JP2012021099A - Method for manufacturing ion exchange membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an ion exchange membrane which solve a problem of being easily torn in a specific direction, and has not only a high membrane strength but also a low membrane resistance.SOLUTION: The ion exchange membrane has a structure containing, as a base material sheet, a laminated sheet obtained by laminating a plurality of porous resin sheets having different longitudinal and traverse orientation strengths, wherein pores of the porous resin sheets constituting the laminated sheet are filled with an ion exchange resin. The method for manufacturing the ion exchange membrane includes a step in which: a polymerizable composition containing a monomer having a functional group capable of incorporating an ion exchange group or having an ion exchange group, a crosslinkable monomer and a polymerization initiator is prepared; an ion exchange membrane precursor is fabricated which has a structure in which the plurality of porous resin sheets are superposed so that high orientation strength directions of the adjacent porous resin sheets cross each other, and the pores of the porous resin sheets are filled with the polymerizable composition; and the polymerizable composition is polymerized at a lower temperature than the melting point of the porous resin sheets under pressurization of the ion exchange membrane precursor.

Description

  The present invention relates to a novel method for producing an ion exchange membrane comprising a laminated sheet in which a plurality of porous resin sheets having different vertical and horizontal orientation strengths are laminated as a base sheet.

  Ion exchange membranes are industrially used for electrodialysis used in desalination processes in the field of salt production and foods, and as electrolyte membranes for fuel cells. Such an ion exchange membrane has a structure in which a base sheet having a function as a reinforcing material is provided in an ion exchange resin as a core material, whereby a certain membrane strength is maintained.

  Conventionally, an ion exchange membrane in which a porous resin sheet is used as the substrate sheet is known. In the ion exchange membrane of such a form, the space | gap part in the porous resin sheet which is a base material is filled with ion exchange resin, As a result, there exists an advantage that membrane resistance is low. As this porous resin sheet, a thin film such as polytetrafluoroethylene or high molecular weight polyethylene resin is generally used, but this thin film is usually uniaxial or biaxial in order to avoid a decrease in strength due to porous formation. Stretched in the direction.

  Since the stretched porous resin sheet has a high molecular orientation in the stretching direction (or the direction in which the stretching degree is large), an ion exchange membrane using such a porous resin sheet as a base sheet is There is a drawback that it is easy to tear in the direction (stretching direction), and the film strength is not so high.

  As an ion exchange membrane in which the above problems are solved, Patent Document 1 uses a laminated sheet obtained by laminating two or more porous resin sheets having strength anisotropy in two orthogonal directions as a base sheet. What has been proposed.

JP 2008-4500 A

  The ion exchange membrane disclosed in Patent Document 1 uses a laminated sheet obtained by laminating two or more porous resin sheets having strength anisotropy so that the maximum strength directions are different as a base sheet. The disadvantage that the film is easy to tear in one direction is solved, and the film strength is also improved. However, there is a new drawback of high membrane resistance. For this reason, when it uses for uses, such as electrodialysis, the problem of requiring a high voltage arises and the further improvement is calculated | required.

  Accordingly, an object of the present invention is to solve the problem of being easily broken in a specific direction, and to provide a method for producing an ion exchange membrane having not only high membrane strength but also low membrane resistance.

  As a result of studying a method for producing an ion exchange membrane using a laminated sheet of porous resin sheets as a base sheet, the present inventors have found that the bonding means of the porous resin sheet when forming the laminated sheet has a membrane resistance. For example, the inventors have found that when the porous resin sheet is joined without using heat fusion, the membrane resistance is greatly reduced, and the present invention has been completed.

According to the present invention, a laminate sheet in which a plurality of porous resin sheets having different longitudinal and transverse orientation strengths are laminated is included as a base sheet, and each void portion of the porous resin sheet constituting the laminate sheet is provided. In the method for producing an ion exchange membrane having a structure filled with an ion exchange resin,
A step of preparing a polymerizable composition containing a functional group capable of introducing an ion exchange group or a monomer having an ion exchange group, a crosslinkable monomer, and a polymerization initiator;
A plurality of the porous resin sheets were superposed so that the high orientation strength directions of the adjacent porous resin sheets intersected, and the polymerizable composition was filled in the voids of each porous resin sheet Producing an ion exchange membrane precursor having a structure;
A polymerization step of polymerizing the polymerizable composition at a temperature lower than the melting point of the porous resin sheet while pressurizing the ion-exchange membrane precursor;
A process for producing an ion exchange membrane characterized by comprising:

  In the production method of the present invention, when a monomer having a functional group capable of introducing an ion exchange group is used as the monomer component of the polymerizable composition, the polymerizable property is added after the polymerization step. By providing a step of introducing ion exchange groups into the polymer of the composition, an ion exchange membrane as a final product can be obtained.

