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

Abstract

Provided is a method for producing an aqueous fluorine-containing polymer dispersion, in which an aqueous fluorine-containing polymer dispersion is prepared by polymerizing a fluorine-containing monomer in the presence of a fluorine-containing surfactant, a polymerization initiator, and an aqueous medium, an oxygen-containing gas is blown into the aqueous dispersion, and the aqueous fluorine-containing polymer dispersion is obtained. The aqueous dispersion of the fluorine-containing polymer is obtained by bringing the aqueous dispersion into contact with an oxidizing agent, or bringing the aqueous dispersion into contact with an alcohol.

Description

Technical Field

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

[0002] Patent Documents 1 and 2 describe that in examples of tetrafluoroethylene polymerization, the supply of tetrafluoroethylene to the autoclave was stopped, and the autoclave was kept under nitrogen bubbling for 16 hours to remove residual monomers from the polymerization, and the latex was then taken out.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application No. 2020-510737

[0006] Patent Document 2: Japanese Patent Application No. 2020-512447 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] An object of the present invention is to provide a novel method for producing a fluorinated polymer and a novel aqueous dispersion containing the fluorinated polymer.

[0009] Means for solving problems

[0010] According to the present invention, there is provided a method for producing an aqueous fluoropolymer dispersion, comprising polymerizing a fluoromonomer in the presence of a fluorosurfactant, a polymerization initiator, and an aqueous medium to prepare an aqueous dispersion containing the fluoropolymer, and blowing an oxygen-containing gas into the aqueous dispersion, or contacting the aqueous dispersion with an oxidizing agent, or contacting the aqueous dispersion with an alcohol to obtain the aqueous fluoropolymer dispersion.

[0011] Effects of the Invention

[0012] An object of the present invention is to provide a novel method for producing a fluorinated polymer and a novel aqueous dispersion containing the fluorinated polymer. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 These are first-order differential spectra obtained by analyzing the aqueous dispersions obtained in Examples 6, 8, 13, 14, and Comparative Example 1 using an electron spin resonance method. 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, melt processability refers to the ability to melt and process the polymer 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.

[0016] 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 polymerized units.

[0017] In the present invention, the content of each monomer constituting the fluorinated polymer can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and fluorescent X-ray analysis depending on the type of the monomer.

[0018] In the present invention, an "organic group" refers to a group containing one or more carbon atoms, or a group formed by removing one hydrogen atom from an organic compound. The organic group is preferably an alkyl group which may have one or more substituents.

[0019] In the present invention, ranges represented by endpoints include all numerical values ​​included in the ranges (for example, 1 to 10 includes 1.4, 1.9, 2.33, 5.75, 9.98, etc.).

[0020] In the present invention, the term "at least 1" includes all numerical values ​​greater than or equal to 1 (e.g., at least 2, at least 4, at least 6, at least 8, at least 10, at least 25, at least 50, at least 100, etc.).

[0021] Hereinafter, specific embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0022] In the production method of the present invention, a fluorinated monomer is polymerized in the presence of a fluorinated surfactant, a polymerization initiator, and an aqueous medium to prepare an aqueous dispersion containing a fluorinated polymer. An oxygen-containing gas is blown into the aqueous dispersion, or the aqueous dispersion is contacted with an oxidizing agent, or the aqueous dispersion is contacted with an alcohol to obtain an aqueous dispersion of the fluorinated polymer.

[0023] Each step and the materials used in each step are described in detail below.

[0024] (Polymerization of fluorinated monomers)

[0025] In the production method of the present invention, first, a fluorinated monomer is polymerized in the presence of a fluorinated surfactant, a polymerization initiator, and an aqueous medium to prepare an aqueous dispersion containing a fluorinated polymer.

[0026] The polymerization of tetrafluoroethylene can be carried out as follows: a fluorinated monomer, a fluorinated surfactant, a polymerization initiator, an aqueous medium, and other additives as needed are placed in a reactor, the contents of the reactor are stirred, and the reactor is then maintained at a specified polymerization temperature. A specified amount of polymerization initiator is then added to initiate the polymerization reaction. After the polymerization reaction begins, additional fluorinated monomers, polymerization initiators, fluorinated surfactants, chain transfer agents, etc. may be added depending on the intended purpose. The polymerization method for the fluorinated monomer is not particularly limited, but emulsion polymerization is preferred.

[0027] (Fluorinated surfactant)

[0028] The fluorinated surfactant used in the polymerization of the fluorinated monomer is not particularly limited as long as it contains at least one fluorine atom, and conventionally known fluorinated surfactants can be used.

[0029] 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.

[0030] Furthermore, the fluorine-containing surfactant may be a surfactant containing fluorine whose anionic portion has a molecular weight of 1000 or less.

