Method for producing aqueous fluorine-containing polymer dispersion, aqueous fluorine-containing polymer dispersion, and coating composition

Abstract

Provided is a method for producing a fluorine-containing polymer aqueous dispersion containing a fluorine-containing polymer, in which a fluorine-containing monomer is polymerized in a reactor in the presence of a fluorine-containing surfactant, a polymerization initiator, and an aqueous medium, and a fluorine-containing polymer is obtained by polymerizing a fluorine-containing monomer in the presence of a fluorine-containing surfactant, a polymerization initiator, and an aqueous medium. An aqueous dispersion containing a fluorine-containing polymer is thus prepared, the aqueous dispersion is heat-treated, a nonionic surfactant is added to the heat-treated aqueous dispersion, the aqueous dispersion containing the nonionic surfactant is brought into contact with an ion exchange resin, and the fluorine-containing polymer is obtained. And concentrating the aqueous dispersion liquid obtained after contact with the ion exchange resin.

Description

Technical Field

[0001] The present invention relates to a method for producing a fluorine-containing polymer aqueous dispersion, a fluorine-containing polymer aqueous dispersion and a coating composition. Background Art

[0002] Patent Document 1 describes a method for decomposing fluorinated carboxylic acids, characterized in that at least one fluorinated carboxylic acid selected from fluorinated carboxylic acids, salts thereof and precursors thereof is subjected to hot water treatment in a closed container in the presence of peroxodisulfate ions.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2008-285449 Summary of the invention

[0006] Problems to be solved by the invention

[0007] An object of the present invention is to provide a method for producing an aqueous fluorinated polymer dispersion having a reduced content of a fluorinated compound having a hydrophilic group having 7 or less carbon atoms.

[0008] Another object of the present invention is to provide an aqueous fluorinated polymer dispersion having a reduced content of a fluorinated compound having a hydrophilic group having 7 or less carbon atoms.

[0009] Means for solving problems

[0010] According to the present invention, there is provided a method for producing an aqueous fluorine-containing polymer dispersion, which is a method for producing an aqueous fluorine-containing polymer dispersion containing a fluorine-containing polymer, wherein a fluorine-containing monomer is polymerized in a reactor in the presence of a fluorine-containing surfactant, a polymerization initiator and an aqueous medium to prepare an aqueous dispersion containing a fluorine-containing polymer, the aqueous dispersion is heat-treated, a nonionic surfactant is added to the heat-treated aqueous dispersion, the aqueous dispersion containing the nonionic surfactant is contacted with an ion exchange resin, and the aqueous dispersion obtained after contact with the ion exchange resin is concentrated.

[0011] Effects of the Invention

[0012] According to the present invention, there can be provided a method for producing an aqueous fluorinated polymer dispersion in which the content of a fluorinated compound having a hydrophilic group having 7 or less carbon atoms is reduced.

[0013] Furthermore, according to the present invention, there can be provided an aqueous fluorinated polymer dispersion having a reduced content of a fluorinated compound having a hydrophilic group and having 7 or less carbon atoms. DETAILED DESCRIPTION

[0014] Before describing the present invention in detail, some terms used in the present invention are defined or described.

[0015] In the present invention, fluororesin refers to a partially crystalline fluorine-containing polymer, which is a fluoroplastic. Fluororesin has a melting point, is thermoplastic, and can be melt-processable or non-melt-processable.

[0016] In the present invention, melt processability means that the polymer can be melted and processed using existing processing equipment such as extruders and injection molding machines. Therefore, melt-processable fluororesins generally have a melt flow rate of 0.01 g / 10 min to 500 g / 10 min as measured by the measurement method described below.

[0017] In the present invention, fluororubber refers to an amorphous fluorine-containing polymer. "Amorphous" means that the size of the melting peak (ΔH) appearing in the differential scanning calorimetry [DSC] (heating rate 10°C / min) or differential thermal analysis [DTA] (heating rate 10°C / min) of the fluoropolymer is less than 4.5 J / g. Fluororubber exhibits elastomeric properties by cross-linking. Elastomeric properties refer to the following properties: the polymer can be stretched and can maintain its original length when the force required to stretch the polymer is no longer applied.

[0018] The monomer providing a crosslinking site is a monomer having a crosslinking group (curing site monomer) which provides a crosslinking site for forming a crosslink with a curing agent to the fluorine-containing polymer.

[0019] In the present invention, the polytetrafluoroethylene [PTFE] is preferably a fluorine-containing polymer having a tetrafluoroethylene unit content of 99 mol % or more based on all polymer units.

[0020] In the present invention, both the fluororesin (excluding polytetrafluoroethylene) and the fluororubber are preferably fluorine-containing polymers in which the content of tetrafluoroethylene units relative to all polymer units is less than 99 mol %.

[0021] In the present invention, the content of each monomer constituting the fluorine-containing polymer can be calculated by appropriately combining NMR, FT-IR, elemental analysis and fluorescent X-ray analysis according to the types of monomers.

[0022] In the present invention, the "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.

[0023] Examples of the "organic group" include:

[0024] an alkyl group which may have one or more substituents, an alkenyl group which may have one or more substituents, an alkynyl group which may have one or more substituents, a cycloalkyl group which may have one or more substituents, a cycloalkenyl group which may have one or more substituents, a cycloalkadienyl group which may have one or more substituents, an aryl group which may have one or more substituents, an aralkyl group which may have one or more substituents, a non-aromatic heterocyclic group which may have one or more substituents, a heteroaryl group which may have one or more substituents, a cyano group,

[0025] Formyl,

[0026] RaO-,

[0027] RaCO-,

[0028] RaSO2-,

[0029] RaCOO-

[0030] RaNRaCO-,

[0031] RaCONRa-

[0032] RaOCO-,

[0033] RaOSO2-, and

[0034] RaNRbSO2-

[0035] (In these formulas, Ra is independently an alkyl group which may have one or more substituents, an alkenyl group which may have one or more substituents, an alkynyl group which may have one or more substituents, a cycloalkyl group which may have one or more substituents, a cycloalkenyl group which may have one or more substituents, a cycloalkadienyl group which may have one or more substituents,

[0036] an aryl group which may have one or more substituents,

[0037] an aralkyl group which may have one or more substituents,

[0038] A non-aromatic heterocyclic group which may have one or more substituents, or

[0039] a heteroaryl group which may have one or more substituents,

[0040] Rb is independently H or an alkyl group which may have one or more substituents).

[0041] As the organic group, an alkyl group which may have one or more substituents is preferred.

[0042] In the present invention, a "substituent" refers to a group that can be substituted. Examples of the "substituent" include an aliphatic group, an aromatic group, a heterocyclic group, an acyl group, an acyloxy group, an acylamino group, an aliphatic oxy group, an aromatic oxy group, a heterocyclic oxy group, an aliphatic oxycarbonyl group, an aromatic oxycarbonyl group, a heterocyclic oxycarbonyl group, a carbamoyl group, an aliphatic sulfonyl group, an aromatic sulfonyl group, a heterocyclic sulfonyl group, an aliphatic sulfonyloxy group, an aromatic sulfonyloxy group, a heterocyclic sulfonyloxy group, a sulfamoyl group, an aliphatic sulfonamide group, an aromatic sulfonamide group, a heterocyclic sulfonamide group, an amino group, an aliphatic an aliphatic amino group, an aromatic amino group, a heterocyclic amino group, an aliphatic oxycarbonylamino group, an aromatic oxycarbonylamino group, a heterocyclic oxycarbonylamino group, an aliphatic sulfinyl group, an aromatic sulfinyl group, an aliphatic thiol group, an aromatic thiol group, a hydroxyl group, a cyano group, a sulfo group, a carboxyl group, an aliphatic oxyamino group, an aromatic oxyamino group, a carbamoylamino group, a sulfamoylamino group, a halogen atom, a sulfamoylcarbamoyl group, a carbamoylsulfamoyl group, a dialiphatic oxyphosphinyl group, and a diaromatic oxyphosphinyl group.

[0043] The aliphatic group may be saturated or unsaturated, and may have a hydroxyl group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thiol group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aliphatic group include an alkyl group having a total carbon number of 1 to 8, preferably 1 to 4, such as a methyl group, an ethyl group, a vinyl group, a cyclohexyl group, a carbamoylmethyl group, etc.

[0044] The aromatic group may have, for example, a nitro group, a halogen atom, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thiol group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aromatic group include an aryl group having 6 to 12 carbon atoms, preferably 6 to 10 carbon atoms in total, such as a phenyl group, a 4-nitrophenyl group, a 4-acetylaminophenyl group, and a 4-methylsulfonylphenyl group.

[0045] The heterocyclic group may have a halogen atom, a hydroxyl group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thiol group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the heterocyclic group include a 5- to 6-membered heterocyclic ring having a total carbon number of 2 to 12, preferably 2 to 10, such as a 2-tetrahydrofuranyl group and a 2-pyrimidinyl group.

[0046] The acyl group may have an aliphatic carbonyl group, an arylcarbonyl group, a heterocyclic carbonyl group, a hydroxyl group, a halogen atom, an aromatic group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thiol group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the acyl group include an acyl group having a total carbon number of 2 to 8, preferably 2 to 4, such as an acetyl group, a propionyl group, a benzoyl group, a 3-pyridinecarbonyl group, etc.

[0047] The acylamino group may have an aliphatic group, an aromatic group, a heterocyclic group, etc., and may have, for example, an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, a propionylamino group, etc. Examples of the acylamino group include acylamino groups having a total carbon number of 2 to 12, preferably 2 to 8, and alkylcarbonylamino groups having a total carbon number of 2 to 8, such as acetylamino groups, benzoylamino groups, 2-pyridinecarbonylamino groups, and propionylamino groups.

[0048] The aliphatic oxycarbonyl group may be saturated or unsaturated, and may have a hydroxyl group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thiol group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aliphatic oxycarbonyl group include an alkoxycarbonyl group having a total carbon number of 2 to 8, preferably 2 to 4, such as a methoxycarbonyl group, an ethoxycarbonyl group, a tert-butoxycarbonyl group, etc.

[0049] The carbamoyl group may have an aliphatic group, an aromatic group, a heterocyclic group, etc. Examples of the carbamoyl group include an unsubstituted carbamoyl group and an alkyl carbamoyl group having 2 to 9 carbon atoms in total, preferably an unsubstituted carbamoyl group and an alkyl carbamoyl group having 2 to 5 carbon atoms in total, such as N-methyl carbamoyl group, N,N-dimethyl carbamoyl group, N-phenyl carbamoyl group, etc.

[0050] The aliphatic sulfonyl group may be saturated or unsaturated, and may have a hydroxyl group, an aromatic group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thiol group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aliphatic sulfonyl group include an alkylsulfonyl group having a total carbon number of 1 to 6, preferably a total carbon number of 1 to 4, such as a methylsulfonyl group.

[0051] The aromatic sulfonyl group may have a hydroxyl group, an aliphatic group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thiol group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, etc. Examples of the aromatic sulfonyl group include an arylsulfonyl group having a total carbon number of 6 to 10, such as a benzenesulfonyl group.

[0052] The amino group may have an aliphatic group, an aromatic group, a heterocyclic group or the like.

[0053] The acylamino group may include, for example, acetylamino, benzoylamino, 2-pyridinecarbonylamino, propionylamino, etc. Examples of the acylamino group include acylamino groups having a total carbon number of 2 to 12, preferably acylamino groups having a total carbon number of 2 to 8, and more preferably alkylcarbonylamino groups having a total carbon number of 2 to 8, such as acetylamino, benzoylamino, 2-pyridinecarbonylamino, propionylamino, etc.

[0054] The aliphatic sulfonamide group, aromatic sulfonamide group, and heterocyclic sulfonamide group may be, for example, a methanesulfonamide group, a benzenesulfonamide group, a 2-pyridinesulfonamide group, or the like.

[0055] The sulfamoyl group may have an aliphatic group, an aromatic group, a heterocyclic group, etc. Examples of the sulfamoyl group include a sulfamoyl group, an alkylsulfamoyl group having 1 to 9 total carbon atoms, a dialkylsulfamoyl group having 2 to 10 total carbon atoms, an arylsulfamoyl group having 7 to 13 total carbon atoms, and a heterocyclic sulfamoyl group having 2 to 12 total carbon atoms. More preferred examples include a sulfamoyl group, an alkylsulfamoyl group having 1 to 7 total carbon atoms, a dialkylsulfamoyl group having 3 to 6 total carbon atoms, an arylsulfamoyl group having 6 to 11 total carbon atoms, and a heterocyclic sulfamoyl group having 2 to 10 total carbon atoms, such as a sulfamoyl group, a methylsulfamoyl group, an N,N-dimethylsulfamoyl group, a phenylsulfamoyl group, and a 4-pyridylsulfamoyl group.

[0056] The aliphatic oxy group may be saturated or unsaturated, and may include methoxy, ethoxy, isopropoxy, cyclohexyloxy, methoxyethoxy, etc. Examples of the aliphatic oxy group include alkoxy groups having a total carbon number of 1 to 8, preferably 1 to 6, such as methoxy, ethoxy, isopropoxy, cyclohexyloxy, methoxyethoxy, etc.

[0057] The aromatic amino group and heterocyclic amino group may have an aliphatic group, an aliphatic oxy group, a halogen atom, a carbamoyl group, a heterocyclic group condensed with the aromatic group, or an aliphatic oxycarbonyl group, and preferably may have an aliphatic group having a total carbon number of 1 to 4, an aliphatic oxy group having a total carbon number of 1 to 4, a halogen atom, a carbamoyl group having a total carbon number of 1 to 4, a nitro group, or an aliphatic oxycarbonyl group having a total carbon number of 2 to 4.

[0058] The aliphatic thiol group may be saturated or unsaturated, and examples thereof include alkylthio groups having 1 to 8 total carbon atoms, more preferably 1 to 6 total carbon atoms, such as methylthio, ethylthio, carbamoylmethylthio, tert-butylthio and the like.

[0059] The carbamoylamino group may have an aliphatic group, an aryl group, a heterocyclic group, etc. Examples of the carbamoylamino group include carbamoylamino groups, alkylcarbamoylamino groups having 2 to 9 total carbon atoms, dialkylcarbamoylamino groups having 3 to 10 total carbon atoms, arylcarbamoylamino groups having 7 to 13 total carbon atoms, and heterocycliccarbamoylamino groups having 3 to 12 total carbon atoms. Carbamoylamino groups, alkylcarbamoylamino groups having 2 to 7 total carbon atoms, dialkylcarbamoylamino groups having 3 to 6 total carbon atoms, arylcarbamoylamino groups having 7 to 11 total carbon atoms, and heterocycliccarbamoylamino groups having 3 to 10 total carbon atoms are preferred, such as carbamoylamino groups, methylcarbamoylamino groups, N,N-dimethylcarbamoylamino groups, phenylcarbamoylamino groups, and 4-pyridylcarbamoylamino groups.

[0060] In the present invention, the range represented by endpoints includes all the numerical values ​​included in the range (for example, 1 to 10 includes 1.4, 1.9, 2.33, 5.75, 9.98, etc.).

[0061] In the present invention, the term "at least 1" includes all numerical values ​​greater than or equal to 1 (for example, 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.).

[0062] Hereinafter, specific embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0063] 1. Method for producing aqueous fluorinated polymer dispersion

[0064] In the aqueous dispersion obtained by polymerizing the fluorinated monomer, in addition to the fluorinated polymer, a fluorinated compound having a hydrophilic group is sometimes contained. The fluorinated compound having a hydrophilic group includes a fluorinated surfactant added during polymerization and a fluorinated compound having a hydrophilic group generated by the polymerization of the fluorinated monomer.

[0065] In the production method of the present invention, after preparing an aqueous dispersion, the obtained aqueous dispersion is heat-treated, and then a nonionic surfactant is added to the heat-treated aqueous dispersion, thereby contacting the aqueous dispersion with an ion exchange resin while maintaining the content of the nonionic surfactant in the aqueous dispersion at a certain level or above, and then concentrating the aqueous dispersion. It was found that by using such a production method, even when compared with the conventional method of ion-exchanging the aqueous dispersion and the conventional method of concentrating the aqueous dispersion by phase separation, an aqueous dispersion having a surprisingly low content of a fluorinated compound having a hydrophilic group can be produced.

[0066] That is, the production method of the present invention is a production method for an aqueous fluorine-containing polymer dispersion, which is a production method for an aqueous fluorine-containing polymer dispersion containing a fluorine-containing polymer, wherein a fluorine-containing monomer is polymerized in a reactor in the presence of a fluorine-containing surfactant, a polymerization initiator and an aqueous medium to prepare an aqueous dispersion containing a fluorine-containing polymer, the aqueous dispersion is heat-treated, a nonionic surfactant is added to the heat-treated aqueous dispersion, the aqueous dispersion containing the nonionic surfactant is brought into contact with an ion exchange resin, and the aqueous dispersion obtained after the contact with the ion exchange resin is concentrated.

[0067] By using the production method of the present invention, the content of the fluorinated compound having a hydrophilic group and having a carbon number of 7 or less in the aqueous dispersion of the fluorinated polymer can be reduced. Furthermore, by using the production method of the present invention, not only the content of the fluorinated compound having a hydrophilic group and having a carbon number of 7 or less can be reduced, but also the content of the fluorinated compound having a hydrophilic group in the aqueous dispersion of the fluorinated polymer can be reduced.

[0068] Each process and the materials used in each process are described in detail below.

[0069] (Polymerization of fluorinated monomers)

[0070] In the production method of the present invention, first, a fluorinated monomer is polymerized in a reactor in the presence of a fluorinated surfactant, a polymerization initiator and an aqueous medium to prepare an aqueous dispersion containing a fluorinated polymer.

[0071] The polymerization of fluorinated monomers can be carried out as follows: fluorinated monomers, fluorinated surfactants, polymerization initiators, aqueous media and other additives as needed are added to a reactor, the contents of the reactor are stirred, and then the reactor is maintained at a specified polymerization temperature, followed by adding a specified amount of polymerization initiator to initiate the polymerization reaction. After the polymerization reaction begins, additional fluorinated monomers, polymerization initiators, fluorinated surfactants, chain transfer agents, etc. may be added according to the purpose. The polymerization method of the fluorinated monomer is not particularly limited, and emulsion polymerization is preferred.

[0072] (Fluorinated surfactant)

[0073] The fluorinated surfactant used for the polymerization of the fluorinated monomer is not particularly limited as long as it is a surfactant containing at least one fluorine atom, and a conventionally known fluorinated surfactant can be used.

[0074] Examples of the fluorinated surfactant include anionic fluorinated surfactants, etc. The anionic fluorinated surfactant may be, for example, a surfactant containing fluorine atoms and having a total carbon number of 20 or less in the moiety excluding the anionic group.

[0075] Furthermore, the fluorine-containing surfactant may be a surfactant containing fluorine whose anionic part has a molecular weight of 1,000 or less.

[0076] It should be noted that the above-mentioned "anionic part" refers to the part of the above-mentioned fluorinated surfactant other than the cation. For example, in the F(CF2) shown in the formula (I) described below n1 In the case of COOM, it is "F(CF2) n1 COO” part.

[0077] In addition, as the above-mentioned fluorinated surfactant, a fluorinated surfactant having a LogPOW of 3.5 or less can be cited. The above-mentioned LogPOW is the partition coefficient between 1-octanol and water, and is represented by LogP [wherein P represents the ratio of the fluorinated surfactant concentration in octanol to the fluorinated surfactant concentration in water when a fluorinated surfactant-containing octanol / water (1:1) mixed solution undergoes phase separation].

[0078] The above LogPOW is calculated as follows: On column: TOSOH ODS-120T column ( HPLC was performed on standard substances (heptanoic acid, octanoic acid, nonanoic acid and decanoic acid) with known octanol / water partition coefficients under the following conditions: (a) elution solvent: acetonitrile / 0.6 mass% HClO4 water = 1 / 1 (vol / vol%), flow rate: 1.0 ml / min, sample amount: 300 μL, column temperature: 40°C, detection light: UV210 nm, and a calibration curve of each elution time and the known octanol / water partition coefficient was prepared. Based on the calibration curve, the elution time of HPLC in the sample solution was calculated.

[0079] Specific examples of the fluorinated surfactant include U.S. Patent Application Publication No. 2007 / 0015864, U.S. Patent Application Publication No. 2007 / 0015865, U.S. Patent Application Publication No. 2007 / 0015866, U.S. Patent Application Publication No. 2007 / 0276103, U.S. Patent Application Publication No. 2007 / 0117914, U.S. Patent Application Publication No. 2007 / 142541, U.S. Patent Application Publication No. 2008 / 0015319, and U.S. Patent No. 3250808. Fluorinated surfactants described in Japanese Unexamined Patent Application No. 3,271,341, Japanese Unexamined Patent Application No. 2003-119204, International Publication No. 2005 / 042593, International Publication No. 2008 / 060461, International Publication No. 2007 / 046377, Japanese Unexamined Patent Application No. 2007-119526, International Publication No. 2007 / 046482, International Publication No. 2007 / 046345, U.S. Patent Application Publication No. 2014 / 0228531, International Publication No. 2013 / 189824, and International Publication No. 2013 / 189826.

[0080] Examples of the anionic fluorinated surfactant include the following general formula (N 0 ):

[0081] X n0 -Rf n0 -Y 0 (N 0 )

[0082] (Where X n0 is H, Cl or and F. Rf n0 It is a chain, branched or cyclic alkylene group having 3 to 20 carbon atoms, in which some or all of the H groups are replaced by F. The alkylene group may contain one or more ether bonds, and some of the H groups may be replaced by Cl. 0 is an anionic group).

[0083] Y 0 The anionic group may be -COOM, -SO2M or -SO3M, or may be -COOM or -SO3M.

[0084] M is H, metal atom, NR 7 4. an imidazolium which may be substituted, a pyridinium which may be substituted, or a phosphonium which may be substituted, R 7 is H or an organic group.

[0085] Examples of the metal atom include alkali metals (Group 1) and alkaline earth metals (Group 2), such as Na, K, or Li.

[0086] As R 7 , can be H or C 1-10 The organic group can also be H or C 1-4 The organic group can also be H or C 1-4 of alkyl.

[0087] M can be H, metal atom or NR 7 4, may also be H, alkali metal (Group 1), alkaline earth metal (Group 2) or NR 7 4, and can also be H, Na, K, Li or NH4.

[0088] The above Rf n0 In the above formula (A), more than 50% of the H can be replaced by fluorine.

[0089] As the above general formula (N 0 ) can include:

[0090] The following general formula (N 1 ):

[0091] X n0 -(CF2) m1 -Y 0 (N 1 )

[0092] (Where X n0 is H, Cl and F, m1 is an integer from 3 to 15, Y 0 The compound represented by the following general formula (N 2 ):

[0093] R n1 -O-(CF(CF3)CF2O) m2 CFX n1 -Y 0 (N 2 )

[0094] (Where Rf n1 is a perfluoroalkyl group having 1 to 5 carbon atoms, m2 is an integer of 0 to 3, and X n1 F or CF3, Y 0 The compound represented by the following general formula (N 3 ):

[0095] R n2 (CH2) m3 -(Rf n3 ) q -Y0 (N 3 )

[0096] (Where Rf n2 is a partially or completely 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, Rf n3 is a linear or branched perfluoroalkylene group having 1 to 3 carbon atoms, q is 0 or 1, and Y 0 The compound represented by the following general formula (N 4 ):

[0097] R n4 -O-(CY n1 Y n2 ) p CF2-Y 0 (N 4 )

[0098] (Where Rf n4 is a linear or branched partially or completely fluorinated alkyl group having 1 to 12 carbon atoms which may contain an ether bond, n1 and Y n2 The same or different, H or F, p is 0 or 1, Y 0 The compound represented by the above-defined substance); and the general formula (N 5 ):

[0099] [Chemistry 1]

[0100]

[0101] (Where X n2 , X n3 and X n4 Rf may be the same or different and is H, F, or a linear or branched partially or fully fluorinated alkyl group having 1 to 6 carbon atoms which may contain an ether bond. n5 is a linear or branched partially or completely fluorinated alkylene group having 1 to 3 carbon atoms and may contain an ether bond, L is a connecting group, Y 0 is the substance defined above. n2 , X n3 , X n4 and Rf n5 The total number of carbon atoms is 18 or less).

[0102] As the above general formula (N 0), more specifically, a perfluorocarboxylic acid (I) represented by the following general formula (I), an ω-H perfluorocarboxylic acid (II) represented by the following general formula (II), a perfluoroether carboxylic acid (III) represented by the following general formula (III), a perfluoroalkyl alkylene carboxylic acid (IV) represented by the following general formula (IV), a perfluoroalkoxy fluorocarboxylic acid (V) represented by the following general formula (V), a perfluoroalkyl sulfonic acid (VI) represented by the following general formula (VI), an ω-H perfluorosulfonic acid (VII) represented by the following general formula (VII), a perfluoroalkyl alkylene sulfonic acid (VIII) represented by the following general formula (VIII), an alkyl alkylene carboxylic acid (IX) represented by the following general formula (IX), a fluorocarboxylic acid (X) represented by the following general formula (X), an alkoxy fluorosulfonic acid (XI) represented by the following general formula (XI), a compound (XII) represented by the following general formula (XII), a compound (XIII) represented by the following general formula (XIII), and the like.

[0103] The above perfluorocarboxylic acid (I) is represented by the following general formula (I):

[0104] F(CF2) n1 COOM(I)

[0105] (where n1 is an integer from 3 to 14, M is H, a metal atom, NR 7 4. an imidazolium which may be substituted, a pyridinium which may be substituted, or a phosphonium which may be substituted, R 7 is H or an organic group).

[0106] The above-mentioned ω-H perfluorocarboxylic acid (II) is represented by the following general formula (II):

[0107] H(CF2) n2 COOM(II)

[0108] (wherein n2 is an integer of 4 to 15, and M is the substance defined above).

[0109] The above perfluoroether carboxylic acid (III) is represented by the following general formula (III):

[0110] R 1 -O-(CF(CF3)CF2O) n3 CF(CF3)COOM(III)

[0111] (Where Rf 1 is a perfluoroalkyl group having 1 to 5 carbon atoms, n3 is an integer of 0 to 3, and M is the substance defined above).

[0112] The above perfluoroalkyl alkylene carboxylic acid (IV) is represented by the following general formula (IV):

[0113] R2 (CH2) n4 R 3 COOM(IV)

[0114] (Where Rf 2 is a perfluoroalkyl group having 1 to 5 carbon atoms, 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 the substance defined above).

[0115] The above alkoxy fluorocarboxylic acid (V) is represented by the following general formula (V):

[0116] R 4 -O-CY 1 Y 2 CF2-COOM(V)

[0117] (Where Rf 4 is a linear or branched partially or completely fluorinated alkyl group having 1 to 12 carbon atoms which may contain an ether bond and / or a chlorine atom, 1 and Y 2 are the same or different, are H or F, and M is the substance defined above).

[0118] The above perfluoroalkylsulfonic acid (VI) is represented by the following general formula (VI):

[0119] F(CF2) n5 SO3M(VI)

[0120] (wherein n5 is an integer of 3 to 14, and M is the substance defined above).

[0121] The above-mentioned ω-H perfluorosulfonic acid (VII) is represented by the following general formula (VII):

[0122] H(CF2) n6 SO3M(VII)

[0123] (wherein n6 is an integer of 4 to 14, and M is the substance defined above).

[0124] The above perfluoroalkyl alkylene sulfonic acid (VIII) is represented by the following general formula (VIII):

[0125] R 5 (CH2) n7 SO3M(VIII)

[0126] (Where Rf 5 is a perfluoroalkyl group having 1 to 13 carbon atoms, n7 is an integer of 1 to 3, and M is the substance defined above).

[0127] The above alkyl alkylene carboxylic acid (IX) is represented by the following general formula (IX):

[0128] R 6 (CH2) n8 COOM(IX)

[0129] (Where Rf 6 It is a linear or branched partially or completely fluorinated alkyl group having 1 to 13 carbon atoms which may contain an ether bond, n8 is an integer of 1 to 3, and M is the substance defined above).

[0130] The above fluorocarboxylic acid (X) is represented by the following general formula (X):

[0131] R 7 -O-Rf 8 -O-CF2-COOM(X)

[0132] (Where Rf 7 is a linear or branched partially or completely fluorinated alkyl group having 1 to 6 carbon atoms and which may contain an ether bond and / or a chlorine atom, Rf 8 is a linear or branched partially or completely fluorinated alkyl group having 1 to 6 carbon atoms, and M is the substance defined above).

[0133] The above alkoxy fluorosulfonic acid (XI) is represented by the following general formula (XI):

[0134] R 9 -O-CY 1 Y 2 CF2-SO3M(XI)

[0135] (Where 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, which may be partially or completely fluorinated, 1 and Y 2 are the same or different, are H or F, and M is the substance defined above).

[0136] The above compound (XII) is represented by the following general formula (XII):

[0137] [Chemistry 2]

[0138]

[0139] (Where X 1 , X 2 and X 3 Rf may be the same or different and is H, F and a linear or branched partially or fully fluorinated alkyl group having 1 to 6 carbon atoms and may contain an ether bond. 10is a perfluoroalkylene group having 1 to 3 carbon atoms, L is a connecting group, Y 0 is an anionic group).

[0140] Y 0 It can be -COOM, -SO2M or -SO3M, or -SO3M or COOM (wherein M is the substance defined above).

[0141] Examples of L include a single bond and a partially or completely fluorinated alkylene group having 1 to 10 carbon atoms which may include an ether bond.

[0142] The above compound (XIII) is represented by the following general formula (XIII):

[0143] R 11 -O-(CF2CF(CF3)O) n9 (CF2O) n10 CF2COOM(XIII)

[0144] (Where Rf 11 is a fluorinated alkyl group having 1 to 5 carbon atoms and containing chlorine, n9 is an integer of 0 to 3, n10 is an integer of 0 to 3, and M is the substance defined above). Examples of compound (XIII) include CF2ClO(CF2CF(CF3)O) n9 (CF2O) n10 CF2COONH4 (mixture with an average molecular weight of 750, wherein n9 and n10 are the numbers defined above).

[0145] As described above, examples of the anionic fluorinated surfactant include carboxylic acid-based surfactants and sulfonic acid-based surfactants.

[0146] The fluorinated surfactant may be a single type of fluorinated surfactant or a mixture containing two or more types of fluorinated surfactants.

[0147] The fluorinated surfactant preferably has no methylene group (-CH2), and more preferably has no CH bond. By using a fluorinated surfactant having no methylene group (-CH2) or CH bond in the molecule, polymerization of the fluorinated monomer in the presence of an aqueous medium can be smoothly performed.

[0148] The number of H atoms possessed by the hydrophobic group of the fluorinated surfactant is preferably 0 or 1, more preferably 0. By using a fluorinated surfactant having a small number of H atoms bonded to the carbon atoms constituting the hydrophobic group, the polymerization of the fluorinated monomer in the presence of an aqueous medium can be smoothly carried out. The number of carbon atoms in the hydrophobic group of the fluorinated surfactant having a hydrophobic group and a hydrophilic group is preferably 1 to 50, more preferably 3 to 20, and further preferably 6 to 12. The hydrophobic group usually constitutes the above-mentioned "portion other than the anionic group" in the molecular structure of the fluorinated surfactant. Examples of the hydrophilic group include Y 0 The fluorinated surfactant may be a saturated fluorinated surfactant in which all carbon atoms bonded to the hydrophobic group are substituted with fluorine atoms.

[0149] As the fluorinated surfactant, among the above anionic fluorinated surfactants, there can be mentioned the general formula (N 1 ) represented by the general formula (N 2 ) represented by the general formula (N 4 ):

[0150] R n4 -O-(CY n1 F) p CF2-Y 0 (N 4 )

[0151] (Where Rf n4 is a linear or branched partially or completely fluorinated alkyl group having 1 to 12 carbon atoms which may contain an ether bond (excluding alkyl groups having -CH2-), n1 is H or F, p is 0 or 1, Y 0 As defined above), and the compound represented by the general formula (N 5 ):

[0152] [Chemistry 3]

[0153]

[0154] (Where X n2 , X n3 and X n4 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 and which may contain an ether bond (excluding an alkyl group having -CH2-), wherein X n3 and X n4 Neither of them is H. Rf n5is a linear or branched partially or completely fluorinated alkylene group having 1 to 3 carbon atoms and which may contain an ether bond (excluding alkylene groups having -CH2-), L is a connecting group, and Y 0 As defined above. Where X n2 , X n3 , X n4 and Rf n5 The total number of carbon atoms is 18 or less).

[0155] As the fluorinated surfactant, among the above-mentioned anionic fluorinated surfactants, at least one selected from the group consisting of the following substances is more preferred, the substance being a perfluorocarboxylic acid (I) represented by the general formula (I), an ω-H perfluorocarboxylic acid (II) represented by the general formula (II), a perfluoroether carboxylic acid (III) represented by the general formula (III), a perfluoroalkyl alkylene carboxylic acid (IV) represented by the general formula (IV), a perfluoroalkoxy fluorocarboxylic acid (V) represented by the general formula (V), a perfluoroalkyl sulfonic acid (VI) represented by the general formula (VI), an ω-H perfluorosulfonic acid (VII) represented by the general formula (VII), a perfluoroalkyl alkylene sulfonic acid (VIII) represented by the general formula (VIII), and a general formula (X): Rf 7 -O-Rf 8 -O-CF2-COOM

[0156] (Where Rf 7 is a linear or branched partially or completely fluorinated alkyl group having 1 to 6 carbon atoms and which may contain an ether bond and / or a chlorine atom (excluding an alkyl group having -CH2-), Rf 8 is a linear or branched partially or completely fluorinated alkyl group having 1 to 6 carbon atoms (excluding alkyl groups having -CH2-), and M is as defined above. ) is a fluorinated carboxylic acid (X) represented by the general formula (XI): Rf 9 -O-CY 1 FCF2-SO3M

[0157] (Where Rf 9 is a linear or branched, partially or fully fluorinated alkyl group having 1 to 12 carbon atoms, which may contain an ether bond, and may contain chlorine (excluding alkyl groups having -CH2-), 1 is H or F, and M is as defined above. ) represented by an alkoxy fluorosulfonic acid (XI), general formula (XII):

[0158] [Chemistry 4]

[0159]

[0160] (Where X 1 , X 2 and X 3may be the same or different and are H, F and a linear or branched partially or fully fluorinated alkyl group having 1 to 6 carbon atoms and which may contain an ether bond (excluding an alkyl group having -CH2-), wherein X 2 and X 3 Neither of them is H, Rf 10 is a perfluoroalkylene group having 1 to 3 carbon atoms, L is a connecting group, Y 0 is an anionic group. ) and the compound (XII) represented by the general formula (XIII):

[0161] R 11 -O-(CF2CF(CF3)O) n9 (CF2O) n10 CF2COOM

[0162] (Where Rf 11 The compound (XIII) is a fluorinated alkyl group having 1 to 5 carbon atoms containing chlorine (excluding fluorinated alkyl groups having -CH2-), n9 is an integer of 0 to 3, n10 is an integer of 0 to 3, and M is as defined above. By using these fluorinated surfactants, the polymerization of fluorinated monomers in the presence of an aqueous medium can be smoothly carried out.

