JP2015009162A - Ion exchange membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ion exchange membrane which has low membrane resistance and is excellent in organic contamination resistance.SOLUTION: The ion exchange membrane A is provided which is constituted of a block or graft copolymer (P) with a vinyl alcohol-based polymer component (a) and a polymer component (b) having an ion group as a constituent and a polymer (B) having an ion group, and in which the polymer component (b) having the ion group and the polymer (B) having the ion group are each constituted of a monomer having an ion group, and in which the molar ratio (M/M×100) of the mol number (M) of the monomer (M) having the ion group included in the block or graft copolymer (P) to the total mol number (M) of the monomer (M) having the ion group included in the block or graft copolymer (P) and the polymer (B), falls within a range of 30.0%-99.9%.

Description

  The present invention relates to an ion exchange membrane comprising a block or graft copolymer (P) comprising a vinyl alcohol polymer component (a) and a polymer component (b) having an ionic group as constituent components.

  Ion exchange membranes are currently used for a wide variety of applications such as seawater concentration, desalination of groundwater for drinking water and removal of nitrate nitrogen, salt removal in food manufacturing processes, and concentration of active pharmaceutical ingredients. It is used as a membrane in electrodialysis and diffusion dialysis. The useful ion exchange membranes used in these are mainly styrene-divinylbenzene-based homogeneous ion exchange membranes, and various kinds such as monovalent and divalent ion selection, increased specific ion selectivity, low membrane resistance, etc. Technology has been developed and industrially useful separation has been achieved.

   In general, in the synthesis process of organic substances in the above-mentioned fields such as foods, pharmaceuticals, and agricultural chemicals, salts and the like are often by-produced. Salts contained in such organic substances are often separated by electrodialysis. In salt separation by electrodialysis, cation exchange membranes and anion exchange membranes are arranged alternately, and direct current is applied to cause cations to flow on the cathode side of the cation exchange membrane and on the anode side of the anion exchange membrane. Desalting is realized by eliminating the anion and thus removing the salt from the electrolyte solution concentrated in the chamber formed by being sandwiched between the cation exchange membrane on the cathode side and the anion exchange membrane on the anode side. When desalting the treatment liquid by electrodialysis, organic pollutants in the liquid to be treated, especially macromolecules having a charge (hereinafter referred to as giant organic ions) adhere to the ion exchange membrane and reduce the performance of the membrane. The problem of organic contamination of the film arises.

  On the other hand, a polymer electrolyte membrane (Patent Document 1) comprising a block copolymer comprising a vinyl alcohol polymer block and a polymer block having an ion conductive group as constituent components, a vinyl alcohol polymer component, and a cationic property An anion exchange membrane comprising a block copolymer having a polymer component having a group as a constituent component is known (Patent Document 2). In particular, in Patent Document 2, the above anion exchange membrane is resistant to organic contamination. It is disclosed to have.

Japanese Patent No. 4776683 WO2010 / 110333

  The inventors of the present invention have attracted attention because an ion exchange membrane comprising a block polymer comprising a vinyl alcohol polymer component and a polymer component having an ionic group as constituent components is excellent in resistance to organic contamination. Recognizing that it is necessary to improve the basic performance such as lowering the membrane resistance, this was set as a problem to be solved.

  The present invention has been made to solve the above-mentioned problems, and is to provide a polyvinyl alcohol ion exchange membrane that is excellent in basic characteristics such as membrane resistance and is also useful for electrodialysis.

  As a result of intensive studies to achieve the above object, the present inventors have made a block or graft copolymer comprising a vinyl alcohol polymer component (a) and a polymer component (b) having an ionic group as constituent components. In the production of an ion exchange membrane composed of (P), a polymer (B) having an ionic group as a by-product inevitably generated during block or graft copolymerization (however, block or graft copolymer) It has been found that suppressing mixing (except for coalescence) is effective in obtaining a polyvinyl alcohol ion exchange membrane having good basic properties such as membrane resistance, and the present invention has been completed.

The present invention comprises a block or graft copolymer (P) comprising as constituent components a vinyl alcohol polymer component (a) and a polymer component (b) having an ionic group,
A polymer (B) having an ionic group,
The polymer component (b) having an ionic group and the polymer (B) having an ionic group are each composed of a monomer (M) having an ionic group,
The block or graft copolymer (M _{P + B} ) with respect to the total number of moles (M _{P + B} ) of the monomer (M) having an ionic group contained in both the block or graft copolymer (P) and the polymer (B) ( The molar ratio [(M _P / M _{P + B} ) × 100] of the number of moles (M _P ) of the monomer (M) having an ionic group contained in P) is 30.0% or more and 99.9% or less. It is an ion exchange membrane characterized by being in the range.

  The molar ratio is preferably 50.0% or more and 95% or less.

  The polymer component (b) preferably has an anionic group or a cationic group as an ionic group.

  It is preferable that the polymer component (b) has a monomer represented by the following general formula (a-1) as a repeating unit.

［式中、Ｒ^１は水素原子またはアルカリ金属原子である。］

[Wherein, R ¹ represents a hydrogen atom or an alkali metal atom. ]

  Since the ion exchange membrane of the present invention has high hydrophilicity, it is highly resistant to organic contamination, and the monomer (M) having an ionic group is efficiently incorporated into the block or graft copolymer (P). Therefore, it has excellent basic characteristics such as low film resistance. Therefore, it is expected to be suitably used for electrodialysis.

It is the schematic which shows the apparatus used for evaluation of the membrane resistance of an ion exchange membrane.

The ion exchange membrane of the present invention comprises a block or graft copolymer (P) comprising a vinyl alcohol polymer component (a) and a polymer component (b) having an ionic group as constituent components, and a polymer having an ionic group. (B), and the vinyl alcohol polymer (A) may be contained in the above-mentioned constituent elements. The polymer component (b) having an ionic group and the polymer (B) having an ionic group are each composed of a monomer (M) having an ionic group, and the block or graft copolymer ( Ionic groups contained in the block or graft copolymer (P) with respect to the total number of moles (M _{P + B} ) of the monomer (M) having ionic groups contained in P) and the polymer (B) The molar ratio [(M _P / M _{P + B} ) × 100] of the number of moles (M _P ) of the monomer (M) possessed is within the range of 30.0% or more and 99.9% or less. It is a feature.

(Block copolymer)
A preferred structure of the block copolymer (P) constituting the ion exchange membrane of the present invention includes a block copolymer (P1) represented by the following general formula (1).

