JP2022011547A - Separation membrane and method for producing the same - Google Patents

Abstract

To provide a separation membrane which has a high permeated water amount and is usable for a long period, and a method for producing the same.SOLUTION: A separation membrane has a filtration film and a polymer layer formed on the surface of the filtration film. The polymer layer contains a polymer having an acidic group and a basic compound, and an ion exchange capacity of the polymer layer is more than 2 milli-equivalent/g. A method for producing a separation membrane having a filtration film includes a step of treating the surface of the filtration film using a composition containing a polymer having an acidic group and a basic compound.SELECTED DRAWING: None

Description

The present invention relates to a separation membrane and a method for producing the same.

Membrane separation technology using separation membranes such as reverse osmosis membranes, ultrafiltration membranes, and precision filtration membranes is used in the fields of drinking water, ultrapure water for cleaning semiconductors, and water for water purification and wastewater treatment. It is used in various fields such as the processing field.
As separation membranes used for such applications, those using a large number of polymer materials have been studied, and various membranes have been developed.
For example, a reverse osmosis composite membrane containing a porous support membrane layer and a separation active layer as a separation membrane having a high water permeability and having an organic polymer layer having an anionic hydrophilic group formed on the surface of the separation active layer. It has been proposed (see Patent Document 1).

Japanese Unexamined Patent Publication No. 10-75783

However, the reverse osmosis composite membrane described in Patent Document 1 is not suitable for long-term use because the organic polymer layer gradually dissolves in water when used for a long period of time.
An object of the present invention is to provide a separation membrane having a high water permeability and which can be used for a long period of time and a method for producing the same.

As a result of diligent studies, the present inventors have found that the amount of water permeation is increased by forming a polymer layer on the surface of the filtration membrane constituting the separation membrane using a polymer having an acidic group.
By the way, in order to make the polymer layer less soluble in water, the ion exchange capacity of the polymer layer may be lowered, but if the ion exchange capacity is lowered, the removal rate of sodium chloride is lowered. Therefore, as a result of further diligent studies, the present inventors have formed an ion-crosslinked structure between the basic compound and the acidic group of the polymer in the polymer layer by using the polymer having an acidic group and the basic compound in combination. It has been found that the water resistance of the polymer layer is increased without lowering the ion exchange capacity of the polymer layer and that the polymer layer can be used for a long period of time, and the present invention has been completed.

That is, the present invention has the following aspects.
[1] A separation membrane having a filtration membrane and a polymer layer formed on the surface of the filtration membrane.
The polymer layer contains a polymer having an acidic group and a basic compound.
A separation membrane in which the ion exchange capacity of the polymer layer is more than 2 milliequivalent / g.
[2] The separation membrane of the above [1], wherein the polymer having an acidic group has a unit represented by the following general formula (5).

In the formula (5), R ¹⁸ to R ²¹ each independently have a hydrogen atom, a linear or branched alkyl group having 1 to 24 carbon atoms, and a linear or branched alkoxy group having 1 to 24 carbon atoms. It represents an acidic group, a hydroxy group, a nitro group, or a halogen atom, and at least one of R ¹⁸ to R ²¹ is an acidic group.

[3] A method for producing a separation membrane provided with a filtration membrane.
A method for producing a separation membrane, which comprises a step of treating the surface of the filtration membrane using a composition containing a polymer having an acidic group and a basic compound.
[4] The method for producing a separation membrane according to the above [3], wherein the polymer having an acidic group has a unit represented by the following general formula (5).

In the formula (5), R ¹⁸ to R ²¹ each independently have a hydrogen atom, a linear or branched alkyl group having 1 to 24 carbon atoms, and a linear or branched alkoxy group having 1 to 24 carbon atoms. It represents an acidic group, a hydroxy group, a nitro group, or a halogen atom, and at least one of R ¹⁸ to R ²¹ is an acidic group.

According to the present invention, it is possible to provide a separation membrane having a high water permeability and which can be used for a long period of time and a method for producing the same.

Hereinafter, the present invention will be described in detail. The following embodiments are merely exemplary to illustrate the invention and are not intended to limit the invention to this embodiment alone. The present invention can be carried out in various embodiments as long as it does not deviate from the gist thereof.

In addition, in this specification, "solubility" means mere water, water containing at least one of a base and a basic salt, water containing an acid, and one or more solvents of a mixture of water and a water-soluble organic solvent. It means that 0.1 g or more is uniformly dissolved in 10 g (liquid temperature 25 ° C.).
Further, in the present specification, the "mass average molecular weight" is a mass average molecular weight (in terms of sodium polystyrene sulfonate) measured by gel permeation chromatography (GPC).

[Separation membrane]
The separation membrane of the present invention has a filtration membrane and a polymer layer formed on the surface of the filtration membrane.
In the present invention, "on the surface of the filtration membrane" is expressed in order to clarify the positional relationship between the filtration membrane and the polymer layer, but a part of the polymer layer is impregnated inside the filtration membrane. In some cases.

<Filtration membrane>
Examples of the filtration membrane include a porous membrane used for a reverse osmosis membrane, an ultrafiltration membrane, a microfiltration membrane and the like.
Examples of the material of the filter membrane include cellulose, cellulose acetate, polysulfone, polypropylene, polyester, polyethersulfone, polyvinylidene fluoride, nylon and the like.
The form of the filtration membrane is not particularly limited, and a hollow fiber membrane, a flat membrane, or the like can be formed according to the application.

