Method for producing fluoropolymer

Abstract

Provided is a method for producing a fluoropolymer, the method comprising: preparing a composition containing an aqueous medium and a fluoropolymer by polymerizing a fluoromonomer in the presence of a polymerization initiator and the aqueous medium in a reactor; and bringing the composition into contact with a gas containing at least oxygen.

Description

Fluoropolymer manufacturing method

[0001] The present disclosure relates to methods for making fluoropolymers.

[0002] Patent Document 1 describes a method for producing polytetrafluoroethylene, which comprises bringing tetrafluoroethylene into contact with an aqueous medium containing a water-soluble polymerization initiator to carry out a polymerization reaction, recovering unreacted tetrafluoroethylene after the polymerization reaction, and then washing the contents with an inert gas.

[0003] Special Publication No. 48-034399

[0004] An object of the present disclosure is to provide a method for producing a fluoropolymer, in which a fluoropolymer composition obtained by polymerization is treated by a novel method.

[0005] According to the present disclosure, a method for producing a fluoropolymer is provided, which comprises polymerizing a fluoromonomer in the presence of a polymerization initiator and an aqueous medium in a reactor to prepare a composition containing an aqueous medium and a fluoropolymer, and contacting the composition with a gas containing at least oxygen.

[0006] According to the present disclosure, a method for producing a fluoropolymer can be provided in which a fluoropolymer composition obtained by polymerization is treated by a novel method.

[0007] Before specifically describing the present disclosure, some terms used in the present disclosure will be defined or explained.

[0008] In the present disclosure, fluororesins are partially crystalline fluoropolymers, or fluoroplastics. Fluororesins have a melting point and are thermoplastic, but may be melt-processable or non-melt-processable.

[0009] In the present disclosure, 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, melt-processable fluororesins usually have a melt flow rate of 0.01 to 500 g / 10 min, as measured by the measurement method described below.

[0010] In this disclosure, fluororubber 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. Fluororubber exhibits 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.

[0011] The monomer that provides a crosslinking site is a monomer (cure site monomer) having a crosslinkable group that provides a fluoropolymer with a crosslinking site for forming a crosslink with a curing agent.

[0012] In the present disclosure, polytetrafluoroethylene [PTFE] is preferably a fluoropolymer having a content of tetrafluoroethylene units relative to all polymer units of 99 mol % or more.

[0013] In the present disclosure, the fluororesin (excluding polytetrafluoroethylene) and the fluororubber are both preferably fluoropolymers having a tetrafluoroethylene unit content of less than 99 mol% relative to all polymerized units.

[0014] In the present disclosure, 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.

[0015] In the present disclosure, the term "organic group" refers to a group containing one or more carbon atoms or a group formed by removing one hydrogen atom from an organic compound. The organic group is preferably an alkyl group which may have one or more substituents.

[0016] In this disclosure, 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.).

[0017] In this disclosure, the term "at least 1" includes 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.).

[0018] Specific embodiments of the present disclosure will be described in detail below, but the present disclosure is not limited to the following embodiments.

[0019] The composition obtained by polymerizing a fluoromonomer may contain a fluorine-containing compound having a hydrophilic group in addition to the fluoropolymer.

[0020] In the production method of the present disclosure, a composition containing an aqueous medium and a fluoropolymer is prepared by polymerizing the fluoropolymer, and then the resulting composition is contacted with a gas containing at least oxygen. By using such a production method, a fluoropolymer having a low content of a fluorine-containing compound having a hydrophilic group can be produced.

[0021] That is, the present disclosure relates to a method for producing a fluoropolymer, which comprises polymerizing a fluoromonomer in the presence of a polymerization initiator and an aqueous medium in a reactor to prepare a composition containing an aqueous medium and a fluoropolymer, and then contacting the composition with a gas containing at least oxygen.

[0022] Each step and the materials used in each step will be described in detail below.

[0023] (Fluoromonomer Polymerization) In the production method of the present disclosure, a composition containing an aqueous medium and a fluoropolymer is prepared by polymerizing a fluoromonomer in a reactor in the presence of a polymerization initiator and an aqueous medium.

[0024] The polymerization of the fluoromonomer can be carried out by charging the fluoromonomer, the aqueous medium and, if necessary, other additives into a reactor, stirring the contents of the reactor, maintaining the reactor at a predetermined polymerization temperature, and then adding a predetermined amount of polymerization initiator to start the polymerization reaction. After the start of the polymerization reaction, additional fluoromonomer, polymerization initiator, chain transfer agent, etc. may be added depending on the purpose.

[0025] The method for polymerizing the fluoromonomer is not particularly limited, but emulsion polymerization or suspension polymerization is preferred. When emulsion polymerization is used, a surfactant such as a fluorine-containing surfactant can be charged into the reactor.

[0026] In the suspension polymerization method, usually, without using surfactant or with a small amount of surfactant, fluoromonomer is polymerized in aqueous medium to produce suspension polymerization particles.For example, when tetrafluoroethylene is used as fluoromonomer, suspension polymerization of tetrafluoroethylene is carried out to produce suspension polymerization particles of polytetrafluoroethylene, and the obtained suspension polymerization particles are collected and dried to obtain molding powder of polytetrafluoroethylene.

[0027] In emulsion polymerization, generally, in the presence of surfactant, fluoromonomer is polymerized in aqueous medium, thereby obtain the aqueous dispersion in which the primary particles of fluoropolymer are stably dispersed in aqueous medium.For example, use tetrafluoroethylene as fluoromonomer, carry out emulsion polymerization of tetrafluoroethylene, obtain the aqueous dispersion in which the primary particles of polytetrafluoroethylene are stably dispersed in aqueous medium, and then, by coagulating and drying the primary particles in the obtained aqueous dispersion, can obtain the fine powder of polytetrafluoroethylene.

[0028] (Polymerization initiator) The polymerization initiator used for the polymerization of fluoromonomer 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, it can also be combined with a reducing agent or the like to initiate polymerization as a redox. The concentration of the polymerization initiator is appropriately determined depending on the type of monomer, the molecular weight of the target fluoropolymer, and the reaction rate.

[0029] As the polymerization initiator, an oil-soluble radical polymerization initiator or a water-soluble radical polymerization initiator can be used.

[0030] The oil-soluble radical polymerization initiator may be a known oil-soluble peroxide, for example, dialkyl peroxycarbonates such as diisopropyl peroxydicarbonate and disec-butyl peroxydicarbonate, peroxyesters such as t-butyl peroxyisobutyrate and t-butyl peroxypivalate, dialkyl peroxides such as di-t-butyl peroxide, and the like. Also usable are di(ω-hydro-dodecafluoroheptanoyl) peroxide, di(ω-hydro-tetradecafluorooctanoyl) 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-chlorohexafluorobutyryl)peroxide, di(ω-chlorodecafluorohexanoyl)peroxide, di(ω-chlorotetradecafluorooctanoyl)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.

[0031] 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, perboric acid, perchloric acid, perphosphoric acid, or percarbonate; organic peroxides such as disuccinic acid peroxide or diglutaric acid peroxide; t-butyl permaleate; t-butyl hydroperoxide; etc. A reducing agent such as a sulfite may also be contained, and the amount used may be 0.1 to 20 times the amount of the peroxide.

[0032] For example, when polymerization is carried out at a low temperature of 30°C or less, it is preferable to use a redox initiator that 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. In order 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.

[0033] Examples of the redox initiator include potassium permanganate / oxalic acid, potassium permanganate / ammonium oxalate, 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.

[0034] 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 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.

[0035] The radical concentration during polymerization of fluoromonomers can be adjusted by adding a decomposer. Examples of decomposers include sulfites, bisulfites, bromates, diimines, oxalic acid, 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 decomposer added is in the range of 25 to 300% by mass relative to the amount of oxidizing agent combined as a polymerization initiator (redox initiator). The amount of decomposer added is preferably 25 to 150% by mass, more preferably 50 to 100% by mass. The decomposer is preferably added after 5% by mass of the total fluoromonomer consumed in the polymerization reaction has been polymerized, and more preferably after 10% by mass has been polymerized. The amount of decomposer added is preferably an amount equivalent to 0.1 to 20 ppm by mass of the aqueous medium used, and more preferably an amount equivalent to 3 to 10 ppm by mass.

[0036] (Aqueous medium) The aqueous medium used for the polymerization of the fluoromonomer 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 ether or a ketone, and / or a fluorine-containing organic solvent having a boiling point of 40° C. or less.

[0037] As the aqueous medium, an aqueous medium containing only water or an aqueous medium containing only water and a fluorine-free organic solvent is preferred, as it allows the polymerization of the fluoromonomer to proceed smoothly, and an aqueous medium containing only water is more preferred.

[0038] The content of water in the aqueous medium is preferably 90% or more, more preferably 95% or more, even more preferably 99.0% or more, still more preferably 99.5% or more, particularly preferably 99.9% or more, and may be 100%, based on the mass of the aqueous medium, because this allows the polymerization of the fluoromonomer to proceed smoothly.

[0039] (Fluoromonomer) The fluoromonomer used in polymerization has at least one fluorine atom and at least one double bond.As the fluoromonomer, 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, 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 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.

[0040] In one embodiment of the manufacturing method of the present disclosure, at least TFE is used as the fluoromonomer.In one embodiment of the manufacturing method of the present disclosure, at least fluoroalkyl vinyl ether such as perfluoro(alkyl vinyl ether) is used as the fluoromonomer.In one embodiment of the manufacturing method of the present disclosure, at least TFE and perfluoro(alkyl vinyl ether) are used as the fluoromonomer.

[0041] The fluoroalkyl vinyl ether [FAVE] is, for example, a compound represented by the general formula (110): CF ２ =CF-ORf １１１(wherein, Rf １１１ represents a perfluoroorganic group.) A fluoromonomer represented by general formula (120): CF ２ =CF-OCH ２ -Rf １２１ (wherein, Rf １２１ is a perfluoroalkyl group having 1 to 5 carbon atoms), a fluoromonomer represented by the general formula (130): CF ２ = CFOCF ２ ORf １３１ (wherein, 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.) Fluoromonomers represented by general formula (140): CF ２ = CFO (CF ２ CF (Y １４１ ) O) ｍ (CF ２ ) ｎ F (wherein, 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.) and a fluoromonomer represented by the general formula (150): CF ２ =CF-O-(CF ２ CFY １５１ -O) ｎ -(CFY １５２ ) ｍ -A １５１ (In the formula, Y １５１ represents a fluorine atom, a chlorine atom, -SO ２ It represents a F group or a perfluoroalkyl group. The perfluoroalkyl group is an etheric oxygen and -SO ２ The group n may contain an F group. n represents an integer of 0 to 3. １５１ may be the same or different. １５２ represents a fluorine atom, a chlorine atom, or —SO ２ represents an F group, and m represents an integer of 1 to 5. １５２ may be the same or different. １５１ is -SO ２ X １５１, -COZ １５１ or -POZ １５２ Z １５３ represents. １５１ is 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 represent -NR １５４ R １５５ Or -OR １５６ Represents R １５１ , 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.

[0042] In the present disclosure, 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 atom.

[0043] 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.

[0044] 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 of the following formula:

[0045]

[0046] (wherein m represents 0 or an integer of 1 to 4), Rf １１１ is of the following formula:

[0047]

[0048] (wherein n represents an integer of 1 to 4).

[0049] Among the fluoromonomers represented by the general formula (110), those represented by the general formula (160): CF ２ =CF-ORf １６１ (wherein, Rf １６１ Rf represents a perfluoroalkyl group having 1 to 10 carbon atoms. １６１ is preferably a perfluoroalkyl group having 1 to 5 carbon atoms.

[0050] The fluoroalkyl vinyl ether is preferably at least one selected from the group consisting of fluoromonomers represented by the general formulae (160), (130) and (140).

[0051] The fluoromonomer represented by the general formula (160) is generally called perfluoro(alkyl vinyl ether). As the fluoromonomer represented by the general formula (160), at least one selected from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), and perfluoro(propyl vinyl ether) is preferred, and at least one selected from the group consisting of perfluoro(methyl vinyl ether) and perfluoro(propyl vinyl ether) is more preferred.

[0052] The fluoromonomer represented by the general formula (130) is CF ２ = CFOCF ２ OCF ３ , C.F. ２ = CFOCF ２ OCF ２ CF ３ and C.F. ２ = CFOCF ２ OCF ２ CF ２ OCF ３At least one selected from the group consisting of:

[0053] The fluoromonomer represented by the general formula (140) is CF ２ = CFOCF ２ CF (CF ３ ) O(CF ２ ) ３ F, CF ２ = CFO (CF ２ CF (CF ３ ) O) ２ (CF ２ ) ３ F and CF ２ = CFO (CF ２ CF (CF ３ ) O) ２ (CF ２ ) ２ At least one selected from the group consisting of F is preferred.

[0054] The fluoromonomer represented by the general formula (150) is CF ２ = CFOCF ２ CF ２ SO ２ F, CF ２ = CFOCF ２ CF (CF ３ ) OCF ２ CF ２ SO ２ F, CF ２ = CFOCF ２ CF (CF ２ CF ２ SO ２ F) OCF ２ CF ２ SO ２ F and CF ２ = CFOCF ２ CF (SO ２ F) ２ At least one selected from the group consisting of:

[0055] 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 of the fluoromonomer represented by the general formula (100) is preferably 1 to 6. ２ =CFCF ３ , C.H. ２ =CFCF ２ CF ３ , C.H. ２ =CFCF ２ CF ２ CF ３ , C.H. ２ =CFCF ２ CF ２ CF ２ H, CH ２ =CFCF ２ CF ２ CF ２ CF ３ , CHF=CHCF ３ (E form), CHF=CHCF ３ (Z-isomer), among which CH ２ =CFCF ３ Preferred is 2,3,3,3-tetrafluoropropylene represented by the following formula:

[0056] The fluoroalkylethylene includes fluoroalkyl ethylenes represented by the general formula (170): CH ２ =CH-(CF ２ ) ｎ -X １７１ (In the formula, X １７１ is H or F, and n is an integer of 3 to 10.) is preferred, and CH ２ =CH-C ４ F ９ and C.H. ２ =CH-C ６ F １３ At least one selected from the group consisting of:

[0057] The fluoroalkyl allyl ether is, for example, a compound represented by the general formula (180): CF ２ =CF-CF ２ -ORf １１１ (wherein, Rf １１１ represents a perfluoroorganic group.

[0058] Rf of general formula (180)１１１ is Rf in general formula (110). １１１ Rf is the same as １１１ As the fluoroalkyl aryl ether represented by the general formula (180), a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluoroalkoxyalkyl group having 1 to 10 carbon atoms is preferred. ２ =CF-CF ２ -O-CF ３ , C.F. ２ =CF-CF ２ -O-C ２ F ５ , C.F. ２ =CF-CF ２ -O-C ３ F ７ and C.F. ２ =CF-CF ２ -O-C ４ F ９ At least one selected from the group consisting of CF ２ =CF-CF ２ -O-C ２ F ５ , C.F. ２ =CF-CF ２ -O-C ３ F ７ and C.F. ２ =CF-CF ２ -O-C ４ F ９ More preferably, at least one selected from the group consisting of CF ２ =CF-CF ２ -O-CF ２ CF ２ CF ３ is more preferred.

[0059] The fluorinated vinyl heterocycle may be a compound represented by the general formula (230): (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.

[0060] (In the formula, Z ２３１ and Z ２３２are independently F or a fluorinated alkyl group having 1 to 3 carbon atoms.

[0061] The monomer that provides the crosslinking site is represented by the 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 CH ３ , 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 CH ３ , X １８３ is an iodine atom or a bromine atom, a fluoromonomer represented by 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 CH ３ , 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.) A fluoromonomer represented by the general formula (200): CF ２ = CFO (CF ２ CF (CF ３ ) O) ｍ (CF ２ ) ｎ -X ２０１ (wherein m is an integer of 0 to 5, n is an integer of 1 to 3, X ２０１ represents a cyano group, a carboxyl group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or —CH ２I.) and a fluoromonomer represented by the general formula (210): CH ２ =CFCF ２ O(CF(CF ３ )CF ２ O) ｍ (CF (CF ３ )) ｎ -X ２１１ (wherein m is an integer of 0 to 5, n is an integer of 1 to 3, X ２１１ represents a cyano group, a carboxyl group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or —CH ２ OH.) and a fluoromonomer represented by the 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 -(Q) is a linear or branched alkylene group having 1 to 18 carbon atoms, a cycloalkylene group having 3 to 18 carbon atoms, or an at least partially fluorinated alkylene or oxyalkylene group having 1 to 10 carbon atoms, which may contain an oxygen atom; ｐ -CF ２ O-(CF ２ CF ２ O) ｍ (CF ２ O) ｎ -CF ２ -(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.

[0062] X １８３ and X １９３is preferably an iodine atom. ｆ １８１ and R ｆ １９１ is preferably a perfluoroalkylene group having 1 to 5 carbon atoms. １８１ is preferably a hydrogen atom. ２０１ represents a cyano group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or —CH ２ Preferably, X is I. ２１１ represents a cyano group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or —CH ２ It is preferably OH.

[0063] The monomer that provides the crosslinking site is CF ２ = CFOCF ２ CF (CF ３ ) OCF ２ CF ２ C.N., C.F. ２ = CFOCF ２ CF (CF ３ ) OCF ２ CF ２ COOH, C.F. ２ = CFOCF ２ CF (CF ３ ) OCF ２ CF ２ CH ２ I, CF ２ = CFOCF ２ CF ２ CH ２ I, CH ２ =CFCF ２ OCF (CF ３ )CF ２ OCF (CF ３ ) CN, CH ２ =CFCF ２ OCF (CF ３ )CF ２ OCF (CF ３ ) COOH, CH ２ =CFCF ２ OCF (CF ３ )CF ２ OCF (CF ３ ) CH ２ OH, CH ２ = CHCF ２ CF２ I, CH ２ =CH(CF ２ ) ２ CH=CH ２ , C.H. ２ =CH(CF ２ ) ６ CH=CH ２ and C.F. ２ = CFO (CF ２ ) ５ CN, and CF ２ = CFOCF ２ CF (CF ３ ) OCF ２ CF ２ CN and CF ２ = CFOCF ２ CF ２ CH ２ I is more preferred.

[0064] In the polymerization, 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 para-t-butylbenzoate, vinyl cyclohexanecarboxylate, vinyl monochloroacetate, vinyl adipate, vinyl acrylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl cinnamate, vinyl undecylenate, vinyl hydroxyacetate, vinyl hydroxybenzo ... vinyl esters such as vinyl hydroxypropioate, 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; alkyl allyl esters such as ethyl allyl ester, propyl allyl ester, butyl allyl ester, isobutyl allyl ester, and cyclohexyl allyl ester; and (meth)acrylic acid esters such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, and vinyl methacrylate.