[0163] Examples of the fluorinated surfactant include compounds represented by the following formula: The fluorinated surfactant may be a mixture of these compounds.

[0164] F(CF2)7COOM,

[0165] F(CF2)5COOM,

[0166] H(CF2)6COOM,

[0167] H(CF2)7COOM,

[0168] CF3O(CF2)3OCHFCF2COOM,

[0169] C3F7OCF(CF3)CF2OCF(CF3)COOM,

[0170] CF3CF2CF2OCF(CF3)COOM,

[0171] CF3CF2OCF2CF2OCF2COOM,

[0172] C2F5OCF(CF3)CF2OCF(CF3)COOM,

[0173] CF3OCF(CF3)CF2OCF(CF3)COOM,

[0174] CF2ClCF2CF2OCF(CF3)CF2OCF2COOM,

[0175] CF2ClCF2CF2OCF2CF(CF3)OCF2COOM,

[0176] CF2ClCF(CF3)OCF(CF3)CF2OCF2COOM,

[0177] CF2ClCF(CF3)OCF2CF(CF3)OCF2COOM,

[0178] [Chemistry 5]

[0179]

[0180] (In each formula, M is H, metal atom, NR 7 4. An imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent. 7 is H or an organic group. )

[0181] In the production method of the present invention, as the fluorinated surfactant used for the polymerization of the fluorinated monomer, a fluorinated surfactant having a carbon number of 7 or less can be particularly preferably used. By using a fluorinated surfactant having a carbon number of 7 or less, the polymerization of the fluorinated monomer can be smoothly carried out, and the content of fluorinated compounds having a hydrophilic group of 7 or less, such as the fluorinated surfactant having a carbon number of 7 or less, can be efficiently removed from the fluorinated polymer aqueous dispersion by heat treatment, ion exchange treatment and concentration treatment after polymerization.

[0182] Examples of the fluorinated surfactant having 7 or less carbon atoms include compounds having 7 or less carbon atoms among the compounds represented by the above general formulae (I) to (XIII). That is, examples of the fluorinated compound having 7 or less carbon atoms and having a hydrophilic group include the following compounds.

[0183] The perfluorocarboxylic acid (I) having a carbon number of 7 or less is represented by the following general formula (I):

[0184] F(CF2) n1 COOM(I)

[0185] (where n1 is an integer of 3 to 6, M is H, a metal atom, NR 7 4. an imidazolium which may be substituted, a pyridinium which may be substituted, or a phosphonium which may be substituted, R 7 is H or an organic group).

[0186] The ω-H perfluorocarboxylic acid (II) having a carbon number of 7 or less is represented by the following general formula (II):

[0187] H(CF2) n2 COOM(II)

[0188] (wherein n2 is an integer of 4 to 6, and M is the substance defined above).

[0189] The perfluoroether carboxylic acid (III) having a carbon number of 7 or less is represented by the following general formula (III):

[0190] R 1 -O-(CF(CF3)CF2O) n3 CF(CF3)COOM(III)

[0191] (Where Rf 1 is trifluoromethyl, n3 is 1, and M is the substance defined above).

[0192] The perfluoroalkyl alkylene carboxylic acid (IV) having a carbon number of 7 or less is represented by the following general formula (IV):

[0193] R 2 (CH2) n4 R 3 COOM(IV)

[0194] (Where Rf 2 is a perfluoroalkyl group having 1 to 4 carbon atoms, Rf 3 is a linear or branched perfluoroalkylene group having 1 to 3 carbon atoms, n4 is an integer of 1 to 3, wherein Rf 2 , Rf 3 and n4 are combined in such a way that the total number of carbon atoms is 6 or less, and M is the substance defined above).

[0195] The alkoxy fluorocarboxylic acid (V) having a carbon number of 7 or less is represented by the following general formula (V):

[0196] R 4 -O-CY 1 Y 2 CF2-COOM(V)

[0197] (Where Rf 4 is a linear or branched partially or completely fluorinated alkyl group having 1 to 4 carbon atoms which may contain an ether bond and / or a chlorine atom, 1 and Y 2 are the same or different, are H or F, and M is the substance defined above).

[0198] The perfluoroalkylsulfonic acid (VI) having a carbon number of 7 or less is represented by the following general formula (VI):

[0199] F(CF2)n5 SO3M(VI)

[0200] (wherein n5 is an integer of 3 to 7, and M is the substance defined above).

[0201] The ω-H perfluorosulfonic acid (VII) having a carbon number of 7 or less is represented by the following general formula (VII):

[0202] H(CF2) n6 SO3M(VII)

[0203] (wherein n6 is an integer of 4 to 7, and M is the substance defined above).

[0204] The perfluoroalkyl alkylene sulfonic acid (VIII) having a carbon number of 7 or less is represented by the following general formula (VIII):

[0205] R 5 (CH2) n7 SO3M(VIII)

[0206] (Where Rf 5 is a perfluoroalkyl group having 1 to 4 carbon atoms, n7 is an integer of 1 to 3, and M is the substance defined above).

[0207] The alkyl alkylene carboxylic acid (IX) having a carbon number of 7 or less is represented by the following general formula (IX):

[0208] R 6 (CH2) n8 COOM(IX)

[0209] (Where Rf 6 It is a linear or branched partially or completely fluorinated alkyl group having 1 to 4 carbon atoms which may contain an ether bond, n8 is an integer of 1 to 3, and M is the substance defined above).

[0210] The fluorinated carboxylic acid (X) having 7 or less carbon atoms is represented by the following general formula (X):

[0211] R 7 -O-Rf 8 -O-CF2-COOM(X)

[0212] (Where Rf 7 is a linear or branched partially or completely fluorinated alkyl group having 1 to 2 carbon atoms and which may contain an ether bond and / or a chlorine atom, Rf 8 is a linear or branched partially or completely fluorinated alkyl group having 1 to 3 carbon atoms, and M is the substance defined above).

[0213] The alkoxy fluorosulfonic acid (XI) having 7 or less carbon atoms is represented by the following general formula (XI):

[0214] R 9 -O-CY 1 Y 2 CF2-SO3M(XI)

[0215] (Where Rf 9 is a linear or branched alkyl group having 1 to 5 carbon atoms, which may contain an ether bond, and which may contain chlorine, which may be partially or completely fluorinated, 1 and Y 2 are the same or different, are H or F, and M is the substance defined above).

[0216] The compound (XII) having 7 or less carbon atoms is represented by the following general formula (XII):

[0217] [Chemistry 6]

[0218]

[0219] (Where X 1 , X 2 and X 3 may be the same or different and are H, F and a linear or branched partially or fully fluorinated alkyl group having 1 to 3 carbon atoms which may contain an ether bond, Rf 10 is a perfluoroalkylene group having 1 to 3 carbon atoms, L is a connecting group, Y 0 is an anionic group).

[0220] Y 0 It can be -COOM, -SO2M or -SO3M, or -SO3M or COOM (wherein M is the substance defined above).

[0221] Examples of L include a single bond and a partially or completely fluorinated alkylene group having 1 to 4 carbon atoms which may contain an ether bond.

[0222] Among them, X 1 , X 2 , X 3 , Rf 10 , L and Y 0 The total number of carbon atoms is 7 or less.

[0223] The compound (XIII) having 7 or less carbon atoms is represented by the following general formula (XIII):

[0224] R 11 -O-(CF2CF(CF3)O) n9 (CF2O) n10 CF2COOM(XIII)

[0225] (Where Rf11 It is a fluorinated alkyl group having 1 to 2 carbon atoms and containing chlorine, n9 is an integer of 0 to 1, n10 is an integer of 0 to 1, and M is the substance defined above).

[0226] As the fluorinated surfactant having a carbon number of less than 7, it is preferred that at least one be selected from the group consisting of compounds represented by the general formula (I), the general formula (III), the general formula (IX) and the general formula (X), and it is more preferred that at least one be selected from the group consisting of compounds represented by the general formula (I) and the general formula (III).

[0227] Examples of the fluorinated surfactant having 7 or less carbon atoms include compounds represented by the following formulas. The fluorinated surfactant having 7 or less carbon atoms may be a mixture of these compounds.

[0228] F(CF2)5COOM,

[0229] CF3CF2CF2OCF(CF3)COOM,

[0230] CF3CF2OCF2CF2OCF2COOM,

[0231] CF3OCF(CF3)CF2OCF(CF3)COOM,

[0232] [Chemistry 7]

[0233]

[0234] (In each formula, M is H, metal atom, NR 7 4. An imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent. 7 is H or an organic group. )

[0235] The amount of the fluorinated surfactant added is preferably 10 to 10 mass ppm, more preferably 100 mass ppm or more, further preferably 300 mass ppm or more, more preferably 5 mass % or less, further preferably 1 mass % or less, relative to the aqueous medium.

[0236] (Polymerization initiator)

[0237] The polymerization initiator used in the polymerization of the fluorinated monomer is not particularly limited as long as it can generate free radicals within the polymerization temperature range, and a known oil-soluble and / or water-soluble polymerization initiator can be used. Furthermore, it can also be combined with a reducing agent to initiate polymerization in a redox form. The concentration of the above-mentioned polymerization initiator is appropriately determined according to the type of monomer, the molecular weight of the target fluorinated polymer, and the reaction rate.

[0238] As the polymerization initiator, an oil-soluble radical polymerization initiator or a water-soluble radical polymerization initiator can be used.

[0239] The oil-soluble free radical polymerization initiator may be a known oil-soluble peroxide, and for example, the following peroxides may be cited as representative substances: dialkyl peroxycarbonates such as diisopropyl peroxydicarbonate and di-sec-butyl peroxydicarbonate; peroxyesters such as tert-butyl peroxyisobutyrate and tert-butyl peroxypivalate; dialkyl peroxides such as di-tert-butyl peroxide; and di(ω-hydro-dodecafluoroheptanoyl) peroxide, di(ω-hydro-tetrafluorooctanoyl) peroxide, di(ω-hydro-hexafluorononanoyl) peroxide, di(perfluorobutyryl) peroxide, di(perfluorovaleranoyl) peroxide, di(perfluorohexanoyl) peroxide, di(perfluoroheptanoyl) peroxide, di(perfluorooctanoyl) peroxide, peroxide, di(perfluorononanoyl)peroxide, di(ω-chloro-hexafluorobutyryl)peroxide, di(ω-chloro-decafluorohexanoyl)peroxide, di(ω-chloro-tetrafluorooctanoyl)peroxide, ω-hydro-dodecafluoroheptanoyl-ω-hydrohexafluorononanoyl-peroxide, ω-chloro-hexafluorobutyryl-ω-chloro-decafluorohexanoyl-peroxide, ω-hydro-dodecafluoroheptanoyl-perfluorobutyryl-peroxide, di(dichloropentafluorobutyryl)peroxide, di(trichlorooctafluorohexanoyl)peroxide, di(tetrachloroundecanoyl)peroxide, di(pentachlorotetrafluorodecanoyl)peroxide, di(undecanotridodecanoyl)peroxide and the like di[perfluoro(or fluorochloro)acyl]peroxides; and the like.

[0240] As the water-soluble free radical polymerization initiator, it can be a known water-soluble peroxide, for example, ammonium salts, potassium salts, sodium salts of persulfuric acid, perboric acid, perchloric acid, perphosphoric acid, percarbonic acid, etc., organic peroxides such as disuccinic acid peroxide and diglutaric acid peroxide, tert-butyl peroxymaleate, tert-butyl hydroperoxide, etc. It can also contain a reducing agent such as sulfites, and its use amount can be 0.1 to 20 times that of the peroxide.

[0241] For example, in the case of implementing polymerization at a low temperature below 30°C, etc., as a polymerization initiator, it is preferred to use a redox initiator composed of an oxidant and a reducing agent. As the oxidant, persulfate, organic peroxide, potassium permanganate, manganese triacetate, ammonium cerium nitrate, etc. can be mentioned. As the reducing agent, sulfite, bisulfite, bromate, diimide, oxalic acid, etc. can be mentioned. As persulfate, ammonium persulfate and potassium persulfate can be mentioned. As sulfite, sodium sulfite and ammonium sulfite can be mentioned. In order to increase the decomposition rate of the initiator, it is also preferred to add copper salts and iron salts to the combination of redox initiators. As the copper salt, copper (II) sulfate can be mentioned, and as the iron salt, iron (II) sulfate can be mentioned.

[0242] As the above-mentioned redox initiator, for example, potassium permanganate / oxalic acid, potassium permanganate / ammonium oxalate, ammonium persulfate / bisulfite / ferric sulfate, manganese triacetate / oxalic acid, cerium ammonium nitrate / oxalic acid, bromate / bisulfite, etc. can be cited, preferably potassium permanganate / oxalic acid. In the case of using a redox initiator, either the oxidant or the reductant can be put into a polymerization kettle in advance, and then the other can be added continuously or intermittently to initiate polymerization. For example, in the case of using potassium permanganate / oxalic acid, it is preferred to put oxalic acid into the polymerization kettle and continuously add potassium permanganate thereto.

[0243] The amount of polymerization initiator added is not particularly limited, and may be added once, sequentially, or continuously at the initial stage of polymerization in an amount that does not significantly reduce the polymerization rate (e.g., a concentration of several ppm relative to water). The upper limit is a range in which the heat of polymerization reaction can be used to remove heat from the device surface and the reaction temperature can be increased, and a more preferred upper limit is a range in which the heat of polymerization reaction can be removed from the device surface.

[0244] During the polymerization of fluorinated monomers, the free radical concentration in the polymerization can be adjusted by adding a decomposition agent. As decomposition agents, sulfites, bisulfites, bromates, diimides, oxalic acid, copper salts, iron salts, etc. can be mentioned. As sulfites, sodium sulfite and ammonium sulfite can be mentioned. As copper salts, copper sulfate (II) can be mentioned, and as iron salts, iron sulfate (II) can be mentioned. The amount of the decomposition agent added is in the range of 25 mass % to 300 mass % relative to the amount of the oxidant combined as a polymerization initiator (redox initiator). As the amount of the decomposition agent added, it is preferably 25 mass % to 150 mass %, and more preferably 50 mass % to 100 mass %. In addition, it is preferred to add the decomposition agent after 5 mass % of all fluorinated monomers consumed in the polymerization reaction are polymerized, and more preferably after 10 mass % are polymerized. The amount of the decomposition agent added is preferably an amount equivalent to 0.1 mass ppm to 20 mass ppm of the mass of the aqueous medium used, and more preferably an amount equivalent to 3 mass ppm to 10 mass ppm.

[0245] (Aqueous medium)

[0246] The aqueous medium used in the polymerization of the fluorinated monomer refers to the reaction medium for the polymerization, which is a liquid containing water. The aqueous medium is not particularly limited as long as it contains water, and may contain water and a non-fluorinated organic solvent such as alcohol, ether, ketone, and / or a fluorinated organic solvent having a boiling point of 40° C. or less.

[0247] As the aqueous medium, from the perspective of being able to smoothly carry out the polymerization of the fluorinated monomer and also being able to suppress the reduction in the removal efficiency of the fluorinated compound having a hydrophilic group, an aqueous medium containing only water, or an aqueous medium containing only water and a non-fluorinated organic solvent is preferred, and an aqueous medium containing only water is more preferred.

[0248] From the perspective of being able to smoothly carry out the polymerization of the fluorinated monomer and also being able to suppress the reduction in the removal efficiency of the fluorinated compound having a hydrophilic group, the mass of the aqueous medium is preferably 90% or more, more preferably 95% or more, further preferably 99.0% or more, further preferably 99.5% or more, particularly preferably 99.9% or more, and may also be 100%.

[0249] (Fluorinated monomers)

[0250] The fluorinated monomer used in the polymerization has at least one fluorine atom and at least one double bond. As the fluorinated monomer, it is preferably selected from tetrafluoroethylene [TFE], hexafluoropropylene [HFP], trifluorochloroethylene [CTFE], vinyl fluoride, vinylidene fluoride [VdF], trifluoroethylene, fluoroalkyl vinyl ether, fluoroalkyl ethylene, fluoroalkyl allyl ether, trifluoropropylene, pentafluoropropylene, trifluorobutylene, tetrafluoroisobutylene, hexafluoroisobutylene, general formula (100): CHX 101 =CX 102 R 101 (Where X 101 and X 102 One of them is H and the other is F, Rf 101 It is at least one selected from the group consisting of a fluorinated monomer represented by a linear or branched fluorinated alkyl group having 1 to 12 carbon atoms, a fluorinated vinyl heterocyclic compound, and a monomer providing a crosslinking site.

[0251] As the fluoroalkyl vinyl ether [FAVE], for example, at least one selected from the group consisting of the following fluorinated monomers is preferred, and the monomer is:

[0252] General formula (110): CF2=CF-ORf 111

[0253] (Where Rf 111 represents a perfluorinated organic group),

[0254] General formula (120): CF2=CF-OCH2-Rf 121

[0255] (Where Rf 121 is a fluorine-containing monomer represented by a perfluoroalkyl group having 1 to 5 carbon atoms,

[0256] General formula (130): CF2=CFOCF2ORf 131

[0257] (Where Rf 131 a fluorine-containing monomer represented by 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 containing 1 to 3 oxygen atoms,

[0258] General formula (140): CF2=CFO(CF2CF(Y 141 )O) m (CF2) n F

[0259] (Where Y 141 represents a fluorine atom or a trifluoromethyl group. m is an integer of 1 to 4. n is an integer of 1 to 4) and

[0260] General formula (150): CF2=CF-O-(CF2CFY 151 -O) n -(CFY 152 ) m -A 151

[0261] (Where Y 151 represents a fluorine atom, a chlorine atom, a -SO2F group or a perfluoroalkyl group. The perfluoroalkyl group may contain an ethereal oxygen and a -SO2F group. n represents an integer of 0 to 3. 151 Can be the same or different. 152 represents a fluorine atom, a chlorine atom or a -SO2F group. m represents an integer of 1 to 5. m Y 152 Can be the same or different. 151 Represents -SO2X 151 、-COZ 151 or-POZ 152 Z 153 .X 151 Indicates F, Cl, Br, I, -OR 151 or -NR 152 R 153 . Z 151 , Z 152 and Z 153 Same or different, indicates -NR 154 R 155 OR 156 . R 151 , R 152 , R 153 , R 154 , R 155 and R 156The fluorine-containing monomer is the same or different and represents H, ammonium, an alkali metal, an alkyl group containing or not containing a fluorine atom, an aryl group, or a sulfonyl group-containing group).

[0262] In the present invention, the "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.

[0263] Examples of the fluorinated monomer represented by the general formula (110) include Rf 111 It is a fluorine-containing monomer having a perfluoroalkyl group having 1 to 10 carbon atoms. The perfluoroalkyl group preferably has 1 to 5 carbon atoms.

[0264] Examples of the perfluoro organic 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.

[0265] As the fluorinated monomer represented by the general formula (110), further examples include Rf in the general formula (110): 111 It is a monomer of a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms, Rf 111 is the following formula:

[0266] [Chemistry 8]

[0267]

[0268] (wherein m represents 0 or an integer of 1 to 4) represented by a monomer, Rf 111 is the following formula:

[0269] [Chemistry 9]

[0270]

[0271] (wherein n represents an integer of 1 to 4) and the like.

[0272] As the fluorine-containing monomer represented by the general formula (110), preferably

[0273] General formula (160): CF2=CF-ORf 161

[0274] (Where Rf 161 represents a fluorinated monomer represented by a perfluoroalkyl group having 1 to 10 carbon atoms. 161 A perfluoroalkyl group having 1 to 5 carbon atoms is preferred.

[0275] The fluoroalkyl vinyl ether is preferably at least one selected from the group consisting of fluorinated monomers represented by general formulae (160), (130) and (140).

[0276] The fluorinated monomer represented by the general formula (160) is generally referred to as perfluoro(alkyl vinyl ether). The fluorinated monomer represented by the general formula (160) is preferably at least one selected from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether) and perfluoro(propyl vinyl ether), and more preferably at least one selected from the group consisting of perfluoro(methyl vinyl ether) and perfluoro(propyl vinyl ether).

[0277] The fluorinated monomer represented by the general formula (130) is preferably at least one selected from the group consisting of CF2=CFOCF2OCF3, CF2=CFOCF2OCF2CF3 and CF2=CFOCF2OCF2CF2OCF3.

[0278] The fluorinated monomer represented by the general formula (140) is preferably at least one selected from the group consisting of CF2=CFOCF2CF(CF3)O(CF2)3F, CF2=CFO(CF2CF(CF3)O)2(CF2)3F and CF2=CFO(CF2CF(CF3)O)2(CF2)2F.

[0279] The fluorinated monomer represented by the general formula (150) is preferably at least one selected from the group consisting of CF2=CFOCF2CF2SO2F, CF2=CFOCF2CF(CF3)OCF2CF2SO2F, CF2=CFOCF2CF(CF2CF2SO2F)OCF2CF2SO2F and CF2=CFOCF2CF(SO2F)2.

[0280] As the fluorinated monomer represented by the general formula (100), Rf is preferably 101 is a fluorinated monomer having a linear fluoroalkyl group, more preferably Rf 101 It is a straight-chain perfluoroalkyl fluorinated monomer. 101 The number of carbon atoms is preferably 1 to 6. Examples of the fluorinated monomer represented by the general formula (100) include CH2=CFCF3, CH2=CFCF2CF3, CH2=CFCF2CF2CF3, CH2=CFCF2CF2CF3, CH2=CFCF2CF2CF2H, CH2=CFCF2CF2CF2CF3, CHF=CHCF3 (E form), CHF=CHCF3 (Z form), etc. Among them, 2,3,3,3-tetrafluoropropylene represented by CH2=CFCF3 is preferred.

[0281] As the fluoroalkylethylene, preferably

[0282] General formula (170): CH2=CH-(CF2) n -X 171

[0283] (Where X 171is H or F, n is an integer of 3 to 10), more preferably selected from CH2=CH-C4F9 and CH2=CH-C6F 13 At least one of the group consisting of.

[0284] Examples of the fluoroalkyl allyl ether include

[0285] General formula (180): CF2=CF-CF2-ORf 111

[0286] (Where Rf 111 represents a perfluorinated organic group).

[0287] Rf of general formula (180) 111 With the Rf of general formula (110) 111 Same as Rf 111 , preferably a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluoroalkoxyalkyl group having 1 to 10 carbon atoms. The fluoroalkyl allyl ether represented by the general formula (180) is preferably at least one selected from the group consisting of CF2=CF-CF2-O-CF3, CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7 and CF2=CF-CF2-O-C4F9, more preferably at least one selected from the group consisting of CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7 and CF2=CF-CF2-O-C4F9, and further preferably CF2=CF-CF2-O-CF2CF2CF3.

[0288] Examples of the fluorinated vinyl heterocyclic compound include those of the general formula (230):

[0289] [Chemistry 10]

[0290]

[0291] (Where X 231 and X 232 are independently F, Cl, methoxy or fluoromethoxy, Y 231 Formula Y 232 Or Y 233 .

[0292] [Chemistry 11]

[0293]

[0294] (Where Z 231 and Z 232 and (ii) independently represents F or a fluoroalkyl group having 1 to 3 carbon atoms.

[0295] The monomer providing a crosslinking site is preferably at least one selected from the group consisting of the following monomers:

[0296] General formula (180): CX 181 2=CX 182 -R f 181 CHR 181 X 183

[0297] (Where X 181 and X 182 are independently a hydrogen atom, a fluorine atom or CH3, R f 181 is a fluoroalkylene group, a perfluoroalkylene group, a fluoro(poly)oxyalkylene group or a perfluoro(poly)oxyalkylene group, R 181 is a hydrogen atom or CH3, X 183 is an iodine atom or a bromine atom),

[0298] General formula (190): CX 191 2=CX 192 -R f 191 X 193

[0299] (Where X 191 and X 192 are independently a hydrogen atom, a fluorine atom or CH3, R f 191 is a fluoroalkylene group, a perfluoroalkylene group, a fluoropolyoxyalkylene group or a perfluoropolyoxyalkylene group, X 193 is an iodine atom or a bromine atom),

[0300] General formula (200): CF2=CFO(CF2CF(CF3)O) m (CF2) n -X 201

[0301] (wherein, m is an integer from 0 to 5, n is an integer from 1 to 3, and X 201 is a fluorine-containing monomer represented by a cyano group, a carboxyl group, an alkoxycarbonyl group, an iodine atom, a bromine atom or -CH2I), and

[0302] General formula (210): CH2=CFCF2O(CF(CF3)CF2O) m (CF(CF3)) n -X 211

[0303] (wherein, m is an integer from 0 to 5, n is an integer from 1 to 3, and X 211 is a fluorine-containing monomer represented by a cyano group, a carboxyl group, an alkoxycarbonyl group, an iodine atom, a bromine atom or -CH2OH), and

[0304] General formula (220): CR 221 R 222 =CR 223 -Z 221 -CR 224 =CR 225 R 226

[0305] (Where R 221 , R 222 , R 223 , R 224 , R 225 and R 226 are the same or different and are a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. 221 A linear or branched alkylene group having 1 to 18 carbon atoms, a cycloalkylene group having 3 to 18 carbon atoms, an at least partially fluorinated alkylene group having 1 to 10 carbon atoms, or an oxyalkylene group;

[0306] -(Q) p -CF2O-(CF2CF2O) m (CF2O) n -CF2-(Q) p -

[0307] (wherein, Q is an alkylene group or an oxyalkylene group. p is 0 or 1. m / n is 0.2 to 5) and a (per)fluoropolyoxyalkylene group having a molecular weight of 500 to 10000) is a monomer.

[0308] X 183 and X 193 Preferably it is an iodine atom. f 181 and R f 191 It is preferably a perfluoroalkylene group having 1 to 5 carbon atoms. 181 Preferably, it is a hydrogen atom. 201 Preferably, it is a cyano group, an alkoxycarbonyl group, an iodine atom, a bromine atom or -CH2I. 211 Preferred is a cyano group, an alkoxycarbonyl group, an iodine atom, a bromine atom or -CH2OH.

[0309] As the monomer providing a crosslinking site, it is preferably selected from CF2=CFOCF2CF(CF3)OCF2CF2CN, CF2=CFOCF2CF(CF3)OCF2CF2COOH, CF2=CFOCF2CF(CF3)OCF2CF2CH2I, CF2=CFOCF2CF2CH2I, CH2=CFCF2OCF(CF3)CF2OCF(CF3)CN, CH2=CFCF2OCF(CF3)CF2OCF(CF3) At least one selected from the group consisting of COOH, CH2=CFCF2OCF(CF3)CF2OCF(CF3)CH2OH, CH2=CHCF2CF2I, CH2=CH(CF2)2CH=CH2, CH2=CH(CF2)6CH=CH2 and CF2=CFO(CF2)5CN, more preferably at least one selected from the group consisting of CF2=CFOCF2CF(CF3)OCF2CF2CN and CF2=CFOCF2CF2CH2I.

[0310] In the above-mentioned polymerization, the above-mentioned fluorine-containing monomer and the non-fluorine-containing monomer can be polymerized. Examples of the above-mentioned non-fluorine-containing monomer include hydrocarbon monomers reactive with the above-mentioned fluorine-containing monomer. Examples of the above-mentioned hydrocarbon monomer include olefins such as ethylene, propylene, butene, 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 butyrate, vinyl isobutyrate, vinyl valerate, vinyl pivalate, vinyl caproate, vinyl octanoate, vinyl caprate, vinyl versatate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl benzoate, vinyl p-tert-butylbenzoate, vinyl cyclohexanecarboxylate, vinyl monochloroacetate, vinyl adipate, vinyl acrylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, ethyl cinnamate, etc. Vinyl esters such as vinyl ester, vinyl undecylenate, vinyl hydroxyacetate, vinyl hydroxypropionate, vinyl hydroxybutyrate, vinyl hydroxyvalerate, vinyl hydroxyisobutyrate, and vinyl hydroxycyclohexanecarboxylate; alkyl allyl ethers such as ethyl allyl ether, propyl allyl ether, butyl allyl ether, isobutyl allyl ether, and cyclohexyl allyl ether; alkyl allyl esters such as ethyl allyl ester, propyl allyl ester, butyl allyl ester, isobutyl allyl ester, and cyclohexyl allyl ester; (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, etc.

[0311] In addition, as the above-mentioned non-fluorine-containing monomer, it can also be a hydrocarbon monomer containing a functional group (wherein, monomers providing crosslinking sites are not included). As the above-mentioned hydrocarbon monomer containing a functional group, for example, hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, hydroxyisobutyl vinyl ether, and hydroxycyclohexyl vinyl ether can be cited; non-fluorine-containing monomers having carboxyl groups 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; non-fluorine-containing monomers having sulfonic groups such as vinyl sulfonic acid; non-fluorine-containing monomers having glycidyl groups such as glycidyl vinyl ether and glycidyl allyl ether; non-fluorine-containing monomers having amino groups such as aminoalkyl vinyl ether and aminoalkyl allyl ether; non-fluorine-containing monomers having amide groups such as (meth)acrylamide and hydroxymethyl acrylamide; non-fluorine-containing monomers having nitrile groups such as acrylonitrile and methacrylonitrile; and the like.

[0312] In the above-mentioned polymerization, by polymerizing one or two or more kinds of the above-mentioned fluorinated monomers, desired fluorinated polymer particles can be obtained.

[0313] (Chain transfer agent)

[0314] In the production method of the present invention, the fluorinated monomer can also be polymerized in the presence of a chain transfer agent. By using a chain transfer agent, the polymerization rate and molecular weight can be adjusted. As the chain transfer agent, for example, in addition to esters such as dimethyl malonate, diethyl malonate, methyl acetate, ethyl acetate, butyl acetate, and dimethyl succinate, various halogenated hydrocarbons such as isopentane, methane, ethane, propane, methanol, isopropanol, acetone, various mercaptans, and carbon tetrachloride, cyclohexane, etc. can also be cited.

[0315] Bromine compounds or iodine compounds can be used as chain transfer agents. As a polymerization method using a bromine compound or an iodine compound, for example, a method of polymerizing a fluorinated monomer 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) can be cited. As a representative example of the bromine compound or iodine compound used, for example, the general formula:

[0316] R a I x Br y

[0317] (where x and y are integers from 0 to 2 and satisfy 1≤x+y≤2, R a is a saturated or unsaturated fluorocarbon or chlorofluorocarbon group having 1 to 16 carbon atoms, or a hydrocarbon group having 1 to 3 carbon atoms, wherein R a By using a bromine compound or an iodine compound, iodine or bromine is introduced into the polymer to function as a crosslinking point.

[0318] Examples of the bromine compound or iodine compound include 1,3-diiodoperfluoropropane, 2-iodoperfluoropropane, 1,3-diiodoperfluoropropane-2-chloroperfluoropropane, 1,4-diiodoperfluorobutane, 1,5-diiodoperfluoropentane-2,4-dichloroperfluoropentane, 1,6-diiodoperfluorohexane, 1,8-diiodoperfluorooctane, 1,12-diiodoperfluorododecane, 1,16-diiodoperfluorohexadecane, diiodomethane, 1,2-diiodethane, 1,3-diiodoperfluoropropane, CF2Br2, BrCF2CF2Br, CF3CFBrCF2Br, CFClBr2, BrCF2CFClBr, CFBrClCFClBr, BrCF2CF2CF2Br, BrCF2CFBrOCF3, 1-bromo-2-iodoperfluoroethane, 1-bromo-3-iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane, 2-bromo-3-iodoperfluorobutane, 3-bromo-4-iodoperfluoro-1-butene, 2-bromo-4-iodoperfluoro-1-butene, mono-iodine and mono-bromine substitution products of benzene, di-iodine and mono-bromine substitution products, and (2-iodoethyl) and (2-bromoethyl) substitution products, etc. These compounds can be used alone or in combination with each other.

[0319] Among these, 1,4-diiodoperfluorobutane, 1,6-diiodoperfluorohexane, and 2-iodoperfluoropropane are preferably used in view of polymerization reactivity, crosslinking reactivity, and availability.

[0320] The amount of the chain transfer agent used is usually 1 to 50,000 ppm by mass, preferably 1 to 20,000 ppm by mass, relative to the total amount of the supplied fluorinated monomer. The amount of the chain transfer agent used is preferably an amount that is completely consumed in the polymerization of the fluorinated monomer and does not remain in the aqueous dispersion containing the fluorinated polymer, so as not to reduce the removal efficiency of the fluorinated compound having a hydrophilic group as much as possible. Therefore, the amount of the chain transfer agent used is more preferably 10,000 ppm by mass or less, further preferably 5,000 ppm by mass or less, further preferably 1,000 ppm by mass or less, particularly preferably 500 ppm by mass or less, and most preferably 200 ppm by mass or less, relative to the total amount of the supplied fluorinated monomer.

[0321] The chain transfer agent may be added to the reaction vessel all at once before the start of polymerization, may be added all at once after the start of polymerization, may be added in several portions during polymerization, or may be added continuously during polymerization.

[0322] (Other additives)

[0323] In the polymerization of fluorinated monomers, additives such as buffers, pH regulators, stabilizing aids, and dispersion stabilizers may be used. In addition, in the polymerization of fluorinated monomers, free radical scavengers and decomposers may be added to adjust the polymerization rate and molecular weight. In addition, in the polymerization of fluorinated monomers, non-fluorinated anionic surfactants, non-fluorinated nonionic surfactants, non-fluorinated cationic surfactants, etc. may also be used.

