阅读说明：本技术 复合半透膜及其制造方法 (Composite semipermeable membrane and method for producing same ) 是由 川岛敏行 井上真一 广濑雅彦 大下净治 都留稔了 山本一树 于 2019-01-23 设计创作，主要内容包括：本发明的目的在于提供复合半透膜的制造方法,其能够再现性良好地在多孔性支撑体的表面形成非常薄且分离性能优异的分离层。另外,本发明的目的在于提供在多孔性支撑体的表面具有非常薄且分离性能优异的有机-无机杂化型分离层的复合半透膜。本发明的复合半透膜的制造方法包括下述工序：使包含有机硅化合物的有机溶液与水或水溶液在多孔性支撑体上接触,使上述有机硅化合物进行界面缩聚,由此在多孔性支撑体的表面形成包含具有硅氧烷键的交联缩合体的分离层,所述有机硅化合物具有三个以上的选自水解性基团及羟基中的至少一种反应性官能团。(The purpose of the present invention is to provide a method for producing a composite semipermeable membrane, which is capable of forming a very thin separation layer having excellent separation performance on the surface of a porous support with good reproducibility. Another object of the present invention is to provide a composite semipermeable membrane having an organic-inorganic hybrid separation layer that is very thin and has excellent separation performance on the surface of a porous support. The method for producing a composite semipermeable membrane of the present invention comprises the steps of: a separation layer comprising a crosslinked condensate having a siloxane bond is formed on the surface of a porous support by bringing an organic solution containing an organosilicon compound having three or more reactive functional groups selected from at least one of a hydrolyzable group and a hydroxyl group into contact with water or an aqueous solution on the porous support and subjecting the organosilicon compound to interfacial polycondensation.)

1. A method for producing a composite semipermeable membrane, comprising the steps of: a separation layer comprising a crosslinked condensate having a siloxane bond is formed on the surface of a porous support by bringing an organic solution comprising an organosilicon compound having three or more reactive functional groups selected from at least one of a hydrolyzable group and a hydroxyl group into contact with water or an aqueous solution on the porous support and subjecting the organosilicon compound to interfacial polycondensation.

2. The method for producing a composite semipermeable membrane according to claim 1, wherein the hydrolyzable group is halogen, alkoxy, alkenyloxy, acyloxy, aryloxy, ketoximino, aminohydroxy, amino, alkylamino, cyano, or isocyanate.

3. The method for producing a composite semipermeable membrane according to claim 1 or 2, wherein the organic silicon compound comprises a compound represented by the following general formula (1),

[ chemical formula 1]

In the formula (1), R¹～R⁶Each independently hydrogen, hydroxy, halogen, C1-12 alkyl, C1-12 alkoxy, C2-12 alkenyloxy, C2-12 acyloxy, aryloxy, ketoximino, amino, alkylamino, cyano, aminohydroxy, or isocyanato, X is C1-12 saturated hydrocarbon, C2-12 unsaturated hydrocarbon, heterocyclic functional group, or-R⁷-NR⁸-R⁹-, formula-R⁷-NR⁸-R⁹In (A) R⁷And R⁹Each independently a saturated hydrocarbon having 1 to 12 carbon atomsA group or an unsaturated hydrocarbon group having 2 to 12 carbon atoms, R⁸The alkyl group has 1 to 12 carbon atoms, or the alkenyl group has 2 to 12 carbon atoms.

4. The method for producing a composite semipermeable membrane according to any one of claims 1 to 3, wherein the aqueous solution contains a surfactant.

5. A composite semipermeable membrane comprising a porous support and a separation layer provided on the surface of the porous support,

the separation layer contains a siloxane bond and-Si-R⁷-NR⁸-R⁹A crosslinked condensate of-Si-bonds, wherein R⁷And R⁹Each independently a saturated hydrocarbon group having 1 to 12 carbon atoms or an unsaturated hydrocarbon group having 2 to 12 carbon atoms, R⁸The alkyl group has 1 to 12 carbon atoms, or the alkenyl group has 2 to 12 carbon atoms.

6. A composite semipermeable membrane comprising a porous support and a separation layer provided on the surface of the porous support,

the separation layer contains a crosslinked condensate having a siloxane bond and a-Si-Y-Si-bond, wherein Y is a functional group having a heterocyclic ring.

