JP5844653B2 - Cation exchange membrane and electrolytic cell using the same - Google Patents

Description

  The present invention relates to a cation exchange membrane and an electrolytic cell using the same.

  Fluorine-containing cation exchange membranes have excellent heat resistance and chemical resistance, so cation exchange for electrolysis to produce chlorine and alkali in electrolysis of alkali chloride (hereinafter referred to as electrolysis). Used as a membrane. In addition, it is used as various membranes for electrolysis such as ozone generating membranes, fuel cells, water electrolysis and hydrochloric acid electrolysis. Among them, in the electrolysis of alkali chloride, which electrolyzes salt water and the like to produce caustic soda, chlorine and hydrogen, a carboxylic acid layer having a high anion-exclusion carboxylic acid group as an ion exchange group and a low-resistance sulfonic acid group In general, a cation exchange membrane composed of at least two layers including a sulfonic acid layer having an ion exchange group as a cation exchange membrane is used.

  Electrolysis performance in electrolysis using this cation exchange membrane is as follows: (1) From the viewpoint of productivity, the production efficiency (current efficiency) with respect to the flowed current is high; (2) From the viewpoint of economy, the electrolysis voltage is From the standpoint of product quality, low concentrations of impurities (such as sodium chloride) in alkali (such as caustic soda) are desired.

  Further, since the cation exchange membrane is in direct contact with chlorine and caustic soda at 80 to 90 ° C. during electrolysis, a fluorine-containing polymer having high chemical durability is used as a material for the cation exchange membrane.

  However, the fluorine-containing polymer alone does not have sufficient mechanical strength as a cation exchange membrane. For this reason, a woven fabric made of polytetrafluoroethylene (PTFE) or the like is embedded in a film as a reinforcing core material to be reinforced.

  Furthermore, in order to reduce the electrolysis voltage, a woven fabric in which a sacrificial core material is woven into a reinforced core material is employed. The sacrificial core material is eluted by being hydrolyzed, thereby forming a cavity (flow path). By forming the flow path inside the cation exchange membrane, the electrolyte solution penetrates into the cation exchange membrane. As a result, the resistance of the cation exchange membrane approaches that of the electrolytic solution, and further, the thickness of the membrane is substantially reduced, so that the electrolysis voltage is considered to decrease.

  In Patent Document 1, a cation exchange membrane having a reinforcing member inside a cation exchange membrane, the cation exchange membrane having channels in the membrane leading from the window region surrounded by the reinforcing material to the blind region. It is described that a reduction in electrolysis voltage can be achieved with a membrane. In Patent Document 2, the electrical resistance of the cation exchange membrane is reduced by disposing at least a reinforcing material including a sacrificial core material that is dissolved by hydrolysis treatment of ion exchange groups in the third layer and the fourth layer. Is described.

JP-A-01-308435 JP-A-63-113029

  However, when a conventional cation exchange membrane having a flow path is attached to an electrolytic cell and used for electrolysis, the electrolytic solution in the electrolytic cell leaks out from the electrolytic cell via the flow channel. There was a problem that.

  This invention is made | formed in view of the said situation, and it aims at providing the cation exchange membrane which can suppress that an electrolyte solution leaks out of the electrolytic vessel at the time of electrolysis (leak).

  As a result of intensive studies to solve the above problems, the inventors of the present invention are cation exchange membranes having a membrane body containing a fluorine-containing polymer having an ion exchange group, and a flow path inside the membrane body. The above problems can be solved by forming a cation exchange membrane in which a sacrificial core material that dissolves in acid or alkali is present in at least a part of the interior of the flow channel located at the peripheral edge of the membrane body. As a result, the present invention has been completed.

That is, the present invention is as follows.
[1]
A cation exchange membrane having a membrane body containing a fluorine-containing polymer having an ion exchange group;
A cation exchange membrane in which a flow path is formed inside the membrane body, and a sacrificial core material that dissolves in acid or alkali is present in at least part of the inside of the flow channel located at the peripheral edge of the membrane body .
[2]
The cation exchange membrane according to [1], wherein the ratio of the cross-sectional area of the sacrificial core material to the cross-sectional area of the flow path (sacrificial core material remaining ratio) is 20 to 99%.
[3]
The cation exchange membrane according to [1] or [2], wherein the channel is formed over the entire interior of the membrane body.
[4]
The cation exchange membrane according to any one of [1] to [3], wherein the sacrificial core material is present in all of the flow paths.
[5]
The ratio of the total projected area of the sacrificial core material (sacrificial core area ratio) to the total projected area of the flow path when the cation exchange membrane is viewed from above is 10 to 99%. 4].
[6]
The cation exchange membrane according to any one of [1] to [5], wherein the flow path is tubular.
[7]
The sacrificial core material includes any one selected from the group consisting of polyvinyl alcohol (PVA), rayon, polyethylene terephthalate (PET), cellulose, and polyamide, according to any one of [1] to [6]. The cation exchange membrane as described.
[8]
The anode,
A cathode,
The cation exchange membrane according to any one of [1] to [7], disposed between the anode and the cathode;
An electrolytic cell comprising:
[9]
The electrolytic cell according to [8], further comprising a gasket in contact with any one surface of the cation exchange membrane.
[10]
The anode,
A cathode,
An anode side gasket having a first opening disposed on the anode side;
A cathode-side gasket having a second opening disposed on the cathode side;
The cation exchange membrane according to any one of [1] to [7], sandwiched between the anode side gasket and the cathode side gasket,
And having
In the membrane body of the cation exchange membrane, the cation exchange membrane and the cation exchange membrane so that at least a part of the portion where the sacrificial core material is present inside the flow path is pressed by the anode side gasket. An electrolytic cell in which the anode side gasket is disposed.

  ADVANTAGE OF THE INVENTION According to this invention, the cation exchange membrane which can suppress that electrolyte solution leaks outside the electrolytic cell (leakage) at the time of electrolysis can be provided.

It is the conceptual diagram which looked at the cation exchange membrane of this embodiment from the top. It is a sectional side view which follows the AA 'line of FIG. It is the conceptual diagram which looked at the upper surface about another one Embodiment of the cation exchange membrane of this embodiment. It is a conceptual diagram for demonstrating the aperture ratio of the cation exchange membrane of this embodiment. It is a fragmentary sectional view of another one embodiment of a cation exchange membrane of this embodiment. It is a schematic diagram for demonstrating an example of the method of forming the communicating hole of the cation exchange membrane in this embodiment, and forming a sacrificial core material in the inside. It is a mimetic diagram of one embodiment of an electrolyzer concerning this embodiment.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiment, and can be implemented with various modifications within the scope of the gist. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios. Further, in this specification, the term with “abbreviation” indicates the meaning of the term excluding the “abbreviation” within the technical common sense of those skilled in the art. Shall also be included.

  FIG. 1 is a top conceptual view of the cation exchange membrane of the present embodiment, and FIG. 2 is a side sectional view of the cation exchange membrane of the same embodiment. The cation exchange membrane 1 of the present embodiment is a cation exchange membrane having a membrane body 2 containing a fluorine-containing polymer having an ion exchange group, and a flow path 3 is formed inside the membrane body 2. A cation exchange membrane in which a sacrificial core material 4 dissolved in acid or alkali is present in at least a part of the inside of the flow path 3 located at the peripheral edge of the main body 2. By using the cation exchange membrane 1 having such a structure, the electrolytic solution can be electrolyzed without leaking outside the electrolytic cell during electrolysis.

(Membrane body)
The membrane body 2 may have any function as long as it contains a fluorine-containing polymer having a function of selectively permeating cations and having an ion exchange group, and its configuration and materials are not particularly limited, and is suitably suitable. Can be selected. The fluorine-containing polymer having an ion exchange group as used herein refers to a fluorine-containing polymer having an ion exchange group or an ion exchange group precursor that can be converted into an ion exchange group by hydrolysis. For example, a polymer having a main chain of a fluorinated hydrocarbon, having a functional group that can be converted into an ion exchange group by hydrolysis or the like as a pendant side chain, and capable of being melt-processed can be used. Such a fluorine-containing polymer will be described below.

  The fluorine-containing polymer, for example, contains at least one monomer selected from the following first group and at least one monomer selected from the following second group and / or the following third group. It can be produced by polymerization. Moreover, it can also manufacture by the homopolymerization of the monomer of 1 type chosen from either the following 1st group, the following 2nd group, and the following 3rd group.

  Examples of the first group of monomers include vinyl fluoride compounds. Examples of the vinyl fluoride compound include vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, perfluoro (alkyl vinyl ether) and the like. In particular, when the cation exchange membrane according to this embodiment is used as a cation exchange membrane for alkaline electrolysis, the vinyl fluoride compound is preferably a perfluoromonomer, such as tetrafluoroethylene, hexafluoropropylene, perfluoro. A perfluoromonomer selected from the group consisting of (alkyl vinyl ether) is preferred.