The filtration membrane may be provided with a support (for example, a fibrous material such as a braid or braid) for reinforcing the filtration membrane. For example, when the form of the filtration membrane is a hollow fiber membrane, a membrane having a porous membrane formed on a hollow support may be used as the filtration membrane.
As the filtration membrane, a commercially available product can be used, and examples thereof include a commercially available polypropylene filtration membrane and a polyether sulfone filtration membrane.

<Polymer layer>
The polymer layer is a layer formed on the surface of the filtration membrane, and contains a polymer having an acidic group (hereinafter, also referred to as “polymer (A)”) and a basic compound (B).
The polymer layer may contain one or more of any components, if desired.
The surface of the filtration membrane is the surface on the side where the water to be treated flows. For example, when the form of the filtration membrane is a hollow fiber membrane, the polymer layer is formed on the outer surface of the filtration membrane.

(Polymer (A))
The polymer (A) is a polymer having an acidic group. When the polymer layer contains the polymer (A), the surface of the filtration membrane is hydrophilized and the amount of water permeation is increased.
The polymer (A) may have two kinds of acidic groups in one molecule.

As the polymer (A), a known polymer can be used as long as it has an acidic group in the molecule, as long as it has the effect of the present invention. For example, JP-A-61-197633, JP-A-63-39916, JP-A-1-301714, JP-A-5-504153, JP-A-5-503953, JP-A-4-32848. JP, Japanese Patent Laid-Open No. 4-328181, JP-A-6-145386, JP-A-6-56987, JP-A-5-226238, JP-A-5-1788989, JP-A-6-293828, JP. JP-A-7-118524, JP-A-6-32845, JP-A-6-87949, JP-A-6-256516, JP-A-7-41756, JP-A-7-48436, JP-A. Polymers having an acidic group shown in Japanese Patent Laid-Open No. 4-268331, Japanese Patent Application Laid-Open No. 2014-65598 and the like are preferable from the viewpoint of solubility.

Specific examples of the polymer (A) include phenylene vinylene, vinylene, thienylene, pyrrolylene, and phenylene in which the α-position or β-position is substituted with at least one group selected from the group consisting of a sulfonic acid group and a carboxy group. , Π-conjugated polymer containing at least one selected from the group consisting of iminophenylene, isothianaften, furylene, and carbazolylen as a repeating unit.
When the π-conjugated polymer contains at least one repeating unit selected from the group consisting of iminophenylene and carbazolylene, the group consisting of a sulfonic acid group and a carboxy group on the nitrogen atom of the repeating unit. An alkyl group having at least one group selected from the above, or an alkyl group substituted with at least one group selected from the group consisting of a sulfonic acid group and a carboxy group, or an alkyl group containing an ether bond is placed on the nitrogen atom. Examples include the polymer having.
Among these, from the viewpoint of solubility, thienylene, pyrrolylene, iminophenylene, phenylene vinylene, carbazolylen, and isotianaften in which the β-position is substituted with at least one group selected from the group consisting of a sulfonic acid group and a carboxy group. A polymer having at least one selected from the group consisting of the above as a monomer unit (unit) is preferably used.

As the polymer (A), from the viewpoint of exhibiting high solubility, one or more monomer units selected from the group consisting of the units represented by the following general formulas (1) to (4) may be used as the polymer (A). A polymer containing 20 to 100 mol% in all the constituent units (100 mol%) is preferable.

In formulas (1) to (4), X represents a sulfur atom or a nitrogen atom, and R ¹ to R ¹⁵ are independently hydrogen atoms, linear or branched alkyl groups having 1 to 24 carbon atoms, and carbon. Alkoxy group, acidic group, hydroxy group, nitro group, halogen atom (-F, -Cl, -Br or -I), -N (R ¹⁶ ) ₂ , -NHCOR ¹⁶ of linear or branched chain of number 1 to 24 , -SR ¹⁶ , -OCOR ¹⁶ , -COOR ¹⁶ , -COR ¹⁶ , -CHO, or -CN. R ¹⁶ represents an alkyl group having 1 to 24 carbon atoms, an aryl group having 6 to 24 carbon atoms, or an aralkyl group having 7 to 24 carbon atoms.
However, at least one of R ¹ and R ² of the general formula (1), at least one of R ³ to R ⁶ of the general formula (2), and R ⁷ to R ¹⁰ of the general formula (3). At least one of them, at least one of R ¹¹ to R ¹⁵ of the general formula (4), is an acidic group, respectively.

The acidic group is preferably at least one of a sulfonic acid group and a carboxy group.
The sulfonic acid group (sulfo group) may be contained in an acid state (—SO ₃ H) or in an ionic state (—SO ₃ ⁻ ). Further, the sulfonic acid group also includes a substituent having a sulfonic acid group (-R ¹⁷ SO ₃ H).
On the other hand, the carboxy group (carboxylic acid group) may be contained in the acid state (-COOH) or in the ionic state (-COO- ⁾ . Further, the carboxylic acid group also includes a substituent having a carboxylic acid group (-R ¹⁷ COOH).
The R ¹⁷ contains a linear or branched alkylene group having 1 to 24 carbon atoms, an arylene group having a linear or branched chain having 6 to 24 carbon atoms, or an aralkylene group having a linear or branched chain having 7 to 24 carbon atoms. show.

