Method for producing aqueous fluoropolymer dispersion, method for treating wastewater, and aqueous fluoropolymer dispersion

Abstract

To provide a method for producing an aqueous fluoropolymer dispersion with reduced coloration.SOLUTION: The method for producing an aqueous fluoropolymer dispersion includes a step A of performing ultrafiltration, microfiltration or dialysis membrane treatment, or a combination thereof on an aqueous dispersion before treatment that contains a fluoropolymer that is obtained by polymerization in the presence of a polymer (I) containing a polymerization unit (I) based on a monomer, represented by the following general formula (I), (excluding the above polymer (I)). CX1X3=CX2R(-CZ1Z2-A0)m (I) (wherein X1 and X3 are each independently F, Cl, H or CF3; X2 is H, F, an alkyl group or a fluorine-containing alkyl group; A0 is an anionic group; R is a linking group; Z1 and Z2 are each independently H, F, an alkyl group, or a fluorine-containing alkyl group; and m is an integer of 1 or more.)SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing an aqueous fluoropolymer dispersion, a method for treating wastewater, and an aqueous fluoropolymer dispersion. [Background technology]

[0002] In the production of fluoropolymers, a method of using a specific fluorine-containing polymer is known.

[0003] For example, Patent Document 1 describes a method for producing an aqueous dispersion containing rod-shaped polytetrafluoroethylene microparticles having an average aspect ratio of 2 or more, which is characterized by polymerizing tetrafluoroethylene in the presence of a polymer consisting of polymerization units represented by Formula 1, or a copolymer consisting of polymerization units represented by Formula 1 and polymerization units represented by Formula 2 (provided that the proportion of polymerization units represented by Formula 1 relative to all polymerization units is 40 mol % or more). [ka] -CF2CFX- ...Formula 2 However, in Equation 1, R f is a perfluoroperfluoroalkylene group having 1 to 6 carbon atoms, M is an alkali metal ion or an ammonium ion, and in formula 2, X is a fluorine atom or a chlorine atom.

[0004] Patent Document 2 describes the use of ultrafiltration to concentrate a dispersion containing an ammonium salt of perfluorooctanoic acid obtained by emulsion polymerization, thereby increasing the amount of fluoropolymer solids. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-181009 [Patent Document 2] Special Publication No. 2006-523758 Summary of the Invention [Problem to be solved by the invention]

[0006] The present disclosure provides a method for producing an aqueous fluoropolymer dispersion having reduced color. [Means for solving the problem]

[0007] The present disclosure provides a method for producing an aqueous fluoropolymer dispersion, comprising step A of subjecting a pre-treatment aqueous dispersion containing a fluoropolymer (excluding the polymer (I)) obtained by polymerization in the presence of a polymer (I) containing polymerization units (I) based on a monomer represented by the following general formula (I) to ultrafiltration, microfiltration, or dialysis membrane treatment, or a combination thereof: CX 1 X 3 =CX 2 R(-CZ 1 Z 2 -A 0 ) m (I) (In the formula, X 1 and X 3 are each independently F, Cl, H, or CF; X 2 is H, F, an alkyl group or a fluorine-containing alkyl group; A 0 is an anionic group; R is a linking group; Z 1 and Z 2 are each independently H, F, an alkyl group or a fluorine-containing alkyl group; and m is an integer of 1 or more.

[0008] The above step A is preferably carried out at a temperature of 3°C or higher.

[0009] The above step A preferably involves at least microfiltration, more preferably using a microfiltration membrane having an average pore size of 0.05 μm or more, even more preferably using a microfiltration membrane having an average pore size of 0.075 μm or more, even more preferably using a microfiltration membrane having an average pore size of 0.10 μm or more, and particularly preferably using a microfiltration membrane having an average pore size of 0.15 μm or more.

[0010] The microfiltration is preferably carried out at a pressure of 0.01 MPa or more.

[0011] The ultrafiltration is preferably carried out at a pressure of 0.01 MPa or higher.

[0012] It is preferable to include a step B of adding a hydrocarbon surfactant to the pre-treatment aqueous dispersion before the step A. The hydrocarbon surfactant added in the step B is preferably a nonionic surfactant, and is represented by the following general formula (i): R 3 -OA 1 -H(i) (In the formula, R 3 is a linear or branched primary or secondary alkyl group having 8 to 18 carbon atoms, and A 1 is a polyoxyalkylene chain.) and a compound represented by the following general formula (ii): R 4 -C6H4-OA 2 -H (ii) (In the formula, R 4 is a linear or branched primary or secondary alkyl group having 4 to 12 carbon atoms, and A 2 is a polyoxyalkylene chain.

[0013] The fluoropolymer is preferably polytetrafluoroethylene, a tetrafluoroethylene / hexafluoropropylene copolymer or a tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer, and more preferably polytetrafluoroethylene.

[0014] The present disclosure further provides a method for producing an aqueous fluoropolymer dispersion, comprising a step A' of subjecting a pre-treatment aqueous dispersion containing a fluoropolymer (excluding the water-soluble polymer) obtained by polymerization in the presence of a water-soluble polymer in which 50% or more of hydrogen atoms bonded to carbon atoms have been substituted with fluorine atoms to ultrafiltration, microfiltration, or dialysis membrane treatment, or a combination thereof.

[0015] The present disclosure further provides a method for producing an aqueous fluoropolymer dispersion, comprising step A'' of carrying out ultrafiltration, microfiltration or dialysis membrane treatment, or a combination thereof, on a pre-treatment aqueous dispersion containing a fluoropolymer (excluding the above polymer) obtained by polymerization in the presence of a polymer in which the proportion of hydrogen atoms bonded to carbon atoms substituted with fluorine atoms is 50% or more, the polymer contains ionic groups, and the ion exchange rate is 53 or less. The present disclosure also provides a method for treating wastewater, comprising a step of recovering the polymer (I) from wastewater recovered in a step A in which a pre-treatment aqueous dispersion containing a fluoropolymer (excluding the polymer (I)) obtained by polymerizing a fluoromonomer (excluding the monomer represented by the following general formula (I)) in the presence of the polymer (I) comprising polymerization units (I) based on a monomer represented by the following general formula (I): CX 1 X 3 =CX 2 R(-CZ 1 Z 2 -A 0 ) m (I) (In the formula, X 1 and X 3 are each independently F, Cl, H, or CF; X2 is H, F, an alkyl group or a fluorine-containing alkyl group; A 0 is an anionic group; R is a linking group; Z 1 and Z 2 are each independently H, F, an alkyl group or a fluorine-containing alkyl group; and m is an integer of 1 or more. The present disclosure further provides an aqueous fluoropolymer dispersion comprising a polymer (I) containing polymerized units (I) based on a monomer represented by the following general formula (I), water, and a fluoropolymer (excluding the polymer (I)), The aqueous fluoropolymer dispersion has a difference ΔL* of less than 16 between the lightness L* of the aqueous fluoropolymer dispersion and the lightness L* of a post-microfiltration aqueous fluoropolymer dispersion obtained by microfiltration of the aqueous fluoropolymer dispersion. CX 1 X 3 =CX 2 R(-CZ 1 Z 2 -A 0 ) m (I) (In the formula, X 1 and X 3 are each independently F, Cl, H, or CF; X 2 is H, F, an alkyl group or a fluorine-containing alkyl group; A 0 is an anionic group; R is a linking group; Z 1 and Z 2 are each independently H, F, an alkyl group or a fluorine-containing alkyl group; and m is an integer of 1 or more. [Effects of the Invention]

[0016] The manufacturing method of the present disclosure can provide aqueous fluoropolymer dispersions with reduced coloration. DETAILED DESCRIPTION OF THE INVENTION

[0017] Before specifically describing the manufacturing method of the present disclosure, some terms used herein will be defined or explained.

[0018] In this specification, fluororesin refers to a partially crystalline fluoropolymer, or fluoroplastic. Fluororesin has a melting point and thermoplastic properties, but may be melt-processable or non-melt-processable.

[0019] In this specification, melt-processable means that the polymer can be melted and processed using conventional processing equipment such as an extruder, an injection molding machine, etc. Therefore, a melt-processable fluororesin usually has a melt flow rate of 0.01 to 500 g / 10 min, as measured by the measurement method described below.

[0020] In this specification, fluoroelastomer refers to an amorphous fluoropolymer. "Amorphous" means that the magnitude of the melting peak (ΔH) appearing in differential scanning calorimetry (DSC) (heating rate 10°C / min) or differential thermal analysis (DTA) (heating rate 10°C / min) of the fluoropolymer is 4.5 J / g or less. Fluoroelastomers exhibit elastomeric properties through crosslinking. Elastomeric properties refer to the ability of a polymer to be stretched and to retain its original length when the force required to stretch the polymer is no longer applied.

[0021] In this specification, the partially fluorinated rubber is a fluoropolymer that contains fluoromonomer units and has a perfluoromonomer unit content of less than 90 mol% relative to all polymerized units, and has a glass transition temperature of 20°C or lower and a melting peak (ΔH) magnitude of 4.5 J / g or lower.

[0022] In this specification, perfluororubber (perfluoroelastomer) is a fluoropolymer having a perfluoromonomer unit content of 90 mol% or more relative to all polymerized units, a glass transition temperature of 20°C or less, a melting peak (ΔH) magnitude of 4.5 J / g or less, and a fluorine atom concentration of 71 mass% or more. In this specification, the fluorine atom concentration in the fluoropolymer is determined by calculation from the type and content of each monomer constituting the fluoropolymer.

[0023] In this specification, a perfluoromonomer is a monomer that does not contain a carbon atom-hydrogen atom bond in the molecule. The perfluoromonomer may be a monomer containing carbon atoms and fluorine atoms, or a monomer in which some of the fluorine atoms bonded to carbon atoms are substituted with chlorine atoms, or may contain nitrogen atoms, oxygen atoms, sulfur atoms, phosphorus atoms, boron atoms, or silicon atoms in addition to carbon atoms. The perfluoromonomer is preferably a monomer in which all hydrogen atoms are substituted with fluorine atoms. The perfluoromonomer does not include monomers that provide crosslinking sites.

[0024] The monomer that provides a crosslinking site is a monomer (cure site monomer) having a crosslinkable group that provides a crosslinking site to the fluoropolymer for forming a crosslink with a curing agent.

[0025] In this specification, polytetrafluoroethylene [PTFE] is preferably a fluoropolymer having a tetrafluoroethylene content of 99 mol % or more relative to all polymer units.

[0026] In this specification, both the fluororesin (excluding polytetrafluoroethylene) and the fluororubber are preferably fluoropolymers having a tetrafluoroethylene content of less than 99 mol% relative to all polymerized units.

[0027] In this specification, the content of each monomer constituting the fluoropolymer can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and X-ray fluorescence analysis depending on the type of monomer.

[0028] As used herein, "organic group" means a group containing one or more carbon atoms or a group formed by removing one hydrogen atom from an organic compound. Examples of the "organic group" are: an alkyl group optionally having one or more substituents; an alkenyl group optionally having one or more substituents; an alkynyl group optionally having one or more substituents; a cycloalkyl group optionally having one or more substituents; a cycloalkenyl group optionally having one or more substituents, a cycloalkadienyl group optionally having one or more substituents, an aryl group optionally having one or more substituents; an aralkyl group optionally having one or more substituents; a non-aromatic heterocyclic group optionally having one or more substituents, a heteroaryl group optionally having one or more substituents; cyano group, formyl group, RaO-, RaCO-, RaSO2-, RaCOO-, RaNRaCO-, RaCONRa-, RaOCO-, RaOSO2- and, RaNRbSO2- (In these formulas, Ra independently represents: an alkyl group optionally having one or more substituents; an alkenyl group optionally having one or more substituents; an alkynyl group optionally having one or more substituents; a cycloalkyl group optionally having one or more substituents; a cycloalkenyl group optionally having one or more substituents, a cycloalkadienyl group optionally having one or more substituents, an aryl group optionally having one or more substituents; an aralkyl group optionally having one or more substituents; a non-aromatic heterocyclic group optionally having one or more substituents, or a heteroaryl group optionally having one or more substituents; Rb is independently H or an alkyl group which may have one or more substituents. Includes. The organic group is preferably an alkyl group which may have one or more substituents.

[0029] In addition, in this specification, the term "substituent" means a substitutable group. Examples of the "substituent" include an aliphatic group, an aromatic group, a heterocyclic group, an acyl group, an acyloxy group, an acylamino group, an aliphatic oxy group, an aromatic oxy group, a heterocyclic oxy group, an aliphatic oxycarbonyl group, an aromatic oxycarbonyl group, a heterocyclic oxycarbonyl group, a carbamoyl group, an aliphatic sulfonyl group, an aromatic sulfonyl group, a heterocyclic sulfonyl group, an aliphatic sulfonyloxy group, an aromatic sulfonyloxy group, a heterocyclic sulfonyloxy group, a sulfamoyl group, an aliphatic sulfonamido group, an aromatic sulfonamido group, a heterocyclic sulfonamido group, an amino group, an aliphatic amino group, an These include an amino group, an aromatic amino group, a heterocyclic amino group, an aliphatic oxycarbonylamino group, an aromatic oxycarbonylamino group, a heterocyclic oxycarbonylamino group, an aliphatic sulfinyl group, an aromatic sulfinyl group, an aliphatic thio group, an aromatic thio group, a hydroxy group, a cyano group, a sulfo group, a carboxy group, an aliphatic oxyamino group, an aromatic oxyamino group, a carbamoylamino group, a sulfamoylamino group, a halogen atom, a sulfamoylcarbamoyl group, a carbamoylsulfamoyl group, a dialiphatic oxyphosphinyl group, and a diaromatic oxyphosphinyl group.

[0030] The aliphatic group may be saturated or unsaturated and may have a hydroxy group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aliphatic group include alkyl groups having a total of 1 to 8, preferably 1 to 4, carbon atoms, such as a methyl group, an ethyl group, a vinyl group, a cyclohexyl group, and a carbamoylmethyl group.

[0031] The aromatic group may have, for example, a nitro group, a halogen atom, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aromatic group include aryl groups having 6 to 12 carbon atoms, preferably 6 to 10 carbon atoms in total, such as a phenyl group, a 4-nitrophenyl group, a 4-acetylaminophenyl group, and a 4-methanesulfonylphenyl group.

[0032] The heterocyclic group may have a halogen atom, a hydroxy group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the heterocyclic group include a 5- or 6-membered heterocycle having a total of 2 to 12, preferably 2 to 10, carbon atoms, such as a 2-tetrahydrofuryl group and a 2-pyrimidyl group.

[0033] The acyl group may have an aliphatic carbonyl group, an arylcarbonyl group, a heterocyclic carbonyl group, a hydroxy group, a halogen atom, an aromatic group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the acyl group include acyl groups having a total of 2 to 8, preferably 2 to 4, carbon atoms, such as an acetyl group, a propanoyl group, a benzoyl group, and a 3-pyridinecarbonyl group.

[0034] The acylamino group may have an aliphatic group, an aromatic group, a heterocyclic group, etc., such as an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, a propanoylamino group, etc. Examples of the acylamino group include acylamino groups having a total of 2 to 12 carbon atoms, preferably 2 to 8 carbon atoms, and alkylcarbonylamino groups having a total of 2 to 8 carbon atoms, such as an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, a propanoylamino group, etc.

[0035] The aliphatic oxycarbonyl group may be saturated or unsaturated and may have a hydroxy group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aliphatic oxycarbonyl group include alkoxycarbonyl groups having a total of 2 to 8, preferably 2 to 4, carbon atoms, such as a methoxycarbonyl group, an ethoxycarbonyl group, and a (t)-butoxycarbonyl group.

[0036] The carbamoyl group may have an aliphatic group, an aromatic group, a heterocyclic group, etc. Examples of the carbamoyl group include an unsubstituted carbamoyl group, an alkylcarbamoyl group having a total of 2 to 9 carbon atoms, preferably an unsubstituted carbamoyl group, an alkylcarbamoyl group having a total of 2 to 5 carbon atoms, such as an N-methylcarbamoyl group, an N,N-dimethylcarbamoyl group, and an N-phenylcarbamoyl group.

[0037] The aliphatic sulfonyl group may be saturated or unsaturated and may have a hydroxy group, an aromatic group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aliphatic sulfonyl group include alkylsulfonyl groups having a total of 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, such as a methanesulfonyl group.

[0038] The aromatic sulfonyl group may have a hydroxy group, an aliphatic group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aromatic sulfonyl group include arylsulfonyl groups having a total of 6 to 10 carbon atoms, such as a benzenesulfonyl group.

[0039] The amino group may have an aliphatic group, an aromatic group, a heterocyclic group, or the like.

[0040] The acylamino group may have, for example, an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, a propanoylamino group, etc. Examples of the acylamino group include an acylamino group having a total of 2 to 12 carbon atoms, preferably a total of 2 to 8 carbon atoms, and more preferably an alkylcarbonylamino group having a total of 2 to 8 carbon atoms, such as an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, a propanoylamino group, etc.

[0041] The aliphatic sulfonamide group, aromatic sulfonamide group, and heterocyclic sulfonamide group may be, for example, a methanesulfonamide group, a benzenesulfonamide group, or a 2-pyridinesulfonamide group.

[0042] The sulfamoyl group may have an aliphatic group, an aromatic group, a heterocyclic group, etc. Examples of the sulfamoyl group include a sulfamoyl group, an alkylsulfamoyl group having 1 to 9 carbon atoms in total, a dialkylsulfamoyl group having 2 to 10 carbon atoms in total, an arylsulfamoyl group having 7 to 13 carbon atoms in total, and a heterocyclic sulfamoyl group having 2 to 12 carbon atoms in total, more preferably a sulfamoyl group, an alkylsulfamoyl group having 1 to 7 carbon atoms in total, a dialkylsulfamoyl group having 3 to 6 carbon atoms in total, an arylsulfamoyl group having 6 to 11 carbon atoms in total, and a heterocyclic sulfamoyl group having 2 to 10 carbon atoms in total, such as a sulfamoyl group, a methylsulfamoyl group, an N,N-dimethylsulfamoyl group, a phenylsulfamoyl group, and a 4-pyridine sulfamoyl group.

[0043] The aliphatic oxy group may be saturated or unsaturated and may have a methoxy group, an ethoxy group, an i-propyloxy group, a cyclohexyloxy group, a methoxyethoxy group, etc. Examples of the aliphatic oxy group include alkoxy groups having a total of 1 to 8 carbon atoms, preferably 1 to 6 carbon atoms, such as a methoxy group, an ethoxy group, an i-propyloxy group, a cyclohexyloxy group, and a methoxyethoxy group.

[0044] The aromatic amino group and heterocyclic amino group may have an aliphatic group, an aliphatic oxy group, a halogen atom, a carbamoyl group, a heterocyclic group fused with the aryl group, an aliphatic oxycarbonyl group, preferably an aliphatic group having 1 to 4 carbon atoms in total, an aliphatic oxy group having 1 to 4 carbon atoms in total, a halogen atom, a carbamoyl group having 1 to 4 carbon atoms in total, a nitro group, or an aliphatic oxycarbonyl group having 2 to 4 carbon atoms in total.

[0045] The aliphatic thio group may be saturated or unsaturated and is an alkylthio group having a total of 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, such as a methylthio group, an ethylthio group, a carbamoylmethylthio group, or a t-butylthio group.

[0046] The carbamoylamino group may have an aliphatic group, an aryl group, a heterocyclic group, etc. Examples of the carbamoylamino group include a carbamoylamino group, an alkylcarbamoylamino group having a total of 2 to 9 carbon atoms, a dialkylcarbamoylamino group having a total of 3 to 10 carbon atoms, an arylcarbamoylamino group having a total of 7 to 13 carbon atoms, and a heterocyclic carbamoylamino group having a total of 3 to 12 carbon atoms, preferably a carbamoylamino group, an alkylcarbamoylamino group having a total of 2 to 7 carbon atoms, a dialkylcarbamoylamino group having a total of 3 to 6 carbon atoms, an arylcarbamoylamino group having a total of 7 to 11 carbon atoms, and a heterocyclic carbamoylamino group having a total of 3 to 10 carbon atoms, such as a carbamoylamino group, a methylcarbamoylamino group, an N,N-dimethylcarbamoylamino group, a phenylcarbamoylamino group, and a 4-pyridinecarbamoylamino group.

[0047] Further herein, ranges expressed by endpoints include all numbers subsumed within that range (eg, 1 to 10 includes 1.4, 1.9, 2.33, 5.75, 9.98, etc.).

[0048] Further, as used herein, references to "at least 1" include all numbers greater than or equal to 1 (e.g., at least 2, at least 4, at least 6, at least 8, at least 10, at least 25, at least 50, at least 100, etc.).

[0049] Next, the manufacturing method of the present disclosure will be specifically described.

[0050] The production method of the present disclosure includes a step A of carrying out ultrafiltration, microfiltration, or dialysis membrane treatment, or a combination thereof, on a pre-treatment aqueous dispersion containing a fluoropolymer obtained by polymerization in the presence of a polymer (I) containing polymerization units (I) based on a monomer represented by the following general formula (I) (hereinafter also referred to as the "first production method of the present disclosure"). CX 1 X 3 =CX 2 R(-CZ 1 Z 2 -A 0) m (I) (In the formula, X 1 and X 3 are each independently F, Cl, H, or CF; X 2 is H, F, an alkyl group or a fluorine-containing alkyl group; A 0 is an anionic group; R is a linking group; Z 1 and Z 2 are each independently H, F, an alkyl group or a fluorine-containing alkyl group; and m is an integer of 1 or more. An aqueous dispersion containing a fluoropolymer obtained by polymerization in the presence of the polymer (I) may be colored. The first production method of the present disclosure was completed based on the discovery that coloration can be significantly reduced by subjecting the untreated aqueous dispersion to a specific treatment, i.e., at least one of ultrafiltration, microfiltration, and dialysis membrane treatment. The aqueous fluoropolymer dispersion obtained by the first production method of the present disclosure can also reduce the coloration of the fluoropolymer powder obtained from the aqueous dispersion. Furthermore, by carrying out the above step A, the amount of hydrogen fluoride generated when the resulting aqueous fluoropolymer dispersion is heated can be significantly reduced. In the first production method of the present disclosure, by subjecting the pre-treatment aqueous dispersion to the step A, a liquid that does not permeate the ultrafiltration membrane, microfiltration membrane, or dialysis membrane can be collected as an aqueous fluoropolymer dispersion containing a fluoropolymer, while a liquid that permeates the ultrafiltration membrane, microfiltration membrane, or dialysis membrane can be collected as wastewater. In the first production method of the present disclosure, the polymer (I) can be removed from the pre-treatment aqueous dispersion by subjecting the pre-treatment aqueous dispersion to the step A. Furthermore, dimers and trimers of the polymer (I) can be removed from the pre-treatment aqueous dispersion. As the dimers and trimers, dimers and trimers of the monomer represented by the general formula (I) (hereinafter, sometimes referred to as the monomer (I)) may be preferred. The dimers and trimers may be formed from one type of monomer (I) as the monomer (I) represented by the general formula (I), or may be formed from two or more types of monomers (I) with different structures.

[0051] The ultrafiltration or microfiltration may be performed by either a cross-flow method or a dead-end method, but is not limited thereto. From the viewpoint of reducing clogging of the membrane, the cross-flow method is preferred.

[0052] The ultrafiltration can be carried out using an ultrafiltration membrane, for example, an ultrafiltration device having an ultrafiltration membrane, and methods such as centrifugal ultrafiltration, batch ultrafiltration, and circulating ultrafiltration can be used.

[0053] The molecular weight cutoff of the ultrafiltration membrane is usually 0.1 × 10 4 ~30×10 4 The above ultrafiltration membrane can suppress clogging of the membrane and efficiently reduce coloration and the amount of hydrogen fluoride generated, so the molecular weight cutoff is about 1.0 × 10 4 The molecular weight cutoff is preferably 1.5 × 10 Da or more. 4 Da or more is more preferable, 3.0 × 10 4 Da or more is more preferable, and 5.0 × 10 4 Da or more is even more preferable, and 8.0 × 10 4 Da or more is particularly preferred, and 10.0 × 10 4 Da or more is particularly preferable, and 15.0 × 10 4 Da or more is most preferred. In addition, the molecular weight cutoff is set to 30.0×10 from the viewpoint of reducing coloration and reducing the amount of hydrogen fluoride generated. 4 Da or less is preferable, 25.0 × 10 4 Da or less is more preferable. The molecular weight cutoff of the ultrafiltration membrane can be determined by, for example, passing polystyrene with a known weight-average molecular weight through the membrane and determining the molecular weight at which 90% of the polystyrene is rejected. Quantitative determination of polystyrene can be performed using gel permeation chromatography.

[0054] The above ultrafiltration membrane has an effective membrane area of ​​0.01 to 50 m 2 The effective membrane area is preferably 0.012 m 2 More than 0.015m is preferable. 2 More than 45m is more preferable. 2 Less than 40m is preferable 2 The following is even more preferred:

[0055] The shape of the ultrafiltration membrane may be any of the conventionally known types, including, but not limited to, hollow fiber, flat membrane, spiral, tubular, etc. From the viewpoint of preventing clogging, the hollow fiber type is preferred. The inner diameter of the hollow fiber ultrafiltration membrane is not limited, but may be, for example, 0.1 to 2 mm, and preferably 0.8 to 1.4 mm. The length of the hollow fiber ultrafiltration membrane is not limited, but may be, for example, 0.05 to 3 m, and preferably 0.05 to 2 m.

[0056] The material of the ultrafiltration membrane is not particularly limited, but examples thereof include organic materials such as cellulose, cellulose ester, polysulfone, sulfonated polysulfone, polyethersulfone, sulfonated polyethersulfone, chlorinated polyethylene, polypropylene, polyolefin, polyvinyl alcohol, polymethyl methacrylate, polyacrylonitrile, polyvinylidene fluoride, and polytetrafluoroethylene; metals such as stainless steel; and inorganic materials such as ceramics. The material of the ultrafiltration membrane is preferably an organic material, more preferably chlorinated polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile, polysulfone, or polyethersulfone, and even more preferably polyacrylonitrile or polyvinylidene fluoride.

[0057] Specific examples of the ultrafiltration membrane include DESAL's G-5 type, G-10 type, G-20 type, G-50 type, PW type, and HWS UF type; KOCH's HFM-180, HFM-183, HFM-251, HFM-300, HFM-116, HFM-183, HFM-300, HFK-131, HFK-328, MPT-U20, MPS-U20P, and MPS-U20S; Synder's SPE1, SPE3, SPE5, SPE10, SPE30, SPV5, SPV50, and SOW30; Asahi Kasei's Microza (registered trademark) UF series; and Nitto Denko's NTR7410.

[0058] From the viewpoint of reducing coloration and reducing the amount of hydrogen fluoride generated, the ultrafiltration is preferably carried out at a pressure (water pressure) of 0.01 MPa or more. More preferably, it is 0.03 MPa or more, and even more preferably, it is 0.05 MPa or more. Furthermore, from the viewpoint of pressure resistance, the pressure is preferably 0.5 MPa or less, more preferably 0.25 MPa or less, and even more preferably, 0.2 MPa or less.

[0059] The microfiltration can be carried out using a microfiltration membrane, which typically has an average pore size of 0.05 to 1.0 μm. The microfiltration membrane preferably has an average pore diameter of 0.075 μm or more, more preferably 0.10 μm or more, and even more preferably 0.15 μm or more, because coloration can be efficiently reduced. Furthermore, the average pore diameter is preferably 1.0 μm or less, more preferably 0.50 μm or less, and even more preferably 0.25 μm or less. The average pore size of the microfiltration membrane can be measured in accordance with ASTM F316-03 (bubble point method).

[0060] The above microfiltration membrane has an effective membrane area of ​​0.01 to 50 m 2 The effective membrane area is preferably 0.012 m 2 More than 0.015m is preferable. 2More than 45m is more preferable. 2 Less than 40m is preferable 2 The following is even more preferred:

[0061] The shape of the microfiltration membrane is not limited to any particular shape, and examples thereof include hollow fiber, flat membrane, spiral, tubular, etc. From the viewpoint of preventing clogging, hollow fiber membranes are preferred. The inner diameter of the hollow fiber microfiltration membrane is not limited, but may be, for example, 0.1 to 2 mm, and preferably 0.8 to 1.4 mm. The length of the hollow fiber microfiltration membrane is not limited, but may be, for example, 0.05 to 3 m, and preferably 0.05 to 2 m.

[0062] Examples of materials for the microfiltration membrane include cellulose-based materials, aromatic polyamides, polyvinyl alcohol, polysulfone, polyethersulfone, polyvinylidene fluoride, polyethylene, polyacrylonitrile, polypropylene, polycarbonate, polytetrafluoroethylene, ceramics, metals, etc. Among these, aromatic polyamides, polyvinyl alcohol, polysulfone, polyvinylidene fluoride, polyethylene, polyacrylonitrile, polypropylene, polycarbonate, and polytetrafluoroethylene are preferred, and polyacrylonitrile or polyvinylidene fluoride is particularly preferred.

[0063] Specific examples of microfiltration membranes include Cefilt manufactured by NGK Insulators, Ltd.; Microza U series and Microza P series manufactured by Asahi Kasei Corporation; Poreflon SPMW, Poreflon OPMW, and Poreflon PM manufactured by Sumitomo Electric Industries, Ltd.; Trefil manufactured by Toray Industries, Inc.; NADIR MP005 and NADIR MV020 manufactured by Microdyne-Nadia; and X-flow manufactured by Norit.

[0064] From the viewpoint of reducing coloration and reducing the amount of hydrogen fluoride generated, the microfiltration is preferably carried out at a pressure (water pressure) of 0.01 MPa or more. More preferably, it is 0.03 MPa or more, and even more preferably, it is 0.05 MPa or more. Furthermore, from the viewpoint of pressure resistance, the pressure is preferably 0.5 MPa or less, more preferably 0.25 MPa or less, and even more preferably, 0.2 MPa or less.

[0065] The dialysis membrane treatment is carried out using a dialysis membrane. 4 ~100×10 4 It has a molecular weight cutoff of 100 Da. The above dialysis membrane can suppress clogging of the membrane and efficiently reduce coloration and hydrogen fluoride generation, and therefore has a molecular weight cutoff of 1.0 × 10 4 The molecular weight cutoff is preferably 1.5 × 10 Da or more. 4 Da or more is more preferable, 3.0 × 10 4 Da or more is more preferable, and 5.0 × 10 4 Da or more is even more preferable, and 8.0 × 10 4 Da or more is particularly preferred, and 10.0 × 10 4 Da or more is particularly preferable, and 15.0 × 10 4 Da or more is most preferred. In addition, the molecular weight cutoff is set to 30.0×10 4 Da or less is preferable, 20.0 × 10 4 Da or less is more preferable. The molecular weight cutoff of the dialysis membrane can be measured, for example, by the same method as that for the ultrafiltration membrane.

[0066] The material of the dialysis membrane is not particularly limited, but examples thereof include polyethylene, cellulose, polyacrylonitrile, polymethyl methacrylate, ethylene vinyl alcohol copolymer, polysulfone, polyamide, and polyester polymer alloy.

[0067] Specific examples of dialysis membranes include Spectra / Por (registered trademark) Float-A-Lyzer, Tube-A-Lyzer, Dialysis tubing, 6Dialysis tubing, and 7Dialysis tubing manufactured by Spectrum Laboratories.

[0068] The above step A (the above ultrafiltration, microfiltration or dialysis membrane treatment) is preferably carried out at a temperature of 3°C or higher. More preferably, it is 5°C or higher, even more preferably, it is 7°C or higher, and particularly preferably, it is 10°C or higher. By setting the temperature within the above range, it is possible to further reduce coloration and the amount of hydrogen fluoride generated. The above temperature is preferably 80°C or lower, more preferably, 78°C or lower, even more preferably, 75°C or lower, and particularly preferably, 70°C or lower.

[0069] The time for the ultrafiltration, microfiltration or dialysis membrane treatment is not particularly limited, but is preferably 30 minutes or more, more preferably 60 minutes or more, and is preferably 7200 minutes or less, more preferably 4320 minutes or less.

[0070] The processing volume in the ultrafiltration, microfiltration, or dialysis membrane treatment is not particularly limited, but is preferably 0.001 L / min or more, more preferably 0.01 L / min or more, and is preferably 100 L / min or less, more preferably 50 L / min or less.

[0071] The ultrafiltration, microfiltration, or dialysis membrane treatment may each be carried out once or repeatedly multiple times, for example, once or more times, twice or more times, or three or more times, or up to 10 times. Furthermore, ultrafiltration, microfiltration, and dialysis membrane treatment may be performed in combination. For example, ultrafiltration and microfiltration may be combined, or ultrafiltration and dialysis membrane treatment may be combined, or microfiltration and dialysis membrane treatment may be combined, or ultrafiltration, microfiltration, and dialysis membrane treatment may be combined.

[0072] Among the above-mentioned ultrafiltration, microfiltration and dialysis membrane treatment, ultrafiltration or microfiltration is preferred, and microfiltration is more preferred.

[0073] The above step A is preferably carried out using a microfiltration membrane having an average pore size of 0.1 μm or more, at a pressure of 0.01 MPa or more, and at a temperature of 3 to 80°C.

[0074] In the method for producing an aqueous fluoropolymer dispersion of the present disclosure, a step of adding water to the aqueous dispersion before treatment and a step of adjusting the pH of the aqueous dispersion before treatment by adding a pH adjuster may be carried out while carrying out ultrafiltration, microfiltration or dialysis membrane treatment. Step A may include adding water to the pre-treatment aqueous dispersion, and the water may be added stepwise or continuously. Step A may also include adding a pH adjuster to the pre-treatment aqueous dispersion.

[0075] The endpoint of the ultrafiltration, microfiltration or dialysis membrane treatment may be determined appropriately without any particular limitation, and may be determined, for example, based on the color of the resulting aqueous fluoropolymer dispersion.

[0076] The pre-treatment aqueous dispersion contains a fluoropolymer obtained by polymerization in the presence of polymer (I). The pre-treatment aqueous dispersion may be an aqueous dispersion immediately after polymerization, or may be an aqueous dispersion obtained by diluting or concentrating an aqueous dispersion immediately after polymerization, or may be an aqueous dispersion that has been subjected to a dispersion stabilization treatment.

[0077] From the viewpoints of reducing coloration and reducing the amount of hydrogen fluoride generated, the fluoropolymer content of the pre-treatment aqueous dispersion is preferably 70% by mass or less, more preferably 40% by mass or less, and even more preferably 25% by mass or less, and from the viewpoint of treatment time, it is preferably 0.1% by mass or more, more preferably 1.0% by mass or more, and even more preferably 2.0% by mass or more.

[0078] From the viewpoint of further reducing coloration and the amount of hydrogen fluoride generated, the pre-treatment aqueous dispersion preferably has a pH of 1 to 10, more preferably 2 to 9. The pH can be adjusted using a pH adjuster. The pH adjuster may be an acid or alkali, and examples thereof include phosphate, sodium hydroxide, potassium hydroxide, and aqueous ammonia.

