JP2001160410A - Manufacturing method of diaphragm for redox flow battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diaphragm for redox flow battery which contains a strong oxidizer such as pentavalent vanadium, that has a small amount of metallic ion permeation and a high charging/discharging efficiency, and is excellent especially in durability and is inexpensive. SOLUTION: A mixture composed of a monomer which contains a functional group capable of introducing an ion exchange group or an ion exchange group, a crosslinking agent, a polymerization initiator and a copolymer made of a monomer unit derived from an aliphatic hydrocarbon monomer having essentially no unsaturated bond and a monomer unit based on acrylonitrile, such as, a copolymer of acrylonitrile butadiene added with hydrogen, is mold-polymerized attached to base material. And after that process, ion exchange group is introduced as necessary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a membrane for a redox flow battery having excellent durability, and more particularly to a method for manufacturing a membrane for a vanadium-based redox flow battery.

[0002]

2. Description of the Related Art A redox flow battery uses a redox reaction in which a battery active material of a positive electrode and a negative electrode is passed through a liquid permeable electrolytic cell having a positive electrode chamber and a negative electrode chamber in which a positive electrode and a negative electrode are separated by a diaphragm. To perform charging and discharging. In general, a membrane having an ion function, for example, an ion exchange membrane is used as a diaphragm for the purpose of preventing permeation of metal ions. Various kinds of metals are considered to be used as the battery active material, but recently, a vanadium-based redox flow battery using vanadium as the battery active material (Japanese Patent Application Laid-Open No. Sho 62-62).
186473) has been proposed.

[0003] This battery is excellent in electromotive force, battery capacity, and the like as compared with the iron / chromium-based redox flow battery that has been conventionally studied. Even if the positive and negative electrode solutions are mixed with each other, they have the advantage that they can be easily regenerated by charging.

[0004]

Generally, as an ion exchange membrane, a resin that functions as a matrix without introducing an ion exchange group (hereinafter simply referred to as a matrix resin)
It is widely known that a resin composition of a resin and an ion exchange resin is adhered to a substrate. Here, as the matrix resin, for example, a styrene-butadiene copolymer, an acrylonitrile-butadiene copolymer, or the like is used.

When an ion exchange membrane containing such a matrix resin is used as a membrane for a redox flow battery, the redox flow battery uses an oxidizing substance such as pentavalent vanadium ion or 3 Valent iron ions and the like act on the matrix resin in the ion-exchange membrane to cause a change in the ion-exchange resin portion, causing problems such as partial separation of the ion-exchange resin portion from the substrate. In particular, pentavalent vanadium ions have a strong oxidizing power and have caused a serious problem in durability when a general ion exchange membrane is used for a diaphragm.

Therefore, as a membrane having oxidation resistance, a perfluoro-based membrane or a polysulfone-based membrane (Japanese Patent Laid-Open No.
No. 88005).

However, the membrane proposed above does not satisfy all the required functions, and when used as an industrial membrane for a redox flow battery, the amount of permeation of metal ions is small and the charge / discharge efficiency is low. In particular, there has been a demand for an inexpensive diaphragm having high durability and excellent durability.

[0008]

DISCLOSURE OF THE INVENTION The present inventors have conducted intensive studies in view of the above-mentioned problems, and as a result, as a matrix resin, have substantially no unsaturated bonds derived from aliphatic hydrocarbon monomers. The present inventors have found that the above-mentioned problems can be solved by using a copolymer of a monomer unit and a monomer unit based on acrylonitrile, and have led to the present invention.

That is, according to the present invention, a functional group capable of introducing an ion-exchange group or a monomer having an ion-exchange group, a crosslinking agent, a polymerization initiator, and a substance derived from an aliphatic hydrocarbon-based monomer A mixture consisting of a copolymer of a monomer unit having no unsaturated bond and a monomer unit based on acrylonitrile is adhered to a base material and molded and polymerized. A method for producing a membrane for a redox flow battery is provided.