[0324] As the stabilizing aid, paraffin, fluorine oil, fluorine solvent, silicone oil and the like are preferred. The stabilizing aid can be used alone or in combination of two or more. As the stabilizing aid, paraffin is more preferred. Paraffin can be liquid, semi-solid or solid at room temperature, but preferably a saturated hydrocarbon having 12 or more carbon atoms. The melting point of paraffin is usually preferably 40°C to 65°C, more preferably 50°C to 65°C.

[0325] The amount of the stabilizing agent 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. The stabilizing agent is preferably sufficiently hydrophobic to be completely separated and removed from the aqueous dispersion after polymerization and not to become a contaminating component.

[0326] (Polymerization conditions)

[0327] The polymerization of fluorinated monomers can be carried out at normal pressure and temperature. Usually, the polymerization temperature is 5°C to 120°C and the polymerization pressure is 0.05 MPaG to 10 MPaG. The polymerization temperature and polymerization pressure are appropriately determined according to the type of monomer, the molecular weight of the target fluorinated polymer, the reaction rate, etc.

[0328] (Aqueous dispersion obtained by polymerization)

[0329] The fluorinated monomer is polymerized to obtain an aqueous dispersion containing a fluorinated polymer. The content of the fluorinated polymer in the aqueous dispersion after the polymerization is usually 8 to 50% by mass based on the aqueous dispersion.

[0330] In the aqueous dispersion obtained by polymerizing the fluorinated monomer, in addition to the fluorinated polymer, a fluorinated surfactant used in the polymerization of the fluorinated monomer is usually contained. In addition, in the aqueous dispersion obtained by polymerizing the fluorinated monomer, in addition to the fluorinated polymer, a fluorinated compound having a hydrophilic group generated by the polymerization of the fluorinated monomer is sometimes contained. In the present invention, the fluorinated compound having a hydrophilic group includes the fluorinated surfactant added during the polymerization and the fluorinated compound having a hydrophilic group generated by the polymerization of the fluorinated monomer.

[0331] In the present invention, as the hydrophilic group possessed by the fluorine-containing compound, anionic groups such as acid groups are preferred, for example, -NH2, -PO3M, -OPO3M, -SO3M, -OSO3M, -COOM (in each formula, M represents a cation). As the above-mentioned hydrophilic group, -SO3M or -COOM is preferred, and -COOM is more preferred.

[0332] As the fluorinated compound having a hydrophilic group in the aqueous dispersion obtained by polymerization, a typical compound is a fluorinated compound having a hydrophilic group with a molecular weight of 1000 g / mol or less. According to the production method of the present invention, it is possible to produce an aqueous fluorinated polymer dispersion having a reduced content of the fluorinated compound having a hydrophilic group with a molecular weight of 1000 g / mol or less.

[0333] In one embodiment of the aqueous dispersion obtained by polymerization, a fluorinated surfactant added during polymerization is contained as a fluorinated compound having a hydrophilic group. The fluorinated surfactant added during polymerization is as described above as the fluorinated surfactant used for polymerization of the fluorinated monomer.

[0334] The content of the fluorinated surfactant in the aqueous dispersion obtained by polymerization may be 10 mass ppm or more, 100 mass ppm or more, or 1000 mass ppm or more, or may be 10 mass % or less, 5 mass % or less, or 1 mass % or less, relative to the fluorinated polymer in the aqueous dispersion.

[0335] In one embodiment of the aqueous dispersion obtained by polymerization, as the fluorinated compound having a hydrophilic group, a fluorinated surfactant having a carbon number of 7 or less added during polymerization is contained. The fluorinated surfactant having a carbon number of 7 or less added during polymerization is as described above as the fluorinated surfactant used in the polymerization of the fluorinated monomer.

[0336] The content of the fluorinated surfactant having 7 or less carbon atoms in the aqueous dispersion obtained by polymerization may be 10 mass ppm or more, 100 mass ppm or more, or 1000 mass ppm or more, and may be 10 mass % or less, 5 mass % or less, or 1 mass % or less, relative to the fluorinated polymer in the aqueous dispersion.

[0337] The content of the fluorinated compound having a hydrophilic group in the aqueous dispersion obtained by polymerization (the total amount of the content of the fluorinated surfactant added during polymerization and the content of the fluorinated compound having a hydrophilic group generated by polymerization of the fluorinated monomer) may be 10 mass ppm or more, 100 mass ppm or more, or 1000 mass ppm or more, or may be 10 mass % or less, or may be 5 mass % or less, or may be 1 mass % or less, relative to the fluorinated polymer in the aqueous dispersion.

[0338] In one embodiment of the aqueous dispersion obtained by polymerization, the compound represented by the following general formula (1) is contained as the fluorine-containing compound having a hydrophilic group.

[0339] General formula (1): [X-Rf-A - ] i M i+

[0340] (wherein X represents H, Cl, Br, F or I, Rf represents a linear or branched partially fluorinated or fully fluorinated aliphatic group, or a linear or branched partially fluorinated or fully fluorinated aliphatic group interrupted by at least one oxygen atom, A - Indicates acid group, M i+ represents a cation having a valence number i, where i represents an integer from 1 to 3)

[0341] In one embodiment of the aqueous dispersion obtained by polymerization, the fluorine-containing compound having a hydrophilic group contains a compound represented by the following general formula (2).

[0342] General formula (2): [C n-1 F 2n-1 COO - ]M +

[0343] (where n represents an integer from 9 to 14, M + represents a cation.)

[0344] It is known that the compound represented by the general formula (2) (perfluoroalkanoic acid) is formed during polymerization when perfluoro(alkyl vinyl ether) or the like is used as a fluorine-containing monomer (see International Publication No. 2019 / 161153).

[0345] In one embodiment of the aqueous dispersion obtained by polymerization, the fluorine-containing compound having a hydrophilic group contains a compound represented by the following general formula (3).

[0346] General formula (3): [R 1 -OL-CO2 - ]M +

[0347] (Where R 1 represents a linear or branched partially fluorinated or fully fluorinated aliphatic group, or a linear or branched partially fluorinated 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 cation.)

[0348] In one embodiment of the aqueous dispersion obtained by polymerization, the compound represented by the general formula (4) is contained as the fluorine-containing compound having a hydrophilic group.

[0349] General formula (4): [H-(CF2) m CO2 - ]M +

[0350] (wherein, m represents an integer from 3 to 19, M + represents a cation.)

[0351] (Removal of fluorinated monomers or recovery of aqueous dispersions)

[0352] In the production method of the present invention, after the aqueous dispersion is prepared by polymerization and before the aqueous dispersion is heat-treated, at least one of (a) removing the fluorinated monomer remaining in the reactor from the reactor and (b) recovering the aqueous dispersion in the reactor and storing it in a container different from the reactor can be performed. In particular, when the method of removing the fluorinated monomer in the reactor is used, the subsequent steps can be carried out in the same reactor used in the polymerization, and the productivity of the fluorinated polymer aqueous dispersion is improved, which is preferred.

[0353] After the aqueous dispersion is prepared, it is preferred to remove the fluorinated monomer or recover the aqueous dispersion after stopping the stirring of the contents of the reactor, because the subsequent operations become easy and the polymerization of the fluorinated monomer can be stopped smoothly.

[0354] The method for removing the fluorinated monomer from the reactor is not particularly limited. After the aqueous dispersion is prepared, the stirring of the contents of the reactor can be stopped as needed, and the pressure in the reactor can be exhausted to reach normal pressure, thereby removing the fluorinated monomer from the reactor. The pressure in the reactor can also be reduced to less than 0.0MPaG, thereby removing the fluorinated monomer from the reactor. Inert gas can also be supplied to the reactor, thereby replacing the fluorinated monomer in the reactor with inert gases such as nitrogen. In addition, the entire amount of the fluorinated monomer in the reactor can be reacted and converted into a fluorinated polymer, resulting in the removal of the fluorinated monomer from the reactor. As long as the removal of the fluorinated monomer remaining in the reactor can be carried out to the extent that the polymerization reaction of the fluorinated monomer is fully stopped, a small amount of fluorinated monomer can also remain in the reactor. The removed fluorinated monomer can be recovered by known means. The recovered fluorinated monomer can also be reused in the manufacture of fluorinated polymers.

[0355] As a method for removing the fluorinated monomer from the reactor, the following method is also preferred: after preparing the aqueous dispersion, the stirring of the contents of the reactor is stopped as needed to reduce the pressure in the reactor to less than 0.0 MPaG, and then an inert gas is supplied to the reactor. The decompression in the reactor and the supply of the inert gas may be repeated multiple times.

[0356] When the polymerization of the fluorinated monomer is carried out at a temperature exceeding room temperature, the reactor may be cooled before or after the fluorinated monomer is removed from the reactor. When the fluorinated monomer is removed from the reactor by exhaust gas, nitrogen substitution, etc., unreacted fluorinated monomer, especially liquid, may remain in the reactor, but by cooling the reactor, the reaction of the unreacted fluorinated monomer can be sufficiently suppressed.

[0357] The method of recovering the aqueous dispersion in the reactor and containing it in a container different from the reactor used for polymerization is not particularly limited. For example, after preparing the aqueous dispersion, the stirring of the contents of the reactor may be stopped as needed, the reactor may be opened, and the aqueous dispersion in the reactor may be injected into another container. Alternatively, after preparing the aqueous dispersion, the stirring of the contents of the reactor may be stopped as needed, and the aqueous dispersion may be supplied from the reactor to the other container via a pipe connecting the reactor and the other container.

[0358] In order to stop the polymerization reaction of the fluorinated monomer, a polymerization inhibitor (radical scavenger) may be added.

[0359] As a polymerization inhibitor, a compound that is added to the free radical in the polymerization system or has no reinitiation ability after chain transfer is used. Specifically, a compound having the following functions is used: it is easy to undergo a chain transfer reaction with a primary free radical or a growing free radical, and then generate a stable free radical that does not react with the monomer, or it is easy to undergo an addition reaction with a primary free radical or a growing free radical to generate a stable free radical. The activity of a substance generally referred to as a chain transfer agent is characterized by a chain transfer constant and a reinitiation efficiency. Among chain transfer agents, a substance with a reinitiation efficiency of substantially 0% is referred to as a polymerization inhibitor. As a polymerization inhibitor, it is preferred that at least one of the group consisting of, for example, aromatic hydroxy compounds, aromatic amines, N,N-diethylhydroxylamine, quinone compounds, terpenes, thiocyanates, and copper chloride (CuCl2) be selected. As aromatic hydroxy compounds, non-substituted phenols, polyphenols, salicylic acid, m-salicylic acid or p-salicylic acid, gallic acid, naphthol, etc. can be cited. As the above-mentioned unsubstituted phenol, o-nitrophenol, m-nitrophenol or p-nitrophenol, o-aminophenol, m-aminophenol or p-aminophenol, p-nitrosophenol, etc. can be mentioned. As the polyphenol, catechol, resorcinol, hydroquinone, pyrogallol, pyrogallol, naphthol resorcinol, etc. can be mentioned. As aromatic amines, o-phenylenediamine, m-phenylenediamine or p-phenylenediamine, benzidine, etc. can be mentioned. As the above-mentioned quinone compound, hydroquinone, o-benzoquinone, m-benzoquinone or p-benzoquinone, 1,4-naphthoquinone, alizarin, etc. can be mentioned. As thiocyanate, ammonium thiocyanate (NH4SCN), potassium thiocyanate (KSCN), sodium thiocyanate (NaSCN), etc. can be mentioned. As the above-mentioned inhibitor, quinone compounds are preferred, and hydroquinone is more preferred.

[0360] In one embodiment of the production method of the present invention, an aqueous dispersion containing a fluorinated polymer may be prepared, an inert gas may be supplied into a reactor, and the aqueous dispersion in the reactor may be heat treated. In this case, it is also a preferred embodiment not to add a free radical generator described below to the aqueous dispersion.

[0361] (Free Radical Generator)

[0362] In one embodiment of the manufacturing method of the present invention, after the aqueous dispersion is prepared by polymerization and before the aqueous dispersion is heat-treated, a free radical generator is added to the aqueous dispersion. In one embodiment of the manufacturing method of the present invention, after at least one of (a) and (b) is performed and before the aqueous dispersion is heat-treated, a free radical generator is added to the aqueous dispersion. By adding a free radical generator, the content of the fluorine-containing compound having a hydrophilic group can be further reduced.

[0363] The aqueous dispersion to which the radical generator is added may be the aqueous dispersion remaining in the reactor, or may be the aqueous dispersion recovered from the reactor and contained in another container.

[0364] The radical generator is not particularly limited as long as it is a compound that can decompose at the temperature during the heat treatment to generate radicals. As the radical generator, a water-soluble radical generator is preferred because it can easily diffuse radicals into the aqueous dispersion.

[0365] Examples of the radical generator include organic peroxides, inorganic peroxides, organic azo compounds, and combinations of oxidants and reducing agents. Preferably, the radical generator is at least one selected from the group consisting of inorganic peroxides, organic peroxides, and combinations of oxidants and reducing agents.

[0366] As the inorganic peroxide, a water-soluble inorganic peroxide is preferred. As the inorganic peroxide, hydrogen peroxide, perchlorate, perborate, perphosphate, percarbonate, persulfate, etc. can be cited, and persulfate is preferred. As the persulfate, at least one selected from the group consisting of ammonium persulfate, sodium persulfate and potassium persulfate is preferred, and ammonium persulfate is more preferred.

[0367] As the organic peroxide, a water-soluble organic peroxide is preferred. As the organic peroxide, peroxydicarbonates such as disuccinic acid peroxide and diglutaric acid peroxide can be mentioned.

[0368] As the free radical generator, an oxidizing agent and a reducing agent may be used in combination. By using the oxidizing agent and the reducing agent in combination, free radicals can be generated from the free radical generator by a redox reaction between the oxidizing agent and the reducing agent, so that the temperature during the heat treatment can be lowered.

[0369] As the oxidizing agent, persulfate, organic peroxide, potassium permanganate, manganese triacetate, ammonium cerium nitrate, etc. can be mentioned. As the reducing agent, sulfite, bisulfite, bromate, diimide, oxalic acid, etc. can be mentioned. As the persulfate, ammonium persulfate and potassium persulfate can be mentioned. As the sulfite, sodium sulfite and ammonium sulfite can be mentioned. In order to increase the decomposition rate of the oxidizing agent, it is also preferred to add copper salts and iron salts. As the copper salt, copper (II) sulfate can be mentioned, and as the iron salt, iron (II) sulfate can be mentioned.

[0370] As a combination of an oxidizing agent and a reducing agent, for example, potassium permanganate / oxalic acid, ammonium persulfate / bisulfite / ferric sulfate, manganese triacetate / oxalic acid, cerium ammonium nitrate / oxalic acid, bromate / bisulfite, etc. can be mentioned, preferably potassium permanganate / oxalic acid. When a combination of an oxidizing agent and a reducing agent is used, either the oxidizing agent or the reducing agent can be added to the aqueous dispersion in advance, and then the other can be added continuously or intermittently.

[0371] From the perspective of being able to further improve the removal efficiency of the fluorinated compound having a hydrophilic group, the amount of the free radical generator added is preferably 0.0001 mole times or more, more preferably 0.001 mole times or more, further preferably 0.01 mole times or more, preferably 1000 mole times or less, more preferably 500 mole times or less, and further preferably 100 mole times or less, relative to the molar number of the fluorinated compound having a hydrophilic group in the aqueous dispersion.

[0372] From the perspective of being able to further improve the removal efficiency of the fluorinated compound having a hydrophilic group, the content of the free radical generator in the aqueous dispersion subjected to the heat treatment is preferably 0.0001 mole times or more, more preferably 0.001 mole times or more, further preferably 0.01 mole times or more, preferably 1000 mole times or less, more preferably 500 mole times or less, and further preferably 100 mole times or less, relative to the mole number of the fluorinated compound having a hydrophilic group in the aqueous dispersion.

[0373] The radical generator content in the aqueous dispersion subjected to heat treatment refers to the radical generator content in the aqueous dispersion at the time when the temperature of the aqueous dispersion reaches the heat treatment temperature when the aqueous dispersion is heated for heat treatment after adding the radical generator to the aqueous dispersion.

[0374] The radical generator content in the aqueous dispersion subjected to heat treatment refers to the radical generator content in the aqueous dispersion at the time when the addition of the radical generator is completed when the radical generator is added to the aqueous dispersion after the aqueous dispersion is heated to the temperature for heat treatment.

[0375] The content of the radical generator can be determined by calculation based on the amount of the radical generator added, the half-life of the radical generator and the time from the time of addition, and the temperature used for the heat treatment.

[0376] When the amount of the free radical generator added is relatively large, a part or all of the fluorinated polymer in the aqueous dispersion may be precipitated by heat treatment. From the perspective of being able to suppress the precipitation of the fluorinated polymer caused by the heat treatment and being able to produce the fluorinated polymer aqueous dispersion with high productivity without damaging the removal efficiency of the fluorinated compound having a hydrophilic group, the amount of the free radical generator added is preferably 50 mole times or less, more preferably 25 mole times or less, and further preferably 10 mole times or less relative to the mole number of the fluorinated compound having a hydrophilic group in the aqueous dispersion.

[0377] The method for adding the free radical generator is not particularly limited. The free radical generator may be added directly to the aqueous dispersion, or a solution containing the free radical generator may be prepared and added to the aqueous dispersion. In addition, the free radical generator may be added while stirring the aqueous dispersion, or the aqueous dispersion may be stirred after the free radical generator is added.

[0378] The temperature of the aqueous dispersion to which the free radical generator is added is not particularly limited, and may be the temperature of the aqueous dispersion after the fluorinated monomer is polymerized, may be the temperature reached by cooling the aqueous dispersion after the fluorinated monomer is polymerized, or may be the temperature of the heat treatment. That is, after adding the free radical generator to the aqueous dispersion, the aqueous dispersion may be heated for the heat treatment, or after heating the aqueous dispersion to the temperature for the heat treatment, the free radical generator may be added to the aqueous dispersion.

[0379] (Heat Treatment)

[0380] In the production method of the present invention, the aqueous dispersion obtained by polymerization or the aqueous dispersion to which a free radical generator is added (the aqueous dispersion containing a free radical generator) is subjected to heat treatment. By heat-treating the aqueous dispersion before contacting the aqueous dispersion with the ion exchange resin, the content of the fluorine-containing compound having a hydrophilic group in the aqueous dispersion can be surprisingly reduced.

[0381] The aqueous dispersion for heat treatment preferably does not substantially contain a nonionic surfactant. The content of the nonionic surfactant in the aqueous dispersion for heat treatment may be less than 1% by mass, and may be 0 to 0.5% by mass, relative to the fluorinated polymer in the aqueous dispersion. In addition, the content of the nonionic surfactant in the aqueous dispersion for heat treatment is preferably less than 1% by mass, more preferably 0.5% by mass or less, and further preferably 0.1% by mass or less. In addition, the aqueous dispersion for heat treatment particularly preferably does not contain a nonionic surfactant.

[0382] Before the heat treatment, the content of the fluorinated polymer in the aqueous dispersion may be adjusted. The content of the fluorinated polymer may be adjusted by a known method such as concentration or dilution.

[0383] From the aspect of being able to produce the fluoropolymer aqueous dispersion with high productivity without damaging the removal efficiency of the fluorochemical having a hydrophilic group, the content of the fluoropolymer in the aqueous dispersion for heat treatment is preferably 1% by mass or more, more preferably 5% by mass or more, and further preferably 10% by mass or more relative to the mass of the aqueous dispersion. The upper limit of the content of the fluoropolymer is preferably 60% by mass or less, more preferably 55% by mass or less, and further preferably 50% by mass or less.

[0384] The content of the fluorinated surfactant added during the polymerization in the aqueous dispersion subjected to the heat treatment may be 10 mass ppm or more, 100 mass ppm or more, or 1000 mass ppm or more, and may be 10 mass % or less, 5 mass % or less, or 1 mass % or less, relative to the mass of the fluorinated polymer in the aqueous dispersion.

[0385] The content of the fluorinated surfactant having 7 or less carbon atoms in the aqueous dispersion subjected to heat treatment may be 10 mass ppm or more, 100 mass ppm or more, or 1000 mass ppm or more, and may be 10 mass % or less, 5 mass % or less, or 1 mass % or less, relative to the fluorinated polymer in the aqueous dispersion.

[0386] The content of the fluorinated compound having a hydrophilic group generated by polymerization of the fluorinated monomer in the aqueous dispersion subjected to the heat treatment is preferably 1 ppb by mass or more, more preferably 10 ppb by mass or more, and is preferably 1000 ppm by mass or less, more preferably 500 ppm by mass, and further preferably 50 ppm by mass or less, relative to the mass of the fluorinated polymer in the aqueous dispersion.

[0387] The content of the fluorinated compound having a hydrophilic group in the aqueous dispersion subjected to the heat treatment (the total amount of the content of the fluorinated surfactant added during the polymerization and the content of the fluorinated compound having a hydrophilic group generated by the polymerization of the fluorinated monomer) may be 10 mass ppm or more, 100 mass ppm or more, or 1000 mass ppm or more, or may be 10 mass % or less, or may be 5 mass % or less, or may be 1 mass % or less, relative to the fluorinated polymer in the aqueous dispersion.

[0388] From the aspect of being able to further improve the removal efficiency of the fluorine-containing compound having a hydrophilic group, the temperature of the heat treatment is preferably 35° C. or more, more preferably 40° C. or more, further preferably 45° C. or more, particularly preferably 50° C. or more, preferably 120° C. or less, more preferably 110° C. or less, further preferably 100° C. or less, particularly preferably 90° C. or less. When the aqueous dispersion to which the free radical generator is added is heat-treated, the temperature of the heat treatment is preferably a temperature (decomposition temperature) or more at which the free radical generator decomposes to generate free radicals.

[0389] When the heat treatment temperature is relatively high, a part or all of the fluorinated polymer in the aqueous dispersion may be precipitated by the heat treatment. From the perspective of being able to suppress the precipitation of the fluorinated polymer caused by the heat treatment and being able to produce the fluorinated polymer aqueous dispersion with high productivity without impairing the removal efficiency of the fluorinated compound having a hydrophilic group, the heat treatment temperature is preferably 95° C. or less, more preferably 90° C. or less, and further preferably 85° C. or less.

[0390] In the heat treatment of the aqueous dispersion, it is not necessary to heat the aqueous dispersion as long as the aqueous dispersion can be maintained at a temperature above the desired temperature. For example, when the temperature of the fluorinated monomer polymerization is sufficiently high and the temperature of the obtained aqueous dispersion is also sufficiently high, the heat treatment can be started before the obtained aqueous dispersion is cooled. However, from the perspective of being able to suppress the precipitation of the fluorinated polymer caused by the heat treatment and being able to produce the fluorinated polymer aqueous dispersion with high productivity without damaging the removal efficiency of the fluorinated compound having a hydrophilic group, it is preferred to cool the aqueous dispersion before and after removing the fluorinated monomer from the reactor or recovering the aqueous dispersion in the reactor, heat the aqueous dispersion to the above-mentioned temperature range, and maintain the temperature for a certain period of time. The temperature of the aqueous dispersion provided for the heat treatment can be, for example, below 30°C.

[0391] The heating means for heat treatment while heating the aqueous dispersion is not particularly limited. For example, the container containing the aqueous dispersion may be placed in a thermostatic bath for heating, or the aqueous dispersion may be contained in a container equipped with a heater and heated by the heater.

[0392] The pressure of the heat treatment is not particularly limited and may be normal pressure. For example, when the temperature of the heat treatment is relatively high and boiling of the aqueous dispersion needs to be suppressed, the pressure of the heat treatment may be a pressure exceeding normal pressure.

[0393] From the perspective of being able to further improve the removal efficiency of fluorine-containing compounds having hydrophilic groups, the heat treatment time is preferably 15 minutes or more, more preferably 30 minutes or more, further preferably 60 minutes or more, preferably 1200 minutes or less, more preferably 900 minutes or less, further preferably 600 minutes or less.

[0394] The heat treatment may be performed while stirring the aqueous dispersion.

[0395] (Addition of a nonionic surfactant to the heat-treated aqueous dispersion)

[0396] In the manufacturing method of the present invention, a nonionic surfactant is added to the aqueous dispersion subjected to heat treatment. By adding the nonionic surfactant, the dispersibility of the fluoropolymer in the aqueous dispersion subjected to heat treatment can be improved, and the dispersibility of the fluoropolymer can be maintained even in the ion exchange treatment, so as a result, the content of the fluorinated compound having a hydrophilic group in the aqueous dispersion can be surprisingly reduced, and an aqueous dispersion with excellent dispersion stability can be manufactured. In one embodiment of the manufacturing method of the present invention, after the aqueous dispersion not containing the nonionic surfactant is heat treated, the nonionic surfactant is added to the aqueous dispersion subjected to heat treatment.

[0397] Nonionic surfactants generally do not contain charged groups and have a hydrophobic portion that is a long-chain hydrocarbon. The hydrophilic portion of nonionic surfactants contains water-soluble functional groups such as chains of vinyl ethers derived from polymerization with ethylene oxide.

[0398] Examples of the nonionic surfactant include the following.

[0399] Polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, polyoxyethylene sorbitan alkyl esters, glycerides, and derivatives thereof.

[0400] Specific examples of the polyoxyethylene alkyl ethers include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene behenyl ether, and the like.

[0401] Specific examples of polyoxyethylene alkylphenyl ether include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, and the like.

[0402] Specific examples of polyoxyethylene alkyl esters include polyethylene glycol monolaurate, polyethylene glycol monooleate, polyethylene glycol monostearate, and the like.

[0403] Specific examples of sorbitan alkyl esters include polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, and the like.

[0404] Specific examples of polyoxyethylene sorbitan alkyl esters include polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, and the like.

[0405] Specific examples of glycerides include glyceryl monotetradecanoate, glyceryl monostearate, glyceryl monooleate, and the like.

[0406] Specific examples of the above derivatives include polyoxyethylene alkylamines, polyoxyethylene alkylphenyl-formaldehyde condensates, polyoxyethylene alkyl ether phosphates, and the like.

[0407] The above ethers and esters may have an HLB value of 10-18.

[0408] Examples of the nonionic surfactant include Triton (registered trademark) X series (X15, X45, X100, etc.), Tergitol (registered trademark) 15-S series, Tergitol (registered trademark) TMN series (TMN-6, TMN-10, TMN-100X, etc.), Tergitol (registered trademark) L series, Pluronic (registered trademark) R series (31R1, 17R2, 10R5, 25R4 (m to 22, n to 23) manufactured by BASF, and Iconol (registered trademark) TDA series (TDA-6, TDA-9, TDA-10).

[0409] As the above-mentioned nonionic surfactant, a fluorine-free nonionic surfactant is preferred. Examples thereof include: ether-type nonionic surfactants such as polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether, polyoxyethylene alkylene alkyl ether; polyoxyethylene derivatives such as ethylene oxide / propylene oxide block copolymers; ester-type nonionic surfactants such as sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerol fatty acid esters, polyoxyethylene fatty acid esters; amine-based nonionic surfactants such as polyoxyethylene alkylamines and alkyl alkanolamides; and the like.

[0410] In the above nonionic surfactant, the hydrophobic group may be any one of an alkylphenol group, a linear alkyl group and a branched alkyl group.

[0411] As the nonionic surfactant, a nonionic surfactant represented by the general formula (i) is preferred.

[0412] R 6 -OA 1 -H(i)

[0413] (Where R 6 is a linear or branched primary or secondary alkyl group having 8 to 18 carbon atoms, 1 is a polyoxyalkylene chain.)

[0414] In the general formula (i), R 6 The number of carbon atoms in R is preferably 10 to 16, more preferably 12 to 16. 6 The number of carbon atoms in R is 18 or less, and thus it is easy to obtain excellent sedimentation stability of the aqueous dispersion. 6 If the number of carbon atoms exceeds 18, the flow temperature is high and it is difficult to handle. 6When the number of carbon atoms is less than 8, the surface tension of the aqueous dispersion increases, and the permeability or wettability tends to decrease.

[0415] A 1 The polyoxyalkylene chain may be composed of ethylene oxide and propylene oxide. It is a polyoxyalkylene chain composed of an average repeating number of ethylene oxide groups of 5 to 20 and an average repeating number of propylene oxide groups of 0 to 2, and is a hydrophilic group. The number of ethylene oxide units may include any one of the broad or narrow unimodal distributions generally provided, or a broader or bimodal distribution obtained by blending. When the average repeating number of propylene oxide groups exceeds 0, the ethylene oxide groups and propylene oxide groups in the polyoxyalkylene chain may be arranged in blocks or randomly. From the aspects of the viscosity and sedimentation stability of the aqueous dispersion, a polyoxyalkylene chain composed of an average repeating number of ethylene oxide groups of 7 to 12 and an average repeating number of propylene oxide groups of 0 to 2 is preferred. In particular, if A 1 It is preferred that the polyurethane foam has an average of 0.5 to 1.5 oxypropylene groups because low foaming properties are good.

[0416] More preferably R 6 (R')(R")HC-, wherein R' and R" are the same or different linear, branched or cyclic alkyl groups, and the total number of carbon atoms is at least 5, preferably 7 to 17. Preferably, at least one of R' or R" is a branched or cyclic hydrocarbon group.

[0417] Specific examples of the polyoxyethylene alkyl ether include C 13 H 27 -O-(C2H4O) n -H, C 12 H 25 -O-(C2H4O) n -H, C 10 H 21 CH(CH3)CH2-O-(C2H4O) n -H, C 13 H 27 -O-(C2H4O) n -(CH(CH3)CH2O)-H、C 16 H 33 -O-(C2H4O) n -H、HC(C5H 11 )(C7H 15 )-O-(C2H4O) n-H (in each formula, n is an integer of 1 or more), etc. Examples of commercially available products of the polyoxyethylene alkyl ethers include Genapol X series (manufactured by Clariant) such as Genapol X080 (trade name), Noigen TDS series (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) such as Noigen TDS-80 (trade name), Leocol TD series (manufactured by LION) such as Leocol TD-90 (trade name), LIONOL (registered trademark) TD series (manufactured by LION), T-Det A series (manufactured by Harcros Chemicals) such as T-Det A138 (trade name), and Tergitol (registered trademark) 15-S series (manufactured by The Dow Chemical Company).

[0418] The above nonionic surfactant is also preferably an ethoxylate of 2,6,8-trimethyl-4-nonanol having an average of about 4 to about 18 ethylene oxide units, an ethoxylate of 2,6,8-trimethyl-4-nonanol having an average of about 6 to about 12 ethylene oxide units, or a mixture thereof. This type of nonionic surfactant is also commercially available as TERGITOL TMN-6, TERGITOL TMN-10, and TERGITOL TMN-100X (all product names, manufactured by The Dow Chemical Company).

[0419] In addition, the hydrophobic group of the nonionic surfactant may be any one of an alkylphenol group, a linear alkyl group and a branched alkyl group. For example, as a nonionic surfactant, for example, the general formula (ii)

[0420] R 7 -C6H4-OA 2 -H(ii)

[0421] (Where R 7 is a linear or branched alkyl group having 4 to 12 carbon atoms, 2 A nonionic surfactant represented by (wherein (i) is a polyoxyalkylene chain). Specific examples of the nonionic surfactant include Triton (registered trademark) X-100 (trade name, manufactured by The Dow Chemical Company).

[0422] A 2The polyoxyalkylene chain may be composed of ethylene oxide and propylene oxide. It is a polyoxyalkylene chain composed of an average repeating number of ethylene oxide groups of 5 to 20 and an average repeating number of propylene oxide groups of 0 to 2, and is a hydrophilic group. The number of ethylene oxide units may include any one of the broad or narrow unimodal distributions generally provided, or a broader or bimodal distribution obtained by blending. When the average repeating number of propylene oxide groups exceeds 0, the ethylene oxide groups and propylene oxide groups in the polyoxyalkylene chain may be arranged in blocks or randomly. From the aspects of the viscosity and sedimentation stability of the aqueous dispersion, a polyoxyalkylene chain composed of an average repeating number of ethylene oxide groups of 7 to 12 and an average repeating number of propylene oxide groups of 0 to 2 is preferred. In particular, if A 2 It is preferred that the polyurethane foam has an average of 0.5 to 1.5 oxypropylene groups because low foaming properties are good.

[0423] More preferably, R 7 It is a primary alkyl group or a secondary alkyl group, more preferably (R')(R")HC-, wherein R' and R" are the same or different linear, branched or cyclic alkyl groups, and the total number of carbon atoms is at least 5, preferably 7 to 17. Preferably, at least one of R' or R" is a branched or cyclic hydrocarbon group.

[0424] As the above-mentioned nonionic surfactant, polyol compounds can also be mentioned. Specifically, polyol compounds described in International Publication No. 2011 / 014715 can be mentioned. As a typical example of a polyol compound, a compound having one or more sugar units as a polyol unit can be mentioned. The sugar unit can be modified to contain at least one long chain. As a suitable polyol compound containing at least one long chain part, for example, alkyl glycosides, modified alkyl glycosides, sugar esters and combinations thereof can be mentioned. As sugars, monosaccharides, oligosaccharides and sorbitan can be mentioned, but are not limited to this. As monosaccharides, pentose and hexose can be mentioned. As typical examples of monosaccharides, ribose, glucose, galactose, mannose, fructose, arabinose, and xylose can be mentioned. As oligosaccharides, oligomers of 2 to 10 identical or different monosaccharides can be mentioned. As examples of oligosaccharides, sucrose, maltose, lactose, raffinose and isomaltose can be mentioned, but are not limited to this.

[0425] Typically, as sugars suitable for use as polyol compounds, there can be mentioned cyclic compounds of five-membered rings containing four carbon atoms and one heteroatom (typically oxygen or sulfur, preferably oxygen atom) or cyclic compounds of six-membered rings containing five carbon atoms and the above-mentioned one heteroatom, preferably oxygen atom. They further contain at least two or at least three hydroxyl groups (-OH groups) bonded to carbon ring atoms. Typically, in order to make ether or ester bonds between long-chain residues and sugar moieties, sugars are modified in the following aspects: one or more hydrogen atoms of hydroxyl groups (and / or hydroxyalkyl groups) bonded to carbon ring atoms are replaced by long-chain residues. Sugar-based polyols can contain one sugar unit or two or more sugar units. One sugar unit or two or more sugar units can be modified using the above-mentioned long-chain moieties. As specific examples of sugar-based polyol compounds, glycosides, sugar esters, sorbitan esters, and mixtures and combinations thereof can be mentioned.