[0065] The above-mentioned fluorine-free monomer may also be a functional group-containing hydrocarbon monomer (excluding the monomer that provides a crosslinking site).Examples of the above-mentioned 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 acrylic acid, methacrylic acid, itaconic acid, succinic acid, succinic anhydride, fumaric acid, fumaric anhydride, crotonic acid, maleic acid, maleic anhydride, and perfluorobutenoic acid; fluorine-free monomers having a sulfo group such as vinyl sulfonic 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; fluorine-free monomers having an amide group such as (meth)acrylamide and methylolacrylamide; fluorine-free monomers having a nitrile group such as acrylonitrile and methacrylonitrile.

[0066] In the above polymerization, the desired fluoropolymer can be obtained by polymerizing one or more of the above fluoromonomers.

[0067] (Chain Transfer Agent) In the production method of the present disclosure, the fluoromonomer can be polymerized in the presence of a chain transfer agent. The use of a chain transfer agent can adjust the polymerization rate and molecular weight. 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.

[0068] Bromine compounds or iodine compounds may be used as chain transfer agents. The polymerization method using a bromine compound or an iodine compound may, for example, be a method of polymerizing a fluoromonomer 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 compound or iodine compound to be 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 ａ is 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.

[0069] 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, CF ２ Br ２ , BrCF ２ CF ２ Br, CF ３ CFBrCF ２ Br, CFClBr ２ , BrCF ２ CFClBr, CFBrClCFClBr, BrCF ２ CF ２ CF ２ Br, BrCF ２ CFBrOCF ３, 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, and these compounds may be used alone or in combination with each other.

[0070] 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.

[0071] The amount of chain transfer agent used is usually 1 to 50,000 mass ppm, preferably 1 to 20,000 mass ppm, based on the total amount of fluoromonomers supplied. The amount of chain transfer agent used is preferably an amount that is completely consumed during the polymerization of the fluoromonomers and does not remain in the composition containing the fluoropolymer. Therefore, the amount of chain transfer agent used is more preferably 10,000 mass ppm or less, even more preferably 5,000 mass ppm or less, still more preferably 1,000 mass ppm or less, particularly preferably 500 mass ppm or less, and most preferably 200 mass ppm or less, based on the total amount of fluoromonomers supplied.

[0072] The chain transfer agent may be added to the reactor all at once before the start of polymerization, may be added all at once after the start of polymerization, may be added in multiple divided portions during polymerization, or may be added continuously during polymerization.

[0073] (Fluorine-containing surfactant) In the production method of the present disclosure, a fluorine-containing surfactant may be used. Whether the polymerization method of the fluoromonomer is a suspension polymerization method or an emulsion polymerization method, a fluorine-containing surfactant can be used. In particular, by using a fluorine-containing surfactant, the polymerization of the fluoromonomer by the emulsion polymerization method can be smoothly carried out. The fluorine-containing surfactant used for the polymerization of the fluoromonomer is not particularly limited as long as it is a surfactant containing at least one fluorine atom, and conventionally known fluorine-containing surfactants can be used.

[0074] 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.

[0075] The fluorine-containing surfactant may also be a surfactant containing fluorine, the molecular weight of the anionic moiety of which is 1,000 or less. The "anionic moiety" means the part of the fluorine-containing surfactant excluding the cation. For example, F(CF) represented by the formula (I) below may be used. ２ ) ｎ１ In the case of COOM, "F(CF ２ ) ｎ１ This is the "COO" part.

[0076] The fluorine-containing surfactant also includes a fluorine-containing surfactant having a Log POW of 3.5 or less. The Log POW is the partition coefficient between 1-octanol and water, and is expressed as Log P [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 Log POW can be measured using a column: TOSOH ODS-120T column (φ4.6 mm×250 mm, manufactured by Tosoh Corporation), an eluent: acetonitrile / 0.6% by mass HClO ４HPLC is performed on standard substances (heptanoic acid, octanoic acid, nonanoic acid, and decanoic acid) with known octanol / water partition coefficients under conditions of water=1 / 1 (vol / vol %), flow rate: 1.0 ml / min, sample amount: 300 μL, column temperature: 40°C, and detection light: UV 210 nm. A calibration curve is prepared between each elution time and the known octanol / water partition coefficient, and the elution time is calculated from the HPLC elution time of the sample solution based on this calibration curve.

[0077] 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. Patent No. 3,271,341, JP 2003-119204 A, WO 2005 / 042593, WO 2008 / 060461, WO 2007 / 046377, JP 2007-119526 A, WO 2007 / 046482, WO 2007 / 046345, U.S. Patent Application Publication No. 2014 / 0228531, WO 2013 / 189824, and those described in WO 2013 / 189826, and the like.

[0078] 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 ) (wherein, X ｎ０ is H, Cl or F. ｎ０ is a linear, branched or cyclic alkylene group having 3 to 20 carbon atoms, in which some or all of the H atoms are substituted with F, and the alkylene group may contain one or more ether bonds, and some of the H atoms may be substituted with Cl. ０ is an anionic group. ０The anionic group is -COOM, -SO ２ M or -SO ３ M, -COOM or -SO ３ M. M may be H, a metal atom, NR ７ ４ , optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium, and R ７ is H or an organic group. The metal atom includes alkali metals (Group 1), alkaline earth metals (Group 2), etc., such as Na, K, or Li. ７ As the group, H or C １－１０ and may be an organic group of the formula: １－４ and may be an organic group of the formula: １－４ M may be H, a metal atom, or an alkyl group of the formula NR ７ ４ may be H, an alkali metal (Group 1), an alkaline earth metal (Group 2), or NR ７ ４ may be H, Na, K, Li or NH ４ The above Rf ｎ０ may be one in which 50% or more of H is substituted with fluorine.

[0079] The general formula (N ０ The compound represented by the following general formula (N １ ): X ｎ０ -(CF ２ ) ｍ１ -Y ０ (N １ ) (wherein, X ｎ０ is H, Cl, and F, m1 is an integer from 3 to 15, and Y ０ is as defined above), a compound represented by the following general formula (N ２ ): Rf ｎ１ -O-(CF(CF ３ )CF ２ O) ｍ２ CFX ｎ１ -Y ０ (N ２ ) (wherein, Rf ｎ１is a perfluoroalkyl group having 1 to 5 carbon atoms, m2 is an integer of 0 to 3, and X ｎ１ is F or CF ３ and Y ０ is as defined above), a compound represented by the following general formula (N ３ ): Rf ｎ２ (CH ２ ) ｍ３ -(Rf ｎ３ ) ｑ -Y ０ (N ３ ) (wherein, Rf ｎ２ is a partially or fully fluorinated alkyl group having 1 to 13 carbon atoms, which may contain an ether bond and / or a chlorine atom, 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 CF ２ -Y ０ (N ４ ) (wherein, 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 ): (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 linkage. 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 ０is as defined above, where X ｎ２ , X ｎ３ , X ｎ４ and Rf ｎ５ wherein the total number of carbon atoms is 18 or less.

[0080] The general formula (N ０ ) More specifically, the compounds represented by the formula (I) below include perfluorocarboxylic acids (I), ω-H perfluorocarboxylic acids (II), perfluoroether carboxylic acids (III), perfluoroalkyl alkylene carboxylic acids (IV), perfluoroalkoxy fluorocarboxylic acids (V), perfluoroalkyl sulfonic acids (VI), ω-H perfluoro sulfonic acids (VII), perfluoroalkyl alkylene sulfonic acids (VIII), alkyl alkylene carboxylic acids (IX), fluorocarboxylic acids (X), alkoxy fluorosulfonic acids (XI), alkoxy fluorosulfonic acids (XI), and the like.

[0081] The perfluorocarboxylic acid (I) is represented by the following general formula (I): F(CF ２ ) ｎ１ COOM (I) (wherein n1 is an integer of 3 to 14, and M is H, a metal atom, NR ７ ４ , optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium, and R ７ is H or an organic group.

[0082] The ω-H perfluorocarboxylic acid (II) is represented by the following general formula (II): H(CF ２ ) ｎ２COOM (II) (wherein n2 is an integer of 4 to 15, and M is as defined above).

[0083] The perfluoroethercarboxylic acid (III) is a compound represented by the following general formula (III): １ -O-(CF(CF ３ )CF ２ O) ｎ３ CF (CF ３ ) COOM (III) (wherein, 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.

[0084] The perfluoroalkyl alkylene carboxylic acid (IV) is represented by the following general formula (IV): ２ (CH ２ ) ｎ４ Rf ３ COOM (IV) (wherein, 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.

[0085] The alkoxyfluorocarboxylic acid (V) is represented by the following general formula (V): Rf ４ -O-CY １ Y ２ CF ２ -COOM (V) (wherein, Rf ４ is a linear or branched partially or fully fluorinated alkyl group having 1 to 12 carbon atoms, which may contain ether bonds and / or chlorine atoms; Y １ and Y ２ are the same or different and are H or F, and M is as defined above.

[0086] The perfluoroalkylsulfonic acid (VI) is represented by the following general formula (VI): F(CF ２ ) ｎ５ SO ３M (VI) (wherein n5 is an integer of 3 to 14, and M is as defined above).

[0087] The ω-H perfluorosulfonic acid (VII) is represented by the following general formula (VII): H(CF ２ ) ｎ６ SO ３ M (VII) (wherein n6 is an integer of 4 to 14, and M is as defined above).

[0088] The perfluoroalkyl alkylene sulfonic acid (VIII) is a compound represented by the following general formula (VIII): ５ (CH ２ ) ｎ７ SO ３ M (VIII) (wherein, 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.

[0089] The alkyl alkylene carboxylic acid (IX) is represented by the following general formula (IX): ６ (CH ２ ) ｎ８ COOM (IX) (wherein, 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.

[0090] The fluorocarboxylic acid (X) is represented by the following general formula (X): ７ -O-Rf ８ -O-CF ２ -COOM (X) (wherein, 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 and / or a chlorine atom, and 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.

[0091] The alkoxyfluorosulfonic acid (XI) is represented by the following general formula (XI): Rf ９ -O-CY １ Y ２ CF ２ -SO ３ M (XI) (wherein, 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.

[0092] The compound (XII) is represented by the following general formula (XII): (In the formula, X １ , X ２ and X ３ Rf 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; １０ is a perfluoroalkylene group having 1 to 3 carbon atoms, L is a linking group, and Y ０ is an anionic group. ０ is -COOM, -SO ２ M or -SO ３ M, and -SO ３ M or COOM (wherein M is as defined above). Examples of L include a single bond, a partially or fully fluorinated alkylene group having 1 to 10 carbon atoms which may contain an ether bond.

[0093] The compound (XIII) has the following general formula (XIII): １１ -O-(CF ２ CF (CF ３ ) O) ｎ９ (CF ２ O) ｎ１０ CF ２ COOM (XIII) (wherein, Rf １１is 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. ２ ClO(CF ２ CF (CF ３ ) O) ｎ９ (CF ２ O) ｎ１０ CF ２ COONH ４ (a mixture having an average molecular weight of 750, wherein n9 and n10 are defined above).

[0094] As mentioned above, examples of the anionic fluorine-containing surfactant include carboxylic acid surfactants and sulfonic acid surfactants.

[0095] The fluorine-containing surfactant may be one type of fluorine-containing surfactant or a mixture containing two or more types of fluorine-containing surfactants.

[0096] The fluorine-containing surfactant preferably has a methylene group (—CH ２ -), and more preferably, does not have a C-H bond. ２ By using a fluorine-containing surfactant having no - or C--H bond, the polymerization of the fluoromonomer can be smoothly carried out in the presence of an aqueous medium.

[0097] The number of H atoms in the hydrophobic group of the fluorine-containing surfactant is preferably 0 or 1, more preferably 0. By using a fluorine-containing surfactant having a small number of H atoms bonded to the carbon atoms constituting the hydrophobic group, the polymerization of the fluoromonomer can be smoothly carried out in the presence of an aqueous medium. The number of carbon atoms in the hydrophobic group of the fluorine-containing surfactant having a hydrophobic group and a hydrophilic group is preferably 1 to 50, more preferably 3 to 20, and even more preferably 6 to 12. The hydrophobic group usually constitutes the above-mentioned "portion excluding the anionic group" of the molecular structure of the fluorine-containing surfactant. As the hydrophilic group, Y ０Examples of the anionic group include the groups exemplified above for the anionic group of the formula (I). The fluorine-containing surfactant may be a saturated fluorinated surfactant in which all of the carbon atoms bonded to the hydrophobic group have been substituted with fluorine atoms.

[0098] As the fluorine-containing surfactant, among the above-mentioned anionic fluorine-containing surfactants, those represented by the general formula (N １ ), a compound represented by the general formula (N ２ ), a compound represented by the general formula (N ４ ): Rf ｎ４ -O-(CY ｎ１ F) ｐ CF ２ -Y ０ (N ４ ) (wherein, Rf ｎ４ is a linear or branched or fully fluorinated alkyl group having 1 to 12 carbon atoms, which may contain an ether linkage (provided that -CH ２ -), and Y ｎ１ is 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 ): (In the formula, X ｎ２ , X ｎ３ and X ｎ４ may be the same or different and are H, F, or a linear or branched alkyl group having 1 to 6 carbon atoms, which may contain an ether bond, or a fully fluorinated alkyl group (provided that -CH ２ -), except that X ｎ３ and X ｎ４ Both of Rf cannot be H. ｎ５ is a linear or branched or fully fluorinated alkylene group having 1 to 3 carbon atoms, which may contain an ether bond (provided that -CH ２ -), L is a linking group, and Y ０ is as defined above, where X ｎ２ , X ｎ３ , X ｎ４ and Rf ｎ５ wherein the total number of carbon atoms is 18 or less.

[0099] As the fluorine-containing surfactant, among the above-mentioned anionic fluorine-containing surfactants, perfluorocarboxylic acid (I) represented by general formula (I), ω-H perfluorocarboxylic acid (II) represented by general formula (II), perfluoroether carboxylic acid (III) represented by general formula (III), perfluoroalkyl alkylene carboxylic acid (IV) represented by general formula (IV), perfluoroalkoxy fluorocarboxylic acid (V) represented by general formula (V), perfluoroalkyl sulfonic acid (VI) represented by general formula (VII), ω-H perfluoro sulfonic acid (VII) represented by general formula (VII), perfluoroalkyl alkylene sulfonic acid (VIII) represented by general formula (VIII), general formula (X): Rf ７ -O-Rf ８ -O-CF ２ -COOM (where Rf ７ is a linear or branched partially or fully fluorinated alkyl group having 1 to 6 carbon atoms, which may contain ether bonds and / or chlorine atoms (provided that -CH ２ -), and Rf ８ is a linear or branched partially or fully fluorinated alkyl group having 1 to 6 carbon atoms (provided that -CH ２ Fluorocarboxylic acid (X) represented by general formula (XI): Rf ９ -O-CY １ FCF ２ -SO ３ M (wherein, 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 (provided that -CH ２ -), and Y １ is H or F, and M is as defined above.) an alkoxyfluorosulfonic acid (XI) represented by the general formula (XII): (In the formula, X １ , X ２ and X ３may be the same or different and are H, F and straight or branched or fully fluorinated alkyl groups which may contain ether bonds and have 1 to 6 carbon atoms (provided that -CH ２ -), except that X ２ and X ３ Both of Rf １０ is a perfluoroalkylene group having 1 to 3 carbon atoms, L is a linking group, and Y ０ is an anionic group.) and a compound (XII) represented by the general formula (XIII): Rf １１ -O-(CF ２ CF (CF ３ ) O) ｎ９ (CF ２ O) ｎ１０ CF ２ COOM (where Rf １１ represents a fluoroalkyl group having 1 to 5 carbon atoms and containing chlorine (wherein -CH ２ n9 is an integer of 0 to 3, n10 is an integer of 0 to 3, and M is as defined above. The use of these fluorine-containing surfactants allows the polymerization of fluoromonomers to proceed smoothly in the presence of an aqueous medium.

[0100] Examples of the fluorine-containing surfactant include compounds represented by the following formula: F(CF ２ ) ７ COOM, F(CF ２ ) ５ COOM, H(CF ２ ) ６ COOM, H(CF ２ ) ７ COOM, C.F. ３ O (CF ２ ) ３ OCHFCF ２ COOM, C. ３ F ７ OCF (CF ３ )CF ２ OCF (CF ３ ) COOM, C.F.３ CF ２ CF ２ OCF (CF ３ ) COOM, C.F. ３ CF ２ OCF ２ CF ２ OCF ２ COOM, C. ２ F ５ OCF (CF ３ )CF ２ OCF (CF ３ ) COOM, C.F. ３ OCF (CF ３ )CF ２ OCF (CF ３ ) COOM, C.F. ２ ClCF ２ CF ２ OCF (CF ３ )CF ２ OCF ２ COOM, C.F. ２ ClCF ２ CF ２ OCF ２ CF (CF ３ ) OCF ２ COOM, C.F. ２ ClCF(CF ３ ) OCF (CF ３ )CF ２ OCF ２ COOM, C.F. ２ ClCF(CF ３ ) OCF ２ CF (CF ３ ) OCF ２ COOM, (In each formula, M is H, metal atom, NR ７ ４ , optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium. ７ is H or an organic group.

[0101] The amount of the fluorine-containing surfactant added is preferably 10 ppm by mass to 10% by mass, more preferably 100 ppm by mass or more, even more preferably 300 ppm by mass or more, and more preferably 5% by mass or less, and even more preferably 1% by mass or less, relative to the aqueous medium.

[0102] Suspension polymerization can be carried out in the presence or absence of a fluorine-containing surfactant. The amount of fluorine-containing surfactant added in the suspension polymerization method is preferably 2000 mass ppm or less, more preferably 1000 mass ppm or less, still more preferably 500 mass ppm or less, particularly preferably 200 mass ppm or less, and most preferably 100 mass ppm or less, relative to the aqueous medium. The amount of fluorine-containing surfactant may be 0 mass ppm.

[0103] (Other Additives) In the polymerization of fluoromonomers, additives such as buffers, pH adjusters, stabilizing aids, and dispersion stabilizers can be used. In addition, in the polymerization of fluoromonomers, radical scavengers and decomposers can be added to adjust the polymerization rate and molecular weight. In addition, in the polymerization of fluoromonomers, fluorine-free anionic surfactants, fluorine-free nonionic surfactants, fluorine-free cationic surfactants, etc. may be used.

[0104] Preferred stabilizing aids include paraffin wax, fluorine-based oil, fluorine-based solvent, and silicone oil. The stabilizing aids may be used alone or in combination of two or more. Paraffin wax is more preferred as the stabilizing aid. Paraffin wax may be liquid, semi-solid, or solid at room temperature, but saturated hydrocarbons having 12 or more carbon atoms are preferred. The melting point of the paraffin wax is generally preferably 40 to 65°C, more preferably 50 to 65°C.