[0079] The pre-treatment aqueous dispersion may be irradiated with ultraviolet light, preferably with ultraviolet light having a wavelength of 10 to 400 nm, more preferably with ultraviolet light having a wavelength of 100 to 280 nm. The first production method of the present disclosure also preferably includes, before step A, a step of irradiating the pre-treatment aqueous dispersion with ultraviolet light.

[0080] The pre-treatment aqueous dispersion may be treated with an oxygen source. That is, the first production method of the present disclosure preferably includes a step of adding an oxygen source to the pre-treatment aqueous dispersion before step A. From the viewpoint of reducing coloration and reducing the amount of hydrogen fluoride generated, the amount of the oxygen source added is preferably 2% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, relative to the pre-treatment aqueous dispersion. Furthermore, from the viewpoint of safety, the amount is preferably 30% by mass or less, more preferably 20% by mass or less. Examples of oxygen sources include air, oxygen-rich gas, ozone-containing gas, hydrogen peroxide, hypochlorous acid, and nitrites.

[0081] The pre-treatment aqueous dispersion contains the fluoropolymer and an aqueous medium, and may also contain the polymer (I) used in the polymerization, or may have a hydrocarbon surfactant added thereto after polymerization.

[0082] The aqueous medium refers to a liquid containing water. The aqueous medium is not particularly limited as long as it contains water, and may contain water and, for example, a fluorine-free organic solvent such as an alcohol, an ether, or a ketone, and / or a fluorine-containing organic solvent having a boiling point of 40° C. or lower.

[0083] The pre-treatment aqueous dispersion may have a lightness L* of 95 or less, 91 or less, or 86 or less. The lightness L* is measured by an X-rite colorimeter.

[0084] The polymer (I) contains polymerized units (I) based on a monomer represented by the following general formula (I): The polymer (I) preferably contains two or more polymerized units (I). CX 1 X 3 =CX 2 R(-CZ 1 Z 2 -A 0 ) m (I) (In the formula, X 1 and X 3 are each independently F, Cl, H, or CF; X 2 is H, F, an alkyl group or a fluorine-containing alkyl group; A 0 is an anionic group; R is a linking group; Z 1 and Z 2 are each independently H, F, an alkyl group or a fluorine-containing alkyl group; and m is an integer of 1 or more. X 2 is preferably F, Cl, H or CF3. 1 and Z 2 is preferably F or CF3. The anionic group includes functional groups that provide anionic groups such as sulfate groups, carboxylate groups, acid groups such as -COOH, and acid-base groups such as -COONH. Among these, sulfate groups, carboxylate groups, phosphate groups, phosphonate groups, sulfonate groups, or -C(CF)OM (wherein M is -H, a metal atom, -NR 7 4. An optionally substituted imidazolium, an optionally substituted pyridinium, or an optionally substituted phosphonium, wherein R 7 is H or an organic group. Preferably, the anionic group is The polymer (I) may contain only polymerized units (I) based on one type of monomer represented by general formula (I), or may contain polymerized units (I) based on two or more types of monomers represented by general formula (I).

[0085] The above R is a linking group. In this specification, a "linking group" is an (m+1)-valent linking group, and when m is 1, it is a divalent linking group. The linking group may be a single bond and preferably contains at least one carbon atom, and the number of carbon atoms may be 2 or more, 4 or more, 8 or more, 10 or more, or 20 or more. There is no upper limit, but it may be, for example, 100 or less, or 50 or less. The linking group may be linear or branched, cyclic or acyclic in structure, saturated or unsaturated, substituted or unsubstituted, and may optionally contain one or more heteroatoms selected from the group consisting of sulfur, oxygen, and nitrogen, and may optionally contain one or more functional groups selected from the group consisting of ester, amide, sulfonamide, carbonyl, carbonate, urethane, urea, and carbamate. The linking group may not contain carbon atoms but may be a catenary heteroatom such as oxygen, sulfur, or nitrogen. m is an integer of 1 or more, preferably 1 or 2, and more preferably 1. When m is an integer of 2 or more, Z 1 , Z 2 and A 0 may be the same or different. Next, a preferred structure when m is 1 in general formula (I) will be described.

[0086] The above R is preferably, for example, a catenary heteroatom such as oxygen, sulfur, or nitrogen, or a divalent organic group. When R is a divalent organic group, the hydrogen atom bonded to the carbon atom may be replaced with a halogen atom other than fluorine, such as chlorine, and may or may not contain a double bond. R may be either linear or branched, and may be cyclic or acyclic. R may also contain a functional group (e.g., ester, ether, ketone, amine, halide, etc.). R may also be a non-fluorinated divalent organic group, or a partially fluorinated or perfluorinated divalent organic group. R may be, for example, a hydrocarbon group in which no fluorine atoms are bonded to the carbon atoms, a hydrocarbon group in which some of the hydrogen atoms bonded to the carbon atoms are substituted with fluorine atoms, or a hydrocarbon group in which all of the hydrogen atoms bonded to the carbon atoms are substituted with fluorine atoms, and these may contain an oxygen atom, a double bond, or a functional group.

[0087] R is preferably a hydrocarbon group having 1 to 100 carbon atoms which may contain an ether bond, and in the hydrocarbon group, some or all of the hydrogen atoms bonded to the carbon atoms may be substituted with fluorine. R is preferably -(CH2) a -, -(CF2) a -, -O-(CF2) a -, -(CF2) a -O-(CF2) b -, -O(CF2) a -O-(CF2) b -, -(CF2) a -[O-(CF2) b ] c -, -O(CF2) a -[O-(CF2) b ] c -, -[(CF2) a -O] b -[(CF2) c -O] d -, -O[(CF2) a -O] b -[(CF2) c -O] d -, -O-[CF2CF(CF3)O] a -(CF2) b -, -[CF2CF(CF3)O] a -, -[CF(CF3)CF2O] a -, -(CF2) a -O-[CF(CF3)CF2O] a -, -(CF2) a -O-[CF(CF3)CF2O]a -(CF2) b - and at least one selected from the combinations thereof. In the formula, a, b, c, and d are independently at least 1. a, b, c, and d may independently be 2 or more, 3 or more, 4 or more, 10 or more, or 20 or more. The upper limit of a, b, c, and d is, for example, 100.

[0088] R is represented by the following general formula (r1): -CF2-O-(CX 6 2) e -{O-CF(CF3)} f -(O) g - (r1) (In the formula, X 6 are each independently H, F, or CF3, e is an integer of 0 to 3, f is an integer of 0 to 3, and g is 0 or 1), and a divalent group represented by the following general formula (r2): -CF2-O-(CX 7 2) e -(O) g - (r2) (In the formula, X 7 are each independently H, F or CF3, e is an integer of 0 to 3, and g is 0 or 1), and a divalent group represented by the formula:

[0089] Specific examples of suitable R include -CF2-O-, -CF2-O-CF2-, -CF2-O-CH2-, -CF2-O-CH2CF2-, -CF2-O-CF2CF2-, -CF2-O-CF2CH2-, -CF2-O-CF2CF2CH2-, -CF2-O-CF(CF3)-, -CF2-O-CF(CF3)CF2-, -CF2-O-CF(CF3)CF2-O-, -CF2-O-CF(CF3)CF2-O-CF2-, -CF2-O-CF(CF3)CH2-, and the like. Among these, the above R is preferably a perfluoroalkylene group which may contain an oxygen atom, specifically, -CF2-O-, -CF2-O-CF2-, -CF2-O-CF2CF2-, -CF2-O-CF(CF3)-, -CF2-O-CF(CF3)CF2-, or -CF2-O-CF(CF3)CF2-O-.

[0090] -R-CZ of the above general formula (I) 1 Z 2 - is the following formula (s1): -CF2-O-(CX 6 2) e -{O-CF(CF3)} f -(O) g -CZ 1 Z 2 - (s1) (In the formula, X 6 are each independently H, F, or CF3, e is an integer of 0 to 3, f is an integer of 0 to 3, g is 0 or 1, and Z 1 and Z 2 are each independently H, F, an alkyl group or a fluorine-containing alkyl group), and in formula (s1), Z 1 and Z 2 More preferably, they are F or CF3, and even more preferably, one is F and the other is CF3. In addition, in the above general formula (I), -R-CZ 1 Z 2 - is the following formula (s2): -CF2-O-(CX 7 2) e -(O) g -CZ 1 Z 2- (s2) (In the formula, X 7 are each independently H, F, or CF3, e is an integer of 0 to 3, g is 0 or 1, and Z 1 and Z 2 are each independently H, F, an alkyl group or a fluorine-containing alkyl group), and in formula (s2), Z 1 and Z 2 More preferably, they are F or CF3, and even more preferably, one is F and the other is CF3.

[0091] -R-CZ of the above general formula (I) 1 Z 2 - as -CF2-O-CF2-, -CF2-O-CF(CF3)-, -CF2-OC(CF3)2-, -CF2-O-CF2-CF2-, -CF2-O-CF2-C F(CF3)-, -CF2-O-CF2-C(CF3)2-, -CF2-O-CF2CF2-CF2-, -CF2-O-CF2CF2-CF(CF3)-, -CF2-O-C F2CF2-C(CF3)2-, -CF2-O-CF(CF3)-CF2-, -CF2-O-CF(CF3)-CF(CF3)-, -CF2-O-CF(CF3)-C(CF 3)2-, -CF2-O-CF(CF3)-CF2-, -CF2-O-CF(CF3)-CF(CF3)-, -CF2-O-CF(CF3)-C(CF3)2-, -CF2- O-CF(CF3)CF2-CF2-, -CF2-O-CF(CF3)CF2-CF(CF3)-, -CF2-O-CF(CF3)CF2-C(CF3)2-, -CF2- O-CF(CF3)CF2-O-CF2-, -CF2-O-CF(CF3)CF2-O-CF(CF3)-, or -CF2-O-CF(CF3)CF2-OC(CF3)2 - is preferred, -CF2-O-CF(CF3)-, -CF2-O-CF2-CF(CF3)-, -CF2-O-CF2CF2-CF(CF3)-, -CF2-O-CF(CF 3) -CF(CF3)-, -CF2-O-CF(CF3)CF2-CF(CF3)-, or -CF2-O-CF(CF3)CF2-O-CF(CF3)- is more preferable.

[0092] The polymer (I) is also preferably highly fluorinated. For example, anionic groups (A) such as phosphate group moieties (e.g., CH2OP(O)(OM)2) and sulfate group moieties (e.g., CH2OS(O)2OM) are preferably present. 0 ), it is preferred that 80% or more, 90% or more, 95% or more, or 100% of the C—H bonds in the polymer (I) are substituted with C—F bonds.

[0093] The polymer (I) contains an anionic group (A 0 ) except for the C—F bond, it is also preferable that the compound has no C—H bond. 1 , X 2 , and X 3 are all F, and R is preferably a perfluoroalkylene group having one or more carbon atoms, and the perfluoroalkylene group may be either linear or branched, may be cyclic or acyclic, and may contain at least one catenary heteroatom. The number of carbon atoms in the perfluoroalkylene group may be 2 to 20, or may be 4 to 18.

[0094] The polymer (I) may be partially fluorinated. That is, the polymer (I) may contain an anionic group (A 0 ), it is also preferred that the alkyl group has at least one hydrogen atom bonded to a carbon atom and at least one fluorine atom bonded to a carbon atom.

[0095] The anionic group (A 0) may be —SO3M, —OSO3M, —COOM, —SONR′CH2COOM, —CH2OP(O)(OM)2, [—CH2O]2P(O)(OM), —CH2CH2OP(O)(OM)2, [—CH2CH2O]2P(O)(OM), —CH2CH2OSO3M, —P(O)(OM)2, —SONR′CH2CH2OP(O)(OM)2, [—SONR′CH2CH2O]2P(O)(OM), —CH2OSO3M, —SONR′CH2CH2OSO3M, or —C(CF3)2OM. Among these, -SO3M, -OSO3M, -COOM, or -P(O)(OM)2 is preferred, -COOM, -SO3M, -OSO3M, or -C(CF3)2OM is more preferred, -SO3M, -COOM, or -P(O)(OM)2 is even more preferred, -SO3M or -COOM is particularly preferred, and -COOM is most preferred. The above M represents H, a metal atom, or NR 7 4. An optionally substituted imidazolium, an optionally substituted pyridinium, or an optionally substituted phosphonium, wherein R 7 is H or an organic group. The metal atom includes alkali metals (Group 1) and alkaline earth metals (Group 2), and is preferably Na, K or Li. The above M is —H, a metal atom, or —NR 7 4 is preferred, and -H, an alkali metal (Group 1), an alkaline earth metal (Group 2) or -NR 7 4 is more preferred, -H, -Na, -K, -Li or -NH4 is even more preferred, -Na, -K or -NH4 is even more preferred, -Na or -NH4 is especially preferred, and -NH4 is most preferred. In the polymer (I), each polymer unit (I) may have a different anionic group or may have the same anionic group.

[0096] The polymer (I) is also preferably a polymer containing polymerized units (Ia) based on a monomer represented by the following formula (Ia). CF2=CF-O-Rf 0 -A 0 (Ia) (In the formula, A0 is an anionic group, and Rf 0 is a perfluorinated divalent linking group which may be linear or branched, cyclic or acyclic in structure, saturated or unsaturated, substituted or unsubstituted, and which optionally contains one or more heteroatoms selected from the group consisting of sulfur, oxygen, and nitrogen.

[0097] The polymer (I) is also preferably a polymer containing polymerized units (Ib) based on a monomer represented by the following formula (Ib). CH2=CH-O-Rf 0 -A 0 (Ib) (In the formula, A 0 is an anionic group, and Rf 0 is a perfluorinated divalent linking group defined by formula Ia.

[0098] In general formula (I), A 0 is a sulfate group. 0 is, for example, -CH2OSO3M, -CH2CH2OSO3M, or -SO2NR'CH2CH2OSO3M, where R' is H or an alkyl group having 1 to 4 carbon atoms, and M is the same as above. A 0 is a sulfate group, examples of the monomer represented by general formula (I) include CF2=CF(OCF2CF2CH2OSO3M), CH2=CH((CF2)4CH2OSO3M), CF2=CF(O(CF2)4CH2OSO3M), CF2=CF(OCF2CF(CF3)CH2OSO3M), CF2=CF(OCF2CF(CF3)OCF2CF2CH2OSO3M), CH2=CH((CF2)4CH2OSO3M), CF2=CF(OCF2CF2SON(CH3)CH2CH2OSO3M), CH2=CH(CF2CF2CH2OSO3M), CF2=CF(OCF2CF2CF2CF2SON(CH3)CH2CH2OSO3M), CH2=CH(CF2CF2CH2OSO3M), and the like. In the above formula, M is the same as above.

[0099] In general formula (I), A0 In one preferred embodiment, A is a sulfonate group. 0 An example of such a group is -SO3M, where M is the same as above. A 0 is a sulfonate group, examples of the monomer represented by general formula (I) include CF2=CF(OCF2CF2SO3M), CF2=CF(O(CF2)3SO3M), CF2=CF(O(CF2)4SO3M), CF2=CF(OCF2CF(CF3)SO3M), CF2=CF(OCF2CF(CF3)OCF2CF2SO3M), CH2=CH(CF2CF2SO3M), CF2=CF(OCF2CF(CF3)OCF2CF2CF2CF2SO3M), CH2=CH(CF2CF2SO3M), CH2=CH(CF2CF2SO3M), CH2=CH(CF2CF2SO3M), CH2=CH((CF2)4SO3M), CH2=CH(CF2CF2SO3M), CH2=CH((CF2)3SO3M), etc. In the above formulas, M is the same as above.

[0100] In general formula (I), A 0 A is preferably a carboxylate group. 0 Examples of A include COOM or SO2NR'CH2COOM, where R' is H or an alkyl group having 1 to 4 carbon atoms, and M is the same as above. 0 is a carboxylate group, examples of the monomer represented by general formula (I) include CF2=CF(OCF2CF2COOM), CF2=CF(O(CF2)3COOM), CF2=CF(O(CF2)5COOM), CF2=CF(OCF2CF(CF3)COOM), CF2=CF(OCF2CF(CF3)O(CF2) nCOOM) (n is greater than 1), CH2=CH(CF2CF2COOM), CH2=CH((CF2)4COOM), CH2=CH(CF2CF2COOM), CH2=CH((CF2)3COOM), CF2=CF(OCF2CF2SO2NR'CH2COOM), CF2=CF(O(CF2)4SO2NR'CH2COOM), CF2=CF(OCF2CF(CF3)SO2NR'CH2COOM), CF2=CF(OCF2 CF(CF3)OCF2CF2SO2NR'CH2COOM), CH2=CH(CF2CF2SO2NR'CH2COOM), CF2=CF(OCF2CF(CF3)OCF2CF2CF2CF2SO2NR'CH2COOM), CH2=CH((CF2)4SO2NR'CH2COOM), CH2=CH(CF2CF2SO2NR'CH2COOM), CH2=CH((CF2)3SO2NR'CH2COOM), etc. In the above formula, R' is H or C 1-4 is an alkyl group, and M is the same as above.

[0101] In formula (I), A 0 In one preferred embodiment, A is a phosphate group. 0 Examples of the alkyl group include -CH2OP(O)(OM)2, [-CH2O]2P(O)(OM), -CH2CH2OP(O)(OM)2, [-CH2CH2O]2P(O)(OM), [-SON2NR'CH2CH2O]2P(O)(OM) and -SON2NR'CH2CH2OP(O)(OM), where R' is an alkyl group having 1 to 4 carbon atoms and M is the same as above. A 0is a phosphate, examples of the monomer represented by general formula (I) include CF2=CF(OCF2CF2CH2OP(O)(OM)2), CF2=CF(O(CF2)4CH2OP(O)(OM)2), CF2=CF(OCF2CF(CF3)CH2OP(O)(OM)2), CF2=CF(OCF2CF(CF3)OCF2CF2CH2OP(O)(OM)2), CF2=CF(OCF2CF2SO2N(CH3 )CH2CH2OP(O)(OM)2), CF2=CF(OCF2CF2CF2CF2SO2N(CH3)CH2CH2OP(O)(OM)2), CH2=CH(CF2CF2CH2OP(O)(OM)2), CH2=CH((CF2)4CH2OP(O)(OM)2), CH2=CH(CF2CF2CH2OP(O)(OM)2), CH2=CH((CF2)3CH2OP(O)(OM)2), etc. In the above formula, M is the same as above.

[0102] In formula (I), A 0 In one preferred embodiment, A is a phosphonate group. 0 is a phosphonate group, examples of the monomer represented by general formula (I) include CF2=CF(OCF2CF2P(O)(OM)2), CF2=CF(O(CF2)4P(O)(OM)2), CF2=CF(OCF2CF(CF3)P(O)(OM)2), CF2=CF(OCF2CF(CF3)OCF2CF2P(O)(OM)2), CH2=CH(CF2CF2P(O)(OM)2), CH2=CH((CF2)4P(O)(OM)2), CH2=CH(CF2CF2P(O)(OM)2), CH2=CH((CF2)3P(O)(OM)2), where M is the same as above.

[0103] The polymer (I) is preferably a polymer (1) containing polymerized units (1) based on a monomer represented by the following general formula (1). CX2=CY(-CZ2-O-Rf-A) (1) (In the formula, X's are the same or different and are -H or -F; Y's are -H, -F, an alkyl group or a fluorine-containing alkyl group; Z's are the same or different and are -H, -F, an alkyl group or a fluoroalkyl group; Rf's are fluorine-containing alkylene groups having 1 to 40 carbon atoms or fluorine-containing alkylene groups having 2 to 100 carbon atoms and an ether bond; A's are -COOM, -SO3M, -OSO3M or -C(CF3)2OM (M's are -H, a metal atom, -NR 7 4. An optionally substituted imidazolium, an optionally substituted pyridinium, or an optionally substituted phosphonium, wherein R 7 is H or an organic group.) However, at least one of X, Y, and Z contains a fluorine atom.) When the polymer (1) contains the polymerization unit (1), an aqueous fluoropolymer dispersion containing a fluoropolymer such as polytetrafluoroethylene can be produced stably and efficiently. Furthermore, an aqueous fluoropolymer dispersion containing a fluoropolymer such as high-molecular-weight polytetrafluoroethylene can be obtained in high yield. The fluorine-containing alkylene group having an ether bond and having 2 to 100 carbon atoms is an alkylene group that does not contain a structure in which an oxygen atom is at the terminal and that contains an ether bond between carbon atoms.

[0104] In the above general formula (1), X is -H or -F. Both Xs may be -F, or at least one X may be -H. For example, one X may be -F and the other -H, or both Xs may be -H.

[0105] In the above general formula (1), Y is —H, —F, an alkyl group or a fluorine-containing alkyl group. The alkyl group is an alkyl group that does not contain a fluorine atom, and may have a carbon number of at least 1. The alkyl group preferably has 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms. The fluorine-containing alkyl group is an alkyl group containing at least one fluorine atom, and may have a carbon number of at least 1. The fluorine-containing alkyl group preferably has 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms. The above Y is preferably -H, -F or -CF3, and more preferably -F.

[0106] In the above general formula (1), Z may be the same or different and is —H, —F, an alkyl group or a fluoroalkyl group. The alkyl group is an alkyl group that does not contain a fluorine atom, and may have a carbon number of at least 1. The alkyl group preferably has 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms. The fluorine-containing alkyl group is an alkyl group containing at least one fluorine atom, and may have a carbon number of at least 1. The fluorine-containing alkyl group preferably has 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms. The above Z is preferably -H, -F or -CF3, and more preferably -F.

[0107] In the general formula (1), at least one of X, Y, and Z contains a fluorine atom. For example, X may be —H, and Y and Z may be —F.

[0108] In the general formula (1), Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having 2 to 100 carbon atoms and an ether bond. The number of carbon atoms in the fluorine-containing alkylene group is preferably 2 or more. The number of carbon atoms in the fluorine-containing alkylene group is preferably 30 or less, more preferably 20 or less, and even more preferably 10 or less. Examples of the fluorine-containing alkylene group include -CF2-, -CH2CF2-, -CF2CF2-, -CF2CH2-, -CF2CF2CH2-, -CF(CF3)-, -CF(CF3)CF2-, and -CF(CF3)CH2-. The fluorine-containing alkylene group is preferably a perfluoroalkylene group.

[0109] The number of carbon atoms in the fluorine-containing alkylene group having an ether bond is preferably 3 or more. The number of carbon atoms in the fluorine-containing alkylene group having an ether bond is preferably 60 or less, more preferably 30 or less, and even more preferably 12 or less. The fluorine-containing alkylene group having an ether bond is, for example, a group represented by the general formula: [ka] (In the formula, Z 1 is F or CF3;Z 2 and Z 3 are H or F;Z respectively 4 is also preferably a divalent group represented by the formula: H, F, or CF3; p1+q1+r1 is an integer of 1 to 10; s1 is 0 or 1; and t1 is an integer of 0 to 5). Specific examples of the fluorine-containing alkylene group having an ether bond include -CF(CF3)CF2-O-CF(CF3)-, -(CF(CF3)CF2-O) n -CF(CF3)- (wherein n is an integer of 1 to 10), -CF(CF3)CF2-O-CF(CF3)CH2-, -(CF(CF3)CF2-O) n Examples thereof include -CF(CF3)CH2- (wherein n is an integer of 1 to 10), -CH2CF2CF2O-CH2CF2CH2-, -CF2CF2CF2O-CF2CF2-, -CF2CF2CF2O-CF2CF2CH2-, -CF2CF2O-CF2-, -CF2CF2O-CF2CH2- and the like. The fluorine-containing alkylene group having an ether bond is preferably a perfluoroalkylene group.

[0110] In the above general formula (1), A is -COOM, -SO3M, -OSO3M, or -C(CF3)2OM (M is -H, a metal atom, or -NR 7 4. An optionally substituted imidazolium, an optionally substituted pyridinium, or an optionally substituted phosphonium, wherein R 7 is H or an organic group). R 7 As for H or C 1-10 is preferably an organic group represented by the formula: 1-4The organic group is more preferably H or C 1-4 More preferred are alkyl groups of the formula: The metal atom includes alkali metals (Group 1) and alkaline earth metals (Group 2), and is preferably Na, K or Li. The above M is —H, a metal atom, or —NR 7 4 is preferred, and -H, an alkali metal (Group 1), an alkaline earth metal (Group 2) or -NR 7 4 is more preferred, -H, -Na, -K, -Li or -NH4 is even more preferred, -Na, -K or -NH4 is even more preferred, -Na or -NH4 is especially preferred, and -NH4 is most preferred. The above A is preferably -COOM or -SO3M, and more preferably -COOM.

[0111] Examples of the monomer represented by general formula (1) include the following formula (1a): CX2=CFCF2-O-(CF(CF3)CF2O) n5 -CF(CF3)-A (1a) (wherein each X is the same and represents F or H, n5 represents 0 or an integer of 1 to 10, and A is as defined above) is a suitable example of a fluoroallyl ether compound. In the above formula (1a), n5 is preferably 0 or an integer of 1 to 5, more preferably 0, 1 or 2, and even more preferably 0 or 1, in that particles with a small primary particle size can be obtained. The polymer (1) may be a homopolymer of the fluoroallyl ether compound represented by the general formula (1a), or a copolymer with other monomers.

[0112] The polymerized units (1) are preferably polymerized units (1A) based on a monomer represented by the following general formula (1A). CH2=CF(-CF2-O-Rf-A) (1A) (wherein Rf and A are the same as above.) The polymer (1) may be a homopolymer of the monomer represented by the general formula (1A) or a copolymer with other monomers.

[0113] Specific examples of the monomer represented by formula (1A) include those represented by the following formula:

[0114] [ka]

[0115] (In the formula, Z 1 is F or CF3;Z 2 and Z 3 are H or F;Z respectively 4 is H, F, or CF3; p1+q1+r1 are integers from 0 to 10; s1 is 0 or 1; t1 is an integer from 0 to 5, except for Z 3 and Z 4 are both H, then p1+q1+r1+s1 is not 0; A is the same as defined above). More specifically,

[0116] [ka]

[0117] Among them,

[0118] [ka]

[0119] It is preferable that:

[0120] As the monomer represented by the above general formula (1A), it is preferable that A in formula (1A) is -COOM, and in particular, at least one selected from the group consisting of CH2=CFCF2OCF(CF3)COOM and CH2=CFCF2OCF(CF3)CF2OCF(CF3)COOM (wherein M is as defined above) is preferred, with CH2=CFCF2OCF(CF3)COOM being more preferred.

[0121] Further, examples of the monomer represented by the general formula (1) include the monomer represented by the following formula:

[0122] CF2=CFCF2-O-Rf-A (wherein Rf and A are the same as above)

[0123] More specifically, [ka] etc.

[0124] The polymer (I) is also preferably a polymer (2) containing polymerized units (2) based on a monomer represented by the following general formula (2). CX2=CY(-O-Rf-A) (2) (In the formula, X's are the same or different and represent -H or -F; Y represents -H, -F, an alkyl group or a fluorine-containing alkyl group; Rf represents a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having 2 to 100 carbon atoms and an ether bond; and A is the same as defined above.)

[0125] The polymer (2) may be a homopolymer of the monomer represented by the general formula (2) or a copolymer with other monomers. In the above general formula (2), X is -H or -F. Both Xs may be -F, or at least one X may be -H. For example, one X may be -F and the other -H, or both Xs may be -H.

[0126] In the above general formula (2), Y is —H, —F, an alkyl group or a fluorine-containing alkyl group. The alkyl group is an alkyl group that does not contain a fluorine atom, and may have a carbon number of at least 1. The alkyl group preferably has 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms. The fluorine-containing alkyl group is an alkyl group containing at least one fluorine atom, and may have a carbon number of at least 1. The fluorine-containing alkyl group preferably has 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms. The above Y is preferably -H, -F or -CF3, and more preferably -F.

[0127] In the general formula (2), it is preferable that at least one of X and Y contains a fluorine atom. For example, X may be —H, and Y and Z may be —F.

[0128] In the general formula (2), Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having an ether bond having 2 to 100 carbon atoms. The fluorine-containing alkylene group having an ether bond having 2 to 100 carbon atoms is an alkylene group that does not contain a structure in which an oxygen atom is at the terminal and that contains an ether bond between carbon atoms. The carbon number of the fluorine-containing alkylene group of Rf is preferably 2 or more. Also, it is preferably 30 or less, more preferably 20 or less, and even more preferably 10 or less. Examples of the fluorine-containing alkylene group include -CF2-, -CH2CF2-, -CF2CF2-, -CF2CH2-, -CF2CF2CH2-, -CF(CF3)-, -CF(CF3)CF2-, and -CF(CF3)CH2-. The fluorine-containing alkylene group is preferably a perfluoroalkylene group.

[0129] The monomer represented by the general formula (2) is preferably at least one selected from the group consisting of monomers represented by the following general formulae (2a), (2b), (2c), (2d) and (2e): CF2=CF-O-(CF2) n1 -A (2a) (wherein n1 represents an integer of 1 to 10, and A is the same as defined above.) CF2=CF-O-(CF2C(CF3)F) n2 -A (2b) (wherein n2 represents an integer of 1 to 5, and A is as defined above.) CF2=CF-O-(CFX 1 ) n3 -A (2c) (In the formula, X 1 represents F or CF3, n3 represents an integer of 1 to 10, and A is as defined above. CF2=CF-O-(CF2CFX 1 O) n4 -(CF2) n6 -A (2d) (wherein n4 represents an integer of 1 to 10, n6 represents an integer of 1 to 3, and A and X 1 is the same as the definition above.) CF2=CF-O-(CF2CF2CFX 1 O) n5 -CF2CF2CF2-A (2e) (wherein n5 represents an integer of 0 to 10, and A and X 1 is the same as the definition above.)

[0130] In the formula (2a), n1 is preferably an integer of 5 or less, and more preferably an integer of 2 or less.

[0131] Examples of the monomer represented by the above formula (2a) include CF2=CF-O-CF2COOM, CF2=CF(OCF2CF2COOM), and CF2=CF(O(CF2)3COOM) (wherein M is as defined above).

[0132] In the above formula (2b), the above n2 is preferably an integer of 3 or less, from the viewpoint of the stability of the resulting aqueous dispersion.

[0133] In the formula (2c), n3 is preferably an integer of 5 or less from the viewpoint of water solubility, A is preferably -COOM, and M is preferably H or NH4.

[0134] In the above formula (2d), the above X 1is preferably -CF3 from the viewpoint of stability of the aqueous dispersion, n4 is preferably an integer of 5 or less from the viewpoint of water solubility, A is preferably -COOM, and M is preferably H or NH4.

[0135] Examples of the monomer represented by the above formula (2d) include CF2=CFOCF2CF(CF3)OCF2CF2COOM, CF2=CFOCF2CF(CF3)OCF2COOM, and CF2=CFOCF2CF(CF3)OCF2CF2CF2COOM (wherein M represents H, NH4, or an alkali metal). In general formula (2e), n5 is preferably an integer of 5 or less from the viewpoint of water solubility, A is preferably -COOM, and M is preferably H or NH4. An example of the monomer represented by general formula (2e) is CF2=CFOCF2CF2CF2COOM (wherein M represents H, NH4 or an alkali metal).

[0136] The polymer (I) is also preferably a polymer (3) containing polymerized units (3) based on a monomer represented by the following general formula (3). General formula (3): CX2=CY(-Rf-A) (3) (In the formula, X's are the same or different and represent -H or -F; Y represents -H, -F, an alkyl group or a fluorine-containing alkyl group; Rf represents a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having 2 to 100 carbon atoms and an ether bond; and A is the same as defined above.) The polymer (3) may be a homopolymer of the monomer represented by the general formula (3) or a copolymer with other monomers. The fluorine-containing alkylene group having 2 to 100 carbon atoms and an ether bond is an alkylene group that does not contain a structure in which an oxygen atom is at the terminal and that contains an ether bond between carbon atoms.

[0137] In the above general formula (3), Rf is preferably a fluorine-containing alkylene group having a carbon number of 1 to 40. In general formula (3), at least one of X and Y preferably contains a fluorine atom.

[0138] The monomer represented by the above general formula (3) is represented by the following general formula (3a): CF2=CF-(CF2) n1 -A (3a) (wherein n1 represents an integer of 1 to 10, and A is as defined above), and a monomer represented by the following general formula (3b): CF2=CF-(CF2C(CF3)F) n2 -A (3b) (wherein n2 represents an integer of 1 to 5, and A is as defined above), is preferred. In the general formula (3a) and the general formula (3b), A is preferably —SO3M or COOM, and M is H, a metal atom, NR 7 4. It is preferably an imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent. 7 represents H or an organic group.

[0139] In the formula (3a), n1 is preferably an integer of 5 or less, and more preferably an integer of 2 or less. A is preferably —COOM, and M is preferably H or NH4. An example of the monomer represented by the above formula (3a) is CF2=CFCF2COOM (wherein M is as defined above).

[0140] In the above formula (3b), n2 is preferably an integer of 3 or less from the viewpoint of the stability of the resulting aqueous dispersion, A is preferably —COOM, and M is preferably H or NH 4 .

[0141] Next, a preferred configuration when m in general formula (I) is an integer of 2 or more will be described.

[0142] It is also preferable that the monomer (I) is at least one selected from the group consisting of monomers represented by general formula (4a) and general formula (4b). It is also preferable that the polymer (I) is a polymer (4) containing polymerization units (4) based on at least one monomer selected from the group consisting of monomers represented by general formula (4a) and general formula (4b). CF2=CF-CF2-OQ F1 -CF(-Q F2 -CZ 1 Z 2 -A)2(4a) (In the formula, Z 1 , Z 2 and A are the same as above, Q F1 and Q F2 are the same or different and are a single bond, a fluorine-containing alkylene group which may contain an ether bond between carbon atoms, or a fluorine-containing oxyalkylene group which may contain an ether bond between carbon atoms. CF2=CF-OQ F1 -CF(-Q F2 -CZ 1 Z 2 -A)2(4b) (In the formula, Z 1 , Z 2 , A, Q F1 and Q F2 is the same as above)

[0143] The monomers represented by general formula (4a) and general formula (4b) include: [ka] etc.

[0144] The polymer (I) is preferably at least one selected from the group consisting of the polymer (1), the polymer (2) and the polymer (3), and more preferably the polymer (1).

[0145] The polymer (I) may be a homopolymer consisting of only the polymerized unit (I), or may be a copolymer containing the polymerized unit (I) and a polymerized unit based on another monomer copolymerizable with the monomer represented by general formula (I). From the viewpoint of solubility in the polymerization medium, a homopolymer consisting of only the polymerized unit (I) is preferred. The polymerized units (I) may be the same or different in each occurrence, and the polymer (I) may contain polymerized units (I) based on two or more different monomers represented by general formula (I).

[0146] The other monomer is preferably a fluorine-containing ethylenic monomer having 2 or 3 carbon atoms, such as CF2=CF2, CF2=CFCl, CH2=CF2, CFH=CH2, CFH=CF2, CF2=CFCF3, CH2=CFCF3, CH2=CHCF3, CHF=CHCF3 (E-isomer), CHF=CHCF3 (Z-isomer), etc. Among these, at least one selected from the group consisting of tetrafluoroethylene (CF2=CF2), chlorotrifluoroethylene (CF2=CFCl) and vinylidene fluoride (CH2=CF2) is preferred, with tetrafluoroethylene being more preferred, due to its favorable copolymerizability. Therefore, the polymerized units based on the other monomer are preferably polymerized units based on tetrafluoroethylene. The polymerized units based on the other monomers may be the same or different in each occurrence, and the polymer (I) may contain polymerized units based on two or more different types of other monomers.

