WO2008001894A1

WO2008001894A1 - Method for producing fluorine-containing polymer

Info

Publication number: WO2008001894A1
Application number: PCT/JP2007/063135
Authority: WO
Inventors: Tadashi Ino; Tadaharu Isaka; Masaharu Nakazawa; Masahiro Kondo
Original assignee: Daikin Industries, Ltd.
Priority date: 2006-06-30
Filing date: 2007-06-29
Publication date: 2008-01-03
Also published as: JP5287245B2; JPWO2008001894A1

Abstract

Disclosed is a method for producing a fluorine-containing polymer, which is excellent in productivity. Specifically disclosed is a method for producing a fluorine-containing polymer by radically polymerizing a fluorine-containing monomer in an aqueous medium. This method for producing a fluorine-containing polymer is characterized in that the radical polymerization is performed in the presence of a fluorine-containing compound (1) having a vinyl group, which also contains a radically polymerizable unsaturated bond and a hydrophilic group, and a fluorine-containing compound (2) containing a fluorocarbon group, wherein 1-6 carbon atoms to each of which a fluorine atom is directly bonded are continuously connected, and a hydrophilic group.

Description

Specification

Method for producing fluorine-containing polymer

Technical field

The present invention relates to a method for producing a fluorine-containing polymer.

Background art

[0002] In emulsion polymerization in an aqueous medium to obtain a fluorine-containing polymer, F (CF) C

2 7

Fluorine containing long-chain fluoroalkyl groups such as OONH and F (CF) COONH

4 2 8 4

Surfactants are mainly used as emulsifiers. These emulsifiers have high surface activity, but are difficult to wash due to their low solubility in water, and remain in the resulting fluoropolymer. Remaining fluorine-containing surfactant in the fluorine-containing polymer leads to foaming and coloring problems during molding.

[0003] For the purpose of solving such a problem, a compound having a radical polymerizable unsaturated bond and a hydrophilic group in the molecule without using a surfactant containing a long-chain fluoroalkyl group as described above. was used as an emulsifier, a method of polymerizing a fluorine-containing polymer in an aqueous medium have been proposed (e.g., see Patent Document 1, 2 and 3.) ₀

As the compound having a radical polymerizable unsaturated bond and a hydrophilic group in the molecule, have been proposed also a compound having a specific terminal group (e.g., see Patent Document 4.) ₀

In these methods, since a compound having a radically polymerizable unsaturated bond and a hydrophilic group in the molecule is copolymerized with the fluorine-containing polymer, the problem that this compound remains in the fluorine-containing polymer with a low molecular weight is prevented. be able to.

However, the emulsion obtained by polymerization using a compound having a radical polymerizable unsaturated bond and a hydrophilic group in the molecule as a demulcent is copolymerized with a fluorine-containing polymer. In general, it is unstable. This tendency is particularly pronounced when producing a pero-oral polymer. In the method using a compound having a radical polymerizable unsaturated bond and a hydrophilic group in the molecule, a perhalo polymer is produced with high productivity. It was difficult to manufacture.

[0005] In Patent Document 5, as the polymerization reaction of tetrafluoroethylene progresses, fluorine-containing The addition of the group-containing emulsifier gave a high polymer concentration and emulsion, but the production method was complicated and it was not satisfactory in terms of productivity.

Patent Document 1: Japanese Patent Laid-Open No. 55-029519

Patent Document 2: JP 59-196308 A

Patent Document 3: Japanese Patent Laid-Open No. 08-067795

Patent Document 4: Pamphlet of International Publication No.04Z018527

Patent Document 5: Pamphlet of International Publication No. 05Z037880

Disclosure of the invention

Problems to be solved by the invention

[0006] In view of the above situation, an object of the present invention is to provide a method for producing a fluoropolymer having excellent productivity.

Means for solving the problem

[0007] The present invention is a method for producing a fluorine-containing polymer by radical polymerization of a fluorine-containing monomer in an aqueous medium, wherein the radical polymerization includes a radically polymerizable unsaturated bond and a hydrophilic group. Fluorovinyl group-containing compound (1) and fluorine-containing compound (2) having a fluorocarbon group and a hydrophilic group in which carbon atoms to which fluorine atoms are directly bonded are bonded in the range of 1 to 6 in succession. This is a method for producing a fluorine-containing polymer, which is carried out in the presence.

[0008] The present invention is a fluorine-containing polymer obtained by the above-described method for producing a fluorine-containing polymer of the present invention.

The present invention is an electrolyte membrane comprising the above-described fluoropolymer of the present invention. The present invention is a membrane electrode assembly comprising the above-mentioned fluoropolymer of the present invention.

The present invention is a fuel cell comprising the electrolyte membrane or the membrane electrode assembly.

The present invention is described in detail below.

[0009] The method for producing a fluorine-containing polymer of the present invention is a method for producing a fluorine-containing polymer by radical polymerization of a fluorine-containing monomer in an aqueous medium. [0010] The fluorine-containing monomer is not particularly limited as long as it contains a fluorine atom as an atom directly bonded to carbon. For example, hexafluoropropylene [HFP], tetrafluoroethylene [TFE] Chlorofluoroethylene [CTFE], perfluoro (alkyl ether) [PAVE], vinylidene fluoride, and a fluorine-containing monomer containing a hydrolyzable functional group.

In the present invention, only one type of fluorine-containing monomer may be used, or two or more types may be used.

[0011] The PAVE preferably has a structure represented by the following general formula (O).

CF = CF— O— (CF CFXO) (CF) CF (O)

2 2 f 2 g 3

(Here, X represents CF or F. f is preferably 0 to 3, and g is preferably 0 to 7.)

Three

In particular, perfluoro (methyl vinyl ether) [PMVE], perfluoro (ethyl vinyl ether) [PEVE], perfluoro (propyl vinyl ether) [PPVE], CF = CF

2

— O— (CF CFXO)-(CF) — CF (where X is the same as above) is preferable.

2 2 2 2 3

[0012] The fluorine-containing monomer containing a hydrolyzable functional group is preferably one having a structure of the following general formula (P).

CR R ¹² = CR ¹³ (CR ¹⁴ R ¹⁵ ) — (O) -R ^W ~ Z (P)

a b

[In the formula, ¹ , R ¹² , R ¹³ , R ¹⁴ and R ¹⁵ are the same or different and represent F or a perfluoroalkyl group having 1 to 3 carbon atoms, and R ^1C> represents oxygen in the main chain. Represents a linear or branched perfluoroalkylene group having 1 to 8 carbon atoms which may have an atom, a represents an integer of 0 to 6, b represents an integer of 0 or 1, Z represents a hydrolyzable functional group. ]

[0013] As the fluorine-containing monomer containing the hydrolyzable functional group, those having the following structures (P1) to (P3) are preferred.