Moreover, in the manufacturing method of this invention, the following aspects are preferable.
(1) For each of a plurality of the porous resin sheets, after filling the voids with the polymerizable composition, the porous resin sheets are overlapped to produce the ion exchange membrane precursor. .
(2) The polymerization of the polymerizable composition is performed in the range of 40 to 130 ° C.
(3) Use a long sheet as each of the plurality of porous resin sheets, and prepare a dedicated original fabric roller corresponding to each of the long sheets,
Each of the long sheets is wound around a dedicated original fabric roller and held,
While winding up each long sheet from each original fabric roller using a winding roller,
While each long sheet is moved from each original fabric roller to the take-up roller, each long sheet is brought into contact with the polymerizable composition, and the polymerizable composition is filled in the gap of each long sheet. To obtain the ion exchange membrane precursor in a state of being wound on the winding roller,
The wound ion exchange membrane precursor is pressurized and polymerized with the polymerizable composition.
(4) The long sheets are superposed on the winding roller after the polymerizable composition is filled into the gaps of the long sheets.

  The ion exchange membrane obtained by the production method of the present invention includes, as a base material sheet, a laminated sheet in which porous resin sheets having different vertical and horizontal orientation strengths are laminated so that the high orientation strength directions intersect. Therefore, as with known ion exchange membranes, the problem that mechanical properties such as tear resistance are not anisotropic and are easily torn in a specific direction has been solved, and the membrane strength is also high.

  In the production method of the present invention, the most important feature is that pressure (compression bonding) is performed in a state in which a void portion of a porous resin sheet on which a polymerizable composition for forming an ion exchange resin is superimposed is filled. ) In that the polymerization is carried out below. That is, by performing polymerization in this way, the polymerizable composition (ion exchange resin) functions as a bonding agent, the porous resin sheets are firmly bonded to each other, and each porous resin sheet in the laminated sheet The ion exchange resin is formed so as to penetrate the inside of the sheet in the thickness direction, and the ion exchange resin continuously extends in the laminated sheet so as to straddle the bonding interface of the porous resin sheet. As a result, the membrane resistance of the ion exchange membrane obtained by this method is extremely low.

  For example, when the laminated porous resin sheets are joined by means such as heat fusion to form a laminated sheet as a base sheet, voids in the porous resin sheet may be crushed, The gap is blocked at the bonding interface. For this reason, even if the porous resin sheets are heat-sealed with the polymerizable composition for the ion exchange resin filled in the voids of the porous resin sheet, the interface between the porous resin sheets is almost the same. The ion exchange resin formed by subsequent polymerization is divided at the interface of the porous resin sheet, and as a result, the membrane resistance of the obtained ion exchange membrane increases.

The figure which shows an example of the manufacturing process employ | adopted as implementation of the manufacturing method of the ion exchange membrane of this invention.

<Structure of ion exchange membrane>
The ion exchange membrane produced by the production method of the present invention has a laminated sheet in which a plurality of porous resin sheets are laminated as a base sheet, and forms this base sheet (laminated sheet). Each porous resin sheet has a structure in which the voids are filled with an ion exchange resin.

