JP2008045068A - Cation exchange membrane and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cation exchange membrane using a polyolefinic resin as a base material, which exhibits excellent durability since it has such high adhesion of the base material to a cation exchange resin layer that causes no separation of the base material from the cation exchange resin layer even after repeated bending, and also can be produced at a low cost without requiring specific processes and apparatus. <P>SOLUTION: The membrane is composed of the base material made of the polyolefinic resin, and a hydrocarbon-based cation exchange resin layer covering the base material. Where the followings are characterized: the hydrocarbon-based cation exchange resin has a crosslinking structure, and also a unit deriving from at least one monomer selected from among the group consisting of an α-alkyl styrene, an α-alkyl styrene dimer and an α-alkyl stilbene; and the number of bending times until to separate the base material from the resin layer is at least 100 in the repeated bending test. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydrocarbon-based cation exchange membrane comprising a polyolefin-based resin as a base material and a hydrocarbon-based cation exchange resin layer provided on the base material.

  The ion exchange membrane is a membrane of an ion exchange resin, but as it is, it is mechanically fragile because it has a crosslinked structure. Therefore, in order to improve the mechanical strength, a base material having a function as a reinforcing material is used, and this base material is used as a core and an ion exchange resin layer is provided. As a method for producing such an ion exchange membrane, a so-called paste method is known. According to such a paste method, a polymerizable monomer paste having an ion exchange group or capable of introducing an ion exchange group is applied to a substrate having a function as a reinforcing material and polymerized, and then, if necessary, an ion exchange group. The ion exchange membrane is manufactured by introduce | transducing (refer patent document 1).

  By the way, as a base material having a function as a reinforcing material, polyvinyl chloride, polyolefin resin, or the like is generally used. Of these, polyolefin resins are superior to polyvinyl chloride in terms of strength and heat resistance. Therefore, in an ion exchange membrane used in a region where strength and heat resistance are required, a polyolefin resin is used as the base material. Such a polyolefin resin substrate is often used in the form of a woven fabric, a nonwoven fabric, a porous sheet, or the like.

  However, although the polyolefin resin substrate is superior to the polyvinyl chloride substrate in terms of strength and heat resistance, it is difficult to impregnate the polymerizable monomer, polymerizes the monomer, and introduces ion exchange groups as necessary. There exists a fault that adhesiveness with the ion exchange resin obtained by doing is inferior to the base material made from a polyvinyl chloride. That is, in the case of a base material made of polyvinyl chloride, the polymerization is carried out in a state in which the polymerizable monomer is well impregnated into the polyvinyl chloride base material, and the polymer (ion exchange resin or ion ion) is incorporated in the base material. The exchange group introduces a polymer that becomes an ion exchange resin), and an interpenetrating polymer network structure is formed inside and outside the substrate. As a result, the adhesion between the polyvinyl chloride substrate and the ion exchange resin is It will be good. On the other hand, in the polyolefin resin base material, the polymerizable monomer is difficult to impregnate the base material, so that the network structure as described above is not formed. As a result, the adhesion between the ion exchange resin and the base material is low, for example, The base material and the ion exchange resin easily peel off due to repeated bending, and the function as an ion exchange membrane cannot be achieved.

In order to improve the disadvantages of such polyolefin-based resin base materials, for example, in Patent Document 2, after the polyolefin resin base material is exposed to the vapor of a polymerizable monomer, a polymerizable monomer paste is applied and polymerized. A method of performing is proposed.
Japanese Patent No. 3193522 JP 09-52968

  However, the method proposed in Patent Document 2 not only increases the number of steps of exposing the polyolefin resin substrate to steam, but also requires an apparatus for exposing the substrate to steam, increasing the production cost, There are problems such as a decrease in productivity, and there is a difficulty in industrial practical use.

  Therefore, the object of the present invention is to provide a base material of a polyolefin resin, and the adhesiveness between the base material and the cation exchange resin layer is high. An object of the present invention is to provide a cation exchange membrane and a method for producing the same, which do not cause peeling, exhibit excellent durability, and can be produced at low cost without using a special process or apparatus.