Some or all of the acidic groups may form salts.
Examples of the salt of the acidic group include an alkali metal salt of a sulfonic acid group or a carboxylic acid group, an alkaline earth metal salt, an ammonium salt, a substituted ammonium salt and the like.
Examples of the alkali metal salt include lithium sulfate, lithium carbonate, lithium hydroxide, sodium sulfate, sodium carbonate, sodium hydroxide, potassium sulfate, potassium carbonate, potassium hydroxide and derivatives having a skeleton thereof.
Examples of the alkaline earth metal salt include magnesium salt and calcium salt.
Examples of the substituted ammonium salt include an aliphatic ammonium salt, a saturated alicyclic ammonium salt, and an unsaturated alicyclic ammonium salt.
Examples of the aliphatic ammonium salt include methylammonium, dimethylammonium, trimethylammonium, ethylammonium, diethylammonium, triethylammonium, methylethylammonium, diethylmethylammonium, dimethylethylammonium, propylammonium, dipropylammonium, isopropylammonium, and diisopropylammonium. , Butylammonium, dibutylammonium, methylpropylammonium, ethylpropylammonium, methylisopropylammonium, ethylisopropylammonium, methylbutylammonium, ethylbutylammonium, tetramethylammonium, tetramethylolammonium, tetraethylammonium, tetran-butylammonium, tetrasec -Butylammonium, tetrat-butylammonium and the like can be mentioned.
Examples of the saturated alicyclic ammonium salt include piperidinium, pyrrolidinium, morpholinium, piperazinium and derivatives having a skeleton thereof.
Examples of unsaturated alicyclic ammonium salts include pyridinium, α-picolinium, β-picolinium, γ-picolinium, quinolinium, isoquinolinium, pyrrolinium, and derivatives having a skeleton thereof.

The polymer (A) preferably has a unit represented by the above general formula (4), and among them, particularly from the viewpoint of being more excellent in solubility, it may have a unit represented by the following general formula (5). More preferred.

In the formula (5), R ¹⁸ to R ²¹ each independently have a hydrogen atom, a linear or branched alkyl group having 1 to 24 carbon atoms, and a linear or branched alkoxy group having 1 to 24 carbon atoms. Represents an acidic group, a hydroxy group, a nitro group, or a halogen atom (-F, -Cl, -Br or -I). Further, at least one of R ¹⁸ to R ²¹ is an acidic group.

As the unit represented by the general formula (5), any one of R ¹⁸ to R ²¹ is a linear or branched alkoxy group having 1 to 4 carbon atoms because it is easy to manufacture. It is preferable that any one of the other is a sulfonic acid group and the rest is hydrogen.

The polymer (A) is a unit represented by the general formula (5) among all the units (100 mol%) constituting the polymer (A) from the viewpoint of excellent solubility in water and organic solvents regardless of pH. Is preferably contained in an amount of 10 to 100 mol%, more preferably 50 to 100 mol%, and particularly preferably 100 mol%.
Further, the polymer (A) preferably contains 10 or more units represented by the general formula (5) in one molecule.

Further, from the viewpoint of further improving the water permeability of the separation membrane, in the polymer (A), the number of aromatic rings to which acidic groups are bonded is preferably 50% or more with respect to the total number of aromatic rings in the polymer, and is 70. % Or more is more preferable, 80% or more is further preferable, 90% or more is particularly preferable, and 100% is most preferable.
The number of aromatic rings to which an acidic group is bonded with respect to the total number of aromatic rings in the polymer refers to a value calculated from the charging ratio of the monomers at the time of producing the polymer (A).

Further, in the polymer (A), the substituent other than the acidic group on the aromatic ring of the monomer unit is preferably an electron donating group from the viewpoint of imparting reactivity to the monomer, and specifically, has 1 to 24 carbon atoms. Alkyl groups, alkoxy groups having 1 to 24 carbon atoms, halogen groups (-F, -Cl, -Br or I) and the like are preferable, and among these, an alkoxy group having 1 to 24 carbon atoms is preferable from the viewpoint of electron donating. Is most preferable.

Further, the polymer (A) is a structural unit other than the unit represented by the general formula (5), and is a thiophene, pyrrole, phenylene, vinylene, or divalent unsaturated group as long as it does not affect the effect of the present invention. , It may contain one or more units selected from the group consisting of divalent saturated groups.

The polymer (A) is preferably a compound having a structure represented by the following general formula (6), and is preferably a compound represented by the following general formula (6), from the viewpoint of exhibiting high solubility and water permeability. Among the compounds having the above, poly (2-sulfo-5-methoxy-1,4-iminophenylene) and poly (2-methoxyaniline-5-sulfonic acid) are particularly preferable.

In the formula (6), R ²² to R ³⁷ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, a linear or branched alkoxy group having 1 to 4 carbon atoms, and the like. Represents an acidic group, a hydroxy group, a nitro group, or a halogen atom (-F, -Cl, -Br or I). Further, at least one of R ²² to R ³⁷ is an acidic group. Further, n indicates the degree of polymerization. In the present invention, n is preferably an integer of 5 to 2500.

