JP7212878B2 - Method for producing modified membrane - Google Patents

Description

The present invention relates to a method for producing modified membranes.

In recent years, films with various functions have been developed. One of the typical examples is a semipermeable membrane, and its typical function is desalination of seawater. In addition, semipermeable membranes are useful for selectively separating certain components from liquid or gas mixtures, such as for the production of high-purity water or for separating specific solutes from solutions. used for

One aspect of the semipermeable membrane is a forward osmosis membrane. Patent Document 1 discloses a nonwoven fabric, a polymer layer such as polysulfone formed thereon, and a dense polyamide-based layer formed thereon. A forward osmosis membrane is disclosed.

Patent Document 2 discloses a composite semipermeable membrane composed of a fibrous support layer, a microporous support membrane, and a crosslinked polyamide thin film layer, which can also be used as a forward osmosis membrane for concentration difference power generation. _High salt rejection and high It is stated that water permeability can be achieved.

Further, Patent Document 3 discloses a forward osmosis membrane using an aromatic polyether (for example, an aromatic polyetherketone having an SO ₃ Na group) self-supporting membrane having sulfonic acid groups.

JP 2014-213262 A JP-A-2014-533 WO2018/079733

On the other hand, membranes are required to have higher functions.
Introduction of functional groups into the membrane material is an effective means for improving the function.
On the other hand, it is known that modification of a polymer by radical modification, which is a conventional means for introducing functional groups, may lead to unintended reactions such as reduction in the molecular weight of the polymer and cross-linking. This may lead to side effects such as a decrease in film strength.

The present inventors thought that the above problem could be solved if the surface of the membrane could be selectively denatured, since the function of the functional group is expressed mainly on the surface of the membrane.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a denatured membrane which is efficiently denatured to enhance its function and has other performances similar to those of the conventional ones.

As a result of the research conducted by the present inventors, it was found that the above problems can be solved by the following configuration example. A configuration example of the present invention is as follows.
[1] In one molecule, an atom (α) of an element selected from Group 15 elements and Group 16 elements and an atom (β) of a Group 17 element are added in an atomic number ratio of atom (α): atom (β) = At least selected from polysulfone, polyethersulfone, polyphenylsulfone, polyetherketone, polyimide, polyamide and sulfonated polymers thereof, including step 1 of irradiating the radicals contained in a ratio of 1: 1 to 4: 1 with light A method for producing a modified membrane by modifying a membrane containing one kind of polymer.
[2] The method for producing a modified film according to [1], wherein the step 1 is a step of modifying the film by irradiating the radicals with light in an environment where the film and the radicals coexist.
[3] The method for producing a modified film according to [2], wherein the step 1 is a step of irradiating the film and the radicals with light.
[4] The method for producing a modified membrane according to any one of [1] to [3], wherein the polymer is sulfonated polyetherketone.
[5] The polymer contains a sulfonic acid group-containing aromatic polyether resin containing a structural unit (1) represented by the following formula (1) and a structural unit (2) represented by the following formula (2) , the method for producing a modified membrane according to the above [4].

［式（１）および（２）において、
Ｒ¹～Ｒ¹⁰は、それぞれ独立して、Ｈ、Ｃｌ、Ｆ、ＣＦ₃またはＣ_mＨ_2m+1（ｍは１～１０の整数を示す。）であり、
Ｒ¹～Ｒ¹⁰の少なくとも１つはＣ_mＨ_2m+1（ｍは１～１０の整数を示す。）であり、
Ｒ¹～Ｒ¹⁰は、それぞれ芳香環に２つ以上存在してもよく、１つの芳香環にＣ_mＨ_2m+1が２つ以上存在する場合には、各Ｃ_mＨ_2m+1は互いに同一であっても異なっていてもよい。
Ｘ¹～Ｘ⁵は、それぞれ独立して、Ｈ、Ｃｌ、Ｆ、ＣＦ₃またはスルホン酸基含有基であり、
Ｘ¹～Ｘ⁵の少なくとも１つはスルホン酸基含有基であり、
Ｘ¹～Ｘ⁵は、それぞれ芳香環に２つ以上存在してもよく、１つの芳香環にスルホン酸基含有基が２つ以上存在する場合には、各スルホン酸基含有基は互いに同一であっても異なっていてもよい。
Ａ¹～Ａ⁶は、それぞれ独立して、直接結合、－ＣＨ₂－、－Ｃ（ＣＨ₃）₂－、－Ｃ（ＣＦ₃）₂－、－Ｏ－または－ＣＯ－であり、Ａ¹～Ａ⁶の少なくとも１つは－ＣＯ－である。
ｉ，ｊ，ｋおよびｌは、それぞれ独立して、０または１を示す。］
［６］前記ラジカルが、二酸化塩素ラジカルである前記［１］～［５］のいずれかに記載の変性膜の製造方法。
［７］前記膜が、半透膜である前記［１］～［６］のいずれかに記載の変性膜の製造方法。

[In formulas (1) and (2),
R ¹ to R ¹⁰ are each independently H, Cl, F, CF ₃ or C _m H _2m+1 (m is an integer of 1 to 10);
at least one of R ¹ to R ¹⁰ is C _m H _2m+1 (m is an integer of 1 to 10);
Two or more of each of R ¹ to R ¹⁰ may be present in an aromatic ring, and when two or more C _m H _2m+1 are present in one aromatic ring, each C _m H _2m+1 is They may be the same or different.
X ¹ to X ⁵ are each independently H, Cl, F, CF ₃ or a group containing a sulfonic acid group;
at least one of X ¹ to X ⁵ is a sulfonic acid group-containing group;
Two or more of each of X ¹ to X ⁵ may be present in the aromatic ring, and when two or more sulfonic acid group-containing groups are present in one aromatic ring, each sulfonic acid group-containing group is the same. There may be or may be different.
A ¹ to A ⁶ are each independently a direct bond, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -O- or -CO-, and A ¹ At least one of ~ ^A6 is -CO-.
i, j, k and l each independently represent 0 or 1; ]
[6] The method for producing a modified film according to any one of [1] to [5], wherein the radical is a chlorine dioxide radical.
[7] The method for producing a modified membrane according to any one of [1] to [6], wherein the membrane is a semipermeable membrane.

According to the production method of the present invention, it is possible to provide a modified membrane that can maintain the basic performance of a conventional membrane while efficiently modifying the membrane, for example, mainly modifying the surface to improve the function.
As will be described later, for example, when this technology is applied to a forward osmosis membrane, the water permeation flux performance can be enhanced while maintaining the salt rejection rate.

