JP2016069606A - Fluorine-containing copolymer fluid dispersion, coating liquid, and fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluorine-containing polymer fluid dispersion having excellent dispersibility of a fluorine-containing polymer in a solvent, a coating liquid having good dispersibility of an electrode material, and a fuel cell having a catalyst layer formed by using the coating liquid.SOLUTION: The fluorine-containing copolymer fluid dispersion which comprises a fluorine-containing a copolymer obtained by introducing a graft chain in an ethylene/tetrafluoroethylene copolymer by graft polymerization, and a solvent, and in which the graft chain has an ion exchange group. The coating liquid comprises the fluorine-containing copolymer fluid dispersion and an electrode material. The fuel cell comprises a catalyst layer formed by using the coating liquid.SELECTED DRAWING: None

Description

  The present invention relates to a fluorine-containing copolymer dispersion, a coating liquid, and a fuel cell.

In a polymer electrolyte fuel cell, an ethylene / tetrafluoroethylene copolymer membrane having an ion exchange group is used as a solid electrolyte (see, for example, Patent Document 1). However, the ethylene / tetrafluoroethylene copolymer having the ion exchange group has high chemical resistance, and therefore has low solubility in a solvent. Therefore, it is difficult to form a fuel cell electrode using an ethylene / tetrafluoroethylene copolymer having an ion exchange group as a binder.
As a method for dissolving an ethylene / tetrafluoroethylene copolymer in a solvent, a method using a hydrocarbon solvent having a carbonyl group is known (for example, see Patent Document 2).

JP 2000-331693 A International Publication No. 2011/002041

  In the method described in Patent Document 2, the ethylene / tetrafluoroethylene copolymer can be dissolved at a relatively high temperature, but the ethylene / tetrafluoroethylene copolymer is dispersed in the solvent even at a lower temperature. A dispersion is desired.

  An object of the present invention is to provide a fluorine-containing copolymer dispersion having excellent dispersibility of the fluorine-containing copolymer in a solvent. Another object of the present invention is to provide a coating solution that is excellent in dispersibility of an electrode material, and to provide a fuel cell having a catalyst layer formed using the coating solution.

  As a result of intensive studies, the present inventor has found that a fluorine-containing copolymer dispersion containing an ethylene / tetrafluoroethylene copolymer having an ion exchange group and a solvent is excellent in dispersibility. The present invention was invented based on such findings.

  According to the present invention, there are provided a fluorinated copolymer dispersion, a coating liquid and a fuel cell having the following constitution.

[1] A fluorine-containing copolymer obtained by introducing a graft chain into an ethylene / tetrafluoroethylene copolymer by graft polymerization, and a solvent, wherein the graft chain has an ion exchange group, Fluorine-containing copolymer dispersion.

[2] The ethylene / tetrafluoroethylene copolymer is
Ethylene / tetrafluoroethylene / fluoroolefin copolymer having no hydrogen atom in the unsaturated group,
Ethylene / tetrafluoroethylene / fluoroalkylethylene copolymer,
Ethylene / tetrafluoroethylene / fluoroolefin / fluoroalkylethylene copolymer having no hydrogen atom in unsaturated group, and ethylene / tetrafluoroethylene / fluoroolefin / fluoroalkylethylene / polar functional group having no hydrogen atom in unsaturated group The fluorine-containing copolymer dispersion according to [1] above, which is a copolymer selected from the group consisting of a monomer copolymer having a group.

[3] The fluorinated copolymer dispersion according to [2], wherein the fluoroolefin having no hydrogen atom in the unsaturated group is hexafluoropropylene.

[4] The fluorine-containing copolymer dispersion according to any one of [1] to [3], wherein the fluoroalkylethylene is a compound represented by the following general formula (M1): liquid.
CH ₂ = CX (CF ₂ ) _n Y (M1)
(In the general formula (M1),
X and Y are independently hydrogen or a fluorine atom;
n is an integer of 2-8. )

[5] The above fluoroalkylethylene is a compound in which X in the general formula (M1) is a hydrogen atom, Y is a fluorine atom, and n is 4. Fluorine-containing copolymer dispersion.

[6] The fluorine-containing copolymer dispersion according to any one of [2] to [5], wherein the monomer having a polar functional group is a monomer having an acid anhydride residue. liquid.

[7] The fluorine-containing copolymer according to any one of [1] to [6], wherein the ethylene / tetrafluoroethylene copolymer has a melting point of 120 ° C. or higher and 230 ° C. or lower. Dispersion.

[8] The above [1] to [7], wherein the fluorine-containing copolymer has an ion exchange capacity of 1.0 meq / g dry resin to 5.0 meq / g dry resin. The fluorinated copolymer dispersion according to any one of the above.

[9] The fluorine-containing copolymer dispersion according to any one of [1] to [8], wherein the solvent is a chain ketone.

[10] The fluorinated copolymer dispersion according to any one of [1] to [8], wherein the solvent is diisopropyl ketone.

[11] A coating liquid comprising the fluorine-containing copolymer dispersion liquid according to any one of [1] to [10], and an electrode material.

[12] A fuel cell having a catalyst layer formed using the coating liquid according to [11].

  ADVANTAGE OF THE INVENTION According to this invention, the fluorine-containing copolymer dispersion liquid which is excellent in the dispersibility of the fluorine-containing copolymer in a solvent can be provided. Moreover, according to this invention, the fuel cell which has the coating liquid which is excellent in the dispersibility of electrode material, and the catalyst layer formed using the said coating liquid can be provided.

  The fluorine-containing copolymer dispersion of the present invention contains a fluorine-containing copolymer having a graft chain and a solvent. The fluorine-containing copolymer having a graft chain is dispersed in a solvent. The fluorine-containing copolymer in the present invention has a structure in which a graft chain is introduced into an ethylene / tetrafluoroethylene copolymer by graft polymerization, and this graft chain has an ion exchange group. In this specification, “dispersed” means a state in which the fluorinated copolymer is dissolved in a solvent, or fine particles of the fluorinated copolymer are not uniformly dispersed and precipitated in the solvent. State.

(Ethylene / tetrafluoroethylene copolymer)
An ethylene / tetrafluoroethylene copolymer (hereinafter, also referred to as “ETFE”) includes ethylene (hereinafter, ethylene is also referred to as “E”), tetrafluoroethylene (hereinafter, also referred to as “TFE”), Is obtained by copolymerization. The molar ratio of the repeating unit based on ethylene and the repeating unit based on tetrafluoroethylene in ETFE is preferably 80/20 to 20/80, more preferably 70/30 to 30/70, and more preferably 50/50 to 35/65. Further preferred. When the molar ratio M _E / M _{TFE of} (repeating unit based on E) / (repeating unit based on TFE) is in the above range, the heat resistance, weather resistance, chemical resistance and chemical solution permeation resistance of the fluorine-containing copolymer , Mechanical strength, melt moldability and the like are excellent. When the molar ratio M _E / M _TFE is extremely larger than 80/20, the heat resistance, weather resistance, chemical resistance, chemical liquid permeation prevention and the like of the fluorinated copolymer may be lowered. On the other hand, if the molar ratio M _E / M _TFE is extremely smaller than 20/80, the mechanical strength and melt moldability of the fluorinated copolymer may be lowered.

ETFE may be composed of only a repeating unit based on E and a repeating unit based on TFE. Further, ETFE may contain a repeating unit based on another monomer in addition to the repeating unit based on E and the repeating unit based on TFE as long as the essential characteristics of ETFE are not impaired.
Examples of the other monomer include compounds selected from the group consisting of monomers shown in the following (1) to (7), and one or more other monomers can be used.

(1) α-olefins (2) Fluoroolefin having a hydrogen atom in an unsaturated group (3) Fluoroolefin not having a hydrogen atom in an unsaturated group (excluding TFE)
(4) Perfluoro (alkyl vinyl ether) (PAVE)
(5) Perfluorovinyl ethers having two unsaturated bonds (6) Fluorinated monomers having an aliphatic ring structure (7) Monomers having a polar functional group

  Examples of the α-olefins of (1) include propylene and butene.