Laminated sheet and porous resin sheet;
The porous resin sheet used for forming the laminated sheet is stretched and has a molecular orientation in the stretching direction, and has a high tensile strength in the orientation direction. Such a porous resin sheet is laminated by stretching so that the high orientation strength directions (stretched directions) of adjacent porous resin sheets intersect to form a laminated sheet to be a base sheet. . That is, the base sheet made of such a laminated sheet as a whole exhibits high tensile strength in both the vertical and horizontal directions, thereby achieving high ion exchange membrane strength and orientation. The disadvantage of being easily torn along the direction is avoided. That is, the molecularly oriented resin sheet has the property of being easily torn along this orientation direction (stretching direction), but is laminated so that the high orientation strength directions cross each other. The tearing along is effectively prevented.
As the porous resin sheet, a uniaxially stretched sheet (for example, a stretch ratio of 2 times or more) is usually used in order to maximize the increase in strength in the orientation direction. As long as the orientation strengths are different, it is possible to use a biaxially stretched one.

  The crossing angle in the direction of high orientation strength of adjacent porous resin sheets can be appropriately changed according to the number of laminated porous resin sheets, but is generally set so that the crossing angle is 90 ± 45 degrees. (In other words, the layers are stacked so that the high orientation strength directions are staggered). Of course, it is also possible to laminate so that the high orientation strength direction (stretching direction) is evenly distributed. For example, when three porous resin sheets are laminated, the crossing angle is 120 degrees (60 degrees). It can also be laminated so that

  Moreover, this porous resin sheet has many fine pores which communicate the front and back, and the porosity is generally 20 to 90%, particularly preferably 30 to 70%. If this porosity is too small, it will be difficult to sufficiently fill the gap with ion exchange resin, and further, the amount of ion exchange resin per unit volume will be small and sufficient ion exchange capacity will not be exhibited, resulting in membranes. There is a risk that the resistance becomes high. On the other hand, if the porosity is too high, the amount of ion-exchange resin per unit volume increases, and when used for practical use, the ion-exchange resin swells and shrinks and tends to lack dimensional stability and mechanical strength. .

  As a resin material constituting the porous resin sheet, a thermoplastic resin having substantially no ion exchange group, for example, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer , Vinyl chloride resins such as vinyl chloride-olefin polymers; polytetrafluoroethylene, polytrifluoroethylene, polychlorotrifluoroethylene, poly (tetrafluoroethylene-hexafluoropropylene), poly (tetrafluoroethylene-perfluoroalkyl ether) ), Etc .; polyamide resins such as nylon 6 and nylon 66; ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 4-methyl-1-pentene, Homopolymer of α-olefin such as 5-methyl-1-heptene It can be exemplified copolymers. In general, polyethylene is particularly preferable from the viewpoints of moldability, orientation, cost, and the like.

  Such a porous resin sheet is formed by, for example, extrusion molding using a resin composition in which additives (for example, paraffin or various inorganic powders) that can be removed after stretching are blended with the thermoplastic resin. It is obtained by stretching at a temperature not lower than the softening point and lower than the melting point of the thermoplastic resin, and removing the additive from the obtained stretch-molded sheet. For removing the additive from the stretched sheet, a known method such as extraction with a solvent or dissolution with an acid is carried out without particular limitation.

  Further, the thickness of the porous resin sheet may be in an appropriate range depending on the number of laminated sheets and the thickness of the ion exchange membrane, but generally it may be about 5 to 200 μm.

Ion exchange resins;
The ion exchange resin filled in the voids of the porous resin sheet may be a known one, for example, an ion exchange group that expresses ion exchange ability in a hydrocarbon-based or fluorine-based resin, specifically, a positive ion resin. An ion exchange group or an anion exchange group is introduced.

Examples of the hydrocarbon resins include styrene resins and acrylic resins, and examples of the fluorine-based materials include perfluorocarbon resins.
The ion exchange group is a functional group that can be negatively or positively charged in an aqueous solution. In the case of a cation exchange group, examples thereof include a sulfonic acid group, a carboxylic acid group, and a phosphonic acid group. A sulfonic acid group which is a strongly acidic group is preferred. In the case of an anion exchange group, examples thereof include primary to tertiary amino groups, quaternary ammonium groups, pyridyl groups, imidazole groups, and quaternary pyridinium groups. Groups and quaternary pyridinium groups are preferred.

  The ion exchange resin having an ion exchange group as described above has an appropriate ion exchange capacity (depending on the porosity of the base sheet made of the laminated sheet described above and the amount of ion exchange groups introduced into the ion exchange resin ( For example, it is present in the ion exchange membrane in such an amount as to be about 0.1 to 4.0 meq / g.