CF = CF- (CF) Z (P1)

2 2 c

CF = CF- (CF C (CF) F) Z (P2)

2 2 3 d

CF = CF (CF) One O— (CF CFXO) One (CF) One Z (P3)

2 2 e 2 f 2 g

[In each formula, X represents F or CF, c represents an integer of 0 to 8, and d represents an integer of 1 to 2.

Three

E represents an integer of 0 to 2, f represents an integer of 0 to 3, g represents an integer of 1 to 8, and Z represents a hydrolyzable functional group. ] Z is SO ² A ³ [where A ¹ is fluoro

Represents an alkyl group, and A ² and A ³ are the same or different and each represents a fluoroalkyl group. ] Is preferable.

[0014] The fluorine-containing monomer containing the hydrolyzable functional group is more preferably represented by the following formula.

CF = CF— SO F

twenty two

CF = CFCF -SO F

2 2 2

CF = CFOCF CF SO F

2 2 2 2

CF = CFOCF CF CF CF SO F

2 2 2 2 2 2

CF = CFCF OCF CF SO F

2 2 2 2 2

CF = CFOCF CF (CF) OCF CF SO F

2 2 3 2 2 2

CF = CFOCF CF COOCF

2 2 2 3

CF = CFOCF CF (CF) OCF CF COOCF

2 2 3 2 2 3

[0015] The fluorine-containing polymer in the present invention may be obtained by radical polymerization of not only fluorine-containing monomers but also fluorine-free ethylenic monomers.

The fluorine-free ethylenic monomer is preferably selected from ethylenic monomer power having 5 or less carbon atoms from the viewpoint of maintaining heat resistance and chemical resistance. Examples of the monomer include ethylene, propylene, 1-butene, 2-butene, vinyl chloride, and vinylidene chloride.

[0016] Examples of the fluorine-containing polymer in the present invention include non-melt processable polymers such as polytetrafluoroethylene [PTFE]; TFEZHFP copolymer [FEP], TFEZPAVE copolymer, TFEZCTFEZPAVE copolymer EtZTFE copolymer [ETFE], Et / HF PZTFE copolymer [EFEP], polyvinylidene fluoride [PVdF], copolymers of TFE and monomers containing hydrolyzable functional groups, etc. Examples include melt-processable polymers.

In the present specification, the PTFE is a concept including not only a TFE homopolymer but also a modified polytetrafluoroethylene [modified PTFE].

In the present specification, the above-mentioned “modified PTFE” means that TFE is combined with a trace monomer other than TFE. It means a polymer that is non-melt processable.

Examples of the trace monomer include fluororefin such as HFP and PAVE; perfluoroalkylethylene; _ω -hydroperfluororefin and the like.

In the modified PTFE, the content of the trace monomer units derived from the trace monomer in the total monomer units is usually in the range of 0.001 to 2 mol%.

[0018] The PTFE preferably has a number average molecular weight of 1 million to 10 million. The above-mentioned number average molecular weight is a value obtained by calculating the standard specific gravity (SSG) force in accordance with ASTM D 4895. For the purposes of this specification, the “content ratio of trace monomer units in all monomer units” `` (Mol%) '' refers to the monomer from which the above “total monomer unit” is derived, that is, the above-mentioned trace monomer unit occupying the total amount of the monomer constituting the fluoropolymer. This means the mole fraction (mol%) of the trace monomer.

[0019] The TFEZHFP copolymer preferably has a HFP content of 8 to 20 mol%. The TFEZPAVE copolymer preferably has a PAVE content of 1 to 10 mol%.

Examples of the TFEZPAVE copolymer include TFEZ perfluoro (methyl vinyl ether) [PMVE] copolymer [MFA], TFEZ perfluoro (ethyl vinyl ether) [PEVE] copolymer, TFEZ perfluoro (propyl butyl ether) [PPVE] copolymer. Examples thereof include polymers.

[0020] The copolymer of the TFE and the monomer containing a hydrolyzable functional group has a content of the monomer containing a hydrolyzable functional group of 5 to 30 mol%. preferable.

These melt-processable polymers preferably have a melt flow rate (MFR) of 0.1 to L00 (gZl0 min).

According to ASTM D 1238, the above MFR is 372 ° C for polymers with a melting point of 240 ° C or higher, 270 ° C for polymers with a melting point of less than 240 ° C at 372 ° C and a load of 5kg, 2. Values measured at 16 kg.

[0021] The fluorine-containing polymer in the present invention is preferably a plastomer. The above-mentioned plastomer has a force having a diffraction peak in X-ray diffraction measurement, or in the absence of this, Young's modulus measured at 25 ° C is 1 X 10 ⁷ Pa or more in accordance with JIS K6394. Preferably there is. The Young's modulus is more preferably IX 10 ⁸ Pa or more, and may be less than 1 X lO ^ Pa within this range.

[0022] The fluorine-containing polymer in the present invention is preferably a perhalopolymer in terms of heat resistance, chemical resistance, and the like.

The perhalopolymer is a polymer in which halogen atoms are bonded to all the carbon atoms constituting the main chain of the polymer.

[0023] The average particle size of the fluoropolymer is usually 50 to 500 nm, and preferably 100 to 350 nm.

The average particle size is determined by measuring the transmittance of 550 nm projection light with respect to the unit length of the aqueous dispersion with the fluorine-containing polymer concentration adjusted to 0.22% by mass and the unidirectional diameter in the transmission electron micrograph. It was determined from the transmittance based on a calibration curve with the average particle diameter.

[0024] The fluorine-containing polymer in the present invention may be in any form such as a dispersion or a powder.

[0025] The aqueous medium is not particularly limited as long as it is a liquid containing water, and in addition to water, for example, a fluorine-free organic solvent such as alcohol, ether, ketone, paraffin wax and / or a fluorine-containing organic solvent. May also contain.

In the method for producing a fluorine-containing polymer of the present invention, radical polymerization is carried out by using a fluorine-containing vinyl group-containing compound (1) having a radically polymerizable unsaturated bond and a hydrophilic group (hereinafter simply referred to as a fluorine-containing bull group-containing compound (1 ), And a fluorine-containing compound (2) having a fluorocarbon group and a hydrophilic group in which carbon atoms to which fluorine atoms are directly bonded are successively bonded in the range of 1 to 6 (Hereinafter, this may be simply referred to as a fluorine-containing compound (2)).