[式中、０．５０００≦ｏ^１／（ｎ^１＋ｏ^１）≦０．９９９９であり、０．０１≦ｍ^１／（ｍ^１＋ｎ^１＋ｏ^１）≦０．５０であり、Ｍはイオン基を有する単量体である。]

[Wherein, 0.5000 ≦ o ¹ / (n ¹ + o ¹ ) ≦ 0.9999, 0.01 ≦ m ¹ / (m ¹ + n ¹ + o ¹ ) ≦ 0.50, and M is an ionic group It is a monomer having ]

In the general formula (1), o ¹ / (n ¹ + o ¹ ) represents a ratio other than vinyl acetate units contained in the vinyl alcohol polymer component (a). About a minimum, it is 0.5000 or more, More preferably, it is 0.7000 or more, More preferably, it is 0.8000 or more. On the other hand, the upper limit is preferably 0.9999, more preferably 0.999 or less, and still more preferably 0.995 or less.

In the above general formula (1), m ¹ / (m ¹ + n ¹ + o ¹ ) is a polymer component having an ionic group contained in a vinyl alcohol polymer component (a) and a polymer component (b) having an ionic group ( The ratio of b) is shown. The lower limit is 0.01 or more, preferably 0.03 or more, and more preferably 0.05 or more. The upper limit is 0.50 or less, more preferably 0.30 or less, and preferably 0.25 or less.

[式中、０．５０００≦ｏ^２／（ｎ^２＋ｏ^２）≦０．９９９９であり、０．００１≦ｐ^２／（ｎ^２＋ｏ^２＋ｐ^２）≦０．０５であり、０．０１≦ｍ^２／（ｍ^２＋ｎ^２＋ｏ^２）≦０．５０であり、Ｒ^２は、水素原子又はカルボキシル基であり、Ｒ^３は、水素原子、メチル基、カルボキシル基又はカルボキシメチル基であり、Lは、窒素原子及び／又は酸素原子を含んでいてもよい炭素数１〜２０の２価の脂肪族炭化水素基であり、Ｒ^２がカルボキシル基の場合やＲ^３がカルボキシル基又はカルボキシルメチル基の場合は、隣接する水酸基と環を形成していてもよい。Ｍはイオン基を有する単量体である。] (Graft copolymer)
A preferred structure of the graft copolymer (P) constituting the ion exchange membrane of the present invention is a graft copolymer (P2) represented by the following general formula (2).

[In the formula, 0.5000 ≦ o ² / (n ² + o ² ) ≦ 0.9999, 0.001 ≦ p ² / (n ² + o ² + p ² ) ≦ 0.05, 0.01 ≦ m ² / (m ² + n ² + o ² ) ≦ 0.50, R ² is a hydrogen atom or a carboxyl group, R ³ is a hydrogen atom, a methyl group, a carboxyl group or a carboxymethyl group, L Is a divalent aliphatic hydrocarbon group having 1 to 20 carbon atoms which may contain a nitrogen atom and / or an oxygen atom, and R ² is a carboxyl group or R ³ is a carboxyl group or a carboxylmethyl group. In some cases, a ring may be formed with an adjacent hydroxyl group. M is a monomer having an ionic group. ]

In the general formula (2), o ² / (n ² + o ² ) represents a ratio other than vinyl acetate units contained in the vinyl alcohol polymer component (a). About a minimum, it is 0.5000 or more, More preferably, it is 0.7000 or more, More preferably, it is 0.8000 or more. On the other hand, the upper limit is preferably 0.9999, more preferably 0.999 or less, and still more preferably 0.995 or less.

Formula (2) in ^{m 2 / (m 2 + n} 2 + o 2) the polymer component having an ionic group contained in the polymer component having a vinyl alcohol polymer component (a) and ionic groups (b) ( The ratio of b) is shown. The lower limit is 0.01 or more, preferably 0.03 or more, and more preferably 0.05 or more. The upper limit is 0.50 or less, more preferably 0.30 or less, and preferably 0.25 or less.

In the general formulas (1) and (2), it means that the monomer repeating units n ¹ , o ¹ , n ² , o ² and p ² are arranged as indicated. However, it simply indicates that each unit exists and is usually randomly arranged, but the same unit may be continuous.

  In the said General formula (2), L should just be a C1-C20 bivalent aliphatic hydrocarbon group which may contain the nitrogen atom and / or an oxygen atom, and is not specifically limited. The number of nitrogen atoms and oxygen atoms contained in L is not particularly limited. The aliphatic hydrocarbon group may be linear, branched or cyclic, and is preferably linear or branched. In the case where the aliphatic hydrocarbon group is branched, the number of carbon atoms at the site branched from the main chain of the aliphatic hydrocarbon group (a chain in which atoms are continuous between a sulfur atom and a nitrogen atom) is 1 to 5 is preferable. In the case where L contains a nitrogen atom and / or an oxygen atom, for example, the aliphatic hydrocarbon group is a carbonyl bond (—CO 2) in which a nitrogen atom and / or an oxygen atom is inserted into the aliphatic hydrocarbon group. -), An ether bond (-O-), an amino bond [-NR- (R is a hydrogen atom or a group containing carbon bonded to N)], an amide bond (-CONH-) or the like, The aliphatic hydrocarbon group may contain a nitrogen atom and / or an oxygen atom as a carboxyl group (—COOH), a hydroxyl group (—OH), or the like that replaces the aliphatic hydrocarbon group. From the viewpoint of raw material availability and ease of synthesis, L is preferably a linear or branched alkylene group having a total carbon number of 1 to 20, which may have a carboxyl group, more preferably, A linear or branched alkylene group having 2 to 15 carbon atoms and optionally having a carboxyl group, more preferably 2 to 10 carbon atoms having a carboxyl group. A good linear or branched alkylene group.

(Monomer having an ionic group)
Examples of the ionic group in the monomer (M) having an ionic group constituting the block copolymer or graft copolymer include an anionic group and a cationic group.

Examples of the anionic group include a sulfonic acid group, a phosphoric acid group, a carboxylic acid group, a boronic acid group, and a sulfonylimide group. Although it does not specifically limit as a cation of a counter, Monovalent cations, such as an alkali metal ion, H ^<+> , quaternary ammonium ion, are preferable.