FIG. 1 is a schematic diagram showing a mode of membrane denaturation performed in Examples. FIG. 2 is a schematic diagram showing a mode of membrane denaturation performed in Examples. FIG. 3 is a schematic diagram of an apparatus used for evaluating separation performance of forward osmosis membranes in Examples.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the invention is not limited by the following description.
<<Method for producing modified membrane>>
The method for producing a modified membrane according to the present invention (hereinafter also referred to as "this method") comprises:
Atoms (α) of elements selected from Group 15 and Group 16 elements and atoms (β) of Group 17 elements are contained in one molecule in an atomic number ratio of atoms (α): atoms (β) = 1:1. Including step 1 of irradiating light to the radicals contained in a ratio of ~4: 1,
A method for producing a modified membrane by modifying a membrane containing at least one polymer selected from polysulfone, polyethersulfone, polyphenylsulfone, polyetherketone, polyimide, polyamide and sulfonated polymers thereof.

The step 1 is preferably a step of modifying the film by irradiating the radicals with light in an environment where the film and the radicals coexist.
In step 1, the film and the radicals are preferably irradiated with light. "The film and the radicals are irradiated with light" does not mean that the film and the radicals are irradiated with light independently. It means that the radical is irradiated. Further, it is preferable that the film and the radicals are irradiated with light at the same time.

As will be described later, not only the portion of the film irradiated with light is denatured, but the peripheral portion and deep layer portion thereof may also be denatured.
As the production method of the present invention, there is also an embodiment in which, after irradiating the system containing the radicals with light, the system and the film are brought into contact with each other to denature the film.

According to this method, the membrane can be efficiently used. It is possible to improve the water permeation speed while maintaining the performance.

According to this method, the film can be efficiently denatured (eg, oxidized) by a very simple method of only irradiating the radicals with light, and even under extremely mild conditions such as normal temperature and normal pressure. can be done. Furthermore, according to this method, the film can be efficiently modified (eg, oxidation reaction) without using a radical generator such as a peroxide or an azo compound, which may be unstable at the handling temperature. .

<Step 1>
In step 1, an atom (α) of an element selected from group 15 elements and group 16 elements and an atom (β) of a group 17 element are added to one molecule in an atomic number ratio of atom (α): atom (β )=1:1 to 4:1 in the step of irradiating the radicals with light.

In step 1, at least the radicals are irradiated with light, and the film may or may not be irradiated with light.
The step 1 may be a liquid phase method in which the film is immersed in or brought into contact with an aqueous phase and/or organic phase containing the radicals, and the aqueous phase and/or organic phase containing the radicals and the film are combined. It may be a vapor-phase method conducted without contact, or a vapor-phase method conducted in a gas phase containing the radicals and the film. For example, in applications where the influence of residual water or solvent is strictly limited, reaction in the gas phase is preferred.

The radical contains atoms (α) of elements selected from group 15 and group 16 elements and atoms (β) of group 17 elements in a specific composition ratio in one molecule.
The radical may contain two or more Group 15 element atoms, may contain two or more Group 16 element atoms, and may contain one or more Group 15 element and Group 16 element atoms. It may contain two or more Group 17 element atoms. However, in these cases, the atomic number ratio is the ratio between the total number of atoms of group 15 and group 16 elements and the total number of atoms of group 17 elements.

Atom (α) is preferably nitrogen, oxygen or sulfur, with oxygen being particularly preferred.
The atom (β) is preferably chlorine, bromine or iodine, more preferably chlorine or bromine. Among these, chlorine is more preferable because chlorine-containing radicals are readily available or easily generated. When radicals containing chlorine are used, light containing ultraviolet rays is preferable as irradiation light, and when radicals containing bromine or iodine are used, it is considered that light with a longer wavelength than ultraviolet rays can also be used. Therefore, bromine and iodine are sometimes preferred from the viewpoint of the degree of freedom of light selection and the need for a mild environment for the polymer.

The atomic number ratio (atom (α):atom (β)) in the radical is preferably 1:1 to 2:1, more preferably 2:1.
A chlorine dioxide radical is preferable as the radical. For example, it is considered that chlorine radicals (Cl.) and oxygen molecules (O ₂ ) are generated by irradiating chlorine dioxide radicals with light.

The light (wavelength) used for the light irradiation may be appropriately selected according to the radicals to be used. Specifically, it is possible to select a wide range from the infrared region to the ultraviolet region, and it is, for example, 200 nm or more and, for example, 800 nm or less. Although the light irradiation time is not particularly limited, it is, for example, 1 minute or more and, for example, 1000 hours or less.

The light source for the light irradiation is not particularly limited, but natural light such as sunlight can be used from the viewpoint of convenience. Further, for example, instead of or in addition to the natural light, a light source such as a xenon lamp, a halogen lamp, a fluorescent lamp, or a mercury lamp may be appropriately used. Furthermore, if necessary, a filter that cuts wavelengths other than the required wavelength may be used as appropriate.

The temperature, pressure, and atmosphere in performing Step 1 are not particularly limited, but the reaction temperature is, for example, 0° C. or higher and, for example, 100° C. or lower, and the pressure is, for example, 0.1 MPa or higher and 100 MPa or lower. The atmosphere includes, for example, an air atmosphere and an inert gas atmosphere.

For example, as shown in the examples below, this method is carried out in the atmosphere at normal temperature (eg, 5 to 35° C.) and normal pressure (atmospheric pressure) without any heating, pressurization, pressure reduction, etc. is also possible.
The light irradiation is performed, for example, on the radicals present in an aqueous phase, an organic phase and/or a gas phase. When emphasis is placed on reducing the load on the environment and the effects on the human body, it is preferable to perform the treatment on radicals present in the water phase or the gas phase. Step 1, in one embodiment, may be in an environment in which two or more phases of aqueous, organic and gaseous phases are present. Further, for example, when the radicals are present in the liquid phase, the film to be modified may also be present in the liquid phase, but may also be present in other phases such as the gas phase. .

In one embodiment, the concentration of radicals containing atoms (α) and atoms (β) in the aqueous phase and/or organic phase is not particularly limited, but is, for example, 0.0001 mol/L or more, such as 1 mol/L. It is below.

The aqueous phase is not particularly limited as long as it contains water.
The organic phase is not particularly limited as long as it contains an organic solvent.
Although the organic solvent is not particularly limited, examples thereof include hydrocarbon solvents and halogenated solvents.

One kind of the organic solvent may be used, or two or more kinds thereof may be used.
Examples of the hydrocarbon solvent include, but are not limited to, n-hexane, cyclohexane, benzene, toluene, o-xylene, m-xylene, and p-xylene.