7. The composite semipermeable membrane according to claim 5 or 6, wherein the thickness of the separation layer is 400nm or less.

Technical Field

The present invention relates to a composite semipermeable membrane having an organic-inorganic hybrid separation layer formed on the surface of a porous support, and a method for producing the same. The composite semipermeable membrane is suitable for production of ultrapure water, desalination of salt water or seawater, and the like, and can remove and recover a pollutant source or an effective substance contained in a pollutant or the like which causes pollution, such as dyeing wastewater or electrodeposition coating wastewater, and contributes to sealing of wastewater. In addition, the method can be used for high-level treatments such as concentration of effective components in food applications and the like, purification of water, removal of harmful components in sewage applications and the like. In addition, the method can be used for wastewater treatment in oil fields, shale gas fields and the like. The composite semipermeable membrane can be used as a gas separation membrane for selectively separating a specific gas species from a mixed gas. The composite semipermeable membrane can be used as a separation membrane for a PV method (pervaporation method) or a VP method (vapor permeation method) for separating alcohol and water from an alcohol-water solution.

Background

Composite semipermeable membranes are called RO (reverse osmosis) membranes, NF (nanofiltration) membranes, and FO (forward osmosis) membranes in terms of filtration performance and treatment method, and have been used for production of ultrapure water, desalination of seawater, desalination of salt water, and reuse of wastewater.

Examples of the composite semipermeable membrane that is industrially used include a composite semipermeable membrane in which a skin-like layer containing a polyamide resin is formed on the surface of a porous support.

However, the composite semipermeable membrane has a problem in terms of heat resistance, chemical resistance, and abrasion resistance because the skin layer is formed of a polyamide resin.

On the other hand, an inorganic film made of a ceramic material such as silica is excellent in heat resistance, chemical resistance, and abrasion resistance, and therefore is expected as a durable (robust) separation film.

For example, patent document 1 proposes a water treatment separation membrane including a separation functional layer having an organic-inorganic hybrid (hybrid) structure containing an Si element or the like. It is stated that the separating function layer is formed by: the porous layer is coated with a reaction solution containing a silicon compound having an ethylenically unsaturated group and a hydrolyzable group and a compound having an ethylenically unsaturated group, and the hydrolyzable group is condensed to polymerize the ethylenically unsaturated group, thereby increasing the molecular weight of these compounds.

In addition, patent documentsDocument 2 proposes a method for manufacturing a separation filter, which includes the following steps: polymer sol preparation Process (RO)₃Si-X-Si(OR)₃Preparing a polymer sol by mixing the compound represented by (a) with a solvent containing water; a coating step of coating the polymer sol on a heat-resistant polymer support composed of a film-like or hollow porous material; and a firing step of firing the resultant to form an inorganic-organic hybrid film having a-Si-X-Si-bond on the heat-resistant polymer support.

On the other hand, as for the materials formed of the high molecular compound, each of the materials has a characteristic gas permeability. Based on this property, a specific gas component (for example, carbon dioxide, hydrogen, oxygen, nitrogen, methane, or the like) can be selectively permeated and separated through a membrane made of a specific polymer compound. This technique is applicable to separation and recovery of carbon dioxide from, for example, an oil field exhaust gas, an exhaust gas from refuse incineration or thermal power generation, a natural gas, or a mixed gas obtained by gasifying coal.

For example, patent document 3 proposes a gas separation membrane including a resin layer containing a compound having a siloxane bond, wherein a positron lifetime τ 3 of a third component when a positron is bombarded from a surface of the resin layer containing the compound having a siloxane bond at an intensity of 1keV is 3.40 to 4.20 ns.

Disclosure of Invention

Problems to be solved by the invention

However, in the methods for producing the separation membranes (separation filters) described in patent documents 1 to 3, it is difficult to form a very thin separation layer having excellent separation performance on a support with good reproducibility.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for producing a composite semipermeable membrane, which can form a very thin separation layer having excellent separation performance on the surface of a porous support with good reproducibility. Another object of the present invention is to provide a composite semipermeable membrane having an organic-inorganic hybrid separation layer that is very thin and has excellent separation performance on the surface of a porous support.

