JP2013203998A - Porous membrane, electrolyte membrane, secondary battery and fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous membrane which is reduced in formation of a skin layer, and thus can exert excellent ion conductivity when used for electrolyte.SOLUTION: A porous membrane is composed of a membrane-like porous structure having a bicontinuous structure. At least one main surface of the porous structure is modified with a modifying compound different from a compound constituting the porous structure.

Description

  The present invention relates to a porous membrane, an electrolyte membrane, a secondary battery, and a fuel cell.

  A porous body having a continuous skeleton having a three-dimensional network structure and voids is generally called a monolith type porous body. Such a monolithic porous body is mainly used as a separation medium called a column in the chromatography field, but in recent years, its use as an electrolyte membrane or separator of a secondary battery or a fuel cell has been studied. For example, Patent Document 1 discloses a monolithic porous body having a three-dimensional network structure skeleton made of a cured epoxy resin and voids, and having mesopores having a pore diameter of 1 nm to 1 μm in the skeleton.

JP 2009-269948 A

  On the other hand, in order to apply the above-described monolithic porous body to electrolyte membranes and separators for secondary batteries and fuel cells, for example, by applying a raw material constituting the monolithic porous body on the substrate. In addition, when the monolithic porous body is formed into a thin film shape, a non-porous skin layer is formed on the surface in contact with air on the side opposite to the base material. There was a problem that ionic conductivity could not be obtained.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a porous membrane capable of exhibiting excellent ionic conductivity when used in an electrolyte application, in which the formation of a skin layer is suppressed. For the purpose.

That is, according to the present invention,
[1] A porous membrane comprising a membrane-like porous structure having a co-continuous structure, wherein at least one main surface of the porous structure is different from a compound constituting the porous structure A porous membrane characterized by being modified by a compound,
[2] At least one main surface of the porous structure is coated with the main surface, and a denatured layer composed of the modifying compound is formed. The porous film according to the above [1], which is a porous layer having an average pore size smaller than the average pore size of the voids of the structure, or a non-porous layer,
[3] The porous film according to [2], wherein the thickness of the modified layer is 1000 nm or less,
[4] The porous membrane according to any one of [1] to [3], wherein both main surfaces of the porous structure are modified with the modifying compound,
[5] The porous membrane according to any one of [1] to [4], wherein the porous membrane structure is made of a cured epoxy resin.
[6] The porous membrane as described in any one of [1] to [5], wherein the modifying compound has a functional group that reacts with a compound constituting the porous membrane structure. ,
[7] The porous membrane according to any one of [1] to [6], wherein the porous membrane structure contains an ionic liquid in the voids,
[8] The porous membrane according to any one of [1] to [7], wherein the porous membrane structure includes a mesopore having a pore diameter of 1 nm to 1 μm in a skeleton.
[9] The porous membrane structure is compatible with the monomer constituting the porous membrane structure and the polymer obtained by polymerizing the monomer. The porous film according to any one of [1] to [8], wherein the porous film is formed by polymerization-induced phase separation using an incompatible compound.
[10] An electrolyte membrane obtained by impregnating the porous membrane according to any one of [1] to [9] with an electrolyte,
[11] A secondary battery comprising the electrolyte membrane according to [10],
[12] A fuel cell comprising the electrolyte membrane according to [10],
[13] An electric double layer capacitor comprising the electrolyte membrane according to [10], and
[14] A dye-sensitized solar cell including the electrolyte membrane according to [10],
Is provided.

  According to the present invention, the formation of a skin layer is suppressed, whereby a porous film that can exhibit excellent ionic conductivity when used in an electrolyte application, and an electrolyte film comprising the porous film, Secondary batteries and fuel cells can be provided.

FIG. 1 is a schematic view showing a cross section of an example of a porous membrane according to the present invention. FIG. 2 is a schematic view for explaining a method for producing a porous membrane according to the present invention. FIG. 3 is an SEM photograph of the porous structure 10 (porous structure containing an ionic liquid) portion of the porous film obtained in Example 5 of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view showing a cross section of an example of a porous membrane according to the present invention. As shown in FIG. 1, the porous membrane of the present invention includes a membrane-like porous structure 10 having a co-continuous structure, and a modified layer 20 that covers both main surfaces of the porous structure 10. .

  In the following, a configuration in which the modified layer 20 is formed on both main surfaces of the porous structure 10 will be described as an example. However, the present invention is not limited to such a configuration, and the porous structure 10 is not limited thereto. Alternatively, the modified layer 20 may be formed only on one main surface.

  The porous structure 10 is a film-like structure having a co-continuous structure. Although it does not specifically limit as the porous structure 10, For example, what has the three-dimensional branch network structure of the cured | curing material of resin as a skeleton, and has a space | gap (macropore) between skeletons is preferable.

  That is, the structure serving as the basis of the porous structure 10 preferably has, for example, a three-dimensional network structure in which a skeleton of 1 μm or more and voids (macropores) are entangled with each other.

  In the present invention, the resin for forming the skeleton of the porous structure 10 is not particularly limited, and any resin that can form a porous structure as described above may be used. For example, an epoxy resin, (Meth) acrylate resin, polystyrene resin, polyester resin, phenol resin, polyurethane resin and the like can be mentioned, and an epoxy resin is preferably used from the viewpoint that an extremely fine porous structure can be formed.

  In addition, the average pore diameter of the voids (macropores) of the porous structure 10 is preferably 0.1 to 100 μm, more preferably 0.1 to 50 μm, and still more preferably 0.1 to 10 μm.

  The porous structure 10 may have mesopores in the skeleton of the porous structure 10 in addition to the macropores. The mesopores formed in the skeleton are usually pores having a pore diameter smaller than that of the macropores. In addition, the mesopore structure in the skeleton does not necessarily need to form a continuous hole like a three-dimensional network structure. You may have. The pore diameter of the mesopore is preferably 1 nm to 1 μm, more preferably 1 to 500 nm, and further preferably 1 to 300 nm.

  The average pore diameter of the voids (macropores) and the diameter of the mesopores are the simplest method, for example, to be confirmed by an electron microscope image, but can also be measured by a mercury intrusion method or a nitrogen adsorption method.