Examples of the halogenated solvent include, but are not limited to, methylene chloride, chloroform, carbon tetrachloride, carbon tetrabromide, and fluorous solvents.
The fluorous solvent refers to a solvent in which all or most of the hydrogen atoms of a hydrocarbon are substituted with fluorine atoms. The fluorous solvent may be, for example, a solvent in which 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more of the hydrogen atoms in the hydrocarbon are substituted with fluorine atoms.

Examples of the fluorous solvent include CF ₃ —(CF ₂ ) _n —CF ₃ (n is 4 to 7), N—((CF ₂ ) _n CF ₃ ) ₃ (n is 1 or 4), hexafluorobenzene , 1-(trifluoromethyl)undecafluorocyclohexane, 1-(trifluoromethyl)pentafluorobenzene, octadecafluorodecahydronaphthalene, among which CF ₃ (CF ₂ ) ₄ CF ₃ is preferred. .

A fluorous solvent has the advantage of suppressing or preventing side reactions, for example, because the solvent itself has low reactivity. Examples of the side reaction include oxidation reaction of the solvent, hydrogen abstraction reaction and chlorination reaction of the solvent by radicals, and reaction between radicals derived from the polymer forming the film and the solvent.

When the membrane is immersed in an aqueous phase or an organic phase, the amount of the membrane, which is a raw material (substrate), used in the aqueous phase or the organic phase is not particularly limited. /L or more, or 10 g/L or less.

The aqueous phase and/or the organic phase may contain components other than the radicals.
Examples of the other component include, but are not particularly limited to, the radical generating source, Bronsted acid, Lewis acid, and oxygen (O ₂ ).

Each of these may be used alone or in combination of two or more.
Said other ingredients may be dissolved in the aqueous phase and/or the organic phase, but they do not have to be dissolved.
In addition, one substance may serve as both the Lewis acid and the Bronsted acid. The term "Lewis acid" refers to a substance that acts as a Lewis acid against the above radical generation source.

The source of the radical is not particularly limited, but when the radical is a chlorine dioxide radical, for example, chlorous acid (HClO ₂ ) or a salt thereof may be used. Salts of chlorous acid are not particularly limited, and examples thereof include metal salts. Examples of the metal salt include alkali metal salts, alkaline earth metal salts and rare earth salts.

More specifically, the chlorine dioxide radical generation source is, for example, sodium chlorite (NaClO ₂ ), lithium chlorite (LiClO ₂ ), potassium chlorite (KClO ₂ ), magnesium chlorite (Mg (ClO ₂ ) ₂ ) and calcium chlorite (Ca(ClO ₂ ) ₂ ). Among these, sodium chlorite is preferable from the viewpoint of cost, ease of handling, and the like.

Although the concentration of the radical generation source in the aqueous phase and/or organic phase is not particularly limited, it is, for example, 0.0001 mol/L or more and 1 mol/L or less.
The Lewis acid is not particularly limited, and may be, for example, an organic substance or an inorganic substance.

Examples of the organic substances include ammonium ions and organic acids (eg, carboxylic acids).
The inorganic substance may contain one or both of metal ions and non-metal ions. The metal ions may contain one or both of typical metal ions and transition metal ions.

The inorganic substance includes, for example, alkaline earth metal ions (e.g. Ca ²⁺ etc.), rare earth ions, Mg ²⁺ , Sc ³⁺ , Li ⁺ , Fe ²⁺ , Fe ³⁺ , Al ³⁺ , silicate ions and It may be at least one selected from the group consisting of borate ions.

The alkaline earth metal ions include, for example, calcium, strontium, barium or radium ions, more specifically Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Ra ²⁺ .

The "rare earth" is a general term for a total of 17 elements, including two elements of scandium and yttrium and 15 elements (lanthanides) from lanthanum to lutetium. Examples of rare earth ions include trivalent cations.

Further, when the Lewis acid is an ion, the Lewis acid may be a substance having a counter ion of the ion, and the counter ion is, for example, trifluoromethanesulfonate ion (CF ₃ SO ₃ ⁻ ). , trifluoroacetate ion (CF ₃ COO ⁻ ), acetate ion, fluoride ion, chloride ion, bromide ion, iodide ion, sulfate ion, hydrogen sulfate ion, sulfite ion, nitrate ion, nitrite ion, phosphate ion , phosphite ion.

Also, the Lewis acid may be at least one selected from the group consisting of AlCl ₃ , AlMeCl ₂ , AlMe ₂ Cl, BF ₃ , BPh ₃ , BMe ₃ , TiCl ₄ , SiF ₄ and SiCl ₄ . In addition, among these, "Ph" represents a phenyl group, and "Me" represents a methyl group.

The Lewis acidity of the Lewis acid is, for example, 0.4 eV or more, but is not limited thereto. Although the upper limit of the Lewis acidity is not particularly limited, it is, for example, 20 eV or less. The Lewis acidity is described, for example, in Ohkubo, K.; Fukuzumi, S. Chem. Eur. J., 2000, 6, 4532, J. AM. CHEM. SOC. Org. Chem. 2003, 68, 4720-4726.

The Bronsted acid is not particularly limited, and examples thereof include inorganic acids and organic acids. Specific examples include trifluoromethanesulfonic acid, trifluoroacetic acid, acetic acid, hydrofluoric acid, hydrochloric acid, bromo Hydrochloric acid, hydroiodic acid, sulfuric acid, sulfurous acid, nitric acid, nitrous acid, phosphoric acid, phosphorous acid.

The acid dissociation constant pK _a of the Bronsted acid is, for example, 10 or less. Although the lower limit of the pK _a is not particularly limited, it is -10 or more, for example.
The concentration of at least one of the Lewis acid and Bronsted acid in the aqueous phase and/or the organic phase is not particularly limited and can be set as appropriate. is.

For example, oxygen (O ₂ ) can be dissolved in the aqueous and/or organic phase by blowing air or oxygen gas through the aqueous and/or organic phase. At this point, for example, the aqueous phase and/or the organic phase may be saturated with oxygen (O ₂ ). By including the oxygen (O ₂ ) in the aqueous phase and/or the organic phase, for example, the modification (oxidation reaction) of the film containing the polymer can be promoted.

<Radical generation step>
The method may include a step of generating the radicals (radical generation step), and specifically includes a step of generating the radicals from the radical generation source.