According to the present invention, in a cation exchange membrane comprising a polyolefin resin substrate and a hydrocarbon cation exchange resin layer covering the substrate,
The hydrocarbon-based cation exchange resin has a crosslinked structure and a unit derived from at least one monomer selected from the group consisting of α-alkylstyrene, α-alkylstyrene dimer and α-alkylstilbene. Have
Provided is a cation exchange membrane characterized in that the number of times until the base material and the hydrocarbon-based cation exchange resin layer are peeled is 100 times or more when subjected to a repeated bending test.
In the present invention, the repeated bending test is performed in accordance with ASTM-D2176, and uses an MIT type bending test machine for evaluating the crease strength of paper, film, woven fabric, etc., and both ends of the ion exchange membrane. The chuck is clamped, given a constant tension, one of the chucks is reciprocally rotated left and right at a predetermined angle, and the number of operations until the base material and the ion exchange resin layer are separated by the reciprocating R of the chuck tip is countered. It is carried out by reading in.

In the above cation exchange membrane,
(1) the ion exchange capacity is 0.1 to 4.0 meq / g,
Is preferred.

According to the invention,
100 to 100 parts by weight of a reactive monomer capable of introducing a cation exchange group, and 30 to 200 monomers other than at least one reactive monomer selected from the group consisting of α-alkylstyrene, α-alkylstyrene dimer and α-alkylstilbene A mixed monomer paste containing parts by weight and 20 to 80 parts by weight of a crosslinkable polyfunctional monomer is prepared,
The monomer paste is applied to a polyolefin substrate and polymerized,
Then introducing a cation exchange group,
A method for producing a cation exchange membrane is provided.

  The cation exchange membrane of the present invention is composed of a polyolefin resin base material and a hydrocarbon cation exchange resin layer covering the polyolefin resin base material. In addition to units derived from a polymerizable monomer and a crosslinkable polyfunctional monomer that are normally possessed by this type of exchange resin, the group consisting of α-alkylstyrene, α-alkylstyrene dimer and α-alkylstilbene Units derived from at least one selected (hereinafter referred to as functional monomers) are introduced. That is, since a unit derived from such a functional monomer is introduced, the cation exchange membrane of the present invention comprises a polyolefin resin base material and a hydrocarbon cation exchange resin layer (hereinafter simply referred to as a cation exchange resin layer). High adhesion between the base material and the cation exchange resin layer when subjected to repeated bending tests, as will be understood from the experimental results of the examples described later. The number of times until this is 100 times or more, particularly 500 times or more, shows excellent durability and mechanical strength. For example, as shown in a comparative example to be described later, when a unit derived from a functional monomer is not introduced into the cation exchange resin, in the above repeated bending test, the base material and the cation exchange resin layer The number of times until and peels is at most about 50 times.

  Therefore, according to the present invention, the disadvantages of the polyolefin resin substrate can be effectively eliminated, and the excellent properties of the polyolefin resin substrate that are excellent in strength and heat resistance can be effectively exhibited. It can be used for a long time as a cation exchange membrane in a region where strength and heat resistance are required.

  In the present invention, the high adhesion between the polyolefin resin substrate and the cation exchange resin layer as described above can be expressed simply by blending the functional monomer in the monomer component. Other than that, a cation exchange membrane may be produced by a normal paste method. Therefore, no special process or apparatus is required at all, and the cation exchange membrane can be produced with low cost and high productivity, which is extremely useful in terms of industrialization.

<Manufacture of cation exchange membrane>
In the cation exchange membrane of the present invention, a monomer sheet having a predetermined composition is applied to a polyolefin resin substrate to produce a polymerizable sheet, and this polymerizable sheet is polymerized to form an ion exchange membrane precursor (original membrane). This is produced by introducing an ion exchange group into the original membrane.