[0105] The amount of the stabilizing aid used is preferably 0.1 to 12% by mass, more preferably 0.1 to 8% by mass, based on the mass of the aqueous medium used. It is desirable that the stabilizing aid is sufficiently hydrophobic so that it is completely separated from the aqueous dispersion after polymerization and does not become a contaminating component.

[0106] (Polymerization conditions) Polymerization of fluoromonomers can be carried out under normal pressure and temperature. Usually, the polymerization temperature is 5 to 120°C, and the polymerization pressure is 0.05 to 10 MPaG. The polymerization temperature and polymerization pressure are appropriately determined depending on the type of monomer, the molecular weight of the target fluoropolymer, the reaction rate, etc.

[0107] (Termination of Polymerization) The polymerization of the fluoromonomer can be terminated, for example, by removing the fluoromonomer remaining in the reactor.

[0108] The method for removing the fluoromonomer from the reactor is not particularly limited. After preparing the composition, if desired, the stirring of the contents of the reactor may be stopped, and the pressure in the reactor may be vented until normal pressure is reached to remove the fluoromonomer from the reactor. Alternatively, the pressure in the reactor may be reduced to less than 0.0 MPaG to remove the fluoromonomer from the reactor. Alternatively, the fluoromonomer in the reactor may be replaced with an inert gas such as nitrogen gas by supplying an inert gas into the reactor. Alternatively, the entire amount of the fluoromonomer in the reactor may be reacted and converted into a fluoropolymer, thereby removing the fluoromonomer from the reactor. The removal of the fluoromonomer remaining in the reactor from the reactor can be carried out to a degree that sufficiently stops the polymerization reaction of the fluoromonomer, so that a small amount of the fluoromonomer may remain in the reactor. The removed fluoromonomer can be recovered by known means. The recovered fluoromonomer may be reused to produce a fluoropolymer.

[0109] As a method for removing the fluoromonomer from the reactor, after preparing the composition, if desired, stopping stirring of the contents of the reactor, reducing the pressure in the reactor to less than 0.0 MPaG, and then supplying an inert gas into the reactor is also suitable. The reduction in pressure in the reactor and the supply of an inert gas may be repeated several times.

[0110] When the polymerization of fluoromonomer is carried out at a temperature higher than room temperature, the reactor may be cooled before or after removing the fluoromonomer from the reactor.When removing the fluoromonomer from the reactor by means of evacuation or nitrogen substitution, there is a possibility that unreacted fluoromonomer, particularly in liquid form, remains in the reactor, but by cooling the reactor, the progress of the reaction of the unreacted fluoromonomer can be sufficiently suppressed.

[0111] To terminate the polymerization reaction of the fluoromonomer, a polymerization terminator (radical scavenger) may be added.

[0112] As the polymerization terminator, a compound that does not have the ability to re-initiate after addition or chain transfer to a free radical in the polymerization system is used. 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 a 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. The activity of what is generally called a chain transfer agent is characterized by the chain transfer constant and the re-initiation efficiency, and among chain transfer agents, those with a re-initiation efficiency of almost 0% are called polymerization terminators. Examples of polymerization terminators include aromatic hydroxy compounds, aromatic amines, N,N-diethylhydroxylamine, quinone compounds, terpenes, thiocyanates, and cupric chloride (CuCl ２) is preferred. Examples of aromatic hydroxy compounds include unsubstituted phenol, polyhydric phenol, salicylic acid, m- or p-salicylic acid, gallic acid, naphthol, etc. Examples of the unsubstituted phenol include o-, m-, or p-nitrophenol, o-, m-, or p-aminophenol, p-nitrosophenol, etc. Examples of polyhydric phenols include catechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, naphthresorcinol, etc. Examples of aromatic amines include o-, m-, or p-phenylenediamine, benzidine, etc. Examples of the quinone compounds include hydroquinone, o-, m-, or p-benzoquinone, 1,4-naphthoquinone, alizarin, etc. Examples of thiocyanates include ammonium thiocyanate (NH ４ Examples of the polymerization terminator include potassium thiocyanate (KSCN), sodium thiocyanate (NaSCN), etc. Among these, quinone compounds are preferred, and hydroquinone is more preferred.

[0113] (Composition obtained by polymerization) By polymerization of fluoromonomer, a composition containing an aqueous medium and a fluoropolymer is obtained. When suspension polymerization is used as the polymerization method of fluoromonomer, a composition containing an aqueous medium and suspension-polymerized particles of fluoropolymer is usually obtained as the composition. When emulsion polymerization is used as the polymerization method of fluoromonomer, an aqueous dispersion in which primary particles of fluoropolymer are stably dispersed in an aqueous medium is usually obtained as the composition.

[0114] When a fluorine-containing surfactant is used in the polymerization of a fluoromonomer, the resulting composition usually contains, in addition to the fluoropolymer, the fluorine-containing surfactant used in the polymerization of the fluoromonomer. The composition obtained by polymerization of a fluoromonomer may contain, in addition to the fluoropolymer, a fluorine-containing compound having a hydrophilic group produced by the polymerization of the fluoromonomer.

[0115] In the present disclosure, the hydrophilic group possessed by the fluorine-containing compound is preferably an anionic group such as an acid group, for example, —NH２ , -PO ３ M, -OPO ３ M, -SO ３ M, -OSO ３ Examples of the hydrophilic group include -M and -COOM (in each formula, M represents a cation). ３ M or -COOM is preferred, and -COOM is more preferred.

[0116] The fluorine-containing compound having a hydrophilic group in the composition obtained by polymerization is typically a fluorine-containing compound having a hydrophilic group with a molecular weight of 1000 g / mol or less. According to the production method of the present disclosure, a fluoropolymer having a low content of a fluorine-containing compound having a hydrophilic group with a molecular weight of 1000 g / mol or less can be produced.

[0117] In one embodiment of the composition obtained by polymerization, the fluorine-containing compound having a hydrophilic group contains a fluorine-containing surfactant added during polymerization. The fluorine-containing surfactant added during polymerization is as described above for the fluorine-containing surfactant used in polymerization of the fluoromonomer.

[0118] The content of the fluorine-containing surfactant in the composition obtained by polymerization may be 10 ppm by mass or more, 100 ppm by mass or more, or 1000 ppm by mass or more, and may be 10% by mass or less, 5% by mass or less, or 1% by mass or less, based on the fluoropolymer in the composition.

[0119] The content of the fluorine-containing compound having a hydrophilic group in the composition obtained by polymerization (the total content of the fluorine-containing surfactant added during polymerization and the content of the fluorine-containing compound having a hydrophilic group produced by polymerization of the fluoromonomer) may be 10 ppm by mass or more, 100 ppm by mass or more, or 1000 ppm by mass or more, and may be 10% by mass or less, 5% by mass or less, or 1% by mass or less, relative to the fluoropolymer in the composition.

[0120] In one embodiment of the composition obtained by polymerization, the fluorine-containing compound having a hydrophilic group contains a compound represented by the following general formula (1): General formula (1): [X-Rf-A － ] ｉ M ｉ＋ (Wherein, X represents H, Cl, Br, F or I; Rf represents a linear or branched partially or fully fluorinated aliphatic group, or a linear or branched partially or fully fluorinated aliphatic group interrupted by at least one oxygen atom; A － is an acid group, M ｉ＋ represents a cation having a valence i, where i is an integer from 1 to 3.

[0121] In one embodiment of the composition obtained by polymerization, the fluorine-containing compound having a hydrophilic group contains a compound represented by the following general formula (2): General formula (2): [C ｎ－１ F ２ｎ－１ COO － ]M ＋ (wherein n is an integer of 9 to 14, M ＋ represents a cation.)

[0122] It is known that compounds represented by general formula (2) (perfluoroalkanoic acids) are formed during polymerization when perfluoro(alkyl vinyl ether) or the like is used as a fluoromonomer (see WO 2019 / 161153).

[0123] In one embodiment of the composition obtained by polymerization, the fluorine-containing compound having a hydrophilic group contains a compound represented by the following general formula (3): General formula (3): [R １ -O-L-CO ２ － ]M ＋ (In the formula, R １ represents a linear or branched partially or fully fluorinated aliphatic group, or a linear or branched partially or fully fluorinated aliphatic group interrupted by at least one oxygen atom; L represents a linear or branched non-fluorinated, partially fluorinated or fully fluorinated alkylene group; M represents a linear or branched non-fluorinated, partially fluorinated or fully fluorinated alkylene group; ＋ represents a cation.)

[0124] In one embodiment of the composition obtained by polymerization, the fluorine-containing compound having a hydrophilic group contains a compound represented by general formula (4). General formula (4): [H—(CF ２ ) ｍ CO ２ － ]M ＋ (wherein m is an integer of 3 to 19, M ＋ represents a cation.)

[0125] (Treatment using oxygen-containing gas) In the production method of the present disclosure, after preparing a composition containing an aqueous medium and a fluoropolymer, the composition is contacted with a gas containing at least oxygen. By treating the composition obtained by polymerization with a gas containing at least oxygen, a fluoropolymer having a low content of fluorine-containing compounds having hydrophilic groups can be obtained.

[0126] Examples of gases containing at least oxygen include oxygen gas, air, and oxygen gas diluted with nitrogen gas.

[0127] The polymerization of fluoromonomer and the treatment of composition with the gas containing oxygen are usually carried out in the same reactor.The contact of composition with the gas containing at least oxygen can be carried out, for example, by removing the fluoromonomer remaining in reactor, and then supplying the gas containing at least oxygen into the same reactor.In one embodiment of the present disclosure, after preparing composition, release a part of the fluoromonomer in the reactor that is in a pressurized state from the reactor, thereby reducing the pressure in the reactor to normal pressure, and supply an inert gas such as nitrogen gas into the reactor, thereby replacing the fluoromonomer in the reactor with inert gas, and then reduce the pressure in the reactor to reduced pressure, and supply the gas containing at least oxygen into the reactor.

[0128] The form of the composition to be treated with a gas containing at least oxygen is not particularly limited.For example, when suspension polymerization is used as the polymerization method of fluoromonomer, a composition containing an aqueous medium and suspension-polymerized particles of fluoropolymer is obtained as the composition, and the obtained composition can be directly subjected to treatment.When emulsion polymerization is used as the polymerization method of fluoromonomer, an aqueous dispersion in which primary particles of fluoropolymer are stably dispersed in an aqueous medium is obtained as the composition, and the obtained aqueous dispersion (composition) can be directly subjected to treatment.

[0129] The contact of the composition with at least an oxygen-containing gas is preferably carried out promptly after the preparation of the composition containing an aqueous medium and a fluoropolymer. By treating the composition obtained by polymerization with an oxygen-containing gas at an early stage without leaving it, a fluoropolymer having a lower content of fluorine-containing compounds having hydrophilic groups can be obtained.

[0130] For example, it is preferred to supply a gas containing at least oxygen into the reactor preferably within 10 minutes, more preferably within 5 minutes, from the time when the fluoromonomer remaining in the reactor has been removed.

[0131] The fluoropolymer content in the composition to be treated with a gas containing at least oxygen may be, for example, 5 to 75 mass %. The fluoropolymer content in the composition is a value obtained by drying 1 g of the composition in a blower dryer at 150°C for 60 minutes, measuring the mass of the heating residue, and calculating the ratio of the mass of the heating residue to the mass (1 g) of the polymer dispersion as a percentage.

[0132] In one embodiment of the production method of the present disclosure, the amount of dissolved oxygen in the composition when the composition is contacted with at least an oxygen-containing gas is adjusted to 0.001 mg / L or more. By dissolving a sufficient amount of oxygen in the composition, a fluoropolymer having a lower content of fluorine-containing compounds having hydrophilic groups can be obtained.

[0133] When the composition is brought into contact with a gas containing at least oxygen, the lower limit of the amount of dissolved oxygen in the composition may be 0.01 mg / L, 0.10 mg / L, 0.50 mg / L, 1.0 mg / L, 1.5 mg / L, 2.0 mg / L, 3.0 mg / L, 4.0 mg / L, or 5.0 mg / L.When the composition is brought into contact with a gas containing at least oxygen, the upper limit of the amount of dissolved oxygen in the composition may be 10.0 mg / L, 9.0 mg / L, 8.0 mg / L, 7.0 mg / L, or 6.0 mg / L.

[0134] The dissolved oxygen concentration in the composition can be measured by a method such as titration, a diaphragm electrode method, or a fluorescence method.

[0135] In one embodiment of the production method of the present disclosure, polymerization of the fluoromonomer is carried out using an aqueous medium in an amount that occupies 1 to 95% by volume of the internal volume of the reactor. By forming a gas phase portion of an appropriate size in the reactor, the fluoromonomer can be polymerized smoothly.

[0136] In one embodiment of the production method of the present disclosure, when polymerizing a fluoromonomer, the oxygen concentration in the gas phase in the reactor is adjusted to 20 volume ppm or less. By sufficiently lowering the oxygen concentration in the reactor, the fluoromonomer can be smoothly polymerized while suppressing side reactions. In conventional techniques, the polymerization of a fluoromonomer is usually carried out under conditions in which the oxygen concentration in the reactor is sufficiently lowered.

[0137] The upper limit of the oxygen concentration in the gas phase in the reactor when polymerizing the fluoromonomer may be 100 volume ppm, 50 volume ppm, 30 volume ppm, 20 volume ppm, or 10 volume ppm or less, and the lower limit is not particularly limited, but may be 1 volume ppm or more.

[0138] The oxygen concentration in the gas phase in the reactor can be measured by a method such as a laser spectroscopic method, a zirconia method, a magnetic method, or an electrode method.

[0139] In one embodiment of the manufacturing method of the present disclosure, the amount of dissolved oxygen in the composition obtained by polymerization of the fluoromonomer (i.e., the amount of dissolved oxygen in the composition before contact with at least an oxygen-containing gas) is 0.1 mg / L or less. A composition with a low dissolved oxygen amount can be obtained by polymerizing the fluoromonomer under conditions in which the oxygen concentration in the reactor is sufficiently reduced. In one embodiment of the manufacturing method of the present disclosure, after preparing a composition with a low dissolved oxygen amount in this way, the composition is contacted with at least an oxygen-containing gas to increase the dissolved oxygen amount in the composition to the above-mentioned range.

[0140] The upper limit of the amount of dissolved oxygen in the composition obtained by polymerization of the fluoromonomer may be 0.05 mg / L or 0.01 mg / L, and the lower limit is not particularly limited, but may be 0.001 mg / L.

[0141] The temperature of the composition when it is brought into contact with a gas containing at least oxygen is preferably 5°C or higher, more preferably 15°C or higher, even more preferably 30°C or higher, still more preferably 35°C or higher, and preferably 85°C or lower, more preferably 75°C or lower, even more preferably 65°C or lower, still more preferably 55°C or lower, and particularly preferably 50°C or lower.

[0142] The time for contacting the composition with a gas containing at least oxygen is preferably 1 minute or more, more preferably 5 minutes or more, even more preferably 10 minutes or more, still more preferably 15 minutes or more, and preferably 400 minutes or less, more preferably 300 minutes or less, even more preferably 150 minutes or less.

[0143] The contact of the composition with at least an oxygen-containing gas can be carried out while stirring the aqueous medium and the composition containing the fluoropolymer. The stirring is preferably carried out with a stirring force sufficient to bring the composition into sufficient contact with oxygen while suppressing aggregation and fibrillation of the fluoropolymer in the composition.

[0144] In one embodiment, the composition is stirred with a stirring force sufficient to generate bubbles in the composition. By sufficiently stirring the composition in this manner and bringing the composition into contact with oxygen, a fluoropolymer having a lower content of fluorine-containing compounds having hydrophilic groups can be obtained.

[0145] In one embodiment, the composition is stirred at a power number of 0.3 or more. By sufficiently stirring the composition in this manner and sufficiently contacting the composition with oxygen, a fluoropolymer having a lower content of fluorine-containing compounds having hydrophilic groups can be obtained.

[0146] The power number is preferably 0.4 or more, more preferably 0.5 or more, and although there is no particular upper limit, it may be 0.9 or less.

[0147] The power number (Np) can be calculated according to the following formula: The following formula can be suitably used to calculate the power number, particularly when a cylindrical stirring vessel is used. Np=A / Re+B((10^3+1.2*Re^0.66) / (10^3+3.2*Re^0.66))^p*(H / D)^(0.35+b / D)*(sinθ)^1.2 Re=nd^2ρ / μ A=14+(b / D)*((670*(d / D-0.6)^2+185)) B=10^(1.3-4*(b / D-0.5)^2-1.14*(d / D)) p=1.1+4(b / D)-2.5*(d / D-0.5)^2-7*(b / D)^4 Here, the factors related to the stirring blade are blade length d[m], blade width b[m], blade degree θ[°], rotation speed n[1 / sec], Factors related to the mixing vessel are the vessel diameter D [m] and liquid depth H [m]. Factors related to the mixing liquid are the liquid density ρ [kg / m^3] and liquid viscosity μ [kg / m sec].

[0148] In one embodiment, the composition may be stirred, stopped, and then allowed to stand for a period of preferably 1 minute or more, more preferably 5 minutes or more, even more preferably 10 minutes or more, still more preferably 15 minutes or more, and preferably 200 minutes or less, more preferably 150 minutes or less.

[0149] In one embodiment, a composition is prepared by polymerizing a fluoromonomer while stirring an aqueous medium, and then the composition is contacted with at least an oxygen-containing gas while stirring at a stirring speed that is -80% or more and +50% or less compared to the stirring speed during polymerization. The lower limit of the stirring speed is, in order of preference, -75% or more, -50% or more, -25% or more, and -10% or more, and the upper limit of the stirring speed is preferably +25% or less, more preferably +0% or less. In this way, by contacting the composition with at least an oxygen-containing gas while stirring the composition with a stirring force similar to that employed during polymerization of a fluoromonomer, the composition can be sufficiently contacted with oxygen while suppressing aggregation and fibrillation of the fluoropolymer in the composition, and therefore a fluoropolymer with an even lower content of a fluorine-containing compound having a hydrophilic group can be obtained.

[0150] (Washing, Drying, Pulverization, and Molding) After treating the composition obtained by polymerization with an oxygen-containing gas, the fluoropolymer in the composition can be washed or dried.

[0151] When emulsion polymerization is used as the polymerization method of fluoromonomer, the aqueous dispersion in which the primary particles of fluoropolymer are stably dispersed in the aqueous medium is usually obtained as the composition.The primary particles of fluoropolymer in the aqueous dispersion are coagulated, and the fluoropolymer is recovered as the coagulated product, and the recovered fluoropolymer can be washed or dried.