  The modified layer 20 is a layer made of a compound different from the compound constituting the porous structure 10 and covering both main surfaces of the porous structure 10. The modified layer 20 is usually formed as a porous layer or a non-porous layer having an average pore size smaller than the average pore size of the voids of the porous structure 10.

  As the compound constituting the denatured layer 20, a compound having a functional group capable of forming a chemical bond with the compound constituting the porous structure 10 by reacting with the compound constituting the porous structure 10 is preferable. . That is, the modified layer 20 is preferably chemically bonded to the porous structure 10.

  Examples of the compound constituting the modified layer 20 include a case where an epoxy resin is used as the compound for forming the porous structure 10, and examples of the functional group include a primary amino group and a secondary class. Examples thereof include compounds having an amino group, a mercapto group, a carboxyl group, a carboxylic anhydride group, a hydroxy group, and the like. Among these, those having high ion solubility are preferable from the viewpoint of ionic conductivity when used as an electrolyte application such as a secondary battery or a fuel cell. Particularly, amino groups, carboxyl groups, oxyalkylene groups, ionic properties are preferable. A compound having a group, a cyano group, a carbonate, a halogen group, a thiol group or a hydroxy group is preferable, and a compound having a hydroxy group is particularly preferable. As shown in FIG. 1, when the modified layers 20 are formed on both main surfaces of the porous structure 10, each modified layer 20 may be composed of the same compound. Alternatively, it may be composed of different compounds.

  The thickness of the modified layer 20 is preferably 1000 nm or less, more preferably 100 nm or less, and still more preferably 50 nm or less. If the thickness of the modified layer 20 is too thick, the ionic conductivity may be reduced when used as an electrolyte application for a secondary battery, a fuel cell, or the like. In addition, although the minimum of the thickness of the modified layer 20 is not specifically limited, Usually, it is about 10 nm. When the modified layer 20 is a porous layer, the porosity of the modified layer 20 is preferably 40% or more, more preferably 60% or more, and further preferably 80% or more. In the case where the modified layer 20 is a porous layer, depending on the porosity of the modified layer 20 and the material constituting the modified layer 20, when used in an electrolyte application, the electrolyte layer swells, It may be non-porous.

Subsequently, the manufacturing method of the porous film of this invention is demonstrated.
The porous film of the present invention can be produced, for example, by the following method. That is, as shown in FIG. 2 (A), first, a modified layer composition layer 20a that will form the modified layer 20 is formed on the base material 30, whereby the modified layer composition layer 20a is formed. The base material 30 provided is prepared. Next, as shown in FIG. 2 (B), the porous structure 10 will constitute the porous structure 10 on the modified layer composition layer 20a side of the base material 30 provided with the modified layer composition layer 20a. The body composition layer 10a is formed.

  Next, as shown in FIG. 2 (C), the substrate 30 having the modified layer composition layer 20a on the porous structure composition layer 10a, the surface on the modified layer composition layer 20a side, It mounts | wears so that the composition layer 10a for porous structures may be contact | connected. And about the laminated body obtained in this way, the process which hardens the sclerosing | hardenable component which comprises the composition layer 10a for porous structures is performed, and the base material 30 is peeled after that, FIG. A porous membrane of the present invention as shown can be formed.

  In the present invention, the composition layer 20a for the modified layer is formed between the composition layer 10a for the porous structure and the base material 30. Thus, when the base material 30 is peeled off, A part acts as a sacrificial layer to be peeled off together with the substrate 30. That is, when the composition layer 20a for the modified layer is formed on the base material 30, the base material 30 and the composition layer 10a for the porous structure are in close contact with each other, and poor peeling occurs between them. This is a layer that is provided so as not to occur, and a part thereof is peeled off together with the base material 30, while the remaining part remains as the modified layer 20 shown in FIG. 1. As a result, the porous film of the present invention can have a configuration in which the modified layers 20 are formed on both main surfaces of the porous structure 10, as shown in FIG.

  Hereafter, the manufacturing method of the porous film of this invention is demonstrated concretely. In the following, a case where a cured product of an epoxy resin is used as the cured product of the resin for forming the skeleton of the porous structure 10 will be described as an example.

  First, as shown in FIG. 2 (A), a modified layer composition layer 20a for forming a modified layer 20 is formed on a substrate 30, and a modified layer composition layer 20a is formed. A base material 30 is prepared. Although it will not specifically limit as the base material 30 if the composition layer 20a for modified layers can be formed in the surface, For example, a glass plate, a plastic plate, etc. are mentioned.

  Further, the compound constituting the composition layer 20a for the modified layer is not particularly limited as long as it is a compound having excellent affinity and adhesion to the substrate 30 and the composition layer 10a for the porous structure. The compound which comprises the porous structure 10 in the porous film formed, ie, the compound which has a functional group which can form a chemical bond with an epoxy resin, is preferable. Specific examples include a compound having a primary amino group, a secondary amino group, a mercapto group, a carboxyl group, a carboxylic acid anhydride group, and a hydroxy group. As described above, a part of the composition layer 20a for the modified layer is removed as the sacrificial layer, while the remaining part remains as the modified layer 20, so that the secondary battery, the fuel cell, etc. From the viewpoint of ionic conductivity when used as an electrolyte, those having high ion solubility are preferred, and in particular, amino groups, carboxyl groups, oxyalkylene groups, ionic groups, cyano groups, carbonate groups, halogen groups, thiols. A compound having a group or a hydroxy group is preferable, and a compound having a hydroxy group is particularly preferable.

  Specific examples of the compound constituting the composition layer 20a for the modified layer include various resins such as polyvinyl alcohol, silicone, fluorine-based polymer, and self-crosslinking polymer. Among these, Polyvinyl alcohol or a modified product thereof (for example, a porous structure) from the viewpoint of good affinity and adhesion with the material 30 and the composition layer 10a for the porous structure and high reactivity with the epoxy resin For example, a modified product obtained by modifying with a functional group having a higher reactivity to the compound constituting the composition layer 10a.