Polyolefin resin substrate;
The polyolefin-based resin forming the base material may be known per se, and examples thereof include olefin polymers such as ethylene, propylene, and butene or copolymers thereof, and blends thereof. it can. The form of the substrate is not particularly limited, and any material such as a woven fabric, a nonwoven fabric, or a porous film may be used. Moreover, the thickness should just be in an appropriate range according to a use.

Monomer paste;
The monomer paste applied to the substrate contains, as monomer components, a reactive monomer capable of introducing a cation exchange group, the functional monomer described above, and a crosslinkable polyfunctional monomer.

  The reactive monomer capable of introducing a cation exchange group is a monofunctional monomer that has been conventionally used in the production of crosslinkable polyfunctional membranes, such as styrene, vinyl toluene, vinyl xylene, chloromethyl styrene. , Α-halogenated vinyl sulfonic acid, α, β, β′-halogenated vinyl sulfonic acid, methacrylic acid, acrylic acid, styrene sulfonic acid, vinyl sulfonic acid, maleic acid, itaconic acid, styrene phosphonic acid, maleic anhydride , Vinyl phosphoric acid, and salts and esters thereof can be preferably used. These may be used individually by 1 type, or can also be used in combination of 2 or more type mutually copolymerizable.

  As described above, α-alkyl styrene, α-alkyl styrene dimer and α-alkyl stilbene are used as the functional monomer, and these may be used alone or in combination of two or more. You can also The α-alkylstyrene is, for example, a compound in which a hydrocarbon chain is bonded to the α-position of styrene. Specific examples include α-methylstyrene, α-ethylstyrene, α-propylstyrene, α-butylstyrene, and the like. The α-alkylstyrene dimer is a dimer of α-alkylstyrene having the same carbon number in the α-position alkyl chain, such as α-methylstyrene dimer, α-ethylstyrene dimer, or the like, and the alkyl chain has a different carbon number. There are α-alkylstyrene dimers, such as 2,4-diphenyl-4-methyl-1-hexene. Examples of α-alkyl stilbene include α-methyl stilbene, α-ethyl stilbene, α-propyl styrene and the like. These may be used alone or in combination of two or more. That is, by using such a functional monomer and introducing a unit derived from the monomer into the cation exchange resin, the adhesion between the polyolefin resin substrate and the cation exchange resin layer is significantly improved. Become.

It is known that an ion exchange resin can be produced by using such a functional monomer, and the remarkable improvement in adhesion due to the use of this functional monomer has been found as a phenomenon, and the reason is clear However, the present inventors have estimated as follows.
That is, the three functional monomers shown above have a steric hindrance because they have a branched structure starting from one of two carbons having a double bond as a reaction site. As a result, the polymerization reaction with other monomers proceeds slowly. Therefore, the time during which the high-temperature monomer paste is in contact with the surface of the polyolefin resin base material (hereinafter simply referred to as the polyolefin base material) is increased. For this reason, the surface of the polyolefin base material is dissolved in the monomer paste, Polymerization proceeds in this state, and as a result, a polymer layer having high adhesion to the surface of the polyolefin-based resin may be formed. In addition, the slow progress of the polymerization reaction makes it easier for the reactive monomer to react randomly, thereby expressing the flexibility of the ion exchange resin and suppressing the resin peeling from the substrate. It is thought that there is not. Here, it is considered that the above object can be achieved by simply using a monomer having a branched structure. However, if the monomer does not have an aromatic ring into which an ion exchange group can be introduced as in the functional monomer of the present invention, the monomer has too high a resistance and cannot function as a membrane.

  In the present invention, the functional monomer is used in an amount of 30 to 200 parts by weight, particularly 40 to 180 parts by weight, per 100 parts by weight of the reactive monomer capable of introducing the ion exchange group. When the amount of functional monomer used is less than the above range, sufficient adhesion improvement effect is not exhibited, and when used in a larger amount than the above range, further adhesion improvement effect is achieved. Rather, productivity is reduced by polymerization delay.