<Manufacture of ion exchange membrane>
In the present invention, the ion exchange membrane having the structure as described above prepares a polymerizable composition for forming the ion exchange resin (polymerizable composition preparation step), and a plurality of the porous resin sheets are provided. An ion exchange membrane precursor having a structure in which the polymerizable composition is filled and the void portion of the porous resin sheet is filled is prepared (ion exchange membrane precursor preparation step), and the polymerizable composition is polymerized under pressure. (Polymerization step), and if necessary, it is produced by introducing ion exchange groups into the polymer (ion exchange resin precursor) obtained in the polymerization step (ion exchange group introduction step).

1. Polymerizable composition preparation step;
The polymerizable composition for forming an ion exchange group is a monomer having an ion exchange group or a monomer having an ion exchange group (hereinafter referred to as a functional group for introducing an exchange group). These monomers are sometimes referred to as “basic monomer components”), contain a crosslinking monomer and a polymerization initiator, and are prepared by mixing these components.

  The monomer having a functional group for introducing an exchange group and the monomer having an ion exchange group may be those conventionally used for producing an ion exchange resin.

Examples of the monomer having a functional group for introducing a cation exchange group include styrene, vinyl toluene, vinyl xylene, α-methyl styrene, vinyl naphthalene, α-halogenated styrenes and the like.
Examples of the monomer having a functional group for introducing an anion exchange group include styrene, vinyl toluene, chloromethyl styrene, vinyl pyridine, vinyl imidazole, α-methyl styrene, vinyl naphthalene and the like.

Examples of the monomer having a cation exchange group include sulfonic acid monomers such as α-halogenated vinyl sulfonic acid, styrene sulfonic acid, and vinyl sulfonic acid, and carboxylic acid monomers such as methacrylic acid, acrylic acid, and maleic anhydride. Examples thereof include monomers, phosphonic acid monomers such as vinyl phosphoric acid, salts and esters thereof, and the like.
Examples of the monomer having an anion exchange group include amine monomers such as vinylbenzyltrimethylamine and vinylbenzyltriethylamine, nitrogen-containing heterocyclic monomers such as vinylpyridine and vinylimidazole, salts and esters thereof. There can be mentioned.

  In addition, when a monomer having an ion exchange group is used as the monomer as described above, a target ion exchange membrane can be obtained at the stage where the polymerization step described later is completed. When a monomer having a functional group for use is used, a target ion exchange membrane can be obtained by carrying out an ion exchange group introduction step after the polymerization step.

The crosslinkable monomer is used to densify the ion exchange resin and enhance swelling suppression, membrane strength, etc., and is not particularly limited. For example, divinylbenzene, divinylsulfone , Divinyl compounds such as butadiene, chloroprene, divinylbiphenyl, trivinylbenzenes, divinylnaphthalene, diallylamine, and divinylpyridine.
Such a crosslinkable monomer is generally preferably 0.1 to 50 parts by weight, more preferably 1 to 40 parts by weight with respect to 100 parts by weight of the basic monomer component described above.

  Furthermore, in addition to the above-mentioned monomer having a functional group for introducing an exchange group, a monomer having an ion exchange group, and a crosslinkable monomer, other copolymerizable with these monomers as required. These monomers may be added. Examples of such other monomers include styrene, acrylonitrile, methylstyrene, acrolein, methyl vinyl ketone, and vinyl biphenyl.

As the polymerization initiator, conventionally known polymerization initiators are used without particular limitation. Specifically, octanoyl peroxide, lauroyl peroxide, t-butylperoxy-2-ethylhexanoate, benzoyl peroxide, t-butylperoxyisobutyrate, t-butylperoxylaurate, t- Organic peroxides such as hexyl peroxybenzoate and di-t-butyl peroxide are used.
Such a polymerization initiator is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the basic monomer component.

In order to adjust the viscosity, a matrix resin can be blended with the polymerizable composition containing the above-described various components as necessary.
Examples of such matrix resins include, for example, saturated aliphatic hydrocarbon polymers such as ethylene-propylene copolymers and polybutylene, styrene polymers such as styrene-butadiene copolymers, polyvinyl chloride, and various kinds thereof. Styrene monomers such as vinyltoluene, vinylxylene, chlorostyrene, chloromethylstyrene, α-methylstyrene, α-halogenated styrene, α, β, β'-trihalogenated styrene, ethylene, butylene, etc. Or a conjugated diolefin such as butadiene or isoprene) can be used.
These matrix resins are used in such an amount that the polymerizable composition has a viscosity that can be quickly filled and held in the voids of the porous resin sheet without causing dripping or the like.