It is desirable that at least a part of the acidic groups contained in the polymer (A) is in the free acid type.

The mass average molecular weight of the polymer (A) is preferably 10 to 1 million, more preferably 15 to 800,000, and further 20 to 500,000 in terms of sodium polystyrene sulfonate of GPC from the viewpoint of solubility and film forming property. It is preferable, and 2000 to 100,000 is particularly preferable. When the mass average molecular weight of the polymer (A) is less than 1000, the solubility is excellent, but the film forming property may be insufficient. On the other hand, when the mass average molecular weight exceeds 1 million, the solubility may be insufficient.
Here, the "film-forming property" refers to the property of forming a uniform film without repellency and the like, and can be evaluated by a method such as spin coating on glass.

The polymer (A) can be obtained, for example, by polymerizing the raw material monomer of the polymer (A) in the presence of a polymerization solvent and an oxidizing agent.
Hereinafter, an example of a method for producing the polymer (A) will be described.

<< Manufacturing method of polymer (A) >>
The method for producing the polymer (A) includes a step (polymerization step) of polymerizing the raw material monomer of the polymer (A) in the presence of a polymerization solvent and an oxidizing agent.

The polymerization step is a step of polymerizing the raw material monomer of the polymer (A) in the presence of a polymerization solvent and an oxidizing agent.
Specific examples of the raw material monomer include the polymerizable monomer from which the above-mentioned monomer unit is derived, and specifically, an acidic group-substituted aniline, an alkali metal salt thereof, an alkaline earth metal salt, an ammonium salt and a substituted ammonium. At least one selected from the group consisting of salts is mentioned.
Examples of the acidic group-substituted aniline include a sulfonic acid group-substituted aniline having a sulfonic acid group as an acidic group.
Typical sulfonic acid group-substituted aniline is aminobenzenesulfonic acid, specifically o-, m-, p-aminobenzenesulfonic acid, aniline-2,6-disulfonic acid, aniline-2,5. -Disulfonic acid, aniline-3,5-disulfonic acid, aniline-2,4-disulfonic acid, aniline-3,4-disulfonic acid and the like are preferably used.

Examples of the sulfonic acid group-substituted aniline other than aminobenzene sulfonic acids include methylaminobenzenesulfonic acid, ethylaminobenzenesulfonic acid, n-propylaminobenzenesulfonic acid, iso-propylaminobenzenesulfonic acid, and n-butylaminobenzenesulfonic acid. , Se-butylaminobenzenesulfonic acid, t-butylaminobenzenesulfonic acid and other alkyl group substituted aminobenzenesulfonic acids; methoxyaminobenzenesulfonic acid (eg 2-methoxyaniline-5-sulfonic acid, 2-methoxyaniline-3- Sulfonic acid, 3-methoxyaniline-2-sulfonic acid, 3-methoxyaniline-5-sulfonic acid, etc.), ethoxyaminobenzenesulfonic acid, propoxyaminobenzenesulfonic acid and other alkoxy group-substituted aminobenzenesulfonic acids; hydroxy group-substituted amino Examples thereof include benzenesulfonic acids; nitro group-substituted aminobenzenesulfonic acids; halogen-substituted aminobenzenesulfonic acids such as fluoroaminobenzenesulfonic acid, chloroaminobenzenesulfonic acid, and bromaminobenzenesulfonic acid.
Among these, alkyl group-substituted aminobenzene sulfonic acids, alkoxy group-substituted aminobenzene sulfonic acids, hydroxy group-substituted aminobenzene sulfonic acids, or halogen-substituted aminobenzene sulfonic acids can be obtained in that the polymer (A) having particularly excellent solubility can be obtained. Acids are preferable, and alkoxy group-substituted aminobenzenesulfonic acids, alkali metal salts thereof, ammonium salts and substituted ammonium salts thereof are particularly preferable because they are easy to produce.
Any one of these sulfonic acid group-substituted anilines may be used alone, or two or more thereof may be mixed and used at an arbitrary ratio.

Examples of the polymerization solvent include water, an organic solvent, and a mixed solvent of water and an organic solvent.
Examples of water include tap water, ion-exchanged water, pure water, ultrapure water, distilled water and the like.
Examples of the organic solvent include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, 2-butanol and tert-butanol; ketones such as acetone and ethyl isobutyl ketone; ethylene glycol and ethylene glycol. Ethylene glycols such as methyl ether; propylene glycols such as propylene glycol, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol butyl ether and propylene glycol propyl ether; N, N-dimethylformamide, N, N-dimethylacetamide and the like. Amids; Examples thereof include pyrrolidones such as N-methylpyrrolidone and N-ethylpyrrolidone.
As the polymerization solvent, water or a mixed solvent of water and an organic solvent is preferable.
When a mixed solvent of water and an organic solvent is used as the polymerization solvent, the mass ratio (water / organic solvent) thereof is preferably 1/100 to 100/1, and 2/100 to 100/2. Is more preferable.

The oxidizing agent is not limited as long as it has a standard electrode potential of 0.6 V or more, but peroxodisulfates such as peroxodisulfate, ammonium peroxodisulfate, sodium peroxodisulfate, and potassium peroxodisulfate; Examples include hydrogen peroxide.
Any one of these oxidizing agents may be used alone, or two or more thereof may be mixed and used at an arbitrary ratio.