[0152] The coagulation of the primary particles of the fluoropolymer in the aqueous dispersion can be carried out, for example, by diluting the aqueous dispersion obtained by polymerization with water to a polymer concentration of 5 to 20% by mass, optionally adjusting the pH to neutral or alkaline, and then stirring the mixture in a vessel equipped with a stirrer with more vigor than during the reaction. The coagulation can be carried out while adding a coagulant such as a water-soluble organic compound such as methanol or acetone, an inorganic salt such as potassium nitrate or ammonium carbonate, or an inorganic acid such as hydrochloric acid, sulfuric acid, or nitric acid. The coagulation can also be carried out continuously using an in-line mixer or the like.

[0153] When suspension polymerization is used as the polymerization method of fluoromonomer, fluoropolymer can be recovered as suspension polymerized particles in wet state without coagulation.Therefore, after treating the composition obtained by polymerization with a gas containing oxygen, the fluoropolymer (suspension polymerized particles) in the composition can be recovered, and then washed or dried.

[0154] In one embodiment of the manufacturing method of the present disclosure, after contacting the composition with an oxygen-containing gas, the fluoropolymer is washed. Water or an organic solvent can be used to wash the fluoropolymer. Washing can be performed one or more times.

[0155] Examples of organic solvents used for washing include ethers, halogenated hydrocarbons, aromatic hydrocarbons, pyridine, nitriles, nitrogen-containing polar organic compounds, dimethyl sulfoxide, and alcohols.

[0156] In one embodiment of the manufacturing method of the present disclosure, after contacting the composition with a gas containing oxygen, the fluoropolymer is dried.

[0157] Examples of methods for drying the fluoropolymer include methods using a dryer, such as a hot air dryer, box dryer, band dryer, tunnel dryer, jet dryer, moving bed dryer, rotary dryer, fluidized bed dryer, flash dryer, disk dryer, cylindrical agitator dryer, inverted cone agitator dryer, microwave device, vacuum heat treatment device, box-type electric furnace, flash dryer, vibration dryer, belt dryer, extrusion dryer, and spray dryer.

[0158] The temperature at which the fluoropolymer is dried is preferably less than 300°C, more preferably 280°C or less, even more preferably 250°C or less, preferably 50°C or more, more preferably 100°C or more, even more preferably 120°C or more, and particularly preferably 140°C or more. The drying temperature is the temperature of the atmosphere surrounding the fluoropolymer, and when hot air is used for drying, it can be specified by measuring the temperature of the hot air. The temperature of the hot air can be measured at the supply port through which hot air is supplied to the dryer or at the exhaust port through which hot air is exhausted from the dryer, but is preferably measured at the exhaust port.

[0159] Before drying, the fluoropolymer may be dehydrated. Examples of a method for dehydrating a wet fluoropolymer include a method using a dehydrator. Examples of dehydrators include a vibration dehydrator, a filter dehydrator, and a centrifugal dehydrator.

[0160] In one embodiment of the manufacturing method of the present disclosure, the fluoropolymer is pulverized after contacting the composition with an oxygen-containing gas. The pulverization may be performed after drying the fluoropolymer, after washing the fluoropolymer, or while washing the fluoropolymer. In one embodiment, the fluoropolymer is pulverized to produce a pulverized fluoropolymer, the pulverized fluoropolymer is washed, and the washed fluoropolymer is dried. In another embodiment, the fluoropolymer is coarsely pulverized to produce a pulverized fluoropolymer, the coarsely pulverized fluoropolymer is finely pulverized while being washed to produce a finely pulverized fluoropolymer, the finely pulverized fluoropolymer is further washed, and the washed fluoropolymer is dried.

[0161] The pulverization may be wet pulverization or dry pulverization. Examples of methods for pulverizing fluoropolymers include pulverization using a pulverizer. Examples of pulverizers include impact pulverizers such as hammer mills, pin mills, high-speed rotary mills, and jet mills, and attrition pulverizers such as cutter mills, feather mills, and colloid mills that pulverize by shearing forces generated by rotary blades and an outer stator (fixed blade). A combination of multiple pulverizers may be used for pulverization.

[0162] The temperature at which the grinding treatment is carried out is preferably −200 to 50° C., more preferably 1° C. or higher, more preferably 40° C. or lower, and even more preferably 30° C. or lower.

[0163] The method of pulverizing the fluoropolymer while washing it includes a method of pulverizing the fluoropolymer in water or an organic solvent. For example, water or an organic solvent and the fluoropolymer may be simultaneously fed into a grinding type grinder such as a cutter mill to pulverize the fluoropolymer, or water or an organic solvent and the fluoropolymer may be mixed in advance, and the mixture may be fed into a grinder to pulverize the fluoropolymer.

[0164] The pulverization may be carried out once, or may be carried out repeatedly until pulverized particles having a desired average particle size or a desired particle size distribution are produced.

[0165] After pulverizing the fluoropolymer, the resulting pulverized particles may be classified by a known method such as air classification, etc. By classifying, very small fine particles and very large coarse particles can be removed to obtain a fluoropolymer having a desired average particle size or a desired particle size distribution.

[0166] In one embodiment of the manufacturing method of the present disclosure, after contacting the composition with an oxygen-containing gas, the fluoropolymer is formed into pellets. A dried fluoropolymer is usually used for forming the fluoropolymer. The fluoropolymer can be formed by a known method such as extrusion.

[0167] (Fluoropolymer) By using the production method of the present disclosure, a fluoropolymer having a low content of a fluorine-containing compound having a hydrophilic group can be obtained.

[0168] The form of the fluoropolymer obtained by the production method of the present disclosure is not particularly limited, and may be, for example, a powder, a pellet, primary particles dispersed in an aqueous dispersion, etc. In one embodiment, the form of the fluoropolymer obtained by the production method of the present disclosure is a powder or a pellet.

[0169] The content of the fluorine-containing compound having a hydrophilic group in the fluoropolymer may be more than 0 mass ppb and less than 300 mass ppb relative to the fluoropolymer. The preferred upper limit of the content of the fluorine-containing compound having a hydrophilic group in the fluoropolymer is 250 mass ppb or less, 200 mass ppb or less, 150 mass ppb or less, 100 mass ppb or less, 75 mass ppb or less, 50 mass ppb or less, or 25 mass ppb or less.

[0170] Examples of the fluorine-containing compound having a hydrophilic group include the fluorine-containing surfactants described above for use in the polymerization of fluoromonomers. Typical fluorine-containing surfactants are those having a molecular weight of 1,000 g / mol or less, preferably 800 g / mol or less.

[0171] In one embodiment of the fluoropolymer, the fluoropolymer is substantially free of a compound represented by the following general formula (1) as a fluorine-containing compound having a hydrophilic group: － ] ｉ M ｉ＋ (Wherein, X represents H, Cl, Br, F or I; Rf represents a linear or branched partially or fully fluorinated aliphatic group, or a linear or branched partially or fully fluorinated aliphatic group interrupted by at least one oxygen atom; A － is an acid group, M ｉ＋ represents a cation having a valence i, where i is an integer from 1 to 3.

[0172] In one embodiment of the fluoropolymer, the fluoropolymer is substantially free of a compound represented by the following general formula (2) as a fluorine-containing compound having a hydrophilic group. ｎ－１ F ２ｎ－１ COO － ]M ＋ (wherein n is an integer of 9 to 14, M ＋ represents a cation.)

[0173] The compound represented by general formula (2) (perfluoroalkanoic acid) is known to be formed during polymerization when perfluoroalkyl vinyl ether or the like is used as a modified monomer (see WO 2019 / 161153).

[0174] In one embodiment of the fluoropolymer, the fluoropolymer is substantially free of a compound represented by the following general formula (3) as a fluorine-containing compound having a hydrophilic group: １ -O-L-CO ２ － ]M ＋ (In the formula, R １ represents a linear or branched partially or fully fluorinated aliphatic group, or a linear or branched partially or fully fluorinated aliphatic group interrupted by at least one oxygen atom; L represents a linear or branched non-fluorinated, partially fluorinated or fully fluorinated alkylene group; M represents a linear or branched non-fluorinated, partially fluorinated or fully fluorinated alkylene group; ＋ represents a cation.)

[0175] In one embodiment of the fluoropolymer, the fluoropolymer is substantially free of a compound represented by general formula (4) as a fluorine-containing compound having a hydrophilic group. ２ ) ｍ CO ２ － ]M ＋ (wherein m is an integer of 3 to 19, M ＋ represents a cation.)

[0176] In the present disclosure, "substantially free of any of the compounds represented by general formulas (1) to (4)" means that the content of any of the compounds represented by general formulas (1) to (4) in the fluoropolymer is 100 mass ppb or less. The content of any of the compounds represented by general formulas (1) to (4) in the fluoropolymer is preferably 80 mass ppb or less, more preferably 60 mass ppb or less, even more preferably 40 mass ppb or less, still more preferably 25 mass ppb or less, particularly preferably 1 mass ppb or less, and most preferably below the detection limit of the fluorine-containing surfactant as measured by liquid chromatography mass spectrometry (LC / MS).

[0177] The content of the fluorine-containing compound having a hydrophilic group in the fluoropolymer can be quantified by known methods. For example, it can be quantified by LC / MS analysis. First, methanol is added to the fluoropolymer, extraction is performed, and the resulting extract is analyzed by LC / MS. To further improve the extraction efficiency, treatments such as Soxhlet extraction and ultrasonic treatment may be performed. The resulting extract is appropriately concentrated with a nitrogen purge, and the fluorine-containing compound having a hydrophilic group in the concentrated extract is measured by LC / MS. Molecular weight information is extracted from the obtained LC / MS spectrum, and its agreement with the structural formula of the candidate fluorine-containing compound having a hydrophilic group is confirmed. Thereafter, aqueous solutions containing five or more levels of the confirmed fluorine-containing compound having a hydrophilic group are prepared, and LC / MS analysis of the aqueous solutions with each content is performed. The relationship between the content and the area area relative to the content is plotted, and a calibration curve is drawn. Then, using the calibration curve, the area area of ​​the LC / MS chromatogram of the fluorine-containing compound having a hydrophilic group in the extract can be converted to the content of the fluorine-containing compound having a hydrophilic group. The resulting extract can be concentrated by purging with nitrogen, which allows the lower limit of quantitation of the measurement method to be lowered.

[0178] The present disclosure also provides a modified polytetrafluoroethylene powder in which the ΔPPVE amount of the modified polytetrafluoroethylene is 0.002 mass% or more and the content of the fluorine-containing compound having a hydrophilic group represented by general formula (2) is 100 mass ppb or less relative to the mass of the modified polytetrafluoroethylene. ｎ－１ F ２ｎ－１ COO － ]M ＋ (wherein n is an integer of 9 to 14, M ＋ represents a cation.)

[0179] The modified polytetrafluoroethylene (modified PTFE) preferably contains a perfluorovinyl ether unit as the modifying monomer unit, and more preferably contains a perfluoro(propyl vinyl ether) (PPVE) unit as the modifying monomer unit.

[0180] The ΔPPVE amount (Δperfluoro(propyl vinyl ether) amount) is preferably 0.003 mass % or more, more preferably 0.005 mass % or more, even more preferably 0.007 mass % or more, and preferably 0.020 mass % or less.

[0181] The ΔPPVE amount is the difference in PPVE content (mass %) in the modified PTFE before and after heating. The ΔPPVE amount can be measured by the measurement method described in the examples.

[0182] The content of the fluorine-containing compound having a hydrophilic group represented by general formula (2) is preferably 90 mass ppb or less, more preferably 80 mass ppb or less, even more preferably 70 mass ppb or less, still more preferably 60 mass ppb or less, particularly preferably 50 mass ppb or less, and preferably 0 mass ppb or more, relative to the mass of the modified PTFE.

[0183] Next, the fluoropolymer obtained by the production method of the present disclosure will be described in more detail.

[0184] Fluoropolymers such as fluororesins and fluororubbers can be obtained by polymerization of fluoromonomers.

[0185] Examples of the fluoropolymer include a TFE polymer 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.

[0186] Preferably, the fluoropolymer has 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 have an ion exchange ratio of 1000 or greater, more preferably 2000 or greater, and even more preferably 5000 or greater.

[0187] 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; ω-hydroperfluoroolefin, etc.

[0188] 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.

[0189] 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.

[0190] 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.

[0191] The CTFE polymer may also be a copolymer of CTFE with 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.

[0192] 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.

[0193] In the production method of the present disclosure, it is preferable to produce a fluororesin as the fluoropolymer.

[0194] In the production method of the present disclosure, for example, (I) a tetrafluoroethylene polymer [TFE polymer (PTFE)] can be suitably produced as a non-melt-processable fluororesin, and (II) an ethylene / TFE copolymer [ETFE], a TFE / HFP copolymer [FEP], a TFE / perfluoro(alkyl vinyl ether) copolymer [PFA, MFA, etc.], a TFE / perfluoroallyl ether copolymer, a TFE / VDF copolymer, or an electrolyte polymer precursor can be suitably produced as a melt-processable fluororesin.

[0195] 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 still 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

[0196] The perfluororesin is preferably a fluororesin having a fluorine substitution rate of 95 to 100%, more preferably polytetrafluoroethylene (PTFE), FEP, or PFA, still more preferably PTFE or PFA, and particularly preferably PTFE. FEP and PFA include TFE / HFP / perfluoro(alkyl vinyl ether) copolymers.

[0197] The fluoropolymer may have a core-shell structure. Examples of fluoropolymers having a core-shell structure include modified PTFE particles containing a core of high molecular weight PTFE and a shell of lower molecular weight PTFE or modified PTFE. Examples of such modified PTFE include the PTFE described in JP-A-2005-527652.

[0198] The core-shell structure may have the following structures: 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

[0199] In the fluoropolymer having the core-shell structure, the lower limit of the core ratio is preferably 0.5% by mass, more preferably 1.0% by mass, even more preferably 2.0% 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 core 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.

[0200] 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 2.0% 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.

[0201] In the fluoropolymer having the core-shell structure, the core or the shell can be configured to have two or more layers. For example, it may be a fluoropolymer having a three-layer structure with a core center portion of modified PTFE, a core outer layer portion of TFE homopolymer, and a shell of modified PTFE.

[0202] The fluoropolymer having the core-shell structure also includes a particle of the fluoropolymer having multiple cores.

[0203] The above-mentioned (I) non-melt-processible fluororesin and (II) melt-processible fluororesin, which are preferably produced by the production method of the present disclosure, are preferably produced in the following manner.

[0204] (I) Non-melt-processable fluororesin In the production method of the present disclosure, 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. Also, it is more preferably 120 ° C or lower, and even more preferably 100 ° C or lower. Also, the polymerization pressure is more preferably 0.3 MPaG or higher, and even more preferably 0.5 MPaG or higher, and also 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 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.

[0205] In one embodiment, the polymerization is carried out by charging pure water into a pressure-resistant reactor equipped with a stirrer, deoxidizing, then charging TFE, adjusting the temperature to a predetermined value, and adding a polymerization initiator to start the reaction. If the pressure decreases as the reaction proceeds, additional TFE is continuously or intermittently supplied to maintain the initial pressure. When a predetermined amount of TFE has been supplied, the supply is stopped, the TFE in the reactor is purged, and the temperature is returned to room temperature to terminate the reaction. Additional TFE may be continuously or intermittently supplied to prevent the pressure from decreasing.

[0206] In the production of above-mentioned TFE polymer (PTFE), also can use various known modified monomers together.In this disclosure, above-mentioned TFE polymer is not only TFE homopolymer, but also the concept of TFE and modified monomer copolymer, which is non-melt processable (hereinafter referred to as "modified PTFE").

[0207] The modifying monomer is not particularly limited as long as it can be copolymerized with TFE, and includes fluoromonomers and non-fluoromonomers. The modifying monomer used may be one type or multiple types.

[0208] The non-fluoromonomer is not particularly limited and may be a monomer represented by the general formula: ２ =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 represents the bonding position with Ｑ２ represents a hydrogen atom, an alkyl group or a nitrile group.

[0209] 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.

[0210] 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.

[0211] The perfluorovinyl ether is not particularly limited, and examples thereof include perfluorovinyl ethers represented by the general formula (A): CF ２ ═CF-ORf (A) (wherein Rf represents a perfluoroorganic group). In the present disclosure, 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.

[0212] Examples of the perfluorovinyl ether include perfluoro(alkyl vinyl ether) [PAVE], which is represented by general formula (A) and in which Rf is a perfluoroalkyl group having 1 to 10 carbon atoms. The number of carbon atoms in the perfluoroalkyl group is preferably 1 to 5.

[0213] 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.

[0214] 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 ... the following formula:

[0215]

[0216] (wherein m represents 0 or an integer of 1 to 4), and Rf is a group represented by the following formula:

[0217] CF ３ CF ２ CF ２ -(O-CF(CF ３ )-CF ２ ) ｎ - (wherein n represents an integer of 1 to 4).

[0218] Hydrogen-containing fluoroolefins include CH ２ =CF ２ , CFH=CH ２ , CFH=CF ２ , C.H. ２ =CFCF ３ , C.H. ２ = CHCF ３ , CHF=CHCF ３ (E form), CHF=CHCF ３ (Z-isomer), etc.

[0219] The (perfluoroalkyl)ethylene (PFAE) is not particularly limited, and examples thereof include (perfluorobutyl)ethylene (PFBE) and (perfluorohexyl)ethylene.

[0220] Examples of perfluoroallyl ethers include those represented by the general formula: CF ２ =CF-CF ２Examples of the fluoromonomer include those represented by —ORf (wherein Rf represents a perfluoroorganic group).

[0221] 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. Examples of perfluoroallyl ethers include CF ２ =CF-CF ２ -O-CF ３ , C.F. ２ =CF-CF ２ -O-C ２ F ５ , C.F. ２ =CF-CF ２ -O-C ３ F ７ , and CF ２ =CF-CF ２ -O-C ４ F ９ At least one selected from the group consisting of CF ２ =CF-CF ２ -O-C ２ F ５ , C.F. ２ =CF-CF ２ -O-C ３ F ７ , and CF ２ =CF-CF ２ -O-C ４ F ９ More preferably, at least one selected from the group consisting of CF ２ =CF-CF ２ -O-CF ２ CF ２ CF ３ is more preferred.

[0222] The modified monomer (3) is also a preferred example of the modified monomer. The modified monomer (3) is preferably at least one selected from the group consisting of modified monomers represented by formulas (3a) to (3d). CH ２ =CH-Rf １ (3a) (wherein, Rf １ is a perfluoroalkyl group having 1 to 10 carbon atoms.) CF２ ═CF—O—Rf ２ (3b) (wherein, Rf ２ is a perfluoroalkyl group having 1 to 2 carbon atoms.) CF ２ =CF-O-(CF ２ ) ｎ CF = CF ２ (3c) (Wherein, n is 1 or 2.)