[0147] The other monomers include those represented by the following formula (n1-2):

[0148] [ka]

[0149] (In the formula, X 1 , X 2 are the same or different H or F;X 3 is H, F, Cl, CH3 or CF3; X 4 , X 5are the same or different and are H or F; a and c are the same or different and are 0 or 1. Rf 3 is a fluorine-containing alkyl group having 1 to 40 carbon atoms or a fluorine-containing alkyl group having 2 to 100 carbon atoms and having an ether bond).

[0150] Specifically, CH2=CFCF2-O-Rf 3 , CF2=CF-O-Rf 3 , CF2=CFCF2-O-Rf 3 , CF2=CF-Rf 3 , CH2=CH-Rf 3 , CH2=CH-O-Rf 3 (In the formula, Rf 3 is the same as the above formula (n1-2)).

[0151] Examples of the other monomers include those of formula (n2-1):

[0152] [ka]

[0153] (In the formula, X 9 is H, F or CH3; Rf 4 Also included are fluorine-containing acrylate monomers represented by Rf (a fluorine-containing alkyl group having 1 to 40 carbon atoms or a fluorine-containing alkyl group having 2 to 100 carbon atoms and an ether bond). 4 The base is

[0154] [ka]

[0155] (wherein d3 is an integer of 1 to 4; e3 is an integer of 1 to 10).

[0156] Examples of the other monomers include those of formula (n2-2): CH2=CHO-Rf 5 (n2-2) (In the formula, Rf 5is a fluorine-containing alkyl group having 1 to 40 carbon atoms or a fluorine-containing alkyl group having 2 to 100 carbon atoms and having an ether bond).

[0157] Specific examples of the monomer of formula (n2-2) include:

[0158] [ka]

[0159] (wherein e6 is an integer of 1 to 10) are preferred.

[0160] More specifically,

[0161] [ka]

[0162] Examples include:

[0163] Others, formula (n2-3): CH2=CHCH2O-Rf 6 (n2-3) (In the formula, Rf 6 is a fluorine-containing alkyl group having 1 to 40 carbon atoms or a fluorine-containing alkyl group having 2 to 100 carbon atoms and having an ether bond), a fluorine-containing allyl ether represented by the formula (n2-4): CH2=CH-Rf 7 (n2-4) (In the formula, Rf 7 is a fluorine-containing alkyl group having 1 to 40 carbon atoms or a fluorine-containing alkyl group having 2 to 100 carbon atoms and having an ether bond), and the like.

[0164] Specific examples of the monomers represented by the above formulas (n2-3) and (n2-4) include:

[0165] [ka]

[0166] Examples of such monomers include:

[0167] The polymer (I) generally has a terminal group. The terminal group is a terminal group generated during polymerization, and typical terminal groups are independently selected from hydrogen, iodine, bromine, linear or branched alkyl groups, and linear or branched fluoroalkyl groups, and may optionally contain at least one catenary heteroatom. The alkyl or fluoroalkyl group preferably has 1 to 20 carbon atoms. These end groups generally originate from the initiator or chain transfer agent used to form polymer (I) or are generated during the chain transfer reaction.

[0168] The polymer (I) preferably has a content of polymerized units (I) of 1.0 mol% or more, more preferably 3.0 mol% or more, even more preferably 5.0 mol% or more, even more preferably 10 mol% or more, particularly preferably 20 mol% or more, and particularly preferably 30 mol% or more, more preferably 40 mol% or more, even more preferably 60 mol% or more, even more preferably 80 mol% or more, particularly preferably 90 mol% or more, particularly preferably substantially 100 mol%, and most preferably consists solely of polymerized units (I). In the polymer (I), the content of polymerization units based on other monomers copolymerizable with the monomer represented by general formula (I) is preferably 99.0 mol% or less, more preferably 97.0 mol% or less, even more preferably 95.0 mol% or less, even more preferably 90 mol% or less, particularly preferably 80 mol% or less, and particularly preferably 70 mol% or less, more preferably 60 mol% or less, even more preferably 40 mol% or less, even more preferably 20 mol% or less, particularly preferably 10 mol% or less, particularly preferably substantially 0 mol%, and particularly preferably does not contain polymerization units based on other monomers.

[0169] The number average molecular weight of the polymer (I) is 0.1×10 4More than 0.2 × 10 is preferable. 4 More preferably, 0.3 × 10 4 More preferably, 0.4×10 4 More preferably, 0.5×10 4 More than 1.0 × 10 4 More than 3.0 × 10 is particularly preferable. 4 The above is particularly preferable, and 3.1 × 10 4 More than 75.0×10 4 The following is preferable: 50.0 x 10 4 Less than 40.0 x 10 is more preferable. 4 More preferably, 30.0 x 10 4 The following is particularly preferred: 20.0 × 10 4 The following are particularly preferred. The number average molecular weight and the weight average molecular weight described below are values ​​calculated by gel permeation chromatography (GPC) using monodisperse polystyrene as a standard. When measurement by GPC is not possible, the number average molecular weight of polymer (I) can be determined from the correlation between the number average molecular weight calculated from the number of terminal groups obtained by NMR, FT-IR, etc. and the melt flow rate. The melt flow rate can be measured in accordance with JIS K 7210.

[0170] The weight average molecular weight of the polymer (I) is 0.2×10 4 More than 0.4 × 10 is preferable. 4 More preferably, 0.6 × 10 4 More preferably, 0.8×10 4 More preferably, 1.0×10 4 More than 5.0 × 10 is particularly preferable. 4 More particularly preferred is 10.0 x 10 4 More particularly, 15.0 × 10 4 More particularly, 20.0 × 10 4 The above is particularly preferable, and 25.0 × 10 4 More than 150.0×10 4 The following is preferable: 100.0 x 10 4Less than 60.0 x 10 is preferable. 4 More preferably, 50.0 x 10 4 The following is particularly preferred: 40.0 x 10 4 The following are particularly preferred:

[0171] The polymer (I) preferably has an ion exchange ratio (IXR) of 53 or less. The IXR is defined as the number of carbon atoms in the polymer backbone relative to the ionic group. Precursor groups that become ionic upon hydrolysis (e.g., -SOF) are not considered ionic groups for purposes of determining the IXR. The IXR is preferably 0.5 or more, more preferably 1 or more, even more preferably 3 or more, even more preferably 4 or more, particularly preferably 5 or more, and particularly preferably 8 or more. The IXR is more preferably 43 or less, more preferably 33 or less, and particularly preferably 23 or less. The ion exchange capacity of the polymer (I) is, in order of preference, 0.80 meg / g or more, 1.50 meg / g or more, 1.75 meg / g or more, 2.00 meg / g or more, 2.50 meg / g or more, 2.60 meg / g or more, 3.00 meg / g or more, and 3.50 meg / g or more. The ion exchange capacity is the content of ionic groups (anionic groups) in the polymer (I) and is calculated from the composition of the polymer (I). In the polymer (I), the ionic groups are typically distributed along the polymer backbone. The polymer (I) comprises a polymer backbone with recurring side chains attached to the backbone, which preferably carry ionic groups. Preferably, polymer (I) comprises ionic groups having a pKa of less than 10, more preferably less than 7. The ionic groups of polymer (I) are preferably selected from the group consisting of sulfonate, carboxylate, phosphonate, and phosphate. The terms "sulfonate, carboxylate, phosphonate, and phosphate" are intended to refer to the respective salts or the respective acids capable of forming salts. When salts are used, preferably the salts are alkali metal or ammonium salts. A preferred ionic group is a sulfonate group. The polymer (I) is preferably water-soluble. Water-soluble means the property of being easily dissolved or dispersed in an aqueous medium. The particle size of the water-soluble polymer (I) cannot be measured by, for example, dynamic light scattering (DLS). On the other hand, the particle size of the water-insoluble polymer (I) can be measured by, for example, dynamic light scattering (DLS).

[0172] The polymer (I) can be produced by a conventional method except for using the above-mentioned monomers.

[0173] The content of polymer (I) in the pre-treatment aqueous dispersion is preferably 0.0001 to 15% by mass relative to the aqueous dispersion. If it is less than 0.0001% by mass, the dispersion stability may be poor, and if it exceeds 15% by mass, the dispersion effect will not be commensurate with the amount present, making it impractical. The content of the polymer (I) may be, for example, 19 It can be determined by F-MAS NMR measurement. The content of the polymer (I) can be measured by methods described in WO 2014 / 099453, WO 2010 / 075497, WO 2010 / 075496, WO 2011 / 008381, WO 2009 / 055521, WO 1987 / 007619, JP 61-293476 A, WO 2010 / 075494, WO 2010 / 075359, WO 2012 / 082454, WO 2006 / 119224, WO 2013 / 085864, WO 2014 / 099453, WO 2014 / 099454, WO 2014 / 099455, WO 2014 / 099456, WO 2014 / 099457, WO 2014 / 099458, WO 2014 / 099459 ... Measurement methods for each polymer described in Publication No. 2012 / 082707, International Publication No. 2012 / 082703, International Publication No. 2012 / 082454, International Publication No. 2012 / 082451, International Publication No. 2006 / 135825, International Publication No. 2004 / 067588, International Publication No. 2009 / 068528, JP 2004-075978, JP 2001-226436, International Publication No. 1992 / 017635, International Publication No. 2014 / 069165, JP 11-181009, etc. are described. Specific examples of the device that can be used include AVANCE III HD400 manufactured by Bruker and AVANCE300 manufactured by Bruker. The rotation speed is set according to the resonance frequency of the apparatus so that the spinning side bands do not overlap with the peaks used to calculate the contents of the fluoropolymer and polymer (I). For example, when polymer (I) is a copolymer of TFE and a monomer represented by CH2=CF(CF2OCFCF3COONH4), the rotation speed may be set to 30 kHz when using AVANCE300 manufactured by Bruker Japan Ltd. to determine the content of the copolymer of TFE and a monomer represented by CH2=CF(CF2OCFCF3COONH4) in the pre-treatment aqueous dispersion. For example, when the polymer (I) is a copolymer of TFE and a monomer represented by CH2=CF(CF2OCFCF3COONH4), the content of the copolymer of TFE and a monomer represented by CH2=CF(CF2OCFCF3COONH4) in the aqueous dispersion before treatment is 19 It can be calculated using the following formula from the spectrum obtained by F-MAS NMR measurement (rotation speed: 30 kHz). Y = (400B / (5xA+3xB)) x 100 Y: Content (mol%) of copolymer of TFE and monomer represented by CH2=CF(CF2OCFCF3COONH4) A: Integrated value of the signal at -120 ppm B: Sum of integrals of CF2 and CF3 signals at -83 ppm The chemical shift value was determined by setting the peak top of the signal derived from the main chain of PTFE at −120 ppm. x: The proportion (mol%) of polymerized units based on the monomer represented by CH2=CF(CF2OCFCF3COONH4) in the copolymer of TFE and the monomer represented by CH2=CF(CF2OCFCF3COONH4)

[0174] The pre-treatment aqueous dispersion is obtained by polymerization in the presence of polymer (I). More specifically, it is obtained by polymerizing a fluoromonomer (excluding the monomer represented by general formula (I)) in an aqueous medium in the presence of polymer (I). The first production method of the present disclosure may include, before step A, step C of polymerizing a fluoromonomer in an aqueous medium in the presence of polymer (I) to obtain an aqueous dispersion containing a fluoropolymer (pre-treatment aqueous dispersion).

[0175] The fluoromonomer preferably has at least one double bond. Examples of the fluoromonomer include tetrafluoroethylene (TFE), hexafluoropropylene (HFP), chlorotrifluoroethylene (CTFE), vinyl fluoride, vinylidene fluoride (VDF), trifluoroethylene, fluoroalkyl vinyl ether, fluoroalkyl ethylene, fluoroalkyl allyl ether, trifluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, hexafluoroisobutene, and compounds represented by the general formula (100): CHX 101 =CX 102 Rf 101 (In the formula, X 101 and X 102 is H on one side and F on the other side, and Rf 101 is preferably at least one selected from the group consisting of a fluoromonomer represented by (a linear or branched fluoroalkyl group having 1 to 12 carbon atoms), a fluorinated vinyl heterocyclic compound, and a monomer that provides a crosslinking site.

[0176] Examples of the fluoroalkyl vinyl ether include: General formula (110): CF2=CF-ORf 111 (In the formula, Rf 111 represents a perfluoroorganic group; General formula (120): CF2=CF-OCH2-Rf 121 (In the formula, Rf 121 is a perfluoroalkyl group having 1 to 5 carbon atoms), General formula (130): CF2=CFOCF2ORf 131 (In the formula, Rf 131 is a linear or branched perfluoroalkyl group having 1 to 6 carbon atoms, a cyclic perfluoroalkyl group having 5 to 6 carbon atoms, or a linear or branched perfluorooxyalkyl group having 2 to 6 carbon atoms and containing 1 to 3 oxygen atoms, General formula (140): CF2=CFO(CF2CF(Y 141 )O) m (CF2) n F (In the formula, Y 141 represents a fluorine atom or a trifluoromethyl group, m is an integer of 1 to 4, and n is an integer of 1 to 4. General formula (150): CF2=CF-O-(CF2CFY 151 -O) n -(CFY 152 ) m -A 151 (In the formula, Y 151 represents a fluorine atom, a chlorine atom, a -SO2F group, or a perfluoroalkyl group. The perfluoroalkyl group may contain an etheric oxygen and a -SO2F group. n represents an integer of 0 to 3. n Y 151 may be the same or different. 152 represents a fluorine atom, a chlorine atom, or a -SO2F group. m represents an integer of 1 to 5. m Y 152 may be the same or different. 151 -SO2X 151 , -COZ 151 or -POZ 152 Z 153 represents X 151 are F, Cl, Br, I, -OR 151 or -NR 152 R 153 represents Z. 151 , Z 152 and Z 153 are the same or different and are -NR 154 R 155 -OR 156 Represents R151 , R 152 , R 153 , R 154 , R 155 and R 156 are the same or different and represent H, ammonium, an alkali metal, an alkyl group which may contain a fluorine atom, an aryl group, or a sulfonyl-containing group. It is preferable that the material is at least one selected from the group consisting of:

[0177] In this specification, the term "perfluoroorganic group" refers to an organic group in which all hydrogen atoms bonded to carbon atoms are substituted with fluorine atoms. The perfluoroorganic group may have an ether oxygen.

[0178] The fluoromonomer represented by the general formula (110) is Rf 111 is a perfluoroalkyl group having 1 to 10 carbon atoms. The number of carbon atoms in the perfluoroalkyl group is preferably 1 to 5.

[0179] Examples of the perfluoroorganic group in the general formula (110) include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, and a perfluorohexyl group. The fluoromonomer represented by the general formula (110) further includes a fluoromonomer represented by the general formula (110) in which Rf 111 is a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms, Rf 111 is the following formula:

[0180] [ka]

[0181] (wherein m represents 0 or an integer of 1 to 4), Rf 111 is the following formula:

[0182] [ka]

[0183] (wherein n represents an integer of 1 to 4).

[0184] Among the fluoromonomers represented by the general formula (110), General formula (160): CF2=CF-ORf 161 (In the formula, Rf 161 Rf represents a perfluoroalkyl group having 1 to 10 carbon atoms. Fluoromonomers represented by 161 is preferably a perfluoroalkyl group having 1 to 5 carbon atoms.

[0185] The fluoroalkyl vinyl ether is preferably at least one selected from the group consisting of fluoromonomers represented by the general formulas (160), (130) and (140).

[0186] The fluoromonomer represented by general formula (160) is preferably at least one selected from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), and perfluoro(propyl vinyl ether), and more preferably at least one selected from the group consisting of perfluoro(methyl vinyl ether) and perfluoro(propyl vinyl ether).

[0187] The fluoromonomer represented by the general formula (130) is preferably at least one selected from the group consisting of CF2=CFOCF2OCF3, CF2=CFOCF2OCF2CF3, and CF2=CFOCF2OCF2CF2OCF3.

[0188] The fluoromonomer represented by general formula (140) is preferably at least one selected from the group consisting of CF2=CFOCF2CF(CF3)O(CF2)3F, CF2=CFO(CF2CF(CF3)O)2(CF2)3F, and CF2=CFO(CF2CF(CF3)O)2(CF2)2F.

[0189] The fluoromonomer represented by general formula (150) is preferably at least one selected from the group consisting of CF2=CFOCF2CF2SO2F, CF2=CFOCF2CF(CF3)OCF2CF2SO2F, CF2=CFOCF2CF(CF2CF2SO2F)OCF2CF2SO2F and CF2=CFOCF2CF(SO2F)2.

[0190] The fluoromonomer represented by the general formula (100) is Rf 101 is a linear fluoroalkyl group, and Rf 101 More preferred is a fluoromonomer in which Rf is a linear perfluoroalkyl group. 101 The number of carbon atoms in the formula (100) is preferably 1 to 6. Examples of the fluoromonomer represented by the formula (100) include CH2=CFCF3, CH2=CFCF2CF3, CH2=CFCF2CF2CF3, CH2=CFCF2CF2CF2H, CH2=CFCF2CF2CF2CF3, CHF=CHCF3 (E-isomer), and CHF=CHCF3 (Z-isomer), and among these, 2,3,3,3-tetrafluoropropylene represented by CH2=CFCF3 is preferred.

[0191] Fluoroalkylethylenes include: General formula (170): CH2=CH-(CF2) n -X 171 (In the formula, X 171 is H or F, and n is an integer of 3 to 10.) is preferred, and fluoroalkylethylenes represented by CH2=CH-C4F9 and CH2=CH-C6F 13 It is more preferable that the material is at least one selected from the group consisting of:

[0192] Examples of the fluoroalkyl allyl ether include: General formula (180): CF2=CF-CF2-ORf 111 (In the formula, Rf 111 represents a perfluoroorganic group.

[0193] Rf of general formula (180) 111 is Rf in general formula (110) 111 is the same as Rf 111 is preferably a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluoroalkoxyalkyl group having 1 to 10 carbon atoms. The fluoroalkyl allyl ether represented by general formula (180) is preferably at least one selected from the group consisting of CF2=CF-CF2-O-CF3, CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7, and CF2=CF-CF2-O-C4F9, more preferably at least one selected from the group consisting of CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7, and CF2=CF-CF2-O-C4F9, and even more preferably CF2=CF-CF2-O-CF2CF2CF3.

[0194] The fluorinated vinyl heterocycle includes a compound represented by the general formula (230): [ka] (In the formula, X 231 and X 232 are independently F, Cl, a methoxy group, or a fluorinated methoxy group; Y 231 is the formula Y 232 or formula Y 233 is.

[0195] [ka] (In the formula, Z 231 and Z 232are independently F or a fluorinated alkyl group having 1 to 3 carbon atoms.

[0196] Examples of monomers that provide crosslinking sites include: General formula (180):CX 181 2=CX 182 -R f 181 CHR 181 X 183 (In the formula, X 181 and X 182 are independently a hydrogen atom, a fluorine atom, or CH3, R f 181 represents a fluoroalkylene group, a perfluoroalkylene group, a fluoro(poly)oxyalkylene group or a perfluoro(poly)oxyalkylene group, R 181 is a hydrogen atom or CH3, X 183 is an iodine atom or a bromine atom. General formula (190):CX 191 2=CX 192 -R f 191 X 193 (In the formula, X 191 and X 192 are independently a hydrogen atom, a fluorine atom, or CH3, R f 191 represents a fluoroalkylene group, a perfluoroalkylene group, a fluoropolyoxyalkylene group or a perfluoropolyoxyalkylene group, X 193 is an iodine atom or a bromine atom. General formula (200): CF2=CFO(CF2CF(CF3)O) m (CF2) n -X 201 (wherein m is an integer of 0 to 5, n is an integer of 1 to 3, X 201 is a cyano group, a carboxyl group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or -CH2I; and General formula (210): CH2=CFCF2O(CF(CF3)CF2O) m (CF(CF3)) n -X 211 (wherein m is an integer of 0 to 5, n is an integer of 1 to 3, X 211 is a cyano group, a carboxyl group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or —CHOH; General formula (220):CR 221 R 222 =CR 223 -Z 221 -CR 224 =CR 225 R 226 (In the formula, R 221 , R 222 , R 223 , R 224 , R 225 and R 226 are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. 221 represents a linear or branched alkylene group having 1 to 18 carbon atoms, a cycloalkylene group having 3 to 18 carbon atoms, an at least partially fluorinated alkylene group or oxyalkylene group having 1 to 10 carbon atoms, which may have an oxygen atom, or -(Q) p -CF2O-(CF2CF2O) m (CF2O) n -CF2-(Q) p - (wherein Q is an alkylene group or an oxyalkylene group, p is 0 or 1, and m / n is 0.2 to 5), and is a (per)fluoropolyoxyalkylene group having a molecular weight of 500 to 10,000. It is preferable that the material is at least one selected from the group consisting of:

[0197] X 183 and X 193 is preferably an iodine atom. f 181 and R f 191is preferably a perfluoroalkylene group having 1 to 5 carbon atoms. 181 is preferably a hydrogen atom. 201 is preferably a cyano group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or —CH2I. 211 is preferably a cyano group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or —CH 2 OH.

[0198] Monomers that provide crosslinking sites include CF2=CFOCF2CF(CF3)OCF2CF2CN, CF2=CFOCF2CF(CF3)OCF2CF2COOH, CF2=CFOCF2CF(CF3)OCF2CF2CH2I, CF2=CFOCF2CF2CH2I, CH2=CFCF2OCF(CF3)CF2OCF(CF3)CN, CH2=CFCF2OCF(CF3)CF2OCF(CF3)COOH, CH2=CFCF2OCF( It is preferably at least one selected from the group consisting of CF3)CF2OCF(CF3)CH2OH, CH2=CHCF2CF2I, CH2=CH(CF2)2CH=CH2, CH2=CH(CF2)6CH=CH2, and CF2=CFO(CF2)5CN, and more preferably at least one selected from the group consisting of CF2=CFOCF2CF(CF3)OCF2CF2CN and CF2=CFOCF2CF2CH2I.

[0199] In the step C, the fluoromonomer and a fluorine-free monomer may be polymerized. Examples of the fluorine-free monomer include hydrocarbon-based monomers reactive with the fluoromonomer. Examples of the hydrocarbon-based monomer include alkenes such as ethylene, propylene, butylene, and isobutylene; alkyl vinyl ethers such as ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, and cyclohexyl vinyl ether; vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl isobutyrate, vinyl valerate, vinyl pivalate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl versatate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl benzoate, vinyl p-t-butylbenzoate, vinyl cyclohexanecarboxylate, vinyl monochloroacetate, and vinyl adipate. vinyl esters such as vinyl allyl ether, vinyl acrylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl cinnamate, vinyl undecylenate, vinyl hydroxyacetate, vinyl hydroxypropionate, vinyl hydroxybutyrate, vinyl hydroxyvalerate, vinyl hydroxyisobutyrate, and vinyl hydroxycyclohexanecarboxylate; alkyl allyl ethers such as ethyl allyl ether, propyl allyl ether, butyl allyl ether, isobutyl allyl ether, and cyclohexyl allyl ether; and alkyl allyl esters such as ethyl allyl ester, propyl allyl ester, butyl allyl ester, isobutyl allyl ester, and cyclohexyl allyl ester.

[0200] The fluorine-free monomer may also be a functional group-containing hydrocarbon monomer (excluding the monomer that provides a crosslinking site). Examples of the functional group-containing hydrocarbon monomer include hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, hydroxyisobutyl vinyl ether, and hydroxycyclohexyl vinyl ether; fluorine-free monomers having a carboxyl group such as itaconic acid, succinic acid, succinic anhydride, fumaric acid, fumaric anhydride, crotonic acid, maleic acid, maleic anhydride, and perfluorobutenoic acid; fluorine-free monomers having a glycidyl group such as glycidyl vinyl ether and glycidyl allyl ether; fluorine-free monomers having an amino group such as aminoalkyl vinyl ether and aminoalkyl allyl ether; and fluorine-free monomers having an amide group such as (meth)acrylamide and methylolacrylamide.

[0201] In the above step C, one or more of the above fluoromonomers are polymerized to obtain a pre-treatment aqueous dispersion containing particles of the desired fluoropolymer.

[0202] In the above step C, the polymer (I) is preferably added in a total amount of 0.0001 to 10% by mass relative to 100% by mass of the aqueous medium. A more preferred lower limit is 0.001% by mass, and a more preferred upper limit is 1% by mass. If the amount is less than 0.0001% by mass, the dispersing power may be insufficient, and if the amount exceeds 10% by mass, the effect commensurate with the amount added may not be obtained, and instead, the polymerization rate may decrease or the reaction may stop. The amount of the compound added is determined appropriately depending on the type of monomer used, the molecular weight of the desired fluoropolymer, etc.

[0203] It is also preferable that the step C further comprises a step of continuously adding the polymer (I). The continuous addition of the polymer (I) means, for example, adding the polymer (I) over time, without interruption, or in portions, rather than all at once. The polymer (I) may be added in the form of an aqueous solution prepared by adding the polymer (I) and water.

[0204] In the step C, the step of continuously adding the polymer (I) preferably starts adding the polymer (I) to the aqueous medium when the solid content of the fluoropolymer formed in the aqueous medium is 0.5% by mass or less, and continues to add the polymer (I) continuously thereafter. The addition of the polymer (I) is more preferably started when the solid content is 0.3% by mass or less, even more preferably when it is 0.2% by mass or less, even more preferably when it is 0.1% by mass or less, and particularly preferably when it starts with the initiation of polymerization. The solid content is the concentration of the fluoropolymer relative to the total of the aqueous medium and the fluoropolymer.

[0205] In step C, the amount of the polymer (I) added is preferably 0.0001 to 10% by mass relative to 100% by mass of the aqueous medium. The preferred lower limit is 0.001% by mass, more preferably 0.01% by mass, and even more preferably 0.1% by mass. The preferred upper limit is 10% by mass, more preferably 1.0% by mass, and even more preferably 0.50% by mass. In the step of continuously adding the polymer (I), the amount of the polymer (I) added is preferably 0.0001 to 10% by mass relative to 100% by mass of the aqueous medium. The preferred lower limit is 0.001% by mass, more preferably 0.01% by mass, and even more preferably 0.1% by mass. The preferred upper limit is 10% by mass, more preferably 1.0% by mass, and even more preferably 0.50% by mass. If the amount is less than 0.0001% by mass, the dispersion force may be insufficient. If the amount exceeds 10% by mass, the effect commensurate with the amount added may not be obtained, and instead, the polymerization rate may decrease or the reaction may stop. The amount of the compound added is determined appropriately depending on the type of monomer used, the molecular weight of the desired fluoropolymer, and other factors.

[0206] In the step C, the fluoropolymer can be efficiently produced by using at least one of the polymers (I). Two or more of the compounds included in the polymer (I) may be used simultaneously as the surfactant, or a compound having surface activity other than the polymer (I) may be used simultaneously as long as it is volatile or may remain in a molded product made of the fluoropolymer.

[0207] A nucleating agent may be used in step C. The preferred amount of the nucleating agent can be appropriately selected depending on the type of nucleating agent, and is, for example, 1000 ppm by mass or less, more preferably 500 ppm by mass or less, even more preferably 100 ppm by mass or less, particularly preferably 50 ppm by mass or less, and especially preferably 10 ppm by mass or less, relative to the aqueous medium.

[0208] The above-mentioned step C preferably further comprises a step of adding a nucleating agent to the aqueous medium before the start of polymerization or when the concentration of the fluoropolymer such as polytetrafluoroethylene particles formed in the aqueous medium is 5.0 mass% or less. By adding the nucleating agent at the early stage of polymerization, an aqueous dispersion having a small average primary particle size and excellent stability can be obtained. The amount of nucleating agent added before the start of polymerization or when the concentration of the fluoropolymer such as PTFE particles formed in the aqueous medium is 5.0 mass% or less is preferably 0.001 mass% or more, more preferably 0.01 mass% or more, even more preferably 0.05 mass% or more, and even more preferably 0.1 mass% or more, based on the fluoropolymer such as polytetrafluoroethylene obtained. The upper limit is not limited, but is, for example, 2000 mass%.

[0209] Use of the nucleating agent results in a fluoropolymer having a smaller primary particle size compared to polymerization carried out in the absence of the nucleating agent.

[0210] Examples of the nucleating agent include dicarboxylic acids, perfluoropolyether (PFPE) acids or salts thereof, hydrocarbon-containing surfactants, etc. The nucleating agent preferably does not contain an aromatic ring and is preferably an aliphatic compound.

[0211] The nucleating agent is preferably added before or simultaneously with the addition of the polymerization initiator, but the particle size distribution can also be adjusted by adding it during the polymerization.

[0212] The amount of the dicarboxylic acid is preferably 1000 ppm by mass or less, more preferably 500 ppm by mass or less, and even more preferably 100 ppm by mass or less, relative to the aqueous medium.

[0213] The perfluoropolyether (PFPE) acid or salt thereof may have any chain structure in which oxygen atoms in the main chain of the molecule are separated by saturated fluorocarbon groups having 1 to 3 carbon atoms. Two or more types of fluorocarbon groups may be present in the molecule. A typical structure has a repeating unit represented by the following formula: (-CFCF3-CF2-O-) n (VII) (-CF2-CF2-CF2-O-) n (VIII) (-CF2-CF2-O-) n -(-CF2-O-) m (IX) (-CF2-CFCF3-O-)n-(-CF2-O-) m (X)

[0214] These structures are described by Kasai in J. Appl. Polymer Sci. 57, 797 (1995). As disclosed therein, the PFPE acid or its salt may have a carboxylic acid group or its salt at one or both ends. The PFPE acid or its salt may also have a sulfonic acid or phosphonic acid group or their salt at one or both ends. The PFPE acid or its salt may also have a different group at each end. For monofunctional PFPEs, the other end of the molecule is usually perfluorinated but may contain a hydrogen or chlorine atom. The PFPE acid or its salt has at least two ether oxygens, preferably at least four ether oxygens, and even more preferably at least six ether oxygens. Preferably, at least one of the fluorocarbon groups separating the ether oxygens, and more preferably at least two of such fluorocarbon groups, has two or three carbon atoms. Even more preferably, at least 50% of the fluorocarbon groups separating the ether oxygens have two or three carbon atoms. Also, preferably, the PFPE acid or salt thereof has a total of at least 15 carbon atoms, for example, the preferred minimum value of n or n+m in the repeating unit structure is at least 5. Two or more of the PFPE acids or salts thereof having acid groups at one or both ends can be used in the first production method of the present disclosure. The PFPE acid or salt thereof preferably has a number average molecular weight of less than 6000 g / mol.

[0215] The amount of the hydrocarbon-containing surfactant added is preferably 50 ppm by mass or less, more preferably 40 ppm by mass or less, even more preferably 30 ppm by mass or less, and even more preferably 20 ppm by mass or less, relative to the aqueous medium. The ppm amount of lipophilic nucleation sites present in the aqueous medium is presumed to be less than the amount added. Therefore, the amount of lipophilic nucleation sites is less than the above-mentioned 50 ppm by mass, 40 ppm by mass, 30 ppm by mass, and 20 ppm by mass, respectively. Since the lipophilic nucleation sites are thought to exist as molecules, even a small amount of the hydrocarbon-containing surfactant can generate a large amount of lipophilic nucleation sites. Therefore, beneficial effects can be obtained even by adding about 1 ppm by mass of the hydrocarbon-containing surfactant to the aqueous medium. The preferred lower limit is 0.01 ppm by mass, more preferably 0.1 ppm by mass.

[0216] The hydrocarbon-containing surfactants include nonionic and cationic surfactants, including siloxane surfactants such as those disclosed in U.S. Pat. No. 7,897,682 (Brothers et al.) and U.S. Pat. No. 7,977,438 (Brothers et al.).

[0217] The hydrocarbon-containing surfactant is preferably a nonionic surfactant (e.g., a nonionic hydrocarbon surfactant). That is, the nucleating agent is preferably a nonionic surfactant. The nonionic surfactant preferably does not contain an aromatic moiety.

[0218] Examples of the nonionic surfactant include those represented by the following general formula (i): R 3 -OA 1 -H(i) (In the formula, R 3 is a linear or branched primary or secondary alkyl group having 8 to 18 carbon atoms, and A 1 is a polyoxyalkylene chain. R 3 The number of carbon atoms in R is preferably 10 to 16, and more preferably 12 to 16.3 When the carbon number of R is 18 or less, good dispersion stability of the aqueous dispersion is easily obtained. 3 If the carbon number exceeds 18, the flow temperature is high and it is difficult to handle. 3 If the number of carbon atoms is less than 8, the surface tension of the aqueous dispersion increases, and the permeability and wettability tend to decrease.

[0219] The polyoxyalkylene chain may be composed of oxyethylene and oxypropylene. The polyoxyalkylene chain has an average repeat number of 5 to 20 oxyethylene groups and an average repeat number of 0 to 2 oxypropylene groups, and is a hydrophilic group. The number of oxyethylene units may include either a broad or narrow unimodal distribution, which is typically provided, or a broader or bimodal distribution obtained by blending. When the average repeat number of oxypropylene groups is greater than 0, the oxyethylene and oxypropylene groups in the polyoxyalkylene chain may be arranged in a block or random configuration. From the viewpoint of viscosity and stability of the aqueous dispersion, a polyoxyalkylene chain having an average repeat number of 7 to 12 oxyethylene groups and an average repeat number of 0 to 2 oxypropylene groups is preferred. 1 If the oxypropylene group has an average of 0.5 to 1.5, low foaming properties are favorable and it is preferable.

[0220] More preferably, R 3 is (R')(R")HC-, where R' and R" are the same or different straight, branched, or cyclic alkyl groups having a total of at least 5, preferably 7 to 17, carbon atoms. Preferably, at least one of R' or R" is a branched or cyclic hydrocarbon group.

[0221] Specific examples of the compound (polyoxyethylene alkyl ether) represented by the above general formula (i) include C 13 H 27 -O-(C2H4O) 10 -H, C 13 H 27 -O-(C2H4O)8-H, C12 H 25 -O-(C2H4O) 10 -H, C 10 H 21 CH(CH3)CH2-O-(C2H4O)9-H, C 13 H 27 -O-(C2H4O)9-(CH(CH3)CH2O)-H, C 16 H 33 -O-(C2H4O) 10 -H, HC(CH 11 )(C7H 15 )-O-(C2H4O)9-H, etc. Commercially available compounds (polyoxyethylene alkyl ethers) represented by the above general formula (i) include, for example, Genapol X080 (product name, manufactured by Clariant), the Noigen TDS series (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) such as Noigen TDS-80 (trade name), the Leocol TD series (manufactured by Lion Chemical) such as Leocol TD-90 (trade name), the Lionol (registered trademark) TD series (manufactured by Lion Chemical), the T-Det A series (manufactured by Harcros Chemicals) such as T-Det A138 (trade name), and the Tergitol (registered trademark) 15S series (manufactured by The Dow Chemical Company).