Examples of the fluoroolefin having a hydrogen atom in the unsaturated group (2) include vinylidene fluoride (VDF), vinyl fluoride (VF), trifluoroethylene, and hexafluoroisobutylene (HFIB).
Moreover, as a fluoroolefin which has a hydrogen atom in the unsaturated group of said (2), it is also preferable that it is a compound represented by the following general formula (M1).
CH ₂ = CX (CF ₂ ) _n Y (M1)
(In the general formula (M1),
X and Y are independently hydrogen or a fluorine atom;
n is an integer of 2-8. )

  Examples of the fluoroolefin having no hydrogen atom in the unsaturated group (3) include hexafluoropropylene (HFP) and chlorotrifluoroethylene (CTFE).

  The perfluoro (alkyl vinyl ether) (PAVE) of (4) is perfluoro (methyl vinyl ether) (PMVE), perfluoro (ethyl vinyl ether) (PEVE), perfluoro (propyl vinyl ether) (PPVE), and perfluoro (butyl vinyl ether) ( PBVE) and the like.

The perfluorovinyl ethers having two unsaturated bonds of the (5), for _{example, CF 2 = CFOCF 2 CF =} CF 2, and _{CF 2 = CFO (CF 2)} 2 CF = CF 2 , and the like.

  Examples of the fluorine-containing monomer having an aliphatic ring structure (6) include perfluoro (2,2-dimethyl-1,3-dioxole) (PDD), 2,2,4-trifluoro-5-tri Examples include fluoromethoxy-1,3-dioxole and perfluoro (2-methylene-4-methyl-1,3-dioxolane).

  As the monomer having a polar functional group (7), for example, a compound selected from the group consisting of vinyl ethers having a hydroxyl group or an epoxy group, acids having a carboxy group, and monomers having an acid anhydride residue is preferable. . Examples of the acid having a carboxy group include maleic acid, itaconic acid, citraconic acid, and undecylenic acid. Examples of the monomer having an acid anhydride residue include maleic anhydride, itaconic anhydride, citraconic anhydride, and hymic anhydride. The monomer (7) having a polar functional group is preferably maleic anhydride, itaconic anhydride or anhydrous hymic acid, more preferably itaconic anhydride or anhydrous hymic acid. By using a monomer having an acid anhydride residue as the other monomer, the adhesiveness of the fluorinated copolymer is improved.

  As the other monomer, a compound represented by the general formula (M1) of the above (2) (hereinafter sometimes referred to as “fluoroalkylethylene” or “FAE”) is preferable. When n in the general formula (M1) is 2 or more, sufficient characteristics such as excellent stress crack resistance of the fluorine-containing copolymer can be obtained. When n in the general formula (M1) is 8 or less, the polymerization reactivity is excellent.

As FAE, the compound represented by the following general formula (M2) is more preferable.
CH ₂ = CH (CF ₂ ) _n Y (M2)
In the general formula (M2), Y is hydrogen or a fluorine atom, and n is preferably an integer of 2 or more and 6 or less, more preferably an integer of 2 or more and 4 or less. In the general formula (M2), when n is within the above range, the stress-resistant crack resistance of the fluorine-containing copolymer is remarkably excellent. In the general formula (M2), Y is preferably a fluorine atom.

As FAE, for example, CH ₂ = CF (CF ₂ ) ₂ F, CH ₂ = CF (CF ₂ ) ₃ F, CH ₂ = CF (CF ₂ ) ₄ F, CH ₂ = CF (CF ₂ ) ₅ F, _{CH 2 = CF (CF 2)} 8 F, CH 2 = CF (CF 2) 2 H, CH 2 = CF (CF 2) 3 H, CH 2 = CF (CF 2) 4 H, CH 2 = CF (CF _{2) 5 H, CH 2 =} CF (CF 2) 8 H, CH 2 = CH (CF 2) 2 F, CH 2 = CH (CF 2) 3 F, CH 2 = CH (CF 2) 4 F, CH ₂ = CH (CF ₂ ) ₅ F, CH ₂ = CH (CF ₂ ) ₈ F, CH ₂ = CH (CF ₂ ) ₂ H, CH ₂ = CH (CF ₂ ) ₃ H, CH ₂ = CH (CF _{2 ) 4 H, CH 2 = CH} (CF 2) 5 H, and _{CH 2 = CH (CF 2)} 8 Etc. The.
One or more FAEs can be used.

  The content of repeating units based on other monomers in ETFE is preferably 0.1 mol% or more and 30 mol% or less, and 0.5 mol% or more and 20 mol% or less with respect to all repeating units of the ETFE. More preferably, it is 1 mol% or more and 15 mol% or less. If the content of the other monomer is 0.1 mol% or more, the fluorine-containing copolymer has excellent stress crack resistance, suppresses the occurrence of fracture phenomena such as cracking under stress, and dispersibility in solvents. Will improve. Furthermore, the dispersion containing the fluorine-containing copolymer is excellent in dispersibility of a catalyst, carbon, and the like. When the content of other monomers is 30 mol% or less, the fluorine-containing copolymer is excellent in mechanical strength or chemical resistance.

ETFE is preferably any of the copolymers shown in the following (CP1) to (CP4).
(CP1) A repeating unit based on E, a repeating unit based on TFE, and a repeating unit based on a fluoroolefin having no hydrogen atom in an unsaturated group (hereinafter also referred to as “FO”). Polymer ''
(CP2) "E / TFE / FAE copolymer" comprising a repeating unit based on E, a repeating unit based on TFE, and a repeating unit based on FAE
(CP3) "E / TFE / FO / FAE copolymer" comprising repeating units based on E, repeating units based on TFE, repeating units based on FO, and repeating units based on FAE, or repeating based on (CP4) E "E / TFE / FO / FAE / monomer copolymer with polar functional group" including units, repeating units based on TFE, repeating units based on FO, repeating units based on FAE, and repeating units based on monomers having polar functional groups Merge

  The fluorine-containing copolymer in which a graft chain is introduced by graft polymerization to the copolymers shown in the above (CP1) to (CP4) and an ion exchange group is introduced into the graft chain is further excellent in dispersibility in a solvent. . Among the ETFEs shown in (CP1) to (CP4), “E / TFE / FO / FAE copolymer” or “E / TFE / FO / FAE / monomer copolymer having a polar functional group” is more preferable. .

In the copolymer shown in (CP1), (CP3) and (CP4), the repeating unit based on fluoroolefin (FO) having no hydrogen atom in the unsaturated group is a repeating unit based on hexafluoropropylene (HFP). Is preferred. In this case, each copolymer is represented by the following (CP1A), (CP3A) and (CP4A), and a copolymer represented by (CP3A) or (CP4A) is preferable.
(CP1A): “E / TFE / HFP copolymer”
(CP3A): “E / TFE / HFP / FAE copolymer”
(CP4A): “E / TFE / HFP / FAE / monomer copolymer having a polar functional group”

  Moreover, as a monomer which has a polar functional group in the copolymer shown to said (CP4) or said (CP4A), the monomer which has an acid anhydride residue is preferable.

  Examples of ETFE include an alternating copolymer, a random copolymer, a block copolymer, and the like. In the present invention, an alternating copolymer in which repeating units based on each monomer constituting ETFE are alternately bonded. A polymer is preferred.

  The melting point of ETFE is preferably 120 ° C. or higher and 230 ° C. or lower, more preferably 130 ° C. or higher and 210 ° C. or lower, and further preferably 150 ° C. or higher and 200 ° C. or lower. When the melting point of ETFE is 120 ° C. or higher, the resin can be prevented from melting when the fluorine-containing copolymer of the present invention is used, or the mechanical strength can be prevented from being lowered. When the melting point of ETFE is 230 ° C. or lower, the dispersibility of the fluorinated copolymer in the present invention is improved.

The capacity flow rate (hereinafter referred to as Q value) of ETFE is preferably 0.1 mm ³ / sec or more and 500 mm ³ / sec or less, more preferably 0.5 mm ³ / sec or more and 200 mm ³ / sec or less. More preferably, it is 1 mm ³ / sec or more and 100 mm ³ / sec or less.
The Q value is an index representing the melt fluidity of ETFE and is a measure of molecular weight. A large Q value indicates a low molecular weight, and a small Q value indicates a high molecular weight. The Q value was measured using a Shimadzu flow tester (furnace cross-sectional area = 1 cm ² ) at a temperature about 50 ° C higher than the melting point of the resin in an orifice with a diameter of 2.1 mm and a length of 8 mm under a load of 7 kg. It is the extrusion speed of ETFE when taking out. When the Q value is in the above range, ETFE is excellent in chemical resistance.