[0426] Preferred types of polyol compounds are alkyl or modified alkyl glucosides. These types of surfactants contain at least one glucose moiety. Examples include

[0427] [Chemistry 12]

[0428]

[0429] (wherein x represents 0, 1, 2, 3, 4, or 5, R 1 and R 2 independently represents H or a long chain unit containing at least 6 carbon atoms, wherein R 1 and R 2 In the compound represented by (i) wherein at least one of the R 1 and R 2 Typical examples of aliphatic alcohol residues can be cited. Examples of aliphatic alcohols include hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol (lauryl alcohol), tetradecanol, hexadecanol (cetyl alcohol), heptadecanol, octadecanol (stearyl alcohol), eicosanoic acid and combinations thereof. The above formula shows a specific example of an alkyl polyglucoside representing glucose in the form of pyranose, but it is understood that other sugars or sugars that are the same sugar but in different mirror isomers or diastereoisomers can also be used.

[0430] Alkyl glucoside can be obtained, for example, by the acid-catalyzed reaction of glucose, starch, or n-butyl glucoside with aliphatic alcohols. In a typical example, a mixture of various alkyl glucosides is obtained (Alkylpolygylcoside, Rompp, Lexikon Chemie, Version 2.0, Stuttgart / New York, Georg Thieme Verlag, 1999). Examples of aliphatic alcohols include hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol (lauryl alcohol), tetradecanol, hexadecanol (cetyl alcohol), heptadecanol, octadecanol (stearyl alcohol), eicosanoic acid, and combinations thereof. In addition, alkyl glucoside is commercially available from Cognis GmbH, Düsseldorf, Germany, under the trade name GLUCOPON or DISPONIL.

[0431] Examples of other nonionic surfactants include bifunctional block copolymers supplied by BASF as Pluronic (registered trademark) R series and tridecanol alkoxylates supplied by BASF as Iconol (registered trademark) TDA series.

[0432] The nonionic surfactant is preferably at least one selected from the group consisting of a nonionic surfactant represented by the general formula (i) and a nonionic surfactant represented by the general formula (ii), and more preferably a nonionic surfactant represented by the general formula (i).

[0433] The nonionic surfactant preferably does not contain an aromatic part.

[0434] As the nonionic surfactant, it is preferred to be selected from the group consisting of ethoxylates of 2,6,8-trimethyl-4-nonanol having an average of about 4 to about 18 ethylene oxide units, ethoxylates of 2,6,8-trimethyl-4-nonanol having an average of about 6 to about 12 ethylene oxide units, 13 H 27 -O-(C2H4O) n -H, C 12 H 25 -O-(C2H4O) n -H, C 10 H 21 CH(CH3)CH2-O-(C2H4O) n -H, C 13 H 27 -O-(C2H4O) n -(CH(CH3)CH2O)-H、C 16 H 33 -O-(C2H4O) n-H、HC(C5H 11 )(C7H 15 )-O-(C2H4O) n -H (in each formula, n is an integer greater than or equal to 1).

[0435] In one embodiment of the production method of the present invention, a nonionic surfactant is added to an aqueous dispersion subjected to a heat treatment to prepare an aqueous dispersion in which the content of the nonionic surfactant in the aqueous dispersion is 5% by mass or more relative to the fluorinated polymer. The content of the nonionic surfactant in the aqueous dispersion to which the nonionic surfactant is added is more preferably 7% by mass or more, further preferably 9% by mass or more, preferably 30% by mass or less, more preferably 25% by mass or less, and further preferably 20% by mass or less.

[0436] The content of the nonionic surfactant is a value calculated from the heating residue (Yg) obtained by heating about 1 g (Xg) of the sample at 110°C for 30 minutes, and the heating residue (Zg) obtained by heating the obtained heating residue (Yg) at 300°C for 30 minutes, according to the formula: N = [(YZ) / Z] × 100 (mass %).

[0437] In the production method of the present invention, it is also preferred that the aqueous dispersion is cooled to less than 50° C. after the heat treatment and before the aqueous dispersion is brought into contact with the ion exchange resin. By sufficiently cooling the aqueous dispersion before bringing the aqueous dispersion into contact with the ion exchange resin, turbidity of the aqueous dispersion when a nonionic surfactant is added can be suppressed, or the effect of reducing the content of the fluorinated compound having a hydrophilic group brought about by bringing the aqueous dispersion into contact with the ion exchange resin can be further enhanced.

[0438] (Ion exchange treatment)

[0439] In the production method of the present invention, after adding a nonionic surfactant to an aqueous dispersion, the aqueous dispersion containing the nonionic surfactant is brought into contact with an ion exchange resin. By bringing the heat-treated aqueous dispersion containing the nonionic surfactant into contact with the ion exchange resin, the content of the fluorine-containing compound having a hydrophilic group in the aqueous dispersion can be surprisingly reduced.

[0440] As the ion exchange resin, an anion exchange resin can be preferably used. As the anion exchange resin, it is preferred to have the following general formula (A1):

[0441] -N + R 1 R 2 R 3 X -

[0442] (Where R 1 , R 2 and R 3 are the same or different, and are hydrogen atoms or organic groups, R 1 , R 2 and R 3 At least one of them is an organic group having 3 or more carbon atoms, and X represents a counter ion. ) or the following general formula (A2):

[0443] -NR 4 R 5

[0444] (Where R 4 and R 5 are the same or different, and are hydrogen atoms or organic groups, R 4 and R 5 At least one of them is an organic group having 2 or more carbon atoms. ) is a resin having an ion exchange group shown.

[0445] In the general formula (A1), R 1 , R 2 and R 3 R is the same or different and is a hydrogen atom or an organic group. 1 , R 2 and R 3 All of them may be organic groups, or one may be a hydrogen atom and two may be organic groups. Furthermore, two may be hydrogen atoms and one may be an organic group. The number of carbon atoms in the organic group is 1 or more. The number of carbon atoms in the organic group is preferably 2 or more. 1 , R 2 and R 3 One preferred embodiment is that the organic group has 2 or more carbon atoms.

[0446] In the general formula (A1), R 1 , R 2 and R 3 At least one of them is an organic group having 3 or more carbon atoms. 1 , R 2 and R 3 In the formula, one may be an organic group having 3 or more carbon atoms and two may be hydrogen atoms or organic groups having 1 or 2 carbon atoms. In addition, two may be organic groups having 3 or more carbon atoms and one may be a hydrogen atom or an organic group having 1 or 2 carbon atoms. 1 , R 2 and R 3 All of them are organic groups having 3 or more carbon atoms.

[0447] R 1 , R2 and R 3 In the above, the number of carbon atoms of the organic group is preferably 10 or less, more preferably 8 or less, and further preferably 6 or less. The number of carbon atoms of the organic group may be 5 or less.

[0448] In the general formula (A1), preferably R 1 , R 2 and R 3 At least one of the groups is an organic group having 4 or more carbon atoms. By adopting such a structure, a specific fluorine-containing compound can be removed more efficiently.

[0449] R 1 , R 2 and R 3 The organic group in is preferably an alkyl group, an alkanol group or an alkenyl group, more preferably an alkyl group or an alkanol group, further preferably an alkyl group.

[0450] It should be noted that, in the present invention, "alkyl" is a general term for the remaining group after removing one hydrogen atom from an aliphatic saturated hydrocarbon, and also includes a linear or branched alkyl group having 1 or more carbon atoms or a cyclic alkyl group having 3 or more carbon atoms.

[0451] In the present invention, "alkanol group" is a general term for the remaining group after removing one hydrogen atom from alkanol, and includes linear or branched alkanol groups having 1 or more carbon atoms or cyclic alkanol groups having 3 or more carbon atoms.

[0452] R 1 , R 2 and R 3 are the same or different and are alkyl groups having 2 or more carbon atoms or alkanol groups having 1 or more carbon atoms. 1 , R 2 and R 3 At least one of them is an alkyl group having 3 or more carbon atoms.

[0453] R 1 , R 2 and R 3 are the same or different and are alkyl groups having 2 or more carbon atoms or alkanol groups having 2 or more carbon atoms, R 1 , R 2 and R 3 It is one of the more preferred embodiments that at least one of the groups is an alkyl group having 3 or more carbon atoms.

[0454] R 1 , R 2 and R 3 are the same or different and are an alkyl group having 2 or more carbon atoms or an alkanol group having 1 or more carbon atoms, R 1 , R 2 and R3 It is also a preferred embodiment that at least one of the groups is an alkyl group having 4 or more carbon atoms.

[0455] In addition, R 1 , R 2 and R 3 are the same or different and are alkyl groups having 2 or more carbon atoms or alkanol groups having 2 or more carbon atoms, R 1 , R 2 and R 3 It is also a preferred embodiment that at least one of the groups is an alkyl group having 4 or more carbon atoms.

[0456] The number of carbon atoms in the alkyl group is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. The number of carbon atoms in the alkyl group may be 5 or less.

[0457] The number of carbon atoms in the alkanol group is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. The number of carbon atoms in the alkanol group may be 5 or less.

[0458] In the general formula (A1), X is a counter ion. Examples of X include Cl, OH, Br, I, NO3, SO4, etc., preferably Cl or OH. It should be noted that in the case of a divalent anion such as SO4, one counter ion is coordinated with respect to two molecules of the repeating unit of the general formula (A1).

[0459] In the general formula (A2), R 4 and R 5 are the same or different, are hydrogen atoms or organic groups, R 4 and R 5 At least one of R is an organic group having 2 or more carbon atoms. 4 and R 5 All of them may be organic groups. Alternatively, one may be a hydrogen atom and the other may be an organic group.

[0460] In the general formula (A2), R 4 and R 5 At least one of them is an organic group having 2 or more carbon atoms.

[0461] In R 4 and R 5 In the formula (R), one may be an organic group having 2 or more carbon atoms and the other may be a hydrogen atom or an organic group having 1 carbon atom. 4 and R 5 Both are organic groups having 2 or more carbon atoms.

[0462] R 4 and R 5At least one of them may be an organic group having 3 or more carbon atoms, or may be an organic group having 4 or more carbon atoms.

[0463] In addition, R 4 and R 5 An organic group having 2 or more carbon atoms is also preferred.

[0464] R 4 and R 5 In the above, the number of carbon atoms of the organic group is preferably 10 or less, more preferably 8 or less, and further preferably 6 or less. The number of carbon atoms of the organic group may be 5 or less.

[0465] The above R 4 and R 5 The organic group in is preferably an alkyl group, an alkanol group or an alkenyl group, more preferably an alkyl group or an alkanol group, further preferably an alkyl group.

[0466] R 4 and R 5 The same or different, is an alkyl group or an alkanol group, the above R 4 and R 5 It is one of the more preferred embodiments that at least one of the groups is an alkyl group having 2 or more carbon atoms or an alkanol group having 2 or more carbon atoms.

[0467] The number of carbon atoms in the alkyl group is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. The number of carbon atoms in the alkyl group may be 5 or less.

[0468] The number of carbon atoms in the alkanol group is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. The number of carbon atoms in the alkanol group may be 5 or less.

[0469] The anion exchange resin preferably has a group represented by the general formula (A1) or a group represented by the general formula (A2) bonded to a resin matrix. Examples of the anion exchange resin include a material in which a group represented by the general formula (A1) or a group represented by the general formula (A2) is bonded to a resin matrix composed of a styrene-based or acrylic polymer. The styrene-based or acrylic polymer as the resin matrix is ​​not limited, and for example, a resin matrix used in a known anion exchange resin can be used.

[0470] The basicity of the anion exchange resin can be variously set depending on the type of polymer backbone and / or ion exchange group.

[0471] The pore diameter of the anion exchange resin is preferably From the viewpoint of removal efficiency, the pore diameter is preferably More preferably The above, more preferably In addition, it can be The above can also be In addition, the pore diameter can also be The pore diameter can be calculated by measuring the specific surface area and the total pore volume by a gas adsorption method, for example.

[0472] For anion exchange resin, from the aspect of removal efficiency, the total exchange capacity is preferably 0.1 eq / L-Resin or more. More preferably, it is 0.3 eq / L-Resin or more, further preferably, it is 0.5 eq / L-Resin or more, and particularly preferably, it is 0.7 eq / L-Resin or more. In addition, the upper limit is preferably 5.0 eq / L-Resin or less, more preferably 2.0 eq / L-Resin or less, and particularly preferably 1.5 eq / L-Resin or less.

[0473] The water content of the anion exchange resin is preferably 20% by mass or more, more preferably 30% to 70% by mass, and further preferably 35% to 65% by mass. By making the water content of the anion exchange resin more than 30% by mass, the fluorinated compound can be efficiently removed. In addition, the fluorinated compound is easily diffused into the particles of the anion exchange resin. If the water content of the anion exchange resin is less than 70% by mass, the strength reduction of the particles of the anion exchange resin caused by insufficient crosslinking can be suppressed.

[0474] The water content of anion exchange resin can be measured by the following method. First, accurately measure 10 mL of a sample made into a standard shape with a measuring cylinder, wrap the resin in a cloth and centrifuge it. After removing the attached water, quickly measure the mass of the resin. Then, dry it in a constant temperature dryer at 105°C for 4 hours, cool it in a dryer for 30 minutes, measure the mass of the dried resin, and calculate the water content using the following formula.

[0475] Water content (mass %) = (mass of resin before drying (g) - mass of resin after drying (g)) / mass of resin before drying (g) × 100

[0476] The anion exchange resin is usually spherical. The average particle size of the anion exchange resin is preferably 0.1 mm to 5 mm, more preferably 0.2 mm to 2 mm, and particularly preferably 0.3 mm to 1.5 mm. If the average particle size of the anion exchange resin is within the above range, the anion exchange resin packing tower is difficult to clog. The average particle size is a value obtained by sieving. Specifically, first, take the anion exchange resin to a sieving oscillator and measure the particle size distribution by sieving. Then, the diameter of the sieve corresponding to 50% of the residual component accumulation is obtained and used as the average particle size.

[0477] As the anion exchange resin, a commercially available product may be used, and examples thereof include PFA694E and A592 E manufactured by Purolite Corporation.

[0478] In addition, as an anion exchange resin, a resin having an ion exchange group (wherein the group represented by the above general formula (A1) and the group represented by the general formula (A2) are not included) can also be used. As such an anion exchange resin, a resin having at least one ion exchange group selected from the group consisting of an amino group and a quaternary ammonium group (wherein the group represented by the above general formula (A1) and the group represented by the general formula (A2) are not included) can be cited. As such an anion exchange resin, the following general formula (B1) is preferred:

[0479] -N + (CH3)3X -

[0480] (wherein X represents a counter ion.) or the following general formula (B2):

[0481] -N + (CH3)2(C2H4OH)X -

[0482] (wherein X represents a counter ion.) As X in the general formulae (B1) and (B2), Cl, OH, Br, I, NO3, SO4, etc. can be cited, preferably Cl or OH. In addition, in the case of a divalent anion such as SO4, one counter ion is coordinated to two molecules of the repeating unit of the general formula (A1).

[0483] As the anion exchange resin, it is preferred that the ion exchange group (wherein, the group represented by the above general formula (A1) and the group represented by the general formula (A2) are not included) is bonded to a resin matrix, and as the above resin matrix, a styrene-based or acrylic polymer can be cited. The styrene-based or acrylic polymer as the resin matrix is ​​not limited, and for example, a resin matrix used in a known anion exchange resin can be used. From the viewpoint of the removal efficiency of the fluorine-containing compound having a hydrophilic group, the anion exchange resin B preferably has a styrene-based resin matrix.

[0484] The resin having an ion exchange group (excluding the group represented by the general formula (A1) and the group represented by the general formula (A2)) may be weakly basic or strongly basic. Preferably, it is a strongly basic anion exchange resin. The basicity of the anion exchange resin may be variously set according to the type of polymer backbone and / or ion exchange group.

[0485] The pore diameter of the resin having an ion exchange group (excluding the group represented by the general formula (A1) and the group represented by the general formula (A2)) is preferably From the viewpoint of removal efficiency, the pore diameter is preferably More preferably The above, more preferably In addition, it can be The above can also be In addition, the pore diameter can also be The pore diameter can be calculated by measuring the specific surface area and the total pore volume by, for example, a gas adsorption method.

[0486] From the viewpoint of removal efficiency, the total exchange capacity of the resin having ion exchange groups (wherein, excluding the group represented by the above-mentioned general formula (A1) and the group represented by the general formula (A2)) is preferably 0.1 eq / L-Resin or more. More preferably, it is 0.3 eq / L-Resin or more, further preferably 0.5 eq / L-Resin or more, and particularly preferably 0.7 eq / L-Resin or more. In addition, the larger the total exchange capacity, the better, for example, the upper limit is preferably 5.0 eq / L-Resin, more preferably 2.0 eq / L-Resin or less, and particularly preferably 1.5 eq / L-Resin or less.

[0487] The water content of the resin having ion exchange groups (excluding the groups represented by the general formula (A1) and the groups represented by the general formula (A2)) is preferably 20% by mass or more, more preferably 30% to 70% by mass, and further preferably 35% to 65% by mass.

[0488] The resin having an ion exchange group (excluding the group represented by the general formula (A1) and the group represented by the general formula (A2)) is usually spherical.

[0489] The average particle size of the resin having an ion exchange group (excluding the group represented by the above general formula (A1) and the group represented by the general formula (A2)) is preferably 0.1 mm to 5 mm, more preferably 0.2 mm to 2 mm, and particularly preferably 0.3 mm to 1.5 mm. If the average particle size is within the above range, the filling tower of the anion exchange resin is not easily clogged. The above average particle size is a value obtained by sieving. Specifically, first, take the anion exchange resin to a sieving oscillator and measure the particle size distribution by sieving. Then, the diameter of the sieve corresponding to 50% accumulation of the residual components is obtained and used as the average particle size.

[0490] As the resin having an ion exchange group (excluding the group represented by the above-mentioned general formula (A1) and the group represented by the general formula (A2)), commercially available products can be used, for example, Diaion (trademark) SA series manufactured by Mitsubishi Chemical Corporation, A400, A300, etc. manufactured by Purolite Co., Ltd., Amberlite (trademark) series manufactured by DuPont Co., Ltd., Amberjet (trademark) series such as IRA4002OH, etc., etc. can be used.

[0491] The ion exchange resin is preferably at least one selected from the group consisting of a resin in which a group represented by the general formula (B1) is bonded to a styrene polymer and a resin in which a group represented by the general formula (B2) is bonded to a styrene polymer. X in the general formulas (B1) and (B2) is preferably OH.

[0492] The pH of the aqueous dispersion obtained by adding the nonionic surfactant is usually less than 7, and the temperature is lower than 35° C. In the production method of the present invention, it is preferred that after adding the nonionic surfactant to the aqueous dispersion and before performing the ion exchange treatment, the pH of the aqueous dispersion containing the nonionic surfactant is adjusted to 7 or more, and the temperature of the aqueous dispersion containing the nonionic surfactant is adjusted to 35° C. or more. By pre-adjusting the pH and temperature of the aqueous dispersion before performing the ion exchange treatment, the content of the fluorinated compound having a hydrophilic group in the finally obtained aqueous dispersion can be surprisingly reduced.

[0493] The pH of the aqueous dispersion subjected to the ion exchange treatment is preferably 7 or higher, more preferably 8 or higher, and even more preferably 9 or higher, and is preferably 14 or lower, more preferably 13 or lower, and even more preferably 12 or lower.

[0494] The pH can be adjusted by adding a base such as ammonia to the aqueous dispersion.

[0495] The temperature of the aqueous dispersion subjected to the ion exchange treatment is preferably 35° C. or higher, more preferably 37° C. or higher, and further preferably 39° C. or higher, and is preferably lower than the cloud point of the nonionic surfactant, and more preferably lower than a temperature 10° C. lower than the cloud point of the nonionic surfactant. The temperature of the aqueous dispersion subjected to the ion exchange treatment may be, for example, 50° C. or lower, or 45° C. or lower.

[0496] In the production method of the present invention, the temperature of the aqueous dispersion is preferably maintained at 35° C. or higher during the ion exchange treatment. The temperature of the aqueous dispersion during the ion exchange treatment is preferably 37° C. or higher, more preferably 39° C. or higher, preferably lower than the cloud point of the nonionic surfactant, more preferably lower than a temperature 10° C. lower than the cloud point of the nonionic surfactant. The temperature of the aqueous dispersion during the ion exchange treatment may be, for example, 50° C. or lower, or 45° C. or lower.

[0497] In the production method of the present invention, the pH of the aqueous dispersion may also be changed during the ion exchange treatment. When the ion exchange treatment is repeated, it is preferred to check the pH of the aqueous dispersion each time the ion exchange treatment is started, and when the pH is lower than 7, adjust the pH to 7 or more. The pH of the aqueous dispersion before each ion exchange treatment is preferably 8 or more, more preferably 9 or more, preferably 14 or less, more preferably 13 or less, and even more preferably 12 or less.

[0498] The pressure at which the aqueous dispersion is brought into contact with the ion exchange resin is not particularly limited, and may be, for example, 0.1 atmosphere to 10 atmospheres, and may be carried out under normal pressure (about 1 atmosphere).

[0499] The time for which the aqueous dispersion is brought into contact with the ion exchange resin is not particularly limited, and may be 0.1 second to 100 hours, 1 second to 50 hours, or 1 second to 10 hours.

[0500] The amount of the ion exchange resin in contact with the aqueous dispersion is preferably 10,000 g or less, preferably 0.1 g or more, more preferably 1 g or more, further preferably 5 g or more, further preferably 10 g or more, particularly preferably 100 g or more, based on 1,000 g of the fluorinated polymer in the aqueous dispersion.

[0501] After the aqueous dispersion is brought into contact with the ion exchange resin, the aqueous dispersion is separated from the ion exchange resin to recover the aqueous dispersion.

[0502] The aqueous dispersion may be brought into contact with the ion exchange resin in a batch manner or in a flow manner.

[0503] The number of times the aqueous dispersion is contacted with the ion exchange resin may be 1 time or 2 times or more. By repeating the contact of the aqueous dispersion with the ion exchange resin 2 times or more, the content of the fluorine-containing compound having a hydrophilic group in the aqueous dispersion can be further reduced. The number of times the aqueous dispersion is contacted with the ion exchange resin may be 10 times or less.

[0504] As a method for contacting the aqueous dispersion with the ion exchange resin, a conventional method can be adopted. For example, it can be implemented by a method of adding an ion exchange resin to the aqueous dispersion and stirring it, a column method of flowing the aqueous dispersion through a column filled with the ion exchange resin, etc. The packed column used in the column method can be any one of a mobile type, a fixed bed type, or a fluidized bed type.

[0505] When the method of adding an ion exchange resin to an aqueous dispersion and stirring is used, the ion exchange resin is separated from the aqueous dispersion after the aqueous dispersion and the ion exchange resin are brought into contact. The method of separating the ion exchange resin from the aqueous dispersion is not limited, and for example, filtration can be used.

[0506] (Addition of a nonionic surfactant to an aqueous dispersion subjected to ion exchange treatment)

[0507] In one embodiment of the production method of the present invention, a nonionic surfactant is added to the aqueous dispersion obtained after contact with the ion exchange resin. By adding the nonionic surfactant, the dispersibility of the fluorinated polymer in the aqueous dispersion subjected to the ion exchange treatment can be improved, and the aqueous dispersion can be smoothly concentrated. As a result, the content of the fluorinated compound having a hydrophilic group in the aqueous dispersion can be surprisingly reduced, and an aqueous dispersion with excellent dispersion stability can be produced.

[0508] As the nonionic surfactant added to the aqueous dispersion obtained after contact with the ion exchange resin, there can be mentioned the nonionic surfactant added to the aqueous dispersion subjected to heat treatment. The substance that can be suitably used as the nonionic surfactant added to the aqueous dispersion subjected to heat treatment can also be suitably used as the nonionic surfactant added to the aqueous dispersion obtained after contact with the ion exchange resin.

[0509] Preferably, a nonionic surfactant is added to an aqueous dispersion subjected to an ion exchange treatment to prepare an aqueous dispersion in which the content of the nonionic surfactant in the aqueous dispersion is 1% to 40% by mass relative to the fluorinated polymer. The content of the nonionic surfactant in the aqueous dispersion subjected to the ion exchange treatment is more preferably 5% by mass or more, and more preferably 30% by mass or less.

[0510] (Concentration treatment)

[0511] In the production method of the present invention, the aqueous dispersion obtained after contact with the ion exchange resin is concentrated.

[0512] As the concentration method, phase separation concentration, electrophoresis, ion exchange method, membrane concentration, etc. can be mentioned. Phase separation concentration, ion exchange method and membrane concentration can be carried out under conventionally known treatment conditions, and are not particularly limited, and can be carried out by the method described in International Publication No. 2004 / 050719, Japanese Unexamined Patent Publication No. 2002-532583 or Japanese Unexamined Patent Publication No. 55-120630.

[0513] As a concentration method, a method of separating the aqueous dispersion into two or more phases and recovering the concentrated phase is preferred, and phase separation concentration or concentration using electrophoresis is preferred, and phase separation concentration is more preferred. Phase separation concentration can be performed, for example, as follows: heating the aqueous dispersion to separate the phase into a phase not containing the fluorinated polymer (supernatant phase) and a phase containing the fluorinated polymer (concentrated phase), removing the phase not containing the fluorinated polymer, and recovering the phase containing the fluorinated polymer (concentrated phase).

[0514] The recovered fluorine-containing polymer phase (concentrated phase) contains the fluorine-containing polymer, the nonionic surfactant and the aqueous medium, and contains the fluorine-containing compound having a hydrophilic group in a reduced content compared to that before concentration.

[0515] The temperature for phase separation and concentration can be selected based on the cloud point of the nonionic surfactant contained in the aqueous dispersion. The temperature for phase separation and concentration is preferably 10°C lower than the cloud point of the nonionic surfactant or higher than 10°C.

[0516] In the production method of the present invention, it is also preferred to repeat phase separation and concentration. By repeating phase separation and concentration, the content of the fluorine-containing compound having a hydrophilic group in the aqueous dispersion can be easily reduced to a desired content.

[0517] The number of repetitions is not particularly limited, but is preferably 2 or more times, more preferably 3 or more times. The upper limit of the number of repetitions is not limited, but may be, for example, 10 or less times. By repeatedly performing phase separation and concentration, the content of the fluorine-containing compound having a hydrophilic group can be further reduced.

[0518] When phase separation and concentration are performed two or more times, the first phase separation and concentration is preferably heated at a temperature 10°C lower than the cloud point of the nonionic surfactant and then left to stand, and separated into a supernatant phase and a concentrated phase. In addition, the second or subsequent phase separation and concentration is preferably heated at a temperature 10°C lower than the cloud point of the nonionic surfactant and then left to stand, and separated into a supernatant phase and a concentrated phase.

[0519] In the case of repeating multiple phase separation concentrations, the phase separation concentration can be stopped when the solid content concentration of the fluorinated polymer in the aqueous dispersion reaches 48% to 52% by mass except for the final phase separation concentration, and an aqueous medium is added to the concentrated aqueous dispersion, and then the phase separation concentration is repeated. By stopping the phase separation concentration when the solid content concentration of the fluorinated polymer reaches the above range, each phase separation concentration can be completed in a short time without reducing the removal efficiency of the fluorinated compound having a hydrophilic group in each phase separation concentration, and thus, as a result, the total time required for the phase separation concentration can be shortened.

[0520] The pH of the aqueous dispersion to be concentrated is preferably 4.0 to 12.0, more preferably 7.0 or more, further preferably 8.0 or more, and particularly preferably 9.0 or more. By adjusting the pH of the aqueous dispersion to the above range, the rate of increasing the concentration of the fluorinated polymer in the aqueous dispersion and the rate of removing the fluorinated compound having a hydrophilic group in the aqueous dispersion can be increased, and the concentration of the fluorinated polymer in the aqueous dispersion finally obtained becomes higher.

[0521] The content of the fluoropolymer in the fluoropolymer aqueous dispersion obtained by concentrating is preferably 50% by mass or more, more preferably 55% by mass or more, further preferably 60% by mass or more, preferably 70% by mass or less, more preferably 68% by mass or less, further preferably 67% by mass or less, relative to the aqueous dispersion. The higher the content of the fluoropolymer in the fluoropolymer aqueous dispersion, the higher the content of the fluoropolymer can be easily maintained even when various additives are added to the fluoropolymer aqueous dispersion.

[0522] The content of the fluorinated polymer in the aqueous dispersion can be determined by measuring the solid content concentration of the aqueous dispersion and the content of the nonionic surfactant in the aqueous dispersion, and subtracting the content of the nonionic surfactant from the solid content concentration of the aqueous dispersion. The solid content concentration of the aqueous dispersion is a value calculated from the heating residue (Zg) of about 1 g (Xg) of a sample heated at 110°C for 30 minutes and then at 300°C for 30 minutes according to the formula: P = Z / X × 100 (mass %).

[0523] (Handling of concentrated aqueous dispersion)

[0524] In the production method of the present invention, a nonionic surfactant may be added to the concentrated aqueous dispersion. In particular, when the aqueous dispersion is concentrated by phase separation concentration, the content of the nonionic surfactant in the obtained aqueous dispersion may be reduced. However, by adding the nonionic surfactant to the concentrated aqueous dispersion, the dispersibility of the fluorinated polymer in the concentrated aqueous dispersion can be improved.

[0525] As the nonionic surfactant added to the concentrated aqueous dispersion, it is preferred to add two nonionic surfactants having different hydrophilicities. As an index indicating the difference in hydrophilicity, HLB can be cited. For example, it is preferred to include a nonionic surfactant having an HLB of 13.00 or more and less than 13.50 and a nonionic surfactant having an HLB of 13.50 or more and 15.00 or less (preferably 14.50 or less, more preferably 14.00 or less). If nonionic surfactants having different HLBs are added, foaming can be suppressed without adding a defoaming agent.

[0526] Preferably, a nonionic surfactant is added to the concentrated aqueous dispersion to prepare an aqueous dispersion in which the content of the nonionic surfactant in the aqueous dispersion is 4.0% to 12.0% by mass relative to the fluorinated polymer. The content of the nonionic surfactant in the aqueous dispersion is more preferably 4.5% by mass or more, further preferably 5.0% by mass or more, more preferably 10% by mass or less, further preferably 8.0% by mass or less, and further preferably 7.0% by mass or less.

[0527] In the production method of the present invention, a viscosity modifier may be added to the concentrated aqueous dispersion.

[0528] As the viscosity modifier, a non-fluorinated anionic surfactant can be preferably used. The non-fluorinated anionic surfactant generally has a hydrophilic portion such as a carboxylate, sulfonate, or sulfate and a hydrophobic portion such as an alkyl group as a long-chain hydrocarbon portion.

[0529] Examples of the non-fluorinated anionic surfactant include alkylsulfuric acids such as laurylsulfuric acid, alkylarylsulfonic acids such as dodecylbenzenesulfonic acid, alkylsulfosuccinates and salts thereof. The non-fluorinated anionic surfactant may be one of these compounds or a combination of two or more thereof.

[0530] The alkyl sulfosuccinates and their salts may be monoesters, but are preferably diesters.

[0531] Examples of alkyl sulfosuccinates and salts thereof include those of the general formula: 21 -OCOCH(SO3A 21 )CH2COO-R 22 (Where R 21 and R 22 are the same or different, and represent an alkyl group having 4 to 12 carbon atoms, A 21 represents an alkali metal, an alkaline earth metal or NH4) and a sulfosuccinic acid alkyl ester and a salt thereof.

[0532] As R 21and R 22 , for example, straight-chain or branched alkyl groups such as n-butyl, isobutyl, sec-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, n-hexyl, isohexyl, tert-hexyl, n-heptyl, isoheptyl, tert-heptyl, n-octyl, isooctyl, tert-octyl, n-nonyl, isononyl, tert-nonyl, n-decyl and 2-ethylhexyl can be mentioned.

[0533] As A 21 , preferably Na, NH4, etc. Examples of the alkyl sulfosuccinate include di-n-octyl sulfosuccinate and di-2-ethylhexyl sulfosuccinate.

[0534] The non-fluorine-containing anionic surfactant may have an acid group. As the acid group, it is preferably an acid group selected from the group consisting of carboxyl, sulfate, sulfonic acid, phosphoric acid and their salts, wherein it is preferably an acid group selected from the group consisting of carboxyl, sulfate and sulfonic acid, and their salts.

[0535] The non-fluorinated anionic surfactant may have, in addition to the above-mentioned acid groups, other groups such as a polyoxyalkylene group containing an oxyalkylene group having 2 to 4 carbon atoms, an amino group, etc. The above-mentioned amino group is not protonated.

[0536] As the non-fluorinated anionic surfactant, an anionic hydrocarbon surfactant having a hydrocarbon as a main chain is preferred. As hydrocarbon, for example, a hydrocarbon having a saturated or unsaturated aliphatic chain having 6 to 40 carbon atoms, preferably 8 to 20 carbon atoms, can be cited. The saturated or unsaturated aliphatic chain can be any one of a straight chain or a branched chain, and can also have a cyclic structure. The hydrocarbon can be aromatic or have an aromatic group. The hydrocarbon can also have heteroatoms such as oxygen, nitrogen, and sulfur.

[0537] As the non-fluorine-containing anionic surfactant, there can be mentioned: alkyl sulfonic acids such as lauryl sulfonic acid and salts thereof; alkyl aryl sulfates and salts thereof; aliphatic (carboxylic) acids such as lauric acid and salts thereof; alkyl phosphates, alkyl aryl phosphates or salts thereof; etc., among which substances selected from the group consisting of sulfonic acids and carboxylic acids and salts thereof are preferred, and aliphatic carboxylic acids or salts thereof are preferred. As the above-mentioned aliphatic carboxylic acid or salt thereof, for example, a saturated or unsaturated aliphatic carboxylic acid having 9 to 13 carbon atoms and a terminal H which can be substituted with -OH or a salt thereof is preferred, and as the aliphatic carboxylic acid, a monocarboxylic acid is preferred, and as the monocarboxylic acid, decanoic acid, undecanoic acid, undecenoic acid, lauric acid, and hydroxydodecanoic acid are preferred.