[0223] (In the formula, X ３ and X ４ is F, Cl or a methoxy group, and Y is of formula Y1 or Y2.

[0224] (In formula Y2, Z and Z′ are F or a fluorinated alkyl group having 1 to 3 carbon atoms.)

[0225] The content of the modified monomer (3) unit 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, more preferably 0.0005% 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% by mass, 0.50% by mass, 0.40% by mass, 0.30% by mass, 0.20% by mass, 0.15% by mass, 0.10% by mass, 0.08% by mass, 0.05% by mass, and 0.01% by mass.

[0226] As the above-mentioned modified monomer, because it can obtain the aqueous dispersion of the average primary particle diameter of primary particle is small, the aspect ratio of primary particle is small, and excellent stability, it is preferred to be selected from the group consisting of hexafluoropropylene, chlorotrifluoroethylene, vinylidene fluoride, perfluoro(alkyl vinyl ether), (perfluoroalkyl)ethylene, ethylene, and the modified monomer of the functional group and hydrophilic group that can react by radical polymerization.By using the above-mentioned modified monomer, it can obtain the aqueous dispersion of PTFE that has the average primary particle diameter smaller, the aspect ratio of primary particle is small, and excellent dispersion stability.In addition, it can obtain the aqueous dispersion of less uncoagulated polymer.

[0227] From the viewpoint of reactivity with TFE, the modified monomer preferably contains at least one selected from the group consisting of hexafluoropropylene, perfluoro(alkyl vinyl ether), and (perfluoroalkyl)ethylene. More preferably, it contains at least one selected from the group consisting of hexafluoropropylene, perfluoro(methyl vinyl ether), perfluoro(propyl vinyl ether), (perfluorobutyl)ethylene, (perfluorohexyl)ethylene, and (perfluorooctyl)ethylene. The total amount of the hexafluoropropylene unit, perfluoro(alkyl vinyl ether) unit, and (perfluoroalkyl)ethylene unit is preferably in the range of 0.00001 to 1% by mass relative to the total polymerization units of PTFE. The lower limit of the total amount is more preferably 0.0001% by mass, more preferably 0.0005% 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, 0.80 mass%, 0.70 mass%, 0.50 mass%, 0.40 mass%, 0.30 mass%, 0.20 mass%, 0.15 mass%, 0.10 mass%, and 0.08 mass%.

[0228] The 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)").

[0229] By making the above-mentioned modified monomer (A) exist, it is possible to obtain the PTFE particles with small primary particle diameter, and obtain the aqueous dispersion with high dispersion stability.In addition, it is also possible to reduce the amount of uncoagulated polymer.Furthermore, it is possible to reduce the aspect ratio of primary particle.

[0230] The amount of the modified monomer (A) used is preferably more than the 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 diameter of the resulting PTFE may not be small. 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 addition, 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.

[0231] The 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 steps.

[0232] The above-mentioned modified monomer (A) is incorporated into the produced polymer during the polymerization process, but since the concentration of the modified 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.

[0233] The hydrophilic group in the modified monomer (A) is, for example, —NH ２ , -PO ３ M, -OPO ３ M, -SO ３ M, -OSO ３ M, -COOM (in each formula, M is H, a metal atom, NR ７ｙ ４ , optionally substituted imidazolium, optionally substituted pyridinium or optionally substituted phosphonium, 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.) Among the above hydrophilic groups, -SO ３ M or -COOM is preferred. ７ｙ The organic group in R is preferably an alkyl group. ７ｙAs the group, H or C １－１０ is preferably an organic group represented by the formula: １－４ More preferred are organic groups represented by the formula: １－４ The metal atom is preferably a monovalent or divalent metal atom, such as an alkali metal (Group 1) or an alkaline earth metal (Group 2), and more preferably Na, K, or Li.

[0234] 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- (wherein, X ｅ , X ｆ and X ｇ are each independently F, Cl, H, or CF ３ , C.F. ２ H, C.F.H. ２ , or CH ３ and R is a linking group. The linking group of R can be represented by the formula: ａ Preferably, the linking group is -CH=CH ２ , -CF=CH ２、 -CH=CF ２、 -CF = CF ２ , -CH ２ -CH=CH ２ , -CF ２ -CF=CH ２ , -CF ２ -CF = CF ２ , -(C=O)-CH=CH ２ , -(C=O)-CF=CH ２ , -(C=O)-CH=CF ２ , -(C=O)-CF=CF ２ , -(C=O)-C(CH ３ ) = CH ２ , -(C=O)-C(CF ３ ) = CH ２ , -(C=O)-C(CH ３ ) = CF ２ , -(C=O)-C(CF ３ ) = CF ２, —O—CH ２ -CH=CH ２ , —O—CF ２ -CF=CH ２ , —O—CH ２ -CH=CF ２ , —O—CF ２ -CF = CF ２ Examples of groups having an unsaturated bond include the following.

[0235] The modified monomer (A) has a functional group that can react by radical polymerization, so when used in the polymerization, it is assumed that it will react with the fluorine-containing monomer at the initial stage of the polymerization reaction, and form particles that have hydrophilic groups derived from the modified monomer (A) and have high stability.Therefore, it is thought that when polymerization is carried out in the presence of the modified monomer (A), the number of particles will increase.

[0236] 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 thereof.

[0237] In the polymerization, a compound having an unsaturated bond can be used as the modifying monomer (A).

[0238] The modifying monomer (A) is a compound represented by the general formula (4): ｉ X ｋ =CX ｊ R ａ - (CZ １ Z ２ ) ｋ -Y ３ (4) (wherein, X ｉ , X ｊ and X ｋ are each independently F, Cl, H or CF ３ and Y ３ is a hydrophilic group; R ａ is a linking group; Z １ and Z ２ are each independently H, F or CF ３ and k is 0 or 1. Examples of the hydrophilic group include —NH ２ , -PO ３ M, -OPO ３ M, -SO ３ M, -OSO３ M, -COOM (in each formula, M is H, a metal atom, NR ７ｙ ４ , optionally substituted imidazolium, optionally substituted pyridinium or optionally substituted phosphonium, 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.) Among the above hydrophilic groups, -SO ３ M or -COOM is preferred. ７ｙ The organic group in R is preferably an alkyl group. ７ｙ As the group, H or C １－１０ is preferably an organic group represented by the formula: １－４ More preferred are organic groups represented by the formula: １－４ The alkyl group represented by the formula (I) is more preferred. Examples of the metal atom include monovalent and divalent metal atoms, such as alkali metals (Group 1) and alkaline earth metals (Group 2), with Na, K, or Li being preferred. By using the modified monomer (A), an aqueous dispersion having a smaller average primary particle size and better stability can be obtained. Furthermore, the aspect ratio of the primary particles can be made smaller.

[0239] The above R ａ is a linking group. In the present disclosure, a "linking group" refers to a divalent linking group. The linking group may be a single bond and preferably contains at least one carbon atom. 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 have a linear or branched, cyclic or acyclic 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 contain a catenary heteroatom such as oxygen, sulfur, or nitrogen.

[0240] The above R ａ is preferably a catenary heteroatom such as oxygen, sulfur, or nitrogen, or a divalent organic group. ａ When 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 the group may or may not contain a double bond. ａ may be either linear or branched, and may be either cyclic or acyclic. ａ R may contain functional groups (e.g., esters, ethers, ketones, amines, halides, etc.). ａ R may also be a non-fluorinated divalent organic group, or a partially fluorinated or perfluorinated divalent organic group. 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 an ether bond, which may contain an oxygen atom, a double bond, or a functional group.

[0241] 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 and may contain a carbonyl group, and in the hydrocarbon group, some or all of the hydrogen atoms bonded to the carbon atoms may be substituted with fluorine. ａ is preferably —(CH ２ ) ａ -, - (CF ２ ) ａ -, -O-(CF ２ ) ａ -, - (CF ２ ) ａ -O-(CF ２ ) ｂ -, -O(CF ２ ) ａ -O-(CF ２ ) ｂ -, - (CF ２ ) ａ-[O-(CF ２ ) ｂ ] ｃ -、-O(CF ２ ) ａ -[O-(CF ２ ) ｂ ] ｃ -、-[(CF ２ ) ａ -O] ｂ -[(CF ２ ) ｃ -O] ｄ -、-O[(CF ２ ) ａ -O] ｂ -[(CF ２ ) ｃ -O] ｄ -、-O-[CF ２ CF(CF ３ )O] ａ -(CF ２ ) ｂ -、-(C=O)-、-(C=O)-O-、-(C=O)-(CH ２ ) ａ -、-(C=O)-(CF ２ ) ａ -、-(C=O)-O-(CH ２ ) ａ -、-(C=O)-O-(CF ２ ) ａ -、-(C=O)-[(CH ２ ) ａ -O] ｂ -、-(C=O)-[(CF ２ ) ａ -O] ｂ -、-(C=O)-O[(CH ２ ) ａ -O] ｂ -、-(C=O)-O[(CF ２ ) ａ -O] ｂ -、-(C=O)-O[(CH ２ ) ａ -O] ｂ -(CH ２ ) ｃ -、-(C=O)-O[(CF ２ ) ａ -O] ｂ -(CF ２ ) ｃ-, -(C=O)-(CH ２ ) ａ -O-(CH ２ ) ｂ -, -(C=O)-(CF ２ ) ａ -O-(CF ２ ) ｂ -, -(C=O)-O-(CH ２ ) ａ -O-(CH ２ ) ｂ -, -(C=O)-O-(CF ２ ) ａ -O-(CF ２ ) ｂ -, -(C=O)-OC ６ H ４ - and at least one selected from 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 limits of a, b, c, and d are, for example, 100.

[0242] R ａ A specific example of a suitable group is —CF ２ —O—, —CF ２ -O-CF ２ -, -CF ２ -O-CH ２ -, -CF ２ -O-CH ２ CF ２ -, -CF ２ -O-CF ２ CF ２ -, -CF ２ -O-CF ２ CH ２ -, -CF ２ -O-CF ２ CF ２ CH ２ -, -CF ２ -O-CF(CF ３ ) -, -CF ２ -O-CF(CF ３ )CF ２ -, -CF ２ -O-CF(CF ３ )CF ２-O-, -CF ２ -O-CF(CF ３ )CH ２ -(C=O)-, -(C=O)-O-, -(C=O)-(CH ２ )-, -(C=O)-(CF ２ )-, -(C=O)-O-(CH ２ )-, -(C=O)-O-(CF ２ )-, -(C=O)-[(CH ２ ) ２ -O] ｎ -, -(C=O)-[(CF ２ ) ２ -O] ｎ -, -(C=O)-O[(CH ２ ) ２ -O] ｎ -, -(C=O)-O[(CF ２ ) ２ -O] ｎ -, -(C=O)-O[(CH ２ ) ２ -O] ｎ -(CH ２ )-, -(C=O)-O[(CF ２ ) ２ -O] ｎ -(CF ２ )-, -(C=O)-(CH ２ ) ２ -O-(CH ２ )-, -(C=O)-(CF ２ ) ２ -O-(CF ２ )-, -(C=O)-O-(CH ２ ) ２ -O-(CH ２ )-, -(C=O)-O-(CF ２ ) ２ -O-(CF ２ )-, -(C=O)-O-C ６ H ４ - etc. are included. Among them, the above R ａ is specifically, -CF ２ -O-, -CF ２ -O-CF ２ -, -CF ２ -O-CF ２ CF ２ -, -CF ２-O-CF(CF ３ ) -, -CF ２ -O-CF(CF ３ )CF ２ -, -CF ２ -O-CF(CF ３ )CF ２ -O-, -(C=O)-, -(C=O)-O-, -(C=O)-(CH ２ )-,-(C=O)-O-(CH ２ )-,-(C=O)-O[(CH ２ ) ２ -O] ｎ -, -(C=O)-O[(CH ２ ) ２ -O] ｎ - (CH ２ )-,-(C=O)-(CH ２ ) ２ -O-(CH ２ )-, or -(C=O)-O-C ６ H ４ In the above formula, n is an integer of 1 to 10.

[0243] -R in general formula (4) ａ - (CZ １ Z ２ ) ｋ - is -CF ２ -O-CF ２ -, -CF ２ -O-CF(CF ３ ) -, -CF ２ -O-C(CF ３ ) ２ -, -CF ２ -O-CF ２ -CF ２ -, -CF ２ -O-CF ２ -CF (CF ３ ) -, -CF ２ -O-CF ２ -C(CF ３ ) ２ -, -CF ２ -O-CF ２ CF ２ -CF ２ -, -CF ２ -O-CF ２ CF ２ -CF (CF３ )-、-CF ２ -O-CF ２ CF ２ -C(CF ３ ) ２ -、-CF ２ -O-CF(CF ３ )-CF ２ -、-CF ２ -O-CF(CF ３ )-CF(CF ３ )-、-CF ２ -O-CF(CF ３ )-C(CF ３ ) ２ -、-CF ２ -O-CF(CF ３ )CF ２ -CF ２ -、-CF ２ -O-CF(CF ３ )CF ２ -CF(CF ３ )-、-CF ２ -O-CF(CF ３ )CF ２ -C(CF ３ ) ２ -、-CF ２ -O-CF(CF ３ )CF ２ -O-CF ２ -、-CF ２ -O-CF(CF ３ )CF ２ -O-CF(CF ３ )-、-CF ２ -O-CF(CF ３ )CF ２ -O-C(CF ３ ) ２ -、-(C=O)-、-(C=O)-O-、-(C=O)-(CH ２ )-、-(C=O)-(CF ２ )-、-(C=O)-O-(CH ２ )-、-(C=O)-O-(CF ２ )-、-(C=O)-[(CH ２ ) ２ -O] ｎ -(CH ２ )-、-(C=O)-[(CF ２ ) ２ -O]ｎ -(CF ２ )-、-(C=O)-[(CH ２ ) ２ -O] ｎ -(CH ２ )-(CH ２ )-、-(C=O)-[(CF ２ ) ２ -O] ｎ -(CF ２ )-(CF ２ )-、-(C=O)-O[(CH ２ ) ２ -O] ｎ -(CF ２ )-、-(C=O)-O[(CH ２ ) ２ -O] ｎ -(CH ２ )-(CH ２ )-、-(C=O)-O[(CF ２ ) ２ -O] ｎ -(CF ２ )-、-(C=O)-O[(CF ２ ) ２ -O] ｎ -(CF ２ )-(CF ２ )-、-(C=O)-(CH ２ ) ２ -O-(CH ２ )-(CH ２ )-、-(C=O)-(CF ２ ) ２ -O-(CF ２ )-(CF ２ )-、-(C=O)-O-(CH ２ ) ２ -O-(CH ２ )-(CH ２ )-、-(C=O)-O-(CF ２ ) ２ -O-(CF ２ )-(CF ２ )-、-(C=O)-O-(CH ２ ) ２ -O-(CH ２ )-C(CF ３ ) ２ -、-(C=O)-O-(CF ２ ) ２ -O-(CF２ )-C(CF ３ ) ２ - or -(C=O)-O-C ６ H ４ -C(CF ３ ) ２ - is preferred, and -CF ２ -O-CF(CF ３ ) -, -CF ２ -O-CF ２ -CF (CF ３ ) -, -CF ２ -O-CF ２ CF ２ -CF (CF ３ ) -, -CF ２ -O-CF(CF ３ )-CF(CF ３ ) -, -CF ２ -O-CF(CF ３ )CF ２ -CF (CF ３ ) -, -CF ２ -O-CF(CF ３ )CF ２ -O-CF(CF ３ )-, -(C=O)-, -(C=O)-O-(CH ２ )-,-(C=O)-O-(CH ２ )-(CH ２ )-,-(C=O)-O[(CH ２ ) ２ -O] ｎ - (CH ２ )-(CH ２ )-,-(C=O)-O-(CH ２ ) ２ -O-(CH ２ )-C(CF ３ ) ２ - or -(C=O)-O-C ６ H ４ -C(CF ３ ) ２ In the above formula, n is an integer of 1 to 10.

[0244] Specific examples of the compound represented by formula (4) include: (In the formula, X ｊ and Y ３ is the same as above. n is an integer of 1 to 10.

[0245] R ａ As the general formula (r1): -(C=O) ｈ -(O) ｉ -CF ２ -O-(CX ６ ２ ) ｅ -{O-CF(CF ３ ) ｆ -(O) ｇ - (r1) (wherein, X ６ are each independently H, F or CF ３ wherein 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 -CF ２ -O-(CX ７ ２ ) ｅ -(O) ｇ - (r2) (wherein, X ７ are each independently H, F or CF ３ wherein e is an integer of 0 to 3, g is 0 or 1, h is 0 or 1, and i is 0 or 1.) is also preferred.

[0246] -R in general formula (4) ａ - (CZ １ Z ２ ) ｋ - may also be represented by the following formula (t1): -(C=O) ｈ -(O) ｉ -CF ２ -O-(CX ６ ２ ) ｅ -{O-CF(CF ３ ) ｆ -(O) ｇ -CZ １ Z ２ - (t1) (wherein, X ６ are each independently H, F or CF ３ wherein 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 １and Z ２ are each independently F or CF ３ In formula (t1), a divalent group represented by １ and Z ２ is one F and the other CF ３ In addition, in the general formula (4), -R ａ - (CZ １ Z ２ ) ｋ - is the following formula (t2): -(C=O) ｈ -(O) ｉ -CF ２ -O-(CX ７ ２ ) ｅ -(O) ｇ -CZ １ Z ２ - (t2) (wherein, X ７ are each independently H, F or CF ３ wherein 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 CF ３ In formula (t2), a divalent group represented by １ and Z ２ is one F and the other CF ３ It is more preferable that:

[0247] The compound represented by the general formula (4) is a compound having a hydrophilic group (Y ３ ) except for the above, 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 number of carbon atoms in the perfluoroalkylene group may be 2 to 20, or may be 4 to 18.

[0248] 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.

[0249] The compound represented by general formula (4) is also preferably a compound represented by the following formula (4a): CF ２ ═CF—O—Rf ０ -Y ３ (4a) (wherein, 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.

[0250] The compound represented by general formula (4) is also preferably a compound represented by the following formula (4b): CH ２ =CH-O-Rf ０ -Y ３ (4b) (wherein, Y ３ is a hydrophilic group, and Rf ０ is a perfluorinated divalent linking group defined by formula (4a).