[0031] It should be noted that the above-mentioned "anionic part" refers to the part other than the cation of the above-mentioned fluorinated surfactant. For example, in the F(CF2) shown in the formula (I) described later n1 In the case of COOM, it is "F(CF2) n1 COO” part.

[0032] Examples of the fluorinated surfactant include those having a LogPOW of 3.5 or less. The LogPOW is the partition coefficient between 1-octanol and water and is represented by LogP [where P represents the ratio of the fluorinated surfactant concentration in octanol to the fluorinated surfactant concentration in water when a 1:1 octanol / water mixture containing the fluorinated surfactant undergoes phase separation].

[0033] The above LogPOW is calculated as follows: On column: TOSOH ODS-120T column ( HPLC was performed on standard substances with known octanol / water partition coefficients (heptanoic acid, octanoic acid, nonanoic acid, and decanoic acid) under the following conditions: (a) a column having a 1:1 ratio of 1:1 and a column temperature of 40°C; (b) a column having a 1:1 ratio of 1:1 and a column temperature of 40°C; (c) a column having a 1:1 ratio of 1:1 and a column temperature of 40°C; (d) a column having a 1:1 ratio of 1:1 and a column temperature of 40°C; (e) a column having a 1:1 ratio of 1:1 and a column temperature of 40°C; (e) a column having a 1:1 ratio of 1:1 and a column temperature of 50°C; (f) a column having a 1:1 ratio of 1:1 and a column temperature of 50°C; (f) a column having a 1:1 ratio of 1:1 and a column temperature of 50°C; (g) a column having a 1:1 ratio of 1:1 and a column temperature of 50°C; (h ...

[0034] Specific examples of the fluorinated surfactants 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. 3,250,808. 3271341, Japanese Patent Application Publication No. 2003-119204, International Publication No. 2005 / 042593, International Publication No. 2008 / 060461, International Publication No. 2007 / 046377, Japanese Patent Application Publication 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.

[0035] Examples of the anionic fluorinated surfactant include the following general formula (N 0 ):

[0036] X n0 -Rf n0 -Y 0 (N 0 )

[0037] (Where, X n0 For 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).

[0038] Y 0The anionic group may be -COOM, -SO2M or -SO3M, or may be -COOM or -SO3M.

[0039] M is H, metal atom, NR 7 4. an imidazolium with or without a substituent, a pyridinium with or without a substituent, or a phosphonium with or without a substituent, R 7 is H or an organic group.

[0040] Examples of the metal atom include alkali metals (Group 1) and alkaline earth metals (Group 2), such as Na, K, and Li.

[0041] As R 7 , which 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.

[0042] M can be H, metal atom or NR 7 4, can also be H, alkali metal (Group 1), alkaline earth metal (Group 2) or NR 7 4, can also be H, Na, K, Li or NH4.

[0043] The above Rf n0 In the present invention, more than 50% of the H can be replaced by fluorine.

[0044] As the above general formula (N 0 ) can be exemplified by:

[0045] The following general formula (N 1 ):

[0046] X n0 -(CF2) m1 -Y 0 (N 1 )

[0047] (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 ):

[0048] Rf n1 -O-(CF(CF3)CF2O) m2 CFX n1 -Y 0 (N 2 )

[0049] (Where Rf n1is a perfluoroalkyl group having 1 to 5 carbon atoms, m2 is an integer of 0 to 3, X n1 F or CF3, Y 0 The compound represented by the following general formula (N 3 ):

[0050] Rf n2 (CH2) m3 -(Rf n3 ) q -Y 0 (N 3 )

[0051] (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 ):

[0052] Rf n4 -O-(CY n1 Y n2 ) p CF2-Y 0 (N 4 )

[0053] (Where Rf n4 is a linear or branched partially or fully fluorinated alkyl group having 1 to 12 carbon atoms which may contain an ether bond, 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 ):

[0054] [Chemistry 1]

[0055]

[0056] (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 fully fluorinated alkylene group having 1 to 3 carbon atoms and which may contain an ether bond, L is a connecting group, Y 0 is the substance defined above. n2 、Xn3 、X n4 and Rf n5 The total number of carbon atoms is 18 or less).

[0057] As the above general formula (N 0 ), more specifically, the compounds represented by the following general formula (I), perfluorocarboxylic acid (I) represented by the following general formula (II), perfluoroether carboxylic acid (III) represented by the following general formula (III), perfluoroalkylalkylene carboxylic acid (IV) represented by the following general formula (IV), perfluoroalkoxyfluorocarboxylic acid (V) represented by the following general formula (V), perfluoroalkylsulfonic acid (VI) represented by the following general formula (VI), ω-H perfluorosulfonic acid (VII) represented by the following general formula (VII), perfluoroalkylalkylenesulfonic acid (VIII) represented by the following general formula (VIII), alkylalkylene carboxylic acid (IX) represented by the following general formula (IX), fluorocarboxylic acid (X) represented by the following general formula (X), alkoxyfluorosulfonic acid (XI) represented by the following general formula (XI), compound (XII) represented by the following general formula (XII), compound (XIII) represented by the following general formula (XIII), etc.