[0222] The nonionic surfactant is preferably an ethoxylate of 2,6,8-trimethyl-4-nonanol having an average of about 4 to about 18 ethylene oxide units, an ethoxylate of 2,6,8-trimethyl-4-nonanol having an average of about 6 to about 12 ethylene oxide units, or a mixture thereof. Nonionic surfactants of this type are also commercially available, for example, as TERGITOL TMN-6, TERGITOL TMN-10, and TERGITOL TMN-100X (all product names, manufactured by The Dow Chemical Company).

[0223] The hydrophobic group of the nonionic surfactant may be any of an alkylphenol group, a linear alkyl group, and a branched alkyl group. For example, the polyoxyethylene alkylphenyl ether-based nonionic compound may be, for example, a compound represented by the following general formula (ii): R 4 -C6H4-OA 2 -H (ii) (In the formula, R 4 is a linear or branched primary or secondary alkyl group having 4 to 12 carbon atoms, and A 2 is a polyoxyalkylene chain.) Specific examples of the polyoxyethylene alkylphenyl ether-based nonionic compounds include Triton (registered trademark) X-100 (trade name, manufactured by Dow Chemical Company).

[0224] The nonionic surfactant also includes a polyol compound, specifically, those described in WO 2011 / 014715. Typical examples of polyol compounds include compounds having one or more sugar units as polyol units. The sugar units may be modified to contain at least one long chain. Suitable polyol compounds containing at least one long chain moiety include, for example, alkyl glycosides, modified alkyl glycosides, sugar esters, and combinations thereof. Sugars include, but are not limited to, monosaccharides, oligosaccharides, and sorbitan. Monosaccharides include pentoses and hexoses. Typical examples of monosaccharides include ribose, glucose, galactose, mannose, fructose, arabinose, and xylose. Oligosaccharides include oligomers of 2 to 10 identical or different monosaccharides. Examples of oligosaccharides include, but are not limited to, sucrose, maltose, lactose, raffinose, and isomaltose.

[0225] Typically, sugars suitable for use as polyol compounds include cyclic compounds containing a five-membered ring with four carbon atoms and one heteroatom (typically oxygen or sulfur, but preferably an oxygen atom), or a six-membered ring with five carbon atoms and one heteroatom, preferably an oxygen atom, as described above. These further contain at least two or at least three hydroxy groups (-OH groups) attached to the carbon ring atoms. Typically, the sugars are modified in that one or more of the hydrogen atoms of the hydroxy groups (and / or hydroxyalkyl groups) attached to the carbon ring atoms are replaced by a long-chain residue, such that an ether or ester bond is created between the long-chain residue and the sugar moiety. The sugar-based polyol may contain one or more sugar units. The sugar unit or units may be modified with long chain moieties as described above. Specific examples of sugar-based polyol compounds include glycosides, sugar esters, sorbitan esters, and mixtures and combinations thereof.

[0226] A preferred class of polyol compounds are the alkyl or modified alkyl glucosides. These classes of surfactants contain at least one glucose moiety. [ka] (wherein x represents 0, 1, 2, 3, 4, or 5; R 1 and R 2 independently represent H or a long chain unit containing at least 6 carbon atoms, with the proviso that R 1 and R 2 and at least one of R is not H. 1 and R 2Typical examples of the fatty alcohol include hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol (lauryl alcohol), tetradecanol, hexadecanol (cetyl alcohol), heptadecanol, octadecanol (stearyl alcohol), eicosanoic acid, and combinations thereof. While the above formula represents a specific example of an alkyl polyglucoside showing glucose in the pyranose form, it is understood that other sugars or sugars that are the same sugar but in different enantiomeric or diastereomeric forms may also be used. Alkyl glucosides can be obtained, for example, by the acid-catalyzed reaction of glucose, starch, or n-butyl glucoside with aliphatic alcohols, typically resulting in a mixture of various alkyl glucosides (Alkylpolygylcoside, Rompp, Lexikon Chemie, Version 2.0, Stuttgart / New York, Georg Thieme Verlag, 1999). Examples of aliphatic alcohols include hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol (lauryl alcohol), tetradecanol, hexadecanol (cetyl alcohol), heptadecanol, octadecanol (stearyl alcohol), eicosanoic acid, and combinations thereof. Alkyl glucosides are also commercially available from Cognis GmbH, Dusseldorf, Germany, under the trade names GLUCOPON or DISPONIL.

[0227] Other nonionic surfactants include difunctional block copolymers supplied by BASF as the Pluronic® R series, tridecyl alcohol alkoxylates supplied by BASF as the Iconol® TDA series, and hydrocarbon-containing siloxane surfactants, preferably hydrocarbon surfactants, in which the hydrocarbyl groups, which may be substituted by halogens such as fluorine, are fully substituted by hydrogen atoms, whereby these siloxane surfactants can also be considered hydrocarbon surfactants, i.e., the monovalent substituents on the hydrocarbyl groups are hydrogen.

[0228] In the step C, a compound having a functional group reactive by radical polymerization and a hydrophilic group may be used together with the polymer (I). The compound having a functional group reactive by radical polymerization and a hydrophilic group can be the same compound as the modifying monomer (A) described below.

[0229] In addition to the polymer (I) and other surfactant compounds, additives for stabilizing each compound may be used in step C. Examples of such additives include buffers, pH adjusters, stabilizing aids, and dispersion stabilizers.

[0230] The stabilizing aid is preferably paraffin wax, fluorine-based oil, fluorine-based solvent, silicone oil, etc. The stabilizing aid may be used alone or in combination of two or more. The stabilizing aid is more preferably paraffin wax. The paraffin wax may be liquid, semi-solid, or solid at room temperature, but is preferably a saturated hydrocarbon having 12 or more carbon atoms. The melting point of the paraffin wax is usually preferably 40 to 65°C, more preferably 50 to 65°C.

[0231] The amount of the stabilizing aid used is preferably 0.1 to 12 mass % based on the mass of the aqueous medium used, and more preferably 0.1 to 8 mass %. It is desirable that the stabilizing aid is sufficiently hydrophobic so that after polymerization of a fluoropolymer such as PTFE, it can be completely separated and removed from the pre-treatment aqueous dispersion containing a fluoropolymer such as a PTFE dispersion, so as not to become a contaminating component.

[0232] In the above step C, the polymerization is carried out by charging an aqueous medium, the polymer (I), a monomer, and, if necessary, other additives into a polymerization reactor, stirring the contents of the reactor, and maintaining the reactor at a predetermined polymerization temperature, and then adding a predetermined amount of a polymerization initiator to initiate the polymerization reaction. After the initiation of the polymerization reaction, a monomer, a polymerization initiator, a chain transfer agent, the polymer (I), etc. may be additionally added depending on the purpose. The polymer (I) may be added after the initiation of the polymerization reaction.

[0233] In the above step C, the polymerization temperature is usually 5 to 120°C, and the polymerization pressure is usually 0.05 to 10 MPaG. The polymerization temperature and polymerization pressure are appropriately determined depending on the type of monomer used, the molecular weight of the target fluoropolymer, and the reaction rate.

[0234] The polymerization initiator is not particularly limited as long as it can generate radicals within the polymerization temperature range, and known oil-soluble and / or water-soluble polymerization initiators can be used. Furthermore, polymerization can also be initiated as a redox reaction in combination with a reducing agent, etc. The concentration of the polymerization initiator is determined appropriately depending on the type of monomer, the molecular weight of the desired fluoropolymer, and the reaction rate.

[0235] As the polymerization initiator, an oil-soluble radical polymerization initiator or a water-soluble radical polymerization initiator can be used.

[0236] The oil-soluble radical polymerization initiator may be a known oil-soluble peroxide, for example, dialkyl peroxycarbonates such as diisopropyl peroxydicarbonate and di-sec-butyl peroxydicarbonate, peroxyesters such as t-butyl peroxyisobutyrate and t-butyl peroxypivalate, dialkyl peroxides such as di-t-butyl peroxide, and the like. Also, di(ω-hydro-dodecafluorohexanoyl) peroxide, di(ω-hydro-tetradecafluoroheptanoyl) peroxide, di(ω-hydro-hexadecafluorononanoyl) peroxide, di(perfluorobutyryl) peroxide, di(perfluorovaleryl) peroxide, di(perfluorohexanoyl) peroxide, di(perfluoroheptanoyl) peroxide, di(perfluorooctanoyl) peroxide, di(perfluorononanoyl) peroxide, di(ω-chloro Representative examples include di[perfluoro(or fluorochloro)acyl]peroxides such as di(ω-chlorohexafluorobutanoyl)peroxide, di(ω-chloro-decafluorohexanoyl)peroxide, di(ω-chloro-tetradecafluorooctanoyl)peroxide, ω-hydro-dodecafluoroheptanoyl-ω-hydrohexadecafluorononanoyl-peroxide, ω-chloro-hexafluorobutyryl-ω-chloro-decafluorohexanoyl-peroxide, ω-hydrododecafluoroheptanoyl-perfluorobutyryl-peroxide, di(dichloropentafluorobutanoyl)peroxide, di(trichlorooctafluorohexanoyl)peroxide, di(tetrachloroundecafluorooctanoyl)peroxide, di(pentachlorotetradecafluorodecanoyl)peroxide, and di(undecachlorodotriacontafluorodocosanoyl)peroxide.

[0237] The water-soluble radical polymerization initiator may be a known water-soluble peroxide, such as ammonium salts, potassium salts, or sodium salts of persulfuric acid, perborate, perchloric acid, perphosphoric acid, or percarbonate; organic peroxides such as disuccinic acid peroxide or diglutaric acid peroxide; t-butyl permaleate; or t-butyl hydroperoxide. A reducing agent such as sulfites or sulfites may also be contained, and the amount used may be 0.1 to 20 times the amount of the peroxide.

[0238] For example, when polymerization is carried out at low temperatures below 30°C, it is preferable to use a redox initiator, which combines an oxidizing agent and a reducing agent, as the polymerization initiator. Examples of oxidizing agents include persulfates, organic peroxides, potassium permanganate, manganese triacetate, and cerium ammonium nitrate. Examples of reducing agents include sulfites, bisulfites, bromates, diimines, and oxalic acid. Examples of persulfates include ammonium persulfate and potassium persulfate. Examples of sulfites include sodium sulfite and ammonium sulfite. To increase the decomposition rate of the initiator, it is also preferable to add a copper salt or an iron salt to the redox initiator combination. Examples of copper salts include copper(II) sulfate, and examples of iron salts include iron(II) sulfate.

[0239] Examples of the redox initiator include potassium permanganate / oxalic acid, ammonium persulfate / bisulfite / iron sulfate, manganese triacetate / oxalic acid, cerium ammonium nitrate / oxalic acid, and bromate / bisulfite, with potassium permanganate / oxalic acid being preferred. When using a redox initiator, either an oxidizing agent or a reducing agent may be charged into a polymerization vessel in advance, and then the other may be added continuously or intermittently to initiate polymerization. For example, when potassium permanganate / oxalic acid is used, it is preferred to charge oxalic acid into a polymerization vessel and then continuously add potassium permanganate thereto.

[0240] The amount of polymerization initiator to be added is not particularly limited, but may be added all at once, stepwise, or continuously at the beginning of polymerization in an amount (for example, several ppm relative to the water concentration) that does not significantly decrease the polymerization rate. The upper limit is a range in which the reaction temperature can be increased while removing heat from the equipment using the heat of polymerization reaction, and a more preferred upper limit is a range in which the heat of polymerization reaction can be removed from the equipment.

[0241] The aqueous medium is a reaction medium for polymerization and refers to a liquid containing water. The aqueous medium is not particularly limited as long as it contains water, and may contain water and, for example, a fluorine-free organic solvent such as an alcohol, ether, or ketone, and / or a fluorine-containing organic solvent having a boiling point of 40° C. or lower.

[0242] In the above step C, a known chain transfer agent, radical scavenger, or decomposer may be further added depending on the purpose to adjust the polymerization rate and molecular weight.

[0243] Examples of the chain transfer agent include esters such as dimethyl malonate, diethyl malonate, methyl acetate, ethyl acetate, butyl acetate, and dimethyl succinate, as well as isopentane, methane, ethane, propane, methanol, isopropanol, acetone, various mercaptans, various halogenated hydrocarbons such as carbon tetrachloride, and cyclohexane.

[0244] Bromine compounds or iodine compounds may be used as chain transfer agents. Polymerization methods using bromine compounds or iodine compounds include, for example, a method of polymerizing fluoromonomers in an aqueous medium in the presence of a bromine compound or an iodine compound in a substantially oxygen-free state (iodine transfer polymerization method). Representative examples of the bromine compounds or iodine compounds used include, for example, compounds represented by the general formula: R a I x Br y (wherein x and y are each an integer of 0 to 2 and satisfy 1≦x+y≦2; R ais a saturated or unsaturated fluorohydrocarbon group or chlorofluorohydrocarbon group having 1 to 16 carbon atoms, or a hydrocarbon group having 1 to 3 carbon atoms, which may contain an oxygen atom). By using a bromine compound or an iodine compound, iodine or bromine is introduced into the polymer and functions as a crosslinking point.

[0245] Examples of bromine compounds or iodine compounds include 1,3-diiodoperfluoropropane, 2-iodoperfluoropropane, 1,3-diiodo-2-chloroperfluoropropane, 1,4-diiodoperfluorobutane, 1,5-diiodo-2,4-dichloroperfluoropentane, 1,6-diiodoperfluorohexane, 1,8-diiodoperfluorooctane, 1,12-diiodoperfluorododecane, 1,16-diiodoperfluorohexadecane, diiodomethane, 1,2-diiodoethane, 1,3-diiodo-n-propane, CF2Br2, BrCF2CF2Br, CF3CFBrCF2Br, CFClBr2, BrCF2 Examples include CFClBr, CFBrClCFClBr, BrCFCFCFBr, BrCFCFBrOCF, 1-bromo-2-iodoperfluoroethane, 1-bromo-3-iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane, 2-bromo-3-iodoperfluorobutane, 3-bromo-4-iodoperfluorobutene-1, 2-bromo-4-iodoperfluorobutene-1, monoiodomonobromo-substituted benzene, diiodomonobromo-substituted benzene, and (2-iodoethyl) and (2-bromoethyl) substituted benzenes. These compounds may be used alone or in combination with each other.

[0246] Among these, it is preferable to use 1,4-diiodoperfluorobutane, 1,6-diiodoperfluorohexane, and 2-iodoperfluoropropane in terms of polymerization reactivity, crosslinking reactivity, availability, and the like.

[0247] The amount of the chain transfer agent used is usually 1 to 50,000 ppm by mass, and preferably 1 to 20,000 ppm by mass, based on the total amount of fluoromonomers supplied.

[0248] The chain transfer agent may be added all at once to the reaction vessel before the initiation of polymerization, may be added all at once after the initiation of polymerization, may be added in multiple divided portions during the polymerization, or may be added continuously during the polymerization.

[0249] The radical scavenger is a compound that does not have the ability to restart after addition or chain transfer to a free radical in the polymerization system. Specifically, a compound that easily undergoes a chain transfer reaction with a primary radical or a propagating radical to generate a stable radical that does not subsequently react with the monomer, or a compound that easily undergoes an addition reaction with a primary radical or a propagating radical to generate a stable radical, is used. Generally, the activity of what is called a chain transfer agent is characterized by the chain transfer constant and the reinitiation efficiency, but among chain transfer agents, those with a reinitiation efficiency of almost 0% are called radical scavengers. The radical scavenger can also be described as a compound whose chain transfer constant to the fluoromonomer at the polymerization temperature is greater than the polymerization rate constant and whose reinitiation efficiency is substantially zero percent. "Reinitiation efficiency is substantially zero percent" means that the generated radicals turn the radical scavenger into stable radicals. Preferably, the compound has a chain transfer constant (Cs) to the fluoromonomer at the polymerization temperature (= chain transfer rate constant (kc) / polymerization rate constant (kp)) of more than 0.1, and the above compound has a chain transfer constant (Cs) of more preferably 0.5 or more, even more preferably 1.0 or more, even more preferably 5.0 or more, and particularly preferably 10 or more.

[0250] The radical scavenger in the present disclosure is preferably at least one selected from the group consisting of, for example, aromatic hydroxy compounds, aromatic amines, N,N-diethylhydroxylamine, quinone compounds, terpenes, thiocyanates, and cupric chloride (CuCl). Examples of aromatic hydroxy compounds include unsubstituted phenol, polyhydric phenol, salicylic acid, m- or p-salicylic acid, gallic acid, and naphthol. Examples of the unsubstituted phenol include o-, m-, or p-nitrophenol, o-, m-, or p-aminophenol, p-nitrosophenol, etc. Examples of the polyhydric phenol include catechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, naphthresorcinol, etc. Examples of aromatic amines include o-, m-, or p-phenylenediamine, benzidine, and the like. Examples of the quinone compound include o-, m-, or p-benzoquinone, 1,4-naphthoquinone, and alizarin. Examples of thiocyanates include ammonium thiocyanate (NH4SCN), potassium thiocyanate (KSCN), and sodium thiocyanate (NaSCN). Of the above radical scavengers, aromatic hydroxy compounds are preferred, unsubstituted phenols or polyhydric phenols are more preferred, and hydroquinone is even more preferred.

[0251] The amount of radical scavenger added is preferably an amount equivalent to 3 to 500% (molar basis) of the polymerization initiator concentration, from the viewpoint of reducing the standard specific gravity. A more preferred lower limit is 5% (molar basis), even more preferably 8% (molar basis), even more preferably 10% (molar basis), even more preferably 13% (molar basis) or 15% (molar basis), especially preferably 20% (molar basis), particularly preferably 25% (molar basis), especially preferably 30% (molar basis), especially preferably 35% (molar basis). A more preferred upper limit is 400% (molar basis), even more preferably 300% (molar basis), even more preferably 200% (molar basis), especially preferably 100% (molar basis).

[0252] The polymerization initiator decomposer may be any compound capable of decomposing the polymerization initiator used, and is preferably at least one selected from the group consisting of sulfites, bisulfites, bromates, diimines, diimine salts, oxalic acid, oxalates, copper salts, and iron salts. Examples of sulfites include sodium sulfite and ammonium sulfite. Examples of copper salts include copper(II) sulfate, and examples of iron salts include iron(II) sulfate. The amount of the polymerization initiator decomposer added is in the range of 3 to 300% by mass, preferably 3 to 150% by mass, and more preferably 15 to 100% by mass, based on the amount of the oxidizing agent combined as the polymerization initiator (redox initiator). The amount of decomposer for the polymerization initiator added is preferably an amount corresponding to 3 to 500% (molar basis) of the polymerization initiator concentration, from the viewpoint of reducing the standard specific gravity. A more preferred lower limit is 5% (molar basis), even more preferably 8% (molar basis), even more preferably 10% (molar basis), even more preferably 13% (molar basis), and even more preferably 15% (molar basis). A more preferred upper limit is 400% (molar basis), even more preferably 300% (molar basis), even more preferably 200% (molar basis), and especially preferably 100% (molar basis).

[0253] During the polymerization of the fluoromonomer, it is preferable to add a radical scavenger or a decomposer of the polymerization initiator when the concentration of the fluoropolymer formed in the aqueous medium (concentration relative to the total of the aqueous medium and the fluoropolymer) is 5% by mass or more, more preferably 8% by mass or more, and even more preferably 10% by mass or more. It is also preferable to add it when the concentration of the fluoropolymer formed in the aqueous medium is 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less.

[0254] During the polymerization of the fluoromonomer, the radical scavenger or the decomposer of the polymerization initiator may be added continuously. During the polymerization of the fluoromonomer, the radical scavenger or the decomposer of the polymerization initiator may be added over time, not all at once, and continuously or in portions.

[0255] In the above step C, the polymerization initiator may be a persulfate (e.g., ammonium persulfate), or an organic peroxide such as disuccinic acid peroxide or diglutaric acid peroxide, which may be used alone or in the form of a mixture thereof. It may also be used in combination with a reducing agent such as sodium sulfite to form a redox system. Furthermore, during polymerization, a radical scavenger such as hydroquinone or catechol, or a peroxide decomposer such as ammonium sulfite, may be added to adjust the radical concentration in the system.

[0256] The step C may include a step of polymerizing the fluoromonomer in an aqueous medium in the presence of polymer (I) to produce an aqueous dispersion of fluoropolymer particles, and a step of seed-polymerizing the fluoromonomer to form fluoropolymer particles in the aqueous dispersion of fluoropolymer particles.

[0257] The above step C is preferably a step of polymerizing a fluoromonomer substantially in the absence of a fluorine-containing surfactant. Conventionally, a fluorine-containing surfactant has been used for polymerizing a fluoropolymer in an aqueous medium, but the first production method of the present disclosure makes it possible to obtain an aqueous fluoropolymer dispersion with reduced coloration even when the pre-treatment aqueous dispersion containing a fluoropolymer is obtained without using a fluorine-containing surfactant. As used herein, the phrase "substantially in the absence of a fluorinated surfactant" means that the fluorinated surfactant is present at 10 ppm by mass or less, preferably 1 ppm by mass or less, more preferably 100 ppb by mass or less, even more preferably 10 ppb by mass or less, and still more preferably 1 ppb by mass or less, relative to the aqueous medium.

[0258] Examples of the fluorine-containing surfactant include anionic fluorine-containing surfactants, etc. The anionic fluorine-containing surfactant may be, for example, a surfactant containing fluorine atoms and having a total carbon number of 20 or less excluding the anionic group.

[0259] The fluorine-containing surfactant may also be a surfactant containing fluorine in the anionic moiety having a molecular weight of 800 or less. The "anionic portion" refers to the portion of the fluorine-containing surfactant excluding the cation. For example, F(CF2) represented by the formula (I) below n1 In the case of COOM, "F(CF2) n1 The "COO" part.

[0260] The above-mentioned fluorine-containing surfactant also includes a fluorine-containing surfactant having a LogPOW of not more than 3.5. The LogPOW is a partition coefficient between 1-octanol and water, and is expressed as LogP (where P represents the ratio of the fluorine-containing surfactant concentration in octanol to the fluorine-containing surfactant concentration in water when a 1:1 octanol / water mixture containing the fluorine-containing surfactant undergoes phase separation). The LogPOW is calculated from the HPLC elution time of the sample solution using standard substances (heptanoic acid, octanoic acid, nonanoic acid, and decanoic acid) with known octanol / water partition coefficients under the following conditions: column: TOSOH ODS-120T column (φ4.6 mm×250 mm, manufactured by Tosoh Corporation), eluent: acetonitrile / 0.6% by mass HClO₄ / water=1 / 1 (vol / vol%), flow rate: 1.0 mL / min, sample amount: 300 μL, column temperature: 40°C, detection light: UV 210 nm. A calibration curve between each elution time and the known octanol / water partition coefficient is then prepared, and the LogPOW is calculated from the HPLC elution time of the sample solution based on this calibration curve.

[0261] Specific examples of the fluorine-containing surfactants include those described in U.S. Patent Application Publication Nos. 2007 / 0015864, 2007 / 0015865, 2007 / 0015866, 2007 / 0276103, 2007 / 0117914, 2007 / 142541, 2008 / 0015319, and U.S. Pat. No. 3,250,808. , U.S. Pat. No. 3,271,341, JP 2003-119204 A, WO 2005 / 042593, WO 2008 / 060461, WO 2007 / 046377, WO 2007 / 119526, WO 2007 / 046482, WO 2007 / 046345, U.S. Patent Application Publication No. 2014 / 0228531, WO 2013 / 189824, and WO 2013 / 189826.

[0262] The anionic fluorine-containing surfactant may be a compound represented by the following general formula (N 0 ): X n0 -Rf n0 -Y 0 (N 0 ) (In the formula, X n0 is H, Cl or F. n0is a linear, branched or cyclic alkylene group having 3 to 20 carbon atoms, in which some or all of the H's are substituted with F, and the alkylene group may contain one or more ether bonds, and some of the H's may be substituted with Cl. Y 0 is an anionic group. Y 0 The anionic group may be -COOM, -SO2M, or -SO3M, and may be -COOM or -SO3M. M is H, metal atom, NR 7 4. An optionally substituted imidazolium, an optionally substituted pyridinium, or an optionally substituted phosphonium, wherein R 7 is H or an organic group. The metal atom includes alkali metals (Group 1) and alkaline earth metals (Group 2), such as Na, K, or Li. R 7 As for H or C 1-10 may be an organic group of H or C 1-4 may be an organic group of H or C 1-4 The alkyl group may be: M is H, a metal atom, or NR 7 4, and may be H, an alkali metal (Group 1), an alkaline earth metal (Group 2), or NR 7 4, which may be H, Na, K, Li, or NH4. Above Rf n0 may be one in which 50% or more of H is substituted with fluorine.

[0263] The general formula (N 0 ) as a compound represented by The following general formula (N 1 ): X n0 -(CF2) m1 -Y 0 (N 1 ) (In the formula, X n0 is H, Cl, or F, m1 is an integer of 3 to 15, and Y 0is as defined above, a compound represented by the following general formula (N 2 ): Rf n1 -O-(CF(CF3)CF2O) m2 CFX n1 -Y 0 (N 2 ) (In the formula, Rf n1 is a perfluoroalkyl group having 1 to 5 carbon atoms, m2 is an integer of 0 to 3, and X n1 is F or CF3, and Y 0 is as defined above, a compound represented by the following general formula (N 3 ): Rf n2 (CH2) m3 -(Rf n3 ) q -Y 0 (N 3 ) (In the formula, Rf n2 is a partially or fully fluorinated alkyl group having 1 to 13 carbon atoms which may contain an ether bond, m3 is an integer of 1 to 3, and Rf n3 is a linear or branched perfluoroalkylene group having 1 to 3 carbon atoms, q is 0 or 1, and Y 0 is as defined above, a compound represented by the following general formula (N 4 ): Rf n4 -O-(CY n1 Y n2 ) p CF2-Y 0 (N 4 ) (In the formula, Rf n4 is a linear or branched partially or fully fluorinated alkyl group having 1 to 12 carbon atoms, which may contain an ether bond; Y n1 and Y n2 are the same or different and are H or F, p is 0 or 1, and Y 0 is as defined above.) and a compound represented by the general formula (N 5 ): [ka] (In the formula, X n2 , X n3 and X n4 Rf may be the same or different and are H, F, or a linear or branched partially or fully fluorinated alkyl group having 1 to 6 carbon atoms, which may contain an ether bond. n5 is a linear or branched partially or fully fluorinated alkylene group having 1 to 3 carbon atoms, which may contain an ether bond; L is a linking group; Y 0 is as defined above, where X n2 , X n3 , X n4 and Rf n5 The total number of carbon atoms is 18 or less.

[0264] The general formula (N 0 ) More specifically, the compounds represented by the formula (I) include perfluorocarboxylic acids (I) represented by the following general formula (I), ω-H perfluorocarboxylic acids (II) represented by the following general formula (II), perfluoropolyether carboxylic acids (III) represented by the following general formula (III), perfluoroalkyl alkylene carboxylic acids (IV) represented by the following general formula (IV), perfluoroalkoxy fluorocarboxylic acids (V) represented by the following general formula (V), perfluoroalkyl sulfonic acids (VI) represented by the following general formula (VII), ω-H perfluoro sulfonic acids (VII) represented by the following general formula (VII), perfluoroalkyl alkylene sulfonic acids (VIII) represented by the following general formula (VIII), alkyl alkylene carboxylic acids (IX) represented by the following general formula (IX), fluorocarboxylic acids (X) represented by the following general formula (X), alkoxy fluoro sulfonic acids (XI) represented by the following general formula (XI), compounds (XII) represented by the following general formula (XII), and compounds (XIII) represented by the following general formula (XIII).

[0265] The perfluorocarboxylic acid (I) is represented by the following general formula (I): F(CF2) n1 COOM (I) (wherein n1 is an integer of 3 to 14, and M is H, a metal atom, or NR 7 4. An optionally substituted imidazolium, an optionally substituted pyridinium, or an optionally substituted phosphonium, wherein R 7 is H or an organic group.

[0266] The ω-H perfluorocarboxylic acid (II) is represented by the following general formula (II): H(CF2) n2 COOM (II) (wherein n2 is an integer of 4 to 15, and M is as defined above).

[0267] The perfluoropolyether carboxylic acid (III) is represented by the following general formula (III): Rf 1 -O-(CF(CF3)CF2O) n3 CF(CF3)COOM (III) (In the formula, Rf 1 is a perfluoroalkyl group having 1 to 5 carbon atoms, n3 is an integer of 0 to 3, and M is as defined above.

[0268] The perfluoroalkyl alkylene carboxylic acid (IV) is represented by the following general formula (IV): Rf 2 (CH2) n4 Rf 3 COOM (IV) (In the formula, Rf 2 is a perfluoroalkyl group having 1 to 5 carbon atoms, and Rf 3 is a linear or branched perfluoroalkylene group having 1 to 3 carbon atoms, n4 is an integer of 1 to 3, and M is as defined above.

[0269] The alkoxyfluorocarboxylic acid (V) is represented by the following general formula (V): Rf 4 -O-CY 1 Y 2 CF2-COOM (V) (In the formula, Rf 4 is a linear or branched partially or fully fluorinated alkyl group having 1 to 12 carbon atoms, which may contain an ether bond; Y 1 and Y 2 are the same or different and are H or F, and M is as defined above.

[0270] The perfluoroalkylsulfonic acid (VI) is represented by the following general formula (VI): F(CF2) n5 SO3M (VI) (wherein n5 is an integer of 3 to 14, and M is as defined above).

[0271] The ω-H perfluorosulfonic acid (VII) is represented by the following general formula (VII): H(CF2) n6 SO3M (VII) (wherein n6 is an integer of 4 to 14, and M is as defined above).

[0272] The perfluoroalkyl alkylene sulfonic acid (VIII) is represented by the following general formula (VIII): Rf 5 (CH2) n7 SO3M (VIII) (In the formula, Rf 5 is a perfluoroalkyl group having 1 to 13 carbon atoms, n7 is an integer of 1 to 3, and M is as defined above.

[0273] The alkyl alkylene carboxylic acid (IX) is represented by the following general formula (IX): Rf 6 (CH2) n8 COOM (IX) (In the formula, Rf 6 is a linear or branched partially or fully fluorinated alkyl group having 1 to 13 carbon atoms which may contain an ether bond, n8 is an integer from 1 to 3, and M is as defined above.

[0274] The fluorocarboxylic acid (X) is represented by the following general formula (X): Rf 7 -O-Rf 8 -O-CF2-COOM (X) (In the formula, Rf 7 is a linear or branched partially or fully fluorinated alkyl group having 1 to 6 carbon atoms, which may contain an ether bond; Rf 8 is a linear or branched, partially or fully fluorinated alkyl group having 1 to 6 carbon atoms, and M is as defined above.

[0275] The alkoxyfluorosulfonic acid (XI) is represented by the following general formula (XI): Rf 9 -O-CY 1 Y 2 CF2-SO3M (XI) (In the formula, Rf 9 is a linear or branched alkyl group having 1 to 12 carbon atoms, which may contain an ether bond, and which may contain chlorine, and which is partially or completely fluorinated; Y 1 and Y 2 are the same or different and are H or F, and M is as defined above.

[0276] The compound (XII) is represented by the following general formula (XII): [ka] (In the formula, X 1 , X 2 and X 3 may be the same or different and are H, F and linear or branched partially or fully fluorinated alkyl groups having 1 to 6 carbon atoms which may contain ether bonds; Rf 10 is a perfluoroalkylene group having 1 to 3 carbon atoms, L is a linking group, and Y 0 is an anionic group. Y 0may be -COOM, -SO2M, or -SO3M, and may be -SO3M or COOM (wherein M is as defined above). Examples of L include a single bond and a partially or fully fluorinated alkylene group having 1 to 10 carbon atoms which may contain an ether bond.

[0277] The compound (XIII) is represented by the following general formula (XIII): Rf 11 -O-(CF2CF(CF3)O) n9 (CF2O) n10 CF2COOM (XIII) (In the formula, Rf 11 is a fluoroalkyl group containing chlorine and having 1 to 5 carbon atoms, n9 is an integer of 0 to 3, n10 is an integer of 0 to 3, and M is as defined above. Compound (XIII) is represented by the formula: CF2ClO(CF2CF(CF3)O) n9 (CF2O) n10 CF2COONH4 (a mixture having an average molecular weight of 750, wherein n9 and n10 are defined above).

[0278] As mentioned above, examples of the anionic fluorine-containing surfactant include carboxylic acid surfactants and sulfonic acid surfactants.

[0279] The polymerization can produce a pre-treatment aqueous dispersion containing the fluoropolymer. The fluoropolymer is usually present at a concentration of 8 to 50 mass% in the aqueous dispersion obtained by the polymerization. In the aqueous dispersion, the lower limit of the fluoropolymer concentration is preferably 10 mass%, more preferably 15 mass%, and the upper limit is preferably 40 mass%, more preferably 35 mass%.

[0280] The first production method of the present disclosure preferably includes, before step A, step B of adding a hydrocarbon-based surfactant to the pre-treatment aqueous dispersion. An aqueous dispersion containing a fluoropolymer obtained by polymerization in the presence of polymer (I) typically contains the polymer (I) used in the polymerization. However, ultrafiltration, microfiltration, or dialysis membrane treatment reduces the amount of polymer (I) used in the polymerization, which may result in a decrease in the stability of the aqueous dispersion. Therefore, adding a hydrocarbon-based surfactant before step A improves the stability of the aqueous dispersion during ultrafiltration, microfiltration, or dialysis membrane treatment, thereby efficiently reducing the amount of colored components and the amount of hydrogen fluoride generated. Furthermore, the stability of the aqueous dispersion obtained through step A can be improved. The above step B may be carried out by, for example, adding water containing a hydrocarbon surfactant. When the first manufacturing method of the present disclosure includes the above-described step C, step B is performed after step C and before step A.

[0281] The hydrocarbon surfactant added in the step B is not limited, and the above-mentioned hydrocarbon surfactants can be used, but nonionic surfactants are preferred. As the nonionic surfactant, any of those listed as the nucleating agent in the step C can be used.

[0282] The nonionic surfactant is not limited, but is preferably at least one selected from the group consisting of the compounds represented by the above-mentioned general formula (i) and the compounds represented by the general formula (ii).

[0283] Examples of the fluoropolymer include a TFE polymer (PTFE) in which the monomer having the largest molar fraction in the polymer (hereinafter referred to as the "most abundant monomer") is TFE, a VDF polymer in which the most abundant monomer is VDF, and a CTFE polymer in which the most abundant monomer is CTFE. Examples of the fluoropolymer include (I) non-melt-processable fluororesin such as tetrafluoroethylene polymer [TFE polymer (PTFE)], (II) melt-processable fluororesin such as ethylene / TFE copolymer [ETFE], TFE / HFP copolymer [FEP], TFE / perfluoro(alkyl vinyl ether) copolymer [PFA, MFA, etc.], TFE / perfluoroallyl ether copolymer, TFE / VDF copolymer, and electrolyte polymer precursor, and (III) fluororubber such as TFE / propylene copolymer, TFE / propylene / third monomer copolymer (the third monomer is VDF, HFP, CTFE, fluoroalkyl vinyl ethers, etc.), copolymers of TFE and fluoroalkyl vinyl ethers; HFP / ethylene copolymer, HFP / ethylene / TFE copolymer; PVDF; thermoplastic elastomers such as VDF / HFP copolymer, HFP / ethylene copolymer, and VDF / TFE / HFP copolymer; and fluorine-containing segmented polymers described in Japanese Patent Publication No. 61-49327.