[0538] As the non-fluorinated anionic surfactant, at least one selected from the group consisting of alkyl sulfosuccinates and salts thereof, alkyl sulfuric acid and salts thereof, and monocarboxylic acids and salts thereof is preferred, at least one selected from the group consisting of dioctyl sulfosuccinic acid, lauryl sulfuric acid, capric acid and salts thereof is more preferred, and at least one selected from the group consisting of dioctyl sulfosuccinic acid, ammonium dioctyl sulfosuccinate, ammonium lauryl sulfate and ammonium caprate is further preferred.

[0539] Preferably, the viscosity modifier is added to the concentrated aqueous dispersion to prepare an aqueous dispersion having a viscosity modifier content of 10 to 5000 mass ppm relative to the fluorinated polymer. The viscosity modifier content in the aqueous dispersion is more preferably 50 mass ppm or more, further preferably 100 mass ppm or more, more preferably 4000 mass ppm or less, further preferably 3000 mass ppm or less.

[0540] In the production method of the present invention, a pH adjuster such as ammonia water may be added to the concentrated aqueous dispersion for the purpose of adjusting the pH of the aqueous dispersion. The pH of the aqueous dispersion is preferably 8 to 13, more preferably 9 to 12, and even more preferably 9 to 11.

[0541] The above-mentioned pH can be measured at 25°C in accordance with JIS K6893.

[0542] In the production method of the present invention, a preservative may be added to the concentrated aqueous dispersion. By adding a preservative to the aqueous dispersion, even when the aqueous dispersion is stored for a long time, the corruption of the aqueous dispersion and the growth of bacteria can be suppressed while the precipitation of the fluorinated polymer is suppressed.

[0543] Examples of the preservative include isothiazolone-based preservatives, azole-based preservatives, bromopol, thiophanate-methyl, methylsulfonyl tetrachloropyridine, carbendazim, 2-[(dichlorofluoromethyl)-thio]-1H-isoindole-1,3-(2H)-dione (Fluor Folpet), sodium diacetate, and diiodomethyl-p-tolylsulfone.

[0544] Preferably, the preservative is added to the concentrated aqueous dispersion to prepare an aqueous dispersion having a preservative content of 0.01 to 0.5% by mass relative to the fluoropolymer. The preservative content in the aqueous dispersion is more preferably 0.05% by mass or more, and more preferably 0.2% by mass or less.

[0545] In the production method of the present invention, a water-soluble polymer can be added to the concentrated aqueous dispersion. As the water-soluble polymer compound, methylcellulose, alumina sol, polyvinyl alcohol, carboxylated vinyl polymer, polyethylene oxide (dispersion stabilizer), polyethylene glycol (dispersion stabilizer), polyvinyl pyrrolidone (dispersion stabilizer), phenolic resin, urea resin, epoxy resin, melamine resin, polyester resin, polyether resin, acrylic silicone resin, silicone resin, silicone polyester resin, polyurethane resin, etc. can be cited.

[0546] 2. Fluoropolymer aqueous dispersion

[0547] According to the production method of the present invention, a fluorinated polymer aqueous dispersion having a reduced content of a fluorinated compound having a hydrophilic group of 7 or less carbon atoms can be obtained. According to the present invention, there is provided a fluorinated polymer aqueous dispersion, which contains a fluorinated polymer, a nonionic surfactant, and a fluorinated compound having a hydrophilic group of 7 or less carbon atoms, wherein the content of the fluorinated polymer is 50% to 70% by mass relative to the fluorinated polymer aqueous dispersion, the content of the nonionic surfactant is 4.0% to 12% by mass relative to the fluorinated polymer, and the content of the fluorinated compound having a hydrophilic group of 7 or less carbon atoms is greater than 0 ppb and less than 300 ppb by mass relative to the fluorinated polymer aqueous dispersion.

[0548] The fluorinated polymer aqueous dispersion of the present invention contains a fluorinated compound having a hydrophilic group with a carbon number of 7 or less. The content of the fluorinated compound having a hydrophilic group with a carbon number of 7 or less in the aqueous dispersion is greater than 0 mass ppb and less than 300 mass ppb relative to the aqueous dispersion. The preferred upper limit of the content of the fluorinated compound having a hydrophilic group with a carbon number of 7 or less in the aqueous dispersion is 280 mass ppb or less, 260 mass ppb or less, 240 mass ppb or less, 220 mass ppb or less, 200 mass ppb or less, 180 mass ppb or less, 160 mass ppb or less, or 140 mass ppb or less. The preferred lower limit of the content of the fluorinated compound having a hydrophilic group with a carbon number of 7 or less in the aqueous dispersion is 0.1 mass ppb or more, 1 mass ppb or more, 5 mass ppb or more, 10 mass ppb or more, 20 mass ppb or more, 30 mass ppb or more, 40 mass ppb or more, or 50 mass ppb or more.

[0549] As the fluorinated compound having a hydrophilic group of 7 or less carbon atoms, the above-mentioned fluorinated surfactant having a carbon number of 7 or less used in the polymerization of the fluorinated monomer can be cited. That is, in one embodiment of the aqueous dispersion, as the fluorinated compound having a hydrophilic group of 7 or less carbon atoms, at least a fluorinated surfactant having a carbon number of 7 or less is contained.

[0550] Furthermore, according to the production method of the present invention, not only the content of the fluorinated compound having a hydrophilic group and having 7 or less carbon atoms but also the content of the fluorinated compound having a hydrophilic group in the aqueous fluorinated polymer dispersion can be reduced.

[0551] In one embodiment of the fluoropolymer aqueous dispersion, a fluorinated compound having a hydrophilic group is contained. The content of the fluorinated compound having a hydrophilic group in the aqueous dispersion is greater than 0 mass ppb and less than 300 mass ppb relative to the aqueous dispersion. The preferred upper limit of the content of the fluorinated compound having a hydrophilic group with a carbon number of 7 or less in the aqueous dispersion is 280 mass ppb or less, 260 mass ppb or less, 240 mass ppb or less, 220 mass ppb or less, 200 mass ppb or less, 180 mass ppb or less, 160 mass ppb or less or 140 mass ppb or less. The preferred lower limit of the content of the fluorinated compound having a hydrophilic group with a carbon number of 7 or less in the aqueous dispersion is 0.1 mass ppb or more, 1 mass ppb or more, 5 mass ppb or more, 10 mass ppb or more, 20 mass ppb or more, 30 mass ppb or more, 40 mass ppb or more or 50 mass ppb or more.

[0552] As the fluorinated compound having a hydrophilic group, the above-mentioned substances as the fluorinated surfactant used in the polymerization of the fluorinated monomer can be cited. That is, in one embodiment of the aqueous dispersion, as the fluorinated compound having a hydrophilic group, at least a fluorinated surfactant is contained. As the fluorinated surfactant, a typical compound is a fluorinated surfactant having a molecular weight of 1000 g / mol or less, preferably 800 g / mol or less.

[0553] In one embodiment of the aqueous fluorinated polymer dispersion, the compound represented by the following general formula (1) is substantially not contained as the fluorinated compound having a hydrophilic group.

[0554] General formula (1): [X-Rf-A - ] i M i+

[0555] (wherein X represents H, Cl, Br, F or I, Rf represents a linear or branched partially fluorinated or fully fluorinated aliphatic group, or a linear or branched partially fluorinated or fully fluorinated aliphatic group interrupted by at least one oxygen atom, A - Indicates acid group, M i+ represents a cation having a valence number i, where i represents an integer from 1 to 3)

[0556] In one embodiment of the aqueous fluorinated polymer dispersion, the compound represented by the following general formula (2) is substantially not contained as the fluorinated compound having a hydrophilic group.

[0557] General formula (2): [C n-1 F 2n-1 COO - ]M +

[0558] (where n represents an integer from 9 to 14, M + represents a cation.)

[0559] It is known that when perfluoroalkyl vinyl ether or the like is used as a modifying monomer, a compound represented by the general formula (2) (perfluoroalkanoic acid) is formed during polymerization (see International Publication No. 2019 / 161153).

[0560] In one embodiment of the aqueous fluorinated polymer dispersion, the compound represented by the following general formula (3) is substantially not contained as the fluorinated compound having a hydrophilic group.

[0561] General formula (3): [R 1 -OL-CO2 - ]M +

[0562] (Where R 1 represents a linear or branched partially fluorinated or fully fluorinated aliphatic group, or a linear or branched partially fluorinated 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 cation.)

[0563] In one embodiment of the aqueous fluorinated polymer dispersion, the compound represented by the general formula (4) is substantially not contained as the fluorinated compound having a hydrophilic group.

[0564] General formula (4): [H-(CF2) m CO2 - ]M +

[0565] (wherein, m represents an integer from 3 to 19, M + represents a cation.)

[0566] In the present invention, substantially no compound represented by the general formula (1) to (4) is contained means that the content of the compound represented by the general formula (1) to (4) in the aqueous fluoropolymer dispersion is 50 ppb by mass or less. The content of the compound represented by the general formula (1) to (4) in the aqueous fluoropolymer dispersion is preferably 35 ppb by mass or less, more preferably 25 ppb by mass or less, further preferably 10 ppb by mass or less, further more preferably 1 ppb by mass or less, and particularly preferably below the detection limit of the fluorinated surfactant measured by liquid chromatography-mass spectrometry (LC / MS).

[0567] The content of the fluorine-containing compound having a hydrophilic group in the aqueous fluorine-containing polymer dispersion can be quantified by a known method, for example, by LC / MS analysis.

[0568] First, methanol is added to the aqueous dispersion of the fluorinated polymer to extract, and the obtained extract is analyzed by LC / MS. In order to further improve the extraction efficiency, Soxhlet extraction, ultrasonic treatment, etc. can be used for treatment. The obtained extract is appropriately purged with nitrogen to concentrate, and the fluorinated compounds with hydrophilic groups in the concentrated extract are measured by LC / MS.

[0569] Molecular weight information was extracted from the obtained LC / MS spectrum, and it was confirmed that the molecular weight matched the structural formula of a candidate fluorine-containing compound having a hydrophilic group.

[0570] Then, aqueous solutions having five or more levels of the confirmed fluorinated compound having a hydrophilic group are prepared, and the aqueous solutions having each content are analyzed by LC / MS. The relationship between the content and the area of ​​the region relative to the content is plotted to create a calibration curve.

[0571] Then, using the calibration curve, the area of ​​the LC / MS chromatogram of the fluorine-containing compound having a hydrophilic group in the extract can be converted into the content of the fluorine-containing compound having a hydrophilic group.

[0572] It should be noted that the obtained extract can be concentrated by purging with nitrogen, so that the quantitative lower limit of the measurement method can be reduced.

[0573] The fluorinated polymer contained in the aqueous fluorinated polymer dispersion of the present invention will be described later.

[0574] The content of the fluorinated polymer in the aqueous fluorinated polymer dispersion is preferably 50% by mass or more, more preferably 55% by mass or more, further preferably 57% by mass or more, further preferably 60% by mass or more, and is preferably 70% by mass or less, more preferably 68% by mass or less, further preferably 67% by mass or less, further preferably 65% ​​by mass or less, based on the aqueous dispersion.

[0575] As the nonionic surfactant, there can be mentioned any nonionic surfactant that can be used in the production method of the present invention. The content of the nonionic surfactant in the fluoropolymer aqueous dispersion is 4.0% to 12% by mass relative to the fluoropolymer, more preferably 4.5% by mass or more, further preferably 5.0% by mass or more, more preferably 10% by mass or less, further preferably 8.0% by mass or less, and further preferably 7.0% by mass or less.

[0576] The aqueous fluorinated polymer dispersion of the present invention also preferably contains a non-fluorinated anionic surfactant. As the non-fluorinated anionic surfactant, there can be cited non-fluorinated anionic surfactants that can be used in the production method of the present invention. The content of the non-fluorinated anionic surfactant in the aqueous fluorinated polymer dispersion is preferably 10 mass ppm to 5000 mass ppm relative to the fluorinated polymer, more preferably 50 mass ppm or more, further preferably 100 mass ppm or more, more preferably 4000 mass ppm or less, and further preferably 3000 mass ppm or less.

[0577] The viscosity of the aqueous fluorinated polymer dispersion of the present invention is preferably 2.0 mPa·s or more, more preferably 5.0 mPa·s or more, further preferably 10.0 mPa·s or more, particularly preferably 15.0 mPa·s or more, preferably 100 mPa·s or less, more preferably 80 mPa·s or less, further preferably 70 mPa·s or less, and further preferably 60 mPa·s or less.

[0578] The viscosity of the aqueous dispersion was measured using a B-type rotational viscometer (manufactured by Toki Sangyo Co., Ltd., rotor No. 2) at a rotation speed of 60 rpm, a measurement time of 120 seconds, and a temperature of 25°C.

[0579] The fluoropolymer aqueous dispersion of the present invention also preferably contains a preservative. As the preservative, there can be cited preservatives that can be used in the production method of the present invention. The content of the preservative in the fluoropolymer aqueous dispersion is preferably 0.01 mass % to 0.5 mass %, more preferably 0.05 mass % or more, and more preferably 0.2 mass % or less relative to the fluoropolymer.

[0580] The pH of the aqueous fluorinated polymer dispersion of the present invention is preferably 8-13, more preferably 9-12, further preferably 9-11.

[0581] The above-mentioned pH can be measured at 25°C in accordance with JIS K6893.

[0582] The aqueous fluorine-containing polymer dispersion of the present invention may contain other components. As other components, water-soluble polymer compounds may be mentioned. As water-soluble polymer compounds, methylcellulose, alumina sol, polyvinyl alcohol, carboxylated vinyl polymers, polyethylene oxide (dispersion stabilizer), polyethylene glycol (dispersion stabilizer), polyvinyl pyrrolidone (dispersion stabilizer), phenolic resin, urea resin, epoxy resin, melamine resin, polyester resin, polyether resin, acrylic silicone resin, silicone resin, silicone polyester resin, polyurethane resin, etc. may be mentioned.

[0583] The aqueous fluorine-containing polymer dispersion of the present invention can be used as a water-based coating material for coating by mixing with, for example, known pigments, thickeners, dispersants, defoamers, antifreeze agents, film-forming aids and other compounding agents, or further compounding with other polymer compounds.

[0584] Next, the fluorinated polymer in the aqueous dispersion obtained by the production method of the present invention and the fluorinated polymer in the aqueous dispersion of the present invention will be described in more detail.

[0585] (Fluoropolymer)

[0586] Fluorine-containing polymers such as fluororesins and fluororubbers are obtained by polymerizing fluorine-containing monomers.

[0587] Examples of the fluorine-containing polymer include TFE polymers in which the monomer having the largest molar fraction of monomers in the polymer (hereinafter referred to as "most abundant monomer") is TFE, VDF polymers in which the most abundant monomer is VDF, and CTFE polymers in which the most abundant monomer is CTFE.

[0588] The fluorinated polymer preferably has an ion exchange rate (IXR) higher than 53. The preferred fluorinated polymer has no ionic groups at all, or has a limited number of ionic groups that can bring about an ion exchange rate higher than about 100. The ion exchange rate of the preferred fluorinated polymer is preferably 1000 or higher, more preferably 2000 or higher, and further preferably 5000 or higher.

[0589] The TFE polymer may be a TFE homopolymer or a copolymer consisting of the following components: (1) TFE; (2) one or more fluorinated monomers other than TFE having 2 to 8 carbon atoms, particularly VDF, HFP or CTFE; and (3) other monomers. Examples of the above-mentioned (3) other monomers include fluoro(alkyl vinyl ether) having an alkyl group having 1 to 5 carbon atoms, particularly 1 to 3 carbon atoms; fluorodioxole; perfluoroalkylethylene; ω-hydrogenated perfluoroolefin; and the like.

[0590] The TFE polymer may also be a copolymer of TFE and one or more non-fluorine-containing monomers. Examples of the non-fluorine-containing monomers include olefins such as ethylene and propylene; vinyl esters; and vinyl ethers. The TFE polymer may also be a copolymer of TFE, one or more fluorine-containing monomers having 2 to 8 carbon atoms, and one or more non-fluorine-containing monomers.

[0591] The VDF polymer may be suitably a VDF homopolymer [PVDF] or a copolymer consisting of: (1) VDF; (2) one or more fluoroolefins other than VDF having 2 to 8 carbon atoms, in particular TFE, HFP or CTFE; and (3) a perfluoro(alkyl vinyl ether) having an alkyl group having 1 to 5 carbon atoms, in particular 1 to 3 carbon atoms; etc.

[0592] The CTFE polymer may 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.

[0593] The CTFE polymer may be a copolymer of CTFE and one or more non-fluorine-containing monomers. Examples of the non-fluorine-containing monomers include olefins such as ethylene and propylene; vinyl esters; and vinyl ethers.

[0594] The fluorine-containing polymers may be glassy, ​​plastic or elastomeric. These materials are amorphous or partially crystalline and can be subjected to compression sintering, melt processing or non-melt processing.

[0595] In the production method of the present invention, a fluororesin is preferably produced as the fluoropolymer. The fluoropolymer aqueous dispersion of the present invention preferably contains a fluororesin as the fluoropolymer.

[0596] The production method of the present invention can appropriately produce the following substances, for example: (I) tetrafluoroethylene polymer [TFE polymer (PTFE)] as a non-melt-processable fluororesin, (II) ethylene / TFE copolymer [ETFE], TFE / HFP copolymer [FEP], TFE / perfluoro(alkyl vinyl ether) copolymer [PFA, MFA, etc.], TFE / perfluoroallyl ether copolymer, TFE / VDF copolymer, and electrolyte polymer precursor as melt-processable fluororesins.

[0597] As the above-mentioned fluorine-containing polymer, a fluororesin is preferred, among which 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 further preferred, a fluororesin having a fluorine substitution rate of 55% or more is still more preferred, a fluororesin having a fluorine substitution rate of 60% or more is still 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.

[0598] (Mode)

[0599] Fluorine substitution rate (%) = (the number of fluorine atoms bonded to the carbon atoms constituting the fluorine-containing polymer) / ((the number of hydrogen atoms bonded to the carbon atoms constituting the fluorine-containing polymer) + (the number of fluorine atoms and chlorine atoms bonded to the carbon atoms constituting the fluorine-containing polymer)) × 100

[0600] As the perfluororesin, a fluororesin having a fluorine substitution rate of 95% to 100% is more preferred, polytetrafluoroethylene (PTFE), FEP or PFA is further preferred, PTFE or PFA is further preferred, and PTFE is particularly preferred.

[0601] The above-mentioned fluoropolymer can have a core-shell structure. As the fluoropolymer with a core-shell structure, for example, a modified PTFE that comprises a core of a high molecular weight PTFE and a shell of a lower molecular weight PTFE or modified PTFE in a particle can be enumerated. As such a modified PTFE, for example, the PTFE described in writing in the Japanese Patent Table 2005-527652 communique can be enumerated.

[0602] As the core-shell structure, the following structures can be adopted.

[0603] Core: TFE homopolymer Shell: TFE homopolymer

[0604] Core: modified PTFE Shell: TFE homopolymer

[0605] Core: Modified PTFE Shell: Modified PTFE

[0606] Core: TFE homopolymer Shell: modified PTFE

[0607] Core: low molecular weight PTFE Shell: high molecular weight PTFE

[0608] Core: High molecular weight PTFE Shell: Low molecular weight PTFE

[0609] In the fluorinated polymer having the core-shell structure, the lower limit of the ratio of the core is preferably 0.5% by mass, more preferably 1.0% by mass, further preferably 2.0% by mass, further preferably 3.0% by mass, particularly preferably 5.0% by mass, and most preferably 10.0% by mass. The upper limit of the ratio of the core is preferably 99.5% by mass, more preferably 99.0% by mass, further preferably 98.0% by mass, further more preferably 97.0% by mass, particularly preferably 95.0% by mass, and most preferably 90.0% by mass.

[0610] In the fluorinated polymer having the core-shell structure, the lower limit of the ratio of the shell is preferably 0.5% by mass, more preferably 1.0% by mass, further preferably 2.0% by mass, further preferably 3.0% by mass, particularly preferably 5.0% by mass, and most preferably 10.0% by mass. The upper limit of the ratio of the shell is preferably 99.5% by mass, more preferably 99.0% by mass, further preferably 98.0% by mass, further more preferably 97.0% by mass, particularly preferably 95.0% by mass, and most preferably 90.0% by mass.

[0611] In the fluoropolymer having the core-shell structure, the core or the shell may be formed into two or more layers. For example, the fluoropolymer may be a three-layer structure having a core center portion of modified PTFE, a core outer layer portion of a TFE homopolymer, and a shell of modified PTFE.

[0612] Examples of the fluorinated polymer having a core-shell structure include a fluorinated polymer in which one particle of the fluorinated polymer has a plurality of cores.

[0613] The above-mentioned (I) non-melt-processable fluororesin and (II) melt-processable fluororesin suitably produced by the production method of the present invention are preferably produced as follows.

[0614] (I) Non-melt-processable fluororesins

[0615] In the production method of the present invention, the polymerization of TFE is usually carried out at a polymerization temperature of 10°C to 150°C and a polymerization pressure of 0.05MPaG to 5MPaG. For example, the polymerization temperature is more preferably 30°C or more, and more preferably 50°C or more. In addition, it is more preferably 120°C or less, and more preferably 100°C or less. In addition, the polymerization pressure is more preferably 0.3MPaG or more, and more preferably 0.5MPaG or more, and more preferably 5.0MPaG or less, and more preferably 3.0MPaG or less. In particular, from the aspect of increasing the amount of fluorinated polymer obtained, it is preferably 1.0MPaG or more, more preferably 1.2MPaG or more, more preferably 1.5MPaG or more, and more preferably 2.0MPaG or more.

[0616] In one embodiment, regarding the above-mentioned polymerization, pure water is added to a pressure-resistant reaction vessel equipped with a stirrer, and TFE is added after deoxygenation to make it reach a predetermined temperature, and a polymerization initiator is added to initiate the reaction. When 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 is supplied, the supply is stopped, the TFE in the reaction vessel is purged, the temperature is restored to room temperature, and the reaction is terminated. In order to prevent the pressure from decreasing, additional TFE can be continuously or intermittently supplied.

[0617] In the production of the above-mentioned TFE polymer (PTFE), various known modified monomers may also be used in combination. In the present invention, the above-mentioned TFE polymer is a concept that includes not only TFE homopolymers but also non-melt-processable substances (hereinafter referred to as "modified PTFE") that are copolymers of TFE and modified monomers.

[0618] The modifying monomer is not particularly limited as long as it is copolymerizable with TFE, and examples thereof include fluorine-containing monomers and non-fluorine-containing monomers. The modifying monomer used may be one kind or two or more kinds.

[0619] The non-fluorine-containing monomer is not particularly limited, and examples thereof include the following:

[0620] CH2=CR Q1 -LR Q2

[0621] (Where R Q1 represents a hydrogen atom or an alkyl group. L represents a single bond, -CO-O-*, -O-CO-* or -O-. * represents the same Q2 The bonding position of R Q2 represents a hydrogen atom, an alkyl group or a nitrile group).

[0622] Examples of the non-fluorine-containing monomer 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, and cyclohexyl vinyl ether. Among the non-fluorine-containing monomer, butyl methacrylate, vinyl acetate, and acrylic acid are preferred.

[0623] Examples of the fluorine-containing monomer include perfluoroolefins such as hexafluoropropylene [HFP]; hydrogen-containing fluoroolefins such as trifluoroethylene and vinylidene fluoride [VDF]; perhaloolefins such as chlorotrifluoroethylene; perfluorovinyl ether; (perfluoroalkyl)ethylene; and perfluoroallyl ether.

[0624] The perfluorovinyl ether is not particularly limited, and examples thereof include those of the general formula (A):

[0625] CF2=CF-ORf(A)

[0626] (wherein Rf represents a perfluoro organic group) and the like. In the present invention, the above-mentioned "perfluoro organic group" refers to an organic group in which all hydrogen atoms bonded to carbon atoms are replaced by fluorine atoms. The above-mentioned perfluoro organic group may have an ether oxygen.

[0627] Examples of the perfluorovinyl ether include perfluoro(alkyl vinyl ether) [PAVE] wherein Rf in the general formula (A) is a perfluoroalkyl group having 1 to 10 carbon atoms. The perfluoroalkyl group preferably has 1 to 5 carbon atoms.

[0628] Examples of the perfluoroalkyl group in PAVE include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, and a perfluorohexyl group.

[0629] As the perfluorovinyl ether, further examples include monomers wherein Rf in the general formula (A) is a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms, and Rf is the following formula:

[0630] [Chemistry 13]

[0631]

[0632] (wherein m represents 0 or an integer of 1 to 4) and Rf is the following formula:

[0633] CF3CF2CF2-(O-CF(CF3)-CF2) n -

[0634] (wherein n represents an integer of 1 to 4) and the like.

[0635] Examples of hydrogen-containing fluoroolefins include CH2=CF2, CFH=CH2, CFH=CF2, CH2=CFCF3, CH2=CHCF3, CHF=CHCF3 (E form), and CHF=CHCF3 (Z form).

[0636] The (perfluoroalkyl)ethylene (PFAE) is not particularly limited, and examples thereof include (perfluorobutyl)ethylene (PFBE) and (perfluorohexyl)ethylene.

[0637] Examples of the perfluoroallyl ether include

[0638] General formula: CF2=CF-CF2-ORf

[0639] (wherein Rf represents a perfluoro organic group).

[0640] Rf in the above general formula is the same as Rf in general formula (A). As Rf, a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluoroalkoxyalkyl group having 1 to 10 carbon atoms is preferred. As the perfluoroallyl ether, at least one selected from the group consisting of CF2=CF-CF2-O-CF3, CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7 and CF2=CF-CF2-O-C4F9 is preferred, at least one selected from the group consisting of CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7 and CF2=CF-CF2-O-C4F9 is more preferred, and CF2=CF-CF2-O-CF2CF3 is further preferred.

[0641] Preferred examples of the modified monomer include a modified monomer (3) having a monomer reactivity ratio of 0.1 to 8. The presence of the modified monomer (3) can provide PTFE particles having a small particle size and an aqueous dispersion having high dispersion stability.

[0642] Here, the monomer reactivity ratio in the copolymerization with TFE is a value obtained as follows: when the growth free radical is smaller than the repeating unit based on TFE, the rate constant when the growth free radical reacts with TFE is divided by the rate constant when the growth free radical reacts with the modified monomer, and the obtained value is the above-mentioned monomer reactivity ratio. The lower the value, the higher the reactivity of the modified monomer with TFE. The monomer reactivity ratio can be calculated as follows: copolymerize TFE and the modified monomer, find the composition of the generated polymer immediately after the start, and calculate it by the Fineman-Ross formula.

[0643] The copolymerization is carried out in a stainless steel autoclave with an internal volume of 6.0 L using 3600 g of deionized degassed water, 1000 mass ppm of ammonium perfluorooctanoate relative to the water, and 100 g of paraffin wax at a pressure of 0.78 MPaG and a temperature of 70°C. 0.05 g, 0.1 g, 0.2 g, 0.5 g, and 1.0 g of the modified monomer are added to the reactor respectively, and 0.072 g of ammonium persulfate (20 mass ppm relative to water) is added. In order to maintain a polymerization pressure of 0.78 MPaG, TFE is continuously supplied. When the TFE feed reaches 1000 g, stirring is stopped and depressurization is performed until the reactor reaches atmospheric pressure. After cooling, paraffin wax is separated to obtain an aqueous dispersion containing the generated polymer. The aqueous dispersion is stirred to precipitate the generated polymer and dried at 150°C. The composition of the resulting polymer is calculated by appropriately combining NMR, FT-IR, elemental analysis, and fluorescent X-ray analysis depending on the type of monomer.

[0644] The modified monomer (3) having a monomer reactivity ratio of 0.1 to 8 is preferably at least one selected from the group consisting of modified monomers represented by formulas (3a) to (3d).

[0645] CH2=CH-Rf 1 (3a)

[0646] (Where Rf 1 It is a perfluoroalkyl group having 1 to 10 carbon atoms. )

[0647] CF2=CF-O-Rf 2 (3b)

[0648] (Where Rf 2 It is a perfluoroalkyl group having 1 to 2 carbon atoms. )

[0649] CF2=CF-O-(CF2) n CF=CF2(3c)

[0650] (In the formula, n is 1 or 2.)

[0651] [Chemistry 14]

[0652]

[0653] (Where X 3 and X 4 is F, Cl or methoxy, and Y is of the formula Y1 or Y2.)

[0654] [Chemistry 15]

[0655]

[0656] (In formula Y2, Z and Z' are F or a fluorinated alkyl group having 1 to 3 carbon atoms.)

[0657] The content of the modified monomer (3) unit is preferably in the range of 0.00001% by mass to 1.0% by mass relative to the total polymerized units of PTFE. As the lower limit, it is more preferably 0.0001% by mass, more preferably 0.0005% by mass, further preferably 0.001% by mass, and further more preferably 0.005% by mass. As the upper limit, it is 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, 0.01% by mass in a preferred order.

[0658] As above-mentioned modified monomer, owing to can obtain the aqueous dispersion liquid of the average primary particle diameter of primary particle little, the aspect ratio of primary particle little, excellent stability, thus preferably selected from at least one in the group of the modified monomer composition of hexafluoropropylene, trifluorochloroethylene, vinylidene fluoride, perfluor (alkyl vinyl ether), (perfluoroalkyl) ethylene, ethylene and the functional group that can pass through free radical polymerization and hydrophilic group.By using above-mentioned modified monomer, can obtain the aqueous dispersion liquid of the PTFE of average primary particle diameter little, the aspect ratio of primary particle little, excellent dispersion stability.In addition, can obtain the aqueous dispersion liquid of the few unprecipitated polymer.

[0659] From the viewpoint of reactivity with TFE, the modifying monomer preferably contains at least one selected from the group consisting of hexafluoropropylene, perfluoro(alkyl vinyl ether) and (perfluoroalkyl)ethylene.

[0660] 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.

[0661] The total amount of the above-mentioned hexafluoropropylene unit, perfluoro (alkyl vinyl ether) unit and (perfluoroalkyl) ethylene unit is preferably in the range of 0.00001 mass % to 1 mass % relative to the total polymerized units of PTFE. As the lower limit of the above-mentioned total amount, it is more preferably 0.0001 mass %, more preferably 0.0005 mass %, further preferably 0.001 mass %, further preferably 0.005 mass %. As the upper limit, it is 0.80 mass %, 0.70 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 %, 0.01 mass %.

[0662] The above-mentioned modified monomer also preferably includes a modified monomer having a functional group capable of a radical polymerization reaction and a hydrophilic group (hereinafter referred to as "modified monomer (A)").

[0663] The presence of the modified monomer (A) can provide PTFE particles with a small primary particle size, and an aqueous dispersion with high dispersion stability. In addition, the amount of unprecipitated polymer can be reduced. Furthermore, the aspect ratio of the primary particles can be reduced.

[0664] The amount of the modified monomer (A) is preferably an amount exceeding an amount equivalent to 0.1 mass ppm of the aqueous medium, more preferably an amount exceeding 0.5 mass ppm, further preferably an amount exceeding 1.0 mass ppm, and further more preferably 5 mass ppm or more, particularly preferably 10 mass ppm or more. If the amount of the modified monomer (A) is too little, the average primary particle size of the obtained PTFE may not be reduced.

[0665] The amount of the modified monomer (A) may be within the above range, and the upper limit may be 5000 ppm by mass, for example. In addition, in the above production method, in order to improve the stability of the aqueous dispersion during or after the reaction, the modified monomer (A) may be added to the system during the reaction.

[0666] The modified monomer (A) has high water solubility. Therefore, even if unreacted modified monomer (A) remains in the aqueous dispersion, it can be easily removed in the concentration step or the precipitation / washing step.

[0667] The modified monomer (A) is introduced into the resulting polymer during the polymerization process. However, since the concentration of the modified monomer (A) in the polymerization system is low and the amount introduced into the polymer is small, there is no problem of reduced heat resistance of PTFE or coloration after firing.

[0668] Examples of the hydrophilic group in the modified monomer (A) include -NH2, -PO3M, -OPO3M, -SO3M, -OSO3M, -COOM (wherein M is H, a metal atom, NR 7y 4. an imidazolium which may be substituted, a pyridinium which may be substituted, or a phosphonium which may be substituted, R 7y R is H or an organic group, which may be the same or different. Any two of them may be bonded to each other to form a ring). As the above-mentioned hydrophilic group, -SO3M or -COOM is preferred. 7y The organic group in is preferably an alkyl group. 7y , preferably H or C 1-10 An organic group, more preferably H or C 1-4 The organic group is preferably H or C 1-4 of alkyl.

[0669] Examples of the metal atom include monovalent and divalent metal atoms, such as alkali metals (Group 1) and alkaline earth metals (Group 2), and Na, K or Li is preferred.

[0670] Examples of the "functional group capable of free radical polymerization" in the modified monomer (A) include groups having ethylenically unsaturated bonds such as vinyl and allyl groups. The group having ethylenically unsaturated bonds can be represented by the following formula:

[0671] CX e X g =CX f R-

[0672] (Where X e , X f and X g Each independently represents F, Cl, H, CF3, CF2H, CFH2 or CH3; R represents a linking group). Examples of the linking group of R include the following R a Preferred examples include groups having unsaturated bonds such as -CH=CH2, -CF=CH2, -CH=CF2, -CF=CF2, -CH2-CH=CH2, -CF2-CF=CH2, -CF2-CF=CF2, -(C=O)-CH=CH2, -(C=O)-CF=CH2, -(C=O)-CH=CF2, -(C=O)-CF=CF2, -(C=O)-C(CH3)=CH2, -(C=O)-C(CF3)=CH2, -(C=O)-C(CH3)=CF2, -(C=O)-C(CF3)=CF2, -O-CH2-CH=CH2, -O-CF2-CF=CH2, -O-CH2-CH=CF2, and -O-CF2-CF=CF2.

[0673] Since the modified monomer (A) has a functional group capable of free radical polymerization, if used in the polymerization, it reacts with the fluorinated monomer in the initial stage of the polymerization reaction, and it is presumed that the hydrophilic group derived from the modified monomer (A) can form particles with high stability. Therefore, if the polymerization is carried out in the presence of the modified monomer (A), it is believed that the number of particles increases.