In the polymerization step, the raw material monomer may be polymerized in the presence of a basic reaction aid in addition to the polymerization solvent and the oxidizing agent.
Examples of the basic reaction aid include inorganic bases such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; ammonia; methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylmethylamine, ethyldimethylamine, diethyl. Fatty amines such as methylamine; cyclic saturated amines; cyclic unsaturated amines such as pyridine, α-picolin, β-picolin, γ-picolin, quinoline and the like can be mentioned.
Among these, inorganic bases, fatty amines and cyclic unsaturated amines are preferable, and cyclic unsaturated amines are more preferable.
As these basic reaction aids, any one of them may be used alone, or two or more of them may be mixed and used at an arbitrary ratio.

Examples of the polymerization method include a method of dropping a raw material monomer solution into an oxidizing agent solution, a method of dropping an oxidizing agent solution into a raw material monomer solution, and a method of simultaneously dropping a raw material monomer solution and an oxidizing agent solution into a reaction vessel or the like. And so on. The raw material monomer solution may contain a basic reaction aid, if necessary.
As the solvent of the oxidizing agent solution and the raw material monomer solution, the above-mentioned polymerization solvent can be used.

The reaction temperature of the polymerization reaction is preferably 50 ° C. or lower, more preferably −15 to 40 ° C., still more preferably −10 to 30 ° C. When the reaction temperature of the polymerization reaction is 50 ° C. or lower, particularly 30 ° C. or lower, the progress of the side reaction can be suppressed. When the reaction temperature of the polymerization reaction is −15 ° C. or higher, a sufficient reaction rate can be maintained and the reaction time can be shortened.

By the polymerization step, the polymer (A) which is a reaction product is obtained in a state of being dissolved or precipitated in a polymerization solvent.
If the reaction product is dissolved in the polymerization solvent, the polymerization solvent is distilled off to obtain a reaction product.
When the reaction product is precipitated in the polymerization solvent, the polymerization solvent is filtered off by a filter such as a centrifuge to obtain a reaction product.

The reaction product thus obtained may be dried and used as the polymer (A), or, if necessary, the purified reaction product may be used as the polymer (A).
As a method for purifying the reaction product, any method such as a washing method using a washing solvent, a membrane filtration method, an ion exchange method, removal of impurities by heat treatment, and neutralization precipitation can be used.

(Basic compound (B))
When the polymer layer contains the basic compound (B), the polymer (A) and the basic compound (B) are ion-crosslinked in the polymer layer. Specifically, the basic compound (B) and the acidic group of the polymer (A) form an ionic crosslinked structure. As a result, the water resistance of the polymer layer is increased without lowering the ion exchange capacity of the polymer layer, and the separation membrane can be used for a long period of time.

As the basic compound (B), a compound having two or more nitrogen atoms is preferable. Since the basic compound (B) has two or more nitrogen atoms, the polymer (A) and the two or more nitrogen atoms of the basic compound (B) are stable in at least one of the molecules and between the molecules. It facilitates the formation of networks and further improves the water resistance of the polymer layer.

Examples of the basic compound (B) include 2-aminopyridine, 3-aminopyridine, 4-aminopyridine; 2,6-diaminopyridine, 2,3-diaminopyridine, 3,4-diaminopyridine; 4-dimethylamino. A pyridine derivative substituted with a tertiary amino group such as pyridine, 4-dimethylaminomethylpyridine, 3,4-bis (dimethylamino) pyridine; 1,5-diazabicyclo [4.3.0] -5-nonen (DBN). ), 1,8-diazabicyclo [5.4.0] -7-undecene (DBU), polyvinylpyridine and derivatives thereof; hydrazine, methylenediamine, ethiendiamine, diaminopropane, diaminobutane, diaminopentane, diaminohexane , Diaminoheptane and other aliphatic diamines; polyvalent pyridine compounds having two or more pyridine rings in the molecule such as bipyridyl; polyvalent quinoline compounds having two or more quinoline rings in the molecule; two pyrroles in the molecule Polyvalent pyrrole having the above; examples thereof include polyamine compounds such as polyallylamine.
As these basic compounds (B), any one of them may be used alone, or two or more of them may be mixed and used at an arbitrary ratio.

(Optional ingredient)
The polymer layer may contain components (arbitrary components) other than the polymer (A) and the basic compound (B), if necessary.
Optional components include, for example, binders, dispersants, fluidity modifiers, surfactants, lubricants, UV absorbers, storage stabilizers, adhesive aids, thickeners, leveling agents, antistatic agents, slip agents, organic fillers. And so on.

(Content)
The content of the polymer (A) in the polymer layer is preferably 0.1% by mass or more, more preferably 1% by mass or more, still more preferably 10% by mass or more, based on the total mass of the polymer layer.
When the content of the polymer (A) is at least the above lower limit value, the water permeability of the separation membrane is further increased.

The content of the basic compound (B) is preferably 0.1 to 100 parts by mass, more preferably 1 to 90 parts by mass, still more preferably 5 to 80 parts by mass, based on 100 parts by mass of the polymer (A). Up to 70 parts by mass is particularly preferable, and 20 to 50 parts by mass is most preferable.
When the content of the basic compound (B) is at least the above lower limit value, the water resistance of the polymer layer is further improved. When the content of the basic compound (B) is not more than the above upper limit value, the water permeability of the separation membrane can be well maintained.