[0284] The fluoropolymers preferably have an ion exchange ratio (IXR) greater than 53. Preferred fluoropolymers have no ionic groups or a limited number of ionic groups resulting in an ion exchange ratio greater than about 100. Preferred fluoropolymers preferably have an ion exchange ratio of 1000 or greater, more preferably 2000 or greater, and even more preferably 5000 or greater.

[0285] The TFE polymer may suitably be a TFE homopolymer or a copolymer comprising (1) TFE, (2) one or more fluorine-containing monomers other than TFE having 2 to 8 carbon atoms, particularly VDF, HFP, or CTFE, and (3) other monomers. Examples of the (3) other monomers include fluoro(alkyl vinyl ethers) having an alkyl group having 1 to 5 carbon atoms, particularly 1 to 3 carbon atoms; fluorodioxole; perfluoroalkylethylene; and ω-hydroperfluoroolefin.

[0286] The TFE polymer may also be a copolymer of TFE and one or more fluorine-free monomers. Examples of the fluorine-free monomers include alkenes such as ethylene and propylene; vinyl esters; and vinyl ethers. The TFE polymer may also be a copolymer of TFE and one or more fluorine-containing monomers having 2 to 8 carbon atoms and one or more fluorine-free monomers.

[0287] The VDF polymer may suitably be a VDF homopolymer [PVDF] or a copolymer of (1) VDF, (2) one or more fluoroolefins other than VDF having 2 to 8 carbon atoms, particularly TFE, HFP, or CTFE, and (3) a perfluoro(alkyl vinyl ether) having an alkyl group having 1 to 5 carbon atoms, particularly 1 to 3 carbon atoms.

[0288] The CTFE polymer may suitably be a CTFE homopolymer or a copolymer consisting of (1) CTFE, (2) one or more fluoroolefins other than CTFE having 2 to 8 carbon atoms, particularly TFE or HFP, and (3) a perfluoro(alkyl vinyl ether) having an alkyl group having 1 to 5 carbon atoms, particularly 1 to 3 carbon atoms.

[0289] The CTFE polymer may also be a copolymer of CTFE and one or more non-fluorine-containing monomers, and the non-fluorine-containing monomers include alkenes such as ethylene and propylene; vinyl esters; and vinyl ethers.

[0290] The fluoropolymers may be glassy, ​​plastic or elastomeric. They may be amorphous or partially crystalline and may be subject to compression sintering, melt processing or non-melt processing.

[0291] In step C, for example, (I) as a non-melt-processable fluororesin, tetrafluoroethylene polymer [TFE polymer (PTFE)] is used; (II) as a melt-processable fluororesin, ethylene / TFE copolymer [ETFE], TFE / HFP copolymer [FEP], TFE / perfluoro(alkyl vinyl ether) copolymer [PFA, MFA, etc.], TFE / perfluoroallyl ether copolymer, TFE / VDF copolymer, electrolyte polymer precursor is used; (III) as a fluororubber, TFE / propylene copolymer, TFE / propylene / tertiary fluororubber is used; A pre-treatment aqueous dispersion can be suitably produced that contains a monomer copolymer (wherein the third monomer is VDF, HFP, CTFE, a fluoroalkyl vinyl ether, or the like), a copolymer consisting of TFE and a fluoroalkyl vinyl ether; a thermoplastic elastomer such as an HFP / ethylene copolymer, an HFP / ethylene / TFE copolymer; PVDF; a VDF / HFP copolymer, an HFP / ethylene copolymer, or a VDF / TFE / HFP copolymer; and a fluoropolymer such as the fluorine-containing segmented polymer described in Japanese Patent Publication No. 61-49327.

[0292] The fluoropolymer is preferably a fluororesin, and particularly, a fluororesin having a fluorine substitution rate of 50% or more as calculated by the following formula is more preferred, a fluororesin having a fluorine substitution rate of more than 50% is even more preferred, a fluororesin having a fluorine substitution rate of 55% or more is even more preferred, a fluororesin having a fluorine substitution rate of 60% or more is even more preferred, a fluororesin having a fluorine substitution rate of 75% or more is even more preferred, a fluororesin having a fluorine substitution rate of 80% or more is particularly preferred, and a fluororesin having a fluorine substitution rate of 90 to 100%, i.e., a perfluororesin, is most preferred. (formula) Fluorine substitution rate (%) = (number of fluorine atoms bonded to carbon atoms constituting the fluoropolymer) / ((number of hydrogen atoms bonded to carbon atoms constituting the fluoropolymer) + (number of fluorine atoms and chlorine atoms bonded to carbon atoms constituting the fluoropolymer)) × 100

[0293] The perfluororesin is more preferably a fluororesin having a fluorine substitution rate of 95 to 100%, further preferably PTFE, FEP or PFA, and particularly preferably PTFE.

[0294] The fluoropolymer may have a core-shell structure. Examples of the fluoropolymer having a core-shell structure include PTFE particles containing a core of high molecular weight PTFE and a shell of lower molecular weight PTFE or modified PTFE. Examples of such PTFE include the PTFE described in JP-A-2005-527652.

[0295] The core-shell structure may have, for example, the following structure. Core: TFE homopolymer Shell: TFE homopolymer Core: Modified PTFE Shell: TFE homopolymer Core: Modified PTFE Shell: Modified PTFE Core: TFE homopolymer Shell: Modified PTFE Core: Low molecular weight PTFE Shell: High molecular weight PTFE Core: High molecular weight PTFE Shell: Low molecular weight PTFE

[0296] In the fluoropolymer having the core-shell structure, the lower limit of the core ratio is preferably 0.5 mass%, more preferably 1.0 mass%, even more preferably 3.0 mass%, particularly preferably 5.0 mass%, and most preferably 10.0 mass%. The upper limit of the core ratio is preferably 99.5 mass%, more preferably 99.0 mass%, even more preferably 98.0 mass%, even more preferably 97.0 mass%, particularly preferably 95.0 mass%, and most preferably 90.0 mass%.

[0297] In the fluoropolymer having the core-shell structure, the lower limit of the shell ratio is preferably 0.5% by mass, more preferably 1.0% by mass, even more preferably 3.0% by mass, particularly preferably 5.0% by mass, and most preferably 10.0% by mass. The upper limit of the shell ratio is preferably 99.5% by mass, more preferably 99.0% by mass, even more preferably 98.0% by mass, even more preferably 97.0% by mass, particularly preferably 95.0% by mass, and most preferably 90.0% by mass.

[0298] In the fluoropolymer having the core-shell structure, the core or the shell may be configured to have two or more layers. For example, the fluoropolymer may have a three-layer structure having a core center portion of modified PTFE, a core outer layer portion of TFE homopolymer, and a shell of modified PTFE.

[0299] The fluoropolymer having the core-shell structure also includes a particle of the fluoropolymer having multiple cores.

[0300] The above-mentioned (I) non-melt-processible fluororesin, (II) melt-processible fluororesin and (III) fluororubber are preferably produced in the following manner.

[0301] (I) Non-melt-processable fluororesin In step C, the polymerization of TFE is usually carried out at a polymerization temperature of 10 to 150°C and a polymerization pressure of 0.05 to 5 MPaG. For example, the polymerization temperature is more preferably 30°C or higher, and even more preferably 50°C or higher. It is more preferably 120°C or lower, and even more preferably 100°C or lower. The polymerization pressure is more preferably 0.3 MPaG or higher, and even more preferably 0.5 MPaG or higher, and more preferably 5.0 MPaG or lower, and even more preferably 3.0 MPaG or lower. In particular, from the viewpoint of improving the yield of the fluoropolymer, it is preferably 1.0 MPaG or higher, more preferably 1.2 MPaG or higher, more preferably 1.5 MPaG or higher, and even more preferably 2.0 MPaG or higher.

[0302] In one embodiment, the polymerization is carried out by charging pure water into a pressure-resistant reaction vessel equipped with a stirrer, deoxidizing, then charging TFE, adjusting the temperature to a predetermined level, and adding a polymerization initiator to initiate the reaction. If the pressure decreases as the reaction proceeds, additional TFE is continuously or intermittently supplied to maintain the initial pressure. Once a predetermined amount of TFE has been supplied, the supply is stopped, the TFE in the reaction vessel is purged, and the temperature is returned to room temperature to terminate the reaction. Additional TFE may be continuously or intermittently supplied to prevent a decrease in pressure.

[0303] When the TFE polymer is polytetrafluoroethylene (PTFE), various conventionally known modified monomers can be used in combination with TFE. In this specification, the term "PTFE" refers not only to a TFE homopolymer but also to a copolymer of TFE and a modified monomer that is non-melt-processable (hereinafter referred to as "modified PTFE"). The total amount of the modifying monomers is preferably in the range of 0.00001 to 1.0% by mass relative to all polymerized units of PTFE. The lower limit of the total amount is more preferably 0.0001% by mass, even more preferably 0.001% by mass, and even more preferably 0.005% by mass. The upper limit is, in order of preference, 0.90%, 0.50%, 0.40%, 0.30%, 0.20%, 0.15%, 0.10%, and 0.05% by mass. In this specification, the modified monomer unit means a part of the molecular structure of the TFE polymer that is derived from the modified monomer.

[0304] The modifying monomer is not particularly limited as long as it is copolymerizable with TFE, and examples thereof include fluoromonomers and non-fluoromonomers. The modifying monomer used may be one type or multiple types.

[0305] The non-fluoromonomer is not particularly limited and may be selected from the group consisting of monomers having the general formula: CH2=CR Q1 -LR Q2 (In the formula, R Q1represents a hydrogen atom or an alkyl group. L represents a single bond, -CO-O-*, -O-CO-* or -O-. * represents R Q2 R represents the bond position with Q2 represents a hydrogen atom, an alkyl group or a nitrile group.

[0306] Examples of non-fluoromonomers include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, vinyl methacrylate, vinyl acetate, acrylic acid, methacrylic acid, acrylonitrile, methacrylonitrile, ethyl vinyl ether, cyclohexyl vinyl ether, etc. Of these, butyl methacrylate, vinyl acetate, and acrylic acid are preferred as non-fluoromonomers.

[0307] Examples of fluoromonomers include perfluoroolefins such as hexafluoropropylene (HFP); hydrogen-containing fluoroolefins such as trifluoroethylene and vinylidene fluoride (VDF); perhaloolefins such as chlorotrifluoroethylene; perfluorovinyl ethers; (perfluoroalkyl)ethylenes; and perfluoroallyl ethers. Examples of the modifying monomer include perhaloolefins such as HFP, CTFE, and perfluorovinyl ether; fluoro(alkyl vinyl ethers) having an alkyl group having 1 to 5 carbon atoms, particularly 1 to 3 carbon atoms; cyclic fluorinated monomers such as fluorodioxole; perhaloalkylethylenes such as (perfluoroalkyl)ethylene; ω-hydroperhaloolefins, etc. The modifying monomer can be initially added all at once or added in continuous or intermittent divided portions depending on the purpose and the amount of TFE supplied.

[0308] The perfluorovinyl ether is not particularly limited, and examples thereof include perfluorovinyl ethers represented by the general formula (A): CF2=CF-ORf (A) (wherein Rf represents a perfluoroorganic group). In this specification, the term "perfluoroorganic group" refers to an organic group in which all hydrogen atoms bonded to carbon atoms are substituted with fluorine atoms. The perfluoroorganic group may have an ether oxygen.

[0309] An example of the perfluorovinyl ether is perfluoro(alkyl vinyl ether) [PAVE], where Rf in the general formula (A) is a perfluoroalkyl group having 1 to 10 carbon atoms. The number of carbon atoms in the perfluoroalkyl group is preferably 1 to 5.

[0310] Examples of the perfluoroalkyl group in the PAVE include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, and a perfluorohexyl group.

[0311] The perfluorovinyl ether further includes those in which Rf in the general formula (A) is a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms, and those in which Rf ... formula:

[0312] [ka]

[0313] (wherein m represents 0 or an integer of 1 to 4), and Rf is a group represented by the following formula:

[0314] [ka]

[0315] (wherein n represents an integer of 1 to 4).

[0316] Examples of hydrogen-containing fluoroolefins include CH2=CF2, CFH=CH2, CFH=CF2, CF2=CFCF3, CH2=CFCF3, CH2=CHCF3, CHF=CHCF3 (E-isomer), and CHF=CHCF3 (Z-isomer).

[0317] The (perfluoroalkyl)ethylene (PFAE) is not particularly limited, and examples thereof include (perfluorobutyl)ethylene (PFBE) and (perfluorohexyl)ethylene.

[0318] Examples of perfluoroallyl ethers include: General formula: CF2=CF-CF2-ORf (wherein Rf represents a perfluoro organic group).

[0319] Rf in the above general formula is the same as Rf in general formula (A). Rf is preferably a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluoroalkoxyalkyl group having 1 to 10 carbon atoms. The perfluoroallyl ether is preferably at least one selected from the group consisting of CF2=CF-CF2-O-CF3, CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7, and CF2=CF-CF2-O-C4F9, more preferably at least one selected from the group consisting of CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7, and CF2=CF-CF2-O-C4F9, and even more preferably CF2=CF-CF2-O-CF2CF2CF3.

[0320] When producing an aqueous fluoropolymer dispersion containing polytetrafluoroethylene (PTFE), in step C, at the start of TFE polymerization, (polyfluoroalkyl)ethylene and / or a comonomer (3) having a monomer reactivity ratio rTFE in copolymerization with TFE of 0.1 to 8 can be added to the polymerization system in an amount of 0.001 to 0.01 mass% based on the final amount of PTFE produced. This increases the stability of the aqueous PTFE dispersion obtained in step C to a level that does not impair subsequent processability, moldability, etc. Then, by using the aqueous PTFE dispersion obtained in this way as a pre-treatment aqueous dispersion, an aqueous PTFE dispersion (aqueous fluoropolymer dispersion) that can give molded articles with high heat resistance can be produced.

[0321] Here, the monomer reactivity ratio in copolymerization with TFE is the value obtained by dividing the rate constant of the reaction of the propagating radical with TFE when the propagating radical is less than a repeating unit based on TFE by the rate constant of the reaction of the propagating radical with a comonomer. The lower this value, the higher the reactivity of the comonomer with TFE. The reactivity ratio can be calculated from the composition of the polymer produced immediately after the initiation of copolymerization of the comonomer with TFE using various feed compositions, and the Feynman-Ross equation.

[0322] The copolymerization is carried out, for example, in a 6.0 L stainless steel autoclave using 3600 g of deionized and degassed water, 1000 ppm by mass of ammonium perfluorooctanoate relative to the water, and 100 g of paraffin wax at a pressure of 0.78 MPaG and a temperature of 70°C. 0.05 g, 0.1 g, 0.2 g, 0.5 g, and 1.0 g of comonomer are added to the reactor, respectively, and 0.072 g of ammonium persulfate (20 ppm by mass relative to the water) is added. TFE is continuously fed to maintain the polymerization pressure at 0.78 MPaG. When the TFE charge reaches 1000 g, stirring is stopped and the reactor is depressurized until atmospheric pressure is reached. After cooling, the paraffin wax is separated and removed to obtain an aqueous dispersion containing the resulting polymer. The aqueous dispersion is stirred to coagulate the resulting polymer, which is then dried at 150°C. The composition of the resulting polymer is calculated by appropriately combining NMR, FT-IR, elemental analysis, and X-ray fluorescence analysis depending on the type of monomer.

[0323] A preferred example of the modifying monomer is a comonomer (3) having a monomer reactivity ratio of 0.1 to 8. The presence of the comonomer (3) makes it possible to obtain PTFE particles having a small particle size and an aqueous dispersion with high dispersion stability.

[0324] The comonomer (3) having a monomer reactivity ratio of 0.1 to 8 is preferably at least one selected from the group consisting of comonomers represented by formulas (3a) to (3d). CH2=CH-Rf 1 (3a) (In the formula, Rf 1 is a perfluoroalkyl group having 1 to 10 carbon atoms. CF2=CF-O-Rf 2 (3b) (In the formula, Rf 2 is a perfluoroalkyl group having 1 to 2 carbon atoms. CF2=CF-O-(CF2) n CF=CF2(3c) (wherein n is 1 or 2).

[0325] [ka] (In the formula, X 3 and X 4 is F, Cl or a methoxy group, and Y is of formula Y1 or Y2.

[0326] [ka] (In formula Y2, Z and Z′ are F or a fluorinated alkyl group having 1 to 3 carbon atoms.)

[0327] The content of the comonomer (3) is preferably in the range of 0.00001 to 1.0% by mass relative to the total polymerized units of PTFE. The lower limit is more preferably 0.0001% by mass, even more preferably 0.0005% by mass, even more preferably 0.001% by mass, and especially preferably 0.005% by mass. The upper limit is, in order of preference, 0.90%, 0.50%, 0.40%, 0.30%, 0.20%, 0.15%, 0.10%, 0.08%, 0.05%, and 0.01% by mass.

[0328] The modifying monomer is preferably at least one selected from the group consisting of hexafluoropropylene, chlorotrifluoroethylene, vinylidene fluoride, perfluoro(alkyl vinyl ether), (perfluoroalkyl)ethylene, ethylene, and a modifying monomer having a functional group capable of reacting by radical polymerization and a hydrophilic group, because it can produce an aqueous dispersion with a small average primary particle size, a small aspect ratio of the primary particles, and excellent dispersion stability. By using the modifying monomer, an aqueous PTFE dispersion with a smaller average primary particle size, a small aspect ratio of the primary particles, and excellent dispersion stability can be obtained. By using the aqueous PTFE dispersion obtained in this way as a pre-treatment aqueous dispersion, an aqueous fluoropolymer dispersion with a small average primary particle size, a small aspect ratio of the primary particles, excellent dispersion stability, and little uncoagulated polymer can be produced.

[0329] From the viewpoint of reactivity with TFE, the modifying monomer preferably contains at least one selected from the group consisting of hexafluoropropylene, perfluoro(alkyl vinyl ether), and (perfluoroalkyl)ethylene. The total amount of the hexafluoropropylene units, perfluoro(alkyl vinyl ether) units, and (perfluoroalkyl)ethylene units is preferably in the range of 0.00001 to 1.0% by mass relative to all polymerized units of PTFE. The lower limit of the total amount is more preferably 0.0001% by mass, even more preferably 0.0005% by mass, even more preferably 0.001% by mass, especially preferably 0.005% by mass, and particularly preferably 0.009% by mass. The upper limit is, in order of preference, 0.9%, 0.50%, 0.40%, 0.30%, 0.20%, 0.15%, 0.10%, 0.08%, 0.05%, and 0.01% by mass.

[0330] The above-mentioned modified monomer preferably includes a modified monomer having a functional group capable of reacting by radical polymerization and a hydrophilic group (hereinafter referred to as "modified monomer (A)").

[0331] The presence of the modifying monomer (A) makes it possible to obtain PTFE particles with a small primary particle size, to obtain an aqueous dispersion with high dispersion stability, and to reduce the aspect ratio of the primary particles. That is, by using the modifying monomer (A) in step C, the dispersion stability of the finally obtained aqueous fluoropolymer dispersion becomes high. Furthermore, the PTFE contained in the aqueous fluoropolymer dispersion can be made to have a small primary particle size and a small aspect ratio of the primary particles.

[0332] The amount of the modified monomer (A) used is preferably more than an amount corresponding to 0.1 ppm by mass of the aqueous medium, more preferably more than 0.5 ppm by mass, even more preferably more than 1.0 ppm by mass, even more preferably 5 ppm by mass or more, and particularly preferably 10 ppm by mass or more. If the amount of the modified monomer (A) used is too small, the average primary particle size of the obtained PTFE may not be reduced. The amount of the modified monomer (A) used may be within the above range, but the upper limit can be, for example, 5000 ppm by mass. In the above production method, the modified monomer (A) may be added to the system during the reaction to improve the stability of the aqueous dispersion during or after the reaction.

[0333] The above-mentioned modified monomer (A) is highly water-soluble, so even if unreacted modified monomer (A) remains in the aqueous dispersion, it can be easily removed in the concentration step or the coagulation and washing step.

[0334] The above-mentioned modifying monomer (A) is incorporated into the produced polymer during the polymerization process, but since the concentration of the modifying monomer (A) itself in the polymerization system is low and the amount incorporated into the polymer is small, there are no problems such as a decrease in the heat resistance of PTFE or coloration after baking.

[0335] Examples of the hydrophilic group in the modified monomer (A) include -NH, -PO, -P(O)(OM), -OPO, -OP(O)(OM), -SO, -OSO, and -COOM (in each formula, M represents H, a metal atom, or NR 7y 4. An imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent, R 7y are H or organic groups and may be the same or different. Any two of them may be bonded to each other to form a ring.) Of these, -SO3M or -COOM is preferred as the hydrophilic group. R 7y The organic group in R is preferably an alkyl group. 7yAs for H or C 1-10 is preferably an organic group represented by the formula: 1-4 The organic group is more preferably H or C 1-4 More preferred are alkyl groups of the formula: The metal atom may be a monovalent or divalent metal atom, such as an alkali metal (Group 1) or an alkaline earth metal (Group 2), with Na, K, or Li being preferred.

[0336] Examples of the "functional group capable of reacting by radical polymerization" in the modifying monomer (A) include groups having an ethylenically unsaturated bond, such as a vinyl group and an allyl group. The group having an ethylenically unsaturated bond is a group represented by the following formula: CX e X g =CX f R- (In the formula, X e , X f and X g are each independently F, Cl, H, CF3, CF2H, CFH2, or CH3; and R is a linking group. The linking group for R can be represented by the formula: a Examples of linking groups include: Preferably -CH=CH2, -CF=CH 2、 -CH=CF 2、 Examples include groups having an unsaturated bond such as -CF=CF2, -CH2-CH=CH2, -CF2-CF=CH2, -CF2-CF=CF2, -(C=O)-CH=CH2, -(C=O)-CF=CH2, -(C=O)-CH=CF2, -(C=O)-CF=CF2, -(C=O)-C(CH3)=CH2, -(C=O)-C(CF3)=CH2, -(C=O)-C(CH3)=CF2, -(C=O)-C(CF3)=CF2, -O-CH2-CH=CH2, -O-CF2-CF=CH2, -O-CH2-CH=CF2, and -O-CF2-CF=CF2.

[0337] The modified monomer (A) has a functional group capable of reacting by radical polymerization, and therefore, when used in the polymerization, it is presumed that it reacts with the fluorine-containing monomer at the initial stage of the polymerization reaction, forming highly stable particles having hydrophilic groups derived from the modified monomer (A). Therefore, it is considered that the number of particles increases when polymerization is carried out in the presence of the modified monomer (A).

[0338] The polymerization may be carried out in the presence of one type of the modifying monomer (A), or in the presence of two or more types of the modifying monomer (A).

[0339] In the polymerization, a compound having an unsaturated bond can be used as the modifying monomer (A). The modifying monomer (A) is preferably at least one selected from the group consisting of compounds represented by general formula (4). CX i X k =CX j R a -(CZ 1 Z 2 ) k -Y 3 (4) (In the formula, X i , X j and X k are each independently F, Cl, H, or CF; Y 3 is a hydrophilic group; R a is a linking group; Z 1 and Z 2 are each independently H, F, or CF3, and k is 0 or 1. Examples of the hydrophilic group include -NH, -PO, -P(O)(OM), -OPO, -OP(O)(OM), -SO, -OSO, and -COOM (in each formula, M represents H, a metal atom, or NR 7y 4. An imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent, R 7yare H or organic groups and may be the same or different. Any two of them may be bonded to each other to form a ring. ) are examples of the hydrophilic group. Of these, -SO3M or -COOM is preferred. R 7y As for H or C 1-10 is preferably an organic group represented by the formula: 1-4 The organic group is more preferably H or C 1-4 More preferred are alkyl groups of the formula: The metal atom may be a monovalent or divalent metal atom, such as an alkali metal (Group 1) or an alkaline earth metal (Group 2), with Na, K, or Li being preferred. By using the modifying monomer (A), an aqueous dispersion having a smaller average primary particle size and better stability can be obtained, and the aspect ratio of the primary particles can also be made smaller.

[0340] Above R a is a divalent linking group. a ) may be a single bond and preferably contains at least one carbon atom, and the number of carbon atoms may be 2 or more, 4 or more, 8 or more, 10 or more, or 20 or more. There is no upper limit, but it may be, for example, 100 or less, or 50 or less. The linking group (R a The linking group (R) may be linear or branched, cyclic or acyclic in structure, saturated or unsaturated, substituted or unsubstituted, and may optionally contain one or more heteroatoms selected from the group consisting of sulfur, oxygen, and nitrogen, and may optionally contain one or more functional groups selected from the group consisting of ester, amide, sulfonamide, carbonyl, carbonate, urethane, urea, and carbamate. a ) does not contain carbon atoms and may be a catenary heteroatom such as oxygen, sulfur or nitrogen.

[0341] Above R a is preferably a catenary heteroatom such as oxygen, sulfur, or nitrogen, or a divalent organic group. R aWhen R is a divalent organic group, the hydrogen atom bonded to the carbon atom may be replaced with a halogen other than fluorine, such as chlorine, and may or may not contain a double bond. a may be either linear or branched, and may be either cyclic or acyclic. a may contain functional groups (e.g., esters, ethers, ketones, amines, halides, etc.). R a may also be a non-fluorinated divalent organic group, or a partially fluorinated or perfluorinated divalent organic group. R a Examples of the hydrocarbon group include a hydrocarbon group in which no fluorine atoms are bonded to a carbon atom, a hydrocarbon group in which some of the hydrogen atoms bonded to a carbon atom are substituted with fluorine atoms, a hydrocarbon group in which all of the hydrogen atoms bonded to a carbon atom are substituted with fluorine atoms, -(C=O)-, -(C=O)-O-, or a hydrocarbon group containing -(C=O)-, which may contain an oxygen atom, a double bond, or a functional group.

[0342] R a is preferably -(C=O)-, -(C=O)-O-, or a hydrocarbon group having 1 to 100 carbon atoms which may contain an ether bond or may contain -(C=O)-, and in the hydrocarbon group, some or all of the hydrogen atoms bonded to the carbon atoms may be substituted with fluorine. R a Preferably, -(CH2) a -, -(CF2) a -, -O-(CF2) a -, -(CF2) a -O-(CF2) b -, -O(CF2) a -O-(CF2) b -, -(CF2) a -[O-(CF2) b ] c -, -O(CF2) a -[O-(CF2) b ] c -, -[(CF2) a -O] b-[(CF2) c -O] d -, -O[(CF2) a -O] b -[(CF2) c -O] d -, -O-[CF2CF(CF3)O] a -(CF2) b -, -(C=O)-, -(C=O)-O-, -(C=O)-(CH2) a -, -(C=O)-(CF2) a -, -(C=O)-O-(CH2) a -, -(C=O)-O-(CF2) a -, -(C=O)-[(CH2) a -O] b -, -(C=O)-[(CF2) a -O] b -, -(C=O)-O[(CH2) a -O] b -, -(C=O)-O[(CF2) a -O] b -, -(C=O)-O[(CH2) a -O] b -(CH2) c -, -(C=O)-O[(CF2) a -O] b -(CF2) c -, -(C=O)-(CH2) a -O-(CH2) b -, -(C=O)-(CF2) a -O-(CF2) b -, -(C=O)-O-(CH2) a -O-(CH2) b -, -(C=O)-O-(CF2) a -O-(CF2) b At least one selected from -, -(C=O)-O-C6H4-, and combinations thereof. In the formula, a, b, c, and d are independently at least 1. a, b, c, and d may independently be 2 or more, 3 or more, 4 or more, 10 or more, or 20 or more. The upper limit of a, b, c, and d is, for example, 100.

[0343] R a Specific examples suitable as -CF2-O-, -CF2-O-CF2-, -CF2-O-CH2-, -CF2-O-CH2CF2-, -CF2-O-CF2CF2-, -CF2-O-CF2CH2-, -CF2-O-CF2CF2CH2-, -CF2-O-CF(CF3)-, -CF2-O-CF(CF3) CF2-, -CF2-O-CF(CF3)CF2-O-, -CF2-O-CF(CF3)CH2-, -(C=O)-, -(C=O)-O-, -(C=O)- (CH2)-, -(C=O)-(CF2)-, -(C=O)-O-(CH2)-, -(C=O)-O-(CF2)-, -(C=O)-[(CH2)2-O] n -, -(C=O)-[(CF2)2-O] n -, -(C=O)-O[(CH2)2-O] n -, -(C=O)-O[(CF2)2-O] n -, -(C=O)-O[(CH2)2-O] n -(CH2)-, -(C=O)-O[(CF2)2-O] n -(CF2)-, -(C=O)-(CH2)2-O-(CH2)-, -(C=O)-(CF2)2-O-(CF2)-, -(C=O)-O-(CH2)2-O-(CH2)-, -(C=O)-O-(CF2)2-O-(CF2)-, -(C=O)-O-C6H4-, etc. a Specifically, -CF2-O-, -CF2-O-CF2-, -CF2-O-CF2CF2-, -CF2-O-CF(CF3)-, -CF2-O-CF(CF3)CF2-, -CF2 -O-CF(CF3)CF2-O-, -(C=O)-, -(C=O)-O-, -(C=O)-(CH2)-, -(C=O)-O-(CH2)-, -(C=O)-O[(CH2)2-O] n -, -(C=O)-O[(CH2)2-O] n -(CH2)-, -(C=O)-(CH2)2-O-(CH2)-, or -(C=O)-O-C6H4- is preferred. In the above formula, n is an integer of 1 to 10.

[0344] -R in the above general formula (4) a -(CZ1 Z 2 ) k -としては、-CF2-O-CF2-、-CF2-O-CF(CF3)-、-CF2-OC(CF3)2-、-CF2-O-CF2-CF2-、-CF2-O-CF2-CF(CF3)-、-CF2-O-CF2-C(CF3)2-、-CF2-O-CF2CF2-CF2-、-CF2-O-CF2CF2-CF (CF3)-、-CF2-O-CF2CF2-C(CF3)2-、-CF2-O-CF(CF3)-CF2-、-CF2-O-CF(CF3)-CF(CF 3)-、-CF2-O-CF(CF3)-C(CF3)2-、-CF2-O-CF(CF3)-CF2-、-CF2-O-CF(CF3)-CF(CF3) -、-CF2-O-CF(CF3)-C(CF3)2-、-CF2-O-CF(CF3)CF2-CF2-、-CF2-O-CF(CF3)CF2-CF( CF3)-、-CF2-O-CF(CF3)CF2-C(CF3)2-、-CF2-O-CF(CF3)CF2-O-CF2-、-CF2-O-CF(CF 3)CF2-O-CF(CF3)-、-CF2-O-CF(CF3)CF2-OC(CF3)2-、-(C=O)-、-(C=O)-O-、-(C=O)- (CH2)-、-(C=O)-(CF2)-、-(C=O)-O-(CH2)-、-(C=O)-O-(CF2)-、-(C=O)-[(CH2)2-O] n -(CH2)-、-(C=O)-[(CF2)2-O] n -(CF2)-、-(C=O)-[(CH2)2-O] n -(CH2)-(CH2)-、-(C=O)-[(CF2)2-O] n -(CF2)-(CF2)-、-(C=O)-O[(CH2)2-O] n -(CF2)-、-(C=O)-O[(CH2)2-O] n -(CH2)-(CH2)-、-(C=O)-O[(CF2)2-O] n -(CF2)-、-(C=O)-O[(CF2)2-O] n-(CF2)-(CF2)-, -(C=O)-(CH2)2-O-(CH2)-(CH2)-, -(C=O)-(CF2)2-O-(CF2)-(CF2)-, -(C=O)-O-(CH2)2-O-(CH2)-(CH2)-, -(C=O )-O-(CF2)2-O-(CF2)-(CF2)-, -(C=O)-O-(CH2)2-O-(CH2)-C(CF3)2-, -(C=O)-O-(CF2)2-O-(CF2)-C(CF3)2-, or -(C=O)-O-C6H4- C(CF3)2- is preferred, -CF2-O-CF(CF3)-, -CF2-O-CF2-CF(CF3)-, -CF2-O-CF2CF2-CF(CF3)-, -CF2-O-CF(CF3)-CF(CF3)-, -CF2-O-CF(C F3)CF2-CF(CF3)-, -CF2-O-CF(CF3)CF2-O-CF(CF3)-, -(C=O)-, -(C=O)-O-(CH2)-, -(C=O)-O-(CH2)-(CH2)-, -(C=O)-O[(CH2)2-O] n -(CH2)-(CH2)-, -(C=O)-O-(CH2)2-O-(CH2)-C(CF3)2-, or -(C=O)-O-C6H4-C(CF3)2- is more preferred. In the above formula, n is an integer of 1 to 10.

[0345] Specific examples of the compound represented by general formula (4) include: [ka] (In the formula, X j and Y 3 is the same as above. n is an integer of 1 to 10.

[0346] R a As the general formula (r1): -(C=O) h -(O) i -CF2-O-(CX 6 2) e -{O-CF(CF3)} f -(O) g - (r1) (In the formula, X 6are each independently H, F, or CF3, e is an integer of 0 to 3, f is an integer of 0 to 3, g is 0 or 1, h is 0 or 1, and i is 0 or 1), and a divalent group represented by the general formula (r2): -(C=O) h -(O) i -CF2-O-(CX 7 2) e -(O) g - (r2) (In the formula, X 7 are each independently H, F or CF3, e is an integer of 0 to 3, g is 0 or 1, h is 0 or 1, and i is 0 or 1. Divalent groups represented by the following formula are also preferred.

[0347] -R in the above general formula (4) a -(CZ 1 Z 2 ) k - can also be represented by the following formula (t1): -(C=O) h -(O) i -CF2-O-(CX 6 2) e -{O-CF(CF3)} f -(O) g -CZ 1 Z 2 - (t1) (In the formula, X 6 are each independently H, F, or CF3, e is an integer of 0 to 3, f is an integer of 0 to 3, g is 0 or 1, h is 0 or 1, i is 0 or 1, and Z 1 and Z 2 are each independently F or CF3), and in formula (t1), Z 1 and Z 2 More preferably, one is F and the other is CF3. In addition, in the above general formula (4), -R a -(CZ 1 Z 2 ) k - is the following formula (t2): -(C=O) h -(O) i-CF2-O-(CX 7 2) e -(O) g -CZ 1 Z 2 - (t2) (In the formula, X 7 are each independently H, F, or CF3, e is an integer of 0 to 3, g is 0 or 1, h is 0 or 1, i is 0 or 1, and Z 1 and Z 2 are each independently F or CF3), and in formula (t2), Z 1 and Z 2 More preferably, one is F and the other is CF3.

[0348] The compound represented by the general formula (4) is a hydrophilic group (Y 3 ), it is also preferable that the compound has a C—F bond and does not have a C—H bond. i , X j , and X k All of the are F and R a is preferably a perfluoroalkylene group having one or more carbon atoms, and the perfluoroalkylene group may be either linear or branched, may be either cyclic or acyclic, and may contain at least one catenary heteroatom. The perfluoroalkylene group may have 2 to 20 carbon atoms, or may have 4 to 18 carbon atoms.