Examples of the cationic group include an N-trialkylammonium group, an N-alkylpyridinium group, an N-alkylimidazolium group, a thiouronium group, and an isothiouronium group. The anion of the counter is not particularly limited, but a halogenated anion of a group 5B element such as PF ₆ ⁻ , SbF ₆ ⁻ , AsF ₆ ^—, a halogenated anion of a group 3B element such as BF ₄ ⁻ , I ⁻ (I ₃ ⁻ ), Halogen anions such as Br ⁻ and Cl ⁻ , halogen acid anions such as ClO ₄ ⁻ , metal halide anions such as AlCl ₄ ⁻ , FeCl ₄ ⁻ and SnCl ₅ ⁻ , nitrate anions represented by NO ₃ ⁻ , p− 1 such as toluenesulfonic acid anion, naphthalenesulfonic acid anion, organic sulfonic acid anions such as CH ₃ SO ₃ ⁻ and CF ₃ SO ₃ ^— , carboxylic acid anions such as CF ₃ COO ⁻ and C ₆ H ₅ COO ⁻ , and OH ⁻ A valent anion is preferred.

  Examples of the monomer M having an ionic group include structural units derived from at least one ethylenically unsaturated monomer that is covalently bonded to the ionic group. Examples of the ethylenically unsaturated monomer include α-olefins such as ethylene, propylene, n-butene, and isobutylene; styrenes such as styrene and α-methylstyrene; acrylic acid, methyl acrylate, ethyl acrylate, acrylic Acrylic acid or esters thereof such as n-propyl acid, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate; methacrylic acid, methyl methacrylate, ethyl methacrylate, methacrylic acid Methacrylic acid or esters thereof such as n-propyl, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate; acrylamide, N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetone Acrylamides such as chloramide; Methacrylamides such as methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropyldimethylamine; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n- Vinyl ethers such as butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, 2,3-diacetoxy-1-vinyloxypropane; allyl acetate, 2,3-diacetoxy-1-allyloxypropane, Examples include allyl compounds such as allyl chloride; unsaturated dicarboxylic acids such as maleic acid, itaconic acid, fumaric acid, and esters thereof.

  Examples of the monomer (M) having an ionic group include the following general formulas (a-2) to (a-13) in addition to the above general formula (a-1). It may be used alone or in combination of two or more.

[Wherein, R ¹ represents a hydrogen atom or an alkali metal atom. ]

[Wherein, R ¹ has the same meaning as described above. ]

[Wherein, R ¹ has the same meaning as described above. ]

[Wherein, R ¹ has the same meaning as described above. ]

[Wherein, R ¹ has the same meaning as described above. ]

[Wherein, R ¹ is as defined above, and R ⁴ is a hydrogen atom or a methyl group. ]

[Wherein, R ¹ and R ⁴ are as defined above. ]

[Wherein, X ⁻ represents a halogenated anion of a group 5B element such as PF ₆ ⁻ , SbF ₆ ⁻ , AsF ₆ ^−, a halogenated anion of a group 3B element such as BF ₄ ⁻ , I ⁻ (I ₃ ⁻ ), Halogen anions such as Br ⁻ and Cl ⁻ , halogen acid anions such as ClO ₄ ⁻ , metal halide anions such as AlCl ₄ ⁻ , FeCl ₄ ⁻ and SnCl ₅ ⁻ , nitrate anions represented by NO ₃ ⁻ , p-toluenesulfone Monovalent cation such as acid anion, naphthalene sulfonate anion, organic sulfonate anion such as CH ₃ SO ₃ ⁻ and CF ₃ SO ₃ ^— , carboxylic acid anion such as CF ₃ COO ⁻ and C ₆ H ₅ COO ⁻ , and OH ⁻ An anion, and R ⁴ is as defined above. ]

[Wherein, X ⁻ has the same meaning as described above. ]

[Wherein, X ⁻ has the same meaning as described above. ]

[Wherein, X ⁻ has the same meaning as described above. ]

[Wherein, X ⁻ has the same meaning as described above. ]

(Polymer component having an ionic group)
In the polymer component (b) having an ionic group constituting the block or graft copolymer (P) in the present invention, the monomer (M) having the above ionic group has m ¹ or m ² repetitions. It is composed of a polymer. In forming a polymer from the above monomer, not only a homopolymer of the monomer having the above ionic group but also other ethylenically unsaturated as long as the ion exchange membrane according to the present invention is obtained. It may be a copolymer with a monomer. Examples of the ethylenically unsaturated monomer include the above ethylenically unsaturated monomers.

(Components of ion exchange membrane)
The ion exchange membrane of the present invention is formed with a block or graft copolymer (P) comprising the above-mentioned vinyl alcohol polymer component (a) and a polymer component (b) having an ionic group as constituent components. However, it contains a polymer (B) having an ionic group by-produced during the production of the block or graft copolymer, which will be described later, and the block or graft copolymer (P) and the polymer (B ) Of the monomer (M) having an ionic group contained in the block or graft copolymer (P) with respect to the total number of moles (M _{P + B} ) of the monomer (M) having an ionic group contained in The molar ratio of the number of moles (M _P ) [(M _P / M _{P + B} ) × 100] is in the range of 30.0% or more and 99.9% or less, more preferably 50 0.0% or more and 95.0% or less, Preferably less 70.0 or more and 90.0% to. As shown in Examples and Comparative Examples to be described later, when the molar ratio of the polymer component (b) having an ionic group is 30.0% or more, preferably 50% or more, ions having low film resistance can be obtained. An exchange membrane can be obtained.
Further, the ion exchange membrane of the present invention comprises a vinyl alcohol polymer (A) having no ionic group remaining at the time of producing a block or graft copolymer (P) described later, a monomer (M) having an ionic group. May be included.

  The polymer component (b) having an ionic group contained in the block or graft copolymer constituting the ion exchange membrane of the present invention is a homopolymer or a random copolymer of a cationic monomer or an anionic monomer. The composition, molecular weight, molecular weight distribution, etc. are not particularly limited, but the content of the cationic monomer or anionic monomer is 1 to 90 mol with respect to all the structural units of the block or graft copolymer. %, More preferably 1 to 50 mol%, still more preferably 1 to 40%, and particularly preferably 3 to 30%. When the content is in these preferable ranges, the toughness of the film is easily developed. When the content is less than 1 mol%, the effective charge density in the ion exchange membrane is lowered, and the counter ion selectivity of the membrane may be lowered. If the content exceeds 90 mol%, the strength of the film may be reduced.

  In the present invention, the block or graft copolymer (P) and the ion exchange membrane composed thereof may contain any additive as necessary, and the order of addition is also arbitrarily selected. be able to. The additive can be appropriately selected from known additives, for example, metal fine particles, inorganic fine particles, inorganic salts, ultraviolet absorbers, antioxidants, deterioration inhibitors, dispersants, surfactants, Examples thereof include polymerization inhibitors, thickeners, conductive assistants, surface modifiers, antiseptics, antifungal agents, antibacterial agents, antifoaming agents, and plasticizers. These may be used alone or in combination of two or more.