[0251] In the general formula (4), Y ３ Ha-OSO ３ One of the preferred embodiments is Y. ３ Ga-OSO ３ When M is a compound represented by general formula (4), CF ２ =CF(OCF ２ CF ２ CH ２ OSO ３ M), CF ２ =CF(O(CF ２ ) ４ CH ２ OSO ３ M), CF ２ =CF(OCF ２ CF (CF ３ ) CH２ OSO ３ M), CF ２ =CF(OCF ２ CF (CF ３ ) OCF ２ CF ２ CH ２ OSO ３ M), CH ２ =CH((CF ２ ) ４ CH ２ OSO ３ M), CF ２ =CF(OCF ２ CF ２ SO ２ N (CH ３ ) CH ２ CH ２ OSO ３ M), CH ２ =CH(CF ２ CF ２ CH ２ OSO ３ M), CF ２ =CF(OCF ２ CF ２ CF ２ CF ２ SO ２ N (CH ３ ) CH ２ CH ２ OSO ３ In the above formula, M is the same as above.

[0252] In the general formula (4), Y ３ Ha-SO ３ M is also a preferred embodiment. ３ Ga-SO ３ When M is a compound represented by general formula (4), CF ２ =CF(OCF ２ CF ２ SO ３ M), CF ２ =CF(O(CF ２ ) ４ SO ３ M), CF ２ =CF(OCF ２ CF (CF ３ ) SO ３ M), CF ２=CF(OCF ２ CF (CF ３ ) OCF ２ CF ２ SO ３ M), CH ２ =CH(CF ２ CF ２ SO ３ M), CF ２ =CF(OCF ２ CF (CF ３ ) OCF ２ CF ２ CF ２ CF ２ SO ３ M), CH ２ =CH((CF ２ ) ４ SO ３ M), CH ２ =CH((CF ２ ) ３ SO ３ In the above formula, M is the same as above.

[0253] In the general formula (4), Y ３ It is also a preferred embodiment that Y is -COOM. ３ is -COOM, the compound represented by general formula (4) is CF ２ =CF(OCF ２ CF ２ COOM), C.F. ２ =CF(OCF ２ CF ２ CF ２ COOM), C.F. ２ =CF(O(CF ２ ) ５ COOM), C.F. ２ =CF(OCF ２ CF (CF ３ ) COOM), CF ２ =CF(OCF ２ CF (CF ３ ) O(CF ２ ) ｎ COOM) (n is greater than 1), CH ２ =CH(CF ２ CF ２ COOM), CH ２ =CH((CF ２) ４ COOM), CH ２ =CH((CF ２ ) ３ COOM), C.F. ２ =CF(OCF ２ CF ２ SO ２ NR'CH ２ COOM), C.F. ２ =CF(O(CF ２ ) ４ SO ２ NR'CH ２ COOM), C.F. ２ =CF(OCF ２ CF (CF ３ ) SO ２ NR'CH ２ COOM), C.F. ２ =CF(OCF ２ CF (CF ３ ) OCF ２ CF ２ SO ２ NR'CH ２ COOM), CH ２ =CH(CF ２ CF ２ SO ２ NR'CH ２ COOM), C.F. ２ =CF(OCF ２ CF (CF ３ ) OCF ２ CF ２ CF ２ CF ２ SO ２ NR'CH ２ COOM), CH ２ =CH((CF ２ ) ４ SO ２ NR'CH ２ COOM), CH ２ =CH((CF ２ ) ３ SO ２ NR'CH ２ In the above formula, R' is H or C １－４ is an alkyl group, and M is the same as above.

[0254] In the general formula (4), Y ３ Ha-OPO３ M or -OP(O)(OM) ２ It is also a preferred embodiment that ３ Ga-OPO ３ M or -OP(O)(OM) ２ In this case, the compound represented by the general formula (4) is CF ２ =CF(OCF ２ CF ２ CH ２ OP (O) (OM) ２ ), CF ２ =CF(O(CF ２ ) ４ CH ２ OP (O) (OM) ２ ), CF ２ =CF(OCF ２ CF (CF ３ ) CH ２ OP (O) (OM) ２ ), CF ２ =CF(OCF ２ CF (CF ３ ) OCF ２ CF ２ CH ２ OP (O) (OM) ２ ), CF ２ =CF(OCF ２ CF ２ SO ２ N (CH ３ ) CH ２ CH ２ OP (O) (OM) ２ ), CF ２ =CF(OCF ２ CF ２ CF ２ CF ２ SO ２ N (CH ３ ) CH ２ CH ２ OP (O) (OM) ２ ), C.H. ２ =CH(CF ２ CF ２ CH ２ OP (O) (OM) ２ , C.H. ２ =CH((CF ２ ) ４ CH ２ OP (O) (OM)２ ), C.H. ２ =CH((CF ２ ) ３ CH ２ OP (O) (OM) ２ In the above formula, M is the same as above.

[0255] In the general formula (4), Y ３ Ha-PO ３ M or -P(O)(OM) ２ It is also a preferred embodiment that ３ Ga-PO ３ M or -P(O)(OM) ２ In this case, the compound represented by the general formula (4) is CF ２ =CF(OCF ２ CF ２ P(O)(OM) ２ ), CF ２ =CF(O(CF ２ ) ４ P(O)(OM) ２ ), CF ２ =CF(OCF ２ CF (CF ３ ) P (O) (OM) ２ ), CF ２ =CF(OCF ２ CF (CF ３ ) OCF ２ CF ２ P(O)(OM) ２ ), C.H. ２ =CH(CF ２ CF ２ P(O)(OM) ２ ), C.H. ２ =CH((CF ２ ) ４ P(O)(OM) ２ ), C.H. ２ =CH((CF ２ ) ３ P(O)(OM) ２ ) and the like, in which M is the same as above.

[0256] The compound represented by the general formula (4) includes a compound represented by the general formula (5): CX ２ =CY(-CZ ２ -O-Rf-Y ３) (5) (In the formula, X is the same or different and is -H or -F; Y is -H, -F, an alkyl group or a fluorine-containing alkyl group; Z is the same or different and is -H, -F, an alkyl group or a fluorine-containing alkyl group. 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.), a compound represented by general formula (6): CX ２ =CY(-O-Rf-Y ３ ) (6) (In the formula, X is 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 an ether bond and having 2 to 100 carbon atoms. Y ３ is the same as above.) and a compound represented by general formula (7): CX ２ =CY(-Rf-Y ３ ) (7) (In the formula, X is 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 an ether bond and having 2 to 100 carbon atoms. Y ３ is the same as above.) 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 contains an ether bond between carbon atoms.

[0257] In general formula (5), 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.

[0258] In 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 one or more carbon atoms. The alkyl group preferably has six or fewer carbon atoms, more preferably four or fewer carbon atoms, and even more preferably three or fewer carbon atoms. The fluorine-containing alkyl group is an alkyl group that contains at least one fluorine atom, and may have one or more carbon atoms. The fluorine-containing alkyl group preferably has six or fewer carbon atoms, more preferably four or fewer carbon atoms, and even more preferably three or fewer carbon atoms. Y may be -H, -F or -CF ３ is preferred, and —F is more preferred.

[0259] In general formula (5), Z's may be the same or different and are -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 one or more carbon atoms. The alkyl group preferably has six or fewer carbon atoms, more preferably four or fewer carbon atoms, and even more preferably three or fewer carbon atoms. The fluorine-containing alkyl group is an alkyl group that contains at least one fluorine atom, and may have one or more carbon atoms. The fluorine-containing alkyl group preferably has six or fewer carbon atoms, more preferably four or fewer carbon atoms, and even more preferably three or fewer carbon atoms. The Z's may be -H, -F, or -CF ３ is preferred, and —F is more preferred.

[0260] In 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.

[0261] In 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, the number of carbon atoms 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 -CF ２ -, -CH ２ CF ２ -, -CF ２ CF ２ -, -CF ２ CH ２ -, -CF２ CF ２ CH ２ -, -CF(CF ３ ) -, -CF(CF ３ )CF ２ -, -CF(CF ３ ) CH ２ The fluorine-containing alkylene group is preferably a perfluoroalkylene group.

[0262] The number of carbon atoms of the fluorine-containing alkylene group having an ether bond is preferably 3 or more. The number of carbon atoms 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 those represented by the following formula: (In the formula, Z １ is F or CF ３ ;Z ２ and Z ３ are H or F; Z ４ is H, F or CF ３ ; p1+q1+r1 is an integer of 1 to 10; s1 is 0 or 1; t1 is an integer of 0 to 5). Specific examples of the fluorine-containing alkylene group having an ether bond include -CF(CF ３ )CF ２ -O-CF(CF ３ )-,-(CF(CF ３ )CF ２ -O) ｎ -CF (CF ３ )-(wherein n is an integer from 1 to 10), -CF(CF ３ )CF ２ -O-CF(CF ３ ) CH ２ -, -(CF(CF ３ )CF ２ -O) ｎ -CF (CF ３ ) CH ２ - (wherein n is an integer of 1 to 10), -CH ２ CF ２ CF ２ O-CH ２ CF ２ CH ２ -, -CF ２ CF２ CF ２ O-CF ２ CF ２ -, -CF ２ CF ２ CF ２ O-CF ２ CF ２ CH ２ -, -CF ２ CF ２ O-CF ２ -, -CF ２ CF ２ O-CF ２ CH ２ The fluorine-containing alkylene group having an ether bond is preferably a perfluoroalkylene group.

[0263] In the general formula (5), Y ３ is -COOM, -SO ３ M or -OSO ３ M (M is H, metal atom, NR ７ｙ ４ , optionally substituted imidazolium, optionally substituted pyridinium or optionally substituted phosphonium, 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. ７ｙ The organic group in R is preferably an alkyl group. ７ｙ As the group, H or C １－１０ is preferably an organic group represented by the formula: １－４ More preferred are organic groups represented by the formula: １－４ The metal atom includes alkali metals (Group 1) and alkaline earth metals (Group 2), and Na, K, or Li is preferred. M represents —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, and —H, —Na, —K, —Li or NH ４ is more preferred, and —H, —Na, —K or NH ４is even more preferred, -H, -Na or NH ４ is particularly preferred, and —H or —NH ４ The most preferred is the above Y ３ As the group, -COOM or -SO ３ M is preferred, and —COOM is more preferred.

[0264] The compound represented by general formula (5) is preferably a compound (5a) represented by general formula (5a): CH ２ =CF(-CF ２ -O-Rf-Y ３ ) (5a) (wherein Rf and Y ３ is the same as above.)

[0265] Specific examples of the compound represented by general formula (5a) include compounds represented by the following formula:

[0266]

[0267] (In the formula, Z １ is F or CF ３ ;Z ２ and Z ３ are H or F; Z ４ is H, F or CF ３ p1+q1+r1 are an integer of 0 to 10; s1 is 0 or 1; t1 is an integer of 0 to 5; Y ３ is the same as above. However, Z ３ and Z ４ are both H, then p1+q1+r1+s1 is not 0). More specifically, compounds represented by the following formula are exemplified:

[0268]

[0269] Among them,

[0270]

[0271] It is preferable that:

[0272] The compound represented by general formula (5a) includes compounds represented by formula (5a) ３ is preferably -COOM, and in particular CH ２ =CFCF ２ OCF (CF ３ ) COOM, and CH２ =CFCF ２ OCF (CF ３ )CF ２ OCF (CF ３ )COOM (wherein M is as defined above), and CH ２ =CFCF ２ OCF (CF ３ ) COOM is more preferred.

[0273] The compound represented by general formula (5) is preferably a compound (5b) represented by general formula (5b): CX ２ ２ =CFCF ２ -O-(CF(CF ３ )CF ２ O) ｎ５ -CF (CF ３ )-Y ３ (5b) (where each X ２ are the same and represent F or H. n5 represents 0 or an integer of 1 to 10, Y ３ is the same as the above definition.)

[0274] 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, in terms 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 M is preferably H or NH in that it is less likely to remain as an impurity and the heat resistance of the resulting molded article is improved. ４ It is preferable that:

[0275] Examples of the compound represented by the formula (5b) include CH ２ =CFCF ２ OCF (CF ３ ) COOM, C.H. ２ =CFCF ２ OCF (CF ３ )CF ２ OCF (CF ３ ) COOM (wherein M is as defined above).

[0276] Further, examples of the compound represented by the general formula (5) include a compound represented by the general formula (5c).

[0277] CF ２ =CFCF ２ -O-Rf-Y ３ (5c) (wherein Rf and Y ３ is the same as above)

[0278] More specifically, etc.

[0279] In 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.

[0280] In 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 one or more carbon atoms. The alkyl group preferably has six or fewer carbon atoms, more preferably four or fewer carbon atoms, and even more preferably three or fewer carbon atoms. The fluorine-containing alkyl group is an alkyl group that contains at least one fluorine atom, and may have one or more carbon atoms. The fluorine-containing alkyl group preferably has six or fewer carbon atoms, more preferably four or fewer carbon atoms, and even more preferably three or fewer carbon atoms. The Y may be -H, -F or -CF ３ is preferred, and —F is more preferred.

[0281] In 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.

[0282] In 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 -CF ２ -, -CH ２ CF ２ -, -CF２ CF ２ -, -CF ２ CH ２ -, -CF ２ CF ２ CH ２ -, -CF(CF ３ ) -, -CF(CF ３ )CF ２ -, -CF(CF ３ ) CH ２ The fluorine-containing alkylene group is preferably a perfluoroalkylene group.

[0283] In the above general formula (6), Y ３ is -COOM, -SO ３ M or -OSO ３ M (M is H, metal atom, NR ７ｙ ４ , optionally substituted imidazolium, optionally substituted pyridinium or optionally substituted phosphonium, 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. ７ｙ The organic group in R is preferably an alkyl group. ７ｙ As the group, H or C １－１０ is preferably an organic group represented by the formula: １－４ More preferred are organic groups represented by the formula: １－４ The metal atom includes alkali metals (Group 1) and alkaline earth metals (Group 2), and Na, K, or Li is preferred. M represents —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, and —H, —Na, —K, —Li or NH ４ is more preferred, and —H, —Na, —K or NH ４ is even more preferred, -H, -Na or NH ４ is particularly preferred, and —H or —NH ４ The most preferred is the above Y ３As the group, -COOM or -SO ３ M is preferred, and —COOM is more preferred.

[0284] The compound represented by general formula (6) is preferably at least one selected from the group consisting of compounds represented by general formulas (6a), (6b), (6c), (6d), and (6e). ２ =CF-O-(CF ２ ) ｎ１ -Y ３ (6a) (wherein n1 represents an integer of 1 to 10, and Y ３ is the same as the definition above.) CF ２ =CF-O-(CF ２ C (CF ３ ) F) ｎ２ -Y ３ (6b) (wherein n2 represents an integer of 1 to 5, and Y ３ is the same as the definition above.) CF ２ =CF-O-(CFX １ ) ｎ３ -Y ３ (6c) (wherein, X １ is F or CF ３ n3 represents an integer of 1 to 10; Y ３ is the same as the definition above.) CF ２ =CF-O-(CF ２ CFX １ O) ｎ４ -(CF ２ ) 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.) CF ２ =CF-O-(CF ２ CF ２ CFX １ O) ｎ５ -CF ２ CF ２ CF ２ -Y ３ (6e) (wherein n5 represents an integer of 0 to 10, and Y ３ and X １ is the same as the above definition.)

[0285] In the formula (6a), n1 is preferably an integer of 5 or less, and more preferably an integer of 2 or less. ３ is preferable in that it can provide a suitable water solubility and stability of the aqueous dispersion. ３ M is preferably H or NH, in that M is unlikely to remain as an impurity and the heat resistance of the resulting molded article is improved. ４ It is preferable that:

[0286] Examples of the compound represented by the formula (6a) include CF ２ =CF-O-CF ２ COOM, C.F. ２ =CF(OCF ２ CF ２ COOM), C.F. ２ =CF(OCF ２ CF ２ CF ２ COOM), C.F. ２ =CF-O-CF ２ SO ３ M., C.F. ２ =CF(OCF ２ CF ２ SO ３ M), CF ２ =CF(OCF ２ CF ２ CF ２ SO ３ M) (wherein M is as defined above).

[0287] 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 preferable in that it provides suitable water solubility and stability of the aqueous dispersion. ３ M is preferably H or NH, in that M is unlikely to remain as an impurity and the heat resistance of the resulting molded article is improved. ４ It is preferable that:

[0288] In the formula (6c), n3 is preferably an integer of 5 or less in terms of water solubility, and Y ３ is preferable in that it provides suitable water solubility and stability of the aqueous dispersion.３ M is preferably H or NH in that dispersion stability is improved. ４ It is preferable that:

[0289] In the formula (6d), the X １ In terms of the stability of the aqueous dispersion, -CF ３ In terms of water solubility, n4 is preferably an integer of 5 or less, and Y ３ is preferable to -COOM or -SO in that it provides suitable water solubility and stability of the aqueous dispersion. ３ Preferably, M is H or NH. ４ It is preferable that:

[0290] Examples of the compound represented by the formula (6d) include CF ２ = CFOCF ２ CF (CF ３ ) OCF ２ CF ２ COOM, C.F. ２ = CFOCF ２ CF (CF ３ ) OCF ２ COOM, C.F. ２ = CFOCF ２ CF (CF ３ ) OCF ２ CF ２ CF ２ COOM, C.F. ２ = CFOCF ２ CF (CF ３ ) OCF ２ CF ２ SO ３ M., C.F. ２ = CFOCF ２ CF (CF ３ ) OCF ２ SO ３ M., C.F. ２ = CFOCF ２ CF (CF ３ ) OCF ２ CF ２ CF ２ SO ３ M (wherein M is H, NH ４ or an alkali metal.

[0291] In the general formula (6e), n5 is preferably an integer of 5 or less in terms of water solubility, and Y ３ is preferable to -COOM or -SO in that it provides suitable water solubility and stability of the aqueous dispersion. ３ Preferably, M is H or NH. ４ It is preferable that:

[0292] Examples of the compound represented by general formula (6e) include CF ２ = CFOCF ２ CF ２ CF ２ COOM, C.F. ２ = CFOCF ２ CF ２ CF ２ SO ３ M (wherein M is H, NH ４ or an alkali metal.

[0293] In general formula (7), Rf is preferably a fluorine-containing alkylene group having 1 to 40 carbon atoms. In general formula (7), at least one of X and Y preferably contains a fluorine atom.

[0294] The compound represented by general formula (7) is represented by general formula (7a): CF ２ =CF-(CF ２ ) ｎ１ -Y ３ (7a) (wherein n1 represents an integer of 1 to 10, and Y ３ is the same as defined above.) and a compound represented by general formula (7b): CF ２ =CF-(CF ２ C (CF ３ ) F) ｎ２ -Y ３ (7b) (wherein n2 represents an integer of 1 to 5, and Y ３ is as defined above. ３ is -SO ３ M or -COOM is preferred, where M is H, a metal atom, NR ７ｙ ４, optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium. ７ｙ represents H or an organic group.