Examples of the second group of monomers include vinyl compounds having a functional group that can be converted into a carboxylic acid type ion exchange group (carboxylic acid group). Examples of the vinyl compound having a functional group that can be converted into a carboxylic acid type ion exchange group include a monomer represented by CF ₂ ═CF (OCF ₂ CYF) _s —O (CZF) _t —COOR. (Here, s represents an integer of 0 to 2, t represents an integer of 1 to 12, Y and Z each independently represent F or CF ₃ , and R represents a lower alkyl group.) .

Among _{them, CF 2 = CF (OCF 2} CYF) n -O (CF 2) a compound represented by _m -COOR are preferred. Here, n represents an integer of 0 to 2, m represents an integer of 1 to 4, Y represents F or CF ₃ , and R represents CH ₃ , C ₂ H ₅ , or C ₃ H ₇ .

In particular, when the cation exchange membrane according to the present embodiment is used as a cation exchange membrane for alkaline electrolysis, it is preferable to use at least a perfluoro compound as a monomer. Since the alkyl group (R) is lost from the polymer at the time of decomposition, the alkyl group (R) may not be a perfluoroalkyl group in which all hydrogen atoms are substituted with fluorine atoms. Among these, for example, the monomers shown below are more preferable;

_{CF 2 = CFOCF 2 -CF (CF} 3) OCF 2 COOCH 3,
CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₂ COOCH ₃ ,
_{CF 2 = CF [OCF 2 -CF} (CF 3)] 2 O (CF 2) 2 COOCH 3,
CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₃ COOCH ₃ ,
CF ₂ = CFO (CF ₂ ) ₂ COOCH ₃ ,
_{CF 2 = CFO (CF 2)} 3 COOCH 3.

Examples of the third group of monomers include vinyl compounds having a functional group (sulfonic acid group) that can be converted into a sulfone ion exchange group. As the vinyl compound having a functional group (sulfonic acid group) that can be converted into a sulfone-type ion exchange group, for example, a monomer represented by CF ₂ = CFO—X—CF ₂ —SO ₂ F is preferred (here, , X represents a perfluoro group). Specific examples of these include monomers shown below;

CF ₂ = CFOCF ₂ CF ₂ SO ₂ F,
CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ SO ₂ F,
CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ CF ₂ SO ₂ F,
CF ₂ = CF (CF ₂ ) ₂ SO ₂ F,
CF ₂ = CFO [CF ₂ CF (CF ₃ ) O] ₂ CF ₂ CF ₂ SO ₂ F,
_{CF 2 = CFOCF 2 CF (CF} 2 OCF 3) OCF 2 CF 2 SO 2 F.

Among _{them, CF 2 = CFOCF 2 CF (} CF 3) OCF 2 CF 2 CF 2 SO 2 F, and _{CF 2 = CFOCF 2 CF (CF} 3) OCF 2 CF 2 SO 2 F is more preferred.
Copolymers obtained from these monomers can be produced by polymerization methods developed for homopolymerization and copolymerization of fluorinated ethylene, in particular by general polymerization methods used for tetrafluoroethylene. it can. For example, in the non-aqueous method, an inert solvent such as perfluorohydrocarbon or chlorofluorocarbon is used, and in the presence of a radical polymerization initiator such as perfluorocarbon peroxide or azo compound, the temperature is 0 to 200 ° C., the pressure is 0. The polymerization reaction can be performed under conditions of 1 to 20 MPa.

  In the above copolymerization, the type of monomer combination and the ratio thereof are not particularly limited, and are selected and determined depending on the type and amount of functional groups to be imparted to the resulting fluorine-containing polymer. For example, when a fluorine-containing polymer containing only a carboxylate ester functional group is used, at least one monomer may be selected from the first group and the second group and copolymerized. Further, when a polymer containing only a sulfonyl fluoride functional group is used, at least one monomer may be selected from the first group and third group monomers and copolymerized. Further, when the fluorine-containing polymer having a carboxylic acid ester functional group and a sulfonyl fluoride functional group is used, at least one monomer from each of the first group, second group, and third group monomers is used. It may be selected and copolymerized. In this case, the desired fluorine-containing system can also be obtained by separately polymerizing the copolymer consisting of the first group and the second group and the copolymer consisting of the first group and the third group and mixing them later. A polymer can be obtained. Further, the mixing ratio of each monomer is not particularly limited, but when increasing the amount of the functional group per unit polymer, if the ratio of the monomer selected from the second group and the third group is increased. Good.

  The total ion exchange capacity of the fluorinated copolymer is not particularly limited, but is preferably 0.5 to 2.0 mg equivalent / g, more preferably 0.6 to 1.5 mg equivalent / g. . Here, the total ion exchange capacity refers to the equivalent of exchange groups per unit weight of the dry resin, and can be measured by neutralization titration or the like.

  As shown in FIG. 2, the membrane body 2 constituting the cation exchange membrane 1 of the present embodiment is laminated on a sulfonic acid layer 5 having a sulfonic acid group as an ion exchange group, and the sulfonic acid layer 5. And a carboxylic acid layer 6 having a carboxylic acid group as an ion exchange group.

  Usually, the cation exchange membrane 1 is arranged so that the sulfonic acid layer 5 is located on the anode side of the electrolytic cell and the carboxylic acid layer 6 is located on the cathode side of the electrolytic cell. The sulfonic acid layer 5 is made of a material having low electrical resistance, and is preferably thick from the viewpoint of film strength. The carboxylic acid layer 6 preferably has a high anion exclusion property even if the film thickness is small. The term “anion-exclusion” as used herein refers to a property that tends to prevent the penetration and permeation of anions into the cation exchange membrane 1. By using the membrane body 2 having such a layer structure, the selective permeability of cations such as sodium ions can be further improved.

Examples of the polymer used for the sulfonic acid layer 5 include a fluorine-containing polymer having a sulfonic acid group among the fluorine-containing polymers described above. In particular, CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ SO ₂ F is preferable.

Examples of the polymer used for the carboxylic acid layer 6 include a fluorine-containing polymer having a carboxylic acid group among the fluorine-containing polymers described above. In particular, CF ₂ = CFOCF ₂ CF (CF ₂ ) O (CF ₂ ) ₂ COOCH ₃ is preferable.

  Although not shown, an opening connected to the flow path 3 may be formed on one surface of the cation exchange membrane 1. For example, a part of the flow path 3 disposed inside the membrane body 2 may be opened to the surface of the cation exchange membrane 1 to form an opening.

  The flow path 3 should just be formed in the peripheral part of the film | membrane main body 2 at least. And the sacrificial core material 4 mentioned later should just be arrange | positioned inside the flow path 3 formed in the peripheral part. The peripheral edge of the membrane body 2 is a region sandwiched by a gasket described later. Usually, when mounting | wearing with an electrolytic cell, the peripheral part of the film | membrane main body 2 is pressed with a gasket. As a result, the space of the flow path 3 is crushed and becomes smaller. However, since the sacrificial core material 4 is disposed inside the flow path 3, the crushed internal space of the flow path 3 becomes the sacrificial core. The material 4 can be efficiently closed. As a result, electrolyte leakage can be effectively prevented.

  Usually, the cation exchange membrane is rectangular, but in that case, the flow path arranged at the peripheral edge of the cation exchange membrane is arranged in an area of 0 to 5% of the length of one side from the end side. It is preferable. For example, the cation exchange membrane 1 has a rectangular shape, but in the longitudinal direction of the cation exchange membrane 1, the cation exchange membrane 1 is arranged in a region of 0 to 5% of the length of the long side from each short side. Is more preferable, and it is more preferable that it is disposed in a region of 2 to 5%. In the width direction, each long side is preferably arranged in a region of 0 to 5% of the length of the short side, and more preferably in a region of 2 to 5%.

  The flow path 3 may be disposed inside so as to undulate in a cross-sectional view (refer to FIG. 2 (α) side and (β) side alternately undulating shape). This is formed by plain weaving warp and weft (weft) or the like (weft is not shown in FIG. 2). Further, although not shown, the flow path 3 may be arranged in a substantially straight line in a cross-sectional view.

  The shape of the flow path 3 is preferably tubular. When the flow path 3 is tubular, it is preferable that the sacrificial core material 4 is disposed at the center of the flow path 3 in a state where the flow path 3 is viewed in cross section. Although the sacrificial core material 4 will be described later, the leakage of the electrolytic solution can be more effectively prevented by adopting such a shape and arrangement.