The present invention relates to a redox flow battery comprising a copolymer of a monomer unit having substantially no unsaturated bond derived from an aliphatic hydrocarbon monomer and a monomer unit based on acrylonitrile. It is characterized in that it is used as a matrix resin in the production of an ion-exchange membrane that is a membrane for use.In this way, a resin having an unsaturated bond such as an acrylonitrile-butadiene copolymer is used as a matrix resin. Compared with the manufactured membrane, a membrane having particularly excellent durability can be obtained.

In the present invention, the copolymer of a monomer unit having substantially no unsaturated bond derived from the aliphatic hydrocarbon monomer and a monomer unit based on acrylonitrile includes Known compounds consisting of each structural unit can be used without any limitation. As the aliphatic hydrocarbon-based monomer, an unsaturated aliphatic hydrocarbon, preferably an unsaturated aliphatic hydrocarbon having 2 to 9 carbon atoms is used without any particular limitation. In this case, as the unsaturated aliphatic hydrocarbon, specifically, it is preferable to use an olefin such as ethylene, propylene or butylene, or a conjugated diolefin such as butadiene or isoprene.

In the present invention, the above-mentioned copolymer used as a matrix resin is prepared in such a manner that a monomer unit derived from an aliphatic hydrocarbon monomer constitutes the copolymer. It has substantially no unsaturated bond in the unit. Therefore, when an aliphatic hydrocarbon-based monomer having a plurality of unsaturated bonds such as the conjugated diolefin is used as a copolymer component, the copolymer is further subjected to a hydrogenation treatment after the copolymerization. It is necessary to eliminate unsaturated bonds remaining in the unit based on the formula (1). In addition, as a form of copolymerization, so-called AB type diblock type, A
Any type such as a -BA type triblock type or a random type may be used. Further, it may contain a small amount of a third monomer such as divinylbenzene, methacrylic acid, and acrylic acid.

In the present invention, the copolymer of a monomer unit having substantially no unsaturated bond derived from the aliphatic hydrocarbon monomer most preferably used and a monomer unit based on acrylonitrile is used. Examples of the polymer include a resin obtained by copolymerizing acrylonitrile and butadiene, and further hydrogenating the obtained copolymer. When the copolymer having an unsaturated bond is subjected to a hydrogenation treatment, some unsaturated bonds may remain in the obtained copolymer. Usually, the number of such residual unsaturated bonds is preferably 10 or less, more preferably 5 or less in iodine value. The iodine value is represented by the number of grams of iodine absorbed by 100 g of the copolymer. When the iodine value is 10 or more, the iodine value is deteriorated by an oxidation reaction with a chemical species having oxidizing power contained in the redox flow battery solution, particularly, pentavalent vanadium.

In the copolymer of a monomer unit having substantially no unsaturated bond derived from the aliphatic hydrocarbon monomer and a monomer unit based on acrylonitrile, the content of each constituent unit is as follows: Although it is not particularly limited, it is suitable that the monomer unit based on acrylonitrile is 10 to 60% by weight, preferably 20 to 50% by weight based on the total weight of the copolymer. The molecular weight of the copolymer is
Although not particularly limited, usually, 1,000 to
1,000,000, preferably 50,000-500,
It is preferably in the range of 000.