[0349] The compound represented by the general formula (4) may be partially fluorinated. That is, the compound represented by the general formula (4) may have a hydrophilic group (Y 3 ), it is also preferred that the alkyl group has at least one hydrogen atom bonded to a carbon atom and at least one fluorine atom bonded to a carbon atom.

[0350] The compound represented by general formula (4) is also preferably a compound represented by the following formula (4a). CF2=CF-O-Rf 0 -Y 3 (4a) (In the formula, Y 3 is a hydrophilic group, and Rf 0 is a perfluorinated divalent linking group which may be linear or branched, cyclic or acyclic in structure, saturated or unsaturated, substituted or unsubstituted, and which optionally contains one or more heteroatoms selected from the group consisting of sulfur, oxygen, and nitrogen.

[0351] The compound represented by general formula (4) is also preferably a compound represented by the following formula (4b). CH2=CH-O-Rf 0 -Y 3 (4b) (In the formula, Y 3 is a hydrophilic group, and Rf 0 is a perfluorinated divalent linking group defined by formula (4a).

[0352] In general formula (4), Y 3 One of the preferred embodiments is -OSO3M. 3 is -OSO3M, examples of the compound represented by general formula (4) include CF2=CF(OCF2CF2CH2OSO3M), CH2=CH((CF2)4CH2OSO3M), CF2=CF(O(CF2)4CH2OSO3M), CF2=CF(OCF2CF(CF3)CH2OSO3M), CF2=CF(OCF2CF(CF3)OCF2CF2CH2OSO3M), CH2=CH((CF2)4CH2OSO3M), CF2=CF(OCF2CF2SON(CH3)CH2CH2OSO3M), CH2=CH(CF2CF2CH2OSO3M), CF2=CF(OCF2CF2CF2CF2SON(CH3)CH2CH2OSO3M), CH2=CH(CF2CF2CH2OSO3M), and the like. In the above formulas, M is the same as above.

[0353] In general formula (4), Y 3 Another preferred form is -SO3M. 3is -SO3M, examples of the compound represented by general formula (4) include CF2=CF(OCF2CF2SO3M), CF2=CF(O(CF2)4SO3M), CF2=CF(OCF2CF(CF3)SO3M), CF2=CF(OCF2CF(CF3)OCF2CF2SO3M), CH2=CH(CF2CF2SO3M), CF2=CF(OCF2CF(CF3)OCF2CF2CF2CF2SO3M), CH2=CH((CF2)4SO3M), CH2=CH(CF2CF2SO3M), CH2=CH((CF2)3SO3M), etc. In the above formulas, M is the same as above.

[0354] In general formula (4), Y 3 -COOM is also a preferred form. 3 is -COOM, the compounds represented by general formula (4) include CF2=CF(OCF2CF2COOM), CF2=CF(OCF2CF2CF2COOM), CF2=CF(O(CF2)5COOM), CF2=CF(OCF2CF(CF3)COOM), CF2=CF(OCF2CF(CF3)O(CF2) n COOM) (n is greater than 1), CH2=CH(CF2CF2COOM), CH2=CH((CF2)4COOM), CH2=CH(CF2CF2COOM), CH2=CH((CF2)3COOM), CF2=CF(OCF2CF2SO2NR'CH2COOM), CF2=CF(O(CF2)4SO2NR'CH2COOM), CF2=CF(OCF2CF(CF3)SO2NR'CH2COOM), CF2=CF(OCF2 CF(CF3)OCF2CF2SO2NR'CH2COOM), CH2=CH(CF2CF2SO2NR'CH2COOM), CF2=CF(OCF2CF(CF3)OCF2CF2CF2CF2SO2NR'CH2COOM), CH2=CH((CF2)4SO2NR'CH2COOM), CH2=CH(CF2CF2SO2NR'CH2COOM), CH2=CH((CF2)3SO2NR'CH2COOM), etc. In the above formula, R' is H or C 1-4 is an alkyl group, and M is the same as above.

[0355] In general formula (4), Y 3 In another preferred embodiment, Y is -OPO3M or -OP(O)(OM)2. 3 is -OPO3M or -OP(O)(OM)2, the compounds represented by general formula (4) include CF2=CF(OCF2CF2CH2OP(O)(OM)2), CF2=CF(O(CF2)4CH2OP(O)(OM)2), CF2=CF(OCF2CF(CF3)CH2OP(O)(OM)2), CF2=CF(OCF2CF(CF3)OCF2CF2CH2OP(O)(OM)2), CF2=CF(OCF2CF2SO2N(CH3 )CH2CH2OP(O)(OM)2), CF2=CF(OCF2CF2CF2CF2SO2N(CH3)CH2CH2OP(O)(OM)2), CH2=CH(CF2CF2CH2OP(O)(OM)2, CH2=CH((CF2)4CH2OP(O)(OM)2), CH2=CH(CF2CF2CH2OP(O)(OM)2), CH2=CH((CF2)3CH2OP(O)(OM)2), etc. In the above formula, M is the same as above.

[0356] In general formula (4), Y 3 In another preferred embodiment, Y is -PO3M or -P(O)(OM)2. 3 is -PO3M or -P(O)(OM)2, examples of the compound represented by general formula (4) include CF2=CF(OCF2CF2P(O)(OM)2), CF2=CF(O(CF2)4P(O)(OM)2), CF2=CF(OCF2CF(CF3)P(O)(OM)2), CF2=CF(OCF2CF(CF3)OCF2CF2P(O)(OM)2), CH2=CH(CF2CF2P(O)(OM)2), CH2=CH((CF2)4P(O)(OM)2), CH2=CH(CF2CF2P(O)(OM)2), CH2=CH((CF2)3P(O)(OM)2), and the like, where M is the same as above.

[0357] The compound represented by the above general formula (4) includes compounds represented by the following general formula (5): CX2=CY(-CZ2-O-Rf-Y 3 ) (5) (In the formula, X's may be the same or different and each represent -H or -F; Y's may be -H, -F, an alkyl group or a fluorine-containing alkyl group; and Z's may be the same or different and each represent -H, -F, an alkyl group or a fluorine-containing alkyl group. Rf's may be a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having 2 to 100 carbon atoms and an ether bond. Y 3 is the same as above, a monomer represented by the following general formula (6): CX2=CY(-O-Rf-Y 3 ) (6) (In the formula, X may be the same or different and is -H or -F; Y is -H, -F, an alkyl group or a fluorine-containing alkyl group; and Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having 2 to 100 carbon atoms and an ether bond. Y 3 is the same as above.) and a monomer represented by the following general formula (7): CX2=CY(-Rf-Y 3 ) (7) (In the formula, X may be the same or different and is -H or -F; Y is -H, -F, an alkyl group or a fluorine-containing alkyl group; and Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having 2 to 100 carbon atoms and an ether bond. Y 3 is the same as above. Preferably, the monomer is at least one selected from the group consisting of: The fluorine-containing alkylene group having 2 to 100 carbon atoms and an ether bond is an alkylene group that does not contain a structure in which an oxygen atom is at the terminal and that contains an ether bond between carbon atoms.

[0358] In the above general formula (5), X is -H or -F. Both Xs may be -H, both may be -F, or at least one may be -H. For example, one may be -F and the other may be -H, or both may be -H.

[0359] In the above general formula (5), Y is —H, —F, an alkyl group or a fluorine-containing alkyl group. The alkyl group is an alkyl group that does not contain a fluorine atom, and may have a carbon number of at least 1. The alkyl group preferably has 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms. The fluorine-containing alkyl group is an alkyl group containing at least one fluorine atom, and may have a carbon number of at least 1. The fluorine-containing alkyl group preferably has 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms. The above Y is preferably -H, -F or -CF3, and more preferably -F.

[0360] In the above general formula (5), Z may be the same or different and is —H, —F, an alkyl group or a fluoroalkyl group. The alkyl group is an alkyl group that does not contain a fluorine atom, and may have a carbon number of at least 1. The alkyl group preferably has 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms. The fluorine-containing alkyl group is an alkyl group containing at least one fluorine atom, and may have a carbon number of at least 1. The fluorine-containing alkyl group preferably has 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms. The above Z is preferably -H, -F or -CF3, and more preferably -F.

[0361] In the general formula (5), it is preferable that at least one of X, Y, and Z contains a fluorine atom. For example, X may be —H, and Y and Z may be —F.

[0362] In the general formula (5), Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having 2 to 100 carbon atoms and an ether bond. The number of carbon atoms in the fluorine-containing alkylene group is preferably 2 or more. Also, it is preferably 30 or less, more preferably 20 or less, and even more preferably 10 or less. Examples of the fluorine-containing alkylene group include -CF2-, -CH2CF2-, -CF2CF2-, -CF2CH2-, -CF2CF2CH2-, -CF(CF3)-, -CF(CF3)CF2-, and -CF(CF3)CH2-. The fluorine-containing alkylene group is preferably a perfluoroalkylene group.

[0363] The carbon number of the fluorine-containing alkylene group having an ether bond is preferably 3 or more. The carbon number of the fluorine-containing alkylene group having an ether bond is preferably 60 or less, more preferably 30 or less, and even more preferably 12 or less. Examples of the fluorine-containing alkylene group having an ether bond include a group represented by the following formula: [ka] (In the formula, Z 1 is F or CF3;Z 2 and Z 3 are H or F;Z respectively 4 is also preferably a divalent group represented by the formula: H, F, or CF3; p1+q1+r1 is an integer of 1 to 10; s1 is 0 or 1; and t1 is an integer of 0 to 5). Specific examples of the fluorine-containing alkylene group having an ether bond include -CF(CF3)CF2-O-CF(CF3)-, -(CF(CF3)CF2-O) n -CF(CF3)- (wherein n is an integer of 1 to 10), -CF(CF3)CF2-O-CF(CF3)CH2-, -(CF(CF3)CF2-O) n Examples thereof include -CF(CF3)CH2- (wherein n is an integer of 1 to 10), -CH2CF2CF2O-CH2CF2CH2-, -CF2CF2CF2O-CF2CF2-, -CF2CF2CF2O-CF2CF2CH2-, -CF2CF2O-CF2-, -CF2CF2O-CF2CH2- and the like. The fluorine-containing alkylene group having an ether bond is preferably a perfluoroalkylene group.

[0364] In the above general formula (5), Y 3 is -COOM, -SO3M or -OSO3M (M is H, a metal atom, NR 7y 4. An imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent, R 7y are H or organic groups and may be the same or different. Any two of them may be bonded to each other to form a ring. R 7y The organic group in is preferably an alkyl group. R 7y As for H or C 1-10 is preferably an organic group represented by the formula: 1-4 The organic group is more preferably H or C 1-4 More preferred are alkyl groups of the formula: The metal atom includes alkali metals (Group 1) and alkaline earth metals (Group 2), and is preferably Na, K or Li. The above M is —H, a metal atom, or —NR 7y 4 is preferred, and -H, an alkali metal (Group 1), an alkaline earth metal (Group 2) or -NR 7y 4 is more preferred, -H, -Na, -K, -Li or -NH4 is even more preferred, -Na, -K or -NH4 is even more preferred, -Na or -NH4 is especially preferred, and -NH4 is most preferred. Above Y 3 As the alkyl group, -COOM or -SO3M is preferred, and -COOM is more preferred.

[0365] The monomer represented by the general formula (5) is preferably a monomer (5a) represented by the general formula (5a). CH2=CF(-CF2-O-Rf-Y 3 ) (5a) (Wherein Rf and Y 3 is the same as above.)

[0366] Specific examples of the monomer represented by the general formula (5a) include those represented by the following formula:

[0367] [ka]

[0368] (In the formula, Z 1 is F or CF3;Z 2 and Z 3 are H or F;Z respectively 4 is H, F, or CF3; p1+q1+r1 are integers between 0 and 10; s1 is 0 or 1; t1 is an integer between 0 and 5; Y 3 is the same as above, except for Z 3 and Z 4 are both H, then p1+q1+r1+s1 is not 0). More specifically,

[0369] [ka]

[0370] Among them,

[0371] [ka]

[0372] It is preferable that:

[0373] The monomer represented by general formula (5a) includes, for example, Y 3 is preferably -COOM, and particularly preferably at least one selected from the group consisting of CH2=CFCF2OCF(CF3)COOM and CH2=CFCF2OCF(CF3)CF2OCF(CF3)COOM (wherein M is as defined above), and more preferably CH2=CFCF2OCF(CF3)COOM.

[0374] The monomer represented by the general formula (5) is preferably a monomer (5b) represented by the general formula (5b). CX 2 2=CFCF2-O-(CF(CF3)CF2O) n5 -CF(CF3)-Y 3(5b) (In the formula, each 2 are the same and represent F or H. n5 represents 0 or an integer of 1 to 10, and Y 3 is the same as the definition above.)

[0375] In the formula (5b), n5 is preferably 0 or an integer of 1 to 5, more preferably 0, 1 or 2, and even more preferably 0 or 1, from the viewpoint of the stability of the resulting aqueous dispersion. 3 is preferably -COOM in that it provides adequate water solubility and stability of the aqueous dispersion, and the above M is preferably H or NH4 in that it is less likely to remain as an impurity and the heat resistance of the obtained molded body is improved.

[0376] Examples of the perfluorovinyl alkyl compound represented by the above formula (5b) include CH2=CFCF2OCF(CF3)COOM and CH2=CFCF2OCF(CF3)CF2OCF(CF3)COOM (wherein M is as defined above).

[0377] Further, examples of the monomer represented by the general formula (5) include a monomer represented by the general formula (5c).

[0378] CF2=CFCF2-O-Rf-Y 3 (5c) (Wherein Rf and Y 3 is the same as above)

[0379] More specifically, [ka] etc.

[0380] In the above general formula (6), X is -H or -F. Both Xs may be -F, or at least one X may be -H. For example, one X may be -F and the other may be -H, or both Xs may be -H.

[0381] In the above general formula (6), Y is —H, —F, an alkyl group or a fluorine-containing alkyl group. The alkyl group is an alkyl group that does not contain a fluorine atom, and may have a carbon number of at least 1. The alkyl group preferably has 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms. The fluorine-containing alkyl group is an alkyl group containing at least one fluorine atom, and may have a carbon number of at least 1. The fluorine-containing alkyl group preferably has 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms. The above Y is preferably -H, -F or -CF3, and more preferably -F.

[0382] In the general formula (6), it is preferable that at least one of X and Y contains a fluorine atom. For example, X may be —H, and Y and Z may be —F.

[0383] In the general formula (6), Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having 2 to 100 carbon atoms and an ether bond. The number of carbon atoms in the fluorine-containing alkylene group is preferably 2 or more. The number of carbon atoms in the fluorine-containing alkylene group is preferably 30 or less, more preferably 20 or less, and even more preferably 10 or less. Examples of the fluorine-containing alkylene group include -CF2-, -CH2CF2-, -CF2CF2-, -CF2CH2-, -CF2CF2CH2-, -CF(CF3)-, -CF(CF3)CF2-, and -CF(CF3)CH2-. The fluorine-containing alkylene group is preferably a perfluoroalkylene group.

[0384] In the above general formula (6), Y 3 is -COOM, -SO3M or -OSO3M (M is H, a metal atom, NR 7 4. An imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent, R 7are H or organic groups and may be the same or different. Any two of them may be bonded to each other to form a ring. R 7 The organic group in R is preferably an alkyl group. 7 As for H or C 1-10 is preferably an organic group represented by the formula: 1-4 The organic group is more preferably H or C 1-4 More preferred are alkyl groups of the formula: The metal atom includes alkali metals (Group 1) and alkaline earth metals (Group 2), and is preferably Na, K or Li. The above M is —H, a metal atom, or —NR 7 4 is preferred, and -H, an alkali metal (Group 1), an alkaline earth metal (Group 2) or -NR 7 4 is more preferred, -H, -Na, -K, -Li or -NH4 is even more preferred, -Na, -K or -NH4 is even more preferred, -Na or -NH4 is especially preferred, and -NH4 is most preferred. Above Y 3 As the alkyl group, -COOM or -SO3M is preferred, and -COOM is more preferred.

[0385] The monomer represented by the general formula (6) is preferably at least one selected from the group consisting of monomers represented by the following general formulae (6a), (6b), (6c), (6d) and (6e): CF2=CF-O-(CF2) n1 -Y 3 (6a) (wherein n1 represents an integer of 1 to 10, and Y 3 is the same as the definition above.) CF2=CF-O-(CF2C(CF3)F) n2 -Y 3 (6b) (wherein n2 represents an integer of 1 to 5, and Y 3 is the same as the definition above.) CF2=CF-O-(CFX 1 ) n3 -Y 3 (6c) (In the formula, X 1represents F or CF3, n3 represents an integer of 1 to 10, and Y 3 is the same as the definition above.) CF2=CF-O-(CF2CFX 1 O) n4 -(CF2) n6 -Y 3 (6d) (wherein n4 represents an integer of 1 to 10, n6 represents an integer of 1 to 3, and Y 3 and X 1 is the same as the definition above.) CF2=CF-O-(CF2CF2CFX 1 O) n5 -CF2CF2CF2-Y 3 (6e) (wherein n5 represents an integer of 0 to 10, and Y 3 and X 1 is the same as the definition above.)

[0386] In the formula (6a), n1 is preferably an integer of 5 or less, and more preferably an integer of 2 or less. 3 is preferably -COOM in that it provides suitable water solubility and stability of the aqueous dispersion, and M is preferably H or NH4 in that it is less likely to remain as an impurity and the heat resistance of the resulting molded article is improved.

[0387] Examples of the monomer represented by the above formula (6a) include CF2=CF-O-CF2COOM, CF2=CF(OCF2CF2COOM), and CF2=CF(OCF2CF2CF2COOM) (wherein M is as defined above).

[0388] In the formula (6b), n2 is preferably an integer of 3 or less in terms of the stability of the resulting aqueous dispersion, and Y 3 is preferably -COOM in that it provides suitable water solubility and stability of the aqueous dispersion, and M is preferably H or NH4 in that it is less likely to remain as an impurity and the heat resistance of the resulting molded article is improved.

[0389] In the formula (6c), n3 is preferably an integer of 5 or less in terms of water solubility, and Y 3 is preferably -COOM in that it provides suitable water solubility and stability of the aqueous dispersion, and the above M is preferably H or NH4 in that it provides good dispersion stability.

[0390] In the above formula (6d), the above X 1 is preferably —CF3 from the viewpoint of stability of the aqueous dispersion, n4 is preferably an integer of 5 or less from the viewpoint of water solubility, and Y 3 is preferably -COOM in that it provides adequate water solubility and stability of the aqueous dispersion, and the above M is preferably H or NH4.

[0391] Examples of the monomer represented by the above formula (6d) include CF2=CFOCF2CF(CF3)OCF2CF2COOM, CF2=CFOCF2CF(CF3)OCF2COOM, and CF2=CFOCF2CF(CF3)OCF2CF2CF2COOM (wherein M represents H, NH4, or an alkali metal). In the general formula (6e), n5 is preferably an integer of 5 or less in terms of water solubility, and Y 3 is preferably -COOM in that it provides adequate water solubility and stability of the aqueous dispersion, and the above M is preferably H or NH4. Examples of the monomer represented by general formula (6e) include CF2=CFOCF2CF2CF2COOM (wherein M represents H, NH4 or an alkali metal).

[0392] In the above general formula (7), Rf is preferably a fluorine-containing alkylene group having a carbon number of 1 to 40. In general formula (7), at least one of X and Y preferably contains a fluorine atom.

[0393] The monomer represented by the above general formula (7) is represented by the following general formula (7a): CF2=CF-(CF2) n1 -Y 3 (7a) (wherein n1 represents an integer of 1 to 10, and Y 3 is as defined above.) and a monomer represented by the following general formula (7b): CF2=CF-(CF2C(CF3)F) n2 -Y 3 (7b) (wherein n2 represents an integer of 1 to 5, and Y 3 is as defined above. At least one selected from the group consisting of monomers represented by Above Y 3 is preferably -SO3M or -COOM, and M is H, a metal atom, NR 7y 4. It is preferably an imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent. 7y represents H or an organic group.

[0394] In the formula (7a), n1 is preferably an integer of 5 or less, and more preferably an integer of 2 or less. 3 is preferably -COOM in that it provides suitable water solubility and stability of the aqueous dispersion, and M is preferably H or NH4 in that it is less likely to remain as an impurity and the heat resistance of the resulting molded article is improved. An example of the perfluorovinyl alkyl compound represented by the above formula (7a) is CF2=CFCF2COOM (wherein M is as defined above).

[0395] In the formula (7b), n2 is preferably an integer of 3 or less in terms of the stability of the resulting aqueous dispersion, and Y 3 is preferably -COOM in that it provides suitable water solubility and stability of the aqueous dispersion, and M is preferably H or NH4 in that it is less likely to remain as an impurity and the heat resistance of the resulting molded article is improved.

[0396] The above-mentioned modifying monomer preferably contains a modifying monomer (A), and preferably contains at least one selected from the group consisting of compounds represented by general formula (5a), general formula (5b), general formula (6a), general formula (6b), general formula (6c), and general formula (6d), and more preferably contains a compound represented by general formula (5a) or general formula (5b).

[0397] When a modifying monomer (A) is used as the modifying monomer, the content of the modifying monomer (A) units is preferably in the range of 0.00001 to 1.0% by mass relative to the total polymerized units of the TFE polymer (PTFE). The lower limit is more preferably 0.0001% by mass, even more preferably 0.0005% by mass, even more preferably 0.001% by mass, and especially preferably 0.005% by mass. The upper limit is, in order of preference, 0.90%, 0.50%, 0.40%, 0.30%, 0.20%, 0.15%, 0.10%, 0.08%, 0.05%, and 0.01% by mass.

[0398] In the production of the TFE polymer, the amount of polymer (I) added can be the same as the amount of polymer (I) added in the above-mentioned step C. The amount of polymer (I) added is not particularly limited as long as it is within the above range. If the amount added is too large, acicular particles with a large aspect ratio are formed, and the aqueous dispersion may become gel-like, resulting in a loss of stability. The lower limit of the amount of polymer (I) used (added) is preferably 0.0001% by mass, more preferably 0.001% by mass, still more preferably 0.01% by mass, and particularly preferably 0.02% by mass, relative to the aqueous medium. The upper limit of the amount of polymer (I) used (added) is preferably 10% by mass, more preferably 5% by mass, relative to the aqueous medium.

[0399] The polymer (I) may be added to a reaction vessel all at once before the start of polymerization, all at once after the start of polymerization, or divided into several portions during polymerization, or may be added continuously during polymerization.

[0400] In the production of the TFE polymer, persulfates (e.g., ammonium persulfate) and organic peroxides such as disuccinic acid peroxide and diglutaric acid peroxide can be used as polymerization initiators, either alone or in the form of a mixture thereof. They may also be used in combination with a reducing agent such as sodium sulfite to form a redox system. Furthermore, during polymerization, a radical scavenger such as hydroquinone or catechol, or a peroxide decomposer such as ammonium sulfite, can be added to adjust the radical concentration in the system.

[0401] As the redox polymerization initiator, it is preferable to use a redox initiator that combines an oxidizing agent and a reducing agent. Examples of oxidizing agents include persulfates, organic peroxides, potassium permanganate, manganese triacetate, and cerium ammonium nitrate. Examples of reducing agents include sulfites, bisulfites, bromates, diimines, and oxalic acid. Examples of persulfates include ammonium persulfate and potassium persulfate. Examples of sulfites include sodium sulfite and ammonium sulfite. To increase the decomposition rate of the initiator, it is also preferable to add a copper salt or an iron salt to the combination of redox initiators. Examples of copper salts include copper(II) sulfate, and examples of iron salts include iron(II) sulfate.

[0402] Examples of the redox initiator include potassium permanganate / oxalic acid, ammonium persulfate / bisulfite / iron sulfate, manganese triacetate / oxalic acid, cerium ammonium nitrate / oxalic acid, and bromate / bisulfite, with potassium permanganate / oxalic acid being preferred. When using a redox initiator, either an oxidizing agent or a reducing agent may be charged into a polymerization vessel in advance, and then the other may be added continuously or intermittently to initiate polymerization. For example, when potassium permanganate / oxalic acid is used, it is preferred to charge oxalic acid into a polymerization vessel and then continuously add potassium permanganate thereto.

[0403] In the production of the TFE polymer, known chain transfer agents can be used, including, for example, saturated hydrocarbons such as methane, ethane, propane, and butane; halogenated hydrocarbons such as chloromethane, dichloromethane, and difluoroethane; alcohols such as methanol, ethanol, and isopropanol; and hydrogen. However, those that are in a gaseous state at room temperature and normal pressure are preferred.

[0404] The amount of the chain transfer agent used is usually 1 to 10,000 ppm by mass, and preferably 1 to 5,000 ppm by mass, based on the total amount of TFE supplied.

[0405] In the production of the TFE polymer, a saturated hydrocarbon having 12 or more carbon atoms that is substantially inert to the reaction and becomes liquid under the reaction conditions can also be used as a dispersion stabilizer for the reaction system in an amount of 2 to 10 parts by mass per 100 parts by mass of the aqueous medium. Furthermore, ammonium carbonate, ammonium phosphate, or the like can be added as a buffer to adjust the pH during the reaction.

[0406] Upon completion of the polymerization of the TFE polymer, a pre-treatment aqueous dispersion containing a TFE polymer having a solids concentration of 1.0 to 70% by mass and an average primary particle size of 50 to 500 nm can usually be obtained. The pre-treatment aqueous dispersion contains a surfactant containing at least the polymer (I) and a fluoropolymer. Furthermore, by using a surfactant containing at least the polymer (I), a pre-treatment aqueous dispersion containing particles made of a TFE polymer with a fine particle size of 0.5 μm or less can be obtained. The lower limit of the solid content concentration in the pre-treatment aqueous dispersion is preferably 5% by mass, more preferably 8% by mass, and the upper limit is not particularly limited, but may be 40% by mass or 35% by mass. The lower limit of the average primary particle size of the TFE polymer is preferably 100 nm, more preferably 150 nm, and the upper limit is preferably 400 nm, more preferably 350 nm. The average primary particle size can be measured by dynamic light scattering. An aqueous dispersion adjusted to a solids concentration of approximately 1.0% by mass is prepared, and the average primary particle size is measured by dynamic light scattering at 25°C, with a refractive index of 1.3328 and a viscosity of 0.8878 mPa·s for the solvent (water), and 70 cumulative measurements. For example, an ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.) can be used for the dynamic light scattering method.

[0407] By subjecting the pre-treatment aqueous dispersion containing the TFE polymer to step A, an aqueous dispersion of TFE polymer (aqueous fluoropolymer dispersion) can be obtained. The aqueous dispersion of TFE polymer is coagulated (flocculated) and the coagulates containing the TFE polymer are recovered to produce a TFE polymer fine powder. The aqueous dispersion of TFE polymer can be used for various applications as a TFE polymer fine powder after coagulation, washing, and drying. When coagulating the aqueous dispersion of TFE polymer, the aqueous dispersion obtained by polymerization of a polymer latex or the like is usually diluted with water to a polymer concentration of 5 to 20% by mass, and the pH is adjusted to neutral or alkaline as needed. The coagulation is then carried out in a vessel equipped with a stirrer, with stirring more vigorously than during the reaction. The coagulation may be carried out while adding a coagulant, such as a water-soluble organic compound (e.g., methanol or acetone), an inorganic salt (e.g., potassium nitrate or ammonium carbonate), or an inorganic acid (e.g., hydrochloric acid, sulfuric acid, or nitric acid). The coagulation may also be carried out continuously using an in-line mixer or the like.

[0408] The concentration of the unaggregated TFE polymer in the wastewater resulting from the aggregation is preferably low from the viewpoint of productivity, more preferably less than 0.4% by mass, and particularly preferably less than 0.3% by mass.

[0409] By adding pigments for coloring or various fillers for improving mechanical properties before or during the coagulation, it is possible to obtain a pigmented or filled TFE polymer fine powder in which the pigments and fillers are uniformly mixed.

[0410] The wet powder obtained by coagulating the aqueous dispersion of the TFE polymer is usually dried by means of vacuum, high frequency, hot air, or the like, while keeping the wet powder in a state where it is not fluidized much, preferably in a static state. Friction between powders, particularly at high temperatures, generally has an undesirable effect on fine powder-type TFE polymers. This is because particles made of this type of TFE polymer tend to easily fibrillate even with a small shear force, losing their original stable particle structure.

[0411] The drying is carried out at a drying temperature of 10 to 300°C (10 to 250°C), preferably 100 to 300°C (100 to 200°C).

[0412] The resulting TFE polymer fine powder is suitable for molding, and suitable applications include tubes for hydraulic and fuel systems in aircraft and automobiles, flexible hoses for chemical solutions, steam, etc., and for electrical wire coating.

[0413] The aqueous dispersion of the TFE polymer can also be stabilized and further concentrated by adding a nonionic surfactant, and used in various applications as a composition to which an organic or inorganic filler is added depending on the purpose. By coating the composition on a metal or ceramic substrate, it is possible to form a coating surface that has non-adhesive properties and a low coefficient of friction, and is excellent in gloss, smoothness, abrasion resistance, weather resistance, and heat resistance, and is suitable for painting rolls, cooking utensils, etc., and for impregnating glass cloth, etc.

[0414] An organosol of a TFE polymer can also be prepared from the aqueous dispersion of the TFE polymer. The organosol can contain the TFE polymer and an organic solvent. Examples of the organic solvent include ether solvents, ketone solvents, alcohol solvents, amide solvents, ester solvents, aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, and halogenated hydrocarbon solvents. N-methyl-2-pyrrolidone, dimethylacetamide, and the like are preferably used. The organosol can be prepared, for example, by the method described in International Publication No. 2012 / 002038.

[0415] The aqueous dispersion of the TFE polymer or the fine powder of the TFE polymer is also preferably used as a processing aid. When used as a processing aid, the aqueous dispersion or the fine powder is mixed with a host polymer or the like to improve the melt strength during melt processing of the host polymer, and the mechanical strength, electrical properties, flame retardancy, anti-dripping property during combustion, and sliding properties of the resulting polymer.

[0416] The above-mentioned aqueous dispersion of the TFE polymer or the above-mentioned TFE polymer fine powder is also preferably used as a binder for batteries and for dust prevention purposes.

[0417] The aqueous dispersion of the TFE polymer or the fine powder of the TFE polymer is preferably used as a processing aid after being compounded with a resin other than the TFE polymer. The aqueous dispersion or fine powder of the TFE polymer is suitable as a raw material for PTFE, as described in, for example, JP-A-11-49912, U.S. Pat. No. 5,804,654, JP-A-11-29679, and JP-A-2003-2980. Processing aids using the aqueous dispersion or fine powder are in no way inferior to the processing aids described in the above publications.

[0418] Also preferably, the aqueous dispersion of above-mentioned TFE polymer is mixed with the aqueous dispersion of melt-processable fluororesin to be coagulated, and form coprecipitated powder.Above-mentioned coprecipitated powder is suitable as processing aid.

[0419] Examples of the melt-processable fluororesin include FEP, PFA, TFE / perfluoroallyl ether copolymer, ETFE, ethylene / TFE / HFP copolymer [EFEP], etc., with FEP being preferred.

[0420] The aqueous dispersion preferably contains the melt-processable fluororesin. Examples of the melt-processable fluororesin include FEP, PFA, TFE / perfluoroallyl ether copolymer, ETFE, and EFEP. The aqueous dispersion of the TFE polymer containing the melt-processable fluororesin can be used as a coating material. The melt-processable fluororesin can sufficiently fuse the TFE polymer particles together, improving film-forming properties and imparting gloss to the resulting coating.

[0421] The fluorine-free resin that adds above-mentioned coprecipitated powder can be powder, can be pellet, can be emulsion.In order to thoroughly mix each resin, it is preferable to add above-mentioned by known method such as extrusion kneading, roll kneading, etc., while applying shearing force.

[0422] The aqueous dispersion of the TFE polymer is also preferably used as a dust-suppressing treatment. The dust-suppressing treatment can be used in a method of mixing the TFE polymer with a dust-generating substance and subjecting the mixture to a compression-shear action at a temperature of 20 to 200°C to fibrillate the TFE polymer and suppress dust from the dust-generating substance, such as the methods described in Japanese Patent No. 2827152 and Japanese Patent No. 2538783. The aqueous dispersion of the TFE polymer can be suitably used, for example, in the dust suppression treatment composition described in WO 2007 / 004250, and can also be suitably used in the dust suppression treatment method described in WO 2007 / 000812.

[0423] The dust suppression treatment agent is suitable for use in the fields of building materials, soil stabilization materials, solidification materials, fertilizers, landfill disposal of incineration ash and hazardous substances, explosion prevention, cosmetics, and dust suppression treatment of sand for pet excretion, such as cat litter.

[0424] The above aqueous dispersion of the TFE polymer is also preferably used as a raw material for obtaining TFE polymer fibers by the dispersion spinning method. The dispersion spinning method is a method in which an aqueous dispersion of the TFE polymer and an aqueous dispersion of a matrix polymer are mixed, the mixture is extruded to form an intermediate fiber structure, and the intermediate fiber structure is fired to decompose the matrix polymer and sinter the TFE polymer particles, thereby obtaining TFE polymer fibers.

[0425] The high-molecular-weight PTFE powder obtained by polymerization has extensibility and non-melt processability, and is also useful as a raw material for an extruded body (porous body). In the first production method of the present disclosure, the fluoropolymer may be high-molecular-weight PTFE. When the aqueous fluoropolymer dispersion contains high-molecular-weight PTFE, it is also useful as a raw material for an extruded body (porous body). When this stretched body is a membrane (a stretched PTFE membrane or a porous PTFE membrane), it can be stretched by a known PTFE stretching method. By stretching, the high-molecular-weight PTFE is easily fibrillated, forming a porous PTFE body (membrane) consisting of nodes and fibers. Preferably, a sheet-like or rod-like paste extrudate is roll-stretched in the extrusion direction to obtain a uniaxially stretched film. Furthermore, a biaxially stretched film can also be obtained by stretching the film in the width direction using a tenter or the like. It is also preferable to carry out a semi-baking treatment before stretching.

[0426] This expanded PTFE body is a porous body with high porosity and can be suitably used as a filter medium for various precision filters such as air filters and chemical filters, a support material for polymer electrolyte membranes, and the like. It is also useful as a material for products used in the fields of textiles, medicine, electrochemicals, sealing materials, air filtration, ventilation / internal pressure adjustment, liquid filtration, and general consumer goods. Specific examples of applications are given below.

[0427] Electrochemical field Dielectric material prepreg, EMI shielding material, heat transfer material, etc. More specifically, printed wiring boards, electromagnetic shielding materials, insulating heat transfer materials, insulating materials, etc. Sealing materials field Gaskets, packing, pump diaphragms, pump tubes, aircraft sealing materials, etc.