According to the study by the present inventors, it is considered that the polymerization of the fluorine-containing monomer in the aqueous medium mainly occurs around the emulsified particles having a fluorine-containing oligomer force dispersed in the aqueous medium by the surfactant. . The fluorine-containing oligomer is formed by a reaction between a fluorine-containing monomer and a radical species at the initial stage of polymerization, and the number of emulsified particles in the aqueous medium. As the amount increases, the polymerization reaction proceeds more rapidly and the emulsion tends to become more stable. In general, the number of emulsified particles is considered to be determined at the beginning of the polymerization reaction, and the surfactant is considered to have a great influence on the number of the surfactants.

In the polymerization of the fluorinated monomer using the fluorinated vinyl group-containing compound (1) having a radical polymerizable unsaturated bond and a hydrophilic group in the molecule, the fluorinated vinyl group-containing compound ( 1) plays an important role in the early stages of polymerization, such as the formation of emulsion particles and dispersion stability. However, since most of the fluorine-containing vinyl group-containing compound (1) is consumed in the initial stage of polymerization, the stability of the formed fluorine-containing polymer particles deteriorates as the polymerization proceeds. Tend to.

On the other hand, since the fluorine-containing compound (2) has a fluorocarbon group in which the number of carbon atoms to which fluorine atoms are directly bonded is within the above range, a fluorine-containing compound having a long-chain fluoroalkyl group that has been conventionally used. Since it is more hydrophilic than a surfactant, when used alone, the number of emulsified particles having a low function of causing initial induction tends to decrease. As a result, the polymerization rate was slow, and it was difficult to increase the polymer concentration in the emulsion, so it was difficult to produce a fluorine-containing polymer with high productivity.

However, the present inventors, as a means for improving such a tendency to deteriorate, have not obtained a sufficient effect when used alone as described above, and the fluorine-containing vinyl group-containing compound (1). The inventors have found that it is effective to coexist with the fluorine-containing compound (2), and have reached the present invention.

That is, the inventors of the present invention provide a fluorine-containing beryl group-containing compound (1) that facilitates the formation of emulsified particles and improves the yield, and a fluorine-containing compound (2) that has the ability to stabilize emulsion particles. It was found that a fluorine-containing polymer can be produced with high productivity by combining the above and complementing the above-mentioned drawbacks.

There is no description in the public literature regarding the combined use of these two types of compounds. For example, in the above Patent Document 5, the fluorine-containing compound (2) is only described as an optional component, and there is no mention of the combined use effect with the fluorine-containing vinyl group-containing compound (1).

[0029] The fluorine-containing vinyl group-containing compound (1) has a radical polymerizable unsaturated bond and a hydrophilic group. The fluorinated bur group-containing compound (1) is characterized in that it is copolymerized with the fluorinated monomer and incorporated into the polymer chain. Furthermore, since the polymer having a monomer unit derived from the fluorine-containing vinyl group-containing compound (1) exhibits a kind of emulsifying action, it is more thermally stable than conventional polymers and can be molded. Volatilization due to heat applied from time to time • Foaming due to decomposition 'Coloring hardly occurs.

[0030] Examples of the radical polymerizable unsaturated bond in the fluorine-containing vinyl group-containing compound (1) include an unsaturated bond in CF = CF-.

2

As the hydrophilic group in the fluorine-containing vinyl group-containing compound (1), those exemplified for z ¹ and z ² in the general formula (I) described later are preferable.

The fluorine-containing vinyl group-containing compound (1) is preferably a compound having 4 to 26 carbon atoms in total.

[0031] The fluorine-containing vinyl group-containing compound (1) has the following general formula (I)

CR'R ^ CR ^ CR)

j-(O) k -RZ ¹ (I)

The fluorine-containing vinyl group-containing compound (la) represented by

In the general formula (1), R ² , R ³ , R ⁴ and R ⁵ are the same or different and each represents a fluoroalkyl group, H, F, Cl, Br or I. The fluoroalkyl group as R ² , R ³ , R ⁴ and R ⁵ preferably has 1 to 3 carbon atoms. R ² , R ³ , R ⁴ and R ⁵ are preferably F.

The above R may have an oxygen atom [one O—] in the main chain, and represents a linear or branched perfluoroalkylene group.

R preferably has 1 to 23 main chain carbon atoms.

When the perfluoroalkylene group has an oxygen atom in the main chain, the oxygen atom constitutes 1 to 10 oxyalkylene units (preferably having 2 to 3 carbon atoms). It is preferred to be an oxygen atom.

When the perfluoroalkylene group is branched, it may have CF as a side chain.

3 is preferred.

J represents an integer of 0 to 6, and is preferably an integer of 0 to 2.

K represents an integer of 0 or 1. Z ¹ represents a hydrophilic group.

Examples of the hydrophilic group represented by Z ¹ include -COOM ¹ , -SO M ² , -SO NR ⁶ R ⁷ or -P

3 2

OM ³ M ⁴ is mentioned. M \ M ² , M ³ and M ⁴ are the same or different and H or one

Three

R ⁶ and R ⁷ are the same or different and each represents a hydrogen atom, an alkali metal, an alkyl group, or a sulfonyl-containing group.

Examples of the monovalent cation include —Na, monosodium, and soot.

Four

As the fluorine-containing vinyl group-containing compound (1), the following general formula (II)

CF = CFO— (CF CF (CF) θ) (CF) Z ² (II)

2 2 3 1 2 m

And a fluorine-containing bull group-containing compound (lb).

In the above general formula (Π), 1 represents an integer of 0 to 3, and m represents an integer of 2 to 8.

Z ² is -COOM ¹ , -SO M ² , M

³ and M ⁴ are the same or different and represent H or a monovalent cation, and R ⁶ and R ⁷ are the same or different and represent a hydrogen atom, an alkali metal, an alkyl group, or a sulfonyl-containing group.

[0033] As the fluorine-containing vinyl group-containing compound (1), compounds represented by the following general formulas (i) to (iv) are preferable.