Means for solving the problems

The present invention relates to a method for producing a composite semipermeable membrane, comprising the steps of: a separation layer comprising a crosslinked condensate having a siloxane bond is formed on the surface of a porous support by bringing an organic solution containing an organosilicon compound having three or more reactive functional groups selected from at least one of a hydrolyzable group and a hydroxyl group into contact with water or an aqueous solution on the porous support and subjecting the organosilicon compound to interfacial polycondensation.

The hydrolyzable group is preferably a halogen, alkoxy, alkenyloxy, acyloxy, aryloxy, ketoximino, aminohydroxy, amino, alkylamino, cyano, or isocyanate group.

The organosilicon compound preferably contains a compound represented by the following general formula (1).

[ chemical formula 1]

[ in the formula, R¹～R⁶Each independently hydrogen, hydroxy, halogen, C1-12 alkyl, C1-12 alkoxy, C2-12 alkenyloxy, C2-12 acyloxy, aryloxy, ketoximino, amino, alkylamino, cyano, aminohydroxy, or isocyanato, X is C1-12 saturated hydrocarbon, C2-12 unsaturated hydrocarbon, heterocyclic functional group, or-R⁷-NR⁸-R⁹- (in the formula, R⁷And R⁹Each independently a saturated hydrocarbon group having 1 to 12 carbon atoms or a non-saturated hydrocarbon group having 2 to 12 carbon atomsSaturated hydrocarbon radicals, R⁸Hydrogen, an alkyl group having 1 to 12 carbon atoms, or an alkenyl group having 2 to 12 carbon atoms) ]

In addition, the aqueous solution preferably contains a surfactant.

The present invention is also characterized by a composite semipermeable membrane having a separation layer on the surface of a porous support,

the separation layer contains a siloxane bond and-Si-R⁷-NR⁸-R⁹-Si-bond (R)⁷And R⁹Each independently a saturated hydrocarbon group having 1 to 12 carbon atoms or an unsaturated hydrocarbon group having 2 to 12 carbon atoms, R⁸Hydrogen, an alkyl group having 1 to 12 carbon atoms, or an alkenyl group having 2 to 12 carbon atoms).

The present invention is also characterized by a composite semipermeable membrane having a separation layer on the surface of a porous support,

the separation layer contains a crosslinked condensate having a siloxane bond and a-Si-Y-Si-bond (Y is a functional group having a heterocyclic ring).

The thickness of the separation layer is preferably 500nm or less.

ADVANTAGEOUS EFFECTS OF INVENTION

The method for producing a composite semipermeable membrane of the present invention is characterized in that the organic silicon compound is polycondensed at the interface between the organic solution and water or the aqueous solution. This enables formation of a very thin separation layer having excellent separation performance on the surface of the porous support. In addition, the method for producing a composite semipermeable membrane of the present invention does not require a complicated and special process, and can form a separation layer by a simple method, and therefore has the following advantages: the composite semipermeable membrane can be produced in large quantities at low cost, and the performance unevenness of the composite semipermeable membrane can be suppressed. In addition, the separation layer of the composite semipermeable membrane of the present invention is very thin and is composed of a material having a siloxane bond and-Si-R⁷-NR⁸-R⁹A crosslinked condensate of an-Si-bond or a crosslinked condensate having a siloxane bond and an-Si-Y-Si-bond (Y is a functional group having a heterocycle), and therefore the composite semipermeable membrane of the present invention is excellent in separation performance, heat resistance, chemical resistance, and abrasion resistance.

Drawings

FIG. 1 is an SEM photograph of a cross section of a composite semipermeable membrane produced in example 1.

FIG. 2 is an SEM photograph of a cross section of the composite semipermeable membrane produced in example 2.

FIG. 3 is an SEM photograph of a cross section of the composite semipermeable membrane produced in comparative example 1.

FIG. 4 shows the results of EDX measurement of the surface of the composite semipermeable membrane produced in example 1.

Detailed Description

Hereinafter, embodiments of the present invention will be described. The method for producing a composite semipermeable membrane of the present invention comprises the steps of: a separation layer comprising a crosslinked condensate having a siloxane bond is formed on the surface of a porous support by bringing an organic solution containing an organosilicon compound having three or more reactive functional groups selected from at least one of a hydrolyzable group and a hydroxyl group into contact with water or an aqueous solution on the porous support and subjecting the organosilicon compound to interfacial polycondensation.