[0674] In the above polymerization, the above-mentioned modified monomer (A) may be present alone or in combination of two or more.

[0675] In the above-mentioned polymerization, a compound having an unsaturated bond can be used as the above-mentioned modified monomer (A).

[0676] The modified monomer (A) is preferably of the general formula (4):

[0677] CX i X k =CX j R a -(CZ 1 Z 2 ) k -Y 3 (4)

[0678] (Where X i , X j and X k Each independently represents F, Cl, H or CF3; Y 3 is a hydrophilic group; R a is a connecting group; Z 1 and Z 2 Each independently represents H, F or CF3, and k represents 0 or 1).

[0679] Examples of the hydrophilic group include -NH2, -PO3M, -OPO3M, -SO3M, -OSO3M, -COOM (wherein M is H, a metal atom, NR 7y 4. an imidazolium which may be substituted, a pyridinium which may be substituted, or a phosphonium which may be substituted, R 7y R is H or an organic group, which may be the same or different. Any two of them may be bonded to each other to form a ring). As the above-mentioned hydrophilic group, -SO3M or -COOM is preferred. 7y The organic group in is preferably an alkyl group. 7y , preferably H or C 1-10 An organic group, more preferably H or C 1-4 The organic group is preferably H or C 1-4 The metal atom may be a monovalent or divalent metal atom, and may be an alkali metal (Group 1) or an alkaline earth metal (Group 2). Preferably, Na, K or Li is used.

[0680] By using the modified monomer (A), an aqueous dispersion having a smaller average primary particle size and better stability can be obtained, and the aspect ratio of the primary particles can be further reduced.

[0681] The above R a is a linking group. In the present invention, "linking group" refers to a divalent linking group. The linking group may be a single bond, preferably contains at least one carbon atom, and the number of carbon atoms may be 2 or more, 4 or more, 8 or more, 10 or more, or 20 or more. The upper limit is not limited, for example, it may be 100 or less, or 50 or less.

[0682] The linking group may be a chain or branched chain, a cyclic or acyclic structure, saturated or unsaturated, substituted or unsubstituted, and may contain one or more heteroatoms selected from the group consisting of sulfur, oxygen and nitrogen as desired, and may contain one or more functional groups selected from the group consisting of ester, amide, sulfonamide, carbonyl, carbonate, carbamate, urea and carbamate as desired. The linking group does not contain carbon atoms and may be a chain heteroatom such as oxygen, sulfur or nitrogen.

[0683] The above R a Preferred are, for example, chain heteroatoms such as oxygen, sulfur, and nitrogen, or divalent organic groups.

[0684] R a In the case of a divalent organic group, the hydrogen atom bonded to the carbon atom may be replaced by a halogen other than fluorine, such as chlorine, and may or may not contain a double bond. a It may be in the form of a chain or a branched chain, or in the form of a ring or an acyclic ring. a Functional groups (eg, ester, ether, ketone, amine, halide, etc.) may be included.

[0685] In addition, R a It may be a non-fluorinated divalent organic group or a partially fluorinated or perfluorinated divalent organic group.

[0686] As R a , and can be, for example: a hydrocarbon group in which no fluorine atoms are bonded to the carbon atom; a hydrocarbon group in which a part of the hydrogen atoms bonded to the carbon atom are substituted by fluorine atoms; a hydrocarbon group in which all the hydrogen atoms bonded to the carbon atom are substituted by fluorine atoms; a hydrocarbon group containing -(C=O)-, -(C=O)-O- or -(C=O)-, which may contain oxygen atoms, double bonds, and functional groups.

[0687] R a Preferably, it is a hydrocarbon group having 1 to 100 carbon atoms which may contain -(C=O)-, -(C=O)-O- or an ether bond and may contain a carbonyl group, and a part or all of the hydrogen atoms bonded to the carbon atoms in the hydrocarbon group may be substituted with fluorine.

[0688] As R a , preferably selected from -(CH2) a -、-(CF2) a -、-O-(CF2) a -、-(CF2) a -O-(CF2) b -、-O(CF2) a -O-(CF2) b -、-(CF2) a -[O-(CF2) b ]c -、-O(CF2) a -[O-(CF2) b ] c -、-[(CF2) a -O] b -[(CF2) c -O] d -、-O[(CF2) a -O] b -[(CF2) c -O] d -、-O-[CF2CF(CF3)O] a -(CF2) b -, -(C=O)-, -(C=O)-O-, -(C=O)-(CH2) a -、-(C=O)-(CF2) a -、-(C=O)-O-(CH2) a -、-(C=O)-O-(CF2) a -、-(C=O)-[(CH2) a -O] b -、-(C=O)-[(CF2) a -O] b -、-(C=O)-O[(CH2) a -O] b -、-(C=O)-O[(CF2) a -O] b -、-(C=O)-O[(CH2) a -O] b -(CH2) c -、-(C=O)-O[(CF2) a -O] b -(CF2) c -、-(C=O)-(CH2) a -O-(CH2) b -、-(C=O)-(CF2) a -O-(CF2) b -、-(C=O)-O-(CH2) a -O-(CH2) b -、-(C=O)-O-(CF2) a -O-(CF2) b At least one of -, -(C=O)-O-C6H4- and combinations thereof.

[0689] In the formula, a, b, c and d are independently at least 1. a, b, c and d can independently be 2 or more, 3 or more, 4 or more, 10 or more, or 20 or more. The upper limit of a, b, c and d is, for example, 100.

[0690] As R a Preferred specific examples include -CF2-O-, -CF2-O-CF2-, -CF2-O-CH2-, -CF2-O-CH2CF2-, -CF2-O-CF2CF2-, -CF2-O-CF2CH2-, -CF2-O-CF2CF2CH2-, -CF2-O-CF(CF3)-, -CF2-O-CF(CF3)CF2-, -CF2-O-CF(CF3)CF2-, -CF2-O-CF(CF3)CF2-O-, -CF2-O-CF(CF3)CH2-, -(C=O)-, -(C=O)-O-, -(C=O)-(CH2)-, -(C=O)-(CF2)-, -(C=O)-O-(CH2)-, -(C=O)-O-(CF2)-, -(C=O)-[(CH2)2-O] n -、-(C=O)-[(CF2)2-O] n -、-(C=O)-O[(CH2)2-O] n -、-(C=O)-O[(CF2)2-O] n -、-(C=O)-O[(CH2)2-O] n -(CH2)-, -(C=O)-O[(CF2)2-O] n -(CF2)-, -(C=O)-(CH2)2-O-(CH2)-, -(C=O)-(CF2)2-O-(CF2)-, -(C=O)-O-(CH2)2-O-(CH2)-, -(C=O)-O-(CF2)2-O-(CF2)-, -(C=O)-O-C6H4-, etc. Specifically, the above R a Preferably -CF2-O-, -CF2-O-CF2-, -CF2-O-CF2CF2-, -CF2-O-CF(CF3)-, -CF2-O-CF(CF3)CF2-, -CF2-O- CF(CF3)CF2-O-, -(C=O)-, -(C=O)-O-, -(C=O)-(CH2)-, -(C=O)-O-(CH2)-, -(C=O)-O[(CH2)2-O] n -、-(C=O)-O[(CH2)2-O] n -(CH2)-, -(C=O)-(CH2)2-O-(CH2)-, or -(C=O)-O-C6H4-.

[0691] In the above formula, n is an integer from 1 to 10.

[0692] As -R in the general formula (4) a -(CZ 1 Z 2 ) k -, preferably -CF2-O-CF2-, -CF2-O-CF(CF3)-, -CF2-O-C(CF3)2-, -CF2-O-CF2-CF2-, -CF2-O-CF2-CF(CF3)-, -CF2-O-CF2-C(CF3)2-, -CF2-O-CF2CF2-CF2-, -CF2-O-CF2CF2-CF(CF3)-, -CF2-O-CF2CF2-C(CF3)2-, -CF2-O-CF(CF3)-CF2-, -CF2-O-CF(CF3)-CF(CF3)-, -CF2-O-CF(CF3)-C(CF3)2-, -CF2-O-CF(CF3)CF2-CF2-, -CF2-O-CF(CF3)CF2-CF(CF3)-, -CF2-O-CF(CF3)CF2-C(CF3)2-, -CF2-O-CF(CF3)CF2-O-CF2-, -CF2-O-CF(CF3)CF2-O-CF(CF3)-, -CF2-O-CF(CF3)CF2-O-C(CF3)2-, -(C=O)-, -(C=O)-O-, -(C=O)-(CH2)-, -(C=O)-(CF2)-, -(C=O)-O-(CH2)-, -(C=O)-O-(CF2)-, -(C=O)-[(CH2)2-O] n -(CH2)-, -(C=O)-[(CF2)2-O] n -(CF2)-, -(C=O)-[(CH2)2-O] n -(CH2)-(CH2)-, -(C=O)-[(CF2)2-O] n -(CF2)-(CF2)-, -(C=O)-O[(CH2)2-O] n -(CF2)-, -(C=O)-O[(CH2)2-O] n -(CH2)-(CH2)-, -(C=O)-O[(CF2)2-O] n -(CF2)-, -(C=O)-O[(CF2)2-O] n-(CF2)-(CF2)-, -(C=O)-(CH2)2-O-(CH2)-(CH2)-, -(C=O)-(CF2)2-O-(CF2)-(CF2)-, -(C=O)-O-(CH2)2-O-(CH2)-(CH2)-, -(C= O)-O-(CF2)2-O-(CF2)-(CF2)-, -(C=O)-O-(CH2)2-O-(CH2)-C(CF3)2-, -(C=O)-O-(CF2)2-O-(CF2)-C(CF3)2-, or -(C=O)-O-C6H4 -C(CF3)2-, more preferably -CF2-O-CF(CF3)-, -CF2-O-CF2-CF(CF3)-, -CF2-O-CF2CF2-CF(CF3)-, -CF2-O-CF(CF3)-CF(CF3)-, -CF2-O-CF(CF 3)CF2-CF(CF3)-, -CF2-O-CF(CF3)CF2-O-CF(CF3)-, -(C=O)-, -(C=O)-O-(CH2)-, -(C=O)-O-(CH2)-(CH2)-, -(C=O)-O[(CH2)2-O] n -(CH2)-(CH2)-, -(C=O)-O-(CH2)2-O-(CH2)-C(CF3)2-, or -(C=O)-O-C6H4-C(CF3)2-.

[0693] In the above formula, n is an integer of 1-10.

[0694] Specific examples of the compound represented by the general formula (4) include:

[0695] [Chemistry 16]

[0696]

[0697] (Where X j and Y 3 Same as above. n is an integer from 1 to 10) and the like.

[0698] As R a , preferably general formula (r1):

[0699] -(C=O) h -(O) i -CF2-O-(CX 6 2) e -{O-CF(CF3)} f -(O) g -(r1)

[0700] (Where X 6Each independently represents H, F or CF3, e represents an integer of 0 to 3, f represents an integer of 0 to 3, g represents 0 or 1, h represents 0 or 1, and i represents 0 or 1), and the general formula (r2) is also preferred:

[0701] -(C=O) h -(O) i -CF2-O-(CX 7 2) e -(O) g -(r2)

[0702] (Where X 7 Each independently represents H, F or CF3, e is an integer of 0 to 3, g is 0 or 1, h is 0 or 1, and i is 0 or 1).

[0703] As -R in the general formula (4) a -(CZ 1 Z 2 ) k -, the following formula (t1) is also preferred:

[0704] -(C=O) h -(O) i -CF2-O-(CX 6 2) e -{O-CF(CF3)} f -(O) g -CZ 1 Z 2 -(t1)

[0705] (Where X 6 Each independently represents H, F or CF3, e represents an integer of 0 to 3, f represents an integer of 0 to 3, g represents 0 or 1, h represents 0 or 1, i represents 0 or 1, Z 1 and Z 2 Each independently represents a divalent group represented by F or CF3, wherein Z 1 and Z 2 More preferably, one is F and the other is CF3.

[0706] In the general formula (4), -R a -(CZ 1 Z 2 ) k -, the following formula (t2) is also preferred:

[0707] -(C=O) h -(O) i -CF2-O-(CX 7 2) e -(O) g -CZ1 Z 2 -(t2)

[0708] (Where X 7 Each independently represents H, F or CF3, e represents an integer from 0 to 3, g represents 0 or 1, h represents 0 or 1, i represents 0 or 1, Z 1 and Z 2 Each independently represents a divalent group represented by F or CF3, wherein Z 1 and Z 2 More preferably, one is F and the other is CF3.

[0709] The compound represented by the general formula (4) also preferably has a hydrophilic group (Y 3 ) has a CF bond and does not have a CH bond. That is, in the general formula (4), preferably X i , X j and X k All are F, R a The perfluoroalkylene group has 1 or more carbon atoms, and the perfluoroalkylene group may be any one of a chain or branched chain, may be any one of a cyclic or acyclic chain, and may contain at least one chain heteroatom. The perfluoroalkylene group may have 2 to 20 carbon atoms, or may have 4 to 18 carbon atoms.

[0710] The compound represented by the general formula (4) may also be partially fluorinated. That is, the compound represented by the general formula (4) also preferably has, in addition to the hydrophilic group (Y 3 ) has at least one hydrogen atom bonded to a carbon atom and at least one fluorine atom bonded to a carbon atom.

[0711] The compound represented by the general formula (4) is also preferably a compound represented by the following formula (4a).

[0712] CF2=CF-O-Rf 0 -Y 3 (4a)

[0713] (In the formula, Y 3 is a hydrophilic group, Rf 0 It is perfluorinated and may be chain or branched, cyclic or acyclic, saturated or unsaturated, substituted or unsubstituted, and is a perfluorinated divalent linking group that optionally contains one or more heteroatoms selected from the group consisting of sulfur, oxygen and nitrogen.

[0714] The compound represented by the general formula (4) is also preferably a compound represented by the following formula (4b).

[0715] CH2=CH-O-Rf 0 -Y 3 (4b)

[0716] (In the formula, Y 3 is a hydrophilic group, Rf 0 is a perfluorinated divalent linking group defined by formula (4a).

[0717] In the general formula (4), Y 3 -OSO3M is one of the preferred methods. 3 In the case of -OSO3M, examples of the compound represented by the general formula (4) include CF2=CF(OCF2CF2CH2OSO3M), CF2=CF(O(CF2)4CH2OSO3M), CF2=CF(OCF2CF(CF3)CH2OSO3M), CF2=CF(OCF2CF(CF3)OCF2CF2CH2OSO3M), CH2=CH((CF2)4CH2OSO3M), CF2=CF(OCF2CF2SO2N(CH3)CH2CH2OSO3M), CH2=CH(CF2CF2CH2OSO3M), CF2=CF(OCF2CF2CF2CF2SO2N(CH3)CH2CH2OSO3M). In the above formula, M is the same as above.

[0718] In the general formula (4), Y 3 -SO3M is also one of the preferred forms. 3 In the case of -SO3M, examples of the compound represented by the general formula (4) include CF2=CF(OCF2CF2SO3M), CF2=CF(O(CF2)4SO3M), CF2=CF(OCF2CF(CF3)SO3M), CF2=CF(OCF2CF(CF3)OCF2CF2SO3M), CH2=CH(CF2CF2SO3M), CF2=CF(OCF2CF(CF3)OCF2CF2CF2CF2SO3M), CH2=CH((CF2)4SO3M), and CH2=CH((CF2)3SO3M). In the above formula, M is the same as above.

[0719] In the general formula (4), Y 3 -COOM is also one of the preferred methods. 3 In the case of -COOM, examples of the compound represented by the general formula (4) include CF2=CF(OCF2CF2COOM), CF2=CF(OCF2CF2CF2COOM), CF2=CF(O(CF2)5COOM), CF2=CF(OCF2CF(CF3)COOM), CF2=CF(OCF2CF(CF3)O(CF2) nCOOM) (n is greater than 1), CH2=CH(CF2CF2COOM), CH2=CH((CF2)4COOM), CH2=CH((CF2)3COOM), CF2=CF(OCF2CF2SO2NR'CH2COOM), CF2=CF(O(CF2)4SO2NR'CH2COOM), CF2=CF(OCF2CF(CF3)SO2NR'CH2COOM), CF2=CF(OCF2CF(CF3)OCF2CF2SO2NR'CH2COOM), CH2=CH(CF2CF2SO2NR'CH2COOM), CF2=CF(OCF2CF(CF3)OCF2CF2CF2SO2NR'CH2COOM), CH2=CH((CF2)4SO2NR'CH2COOM), CH2=CH((CF2)3SO2NR'CH2COOM), etc. In the above formula, R' is H or C 1-4 The alkyl group and M are the same as described above.

[0720] In the general formula (4), Y 3 It is also one of the preferred embodiments to be -OPO3M or -OP(O)(OM)2. 3 In the case of -OPO3M or -OP(O)(OM)2, examples of the compound represented by the general formula (4) include CF2=CF(OCF2CF2CH2OP(O)(OM)2), CF2=CF(O(CF2)4CH2OP(O)(OM)2), CF2=CF(OCF2CF(CF3)CH2OP(O)(OM)2), CF2=CF(OCF2CF(CF3)OCF2CF2CH2OP(O)(OM)2), and CF2=C F(OCF2CF2SO2N(CH3)CH2CH2OP(O)(OM)2), CF2=CF(OCF2CF2CF2CF2SO2N(CH3)CH2CH2OP(O)(OM)2), CH2=CH(CF2CF2CH2OP(O)(OM)2, CH2=CH((CF2)4CH2OP(O)(OM)2), CH2=CH((CF2)3CH2OP(O)(OM)2), etc. In the above formula, M is the same as above.

[0721] In the general formula (4), Y 3 It is also one of the preferred forms to be -PO3M or -P(O)(OM)2. 3In the case of -PO3M or -P(O)(OM)2, the compound represented by the general formula (4) may include CF2=CF(OCF2CF2P(O)(OM)2), CF2=CF(O(CF2)4P(O)(OM)2), CF2=CF(OCF2CF(CF3)P(O)(OM)2), CF2=CF(OCF2CF(CF3)OCF2CF2P(O)(OM)2), CH2=CH(CF2CF2P(O)(OM)2), CH2=CH((CF2)4P(O)(OM)2), CH2=CH((CF2)3P(O)(OM)2), etc., wherein M is the same as above.

[0722] The compound represented by the general formula (4) is preferably at least one selected from the group consisting of the following compounds, wherein the compound is represented by the general formula (5):

[0723] CX2=CY(-CZ2-O-Rf-Y 3 ) (5)

[0724] (wherein, X is the same or different and is -H or -F, Y is -H, -F, an alkyl group or a fluorinated alkyl group, and Z is the same or different and is -H, -F, an alkyl group or a fluorinated alkyl group. Rf is a fluorinated alkylene group having 1 to 40 carbon atoms, or a fluorinated alkylene group having 2 to 100 carbon atoms and having an ether bond. Y 3 Same as above) and the compound represented by the general formula (6):

[0725] CX2=CY(-O-Rf-Y 3 ) (6)

[0726] (wherein, X is the same or different and is -H or -F, Y is -H, -F, an alkyl group or a fluorinated alkyl group, and Rf is a fluorinated alkylene group having 1 to 40 carbon atoms or a fluorinated alkylene group having an ether bond and having 2 to 100 carbon atoms. 3 Same as above);And general formula (7):

[0727] CX2=CY(-Rf-Y 3 ) (7)

[0728] (wherein, X is the same or different and is -H or -F, Y is -H, -F, an alkyl group or a fluorinated alkyl group, and Rf is a fluorinated alkylene group having 1 to 40 carbon atoms or a fluorinated alkylene group having an ether bond and having 2 to 100 carbon atoms. 3 Same as above).

[0729] The fluorine-containing alkylene group having 2 to 100 carbon atoms and having an ether bond is an alkylene group having no structure with an oxygen atom at the end and having an ether bond between carbon atoms.

[0730] In the general formula (5), X is -H or -F. Both Xs may be -F, or at least one of them may be -H. For example, one may be -F and the other may be -H, or both may be -H.

[0731] In the general formula (5), Y is -H, -F, an alkyl group or a fluorine-containing alkyl group.

[0732] The alkyl group is an alkyl group not containing fluorine atoms and may have at least 1 carbon atom. The alkyl group may have preferably 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms.

[0733] The fluorine-containing alkyl group is an alkyl group containing at least one fluorine atom, and the number of carbon atoms may be 1 or more. The number of carbon atoms in the fluorine-containing alkyl group is preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0734] As the above-mentioned Y, -H, -F or -CF3 is preferred, and -F is more preferred.

[0735] In the general formula (5), Z is the same or different and is -H, -F, alkyl or fluoroalkyl.

[0736] The alkyl group is an alkyl group not containing fluorine atoms and may have at least 1 carbon atom. The alkyl group may have preferably 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms.

[0737] The fluorine-containing alkyl group is an alkyl group containing at least one fluorine atom, and the number of carbon atoms may be 1 or more. The number of carbon atoms in the fluorine-containing alkyl group is preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0738] As the above-mentioned Z, -H, -F or -CF3 is preferred, and -F is more preferred.

[0739] In the general formula (5), at least one of X, Y and Z preferably contains a fluorine atom. For example, X may be -H, and Y and Z may be -F.

[0740] In the general formula (5), Rf is a fluorinated alkylene group having 1 to 40 carbon atoms or a fluorinated alkylene group having 2 to 100 carbon atoms and having an ether bond.

[0741] The number of carbon atoms of the fluorinated alkylene group is preferably 2 or more. In addition, it is preferably 30 or less, more preferably 20 or less, and further preferably 10 or less. Examples of the fluorinated alkylene group include -CF2-, -CH2CF2-, -CF2CF2-, -CF2CH2-, -CF2CF2CH2-, -CF(CF3)-, -CF(CF3)CF2-, -CF(CF3)CH2-, etc. The fluorinated alkylene group is preferably a perfluoroalkylene group.

[0742] The number of carbon atoms in the fluorinated alkylene group having an ether bond is preferably 3 or more. The number of carbon atoms in the fluorinated alkylene group having an ether bond is preferably 60 or less, more preferably 30 or less, and further preferably 12 or less.

[0743] As the fluorine-containing alkylene group having an ether bond, for example, the following formula is also preferred:

[0744] [Chemistry 17]

[0745]

[0746] (Where Z 1 F or CF3; Z 2 and Z 3 H or F; Z 4 is a divalent group represented by H, F or CF3; p1+q1+r1 is an integer from 1 to 10; s1 is 0 or 1; t1 is an integer from 0 to 5).

[0747] Specific examples of the fluorinated alkylene group having an ether bond include -CF(CF3)CF2-O-CF(CF3)-, -(CF(CF3)CF2-O) n -CF(CF3)- (wherein n is an integer from 1 to 10), -CF(CF3)CF2-O-CF(CF3)CH2-, -(CF(CF3)CF2-O) n -CF(CF3)CH2- (wherein n is an integer of 1 to 10), -CH2CF2CF2O-CH2CF2CH2-, -CF2CF2CF2O-CF2CF2-, -CF2CF2CF2O-CF2CF2CH2-, -CF2CF2O-CF2-, -CF2CF2O-CF2CH2-, etc. The fluorine-containing alkylene group having an ether bond is preferably a perfluoroalkylene group.

[0748] In the general formula (5), Y 3 Preferably -COOM, -SO3M or -OSO3M (M is H, metal atom, NR 7y 4. an imidazolium which may be substituted, a pyridinium which may be substituted, or a phosphonium which may be substituted, R 7y is H or an organic group, which may be the same or different. Any two of them may be bonded to each other to form a ring).

[0749] As R 7y The organic group in is preferably an alkyl group.

[0750] As R 7y , preferably H or C 1-10 An organic group, more preferably H or C 1-4The organic group is preferably H or C 1-4 of alkyl.

[0751] Examples of the metal atom include alkali metals (Group 1) and alkaline earth metals (Group 2), and Na, K, or Li is preferred.

[0752] As M, -H, a metal atom or NR 7 4, more preferably -H, alkali metal (Group 1), alkaline earth metal (Group 2) or NR 7 4, further preferably -H, -Na, -K, -Li or NH4, still more preferably -H, -Na, -K or NH4, particularly preferably -H, -Na or NH4, most preferably -H or -NH4.

[0753] As the above Y 3 , preferably -COOM or -SO3M, more preferably -COOM.

[0754] The compound represented by the general formula (5) is preferably a compound (5a) represented by the general formula (5a).

[0755] CH2=CF(-CF2-O-Rf-Y 3 )(5a)

[0756] (In the formula, Rf and Y 3 Same as above.)

[0757] Specific examples of the compound represented by the general formula (5a) include the following:

[0758] [Chemistry 18]

[0759]

[0760] (Where Z 1 F or CF3; Z 2 and Z 3 H or F; Z 4 is H, F or CF3; p1+q1+r1 is an integer from 0 to 10; s1 is 0 or 1; t1 is an integer from 0 to 5, Y 3 Same as above. Where Z 3 and Z 4 When all are H, p1+q1+r1+s1 is not 0). More specifically, preferably,

[0761] [Chemistry 19]

[0762]

[0763] etc., among which preferably

[0764] [Chemistry 20]

[0765]

[0766] As the compound represented by the general formula (5a), Y in the formula (5a) is preferably 3 It is -COOM, and is particularly preferably at least one selected from the group consisting of CH2=CFCF2OCF(CF3)COOM and CH2=CFCF2OCF(CF3)CF2OCF(CF3)COOM (wherein M has the same meaning as above), and more preferably CH2=CFCF2OCF(CF3)COOM.

[0767] The compound represented by the general formula (5) is preferably a compound (5b) represented by the general formula (5b).

[0768] CX 2 2=CFCF2-O-(CF(CF3)CF2O) n5 -CF(CF3)-Y 3 (5b)

[0769] (In the formula, each X 2 The same, represents F or H. n5 represents 0 or an integer from 1 to 10, Y 3 Same as the above definition.)

[0770] In the above formula (5b), from the perspective of stability of the obtained aqueous dispersion, the above n5 is preferably 0 or an integer of 1 to 5, more preferably 0, 1 or 2, and even more preferably 0 or 1. From the perspective of obtaining appropriate water solubility and stability of the aqueous dispersion, the above Y 3 -COOM is preferred, and M is preferably H or NH 4 because it is less likely to remain as an impurity and the heat resistance of the obtained molded body is improved.

[0771] Examples of the compound represented by the above formula (5b) include CH2=CFCF2OCF(CF3)COOM and CH2=CFCF2OCF(CF3)CF2OCF(CF3)COOM (wherein M has the same meaning as defined above).

[0772] In addition, examples of the compound represented by the general formula (5) include compounds represented by the general formula (5c) and the like.

[0773] CF2=CFCF2-O-Rf-Y 3 (5c)

[0774] (In the formula, Rf and Y 3 Same as above.)

[0775] More specifically, we can cite

[0776] [Chemistry 21]

[0777] CF2=CFCF2OCF2CF2CF2-Y 3 ,

[0778]

[0779] In the general formula (6), X is -H or -F. Both Xs may be -F, or at least one of them may be -H. For example, one may be -F and the other may be -H, or both may be -H.

[0780] In the general formula (6), Y is -H, -F, an alkyl group or a fluorine-containing alkyl group.

[0781] The alkyl group is an alkyl group not containing fluorine atoms and may have at least 1 carbon atom. The alkyl group may have preferably 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms.

[0782] The fluorine-containing alkyl group is an alkyl group containing at least one fluorine atom, and the number of carbon atoms may be 1 or more. The number of carbon atoms in the fluorine-containing alkyl group is preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0783] As the above-mentioned Y, -H, -F or -CF3 is preferred, and -F is more preferred.

[0784] In the general formula (6), at least one of X and Y preferably contains a fluorine atom. For example, X may be -H, and Y and Z may be -F.

[0785] In the general formula (6), Rf is a fluorinated alkylene group having 1 to 40 carbon atoms or a fluorinated alkylene group having 2 to 100 carbon atoms and having an ether bond.

[0786] The number of carbon atoms of the fluorinated alkylene group is preferably 2 or more. In addition, the number of carbon atoms of the fluorinated alkylene group is preferably 30 or less, more preferably 20 or less, and further preferably 10 or less. Examples of the fluorinated alkylene group include -CF2-, -CH2CF2-, -CF2CF2-, -CF2CH2-, -CF2CF2CH2-, -CF(CF3)-, -CF(CF3)CF2-, -CF(CF3)CH2-, etc. The fluorinated alkylene group is preferably a perfluoroalkylene group.

[0787] In the above general formula (6), Y 3 Preferably -COOM, -SO3M or -OSO3M (M is H, metal atom, NR 7y 4. an imidazolium with or without a substituent, a pyridinium with or without a substituent, or a phosphonium with or without a substituent, R 7yis H or an organic group, which may be the same or different. Any two of them may be bonded to each other to form a ring).

[0788] As R 7y As R 7y , preferably H or C 1-10 An organic group, more preferably H or C 1-4 The organic group is preferably H or C 1-4 of alkyl.

[0789] Examples of the metal atom include alkali metals (Group 1) and alkaline earth metals (Group 2), and Na, K, or Li is preferred.

[0790] As M, -H, a metal atom or NR 7 4, more preferably -H, alkali metal (Group 1), alkaline earth metal (Group 2) or NR 7 4, further preferably -H, -Na, -K, -Li or NH4, still more preferably -H, -Na, -K or NH4, particularly preferably -H, -Na or NH4, most preferably -H or -NH4.

[0791] As the above Y 3 , preferably -COOM or -SO3M, more preferably -COOM.

[0792] The compound represented by the general formula (6) is preferably at least one selected from the group consisting of compounds represented by the general formulae (6a), (6b), (6c), (6d) and (6e).

[0793] CF2=CF-O-(CF2) n1 -Y 3 (6a)

[0794] (where n1 represents an integer from 1 to 10, Y 3 Same as the above definition.)

[0795] CF2=CF-O-(CF2C(CF3)F) n2 -Y 3 (6b)

[0796] (where n2 represents an integer from 1 to 5, Y 3 Same as the above definition.)

[0797] CF2=CF-O-(CFX 1 ) n3 -Y 3 (6c)

[0798] (Where X 1 represents F or CF3, n3 represents an integer from 1 to 10, Y3 Same as the above definition.)

[0799] CF2=CF-O-(CF2CFX 1 O) n4 -(CF2) n6 -Y 3 (6d)

[0800] (wherein, n4 represents an integer of 1 to 10, n6 represents an integer of 1 to 3, and Y 3 and X 1 Same as the above definition.)

[0801] CF2=CF-O-(CF2CF2CFX 1 O) n5 -CF2CF2CF2-Y 3 (6e)

[0802] (where n5 represents an integer from 0 to 10, Y 3 and X 1 Same as the above definition.)

[0803] In the above formula (6a), the above n1 is preferably an integer of 5 or less, and more preferably an integer of 2 or less. From the perspective of obtaining appropriate water solubility and stability of the aqueous dispersion, the above Y 3 -COOM or -SO3M is preferred, and M is preferably H or NH4 because it is less likely to remain as an impurity and the heat resistance of the obtained molded body is improved.

[0804] As the compound represented by the above formula (6a), for example, CF2=CF-O-CF2COOM, CF2=CF(OCF2CF2COOM), CF2=CF(OCF2CF2CF2COOM), CF2=CF-O-CF2SO3M, CF2=CF(OCF2CF2SO3M), CF2=CF(OCF2CF2CF2SO3M) (wherein M has the same definition as above).

[0805] In the above formula (6b), from the perspective of the stability of the obtained aqueous dispersion, the above n2 is preferably an integer of 3 or less, and from the perspective of obtaining appropriate water solubility and stability of the aqueous dispersion, Y 3 -COOM or -SO3M is preferred, and M is preferably H or NH4 because it is less likely to remain as an impurity and the heat resistance of the obtained molded body is improved.

[0806] In the above formula (6c), from the viewpoint of water solubility, the above n3 is preferably an integer of 5 or less, and from the viewpoint of obtaining appropriate water solubility and stability of the aqueous dispersion, the above Y 3It is preferably -COOM or -SO3M, and from the viewpoint of improving dispersion stability, the above-mentioned M is preferably H or NH4.

[0807] In the above formula (6d), from the perspective of the stability of the aqueous dispersion, the above X 1 Preferably -CF3, from the perspective of water solubility, the above n4 is preferably an integer of 5 or less, from the perspective of obtaining appropriate water solubility and stability of the aqueous dispersion, the above Y 3 It is preferably -COOM or -SO3M, and the above-mentioned M is preferably H or NH4.

[0808] As the compound represented by the above formula (6d), for example, CF2=CFOCF2CF(CF3)OCF2CF2COOM, CF2=CFOCF2CF(CF3)OCF2COOM, CF2=CFOCF2CF(CF3)OCF2CF2CF2COOM, CF2=CFOCF2CF(CF3)OCF2CF2CF2COOM, CF2=CFOCF2CF(CF3)OCF2CF2SO3M, CF2=CFOCF2CF(CF3)OCF2SO3M, CF2=CFOCF2CF(CF3)OCF2CF2CF2SO3M (wherein M represents H, NH4 or an alkali metal).

[0809] In the general formula (6e), from the viewpoint of water solubility, the above n5 is preferably an integer of 5 or less, and from the viewpoint of obtaining appropriate water solubility and stability of the aqueous dispersion, the above Y 3 It is preferably -COOM or -SO3M, and the above-mentioned M is preferably H or NH4.

[0810] Examples of the compound represented by the general formula (6e) include CF2=CFOCF2CF2CF2COOM and CF2=CFOCF2CF2CF2SO3M (wherein M represents H, NH4 or an alkali metal).

[0811] In the general formula (7), Rf is preferably a fluorine-containing alkylene group having 1 to 40 carbon atoms. In the general formula (7), at least one of X and Y preferably contains a fluorine atom.

[0812] The compound represented by the general formula (7) is preferably selected from the general formula (7a):

[0813] CF2=CF-(CF2) n1 -Y 3 (7a)

[0814] (where n1 represents an integer from 1 to 10, Y 3 The compound represented by the following formula (7b):

[0815] CF2=CF-(CF2C(CF3)F)n2 -Y 3 (7b)

[0816] (where n2 represents an integer from 1 to 5, Y 3 At least one of the group consisting of compounds represented by (same as defined above).

[0817] The above Y 3 Preferably -SO3M or -COOM, M is preferably H, metal atom, NR 7y 4. An imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent. 7y represents H or an organic group.