(Method for producing block copolymer)
The block copolymer (P1) constituting the ion-exchange membrane of the present invention uses a terminal mercapto group-containing vinyl alcohol polymer (Q1) and a monomer (M) having an ionic group. 1 and Patent Document 2 and the like. The terminal mercapto group-containing vinyl alcohol polymer (Q1) is obtained by radical polymerization of a vinyl acetate monomer in the presence of thioacetic acid by the method described in Japanese Patent Publication No. 3-57923 and the like. It can obtain by processing with.

  Although the content rate of the vinyl alcohol unit in the terminal mercapto group-containing vinyl alcohol polymer (Q1) (that is, the degree of saponification of the terminal mercapto group-containing vinyl alcohol polymer) is not particularly limited, all the structural units in the polymer Is 100 mol%, preferably 50 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more. On the other hand, regarding the upper limit, the total structural unit in the polymer is 100 mol%, preferably 99.99 mol% or less, more preferably 99.9 mol% or less, and further preferably 99.5 mol%. It is as follows.

  The viscosity average degree of polymerization of the above-mentioned terminal mercapto group-containing vinyl alcohol polymer (Q1) measured according to JIS K6726 is not particularly limited, and is preferably 100 to 5,000, more preferably 200 to 4, more preferably. 000. When the viscosity average degree of polymerization is less than 100, the mechanical strength of the derived resin composition may be lowered. A vinyl alcohol polymer having a viscosity average polymerization degree exceeding 5,000 is difficult to produce industrially.

(Method for producing graft copolymer)
The graft copolymer (P2) constituting the ion exchange membrane of the present invention is represented by the following general formula (4), which is composed of a structural unit represented by the following general formula (3) and a vinyl alcohol-based structural unit. It is produced by polymerizing a monomer (M) having an ionic group by the method described in Patent Document 1 or Patent Document 2 using the side chain mercapto group-containing vinyl alcohol polymer (Q2) shown as a backbone polymer. can do.

[Wherein, R ² and R ³ are as defined above. ]

[Wherein, n ² , o ² , p ² , L, R ¹ and R ² are as defined above. ]

  The structural unit represented by the general formula (3) can be derived from an unsaturated monomer that can be converted into the structural unit, and preferably has an unsaturated double bond represented by the following general formula (5). It can derive from the thioester type monomer which has.

[Wherein, R ^2a and R ^2b are a hydrogen atom or a carboxyl group, at least one is a hydrogen atom, R ⁵ is a methyl group, or is bonded to a specific carbon atom contained in L and is cyclic A structure is formed, and R ³ and X are as defined above. ]

  The thioester monomer having an unsaturated double bond represented by the general formula (5) can be produced according to a known method.

  Preferred specific examples of the thioester monomer having an unsaturated double bond represented by the general formula (5) include, for example, thioacetic acid S- (3-methyl-3-buten-1-yl) ester, thio Acetic acid S-17-octadecene-1-yl ester, thioacetic acid S-15-hexadecene-1-yl ester, thioacetic acid S-14-pentadecene-1-yl ester, thioacetic acid S-13-tetradecene-1-yl ester Thioacetic acid S-12-tridecen-1-yl ester, thioacetic acid S-11-dodecen-1-yl ester, thioacetic acid S-10-undecen-1-yl ester, thioacetic acid S-9-decene-1- Yl ester, thioacetic acid S-8-nonen-1-yl ester, thioacetic acid S-7-octen-1-yl ester, thioacetic acid S-6-hepten-1-yl ester Tellurium, thioacetic acid S-5-hexen-1-yl ester, thioacetic acid S-4-penten-1-yl ester, thioacetic acid S-3-buten-1-yl ester, thioacetic acid S-2-propene-1 -Yl ester, thioacetic acid S- [1- (2-propen-1-yl) hexyl] ester, thioacetic acid S- (2,3-dimethyl-3-buten-1-yl) ester, thioacetic acid S- ( 1-ethenylbutyl) ester, thioacetic acid S- (2-hydroxy-5-hexen-1-yl) ester, thioacetic acid S- (2-hydroxy-3-buten-1-yl) ester, thioacetic acid S- (1 , 1-dimethyl-2-propen-1-yl) ester, 2-[(acetylthio) methyl] -4-pentenoic acid, thioacetic acid S- (2-methyl-2-propen-1-yl) ester, etc. The following chemical formula ( -1) and the ~ (b-30).

  Among the above compound groups, from the viewpoint of raw material availability and ease of synthesis, thioacetic acid S-7-octen-1-yl ester, (b-6), (b-7), (b-9), (B-10), (b-11), (b-12), (b-14), (b-15), (b-16), (b-17), (b-19), (b -20), (b-21), (b-22), (b-24), (b-25), (b-26), (b-27), (b-29), (b-30) ) Is preferred.

  Although the content rate of the structural unit shown by the said General formula (3) in the side chain mercapto group containing vinyl alcohol polymer (Q2) shown by the said General formula (4) is not specifically limited, All the structural units in a polymer 100 mol%, preferably 0.05 to 10 mol%, more preferably 0.1 to 7 mol%, particularly preferably 0.3 to 6 mol%.

  The side chain mercapto group-containing vinyl alcohol polymer (Q2) represented by the general formula (4) can have one or more structural units represented by the formula (3). When it has 2 or more types of the said structural unit, it is preferable that the sum total of the content rate of these 2 or more types of structural units exists in the said range.

  The content of vinyl alcohol units in the side chain mercapto group-containing vinyl alcohol polymer (Q2) represented by the general formula (4) (that is, the degree of saponification of the side chain mercapto group-containing vinyl alcohol polymer) is not particularly limited. However, the total structural unit in the polymer is 100 mol%, preferably 50 mol% or more, more preferably 70 mol% or more, and further preferably 80 mol% or more. On the other hand, regarding the upper limit, the total structural unit in the polymer is 100 mol%, preferably 99.99 mol% or less, more preferably 99.9 mol% or less, and further preferably 99.5 mol%. It is as follows.

  The vinyl alcohol unit in the side chain mercapto group-containing vinyl alcohol polymer (Q2) represented by the general formula (4) can be derived from the vinyl ester unit by hydrolysis, alcoholysis or the like. Although it does not specifically limit as vinyl ester of a vinyl ester unit, Vinyl acetate is preferable from an industrial viewpoint.