In the present invention, a copolymer of a monomer unit having substantially no unsaturated bond derived from the aliphatic hydrocarbon monomer and a monomer unit based on acrylonitrile,
A mixture comprising a functional group capable of introducing an ion-exchange group or a monomer having an ion-exchange group, a crosslinking agent, and a polymerization initiator is adhered to a base material and molded and polymerized. To produce a membrane for a redox flow battery. Here, as the functional group capable of introducing an ion exchange group or a monomer having an ion exchange group, a conventionally known monomer used in the production of an ion exchange membrane is used without any particular limitation. Specific examples include styrene, vinyl toluene, vinyl xylene, acenaphrene, vinyl naphthalene, α-halogenated styrene, α, β, β′-trihalogenated styrene, chlorostyrenes, and the like. Particularly in the case of a diaphragm for a cationic redox flow battery, α-halogenated vinyl sulfonic acid, α, β, β′-halogenated vinyl sulfonic acid, methacrylic acid, acrylic acid, styrene sulfonic acid,
Salts and esters thereof, such as vinylsulfonic acid, maleic acid, itaconic acid, styrenephosphonic acid, maleic anhydride, and vinylphosphoric acid, are used. In the case of a diaphragm for an anionic redox flow battery, vinyl pyridine, methyl vinyl pyridine, ethyl vinyl pyridine, vinyl pyrrolidone, vinyl carbazole, vinyl imidazole, amino styrene, alkyl amino styrene, dialkyl amino styrene, trialkyl amino styrene , Methyl vinyl ketone, chloromethyl styrene,
Acrylic amide, acrylamide, oxime, styrene, vinyltoluene and the like are used.

As the cross-linking agent, a conventionally known monomer used in the production of an ion exchange membrane is used without any particular limitation. Specifically, for example, m-, p-, o-
Examples thereof include divinyl compounds such as divinylbenzene, divinylsulfone, butadiene, chloroprene, isoprene, divinylnaphthalene, diallylamine, triallylamine, and divinylpyridines, and trivinyl compounds such as trivinylbenzenes.

Further, as the polymerization initiator, a conventionally known polymerization initiator is used without any particular limitation, and may be appropriately selected according to the base material used and the molding conditions. For example, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butylperoxy-2-ethylhexanoate, lauryl peroxide, stearyl peroxide, methyl isobutyl ketone peroxide,
Cyclohexane peroxide, o-methylbenzoyl peroxide, 2,4,4-trimethylpentylperoxy-phenoxyacetate, α-cumylperoxy neodecanoate, di-tert-butylperoxy-
Hexahydroterephthalate, tert-butylperoxybenzoate, diisopropylbenzene hydroperoxide, di-tert-butylperoxide,
1,1-bis-tert-butylperoxy-3,3
5-trimethylcyclohexane or the like is used.

In the present invention, if necessary, the mixture of the above-mentioned monomer having a functional group capable of introducing an ion-exchange group or an ion-exchange group, a crosslinking agent, a polymerization initiator, and the matrix resin may be used. As a monomer having a functional group capable of introducing an ion exchange group and a monomer copolymerizable with a crosslinking agent, for example, styrene, acrylonitrile,
Ethyl styrene, vinyl chloride, acrolein, methyl vinyl ketone, maleic anhydride, salts or esters thereof, itaconic acid, salts or esters thereof, and the like may be appropriately mixed. In addition, a plasticizer such as dioctyl phthalate, dibutyl phthalate, tributyl phosphate, tributyl acetyl citrate or an aliphatic acid or an alcohol ester of an aromatic acid, and a solvent for diluting the monomer are appropriately added thereto. Is also good.

In the present invention, the mixing ratio of each of the above-mentioned components is not particularly limited, but generally, a functional group capable of introducing an ion exchange group or 100 parts by weight of a monomer having an ion exchange group is used. On the other hand, 1 to 100 parts by weight of a crosslinking agent, copolymerization of a monomer unit having substantially no unsaturated bond derived from the aliphatic hydrocarbon monomer and a monomer unit based on acrylonitrile It is preferable to blend the coalescing in the range of 2 to 200 parts by weight and the polymerization initiator in the range of 0.1 to 30 parts by weight based on 100% by weight of the total monomers.

The mixture thus obtained is adhered to a substrate and polymerized. Here, as the base material, those which use polyvinyl chloride, polyolefin or the like as a material resin, which has been conventionally used as a base material for an ion exchange membrane, are used without any limitation. Woven fabric, non-woven fabric,
Nets or their porous sheets can be used without limitation.

The thickness of these substrates is not particularly limited, but is in the range of 10 to 200 μm, especially 50 to 12 μm.
Those having a thickness of 0 μm are preferred.