[0818] In the above formula (7a), the above n1 is preferably an integer of 5 or less, and more preferably an integer of 2 or less. From the perspective of obtaining appropriate water solubility and stability of the aqueous dispersion, the above Y 3 -COOM or -SO3M is preferred, and M is preferably H or NH4 because it is less likely to remain as an impurity and the heat resistance of the obtained molded body is improved.

[0819] Examples of the compound represented by the above formula (7a) include CF2=CFCF2COOM and CF2=CFCF2SO3M (wherein M has the same meaning as defined above).

[0820] In the above formula (7b), from the perspective of the stability of the obtained aqueous dispersion, the above n2 is preferably an integer of 3 or less, and from the perspective of obtaining appropriate water solubility and stability of the aqueous dispersion, Y 3 -COOM or -SO3M is preferred, and M is preferably H or NH4 because it is less likely to remain as an impurity and the heat resistance of the obtained molded body is improved.

[0821] The above-mentioned modified monomer preferably includes a modified monomer (A), preferably includes 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 includes a compound represented by general formula (5a) or general formula (5c).

[0822] When using modified monomer (A) as modified monomer, the content of modified monomer (A) unit is preferably in the range of 0.00001 mass % to 1.0 mass % relative to the total polymerized units of the above-mentioned TFE polymer (PTFE). As the lower limit, it is more preferably 0.0001 mass %, more preferably 0.0005 mass, further preferably 0.001 mass %, and further more preferably 0.005 mass %. As the upper limit, it is 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 %, 0.01 mass %.

[0823] The aqueous dispersion of TFE polymer is also preferably used for various purposes as a composition with an organic or inorganic filler added according to the purpose. The composition can be coated on a substrate formed of metal or ceramic to form a coating surface having non-stickiness and low friction coefficient, gloss, smoothness, wear resistance, weather resistance and heat resistance, and is suitable for coating of rollers or cooking devices, impregnation processing of glass cloth, etc.

[0824] The organosol of TFE polymer can also be prepared by the above-mentioned aqueous dispersion. The above-mentioned organosol can comprise the above-mentioned TFE polymer and an organic solvent. As the above-mentioned organic solvent, ether solvents, ketone solvents, alcohol solvents, amide solvents, ester solvents, aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents can be enumerated, and N-methyl-2-pyrrolidone, dimethylacetamide etc. can be preferably used. The preparation of the above-mentioned organosol can be implemented by the method described in International Publication No. 2012 / 002038.

[0825] The aqueous dispersion of the TFE polymer is also preferably used as a processing aid. When used as a processing aid, the melt strength of the main polymer during melt processing can be improved by mixing the aqueous dispersion with the main polymer, etc., thereby improving the mechanical strength, electrical properties, flame retardancy, anti-drip properties during combustion, and slip properties of the resulting polymer.

[0826] The aqueous dispersion of the TFE polymer is also preferably used as a binder for batteries or for dust prevention purposes.

[0827] 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 PTFE described in Japanese Unexamined Patent Publication No. 11-49912, U.S. Patent No. 5804654, Japanese Unexamined Patent Publication No. 11-29679, and Japanese Unexamined Patent Publication No. 2003-2980, for example. The processing aid using the aqueous dispersion is not inferior to the processing aids described in the above publications.

[0828] The aqueous dispersion of the TFE polymer is preferably mixed with an aqueous dispersion of a melt-processable fluororesin and coagulated to form a co-coagulated powder. The co-coagulated powder is suitable as a processing aid.

[0829] Examples of the melt-processable fluororesin include FEP, PFA, TFE / perfluoroallyl ether copolymer, ETFE, and ethylene / TFE / HFP copolymer [EFEP]. Among them, PFA or FEP is preferred.

[0830] The aqueous dispersion also preferably contains the melt-processable fluororesin. Examples of the melt-processable fluororesin include FEP, PFA, TFE / perfluoroallyl ether copolymer, ETFE, EFEP, and the like. The aqueous dispersion containing the melt-processable fluororesin can be used as a coating. The melt-processable fluororesin can fully fuse the particles of the TFE polymer to each other, thereby improving film-forming properties and making the resulting coating glossy.

[0831] The aqueous dispersion of the TFE polymer is also preferably used as a dust suppressing agent. The dust suppressing agent can be used in the following method: a method of mixing with a dust-generating substance and applying compression-shearing action to the mixture at a temperature of 20°C to 200°C to thereby fibrillate the TFE polymer and suppress dust of the dust-generating substance; for example, the method described in Japanese Patent No. 2827152, Japanese Patent No. 2538783, etc.

[0832] The aqueous dispersion of the TFE polymer can be suitably used in the dust suppression treatment agent composition described in, for example, International Publication No. 2007 / 004250, and can also be suitably used in the dust suppression treatment method described in International Publication No. 2007 / 000812.

[0833] The dust suppression agent is suitable for use in dust suppression in the fields of building materials, soil stabilization materials, solidification materials, fertilizers, filling treatment of incineration ash and harmful substances, explosion-proofing, cosmetics, and litter for pet excretion represented by cat litter.

[0834] The aqueous dispersion of the TFE polymer is also preferably used as a raw material for obtaining TFE polymer fibers by a dispersion spinning method. The dispersion spinning method refers to a method in which the aqueous dispersion of the TFE polymer is mixed with an aqueous dispersion of a matrix polymer, the mixture is extruded to form an intermediate fiber structure, and the intermediate fiber structure is calcined to decompose the matrix polymer and sinter the TFE polymer particles to obtain TFE polymer fibers.

[0835] The production method of the present invention can also produce low-molecular-weight PTFE.

[0836] Low molecular weight PTFE can be produced by polymerization, or by reducing the molecular weight of high molecular weight PTFE obtained by polymerization by a known method (thermal decomposition, radiation irradiation decomposition, etc.).

[0837] Low molecular weight PTFE (also called PTFE powder) with a molecular weight of less than 600,000 has excellent chemical stability, extremely low surface energy, and is not prone to fibrillation. Therefore, it is suitable for the manufacture of plastics, inks, cosmetics, coatings, greases, office automation equipment parts, toners, etc. as an additive for the purpose of improving slippage and the texture of the coating surface (for example, see Japanese Patent Publication No. 10-147617).

[0838] In addition, TFE or a monomer copolymerizable with TFE and TFE may be polymerized in the presence of a chain transfer agent to obtain low molecular weight PTFE. 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 further preferred. At this time, the amount of the chain transfer agent is preferably 10 mass ppm or more relative to the aqueous medium.

[0839] When the low molecular weight PTFE obtained by the above polymerization is used as a powder, it can be made into powder particles by precipitating the above aqueous dispersion.

[0840] In the present invention, high molecular weight PTFE refers to PTFE that is not melt-processable and fibrillating, while low molecular weight PTFE refers to PTFE that is melt-processable and not fibrillating.

[0841] The non-melt processability mentioned above refers to a property in which the melt flow rate cannot be measured at a temperature higher than the crystallization melting point according to ASTM D 1238 and D 2116.

[0842] The presence or absence of fibrillation can be judged by "paste extrusion", which is a representative method for molding a powder made from a polymer of TFE, i.e., "high molecular weight PTFE powder". This is because, usually, when paste extrusion can be performed, high molecular weight PTFE has fibrillation. In the case where the unfired molded product obtained by paste extrusion does not have substantial strength or elongation, for example, in the case where the elongation is 0% and it breaks if stretched, it can be considered as not having fibrillation.

[0843] The standard specific gravity (SSG) of the high molecular weight PTFE is preferably 2.130 to 2.280. The standard specific gravity is measured by the water displacement method according to ASTM D 792 using a sample molded according to ASTM D 4895-89. In the present invention, "high molecular weight" means that the standard specific gravity is within the above range.

[0844] The melt viscosity of the low molecular weight PTFE at 380°C is 1×10 2 Pa·s~7×10 5 Pa·s. In the present invention, "low molecular weight" means that the melt viscosity is within the above range. The melt viscosity is the following value: according to ASTM D 1238, using a flow tester (manufactured by Shimadzu Corporation) and A 2 g sample preheated at 380°C for 5 minutes in a 8 L mold was maintained at the above temperature under a load of 0.7 MPa and the obtained value was the above melt viscosity.

[0845] The melt viscosity of the above-mentioned high molecular weight PTFE is extremely high compared with the above-mentioned low molecular weight PTFE, and it is difficult to measure its accurate melt viscosity. On the other hand, the melt viscosity of the above-mentioned low molecular weight PTFE can be measured, but it is difficult to obtain the molded product that can be used for the measurement of standard specific gravity by the above-mentioned low molecular weight PTFE, and it is difficult to measure its accurate standard specific gravity. Therefore, among the present invention, standard specific gravity is adopted as the index of the molecular weight of the above-mentioned high molecular weight PTFE, and melt viscosity is adopted as the index of the molecular weight of the above-mentioned low molecular weight PTFE. It should be noted that, for the above-mentioned high molecular weight PTFE and the above-mentioned low molecular weight PTFE, the assay method that can directly determine the specific molecular weight is all unknown.

[0846] The peak temperature of the high molecular weight PTFE is preferably 333° C. to 347° C., more preferably 335° C. to 345° C. The peak temperature of the low molecular weight PTFE is preferably 322° C. to 333° C., more preferably 324° C. to 332° C. The peak temperature can be determined by heating PTFE that has not been heated to a temperature of 300° C. or higher at 10° C. / min using TG / DTA (differential thermal and thermogravimetric simultaneous measurement apparatus) to a temperature corresponding to a maximum value that appears in the resulting differential thermal (DTA) curve.

[0847] The peak temperature of PTFE may be 322°C to 347°C.

[0848] When the PTFE is high molecular weight PTFE, the upper limit of the peak temperature of the 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.

[0849] When the PTFE is high molecular weight PTFE, the lower limit of the peak temperature of the PTFE may be 333° C. or higher, or 335° C. or higher.

[0850] When the PTFE is low molecular weight PTFE, the upper limit of the peak temperature of the PTFE may be 333° C. or lower, or 332° C. or lower.

[0851] When the PTFE is low molecular weight PTFE, the lower limit of the peak temperature of the PTFE may be 322° C. or higher, or 324° C. or higher.

[0852] The average primary particle size of the primary particles of low molecular weight PTFE is preferably 10 nm to 300 nm, more preferably 50 nm or more, further preferably 100 nm or more, further preferably 150 nm or more, and more preferably 250 nm or less. A relatively small average primary particle size of the primary particles can be obtained, for example, by adding a modifying monomer to the polymerization system at the initial stage of TFE polymerization.

[0853] The average primary particle size of the primary particles of low molecular weight PTFE can be measured by dynamic light scattering. First, make a low molecular weight PTFE aqueous dispersion adjusted to about 1.0 mass % by polymer solid content concentration, use dynamic light scattering, set the measurement temperature to be 25 ° C, the refractive index of the solvent (water) to be 1.3328, the viscosity of the solvent (water) to be 0.8878mPa·s, and the cumulative number of times to be 70, thus can be measured. In the dynamic light scattering method, for example, ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.) can be used.

[0854] In addition, the above average primary particle size can also be measured by the following method. The dispersion is diluted with water to a solid content concentration of 0.15% by mass, and the transmittance of the projected light at 550 nm relative to the unit length of the obtained diluted latex and the number-based length average particle size determined by measuring the oriented diameter through a transmission electron microscope photograph are measured to prepare a calibration curve. The calibration curve can be used to calculate the average particle size from the measured transmittance of the projected light at 550 nm of each sample.

[0855] The high molecular weight PTFE preferably has at least one endothermic peak in the range of 333°C to 347°C in the heat of fusion curve when the temperature is increased at a rate of 10°C / min using a differential scanning calorimeter [DSC] for PTFE that has not been heated to a temperature of 300°C or higher, and the heat of fusion at 290°C to 350°C calculated from the heat of fusion curve is 52 mJ / mg or higher. The heat of fusion of PTFE is more preferably 55 mJ / mg or higher, and further preferably 58 mJ / mg or higher.

[0856] (II) Melt-processable fluororesin

[0857] (1) In the production method of the present invention, the polymerization of FEP is preferably performed at a polymerization temperature of 10° C. to 150° C. and a polymerization pressure of 0.3 MPaG to 6.0 MPaG.

[0858] The preferred monomer composition (mass %) of FEP is TFE:HFP=(60 to 95):(5 to 40), and more preferably (85 to 92):(8 to 15).

[0859] In addition to TFE and HFP, other monomers that can copolymerize with these monomers can also be polymerized to obtain a copolymer of TFE, HFP and other monomers as FEP. As other monomers, the above-mentioned fluorine-containing monomers (excluding TFE and HFP) and non-fluorine-containing monomers can be cited. As other monomers, one or more can be used. As other monomers, perfluoro (alkyl vinyl ether) is preferred. The content of other monomer units in FEP can be 0.1% to 2% by mass relative to all monomer units.

[0860] In the polymerization of FEP, cyclohexane, methanol, ethanol, propanol, ethane, propane, butane, pentane, hexane, carbon tetrachloride, chloroform, dichloromethane, methyl chloride, etc. are preferably used as the chain transfer agent, and ammonium carbonate, disodium hydrogen phosphate, etc. are preferably used as the pH buffer.

[0861] (2) In the production method of the present invention, the polymerization of TFE / perfluoro(alkyl vinyl ether) copolymers such as PFA and MFA and TFE / perfluoroallyl ether copolymers is usually preferably carried out at a polymerization temperature of 10° C. to 100° C. and a polymerization pressure of 0.3 MPaG to 6.0 MPaG.

[0862] 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). As the above-mentioned perfluoro(alkyl vinyl ether), it is preferred to use a monomer composition of the formula: CF2=CFORf 4 (Where Rf 4 It is a substance represented by a perfluoroalkyl group having 1 to 6 carbon atoms).

[0863] In addition to TFE and perfluoro(alkyl vinyl ether), by polymerizing other monomers that can copolymerize with these monomers, a copolymer of TFE, perfluoro(alkyl vinyl ether) and other monomers as a TFE / perfluoro(alkyl vinyl ether) copolymer can be obtained. As other monomers, the above-mentioned fluorine-containing monomers (excluding TFE and perfluoro(alkyl vinyl ether)) and non-fluorine-containing monomers can be cited. As other monomers, one or more can be used. The content of other monomer units in the TFE / perfluoro(alkyl vinyl ether) copolymer can be 0.1% to 2% by mass relative to all monomer units.

[0864] 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). As the above-mentioned perfluoroallyl ether, it is preferred to use a monomer of the formula: CF2=CFCF2ORf 4 (Where Rf 4 It is a substance represented by a perfluoroalkyl group having 1 to 6 carbon atoms).

[0865] In addition to TFE and perfluoroallyl ether, by polymerizing other monomers that can copolymerize with these monomers, a copolymer of TFE, perfluoroallyl ether and other monomers as a TFE / perfluoroallyl ether copolymer can be obtained. As other monomers, the above-mentioned fluorinated monomers (wherein TFE and perfluoroallyl ether are not included) and non-fluorinated monomers can be cited. As other monomers, one or more can be used. The content of other monomer units in the TFE / perfluoroallyl ether copolymer can be 0.1% to 2% by mass relative to all monomer units.

[0866] In the polymerization of the above-mentioned TFE / perfluoro(alkyl vinyl ether) copolymer and TFE / perfluoroallyl ether copolymer, cyclohexane, methanol, ethanol, propanol, propane, butane, pentane, hexane, carbon tetrachloride, chloroform, dichloromethane, methyl chloride, methane, ethane, etc. are preferably used as chain transfer agents, and ammonium carbonate, disodium hydrogen phosphate, etc. are preferably used as pH buffers.

[0867] Furthermore, a nonionic surfactant can be appropriately added to an aqueous dispersion of a TFE / perfluoro(alkyl vinyl ether) copolymer and a TFE / perfluoroallyl ether copolymer such as PFA and MFA, and polyethersulfone, polyamideimide and / or polyimide and metal powder can be dissolved or dispersed in an organic solvent as needed to obtain a primer composition. It can also be used in a coating method for coating a metal surface with a fluororesin, the method comprising: applying the primer composition to a metal surface, applying a melt-processable fluororesin composition on the primer layer thus formed, and firing the melt-processable fluororesin composition layer together with the primer layer.

[0868] (3) In the production method of the present invention, the polymerization of ETFE is preferably performed at a polymerization temperature of 10° C. to 100° C. and a polymerization pressure of 0.3 MPaG to 2.0 MPaG.

[0869] The preferred monomer composition (mol %) of ETFE is TFE:ethylene=(50-99):(50-1).

[0870] In addition to ethylene and TFE, by polymerizing other monomers that can copolymerize with these monomers, a copolymer of ethylene, TFE and other monomers as ETFE can be obtained. As other monomers, the above-mentioned fluorine-containing monomers (wherein not including TFE) and non-fluorine-containing monomers (wherein not including ethylene) can be enumerated. As other monomers, one or more can be used.

[0871] As other monomers, hexafluoropropylene, perfluorobutylethylene, perfluorohexylethylene, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-1-octene, 2,3,3,4,4,5,5-heptafluoro-1-pentene (CH2=CFCF2CF2CF2H), and 2-trifluoromethyl-3,3,3-trifluoropropylene ((CF3)2CF=CH2) are preferred.

[0872] The content of other monomer units in ETFE may be 0 to 20% by mass relative to all monomer units. A preferred mass ratio is TFE:ethylene:other monomers=(63 to 94):(27 to 2):(1 to 10).

[0873] In the polymerization of ETFE, cyclohexane, methanol, ethanol, propanol, ethane, propane, butane, pentane, hexane, carbon tetrachloride, chloroform, methylene chloride, methyl chloride, etc. are preferably used as a chain transfer agent.

[0874] (4) The production method of the present invention can also be used to produce an electrolyte polymer precursor. In the production method of the present invention, the polymerization of the electrolyte polymer precursor is preferably carried out at a polymerization temperature of 10°C to 100°C and a polymerization pressure of 0.1 MPaG to 2.0 MPaG. The electrolyte polymer precursor is composed of -SO2X 151 、-COZ 151 or-POZ 152 Z 153 (X 151 , Z 151 , Z 152 and Z 153 As described later, the monomer structure having the functional groups shown in (a) can be converted into an ion exchange polymer by hydrolysis treatment.

[0875] Examples of monomers used in the electrolyte polymer precursor include

[0876] General formula (150): CF2=CF-O-(CF2CFY 151 -O) n -(CFY 152 ) m -A 151

[0877] (In the formula, Y 151 represents a fluorine atom, a chlorine atom, a -SO2F group or a perfluoroalkyl group. The perfluoroalkyl group may contain an ethereal oxygen and a -SO2F group. n represents an integer of 0 to 3. 151 Can be the same or different. 152 represents a fluorine atom, a chlorine atom or a -SO2F group. m represents an integer of 1 to 5. m Y 152 Can be the same or different. 151 Represents -SO2X 151 、-COZ 151 or-POZ 152 Z 153 .X 151 Indicates F, Cl, Br, I, -OR 151 or -NR 152 R 153 . Z 151 , Z 152 and Z 153 Same or different, indicates -NR 154 R 155 OR 156 . R 151 , R152 , R 153 , R 154 , R 155 and R 156 The same or different, represents H, ammonium, alkali metal, alkyl containing or not containing fluorine atoms, aryl, or sulfonyl group) as a fluorine-containing monomer. As the monomer used in the electrolyte polymer precursor, there can also be mentioned the compound containing two fluorinated sulfonyl groups described in International Publication No. 2007 / 013532, the perfluoromonomer having -SO2F group and dioxolane described in International Publication No. 2014 / 175123, etc. The preferred monomer composition (mol %) of the electrolyte polymer precursor is TFE:vinyl ether = (50~99): (50~1), and more preferably TFE:vinyl ether = (50~93): (50~7).

[0878] The electrolyte polymer precursor can be modified by a third monomer in the range of 0 to 20 mass % of all monomers. Examples of the third monomer include CTFE, vinylidene fluoride, perfluoroalkyl vinyl ether, perfluorobutylene 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.

[0879] The electrolyte polymer precursor thus obtained can be formed into a film, for example, and then subjected to hydrolysis with an alkaline solution and treatment with an inorganic acid to be used as a polymer electrolyte membrane for fuel cells, electrolysis devices, redox flow batteries, and the like.

[0880] Alternatively, the electrolyte polymer dispersion may be obtained by performing hydrolysis with an alkali solution while maintaining the dispersed state of the electrolyte polymer precursor.

[0881] Next, by heating to 120° C. or higher in a pressure container, the material can be dissolved in, for example, a water / alcohol mixed solvent to form a solution.

[0882] The solution thus obtained can be used as, for example, a binder for an electrode, or can be compounded with various additives and cast to form a film, and used in, for example, an antifouling coating film, an organic actuator, and the like.

[0883] (5) TFE / VDF copolymer

[0884] In the production method of the present invention, the polymerization temperature of the TFE / VDF copolymer is not particularly limited and may be 0° C. to 100° C. The polymerization pressure is appropriately determined depending on other polymerization conditions such as the polymerization temperature and may generally be 0 MPaG to 9.8 MPaG.

[0885] The preferred monomer composition (mol%) of the TFE / VDF copolymer is TFE:VDF=(5-90):(95-10). As the TFE / VDF copolymer, a third monomer may be further used to modify the copolymer in the range of 0-50 mol% of the total monomers. Preferably, TFE:ethylene:third monomer=(30-85):(10-69.9):(0.1-10).

[0886] As the third monomer, preferably

[0887] Type: CX 11 X 12 =CX 13 (CX 14 X 15 ) n11 X 16

[0888] (Where X 11 ~X 16 are the same or different, represents H, F or Cl, and n11 represents an integer from 0 to 8. TFE and VDF are not included, or

[0889] Type: CX 21 X 22 =CX 23 -O(CX 24 X 25 ) n21 X 26

[0890] (Where X 21 ~X 26 are the same or different, represent H, F or Cl, and n21 represents an integer of 0 to 8).

[0891] In addition, the third monomer may be a non-fluorinated ethylenic monomer. From the aspect of maintaining heat resistance and chemical resistance, the non-fluorinated ethylenic monomer is preferably selected from ethylenic monomers having a carbon number of 6 or less. Examples thereof 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, methacrylic acid, etc.

[0892] It is also preferred that the aqueous dispersion of the above-mentioned TFE / VDF copolymer is coated on a porous substrate consisting of a polyolefin resin and used as a composite porous membrane. It is also preferred that inorganic particles and / or organic particles are dispersed in an aqueous dispersion and coated on a porous substrate and used as a composite porous membrane. The composite porous membrane obtained in this way can be used as a separator of a lithium secondary battery, etc.

[0893] The fluoropolymer aqueous dispersion of the present invention can be suitable for coating compositions and can be suitable for liquid coating compositions. The coating composition of the present invention provides a film having a large contact angle and a small friction coefficient because the content of the fluoropolymer aqueous dispersion containing the fluorochemical with a hydrophilic group of less than 7 carbon atoms is reduced. The reason is not clear, but it is speculated that the dispersion stability of the fluoropolymer particles in the coating composition is moderately low because the fluoropolymer aqueous dispersion containing the low content of the fluorochemical with a hydrophilic group is contained. Therefore, when forming a film, the fluoropolymer particles are more likely to float on the surface of the film than other components, and the proportion of the fluoropolymer on the film surface increases as a result.

[0894] The coating composition of the present invention may contain other components in addition to the above-mentioned fluorinated polymer aqueous dispersion. Examples of other components include a film-forming agent and a binder resin.

[0895] The coating composition of the present invention can be prepared by mixing the fluoropolymer aqueous dispersion of the present invention with other components. In addition, the fluoropolymer aqueous dispersion of the present invention can also be mixed with an aqueous medium to prepare a coating composition with adjusted solid content concentration. In addition, the fluoropolymer aqueous dispersion of the present invention can also be mixed with a nonionic surfactant to prepare a coating composition with adjusted nonionic surfactant content. The coating composition of the present invention can have a fluoropolymer content different from that of the fluoropolymer aqueous dispersion of the present invention, and can also have a nonionic surfactant content different from that of the fluoropolymer aqueous dispersion of the present invention.

[0896] In one embodiment, the coating composition of the present invention contains a fluorine-containing compound with a hydrophilic group having a carbon number of 7 or less. The content of the fluorine-containing compound with a hydrophilic group having a carbon number of 7 or less in the coating composition is greater than 0 mass ppb and less than 300 mass ppb relative to the coating composition. The preferred upper limit of the content of the fluorine-containing compound with a hydrophilic group having a carbon number of 7 or less in the coating composition is 280 mass ppb or less, 260 mass ppb or less, 240 mass ppb or less, 220 mass ppb or less, 200 mass ppb or less, 180 mass ppb or less, 160 mass ppb or less or 140 mass ppb or less. The preferred lower limit of the content of the fluorine-containing compound with a hydrophilic group having a carbon number of 7 or less in the coating composition is 0.1 mass ppb or more, 1 mass ppb or more, 5 mass ppb or more, 10 mass ppb or more, 20 mass ppb or more, 30 mass ppb or more, 40 mass ppb or more or 50 mass ppb or more.

[0897] As the fluorinated compound having a hydrophilic group of less than 7 carbon atoms, the above-mentioned fluorinated surfactant having a carbon number of less than 7 used in the polymerization of the fluorinated monomer can be cited. That is, in one embodiment of the coating composition, as the fluorinated compound having a hydrophilic group of less than 7 carbon atoms, at least a fluorinated surfactant having a carbon number of less than 7 carbon atoms is contained.

[0898] In one embodiment, the coating composition of the present invention contains a fluorinated compound with a hydrophilic group. The content of the fluorinated compound with a hydrophilic group in the coating composition is greater than 0 mass ppb and less than 300 mass ppb relative to the coating composition. The preferred upper limit of the content of the fluorinated compound with a hydrophilic group with a carbon number of 7 or less in the coating composition is 280 mass ppb or less, 260 mass ppb or less, 240 mass ppb or less, 220 mass ppb or less, 200 mass ppb or less, 180 mass ppb or less, 160 mass ppb or less or 140 mass ppb or less. The preferred lower limit of the content of the fluorinated compound with a hydrophilic group with a carbon number of 7 or less in the coating composition is 0.1 mass ppb or more, 1 mass ppb or more, 5 mass ppb or more, 10 mass ppb or more, 20 mass ppb or more, 30 mass ppb or more, 40 mass ppb or more or 50 mass ppb or more.

[0899] Examples of the fluorine-containing compound having a hydrophilic group include the above-mentioned fluorine-containing surfactants used in the polymerization of the fluorine-containing monomer.

[0900] <Film-forming agent>

[0901] In one embodiment of the coating composition of the present invention, a film-forming agent is contained. When the film-forming agent is contained, the coating composition can suppress the occurrence of cracks in the obtained film during drying, and has excellent workability.

[0902] Examples of the film-forming agent include acrylic resins such as depolymerizable acrylic resins, urethane resins, polyethylene glycol, and polypropylene glycol.

[0903] When the coating composition of the present invention is applied, dried, and then fired, the depolymerizable acrylic resin slowly decomposes while maintaining its binder effect on the fluorine-containing polymer, thereby preventing the occurrence of cracks.

[0904] In one embodiment of the coating composition of the present invention, a depolymerizable acrylic resin is contained together with PTFE. As a depolymerizable acrylic resin, it is preferred that even if depolymerization starts from below the melting point of PTFE, there is still a residue until the temperature (melting temperature) at which PTFE begins to melt, and decomposition and volatilization occur at the firing (processing) temperature. For example, it is preferred that at least 5% or more, especially at least 50% or more of 10%, preferably at least 20% remain at the melting temperature of PTFE (usually 240°C to 345°C), and only less than 10%, especially less than 5%, remain at the firing (processing) temperature (usually a temperature exceeding the melting temperature of PTFE to 415°C, preferably 360°C to 400°C), and substantially no residue remains when firing is completed. From this aspect, the depolymerization (decomposition) temperature of the depolymerizable acrylic resin is preferably about 200°C or more and lower than the firing (processing) temperature. In particular, regardless of the type of resin, from the perspective of balancing the effect of preventing shrinkage cracks and the effect of preventing coloration, it is preferred that about 25% to 50% of the depolymerizable acrylic resin remain in the temperature range of 300°C to 320°C and about 20% to 10% remain in the temperature range of 330°C to 345°C. Any depolymerizable acrylic resin that satisfies this condition may be used.

[0905] Regarding depolymerization, as described in "Polym. Eng. Sci." Vol. 6, p. 273 (1966), "Plast. Massy." Vol. 75, p. 48 (1971), and "Degradation of Polymer Materials" by Corona, p. 144 (1958), generally, the more branches there are in a polymer chain, the weaker the CC bond and CH bond are, and the easier it is to oxidatively decompose and depolymerize. Examples of depolymerizable acrylic resins include methacrylate resins, and specifically, preferably, for example, those represented by formula (8):

[0906] CH2=C(CH3)COOR

[0907] A methacrylate homopolymer or copolymer having a methacrylate monomer represented by (wherein R is an alkyl group or hydroxyalkyl group having 1 to 5 carbon atoms) as an essential component. Specific examples of methacrylate monomers include methyl methacrylate, ethyl methacrylate, propyl methacrylate, dimethylpropyl methacrylate, butyl methacrylate, and pentyl methacrylate. Among these, a depolymerizable acrylic resin having butyl methacrylate as a monomer is preferred because of its low glass transition temperature and good depolymerization (decomposability).

[0908] Even a homopolymer has no problem as long as it can form a stable emulsion. From the viewpoint of stabilizing the emulsion, a monomer having a carboxyl group or a hydroxyl group can be used as a suitable comonomer.

[0909] As for the depolymerizable acrylic resin, for example, microparticles (depolymerizable acrylic resin emulsion) produced by emulsion polymerization or the like can be used directly, and the average particle size is preferably 0.1 μm to 100 μm, and particularly preferably 0.2 μm to 1 μm. If the average particle size is less than 0.1 μm, cracks tend to be easily generated, and if it exceeds 100 μm, coating tends to be difficult.

[0910] In the coating composition of the present invention, the content of the depolymerizable acrylic resin is preferably 5 to 25 parts, more preferably 7 to 20 parts, and even more preferably 10 to 15 parts based on 100 parts of the fluorinated polymer, from the viewpoint of film-forming properties and prevention of film coloration.

[0911] The depolymerizable acrylic resin is preferably mixed with other components in the form of an emulsion.

[0912] <Binder Resin>

[0913] In one embodiment of the coating composition of the present invention, a binder resin is contained. When the binder resin is contained, the coating composition can provide a film having excellent adhesion to the substrate. The binder resin has the effect of increasing the film hardness and gloss of the obtained film.

[0914] Examples of the binder resin include polyamideimide (PAI), polyimide (PI), polyethersulfone (PES), polyarylether sulfide (PAS), polyetherimide, polyetheretherketone, and aromatic polyester. The binder resin may be used alone or in combination of two or more.

[0915] PAI is a resin composed of a polymer having an amide bond and an imide bond in the molecular structure. The PAI is not particularly limited, and examples thereof include resins composed of high molecular weight polymers obtained by the following reactions: reaction of an aromatic diamine having an amide bond in the molecule with an aromatic tetracarboxylic acid such as pyromellitic acid; reaction of an aromatic tricarboxylic acid such as trimellitic anhydride with a diamine such as 4,4-diaminophenyl ether or a diisocyanate such as diphenylmethane diisocyanate; reaction of a dibasic acid having an aromatic imide ring in the molecule with a diamine; and the like. From the perspective of excellent heat resistance, PAI is preferably composed of a polymer having an aromatic ring in the main chain.

[0916] PI is a resin composed of a polymer having an imide bond in the molecular structure. PI is not particularly limited, and examples thereof include resins composed of high molecular weight polymers obtained by reaction of aromatic tetracarboxylic anhydrides such as pyromellitic dianhydride, etc. From the perspective of excellent heat resistance, PI is preferably composed of a polymer having an aromatic ring in the main chain.

[0917] PES has the following general formula:

[0918] [Chemistry 22]

[0919]

[0920] PES is not particularly limited, and examples thereof include resins composed of polymers obtained by polycondensation of dichlorodiphenyl sulfone and bisphenol.

[0921] PAS is a resin composed of a polymer having a repeating unit represented by the general formula -[Ar-S]- (wherein Ar represents an arylene group). The PAS is not particularly limited, and examples thereof include polyphenylene sulfide (PPS) and the like.

[0922] As the binder resin, since it can provide a film with better adhesion to the substrate, it is preferably selected from at least one of the group consisting of PAI, PI, PES and PPS, and PAI is more preferred. In addition, from the aspect of being able to suppress coloration during firing and being able to increase the degree of freedom of the color tone of the film, as the binder resin, PES is preferred. As the binder resin, using PAI and PES in combination is also one of the preferred methods.

[0923] In the coating composition of the present invention, the content of the binder resin is preferably 5% by mass or more, more preferably 8% by mass or more, preferably 15% by mass or less, more preferably 12% by mass or less relative to the coating composition. If the content of the binder resin is within the above range, a film having better adhesion to the substrate can be provided.

[0924] In the coating composition of the present invention, the mass ratio of the fluorinated polymer to the binder resin (fluorinated polymer / binder resin) is preferably 90 / 10 to 50 / 50, more preferably 85 / 15 to 60 / 40, and further preferably 80 / 20 to 70 / 30. If the mass ratio of the fluorinated polymer to the binder resin is within the above range, a film having better adhesion to the substrate can be provided.

[0925] The coating composition of the present invention may also contain other ingredients. Other ingredients include preservatives, water-soluble polymer compounds, pigments, fillers, defoamers, desiccants, thickeners, organic solvents, leveling agents, anti-cratering agents, dispersants, antifreeze agents, solid lubricants, anti-settling agents, moisture absorbers, surface conditioners, thixotropy imparting agents, viscosity modifiers, anti-gelling agents, ultraviolet light absorbers, HALS (light stabilizers), matting agents, plasticizers, anti-floating agents, anti-skinning agents, anti-scratch agents, rust inhibitors, mildew inhibitors, antibacterial agents, antioxidants, flame retardants, anti-dripping agents, antistatic agents, silane coupling agents, various reinforcing materials, various bulking materials, conductive fillers, colloidal silica, etc.