(Sacrificial core material)
A sacrificial core material 4 that dissolves in an acid or an alkali is present at least inside the flow channel 3 located at the peripheral edge of the membrane body 2 in the flow channel 3. Thereby, the leakage of the electrolyte solution outside the electrolytic cell during electrolysis can be prevented.

  Usually, at the time of electrolysis, the cation exchange membrane is set and used between the electrolysis cells, but at that time, the end of the cation exchange membrane is set in a state of protruding from the frame portion of the electrolysis cell (for example, (See FIG. 7). That is, in the cation exchange membrane, the end part protrudes outside the electrolysis cell, the peripheral part is pressed by the gasket, and the central part (area inside the peripheral part) partitions the space of the electrode chamber. And in contact with the electrolyte. Therefore, during the electrolysis operation, the electrolyte filled in the electrode chamber reaches the peripheral edge of the cation exchange membrane via the flow path provided in the center of the cation exchange membrane, and is provided at the peripheral edge. It may happen that the end of the cation exchange membrane is further reached through the flow path, and then leaks out of the electrolysis cell. However, since the sacrificial core material 4 exists inside the flow path 3 provided at the peripheral edge of the cation exchange membrane 1 of the present embodiment, the peripheral flow path 3 is pressed by the gasket. Thus, the space of the flow path 3 can be closed. Thereby, the flow of the electrolytic solution can be stopped at the peripheral portion of the cation exchange membrane 1, and leakage of the electrolytic solution can be prevented.

  The material of the sacrificial core material 4 may be any material that can be dissolved in acid or alkali, and preferred specific examples include polyvinyl alcohol (PVA), rayon, polyethylene terephthalate (PET), cellulose, and polyamide. . From the viewpoint of high solubility in the electrolytic solution, polyethylene terephthalate (PET) is preferable. By being a material that dissolves in an acid or an alkali, there is an advantage that a flow path can be easily formed from a sacrificial core material during production. In use, the sacrificial core material remains in the flow path at the periphery of the membrane body, while the center of the membrane body (the region inside the periphery of the membrane body) The sacrificial core material can be efficiently dissolved by the contact, and the space of the flow path can be formed. As a result, it is possible to prevent leakage of the electrolytic solution while reducing the electrolytic voltage. In addition, at the time of use, the reason why it is easy to maintain the state in which the sacrificial core material remains in the flow path at the peripheral portion of the membrane body is because the peripheral portion is pressed by a gasket or the like as described above. This is probably because the sacrificial core material does not dissolve so much that it does not come into contact with the electrolyte solution (however, the action is not limited to this).

  In the cation exchange membrane 1, the ratio of the cross-sectional area of the sacrificial core material 4 to the cross-sectional area of the flow path 3 (sacrificial core material residual ratio) is preferably 20 to 99%, and preferably 30 to 80%. Is more preferable, and it is still more preferable that it is 30 to 60%. When the sacrificial core material remaining rate is 20% or more, leakage of the electrolyte can be more effectively prevented. The case where the sacrificial core material remaining rate is 99% is a state in which the interior of the flow path 3 is almost completely filled with the sacrificial core material 4. From the viewpoint of preventing leakage of the electrolyte and the strength of the film, the sacrificial core material remaining ratio is more preferably 30% or more.

  Further, as the electrolysis progresses, the sacrificial core material 4 present in the flow path 3 gradually elutes, and impurities in the electrolytic solution increase. From the viewpoint of preventing an increase in impurities, the sacrificial core material remaining rate is more preferably 80% or less. The sacrificial core material remaining rate can be obtained by calculating the ratio of the cross-sectional area of the sacrificial core material to the cross-sectional area of the communication hole by image analysis to be described later. Note that the sacrificial core material remaining rate is calculated from the cross-sectional area of the flow path 3 and the sacrificial core material 4 to be measured as viewed in a cross section substantially perpendicular to the arrangement direction. Therefore, for example, when the remaining ratio of the sacrificial core material of the cation exchange membrane 1 in FIG. 2 is obtained, the flow path 3 and the sacrificial core material 4 are disposed along the vertical direction of the paper surface, and thus are substantially perpendicular to the paper surface. The cross-sectional areas of the flow path 3 and the sacrificial core material 4 in a cross-sectional view are respectively obtained, and the sacrificial core material remaining rate is calculated based on the cross-sectional areas. When the flow path 3 and the sacrificial core material 4 are disposed along multiple directions, first, the cross section is substantially perpendicular to the flow path 3 and the sacrificial core material 4 disposed along any one direction. The cross-sectional area at the time of viewing is calculated | required, and the cross-sectional area of the flow path 3 and the sacrificial core material 4 which were arrange | positioned along another direction is measured separately in another cross section. The details of the sacrificial core material remaining rate when the flow path 3 and the sacrificial core material 4 are arranged along multiple directions will be described later with reference to FIG.

  When the cation exchange membrane 1 is viewed from above, the ratio of the total projected area of the sacrificial core material 4 to the total projected area of the flow path 3 (sacrificial core area ratio) is 10 to 99%. Preferably, it is 20 to 80%. The area ratio of the sacrificial core material can be calculated by obtaining the projected area occupied by the sacrificial core material in the projected area of the communication hole with a microscope when the cation exchange membrane is viewed from above. Specifically, it can be measured by the method described in the examples.

  FIG. 3 is a conceptual view of a top view of another embodiment of the cation exchange membrane of the present embodiment. The cation exchange membrane 7 includes not only the flow path 3a and the sacrificial core material 4a formed at the peripheral edge of the membrane body 2, but also the flow path 3b and the sacrificial core material 4b are disposed at the center of the membrane body 2. ing. And as a core material, it has not only sacrificial core material 4a, 5b but the reinforcement core material 8 further. Here, the reinforcing core material 8 refers to a core material that does not dissolve in either acid or alkali. Since the cation exchange membrane 7 has the reinforcing core member 8 inside the membrane body 2, the mechanical strength and dimensional stability of the cation exchange membrane 7 can be further improved. Here, the dimensional stability refers to a property that can suppress the expansion and contraction of the ion exchange membrane within a desired range. The cation exchange membrane 7 excellent in dimensional stability does not expand and contract more than necessary by hydrolysis, electrolysis, etc., and can maintain excellent dimensional stability over a long period of time.

  As shown in FIG. 3, the flow path 3 is preferably formed over the entire interior of the membrane body 2. Here, being formed over the entire inside of the membrane body 2 means that the flow path 3 is formed along both the longitudinal direction and the lateral direction at least at the peripheral edge and the center of the membrane body 2. Say. In addition, the arrangement | positioning space | interval of the flow path 3 is not specifically limited, The shape and magnitude | size of a cation exchange membrane, Furthermore, the physical property desired, etc. can be adjusted suitably. Since the flow path 3 is formed over the entire interior of the membrane body 2, a cation or electrolyte flow path can be formed over the entire membrane, so that the electrolysis performance is further improved. The flow path 3 is preferably formed in a mesh shape across the width direction and the longitudinal direction of the cation exchange membrane 1 (for example, the longitudinal direction and the lateral direction in FIG. 1).

  In the cation exchange membrane 7, it is preferable that the sacrificial core materials 4a and 4b exist inside all of the flow paths 3a and 3b. That is, not only the sacrificial core material 4a is arranged inside the flow path 3a formed at the peripheral edge of the membrane body 2, but also the sacrificial core inside the flow path 3b formed at the center of the membrane body 2. It is preferable that the material 4b is arranged. Thereby, leakage of the electrolyte during electrolysis can be prevented more effectively, and the mechanical strength and dimensional stability of the cation exchange membrane 7 are further improved. In particular, damage such as bending of the cation exchange membrane 7 that can occur when the cation exchange membrane 7 is set in an electrolytic cell can be sufficiently suppressed.

(Reinforced core material)
The cation exchange membrane 7 preferably has a plurality of reinforcing core members 8. Although not shown, it is preferable that the reinforcing core member 8 is disposed inside the membrane body 2 so as to cross each other. The arrangement of the reinforcing core member 8 will be described later.

  The material and configuration of the reinforcing core member 8 are not particularly limited, and for example, a material called a reinforcing yarn may be spun. The reinforcing yarn here is a member constituting the reinforcing core material 8, which can impart desired dimensional stability and mechanical strength to the cation exchange membrane 7, and in the cation exchange membrane 7. A thread that can exist stably. By using the reinforcing core 8 obtained by spinning such reinforcing yarns, it is possible to impart more excellent dimensional stability and mechanical strength to the cation exchange membrane 7.