2. Ion exchange membrane precursor production process;
The above-mentioned polymerizable composition is prepared by filling each of a plurality of porous resin sheets into the voids and superimposing the porous resin sheets filled with the polymerizable composition in the voids. Get the body.

  The method of filling the polymerizable composition in the voids of the porous resin sheet is not particularly limited, but generally, a method of immersing the porous resin sheet in the polymerizable composition, or a method in which the polymerizable composition is porous resin is used. Methods such as coating and spraying on the sheet are employed.

In addition, as described above, the plurality of porous resin sheets are overlapped so that the high orientation strength directions of adjacent porous resin sheets intersect at a predetermined angle (for example, 90 degrees).
This superposition is generally performed after filling the voids of each porous resin sheet with the polymerizable composition. However, after superposing a plurality of porous resin sheets, the porous resin sheet is superposed. It is also possible to fill the polymerizable composition in the voids.

3. Polymerization step;
As described above, the ion exchange membrane precursor obtained by filling the void portion of the porous resin sheet with the polymerizable composition and overlaying the porous resin sheet is subjected to a polymerization step under pressure. . That is, when a monomer having an ion exchange group is used as a basic monomer component, the intended ion exchange membrane can be obtained by completing this step. When a monomer having a functional group for introducing an exchange group is used as a basic component, it is necessary to introduce an ion exchange group after completion of this step.

  In the present invention, the superposed porous resin sheets are not joined by heat fusion or the like, and the polymerizable composition in the ion exchange membrane precursor (the polymerizable composition filled in the voids of each porous resin sheet) The product is polymerized under pressure, whereby the ion exchange resin (or its precursor resin) is formed, and at the same time, the bonded porous resin sheets are joined and integrated (formation of the base sheet). That is, in this step, the heat-bonding of the superposed porous resin sheets is not performed, and the excess polymerizable composition present at the interface of the porous resin sheet by pressurization is a void portion of the porous resin sheet. Since the polymerization is performed in a state of being pushed into the inside, the void is not closed at the interface of the porous resin sheet or inside thereof, and as a result, from the upper surface to the lower surface of the stacked porous resin sheets. The ion exchange resin (or its precursor resin) is formed in a continuous form, and the resin obtained by the polymerization of the polymerizable composition does not peel off at the interface of the porous resin sheet. Thus, the joined and integrated porous resin sheets (formation of the base material sheet) are performed.

  The pressurization and polymerization of the ion exchange membrane precursor may be performed so that peeling at the interface of the porous resin sheet does not occur. For example, the ion exchange precursor (superposed porous resin sheet) is used as a release film. It is preferable to perform polymerization by heating in this state.

As the releasable film, a film having heat resistance that can withstand polymerization and that can be easily peeled off after polymerization is used. For example, low density polyethylene, high density polyethylene, polypropylene, poly 1-butene, poly 4-methyl-1-pentene, or random α-olefins such as ethylene, propylene, 1-butene, 4-methyl-1-pentene or the like Polyolefins such as block copolymers, ethylene / vinyl acetate copolymers, ethylene / vinyl alcohol copolymers, ethylene / vinyl compound copolymers such as ethylene / vinyl chloride copolymers, polystyrene, acrylonitrile / styrene copolymers, ABS, styrene resin such as α-methylstyrene / styrene copolymer, polyvinyl chloride, polyvinylidene chloride, vinyl chloride / vinylidene chloride copolymer, polyvinyl compound such as polymethyl acrylate and polymethyl methacrylate, nylon 6 , Nylon 6-6, nylon 6-10, polyamides such as nylon 11, nylon 12 and the like, thermoplastic polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyphenylene oxide, etc., biodegradable resins such as polylactic acid, or mixtures thereof The film which consists of one of these resin can be mentioned, The film which concerns may be biaxially stretched.
That is, an appropriate film may be selected from the above films according to the type of monomer component in the polymerizable composition and used as a releasable film. In particular, a polyester film such as polyethylene terephthalate (PET) is most preferable from the viewpoint of heat resistance and peelability.