In the present invention, an organosilicon compound having three or more reactive functional groups selected from a hydrolyzable group and a hydroxyl group is used as a material for the separation layer. One kind of the organosilicon compound may be used, or two or more kinds of organosilicon compounds having different reactive functional groups may be used.

The organic silicon compound is not particularly limited as long as it has at least one reactive functional group selected from a hydrolyzable group and a hydroxyl group.

The hydrolyzable group is not particularly limited, and known hydrolyzable groups include, for example, hydrogen, halogen, alkoxy, alkenyloxy, acyloxy, aryloxy, ketoximino, aminohydroxy, amino, alkylamino, cyano, and isocyanate groups. Examples of the halogen include fluorine, chlorine, bromine, iodine, and the like, and chlorine is preferable. Examples of the alkoxy group include alkoxy groups having 1 to 12 carbon atoms, and preferably alkoxy groups having 1 to 4 carbon atoms. Examples of the alkenyloxy group include alkenyloxy groups having 2 to 12 carbon atoms, and preferably alkenyloxy groups having 2 to 4 carbon atoms. Examples of the acyloxy group include acyloxy groups having 2 to 12 carbon atoms, and preferably acyloxy groups having 2 to 5 carbon atoms. Examples of the aryloxy group include a phenoxy group and the like. Examples of the ketoximino group include a methylethylketoximino group, a dimethylketoximino group, and a diethylketoximino group. Examples of the aminohydroxy group include a dimethylaminohydroxy group, a diethylaminohydroxy group, and a methylethylaminohydroxy group. Examples of the alkylamino group include a monoalkylamino group having 1 to 4 carbon atoms and a dialkylamino group having 1 to 4 carbon atoms. Among these, chlorine, alkoxy, amino, and acyloxy are particularly preferable from the viewpoint of reactivity and the like.

The organosilicon compound preferably contains a compound represented by the following general formula (1). Specifically, by using a compound represented by the following general formula (1) and X is-R⁷-NR⁸-R⁹A compound having a siloxane bond and-Si-R⁷-NR⁸-R⁹A separation layer of a-Si-bonded crosslinked condensate, which can provide a composite semipermeable membrane having more excellent separation performance, heat resistance, chemical resistance and abrasion resistance. Further, by using a compound represented by the following general formula (1) in which X is a functional group having a heterocyclic ring as the organosilicon compound, a separation layer containing a crosslinked condensate having a siloxane bond and a — Si-Y-Si-bond (Y is a functional group having a heterocyclic ring) can be formed, and a composite semipermeable membrane having more excellent separation performance, heat resistance, chemical resistance, and abrasion resistance can be obtained.

[ chemical formula 2]

[ in the formula, R¹～R⁶Each independently hydrogen, hydroxy, halogen, alkyl of 1 to 12 carbon atoms, alkoxy of 1 to 12 carbon atoms, alkenyloxy of 2 to 12 carbon atoms, acyloxy of 2 to 12 carbon atoms, aryloxy, ketoximino, amino, alkylamino, cyanoAn aminohydroxy group or an isocyanate group, X is a saturated hydrocarbon group having 1 to 12 carbon atoms, an unsaturated hydrocarbon group having 2 to 12 carbon atoms, a functional group having a heterocycle, or-R⁷-NR⁸-R⁹- (in the formula, R⁷And R⁹Each independently a saturated hydrocarbon group having 1 to 12 carbon atoms or an unsaturated hydrocarbon group having 2 to 12 carbon atoms, R⁸Hydrogen, an alkyl group having 1 to 12 carbon atoms, or an alkenyl group having 2 to 12 carbon atoms) ]

In the above formula, the number of carbon atoms of the alkyl group is preferably 2 to 4, the number of carbon atoms of the alkoxy group is preferably 1 to 4, the number of carbon atoms of the alkenyloxy group is preferably 2 to 4, and the number of carbon atoms of the acyloxy group is preferably 2 to 5. Examples of the halogen, aryloxy group, ketoximino group, alkylamino group, and aminohydroxy group include the groups exemplified above. In the above X, the saturated hydrocarbon group preferably has 1 to 4 carbon atoms, and the unsaturated hydrocarbon group preferably has 2 to 4 carbon atoms, from the viewpoint of water permeability.