  In particular, since polyvinyl alcohol has high solubility in water and can be easily removed by dissolving in water, it can act well as a sacrificial layer by using polyvinyl alcohol as the composition layer 20a for the modified layer. Can do. In addition, since polyvinyl alcohol is highly reactive with epoxy resin, a part of it reacts with the epoxy resin constituting the porous structure 10 (the composition layer 10a for porous structure) to form a chemical bond. Therefore, even after the composition layer 20a for the modified layer is removed, a part of the composition layer 20a remains and the modified layer 20 can be formed satisfactorily.

  The polyvinyl alcohol preferably has a weight average polymerization degree of 1,000 to 5,000, more preferably 2,000 to 5,000, and still more preferably 2,000 to 4,000. The saponification degree is preferably 80 to 98%, more preferably 85 to 95%, and still more preferably 85 to 90%.

  The method for forming the modified layer composition layer 20a on the base material 30 is not particularly limited. For example, when polyvinyl alcohol is used, a 1 to 10% by weight aqueous polyvinyl alcohol solution is prepared, and this polyvinyl alcohol is used. After casting the aqueous alcohol solution on the substrate, it is dried to remove moisture, whereby the modified layer composition layer 20a made of polyvinyl alcohol can be formed. Although the thickness of the composition layer 20a for modified layers is not specifically limited, Usually, 10-5000 nm, Preferably it is 10-1000 nm, More preferably, it is 10-500 nm.

  Moreover, in order to improve affinity with the epoxy resin which comprises the porous structure 10 (porous structure composition layer 10a) for the modified layer composition layer 20a, a known silane coupling agent or the like is known. A coupling agent may be contained.

  Next, as shown in FIG. 2 (B), the porous structure 10 is formed on the surface of the substrate 30 having the modified layer composition layer 20a thus obtained on the modified layer composition layer 20a side. The composition layer 10a for porous structure which will be comprised is formed.

The composition layer 10a for porous structure is usually formed using an epoxy resin composition for obtaining a cured product of an epoxy resin that constitutes the porous structure 10.
As an epoxy resin composition, what contains an epoxy resin, a hardening | curing agent, and a porogen can be used.

As an epoxy resin, for example, as an aromatic epoxy resin containing a carbon atom derived from an aromatic ring, bisphenol A type epoxy resin, brominated bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, stilbene type epoxy Resin, biphenyl type epoxy resin, bisphenol A novolac type epoxy resin, cresol novolac type epoxy resin, diaminodiphenylmethane type epoxy resin, polyphenyl base epoxy resin such as tetrakis (hydroxyphenyl) ethane base, fluorene-containing epoxy resin, 2, Epoxy resins containing heteroaromatic rings such as triglycidyl isocyanurates such as 2,2, -tri- (2,3-epoxypropyl) -isocyanate, triazine ring-containing epoxy resins, N N, N ', such as N'- tetraglycidyl -m- xylylenediamine may be mentioned.
Non-aromatic epoxy resins containing no aromatic ring-derived carbon atoms include aliphatic glycidyl ether type epoxy resins, aliphatic glycidyl ester type epoxy resins, alicyclic glycidyl ether type epoxy resins, and alicyclic glycidyl ester type epoxies. Examples thereof include resins and 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane.
Among these, an epoxy resin having two or more glycidyl groups in the molecule is preferable, and bisphenol A type epoxy resin, 2,2,2, -tri- (2,3-epoxypropyl) -isocyanate, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine and 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane are more preferred.

Further, as the curing agent, as an aromatic curing agent containing an aromatic ring-derived carbon atom, metaphenylenediamine, diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, 4,4′-methylene-bis (2-chloroaniline) ), Aromatic amines such as benzyldimethylamine and dimethylaminomethylbenzene, aromatic anhydrides such as phthalic anhydride, trimetic anhydride and pyrometic anhydride, phenolic compounds, phenolic resins, phenol formaldehyde type novolacs and phenol alkyls Novolak type phenolic resins such as type novolak, aromatic hydrazides such as isophthalic acid dihydrazide, aromatic amines having a heteroaromatic ring such as triazine ring, 1,1,1 ′, 1′-tetramethyl-4,4′- (Methylene-di-para-phenylene) disemica Aromatic polyamines and aromatic polyamines hydrazides such Bajido the like.
Non-aromatic curing agents that do not contain aromatic ring-derived carbon atoms include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, iminobispropylamine, bis (hexamethylene) triamine, 1,3,6-tris. Aliphatic amines such as aminomethylhexane, polymethylenediamine, trimethylhexamethylenediamine, polyetherdiamine, aliphatic hydrazides such as adipic acid dihydrazide and sebacic acid dihydrazide, dodecanedioic acid dihydrazide, isophoronediamine and menthanediamine, N- Such as aminoethylpiperazine, 3,9-bis (3-aminopropyl) 2,4,8,10-tetraoxaspiro (5,5) undecane adduct, bis (4-aminocyclohexyl) methane and their modified products Of alicyclic polyamines, aliphatic polyamine hydrazides such as 1,6-hexamethylenebis (N, N-dimethylsemicarbazide), aliphatic polyamidoamines composed of polyamines and dimer acids, and polyaminoamides. Oligomer Propylene Glycol Monomethyl Ether Solution with Li- (Hexamethylene-N, N-dimethylsemicarbazide) as Main Component, Oligomer N, N- with Bullettory Tri- (Hexamethylene-N, N-dimethylsemicarbazide) as Main Component Dimethylformamide solutions, glycols such as spiroglycol and 2- (5-ethyl-5-hydroxymethyl-1,3-dioxan-2-yl) -2-methylpropan-1-ol, and other amine adduct curing agents Is mentioned.
Among these, it is preferable to use a polyaminoamide type curing agent having a viscosity at 25 ° C. of 400 mPa · s or more.

  The addition ratio of the epoxy resin and the curing agent in the epoxy resin composition for forming the composition layer 10a for the porous structure is such that the curing agent equivalent (amine equivalent) is 0. It is preferable to adjust so that it may become the range of 6-1.5. When the curing agent equivalent ratio is less than 0.6, the crosslinking density of the cured epoxy resin is lowered, and the heat resistance, solvent resistance, and the like may be lowered. On the other hand, if it exceeds 1.5, the number of unreacted functional groups increases, and it remains unreacted in the cured product or becomes a factor that hinders the improvement of the crosslinking density.