(Film thickness)
The film thickness of the polymer layer is preferably 0.1 to 100 μm. When the film thickness of the polymer layer is at least the above lower limit value, the water permeability is further improved. When the film thickness of the polymer layer is not more than the above upper limit value, the filtration performance of the filtration membrane can be well maintained.

(Ion exchange capacity)
The ion exchange capacity of the polymer layer is more than 2 milliequivalents / g.
When the ion exchange capacity of the polymer layer exceeds the above lower limit, the removal rate (salt removal rate) of sodium chloride increases.

The ion exchange capacity of the polymer layer is determined as follows.
The filter membrane before forming the polymer layer was immersed in YmL of a sodium chloride aqueous solution having a concentration of X mol / L for 10 minutes, filtered, and the filtrate was neutralized and titrated with sodium hydroxide having a concentration of Z mol / L. i) Calculate the ion exchange capacity of the filter membrane from.
Separately, for the separation membrane, similarly, the separation membrane is immersed in YmL of sodium chloride aqueous solution having a concentration of X mol / L for 10 minutes, filtered, and the filtrate is neutralized and titrated with sodium hydroxide having a concentration of Z mol / L as described below. The ion exchange capacity of the separation membrane is calculated from equation (ii).
The ion exchange capacity of the polymer layer is obtained from the following formula (iii).
Ion exchange capacity of the filter membrane [milli equivalent / g] = (X [molar / L] x Y [mL] -Z [molar / L] x amount of sodium hydroxide required for neutralization titration [mL]) / filtration Film weight [g] ・ ・ ・ (i)
Ion exchange capacity of separation membrane [milli equivalent / g] = (X [molar / L] x Y [mL] -Z [molar / L] x amount of sodium hydroxide required for neutralization titration [mL]) / separation Membrane weight [g] ・ ・ ・ (ii)
Ion exchange capacity of polymer layer [milli equivalent / g] = ion exchange capacity of separation membrane-ion exchange capacity of filter membrane ... (iii)

<Action effect>
In the separation membrane of the present invention described above, a polymer layer containing the polymer (A) and the basic compound (B) is formed on the surface of the filtration membrane. Since the polymer (A) and the basic compound (B) are ion-crosslinked in the polymer layer and the polymer layer has excellent water resistance, the separation membrane can be used for a long period of time. Further, since the polymer layer has excellent water resistance, it is not necessary to reduce the ion exchange capacity of the polymer layer, and the amount can be over 2 mm equivalent / g, so that the salt removal rate is high.
Further, since the polymer (A) has an acidic group, the water permeability of the separation membrane is also increased.

<Use>
The separation membrane of the present invention is suitable as a separation membrane used for the production of drinking water, the production of ultrapure water for cleaning semiconductors and the like, and the water treatment such as water purification treatment and wastewater treatment.

[Manufacturing method of separation membrane]
The separation membrane of the present invention can be obtained by treating the surface of the above-mentioned filtration membrane with the composition (X) containing the above-mentioned polymer (A) and the basic compound (B). That is, the method for producing a separation membrane of the present invention includes a step (treatment step) of treating the surface of the filter membrane using the composition (X) containing the polymer (A) and the basic compound (B).

The composition (X) contains the polymer (A) and the basic compound (B). The composition (X) preferably further contains a solvent. Further, the composition (X) may contain an arbitrary component, if necessary.
Since the polymer (A), the basic compound (B) and the optional component are the same as the polymer (A), the basic compound (B) and the optional component exemplified above in the description of the separation membrane, these explanations are omitted. do.
The content of the polymer (A) is preferably 0.075 to 98.9% by mass, more preferably 0.1 to 89.9% by mass, based on the total mass of the composition (X). When the content of the polymer (A) is within the above range, the applicability of the composition (X) to the filtration membrane is improved.

The solvent contained in the composition (X) is not particularly limited as long as it has at least the effect of the present invention as long as it is a solvent capable of dissolving the polymer (A), but water, an organic solvent, water and an organic solvent. A mixed solvent with and can be mentioned.
Examples of water include water among the polymerization solvents exemplified above in the description of the method for producing the polymer (A).
Examples of the organic solvent include organic solvents among the polymerization solvents exemplified above in the description of the method for producing the polymer (A).
When a mixed solvent of water and an organic solvent is used as the solvent, the mass ratio (water / organic solvent) thereof is preferably 1/100 to 100/1, and preferably 2/100 to 100/2. More preferred.

The content of the solvent is preferably 1 to 99.85% by mass, more preferably 10 to 99.5% by mass, still more preferably 50 to 99.5% by mass, based on the total mass of the composition (X). When the content of the solvent is within the above range, the applicability of the composition (X) to the filtration membrane is improved.

In the treatment step, the surface of the filtration membrane is treated with the composition (X). Specific examples of the treatment method include a method in which the composition (X) is applied to the surface of the filtration membrane and then heated.
As a method of applying the composition (X) to the surface of the filter membrane, a method used for general coating can be adopted, for example, a gravure coater, a roll coater, a curtain flow coater, a spin coater, a bar coater, a reverse coater, and a knife coater. , A coating method such as a fan ten coater, a rod coater, an air doctor coater, a knife coater, a blade coater, a cast coater, a screen coater, a spray method such as a spray coating, and a dipping method such as a dip are used.