  The side chain mercapto group-containing vinyl alcohol polymer (Q2) represented by the general formula (4) is a structural unit represented by the formula (3), a vinyl alcohol unit and a vinyl ester unit as long as the effects of the present invention are obtained. It may further have a structural unit other than The structural unit includes, for example, an unsaturated monomer that can be copolymerized with a vinyl ester and can be converted into a structural unit represented by the formula (3), and an ethylenically unsaturated monomer that can be copolymerized with a vinyl ester. It is a derived structural unit. The ethylenically unsaturated monomer has the same meaning as described above.

  In particular, the arrangement order of the structural unit represented by the formula (3), the vinyl alcohol unit, and other arbitrary structural units in the side chain mercapto group-containing vinyl alcohol polymer (Q2) represented by the general formula (4) There is no restriction, and any of random, block, alternating, etc. may be used.

  The viscosity average degree of polymerization measured according to JIS K6726 of the side chain mercapto group-containing vinyl alcohol polymer (Q2) represented by the general formula (4) is not particularly limited, and is preferably 100 to 5,000. More preferably, it is 200-4,000. When the viscosity average degree of polymerization is less than 100, the mechanical strength of the derived resin composition may be lowered. A vinyl alcohol polymer having a viscosity average polymerization degree exceeding 5,000 is difficult to produce industrially.

  The production method of the side chain mercapto group-containing vinyl alcohol polymer (Q2) represented by the general formula (4) is not particularly limited as long as the target side chain mercapto group-containing vinyl alcohol polymer can be produced. For example, as such a production method, (i) a vinyl ester, (ii) an unsaturated monomer that can be copolymerized with the vinyl ester and can be converted into a structural unit represented by the formula (3) Unsaturated monomer capable of converting the vinyl ester unit of the obtained copolymer into a vinyl alcohol unit by copolymerization step and solvolysis while being converted into a vinyl alcohol unit. And a conversion step of converting a unit derived from a body into a structural unit represented by formula (3).

  In particular, a copolymer obtained by copolymerizing a vinyl ester and a thioester monomer having an unsaturated double bond represented by the general formula (5) (hereinafter referred to as thioester monomer (5)) is obtained. A method of hydrolyzing or alcoholic decomposing an ester bond of a vinyl ester unit of a polymer and a thioester bond of a structural unit derived from the thioester monomer (5) is simple and preferably used, and this method will be described below.

  The copolymerization of the vinyl ester and the thioester monomer (5) can be carried out by employing known methods and conditions for homopolymerizing the vinyl ester.

  In the copolymerization, a monomer copolymerizable with the vinyl ester and thioester monomer (5) may be further copolymerized. The copolymerizable monomer is the same as the ethylenically unsaturated monomer.

  The ester bond of the vinyl ester unit of the obtained copolymer and the thioester bond of the structural unit derived from the thioester monomer (5) can be hydrolyzed or alcoholically decomposed under substantially the same conditions. Therefore, the hydrolysis or alcoholysis of the ester bond of the vinyl ester unit and the thioester bond of the structural unit derived from the thioester monomer (5) of the obtained copolymer is used to saponify the vinyl ester homopolymer. The known methods and conditions can be employed.

  The mercapto group content of (Q1) of the terminal mercapto group-containing vinyl alcohol polymer can be changed by changing the amount of thioacetic acid in the production method described in Patent Document 3.

  The mercapto group content of the side chain mercapto group-containing vinyl alcohol polymer (Q2) represented by the general formula (4) is the same as that of the side chain mercapto group-containing vinyl alcohol polymer (Q2) represented by the general formula (4). It can change by changing the content rate of the structural unit shown by the said General formula (3) contained.

As the mercapto group content contained in the terminal mercapto group-containing vinyl alcohol polymer (Q1) and the side chain mercapto group-containing vinyl alcohol polymer (Q2) represented by the general formula (4), the larger the mercapto group content, The total number of moles (M _{P + B} ) of the monomer (M _P ) having an ionic group in the graft copolymer (P) and the monomer having an ionic group in the polymer (M _B ) having an ionic group ) In the block or graft copolymer (P), the molar fraction of the number of moles of the monomer having an ionic group (M _P ) [(M _P / M _{P + B} ) × 100] A high ion exchange membrane is obtained. On the other hand, when the mercapto group content is excessively large, mercapto groups are intermolecularly cross-linked by an oxidative coupling reaction, the aqueous solution viscosity is increased, and workability is rapidly deteriorated. Therefore, the mercapto group content contained in the terminal mercapto group-containing vinyl alcohol polymer (Q1) and the side chain mercapto group-containing vinyl alcohol polymer (Q2) represented by the general formula (4) is 1.0 × The range of 10 ⁻⁵ eq / g to 30 × 10 ⁻⁵ eq / g is preferable, and the range of 2.0 × 10 ⁻⁵ eq / g to 20 × 10 ⁻⁵ eq / g is more preferable. The mercapto group content can be determined by iodometric titration in an aqueous solution.

(Ion exchange membrane)
The ion exchange membrane of the present invention is formed using a block or graft copolymer (P), and the molding method is, for example, from the state of a solution dissolved in the solvent of the polymer as long as the membrane can be formed. Various film forming methods such as a method (for example, cast molding method); a method for plasticizing and molding the polymer by heating (for example, extrusion molding method, inflation molding method, etc.) can be used. Of these molding methods, cast molding is preferably used.

  In cast molding, it can be obtained by forming a film from a solution of a block or graft copolymer. The film forming process includes a preparation process for preparing a solution in which a block or graft copolymer is dissolved in a soluble solvent, and a film forming process for forming the film by flowing the solution as a thin film and drying the thin film. ing.

Examples of the solvent used for the block or graft copolymer solution include water, lower alcohols such as methanol, ethanol, 1-propanol and 2-propanol, and mixed solvents thereof.
In the film forming step, it can be usually obtained by volatilizing the solvent in the solution by casting. The temperature during the film forming step is not particularly limited, but a temperature range of about room temperature to 100 ° C. is appropriate.

  In the manufacturing method of the ion exchange membrane of this invention, it is preferable to heat-process in addition to the said film forming process. By performing the heat treatment, physical crosslinking occurs, and the mechanical strength of the resulting ion exchange membrane is increased. The method of heat treatment is not particularly limited, and a hot air dryer or the like is generally used. Although the temperature of heat processing is not specifically limited, It is preferable that it is 50-250 degreeC. If the temperature of the heat treatment is less than 50 ° C., the mechanical strength of the obtained ion exchange membrane may be insufficient. The temperature is more preferably 80 ° C. or higher, and more preferably 100 ° C. or higher. On the other hand, when the temperature of the heat treatment exceeds 250 ° C., the crystalline polymer may be melted. The temperature is more preferably 230 ° C. or less, and further preferably 200 ° C. or less.