  The crosslinkable polyfunctional monomer (hereinafter simply referred to as a crosslinkable monomer) used together with the above-mentioned reactive monomer and functional monomer is for introducing a crosslinked structure, and conventionally known ones are known. Used without any restrictions. Examples thereof include divinyl compounds such as m-, p- or o-divinylbenzene, divinylbiphenyl, divinylsulfone, butadiene, chloroprene, isoprene, trivinylbenzene, divinylnaphthalene, diallylamine, triallylamine, and divinylpyridine. . Such a crosslinkable monomer is generally used in an amount of 20 to 80 parts by weight, particularly 30 to 60 parts by weight, per 100 parts by weight of the aforementioned monomer. By using such a crosslinkable monomer, the film strength can be improved.

  In addition to the monomer components described above, a polymerization initiator is blended in the monomer paste. As such a polymerization initiator, a radical polymerization initiator having a 10-hour half-life temperature of 110 ° C. to 170 ° C., for example, which can start polymerization without degrading the polyolefin resin as a base material is used. When a polymerization initiator having a lower 10-hour half-life temperature than this is used, the polymerization reaction proceeds before the substrate is dissolved in the monomer paste, and the adhesion between the resin and the substrate becomes incomplete. Further, when a polymerization initiator at a higher temperature is used, the generated radicals are reduced and the polymerization reaction is difficult to proceed. Specific examples of the polymerization initiator include p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, α, α′-bis (tert-butylperoxy-m-isopropyl) benzene, di-tert-butylperoxide, tert -Butyl hydroperoxide, di-tert-amyl peroxide, tert-butyl cumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 2,5- Dimethyl-2,5-di (tert-butylperoxy) hexyne-3, cumene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, 2,5-dimethyl-2,5-dihydroper And oxyhexane, 2,5-dimethyl-2,5-dihydroperoxyhexyne-3, etc. Others are admixed to the monomer paste in combination of two or more. In addition, the amount of such a polymerization initiator used is usually in the range of 10 to 30 parts by weight, particularly 15 to 25 parts by weight, based on 100 parts by weight of the reactive monomer capable of introducing an ion exchange group.

  Further, the monomer paste preferably contains a matrix resin as a viscosity modifier. When such a matrix resin is added, the workability of the monomer paste is improved and applied to the substrate. It is possible to prevent dripping or the like.

  Examples of such matrix resins include saturated aliphatic hydrocarbon polymers such as ethylene-propylene copolymers and polybutylenes; styrene polymers such as styrene-butadiene copolymers; polyvinyl chlorides; Styrene monomers such as toluene, vinyl xylene, chlorostyrene, chloromethyl styrene, α-methyl styrene, α-halogenated styrene, α, β, β'-trihalogenated styrene, monoolefins such as ethylene and butylene, Those obtained by copolymerizing conjugated diolefins such as butadiene and isoprene can be used. The molecular weight of such a matrix resin is not particularly limited, but it is usually preferably in the range of 1,000 to 1,000,000, particularly 50,000 to 500,000. Further, such a matrix resin is blended in the monomer paste according to the molecular weight in an amount that can ensure an appropriate viscosity. For example, the amount is 10 to 10 parts by weight per 100 parts by weight of the reactive monomer into which the ion exchange group can be introduced. About 50 parts by weight.

  In addition to the various components described above, the monomer paste described above contains, as necessary, plasticizers such as dioctyl phthalate, dibutyl phthalate, tributyl phosphate, styrene oxide, or alcohol esters of fatty acids and aromatic acids, and organic solvents. It may be blended.

  The monomer paste can be applied to the substrate by a known means such as a roll coater, a flow coater, a knife coater, a comma coater, spraying or dipping.

  The polymerizable sheet prepared as described above may be subjected to polymerization as it is, but in general, it is wound up with a roller while a release film is attached to one surface of the polymerizable sheet. In view of continuous productivity, it is preferable to perform polymerization by introducing the winding roller into a polymerization apparatus.