  As a method for producing ETFE, a method of copolymerizing ethylene and tetrafluoroethylene can be mentioned. Moreover, when manufacturing ETFE containing the repeating unit based on another monomer, the manufacturing method of copolymerizing E, TFE, and another monomer is mentioned. Examples of the polymerization method include solution polymerization, suspension polymerization, emulsion polymerization, bulk polymerization, and the like.

(Fluorine-containing copolymer)
In order to obtain the fluorine-containing copolymer having a graft chain in the present invention, it is preferable to graft polymerize a monomer having an ion exchange group to ETFE. The ion exchange group may be contained in the graft chain at the time of graft polymerization with respect to ETFE. Alternatively, after the graft polymerization, the graft chain may be treated to form an ion exchange group.

In order to graft polymerize a monomer having an ion exchange group with ETFE, for example, the following method can be employed. First, the ETFE is irradiated with radiation to generate radicals in the polymer chain. Then, the graft chain which has an ion exchange group can be introduce | transduced into ETFE by making the polymer chain of ETFE which generated the radical, and the monomer which has an ion exchange group contact.
The monomer used for the graft polymerization is preferably a monomer containing an anion exchange group or a monomer containing a group capable of introducing an anion exchange group.

  The monomer containing an anion exchange group is selected from the group consisting of vinylbenzyltrimethylammonium salt, quaternary salt of 4-vinylpyridine, quaternary salt of 2-vinylpyridine, and quaternary salt of N-vinylimidazole. More than species are preferred.

  The monomer containing a group capable of introducing an anion exchange group is one or more selected from the group consisting of p-chloromethylstyrene, m-chloromethylstyrene, 4-vinylpyridine, 2-vinylpyridine, and N-vinylimidazole. Is preferred.

When the monomer used for the graft polymerization is a liquid, ETFE may be directly immersed, or ETFE may be immersed after the monomer is diluted with a solvent.
Alternatively, the monomer may be vaporized under reduced pressure and contacted with ETFE. When the monomer is vaporized, it may be diluted with an inert gas such as nitrogen.
When the monomer is solid, it is preferable to prepare a monomer solution by dissolving in a solvent in which the monomer is dissolved, and immerse ETFE in the monomer solution.

Examples of radiation to be irradiated include α-rays, β-rays, γ-rays, electron beams, and ultraviolet rays, and γ-rays or electron beams are preferably used.
The radiation dose is preferably 1 kGy or more and 200 kGy or less, and more preferably 10 kGy or more and 100 kGy or less. If the irradiation dose for ETFE is 1 kGy or more, graft polymerization proceeds efficiently. If the irradiation dose with respect to ETFE is 200 kGy or less, the molecular chain breakage of ETFE is suppressed, and the strength reduction of ETFE is also suppressed. As a result, a decrease in strength of the resulting fluorinated copolymer is also suppressed. If the irradiation dose is 10 kGy or more and 100 kGy or less, it is more preferable because there is no decrease in the strength of ETFE and the graft polymerization proceeds efficiently.

  Examples of the radiation graft polymerization method include the following methods. There is a method in which radiation is irradiated while ETFE is immersed in a monomer solution in which a monomer used for graft polymerization is dissolved. There is also a method of polymerizing by irradiating ETFE with radiation and then immersing it in the monomer solution. Of these two methods, the latter method is preferred from the viewpoint of handleability. In order to obtain the fluorine-containing copolymer having a graft chain in the present invention, the method is not limited to these radiation graft polymerization methods.

Irradiation is preferably performed under reduced pressure or in an inert gas atmosphere such as nitrogen in order to protect the generated radicals.
ETFE after irradiation is preferably kept at a low temperature until contact with the monomer in order to prevent a decrease in radical concentration. Even when ETFE after irradiation is immersed in the monomer solution, it is preferably performed under reduced pressure or in an inert gas atmosphere, and the radiation graft polymerization is preferably performed at a temperature of 40 ° C. or higher and 90 ° C. or lower.

When the monomer to be subjected to radiation graft polymerization contains a group capable of introducing an anion exchange group, the anion exchange group is introduced after the graft polymerization.
For example, when the monomer is chloromethylstyrene, it is preferable that a strong basic anion exchange group is introduced by trialkylamine after polymerization. Examples of the trialkylamine include trimethylamine and triethylamine.
In addition, for example, when the monomer is 4-vinylpyridine, 2-vinylpyridine, N-vinylimidazole, or the like, a strongly basic anion is obtained by alkyl halide such as methyl iodide or dihalogenated alkyl such as dibromohexane. It is preferably converted to an exchange group.

  The total ion exchange capacity of the fluorinated copolymer in the present invention is preferably 1.0 meq / g dry resin or more and 5.0 meq / g dry resin or less, 1.5 meq / g dry resin. More preferably, it is 3.5 meq / g dry resin or less. If the total ion exchange capacity is 1.0 meq / g dry resin or more, the resistance of the fluorine-containing copolymer is suppressed from increasing. If the total ion exchange capacity is 5.0 meq / g dry resin or less, the decrease in strength and chemical resistance of the fluorinated copolymer is suppressed, and the fluorinated copolymer is used as a binder for fuel cell electrodes. In the case where there is, deterioration of the strength and chemical resistance of the electrode is suppressed.

(Fluorine-containing copolymer dispersion)
In the fluorine-containing copolymer dispersion of the present invention, a fluorine-containing copolymer having an ion exchange group is dispersed in a solvent. The solvent is preferably selected from the group consisting of cyclic ketones, chain ketones, chain esters, glycol monoesters, and carbonates, and more preferably chain ketones.