  The material of the reinforcing core material 8 and the reinforcing yarn used therefor is not particularly limited, but a material containing a fluorine-containing polymer is more preferable from the viewpoint of long-term heat resistance and chemical resistance. Examples of the fluorine-containing polymer include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-ethylene copolymer (ETFE), and tetrafluoroethylene-hexa. Examples thereof include a fluoropropylene copolymer, a trifluorochloroethylene-ethylene copolymer, and a vinylidene fluoride polymer (PVDF). Among these, polytetrafluoroethylene (PTFE) is preferable from the viewpoint of long-term heat resistance and chemical resistance.

  As the form of the reinforcing core member 8, a woven fabric or a knitted fabric using reinforcing yarns can be used. Among these, a woven fabric is preferable from the viewpoint of ease of production. As the weaving method of the woven fabric, plain weaving is preferable. Although the thickness of a woven fabric is not specifically limited, It is preferable that it is 30-250 micrometers, and it is more preferable that it is 30-150 micrometers.

  Further, the weaving density of the reinforcing yarn (the number of driving per unit length) is preferably 5 to 50 / inch. If it is 50 lines / inch or less, the apparent thickness of the film can be increased. If it is 5 lines / inch or more, the mechanical strength of the film can be kept high. More preferably, it is 15-30 lines / inch.

  The yarn diameter of the reinforcing yarn used for the reinforcing core material 8 is preferably 20 to 300 denier, and more preferably 50 to 250 denier. The reinforcing yarn may be a monofilament or a multifilament. These yarns, slit yarns, etc. can also be used.

  The weaving method and arrangement of the reinforcing core member 8 in the membrane body 2 are not particularly limited, and are suitably suitable in consideration of the size and shape of the cation exchange membrane 7, the physical properties desired for the cation exchange membrane 7, the usage environment, and the like. Can be arranged. For example, from the viewpoint of dimensional stability, the reinforcing core material 8 is disposed along a predetermined first direction, and another reinforcement is performed along a second direction that is substantially perpendicular to the first direction. It is preferable to arrange the core material 8. By disposing the plurality of reinforcing core members 8 so as to be substantially perpendicular to the inside of the membrane main body 2, it is possible to impart more excellent mechanical strength and dimensional stability in multiple directions. For example, it is preferable that the reinforcing core material 8 (warp yarn) arranged along the vertical direction and the reinforcing core material 8 (weft yarn) arranged along the horizontal direction) are woven on the surface of the membrane body 2. Weaving plain warps and wefts by alternately raising and lowering them and weaving them by weaving the same number of wefts into two or several warp yarns arranged by twisting two warps and twisting them. It is more preferable to use a diagonal weave from the viewpoint of dimensional stability, mechanical strength and manufacturability.

  In particular, it is preferable that the reinforcing core material 8 is disposed along both the MD direction (Machine Direction direction) and the TD direction (Transverse Direction direction) of the cation exchange membrane 7. Specifically, the reinforcing core material 8 is preferably plain woven in the MD direction and the TD direction. Here, the MD direction means that the membrane body 2 and various core materials (for example, the reinforcing core material 8, the reinforcing yarn, the sacrificial core material 4, the sacrificial yarn, etc.) are transported in the manufacturing process of the cation exchange membrane described later. The direction (flow direction) is referred to, and the TD direction refers to a direction substantially perpendicular to the MD direction. And the yarn woven along the MD direction is called MD yarn, and the yarn woven along the TD direction is called TD yarn. Usually, the cation exchange membrane 1 used for electrolysis is rectangular, and the longitudinal direction is often the MD direction and the width direction is often the TD direction. By interweaving the reinforcing core material 8 that is MD yarn and the reinforcing core material 8 that is TD yarn, it is possible to impart more excellent dimensional stability and mechanical strength in multiple directions.

  The aperture ratio of the reinforcing core 8 is not particularly limited, and is preferably 30% or more, more preferably 50 to 90%, still more preferably 60 to 90%, and still more preferably 65 to 90%. It is. When the aperture ratio of the reinforcing core 8 is 30% or more, the electrochemical properties of the cation exchange membrane 7 can be further improved. Furthermore, if the aperture ratio of the reinforcing core 8 is 50% or more, the amount of the resin used for forming the membrane body 2 can at least increase the thickness of the cation exchange membrane 7. Moreover, if the aperture ratio of the reinforced core material 8 is 90% or less, the mechanical strength of the cation exchange membrane can be further improved.

  Here, the aperture ratio is the total surface through which substances such as ions (electrolyte and cations (for example, sodium ions)) such as ions in the area (A) of any one surface of the membrane body 2 can pass. The ratio (B / A) of area (B). The total surface area (B) through which substances such as ions can pass means that in the cation exchange membrane 7, cations, electrolytes, etc. are not blocked by the reinforcing core material or reinforcing yarns contained in the cation exchange membrane 1. This is the total area of the region.

FIG. 4 is a conceptual diagram for explaining the aperture ratio of the cation exchange membrane 1 of the present embodiment. FIG. 4 is an enlarged view of a part of the cation exchange membrane 7 and shows only the arrangement of the reinforcing core member 8 in the region, and illustration of other members is omitted. Here, from the area (A) including the area of the reinforcing core member 8 in the region surrounded by the reinforcing core member 8 disposed along the vertical direction and the reinforcing core member 8 disposed along the horizontal direction. By reducing the total area (C) of the reinforcing core member 8, the total area (B) of the region through which substances such as ions in the area (A) of the region described above can pass can be obtained. That is, the aperture ratio can be obtained by the following formula (I).

Opening ratio = (B) / (A) = ((A)-(C)) / (A) (I)

  A particularly preferred form of the reinforcing core material 8 is a reinforcing core material containing PTFE from the viewpoint of chemical resistance and heat resistance, and from the viewpoint of strength, a tape yarn yarn or a highly oriented monofilament. Specifically, a tape yarn obtained by slitting a high-strength porous sheet made of PTFE into a tape shape, or a highly oriented monofilament made of PTFE of 50 to 300 denier, and a weave density of 10 to 50 / More preferably, the reinforcing core material is a plain weave that is inches, and has a thickness in the range of 50 to 100 μm. The aperture ratio of the cation exchange membrane containing such a reinforcing core is more preferably 60% or more.

  A specific method for measuring the aperture ratio will be described. A surface image of a cation exchange membrane (cation exchange membrane before coating or the like) is taken, and the above (B) is obtained from the area of the portion where the reinforcing core material does not exist. And said (A) is calculated | required from the area of the surface image of a cation exchange membrane, and said aperture ratio is calculated | required by remove | dividing said (B) by said (A).

  FIG. 5 is a partial cross-sectional view of still another embodiment of the cation exchange membrane of the present embodiment. The cation exchange membrane 9 has coating layers 10 and 11 on the surface of the membrane body 2, respectively. A coating layer 10 is provided on the surface of the sulfonic acid layer 5, and a coating layer 11 is provided on the surface of the carboxylic acid layer 6. In the sulfonic acid layer 5, the flow path 3, the sacrificial core material 4, and the reinforcing core material 8 are arranged.

(Coating layer)
By having the coating layers 10 and 11, adhesion of gas to the cathode side surface (see arrow α in FIG. 5) and the anode side surface (see arrow β in FIG. 5) can be prevented during electrolysis.

  Although it does not specifically limit as a material which comprises the coating layers 10 and 11, It is preferable that an inorganic substance is included from a viewpoint of adhesion prevention of gas. Examples of the inorganic substance include zirconium oxide and titanium oxide. The method for forming the coating layer on the film body is not particularly limited, and a known method can be used. For example, a method in which a liquid in which fine particles of inorganic oxide are dispersed in a binder polymer solution is applied by spraying or the like can be used.

  For example, there is a method (spray method) in which a liquid in which fine particles of inorganic oxide are dispersed in a binder polymer solution is applied by spraying or the like. Examples of the binder polymer include vinyl compounds having a functional group that can be converted into a sulfone-type ion exchange group. About application | coating conditions, it is not specifically limited, For example, spray can be used at 30-90 degreeC. Examples of methods other than the spray method include roll coating and the like.

  The average thickness of the coating layer is preferably 1 to 10 μm from the viewpoint of preventing gas adhesion and increasing electric resistance due to thickness.

  Regarding the arrangement of the flow path 3 and the reinforcing core material 8, the cation exchange membrane 9 is viewed in cross-section, and the flow path 3 includes the anode side (sulfonic acid layer 5 side) and the cathode side (carboxylic acid layer 6) of the reinforcing core material 8. Side) is preferably formed so as to pass alternately. By adopting such a structure, the electrolyte flowing in the internal space of the flow path 3 and the cation (for example, sodium ion) contained therein are efficiently transferred between the anode side and the cathode side of the membrane body 2. Can be made. As a result, the cation flow is not shielded, and the electrical resistance of the cation exchange membrane 9 can be further reduced.