[0428] Air Filtration ULPA filters (for semiconductor manufacturing), HEPA filters (for hospitals and semiconductor manufacturing), cylindrical cartridge filters (for industrial use), bag filters (for industrial use), heat-resistant bag filters (for exhaust gas treatment), heat-resistant pleated filters (for exhaust gas treatment), SINBRAN filters (for industrial use), catalytic filters (for exhaust gas treatment), adsorbent filters (for HDD integration), adsorbent vent filters (for HDD integration), vent filters (for HDD integration and others), vacuum cleaner filters (for vacuum cleaners), general-purpose multi-layer felt material, GT cartridge filters (for GT compatible products), cooling filters (for electronic equipment housings), etc.

[0429] Ventilation / internal pressure regulation field Freeze-drying materials such as freeze-drying containers, automotive ventilation materials for electronic circuits and lamps, container applications such as container caps, protective ventilation applications for electronic devices including small terminals such as tablet devices and mobile phones, medical ventilation applications, etc.

[0430] Liquid Filtration Semiconductor liquid filtration filters (for semiconductor manufacturing), hydrophilic PTFE filters (for semiconductor manufacturing), chemical filters (for chemical liquid treatment), filters for pure water production lines (for pure water production), backwash type liquid filtration filters (for industrial wastewater treatment), etc.

[0431] General consumer goods Clothing, cable guides (movable wires for motorcycles), motorcycle clothing, cast liners (medical supporters), vacuum cleaner filters, bagpipes (musical instruments), cables (guitar signal cables, etc.), strings (for stringed instruments), etc.

[0432] Textile field PTFE fiber (textile material), sewing thread (textile), weaving thread (textile), rope, etc.

[0433] Medical field Implants (extended products), artificial blood vessels, catheters, general surgery (tissue reinforcement materials), head and neck products (dura mater replacement), oral health (tissue regenerative medicine), orthopedics (bandages), etc.

[0434] The above-mentioned polymer (I) can also be used to produce low-molecular-weight PTFE. In the first production method of the present disclosure, the fluoropolymer may be low-molecular-weight PTFE. Low-molecular-weight PTFE may be produced by polymerization, or by lowering the molecular weight of high-molecular-weight PTFE obtained by polymerization by a known method (thermal decomposition, decomposition by irradiation, etc.).

[0435] Low-molecular-weight PTFE (also called PTFE micropowder) having a molecular weight of 600,000 or less has excellent chemical stability, extremely low surface energy, and is resistant to fibrillation. Therefore, it is suitable as an additive for improving the slipperiness and texture of coating surfaces in the production of plastics, inks, cosmetics, paints, greases, office automation equipment components, toners, etc. (see, for example, JP-A-10-147617).

[0436] Furthermore, a low-molecular-weight PTFE may be obtained by dispersing a polymerization initiator and the polymer (I) in an aqueous medium in the presence of a chain transfer agent, and polymerizing TFE with TFE or a monomer copolymerizable with TFE.

[0437] When the low-molecular-weight PTFE obtained by the above polymerization is used as a powder, the aqueous dispersion can be coagulated to form powder particles.

[0438] In this disclosure, high molecular weight PTFE refers to non-melt-processible and fibrillating PTFE, while low molecular weight PTFE refers to melt-processible and non-fibrillating PTFE.

[0439] The term "non-melt processable" means that the melt flow rate cannot be measured at a temperature higher than the crystallization melting point in accordance with ASTM D 1238 and D 2116.

[0440] The presence or absence of fibrillating properties can be determined by "paste extrusion," a typical method for molding "high molecular weight PTFE powder," a powder made from a TFE polymer. Paste extrusion is usually possible because high molecular weight PTFE has fibrillating properties. If the unsintered molded product obtained by paste extrusion has no substantial strength or elongation, for example, if it breaks when pulled at 0% elongation, it can be considered to have no fibrillating properties.

[0441] The high-molecular-weight PTFE preferably has a standard specific gravity (SSG) of 2.130 to 2.280. The standard specific gravity is measured by a water displacement method in accordance with ASTM D 792 using a sample molded in accordance with ASTM D4895-89. In the present disclosure, "high molecular weight" means that the standard specific gravity is within the above range.

[0442] The above low molecular weight PTFE has a complex viscosity of 1×10 at 380°C. 2 ~7×10 5 In the present disclosure, "low molecular weight" means that the complex viscosity is within the above range.

[0443] The high-molecular-weight PTFE has a much higher complex viscosity than the low-molecular-weight PTFE, making it difficult to measure its complex viscosity accurately. On the other hand, while the complex viscosity of the low-molecular-weight PTFE can be measured, it is difficult to obtain a molded article from the low-molecular-weight PTFE that can be used to measure its standard specific gravity, making it difficult to measure its standard gravity accurately. Therefore, in this disclosure, standard specific gravity is used as an indicator of the molecular weight of the high-molecular-weight PTFE, and complex viscosity is used as an indicator of the molecular weight of the low-molecular-weight PTFE. There are no known measurement methods that can directly determine the molecular weight of either the high-molecular-weight PTFE or the low-molecular-weight PTFE.

[0444] The high-molecular-weight PTFE preferably has a peak temperature of 333 to 347°C, more preferably 335 to 345°C. The low-molecular-weight PTFE preferably has a peak temperature of 322 to 333°C, more preferably 324 to 332°C. The peak temperature is the temperature corresponding to the maximum value on the heat of fusion curve when PTFE that has not been heated to temperatures above 300°C is heated at a rate of 10°C / min using a differential scanning calorimeter (DSC). The peak temperature can also be identified as the temperature corresponding to the maximum value that appears on a differential thermal (DTA) curve obtained by heating PTFE that has not been heated to temperatures above 300°C at a rate of 10°C / min using a TG / DTA (thermogravimetric / differential thermal analyzer).

[0445] The high-molecular-weight PTFE preferably has at least one endothermic peak in the range of 333 to 347°C in a heat of fusion curve obtained by heating PTFE that has not been heated to a temperature of 300°C or higher at a rate of 10°C / min using a differential scanning calorimeter (DSC), and has a heat of fusion of 62 mJ / mg or more between 290 and 350°C calculated from the heat of fusion curve.

[0446] An unsintered tape (green tape) can also be obtained from the PTFE fine powder obtained using the above-mentioned polymer (I).

[0447] (II) Melt-processable fluororesin (1) In step C, the polymerization of FEP is preferably carried out at a polymerization temperature of 10 to 150° C. and a polymerization pressure of 0.3 to 6.0 MPaG.

[0448] The preferred monomer composition (mass%) of FEP is TFE:HFP=(60-95):(5-40), more preferably (85-92):(8-15). The FEP may also be modified with a perfluoro(alkyl vinyl ether) as a third component in an amount of 0.1-2 mass% of the total monomers.

[0449] In the polymerization of the FEP, the amount of polymer (I) added can be the same as the amount of polymer (I) added in the above-mentioned step C, but it is usually added in an amount of 0.0001 to 10% by mass relative to 100% by mass of the aqueous medium.

[0450] In the polymerization of FEP, it is preferable to use cyclohexane, methanol, ethanol, propanol, ethane, propane, butane, pentane, hexane, carbon tetrachloride, chloroform, methylene chloride, methyl chloride, or the like as a chain transfer agent, and it is preferable to use ammonium carbonate, disodium hydrogen phosphate, or the like as a pH buffer.

[0451] In the first production method of the present disclosure, when the fluoropolymer is FEP, the resulting aqueous dispersion of FEP may be subjected to post-treatment such as concentration as necessary, dried, powdered, and then melt-extruded to form pellets. The aqueous medium in the aqueous dispersion of FEP may contain additives such as a nonionic surfactant as necessary, and may also contain a water-soluble organic solvent such as a water-soluble alcohol, or may not contain a water-soluble organic solvent.

[0452] Furthermore, melt extrusion can be carried out by appropriately setting extrusion conditions as long as the extrusion conditions are generally such that pelletization is possible.

[0453] In the first production method of the present disclosure, when the fluoropolymer is FEP, the FEP may have terminal groups such as -CF3, -CF2H, etc. at least in one of the polymer main chain and polymer side chains, but it is preferable that the content of thermally unstable groups (hereinafter referred to as "unstable terminal groups") such as -COOH, -CH2OH, -COF, -CF=CF-, -CONH2, and -COOCH3 is low or absent.

[0454] The unstable terminal groups are chemically unstable and therefore not only reduce the heat resistance of the resin but also cause an increase in the attenuation of the resulting electric wire.

[0455] In the first production method of the present disclosure, the fluoropolymer has a total number of unstable terminal groups and —CFH terminal groups of 1×10 carbon atoms. 6 Preferably, the number of carbon atoms is 50 or less per unit, more preferably 1×10 6 The number of terminal groups per unit is preferably less than 20, and more preferably not more than 5. The unstable terminal groups and -CF2H terminal groups may be absent, and all may be -CF3 terminal groups.

[0456] Unstable terminal groups and -CF2H terminal groups can be stabilized by converting them to -CF3 terminal groups through fluorination treatment. The fluorination treatment method is not particularly limited, but examples include a method in which the polymer is exposed to a fluorine radical source that generates fluorine radicals under fluorination treatment conditions. Examples of the fluorine radical source include fluorine gas, CoF3, AgF2, UF6, OF2, N2F2, CF3OF, and halogen fluorides such as IF5 and ClF3. Among these, a method in which the fluorination gas is directly contacted with FEP is preferred. From the viewpoint of reaction control, the contact is preferably carried out using diluted fluorine gas with a fluorine gas concentration of 10 to 50 mass%. The diluted fluorine gas can be obtained by diluting fluorine gas with an inert gas such as nitrogen gas or argon gas. The fluorine gas treatment can be carried out at a temperature of, for example, 100 to 250°C. The treatment temperature is not limited to the above range and can be appropriately set depending on the circumstances. The fluorine gas treatment is preferably carried out by continuously or intermittently supplying diluted fluorine gas into a reactor. This fluorination treatment may be carried out on a dry powder after polymerization or on melt-extruded pellets.

[0457] FEP has good moldability and is less likely to produce molding defects, and also has good heat resistance, chemical resistance, solvent resistance, insulating properties, electrical properties, etc.

[0458] The method for producing the above-mentioned FEP powder is a method for obtaining the powder by drying and pulverizing the aqueous fluoropolymer dispersion containing FEP obtained by the production method of the present disclosure described above.

[0459] The powder may be fluorinated. The method for producing the fluorinated powder is a method for obtaining the fluorinated powder by supplying fluorine gas to the powder obtained by the method for producing the powder described above to fluorinate the powder.

[0460] The method for producing the FEP pellets is a method for obtaining pellets by pelletizing FEP powder.

[0461] The pellets may be fluorinated. The method for producing fluorinated pellets is a method for obtaining fluorinated pellets by supplying fluorine gas to the pellets obtained by the above-described method for producing pellets, thereby fluorinating the pellets.

[0462] Therefore, this FEP can be used to produce various molded products such as covering materials for electric wires, foamed electric wires, cables, wires, etc., as well as tubes, films, sheets, filaments, etc.

[0463] (2) In step C, the polymerization of TFE / perfluoro(alkyl vinyl ether) copolymers such as PFA and MFA and TFE / perfluoroallyl ether copolymers is preferably carried out at a polymerization temperature of 10 to 100°C and a polymerization pressure of 0.3 to 6.0 MPaG.

[0464] The preferred monomer composition (mol %) of the TFE / perfluoro(alkyl vinyl ether) copolymer is TFE:perfluoro(alkyl vinyl ether)=(90-99.7):(0.3-10), more preferably (97-99):(1-3). The perfluoro(alkyl vinyl ether) is represented by the formula: CF2=CFORf 4 (In the formula, Rf 4 It is preferable to use one represented by a perfluoroalkyl group having 1 to 6 carbon atoms.

[0465] The preferred monomer composition (mol%) of the TFE / perfluoroallyl ether copolymer is TFE:perfluoroallyl ether=(90-99.7):(0.3-10), more preferably (97-99):(1-3). The perfluoroallyl ether is represented by the formula: CF2=CFCF2ORf 4 (In the formula, Rf 4 It is preferable to use one represented by a perfluoroalkyl group having 1 to 6 carbon atoms.

[0466] In the polymerization of the TFE / perfluoro(alkyl vinyl ether) copolymer and the TFE / perfluoroallyl ether copolymer, the amount of polymer (I) added can be the same as the amount of polymer (I) added in the above-mentioned step C, but it is usually preferable to add it in an amount of 0.0001 to 10% by mass relative to 100% by mass of the aqueous medium.

[0467] In the polymerization of the above TFE / perfluoro(alkyl vinyl ether) copolymer and TFE / perfluoroallyl ether copolymer, it is preferable to use cyclohexane, methanol, ethanol, propanol, propane, butane, pentane, hexane, carbon tetrachloride, chloroform, methylene chloride, methyl chloride, methane, ethane, or the like as a chain transfer agent, and it is preferable to use ammonium carbonate, disodium hydrogen phosphate, or the like as a pH buffer.

[0468] In the first production method of the present disclosure, when the fluoropolymer is a TFE / perfluoro(alkyl vinyl ether) copolymer such as PFA or MFA or a TFE / perfluoroallyl ether copolymer, the resulting aqueous dispersion of the TFE / perfluoro(alkyl vinyl ether) copolymer such as PFA or MFA or the TFE / perfluoroallyl ether copolymer may be subjected to post-treatment such as concentration as necessary, dried, powdered, and then melt-extruded to form pellets. The aqueous medium in the aqueous dispersion may contain additives such as a nonionic surfactant as necessary, and may contain or not contain a water-soluble organic solvent such as a water-soluble alcohol.

[0469] Furthermore, melt extrusion can be carried out by appropriately setting extrusion conditions as long as the extrusion conditions are generally such that pelletization is possible.

[0470] The copolymer is preferably treated with fluorine gas in order to improve its heat resistance and further enhance the effect of inhibiting the permeation of chemical solutions into the molded article.

[0471] Fluorine gas treatment is carried out by contacting fluorine gas with the chemical liquid permeation inhibitor. However, because the reaction with fluorine is highly exothermic, it is preferable to dilute the fluorine with an inert gas such as nitrogen. The fluorine content in the fluorine gas / inert gas mixture is 1 to 100 mass %, preferably 10 to 25 mass %. The treatment temperature is 150 to 250°C, preferably 200 to 250°C, and the fluorine gas treatment time is 3 to 16 hours, preferably 4 to 12 hours. The gas pressure for the fluorine gas treatment ranges from 1 to 10 atmospheres, but atmospheric pressure is preferably used. When the reactor is used at atmospheric pressure, a fluorine gas / inert gas mixture is continuously passed through the reactor. As a result, the unstable terminals of the copolymer are converted to -CF3 terminals, making it thermally stable.

[0472] As a molding method for the copolymer and its composition, molding methods such as compression molding, transfer molding, extrusion molding, injection molding, and blow molding can be used, similar to conventional molding methods for PFA.

[0473] Desired molded products can be obtained by such molding methods, and examples of molded products include sheets, films, packing, round bars, square bars, pipes, tubes, round tanks, square tanks, tanks, wafer carriers, wafer boxes, beakers, filter housings, flow meters, pumps, valves, cocks, connectors, nuts, electric wires, and heat-resistant electric wires.

[0474] Among these, it can be suitably used for tubes, pipes, tanks, connectors, etc. used in various chemical reaction equipment, semiconductor manufacturing equipment, and acid or alkaline chemical supply equipment, which require impermeability to chemicals.

[0475] Furthermore, a primer composition can be obtained by adding a nonionic surfactant to an aqueous dispersion of a TFE / perfluoro(alkyl vinyl ether) copolymer such as PFA or MFA and a TFE / perfluoroallyl ether copolymer, and, if necessary, dissolving or dispersing polyethersulfone, polyamideimide and / or polyimide, and metal powder in an organic solvent. This primer composition can also be used in a method for coating a metal surface with a fluororesin, which comprises applying the primer composition to a metal surface, applying a melt-processable fluororesin composition onto the primer layer thus formed, and baking the melt-processable fluororesin composition layer together with the primer layer.

[0476] (3) In step C, the polymerization of ETFE is preferably carried out at a polymerization temperature of 10 to 100°C and a polymerization pressure of 0.3 to 2.0 MPaG.

[0477] The preferred monomer composition (mol %) of ETFE is TFE:ethylene = (50-99): (50-1). The ETFE may also be modified with a third monomer within the range of 0-20 mass % of the total monomers. A preferred ratio is TFE:ethylene:third monomer = (63-94): (27-2): (1-10). Preferred third monomers include perfluorobutylethylene, perfluorohexylethylene, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene, 2,3,3,4,4,5,5-heptafluoro-1-pentene (CH2=CFCF2CF2CF2H), and 2-trifluoromethyl-3,3,3-trifluoropropene ((CF3)2C=CH2).

[0478] In the above-mentioned ETFE polymerization, the amount of the polymer (I) added can be the same as the amount of the polymer (I) added in the above-mentioned step C, but it is usually added in an amount of 0.0001 to 10% by mass relative to 100% by mass of the aqueous medium.

[0479] In the above polymerization of ETFE, it is preferable to use, as a chain transfer agent, cyclohexane, methanol, ethanol, propanol, ethane, propane, butane, pentane, hexane, carbon tetrachloride, chloroform, methylene chloride, methyl chloride, or the like.

[0480] In the first production method of the present disclosure, when the fluoropolymer is ETFE, the resulting aqueous dispersion of ETFE may be subjected to post-treatment such as concentration as necessary, dried, powdered, and then melt-extruded to form pellets. The aqueous medium in the aqueous dispersion may contain additives such as a nonionic surfactant as necessary, and may also contain a water-soluble organic solvent such as a water-soluble alcohol, or may not contain a water-soluble organic solvent.

[0481] Furthermore, melt extrusion can be carried out by appropriately setting extrusion conditions as long as the extrusion conditions are generally such that pelletization is possible.

[0482] The ETFE sheet can be formed into a sheet by extrusion molding. That is, ETFE powder or pellets can be melted, continuously extruded through a die, and cooled to form a sheet-like molded product. Additives may be added to the ETFE.

[0483] As the additive, known additives can be appropriately used. Specific examples include ultraviolet absorbers, light stabilizers, antioxidants, infrared absorbers, flame retardants, flame-retardant fillers, organic pigments, inorganic pigments, dyes, etc. Inorganic additives are preferred from the viewpoint of excellent weather resistance. The content of the additive in the ETFE sheet is preferably 20% by mass or less, particularly preferably 10% by mass or less, based on the total mass of the ETFE sheet.

[0484] The above-mentioned ETFE sheet has excellent mechanical strength and appearance, and is therefore suitable as a membrane material (roofing material, ceiling material, exterior wall material, interior wall material, covering material, etc.) for membrane structure buildings (sports facilities, horticultural facilities, atriums, etc.). Furthermore, in addition to membrane materials for membrane-structured buildings, they are also useful in, for example, outdoor-use board materials (soundproof walls, windbreak fences, wave fences, garage canopies, shopping malls, walkway walls, roofing materials), glass shatterproof films, heat-resistant and water-resistant sheets, building materials (tent materials for tent warehouses, sunshade membrane materials, partial roof materials for letting in light, window materials in place of glass, fire-retardant partition membrane materials, curtains, exterior wall reinforcement, waterproof membranes, smoke-proof membranes, non-flammable transparent partitions, road reinforcement, interior materials (lighting, walls, brands, etc.), exterior materials (tents, signs, etc.)), lifestyle and leisure goods (fishing rods, rackets, golf clubs, projection screens, etc.), automotive materials (canopies, vibration-damping materials, bodies, etc.), aircraft materials, ship materials, home appliance exteriors, tanks, container inner walls, filters, construction membrane materials, electronic materials (printed circuit boards, wiring boards, insulating films, release films, etc.), surface materials for solar cell modules, mirror protective materials for solar thermal power generation, surface materials for solar water heaters, etc.

[0485] (4) The first production method of the present disclosure can also be used to produce an aqueous fluoropolymer dispersion containing an electrolyte polymer precursor. In step C, the polymerization of the electrolyte polymer precursor is preferably carried out at a polymerization temperature of 10 to 100°C and a polymerization pressure of 0.1 to 2.0 MPaG. The electrolyte polymer precursor is composed of a vinyl ether monomer as shown below, and can be converted into an ion-exchange polymer through hydrolysis treatment.

[0486] Examples of vinyl ether monomers used in the electrolyte polymer precursor include: General formula (150): CF2=CF-O-(CF2CFY 151 -O) n -(CFY 152 ) m -A 151 (In the formula, Y 151 represents a fluorine atom, a chlorine atom, a -SO2F group, or a perfluoroalkyl group. The perfluoroalkyl group may contain an etheric oxygen and a -SO2F group. n represents an integer of 0 to 3. n Y 151 may be the same or different. 152 represents a fluorine atom, a chlorine atom, or a -SO2F group. m represents an integer of 1 to 5. m Y 152 may be the same or different. 151 -SO2X 151 , -COZ 151 or -POZ 152 Z 153 represents X 151 are F, Cl, Br, I, -OR 151 or -NR 152 R 153 represents Z. 151 , Z 152 and Z 153 are the same or different and are -NR 154 R 155 -OR 156 Represents R 151 , R 152 , R 153 , R 154 , R 155 and R 156are the same or different and represent H, ammonium, an alkali metal, an alkyl group which may contain a fluorine atom, an aryl group, or a sulfonyl-containing group. The preferred monomer composition (mol %) of the electrolyte polymer precursor is TFE:vinyl ether=(50-99):(50-1), more preferably TFE:vinyl ether=(50-93):(50-7).

[0487] The electrolyte polymer precursor may be modified with a third monomer in an amount of 0 to 20% by mass of the total monomers, such as polyfunctional monomers such as CTFE, vinylidene fluoride, perfluoroalkyl vinyl ether, and divinylbenzene.

[0488] The electrolyte polymer precursor thus obtained can be formed into a membrane, for example, and then subjected to hydrolysis with an alkaline solution and treatment with a mineral acid, resulting in a polymer electrolyte membrane that can be used in fuel cells, electrolysis devices, redox flow batteries, and the like. Alternatively, an electrolyte polymer dispersion can be obtained by subjecting the electrolyte polymer precursor to hydrolysis with an alkaline solution while maintaining the dispersed state of the electrolyte polymer precursor. Subsequently, by heating to 120° C. or higher in a pressure vessel, the compound can be dissolved in, for example, a water / alcohol mixed solvent to form a solution. The solution thus obtained can be used, for example, as a binder for electrodes, or can be combined with various additives to form a cast film, which can be used, for example, as an antifouling coating film or an organic actuator.

[0489] (5)TFE / VDF copolymer In step C, the polymerization temperature for the TFE / VDF copolymer is not particularly limited and may be 0 to 100° C. The polymerization pressure is appropriately determined depending on other polymerization conditions such as the polymerization temperature, but may usually be 0 to 9.8 MPaG.

[0490] The preferred monomer composition (mol %) of the TFE / VDF copolymer is TFE:VDF=(5-90):(95-10). The TFE / VDF copolymer may also be modified with a third monomer within the range of 0-50 mol % of the total monomers. Preferably, the ratio is TFE:ethylene:third monomer=(30-85):(10-69.9):(0.1-10).

[0491] The third monomer may be: Formula: CX 11 X 12 =CX 13 (CX 14 X 15 ) n11 X 16 (In the formula, X 11 ~X 16 are the same or different and represent H, F or Cl, and n11 represents an integer of 0 to 8, excluding TFE and VDF, or Formula: CX 21 X 22 =CX 23 -O(CX 24 X 25 ) n21 X 26 (In the formula, X 21 ~X 26 are the same or different and represent H, F or Cl, and n21 represents an integer of 0 to 8.) is preferred.

[0492] The third monomer may also be a fluorine-free ethylenic monomer. In order to maintain heat resistance and chemical resistance, the fluorine-free ethylenic monomer is preferably selected from ethylenic monomers having 6 or less carbon atoms. Examples include ethylene, propylene, 1-butene, 2-butene, vinyl chloride, vinylidene chloride, alkyl vinyl ethers (methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, etc.), maleic acid, itaconic acid, 3-butenoic acid, 4-pentenoic acid vinyl sulfonic acid, acrylic acid, and methacrylic acid.

[0493] In the polymerization of the TFE / VDF copolymer, the amount of the polymer (I) added can be the same as the amount of the polymer (I) added in the above-mentioned step C, but it is usually added in an amount of 0.0001 to 5% by mass relative to 100% by mass of the aqueous medium.

[0494] The TFE / VDF copolymer obtained by polymerization may be amidated by contacting it with aqueous ammonia, ammonia gas, or a nitrogen compound capable of generating ammonia.

[0495] The TFE / VDF copolymer obtained by the above-mentioned method is also preferably used as a raw material for obtaining a TFE / VDF copolymer fiber by a spinning and drawing method, in which the TFE / VDF copolymer is melt-spun and then cooled and solidified to obtain an undrawn yarn, and the undrawn yarn is then run through a heated cylinder to be drawn, thereby obtaining a TFE / VDF copolymer fiber.

[0496] The TFE / VDF copolymer can also be dissolved in an organic solvent to obtain a solution of the TFE / VDF copolymer. Examples of the organic solvent include nitrogen-containing organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and dimethylformamide; ketone-based solvents such as acetone, methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone; ester-based solvents such as ethyl acetate and butyl acetate; ether-based solvents such as tetrahydrofuran and dioxane; and mixtures thereof. The solution can be used as a binder for batteries.

[0497] It is also preferable to coat the aqueous dispersion of the TFE / VDF copolymer on a porous substrate made of a polyolefin resin and use it as a composite porous membrane. It is also preferable to disperse inorganic particles and / or organic particles in the aqueous dispersion and coat it on a porous substrate and use it as a composite porous membrane. The composite porous membrane obtained in this way can be used as a separator for a lithium secondary battery, etc.

[0498] The melt-processible fluororesin powder can be suitably used as a powder coating. When a powder coating made of the melt-processible fluororesin powder is applied to a substrate, a coating with a smooth surface can be obtained. Melt-processible fluororesin powders having an average particle size of 1 μm or more and less than 100 μm are particularly suitable as powder coatings to be used in electrostatic coating, and melt-processible fluororesin powders having an average particle size of 100 μm or more and 1000 μm or less are particularly suitable as powder coatings to be used in spin coating or spin molding.

[0499] The melt-processable fluororesin powder can be produced by a method of obtaining a powder by drying the aqueous dispersion of the melt-processable fluororesin obtained by the first production method of the present disclosure. The production method for producing the melt-processable fluororesin powder also constitutes part of the present disclosure.

[0500] (III) Fluorine rubber In step C, the polymerization of the fluororubber is carried out by charging pure water and the polymer (I) into a pressure-resistant reaction vessel equipped with a stirrer, deoxidizing, charging the monomer, adjusting the temperature to a predetermined level, and adding a polymerization initiator to initiate the reaction. As the pressure decreases as the reaction progresses, additional monomer is continuously or intermittently supplied to maintain the initial pressure. Once a predetermined amount of monomer has been supplied, the supply is stopped, the monomer is purged from the reaction vessel, and the temperature is returned to room temperature to terminate the reaction. In this case, the polymer latex can be continuously removed from the reaction vessel.

[0501] In particular, when a thermoplastic elastomer is produced as the fluororubber, as disclosed in International Publication No. 00 / 01741, it is possible to use a method in which fluoropolymer fine particles are first synthesized at a high concentration as described above, then diluted and further polymerized, thereby making it possible to increase the final polymerization rate compared to normal polymerization.

[0502] The polymerization conditions for the fluororubber are appropriately selected from the viewpoints of the desired properties of the polymer and control of the polymerization rate, and the polymerization temperature is usually −20 to 200° C., preferably 5 to 150° C., and the polymerization pressure is usually 0.5 to 10 MPaG, preferably 1 to 7 MPaG. The pH of the polymerization medium is preferably maintained at 2.5 to 13 by a known method or the like using a pH adjuster described below.

[0503] Monomers used in the polymerization of the fluororubber include, in addition to vinylidene fluoride, fluorine-containing ethylenically unsaturated monomers that have at least the same number of fluorine atoms as the carbon atoms and are copolymerizable with vinylidene fluoride. Examples of the fluorine-containing ethylenically unsaturated monomers include trifluoropropene, pentafluoropropene, hexafluorobutene, and octafluorobutene. Among these, hexafluoropropene is particularly suitable due to the properties of the elastomer obtained when it blocks the crystal growth of the polymer. Examples of the fluorine-containing ethylenically unsaturated monomers include trifluoroethylene, TFE, and CTFE. Fluorine-containing monomers having one or more chlorine and / or bromine substituents can also be used. Perfluoro(alkyl vinyl ethers), such as perfluoro(methyl vinyl ether), can also be used. TFE and HFP are preferred for producing fluororubbers.

[0504] The preferred monomer composition (mass%) of the fluororubber is vinylidene fluoride:HFP:TFE=(20-70):(30-48):(0-32). The fluororubber of this composition exhibits good elastomeric properties, chemical resistance, and thermal stability.

[0505] In the polymerization of the fluororubber, the amount of the polymer (I) added can be the same as the amount of the polymer (I) added in the step C, but it is usually added in an amount of 0.0001 to 20% by mass relative to 100% by mass of the aqueous medium, preferably 10% by mass or less, and more preferably 2% by mass or less.

[0506] In the polymerization of the fluororubber, known inorganic radical polymerization initiators can be used as the polymerization initiator. As the inorganic radical polymerization initiator, conventionally known water-soluble inorganic peroxides, such as sodium, potassium, and ammonium persulfates, perphosphates, perborates, percarbonates, or permanganates, are particularly useful. The radical polymerization initiator can be further activated with a reducing agent, such as sodium, potassium, or ammonium sulfites, bisulfites, metabisulfites, hyposulfites, thiosulfates, phosphites, or hypophosphites, or with easily oxidizable metal compounds, such as ferrous salts, cuprous salts, or silver salts. A preferred inorganic radical polymerization initiator is ammonium persulfate, and it is more preferred to use ammonium persulfate and sodium bisulfite in a redox system.

[0507] The concentration of the polymerization initiator added is determined appropriately depending on the molecular weight of the target fluoropolymer and the polymerization reaction rate, but is set to an amount of 0.0001 to 10 mass %, preferably 0.01 to 5 mass %, relative to 100 mass % of the total amount of monomers.

[0508] In the polymerization of the fluororubber, known chain transfer agents can be used, including hydrocarbons, esters, ethers, alcohols, ketones, chlorine compounds, carbonates, etc., and in the polymerization of thermoplastic elastomers, hydrocarbons, esters, ethers, alcohols, chlorine compounds, iodine compounds, etc. Among these, acetone and isopropyl alcohol are preferred, and in the polymerization of thermoplastic elastomers, isopentane, diethyl malonate, and ethyl acetate are preferred from the viewpoint of being less likely to decrease the reaction rate, and diiodine compounds such as I(CF2)4I, I(CF2)6I, and ICH2I are preferred from the viewpoint of being capable of iodinating polymer terminals and being usable as reactive polymers.

[0509] The amount of the chain transfer agent used is usually 0.5 × 10 -3 ~5×10 -3 mol%, preferably 1.0×10 -3~3.5×10 -3 It is preferably expressed as mole percent.

[0510] In the polymerization of the fluororubber, paraffin wax or the like can be preferably used as an emulsion stabilizer, and in the polymerization of the thermoplastic elastomer, phosphates, sodium hydroxide, potassium hydroxide or the like can be preferably used as a pH adjuster.

[0511] The pre-treatment aqueous dispersion containing fluororubber obtained in step C has a solids concentration of 1.0 to 40 mass %, an average particle size of 0.03 to 1 μm, preferably 0.05 to 0.5 μm, and a number average molecular weight of 1,000 to 2,000,000 at the time when the polymerization is completed.

[0512] The aqueous dispersion of fluororubber obtained by the first production method of the present disclosure can be made into a dispersion suitable for rubber molding processing by adding a dispersion stabilizer such as a hydrocarbon surfactant, concentrating it, etc., as necessary. The dispersion is then treated by pH adjustment, coagulation, heating, etc. Each treatment is carried out as follows.

[0513] The pH adjustment is carried out by adding a mineral acid such as nitric acid, sulfuric acid, hydrochloric acid or phosphoric acid, and / or a carboxylic acid having 5 or less carbon atoms and a pK of 4.2 or less to adjust the pH to 2 or less.

[0514] The coagulation is carried out by adding alkaline earth metal salts, such as nitrates, chlorates and acetates of calcium or magnesium.

[0515] Either the pH adjustment or the coagulation may be carried out first, but it is preferable to carry out the pH adjustment first.

[0516] After each operation, the fluororubber is washed with the same volume of water as the fluororubber to remove small amounts of impurities such as buffer solutions and salts present in the fluororubber, and then dried, usually in a drying oven at high temperatures of about 70 to 200°C with circulating air.

[0517] The fluororubber may be a partially fluorinated rubber or a perfluororubber.

[0518] Examples of partially fluorinated rubbers include vinylidene fluoride (VdF)-based fluororubbers, tetrafluoroethylene (TFE) / propylene (Pr)-based fluororubbers, tetrafluoroethylene (TFE) / propylene / vinylidene fluoride (VdF)-based fluororubbers, ethylene / hexafluoropropylene (HFP)-based fluororubbers, ethylene / hexafluoropropylene (HFP) / vinylidene fluoride (VdF)-based fluororubbers, ethylene / hexafluoropropylene (HFP) / tetrafluoroethylene (TFE)-based fluororubbers, etc. Among these, at least one selected from the group consisting of vinylidene fluoride-based fluororubbers and tetrafluoroethylene / propylene-based fluororubbers is preferred.

[0519] The vinylidene fluoride-based fluororubber is preferably a copolymer consisting of 45 to 85 mol % of vinylidene fluoride and 55 to 15 mol % of at least one other monomer copolymerizable with vinylidene fluoride, more preferably a copolymer consisting of 50 to 80 mol % of vinylidene fluoride and 50 to 20 mol % of at least one other monomer copolymerizable with vinylidene fluoride.

[0520] Examples of at least one other monomer copolymerizable with the vinylidene fluoride include tetrafluoroethylene [TFE], hexafluoropropylene [HFP], fluoroalkyl vinyl ether, chlorotrifluoroethylene [CTFE], trifluoroethylene, trifluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, hexafluoroisobutene, vinyl fluoride, and a monomer represented by the general formula (100): CHX 101 =CX 102 Rf 101 (In the formula, X 101 and X 102is H on one side and F on the other side, and Rf 101 is a linear or branched fluoroalkyl group having 1 to 12 carbon atoms), a fluoromonomer represented by the general formula (170): CH2=CH-(CF2) n -X 171 (In the formula, X 171 is H or F, and n is an integer of 3 to 10. Examples of the fluoromonomer include a fluoromonomer represented by the general formula (160), a monomer that provides a crosslinking site, and a non-fluorinated monomer such as ethylene, propylene, or an alkyl vinyl ether. These can be used alone or in any combination. Of these, it is preferable to use at least one selected from the group consisting of TFE, HFP, fluoroalkyl vinyl ether, and CTFE. As the fluoroalkyl vinyl ether, a fluoromonomer represented by the general formula (160) is preferred.