  Examples of the cyclic ketones include 2-propylcyclopropanone, 2-isopropylcyclopropanone, 2,2,3-trimethylcyclopropanone, 2-ethyl-3-methylcyclopropanone, 2-butylcyclopropanone. Non, 2-isobutylcyclopropanone, 2-tert-butylcyclopropanone, 2-methyl-3-propylcyclopropanone, 2-methyl-3-isopropylcyclopropanone, 2-ethyl-3,3-dimethylcyclo Propanone, 2,2,3,3-tetramethylcyclopropanone, 2-pentylcyclopropanone, 2-isopentylcyclopropanone, 2-butyl-3-methylcyclopropanone, 2-ethyl-3-propyl Cyclopropanone, 2-hexylcyclopropanone, 2-methyl-3-pentylcycloprop Non, 2-butyl-3-ethylcyclopropanone, 2,3-dipropylcyclopropanone, 2-heptylcyclopropanone, 2-hexyl-3-methylcyclopropanone, 2-ethyl-3-pentylcyclopropan Non, 2-butyl-3-propylcyclopropanone, 2-ethylcyclobutanone, 3-ethylcyclobutanone, 2,2-dimethylcyclobutanone, 2,3-dimethylcyclobutanone, 3,3-dimethylcyclobutanone, 2,4-dimethylcyclobutanone 2-propylcyclobutanone, 3-propylcyclobutanone, 2-isopropylcyclobutanone, 3-isopropylcyclobutanone, 2,2,3-trimethylcyclobutanone, 2,3,3-trimethylcyclobutanone, 2,3,4-trimethylcyclobutanone, 2, 2,4- Limethylcyclobutanone, 2-butylcyclobutanone, 2-isobutylcyclobutanone, 2-tert-butylcyclobutanone, 3-butylcyclobutanone, 3-isobutylcyclobutanone, 3-tert-butylcyclobutanone, 2-pentylcyclobutanone, 3-pentylcyclobutanone, 2- Isopentylcyclobutanone, 3-isopentylcyclobutanone, 2-hexylcyclobutanone, 3-hexylcyclobutanone, 2-methylcyclopentanone, 3-methylcyclopentanone, 2-ethylcyclopentanone, 3-ethylcyclopentanone, 2, 2-dimethylcyclopentanone, 2,3-dimethylcyclopentanone, 3,3-dimethylcyclopentanone, 2,5-dimethylcyclopentanone, 2,4-dimethylcyclopentanone, 3,4-dimethylcyclopentanone, 2-propylcyclopentanone, 2-isopropylcyclopentanone, 3-propylcyclopentanone, 3-isopropylcyclopentanone, 2,2,5-trimethylcyclopentanone, 2- Butylcyclopentanone, 2-isobutylcyclopentanone, 2-tert-butylcyclopentanone, 3-butylcyclopentanone, 3-isobutylcyclopentanone, 3-tert-butylcyclopentanone, 2,2,5 5-tetramethylcyclopentanone, 2-pentylcyclopentanone, 2-isopentylcyclopentanone, 3-pentylcyclopentanone, 3-isopentylcyclopentanone, cyclohexanone, 2-methylcyclohexanone, 3-methylcyclohexanone, 4-methylcyclopen Non, 2-ethylcyclohexanone, 3-ethylcyclohexanone, 4-ethylcyclohexanone, 2,2-dimethylcyclohexanone, 2,3-dimethylcyclohexanone, 2,4-dimethylcyclohexanone, 2,5-dimethylcyclohexanone, 2,6-dimethyl Cyclohexanone, 2-propylcyclohexanone, 2-isopropylcyclohexanone, 3-propylcyclohexanone, 3-isopropylcyclohexanone, 4-propylcyclohexanone, 4-isopropylcyclohexanone, 2,2,6-trimethylcyclohexanone, 2,2,4-trimethylcyclohexanone, 2,4,4-trimethylcyclohexanone, 3,3,5-trimethylcyclohexanone, 2,4,6-trimethylcyclohexanone, 2-butylsilane Lohexanone, 2-isobutylcyclohexanone, 2-tert-butylcyclohexanone, 3-butylcyclohexanone, 3-isobutylcyclohexanone, 3-tert-butylcyclohexanone, 4-butylcyclohexanone, 4-isobutylcyclohexanone, 4-tert-butylcyclohexanone, 2, 2-diethylcyclohexanone, 2,4-diethylcyclohexanone, 2,6-diethylcyclohexanone, 3,5-diethylcyclohexanone, 2,2,6,6-tetramethylcyclohexanone, cycloheptanone, 2-methylcycloheptanone, 3 -Methylcycloheptanone, 4-methylcycloheptanone, 2-ethylcycloheptanone, 3-ethylcycloheptanone, 4-ethylcycloheptanone, 2,2-dimethylsilane Chloheptanone, 2,7-dimethylcycloheptanone, 2-propylcycloheptanone, 2-isopropylcycloheptanone, 3-propylcycloheptanone, 3-isopropylcycloheptanone, 4-propylcycloheptanone, 4-isopropylcyclo Heptanone, 2,2,7-trimethylcycloheptanone, cyclooctanone, 2-methylcyclooctanone, 3-methylcyclooctanone, 4-methylcyclooctanone, 5-methylcyclooctanone, 2-ethylcyclo Octanone, 3-ethylcyclooctanone, 4-ethylcyclooctanone, 5-ethylcyclooctanone, 2,2-dimethylcyclooctanone, 2,8-dimethylcyclooctanone, cyclononanone, 2-methylcyclononanone , 3-methylcyclononanone, 4-methyl Lucyclononanone, 5-methylcyclononanone, cyclodecanone, isophorone, (−)-fencon ((1R, 4S) -1,3,3-trimethylbicyclo [2.2.1] heptan-2-one), and (+)-Fencon ((1S, 4R) -1,3,3-trimethylbicyclo [2.2.1] heptan-2-one)) and the like.

  Examples of the chain ketones include 2-hexanone, 3-hexanone, methyl isobutyl ketone, ethyl isopropyl ketone, 3,3-dimethyl-2-butanone, 2-heptanone, 3-heptanone, 4-heptanone, and diisopropyl ketone. , 5-methyl-2-hexanone, 2-octanone, 3-octanone, 4-octanone, 5-methyl-3-heptanone, 2-nonanone, 3-nonanone, 4-nonanone, 5-nonanone, diisobutylketone, 2- Examples include decanone, 3-decanone, 4-decanone, and 5-decanone.

  Examples of the chain esters include pentyl formate, isopentyl formate, cyclopentyl formate, hexyl formate, cyclohexyl formate, heptyl formate, octyl formate, 2-ethylhexyl formate, nonyl formate, butyl acetate, isobutyl acetate, sec-butyl acetate, Tert-butyl acetate, pentyl acetate, isopentyl acetate, cyclopentyl acetate, hexyl acetate, cyclohexyl acetate, heptyl acetate, octyl acetate, 2-ethylhexyl acetate, propyl propionate, isopropyl propionate, butyl propionate, isobutyl propionate, sec propionate -Butyl, tert-butyl propionate, pentyl propionate, isopentyl propionate, cyclopentyl propionate, hexyl propionate, cyclohexyl propionate , Heptyl propionate, 2,2,3,3,3-pentafluoropropyl propionate, 2,2,3,3-tetrafluoropropyl propionate, ethyl butyrate, propyl butyrate, isopropyl butyrate, butyl butyrate, isobutyl butyrate, Sec-butyl butyrate, tert-butyl butyrate, pentyl butyrate, isopentyl butyrate, cyclopentyl butyrate, hexyl butyrate, cyclohexyl butyrate, 2,2,2-trifluoroethyl butyrate, 2,2,3,3,3-pentafluoropropyl butyrate 2,2,3,3-tetrafluoropropyl butyrate, ethyl isobutyrate, propyl isobutyrate, isopropyl isobutyrate, butyl isobutyrate, isobutyl isobutyrate, sec-butyl isobutyrate, tert-butyl isobutyrate, pentyl isobutyrate, Isopentyl isobutyrate, cyclopentyl isobutyrate Hexyl isobutyrate, cyclohexyl isobutyrate, 2,2,2-trifluoroethyl isobutyrate, 2,2,3,3,3-pentafluoropropyl isobutyrate, 2,2,3,3-tetrafluoropropyl isobutyrate, Methyl valerate, ethyl valerate, propyl valerate, isopropyl valerate, butyl valerate, isobutyl valerate, sec-butyl valerate, tert-butyl valerate, pentyl valerate, isopentyl valerate, 2,2, valerate 2-trifluoroethyl, 2,2,3,3,3-pentafluoropropyl valerate, 2,2,3,3-tetrafluoropropyl valerate, methyl isovalerate, ethyl isovalerate, propyl isovalerate Isopropyl isovalerate, butyl isovalerate, isobutyl isovalerate, sec-butyl isovalerate, tert-butyl isovalerate Pentyl isovalerate, isopentyl isovalerate, 2,2,2-trifluoroethyl isovalerate, 2,2,3,3,3-pentafluoropropyl isovalerate, 2,2,3, isovaleric acid 3-tetrafluoropropyl, methyl pivalate, ethyl pivalate, propyl pivalate, isopropyl pivalate, butyl pivalate, isobutyl pivalate, sec-butyl pivalate, tert-butyl pivalate, pentyl pivalate, isopentyl pivalate, 2,2,2-trifluoroethyl pivalate, 2,2,3,3,3-pentafluoropropyl pivalate, 2,2,3,3-tetrafluoropropyl pivalate, methyl hexanoate, ethyl hexanoate, Propyl hexanoate, Isopropyl hexanoate, Butyl hexanoate, Isobutyl hexanoate, Hexanoic acid sec Butyl, tert-butyl hexanoate, 2,2,2-trifluoroethyl hexanoate, 2,2,3,3,3-pentafluoropropyl hexanoate, 2,2,3,3-tetrafluoropropyl hexanoate, Methyl heptanoate, ethyl heptanoate, propyl heptanoate, isopropyl heptanoate, 2,2,2-trifluoroethyl heptanoate, 2,2,3,3,3-pentafluoropropyl heptanoate, 2,2 heptanoic acid , 3,3-tetrafluoropropyl, methylcyclohexanecarboxylate, ethylcyclohexanecarboxylate, propylcyclohexanecarboxylate, isopropylcyclohexanecarboxylate, cyclohexanecarboxylic acid 2,2,2-trifluoroethyl, cyclohexanecarboxylic acid 2,2,3 , 3,3-Pentafluoropropi , Cyclohexanecarboxylic acid 2,2,3,3-tetrafluoropropyl, methyl octoate, ethyl octoate, 2,2,2-trifluoroethyl octoate, methyl nonanoate, butyl trifluoroacetate, pentyl trifluoroacetate, Hexyl trifluoroacetate, heptyl trifluoroacetate, octyl trifluoroacetate, propyl pentafluoropropionate, butyl pentafluoropropionate, pentyl pentafluoropropionate, hexyl pentafluoropropionate, heptyl pentafluoropropionate, ethyl perfluorobutanoate, Propyl perfluorobutanoate, butyl perfluorobutanoate, pentyl perfluorobutanoate, hexyl perfluorobutanoate, methyl perfluoropentanoate, ethyl perfluoropentanoate Tyl, propyl perfluoropentanoate, butyl perfluoropentanoate, pentyl perfluoropentanoate, methyl perfluorohexanoate, ethyl perfluorohexanoate, propyl perfluorohexanoate, butyl perfluorohexanoate, methyl perfluoroheptanoate, ethyl perfluoroheptanoate, perfluoroheptanoic acid Examples include propyl, methyl perfluorooctanoate, and ethyl perfluorooctanoate.