The heating temperature is preferably 40 to 120 ° C.
The heating time is preferably 10 seconds to 100 minutes.
Instead of heating the filtration membrane coated with the composition (X), the filtration membrane coated with the composition (X) may be left at room temperature (25 ° C.) for 1 to 60 minutes.

By treating the surface of the filter membrane with the composition (X) in this way, a separation membrane in which a polymer layer containing the polymer (A) and the basic compound (B) is formed on the surface of the filter membrane is formed. can get.
In this polymer layer, the polymer (A) and the basic compound (B) are ion-crosslinked, and the polymer layer has excellent water resistance. Further, since the polymer (A) has an acidic group, the water permeability of the separation membrane is also increased.
Therefore, according to the method for producing a separation membrane of the present invention, a separation membrane having a high water permeability and can be used for a long period of time can be easily produced.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples do not limit the scope of the present invention.

[Measurement / evaluation method]
<Measurement of ion exchange capacity>
The ion exchange capacity of the polymer layer was determined as follows.
First, 2 g of the filtration membrane before forming the polymer layer is immersed in 30 mL of a sodium chloride aqueous solution having a concentration of 1 mol / L for 10 minutes, then filtered, and the filtrate is neutralized and titrated with sodium hydroxide having a concentration of 0.1 mol / L. Then, the ion exchange capacity of the filter membrane was calculated from the following formula (i).
Separately, for the separation membrane, similarly, 2 g of the separation membrane is immersed in 30 mL of a sodium chloride aqueous solution having a concentration of 1 mol / L for 10 minutes, filtered, and the filtrate is neutralized and titrated with sodium hydroxide having a concentration of 0.1 mol / L. Then, the ion exchange capacity of the separation membrane was calculated from the following formula (ii).
The ion exchange capacity of the polymer layer was determined from the following formula (iii).
Ion exchange capacity of the filter membrane [milli equivalent / g] = (X [molar / L] x Y [mL] -Z [molar / L] x amount of sodium hydroxide required for neutralization titration [mL]) / filtration Film weight [g] ・ ・ ・ (i)
Ion exchange capacity of separation membrane [milli equivalent / g] = (X [molar / L] x Y [mL] -Z [molar / L] x amount of sodium hydroxide required for neutralization titration [mL]) / separation Membrane weight [g] ・ ・ ・ (ii)
Ion exchange capacity of polymer layer [milli equivalent / g] = ion exchange capacity of separation membrane-ion exchange capacity of filter membrane ... (iii)
In the formulas (i) and (ii), "X" is the concentration of sodium chloride, "Y" is the amount of sodium chloride used, and "Z" is the concentration of sodium hydroxide.

<Measurement of water permeability>
After bundling the separation membranes and inserting them into a plastic sleeve, thermosetting resin was poured into the sleeves, cured and sealed. An open surface of the separation membrane was obtained by cutting the end portion of the separation membrane cured with a thermosetting resin, and an evaluation module having a membrane area based on the outer diameter of about 0.025 m ² was produced. The obtained evaluation module was connected to a membrane performance test device consisting of a water supply tank and a pump, and the water permeability was measured as follows.
Sodium chloride was dissolved in water so that the concentration was 500 mg / L to prepare water to be treated. The water to be treated was continuously sent from the outside to the inside of the separation membrane under the conditions of 25 ° C. and a pressure of 1.0 MPa. After 1 hour had passed from the start of the liquid feeding, the permeated water was collected from the opening surface of the separation membrane, and the weight of the permeated water was measured with an electronic balance (“LIBROR EB-3200D” manufactured by Shimadzu Corporation). The permeated water weight was converted into the permeated water amount at 25 ° C. from the following formula (iv). In addition, the amount of water permeation was calculated from the following formula (v).
Permeated water amount [L] = Permeated water weight [kg] /0.99704 [kg / L] ・ ・ ・ (iv)
Permeability [L / m ² / day] = Permeability [L] / Outer diameter reference membrane area [m ² ] / Collection time [minutes] x (60 [minutes] x 24 [hours]) ... (v)

From the calculated water permeability, evaluation was made according to the following evaluation criteria.
A: The water permeability is 200 L / m ² / day or more.
B: The water permeability is less than 200 L / m ² / day.

<Measurement of salt removal rate>
Permeable water was collected in the same manner as the measurement of the amount of permeation.
Using an electric conductivity meter (manufactured by DKK-TOA CORPORATION, "CM-25R"), the sodium chloride concentration of the collected permeated water was measured, and the salt removal rate was determined from the following formula (vi).
Salt removal rate [%] = (1-sodium chloride concentration of permeated water [mg / L] / sodium chloride concentration of treated water [mg / L]) x 100 ... (vi)

From the calculated salt removal rate, evaluation was made according to the following evaluation criteria.
A: The salt removal rate is 70% or more.
B: The salt removal rate is less than 70%.

<Evaluation of water resistance>
After immersing the separation membrane in water for 1 hour, the state of dissolution (elution) of the polymer layer of the separation membrane was visually observed, and the water resistance of the polymer layer was evaluated according to the following evaluation criteria.
A: No dissolution of the polymer layer is observed by visual observation.
B: Dissolution of the polymer layer is observed by visual observation.