(Convex)
Although not shown, the cation exchange membrane 9 is preferably formed with a convex portion having a height of 20 μm or more on the surface of the membrane body 2 in a cross-sectional view. In particular, since the convex portion is formed on the surface of the sulfonic acid layer 5, the electrolytic solution is sufficiently supplied to the membrane body 2 during electrolysis, and the influence of impurities can be further reduced.

  Usually, the cation exchange membrane is used in close contact with the anode for the purpose of lowering the electrolysis voltage. When the cation exchange membrane and the anode are in close contact with each other, it tends to be difficult to supply an electrolytic solution (such as salt water). Therefore, by forming a convex portion on the surface of the cation exchange membrane, adhesion between the cation exchange membrane and the anode can be suppressed, so that the electrolyte solution can be supplied smoothly. As a result, accumulation of metal ions, other impurities, and the like in the cation exchange membrane can be prevented. In addition, it is preferable that a convex part consists of resin.

The arrangement density of the convex portions is not particularly limited, but is preferably 20 to 1500 pieces / cm ² and more preferably 50 to 1200 pieces / cm ² from the viewpoint of sufficiently supplying the electrolytic solution to the membrane. .

  The shape of the convex portion is not particularly limited, but is preferably at least one selected from the group consisting of a cone, a polygonal pyramid, a truncated cone, a polygonal truncated cone, and a hemisphere. The hemispherical shape here also includes a shape called a dome shape or the like.

  The height, shape, and arrangement density of the protrusions described above can be measured and confirmed by the following methods. First, on the membrane surface in the 1000 μm square range of the cation exchange membrane, the lowest point is used as a reference. And the part from which the height from the reference point is 20 micrometers or more is made into a convex part.

  The height is measured using “Color 3D Laser Microscope (VK-9710)” manufactured by KEYENCE Corporation. Specifically, a 10 cm × 10 cm portion is arbitrarily cut out from the dried cation exchange membrane, the smooth plate and the anode side of the cation exchange membrane are fixed with a double-sided tape, and the cathode side of the cation exchange membrane is fixed. Set on the measurement stage to face the measurement lens. In each 10 cm × 10 cm membrane, in the 1000 μm square measurement range, observe the shape on the surface of the cation exchange membrane, and measure the height from the point with the lowest height as a reference. It can be observed.

  As for the arrangement density of the convex portions, three arbitrary 10 cm × 10 cm portions of the cation exchange membrane were cut out to make a sample, and in the sample, the measurement range of 1000 μm square was measured at nine locations with the above laser microscope, and the respective measurement locations were measured. It is the value which calculated | required the arrangement density of a convex part and took the arithmetic mean.

Regarding the sacrificial core material area ratio of the cation exchange membrane 9, the sacrificial core material area ratio of the flow path 3 and the sacrificial core material 4 arranged in any one direction (for example, any one of the longitudinal direction and the width direction). Is preferably 10 to 99%, more preferably 20 to 80%.
In addition, the sacrificial core material remaining rate of the flow path 3 and the sacrificial core material 4 is more preferably 10 to 99% in both directions of the cation exchange membrane 9 (for example, both in the longitudinal direction and the width direction). More preferably, it is 20 to 80%.

Here, the case where the sacrificial core material residual rate in multiple directions (for example, the longitudinal direction and the width direction) is measured will be described. First, in the cation exchange membrane 9, only the cross-sectional areas of the flow path 3 and the sacrificial core material 4 arranged along any one direction (for example, any one of the longitudinal direction and the width direction) are measured. And the cross-sectional area of the flow path 3 and the sacrificial core material 4 which were arrange | positioned along another direction is separately measured in another cross section (cross section of the state seen in a cross section substantially perpendicular | vertical with respect to these).
For example, when the cross section is viewed as shown in FIG. 5, first, the flow path 3 and the sacrificial core material 4 (the flow path 3 in which the three flow paths 3 are connected in FIG. 5) viewed in cross section toward the paper surface. The cross-sectional area is measured, and the ratio of the cross-sectional area of the sacrificial core material 4 to the cross-sectional area of the flow path 3 (remaining sacrificial core material remaining ratio in the direction) is obtained.
Then, the cross-sectional areas of the flow path 3 and the sacrificial core material 4 arranged along the vertical direction of the paper surface are separately measured in a state viewed substantially perpendicularly to the paper surface, and the sacrificial core with respect to the cross-sectional area of the flow path 3 is measured. The ratio of the cross-sectional area of the material 4 (remaining sacrificial core material ratio in the direction) is obtained.
The sacrificial core material remaining rate in multiple directions of the cation exchange membrane 9 is determined by calculating the arithmetic average of the sacrificial core material remaining rates thus determined.

[Method for producing cation exchange membrane]
As a suitable manufacturing method of the cation exchange membrane which concerns on this embodiment, the method which has the process of the following (1)-(5) is mentioned.
(1) a step of producing a fluorine-containing polymer having an ion exchange group (carboxylic acid group and / or sulfonic acid group) or an ion exchange group precursor capable of becoming an ion exchange group by hydrolysis;
(2) A step of obtaining a reinforcing material in which the sacrificial core material is disposed by weaving at least a sacrificial core material having a property of dissolving in an acid or an alkali and, if necessary, a plurality of reinforcing core materials;
(3) A step of producing a film by forming a film of a fluoropolymer having an ion exchange group or an ion exchange group precursor that can be converted into an ion exchange group by hydrolysis,
(4) A step of embedding a reinforcing material in the film and obtaining a membrane body in which the reinforcing material is disposed;
(5) By dissolving a part of the sacrificial core material with acid or alkali, a flow path is formed inside the film body, and at least a part of the flow path located at the peripheral edge of the film body is sacrificed. A step of obtaining a cation exchange membrane in which a core material is present (hydrolysis step).

  According to the method described above, the reinforcing material including the sacrificial core material (sacrificial yarn) is woven in the step (2), and the hydrolysis condition performed in the step (5) is controlled, whereby the opening portion and the communication hole are formed in the membrane body. A part of the sacrificial core material can be left in the communication hole.

Hereinafter, each process will be described in more detail.
(1) Process: The process which manufactures a fluorine-containing polymer A fluorine-containing polymer is manufactured using the monomer of the raw material described in the said 1st group-3rd group. In order to control the ion exchange capacity of the fluorine-containing polymer, the mixing ratio of raw material monomers may be adjusted in the production of the fluorine-containing polymer forming each layer.

(2) Step: Step of obtaining a reinforcing material The reinforcing material is a woven sacrificial core material, such as the woven fabric described above. In step (3), a reinforcing material is embedded in the membrane body, and in step (5), a part of the sacrificial core material is dissolved to form an opening and a communication hole in the membrane body, and the inside of the communication hole. A part of the sacrificial core material can remain. When the reinforcing material including the reinforcing core material is used, the amount of the sacrificial core material is preferably 10 to 80% by mass, more preferably 30 to 70% by mass, based on the entire reinforcing material. About the thickness etc. of a sacrificial core material, it is the thickness of 20-50 denier, Polyvinyl alcohol etc. which consist of a monofilament or a multifilament are preferable. Here, when the thickness of the sacrificial core material is increased, the rate of dissolution of the sacrificial core material yarn with respect to acid or alkali is decreased, and the sacrificial core material tends to remain in the communication hole. Therefore, when the thickness of the sacrificial core material is increased, the ratio of the cross-sectional area of the sacrificial core material to the cross-sectional area of the communication hole (sacrificial core material area ratio) can be increased.
Conversely, when the thickness of the sacrificial core material is reduced, the dissolution rate of the sacrificial core material with respect to acid and alkali increases. Therefore, if the thickness of the sacrificial core material is reduced, the sacrificial core material is less likely to remain inside the communication hole, and the area ratio of the sacrificial core material can be reduced.

  In the step (2), the arrangement of the flow path and the sacrificial core material existing therein can be controlled by adjusting the number of reinforcing core materials and the arrangement interval.

(3) Process: Process for producing a film (filming process)
In step (3), the fluoropolymer obtained in step (1) is formed into a film using an extruder. This film becomes the membrane body of the cation exchange membrane. Therefore, in the case of a single layer film, it becomes a single layer film body, and in the case of a multilayer film of two or more layers, it becomes a multilayer film body corresponding thereto. For example, when a two-layer structure of a sulfonic acid layer and a carboxylic acid layer as illustrated in FIG. 2 is used, a film having a two-layer structure including a sulfonic acid layer and a carboxylic acid layer may be prepared in the step (3). .