CF = CF- (CF) Z ¹ (i)

2 2 q

CF = CF— (CF C (CF) F) Z ¹ (ii)

2 2 3 r

CF = CF (CF) One O— (CF CFXO) One (CF) One Z ¹ (iii)

2 2 s 2 t 2 u

CF = CFCF 0 (CF (CF) CF O) CF (CF) l) (iv)

2 2 3 2 v 3

[In each formula, q represents an integer from 1 to 8, r represents an integer from 1 to 5, s represents an integer from 0 to 2, t represents an integer from 0 to 3, u represents Represents an integer of 1 to 8, and V represents an integer of 0 to 10; X represents F or —CF, and Z ¹ represents a hydrophilic group. ]

Three

[0034] Examples of the fluorine-containing vinyl group-containing compound (1) include the following compounds: CF = CFCFCOONH, CF = CFCFCFCOONH,

2 2 4 2 2 2 4

CF = CFOCF CF (CF) OCF CF COONH,

2 2 3 2 2 4

CF = CFCF SO Na, CF = CFCF CF SO Na ゝ CF = CFOCF CF SO Na

2 2 2 3

CF = CFOCF CF (CF) OCF CF SO Na

2 2 3 2 2 3

CF = CFCF OCF CF SO Na

2 2 2 2 3

CH = CHCF CF COONH CH = CHCF CF SO Na

2 2 2 4 2 2 2 3

CH = CFCF OCF (CF) CF OCF (CF) COONH

2 2 3 2 3 4

In the radical polymerization in the present invention, in addition to the above-mentioned fluorine-containing vinyl group-containing compound (1), a fluorocarbon group and a hydrophilic group in which 1 to 6 carbon atoms to which fluorine atoms are directly bonded are continuously bonded. The hydrophilic group in the fluorine-containing compound (2) is the same as that described in the fluorine-containing bull group-containing compound (1). is there.

In the present invention, “bonded in a range of 1 to 6 carbon atoms directly bonded with fluorine atoms” has the following meaning.

The above "carbon atom with fluorine atoms directly bonded" means -CF CF

3 carbon, 2 carbon, CF

H Carbon, CFR Carbon (R is an alkyl group), etc. means a carbon atom to which a fluorine atom is bonded. The above “bonded continuously in the range of 1 to 6” means that the carbon atoms present in the molecule are continuous in the range of 1 to 6 and do not contain 7 or more continuous units. To do. That is, the present invention addresses such problems in view of the fact that the compound containing a unit in which seven or more “carbon atoms directly bonded with fluorine atoms” are bonded continuously decreases the solubility in water. The fluorine-containing compound is selected as the fluorine-containing compound (2) without being generated.

The above-mentioned structure in which “carbon atoms to which fluorine atoms are directly bonded are continuously bonded in the range of 1 to 6” may have two or more in one molecule. In the above fluorine-containing compound (2), this structure can be expressed as Rf—O—Rf Rf—Rh—Rf ^b Rf—COO Rf ^b (in each formula, Rf and Rf ^b are each an arbitrary book) Rh represents an arbitrary alkenyl group), etc., and has two or more via structural units other than this structure.

The emulsion polymerization may be one in which one of the fluorine-containing compounds (2) is present, or 2 It can be more than a species.

[0036] The fluorine-containing compound (2) has the general formula (III)

Y-Rf-Z ³ (III)

The fluorine-containing compound (2a) represented by

[0037] In the general formula (III),! /, Y represents H, C1 or F.

Rf represents a linear or branched saturated fluoroalkylene group having 2 to 16 carbon atoms which may contain ether oxygen (however, it does not include a chain of 7 or more carbon atoms to which fluorine atoms are directly bonded). Rf is preferably a linear or branched saturated fluoroalkylene group having 2 to 5 carbon atoms which may contain ether oxygen. Z ³ above is --COOM ¹ SO Ms and

And M ⁶ are the same or different and each represents H or a monovalent cation. Examples of the monovalent cation include those described above.

[0038] Examples of the fluorine-containing compound (2) include compounds represented by the following general formulas (V) to (viii).

Y ^1- (CF) -Z ⁴ (V)

2 aa

Y ^2- (CF) -0-CF (CF) -Z ⁵ (vi)

2 ab 3

Y ³ — (CF) — O— CF CF— Z ⁶ (vii)

CF CHF-O-CF CF—Z ⁷ (viii)

twenty two

Y ² and Y ³ represent H, F or CI, respectively, and Z ⁶ and Z ⁷ are the same as Z ³ above. aa is 2-5, preferably 3-4. ab represents 1-3. ac represents 1-3. [0039] Examples of the fluorine-containing compound (2) include the following compounds.

CF (CF) COONH, CF (CF) COONH,

3 2 4 4 3 2 3 4

CF (CF) COONH, CF (CF) SO Na ゝ

3 2 2 4 3 2 3 3

CF (CF) SO NH, (CF) CFCF COONH,

3 2 3 2 2 3 2 2 4

H (CF) COONH, CF (CF) O— CF (CF) COONH,

2 4 4 3 2 2 3 4

(CF) CF-0-CF (CF) COONH,

3 2 3 4

CF O — CF (CF) COONH,

3 3 4

HCF CF— O— CF CF SO Na ゝ HCF CF -O-CF CF SO NH,

2 2 2 2 2 2

CF CHF-O-CF CF SO Na

3 2 2 3

[0040] In addition to the fluorine-containing monomer, the fluorine-containing vinyl group-containing compound (1), and the fluorine-containing compound (2), the radical polymerization may optionally include a radical polymerization initiator, a chain transfer agent, and the like in an aqueous medium. Add it and go.

[0041] Examples of the radical polymerization initiator include peroxides of water-soluble inorganic compounds or water-soluble organic compounds, for example, persulfates such as ammonium persulfate and potassium persulfate, psuccinic acid peroxide, and bisdaltalic acid peroxide. These are generally used, and these may be used alone or in combination of two or more. It is preferable to use a redox initiator in the low temperature polymerization. Further, in the range where the stability of the disk purgen is not impaired, either or both of the water-insoluble organic peroxide compound and the azo compound are used alone or a water-soluble inorganic compound or a water-soluble organic compound peroxide. Use with it.

[0042] The chain transfer agent is a saturated hydrocarbon having 1 to 6 carbon atoms or an alcohol having 1 to 4 carbon atoms, a carboxylic acid ester compound having 4 to 8 carbon atoms, a chlorine-substituted hydrocarbon having 1 to 2 carbon atoms, The chain transfer agent is preferably a ketone having 3 to 5 carbon atoms and Z or a mercaptan having 10 to 12 carbon atoms. The chain transfer agent has a dispersibility in a polymerization medium, a chain transfer property, and a removability from a target product. In this respect, ethane, isopentane, methanol, isopropanol, acetone, and / or ethyl acetate are more preferable.

[0043] The radical polymerization may be carried out by appropriately adding additives such as a pH adjuster and a radical scavenger.

Conventionally known pH adjusting agents and radical scavengers can be used.

In the present invention, the fluorine-containing vinyl group-containing compound (1) is preferably added in an amount corresponding to 10 to 300 ppm of the aqueous medium.

If the fluorine-containing vinyl group-containing compound (1) is less than the amount corresponding to lOppm of the aqueous medium, the number of emulsified particles generated at the initial stage of polymerization is reduced and the polymerization rate is reduced. If the amount is higher than the amount corresponding to 300 ppm of the aqueous medium, the induction period until the start of polymerization may become extremely long and the production efficiency may be deteriorated. The addition amount of the fluorine-containing vinyl group-containing compound (1) is more preferably an amount corresponding to 15 ppm or more of an aqueous medium and an amount corresponding to 250 ppm or less, and further preferably an amount corresponding to 20 ppm or more of an aqueous medium. The amount is less than or equal to 200 ppm of the aqueous medium.