Although the radical generation step is not particularly limited, for example, the radical generation source (eg, chlorous acid or a salt thereof) is dissolved in water and allowed to stand, and the radicals are naturally generated from the radical generation source. can be done. At this time, for example, the presence of at least one of the Lewis acid and the Bronsted acid in the water can promote the generation of the radicals. Further, for example, the radicals can be generated by irradiating an aqueous phase in which the radical generating source is dissolved in water with light. This light irradiation may be the light irradiation in step 1, that is, the light irradiation may be performed on the radicals while generating the radicals.

For example, a mechanism (mechanism) for generating chlorine dioxide radicals from chlorite ions is presumed as shown in Scheme 1 below. However, Scheme 1 below is an example of a presumed mechanism and does not limit the present invention in any way.

The first (upper) reaction formula in Scheme 1 below shows the disproportionation reaction of chlorite ion (ClO ₂ ⁻ ), and at least one of Lewis acid and Bronsted acid is present in this reaction system. , the equilibrium tends to shift to the right.

The second (middle) reaction formula in Scheme 1 below shows a dimerization reaction, in which hypochlorite ions (ClO ⁻ ) generated in the disproportionation reaction react with chlorite ions to form dioxide. Chlorine (Cl ₂ O ₂ ) is produced. This reaction is thought to proceed more easily as the amount of protons H ⁺ in the water increases, that is, as the water becomes more acidic.

The third (lower) reaction scheme in Scheme 1 below represents radical generation. In this reaction, dichlorine dioxide produced in the dimerization reaction reacts with chlorite ions to produce chlorine dioxide radicals.

<Membrane denaturation>
In the method, the membrane is denatured.
In the film, a functional group containing an atom (α) contained in the radical may be introduced into the film by the modification. are sometimes introduced. At this time, atoms (β) contained in the radicals may also be introduced into the film.

According to this method, it is conceivable that the atoms (β) may also be introduced into the film in this way, so the effect of the atoms (β) may also be expected in the modified film.
It has been reported that the introduction of group 17 elements is suppressed when modifying low-molecular-weight hydrocarbon compounds such as alkanes using the radicals. In some cases, it can be introduced into the film together with the element. Compared to the case of modifying low-molecular-weight substances such as methane and ethane (see the mechanism (mechanism) of oxidation reaction of ethane described in Japanese Patent Application Laid-Open No. 2017-155017), the formation of carbon-hydrogen bonds in the film is The present inventors believe that the existence density tends to increase and the possibility that the radicals are stabilized by interacting with the polymer are considered to be the reasons for this. However, this speculation does not limit the present invention.

As the functional group containing the atom (α), when the radical contains oxygen, for example, a hydroxy group, a carboxyl group, an aldehyde group, a carbonyl group, an ether bond, an ester bond, -C(=O)OOH, -O -O-.

When atoms (β) are introduced into the film, the ratio ([Cα]/ The lower limit of [Cβ]) is preferably greater than zero, more preferably 0.01, still more preferably 0.1, particularly preferably 0.5, and the upper limit is preferably 5000, more preferably 100, more preferably 20. In some cases, the group 17 element (atom (β)) is not introduced.

The above [Cα] and [Cβ] values are values specified by the XPS method. The measurement is carried out by a conventional method using the product name AXIS-Nova (manufactured by KRATOS).
According to this method, it is expected that mainly the surface of the membrane to be modified is modified. According to this, even if scission or cross-linking of the polymer molecules forming the film occurs during denaturation, it will remain in the vicinity of the surface of the film, and the influence on the performance such as the strength of the whole film can be minimized. Therefore, it is advantageous in maintaining the basic performance of the membrane.

The surface refers to a region whose depth from the surface of the film is preferably 1/10 or less, more preferably 1/20 or less of the thickness of the film. The depth of this denatured portion can be confirmed by, for example, the XPS method.

According to the method, the entire surface of the membrane can be modified, or part of the surface can be modified. Since the method proceeds via light, it is expected that it will be able to modify primarily the location where the light strikes. Further, if only one surface of the film is irradiated with light, it is possible to denature only a specific portion by controlling the portion exposed to the light using a denatured film that is denatured only on the one surface, or a photomask or the like. It is also expected that the ratio of the unmodified portion can be freely controlled.

For example, when the membrane of the present invention is used as a permeable membrane or a filtration membrane, the area of the denatured portion is defined as 100% of the entire surface of the membrane that comes into contact with components such as raw material reagents, and the desired use of the resulting denatured membrane. can be selected as appropriate. The preferred lower limit of the area ratio is 1%, 5%, 10%, 20%, 30% and 50% in that order, and the preferred upper limit is 100%, more preferably 90%. A denatured region can be identified by a known method such as the XPS method.

It is considered that the modification progresses with radicals of the group 17 element generated when the radicals are exposed to light as a starting point. As a matter of course, it is considered that modification occurs at the portion where the radical comes into contact with the raw material film. Therefore, in many cases, the area of the film to be denatured that has been irradiated with light and the area that has been denatured are substantially equivalent.

Although the peripheral portion irradiated with light and the deep layer portion of the pore where the light does not reach may be denatured, the ratio is expected to be small.
In the present invention, irradiating the film with light may not directly involve the denaturation reaction of the film. However, considering the general lifetime of radicals and the case of modifying a specific portion of the film, it is a preferable method to substantially irradiate the film with light.

[film]
The membrane to be modified in this method is a membrane containing at least one polymer selected from polysulfone, polyethersulfone, polyphenylsulfone, polyetherketone, polyimide, polyamide, and sulfonated polymers thereof. . Such polymers can be formed into membranes by conventional methods. The method can be exemplified by the methods described in Patent Documents 1 to 3 above. Preferred specific examples of the polymer include sulfonated polyether ketones, particularly sulfonic acid group-containing aromatic polyether resins described below.

The thickness of the film is, for example, 0.01 μm or more and, for example, 3 μm or less. A more preferable lower limit is 0.03 μm, a more preferable upper limit is 2 μm, and a further preferable upper limit is 1.5 μm.

A semipermeable membrane will be described below as an example of the membrane that is modified in this method.
In one embodiment, the semipermeable membrane comprises a sulfonic acid group-containing aromatic polyether resin. In one embodiment, the sulfonic acid group-containing aromatic polyether resin contains structural units (1) represented by the following formula (1) and structural units (2) represented by the following formula (2).

In formulas (1) and (2),
i, j, k and l each independently represent 0 or 1;
R ¹ to R ¹⁰ each independently represent H, Cl, F, CF ₃ or C _m H _2m+1 (m is an integer of 1 to 10), and C _m H _2m+1 , for example, methyl group, ethyl group, propyl group, butyl group, pentyl group and hexyl group.