  Such a releasable film can be used without any limitation as long as it has heat resistance that can withstand the polymerization process and can be easily peeled off after polymerization. For example, low-density polyethylene, high-density polyethylene Polyolefins such as random or block copolymers of α-olefins such as polypropylene, poly 1-butene, poly 4-methyl-1-pentene or ethylene, propylene, 1-butene, 4-methyl-1-pentene;・ Vinyl acetate copolymer, ethylene / vinyl alcohol copolymer, ethylene / vinyl compound copolymer such as ethylene / vinyl chloride copolymer; polystyrene, acrylonitrile / styrene copolymer, ABS, α-methylstyrene / styrene copolymer Styrene resins such as polymers; polyvinyl chloride, polyvinylidene chloride, chloride Polyvinyl compounds such as vinyl / vinylidene chloride copolymer, polymethyl acrylate and polymethyl methacrylate; polyamides such as nylon 6, nylon 6-6, nylon 6-10, nylon 11 and nylon 12; polyethylene terephthalate, polybutylene terephthalate , Thermoplastic polyester such as polyethylene naphthalate; polycarbonate; polyphenylene oxide; biodegradable resin such as polylactic acid; and mixtures thereof may be used depending on the type of monomer in the monomer paste. it can. In particular, a polyester film such as polyethylene terephthalate (PET) is preferable in terms of good heat resistance and releasability. Of course, such a film may be biaxially stretched.

  The polymerization temperature varies depending on the polymerization initiator used, but is generally set in consideration of the melting point of the polyolefin resin substrate and the solubility of the substrate in the monomer. For example, when using a polyethylene base material, it is desirable to perform polymerization at 90 ° C. to 120 ° C. for 4 to 12 hours, and when using a polypropylene base material, 110 ° C. to 140 ° C. for 4 to 12 hours. It is desirable to carry out the polymerization. Below this temperature range, the solubility of the substrate in the monomer paste is low and the adhesion between the substrate and the resin is not sufficient. On the contrary, above this temperature range, the base material is excessively dissolved in the monomer paste and the strength is lowered.

  The cation exchange resin precursor obtained by polymerization as described above, that is, the original film, is peeled off from the release film, and then cation exchange groups are introduced, thereby covering the polyolefin resin substrate. Thus, the cation exchange membrane of the present invention in which a layer of a hydrocarbon-based cation exchange resin is formed is obtained.

  The introduction of the cation exchange group is carried out by a means known per se, for example, by treatment such as sulfonation, chlorosulfonation, chloromethylation, amination, phosphoniumation, sulfoniumation, hydrolysis and the like. The amount of cation exchange groups introduced is not particularly limited, but generally, the amount of cation exchange groups per 1 g of dry membrane (meq / g) is 0.1 to 4.0 meq / g, preferably 1.0. It is good to be -3.5 meq / g.

<Cation exchange membrane>
The cation exchange membrane of the present invention obtained as described above is not only excellent in strength and heat resistance, but also has the above-mentioned functional monomer (α-alkyl) because a polyolefin resin substrate is used as the substrate. Units derived from styrene, α-alkyl styrene dimer and α-alkyl stilbene) are introduced into the cation exchange resin, so that they have excellent durability and are subjected to cation exchange with the base material when subjected to repeated bending tests. The number of times until the resin layer peels is 100 times or more, particularly 500 times or more. Further, such a cation exchange membrane of the present invention can be produced by a conventionally known paste method except that a functional monomer is used, and does not require any special process or apparatus, so that it is extremely inexpensive. And can be manufactured with high productivity.

  In addition, it is difficult to directly analyze that the unit derived from the functional monomer as described above is introduced into the cation exchange resin because the cation exchange resin has a crosslinked structure. However, by extracting the unreacted monomer remaining in the resin layer and conducting qualitative analysis, it can be confirmed that the unit derived from the functional monomer is introduced. For example, a cation exchange membrane precursor (raw membrane) or a cation exchange membrane is immersed in tetrahydrofuran for a whole day and night. After filtering the obtained tetrahydrofuran solution, gas chromatograph-mass spectrometry can be used to confirm the use of the functional monomer, and as a result, the unit derived from the functional monomer is introduced. Can be confirmed.