  The pressurizing pressure may generally be about 0.1 to 1.0 MPa.

The polymerization temperature may be a temperature that is lower than the melting point of the porous resin sheet and does not impair the orientation of the porous resin sheet, but is generally in the range of 40 to 130 ° C. That is, by performing the polymerization while heating to such a temperature range, a part of the porous resin sheet is dissolved in the polymerizable composition, and the polymerization is performed in this state. As a result, the porous resin sheet Bonding strength can be increased, and film strength can be further improved.
The polymerization time varies depending on the polymerization temperature and the like, but is generally about 3 to 20 hours.

4). Ion exchange group introduction step;
As described above, when a monomer having an ion exchange group is used as a basic monomer component in the polymerization composition, an ion exchange resin is formed by the above polymerization process. In the case where a monomer having a functional group for introducing an exchange group is used as a basic monomer component, the resin obtained in the above polymerization step has an ion exchange group. Therefore, it is necessary to introduce ion exchange groups after the polymerization step.

  The introduction of the ion exchange group is carried out by a method known per se. For example, in the case of producing a cation exchange membrane, it is carried out by a treatment such as sulfonation, chlorosulfonation, phosphoniumation, hydrolysis, and the like. When producing an exchange membrane, it is carried out by a process such as amination or alkylation.

Since the ion exchange membrane manufactured as described above is formed from a laminated sheet in which the base sheet is laminated so that the high orientation strength direction intersects, not only the membrane strength is high, but also in a specific direction. The disadvantage of being easily torn is effectively eliminated. Further, the ion exchange resin in the membrane includes many portions that continuously extend from the upper surface to the lower surface of the base sheet, and thus has an advantage of low membrane resistance.
Such an ion exchange membrane is used in a state where the peelable film is peeled off.

<Preferred manufacturing process>
The manufacturing method described above can be carried out using a porous resin sheet that has been cut into an appropriate size, or can be carried out using a long sheet wound around a roller. Industrially, it is advantageous in terms of productivity to use a long sheet wound around a roller as a porous resin sheet.
FIG. 1 shows an example of a process for producing an ion exchange membrane using such a long sheet.

  In FIG. 1, a long porous resin sheet 10a is wound around an original fabric roller 1a, and a long porous resin sheet 10b is wound around an original fabric roller 1b. The porous resin sheets (hereinafter simply referred to as “long sheets”) 10a and 10b wound around the raw fabric rollers 1a and 1b are wound by the take-up roller 3 through a tension roller or a feed roller as appropriate. It is superimposed while being taken. In this case, the long sheets 10a and 10b are wound around the original fabric rollers 1a and 1b so that the high orientation strength direction intersects at a predetermined angle (for example, 90 degrees) when they are superimposed.

  A dipping tank 5 a containing a polymerizable composition is provided between the original fabric roller 1 a and the take-up roller 3, and the polymerizable composition is provided between the original fabric roller 1 b and the take-up roller 3. Is provided. That is, the long sheet 1a is immersed in the polymerizable composition in the immersion tank 5a, the polymerizable composition is filled in the gap of the sheet 1a and wound up by the winding roller 3, and the long sheet 1b is immersed in the immersion tank. It is immersed in the polymerizable composition in 5 b, the polymerizable composition is filled in the gap portion of the sheet 1 b, and is taken up by the take-up roller 3.

  A releasable film 20 is wound and held on the original fabric roller 7, and this releasable film 20 is passed through a pressure roller 9 disposed facing the take-up roller 3. It is wound around the winding roller 3.

  That is, the long sheet 10a, 10b filled with the polymerizable composition is superposed on the take-up roller 3, and is wound between the release film 20 and pressed. As understood from this, the ion exchange membrane precursor is held between the releasable film 20 and pressed by the roller pressure on the winding roller 3.