In the functional group having a heterocyclic ring, the heterocyclic ring is not particularly limited, and known heterocyclic rings may be used, and examples thereof include nitrogen-containing heterocyclic rings such as a pyrrolidine ring, a pyrrole ring, an imidazole ring, a pyrazole ring, an imidazoline ring, a triazole ring, a piperidine ring, a pyridine ring, a pyridazine ring, a pyrimidine ring, a pyrazine ring, an indole ring, a benzotriazole ring, and a quinoline ring; oxygen-containing heterocyclic rings such as tetrahydrofuran ring, furan ring, oxolane ring, tetrahydropyran ring and dioxane ring; sulfur-containing heterocyclic rings such as tetrahydrothiophene rings, thiophene rings, and tetrahydrothiopyran rings; and nitrogen-and oxygen-containing heterocycles such as oxazole ring and morpholine ring. Among these, nitrogen-containing heterocycles are preferable from the viewpoint of reactivity and hydrophilicity. The functional group may have a linking group for linking the heterocyclic ring and Si. The linking group is not particularly limited, and examples thereof include an alkylene group, an alkyleneoxy group, an alkenylene group, and an alkenylene group.

In addition, the above-mentioned-R⁷-NR⁸-R⁹In (A), R from the viewpoint of water permeability⁷And R⁹Each independently preferably a saturated hydrocarbon group having 1 to 4 carbon atoms or an unsaturated hydrocarbon group having 2 to 4 carbon atoms, more preferably 1 carbon atom4 saturated hydrocarbon groups. In addition, the above-mentioned-R⁷-NR⁸-R⁹In (A), R from the viewpoint of water permeability⁸Preferably hydrogen or an alkyl group having 1 to 4 carbon atoms, more preferably hydrogen.

Among the compounds represented by the above general formula (1), R is preferable¹～R³Two or more of which are C1-4 alkoxy groups and R⁴～R⁶Two or more of them are C1-4 alkoxy groups, and R is more preferably¹～R⁶All of them are C1-C4 alkoxy groups.

Specific examples of the compound represented by the above general formula (1) include bis ((trimethoxysilyl) methyl) amine, bis ((triethoxysilyl) methyl) amine, bis ((2-trimethoxysilyl) ethyl) amine, bis ((2-triethoxysilyl) ethyl) amine, bis ((3-trimethoxysilyl) propyl) amine, bis ((3-triethoxysilyl) propyl) amine, bis ((trimethoxysilyl) methyl) methylamine, bis ((triethoxysilyl) methyl) methylamine, bis (1- (trimethoxysilyl) ethyl) amine, bis (1- (triethoxysilyl) ethyl) amine, bis ((4-trimethoxysilyl) butyl) amine, bis ((4-triethoxysilyl) butyl) amine, 1, 4-bis ((triethoxysilyl) methyl) -1,2, 3-triazole, 4, 6-bis (3- (triethoxysilyl) propoxy) pyrimidine, 1, 2-bis (triethoxysilyl) ethane, and 1, 2-bis (triethoxysilyl) ethylene. One kind of these may be used, or two or more kinds may be used in combination.

In the present invention, in order to obtain a crosslinked condensate having a dense crosslinked structure, it is preferable to use only an organosilicon compound having three or more reactive functional groups, but an organosilicon compound having two or more reactive functional groups selected from a hydrolyzable group and a hydroxyl group may be used in combination within a range not impairing the effect of the present invention. The organic silicon compound is not particularly limited as long as it has at least one reactive functional group selected from two hydrolyzable groups and a hydroxyl group. The reactive functional group is not particularly limited, and the functional groups exemplified above are exemplified.

When an organosilicon compound having three or more reactive functional groups is used in combination with an organosilicon compound having two or more reactive functional groups, the organosilicon compound having three or more reactive functional groups is preferably used in an amount of 20 wt% or more, more preferably 50 wt% or more, further preferably 70 wt% or more, further preferably 80 wt% or more, and particularly preferably 90 wt% or more of the total of the organosilicon compounds.

The porous support is not particularly limited as long as it can support the separation layer. Examples of the material for forming the porous support include various materials such as polyarylethersulfones such as polysulfone and polyethersulfone, polyimide, and polyvinylidene fluoride, and polysulfone and polyarylethersulfone are preferably used particularly in view of chemical stability, mechanical stability, and thermal stability. The thickness of the porous support is usually about 50 to 500 μm, preferably 100 to 200 μm, but is not limited thereto. The porous support may be reinforced by using a base material such as woven fabric or nonwoven fabric as a backing.