[0521] Specific examples of vinylidene fluoride-based fluororubbers include VdF / HFP-based rubbers, VdF / HFP / TFE-based rubbers, VdF / CTFE-based rubbers, VdF / CTFE / TFE-based rubbers, VDF / fluoromonomer-based rubbers represented by general formula (100), VDF / fluoromonomer-based rubbers represented by general formula (100) / TFE-based rubbers, VDF / perfluoro(methyl vinyl ether) [PMVE]-based rubbers, VDF / PMVE / TFE-based rubbers, VDF / PMVE / TFE / HFP-based rubbers, etc. As the VDF / fluoromonomer-based rubbers represented by general formula (100), VDF / CH2=CFCF3-based rubbers are preferred, and as the VDF / fluoromonomer-based rubbers represented by general formula (100), VDF / TFE / CH2=CFCF3-based rubbers are preferred.

[0522] The VDF / CH2=CFCF3 rubber is preferably a copolymer consisting of 40 to 99.5 mol % of VDF and 0.5 to 60 mol % of CH2=CFCF3, and more preferably a copolymer consisting of 50 to 85 mol % of VDF and 20 to 50 mol % of CH2=CFCF3.

[0523] The tetrafluoroethylene / propylene-based fluororubber is preferably a copolymer consisting of 45 to 70 mol % of tetrafluoroethylene, 55 to 30 mol % of propylene, and 0 to 5 mol % of a fluoromonomer that provides a crosslinking site.

[0524] The fluororubber may be a perfluororubber. The perfluororubber is preferably at least one selected from the group consisting of perfluororubbers containing TFE, such as TFE / fluoromonomer copolymers represented by general formula (160), (130) or (140) and TFE / fluoromonomer copolymers represented by general formula (160), (130) or (140) / monomer copolymers that provide cross-linking sites.

[0525] In the case of a TFE / PMVE copolymer, the composition is preferably 45-90 / 10-55 (mol %), more preferably 55-80 / 20-45, and even more preferably 55-70 / 30-45.

[0526] In the case of a copolymer of TFE / PMVE / monomer that provides a crosslinking site, the ratio is preferably 45 to 89.9 / 10 to 54.9 / 0.01 to 4 (mol %), more preferably 55 to 77.9 / 20 to 49.9 / 0.1 to 3.5, and even more preferably 55 to 69.8 / 30 to 44.8 / 0.2 to 3.

[0527] In the case of TFE / fluoromonomer copolymers having 4 to 12 carbon atoms and represented by general formula (160), (130) or (140), the ratio is preferably 50 to 90 / 10 to 50 (mol %), more preferably 60 to 88 / 12 to 40, and even more preferably 65 to 85 / 15 to 35.

[0528] In the case of a copolymer of TFE / fluoromonomer having 4 to 12 carbon atoms represented by general formula (160), (130) or (140) / monomer providing a crosslinking site, the ratio is preferably 50 to 89.9 / 10 to 49.9 / 0.01 to 4 (mol %), more preferably 60 to 87.9 / 12 to 39.9 / 0.1 to 3.5, and even more preferably 65 to 84.8 / 15 to 34.8 / 0.2 to 3.

[0529] If the composition is outside these ranges, the rubber elastic properties will be lost and the properties will tend to become more like those of a resin.

[0530] The perfluororubber is preferably at least one selected from the group consisting of TFE / fluoromonomer copolymer represented by general formula (140) / crosslinkable moiety-providing fluoromonomer, TFE / perfluorovinyl ether copolymer represented by general formula (140), TFE / fluoromonomer copolymer represented by general formula (160), and TFE / fluoromonomer copolymer represented by general formula (160) / crosslinkable moiety-providing monomer copolymer.

[0531] Examples of the perfluororubber include those described in International Publication No. 97 / 24381, Japanese Patent Publication No. 61-57324, Japanese Patent Publication No. 4-81608, and Japanese Patent Publication No. 5-13961.

[0532] The fluororubber has a glass transition temperature of preferably −70° C. or higher, more preferably −60° C. or higher, and even more preferably −50° C. or higher, from the viewpoint of excellent compression set at high temperatures. Also, from the viewpoint of good cold resistance, the glass transition temperature is preferably 5° C. or lower, more preferably 0° C. or lower, and even more preferably −3° C. or lower.

[0533] The glass transition temperature can be determined by obtaining a DSC curve using a differential scanning calorimeter (DSC822e, manufactured by Mettler-Toledo) by heating 10 mg of a sample at a rate of 10°C / min, and by determining the temperature at the midpoint of the two intersections between an extension of the baseline before and after the second-order transition of the DSC curve and a tangent to the inflection point of the DSC curve.

[0534] In terms of good heat resistance, the fluororubber preferably has a Mooney viscosity ML(1+20) at 170°C of 30 or more, more preferably 40 or more, and even more preferably 50 or more. In terms of good processability, the Mooney viscosity ML(1+20) is preferably 150 or less, more preferably 120 or less, and even more preferably 110 or less.

[0535] In terms of good heat resistance, the fluororubber preferably has a Mooney viscosity ML(1+20) at 140°C of 30 or more, more preferably 40 or more, and even more preferably 50 or more. In terms of good processability, the Mooney viscosity ML(1+20) is preferably 180 or less, more preferably 150 or less, and even more preferably 110 or less.

[0536] In terms of good heat resistance, the fluororubber preferably has a Mooney viscosity ML(1+10) at 100°C of 10 or more, more preferably 20 or more, and even more preferably 30 or more. In terms of good processability, the Mooney viscosity ML(1+10) is preferably 120 or less, more preferably 100 or less, and even more preferably 80 or less.

[0537] The Mooney viscosity can be measured using a Mooney viscometer MV2000E manufactured by ALPHA TECHNOLOGIES at 170°C, 140°C or 100°C in accordance with JIS K6300.

[0538] The pre-treatment aqueous dispersion containing fluororubber used in the first production method of the present disclosure may be in any form obtained from the above polymerization, and may be an aqueous dispersion as-polymerized, a diluted or concentrated aqueous dispersion as-polymerized, or a dispersion that has been subjected to a dispersion stabilization treatment. The aqueous fluoropolymer dispersion containing fluororubber obtained by the first production method of the present disclosure can also be used as a gum or crumb obtained by coagulation, drying, or the like using a conventionally known method. The polymer (I) used in step C can improve the stability of the aqueous dispersion, and is preferably used in a polymerization method in which a poorly water-soluble substance, such as an initiator such as an organic peroxide or a chain transfer agent such as an iodine or bromine compound, is added during the polymerization, as described above.

[0539] The gum is a small granular mass made of fluororubber, and the crumb is an amorphous mass formed as a result of the fluororubber being unable to maintain its granular shape as a gum at room temperature and fusing together.

[0540] The above fluororubber can be processed into a fluororubber composition by adding a curing agent, a filler, etc.

[0541] Examples of the curing agent include polyols, polyamines, organic peroxides, organotins, bis(aminophenol)tetraamines, and bis(thioaminophenols).

[0542] The fluororubber composition is made of the above-mentioned fluororubber, and is therefore advantageous in that it does not substantially contain an emulsifier and is easily crosslinked during molding.

[0543] A fluororubber molded article can be obtained by molding the above fluororubber. The method for the molding process is not particularly limited, and includes known methods using the above-mentioned curing agents.

[0544] The fluororubber molded article is suitable for use as a seal, a gasket, a wire coating, a hose, a tube, a laminate, an accessory, etc., and is particularly suitable for use as a part for semiconductor manufacturing equipment, an automobile part, etc.

[0545] The first production method of the present disclosure provides an aqueous fluoropolymer dispersion. The aqueous fluoropolymer dispersion may contain a hydrocarbon surfactant, such as the hydrocarbon surfactants described above. The hydrocarbon surfactants can be suitably used as dispersants for dispersing the fluoropolymer obtained by polymerization in an aqueous medium.

[0546] The present disclosure further provides an aqueous fluoropolymer dispersion comprising a polymer (I) comprising polymerized units (I) based on a monomer represented by the following general formula (I), an aqueous medium, and a fluoropolymer (excluding the polymer (I)), wherein the difference ΔL* between the lightness L* of the aqueous fluoropolymer dispersion and the lightness L* of a post-microfiltration aqueous fluoropolymer dispersion obtained by microfiltration of the aqueous fluoropolymer dispersion (aqueous fluoropolymer dispersion after purification under conditions using a microfiltration membrane) is less than 16: CX 1 X 3 =CX 2 R(-CZ 1 Z 2 -A 0 ) m (I) (In the formula, X 1 and X 3 are each independently F, Cl, H, or CF; X 2 is H, F, an alkyl group or a fluorine-containing alkyl group; A 0 is an anionic group; R is a linking group; Z 1 and Z 2 are each independently H, F, an alkyl group or a fluorine-containing alkyl group; and m is an integer of 1 or more. The specific method of the above purification (microfiltration) was as follows: 1.82 g of a nonionic surfactant was added to 156.4 g of the fluoropolymer aqueous dispersion, and 0.72 g of a nonionic surfactant was added to 156.4 g of pure water to make additional water. The mixture was filtered through a microfiltration membrane (made of polyethylene, inner diameter 0.7 mm, length 130 mm, average pore size 0.1 μm, effective membrane area 150 cm). 2 The microfiltration was carried out under the conditions of bringing the aqueous dispersion into contact with a filter medium under a water pressure of 0.1 MPa and a temperature of 25°C. The above ΔL* is a value represented by the following formula, and is the absolute value of the value obtained by subtracting the lightness L* before purification from the lightness L* after purification. ΔL* = |L* after purification - L* before purification| The above ΔL* is more preferably 12 or less, even more preferably 8 or less, even more preferably 5 or less, particularly preferably 3 or less, and particularly preferably 1 or less.

[0547] The aqueous fluoropolymer dispersion of the present disclosure can be obtained by the first production method of the present disclosure described above.

[0548] The fluoropolymer aqueous dispersion obtained by the first production method of the present disclosure and the fluoropolymer in the fluoropolymer aqueous dispersion of the present disclosure are preferably fluororesins, and among these, the fluororesins having a fluorine substitution rate of 50% or more are even more preferred, those having a fluorine substitution rate of more than 50% are even more preferred, those having a fluorine substitution rate of 55% or more are even more preferred, those having a fluorine substitution rate of 60% or more are even more preferred, those having a fluorine substitution rate of 75% or more are even more preferred, those having a fluorine substitution rate of 80% or more are particularly preferred, and those having a fluorine substitution rate of 90 to 100% are most preferred, i.e., perfluororesins. As the perfluororesin, those having a fluorine substitution rate of 95 to 100% are more preferred, and PTFE, FEP, and PFA are even more preferred, with PTFE being particularly preferred. As the PTFE, any of the embodiments described in the first production method of the present disclosure can be used. The fluoropolymer aqueous dispersion obtained by the first production method of the present disclosure and the fluoropolymer in the fluoropolymer aqueous dispersion of the present disclosure are preferably PTFE, FEP, or TFE / perfluoro(alkyl vinyl ether) copolymer, and more preferably PTFE.

[0549] The aqueous fluoropolymer dispersion obtained by the first production method of the present disclosure and the aqueous fluoropolymer dispersion of the present disclosure preferably have a polymer (I) content of 0.0001 to 10% by mass. If the content is less than 0.0001% by mass, the dispersion stability may be poor, and if the content exceeds 10% by mass, the dispersion effect will not be commensurate with the amount present, making it impractical. The lower limit of the content of the polymer (I) is more preferably 0.001% by mass, the upper limit is more preferably 5% by mass, and the upper limit is still more preferably 3% by mass. The content of the polymer (I) can be measured by solid-state NMR as described above. The aqueous fluoropolymer dispersion obtained by the first production method of the present disclosure, and the aqueous fluoropolymer dispersion of the present disclosure may contain one single type of polymer (I), or may contain two or more different types of polymers (I).

[0550] All of the aspects described in the first production method of the present disclosure can be applied to the polymer (I).

[0551] The aqueous fluoropolymer dispersion of the present disclosure also preferably contains a nonionic surfactant. The nonionic surfactant may be any of the hydrocarbon surfactants listed above, and is preferably at least one selected from the group consisting of the compounds represented by the general formula (i) and the compounds represented by the general formula (ii).

[0552] The fluoropolymer content in the aqueous fluoropolymer dispersion obtained by the production method of the present disclosure and in the aqueous fluoropolymer dispersion of the present disclosure is not limited, but may be, for example, 0.01 to 80% by mass. It is preferably 0.02% by mass or more, more preferably 0.05% by mass or more, even more preferably 20% by mass or more, particularly preferably 30% by mass or more, and preferably 75% by mass or less, more preferably 70% by mass or less, even more preferably 55% by mass or less, particularly preferably 50% by mass or less, and most preferably 45% by mass or less. The fluoropolymer content in the aqueous fluoropolymer dispersion obtained by the production method of the present disclosure and the aqueous fluoropolymer dispersion of the present disclosure can be determined, for example, by a method of separating solid components using an MF membrane. In the aqueous fluoropolymer dispersion obtained by the production method of the present disclosure, and in the aqueous fluoropolymer dispersion of the present disclosure, the total amount of polymer (I), water, and fluoropolymer is preferably 95.0 mass% or more, more preferably 99.0 mass% or more, and even more preferably 99.9 mass% or more, and it is particularly preferable that the aqueous fluoropolymer dispersion consists essentially of polymer (I), water, and fluoropolymer.

[0553] The aqueous fluoropolymer dispersion obtained by the production method of the present disclosure and the above-mentioned aqueous fluoropolymer dispersion preferably have a lightness L* of 70 or more. More preferably, it is 80 or more, and even more preferably, it is 90 or more. The lightness L* may be greater than 86, greater than 91, or greater than 95. The lightness L* is measured by an X-rite colorimeter.

[0554] The aqueous fluoropolymer dispersion obtained by the first production method of the present disclosure and the aqueous fluoropolymer dispersion of the present disclosure are preferably substantially free of fluorine-containing surfactant. In the aqueous fluoropolymer dispersion of the present disclosure, "substantially free of fluorine-containing surfactant" means that the fluorine-containing surfactant is 10 ppm by mass or less relative to the fluoropolymer. The content of fluorine-containing surfactant is preferably 1 ppm by mass or less, more preferably 100 ppb by mass or less, even more preferably 10 ppb by mass or less, and particularly preferably below the detection limit of the fluorine-containing surfactant as measured by liquid chromatography-mass spectrometry (LC / MS / MS). The amount of the fluorine-containing surfactant can be quantified by a known method. For example, it can be quantified by LC / MS / MS analysis. First, the obtained aqueous dispersion is extracted with an organic solvent such as methanol, and molecular weight information of the extract is extracted from the LC / MS / MS spectrum, and its agreement with the structural formula of the candidate surfactant is confirmed. Then, aqueous solutions of the confirmed surfactants at five or more levels of concentration are prepared, and LC / MS / MS analysis is performed at each concentration to create a calibration curve with the area. The resulting aqueous dispersion is subjected to Soxhlet extraction with methanol, and the extract is subjected to LC / MS / MS analysis for quantitative measurement. That is, the content of fluorine-containing surfactant can be quantified, for example, by LC / MS / MS analysis. First, methanol is added to the aqueous dispersion to perform extraction, and the resulting extract is analyzed by LC / MS / MS. To further improve the extraction efficiency, Soxhlet extraction, ultrasonic treatment, or other treatments may be performed. Molecular weight information is extracted from the obtained LC / MS / MS spectrum, and a match with the structural formula of the candidate fluorine-containing surfactant is confirmed. Then, aqueous solutions containing five or more levels of the identified fluorine-containing surfactant are prepared, and LC / MS / MS analysis is performed on each of the solutions. The relationship between the content and the area relative to that content is plotted, and a calibration curve is drawn. Then, using the calibration curve, the area of ​​the LC / MS / MS chromatogram of the fluorine-containing surfactant in the extract can be converted to the fluorine-containing surfactant content. The fluorine-containing surfactant is the same as that exemplified in the first production method of the present disclosure. For example, it may be a surfactant containing fluorine atoms and having a total carbon number of 20 or less excluding the anionic group, a surfactant containing fluorine atoms and having a molecular weight of 800 or less in the anionic group, and a fluorine-containing surfactant having a LogPOW of 3.5 or less. The anionic fluorine-containing surfactants include those represented by the general formula (N 0 ) and specifically, compounds represented by the general formula (N 1 ), a compound represented by the general formula (N 2 ), a compound represented by the general formula (N 3 ), a compound represented by the general formula (N 4 ) and a compound represented by the general formula (N 5) represented by the general formula (IX), fluorocarboxylic acid (X) represented by the general formula (X), alkoxyfluorosulfonic acid (XI) represented by the general formula (XI), ω-H perfluorocarboxylic acid (II) represented by the general formula (II), perfluoropolyether carboxylic acid (III) represented by the general formula (III), perfluoroalkyl alkylene carboxylic acid (IV) represented by the general formula (IV), perfluoroalkoxyfluorocarboxylic acid (V) represented by the general formula (V), perfluoroalkyl sulfonic acid (VI) represented by the general formula (VII), ω-H perfluorosulfonic acid (VII) represented by the general formula (VII), perfluoroalkyl alkylene sulfonic acid (VIII) represented by the general formula (VIII), alkyl alkylene carboxylic acid (IX) represented by the general formula (IX), fluorocarboxylic acid (X) represented by the general formula (X), alkoxyfluorosulfonic acid (XI) represented by the general formula (XI), compound (XII) represented by the general formula (XII), compound (XIII) represented by the general formula (XIII), etc.

[0555] The aqueous fluoropolymer dispersion obtained by the first production method of the present disclosure and the aqueous fluoropolymer dispersion of the present disclosure may be concentrated or subjected to a dispersion stabilization treatment to form a dispersion, or may be subjected to coagulation or aggregation, recovered, and dried to form a powder or other solid.

[0556] The aqueous fluoropolymer dispersion obtained by the first production method of the present disclosure and the aqueous fluoropolymer dispersion of the present disclosure can contain conventionally known additives such as pigments and fillers. The additives may be used within a range that does not impair the effects of the present disclosure.

[0557] The polymer (I) may be removed by the above concentration operation.

[0558] The aqueous fluoropolymer dispersion obtained by carrying out the first production method of the present disclosure can also be subjected to a dispersion stabilization treatment without concentration depending on the application, to prepare an aqueous dispersion having a long pot life. Examples of the dispersion stabilizer to be used include the same as those described above.

[0559] The uses of the aqueous fluoropolymer dispersion are not particularly limited, and examples of applications of the aqueous dispersion as is include coating, which involves applying the dispersion as is to a substrate, drying, and optionally baking; impregnation, which involves impregnating a porous support such as a nonwoven fabric or a resin molded product, drying, and preferably baking; and cast film formation, which involves applying the dispersion to a substrate such as glass, drying, and optionally immersing the substrate in water and peeling it off to obtain a thin film. Examples of these applications include aqueous dispersion-type paints, electrode binders, and electrode water repellents.

[0560] The above-mentioned aqueous fluoropolymer dispersion can be used as an aqueous coating material by blending it with known compounding agents such as pigments, thickeners, dispersants, antifoaming agents, antifreezing agents, film-forming aids, etc., or by further combining it with other polymer compounds. As an additive, it can be used as a binder to prevent the active material of an electrode from falling off, as a compound such as an anti-drip agent, or as a dust suppression treatment to prevent the scattering of soil, sand, dust, etc.

[0561] An anionic surfactant may be preferably contained in order to adjust the viscosity of the aqueous fluoropolymer dispersion or to improve the miscibility of pigments, fillers, etc. The anionic surfactant may be added as appropriate within an economically and environmentally acceptable range.

[0562] The anionic surfactant may be a non-fluorinated anionic surfactant or a fluorine-containing anionic surfactant, but a non-fluorinated anionic surfactant that does not contain fluorine, that is, a hydrocarbon anionic surfactant, is preferred.

[0563] For the purpose of adjusting viscosity, any known anionic surfactant may be used without particular limitation. For example, anionic surfactants described in International Publication Nos. 2013 / 146950 and 2013 / 146947 may be used. Examples include anionic surfactants having a saturated or unsaturated aliphatic chain containing 6 to 40 carbon atoms, preferably 8 to 20 carbon atoms, and more preferably 9 to 13 carbon atoms. The saturated or unsaturated aliphatic chain may be either a linear or branched chain, or may have a cyclic structure. The hydrocarbon may be aromatic or may have an aromatic group. The hydrocarbon may have a heteroatom such as oxygen, nitrogen, or sulfur. Examples of anionic surfactants include alkyl sulfonates, alkyl sulfates, alkylaryl sulfates, and salts thereof; aliphatic (carboxylic) acids and salts thereof; alkyl phosphates, alkylaryl phosphates, and salts thereof; and among these, alkyl sulfonates, alkyl sulfates, aliphatic carboxylic acids, and salts thereof are preferred. The alkyl sulfate or its salt is preferably ammonium lauryl sulfate or sodium lauryl sulfate. The aliphatic carboxylic acid or its salt is preferably succinic acid, decanoic acid, undecanoic acid, undecenoic acid, lauric acid, hydrododecanoic acid, or a salt thereof.

[0564] The amount of anionic surfactant added varies depending on the types of anionic surfactant and other compounding ingredients, but is preferably 10 ppm to 5000 ppm based on the solid content mass of the fluoropolymer. The lower limit of the amount of anionic surfactant added is more preferably 50 ppm or more, and even more preferably 100 ppm or more. If the amount added is too small, the viscosity adjusting effect is poor. The upper limit of the amount of anionic surfactant added is more preferably 3000 ppm or less, and even more preferably 2000 ppm or less. If the amount added is too large, the mechanical stability and storage stability of the aqueous dispersion may be impaired.

[0565] For the purpose of adjusting the viscosity of the aqueous fluoropolymer dispersion, in addition to the anionic surfactant, for example, methyl cellulose, alumina sol, polyvinyl alcohol, carboxylated vinyl polymer, etc. may be blended.

[0566] The above aqueous fluoropolymer dispersion may contain other polymer compounds as required, provided that the characteristics of the aqueous fluoropolymer dispersion are not impaired. The other polymer compounds are not particularly limited, and examples thereof include polyethylene oxide (dispersion stabilizer), polyethylene glycol (dispersion stabilizer), phenol resin, urea resin, epoxy resin, melamine resin, polyester resin, polyether resin, acrylic silicone resin, silicone resin, silicone polyester resin, and polyurethane resin.

[0567] A fluoropolymer can be produced by washing and drying the fluoropolymer-containing coagulate obtained by coagulating the aqueous fluoropolymer dispersion. The polymer (I), decomposition products and by-products of the polymer (I), and residual monomers produced as by-products from the polymer (I) can be recovered and purified from the wastewater generated by the coagulation or washing and / or the off-gas generated during the drying process, allowing the polymer (I), decomposition products and by-products of the polymer (I), and residual monomers can be reused. The recovery and purification methods are not particularly limited, and can be carried out by known methods. For example, the methods described in JP-A-2011-520020, U.S. Patent Application Publication Nos. 2007 / 15937, 2007 / 25902, and 2007 / 27251 are examples. Specific examples include the following methods.

[0568] Examples of a method for recovering the polymer (I), decomposition products and by-products of the polymer (I) that are by-produced from the polymer (I), residual monomers, etc. from the wastewater include a method in which the wastewater is brought into contact with adsorption particles such as ion exchange resin, activated carbon, silica gel, clay, zeolite, etc. to adsorb the polymer (I), etc., and then the wastewater is separated from the adsorption particles, and the adsorption particles that have adsorbed the polymer (I), etc. are recovered. Incineration of the adsorption particles that have adsorbed the polymer (I), etc., can prevent the release of the polymer (I), etc. into the environment.

[0569] Alternatively, the polymer (I) or the like can be recovered by desorbing and eluting it from ion exchange resin particles that have adsorbed the polymer (I) or the like using a known method. For example, when the ion exchange resin particles are anion exchange resin particles, the polymer (I) or the like can be eluted by contacting a mineral acid with the anion exchange resin. Subsequently, when a water-soluble organic solvent is added to the resulting eluate, the mixture usually separates into two phases. The lower phase containing the polymer (I) or the like can be recovered by neutralizing it. Examples of the water-soluble organic solvent include polar solvents such as alcohols, ketones, and ethers.

[0570] Other methods for recovering the polymer (I) and the like from the ion exchange resin particles include a method using an ammonium salt and a water-soluble organic solvent, and a method using an alcohol and, if desired, an acid. In the latter method, an ester derivative of the polymer (I) and the like is produced, which can be easily separated from the alcohol by distillation, and the polymer (I) and the like can be easily recovered.

[0571] If the wastewater contains fluoropolymer particles or other solids, it is preferable to remove them from the wastewater before contacting the wastewater with the adsorbent particles. Methods for removing the fluoropolymer particles and other solids include a method in which aluminum salts or the like are added to precipitate them, followed by separating the wastewater from the precipitate and removing the precipitate, and electrocoagulation. Mechanical methods, such as crossflow filtration, depth filtration, and precoat filtration, may also be used for removal. The concentration of the unagglomerated fluoropolymer in the wastewater is preferably low from the viewpoint of productivity, more preferably less than 0.4 mass %, particularly preferably less than 0.3 mass %.

[0572] A method for recovering the polymer (I) and the like from the off-gas includes using a scrubber to contact the off-gas with deionized water, an aqueous alkali solution, an organic solvent such as a glycol ether solvent, and the like to obtain a scrubber solution containing the polymer (I) and the like. When a highly concentrated aqueous alkali solution is used as the aqueous alkali solution, the scrubber solution can be recovered in a state in which the polymer (I) and the like are phase-separated, facilitating the recovery and reuse of the polymer (I) and the like. Examples of the alkali compound include alkali metal hydroxides and quaternary ammonium salts.

[0573] The scrubber solution containing the polymer (I) and the like may be concentrated using a reverse osmosis membrane or the like. The concentrated scrubber solution usually contains fluoride ions, but by adding alumina after concentration to remove the fluoride ions, it is possible to facilitate the reuse of the polymer (I) and the like. Alternatively, the scrubber solution may be brought into contact with adsorbent particles to adsorb the polymer (I) and the like, and the polymer (I) and the like may be recovered by the method described above.

[0574] The polymer (I) and the like recovered by any of the above methods can be reused in the production of a fluoropolymer.

[0575] The present disclosure also provides a method for producing an aqueous fluoropolymer dispersion, characterized by comprising a step A' of carrying out ultrafiltration, microfiltration, or dialysis membrane treatment, or a combination thereof, on a pre-treatment aqueous dispersion containing a fluoropolymer (excluding the water-soluble polymer) obtained by polymerization in the presence of a water-soluble polymer in which the proportion of hydrogen atoms bonded to carbon atoms substituted with fluorine atoms is 50% or more (hereinafter also referred to as the "second production method of the present disclosure"). The second production method of the present disclosure can employ all of the same methods and aspects as the first production method described above, except that a water-soluble polymer in which 50% or more of hydrogen atoms bonded to carbon atoms have been substituted with fluorine atoms is used instead of polymer (I). The aqueous fluoropolymer dispersion obtained by the second production method of the present disclosure may contain one single water-soluble polymer or may contain two or more different water-soluble polymers.

[0576] The water-soluble polymer is not particularly limited, and any water-soluble polymer of the above-mentioned polymer (I) in which 50% or more of the hydrogen atoms bonded to carbon atoms have been substituted with fluorine atoms can be used, or any water-soluble polymer other than the above-mentioned polymer (I) in which 50% or more of the hydrogen atoms bonded to carbon atoms have been substituted with fluorine atoms can be used.

[0577] Examples of the water-soluble polymer include those represented by the following general formula (I): CX 1 X 3 =CX 2 R-CZ 1 Z 2 -A 0 (I) (In the formula, X 1 , X 2 and X 3 are each independently F, Cl, H, or CF; A 0 is an anionic group; R is a linking group; Z 1 and Z 2 are each independently F or CF3. Examples of suitable water-soluble polymers include those containing polymerized units (I) based on a monomer represented by the following formula: In the water-soluble polymer, the content of the polymerized unit (I) is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 99% by mass or more.

[0578] The water-soluble polymer may contain polymerized units based on a fluorine-containing monomer such as trifluoroethylene, tetrafluoroethylene (TFE), vinylidene fluoride (VdF), vinyl fluoride (VF), chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), hexafluoroisobutylene, perfluoroalkylethylene, or fluorovinyl ether (FVE).

[0579] The water-soluble polymer may also contain polymerized units based on a non-fluorine-containing monomer. The non-fluorine-containing monomer may be a monomer having a radically polymerizable ethylenically unsaturated bond, and examples thereof include acrylic acid esters, methacrylic acid esters, unsaturated carboxylic acids, hydrolyzable silyl group-containing monomers, hydroxyl group-containing alkyl vinyl ethers, carboxylic acid vinyl esters, and α-olefins. Among these, the non-fluorine-containing monomer is preferably at least one selected from the group consisting of acrylic acid esters, methacrylic acid esters, unsaturated carboxylic acids, and hydrolyzable silyl group-containing monomers. The non-fluorine-containing monomer is more preferably at least one monomer selected from the group consisting of acrylic acid esters and methacrylic acid esters, unsaturated carboxylic acids, and at least one monomer selected from the group consisting of hydrolyzable silyl group-containing monomers. In addition, a monomer having a radically polymerizable ethylenically unsaturated bond may be used in combination.

[0580] The acrylic acid ester or methacrylic acid ester is preferably an acrylic acid alkyl ester in which the alkyl group has 1 to 10 carbon atoms, or a methacrylic acid alkyl ester in which the alkyl group has 1 to 10 carbon atoms. Examples of the acrylic acid alkyl ester and the methacrylic acid alkyl ester include (meth)acrylic acid alkyl esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, methyl methacrylate, n-propyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate. The alkyl acrylate or alkyl methacrylate may also be a hydroxyl group-containing acrylic monomer having a hydroxyl group and a (meth)acryloyl group in the molecule, such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, or 4-hydroxybutyl methacrylate. These acrylic acid esters or methacrylic acid esters may be used alone or in combination of two or more kinds, and n-butyl acrylate and methyl methacrylate are preferred.

[0581] Among them, the non-fluorine-containing monomer is preferably at least one (meth)acrylic acid alkyl ester selected from the group consisting of methyl methacrylate, n-butyl acrylate, 2-ethylhexyl methacrylate, and cyclohexyl methacrylate, wherein the acrylic acid ester or methacrylic acid ester does not contain a hydrolyzable silyl group.

[0582] As the acrylic acid ester or methacrylic acid ester, a combination of n-butyl acrylate and methyl methacrylate or a combination of n-butyl acrylate, methyl methacrylate and 2-ethylhexyl methacrylate is more preferred, and a combination of n-butyl acrylate, methyl methacrylate and 2-ethylhexyl methacrylate is particularly preferred. In addition, it is also preferred to combine a hydroxyl group-containing acrylic monomer having a hydroxyl group and a (meth)acryloyl group.

[0583] Specific examples of the unsaturated carboxylic acids include acrylic acid, methacrylic acid, vinylacetic acid, crotonic acid, cinnamic acid, 3-allyloxypropionic acid, 3-(2-allyloxyethoxycarbonyl)propionic acid, itaconic acid, itaconic acid monoester, maleic acid, maleic acid monoester, maleic anhydride, fumaric acid, fumaric acid monoester, vinyl phthalate, vinyl pyromellitic acid, undecylenic acid, etc. Among these, at least one selected from the group consisting of acrylic acid, methacrylic acid, vinylacetic acid, crotonic acid, itaconic acid, maleic acid, maleic acid monoester, fumaric acid, fumaric acid monoester, 3-allyloxypropionic acid, and undecylenic acid is preferred because of its low homopolymerizability, making it difficult to form a homopolymer, and because the introduction of a carboxyl group is easily controlled.

[0584] Examples of the hydrolyzable silyl group-containing monomer include: CH2=CHCOO(CH2)3Si(OCH3)3, CH2=CHCOO(CH2)3Si(CH3)(OCH3)2, CH2=CHCOO(CH2)3Si(OC2H5)3, CH2=CHCOO(CH2)3Si(CH3)(OC2H5)2, CH2=C(CH3)COO(CH2)3Si(OCH3)3, CH2=C(CH3)COO(CH2)3Si(CH3)(OCH3)2, CH2=C(CH3)COO(CH2)3Si(OC2H5)3, CH2=C(CH3)COO(CH2)3Si(CH3)(OC2H5)2, CH2=C(CH3)COO(CH2)2O(CH2)3Si(OCH3)3, CH2=C(CH3)COO(CH2)2(CH2)3Si(CH3)(OCH3)2, CH2=C(CH3)COO(CH2) 11 Si(OCH3)3, CH2=C(CH3)COO(CH2) 11 Si(CH3)(OCH3)2, These hydrolyzable silyl group-containing monomers may be used alone or in combination. Two or more types may be used in combination.

[0585] As the hydrolyzable silyl group-containing monomer, at least one selected from the group consisting of γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltriethoxysilane, and γ-methacryloxypropylmethyldiethoxysilane is preferred, and γ-methacryloxypropyltriethoxysilane is more preferred.

[0586] Examples of the hydroxyl group-containing alkyl vinyl ethers include 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxy-2-methylbutyl vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, 2-hydroxyethyl allyl ether, 4-hydroxybutyl allyl ether, glycerol monoallyl ether, etc. In terms of excellent polymerization reactivity, at least one selected from the group consisting of 4-hydroxybutyl vinyl ether and 2-hydroxyethyl vinyl ether is preferred.

[0587] Examples of vinyl carboxylate esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caproate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl cyclohexylcarboxylate, vinyl benzoate, and vinyl para-t-butylbenzoate.

[0588] Examples of the α-olefins include ethylene, propylene, n-butene, isobutene, and styrene.

[0589] The number average...

Claims

[Claim 1] A fluoropolymer aqueous dispersion comprising a polymer (I) containing a polymerization unit (I) based on a monomer represented by the following general formula (I), water, and a fluoropolymer (excluding the polymer (I)): The lightness L*1 of the aqueous fluoropolymer dispersion is greater than 95; the difference ΔL* between the lightness L*1 of the aqueous fluoropolymer dispersion and the lightness L*2 of the aqueous fluoropolymer dispersion after microfiltration obtained by microfiltration of the aqueous fluoropolymer dispersion is less than 5; The content of the polymer (I) is 0.0001 mass% or more and 735 mass ppm or less, The number average molecular weight of the polymer (I) is 0.3×10 ４ The aqueous fluoropolymer dispersion is as described above. CX １ X ３ =CX ２ R(-CZ １ Z ２ -A ０ ) ｍ (I) (In the formula, X １ and X ３ are each independently F, Cl, H or CF ３ and X ２ is H, F, an alkyl group or a fluorine-containing alkyl group; A ０ is an anionic group; R is a linking group; Z １ and Z ２ are each independently H, F, an alkyl group or a fluorine-containing alkyl group; and m is an integer of 1 or more. However, the microfiltration was carried out by adding 1.82 g of a nonionic surfactant to 156.4 g of the aqueous fluoropolymer dispersion, adding 0.72 g of a nonionic surfactant to 156.4 g of pure water to prepare additional water, and filtering the mixture through a microfiltration membrane (made of polyethylene, inner diameter 0.7 mm, length 130 mm, average pore size 0.1 μm, effective membrane area 150 cm ２ The fluoropolymer aqueous dispersion is brought into contact with the aqueous dispersion of the fluoropolymer under a water pressure of 0.1 MPa and a temperature of 25°C.

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