  The winding roller 3 is introduced into a predetermined polymerization apparatus (for example, a heating oven), and polymerization is performed by heating the polymerizable composition to a predetermined temperature in the apparatus. Therefore, when a monomer having an ion exchange group is used as a basic monomer component in the polymerization composition, a target ion exchange membrane can be obtained by polymerization in a polymerization apparatus. Further, when a monomer having a functional group for introducing an exchange group is used as a basic monomer component, an ion exchange group introduction treatment is further performed after the above-described polymerization, and the intended ion exchange membrane Is obtained.

As described above, if a long sheet is used as a porous resin sheet, an ion exchange membrane can be obtained continuously and efficiently.
Further, in the example of FIG. 1, two long sheets 10a and 10b are used, but it is also possible to use a large number of long sheets. In this case, the number of long sheets It is only necessary to provide a number of original fabric rollers and a dipping tank in which the polymerizable composition is accommodated. Furthermore, in the example of FIG. 1, the long sheets 10a and 10b are immersed in the polymerization composition in different immersion tanks 5a and 5b, but the number of immersion tanks containing the polymerizable composition is one. The long sheets 10a and 10b can be overlapped simultaneously with the immersion in the polymerizable composition in the immersion tank.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.
The characteristics of the porous resin sheets and ion exchange membranes shown in the Examples and Comparative Examples were measured by the following methods.

Membrane resistance;
An ion exchange membrane is sandwiched in a two-chamber cell having a platinum black electrode, a 0.5 mol / L-NaCl solution is filled on both sides of the ion exchange membrane, and the resistance between the electrodes at 25 ° C. by an AC bridge (frequency 1000 cycles / second). The membrane resistance was determined from the difference between the interelectrode resistance and the interelectrode resistance when no ion exchange membrane was installed. The ion exchange membrane used for the above measurement was previously equilibrated in a 0.5 mol / L NaCl solution.

Mechanical strength of ion exchange membranes;
The burst strength was measured with a Murren burst tester (manufactured by Toyo Seiki) in accordance with JIS-P8112.

<Example 1>
First, a porous resin sheet made of polyethylene was uniaxially stretched 2.5 times in the TD direction to obtain a porous resin sheet (thickness 36 μm, porosity 48%) as a base material.
Next, each component was mixed according to the following formulation to prepare a polymerizable composition.
90 parts by weight of chloromethylstyrene 10 parts by weight of divinylbenzene 3 parts by weight of benzoyl peroxide 3 parts by weight of styrene oxide 500 g of this polymerizable composition is put in a 1000 ml glass container, and a porous resin sheet to be a base material sheet is placed here. The sheet was immersed, and the polymer composition was filled into the voids of the porous resin sheet.

Subsequently, one of the porous resin sheets is taken out from the polymerizable composition and placed on a 100 μm polyester film, the other of the porous resin sheets is taken out from the monomer composition, and the porous material previously placed Lamination was performed such that the stretching direction was orthogonal to the resin sheet to obtain a laminated sheet composed of two porous resin sheets.
A polyester film was laminated on the obtained laminated sheet, and after pressurizing the roll with a touch pressure of 0.05 kgf / cm, heat polymerization was carried out at 80 ° C. for 5 hours under a nitrogen pressure of 0.4 MPa. The obtained ion exchange resin precursor membrane was reacted at room temperature for 5 hours in an amination bath consisting of 10 parts of 30% trimethylamine aqueous solution, 5 parts of water and 5 parts of acetone to obtain a quaternary ammonium type anion exchange membrane. It was.
Table 1 shows the measurement results of membrane resistance and burst strength of the obtained anion exchange membrane.

<Example 2>
Except that the prescription of the polymerizable composition was changed as follows, the porous resin sheet stretched in the same manner as in Example 1 was filled, laminated under pressure, and heat polymerized to obtain an ion exchange resin precursor film. It was.
Styrene 90 parts by weight Divinylbenzene 10 parts by weight Benzoyl peroxide 3 parts by weight

  The obtained ion exchange resin precursor membrane was immersed in a 1: 1 (weight ratio) mixture of 98% concentrated sulfuric acid and chlorosulfonic acid having a concentration of 90% or more for 60 minutes at 40 ° C., and sulfonic acid type cation exchange was performed. A membrane was obtained. Table 1 shows the measurement results of membrane resistance and burst strength of the obtained anion exchange membrane.