  In addition, the amount of units derived from the functional monomer cannot be directly quantified, but can be estimated by subjecting the obtained cation exchange membrane to repeated bending tests and measuring the number of peeling described above. it can. That is, it can be understood that the unit derived from the functional monomer is introduced in an appropriate amount when the number of peeling is 100 times or more, particularly 500 times or more.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.
In addition, the repeated bending test and the analysis of the residual monomer in the examples were performed by the following methods.

Repeat bending test:
The obtained cation exchange membrane was cut into a width of 1 cm and a length of 12 cm, and using a MIT fatigue tester (model DA, manufactured by Toyo Seiki Seisakusho), a bending angle of 135 °, a speed of 90 cpm, and a weight weight of 250 g. The bending test was repeated, and the number of times of peeling between the cation exchanger resin layer and the substrate was defined as the number of peelings.

Residual monomer analysis:
After the polymerization, the original film was collected in an area of 16 square centimeters, immersed in tetrahydrofuran, and stirred all day and night. The original membrane was taken out and the tetrahydrofuran was filtered and analyzed by a gas chromatograph mass spectrometer (model HP5890 / HP5973, manufactured by Yokogawa Analytical Systems).

(Example 1)
A monomer paste was prepared according to the following formulation.
Monomer paste formulation:
Reactive monomer: 100 parts by weight (styrene: 60 parts by weight, chloromethylstyrene: 40 parts by weight)
Functional monomer; 25 parts by weight (2,4-diphenyl-4-methyl-1-pentene)
Crosslinkable monomer; 36 parts by weight (industrial divinylbenzene)
Matrix resin; 27 parts by weight (styrene-butadiene rubber)
Polymerization initiator; 16 parts by weight (cumene hydroperoxide)

  The monomer paste was applied to a polyethylene substrate having a thickness of 180 μm, and the polyester film was wound around a winding roller together with the release film. Thereafter, the take-up roller was placed in an autoclave, and polymerization was carried out in nitrogen gas at a pressure of 0.4 MPa at 100 ° C. for 2 hours and then at 110 ° C. for 8 hours to obtain a raw film.

  Next, the obtained original membrane was immersed in a 1: 1 mixed solution of 98% sulfuric acid and 90% chlorosulfonic acid at 40 ° C. for 60 minutes, and then taken out and dried to obtain a cation exchange membrane.

The exchange capacity of the obtained cation exchange membrane was 2.3 meq / g. Further, as a result of the repeated bending test, the resin was not peeled from the substrate even after 500 times or more.
Further, when the residual monomer was analyzed for the original film, the presence of 2,4-diphenyl-4-methyl-1-pentene could be confirmed.

(Example 2)
A cation exchange membrane was prepared in exactly the same manner as in Example 1 except that the monomer paste formulation was changed as follows.

Monomer paste formulation:
Reactive monomer: 100 parts by weight (styrene)
Functional monomer: 70 parts by weight (α-methylstilbene)
Crosslinkable monomer: 42 parts by weight (industrial divinylbenzene)
Matrix resin: 32 parts by weight (acrylonitrile-butadiene rubber)
Polymerization initiator; 24 parts by weight (tert-butyl hydroperoxide)

The exchange capacity of the obtained cation exchange membrane was 2.2 meq / g. As a result of repeated bending tests on the obtained film, resin peeling was not seen even 500 times or more.
Furthermore, when the residual monomer was analyzed about the original film, the presence of α-methylstilbene could be confirmed.

(Example 3)
A monomer paste having the following formulation was prepared.
Monomer paste formulation:
Reactive monomer: 100 parts by weight (styrene)
Functional monomer; 40 parts by weight (2,4-diphenyl-4-methyl-1-pentene)
Crosslinkable monomer: 50 parts by weight (industrial divinylbenzene)
Matrix resin; 34 parts by weight (acrylonitrile-butadiene rubber)
Polymerization initiator; 14 parts by weight (di-tert-butyl peroxide)

  The monomer paste was applied to a polyethylene substrate having a thickness of 190 μm, and the polyester film was wound around a take-up roller together with the release film. Thereafter, the take-up roller was put in an autoclave, and polymerization was carried out by holding at 110 ° C. for 8 hours in nitrogen gas at a pressure of 0.4 Mpa to obtain a raw film.