  The porogen is a component for forming macropores and mesopore voids formed in the porous structure 10 after curing. As the porogen, a compound capable of dissolving the above-described epoxy resin and curing agent and capable of causing reaction-induced phase separation after the epoxy resin and the curing agent are polymerized can be used.

  Examples of such porogens include cellosolves such as methyl cellosolve and ethyl cellosolve, esters such as ethylene glycol monomethyl ether acetate and propylene glycol monomethyl ether acetate, glycols such as polyethylene glycol, polypropylene glycol, triethylene glycol, and diethylene glycol. Can be mentioned. Among these, polyethylene glycol, polypropylene glycol, triethylene glycol, and diethylene glycol having a molecular weight of 200 or less are preferable. Alternatively, polyethylene glycol or polypropylene glycol having a molecular weight of 600 or more, such as waxy (semi-solid) at room temperature, as long as it is compatible with an epoxy resin and a curing agent at a polymerization temperature and becomes liquid, Can be used as a porogen.

  The compounding amount of the porogen is preferably 30 to 90 parts by weight, more preferably 60 to 90 parts by weight with respect to 100 parts by weight of the epoxy resin. By setting the blending amount of the porogen within the above range, the microstructure (macropores and mesopore pore diameter) of the porous structure 10 after curing can be made more appropriate.

  Moreover, as an epoxy resin composition for forming the composition layer 10a for porous structures, in addition to an epoxy resin, a hardening | curing agent, and a porogen, the organic polymer which brings an effect equivalent to a porogen, and metal alkoxide are used. A sol may be further blended. The organic polymer having the same effect as porogen is not particularly limited in molecular weight as long as it can be uniformly and dissolved in the polymerization system. For example, polyethylene glycol, polyethylene oxide, polypropylene oxide, polymethyl methacrylate, polyoxy Examples thereof include ethylene nonyl phenyl ether and copolymers of these represented by ethylene oxide-propylene oxide copolymers. Among these, polyethylene oxide, ethylene oxide-propylene oxide copolymer and the like are preferable. The blending ratio of these organic polymers can be appropriately adjusted according to the mesopore diameter of the skeleton part to be obtained.

Further, by blending a sol made of a metal alkoxide, it can be dissolved later to form pores in which the sol made of the metal alkoxide physically exists as mesopores in the skeleton. As a sol composed of metal alkoxide, as silica alkoxide, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, 1,2-bistrimethoxysilylethane, 1 to 4 alkoxy groups bonded to Si atom Silica alkoxide, silica alkoxide introduced with glycidyl group, etc., titanium alkoxide, titanium n-propoxide, titanium isopropoxide, titanium n-butoxide, titanium t-butoxide, etc., zirconium alkoxide, zirconium propoxide, zirconium isopropoxide As hafnium alkoxide, hafnium propoxide, hafnium isodium, etc., zirconium n-butoxide, zirconium t-butoxide, etc. Ropokishido, hafnium n- butoxide, hafnium t- butoxide.
Among these, a sol composed of a silica alkoxide in which 1 to 4 alkoxy groups are bonded to an Si atom and a silica alkoxide in which a glycidyl group is introduced is preferable, and a sol composed of a silica alkoxide in which a glycidyl group is introduced is particularly preferable.

  Moreover, the epoxy resin composition for forming the composition layer 10a for porous structures has affinity with the compound (for example, polyvinyl alcohol) which comprises the modified layer 20 (modified layer composition layer 20a). In order to improve it, you may contain well-known coupling agents, such as a silane coupling agent.

  The method for forming the composition layer 10a for the porous structure on the surface of the base material 30 provided with the composition layer 20a for the modified layer on the side of the composition layer 20a for the modified layer is not particularly limited. Any method may be used as long as the composition layer 10a for the porous structure can be formed. For example, when the composition layer 10a for the porous structure contains an epoxy resin, the epoxy resin composition described above is used. Is cast on the surface of the base material 30 provided with the composition layer for modified layer 20a on the side of the composition layer for modified layer 20a using a dispenser or the like.

  Next, the substrate 30 provided with the composition layer 20a for the modified layer produced in the same manner as described above on the composition layer 10a for the porous structure, and the surface on the composition layer 20a side for the modified layer has a porous structure. By placing it in contact with the body composition layer 10a, a laminate as shown in FIG. 2C is obtained.

  And about the obtained laminated body, the process which makes the sclerosing | hardenable component which comprises the composition layer 10a for porous structures, specifically, an epoxy resin, and a hardening | curing agent make it harden | cure is performed. The method for curing these is not particularly limited, and may be appropriately selected according to the type of the curing agent to be used. Examples thereof include a method by heating and a method of irradiating electromagnetic waves such as ultraviolet rays and electron beams. It is done. The heating temperature in the method of curing by heating is usually 25 to 200 ° C, preferably 30 to 180 ° C, more preferably 40 to 160 ° C.

  In the present invention, by using the above-described epoxy resin composition as a material constituting the composition layer 10a for the porous structure, the polymer component increases with polymerization by the epoxy resin and the curing agent, and spinodal phase separation Can occur and a co-continuous structure can be developed. In this case, the epoxy resin contained in the porous structure composition layer 10a and the modified layer composition at the interface between the porous structure composition layer 10a and the modified layer composition layer 20a. When the hydroxy group of the polyvinyl alcohol contained in the physical layer 20a reacts, a chemical bond is formed between them.

  Moreover, in this invention, the hardening process of the composition layer 10a for porous structures is carried out in the state which pinched both surfaces of the composition layer 10a for porous structures with the base material 30 provided with the composition layer 20a for modified layers. Therefore, the curing treatment can be performed in a state where the main surface of the composition layer 10a for the porous structure is not in contact with air, whereby a non-porous skin layer is formed on the surface thereof. Can be effectively prevented. In addition, since the non-porous skin layer is non-porous, it cannot be impregnated with the electrolyte. Therefore, if the non-porous skin layer is formed, the ionic conductivity is inhibited. It becomes. On the other hand, according to the present invention, formation of such a skin layer can be effectively prevented.