Examples of the method for forming a film include the following.
A method in which a fluorine-containing polymer having a carboxylic acid group forming the first layer and a fluorine-containing polymer having a sulfonic acid group forming the second layer are separately formed into films.
A method of forming a composite film by co-extrusion of a fluoropolymer having a carboxylic acid group forming a first layer and a fluoropolymer having a sulfonic acid group forming a second layer.
A fluorine-containing polymer having a carboxylic acid group forming the first layer, a fluorine-containing polymer having a sulfonic acid group forming the second layer A, and a fluorine-containing polymer having a sulfonic acid group forming the second layer B layer. A method in which a fluoropolymer is formed into a film separately.
The fluorine-containing polymer having a carboxylic acid group forming the first layer and the fluorine-containing polymer having a sulfonic acid group forming the second layer A are coextruded to form a composite film, and the second layer B A method of forming a film of a fluoropolymer having a sulfonic acid group forming a layer.
Moreover, co-extrusion of the two layers to form a composite film contributes to increasing the adhesive strength at the interface.
The thickness of each film can be controlled by appropriately adjusting the heating temperature, heating time, pressure, and the like when forming the film.

(4) Step: Step of obtaining a membrane main body In (4) Step, the reinforcing material obtained in Step (2) and the film obtained in Step (3) are laminated, and the membrane main body in which the reinforcing material is present, That is, a composite membrane is obtained. Specifically, the following methods are mentioned.
(I) A reinforcing material, a second layer film, and a first layer through a heat-resistant release paper having a heat source and a vacuum source and having air permeability on a flat plate or drum having a large number of pores on the surface thereof A method of laminating in the order of films and integrating them while removing air between layers under reduced pressure at a temperature at which each resin melts.
(Ii) a reinforcing material, a second layer / first layer composite, through a heat-resistant release paper having air permeability on a flat plate or drum having a heating source and a vacuum source and having a large number of pores on the surface thereof A method of laminating in the order of films and integrating them while removing air between layers under reduced pressure at a temperature at which each resin melts.
(Iii) a heat-resistant release paper having a heat source and a vacuum source and having air permeability on a flat plate or drum having a large number of pores on the surface thereof, a B-layer film of the second layer, a reinforcing material, A method in which the A layer film of the second layer and the first layer film are laminated in this order and integrated while removing air between the layers by reducing the pressure at a temperature at which each resin melts.
(Iv) having a heating source and a vacuum source through a heat-resistant release paper having air permeability on a flat plate or drum having a large number of pores on its surface, a B layer film of the second layer, a reinforcing material, A method of laminating in the order of the second layer A layer / first layer composite film and integrating them while removing air between the layers by reducing the pressure at a temperature at which each resin melts.
Co-extrusion of a plurality of layers has the effect of increasing the adhesive strength at the interface.
The method of integrating under reduced pressure has a feature that the thickness of the B layer of the second layer on the reinforcing material is larger than that of the pressure press method. Furthermore, since the reinforcing material is fixed to the inner surface of the membrane, the mechanical strength of the membrane can be sufficiently maintained.

In addition, the variation of the lamination | stacking demonstrated here is an example, it considers the layer structure of a desired film | membrane main body, a physical property, etc., and after selecting a suitable lamination pattern (for example, combination of each layer etc.), it is a coextrusion. can do. For example, in order to further enhance the electrochemical performance of the cation exchange membrane, a third layer containing both carboxylate functional groups and sulfonyl fluoride functional groups is further provided between the first layer and the second layer. It is also possible to intervene or use a layer containing both carboxylic acid ester functional groups and sulfonyl fluoride functional groups instead of the second layer. In this case, as a method of forming a layer containing both a carboxylic acid ester functional group and a sulfonyl fluoride functional group, a polymer containing a carboxylic acid ester functional group, a polymer containing a sulfonyl fluoride functional group, , May be mixed separately after production, or may be a method using a copolymer of both a monomer containing a carboxylate ester functional group and a monomer containing a sulfonyl fluoride functional group .
When the third layer is configured as an ion exchange membrane, a co-extruded composite film of the first layer and the third layer is formed, and the second layer is formed into a film separately and laminated by the above-described method. Alternatively, three layers of the first layer / third layer / second layer may be coextruded at a time to form a composite film.

  Moreover, in the cation exchange membrane which concerns on this embodiment, it does not specifically limit as a method of forming a convex part on the surface of a membrane main body, The well-known method of forming a convex part on the resin surface is employable. In the present embodiment, as a method for forming a convex portion on the surface of the film main body, specifically, a method of embossing the surface of the film main body can be mentioned. For example, when the above-described various composite films and the reinforcing material or the like are integrated, the above-described convex portions can be formed by using a release paper embossed in advance.

  By adjusting the positional relationship between the film and the reinforcing material, such as where the reinforcing material is embedded in the film, the flow path of the membrane main body note and the arrangement of the sacrificial core material can be controlled. For example, when the flow path is formed in the peripheral portion of the membrane body, the reinforcing material is preferably embedded in the film so that the sacrificial core material of the reinforcing material is located in the peripheral portion of the film forming the membrane body. When the flow path and / or the sacrificial core material is formed inside the membrane main body, the sacrificial core material of the reinforcing material is located at the center of the film forming the membrane main body (the inner region of the peripheral edge of the film). A reinforcing material is preferably embedded in the film.

(5) Step: Hydrolysis step (5) In step (5), the composite membrane obtained in step (4) described above is hydrolyzed, and part of the sacrificial core material (sacrificial yarn) is dissolved with acid or alkali. Thereby, a flow path is formed inside the membrane body. At this time, an ion exchange group may be introduced into the ion exchange group precursor.
The amount of the remaining sacrificial core material can be controlled by adjusting the hydrolysis conditions. As a result, the ratio of the cross-sectional area of the sacrificial core material to the cross-sectional area of the flow path (sacrificial core material remaining rate) and the ratio of the total projected area of the sacrificial core material to the total projected area of the flow path (sacrificial core material area ratio) Can be controlled. For example, when the hydrolysis temperature is increased, the rate of dissolution of the sacrificial core material (sacrificial yarn) is increased, and the sacrificial core material is less likely to remain in the flow path, so the ratio of the cross-sectional area of the sacrificial core material to the cross-sectional area of the flow path Can be reduced. Conversely, when the hydrolysis temperature is lowered, the rate of dissolution of the sacrificial core material (sacrificial yarn) is slowed, and the sacrificial core material tends to remain in the flow path. Can be bigger.
Further, when the hydrolysis time is lengthened, the dissolution rate of the sacrificial core material (sacrificial yarn) is increased, and the sacrificial core material is less likely to remain in the flow path. Therefore, the sacrificial core material remaining rate and the sacrificial core material area ratio are reduced. can do. Conversely, when the hydrolysis time is shortened, the dissolution rate of the sacrificial yarn decreases and the sacrificial core material tends to remain in the flow path, so that the sacrificial core material remaining rate and the sacrificial core material area ratio can be increased. .

  Specifically, as a hydrolysis temperature, the range of 40-100 degreeC is preferable, and the range of 70-80 degreeC is more preferable. The hydrolysis time is preferably 5 to 60 minutes, and more preferably 5 to 40 minutes.

  As a specific hydrolysis method, hydrolysis is performed with an aqueous solution containing dimethyl sulfoxide (DMSO) or potassium hydroxide (KOH), followed by treatment with an aqueous sodium hydroxide (NaOH) solution, and the counter ion is Na ion. The method of obtaining a cation exchange membrane is mentioned.

  The acid or alkali used in the step (5) is not particularly limited as long as it can dissolve the sacrificial core material. Examples of the acid include hydrochloric acid, nitric acid, and sulfuric acid. Examples of the alkali include potassium hydroxide and sodium hydroxide.

  In step (5), the composite membrane obtained in step (4) described above can be hydrolyzed to introduce ion exchange groups into the ion exchange group precursor.

  Here, by eluting a part of the sacrificial core material (sacrificial yarn), the process of forming the flow path and leaving the undissolved sacrificial core material in the interior is described in more detail with reference to the drawings. Explained. FIG. 6 is a schematic diagram for explaining an example of a method for forming a flow path of a cation exchange membrane in this embodiment and forming a sacrificial core material therein.

  In FIG. 6, only the reinforcing core material 8 and the sacrificial core material 4c (the flow path 3d formed thereby and the remaining sacrificial core material 4d) are illustrated, and other members such as the membrane main body are not illustrated. doing. First, the reinforcing core material 8 and the sacrificial core material 4c are knitted and used as a reinforcing material. Then, in the step (5), part of the sacrificial core material 4c is eluted to form the flow path 3d and the sacrificial core material 4d remaining inside the flow path 3d (see (ii) in FIG. 6).

  According to the above-described method, the manner in which the reinforcing core material 8 and the sacrificial core material 4c are knitted may be adjusted in accordance with the arrangement of the reinforcing core material 8 and the flow path 3 inside the membrane body of the cation exchange membrane. Therefore, it is simple.