  Examples of the glycol monoester include 2-ethoxyethyl acetate, 2-propoxyethyl acetate, 2-butoxyethyl acetate, 2-pentyloxyethyl acetate, 2-hexyloxyethyl acetate, 1-methoxy-2-acetoxy Propane, 1-ethoxy-2-acetoxypropane, 1-propoxy-2-acetoxypropane, 1-butoxy-2-acetoxypropane, 1-pentyloxy-2-acetoxypropane, 3-methoxybutyl acetate, 3-ethoxybutyl acetate , 3-propoxybutyl acetate, 3-butoxybutyl acetate, 3-methoxy-3-methylbutyl acetate, 3-ethoxy-3-methylbutyl acetate, 3-propoxy-3-methylbutyl acetate, 4-methoxybutyl acetate, 4-ethoxy acetate Butyl, 4-propoxybutyl acetate, and Acetic acid 4-butoxybutyl, and the like.

  Examples of the carbonates include butyl methyl carbonate, ethyl propyl carbonate, dipropyl carbonate, diisopropyl carbonate, butyl propyl carbonate, butyl isopropyl carbonate, isobutyl propyl carbonate, tert-butyl propyl carbonate, tert-butyl isopropyl carbonate, dibutyl carbonate, Diisobutyl carbonate, di tert-butyl carbonate, bis (2,2,3,3,3-pentafluoropropyl) carbonate, bis (2,2,3,3-tetrafluoropropyl) carbonate, bis (1,1,1 , 3,3,3-hexafluoroisopropyl) carbonate, bis (2,2,3,3,4,4,4-heptafluorobutyl) carbonate, and Scan (perfluoro -tert- butyl) carbonate, and the like.

  As a more preferable solvent in the fluorine-containing copolymer dispersion of the present invention, for example, the following compounds may be mentioned.

  More preferable examples of the cyclic ketones include 2-methylcyclopentanone, 3-methylcyclopentanone, 2-ethylcyclopentanone, 3-ethylcyclopentanone, 2,2-dimethylcyclopentanone, 2, 3-dimethylcyclopentanone, 3,3-dimethylcyclopentanone, 2,5-dimethylcyclopentanone, 2,4-dimethylcyclopentanone, 3,4-dimethylcyclopentanone, 2-propylcyclopentanone, 2-isopropylcyclopentanone, 3-propylcyclopentanone, 3-isopropylcyclopentanone, 2,2,5-trimethylcyclopentanone, 2-butylcyclopentanone, 2-isobutylcyclopentanone, 2-tert- Butylcyclopentanone, 3-butylcyclopentanone, 3-isobu Lucyclopentanone, 3-tert-butylcyclopentanone, 2,2,5,5-tetramethylcyclopentanone, cyclohexanone, 2-methylcyclohexanone, 3-methylcyclohexanone, 4-methylcyclopentanone, 2-ethyl Cyclohexanone, 3-ethylcyclohexanone, 4-ethylcyclohexanone, 2,2-dimethylcyclohexanone, 2,3-dimethylcyclohexanone, 2,4-dimethylcyclohexanone, 2,5-dimethylcyclohexanone, 2,6-dimethylcyclohexanone, 2-propyl Cyclohexanone, 2-isopropylcyclohexanone, 3-propylcyclohexanone, 3-isopropylcyclohexanone, 4-propylcyclohexanone, 4-isopropylcyclohexanone, 2,2,6- Limethylcyclohexanone, 2,2,4-trimethylcyclohexanone, 2,4,4-trimethylcyclohexanone, 3,3,5-trimethylcyclohexanone, 2,4,6-trimethylcyclohexanone, 2-butylcyclohexanone, 2-isobutylcyclohexanone, 2-tert-butylcyclohexanone, 3-butylcyclohexanone, 3-isobutylcyclohexanone, 3-tert-butylcyclohexanone, 4-butylcyclohexanone, 4-isobutylcyclohexanone, 4-tert-butylcyclohexanone, 2,2-diethylcyclohexanone, 2, 4-diethylcyclohexanone, 2,6-diethylcyclohexanone, 3,5-diethylcyclohexanone, 2,2,6,6-tetramethylcyclohexanone, cycl Loheptanone, 2-methylcycloheptanone, 3-methylcycloheptanone, 4-methylcycloheptanone, 2-ethylcycloheptanone, 3-ethylcycloheptanone, 4-ethylcycloheptanone, 2,2-dimethylcyclo Heptanone, 2,7-dimethylcycloheptanone, 2-propylcycloheptanone, 2-isopropylcycloheptanone, 3-propylcycloheptanone, 3-isopropylcycloheptanone, 4-propylcycloheptanone, 4-isopropyl Examples include cycloheptanone, 2,2,7-trimethylcycloheptanone, isophorone, (−)-fencon, and (+)-fencon.

  More preferable examples of the chain ketones include 2-hexanone, methyl isobutyl ketone, 3,3-dimethyl-2-butanone, 2-heptanone, 3-heptanone, 4-heptanone, diisopropyl ketone, and 5-methyl-2. -Hexanone, 2-octanone, 3-octanone, 5-methyl-3-heptanone, 2-nonanone, 5-nonanone, diisobutylketone, 2-decanone, 3-decanone and the like.

  More preferable examples of the chain esters include pentyl formate, isopentyl formate, hexyl formate, butyl acetate, isobutyl acetate, sec-butyl acetate, tert-butyl acetate, pentyl acetate, isopentyl acetate, hexyl acetate, cyclohexyl acetate, and acetic acid. Heptyl, octyl acetate, 2-ethylhexyl acetate, propyl propionate, isopropyl propionate, butyl propionate, isobutyl propionate, tert-butyl propionate, pentyl propionate, isopentyl propionate, hexyl propionate, cyclohexyl propionate, ethyl butyrate , Propyl butyrate, isopropyl butyrate, butyl butyrate, isobutyl butyrate, tert-butyl butyrate, pentyl butyrate, isopentyl butyrate, hexyl butyrate, cyclohexyl butyrate, butyric acid , 2,2-trifluoroethyl, ethyl isobutyrate, propyl isobutyrate, isopropyl isobutyrate, butyl isobutyrate, isobutyl isobutyrate, tert-butyl isobutyrate, pentyl isobutyrate, isopentyl isobutyrate, hexyl isobutyrate, cyclohexyl isobutyrate 2,2,2-trifluoroethyl isobutyrate, methyl valerate, ethyl valerate, propyl valerate, isopropyl valerate, butyl valerate, isobutyl valerate, tert-butyl valerate, pentyl valerate, isopentyl valerate 2,2,2-trifluoroethyl valerate, methyl isovalerate, ethyl isovalerate, propyl isovalerate, isopropyl isovalerate, butyl isovalerate, isobutyl isovalerate, tert-butyl isovalerate, Isopentyl isovalerate, isopentyl isovalerate, isovaleric 2,2,2-trifluoroethyl, methyl pivalate, ethyl pivalate, propyl pivalate, isopropyl pivalate, butyl pivalate, isobutyl pivalate, tert-butyl pivalate, pentyl pivalate, isopentyl pivalate, pivalic acid 2,2,2-trifluoroethyl, methyl hexanoate, ethyl hexanoate, propyl hexanoate, isopropyl hexanoate, butyl hexanoate, isobutyl hexanoate, tert-butyl hexanoate, 2,2,2-trifluoro hexanoate Ethyl, methyl heptanoate, ethyl heptanoate, propyl heptanoate, isopropyl heptanoate, 2,2,2-trifluoroethyl heptanoate, methyl cyclohexanecarboxylate, ethyl cyclohexanecarboxylate, propyl cyclohexanecarboxylate, cyclohex Isopropyl sancarboxylate, 2,2,2-trifluoroethyl cyclohexanecarboxylate, methyl octoate, ethyl octoate, 2,2,2-trifluoroethyl octoate, methyl nonanoate, butyl trifluoroacetate, perfluoropentanoic acid Examples include methyl, ethyl perfluoropentanoate, propyl perfluoropentanoate, butyl perfluoropentanoate, pentyl perfluoropentanoate, methyl perfluoroheptanoate, ethyl perfluoroheptanoate, and propyl perfluoroheptanoate.