  Next, a process of extracting the porogen contained in the composition layer 10a for the porous structure after curing and a process of removing the substrate 30 are performed on the laminated body that has undergone the curing reaction. In addition, the process which extracts these porogens, and the process which removes the base material 30 may be performed separately, and may be performed simultaneously. For example, when polyvinyl alcohol is used as the compound constituting the composition layer 20a for the modified layer and the components exemplified above are used as the porogen, both of them are water-soluble, so that the curing reaction is performed. By putting the laminated body in water, a process of extracting the porogen and a process of removing the substrate 30 can be performed.

  And by extracting the porogen contained in the composition layer 10a for porous structures after hardening, the porous structure 10 which has a co-continuous structure as mentioned above is comprised, and also as a sacrificial layer The porous layer of the present invention as shown in FIG. 1 can be obtained by removing the composition layer 20a for the modified layer together with the base material 30 in a state where a part thereof remains.

  Alternatively, instead of such a method, for example, as a material constituting the composition layer 10a for the porous structure, a monomer (for example, epoxy resin) that constitutes the porous structure 10 and the monomer Polymerization is induced by using a compound that contains a compound that is compatible with the monomer and that is incompatible with the polymer obtained by polymerizing the monomer. Thus, a method for obtaining the porous structure 10 may be adopted.

  The porous membrane of the present invention thus obtained can be made into an electrolyte membrane by impregnating an electrolyte such as an electrolyte for a secondary battery or an electrolyte for a fuel cell. The electrolyte membrane of the present invention thus obtained is obtained by using the porous membrane of the present invention described above, and the porous membrane of the present invention is formed with a skin layer that inhibits ionic conductivity on the surface thereof. Instead, the modified layer 20 having high ion solubility is provided. Such a porous membrane of the present invention appropriately retains the electrolyte in the macropores (macropores and mesopores if there are mesopores) formed in the porous structure 10 having a co-continuous structure. In addition, since the surface thereof is provided with the modified layer 20 having high ion solubility, it can exhibit excellent ionic conductivity, and by utilizing such excellent characteristics, a lithium ion secondary battery For example, it can be suitably used as an electrolyte membrane for various secondary batteries such as those described above and an electrolyte membrane for fuel cells.

  In addition, since the porous membrane of the present invention thus obtained is obtained by, for example, the above production method, usually, the modified layer 20 is formed only on both main surfaces (or only one main surface). Thus, the modified layer 20 is not formed on the surface that defines the thickness direction (that is, the surface perpendicular to both main surfaces).

  Furthermore, since the porous film of the present invention thus obtained is obtained, for example, by the above production method, the compound constituting the modified layer 20 in the vicinity of the interface with the modified layer 20 of the porous structure 10 (For example, polyvinyl alcohol) is formed as a thin mixed region formed by impregnating the inside of the porous structure 10. That is, for example, in the porous film of the present invention, the thickness of the mixed region is preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 1 μm or less.

  On the other hand, when the modified layer 20 is formed on the surface of the porous structure 10 by a coating method or the like, the compound that forms the modified layer 20 in the porous structure 10. However, it may infiltrate the inside of the porous structure 10, the thickness of the mixed region becomes thick, and there is a risk of impeding conductivity, and further, when the modified layer 20 is formed by a coating method, The modified layer 20 is also formed on a surface other than the main surface, that is, a surface that defines the thickness direction (that is, a surface perpendicular to both main surfaces). In particular, when the compound constituting the modified layer 20 is highly swellable with respect to the electrolytic solution, the modified layer 20 is formed when the thickness of the mixed region in the porous structure 10 is thick. This is not preferable because the porous structure formed in the porous structure 10 is deformed by the size change caused by the swelling of the compound to be swelled. In addition, in the case of forming by a coating method, it is necessary to dissolve the compound constituting the modified layer 20 in a solvent and adjust the viscosity to be suitable for coating, and thus such a tendency becomes remarkable. On the other hand, according to the present invention, the occurrence of such a problem can be effectively prevented.

  In addition, for example, without using the base material 30 provided with the composition layer 20a for the modified layer, the main surface of the composition layer 10a for the porous structure was exposed to the air, and was obtained by performing a curing treatment. A method of forming a modified layer having high ion solubility on the surface of the obtained porous structure by carrying out the surface treatment of the porous structure can also be considered. However, in such a method, a non-porous skin layer is formed due to the influence of air during the curing process, and the ionic conductivity is inhibited by the non-porous skin layer. The problem that conductivity will deteriorate will generate | occur | produce.

  Further, in order to remove the non-porous skin layer, a method of performing a mechanical method such as a polishing process on the surface of the porous structure on which the skin layer is formed may be considered. When used as an electrolyte for a secondary battery or a fuel cell, it is necessary to make the film thinner, and therefore it is extremely difficult to remove the skin layer by a mechanical method. On the other hand, according to the present invention, such a problem can be effectively solved.

  In addition, in the manufacturing method mentioned above, although the method of employ | adopting the manufacturing process which sandwiches both surfaces of the composition layer 10a for porous structures with the base material 30 provided with the composition layer 20a for modified layers was illustrated, For the upper surface of the composition layer 10a for the porous structure, a method of forming only the composition layer 20a for the modified layer is employed instead of the method of placing the base material 30 provided with the composition layer 20a for the modified layer. May be.

  Moreover, in the manufacturing method mentioned above, both of the composition layer 20a for modified layers which contacts both surfaces of the composition layer 10a for porous structures react with the compound which comprises the composition layer 10a for porous structures. In the obtained porous membrane, the configuration in which the modified layer 20 is formed on both surfaces of the porous structure 10 is exemplified, but the modified layer composition that contacts both surfaces of the porous structure composition layer 10a. Only one of the physical layers 20a may be configured to react with the compound constituting the composition layer 10a for the porous structure. That is, in this case, the modified layer 20 is formed only on one side of the porous structure 10 in the obtained porous film.

  Furthermore, in the manufacturing method mentioned above, an epoxy resin composition is used as the compound constituting the composition layer 10a for the porous structure, and polyvinyl alcohol is used as the compound constituting the composition layer 20a for the modified layer. Although such an aspect was illustrated and demonstrated in particular, it is not limited to these, Of course, various compounds can be used in various combinations.