At least one of R ¹ to R ¹⁰ is C _m H _2m+1 (m is an integer of 1 to 10). Specifically, i, j, k and l and R ¹ to R ¹⁰ are at least groups in which the structural unit (1) and/or the structural unit (2) are represented by C _m H _2m+1 . selected to have one. That is, if i, j, k and l are all 1, at least one of R ¹ to R ¹⁰ is C _m H _2m+1 , for example i=0, j=1, k=0 and l = 1, then at least one of R ¹ -R ³ , R ⁵ -R ⁸ and R ¹⁰ is C _m H _2m+1 .

Two or more of each of R ¹ to R ¹⁰ may be present in an aromatic ring, and when two or more C _m H _2m+1 are present in one aromatic ring, each C _m H _2m+1 is They may be the same or different.
X ¹ to X ⁵ are each independently H, Cl, F, CF ₃ or sulfonic acid group-containing groups.

At least one of X ¹ to X ⁵ is a sulfonic acid group-containing group. Specifically, i and j and X ¹ to X ⁵ are selected so that the structural unit (1) has at least one sulfonic acid group. That is, when i=1 and j=1, at least one of X ¹ to X ⁵ is a sulfonic acid group-containing group, but when j=0, at least one of X ¹ to X ³ is a sulfonic acid group. is a group containing a sulfonic acid group, and when i=0 and j=1, at least one of X ¹ to X ³ and X ⁵ is a sulfonic acid group-containing group.

Two or more of each of X ¹ to X ⁵ may be present in the aromatic ring, and when two or more sulfonic acid group-containing groups are present in one aromatic ring, each sulfonic acid group-containing group is the same. There may be or may be different.

A ¹ to A ⁶ are each independently a direct bond, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -O- or -CO-, and A ¹ At least one of ~ ^A6 is -CO-.
The lines on both ends of formulas (1) and (2) indicate bonds to adjacent structural units.

In the present invention, the sulfonic acid group is a functional group that easily releases protons, and may have a salt structure in which a hydrogen atom is substituted with Na or K. Examples of sulfonic acid group-containing groups include sulfonic acid group (--SO ₃ H) and alkylsulfonic acid group (--(CH ₂ ) _n SO ₃ H) (where n is an integer of 1-10). and those in which terminal hydrogen atoms of these are substituted with Na or K. The sulfonic acid group-containing group is preferably -C _n' H _2n' -SO ₃ Y (n' is an integer of 0 to 10 and Y is H, Na or K).

In addition to sulfonic acid groups, carboxylic acid groups (--COOH), phosphonic acid groups (--PO ₃ H ₂ ), alkylcarboxylic acid groups (--(CH ₂ ) _n COOH), alkylphosphonic acid groups (--(CH ₂ ) _n PO ₃ H ₂ ), and salts thereof may also exhibit favorable performance.

Examples of the structural unit (1) include structural units represented by the following formula (1-1) or (1-2), in which A ¹ is -CO- is preferred,

さらに具体的には下式（１－３）または下式（１－４）で表される構造単位が挙げられる。

Further specific examples include structural units represented by the following formula (1-3) or (1-4).

（式中、Ｚはそれぞれ独立に前記スルホン酸基含有基であり、ｓはそれぞれ独立に０～３の整数であり、ｔはそれぞれ独立に０～４の整数であり、両末端の線は隣り合う構造単位との結合を示す。これら以外の記号の定義は前述したとおりである。）

(Wherein, Z is each independently the sulfonic acid group-containing group, s is each independently an integer of 0 to 3, t is each independently an integer of 0 to 4, and the lines at both ends are adjacent Indicates a bond with a matching structural unit.Definitions of symbols other than these are as described above.)

Examples of the structural unit (2) include structural units represented by the following formula (2-1) or (2-2),

さらに具体的には、下式（２－３）または下式（２－４）で表される構造単位が挙げられる。

More specific examples include structural units represented by the following formula (2-3) or (2-4).

（式中、ｔはそれぞれ独立に０～４の整数であり、両末端の線は隣り合う構造単位との結合を示す。ｔ以外の記号の定義は前述したとおりである。）

(Wherein, t is each independently an integer of 0 to 4, and lines at both ends indicate bonds to adjacent structural units. Definitions of symbols other than t are as described above.)

The molar fraction of the structural unit (1) with respect to the total amount of the structural unit (1) and the structural unit (2) is preferably 0.1 or more, since a semipermeable membrane with high water permeability can be formed. It is preferably 0.2 or more, more preferably 0.3 or more; In addition, the molar fraction is preferably 0.9 or less, because a semipermeable membrane having a high salt blocking rate and not gelling can be formed. It is more preferably 0.7 or less, still more preferably 0.6 or less.

The sulfonic acid group-containing aromatic polyether resin may further contain a structural unit derived from a polyfunctional compound.
The sulfonic acid group-containing aromatic polyether resin may be a crosslinked product or a non-crosslinked product.

The weight-average molecular weight (Mw) of the sulfonic acid group-containing aromatic polyether resin, which is measured by a method measured under the following conditions (1) to (6) using a GPC (Gel Permeation Chromatography) method, is preferably is 70,000 or more, more preferably 80,000 or more, and still more preferably 90,000 or more. When the molecular weight is within the above range, the resulting semipermeable membrane has high mechanical properties and is less likely to break during film formation and use. Moreover, the weight average molecular weight is 180,000 or less from the viewpoint of gel generation rate.
(1) Measurement temperature: 40°C
(2) Developing solvent: N,N-dimethylformamide (DMF)
(3) Flow rate: 1.0ml/min
(4) Injection volume: 500 µl
(5) Detector: UV detector
(6) Molecular weight standard: standard polystyrene

More specifically, the high-performance liquid chromatograph (HPLC) used for the GPC measurement uses the following equipment in combination according to a conventional method.
HPLC: Shimadzu RID-10A-LC-10AT system column oven: Shimadzu CTO-10A device
UV detector: JASCO Corporation (JASCO) 875-UV device Guard column: Nitto Denko MD-G column
GPC column: Two Nitto Denko KD805M columns, one Nitto Denko KD8025 column, and one Nitto Denko 802 column were connected in series and used.

The weight-average molecular weight can be controlled by adjusting the molar ratio of raw material monomers and the amount of terminal blocking agent when producing the sulfonic acid group-containing aromatic polyether resin.