<Example 3>
An anion exchange membrane was prepared in the same manner as in Example 1 except that the stretching ratio of the porous resin sheet was doubled, and membrane resistance and burst strength were measured. The measurement results are shown in Table 1.

<Example 4>
An anion exchange membrane was prepared in the same manner as in Example 1 except that the stretching ratio of the porous resin sheet was set to 3. The membrane resistance and the burst strength were measured. The measurement results are shown in Table 1.

<Comparative Example 1>
An anion exchange membrane was prepared in the same manner as in Example 1 except that no pressurization after lamination was performed. As a result, the obtained anion exchange membrane was peeled off at the interface to obtain a membrane. I could not.

<Comparative example 2>
A porous resin sheet similar to that in Example 1 was previously fused by hot pressing under the conditions of 0.05 kgf / cm ² and 120 ° C. to produce a porous resin sheet having integrated strength anisotropy. The porous resin sheet was filled with the same polymerizable composition as in Example 1. All subsequent operations were performed in the same manner as in Example 1, and an anion exchange membrane was prepared, and membrane resistance and burst strength were measured. The measurement results are shown in Table 1.

As shown in Table 1, in Examples 1 to 4, an ion exchange membrane having low membrane resistance, high tear strength, and no strength anisotropy could be obtained.
In contrast, in Comparative Example 1, peeling of the interface occurred, and a good film could not be obtained. Moreover, in Comparative Example 2, although there was no interfacial peeling and no strength anisotropy, the film resistance was greatly increased.

DESCRIPTION OF SYMBOLS 1a, 1b: Porous resin sheet original fabric roller 3: Winding roller 5a, 5b: Polymeric composition immersion tank 7: Release film original fabric roller 9: Pressure roller 10a, 10b: Long sheet of porous resin 20 : Release film

Claims (6)

It includes a laminated sheet in which a plurality of porous resin sheets having different vertical and horizontal orientation strengths are laminated as a base sheet, and each void portion of the porous resin sheet constituting the laminated sheet is filled with an ion exchange resin. In the method for producing an ion exchange membrane having the structure:
A step of preparing a polymerizable composition containing a functional group capable of introducing an ion exchange group or a monomer having an ion exchange group, a crosslinkable monomer, and a polymerization initiator;
A plurality of the porous resin sheets were superposed so that the high orientation strength directions of the adjacent porous resin sheets intersected, and the polymerizable composition was filled in the voids of each porous resin sheet Producing an ion exchange membrane precursor having a structure;
A polymerization step of polymerizing the polymerizable composition at a temperature lower than the melting point of the porous resin sheet while pressurizing the ion-exchange membrane precursor;
A process for producing an ion exchange membrane, comprising:   As a monomer component of the polymerizable composition, a monomer having a functional group capable of introducing an ion exchange group is used, and after the polymerization step, an ion exchange group is introduced into the polymer of the polymerizable composition. The manufacturing method of the ion exchange membrane of Claim 1 which has a process to do.   The said ion exchange membrane precursor is produced by superimposing these porous resin sheets on each of a plurality of the porous resin sheets after filling the voids with the polymerizable composition, or 2. A method for producing an ion exchange membrane according to 2.   The method for producing an ion exchange membrane according to any one of claims 1 to 3, wherein the polymerization of the polymerizable composition is performed in a range of 40 to 130 ° C. As the plurality of porous resin sheets, each uses a long sheet, and prepares a dedicated original fabric roller corresponding to each of the long sheets,
Each of the long sheets is wound around a dedicated original fabric roller and held,
While winding up each long sheet from each original fabric roller using a winding roller,
While each long sheet is moved from each original fabric roller to the take-up roller, each long sheet is brought into contact with the polymerizable composition, and the polymerizable composition is filled in the gap of each long sheet. To obtain the ion exchange membrane precursor in a state of being wound on the winding roller,
The method for producing an ion exchange membrane according to any one of claims 1 to 4, wherein the ion exchange membrane precursor wound up is subjected to pressurization and polymerization of the polymerizable composition.   6. The production of an ion exchange membrane according to claim 5, wherein the elongate sheets are superposed on the take-up roller after the polymerizable composition is filled in the gaps of the elongate sheets. Method.

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