not particularly limited as long as it does not react with the polyfunctional amine component and the polyfunctional acid halide component, and examples thereof include air, nitrogen, and argon.

  The temperature of the gas used is preferably 10 to 50 ° C, more preferably 15 to 35 ° C. The gas temperature is measured at a position of 10 mm on the undried skin layer.

  The wind speed of the gas sprayed onto the undried skin layer is preferably 1 to 30 m / sec, more preferably 1 to 20 m / sec, and particularly preferably 5 to 15 m / sec. The wind speed of the blowing gas is preferably higher in the second and subsequent stages than in the first stage. Specifically, the wind speed of the first stage gas is preferably 1 to 15 m / sec, more preferably. Is 2 to 10 m / sec. The wind speed after the second stage is preferably increased by about 1 to 5 m / sec than the first stage. The gas wind speed is measured at a position of 10 mm on the undried skin layer.

  The time for blowing the gas is preferably 0.1 to 10 seconds, more preferably 0.5 to 5 seconds at each stage.

  In the present invention, the undried skin layer sprayed by the above method is dried to produce a dry composite semipermeable membrane. Since the dry composite semipermeable membrane of the present invention is a dry type, it is excellent in workability and storage stability.

  When performing a drying process, a semipermeable membrane does not receive a restriction | limiting at all in the shape. That is, it is possible to perform the drying treatment in all conceivable film shapes such as a flat film shape or a spiral shape. For example, the semipermeable membrane may be processed into a spiral shape to produce a membrane unit, and the membrane unit may be dried to produce a dry spiral element.

  The temperature at the time of performing the drying treatment needs to be 90 to 140 ° C, and preferably 90 to 130 ° C.

  The time for performing the drying treatment is preferably 10 to 300 seconds, more preferably 30 to 180 seconds, from the viewpoint of preventing deterioration of the film performance. In particular, it is preferable to dry until the amount of solvent in the semipermeable membrane is 5% by weight or less.

  The drying process is preferably performed in multiple steps (divided into multiple times) under different conditions of drying temperature and drying time. Thereby, the polymerization reaction can be controlled, and a high-performance dry composite semipermeable membrane can be obtained. When drying is performed in two stages, the drying temperature in the first stage is 90 to 130 ° C. and the drying time is 30 to 90 seconds, and the drying temperature in the second stage is 100 to 130 ° C. and the drying time is 30 to 90. Preferably it is seconds.

  The thickness of the skin layer formed on the porous support is not particularly limited, but is usually about 0.05 to 2 μm, preferably 0.1 to 1 μm.

  In order to improve the salt-inhibiting property, water permeability, oxidation resistance, etc. of the dry composite semipermeable membrane or dry spiral element, various conventionally known treatments may be performed.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Production Example 1
(Preparation of porous support)
A film-forming dope in which 18% by weight of polysulfone (manufactured by Solvay, P-3500) was dissolved in N, N-dimethylformamide (DMF) was uniformly applied to a nonwoven fabric substrate with a wet thickness of 200 μm. Then, the porous support body which has a polysulfone microporous layer on a nonwoven fabric base material was produced by solidifying by immediately immersing in 40-50 degreeC water, and completely extracting and wash | cleaning DMF which is a solvent. .

Example 1
A porous amine solution containing 3 parts by weight of m-phenylenediamine, 0.2 parts by weight of sodium lauryl sulfate, 8 parts by weight of camphorsulfonic acid, 4 parts by weight of triethylamine, 10 parts by weight of isopropyl alcohol, and 74.85 parts by weight of water An aqueous solution coating layer was formed by coating on a conductive support. Next, an isooctane solution containing 0.25% by weight of trimesic acid chloride was applied to the surface of the aqueous solution coating layer and subjected to an interfacial polymerization reaction to form an undried skin layer. Then, air having a temperature of 20 ° C. and a wind speed of 5 m / sec was blown on the surface of the undried skin layer for 3 seconds, and then air having a temperature of 20 ° C. and a wind speed of 10 m / sec was further blown for 3 seconds to remove excess solution. Thereafter, the undried composite semipermeable membrane was dried at 130 ° C. for 2 minutes to prepare a dry composite semipermeable membrane.