  In the manufacturing method of the ion exchange membrane of this invention, it is preferable to perform a crosslinking process in addition to the said film forming process. By performing the crosslinking treatment, the mechanical strength of the obtained ion exchange membrane is increased. The method for the crosslinking treatment is not particularly limited as long as it is a method capable of bonding the molecular chains of the polymer by chemical bonding. Usually, a method of immersing in a solution containing a crosslinking agent is used. Examples of the crosslinking agent include formaldehyde or dialdehyde compounds such as glyoxal and glutaraldehyde. In the present invention, the film after the heat treatment is subjected to a crosslinking treatment by immersing it in a solution obtained by dissolving a dialdehyde compound in water, alcohol or a mixed solvent thereof under acidic conditions. preferable. The concentration of the crosslinking agent is usually 0.001 to 5% by volume of the crosslinking agent relative to the solution.

  In the method for producing an ion exchange membrane of the present invention, both heat treatment and crosslinking treatment may be performed, or only one of them may be performed. When both the heat treatment and the crosslinking treatment are performed, the crosslinking treatment may be performed after the heat treatment, the heat treatment may be performed after the crosslinking treatment, or both may be performed simultaneously. It is preferable from the viewpoint of the mechanical strength of the resulting ion exchange membrane to perform a crosslinking treatment after the heat treatment.

The ion exchange membrane of the present invention preferably has a thickness of about 1 to 1000 μm from the viewpoint of ensuring performance, membrane strength, handling properties and the like necessary as an electrolyte membrane for electrodialysis. When the film thickness is less than 1 μm, the mechanical strength of the film tends to be insufficient. On the other hand, when the film thickness exceeds 1000 μm, the membrane resistance increases and sufficient ion exchange properties are not exhibited, so that the electrodialysis efficiency tends to decrease. The film thickness is more preferably 5 to 500 μm, still more preferably 7 to 300 μm.
In particular, since the ion exchange membrane of the present invention has high toughness as a membrane, it can be formed from a single layer as a self-supporting membrane that does not use a support. When used as a single layer, the film thickness may be, for example, 30 μm or more, and preferably 50 μm or more.

  In order to develop sufficient ion exchange properties for use as an ion exchange membrane for electrodialysis, the ion exchange capacity of the ion exchange membrane is preferably 0.30 mmol / g or more, more preferably 0.50 mmol / g or more. It is more preferable that The upper limit of the ion exchange capacity of the block or graft copolymer is preferably 3.0 mmol / g or less because if the ion exchange capacity becomes too large, the hydrophilicity increases and the control of the degree of swelling becomes difficult.

The ion exchange membrane can suppress the degree of swelling in water. For example, the degree of swelling represented by the following formula is preferably 1.00 to 1.68, and 1.10 to 1. It is more preferably 66 or less, and particularly preferably 1.20 to 1.63.
Swelling degree = [W1] / [W2]
(W1 represents the mass of the membrane that has reached the swelling equilibrium in ion-exchanged water at 25 ° C., and W2 represents the mass after the membrane measured by W1 is vacuum-dried at 40 ° C. for 12 hours.)

  Hereinafter, examples will be given to describe the present invention in more detail, but the present invention is not limited to these examples. In the examples, “%” and “parts” are based on weight unless otherwise specified.

1) Measurement of membrane resistance The membrane resistance was measured by sandwiching an ion exchange membrane in a two-chamber cell having a platinum black electrode plate shown in Fig. 1 and filling a 0.5 mol / L-NaCl solution on both sides of the membrane. The resistance between the electrodes at a temperature of 25 ° C. was measured at a frequency of 10 cycles / second), and was determined from the difference between the resistance between the electrodes and the resistance between the electrodes when no cation exchange membrane was installed. The membrane used for the above measurement was previously equilibrated in a 0.5 mol / L-NaCl solution.

2) The total number of moles of the monomer (M _P ) having an ionic group in the block or graft copolymer (P) and the monomer having an ionic group in the polymer (M _B ) having an ionic group ( M _{P + B)} with respect to the number of moles of a monomer having an ionic group in the block or graft copolymer _(P) (M P) mole fraction of the measurement block of the _{[(M P / M P +} B) × 100] Alternatively, an aqueous solution containing tetrabutylammonium hydroxide having the same number of moles as the contained ionic groups was added to the aqueous solution containing the graft copolymer (P) and the polymer containing ionic groups, and stirred at room temperature for 10 minutes. Then, it was dried using a vacuum dryer. After the obtained solid was pulverized with a mixer, Soxhlet extraction was performed for 5 hours using methanol as an extraction solvent to elute the polymer (B) having an ionic group. The residue was dried with a vacuum dryer, and then 1H-NMR measurement was performed using DMSO-d6 as a solvent. Ions in the polymer component (b) having an ionic group contained in the residue from the ratio of the integral value of the peak derived from polyvinyl alcohol calculated from the obtained 1H-NMR and the integrated value of the peak derived from the ionic group component The mol% of the monomer having a group was calculated, and the molar ratio was calculated by the following calculation formula.
[Molar ratio] = [Mole% of polymer component (b) (monomer having ionic group) having ionic groups contained in residue] / [heavy weight having ionic groups contained in block copolymer (P)] Mol% of combined component (b) (monomer having ionic group) and polymer (B) having ionic group (monomer having ionic group)] × 100%

[Synthesis of terminal mercapto group-containing polyvinyl alcohol]
<PVA-1, -2>
Polyvinyl alcohol (PVA-1, 2) having a mercapto group at the end was synthesized by the method described in Japanese Patent Publication No. 3-57923. The viscosity average polymerization degree of the obtained PVA-1 measured according to JIS K6726 was 1500, the saponification degree was 99.9 mol%, and the mercapto group content was 2.4 × 10 ⁻⁵ eq / g. The obtained PVA-2 had a viscosity average polymerization degree measured according to JIS K6726 of 500, a saponification degree of 99.8 mol%, and a mercapto group content of 5.6 × 10 ⁻⁵ eq / g.