[0295] In the formula (7a), n1 is preferably an integer of 5 or less, and more preferably an integer of 2 or less. ３ is preferable in that it can provide a suitable water solubility and stability of the aqueous dispersion. ３ M is preferably H or NH, in that M is unlikely to remain as an impurity and the heat resistance of the resulting molded article is improved. ４ The compound represented by the formula (7a) is preferably, for example, CF ２ =CFCF ２ COOM, C.F. ２ =CFCF ２ SO ３ M (wherein M is as defined above).

[0296] 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 preferable in that it provides suitable water solubility and stability of the aqueous dispersion. ３ M is preferably H or NH, in that M is unlikely to remain as an impurity and the heat resistance of the resulting molded article is improved. ４ It is preferable that:

[0297] The modified monomer preferably contains modified monomer (A), and preferably contains at least one selected from the group consisting of compounds represented by general formula (5a), general formula (5c), 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 (5c).

[0298] When using a modified monomer (A) as the modified monomer, the content of the modified monomer (A) unit is preferably in the range of 0.00001 to 1.0 mass% relative to the total polymerized units of the TFE polymer (PTFE).The lower limit is more preferably 0.0001 mass%, more preferably 0.0005 mass%, even more preferably 0.001 mass%, and even more preferably 0.005 mass%.The upper limit is, in order of preference, 0.90 mass%, 0.50 mass%, 0.40 mass%, 0.30 mass%, 0.20 mass%, 0.15 mass%, 0.10 mass%, 0.08 mass%, 0.05 mass%, and 0.01 mass%.

[0299] According to purpose, the aqueous dispersion of TFE polymer can also be preferably used as the composition that organic or inorganic filler is added to in various applications.By coating above-mentioned composition on the substrate that is made of metal or ceramic, it can make the coating surface that has non-adhesiveness and low friction coefficient, and has excellent gloss, smoothness, abrasion resistance, weather resistance and heat resistance, and is suitable for the coating of rolls, cooking utensils, etc., the impregnation processing of glass cloth, etc.

[0300] An organosol of a TFE polymer can also be prepared from the aqueous dispersion. The organosol can contain the TFE polymer and an organic solvent. Examples of the organic solvent include ether-based solvents, ketone-based solvents, alcohol-based solvents, amide-based solvents, ester-based solvents, aliphatic hydrocarbon-based solvents, aromatic hydrocarbon-based solvents, and halogenated hydrocarbon-based 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.

[0301] The aqueous dispersion of above-mentioned TFE polymer is also preferably used as processing aid.When used as processing aid, by mixing the aqueous dispersion with host polymer etc., it can improve the melt strength during the melt processing of host polymer, and can improve the mechanical strength, electrical properties, flame retardancy, anti-dripping property during burning and sliding property of the obtained polymer.

[0302] The aqueous dispersion of the TFE polymer is also preferably used as a binder for batteries and for dust prevention purposes.

[0303] The aqueous dispersion of the TFE polymer is also preferably used as a processing aid after being compounded with a resin other than the TFE polymer.The aqueous dispersion is suitable as a raw material for the PTFE described in, for example, JP-A-11-49912, U.S. Pat. No. 5,804,654, JP-A-11-29679, and JP-A-2003-2980.The processing aid using the aqueous dispersion is in no way inferior to the processing aids described in the above publications.

[0304] The aqueous dispersion of above-mentioned TFE polymer can also be mixed with the aqueous dispersion of melt-processable fluororesin to be coagulated, and be made into coprecipitated powder.Above-mentioned coprecipitated powder is suitable as processing aid.

[0305] Examples of the melt-processable fluororesin include FEP, PFA, TFE / perfluoroallyl ether copolymer, ETFE, ethylene / TFE / HFP copolymer [EFEP], etc., with PFA or FEP being preferred.

[0306] The aqueous dispersion preferably contains the melt-processable fluororesin.The melt-processable fluororesin can be exemplified by FEP, PFA, TFE / perfluoroallyl ether copolymer, ETFE, EFEP, etc.The aqueous dispersion containing the melt-processable fluororesin can be used as coating material.The melt-processable fluororesin can sufficiently fuse the particles of the TFE polymer together, so that it can improve film-forming property and make the obtained coating film glossy.

[0307] 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 the dust of 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 in the dust-suppressing treatment composition described in WO 2007 / 004250, for example, and can also be suitably used in the dust-suppressing treatment method described in WO 2007 / 000812.

[0308] 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.

[0309] The 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 the aqueous dispersion of the TFE polymer and the 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.

[0310] The manufacturing method of the present disclosure can also be used to manufacture low-molecular-weight PTFE. Low-molecular-weight PTFE can be manufactured by polymerization, or by lowering the molecular weight of high-molecular-weight PTFE obtained by polymerization using a known method (thermal decomposition, decomposition by irradiation, etc.).

[0311] 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).

[0312] Furthermore, low-molecular-weight PTFE may be obtained by polymerizing TFE or a monomer copolymerizable with TFE with TFE in the presence of a chain transfer agent. In this case, the chain transfer agent is preferably at least one selected from the group consisting of alkanes having 2 to 4 carbon atoms. Specifically, methane, ethane, propane, butane, and isobutane are more preferred, and ethane and propane are even more preferred. In this case, the amount of chain transfer agent is preferably 10 mass ppm or more or more than 10 mass ppm relative to the aqueous medium.

[0313] 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.

[0314] 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.

[0315] 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.

[0316] The presence or absence of fibrillation properties can be determined by "paste extrusion," a typical method for molding "high molecular weight PTFE powder," which is a powder made from a TFE polymer. Paste extrusion is usually possible because high molecular weight PTFE has fibrillation 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 fibrillation properties.

[0317] 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 the water displacement method in accordance with ASTM D 792 using a sample molded in accordance with ASTM D 4895-89. In this disclosure, "high molecular weight" means that the standard specific gravity is within the above range.

[0318] The low-molecular-weight PTFE has a melt viscosity of 1×10 at 380° C. ２ ~7 x 10 ５ In the present disclosure, "low molecular weight" means that the melt viscosity is within the above range. The melt viscosity is measured in accordance with ASTM D 1238 using a flow tester (manufactured by Shimadzu Corporation) and a 2φ-8L die, with a 2 g sample preheated at 380°C for 5 minutes, and maintained at the above temperature under a load of 0.7 MPa.

[0319] The melt viscosity of the high molecular weight PTFE is much higher than that of the low molecular weight PTFE, making it difficult to measure its melt viscosity accurately. On the other hand, although the melt viscosity of the low molecular weight PTFE can be measured, it is difficult to obtain a molded product from the low molecular weight PTFE that can be used to measure its standard gravity, making it difficult to measure its accurate standard gravity. Therefore, in this disclosure, standard specific gravity is used as an indicator of the molecular weight of the high molecular weight PTFE, and melt viscosity is used as an indicator of the molecular weight of the low molecular weight PTFE. Note that no measurement method is known that can directly determine the molecular weight of either the high molecular weight PTFE or the low molecular weight PTFE.

[0320] 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 can be specified as the temperature corresponding to the maximum value that appears on a differential thermal (DTA) curve obtained by using a TG / DTA (thermogravimetric / differential thermal analyzer) to raise the temperature of PTFE that has not been heated to a temperature of 300° C. or higher at a rate of 10° C. / min.

[0321] The peak temperature of PTFE may be 322 to 347°C. When PTFE is high molecular weight PTFE, the upper limit of the peak temperature of PTFE may be 347°C or lower, 346°C or lower, 345°C or lower, 344°C or lower, 343°C or lower, 342°C or lower, 341°C or lower, or 340°C or lower. When PTFE is high molecular weight PTFE, the lower limit of the peak temperature of PTFE may be 333°C or higher or 335°C or higher. When PTFE is low molecular weight PTFE, the upper limit of the peak temperature of PTFE may be 333°C or lower or 332°C or lower. When PTFE is low molecular weight PTFE, the lower limit of the peak temperature of PTFE may be 322°C or higher or 324°C or higher.

[0322] The average primary particle diameter of the primary particles of low molecular weight PTFE is preferably 10-300 nm, more preferably 50 nm or more, even more preferably 100 nm or more, still more preferably 150 nm or more, and more preferably 250 nm or less.The relatively small average primary particle diameter of the primary particles can be obtained, for example, by adding a modified monomer to the polymerization system at the initial stage of TFE polymerization.

[0323] The average primary particle size of the primary particles of low-molecular-weight PTFE can be measured by dynamic light scattering. First, an aqueous dispersion of low-molecular-weight PTFE with a polymer solids concentration adjusted to about 1.0% by mass is prepared, and the average primary particle size can be measured using dynamic light scattering at a measurement temperature of 25°C, a refractive index of the solvent (water) of 1.3328, a viscosity of the solvent (water) of 0.8878 mPa s, and an accumulation number of 70. For example, an ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.) can be used for the dynamic light scattering method.

[0324] The average primary particle diameter can also be measured by the following method. The dispersion is diluted with water to a solid content of 0.15% by mass, and the transmittance of 550 nm incident light per unit length of the diluted latex obtained and the number-average particle diameter determined by measuring the unidirectional diameter using a transmission electron microscope photograph are measured to prepare a calibration curve. Using this calibration curve, the average particle diameter can be calculated from the measured transmittance of 550 nm incident light of each sample.

[0325] The high-molecular-weight PTFE preferably exhibits at least one endothermic peak in the range of 333 to 347°C in a heat of fusion curve when PTFE that has not been heated to a temperature of 300°C or higher is heated at a rate of 10°C / min using a differential scanning calorimeter (DSC), and the heat of fusion between 290 and 350°C calculated from the heat of fusion curve is 52mJ / mg or more. The heat of fusion of PTFE is more preferably 55mJ / mg or more, and even more preferably 58mJ / mg or more.

[0326] (II) Melt-processable fluororesin (1) In the production method of the present disclosure, 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.

[0327] The monomer composition (mass %) of FEP is preferably TFE:HFP=(60-95):(5-40), more preferably (85-92):(8-15).

[0328] In addition to TFE and HFP, other monomers copolymerizable with these monomers may be polymerized to obtain a copolymer of TFE, HFP, and other monomers as FEP. Examples of the other monomers include the above-mentioned fluoromonomers (excluding TFE and HFP) and non-fluorine-containing monomers. One or more types of other monomers may be used. Perfluoro(alkyl vinyl ether) is preferred as the other monomer. The content of the other monomer units in FEP may be 0.1 to 2% by mass based on the total monomer units.

[0329] In the polymerization of the above-mentioned FEP, it is preferable to use cyclohexane, methanol, ethanol, propanol, ethane, propane, butane, pentane, hexane, carbon tetrachloride, chloroform, methylene chloride, methyl chloride, etc. as a chain transfer agent, and it is preferable to use ammonium carbonate, disodium hydrogen phosphate, etc. as a pH buffer.

[0330] (2) In the production method of the present disclosure, 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.

[0331] 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 preferably a compound represented by the formula: CF ２ =CFORf ４ (wherein, Rf ４ is a perfluoroalkyl group having 1 to 6 carbon atoms).

[0332] In addition to TFE and perfluoro(alkyl vinyl ether), other monomers copolymerizable with these monomers may be polymerized to obtain a copolymer of TFE, perfluoro(alkyl vinyl ether), and other monomers as a TFE / perfluoro(alkyl vinyl ether) copolymer. Examples of the other monomers include the above-mentioned fluoromonomers (excluding TFE and perfluoro(alkyl vinyl ether)) and fluorine-free monomers. One or more types of other monomers may be used. The content of the other monomer units in the TFE / perfluoro(alkyl vinyl ether) copolymer may be 0.1 to 2 mass% based on the total monomer units.

[0333] 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 a compound represented by the formula: CF ２ =CFCF ２ ORf ４ (wherein, Rf ４ is a perfluoroalkyl group having 1 to 6 carbon atoms).

[0334] In addition to TFE and perfluoroallyl ether, other monomers copolymerizable with these monomers may be polymerized to obtain a copolymer of TFE, perfluoroallyl ether, and other monomers as a TFE / perfluoroallyl ether copolymer. Examples of other monomers include the above-mentioned fluoromonomers (excluding TFE and perfluoroallyl ether) and fluorine-free monomers. One or more types of other monomers may be used. The content of other monomer units in the TFE / perfluoroallyl ether copolymer may be 0.1 to 2 mass% based on the total monomer units.

[0335] In the polymerization of the above-mentioned 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, etc. as a chain transfer agent, and it is preferable to use ammonium carbonate, disodium hydrogen phosphate, etc. as a pH buffer.

[0336] Furthermore, a primer composition can be obtained by adding a nonionic surfactant to the aqueous dispersion of TFE / perfluoro(alkyl vinyl ether) copolymer such as PFA or MFA and TFE / perfluoroallyl ether copolymer, and dissolving or dispersing polyethersulfone, polyamideimide and / or polyimide and metal powder in an organic solvent as required.This primer composition can also be used in the method for coating a metal surface with a fluororesin, which comprises applying this primer composition to a metal surface, applying a melt-processable fluororesin composition on the primer layer thus formed, and baking the melt-processable fluororesin composition layer together with the primer layer.

[0337] (3) In the production method of the present disclosure, 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.

[0338] The preferred monomer composition (mol %) of ETFE is TFE:ethylene=(50 to 99):(50 to 1).

[0339] In addition to ethylene and TFE, other monomers that can be copolymerized with these monomers can also be polymerized to obtain the copolymer of ethylene, TFE and other monomers as ETFE.Other monomers can include the above-mentioned fluoromonomers (but excluding TFE) and non-fluorine-containing monomers (but excluding ethylene).As other monomers, one or more kinds can be used.

[0340] Other monomers include hexafluoropropylene, 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 (CH ２ =CFCF ２ CF ２ CF ２ H), 2-trifluoromethyl-3,3,3-trifluoropropene ((CF ３ ) ２ CF=CH ２ ) is preferred.

[0341] The content of other monomer units in ETFE may be 0 to 20% by mass based on the total monomer units. A preferred mass ratio is TFE:ethylene:other monomer=(63 to 94):(27 to 2):(1 to 10).

[0342] 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.

[0343] (4) An electrolyte polymer precursor can also be produced using the production method of the present disclosure. In the production method of the present disclosure, 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 a polymer having a -SO ２ X １５１ , -COZ １５１ or -POZ １５２ Z １５３ (X１５１ , Z １５１ , Z １５２ and Z １５３ The ion-exchange polymer is composed of a monomer containing a functional group represented by the formula (which will be described later), and can be converted into an ion-exchange polymer through hydrolysis treatment.

[0344] The monomer used for the electrolyte polymer precursor is represented by the general formula (150): CF ２ =CF-O-(CF ２ CFY １５１ -O) ｎ -(CFY １５２ ) ｍ -A １５１ (In the formula, Y １５１ represents a fluorine atom, a chlorine atom, -SO ２ It represents a F group or a perfluoroalkyl group. The perfluoroalkyl group is an etheric oxygen and -SO ２ The group n may contain an F group. n represents an integer of 0 to 3. １５１ may be the same or different. １５２ represents a fluorine atom, a chlorine atom, or —SO ２ represents an F group, and m represents an integer of 1 to 5. １５２ may be the same or different. １５１ is -SO ２ X １５１ , -COZ １５１ or -POZ １５２ Z １５３ represents. １５１ is 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 represent -NR １５４ R １５５ Or -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. ) Examples of the monomer used for the electrolyte polymer precursor include a compound containing two fluorosulfonyl groups described in WO 2007 / 013532, and -SO ２ Examples also include perfluoromonomers having an F group and a dioxolane ring. The preferred monomer composition (mol %) of the electrolyte polymer precursor is TFE:vinyl ether=(50 to 99):(50 to 1), more preferably TFE:vinyl ether=(50 to 93):(50 to 7).

[0345] 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 CTFE, vinylidene fluoride, perfluoroalkyl vinyl ether, perfluorobutenyl vinyl ether, cyclic monomers such as perfluoro-2,2-dimethyl-1,3-dioxolane and perfluoro-2-methylene-4-methyl-1,3-dioxole, and polyfunctional monomers such as divinylbenzene.

[0346] 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 to form a polymer electrolyte membrane, which 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 its dispersed state. Subsequently, the electrolyte polymer precursor can be dissolved in, for example, a water / alcohol mixed solvent by heating to 120°C or higher in a pressure vessel 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 and cast into a membrane, which can be used, for example, as an antifouling coating film or an organic actuator.

[0347] (5) TFE / VDF Copolymer In the production method of the present disclosure, the polymerization temperature for the TFE / VDF copolymer is not particularly limited and may be 0 to 100° C. The polymerization pressure is determined appropriately depending on other polymerization conditions such as the polymerization temperature, but may usually be 0 to 9.8 MPaG.

[0348] 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. The preferred ratio is TFE:ethylene:third monomer=(30-85):(10-69.9):(0.1-10).

[0349] The third monomer may be a compound represented by the 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 a monomer represented by the 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.

[0350] 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.

[0351] It is also preferred to coat the aqueous dispersion of the TFE / VDF copolymer on a porous substrate made of polyolefin resin and use it as a composite porous membrane.It is also preferred to disperse inorganic particles and / or organic particles in the aqueous dispersion, 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 lithium secondary batteries, etc.

[0352] Although the embodiments have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the claims.