The sulfonic acid group equivalent of the sulfonic acid group-containing aromatic polyether resin, that is, the mass of the sulfonic acid group-containing aromatic polyether resin per 1 mol of sulfonic acid group, did not dissolve in water or methanol, and swelling was suppressed. , preferably 200 g/mol or more, since a semipermeable membrane with a small electrolyte permeation amount can be obtained. Further, it is preferably 5000 g/mol or less, more preferably 1000 g/mol or less, since a semipermeable membrane having a high water permeation flux and high economic efficiency can be obtained.

The semipermeable membrane in the above embodiment consists essentially of the sulfonic acid group-containing aromatic polyether resin, but contains other components in small amounts (for example, 1% by mass or less, or 0.1% by mass or less) may be included.

The thickness of the semipermeable membrane is usually 0.01 to 3.0 μm, preferably 0.01 to 1.5 μm. A forward osmosis membrane using a semipermeable membrane having a thickness within this range has sufficient membrane strength and exhibits a practically sufficiently large water permeation flux. The thickness of the semipermeable membrane can be controlled by the manufacturing conditions of the semipermeable membrane, such as temperature and pressure during press molding, varnish concentration and coating thickness during casting, and the like.

The tensile elastic modulus of the semipermeable membrane is preferably 0.8 to 2.0 GPa, more preferably 1.2 to 1.6 GPa. The tensile strength at break of the semipermeable membrane is preferably 40 MPa or more, and its upper limit is, for example, 100 MPa. Moreover, the elongation rate of the semipermeable membrane is preferably 40% or more, and the upper limit thereof is, for example, 200%. These tensile modulus, tensile strength at break and elongation were measured under the following conditions.

<Measurement conditions for tensile modulus, tensile strength at break and elongation>
A test piece of length x width x thickness = 100 mm x 10 mm x 5 μm is prepared, pulled at a speed of 50 mm / min using a tensile tester, and the strength when the test piece is cut (broken) (testing the tensile load value divided by the cross-sectional area of the piece), and the elongation.
Elongation is calculated by the following formula.
Elongation rate (%) = 100 x (L-L ₀ )/L ₀
(L ₀ : test piece length before test L: test piece length at break)
The tensile modulus is obtained by dividing the load at break by the cross-sectional area of the test piece and the strain at break, that is, (L−L ₀ )/L ₀ .

The tensile strength at break and the elongation can be increased, for example, by increasing the molecular weight of the sulfonic acid group-containing aromatic polyether resin.
The solubility of the semipermeable membrane in dimethyl sulfoxide (hereinafter also referred to as “DMSO”) and water can be evaluated by the following mass reduction rates. The mass reduction rate is preferably less than 2% by mass, more preferably 1.0% by mass or less, and particularly preferably 0.5% by mass or less.

<Method for measuring mass reduction rate>
The semipermeable membrane is dried by standing at 150° C. for 4 hours in a nitrogen atmosphere, and then weighed. The semi-permeable membrane is soaked in DMSO or water and left at 25° C. for 24 hours. The semipermeable membrane is removed from DMSO or water, dried by standing at 150° C. for 4 hours under a nitrogen atmosphere, and then weighed. Based on the mass of the semipermeable membrane before and after immersion, the mass reduction rate is calculated from the following formula.
Mass reduction rate = (mass of semipermeable membrane before immersion - mass of semipermeable membrane after immersion) / mass of semipermeable membrane before immersion x 100

The dissolution amount can be reduced, for example, by cross-linking the sulfonic acid group-containing aromatic polyether resin, so that the dissolution amount can be within the above range even if the sulfonic acid group equivalent is small.

(Method for producing semipermeable membrane)
The semipermeable membrane in the above embodiment can be produced as a self-supporting membrane from the sulfonic acid group-containing aromatic polyether resin.

The semipermeable membrane can be easily produced by press molding or extrusion molding the sulfonic acid group-containing aromatic polyether resin. Further, the film of the sulfonic acid group-containing aromatic polyether resin may be subjected to a stretching treatment or the like.

The semipermeable membrane can also be produced from the varnish described above by a casting method. That is, the semipermeable membrane can be obtained by coating the varnish on a support and removing the solvent by volatilization. Furthermore, the semipermeable membrane may be separated from the support to form a self-supporting membrane.

If an organic solvent or the like remains in the semipermeable membrane at the time of casting, the semipermeable membrane may have reduced mechanical strength and be easily damaged. Therefore, the semipermeable membrane produced by the casting method is preferably sufficiently dried and/or washed with water, an aqueous sulfuric acid solution, hydrochloric acid, or the like.

In the sulfonic acid group-containing aromatic polyether resin used for producing the semipermeable membrane, when the hydrogen atoms of the sulfonic acid groups are substituted with Na or K, the sulfonic acid group-containing aromatic polyether resin Na or K of the sulfonic acid group may be substituted with a hydrogen atom by forming an ether resin film and then contacting this film with hydrochloric acid, an aqueous sulfuric acid solution, or the like.

The present invention is characterized by modifying such a membrane by the method described above.
The membrane can also be used in combination with a known porous substrate such as a non-woven fabric, for example, in a form of lamination.

(forward osmosis membrane)
A semipermeable membrane modified by this method (hereinafter also referred to as a "modified semipermeable membrane"), which is an example of the present invention, can be used as a forward osmosis membrane. One embodiment of the configuration includes a modified semipermeable membrane and the porous substrate disposed on at least one surface thereof, and maintains a high filtration function and a high salt rejection rate while maintaining a high water permeation rate. performance can be achieved.

The forward osmosis membrane according to the present invention may comprise the porous substrate on both sides of the modified semipermeable membrane. With this aspect, the strength of the forward osmosis membrane is further improved.
The forward osmosis membrane according to the present invention has a layer other than the porous substrate on both or one side of the modified semipermeable membrane, in the order of modified semipermeable membrane/layer other than the porous substrate/porous substrate. However, from the viewpoint of obtaining a good permeation flux, it is preferable not to include a layer other than the porous substrate. A polyamide layer may be included as a layer other than the porous substrate, but its thickness is preferably 100 μm or less.

According to the studies of the present inventors, when the membrane modified by this method is used as a forward osmosis membrane by the above method, it tends to increase the water permeation rate and maintain the salt rejection rate. found out.

The functional groups (e.g., oxidized groups) introduced by this method probably reduce the resistance to water permeation, and the salt is trapped by the functional groups, so that the anti-diffusion performance is maintained even when the water permeation rate is increased. It is speculated that this may have shown an unexpected effect. It is also conceivable that the functional group functioned to enhance the performance of various substituents such as protonic acid groups such as sulfonic acid groups.
In any case, it was found that the method for producing a modified membrane of the present invention can, as an example, improve the balance between the water permeation rate and the reverse diffusion blocking performance of salts.