In the radical polymerization, when the amount of the fluorine-containing vinyl group-containing compound (1) is larger than the above range, the reason why the induction period until the start of polymerization is long is not clear. They understand as follows.

In the radical polymerization, since the emulsified particles are not present at the initial stage of polymerization, aqueous polymerization that forms an oligomer is caused by the reaction between the monomer dissolved in the aqueous medium and the radical species. After a phase transition occurs in which the product is converted into emulsified particles, the emulsified particles grow by emulsion polymerization and the fluoropolymer chain extends. Here, examples of the water-insoluble oligomer include oligomers having a high ratio of fluorine-containing monomer units. However, in the aqueous solution polymerization, the fluorine-containing vinyl group-containing compound (1) has higher solubility in water, and therefore reacts with the radical species in preference to the fluorine-containing monomer. As a result, the oligomer mainly produced in the aqueous solution polymerization has a high proportion of the fluorine-containing vinyl group-containing compound (1) unit, and thus becomes hydrophilic and cannot undergo phase transition. That is, the fluorine-containing vinyl group-containing compound (1) is consumed, and the abundance ratio of the fluorine-containing bull group-containing compound (1) to the fluorine-containing monomer in the aqueous medium is reduced. Phase transition does not occur until a high proportion of oligomers is produced. Therefore, if the amount of the fluorine-containing bull group-containing compound (1) is large, the induction period is considered to be long.

[0046] In the radical polymerization, the fluorine-containing compound (2) is preferably added in an amount corresponding to 100 to 50,000 ppm of the aqueous medium.

If the amount is less than the amount corresponding to lOOppm of the aqueous medium, the emulsion stabilization effect may not be obtained. If the amount is more than 50000ppm, the post-treatment process may be difficult.

The concentration of the fluorine-containing compound (2) before the start of the radical polymerization is more preferably aqueous 200ppm of the medium [above the amount equivalent to the amount of money, 20000ppm [less than the amount of the amount of money, more preferably the amount equivalent to 500ppm of the aqueous medium, and the amount equivalent to lOOOOppm of the aqueous medium] It is as follows.

[0047] The fluorine-containing compound (2) may be added in advance before radical polymerization, and may be added as appropriate during the polymerization. It is preferable that it is added in advance before the start of radical polymerization in terms of simple operation.

In the present invention, the fluorine-containing vinyl group-containing compound (1) in an amount corresponding to 10 to 300 ppm of the aqueous medium and the aqueous medium 100 are obtained in that the polymer concentration is high at the end of the polymerization and emulsion is obtained. It is preferable to add the fluorine-containing compound (2) in an amount corresponding to ˜50000 ppm to the aqueous medium.

[0048] The amount of the radical polymerization initiator added depends on the composition and yield of the fluorine-containing polymer to be produced, the amount of the fluorine-containing monomer, the fluorine-containing vinyl group-containing compound (1) and the fluorine-containing compound (2) used. And can be set as appropriate. The radical polymerization initiator is preferably added in an amount of 0.0001-3.0 parts by mass with respect to 100 parts by mass of the total amount of the resulting fluoropolymer. 0.005-0. 3 parts by mass It is more preferable to add this amount.

[0049] The chain transfer agent may be added in an amount of 0 to 5 parts by mass with respect to 100 parts by mass of the total addition amount of the fluorine-containing monomer and the fluorine-containing butyl group-containing compound (1). preferable. More preferably, the chain transfer agent is added in an amount of 0.0005 parts by mass or more, more preferably 0.001 parts by mass or more, with respect to the total addition amount of 100 parts by mass, and the total addition amount of 100 parts by mass. On the other hand, it can be added in an amount of 1 part by mass or less, more preferably 0.1 part by mass or less.

[0050] The radical polymerization can be carried out by any of batch operation, semi-batch operation and continuous operation, and a known polymerization method can be applied.

In the radical polymerization, the fluorine-containing monomer, the fluorine-containing group-containing compound (1) and the fluorine-containing compound (2), and additives such as a chain transfer agent and a polymerization initiator that are optionally added are used in the polymerization reaction. In the meantime, it is possible to follow up appropriately depending on the composition and yield of the desired fluoropolymer.

[0051] The radical polymerization is generally performed while maintaining a temperature in the range of 10 to 120 ° C. If the temperature is less than 10 ° C, the reaction rate may not be effective on an industrial scale.If the temperature exceeds 120 ° C, the reaction pressure required to maintain the polymerization reaction may be insufficient. It may become high and the reaction cannot be maintained.

[0052] The radical polymerization is generally performed while maintaining the pressure in the range of 0.2 to 5. OMPa. When the pressure is less than 0.2 MPa, the concentrations of the fluorine-containing monomer and the fluorine-containing vinyl group-containing compound) in the polymerization reaction system become too low to achieve a satisfactory reaction rate. Productivity may deteriorate, and if it exceeds 5. OMPa, a reactor with high pressure resistance is required, which disadvantageously increases equipment costs.

The pressure has a preferable lower limit of 0.4 MPa and a preferable upper limit of 2. OMPa. When the radical polymerization is carried out in a semi-batch operation, the desired polymerization pressure can be achieved at the initial stage of polymerization by adjusting the amount of the fluorine-containing monomer gas at the initial supply, and after the start of the reaction, the fluorine-containing monomer. The pressure can be adjusted by adjusting the additional gas supply.

When the radical polymerization is carried out in a continuous operation, the desired polymerization pressure is adjusted by adjusting the back pressure of the resulting outflow pipe of the emulsion.

The radical polymerization is generally carried out for 0.5 to: LOO time.

[0053] By radical polymerization, an emulsion in which fluorine-containing polymer particles are dispersed in an aqueous medium can be obtained.

Since the emulsion does not contain a conventional surfactant having a long-chain fluorine-containing alkyl group, it can be easily purified without problems caused by the surfactant such as foaming and coloring in polymer molding.

The fluorine-containing polymer particles contain monomer units derived from the fluorine-containing vinyl group-containing compound (1), so that they have excellent dispersibility and can be stably dispersed even in conventional aqueous media that do not contain a surfactant. be able to.

[0054] The fluorine-containing polymer production method of the present invention can obtain emulsion having a fluorine-containing polymer concentration of 20% by mass or more at the end of the radical polymerization.