When the mixture is adhered to the above-mentioned substrate and then polymerized, the temperature is generally raised from normal temperature under pressure, but the rate of temperature rise is not particularly limited and may be appropriately selected. Good. These polymerization conditions also depend on the type of polymerization initiator involved, the composition of the monomer mixture, and the type of base material, and cannot be determined unequivocally, but are optimal for the performance of a redox flow battery diaphragm. May be appropriately selected in consideration of the above. In addition, as a method of attaching the paste-like material to the base material, a known method such as coating, impregnation, or dipping may be appropriately adopted.

The film-like polymer obtained by polymerization as described above may, if necessary, be converted into a known polymer such as sulfonate,
Chlorosulfonation, chloromethylation and amination, quaternary ammonium basification, quaternary pyridinium basification,
A desired ion-exchange group can be introduced by a treatment such as phosphonium conversion, sulfonium conversion, hydrolysis, and protonation to obtain a membrane for a redox flow battery.
The introduction amount of these ion exchange groups is not particularly limited,
Usually, it is suitable that the ion exchange capacity is in the range of 1 to 20 mmol / g-dry membrane, preferably 2 to 6 mmol / g-dry membrane. Further, the thickness of the ion exchange membrane is related to desired charge / discharge efficiency, electric resistance, mechanical strength, durability, and the like, but is generally 10 to 200 μm, preferably 50 to 200 μm.
Preferably, it is in the range of 120 μm.

As described above, a copolymer of a monomer unit having substantially no unsaturated bond derived from an aliphatic hydrocarbon monomer and a monomer unit based on acrylonitrile, and an ion exchange resin An ion exchange membrane obtained by adhering a resin composition to a substrate is obtained. In this ion exchange membrane, as a component of the resin composition, a monomer unit having substantially no unsaturated bond derived from the aliphatic hydrocarbon monomer and a monomer unit based on acrylonitrile Confirmation that the copolymer is used as a matrix resin can be performed, for example, by the following method.

That is, the resin can be extracted by subjecting the ion-exchange membrane to Soxhlet extraction or the like with an organic solvent such as acetone or tetrahydrofuran, and analyzed by infrared spectroscopy or the like. The above copolymer,
2850-2950 cm as measured by infrared spectroscopy
Near ^-1, the carbon vicinity 1440～1460Cm ^-1 - there is a peak derived from a hydrogen bond, there is a peak derived from the nitrile group near 2236cm ^-1. On the other hand, 1
640cm around ^-1, 970 cm ^- near ¹ alkene carbon - peak attributable to carbon double bond shows a characteristic such that substantially absent.

The ion exchange membrane obtained by the method of the present invention is used as a membrane for a redox flow battery. The redox flow battery referred to here is a liquid-permeable electrolytic cell having a positive electrode chamber and a negative electrode chamber in which a positive electrode and a negative electrode are separated by a diaphragm.
The charge / discharge is performed using an oxidation-reduction reaction. Possible combinations of battery active materials include iron / chromium, vanadium / vanadium, chromium / bromine, vanadium / titanium, vanadium / iron, zinc / iron, and the like. In particular, the membrane for redox flow batteries of the present invention is a battery system containing vanadium and has excellent durability.

[0027]

The membrane for a redox flow battery obtained by the method of the present invention uses a copolymer of a monomer unit based on acrylonitrile and a specific aliphatic hydrocarbon-based unit as a matrix resin constituting the membrane. Therefore, it has extremely excellent durability without lowering the charge / discharge efficiency.

[0028]

EXAMPLES Examples of the present invention and comparative examples are shown below, but the present invention is not limited to these examples. Example 1 100 parts by weight of 4-vinylpyridine, purity about 5 as a crosslinking agent
Paste mixture obtained by mixing 5 parts by weight of 7% divinylbenzene, 2 parts by weight of benzoyl peroxide as a polymerization initiator, and 20 parts by weight of a hydrogenated acrylonitrile-butadiene copolymer having an iodine value of 4 as a matrix resin. Was coated on a polyvinyl chloride woven fabric, and covered with a polyester film as a release material, followed by heat polymerization at 75 ° C. for 6 hours.