  For example, a compound that dissolves in an electrolyte solvent used in a secondary battery or a fuel cell can be used as the compound constituting the composition layer 20a for the modified layer. In this case, the composition layer for the modified layer is used. After a part of 20a is removed together with the base material 30, it can be used as an electrolyte application without passing through a drying step or the like.

  Further, when the porous membrane of the present invention is used for such an electrolyte application, for example, when an ionic liquid is used as an electrolyte, as an epoxy resin for forming the porous structure composition layer 10a, a porogen Instead, an ionic liquid may be used. In this case, since it is preferable to leave the ionic liquid in the porous membrane of the present invention, it is desirable to leave the ionic liquid in the porous structure 10 without extraction, unlike the case of porogen.

〔上記一般式（１）中、Ｒ^１〜Ｒ^４は互いに同一もしくは異種の炭素数１〜５のアルキル基、またはＲ’−Ｏ−（ＣＨ_２）_ｎ−で表されるアルコキシアルキル基（Ｒ’はメチル基またはエチル基を示し、ｎは１〜４の整数である。）を示し、これらＲ^１、Ｒ^２、Ｒ^３およびＲ^４のいずれか２個の基が環を形成していても構わない。ただし、Ｒ^１〜Ｒ^４の内少なくとも１つは上記アルコキシアルキル基である。Ｘは窒素原子またはリン原子を示し、Ｙは一価のアニオンを示す。〕 As the ionic liquid, for example, one represented by the following general formula (1) and having a melting point of 50 ° C. or lower, preferably 25 ° C. or lower can be used.

[In General Formula (1), R ^{1 to} R ⁴ are the same or different alkyl groups having 1 to 5 carbon atoms, or an alkoxyalkyl group represented by R′—O— (CH ₂ ) _n — (R 'Represents a methyl group or an ethyl group, and n is an integer of 1 to 4.), and any two groups of R ¹ , R ² , R ³ and R ⁴ form a ring. It doesn't matter. However, at least one of R ^{1 to} R ⁴ is the alkoxyalkyl group. X represents a nitrogen atom or a phosphorus atom, and Y represents a monovalent anion. ]

Examples of the alkyl group having 1 to 5 carbon atoms include methyl group, ethyl group, propyl group, 2-propyl group, butyl group, and pentyl group. Examples of the alkoxyalkyl group represented by R′—O— (CH ₂ ) _n — include a methoxy or ethoxymethyl group, a methoxy or ethoxyethyl group, a methoxy or ethoxypropyl group, and a methoxy or ethoxybutyl group.

In addition, as a compound in which any two groups of R ¹ , R ² , R ³ and R ⁴ form a ring, when a nitrogen atom is employed for X, an aziridine ring, an azetidine ring, a pyrrolidine ring And quaternary ammonium salts having a piperidine ring, etc., on the other hand, when a phosphorus atom is employed for X, quaternary phosphonium salts having a pentamethylenephosphine (phosphorinane) ring and the like can be mentioned.

〔上記一般式（２）中、Ｒ’はメチル基またはエチル基を示し、Ｘは窒素原子またはリン原子を示し、Ｙは一価のアニオンを示す。また、Ｍｅはメチル基を、Ｅｔはエチル基を意味する。〕 In particular, a quaternary ammonium salt having at least one methoxyethyl group in which R ′ is a methyl group and n is 2 is preferable as a substituent.
Moreover, the quaternary salt shown by following General formula (2) which has a methyl group, two ethyl groups, and an alkoxyethyl group as a substituent can also be used suitably.

[In the general formula (2), R ′ represents a methyl group or an ethyl group, X represents a nitrogen atom or a phosphorus atom, and Y represents a monovalent anion. Me represents a methyl group, and Et represents an ethyl group. ]

The monovalent anion Y in the general formulas (1) and (2) is not particularly limited, and BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , AlCl ₄ ⁻ , NbF ₆ ^−. , HSO ₄ ⁻ , ClO ₄ ⁻ , CH ₃ SO ₃ ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ CO ₂ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , Cl ⁻ , Br ⁻ , I ^{− and the} like are used. However, considering the dissociation degree, stability, mobility and the like in a non-aqueous organic solvent, BF ₄ ⁻ , PF ₆ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , CF ₃ SO ₃ ⁻ Or CF ₃ CO ₂ ^— .

In the present invention, among the quaternary salts represented by the general formulas (1) and (2), specific examples of the quaternary ammonium salt and quaternary phosphonium salt that are preferably used include the following compounds (3) to ( 11) (Me represents a methyl group, Et represents an ethyl group), and in particular, 4 4 represented by the following formula (3) or (8) in consideration of obtaining an electricity storage device having excellent low-temperature characteristics and the like. It is more preferable to use a quaternary ammonium salt.

  In addition, when using an ionic liquid instead of a porogen, it is preferable to contain electrolyte salt (For example, electrolyte salt for secondary batteries, electrolyte salt for fuel cells) with an ionic liquid.

〔上記一般式（１２）中、ｍは、１以上１０以下の整数を示す。ｎは、１以上５以下の整数を示す。Ｒ^５は、水素原子、または炭素数１〜３のアルキル基を示す。Ｒ^６、Ｒ^７、Ｒ^８は、炭素数１〜５のアルキル基を示す。Ｒ^６、Ｒ^７、Ｒ^８は、酸素原子、硫黄原子、フッ素原子から選ばれる１種以上のヘテロ原子を含んでいてもよく、Ｒ^６、Ｒ^７、Ｒ^８は、２つ以上が連結して環状構造であってもよい。また、Ｙは上記一般式（１）と同様である。〕 In the case of using an ionic liquid instead of the porogen, in order to improve the affinity between the ionic liquid and the porous structure 10 having a co-continuous structure, the porous structure before curing is used. It is preferable that the epoxy resin composition for forming the composition layer 10a contains a monomer having high affinity with the ionic liquid and polymerizable with the epoxy resin and / or the curing agent. By using such a monomer, a functional group having a high affinity with the ionic liquid can be introduced into the porous structure 10, and thereby the affinity between the porous structure 10 and the ionic liquid. Can be increased. Such a monomer is not particularly limited, and examples thereof include compounds represented by the following general formula (12).