The fluorine-containing polymer concentration in the emulsion is preferably 22% by mass or more, more preferably 25% by mass or more, and may be 60% by mass or less as long as it is within the above range. In this specification, the fluoropolymer concentration (P) is obtained by taking about 1 lg (X) of a sample in an aluminum cup having a diameter of 5 cm, drying at 100 ° C for 1 hour, and further drying at 300 ° C for 1 hour. It is determined by the formula: P = ZZXX 100 (%) based on the heating residue (Z).

[0055] The fluoropolymer production method of the present invention may include post-treatment steps such as concentration, dilution and purification after the radical polymerization as long as it includes the above-mentioned radical polymerization. It may include a process of analyzing the powder and covering the powder.

The operations and conditions in the post-treatment step and the powder processing step are not particularly limited, and a conventionally known method can be performed.

[0056] The method for producing a fluoropolymer of the present invention may include a step of stabilizing an unstable group of the fluoropolymer by fluorination.

When the obtained fluoropolymer is used for applications that require high stability, such as components for semiconductor manufacturing equipment or electrolyte membranes for fuel cells, the fluoropolymer main chain terminal and fluorine-containing vinyl group-containing polymer It is preferable to perform this step because the hydrophilic group derived from the compound (1) becomes an unstable group such as —COOH, —COF, and —CF 2 = CF, which may deteriorate the performance.

2

Good. By performing this stability, problems such as foaming and coloring in the molding of the resulting fluoropolymer can be prevented.

As a method for stabilizing the above, the unstable group is removed by contacting with a fluorinating agent such as fluorine gas.

F

There are a method of converting to 3 groups, a method of converting an unstable terminal group to a carboxylate, and then converting it to a CFH group by decarboxylation reaction. International Publication No. 2005-028522

2

The method of contacting with a fluorine gas described in a lett or the like is the simplest and preferable.

[0057] The fluorine-containing polymer obtained by the method for producing a fluorine-containing polymer of the present invention is also one of the present invention.

As described above, the fluorine-containing polymer of the present invention is useful as a material for an aqueous dispersion of a fluorine-containing polymer that is more stable than conventional ones.

The electrolyte membrane containing the fluorine-containing polymer of the present invention is also one aspect of the present invention.

A membrane electrode assembly containing the above-mentioned fluoropolymer is also one aspect of the present invention.

A fuel cell including the electrolyte membrane or the membrane electrode assembly is also one aspect of the present invention. The electrolyte membrane, the membrane electrode assembly, and the fuel cell can all be produced using the fluorine-containing polymer of the present invention by a conventionally known method.

The invention's effect

[0059] Since the method for producing a fluoropolymer of the present invention has the above-described configuration, the fluoropolymer can be efficiently produced in a short time.

BEST MODE FOR CARRYING OUT THE INVENTION

[0060] The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples and Comparative Examples.

The amount of the composition in each example and comparative example is based on mass unless otherwise specified.

[0061] 1. Fluorine-containing polymer concentration (P)

About 1 lg (X) of the sample is placed in an aluminum cup with a diameter of 5 cm, dried at 100 ° C for 1 hour, and further dried at 300 ° C for 1 hour. Based on the heating residue (Z), the formula: P = ZZXX 100 (%).

[0062] 2. Number of functional groups by infrared absorption spectroscopy [IR] analysis

Each sample was 10 minutes heat-pressed at 270 ° C and, after obtaining a transparent film, was carried out by measuring a range of wave numbers 400～4000Cm ^_1 the film at a Fourier transform type infrared absorption spectroscopy.

As a Fourier transform infrared absorption spectrometer used in the Fourier transform infrared absorption spectroscopy, a Spectrum One type spectrometer manufactured by Perkin Elma Co., Ltd. was used, and the number of scans was eight.

In the analysis of the above measurement, a difference spectrum with a sufficiently fluorinated standard sample until the spectrum no longer shows a substantial difference is obtained, and the absorbance at the wave number attributed to each functional group is read. According to the calculation, the number of functional groups per 10 ⁶ carbon atoms was calculated. Number of end groups per 10 ⁶ carbon atoms = I XK / t

(In the above formula, I is the absorbance, K is the correction factor shown in Table 1, and t is the thickness of the finalem used in the measurement (unit: mm).) Regarding -COO- is two as shown in Table 1 - was COO- number of - COO- wavenumber per above equation or we calculated value sum several 10 ⁶ per carbons indicated.

In addition, if the number of functional groups per 10 ⁶ carbon atoms is less than 1 in this formula, the presence of force functional groups that are below the measurement limit in this measurement method is not denied.

[0063] [Table 1]

[0064] 3. Polymer yarn

It was determined by measuring ¹⁹ F-NMR using a BRUKER NMR measuring apparatus.

[0065] Example 1

In a 6L stainless steel autoclave equipped with a stirrer, 3000ml of deionized water, and CF = CFOCF CF (CF) OCF C as the fluorine-containing bull group-containing compound (1)

2 2 3 2

F SO NaO. 3g (amount equivalent to lOOppm of deionized water) and fluorine-containing compound (2)

twenty three

F (CF) COONH 3g (amount equivalent to lOOOppm of deionized water)

2 4 4

After repeating element pressurization and vacuum degassing, prepare CF CFOCF CF SO F170g under reduced pressure.

2 2 2 2

It was crowded. Subsequently, after vacuum and tetrafluoroethylene [TFE] substitution was repeated twice, the temperature was raised to 50 ° C. and the gauge pressure was increased to 0.7 MPa with TFE. Subsequently, ammonium persulfate in 7.5 mass ^_0/0 as a polymerization initiator - and pressed into the © anhydrous solution 20g to initiate polymerization.

Since the pressure drop started 20 minutes after the polymerization initiator was injected, TFE was supplied so as to keep the polymerization tank pressure at 0.7 MPa. Also, CF = CFOCF CF SO F in an amount equivalent to 0.7 times in mass ratio with respect to the amount of TFE supplied is continuously supplied for polymerization.

2 2 2 2

Continued.

After 11 hours, when the amount of TFE supplied reached 770 g, the pressure in the polymerization tank was released to stop the polymerization, and the mixture was cooled to obtain 4500 g of a white polymer dispersion (emulsion). In the autoclave, the adhering polymer was almost unrecognized.

A portion of the obtained emulsion was dried and the polymer concentration was measured. [0066] 2000 g of the above emulsion was diluted 3 times with water, and nitric acid was added to pour, and the slurry was filtered. The collected slurry was put into a 10 L polyethylene container, re-dispersed with 5 L of ion exchange water, filtered and washed. The pH of the filtrate after further repeating this washing step three times was 5, and it was confirmed that the acid was sufficiently removed.

Subsequent drying at 100 ° C. yielded 580 g of polymer.