  6A illustrates a plain weave reinforcing material in which the reinforcing core material 8 and the sacrificial core material 4c are woven along both the vertical direction and the horizontal direction on the paper surface. However, if necessary, the reinforcing material may be used. The arrangement of the reinforcing core member 8 and the sacrificial core member 4d can be changed.

  After the steps (1) to (5) described above, a coating layer may be formed on the surface of the obtained cation exchange membrane. The coating layer is not particularly limited and can be formed by a known method. For example, there is a method (spray method) in which a liquid in which fine particles of inorganic oxide are dispersed in a binder resin solution is applied by spraying or the like. Examples of the inorganic oxide include zirconium oxide, and examples of the binder resin include a vinyl compound having a functional group that can be converted into a sulfone-type ion exchange group. About application | coating conditions, it is not specifically limited, For example, spray can be used at 60 degreeC. Examples of methods other than the spray method include roll coating and the like.

  Moreover, you may perform the process which further melt | dissolves a part of sacrificial core material by performing electrolysis after coating. The membrane obtained using the electrolytic cell is subjected to electrolytic treatment to elute the sacrificial core material inside the channel disposed at the center of the membrane body, and the inside of the channel disposed at the periphery of the membrane body The sacrificial core material can be left undissolved.

  The cation exchange membrane before the electrolytic treatment (before use) is a cation exchange membrane having a sacrificial core inside the flow path formed over the entire membrane body, and the cation exchange membrane after the electrolytic treatment has a peripheral portion. This is a film in which the sacrificial core material remains inside the flow channel located at the position. The cation exchange membrane before electrolytic treatment has a high mechanical strength because the entire membrane has a sacrificial core material, and has a high strength against bending when the cation exchange membrane is installed in an electrolytic cell. On the other hand, the cation exchange membrane after electrolytic treatment (after use) has no sacrificial core material at the center of the membrane in contact with the electrolytic solution during electrolysis, so that the sacrificial core material does not elute into the electrolytic solution, This has the advantage that the voltage is more stable from the beginning of electrolysis.

[Electrolysis tank]
The cation exchange membrane of this embodiment can be used as an electrolytic cell using this. For example, it can be used as an electrolytic cell comprising an anode, a cathode, and the cation exchange membrane of the present embodiment disposed between the anode and the cathode. The electrolytic cell can further include a gasket in contact with either surface of the cation exchange.

  FIG. 7 is a schematic view of one embodiment of the electrolytic cell according to the present embodiment. The electrolytic cell 12 includes an anode side frame 13 constituting an anode chamber, a cathode side frame 14 constituting a cathode chamber, an anode side gasket 15 having a first opening disposed on the anode side, a cathode And a cathode side gasket 16 having a second opening disposed on the side. And in the membrane body of the cation exchange membrane 1, the cation exchange membrane 1 and the anode side so that at least a part of the portion where the sacrificial core material exists inside the flow path is pressed by the anode side gasket. A gasket 15 is arranged. The cation exchange membrane 1 disposed between the two and the electrolytic cell 12 provided with the cation exchange membrane 1 will be described as an example. However, the electrolytic cell of the present embodiment is not limited to this, Various configurations can be modified and implemented within the scope of the effect of the embodiment.

  In the cation exchange membrane 1, a sacrificial core material 4 is disposed in at least a part of the inside of the flow path 3 located at the peripheral edge of the membrane body 2 (see FIG. 1). In the electrolytic cell 12, this peripheral portion is disposed so as to be pressed by the anode side gasket 15. The internal space of the flow path 3 is crushed and reduced by being pressed by the anode gasket 15, but the sacrificial core material 4 is disposed inside the flow path 3, so that the crushed flow The internal space of the path 3 can be efficiently blocked by the sacrificial core material 4. As a result, electrolyte leakage can be effectively prevented.

  Although this electrolytic cell 12 can be used for various electrolysis, the case where it is used for electrolysis of alkali chloride aqueous solution is demonstrated as a typical example below.

Electrolysis conditions are not particularly limited, and can be performed under known conditions. For example, 2.5 to 5.5 normal (N) alkali chloride aqueous solution is supplied to the anode chamber, water or diluted alkali hydroxide aqueous solution is supplied to the cathode chamber, the electrolysis temperature is 50 to 120 ° C., and the current density is it is possible to electrolysis under the conditions of 5~100A / dm ^2.

  The configuration of the electrolytic cell 12 is not particularly limited, and may be, for example, a monopolar type or a bipolar type. It does not specifically limit as a material which comprises the electrolytic cell 12. As a material of the anode side frame 13, a material resistant to alkali chloride and chlorine is preferable, and specifically titanium or the like can be given. The material of the cathode side frame 14 is preferably a material resistant to alkali hydroxide and hydrogen, and specific examples thereof include nickel.

The anode may be arranged at an appropriate interval between the cation exchange membrane 1 and the anode, but even if the anode and the cation exchange membrane 1 are arranged in contact with each other, they can be used without any problem. it can.
In addition, the cathode is generally arranged at an appropriate interval from the cation exchange membrane 1, but there is no problem even if it is a contact type electrolytic cell (zero gap type electrolytic cell) without this interval. Can be used.

  Hereinafter, the present invention will be described in detail by way of examples. In addition, this invention is not limited to a following example. In the following units, unless otherwise specified, the unit is based on mass.

[Confirmation of cation exchange membrane structure]
In the cation exchange membrane, the presence / absence of an opening in the surface of the membrane main body, the presence / absence of a flow channel in the membrane main body, the presence / absence of a sacrificial core material in the flow channel, and the like were confirmed by a microscope. Specifically, when the sacrificial core material is present inside the flow path of the cation exchange membrane, the cross section of the sacrificial core material can be confirmed in the cross section of the flow path by observing the cross section with a microscope. The boundary of the core material can also be confirmed. The method for observing the cross section will be described later.

[Measurement method of sacrificial core material remaining rate]
The ratio of the cross-sectional area of the sacrificial core material to the cross-sectional area of the flow path of the cation-exchange membrane (sacrificial core material residual ratio) was measured by image analysis of the cross-section of the cation exchange membrane with a microscopic image.
As measurement points, there are four central portions (two points along the longitudinal direction of the cation exchange membrane and two points along the width direction) and four peripheral portions (long along the longitudinal direction of the cation exchange membrane). 2 points and 2 points along the width direction), and the cross-sectional area of each measurement location was measured.
First, in order to observe the cross section of the cation exchange membrane, each measurement location of the cation exchange membrane is cut perpendicularly to the flow path and the sacrificial core material, which are measurement locations, and samples of 1000 mm × 0.05 mm are respectively obtained. Got ready. And the cross-sectional state of each sample was observed with the magnification of 20 times using the microscope (the product made from OLYMPUS, "BH-2").
The sacrificial core material remaining rate of the cation exchange membrane is determined by first measuring the cross-sectional area of the flow channel perpendicular to the cut surface and the cross-sectional area of the remaining sacrificial core material, and the sacrificial core material relative to the cross-sectional area of the flow channel. The ratio of the cross-sectional area (sacrificial core material remaining ratio) was calculated. In addition, although the measurement location is a total of 8 locations of 4 central portions and 4 peripheral portions, the ratio of the cross-sectional area of the sacrificial core material to the cross-sectional area of the flow path is measured for each of these 8 locations, The arithmetic average was taken as the sacrificial core remaining rate of the cation exchange membrane.
Specifically, it was calculated by the following method. An image observed at a magnification of 20 times with “3CCD DIGITAL CAMERA” (OLYMPUS, “F380”) was taken into a personal computer. Then, using the image analysis software “USB SHOT” (manufactured by SCARA), the cross-sectional area of the flow path and the cross-sectional area of the sacrificial core material remaining in the flow path are measured, and the remaining relative to the cross-sectional area of the sacrificial core material The ratio of the cross-sectional area of the sacrificial core material (sacrificial core material remaining ratio) was calculated.

Electrolyte leak test
The cation exchange membranes produced in the examples and comparative examples were mounted in an electrolytic cell, and 3.5N saline solution was supplied to the anode chamber and 32% caustic soda was supplied to the cathode chamber, followed by electrolysis at 4 kA / m ² for 7 days. The presence or absence of leakage of the electrolyte solution outside the tank was confirmed visually. As the electrolytic cell, an electrolytic cell having an anode and a cathode and having a gasket in the anode cell and the cathode cell was used. As the anode, so-called DSA in which ruthenium oxide, iridium oxide and titanium oxide were formed on a titanium base material was used. As the cathode, an electrode obtained by applying nickel oxide as a catalyst to expanded metal of nickel was used. Electrolysis was performed in a state where the anode cell and the cathode cell were separated with a cation exchange membrane sandwiched between rubber gaskets made of EPDM (ethylene propylene diene).