  More preferable monoesters of the glycols include, for example, 2-ethoxyethyl acetate, 2-butoxyethyl acetate, 1-methoxy-2-acetoxypropane, 1-ethoxy-2-acetoxypropane, 1-butoxy-2-acetoxy Examples include propane, 3-methoxybutyl acetate, 3-methoxy-3-methylbutyl acetate, 3-ethoxy-3-methylbutyl acetate, 4-methoxybutyl acetate, 4-ethoxybutyl acetate, and 4-butoxybutyl acetate.

  More preferable carbonates include, for example, dipropyl carbonate, bis (2,2,3,3,3-pentafluoropropyl) carbonate, bis (2,2,3,3-tetrafluoropropyl) carbonate, bis ( 1,1,1,3,3,3-hexafluoroisopropyl) carbonate, bis (2,2,3,3,4,4,4-heptafluorobutyl) carbonate, and bis (perfluoro-tert-butyl) carbonate Etc.

  As a more preferable solvent in the fluorine-containing copolymer dispersion of the present invention, for example, the following compounds may be mentioned.

  More preferable examples of the cyclic ketones include cyclohexanone, 2-methylcyclohexanone, 3-methylcyclohexanone, 4-ethylcyclohexanone, 2,6-dimethylcyclohexanone, 3,3,5-trimethylcyclohexanone, and 4-tert-butylcyclohexanone. , Cycloheptanone, isophorone, and (-)-fencon.

  More preferred chain ketones include 2-hexanone, methyl isobutyl ketone, 2-heptanone, diisopropyl ketone, 5-methyl-2-hexanone, 2-octanone, 2-nonanone, diisobutyl ketone, and 2-decanone. .

  More preferable examples of the chain esters include isopentyl formate, butyl acetate, isobutyl acetate, pentyl acetate, isopentyl acetate, hexyl acetate, cyclohexyl acetate, octyl acetate, 2-ethylhexyl acetate, ethyl butyrate, butyl butyrate, pentyl butyrate, Mention may be made of methyl cyclohexanecarboxylate, 2,2,2-trifluoroethyl cyclohexanecarboxylate, and ethyl perfluoropentanoate.

  More preferable monoesters of the glycols include, for example, 2-ethoxyethyl acetate, 2-butoxyethyl acetate, 1-methoxy-2-acetoxypropane, 1-ethoxy-2-acetoxypropane, 3-methoxybutyl acetate, and An example is 3-methoxy-3-methylbutyl acetate.

  More preferable examples of the carbonates include bis (2,2,3,3-tetrafluoropropyl) carbonate.

  In the fluorinated copolymer dispersion of the present invention, only a solvent selected from the aforementioned compound group may be used as a solvent for dispersing the fluorinated copolymer having an ion exchange group. Moreover, as long as the function as a solvent for dispersing the fluorine-containing copolymer is not impaired, the solvent and an organic solvent other than the solvent may be used. When such a plurality of solvents are mixed and used, the solvent may be referred to as a first solvent, and an organic solvent other than the first solvent may be referred to as a second solvent. For example, the first solvent and one or more second solvents selected from aromatic compounds and aliphatic compounds may be used in combination as a mixed solvent. However, the aliphatic compound used for this mixed solvent does not contain a carbonyl group.

  Examples of the second solvent used for the mixed solvent include aromatic compounds such as benzonitrile, acetophenone, nitrobenzene, methyl benzoate, tetrahydrofuran, 1,4-dioxane, 1,1,1,2,3,3. -Ethers such as hexafluoro-4- (1,1,2,3,3,3-hexafluoropropoxy) pentane are preferred. Moreover, when the fluorine-containing copolymer dispersion liquid of the present invention contains the mixed solvent, the mixing ratio is 9/1 to 1/9 as the first solvent / second solvent (mass ratio). Preferably, 5/5 to 3/7 is more preferable. When the mixed solvent is used, the removal rate can be easily controlled when the solvent is removed from the molded product molded using the fluorine-containing copolymer dispersion.

The fluorine-containing copolymer dispersion of the present invention may contain only one type of fluorine-containing copolymer having a graft chain, or may contain two or more types.
The content of the fluorine-containing copolymer in the fluorine-containing copolymer dispersion of the present invention is not particularly limited, but is preferably 0.1% by mass or more and 80% by mass or less with respect to the total amount of the dispersion. For example, when a thin film is obtained using the fluorine-containing copolymer dispersion of the present invention, the content of the fluorine-containing copolymer in the dispersion is 0.1% by mass or more and 30% by mass or less with respect to the total amount of the dispersion. It is preferably 0.5% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 5% by mass or less. When the content is within this range, the fluorine-containing copolymer dispersion is excellent in handling at the time of preparing a thin film by coating or the like. In addition, a homogeneous fluorine-containing copolymer film can be obtained.

  The fluorine-containing copolymer dispersion of the present invention may contain only the above-mentioned fluorine-containing copolymer and solvent, or may contain a mixed solvent, and other optional components according to the present invention as necessary. It may be included in a range that does not impair the effect. Examples of such optional components include antioxidants, UV stabilizers, crosslinking agents, lubricants, plasticizers, thickeners, fillers (fillers), reinforcing agents, pigments, dyes, flame retardants, and antistatic agents. And various additives. Moreover, as content of these arbitrary components which do not impair the effect of this invention, content of 30 mass% or less can be mentioned with respect to the dispersion liquid whole quantity.

  The method for producing a fluorinated copolymer dispersion of the present invention preferably includes a step of dispersing the fluorinated copolymer having an ion exchange group in the aforementioned solvent. In this dispersion step, it is preferable to heat and stir. Moreover, in this dispersion | distribution process, it is preferable that the temperature which disperse | distributes the fluorine-containing copolymer which has an ion exchange group in a solvent is 230 degrees C or less, It is more preferable that it is 200 degrees C or less. When the dispersion temperature of the fluorinated copolymer is 230 ° C. or lower, the production of the fluorinated copolymer dispersion becomes easy.

  The shape of the fluorinated copolymer used in the dispersion step is preferably in the form of a powder from the viewpoint of shortening the dispersion time and improving the working efficiency, and from the viewpoint of ease of formation, the shape of the pellet Other shapes may be used.

  Further, in the temperature range in which the fluorinated copolymer in the present invention exhibits a good dispersion state, the vapor pressure of the dispersion is preferably at least within the range of not more than the spontaneously generated pressure, and within the range of 3 MPa or less. Is more preferably in the range of 2 MPa or less, particularly preferably in the range of 1 MPa or less, and most preferably not more than normal pressure. If the vapor pressure of the fluorinated copolymer dispersion of the present invention is within this range, it can be easily carried out in actual work.

  The means for dispersing the fluorinated copolymer in the dispersing step may be a general method. What is necessary is just to weigh the required amount of each component constituting the dispersion liquid, uniformly mix these components at a predetermined temperature, and disperse the fluorine-containing copolymer in the solvent. From the viewpoint of dispersion efficiency, it is preferable to use, for example, a general stirring mixer such as a homomixer, a Henschel mixer, a Banbury mixer, a pressure kneader, a single screw extruder, or a twin screw extruder as the dispersing means. When dispersing under pressure, an apparatus such as an autoclave with a stirrer is used. Examples of the stirring blade include a marine propeller blade, a paddle blade, an anchor blade, and a turbine blade.

(Usage example of fluorine-containing copolymer dispersion)
Next, examples using the fluorine-containing copolymer dispersion of the present invention will be given, but the present invention is not limited to these examples.

・ Fluorine-containing copolymer thin film In producing a fluorine-containing copolymer thin film, the fluorine-containing copolymer dispersion of the present invention is applied to a substrate, or the substrate is converted to a fluorine-containing copolymer dispersion. It is preferable to form a coating film of the fluorine-containing copolymer dispersion by a method such as dipping. Subsequently, the fluorine-containing copolymer thin film can be formed on the substrate by removing the solvent from the coating film by heat drying or the like.
As a method for applying the fluorine-containing copolymer dispersion of the present invention, a general method can be used. Examples of such an application method include gravure coating, dip coating, die coating, spray coating, electrostatic coating, brush coating, screen printing, roll coating, and spin coating.
With the fluorinated copolymer dispersion of the present invention, the coating film can be easily formed because the fluorinated copolymer is dispersed in the solvent even at room temperature.