  Subsequently, the obtained original membrane was subjected to cation treatment in the same manner as in Example 1 to introduce a cation exchange group to obtain a cation exchange membrane.

The exchange capacity of the obtained cation exchange membrane was 2.3 meq / g. Further, as a result of the repeated bending test, the resin was not peeled from the substrate even after 500 times or more.
Further, when the residual monomer was analyzed for the original film, the presence of 2,4-diphenyl-4-methyl-1-pentene could be confirmed.

Example 4
A cation exchange membrane was prepared in exactly the same manner as in Example 3 except that the monomer paste formulation was changed as follows.

Monomer paste formulation:
Reactive monomer: 100 parts by weight (styrene: 65 parts by weight, chloromethylstyrene: 35 parts by weight)
Functional monomer: 90 parts by weight (α-methylstyrene)
Crosslinkable monomer: 35 parts by weight (industrial divinylbenzene)
Matrix resin; 30 parts by weight (acrylonitrile-butadiene rubber)
Polymerization initiator: 9 parts by weight (di-tert-butyl peroxide)

The exchange capacity of the obtained cation exchange membrane was 2.3 meq / g. Further, as a result of the repeated bending test, the resin was not peeled from the substrate even after 500 times or more.
Further, when the residual monomer was analyzed for the original film, the presence of α-methylstyrene could be confirmed.

(Example 5)
A monomer paste was prepared according to the following formulation.
Monomer paste formulation:
Reactive monomer: 100 parts by weight (styrene: 70 parts by weight, chloromethylstyrene: 30 parts by weight)
Functional monomer; 23 parts by weight (2,4-diphenyl-4-methyl-1-pentene)
Crosslinkable monomer: 26 parts by weight (industrial divinylbenzene)
Matrix resin; 25 parts by weight (styrene-butadiene rubber)
Polymerization initiator; 17 parts by weight (tert-butyl hydroperoxide)

  The above monomer paste was applied to a polypropylene substrate having a thickness of 190 μm, and the polyester film was wound around a winding roller together with the release film. Thereafter, the take-up roller was put in an autoclave, and polymerization was carried out by holding at 120 ° C. for 9 hours in nitrogen gas at a pressure of 0.4 Mpa to obtain a raw film.

  Subsequently, the obtained original membrane was subjected to cation treatment in the same manner as in Example 1 to introduce a cation exchange group to obtain a cation exchange membrane.

The exchange capacity of the obtained cation exchange membrane was 2.4 meq / g. Further, as a result of the repeated bending test, the resin was not peeled from the substrate even after 500 times or more.
Further, when the residual monomer was analyzed for the original film, the presence of 2,4-diphenyl-4-methyl-1-pentene could be confirmed.

(Example 6)
A monomer paste was prepared according to the following formulation.
Monomer paste formulation:
Reactive monomer: 100 parts by weight (styrene: 70 parts by weight, chloromethylstyrene: 30 parts by weight)
Functional monomer: 100 parts by weight (α-methylstyrene)
Crosslinkable monomer: 30 parts by weight (industrial divinylbenzene)
Matrix resin; 30 parts by weight (acrylonitrile-butadiene rubber)
Polymerization initiator: 10 parts by weight (di-tert-butyl peroxide)

  The monomer paste was applied to a polypropylene substrate having a thickness of 180 μm, and the polyester film was wound around a winding roller together with the release film. Thereafter, the take-up roller was placed in an autoclave, and polymerization was carried out in nitrogen gas at a pressure of 0.4 MPa at 120 ° C. for 1 hour and then at 130 ° C. for 9 hours to obtain a raw film.

  Subsequently, the obtained original membrane was subjected to cation treatment in the same manner as in Example 1 to introduce a cation exchange group to obtain a cation exchange membrane.