Next, the obtained film-form polymer was treated with a 40% by weight methyl iodide solution in hexane at 30 ° C. for 24 hours.
2. Time methylation, thickness 100 μm, exchange capacity 3.
A 5 mmol / g-dry membrane for an anionic redox flow battery was obtained. This redox flow diaphragm was subjected to Soxhlet extraction at 40 ° C. for 3 days using tetrahydrofuran as a solvent, and the obtained extract was analyzed by infrared spectroscopy. As a result, 2850-2950 cm ^-1
Near, carbon vicinity 1440~1460cm ^-1 - there is a peak derived from hydrogen bonding, there is a peak derived from the nitrile group near 2236cm ^-1, on the one hand, 1640C
m around ^-1, 970 cm ^{- 1} in the vicinity, alkene carbon - peak attributable to carbon double bond was not substantially observed.

Next, the obtained membrane for redox flow batteries was used as a positive electrode solution at 2 mol / l of VOSO ₄ +2 mo.
1 / l sulfuric acid mixed solution was used as a negative electrode solution at 2 mol / l of V
Charge / discharge was performed at a current density of 60 mA / cm ² using a mixed solution of ₂ (SO ₄ ) ₃ +2 mol / l sulfuric acid, and the charge / discharge efficiency was determined. The results are shown in Table 1. Furthermore, in order to examine the durability, as an accelerated test, it was immersed in a 1 mol / l pentavalent vanadium sulfate solution at 60 ° C. for 3 months. The immersion film did not change its shape as compared with the blank film. Table 1 also shows the results of measuring the charge / discharge efficiency of the immersion film. Comparative Example 1 An ion-exchange capacity of 3.5 mmol / g-dry film, film thickness under the same conditions as in Example 1 except that a non-hydrogenated acrylonitrile-butadiene copolymer having an iodine value of 250 was used as a matrix resin. A 100 μm diaphragm for an anionic redox flow battery was obtained.

The Soxhlet extraction was performed under the same conditions as in Example 1, and the extract was subjected to infrared spectroscopy.
A peak derived from a carbon-hydrogen bond exists around 0-2950 cm ^{-1 and} around 1440-1460 cm ^-1 , and 223
A peak derived from a nitrile group exists around 6 cm ⁻¹ ,
Further, at around 1640 cm ^{-1 and} around 970 cm ^-1 ,
There was a peak due to the alkene carbon-carbon double bond.

The charge / discharge efficiency of this film was measured under the same conditions as in Example 1. The results are shown in Table 1. Further, as a result of immersion under the same conditions as in Example 1 in order to examine the durability, the resin component was partially peeled off. Table 1 also shows the charge / discharge efficiency of the immersion film. Example 2 100 parts by weight of styrene, 3 parts by weight of divinylbenzene, 20 parts by weight of acrylonitrile, 20 parts by weight of dibutyl phthalate, 2 parts by weight of benzoyl peroxide, and hydrogenated acrylonitrile butadiene copolymer having an iodine value of 4 as a matrix resin A paste-like mixture obtained by mixing 15 parts by weight of the coalesced was applied to a polyvinyl chloride cloth, and a polyester film was coated as a release material.
Heat polymerization was performed at 100 ° C. for 5 hours.

Next, the obtained film-form polymer was immersed in a 1: 1 mixture of 98% concentrated sulfuric acid and chlorosulfonic acid having a purity of 90% or more at 40 ° C. for 60 minutes to obtain a film having a thickness of 100 μm.
m, an exchange capacity of 3.1 mmol / g-a dry membrane for a cation-type redox flow battery was obtained. This membrane for redox flow batteries, using tetrahydrofuran as a solvent,
Soxhlet extraction was performed at 40 ° C. for 3 days, and the obtained extract was analyzed using infrared spectroscopy. As a result, 28
Around 50-2950 cm ^-1 , 1440-1460 cm ^-1
In the vicinity, a peak derived from a carbon-hydrogen bond exists, and 22
A peak derived from a nitrile group was present around 36 cm ^-1 , while a peak derived from the carbon-carbon double bond of the alkene was not substantially observed around 1640 cm ^{-1 and} around 970 cm ^-1 . .