[In the general formula (12), m represents an integer of 1 or more and 10 or less. n represents an integer of 1 to 5. R ⁵ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. R ⁶ , R ⁷ and R ⁸ represent an alkyl group having 1 to 5 carbon atoms. R ⁶ , R ⁷ and R ⁸ may contain one or more heteroatoms selected from an oxygen atom, a sulfur atom and a fluorine atom, and two or more of R ⁶ , R ⁷ and R ⁸ are linked together. It may be a ring structure. Y is the same as in the general formula (1). ]

〔上記一般式（１３）〜（２０）中、ｍ、Ｒ^５、Ｒ^６、Ｙは、上記一般式（１２）と同様である。〕 Among the compounds represented by the general formula (12), compounds represented by the following general formulas (13) to (20) can be particularly preferably used.

[In the general formulas (13) to (20), m, R ⁵ , R ⁶ and Y are the same as those in the general formula (12). ]

  Moreover, when the compound represented by the general formula (12) is blended in the epoxy resin composition for forming the composition layer 10a for the porous structure before curing, the epoxy resin composition contains Instead of containing an ionic liquid, instead of containing the porogen described above and performing a curing treatment on the composition layer 10a for the porous structure, the porogen is extracted, and the porogen is extracted together with the electrolyte salt Alternatively, the structure may be soaked with an ionic liquid.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

Example 1
Preparation of Polyvinyl Alcohol Solution An aqueous solution of polyvinyl alcohol (PVA) (manufactured by Wako Pure Chemical Industries, Ltd.) having an average polymerization degree n of 3500 and a saponification degree of 86 to 90% was prepared as a 2% by weight aqueous solution and used.

Preparation of epoxy resin composition 4 parts by weight of an epoxy compound represented by the following formula (21) having an epoxy equivalent of 95 to 110 (average of 102) (trade name “Tetrad C”, Nissan Chemical Industries, Ltd.), amine value is 0.575 parts by weight of bis (4-aminocyclohexyl) methane (manufactured by Tokyo Chemical Industry Co., Ltd.) represented by the following formula (22) that is 520 to 550, and the following formula (23 An epoxy resin composition was obtained by mixing 1 weight of polyethylene glycol 200 (manufactured by Wako Pure Chemical Industries, Ltd.).

Production of Porous Membrane The 2% by weight aqueous solution of polyvinyl alcohol prepared above was applied to two 75 mm × 75 mm glass plates using a spin coater at 2,000 rpm for 20 seconds, and then at 105 ° C. for 1 hour. The two glass plates in which the polyvinyl alcohol layer (modified layer composition layer 20a) was formed were obtained by performing the annealing treatment.

  Next, by casting 640 mg of the epoxy resin composition prepared above on the surface of the glass plate on which the polyvinyl alcohol layer is formed, the epoxy resin composition layer (the composition layer for porous structure) 10a), and then the glass plate on which the polyvinyl alcohol layer is formed is directly placed on the epoxy resin composition layer so that the polyvinyl alcohol layer-forming surface is in contact with the epoxy resin composition layer. Thus, the laminate shown in FIG. 2C was obtained.

  And the epoxy compound in an epoxy resin composition layer was hardened by heating the obtained laminated body at 110 degreeC for 1 hour, and the cured laminated body was obtained. Next, the cured laminated body after heating is poured into warm water adjusted to a temperature of 50 to 60 ° C. and left for 5 to 20 minutes to extract the polyethylene glycol 200 contained in the heated epoxy resin composition layer. And the porous film which has a structure as shown in FIG. 1 was obtained by peeling a part of polyvinyl alcohol layer with a glass plate. The obtained porous film was collected on a fluorine film (manufactured by Nitto Denko Corporation), washed with methanol for about 30 minutes, and then dried overnight at 105 ° C. under vacuum.

The porous film thus obtained had a total thickness of 25 μm, and the average pore diameter of the macropores of the porous structure 10 measured by scanning electron microscope observation was 0.3 to 0.6 μm. Further, when the obtained porous film was analyzed by infrared absorption spectroscopy, it was confirmed that a modified layer made of polyvinyl alcohol was formed on both main surfaces of the porous structure 10. Specifically, FT-IR measurement is performed on each of a porous film formed with a modified layer made of polyvinyl alcohol and a porous film not formed with a modified layer made of polyvinyl alcohol, and the difference spectrum thereof is taken. Thus, formation of a modified layer made of polyvinyl alcohol was confirmed based on a peak (peak near 1730 cm ⁻¹ ) based on an ester bond (ester bond remaining without being saponified) contained in polyvinyl alcohol. Moreover, when ion conductivity was measured by complex impedance measurement about the obtained porous membrane, it became 10 ^<-4 > S / cm or more, and has confirmed having high ion conductivity.

Example 2
As the polyvinyl alcohol aqueous solution for forming the polyvinyl alcohol layer, a 480 mg amount of the epoxy resin composition cast on the polyvinyl alcohol layer forming surface of the glass plate on which the 3% by weight aqueous solution is used and the polyvinyl alcohol layer is formed. Except for the above, a porous membrane having the structure shown in FIG. 1 was obtained in the same manner as in Example 1.

And the porous film obtained in this way was 20 micrometers in total thickness, and the average hole diameter of the macropore measured like Example 1 was 0.3-0.6 micrometer. Further, when the obtained porous film was analyzed by infrared absorption spectroscopy in the same manner as in Example 1, it was found that modified layers made of polyvinyl alcohol were formed on both main surfaces of the porous structure 10. Was confirmed. Further, when the ionic conductivity of the obtained porous membrane was measured in the same manner as in Example 1, it was 10 ⁻⁴ S / cm or more, and it was confirmed that the ionic conductivity was high.

Example 3
As a polyvinyl alcohol aqueous solution for forming the polyvinyl alcohol layer, a 720 mg amount of the epoxy resin composition to be cast on the polyvinyl alcohol layer forming surface of the glass plate using the 3% by weight aqueous solution and forming the polyvinyl alcohol layer is used. Except for the above, a porous membrane having the structure shown in FIG. 1 was obtained in the same manner as in Example 1.