[0926] The coating composition of the present invention contains a preservative, and thus, even when the coating composition is stored for a long period of time, corruption of the coating composition and growth of bacteria can be suppressed.

[0927] Examples of the preservative include isothiazolone-based preservatives, azole-based preservatives, bromopol, thiophanate-methyl, methylsulfonyl tetrachloropyridine, carbendazim, 2-[(dichlorofluoromethyl)-thio]-1H-isoindole-1,3-(2H)-dione (Fluor Folpet), sodium diacetate, and diiodomethyl-p-tolylsulfone.

[0928] The content of the anticorrosive in the coating composition of the present invention is preferably 0.01 to 0.5% by mass, more preferably 0.05 to 0.2% by mass, based on the fluorinated polymer.

[0929] Examples of water-soluble polymer compounds include methyl cellulose, alumina sol, polyvinyl alcohol, carboxylated vinyl polymers, polyethylene oxide (dispersion stabilizer), polyethylene glycol (dispersion stabilizer), polyvinyl pyrrolidone (dispersion stabilizer), phenolic resins, urea resins, epoxy resins, melamine resins, polyester resins, polyether resins, acrylic silicone resins, silicone resins, silicone polyester resins, polyurethane resins, and the like.

[0930] As the pigment, various conventionally known pigments can be used, such as titanium oxide, carbon black, red iron oxide, extender pigments, etc. In the coating composition of the present invention, the content of the pigment is preferably 0.1% to 20.0% by mass, more preferably 1% to 10% by mass, relative to the coating composition.

[0931] Examples of the filler include inorganic fillers, diamond, fluorinated diamond, carbon black, and the like.

[0932] Inorganic fillers include, in addition to pigments, mica particles, mica particles coated with pigments, titanium-coated mica, inorganic nitrides, carbides, borides and oxides of zirconium, tantalum, titanium, tungsten, silicon, aluminum or beryllium (specifically, aluminum oxide, silicon carbide, zirconium oxide, zirconium carbide, etc.), metal flakes, metal powder, clay, talc, tourmaline, jade, germanium, corundum, silica, chrysoberyl, topaz, beryl, garnet, quartz, garnet, barium sulfate, glass, etc.

[0933] The inorganic filler has the function of improving wear resistance, and mica is preferred from the aspect of giving beauty. The particle size of the mica particles is 10 μm to 100 μm, preferably 15 μm to 50 μm. If the particle size is less than 10 μm, there is a tendency for reduced wear resistance and reduced brilliance, and if it is greater than 100 μm, there is a tendency for reduced non-adhesiveness. Mica particles coated with pigments are obtained by, for example, attaching pigments such as TiO2·Fe2O3 to the above-mentioned mica particles by sintering vapor deposition method or the like.

[0934] As the metal flakes, for example, flakes of titanium, zirconium, aluminum, zinc, antimony, tin, iron, nickel, etc. can be cited, and titanium and zirconium are preferred from the aspect of being less prone to rust. As the size, the size within the range generally used in coatings can be used.

[0935] Examples of the metal powder include powders of gold, silver, copper, platinum, and stainless steel.

[0936] As the defoaming agent, various aqueous defoaming agents can be used, for example: lower alcohols such as methanol, ethanol, butanol, etc.; higher alcohols such as amyl alcohol, polypropylene glycol and its derivatives, etc.; oils and fats such as oleic acid, tall oil, mineral oil, soap, etc.; surfactants such as sorbitan fatty acid esters, polyethylene glycol fatty acid esters, Pluronic (registered trademark) type nonionic surfactants, etc.; silicone-based surfactants such as siloxanes, silicone resins, etc., which can be used alone or in combination. Representative commercial products of defoamers include B-series products such as Adekanate B and Adekanate B1068 (manufactured by Asahi Denka Kogyo Co., Ltd.); SN Defoamer series products such as Foamaster DL, NOPCO NXZ, SN Defoamer 113, 325, 308, and 368; Dehydran 1293 and Dehydran 1513 (manufactured by SAN NOPCO Co., Ltd.); Flownon SB-110N, SB-210, 510, 551, Aqualen 800, 805, and Aqualen 1488 (manufactured by Kyoeisha Chemical Co., Ltd.); Surfynol 104E and 440 (acetylene-based defoamers manufactured by Air Products); KS-607A (manufactured by Shin-Etsu Chemical Co., Ltd.); FS Antifoam (manufactured by Dow Corning); BYK-020, 031, 073, and W (Big Chemi Co., Ltd.); Dehydran 981 (manufactured by Henkel Hakusui Co., Ltd.); Epan-410, 710, 720 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.); Tego Foamex series (manufactured by Tego Goldschmidt Co., Ltd.); Foamlex-747, TY-10, EP series (manufactured by Nikka Chemical Co., Ltd.), etc. The content of the defoaming agent in the coating composition is preferably 0.01% by mass to 10% by mass, and more preferably 0.05% by mass to 5% by mass.

[0937] Examples of the desiccant include cobalt oxide and the like.

[0938] Examples of the thickener include methylcellulose, polyvinyl alcohol, carboxylated vinyl polymers, etc. The content of the thickener in the coating composition of the present invention is preferably 0.1% by mass to 20% by mass, more preferably 0.5% by mass to 10% by mass.

[0939] As the organic solvent, a high boiling point polyol is preferred. The high boiling point polyol can prevent the occurrence of cracks when the coating composition of the present invention is applied and then dried.

[0940] High boiling point polyols (hereinafter referred to as polyols) have two or more hydroxyl groups and a boiling point of 100°C or more. Polyols containing nitrogen atoms are not preferred because they cause coloring due to thermal decomposition during firing. The boiling point is preferably above the drying temperature of the coating composition, more preferably above 150°C, and particularly preferably above 200°C. The preferred number of hydroxyl groups in the polyol is 2 to 3. Substances with 1 or zero hydroxyl groups and a boiling point of 100°C or more have poor hydrophilicity and are therefore difficult to mix uniformly. When the number of hydroxyl groups is 4 or more, most of them are solid at room temperature, and it is difficult to expect an effect of preventing cracking.

[0941] The polyol needs to eventually evaporate or decompose to volatilize light by heating during firing described below. Therefore, the boiling point or thermal decomposition temperature is preferably lower than the melting temperature of the fluorinated polymer or PTFE contained in the coating composition, preferably 340° C. or lower.

[0942] Preferred polyols include, for example, one or more of ethylene glycol (boiling point: 198° C.), 1,2-propylene glycol (boiling point: 188° C.), 1,3-propylene glycol (boiling point: 214° C.), 1,2-butylene glycol (boiling point: 190° C.), 1,3-butylene glycol (boiling point: 208° C.), 1,4-butylene glycol (boiling point: 229° C.), 1,5-pentanediol (boiling point: 242° C.), 2-butene-1,4-diol (boiling point: 235° C.), glycerol (boiling point: 290° C.), 2-ethyl-2-hydroxymethyl-1,3-propanediol (boiling point: 295° C.), and 1,2,6-hexanetriol (boiling point: 178° C. / under a pressure of 5 mmHg). Among them, glycerol is preferred.

[0943] In the coating composition of the present invention, the content of the polyol is generally 5% to 18% by mass, preferably 7% to 15% by mass, and particularly preferably 7% to 12% by mass relative to the fluorinated polymer. By making the content of the polyol within the above range, the coloring of the obtained film can be prevented while preventing the generation of cracks.

[0944] In addition, as required, an organic solvent other than the high boiling point polyol may be mixed within a range that does not impair the effects of the present invention. Examples of such organic solvents include aromatic hydrocarbon solvents such as toluene and xylene, aliphatic hydrocarbon solvents having 9 to 11 carbon atoms, and aliphatic hydrocarbon solvents having 10 to 12 carbon atoms.

[0945] By using the coating composition of the present invention, a coating film can be obtained. The coating film obtained from the coating composition of the present invention has excellent water- and oil-repellency and low friction.

[0946] Although the embodiments have been described above, it should be understood that various modifications may be made to the embodiments and details without departing from the spirit and scope of the claims.

[0947] <1> According to a first aspect of the present invention, there is provided a method for producing an aqueous fluorinated polymer dispersion, which is a method for producing an aqueous fluorinated polymer dispersion containing a fluorinated polymer, wherein:

[0948] In the reactor, in the presence of a fluorinated surfactant, a polymerization initiator and an aqueous medium, a fluorinated monomer is polymerized to prepare an aqueous dispersion containing a fluorinated polymer.

[0949] Heat treatment of the aqueous dispersion,

[0950] A nonionic surfactant is added to the heat-treated aqueous dispersion.

[0951] An aqueous dispersion containing a nonionic surfactant is brought into contact with an ion exchange resin.

[0952] The aqueous dispersion obtained after contacting with the ion exchange resin is concentrated.

[0953] <2> According to a second aspect of the present invention, there is provided a production method based on the first aspect, wherein after preparing the aqueous dispersion by polymerization and before heat-treating the aqueous dispersion, at least one of (a) removing the fluorinated monomer remaining in the reactor from the reactor and (b) recovering the aqueous dispersion in the reactor and storing it in a container different from the reactor is carried out.

[0954] <3> According to a third aspect of the present invention, there is provided the production method according to the second aspect, wherein a radical generator is added to the aqueous dispersion after at least one of the operations (a) and (b) is performed and before the aqueous dispersion is heat treated.

[0955] <4> According to a fourth aspect of the present invention, there is provided a production method based on any one of the first to third aspects, wherein a free radical generator is added to the aqueous dispersion after the aqueous dispersion is prepared by polymerization and before the aqueous dispersion is heat-treated, thereby preparing an aqueous dispersion containing the free radical generator.

[0956] <5> According to a fifth aspect of the present invention, there is provided the production method according to any one of the first to fourth aspects, wherein the temperature of the heat treatment is 50° C. or higher.

[0957] <6> According to a sixth aspect of the present invention, there is provided the production method according to the fifth aspect, wherein the aqueous dispersion is cooled to less than 50° C. after the heat treatment and before the aqueous dispersion is brought into contact with the ion exchange resin.

[0958] <7> According to the seventh aspect of the present invention, there is provided a production method based on any one of the first to sixth aspects, wherein a nonionic surfactant is added to an aqueous dispersion that has been subjected to a heat treatment, thereby preparing an aqueous dispersion in which the content of the nonionic surfactant in the aqueous dispersion is 5% by mass or more relative to the fluorinated polymer.

[0959] <8> According to an eighth aspect of the present invention, there is provided the production method according to any one of the first to seventh aspects, wherein the nonionic surfactant is represented by the general formula (i).

[0960] R 6 -OA 1 -H(i)

[0961] (Where R 6 is a linear or branched primary or secondary alkyl group having 8 to 18 carbon atoms, 1 is a polyoxyalkylene chain.)

[0962] <9> According to a ninth aspect of the present invention, there is provided the production method according to any one of the first to eighth aspects, wherein the contact between the aqueous dispersion and the ion exchange resin is repeated two or more times.

[0963] <10> According to a tenth aspect of the present invention, there is provided a production method according to any one of the first to ninth aspects, wherein the aqueous dispersion is concentrated by separating the aqueous dispersion into two or more phases and recovering the concentrated phase.

[0964] <11> According to an eleventh aspect of the present invention, there is provided the production method according to any one of the first to tenth aspects, wherein a nonionic surfactant is added to the concentrated aqueous dispersion.

[0965] <12> According to a twelfth aspect of the present invention, there is provided an aqueous fluorine-containing polymer dispersion comprising a fluorine-containing polymer, a nonionic surfactant and a fluorine-containing compound having a hydrophilic group having 7 or less carbon atoms.

[0966] The content of the fluorinated polymer is 50% to 70% by mass based on the fluorinated polymer aqueous dispersion.

[0967] The content of the nonionic surfactant is 4.0% to 12% by mass based on the fluorinated polymer.

[0968] The content of the fluorine-containing compound having a hydrophilic group and having 7 or less carbon atoms is more than 0 ppb by mass and less than 300 ppb by mass based on the aqueous fluorine-containing polymer dispersion.

[0969] <13> According to a thirteenth aspect of the present invention, there is provided the aqueous fluorinated polymer dispersion according to the twelfth aspect, wherein the nonionic surfactant is represented by the general formula (i).

[0970] R 6 -OA 1 -H(i)

[0971] (Where R 6 is a linear or branched primary or secondary alkyl group having 8 to 18 carbon atoms, 1 is a polyoxyalkylene chain.)

[0972] <14> According to a fourteenth aspect of the present invention, there is provided the aqueous fluorinated polymer dispersion according to the twelfth aspect or the thirteenth aspect, wherein the fluorinated polymer contains a perfluoro(alkyl vinyl ether) unit.

[0973] <15> According to a fifteenth aspect of the present invention, there is provided the aqueous fluorinated polymer dispersion according to the fourteenth aspect, which substantially does not contain a fluorinated compound having a hydrophilic group represented by the general formula (2).

[0974] General formula (2): [C n-1 F 2n-1 COO - ]M +

[0975] (where n represents an integer from 9 to 14, M + represents a cation.)

[0976] <16> According to a sixteenth aspect of the present invention, there is provided the aqueous fluorinated polymer dispersion according to any one of the twelfth to fifteenth aspects, wherein the fluorinated polymer is polytetrafluoroethylene.

[0977] <17> According to a seventeenth aspect of the present invention, there is provided a coating composition comprising the aqueous fluorinated polymer dispersion according to any one of the twelfth to sixteenth aspects.

[0978] Example

[0979] Next, embodiments of the present invention will be described with reference to examples, but the present invention is not limited to these examples.

[0980] Each numerical value in the examples was measured by the following method.

[0981] (1) Solid content concentration (P)

[0982] About 1 g (Xg) of the sample was taken into an aluminum cup with a diameter of 5 cm, heated at 110°C for 30 minutes, and further heated at 300°C for 30 minutes. The heating residual component (Zg) was determined by the formula: P = Z / X×100 (mass %).

[0983] (2) Average primary particle size

[0984] The PTFE aqueous dispersion was diluted with water to a solid content concentration of 0.15% by mass, and the transmittance of the projected light at 550 nm relative to the unit length of the obtained diluted aqueous dispersion was measured, and the number-based length average primary particle size determined by measuring the oriented diameter using a transmission electron microscope photograph was prepared to prepare a calibration curve. Using this calibration curve, the average primary particle size was determined from the measured transmittance of the projected light at 550 nm of each sample.

[0985] (3) pH

[0986] The pH at 25° C. was measured using a glass electrode (manufactured by Horiba, Ltd.) in accordance with JIS K6893.

[0987] (4) Standard specific gravity (SSG)

[0988] The measurement was performed by the water displacement method according to ASTM D-792 using a sample molded according to ASTM D4895-89.

[0989] (5) Content of modified monomer

[0990] The content of perfluoro(propyl vinyl ether) (PPVE) was determined as follows: a film disk was prepared by press-molding PTFE powder, and the infrared absorbance of the film disk was measured by FT-IR. -1 Absorbance / 935cm -1 The absorbance ratio is multiplied by 0.14.

[0991] (6) Content of nonionic surfactant (N)

[0992] About 1 g (Xg) of the sample was taken from an aluminum cup with a diameter of 5 cm, and the amount obtained by subtracting the stabilizer from the amount calculated by the formula: N = [(YZ) / Z] × 100 (mass %) was used as the content of the nonionic surfactant based on the heating residual component (Yg) obtained by heating at 110°C for 30 minutes and the heating residual component (Zg) obtained by heating the obtained heating residual component (Yg) at 300°C for 30 minutes. The stabilizer was calculated based on the amount added during preparation.

[0993] (7) Viscosity

[0994] The viscosity at 25° C. was measured using a B-type rotational viscometer (manufactured by Toki Sangyo Co., Ltd., rotor No. 2) at a rotation speed of 60 rpm and a measurement time of 120 seconds.

[0995] (8) Determination of the content of fluorinated compounds having a hydrophilic group and having 7 or less carbon atoms

[0996] 5.0 g of the aqueous dispersion was weighed, 10 g of methanol was added, and the mixture was passed through a cylindrical filter paper. Soxhlet extraction was performed with a total amount of 150 g of methanol as an extraction solvent. The obtained extract was fixed to 250 ml with methanol to obtain an extract containing a fluorinated compound having a hydrophilic group with a carbon number of 7 or less.

[0997] Calibration curve

[0998] Five levels of methanol standard solutions of fluorinated compounds with hydrophilic groups having carbon atoms of 7 or less and known concentrations of 0.1 ng / mL to 100 ng / mL were prepared and measured using a liquid chromatography mass spectrometer (Waters, LC-MS ACQUITY UPLC / TQD). A calibration curve was prepared using first order approximation from the concentration of each sample and the integrated value of the peak.

[0999] The content of the fluorinated compound having a hydrophilic group of 7 or less carbon atoms was measured using a liquid chromatography-mass spectrometer. The peak area of ​​the fluorinated compound having a hydrophilic group of 7 or less carbon atoms was determined by the MRM method for the extract, and the content of the fluorinated compound having a hydrophilic group of 7 or less carbon atoms contained in the aqueous dispersion was determined. The quantitative limit was 10 mass ppb.

[1000] (9) Determination of the content of the fluorine-containing compound having a hydrophilic group represented by the general formula (2)

[1001] 5.0 g of the aqueous dispersion was weighed, 10 g of methanol was added, and the mixture was passed through a cylindrical filter paper. Soxhlet extraction was performed with a total amount of 150 g of methanol as the extraction solvent. The obtained extract was fixed to 250 ml with methanol to obtain an extract containing a fluorine-containing compound having a hydrophilic group represented by the general formula (2).

[1002] General formula (2): [C n-1 F 2n-1 COO - ]M +

[1003] (where n represents an integer from 9 to 14, M + represents a cation.)

[1004] Calibration curve

[1005] Five methanol standard solutions of perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnDA), perfluorododecanoic acid (PFDoDA), perfluorotridecanoic acid (PFTrDA), and perfluorotetradecanoic acid (PFTeDA) with known concentrations were prepared at 0.1 ng / mL to 50 ng / mL, and measured using a liquid chromatography mass spectrometer (Waters, LC-MSACQUITY UPLC / TQD). A calibration curve was prepared using first order approximation from the concentration of each sample and the integrated value of the peak.

[1006] The content of the fluorinated compound having a hydrophilic group represented by the general formula (2) was determined using a liquid chromatography mass spectrometer. For the extract, the peak area of ​​the fluorinated compound having a hydrophilic group represented by the general formula (2) was determined by the MRM method, and the content of the fluorinated compound having a hydrophilic group represented by the general formula (2) contained in the aqueous dispersion was determined. The quantitative limit was 10 mass ppb.

[1007] Measurement equipment structure and LC-MS measurement conditions

[1008]

[1009] MRM assay parameters

[1010] [Table 2]

[1011] Table 2

[1012]

[1013] The average molecular structure of the surfactant used in Examples and Comparative Examples is shown below.

[1014] Surfactant (a): C 13 H 27 O(CH2CH2O)8H (average number of methyl groups per molecule: 4.0), HLB 13.30, cloud point 60°C

[1015] Surfactant (b): C 13 H 27 O(CH2CH2O) 10 H (average number of methyl groups per molecule: 4.0), HLB: 13.80, cloud point: 71°C

[1016] Synthesis example 1

[1017] A white solid A was obtained by the method described in Synthesis Example 1 of International Publication No. 2021 / 045228. The obtained white solid A is a fluorine-containing compound having a hydrophilic group and having 7 or less carbon atoms.

[1018] Production Example 1

[1019] 3580 g of deionized water, 160 g of paraffin wax, and 4.7 g of the white solid A obtained in Synthesis Example 1 as a fluorinated surfactant were added to a 6 L SUS reactor with a stirrer. Next, the contents of the reactor were heated to 70°C while being sucked out, and TFE was purged to remove oxygen from the reactor, and the contents were stirred. 6.5 g of PPVE was pressed into the reactor with TFE. 50 mg of APS dissolved in 20 g of deionized water was injected into the reactor as an initiator to a pressure of 1.5 MPaG. TFE was added in such a way that the pressure was constant at 1.5 MPaG. When the TFE consumed in the reaction reached 1543 g, the supply of TFE was stopped, stirring was stopped, and the reaction was terminated.

[1020] Then, the pressure in the reactor was evacuated until it reached atmospheric pressure, and then further reduced to -0.01 MPaG. Nitrogen gas was introduced into the reactor to return to atmospheric pressure (0.00 MPaG), thereby obtaining PTFE aqueous dispersion 1-1.

[1021] The PTFE aqueous dispersion 1-1 was taken out from the reactor into the atmosphere and cooled to remove the paraffin, thereby obtaining the PTFE aqueous dispersion 1-2. The obtained PTFE aqueous dispersion 1-2 had a solid content concentration of 30.0% by mass and an average primary particle size of 270 nm.

[1022] The obtained PTFE aqueous dispersion 1-2 was diluted with deionized water to a solid content concentration of about 10% by mass, and solidified under high-speed stirring conditions, and the solidified wet powder was dried at 150° C. for 18 hours. The standard specific gravity of the obtained PTFE powder was 2.163, and the PPVE content was 0.28% by mass.

[1023] Comparative Example 1

[1024] A PTFE aqueous dispersion C-1 was prepared by adding 10 parts by mass of a surfactant (a) as a nonionic surfactant to the PTFE aqueous dispersion 1-2 obtained in Preparation Example 1. A strongly basic anion exchange resin was added to the PTFE aqueous dispersion C-1 in an amount of 60 parts by mass to the PTFE aqueous dispersion C-1, and the mixture was stirred steadily for 180 minutes, and then the anion exchange resin was separated by filtration to obtain a PTFE aqueous dispersion C-2.

[1025] Furthermore, an anion exchange resin was added again to the PTFE aqueous dispersion C-2, and after stirring steadily for 180 minutes, the anion exchange resin was separated by filtration to obtain a PTFE aqueous dispersion C-3.

[1026] Surfactant (a) was added to the obtained PTFE aqueous dispersion C-3 in an amount of 16 parts by mass relative to 100 parts by mass of PTFE, and the mixture was kept at 63°C for 3 hours to separate into a supernatant phase and a concentrated phase. Only the concentrated phase was recovered to obtain a PTFE aqueous dispersion C-4.

[1027] The solid content concentration of the obtained PTFE aqueous dispersion C-4 was 69.1% by mass, and the content of the nonionic surfactant was 2.7% by mass based on the PTFE.

[1028] To the obtained PTFE aqueous dispersion C-4, surfactant (b) was added in an amount of 5.0% by mass relative to PTFE, ammonium lauryl sulfate was added in an amount of 500 ppm relative to PTFE, an isothiazolone-based preservative was added in an amount of 1000 ppm relative to PTFE, and aqueous ammonia was added in an amount of pH 9.5. Furthermore, deionized water was added in an amount of 63% by mass of solid content to obtain PTFE aqueous dispersion C-5. The obtained PTFE aqueous dispersion C-5 had a solid content concentration of 62.9% by mass, a nonionic surfactant content of 5.0% by mass relative to PTFE, a pH of 9.5, and a viscosity of 26.8 mPa·s.

[1029] The content of the fluorinated compound having a hydrophilic group of 7 or less carbon atoms, such as the fluorinated surfactant, synthesized in Synthesis Example 1 was 560 ppb by mass based on the aqueous dispersion.

[1030] The contents of the fluorine-containing compounds having a hydrophilic group represented by the general formula (2) were all below the quantitative limit (10 mass ppb).

[1031] Example 1

[1032] The entire PTFE aqueous dispersion 1-2 obtained in Preparation Example 1 was transferred to a heat treatment container. The container was heated to 80° C. in an air atmosphere for 30 minutes, and 2.6 g of ammonium persulfate dissolved in 40 g of deionized water was further added as a free radical generator (1.0 mole times the mole of the fluorinated compound having a hydrophilic group with a carbon number of 7 or less in the aqueous dispersion) and maintained for 3 hours to obtain a PTFE aqueous dispersion 1-3.

[1033] A PTFE aqueous dispersion 1-4 was obtained in the same manner as in Comparative Example 1 except that the PTFE aqueous dispersion 1-3 was used instead of the PTFE aqueous dispersion 1-2 obtained in Preparation Example 1, a nonionic surfactant was added, the dispersion was brought into contact with an anion exchange resin twice, phase separation and concentration were performed, and only the concentrated phase was recovered.

[1034] The solid content concentration of the obtained PTFE aqueous dispersion 1-4 was 70.2% by mass, and the content of the nonionic surfactant was 2.6% by mass based on the PTFE.

[1035] To the obtained PTFE aqueous dispersion 1-4, surfactant (b), ammonium lauryl sulfate, isothiazolone-based preservative, and ammonia water were added in the same manner as in Comparative Example 1. Furthermore, deionized water was added so that the solid content became 63% by mass, thereby obtaining a PTFE aqueous dispersion 1-5. The obtained PTFE aqueous dispersion 1-5 had a solid content concentration of 63.0% by mass, a nonionic surfactant content of 5.0% by mass relative to PTFE, a pH of 9.6, and a viscosity of 26.2 mPa·s.

[1036] The content of the fluorinated compound having a hydrophilic group of 7 or less carbon atoms, such as the fluorinated surfactant, synthesized in Synthesis Example 1 was 110 ppb by mass based on the aqueous dispersion.

[1037] The contents of the fluorine-containing compounds having a hydrophilic group represented by the general formula (2) and having a carbon number n of 9 to 14 were all below the quantitative limit (10 mass ppb).

[1038] Example 2

[1039] Surfactant (a) and deionized water were added to the PTFE aqueous dispersion 1-4 obtained in Example 1 so that the ratio of the nonionic surfactant to PTFE and the ratio of water to PTFE were the same as those before phase separation and concentration in Example 1, and the mixture was kept at 61° C. for 3 hours to separate into a supernatant phase and a concentrated phase. Only the concentrated phase was recovered to obtain a PTFE aqueous dispersion 2-1.

[1040] The solid content concentration of the obtained PTFE aqueous dispersion 2-1 was 71.5% by mass, and the content of the nonionic surfactant was 2.4% by mass based on the PTFE.

[1041] To the obtained PTFE aqueous dispersion 2-1, surfactant (b), ammonium lauryl sulfate, isothiazolone-based preservative, and ammonia water were added in the same manner as in Comparative Example 1. Furthermore, deionized water was added so that the solid content became 63% by mass, thereby obtaining PTFE aqueous dispersion 2-2. The obtained PTFE aqueous dispersion 2-2 had a solid content concentration of 62.9% by mass, a nonionic surfactant content of 5.1% by mass relative to PTFE, a pH of 9.5, and a viscosity of 26.0 mPa·s.

[1042] The content of the fluorinated compound having a hydrophilic group of 7 or less carbon atoms, such as the fluorinated surfactant, synthesized in Synthesis Example 1 was 52 ppb by mass based on the aqueous dispersion.

[1043] The contents of the fluorine-containing compounds having a hydrophilic group represented by the general formula (2) and having a carbon number n of 9 to 14 were all below the quantitative limit (10 mass ppb).

[1044] Next, embodiments of coating compositions containing the PTFE aqueous dispersions obtained in the above-mentioned Examples and Comparative Examples will be described with reference to Examples.

[1045] Each numerical value in the examples was measured by the following method.

[1046] <Contact Angle>

[1047] The contact angles with respect to water and n-hexadecane were measured using a contact angle meter CA-DT manufactured by Kyowa Interface Science Co., Ltd.

[1048] <Friction coefficient>

[1049] Using a surface property tester HEIDON Type 38 manufactured by Shinto Scientific Co., Ltd., a load (1 kg) was pressed (ball indenter) to measure the static friction coefficient and the dynamic friction coefficient when moving at a speed of 600 mm / min.

[1050] In Comparative Example 2 and Examples 3 and 4, the following various materials were used.

[1051] Polyamide-imide resin aqueous dispersion:

[1052] Aqueous dispersion of polyamide-imide resin varnish prepared by the method described in Preparation Example 1 of International Publication No. 2016 / 147790

[1053] 50 mass % aqueous solution of nonionic surfactant:

[1054] 50 mass% aqueous solution of polyoxyethylene alkyl ether

[1055] Carbon black pigment grinding base (solid content concentration: 20 mass %):

[1056] Aqueous black pigment paste obtained by grinding commercially available carbon black pigment (average particle size 100 nm or less) with a nonionic surfactant and water in a sand mill using glass beads as a dispersion medium

[1057] Thickener: Methylcellulose

[1058] Leveling agent: acetylenic diol

[1059] Depolymerizable acrylic resin emulsion: butyl methacrylate resin, average particle size 0.3 μm, butyl methacrylate resin content 40% by mass

[1060] Hydrocarbon solvent: a mixture of C10-C12 aliphatic saturated hydrocarbons

[1061] Comparative Example 2

[1062] The following components were stirred and mixed, thereby obtaining a primer composition P-1.

[1063]

[1064] Separately, the following components were stirred and mixed, thereby obtaining a top coating composition T-1.

[1065]

[1066] Next, the primer composition P-1 was applied to the aluminum substrate and dried at 100°C for 20 minutes. Next, the top coating composition T-1 was applied to the primer film, dried at 100°C for 20 minutes, and then heated at 380°C for 20 minutes to obtain a film. The contact angle and friction coefficient of the film were measured. The results are shown in Table 3.

[1067] Example 3

[1068] A film was obtained by the same procedure as in Comparative Example 2 except that PTFE aqueous dispersion 1-5 was used instead of PTFE aqueous dispersion C-5 to obtain primer composition P-2 and top coating composition T-2. The contact angle and friction coefficient of the film were measured. The results are shown in Table 3.

[1069] Example 4

[1070] A film was obtained by the same procedure as in Comparative Example 2 except that PTFE aqueous dispersion 2-2 was used instead of PTFE aqueous dispersion C-5 to obtain primer composition P-3 and top coating composition T-3. The contact angle and friction coefficient of the film were measured. The results are shown in Table 3.

[1071] [Table 3]

[1072] Table 3

[1073] unit Comparative Example 2 Example 3 Example 4 Contact angle (relative to water) Spend 107 111 113 Contact angle (relative to n-hexadecane) Spend 40 44 45 Static friction coefficient － 0.13 0.09 0.08 Dynamic friction coefficient － 0.05 0.03 0.03

Claims

1. A method for producing an aqueous fluorine-containing polymer dispersion, which is a method for producing an aqueous fluorine-containing polymer dispersion containing a fluorine-containing polymer, wherein: In the reactor, in the presence of a fluorinated surfactant, a polymerization initiator and an aqueous medium, a fluorinated monomer is polymerized to prepare an aqueous dispersion containing a fluorinated polymer. Heat treatment of the aqueous dispersion, A nonionic surfactant is added to the heat-treated aqueous dispersion. An aqueous dispersion containing a nonionic surfactant is brought into contact with an ion exchange resin. The aqueous dispersion obtained after contacting with the ion exchange resin is concentrated.

2. The manufacturing method according to claim 1, wherein: After the aqueous dispersion is prepared by polymerization and before the aqueous dispersion is heat-treated, at least one of (a) removing the fluorinated monomer remaining in the reactor from the reactor and (b) recovering the aqueous dispersion in the reactor and storing it in a container different from the reactor is performed.

3. The manufacturing method according to claim 2, wherein: After at least one of the operations (a) and (b) is performed and before the aqueous dispersion is heat-treated, a radical generator is added to the aqueous dispersion.

4. The production method according to any one of claims 1 to 3, wherein After the aqueous dispersion is prepared by polymerization and before the aqueous dispersion is heat-treated, a radical generator is added to the aqueous dispersion to prepare an aqueous dispersion containing a radical generator.

5. The production method according to any one of claims 1 to 4, wherein The temperature of the heat treatment is 50° C. or higher.

6. The manufacturing method according to claim 5, wherein: After the heat treatment, the aqueous dispersion is cooled to below 50° C. before contacting the aqueous dispersion with the ion exchange resin.

7. The production method according to any one of claims 1 to 6, wherein A nonionic surfactant is added to the heat-treated aqueous dispersion to prepare an aqueous dispersion in which the content of the nonionic surfactant in the aqueous dispersion is 5% by mass or more based on the fluorinated polymer.

8. The production method according to any one of claims 1 to 7, wherein The nonionic surfactant is represented by the general formula (i), R 6 -O-A 1 -H(i) In the formula, R 6 is a linear or branched primary or secondary alkyl group having 8 to 18 carbon atoms, 1 It is a polyoxyalkylene chain.

9. The production method according to any one of claims 1 to 8, wherein The contact between the aqueous dispersion and the ion exchange resin was repeated two or more times.

10. The production method according to any one of claims 1 to 9, wherein The aqueous dispersion is concentrated by a method of separating the aqueous dispersion into two or more phases and recovering the concentrated phase.

11. The production method according to any one of claims 1 to 10, wherein A nonionic surfactant is added to the concentrated aqueous dispersion.

12. An aqueous fluorine-containing polymer dispersion comprising a fluorine-containing polymer, a nonionic surfactant and a fluorine-containing compound having a hydrophilic group and having 7 or less carbon atoms, The content of the fluorinated polymer is 50% to 70% by mass based on the fluorinated polymer aqueous dispersion. The content of the nonionic surfactant is 4.0% to 12% by mass based on the fluorinated polymer. The content of the fluorine-containing compound having a hydrophilic group and having 7 or less carbon atoms is more than 0 ppb by mass and less than 300 ppb by mass based on the aqueous fluorine-containing polymer dispersion.

13. The aqueous fluorine-containing polymer dispersion according to claim 12, wherein The nonionic surfactant is represented by the general formula (i), R 6 -O-A 1 -H(i) In the formula, R 6 is a linear or branched primary or secondary alkyl group having 8 to 18 carbon atoms, 1 It is a polyoxyalkylene chain.

14. The aqueous fluorine-containing polymer dispersion according to claim 12 or 13, wherein The fluoropolymer contains perfluoro(alkyl vinyl ether) units.

15. The aqueous fluorine-containing polymer dispersion according to claim 14, wherein It does not substantially contain a fluorine-containing compound having a hydrophilic group represented by the general formula (2), General formula (2): [C n-1 F 2n-1 COO - ]M + In the formula, n represents an integer of 9 to 14, M + Represents a cation.

16. The aqueous fluorinated polymer dispersion according to any one of claims 12 to 15, wherein The fluorinated polymer is polytetrafluoroethylene.

17. A coating composition comprising the aqueous fluorinated polymer dispersion according to any one of claims 12 to 16.

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