  When the fluorine-containing copolymer dispersion of the present invention is used to form a thin film of a fluorine-containing copolymer on a substrate, and this is used as it is as a substrate with a thin film, the adhesion of the thin film to the substrate For the purpose of improving the quality, it is preferable to pre-treat the base material. Examples of the pretreatment include a method of applying a silane coupling agent or polyethyleneimine to the substrate, physically treating the substrate surface by sandblasting, or treating the substrate surface by corona discharge or the like. Can be mentioned.

  The thin film of the fluorine-containing copolymer formed on the substrate can be used as a film-like molded product (hereinafter sometimes simply referred to as “film”) after being separated from the substrate. Thus, when obtaining a film by separating from a base material, it is preferable to use a base material made of a material having releasability or a base material that has been pretreated with a release agent or the like. Thus, if a fluorine-containing copolymer film is produced using the fluorine-containing copolymer dispersion of the present invention, the film thickness is thin and uniform as compared with a film obtained by general melt molding. It is possible to produce a film.

  The film thickness of the fluorine-containing copolymer thin film formed on the substrate or the film-like molded product can be freely selected according to the purpose. If a high concentration fluorine-containing copolymer dispersion is used, a thin film having a large film thickness can be obtained. If a low concentration fluorine-containing copolymer dispersion is used, a thin film having a small thickness can be obtained. Moreover, a thin film with a larger film thickness can be obtained by repeating the coating process a plurality of times. The thickness of the thin film thus obtained is preferably 0.01 μm or more and 1000.0 μm or less, more preferably 0.1 μm or more and 100.0 μm or less, and 0.5 μm or more and 50.0 μm or less. More preferably it is.

  There are no particular limitations on the material and shape of the substrate on which the fluorine-containing copolymer dispersion liquid of the present invention can be used to form a fluorine-containing copolymer thin film on the surface. Examples of the material for the substrate include metal, glass, silicon, plastic, stone, wood, ceramics, cloth, and paper. The fluorine-containing copolymer thin film formed on the base material can be used as a base material with a thin film together with the base material, or separated from the base material and used as a single thin film depending on various applications. .

The thin film of a fluorine-containing copolymer having an ion exchange group in the present invention can also be used as a polymer electrolyte membrane. This polymer electrolyte membrane can be used as an electrolyte layer of a solid polymer fuel cell. The polymer electrolyte membrane can be produced by the aforementioned coating method such as a cast method.
The membrane / catalyst layer assembly may be formed by joining the catalyst layers constituting the electrodes of the fuel cell to both surfaces of the polymer electrolyte membrane. Examples of the bonding method include a method of directly forming a catalyst layer on both surfaces of the polymer electrolyte membrane, a method of transferring a separately formed catalyst layer to the polymer electrolyte membrane, and hot pressing the polymer electrolyte membrane and the catalyst layer. And a method of joining the polymer electrolyte membrane and the catalyst layer using an adhesive. Further, the membrane / electrode assembly may be formed by sandwiching the membrane / catalyst layer assembly between the gas diffusion layers. The gas diffusion layer is formed of a porous base material having conductivity, and examples of the porous base material include carbon cloth, carbon paper, and carbon felt.

-Coating liquid for catalyst layer formation The fluorine-containing copolymer dispersion liquid of this invention can be used also for preparation of the coating liquid used when forming the catalyst layer of a fuel cell. The coating liquid contains the fluorine-containing copolymer dispersion of the present invention and an electrode material such as a carbon-based material or a catalyst. Examples of the catalyst used for the electrodes include catalysts such as platinum, platinum-ruthenium alloys, platinum-tin alloys, and supported catalysts in which fine particles of these catalysts are supported on a carbon carrier such as carbon black or activated carbon. It is done.

Examples of the method for producing the coating liquid include a method in which a predetermined amount of an electrode material is mixed in a fluorine-containing copolymer dispersion and a means for dispersing the electrode material in the same manner as the above-described dispersion step. Moreover, the method of mixing the fluorine-containing copolymer which has an ion exchange group in this invention, a solvent, and electrode material simultaneously, and disperse | distributing the said fluorine-containing copolymer and electrode material in a solvent is mentioned.
In the coating solution, the mass ratio of the fluorine-containing copolymer having an ion exchange group and the metal catalyst is preferably 10/90 to 90/10, and more preferably 40/60 to 80/20.
In the coating solution, the mass ratio of the fluorine-containing copolymer having an ion exchange group and carbon is preferably 30/70 to 70/30, and more preferably 40/60 to 60/40.

As a method for forming the catalyst layer, it is preferable to form a coating film on the substrate by first applying a coating solution, as in the production of the fluorine-containing copolymer thin film described above. Subsequently, a catalyst layer can be formed on a base material by removing the solvent from the coating film by heat drying or the like.
The catalyst layer formed on the base material is separated from the base material, and then joined to the polymer electrolyte membrane to be used as the aforementioned membrane catalyst layer assembly.
The catalyst layer can also be formed by applying a coating solution on the polymer electrolyte membrane to form a coating film and removing the solvent. At that time, the membrane-catalyst layer assembly is also formed. The

  According to the fluorine-containing copolymer dispersion liquid of the present invention, the electrode material can be easily dispersed. Therefore, the coating liquid of the present invention is excellent in dispersibility of the fluorine-containing copolymer and the electrode material. Moreover, the catalyst layer which uses the fluorine-containing copolymer in this invention as a binder can be formed by using the said coating liquid. A fuel cell provided with the catalyst layer exhibits excellent characteristics. The catalyst layer is preferably used for the fuel electrode.

[Modification of Embodiment]
It should be noted that the present invention is not limited to the above-described embodiment, but includes modifications and improvements as long as the object of the present invention can be achieved.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[Capacity flow rate: Q value (mm ³ / sec)]
Using a Shimadzu flow tester, ETFE is extruded from an orifice of 2.1 mm in diameter and 8 mm in length under a load of 7 kg at a temperature about 50 ° C. higher than the melting point of ethylene / tetrafluoroethylene copolymer (ETFE). The extrusion speed (mm ³ / sec) was measured. The measured extrusion speed was taken as the Q value. However, the measurement temperature in this example was 220 ° C.

[Melting point (° C)]
Using a scanning differential thermal analyzer (DSC7020, manufactured by SII), the melting point was determined from the endothermic peak when heated to 300 ° C. under a temperature rising condition of 10 ° C./min in an air atmosphere.

[Polar functional group content (mol%)]
Absorption derived from an acid anhydride residue appearing in the vicinity of 1870 cm ⁻¹ by a Fourier transform infrared spectrometer (Nicollet iS10, manufactured by Thermo Fisher Scientific Co., Ltd.) using a 200 μm thick film obtained by press molding ETFE The strength of was measured. Using the molar extinction coefficient of the acid anhydride residue determined from the model compound, the content of the acid anhydride residue was calculated. Itaconic anhydride was used as a model compound, and the obtained molar extinction coefficient was 237 L / (mol · cm).

[Composition of ETFE (mol%)]
The copolymer composition of ETFE was calculated from the results of total fluorine measurement and melt ¹⁹ F-NMR measurement.

[Ion exchange capacity (milli equivalent / g dry resin)]
The ion exchange capacity of the fluorinated copolymer was determined by a titration method.