(Measurement of permeation flux and salt rejection)
The produced dry composite semipermeable membrane is cut into a predetermined shape and size, and set in a flat membrane evaluation cell. An aqueous solution (25 ° C.) containing 1500 mg / L NaCl and adjusted to pH 6.5 with NaOH is brought into contact with the membrane by applying a differential pressure of 1.5 MPa between the supply side and the permeation side of the membrane. The permeation rate and conductivity of the permeated water obtained by this operation were measured, and the permeation flux (m ³ / m ² · d) and the salt rejection (%) were calculated. The salt rejection was calculated in advance using a correlation (calibration curve) between NaCl concentration and aqueous solution conductivity in advance. The results of the transmission test are shown in Table 1.
Salt rejection (%) = {1− (NaCl concentration in the permeate [mg / L]) / (NaCl concentration in the feed liquid [mg / L])} × 100

  Further, after the permeation test, the dried composite semipermeable membrane was immersed in an alkaline cleaning solution (pH: 14, NaOH: 4% by weight, 25 ° C.) for 60 hours. Thereafter, the membrane was immersed and washed in ultrapure water (20 ° C.) for 60 minutes, and a permeation test was performed again in the same manner as described above. The results of the transmission test are shown in Table 1.

Comparative Example 1
An undried skin layer was formed in the same manner as in Example 1. Thereafter, air having a temperature of 20 ° C. and a wind speed of 5 m / sec was blown onto the surface of the undried skin layer for 3 seconds to remove excess solution. Thereafter, the undried composite semipermeable membrane was dried at 30 ° C. for 10 minutes to produce a dry composite semipermeable membrane. Thereafter, a transmission test was performed in the same manner as in Example 1. The results of the transmission test are shown in Table 1.

Comparative Example 2
An undried skin layer was formed in the same manner as in Example 1. Then, the dry composite semipermeable membrane was produced by drying an undried composite semipermeable membrane for 2 minutes at 130 ° C. without spraying. Thereafter, a transmission test was performed in the same manner as in Example 1. The results of the transmission test are shown in Table 1.

Comparative Example 3
An undried skin layer was formed in the same manner as in Example 1. Thereafter, air having a temperature of 20 ° C. and a wind speed of 5 m / sec was blown onto the surface of the undried skin layer for 3 seconds to remove excess solution. Thereafter, the undried composite semipermeable membrane was dried at 60 ° C. for 5 minutes to prepare a dry composite semipermeable membrane. Thereafter, a transmission test was performed in the same manner as in Example 1. The results of the transmission test are shown in Table 1.

表１から明らかなように、未乾燥スキン層上に気体を多段階的に吹き付けて余剰の溶液を徐々に除去することにより、アルカリ洗浄液に対する耐性が高く、膜洗浄の前後において透過流束及び塩阻止率の変化が少ない乾燥複合半透膜を得ることができる。

As is clear from Table 1, by spraying gas onto the undried skin layer in a multistage manner, the excess solution is gradually removed, so that the resistance to the alkaline cleaning solution is high, and the permeation flux and salt before and after membrane cleaning. A dry composite semipermeable membrane with little change in the blocking rate can be obtained.

Claims (7)

A process of forming an undried skin layer containing a polyamide-based resin obtained by reacting a polyfunctional amine component and a polyfunctional acid halide component on the surface of the porous support, and gas is sprayed on the undried skin layer in multiple stages. A method for producing a dry composite semipermeable membrane comprising a spraying step of removing excess solution and a drying step of drying the undried skin layer at 90 to 140 ° C. 2. The method for producing a dry composite semipermeable membrane according to claim 1, wherein in the spraying step, the wind speed of the gas to be sprayed is higher in the second and subsequent stages than in the first stage. The method for producing a dry composite semipermeable membrane according to claim 1 or 2, wherein in the spraying step, the temperature of the gas is 10 to 50 ° C. The method for producing a dry composite semipermeable membrane according to any one of claims 1 to 3, wherein in the spraying step, the wind speed of the gas is 1 to 30 m / sec. The method for producing a dry composite semipermeable membrane according to any one of claims 1 to 4, wherein, in the spraying step, the time for blowing the gas is 0.1 to 10 seconds at each stage. In the said drying process, drying time is 10 to 300 second, The manufacturing method of the dry composite semipermeable membrane in any one of Claims 1-5. A dry composite semipermeable membrane obtained by the production method according to claim 1.