Par Full O b the resulting polymer was examined for its composition was analyzed by solid NMR, it found that a copolymer of TFE81 mole ^_0/0 and CF = CFOCF CF SO F19 mol ^_0/0.

2 2 2 2

Results of IR analysis, the carbon 10 200 ⁶ per - COO- and sixty - SO H exists child

Three

I understood.

[0067] 100 g of the obtained perfluoropolymer was put into a 500 cc Hastelloy autoclave, sufficiently purged with vacuum and nitrogen, heated to 120 ° C, and diluted with nitrogen to 20% fluorine gas Was allowed to react for 1 hour. The autoclave was then evacuated to vacuum and charged with fluorine gas diluted to 20% with nitrogen and allowed to react for 3 hours. Subsequently, the inside of the auto-tale was purged with vacuum and nitrogen and cooled to room temperature to recover the polymer.

As a result of IR analysis of the obtained perfluoropolymer, the --00_ group and the --30 H group

Three

The field was (both 5 per carbon 10 ⁶⁾ below.

[0068] Example 2

In a 6L stainless steel autoclave equipped with a stirrer, 3L of deionized water, 120g of paraffin wax (melting point 56 ° C), and CF = CFOCF CF SO NaO. As the fluorine-containing vinyl group-containing compound (1). 6g (amount equivalent to 200ppm of deionized water)

2 2 2 3

F (CF) COONH 3g as elemental compound (2) (amount equivalent to lOOOppm of deionized water)

2 5 4

), And the inside of the autoclave was replaced with vacuum ′ and nitrogen. Further, after the autoclave was evacuated, the autoclave was replaced twice with TFE monomer, pressurized to 0.20 MPa and heated to 70 ° C. After pressurizing to 0.80 MPa with TFE, 20 g of 0.15% by weight aqueous ammonium persulfate solution was subsequently injected as a polymerization initiator to initiate polymerization.

Since pressure drop began 20 minutes after the polymerization initiator was injected, TFE was supplied to keep the polymerization tank pressure at 0.8 MPa, and the polymerization was continued.

Nine hours later, when the TFE supply amount reached 800 g, the polymerization tank pressure was released to stop the polymerization. Then, the mixture was cooled and paraffin was recovered to obtain 3750 g of white PTFE Dispurgeon (Emulsion).

A portion of the obtained emulsion was dried and the solid content was measured to be 21.0%.

In the autoclave, the adhering polymer was almost unrecognized.

[0069] The obtained emulsion lOOOOg was put into a stainless steel container with a 6 L internal volume stirrer and a valve attached to the bottom, and diluted with 1 L of ion-exchanged water. Nitric acid was added with stirring to separate the polymer. Valve force at the bottom The operation of collecting drainage, adding 3 L of ion exchange water, stirring and washing was repeated 3 times. The final wastewater had a pH of 5, and it was confirmed that the acid was sufficiently removed.

Bow I followed by drying at 150 ° C. to obtain 100 g of PTFE polymer.

[0070] Example 3

A stainless steel autoclave with an internal volume of 3L equipped with a stirrer is mixed with 1500 g of deionized water and a compound containing fluorine bur group (1) CF = CFOCF CF (CF) OCF CF COONaO

2 2 3 2 2

2 g (amount equivalent to 133 ppm of deionized water), F (CF) C as fluorine-containing compound (2)

twenty five

OONH 7.5g (equivalent to 0.5% of deionized water) is charged and charcoal is used as a pH adjuster.

Four

1. 8 g of acid ammonium (monohydrate) was charged. After the inside of the autoclave was purged with vacuum and nitrogen, hexafluoropropylene [HFP] was introduced so as to be 0.2 MPa, and the temperature was raised to 80 ° C. Subsequently, HFP and TFE were introduced until the pressure became 0.8 MPa, and it was confirmed by gas chromatography that the composition of the gas phase was 25 Z75 mol%. Subsequently, 10 g of a 7.5% by mass ammonium persulfate aqueous solution was injected as a polymerization initiator to initiate the polymerization. Since the pressure drop started 30 minutes after the polymerization initiator was injected, the polymerization was continued by supplying a mixed gas of TFEZHFP = 88Z12 molar ratio so as to keep the polymerization tank pressure at 0.8 MPa. In order to maintain the polymerization rate, 4 g of a 7.5 mass% ammonium persulfate aqueous solution was added every 3 hours. Stirring was stopped 20 hours after the start of polymerization to release the monomer gas, and the reaction was stopped. Thereafter, the mixture was cooled to room temperature to obtain 2050 g of a white TFEZHFP copolymer [FEP] Dispersion (Emulsion).

A portion of the obtained emulsion was dried and the solid content was measured to find 25.8%. I

In the autoclave, the adhering polymer was almost unrecognized.

[0071] 1500 g of the resulting Dispersion was diluted 3 times, and nitric acid was added to pray, and the slurry was filtered. The recovered slurry was put into a 10 L polyethylene container, re-dispersed by adding 5 L of ion exchange water, filtered and washed. The pH of the filtrate after repeating this washing step three more times was 5, and it was confirmed that the acid was sufficiently removed.

Subsequent drying at 100 ° C. yielded 380 g of polymer.

When this polymer was analyzed by NMR, it was TFE88. 5 mole ^_0/0, HFP11. 5 mole ^_0/0 of the FE P.

[0072] Example 4

In a 6L stainless steel autoclave equipped with a stirrer, 3 liters of deionized water and CF = CFOCF CF SO NaO. 6g as the fluorine-containing bur group-containing compound (1) (deionized water

2 2 2 3

F (CF) SO Na6g (deio) as the fluorine-containing compound (2)

2 5 3

The amount of water in the autoclave was replaced with vacuum and nitrogen, and then evacuated and charged with 20 ml of ethane as a chain transfer agent. Subsequently, 45 g of perfluorinated mouth (propyl butyl ether) [PPVE] was sucked, pressurized to 0.20 MPa with TFE monomer, and heated to 70 ° C. Pressurized Thereafter TFE up to 0. 80 MPa, ammonium persulfate of a polymerization initiator 0.30 mass ^_0/0 - a © anhydrous solution 20g to start the polymerization pressed. Since pressure drop began 30 minutes after the polymerization initiator was injected, TFE was supplied so as to keep the polymerization tank pressure at 0.8 MPa. Further, 20 g of PPVE and 8 g of an aqueous 30% by mass ammonium persulfate solution were added every 5 hours to continue the polymerization.

After 15 hours, when the amount of TFE supplied reached 850 g, the polymerization tank pressure was released to stop the polymerization, and the polymerization was stopped by cooling to recover paraffin to obtain 4100 g of white TFEZPAVE copolymer [PFA] Marsillon. It was.