[Synthesis Example 1]
After the stirrer and stainless steel polymerization vessel having an internal volume of 1.3L equipped with a jacket is _{evacuated, CF 3 CH 2 OCF 2 CF} 2 H into the polymerization vessel, and _CH 2 = CH as fluoroalkyl ethylene (FAE) (CF ₂ ) ₃ CF ₃ was charged. The amount of CF ₃ CH ₂ OCF ₂ CF ₂ H charged was 825 g, and the amount of CH ₂ ═CH (CF ₂ ) ₃ CF ₃ charged was 3.2 g.
Thereafter, hexafluoropropylene (HFP), tetrafluoroethylene (TFE), and ethylene (E) were charged while stirring the inside of the polymerization tank. The amount of HFP charged was 350 g, the amount of TFE charged was 118 g, and the amount of E charged was 2.9 g.
After charging the material into the polymerization tank, warm water was passed through the jacket to adjust the internal temperature of the polymerization tank to 66 ° C. The polymerization tank internal pressure at this time was 1.47 MPaG. After the internal temperature of the polymerization tank was stabilized, 7.4 ml of a CF ₃ CH ₂ OCF ₂ CF ₂ H solution containing 5% by mass of tert-butylperoxypivalate was injected into the polymerization tank to initiate polymerization. It was. During the polymerization, a mixed gas of TFE / E = 54/46 molar ratio was added into the polymerization tank so that the internal pressure was constant at 1.47 MPaG. In addition, whenever 5 g of the TFE / E mixed gas added during the polymerization is consumed, 7.1% by mass of CH ₂ ═CH (CF ₂ ) ₃ CF ₃ is contained and 1.3% of itaconic anhydride is contained. 2 ml of CF ₃ CH ₂ OCF ₂ CF ₂ H solution containing mass% was added into the polymerization tank. 370 minutes after the start of the polymerization reaction, when 70 g of the TFE / E mixed gas was added, the polymerization tank was cooled to complete the polymerization. After completion of the polymerization, the residual monomer gas was purged from the polymerization tank to atmospheric pressure. After purging, the slurry was transferred to a container having an internal volume of 2 L, water having the same volume as the slurry was added to the container, and the polymerization medium, the chain transfer agent, the residual monomer, and the polymer were separated while heating. The obtained polymer was dried in an oven at 120 ° C. to obtain white powdered ETFE1.

The melting point of ETFE1 was 183 ° C.
The capacity flow rate of ETFE1 at 220 ° C. was 11 mm ³ / sec.
The composition of ETFE1 is TFE / E / HFP / CH ₂ ═CH (CF ₂ ) ₃ CF ₃ / Itaconic anhydride = 47.5 mol% / 43.4 mol% / 8.2 mol% / 0.6 mol% /0.3 mol%.

[Example 1]
(Graft polymerization)
The white powder of ETFE1 was irradiated with 20 kGy of gamma rays under reduced pressure. The powder of ETFE1 after γ-ray irradiation was immersed in a mixture of p-chloromethylstyrene and m-chloromethylstyrene, and graft polymerization was performed at 60 ° C. for 96 hours.

(Introduction of ion exchange groups)
After graft polymerization, the graft polymer was washed with toluene and dried. The graft polymer after drying was immersed in a methanol solution of 1N trimethylamine at 40 ° C. for 8 hours, and anion exchange group was added to the polymerized units based on the grafted p-chloromethylstyrene and the polymerized units based on m-chloromethylstyrene. (—N ⁺ (CH ₃ ) ₃ .Cl ⁻ ) was introduced. The graft polymer after the introduction of the anion exchange group was washed with hydrochloric acid and ion-exchanged water. After washing, the graft polymer was further immersed in a 0.1N aqueous sodium hydroxide solution to convert the counter ion to OH ion. Then, it washed with water and dried and obtained the fluorine-containing copolymer (henceforth ETFE2) which has an ion exchange group. The ion exchange capacity of ETFE2 was 2.2 meq / g dry resin.

(Preparation of dispersion)
Subsequently, 2 g of ETFE2 powder and 98 g of diisopropyl ketone were placed in an autoclave having an internal volume of 0.5 L and stirred at 150 ° C. for 30 minutes to obtain a dispersion of ETFE2. This dispersion of ETFE2 was a transparent liquid, and ETFE2 did not settle even after being left for several days. The dispersion of ETFE2 according to Example 1 maintained good dispersibility even at room temperature.

[Example 2]
(Production of polymer electrolyte membrane)
The dispersion of ETFE2 according to Example 1 was cast coated on a 100 μm-thick FEP (fluoroethylenepropylene) film with a die coater to form a coating film, and pre-dried at 100 ° C. Such coating and preliminary drying were repeated, and after the film thickness became approximately 50 μm, annealing was performed at 200 ° C. for 30 minutes to obtain a polymer electrolyte membrane having a film thickness of 50 μm. The polymer electrolyte membrane was peeled from the FEP film and used in Example 4 described later.

[Example 3]
(Production of catalyst layer)
1 g of a carbon-supported platinum catalyst (manufactured by NP Chemcat, specific surface area 800 m ² / g) was placed in 22 g of the ETFE2 dispersion 22 according to Example 1, and a homogenizer (trade name: Polytron, manufactured by Kinematica) was used. The carbon-supported platinum catalyst was mixed while being pulverized to prepare a coating solution for forming a catalyst layer. The carbon-supported platinum catalyst was dispersed in the coating solution. The prepared coating solution was cast-coated on a FEP film with a die coater and dried at 100 ° C. for 30 minutes to prepare a catalyst layer.

[Example 4]
(Production of membrane catalyst layer assembly and membrane electrode assembly)
The catalyst layers prepared in Example 3 were disposed on both sides of the polymer electrolyte membrane prepared in Example 2, respectively. Thereafter, the catalyst layer was transferred to the polymer electrolyte membrane by a hot press method, and the catalyst layer was bonded to both surfaces of the polymer electrolyte membrane. A membrane catalyst layer assembly having an anode catalyst layer on one surface of the polymer electrolyte membrane and a cathode catalyst layer on the other surface was obtained. The electrode area of the membrane / catalyst layer assembly was 16 cm ² . This membrane / catalyst layer assembly was sandwiched between two gas diffusion layers made of carbon cloth having a thickness of 350 μm to produce a membrane / electrode assembly.

  The present invention can be used for a fluorine-containing copolymer dispersion. The fluorine-containing copolymer dispersion obtained by the present invention can be used, for example, for the production of polymer electrolyte membranes, catalyst layers, membrane catalyst layer assemblies, membrane electrode assemblies, etc. Available.

Claims (12)

  A fluorine-containing copolymer obtained by introducing a graft chain into an ethylene / tetrafluoroethylene copolymer by graft polymerization, and a solvent, wherein the graft chain has an ion exchange group Copolymer dispersion. The ethylene / tetrafluoroethylene copolymer is
Ethylene / tetrafluoroethylene / fluoroolefin copolymer having no hydrogen atom in the unsaturated group,
Ethylene / tetrafluoroethylene / fluoroalkylethylene copolymer,
Ethylene / tetrafluoroethylene / fluoroolefin / fluoroalkylethylene copolymer having no hydrogen atom in unsaturated group, and ethylene / tetrafluoroethylene / fluoroolefin / fluoroalkylethylene / polar functional group having no hydrogen atom in unsaturated group 2. The fluorinated copolymer dispersion according to claim 1, wherein the dispersion is a copolymer selected from the group consisting of a monomer copolymer having a group.   The fluorine-containing copolymer dispersion according to claim 2, wherein the fluoroolefin having no hydrogen atom in the unsaturated group is hexafluoropropylene. The said fluoroalkyl ethylene is a compound represented by the following general formula (M1), The fluorine-containing copolymer dispersion liquid as described in any one of Claim 1 to 3 characterized by the above-mentioned.
CH ₂ = CX (CF ₂ ) _n Y (M1)
(In the general formula (M1),
X and Y are independently hydrogen or a fluorine atom;
n is an integer of 2-8. )   The fluorine-containing copolymer according to claim 4, wherein the fluoroalkylethylene is a compound in which X in the general formula (M1) is a hydrogen atom, Y is a fluorine atom, and n is 4. Combined dispersion.   The fluorinated copolymer dispersion according to any one of claims 2 to 5, wherein the monomer having a polar functional group is a monomer having an acid anhydride residue.   The fluorine-containing copolymer dispersion according to any one of claims 1 to 6, wherein the melting point of the ethylene / tetrafluoroethylene copolymer is 120 ° C or higher and 230 ° C or lower.   The ion exchange capacity of the fluorine-containing copolymer is 1.0 meq / g dry resin or more and 5.0 meq / g dry resin or less. The fluorine-containing copolymer dispersion liquid described in 1.   The fluorine-containing copolymer dispersion according to any one of claims 1 to 8, wherein the solvent is a chain ketone.   The fluorine-containing copolymer dispersion according to any one of claims 1 to 8, wherein the solvent is diisopropyl ketone.   The coating liquid characterized by including the fluorine-containing copolymer dispersion liquid as described in any one of Claims 1-10, and an electrode material.   A fuel cell having a catalyst layer formed using the coating liquid according to claim 11.