[Synthesis of side chain mercapto group-containing polyvinyl alcohol]
<PVA-3>
In a reactor equipped with a stirrer, a reflux condenser, an argon inlet, a comonomer addition port and a polymerization initiator addition port, 1100 parts by mass of vinyl acetate, and the thioester monomer represented by the chemical formula (b-16) as a comonomer 0.47 parts by mass and 478 parts by mass of methanol were added, and the system was purged with argon for 30 minutes while performing argon bubbling. Separately, a methanol solution (concentration 5 mass%) of the thioester monomer (b-16) was prepared as a comonomer sequential addition solution (hereinafter referred to as a delay solution), and argon was bubbled for 30 minutes. The temperature of the reactor was increased, and when the internal temperature reached 60 ° C., 0.28 parts by mass of 2,2′-azobisisobutyronitrile was added to initiate polymerization. During the polymerization reaction, the prepared delay solution was dropped into the system so that the monomer composition in the polymerization solution (molar ratio of vinyl acetate and thioester monomer (b-16)) became constant. . After polymerization at 60 ° C. for 240 minutes, the polymerization was stopped by cooling. The polymerization rate when the polymerization was stopped was 40%. Next, unreacted vinyl acetate monomer was distilled off while adding methanol under reduced pressure at 30 ° C. to obtain a methanol solution of modified polyvinyl acetate in which the thioester monomer (b-16) was introduced.

Methanol is added to the methanol solution of polyvinyl acetate into which the thioester monomer (b-16) obtained in (2) above is introduced, and sodium hydroxide methanol solution (concentration 14.1%) is further added. Saponification was carried out at 40 ° C. (polyvinyl acetate concentration with 30% polyvinyl acetate introduced with thioester monomer (b-16) of saponified solution, polyvinyl acetate with thioester monomer (b-16) introduced) (Molar ratio of sodium hydroxide to vinyl acetate units in 0.050). A gelled product was formed about 8 minutes after the addition of the sodium hydroxide methanol solution. This was pulverized by a pulverizer and further allowed to stand at 40 ° C. for 52 minutes to allow saponification to proceed. After adding methyl acetate to this and neutralizing the remaining alkali, it washed well with methanol and dried in a vacuum dryer at 40 ° C. for 12 hours to obtain a side chain mercapto group-containing PVA (PVA-3). . ^The amount of modification of the structural unit derived from the thioester monomer (b-16) determined by ¹ H-NMR measurement was 0.3 mol%. Moreover, the viscosity average polymerization degree measured based on JISK6726 was 1500, saponification degree was 98.5 mol%, and mercapto group content was 6.7 * 10 < ^-5 > eq / g.

<PVA-4>
In PVA-32, except that the thioester monomer represented by the chemical formula (b-16) was changed from 0.47 parts by mass to 0.77 parts by mass, and methanol was changed from 478 parts by mass to 473 parts by mass. Performed the same operation as in Synthesis Example 2, and then performed the same operation as in Synthesis Example 3 to obtain a side chain mercapto group-containing PVA (PVA-4). ^The amount of modification of the structural unit derived from the thioester monomer (b-16) determined by ¹ H-NMR measurement was 0.5 mol%. Moreover, the viscosity average polymerization degree measured based on JISK6726 was 1500, saponification degree was 98.3 mol%, and mercapto group content was 8.7 * 10 < ^-5 > eq / g.

<PVA-5>
In PVA-3, the thioester monomer represented by the chemical formula (b-16) was changed from 0.47 parts by mass to 1.56 parts by mass, and methanol was changed from 478 parts by mass to 438 parts by mass. Performed the same operation as in Synthesis Example 2, and then performed the same operation as in Synthesis Example 3 to obtain side chain mercapto group-containing PVA (PVA-5). ^The amount of modification of the structural unit derived from the thioester monomer (b-16) determined by ¹ H-NMR measurement was 1.0 mol%. Moreover, the viscosity average polymerization degree measured based on JISK6726 was 1500, saponification degree was 98.5 mol%, and mercapto group content was 18.2 * 10 < ^-5 > eq / g.

<Synthesis of Block Copolymer BCP-1>
A 300 mL four-necked separable flask equipped with a reflux condenser and a stirring blade was charged with 136 g of water, 25.0 g of PVA-1 as a polyvinyl alcohol having a mercapto group at the end, and 14.0 g of sodium parastyrenesulfonate, The mixture was heated to 90 ° C. with stirring and dissolved while bubbling nitrogen. After nitrogen substitution, 11.8 mL of a 2.0% aqueous solution of 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -2-propionamide] was sequentially added to the above aqueous solution over 1.5 hours. The polymerization is started by adding to the polymer, and then allowed to proceed. Then, the system temperature is maintained at 90 ° C. for 4 hours to further promote the polymerization, followed by cooling, and a block copolymer of polyvinyl alcohol and sodium parastyrenesulfonate An aqueous solution of BCP-1 was prepared. After a part of the aqueous solution was dried, it was dissolved in heavy water and subjected to 1H-NMR measurement at 500 MHz. As a result, the content of sodium parastyrenesulfonate unit relative to the vinyl alcohol unit was 10 mol%.

<Synthesis of Block Copolymer BCP-2>
In the synthesis of BCP-1, the same operation was performed except that PVA-2 was used instead of PVA-1, to prepare an aqueous solution of a block copolymer BCP-2 of polyvinyl alcohol and sodium parastyrenesulfonate. . After a part of the aqueous solution was dried, it was dissolved in heavy water and subjected to 1H-NMR measurement at 500 MHz. As a result, the content of sodium parastyrenesulfonate unit relative to the vinyl alcohol unit was 10 mol%.

<Synthesis of Graft Copolymer BCP-3>
In the synthesis of BCP-1, the same operation was performed except that PVA-3 was used instead of PVA-1, and an aqueous solution of a graft copolymer BCP-3 of polyvinyl alcohol and sodium parastyrenesulfonate was prepared. . After a part of the aqueous solution was dried, it was dissolved in heavy water and subjected to 1H-NMR measurement at 500 MHz. As a result, the content of sodium parastyrenesulfonate unit relative to the vinyl alcohol unit was 10 mol%.

<Synthesis of Graft Copolymer BCP-4>
In the synthesis of BCP-1, the same operation was performed except that PVA-4 was used instead of PVA-1, to prepare an aqueous solution of a graft copolymer BCP-4 of polyvinyl alcohol and sodium parastyrenesulfonate. . After a part of the aqueous solution was dried, it was dissolved in heavy water and subjected to 1H-NMR measurement at 500 MHz. As a result, the content of sodium parastyrenesulfonate unit relative to the vinyl alcohol unit was 10 mol%.