A portion of the obtained emulsion was dried and the solid content was measured to be 23.4%.

In the autoclave, the adhering polymer was almost unrecognized.

Dilute 2000g of the resulting emulsion twice, add nitric acid and pray, and filter the slurry. It was. The recovered slurry was put into a 10 L polyethylene container, re-dispersed by adding 5 L of ion exchange water, filtered and washed. The pH of the filtrate after repeating this washing step three more times was 5, and it was confirmed that the acid was sufficiently removed.

Subsequent drying at 100 ° C. yielded 450 g of polymer.

When this polymer was analyzed by NMR, it was TFE97. 5 mole ^_0/0, PPVE2. 5 mole ^_0/0 of PF A.

[0073] Comparative Example 1

Other than using fluorine-containing compound (2) and using F (CF) COONH 15 g as an emulsifier

2 7 4

Was conducted in the same manner as in Example 1. After 10 hours of polymerization time, 4500 g of PTFE dispersion was obtained.

In the autoclave, the adhering polymer was almost unrecognized.

A portion of the resulting purged yon was dried and the solid content was measured.

The resulting Dispersion 2000g was diluted 3 times, and nitric acid was added to pray and the slurry was filtered. The recovered slurry was put into a 10 L polyethylene container, re-dispersed by adding 5 L of ion exchange water, filtered and washed. The pH of the filtrate was 3 after repeating this washing step three more times. In addition, foaming of the filtrate was observed, and F (CF) C used as a milky additive

2 7

It was suggested that the removal of OONH was insufficient.

Four

[0074] Comparative Example 2

Polymerization was carried out in the same manner as in Example 1 except that the fluorine-containing compound (2) was not used. After 10 hours, when the amount of TFE supplied reached 770 g, the polymerization tank pressure was released to stop the polymerization, and the autoclave was opened after cooling to remove a large amount of perfluoropolymer. It was confirmed.

The polymer was filtered off, the aqueous phase was recovered, and the solid content was measured and found to be 4.5%. From the above, it was shown that the obtained purge was unstable under this condition.

[0075] Comparative Example 3

Polymerization was carried out in the same manner as in Example 2 except that the fluorine-containing compound (2) was not used. When the amount of TFE fed reached 550 g, the pressure did not drop and the polymerization reaction stopped. When the pressure in the polymerization tank was released to stop the polymerization, and after cooling and opening the autoclave, it was confirmed that a large amount of perfluoropolymer was separated.

The polymer was filtered and the aqueous phase was almost transparent, and the polymer particles were almost absent.

From the above, it was shown that the disc purge was unstable under this condition.

Industrial applicability

Since the method for producing a fluoropolymer according to the present invention comprises the above-described configuration, the fluoropolymer can be efficiently produced in a short time.

Claims

The scope of the claims

[1] A method for producing a fluorine-containing polymer by radical polymerization of a fluorine-containing monomer in an aqueous medium,

In the radical polymerization, the fluorine-containing beryl group-containing compound (1) having a radical polymerizable unsaturated bond and a hydrophilic group, and the carbon atom to which the fluorine atom is directly bonded are continuously in the range of 1 to 6 carbon atoms. In the presence of a fluorinated compound (2) having a fluorocarbon group and a hydrophilic group to be bonded

A method for producing a fluorine-containing polymer.

[2] The method for producing a fluoropolymer according to [1], wherein the fluoropolymer is a perhalopolymer.

[3] The fluorine-containing vinyl group-containing compound (1) has the following general formula (I)

CR'R ^ CR ^ CR)

j-(O) k -RZ ¹ (I)

[Wherein R ¹ R ² , R ⁴ and R ⁵ are the same or different and each represents a fluoroalkyl group, H, F, Cl, Br or I, and R represents a linear or branched fluoro group optionally having an oxygen atom in the main chain. Represents an alkylene group. j represents an integer of 0 to 6, k represents an integer of 0 or 1, and Z ¹ represents a hydrophilic group. 3. The method for producing a fluorine-containing polymer according to claim 1, wherein the fluorine-containing bull group-containing compound (la) is represented by the formula:

[4] The fluorine-containing vinyl group-containing compound (1) has the following general formula (II)

CF = CFO— (CF CF (CF) θ) (CF) Z ² (II)

2 2 3 1 2 m

[Wherein, 1 represents an integer of 0 to 3, and m represents an integer of 2 to 8. Z ² is -COOM ¹ , —SOM ² , M ³ and M ⁴ are the same or young

Are different and represent H or a monovalent cation, and R ⁶ and R ⁷ are the same or different and represent a hydrogen atom, an alkali metal, an alkyl group or a sulfol-containing group. ]

The method for producing a fluorinated polymer according to claim 1 or 2, wherein the fluorinated vinyl group-containing compound (lb) is represented by the formula:

[5] The fluorine-containing compound (2) is represented by the following general formula (III)

Y-Rf-Z ³ (III)

(Y represents H, CI or F, and Rf represents 7 or more carbon atoms directly bonded to fluorine atoms. A straight chain or branched saturated fluoroalkylene group having 2 to 16 carbon atoms which does not contain a chain and may contain ether oxygen, Z ³ represents -COOM ¹ , -SO M ² , -SO NM ³ M ⁴ or

3 2

PO M ⁵ and M ⁶ are the same or different and H or

Represents a monovalent cation. The fluorine-containing compound (2a) represented by any one of claims 1 to 4

2. The method for producing a fluorine-containing polymer according to item 1.

[6] The method for producing a fluorine-containing polymer according to any one of [1] to [5], wherein an amount of the fluorine-containing bull group-containing compound (1) corresponding to 10 to 300 ppm of the aqueous medium is added.

[7] The method for producing a fluorinated polymer according to any one of [1] to [6], wherein an amount of the fluorinated compound (2) corresponding to 100 to 50,000 ppm of the aqueous medium is added.

8. The method for producing a fluoropolymer according to any one of claims 1 to 7, wherein an emulsion having a fluoropolymer concentration of 20% by mass or more is obtained at the end of radical polymerization.

[9] The method according to claim 1, further comprising the step of stabilizing the labile group of the fluoropolymer by fluorination.

The method for producing a fluoropolymer according to any one of ˜8.

[10] Obtained by the method for producing a fluoropolymer according to any one of claims 1 to 9.

A fluorine-containing polymer.

[11] Including the fluorine-containing polymer according to claim 10.

An electrolyte membrane characterized by that.

[12] Including the fluoropolymer according to claim 10.

A membrane electrode assembly characterized by the above.

[13] The electrolyte membrane according to claim 11 or the membrane electrode assembly according to claim 12

The fuel cell characterized by the above-mentioned.