(Use of forward osmosis membrane)
A forward osmosis membrane element, which can be cited as an example of the application of the present invention, will be introduced.
The forward osmosis membrane element includes the forward osmosis membrane and spacer according to the present invention described above. In other words, the forward osmosis membrane element according to the present invention is obtained by using the forward osmosis membrane according to the present invention as the forward osmosis membrane in a conventional forward osmosis membrane element comprising a forward osmosis membrane and a spacer. As the spacer, conventionally known spacers used in forward osmosis membrane elements can be used.

A forward osmosis membrane module according to the present invention is obtained by housing the forward osmosis membrane element according to the present invention in a container. In other words, the forward osmosis membrane module according to the present invention is a conventional forward osmosis membrane element in which the forward osmosis membrane element is housed in a container, and the forward osmosis membrane element according to the present invention is used as the forward osmosis membrane element. is. As the container, conventionally known containers used for forward osmosis membrane modules can be used.

The system according to the present invention includes a forward osmosis membrane module according to the present invention, and a feed solution (FS) on one side of the forward osmosis membrane according to the present invention provided in the forward osmosis membrane module, and the feed solution (FS) on the other side. A drive pump for flowing a draw solution (DS) having a higher concentration of solutes such as salts than the solution, so that water contained in the feed solution can be moved to the draw solution through the forward osmosis membrane. It is configured. In one embodiment, the forward osmosis membrane according to the present invention can be arranged such that the side modified by the method of manufacturing the modified membrane of the present invention (eg, the oxidized side) faces the feed solution.

Examples of the present invention will be described below. However, the present invention is not limited to the following examples.
[Example of resin synthesis]
Into a 5-neck reactor equipped with a nitrogen inlet, thermometer, reflux condenser, and stirrer, 64.2 g (0.152 mol) of 5,5′-carbonylbis(sodium 2-fluorobenzenesulfonate), 4 ,4′-difluorobenzophenone 49.8 g (0.228 mol), 3,3′,5,5′-tetramethyl-4,4′-dihydroxydiphenylmethane 97.4 g (0.380 mol) and potassium carbonate 65.7 g ( 0.475 mol) was weighed out. 845.4 g of dimethyl sulfoxide and 281.8 g of toluene were added thereto, and the mixture was stirred under a nitrogen atmosphere and heated at 130° C. for 12 hours. After removing the generated water out of the system, the toluene was distilled off.

Subsequently, reaction was carried out at 160° C. for 12 hours to obtain a viscous polymer solution. After diluting the resulting solution with 570 g of toluene, it was discharged into 2400 g of methanol, and the precipitated polymer powder was filtered, washed and dried at 150° C. for 4 hours to give 168.7 g of polyetherketone powder (yield 86%). ).
The obtained polyether ketone, as the structural unit (1)

で表される構造を、前記構造単位（２）として

as the structural unit (2)

で表される構造を有している。ここで、前記構造単位（１）：前記構造単位（２）＝４０ｍｏｌ：６０ｍｏｌである。

It has a structure represented by Here, the structural unit (1):the structural unit (2)=40 mol:60 mol.

[Example 1]
<Preparation of polyether ketone sheet-1>
A varnish was prepared by dissolving the polyether ketone powder obtained in the resin synthesis example in N,N-dimethylformamide (DMF), casting this varnish on a transparent film, drying at 150 ° C. for 10 minutes, and obtaining a transparent film. and a film (polyetherketone sheet) having a thickness of 0.6 μm formed thereon.

<Oxidation of polyether ketone sheet-1>
Put 0.4 g of sodium chlorite (manufactured by Sigma-Aldrich) and 50 mL of ultrapure water in a circular petri dish with a diameter of about 11 cm, dissolve the sodium chlorite in the ultrapure water, and then add a 35 to 37% hydrochloric acid aqueous solution (Fuji Film Wako Pure Chemical Co., Ltd.) was added. (It was confirmed in advance by the ESR method that chlorine dioxide radicals were generated under these conditions.) Next, the petri dish containing the mixed solution was placed in a polyetherketone double-layer sheet of about 21 cm x 13.5 cm. The petri dish covered with the two-layer sheet was irradiated with light having a wavelength of 365 nm at DC 12 V and 14 mW/cm ² for 5 minutes from above the petri dish covered with the two-layer sheet. An overview is shown in FIG. Thereafter, the entire surface of the sheet was washed with ultrapure water using a washing bottle, and then the sheet was dried under reduced pressure to obtain an oxidized polyetherketone sheet 1.

[Comparative Example 1]
As a comparative example, a two-layer sheet not subjected to the oxidation treatment was separately prepared and designated as comparative example 1.

[Water contact angle evaluation of polyether ketone sheet]
Using an automatic contact angle meter CA-V type (manufactured by Kyowa Interface Science Co., Ltd.), the two-layer polyetherketone sheet of Example 1 and Comparative Example 1 (Example 1: oxidized polyetherketone sheet, Comparative Example 1 : The water contact angle on the side of the polyether ketone sheet not subjected to oxidation treatment was measured with a water droplet amount of about 1.0 μL.

[Evaluation of surface friction force of polyether ketone sheet]
Using an environment-controlled probe microscope E-sweep (manufactured by SII Nanotechnology Co., Ltd.) with a hydrophilized Si ₃ N ₄ cantilever (both sides Au-coated, Olympus Corp.), horizontal force was measured in the atmosphere. The frictional force on the surface of each polyetherketone sheet was measured after static elimination in mode. The frictional force indicated is a corrected frictional force (V) obtained by removing the influence of the load at the time of measurement by a conventional method.

[Example 2]
<Preparation of polyether ketone sheet-2>
A varnish was prepared by dissolving the polyether ketone powder obtained in the above Resin Synthesis Example in DMF. This varnish was cast on a release sheet and dried at 150°C for 10 minutes. A film of 6 μm was formed. This film was peeled off from the release sheet to obtain a polyetherketone sheet.

<Oxidation of polyether ketone sheet-2>
Put 10 g of sodium chlorite (manufactured by Sigma-Aldrich) and 100 mL of ultrapure water in a plastic container, dissolve sodium chlorite in ultrapure water, and then add 35 to 37% hydrochloric acid aqueous solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. ) was added to prepare a mixture. The presence of chlorine dioxide radicals under these conditions was separately confirmed by the ESR method.