The porous support may have a symmetrical structure or an asymmetrical structure, and is preferably an asymmetrical structure in terms of achieving both the support function and the liquid permeability of the separation layer. The average pore diameter of the surface of the porous support on the side where the separation layer is formed is preferably 0.01 to 0.5 μm.

As the porous support, a porous epoxy resin sheet may be used. The average pore diameter of the porous epoxy resin sheet is preferably 0.01 to 0.4 μm.

The separation layer is formed on the surface of the porous support by an interfacial polycondensation method. Specifically, an organic solution containing an organosilicon compound having three or more reactive functional groups is brought into contact with water or an aqueous solution on the porous support, thereby performing interfacial polycondensation of the organosilicon compound. In this way, a separation layer containing a crosslinked condensation product having a siloxane bond can be formed on the surface of the porous support.

In the production method of the present invention, the following method (method a) can be employed: contacting water or an aqueous solution with the porous support to form a water coating film on the porous support, and then contacting the water coating film with an organic solution containing an organosilicon compound having three or more reactive functional groups to cause interfacial polycondensation of the organosilicon compound; the following method (method B) may also be employed: an organic solution containing an organosilicon compound having three or more reactive functional groups is brought into contact with the porous support to form an organic solution coating film on the porous support, and then the organic solution coating film is brought into contact with water or an aqueous solution to cause interfacial polycondensation of the organosilicon compound, which is preferable to method a. The contact method is not particularly limited, and examples thereof include: a method of applying, spraying, or showering the solution or water on the porous support or the formed coating film; a method of immersing the surface of the porous support or the surface of the formed coating film in a bath containing the solution and water; and so on.

The organic solvent of the organic solution is not particularly limited as long as it has low solubility in water, does not deteriorate the porous support, and can dissolve the organic silicon compound, and examples thereof include saturated hydrocarbons such as hexane, heptane, octane, and nonane, and halogenated hydrocarbons such as 1,1, 2-trichlorotrifluoroethane. One kind of these may be used, or two or more kinds may be used in combination. Among these, saturated hydrocarbons are preferably used.

The concentration of the organic silicon compound in the organic solution is not particularly limited, but is preferably 1 to 20% by weight, more preferably 3 to 5% by weight. When the concentration of the organosilicon compound is less than 1% by weight, the salt rejection tends to be low. On the other hand, when the concentration of the organosilicon compound exceeds 20% by weight, the water permeability coefficient tends to decrease.

Various additives may be added to the organic solution and/or the aqueous solution in order to promote interfacial polycondensation or to improve the separation performance of the resulting composite semipermeable membrane. Examples of the additive include surfactants such as sodium dodecylbenzenesulfonate, sodium dodecylsulfate, and sodium lauryl sulfate, catalysts, and neutralizing agents. One kind of these may be used, or two or more kinds may be used in combination.

In the production method of the present invention, it is preferable that after the organic solution is brought into contact with water or an aqueous solution, the excess solution on the porous support is removed, and the formed film on the porous support is heated. This can promote polycondensation of the organosilicon compound, and can improve the mechanical strength, heat resistance, and the like of the separation layer. The heating temperature is usually about 60 to 150 ℃, preferably 100 to 150 ℃, and more preferably 130 to 150 ℃. The heating time is usually about 1 to 60 minutes, preferably 1 to 30 minutes, and more preferably 5 to 15 minutes.

The thickness of the separation layer is not particularly limited, but is preferably 400nm or less, more preferably 300nm or less, further preferably 200nm or less, further preferably 100nm or less, further preferably 60nm or less, further preferably 30nm or less.

The shape of the composite semipermeable membrane of the present invention is not limited at all. That is, the shape of the membrane may be any conceivable shape such as a flat membrane shape or a spiral element shape. In addition, various treatments known in the art may be performed to improve salt rejection, water permeability, and oxidation resistance of the composite semipermeable membrane.

In addition, from the viewpoint of excellent processability and storage stability, a dry type composite semipermeable membrane can be produced. The shape of the composite semipermeable membrane is not limited at all in the case of drying treatment. That is, the drying treatment may be performed in any conceivable film shape such as a flat film shape or a spiral shape. For example, a composite 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-type spiral element.