And the porous film obtained in this way was 40-50 micrometers in total thickness, and the average hole diameter of the macropore measured like Example 1 was 0.3-0.6 micrometer. Further, when the obtained porous film was analyzed by infrared absorption spectroscopy in the same manner as in Example 1, it was found that modified layers made of polyvinyl alcohol were formed on both main surfaces of the porous structure 10. Was confirmed. Further, when the ionic conductivity of the obtained porous membrane was measured in the same manner as in Example 1, it was 10 ⁻⁴ S / cm or more, and it was confirmed that the ionic conductivity was high.

Example 4
As a polyvinyl alcohol aqueous solution for forming a polyvinyl alcohol layer, a 1% by weight aqueous solution is used, a glass plate having a size of 25 mm × 25 mm is used, and a polyvinyl alcohol layer-forming surface of a glass plate on which a polyvinyl alcohol layer is formed In addition, a porous membrane having the structure shown in FIG. 1 was obtained in the same manner as in Example 1 except that the amount of the epoxy resin composition to be cast was 32 mg.

And the porous film obtained in this way was 10 micrometers in total thickness, and the average hole diameter of the macropore measured like Example 1 was 0.3-0.6 micrometer. Further, when the obtained porous film was analyzed by infrared absorption spectroscopy in the same manner as in Example 1, it was found that modified layers made of polyvinyl alcohol were formed on both main surfaces of the porous structure 10. Was confirmed. Further, when the ionic conductivity of the obtained porous membrane was measured in the same manner as in Example 1, it was 10 ⁻⁴ S / cm or more, and it was confirmed that the ionic conductivity was high.

Example 5
Preparation of Epoxy Resin Composition Containing Ionic Liquid 2.4 parts by weight of aromatic epoxy resin (trade name “TEPIC-S”, manufactured by Nissan Chemical Industries, Ltd.) is used as an ionic liquid (N, N-diethyl-N -Methyl-N- (2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) imide (manufactured by Kanto Chemical Co., Ltd.) 6.0 parts by weight, 4,4′-methylenebis (cyclohexylamine) (manufactured by Tokyo Chemical Industry Co., Ltd.) An epoxy resin composition containing an ionic liquid is mixed by mixing 0.54 parts by weight and 0.3 parts by weight of glycidyltrimethylammonium chloride (trade name “SY-GTA-80”, manufactured by Sakamoto Pharmaceutical Co., Ltd.). Obtained.

Production of Porous Membrane The 2% by weight aqueous solution of polyvinyl alcohol prepared above was applied to two 75 mm × 75 mm glass plates using a spin coater at 2,000 rpm for 20 seconds, and then at 105 ° C. for 1 hour. The two glass plates in which the polyvinyl alcohol layer (modified layer composition layer 20a) was formed were obtained by performing the annealing treatment.

  Next, the epoxy resin composition containing the ionic liquid is cast by casting 640 mg of the epoxy resin composition containing the ionic liquid prepared above on the polyvinyl alcohol layer forming surface of the glass plate on which the polyvinyl alcohol layer is formed. Layer (porous structure composition layer 10a), and then a glass plate on which a polyvinyl alcohol layer is formed, and an epoxy resin composition layer on which the polyvinyl alcohol layer-forming surface contains an ionic liquid Directly on the epoxy resin composition layer containing the ionic liquid so as to come into contact, a laminate shown in FIG. 2C was obtained.

  And the epoxy compound in the epoxy resin composition layer containing an ionic liquid was hardened by heating the obtained laminated body at 110 degreeC for 1 hour, and the cured laminated body was obtained. Next, a part of the polyvinyl alcohol layer was peeled off together with the glass plate from the cured laminate to obtain a porous film having a configuration as shown in FIG.

The porous film thus obtained has a total thickness of 25 μm, and the porous structure 10 measured by observation with a scanning electron microscope has (N, N-diethyl-N-methyl-N— as an ionic liquid). (2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) imide is contained, and the average pore diameter of the macropores is 0.3 to 0.6 μm. As a result of analysis by external absorption spectroscopy, it was confirmed that a modified layer made of polyvinyl alcohol was formed on both main surfaces of the porous structure 10. Further, the obtained porous film was measured by complex impedance measurement. measurement of the ionic conductivity was confirmed to have a 10 -4 ^{S / cm} or more and becomes high ionic conductivity. in examples 5, resulting et al And the SEM photograph of the porous structure 10 portion of the membrane shown in FIG.

DESCRIPTION OF SYMBOLS 10 ... Porous structure 10a ... Composition layer 20 for porous structures ... Modified layer 20a ... Composition layer 30 for modified layers ... Base material

Claims (14)

A porous membrane comprising a membrane-like porous structure having a co-continuous structure,
A porous membrane, wherein at least one main surface of the porous structure is modified with a modifying compound different from a compound constituting the porous structure. At least one main surface of the porous structure is coated with the main surface, and a modified layer composed of the modifying compound is formed,
The porous film according to claim 1, wherein the modified layer is a porous layer or a non-porous layer having an average pore size smaller than an average pore size of voids of the porous structure.   The porous membrane according to claim 2, wherein the thickness of the modified layer is 1000 nm or less.   The porous membrane according to claim 1, wherein both main surfaces of the porous structure are modified with the modifying compound.   The porous membrane according to claim 1, wherein the porous membrane structure is made of a cured epoxy resin.   The porous membrane according to claim 1, wherein the modifying compound has a functional group that reacts with a compound constituting the porous membrane structure.   The porous membrane according to claim 1, wherein the porous membrane structure contains an ionic liquid in the voids.   The porous membrane according to any one of claims 1 to 7, wherein the porous membrane structure has mesopores having a pore diameter of 1 nm to 1 µm in the skeleton.   The porous membrane structure is compatible with the monomer constituting the porous membrane structure, and is compatible with the monomer and is incompatible with the polymer obtained by polymerizing the monomer. The porous membrane according to any one of claims 1 to 8, wherein the porous membrane is formed by polymerization-induced phase separation using a soluble compound.   An electrolyte membrane obtained by impregnating the porous membrane according to any one of claims 1 to 9 with an electrolyte.   A secondary battery comprising the electrolyte membrane according to claim 10.   A fuel cell comprising the electrolyte membrane according to claim 10.   An electric double layer capacitor comprising the electrolyte membrane according to claim 10.   A dye-sensitized solar cell comprising the electrolyte membrane according to claim 10.

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