[0353] <1> According to a first aspect of the present disclosure, there is provided a method for producing a fluoropolymer, comprising: polymerizing a fluoromonomer in a reactor in the presence of a polymerization initiator and an aqueous medium to prepare a composition containing an aqueous medium and a fluoropolymer; and contacting the composition with a gas containing at least oxygen. <2> According to a second aspect of the present disclosure, there is provided a production method according to the first aspect, in which the amount of dissolved oxygen in the composition when contacting the composition with the gas is 0.001 mg / L or more. <3> According to a third aspect of the present disclosure, there is provided a production method according to the first or second aspect, in which the oxygen concentration in the gas phase in the reactor when polymerizing the fluoromonomer is adjusted to 20 ppm by volume or less. <4> According to a fourth aspect of the present disclosure, there is provided a production method according to any of the first to third aspects, in which the temperature of the composition when contacting the composition with the gas is adjusted to 30°C or higher. <5> According to a fifth aspect of the present disclosure, there is provided a production method according to any one of the first to fourth aspects, wherein the temperature of the composition is adjusted to 85°C or less when the composition is brought into contact with the gas. <6> According to a sixth aspect of the present disclosure, there is provided a production method according to any one of the first to fifth aspects, wherein bubbles are generated in the composition by stirring the composition when the composition is brought into contact with the gas. <7> According to a seventh aspect of the present disclosure, there is provided a production method according to any one of the first to sixth aspects, wherein the composition is stirred at a power number of 0.3 or more when the composition is brought into contact with the gas. <8> According to an eighth aspect of the present disclosure, there is provided a production method according to any one of the first to seventh aspects, wherein the time for which the composition is brought into contact with the gas is 1 minute or longer. <9> According to a ninth aspect of the present disclosure, there is provided a production method according to any one of the first to eighth aspects, wherein after the composition is prepared, the fluoromonomer is removed from the reactor, and then the gas is supplied into the reactor.<10> According to a tenth aspect of the present disclosure, there is provided a production method according to any of the first to ninth aspects, in which the composition is prepared by polymerizing the fluoromonomer while stirring the aqueous medium, and the composition is brought into contact with the gas while stirring at a stirring speed that is at least -80% and at most +50% of the stirring speed during polymerization. <11> According to an eleventh aspect of the present disclosure, there is provided a production method according to any of the first to tenth aspects, in which the fluoromonomer comprises at least tetrafluoroethylene. <12> According to a twelfth aspect of the present disclosure, there is provided a production method according to any of the first to eleventh aspects, in which the fluoromonomer comprises at least perfluoro(alkyl vinyl ether). <13> According to a thirteenth aspect of the present disclosure, there is provided the production method according to any one of the first to twelfth aspects, wherein the fluoropolymer is at least one selected from the group consisting of polytetrafluoroethylene, tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / hexafluoropropylene / perfluoro(alkyl vinyl ether) copolymer, and tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer. <14> According to a fourteenth aspect of the present disclosure, there is provided the production method according to any one of the first to thirteenth aspects, wherein the fluoropolymer is washed after contacting the composition with the gas. <15> According to a fifteenth aspect of the present disclosure, there is provided the production method according to any one of the first to fourteenth aspects, wherein the fluoropolymer is dried after contacting the composition with the gas. <16> According to a sixteenth aspect of the present disclosure, there is provided the production method according to any one of the first to fifteenth aspects, wherein the fluoropolymer is pulverized after contacting the composition with the gas. <17> According to a seventeenth aspect of the present disclosure, there is provided the production method according to any one of the first to sixteenth aspects, wherein the composition is contacted with the gas, and then the fluoropolymer is formed into pellets.<18> According to an eighteenth aspect of the present disclosure, the polymerization initiator is a persulfate, the fluoromonomer contains at least tetrafluoroethylene and perfluoro(alkyl vinyl ether), the fluoropolymer is modified polytetrafluoroethylene, and the total amount of perfluoro(alkyl vinyl ether) units in the modified polytetrafluoroethylene is 0.00001 to 1 mass% based on all polymerized units of the modified polytetrafluoroethylene, the oxygen concentration in the gas phase in the reactor is adjusted to 20 ppm by volume or less when polymerizing the fluoromonomer, and after preparing the composition, the fluoromonomer in the reactor is purged with an inert gas, and then a gas containing at least oxygen is supplied into the reactor, and the composition in the reactor is stirred at a power number of 0.3 or more, and the composition and the gas are brought into contact at 30 to 50°C for 15 minutes or more, thereby adjusting the amount of dissolved oxygen in the composition to 0.50 mg / L or more, The present disclosure provides a production method according to any one of the first to seventeenth aspects, which comprises contacting the composition with the gas, washing the fluoropolymer, and drying the washed fluoropolymer to obtain a modified polytetrafluoroethylene powder. <19> According to a nineteenth aspect of the present disclosure, there is provided a modified polytetrafluoroethylene powder, wherein the modified polytetrafluoroethylene has a ΔPPVE amount of 0.002 mass% or more, and the content of a fluorine-containing compound having a hydrophilic group represented by general formula (2) is 100 mass ppb or less, relative to the mass of the modified polytetrafluoroethylene. General formula (2): [C. ｎ－１ F ２ｎ－１ COO － ]M ＋ (wherein n is an integer of 9 to 14, M ＋ represents a cation.)

[0354] Next, embodiments of the present disclosure will be described with reference to examples, but the present disclosure is not limited to these examples.

[0355] The values ​​in the examples were measured by the following methods.

[0356] <Apparent Density> Measured in accordance with JIS K6892.

[0357] <Standard Specific Gravity (SSG)> Using a sample molded in accordance with ASTM D4894, the standard specific gravity was measured by the water displacement method in accordance with ASTM D792.

[0358] <Average particle size (50% cumulative particle size)> The average particle size was determined by the following laser diffraction method. A dry method was performed using a HELOS & RODOS system (product name, manufactured by SYMPATEC). The powder to be measured was dispersed with compressed air at a dispersion pressure of 2 bar, and the measurement sensor detected the shadow of the powder projected by a laser. The particle size distribution of the powder to be measured was calculated, and the average particle size (50% cumulative particle size) d50 value was determined on a volume basis. d50 was defined as the particle size corresponding to 50% of the cumulative particle size distribution.

[0359] <PPVE Content> The PPVE content was determined by press-molding PTFE powder to produce a thin film disk, and calculating the ratio (995 cm) from the infrared absorbance obtained by FT-IR measurement of the thin film disk. －１ Absorbance at / 935 cm －１ The absorbance at 1000 nm was calculated and multiplied by 0.14.

[0360] <Measurement of ΔPPVE Amount> The PTFE thin film disk prepared above was heated at 220°C for 3 hours. After cooling the heated thin film disk to room temperature, it was again subjected to FT-IR to measure the PPVE composition. ΔPPVE was calculated by subtracting the PPVE content after heating from the PPVE content before heating. The magnitude of ΔPPVE of PTFE is an indicator of the amount of PPVE that did not fully copolymerize with TFE and remained in the PTFE in the form of a monomer or oligomer. The ΔPPVE of PTFE obtained when almost all of the PPVE used in polymerization is copolymerized with TFE becomes small. Furthermore, the ΔPPVE of PTFE heat-treated at high temperatures and fluorinated PTFE is 0.000% by mass or close to 0.000% by mass.

[0361] <Amount of Dissolved Oxygen (Calculated Value)> The amount of all oxygen contained in the air charged into the reactor that was dissolved in the deionized water charged into the reactor was calculated and taken as the amount of dissolved oxygen.

[0362] <Dissolved oxygen amount (measured value)> The probe of the dissolved oxygen meter was fixed inside the container, the container was sealed, and the sealed container was connected to a reactor. The oxygen in the container was removed, the pressure was reduced, and the valve connected to the reactor was opened to extract a portion of the aqueous medium in the reactor. The amount of dissolved oxygen in the extracted aqueous medium was measured using an optical dissolved oxygen meter (FDO3800, manufactured by AS ONE Corporation).

[0363] <Power Number> The power number Np in the cylindrical mixing vessel was calculated using the following formula. Np=A / Re+B((10^3+1.2*Re^0.66) / (10^3+3.2*Re^0.66))^p*(H / D)^(0.35+b / D)*(sinθ)^1.2 Re=nd^2ρ / μ A=14+(b / D)*((670*(d / D-0.6)^2+185)) B=10^(1.3-4*(b / D-0.5)^2-1.14*(d / D)) p=1.1+4(b / D)-2.5*(d / D-0.5)^2-7*(b / D)^4 Here, the factors related to the stirring blade are blade length d[m], blade width b[m], blade degree θ[°], rotation speed n[1 / sec], Factors related to the mixing vessel are the vessel diameter D [m] and liquid depth H [m]. Factors related to the mixing liquid are the liquid density ρ [kg / m^3] and liquid viscosity μ [kg / m sec].

[0364] <Measurement of Fluorine-Containing Compound Having Hydrophilic Group> The content of the fluorine-containing compound having a hydrophilic group contained in the powder was determined as the content of the fluorine-containing compound having a hydrophilic group extracted from the powder.

[0365] 1. Extraction of fluorine-containing compounds having hydrophilic groups from powder 10 g (12.6 mL) of methanol was added to 1 g of PTFE powder, and ultrasonic treatment was carried out for 120 minutes while heating to 60° C. After allowing to stand at room temperature, the solid content was removed to obtain an extract.

[0366] Five levels of methanol standard solutions of known concentrations of perfluorononanoic acid, perfluorodecanoic acid, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid, and perfluorotetradecanoic acid were prepared, and measurements were performed using a liquid chromatograph mass spectrometer (Agilent, Ultivo triple quadrupole LC-MS). A calibration curve was created for each concentration range by first-order approximation based on the concentration of the methanol standard solution and the peak integral value.

[0367] Measurement equipment configuration and LC-MS measurement conditions

[0368]

[0369] MRM measurement parameters

[0370]

[0371] 3. Content of Compound Represented by General Formula (2) in Powder Using a liquid chromatograph mass spectrometer, the content of the compound represented by general formula (2) and having carbon number n contained in the extract was measured from a calibration curve. The content of the compound represented by general formula (2) and having carbon number n contained in the powder was calculated using the following relational expression (2): Yn = Xn × 12.6 (2) Yn: content of the compound represented by general formula (2) and having carbon number n contained in the powder (mass ppb / powder) Xn: content of the compound represented by general formula (2) and having carbon number n contained in the extract (ng / mL) The lower limit of quantitation for the content of the compound represented by general formula (2) and having carbon number n contained in the powder is 1 mass ppb / powder.

[0372] MRM measurement parameters

[0373]

[0374] (Production Example 1) Suspension polymerization of tetrafluoroethylene was carried out according to the method described in Production Example 3 of International Publication No. 2003 / 035724. That is, 54.8 L of deionized water and 3.3 g of ammonium carbonate were charged into a 170 L autoclave equipped with a stainless steel stirring blade and a temperature-controlling jacket, and the autoclave was sealed. While heating to 70 ° C, the contents were stirred at 110 rpm, and the inside of the autoclave was purged with nitrogen. The oxygen concentration in the autoclave was 10 ppm by volume. The nitrogen was removed by reducing the pressure, and 85 g of perfluoro(propyl vinyl ether) (PPVE) was injected with tetrafluoroethylene, and the pressure was increased with tetrafluoroethylene to a pressure of 0.8 MPaG. Ammonium persulfate was added as a polymerization initiator to initiate polymerization. Tetrafluoroethylene was continuously added so as to maintain the pressure at 0.8 MPaG, and polymerization was carried out until 22.5% by mass of tetrafluoroethylene was consumed relative to the weight of the aqueous medium, after which the monomer was released without stopping stirring.

[0375] (Example 1) After releasing the monomer, the autoclave was quickly purged with nitrogen gas to reduce the pressure, and the pressure was increased from a reduced pressure (-0.08 MPaG) to 0.02 MPaG with air, followed by stirring for 20 minutes at 40°C. The dissolved oxygen amount (calculated value) at this time was 0.76 mg / L, and the dissolved oxygen amount (measured value) was 7.7 mg / L. The stirring power number was 0.5.

[0376] The stirring was stopped, the autoclave was opened, and the aqueous medium containing the resulting polytetrafluoroethylene suspension polymerized particles was removed, drained, and washed twice with pure water. Simultaneously with washing, the mixture was pulverized in a high-speed rotary mill to obtain pulverized particles. After drying, the mixture was pulverized in an air jet mill to obtain polytetrafluoroethylene powder. The results of the physical property evaluation are shown in Tables 4 and 5.

[0377] Comparative Example 1: The same procedure as in Example 1 was carried out, except that the gas used to increase the pressure from a reduced pressure state was changed from air to nitrogen gas, to obtain a polytetrafluoroethylene powder. The amount of dissolved oxygen (calculated value, measured value) at this time was 0.0 mg / L. The results of the physical property evaluation are shown in Tables 4 and 5.

[0378]

[0379]

[0380] (Example 2) After releasing the monomer, the autoclave was quickly purged with nitrogen gas to reduce the pressure, and the pressure was increased from a reduced pressure (-0.08 MPaG) to -0.06 MPaG with air, followed by stirring at 50°C for 20 minutes. The stirring power was 0.5. Stirring was then stopped, and the contents were allowed to stand in the reactor for 120 minutes. The amount of dissolved oxygen (measured value) at this time was 2.2 mg / L.

[0381] Polytetrafluoroethylene powder was obtained by the same procedure as in Example 1. The results of the physical property evaluation are shown in Tables 6 and 7.

[0382] Example 3 The same procedure as in Example 2 was carried out, except that the pressure was increased to 0.06 MPaG with air instead of to −0.06 MPaG. The amount of dissolved oxygen (measured value) after standing was 8.9 mg / L.

[0383] Polytetrafluoroethylene powder was obtained by the same procedure as in Example 1. The results of the physical property evaluation are shown in Tables 6 and 7.

[0384] (Example 4) The same procedure as in Example 1 was carried out, except that instead of stirring for 20 minutes at 40°C, stirring was carried out for 5 minutes at 40°C, and after stopping the stirring, the mixture was allowed to stand in the reactor for 60 minutes. The amount of dissolved oxygen (measured value) after standing was 7.7 mg / L.

[0385] Polytetrafluoroethylene powder was obtained by the same procedure as in Example 1. The results of the physical property evaluation are shown in Tables 6 and 7.

[0386] (Production Example 2) Emulsion polymerization of tetrafluoroethylene was carried out according to the description of Production Example 2 of WO 2022 / 050430. That is, 3580 g of deionized water, 160 g of paraffin wax, and 4.7 g of fluorine-containing surfactant were placed in a 6 L capacity SUS reactor equipped with a stirrer. The contents of the reactor were then heated to 70 ° C. while being aspirated, and simultaneously purged with TFE to remove oxygen from the reactor, and the contents were stirred. The oxygen concentration in the autoclave was 10 ppm by volume. 6.5 g of PPVE was injected into the reactor with TFE. 50 mg of ammonium persulfate dissolved in 20 g of deionized water was injected into the reactor as an initiator, and the pressure was set to 1.5 MPaG. TFE was added so that the pressure was constant at 1.5 MPaG. When the amount of TFE consumed in the reaction reached 1,543 g, the supply of TFE was stopped, stirring was stopped to terminate the reaction, and the monomer was discharged.

[0387] (Example 5) After releasing the monomer, the inside of the reactor was quickly purged with nitrogen gas to reduce the pressure, and the pressure was increased from the reduced pressure (-0.08 MPaG) to 0.00 MPaG with air, and stirring was again carried out for 5 minutes at 70°C. The stirring power was 0.3. Thereafter, stirring was stopped, and the contents were allowed to stand in the reactor for 60 minutes. The amount of dissolved oxygen (measured value) at this time was 3.0 mg / L.

[0388] The autoclave was opened, and a polytetrafluoroethylene aqueous dispersion was obtained. Deionized water was added to the obtained aqueous dispersion so that the solid content concentration was 15% by mass, and high-speed stirring was carried out to cause coagulation, and the mixture was washed twice with deionized water to obtain wet particles. The obtained wet powder was dried at 150 ° C for 18 hours to obtain a polytetrafluoroethylene powder. The results of physical property evaluation are shown in Table 6 and Table 7.

[0389]

[0390]

Claims

1. A method for producing a fluoropolymer, comprising: polymerizing a fluoromonomer in a reactor in the presence of a polymerization initiator and an aqueous medium to prepare a composition containing an aqueous medium and a fluoropolymer; and contacting the composition with a gas containing at least oxygen.

2. The manufacturing method according to claim 1, wherein the amount of dissolved oxygen in the composition when the composition is brought into contact with the gas is 0.001 mg / L or more.

3. The method according to claim 1 or 2, wherein the oxygen concentration in the gas phase in the reactor is adjusted to 20 ppm by volume or less when the fluoromonomer is polymerized.

4. The method according to any one of claims 1 to 3, wherein the temperature of the composition is adjusted to 30°C or higher when the composition is brought into contact with the gas.

5. The method according to any one of claims 1 to 4, wherein the temperature of the composition is adjusted to 85°C or lower when the composition is brought into contact with the gas.

6. The method according to any one of claims 1 to 5, wherein when the composition is brought into contact with the gas, the composition is stirred to generate bubbles in the composition.

7. The method according to any one of claims 1 to 6, wherein the composition is stirred at a power number of 0.3 or more when contacting the composition with the gas.

8. The method according to any one of claims 1 to 7, wherein the composition is contacted with the gas for one minute or longer.

9. The method according to any one of claims 1 to 8, wherein after the composition is prepared, the fluoromonomer is removed from within the reactor, and then the gas is supplied into the reactor.

10. The method according to any one of claims 1 to 9, wherein the composition is prepared by polymerizing the fluoromonomer while stirring the aqueous medium, and the composition is contacted with the gas while stirring at a stirring speed that is -80% or more and +50% or less of the stirring speed during polymerization.

11. The method according to any one of claims 1 to 10, wherein the fluoromonomer contains at least tetrafluoroethylene.

12. The method according to any one of claims 1 to 11, wherein the fluoromonomer contains at least perfluoro(alkyl vinyl ether).

13. The method according to any one of claims 1 to 12, wherein the fluoropolymer is at least one selected from the group consisting of polytetrafluoroethylene, tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / hexafluoropropylene / perfluoro(alkyl vinyl ether) copolymer, and tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer.

14. The process according to any one of claims 1 to 13, wherein the fluoropolymer is washed after contacting the composition with the gas.

15. The process according to any one of claims 1 to 14, wherein after contacting the composition with the gas, the fluoropolymer is dried.

16. The process according to any one of claims 1 to 15, wherein the fluoropolymer is comminuted after contacting the composition with the gas.

17. The process according to any one of claims 1 to 16, wherein after contacting said composition with said gas, said fluoropolymer is formed into pellets.

18. The polymerization initiator is a persulfate, the fluoromonomer contains at least tetrafluoroethylene and perfluoro(alkyl vinyl ether), the fluoropolymer is modified polytetrafluoroethylene, and the total amount of perfluoro(alkyl vinyl ether) units in the modified polytetrafluoroethylene is 0.00001 to 1 mass% based on the total polymerized units of the modified polytetrafluoroethylene, when polymerizing the fluoromonomer, the oxygen concentration in the gas phase in the reactor is adjusted to 20 volume ppm or less, after preparing the composition, the fluoromonomer in the reactor is replaced with an inert gas, and then a gas containing at least oxygen is supplied into the reactor, the composition in the reactor is stirred at a power number of 0.3 or more, and the composition and the gas are brought into contact with each other at 30 to 50°C for 15 minutes or more, thereby adjusting the dissolved oxygen amount in the composition to 0.50 mg / L or more, after the composition and the gas are brought into contact with each other, the fluoropolymer is washed, and the washed fluoropolymer is dried to obtain a powder of modified polytetrafluoroethylene. The method of claim 1 .

19. A modified polytetrafluoroethylene powder, wherein the modified polytetrafluoroethylene has a ΔPPVE amount of 0.002 mass% or more, and the content of a fluorine-containing compound having a hydrophilic group represented by general formula (2) is 100 mass ppb or less relative to the mass of the modified polytetrafluoroethylene. ｎ－１ F ２ｎ－１ COO － ]M ＋ (wherein n is an integer from 9 to 14; M ＋ represents a cation.)

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