[Manufacturing of polymer (A)]
100 mmol of 2-methoxyaniline-5-sulfonic acid was dissolved in 300 mL of a triethylamine solution (solvent: water / acetonitrile = 5/5 (mass ratio)) having a concentration of 4 mol / L at 25 ° C. to obtain a monomer solution.
Separately, 100 mmol of ammonium peroxodisulfate was dissolved in a solution of water / acetonitrile = 5/5 (mass ratio) to obtain an oxidizing agent solution.
Then, the oxidizing agent solution was added dropwise to the monomer solution. After completion of the dropping, the mixture was further stirred at 25 ° C. for 12 hours, and then the reaction product was filtered off by a centrifugal filter. Further, the reaction product was washed with methanol and then dried to obtain 15 g of poly (2-methoxyaniline-5-sulfonic acid) which is a powdery polymer (A-1).

[Example 1]
5.5 parts by mass of polymer (A-1), 1.65 parts by mass of polyvinylpyridine (manufactured by Aldrich), 2.85 parts by mass of water-dispersed polyester (manufactured by Mitsubishi Chemical Co., Ltd., "Nichigo Polyester"), The composition (X) was prepared by mixing 390 parts by mass of water and 600 parts by mass of ethanol as a solvent.
The composition (X) is immersed in a hollow porous membrane made of polyether sulfone as a filtration membrane for 5 seconds, and then held in a hot air dryer at 60 ° C. for 3 minutes to form a film on the surface of the filtration membrane. A separation membrane having a 2 μm polymer layer formed was obtained. The obtained separation membrane is a hollow fiber membrane.
With respect to the obtained separation membrane, the ion exchange capacity, the amount of water permeation and the salt removal rate of the polymer layer were measured, and the water resistance was evaluated. The results are shown in Table 1.

[Example 2]
The composition (X) was prepared in the same manner as in Example 1 except that the water-dispersed polyester was not used, and a separation membrane was produced.
With respect to the obtained separation membrane, the ion exchange capacity, the amount of water permeation and the salt removal rate of the polymer layer were measured, and the water resistance was evaluated. The results are shown in Table 1.

[Comparative Example 1]
The filtration membrane used in Example 1 was used as a separation membrane, and the water permeability and the salt removal rate were measured. The results are shown in Table 1.

[Comparative Example 2]
The composition (X) was prepared in the same manner as in Example 1 except that polyvinylpyridine was not used, and a separation membrane was produced.
With respect to the obtained separation membrane, the ion exchange capacity, the amount of water permeation and the salt removal rate of the polymer layer were measured, and the water resistance was evaluated. The results are shown in Table 1.

As is clear from Table 1, the separation membranes obtained in each example had a high water permeability and a high salt removal rate. It was also shown that the polymer layer has excellent water resistance and can be used for a long time.
On the other hand, in the case of Comparative Example 1 in which the polymer layer was not formed on the surface, the water permeability and the salt removal rate were lower than those of the separation membranes obtained in each example.
The separation membrane of Comparative Example 2 in which a polymer layer containing no polyvinylpyridine is formed on the surface of the filtration membrane is used for a long time because the polymer layer dissolves when immersed in water and the water resistance of the polymer layer is inferior. Is unsuitable. Further, in the case of Comparative Example 2, although the polymer layer contained the polymer (A), the amount of water permeation was low because the polymer layer was dissolved in water. Further, although the ion exchange capacity of the polymer layer was more than 2 milliequivalent / g, the salt removal rate was low because the polymer layer was dissolved in water.

The separation membrane of the present invention has a high water permeability, can be used for a long period of time, and is used for production of drinking water, production of ultrapure water for cleaning semiconductors, water treatment such as water purification treatment and wastewater treatment, and the like. It is useful as a membrane.

Claims (4)

A separation membrane having a filtration membrane and a polymer layer formed on the surface of the filtration membrane.
The polymer layer contains a polymer having an acidic group and a basic compound.
A separation membrane in which the ion exchange capacity of the polymer layer is more than 2 milliequivalent / g. The separation membrane according to claim 1, wherein the polymer having an acidic group has a unit represented by the following general formula (5).

In the formula (5), R ¹⁸ to R ²¹ each independently have a hydrogen atom, a linear or branched alkyl group having 1 to 24 carbon atoms, and a linear or branched alkoxy group having 1 to 24 carbon atoms. It represents an acidic group, a hydroxy group, a nitro group, or a halogen atom, and at least one of R ¹⁸ to R ²¹ is an acidic group. A method for manufacturing a separation membrane equipped with a filtration membrane.
A method for producing a separation membrane, which comprises a step of treating the surface of the filtration membrane using a composition containing a polymer having an acidic group and a basic compound. The method for producing a separation membrane according to claim 3, wherein the polymer having an acidic group has a unit represented by the following general formula (5).

In the formula (5), R ¹⁸ to R ²¹ each independently have a hydrogen atom, a linear or branched alkyl group having 1 to 24 carbon atoms, and a linear or branched alkoxy group having 1 to 24 carbon atoms. It represents an acidic group, a hydroxy group, a nitro group, or a halogen atom, and at least one of R ¹⁸ to R ²¹ is an acidic group.