The mixture was placed in a shallow vat approximately 22 cm x 16 cm x 1.5 cm. Then, the polyetherketone sheet having a thickness of about 0.6 μm prepared in <Preparation of polyetherketone sheet-2> was pasted on a rectangular frame of about 14.5 cm×9.5 cm with holes, and this mount frame was attached. was placed on the shallow vat. Light with a wavelength of 365 nm was irradiated for 30 seconds at 10 mW/cm ² from the upper part of the mount frame by Hololite Kaku (manufactured by Piphotonics Co., Ltd.) DC12V. An overview is shown in FIG. After that, the light irradiation was terminated, and the sample was kept on standby for 30 seconds. After waiting for 30 seconds, the sheet was peeled off from the backing paper, and an oxidized polyetherketone sheet 2 was obtained.

[Comparative Example 2]
As a comparative example, the polyetherketone sheet obtained in <Preparation of polyetherketone sheet-2> and having a thickness of about 0.6 μm, which was not subjected to the oxidation treatment, was separately prepared and designated as comparative example 2.

[Evaluation of forward osmosis membrane of polyether ketone sheet]
A non-woven fabric made of polypropylene ⁽ Syntex ⁽ registered trademark) PS-105, Mitsui Chemical Co., Ltd.) are prepared, and the oxidized polyether ketone sheet 2 shown in Example 2 and the polyether ketone sheet shown in Comparative Example 2 are sandwiched between these nonwoven fabrics, and these are integrated to form an oxidized forward osmosis membrane. , to obtain an untreated forward osmosis membrane.

Next, FIG. 3 shows a schematic diagram of the apparatus 10 used for evaluating the separation performance of the forward osmosis membrane.
Apparatus 10 comprises feed solution tank 1 , flow path 2 , pump 3 , draw solution tank 11 , flow path 12 , pump 13 and evaluation cell 21 . A feed solution tank 1 is placed on a balance 4 and a draw solution tank 11 is equipped with a conductivity meter 15 . At the start of the evaluation, the feed solution tank 1 stores 500 g of Milli-Q water having an electrical conductivity of 50 μS/cm or less as the feed solution FS (Feed Solution), and the draw solution tank 11 stores the draw solution DS. As (Draw Solution), 800 g of NaCl aqueous solution of a predetermined concentration is stored. The feed solution in feed solution tank 1 flows through channel 2 at a rate of 0.6 L/min using pump 3 and the draw solution in draw solution tank 11 flows at 0.6 L/min using pump 13. It flows through channel 12 at a velocity. The feed solution flowing through the flow channel 2 and the draw solution flowing through the flow channel 12 are in contact with each other through the forward osmosis membrane 22 having an effective membrane area of 0.0042 m ² inside the evaluation cell 21 . A portion of the feed solution moves to the draw solution via the feed solution, and a portion of the salt (NaCl) in the draw solution moves (backflow) to the feed solution. In the case of the oxidized forward osmosis membrane, the oxidized forward osmosis membrane was arranged so that the oxidized surface of the oxidized polyetherketone sheet faced the feed solution side.

[Water permeation flux measurement]
The amount of weight loss of the feed solution was measured every minute with a balance 4, and the amount of weight loss per unit time and unit area of the forward osmosis membrane was defined as the water permeation flux (L/(m ² ·h)). An average value was calculated for 30 to 60 minutes after the start of circulation.

[Salt blocking rate]
Measure the change in the electrical conductivity of the draw solution every minute with the electrical conductivity meter 15, convert this to the change in the molar concentration of the draw solution, and change the mass concentration per unit area of the forward osmosis membrane per unit time. was taken as the salt blocking rate (g/(m ² ·h)). It was calculated as the average value for 30 to 60 minutes after the start of circulation.

1 Feed solution tanks 2, 12 Flow paths 3, 13 Pumps 4, 14 Balance 10 Evaluation device 11 Draw solution tank 15 Conductivity meter 21 Evaluation cell 22 Forward osmosis membrane DS Draw solution FS Feed solution

Claims (7)

Atoms (α) of elements selected from Group 15 and Group 16 elements and atoms (β) of Group 17 elements are contained in one molecule in an atomic number ratio of atoms (α): atoms (β) = 1:1. Including step 1 of irradiating light to the radicals contained in a ratio of ~4: 1,
A method for producing a modified membrane by modifying a membrane containing at least one polymer selected from polysulfone, polyethersulfone, polyphenylsulfone, polyetherketone, polyimide, polyamide and sulfonated polymers thereof,
the atom (α) is an oxygen atom, the atom (β) is an atom selected from chlorine, bromine and iodine,
The step 1 is a step performed without contacting the film with the aqueous phase and/or organic phase containing the radicals.
A method for producing a modified membrane . The step 1 is
In an environment where the film and the radicals coexist,
2. The method for producing a modified film according to claim 1, wherein the step of modifying the film by irradiating the radicals with light. 3. The method for producing a modified film according to claim 2, wherein said step 1 is a step of irradiating said film and said radicals with light. The method for producing a modified membrane according to any one of claims 1 to 3 , wherein the polymer is sulfonated polyetherketone. The polymer comprises a sulfonic acid group-containing aromatic polyether resin containing a structural unit (1) represented by the following formula (1) and a structural unit (2) represented by the following formula (2): 5. The method for producing a modified membrane according to 4 .

[In formulas (1) and (2),
R ¹ to R ¹⁰ are each independently H, Cl, F, CF ₃ or C _m H _2m+1 (m is an integer of 1 to 10);
at least one of R ¹ to R ¹⁰ is C _m H _2m+1 (m is an integer of 1 to 10);
Two or more of each of R ¹ to R ¹⁰ may be present in an aromatic ring, and when two or more C _m H _2m+1 are present in one aromatic ring, each C _m H _2m+1 is They may be the same or different.
X ¹ to X ⁵ are each independently H, Cl, F, CF ₃ or a group containing a sulfonic acid group;
at least one of X ¹ to X ⁵ is a sulfonic acid group-containing group;
Two or more of each of X ¹ to X ⁵ may be present in the aromatic ring, and when two or more sulfonic acid group-containing groups are present in one aromatic ring, each sulfonic acid group-containing group is the same. There may be or may be different.
A ¹ to A ⁶ are each independently a direct bond, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -O- or -CO-, and A ¹ At least one of ~ ^A6 is -CO-.
i, j, k and l each independently represent 0 or 1; ] The method for producing a modified film according to any one of claims 1 to 5 , wherein the radicals are chlorine dioxide radicals. The method for producing a modified membrane according to any one of claims 1 to 6 , wherein the membrane is a semipermeable membrane.

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