[Example 1]
As the reinforcing core material, a 90 denier monofilament made of polytetrafluoroethylene (PTFE) was used (hereinafter referred to as PTFE yarn). As the sacrificial yarn, a yarn in which a twist of 35 deniers and 6 filaments of polyethylene terephthalate (PET) was applied 200 times / m was used (hereinafter referred to as PET yarn). First, in each of the TD and MD directions, a plain woven fabric was obtained by plain weaving so that 24 PTFE yarns / inch and two sacrificial yarns were arranged between adjacent PTFE yarns. The obtained woven fabric was pressure-bonded with a roll to obtain a woven fabric having a thickness of 70 μm.

Next, resins A and CF of a dry resin having a ion exchange capacity of 0.87 mg equivalent / g, which is a copolymer of CF ₂ = CF ₂ and CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ COOCH ₃ A resin B of a dry resin having an ion exchange capacity of 1.01 mg equivalent / g, which is a copolymer of ₂ = CF ₂ and CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ SO ₂ F, was prepared.

  Using these resins A and B, a two-layer film X having a resin A layer thickness of 18 μm and a resin B layer thickness of 102 μm was obtained by co-extrusion T-die method.

  Subsequently, on the drum having a heating source and a vacuum source inside, and having fine holes on the surface, release paper (conical embossing with a height of 50 μm), reinforcing material and film X are laminated in this order, and the drum After heating and depressurizing for 2 minutes under conditions of a temperature of 223 ° C. and a degree of vacuum of 0.067 MPa, the release paper was removed to obtain a composite film.

  The obtained composite membrane was saponified by immersing it in an 80 ° C. aqueous solution containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 20 minutes. Then, it was immersed in an aqueous solution containing sodium hydroxide (NaOH) 0.5N at 50 ° C. for 1 hour to replace the counter ion of the ion exchange group with Na, followed by washing with water. Furthermore, it dried at 60 degreeC.

Furthermore, 20% by mass of zirconium oxide having a primary particle diameter of 1 μm was added to a 5% by mass ethanol solution of an acid type resin of resin B, and a dispersed suspension was prepared. Spraying was performed on both sides of the membrane to form a 0.5 mg / cm ² zirconium oxide coating on the surface of the composite membrane to obtain a cation exchange membrane.

About the cation exchange membrane obtained as mentioned above, it confirmed with the microscope that the sacrificial core material existed in the inside of the flow path in the peripheral part and center part of a film | membrane. It was also confirmed that the flow channel had a tubular shape, and a sacrificial core material was present near the center of the tubular flow channel. The ratio of the cross-sectional area of the sacrificial core material to the cross-sectional area of the flow path (sacrificial core material remaining ratio) was 40%. When electrolysis was performed using this cation exchange membrane, leakage of the electrolyte solution outside the electrolytic cell did not occur.
When the cross section of the membrane was confirmed at the peripheral edge of the cation exchange membrane after electrolysis, it was confirmed that a sacrificial core material was provided inside the flow path. In the center of the membrane, it was also confirmed that the sacrificial core material that was inside the flow channel was eluted by the electrolytic solution.
In Example 1, when comparing the cation exchange membrane before electrolysis with the cation exchange membrane after electrolysis, the cation exchange membrane before electrolysis having a sacrificial core material in the flow path formed in the entire membrane. However, the flow path located in the peripheral portion has a sacrificial core material, and the center portion has better handling than the electrolyzed cation exchange membrane that does not have the sacrificial core material and is easy to handle. This is presumably because the cation exchange membrane before electrolysis has higher mechanical strength due to the sacrificial core material remaining in the flow path throughout the membrane.

[Example 2]
A cation exchange membrane was prepared in the same manner as in Example 1 except that the saponification temperature was 90 ° C. and the saponification time was 5 minutes. About the obtained cation exchange membrane, it confirmed with the microscope that it had a sacrificial core material inside the flow path. The ratio of the cross-sectional area of the sacrificial core material to the cross-sectional area of the flow path was 85%. When electrolysis was performed using this cation exchange membrane, leakage of the electrolyte solution outside the electrolytic cell did not occur.
Moreover, when the cross section of the membrane was confirmed at the peripheral edge of the cation exchange membrane after electrolysis, it was confirmed that a sacrificial core material was provided inside the flow path. In addition, in the center part of the film | membrane, it confirmed that there was no sacrificial core material in the inside of a flow path by electrolysis.

[Example 3]
A cation exchange membrane was produced in the same manner as in Example 1 except that the saponification temperature was 60 ° C. and the saponification time was 60 minutes. It was confirmed with a microscope that the obtained cation exchange membrane had a sacrificial core material inside the channel. Moreover, the cross-sectional area of the sacrificial core material with respect to the cross-sectional area of the flow path was 85%. When electrolysis was performed using this cation exchange membrane, leakage of the electrolyte solution outside the electrolytic cell did not occur.
Moreover, when the cross section of the membrane was confirmed at the peripheral edge of the cation exchange membrane after electrolysis, it was confirmed that a sacrificial core material was provided inside the flow path. In addition, in the center part of the film | membrane, it confirmed that there was no sacrificial core material in the inside of a flow path by electrolysis.

[Comparative Example 1]
A cation exchange membrane was produced in the same manner as in Example 1 except that the saponification temperature was 90 ° C. and the saponification time was 20 minutes. It was confirmed with a microscope that the obtained cation exchange membrane did not have a sacrificial core material inside the flow channel at the central portion or the peripheral portion of the membrane. Moreover, the cross-sectional area of the sacrificial core material with respect to the cross-sectional area of the flow path was 0%. When electrolysis was performed using this cation exchange membrane, leakage of the electrolyte solution outside the electrolytic cell was confirmed.

  From the above, it was confirmed that leakage (leakage) of the electrolyte solution outside the electrolytic cell can be suppressed by using the cation exchange membranes of Examples 1 to 3.

  The cation exchange membrane of the present invention can be suitably used as a cation exchange membrane for alkali chloride electrolysis or the like.

DESCRIPTION OF SYMBOLS 1, 7, 9 ... Cation exchange membrane, 2 ... Membrane body, 3, 3a, 3b ... Flow path, 4, 4a, 4b ... Sacrificial core material, 5 ... Sulphonic acid layer, 6 ... Carboxylic acid layer, 8 ... Strengthening Core material 10, 11 ... coating layer, 12 ... electrolytic cell, 13 ... anode side frame, 14 ... cathode side frame, 15 ... anode side gasket, 16 ... cathode side gasket

Claims (9)

A rectangular cation exchange membrane having a membrane body containing a fluorine-containing polymer having an ion exchange group,
A flow path is formed inside the membrane body,
Perimeter that is a region of 0 to 5% of the length from the short side to the long side in the longitudinal direction of the film body and a region of 0 to 5% of the length from the long side to the short side in the width direction of the film body In at least a part of the inside of the flow channel located in the portion, there is a sacrificial core material that dissolves in acid or alkali ,
To the cross-sectional area of the flow path, the ratio of the cross-sectional area of the sacrificial core (sacrifice core residual rate), Ru 20-99% der cation exchange membrane. Said flow path, said at the periphery and the central portion of the film body, are formed along both the longitudinal direction and the width direction, the cation exchange membrane according to claim 1. The cation exchange membrane according to claim 1 or 2 , wherein the sacrificial core material is present in all of the flow paths. The ratio (sacrificial core material area ratio) of the total projected area of the sacrificial core material to the total projected area of the flow path when the cation exchange membrane is viewed from above is 10 to 99%. Item 4. The cation exchange membrane according to Item 3 . The cation exchange membrane according to any one of claims 1 to 4 , wherein the channel is tubular. The said sacrificial core material includes any one selected from the group consisting of polyvinyl alcohol (PVA), rayon, polyethylene terephthalate (PET), cellulose, and polyamide, according to any one of claims 1 to 5 . Cation exchange membrane. The anode,
A cathode,
The cation exchange membrane according to any one of claims 1 to 6 , which is disposed between the anode and the cathode,
An electrolytic cell comprising: Furthermore, the electrolytic cell of Claim 7 provided with the gasket contact | abutted with any one surface of the said cation exchange membrane. The anode,
A cathode,
An anode side gasket having a first opening disposed on the anode side;
A cathode-side gasket having a second opening disposed on the cathode side;
The cation exchange membrane according to any one of claims 1 to 6 , sandwiched between the anode side gasket and the cathode side gasket,
And at least a part of the portion of the cation exchange membrane where the sacrificial core material is present inside the flow path is pressed by the anode side gasket. An electrolytic cell in which an ion exchange membrane and the anode side gasket are disposed.