<Synthesis of Graft Copolymer BCP-5>
In the synthesis of BCP-1, the same operation was performed except that PVA-5 was used instead of PVA-1, and an aqueous solution of a graft copolymer BCP-5 of polyvinyl alcohol and sodium parastyrenesulfonate was prepared. . After a part of the aqueous solution was dried, it was dissolved in heavy water and subjected to 1H-NMR measurement at 500 MHz. As a result, the content of sodium parastyrenesulfonate unit relative to the vinyl alcohol unit was 10 mol%.

<Synthesis of Block Copolymer BCP-6>
In the synthesis of BCP-1, the same operation was performed except that the operation was performed in an air atmosphere without performing nitrogen bubbling and nitrogen substitution, and a block copolymer BCP-6 of polyvinyl alcohol and sodium parastyrenesulfonate was obtained. An aqueous solution was prepared. After a part of the aqueous solution was dried, it was dissolved in heavy water and subjected to 1H-NMR measurement at 500 MHz. As a result, the content of sodium parastyrenesulfonate unit relative to the vinyl alcohol unit was 10 mol%.

<Synthesis of Block Copolymer BCP-7>
In the synthesis of BCP-1, 1M sodium hydroxide aqueous solution was added before adding 2.0% aqueous solution of 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -2-propionamide]. Then, the same operation was performed except that the pH of the reaction solution was adjusted to 10, to prepare an aqueous solution of a block copolymer BCP-7 of polyvinyl alcohol and sodium parastyrenesulfonate. After a part of the aqueous solution was dried, it was dissolved in heavy water and subjected to 1H-NMR measurement at 500 MHz. As a result, the content of sodium parastyrenesulfonate unit relative to the vinyl alcohol unit was 10 mol%.

<Preparation of PVA and poly (sodium parastyrenesulfonate) BCP-8>
A 300 mL four-necked separable flask equipped with a reflux condenser and a stirring blade was charged with 136 g of water and 14.0 g of sodium parastyrene sulfonate, heated to 90 ° C. with stirring, and dissolved while bubbling nitrogen. After nitrogen substitution, 11.8 mL of a 2.0% aqueous solution of 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -2-propionamide] was sequentially added to the above aqueous solution over 1.5 hours. Then, the polymerization was started and proceeded, and then the system temperature was maintained at 90 ° C. for 4 hours to further proceed the polymerization. Thereafter, 25.0 g of PVA-1 was added as a polyvinyl alcohol having a mercapto group at the end, and dissolved at 90 ° C. with stirring. Then, it cooled and produced the aqueous solution of the mixture BCP-8 of polyvinyl alcohol and poly (sodium parastyrene sulfonate). After a part of the aqueous solution was dried, it was dissolved in heavy water and subjected to 1H-NMR measurement at 500 MHz. As a result, the content of sodium parastyrenesulfonate unit relative to the vinyl alcohol unit was 10 mol%.

<Example 1>
[Production of ion exchange membrane]
An aqueous solution of the block copolymer BCP-1 was poured into a cast board made of acrylic having a length of 2 70 mm × width of 2 10 mm, and after removing excess liquid and bubbles, the hot water dryer was used. After drying at 30 ° C. for 30 minutes, heat treatment was performed using a high-temperature heat treatment machine at 160 ° C. for 30 minutes. To 1 L of 350 g / L sodium sulfate aqueous solution, sulfuric acid was added to adjust pH (25 ° C.) to 1.0, and then 40 ml of 25% glutaraldehyde aqueous solution was added to prepare a treatment solution. After the treatment liquid was heated to 50 ° C., each of the obtained films was immersed for 30 minutes and subjected to a crosslinking treatment. Thereafter, it was washed with ion exchange water for 30 minutes or more to obtain a cation exchange membrane BCP-1.

[Evaluation of ion exchange membrane]
The cation exchange membrane BCP-1 produced above was cut into a desired size to produce a measurement sample. Using the obtained measurement sample, the membrane resistance was measured according to the above-described method for measuring membrane resistance. The obtained results are shown in Table 1.

[Measurement of molar ratio]
According to the measurement method, the molar fraction of the polymer component (b) contained in the block or graft copolymer is measured with respect to the polymer component (b) and the polymer (B) in the block or graft copolymer. went. The obtained results are shown in Table 1.

<Examples 2 to 5>
For each of the block copolymer BCP-2 and the graft copolymer BCP-3 to 5, an ion exchange membrane was prepared in the same manner as in Example 1 and evaluated. The obtained results are shown in Table 1.

<Comparative Examples 1-3>
For each of the block copolymers BCP-6 to 7 and the polymer mixture BCP-8, an ion exchange membrane was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

As is clear from the results in Table 1, it can be seen that the film resistance is reduced by the high molar ratio of the polymer component (b) in the copolymer (P). That is, when the block or graft copolymer is produced, the monomer having an ionic group has a small ratio of forming the homopolymer (B) and a high ratio of conversion to the block or graft copolymer. It is possible to provide an ion exchange membrane having a high basic performance such as.

  Since the ion exchange membrane according to the present invention has low membrane resistance and excellent organic contamination resistance, it can be used in various applications such as electrodialysis, and thus has industrial applicability.

  Although the preferred embodiments of the present invention have been described above by way of example, those skilled in the art can make various modifications, additions and substitutions without departing from the scope and spirit of the present invention disclosed in the claims. It will be understandable.

A ion exchange membrane B platinum electrode C aqueous NaCl solution D water bath E LCR meter

Claims (5)

A block or graft copolymer (P) comprising a vinyl alcohol polymer component (a) and a polymer component (b) having an ionic group as constituent components;
A polymer (B) having an ionic group,
The polymer component (b) having an ionic group and the polymer (B) having an ionic group are each composed of a monomer (M) having an ionic group,
The block or graft copolymer (P) with respect to the total number of moles (M _{P + B} ) of the monomer (M) having an ionic group contained in the block or graft copolymer (P) and the polymer (B) ( The molar ratio (M _P / M _{P + B} × 100) of the number of moles (M _P ) of the monomer (M) having an ionic group contained in P) is 30.0% or more and 99.9% or less. An ion exchange membrane characterized by being in the range.   The ion exchange membrane according to claim 1, wherein the molar ratio is 50.0% or more and 95% or less.   The ion exchange membrane according to claim 1 or 2, wherein the polymer component (b) has an anionic group as an ionic group.   The ion exchange membrane according to any one of claims 1 to 3, wherein the polymer component (b) has a sulfonic acid group as an ionic group. The ion exchange membrane according to claim 4, wherein the polymer component (b) has a monomer represented by the following general formula (a-1) as a repeating unit.

[Wherein, R ¹ represents a hydrogen atom or an alkali metal atom. ]

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