The exchange capacity of the obtained cation exchange membrane was 2.2 meq / g. Further, as a result of the repeated bending test, the resin was not peeled from the substrate even after 500 times or more.
Further, when the residual monomer was analyzed for the original film, the presence of α-methylstyrene could be confirmed.

(Example 7)
A monomer paste was prepared according to the following formulation.
Monomer paste formulation:
Reactive monomer: 100 parts by weight (styrene: 75 parts by weight, chloromethylstyrene: 25 parts by weight)
Functional monomer: 100 parts by weight (α-ethylstyrene)
Crosslinkable monomer: 30 parts by weight (industrial divinylbenzene)
Matrix resin; 30 parts by weight (acrylonitrile-butadiene rubber)
Polymerization initiator: 10 parts by weight (di-tert-butyl peroxide)

  The monomer paste was applied to a polypropylene substrate having a thickness of 180 μm, and the polyester film was wound around a winding roller together with the release film. Thereafter, the take-up roller was placed in an autoclave, and polymerization was carried out in nitrogen gas at a pressure of 0.4 MPa at 120 ° C. for 1 hour and then at 130 ° C. for 9 hours to obtain a raw film.

  Subsequently, the obtained original membrane was subjected to cation treatment in the same manner as in Example 1 to introduce a cation exchange group to obtain a cation exchange membrane.

The exchange capacity of the obtained cation exchange membrane was 2.2 meq / g. Further, as a result of the repeated bending test, the resin was not peeled from the substrate even after 500 times or more.
Further, when the residual monomer was analyzed for the above-mentioned original film, the presence of α-ethylstyrene could be confirmed.

(Comparative Example 1)
A cation exchange membrane was prepared in the same manner as in Example 1 except that the functional monomer was not used and the formulation of the monomer paste was changed as follows.

Monomer paste formulation:
Reactive monomer: 100 parts by weight (styrene: 80 parts by weight, chloromethylstyrene: 20 parts by weight)
Crosslinkable monomer: 30 parts by weight (industrial divinylbenzene)
Matrix resin; 45 parts by weight (styrene-butadiene rubber)
Polymerization initiator; 17 parts by weight (tert-butyl hydroperoxide)

  The exchange capacity of the obtained cation exchange membrane was 2.4 meq / g. As a result of repeated bending tests on the obtained film, resin peeling occurred 51 times.

(Comparative Example 2)
A cation exchange membrane was prepared in the same manner as in Example 1 except that the functional monomer was not used and the formulation of the monomer paste was changed as follows.

Monomer paste formulation:
Reactive monomer: 100 parts by weight (styrene)
Crosslinkable monomer: 26 parts by weight (industrial divinylbenzene)
Matrix resin; 23 parts by weight (acrylonitrile-butadiene rubber)
Polymerization initiator; 16 parts by weight (di-tert-butyl peroxide)

  The exchange capacity of the obtained cation exchange membrane was 2.4 meq / g. As a result of repeatedly performing a bending test on the obtained film, resin peeling occurred 23 times.

Claims (3)

In a cation exchange membrane comprising a polyolefin resin base material and a hydrocarbon cation exchange resin layer covering the base material,
The hydrocarbon-based cation exchange resin has a crosslinked structure and a unit derived from at least one monomer selected from the group consisting of α-alkylstyrene, α-alkylstyrene dimer and α-alkylstilbene. Have
A cation exchange membrane characterized in that the number of times until the base material and the hydrocarbon-based cation exchange resin layer peel when subjected to repeated bending tests is 100 times or more.   The cation exchange membrane according to claim 1, which has an ion exchange capacity of 0.1 to 4.0 meq / g. 100 to 100 parts by weight of a reactive monomer capable of introducing a cation exchange group, and 30 to 200 monomers other than at least one reactive monomer selected from the group consisting of α-alkylstyrene, α-alkylstyrene dimer and α-alkylstilbene A mixed monomer paste containing parts by weight and 20 to 80 parts by weight of a crosslinkable polyfunctional monomer is prepared,
The monomer paste is applied to a polyolefin substrate and polymerized,
Then introducing a cation exchange group,
A method for producing a cation exchange membrane characterized by the above.