Next, the charging / discharging efficiency of the obtained membrane for a redox flow battery was measured under the same conditions as in Example 1. The results are shown in Table 1. Furthermore, to check the durability,
Was immersed in a 0.2 mol / l pentavalent vanadium sulfate solution for 1 month. Even after one month, no change was observed in the immersion film itself. Table 1 also shows the charge / discharge efficiency of the immersion film. Comparative Example 2 Under the same conditions as in Example 2 except that the matrix resin was an unhydrogenated acrylonitrile-butadiene copolymer having an iodine value of 250, a thickness of 100 μm and an exchange capacity of 3.1 mmol / g-dry film A membrane for a redox flow battery was obtained. The charge and discharge efficiency of this film was measured under the same conditions as in Example 1. The results are shown in Table 1. Further, as a result of immersion under the same conditions as in Example 2 in order to check the durability, the resin component was partially peeled off. Table 1 also shows the charge / discharge efficiency of the immersion film. Example 3 2 50 parts by weight of vinylpyridine, 50 parts by weight of 4 vinylpyridine, divinylbenzene 1 having a purity of about 57% as a crosslinking agent
0 parts by weight, 2 parts by weight of benzoyl peroxide as a polymerization initiator, and hydrogenated acrylonitrile-butadiene copolymer 2 having an iodine value of 4 as a matrix resin
The paste-like mixture obtained by mixing 0 parts by weight was applied to a polyvinyl chloride woven fabric, and a polyester film was coated as a release material, followed by heat polymerization at 75 ° C. for 6 hours.

Next, the obtained film-like polymer was treated with a 40% by weight hexane solution of methyl iodide at 30 ° C. and 24 ° C.
2. Time methylation, thickness 100 μm, exchange capacity 3.
A 0 mmol / g-dry membrane for an anionic redox flow battery was obtained. This redox flow battery membrane was subjected to Soxhlet extraction at 40 ° C. for 3 days using tetrahydrofuran as a solvent, and the obtained extract was analyzed by infrared spectroscopy. As a result, 2850-2950
around cm ^-1, the carbon vicinity 1440~1460cm ^-1 - there is a peak derived from hydrogen bonding, there is a peak derived from the nitrile group near 2236cm ^-1, on the one hand, 16
Around 40 cm ^-1, in the vicinity of 970 cm ^-1, alkene carbon - peak attributable to carbon double bond was not substantially observed.

The membrane for a redox flow battery was charged and discharged under the same conditions as in Example 1 to determine the charging and discharging efficiency.
The results are shown in Table 1. Furthermore, in order to examine the durability, it was immersed for 3 months under the same conditions as in Example 1. The immersion film did not change its shape as compared with the blank film. Table 1 also shows the results of measuring the charging and discharging efficiency. Comparative Example 3 Except that the matrix resin was an unhydrogenated acrylonitrile-butadiene copolymer having an iodine value of 250, under the same conditions as in Example 3, a thickness of 100 μm, an exchange capacity of 3.0 mmol / g- A membrane for a redox flow battery was obtained. The charge and discharge efficiency of this film was measured under the same conditions as in Example 1. The results are shown in Table 1. As a result of immersion under the same conditions as in Example 1 to check the durability, the resin component was partially peeled off. Table 1 also shows the charge / discharge efficiency of the immersion film.

[0037]

[Table 1]

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Claims (1)

[Claims] 1. A compound having a substantially unsaturated bond derived from a functional group capable of introducing an ion exchange group or a monomer having an ion exchange group, a crosslinking agent, a polymerization initiator and an aliphatic hydrocarbon monomer. A mixture comprising a monomer unit and a copolymer of a monomer unit based on acrylonitrile, which is adhered to a substrate and molded and polymerized, and then ion-exchange groups are introduced as necessary. Of producing a membrane for a redox flow battery.