[0058] The above-mentioned perfluorocarboxylic acid (I) is represented by the following general formula (I):

[0059] F(CF2) n1 COOM(I)

[0060] (where n1 is an integer from 3 to 14, M is H, metal atom, NR 7 4. an imidazolium with or without a substituent, a pyridinium with or without a substituent, or a phosphonium with or without a substituent, R 7 is H or an organic group).

[0061] The above-mentioned ω-H perfluorocarboxylic acid (II) is represented by the following general formula (II):

[0062] H(CF2) n2 COOM(II)

[0063] (wherein n2 is an integer of 4 to 15, and M is the substance defined above).

[0064] The above-mentioned perfluoroether carboxylic acid (III) is represented by the following general formula (III):

[0065] Rf 1 -O-(CF(CF3)CF2O) n3 CF(CF3)COOM(III)

[0066] (Where Rf 1is a perfluoroalkyl group having 1 to 5 carbon atoms, n3 is an integer of 0 to 3, and M is the substance defined above).

[0067] The above-mentioned perfluoroalkyl alkylene carboxylic acid (IV) is represented by the following general formula (IV):

[0068] Rf 2 (CH2) n4 Rf 3 COOM(IV)

[0069] (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).

[0070] The above-mentioned alkoxy fluorocarboxylic acid (V) is represented by the following general formula (V):

[0071] Rf 4 -O-CY 1 Y 2 CF2-COOM(V)

[0072] (Where Rf 4 is a linear or branched partially or fully fluorinated alkyl group having 1 to 12 carbon atoms which may contain an ether bond 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).

[0073] The above-mentioned perfluoroalkylsulfonic acid (VI) is represented by the following general formula (VI):

[0074] F(CF2) n5 SO3M(VI)

[0075] (wherein n5 is an integer of 3 to 14, and M is the substance defined above).

[0076] The above-mentioned ω-H perfluorosulfonic acid (VII) is represented by the following general formula (VII):

[0077] H(CF2) n6 SO3M(VII)

[0078] (wherein n6 is an integer of 4 to 14, and M is the substance defined above).

[0079] The above-mentioned perfluoroalkyl alkylene sulfonic acid (VIII) is represented by the following general formula (VIII):

[0080] Rf 5 (CH2) n7SO3M(VIII)

[0081] (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).

[0082] The above-mentioned alkyl alkylene carboxylic acid (IX) is represented by the following general formula (IX):

[0083] Rf 6 (CH2) n8 COOM(IX)

[0084] (Where Rf 6 is a linear or branched partially or fully fluorinated alkyl group having 1 to 13 carbon atoms which may contain an ether bond, n8 is an integer of 1 to 3, and M is the substance defined above).

[0085] The above-mentioned fluorocarboxylic acid (X) is represented by the following general formula (X):

[0086] Rf 7 -O-Rf 8 -O-CF2-COOM(X)

[0087] (Where Rf 7 is a linear or branched partially or fully fluorinated alkyl group having 1 to 6 carbon atoms which may contain an ether bond and / or a chlorine atom, Rf 8 is a linear or branched partially or fully fluorinated alkyl group having 1 to 6 carbon atoms, and M is defined as above).

[0088] The above-mentioned alkoxy fluorosulfonic acid (XI) is represented by the following general formula (XI):

[0089] Rf 9 -O-CY 1 Y 2 CF2-SO3M(XI)

[0090] (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, 1 and Y 2 are the same or different, are H or F, and M is the substance defined above).

[0091] The above compound (XII) is represented by the following general formula (XII):

[0092] [Chemistry 2]

[0093]

[0094] (Where, X1 、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 which may contain an ether bond. 10 is a perfluoroalkylene group having 1 to 3 carbon atoms, L is a connecting group, Y 0 is an anionic group).

[0095] Y 0 It can be -COOM, -SO2M or -SO3M, or it can be -SO3M or COOM (wherein M is the substance defined above).

[0096] Examples of L include a single bond and a partially or fully fluorinated alkylene group having 1 to 10 carbon atoms which may include an ether bond.

[0097] The above compound (XIII) is represented by the following general formula (XIII):

[0098] Rf 11 -O-(CF2CF(CF3)O) n9 (CF2O) n10 CF2COOM (XIII)

[0099] (Where Rf 11 is a fluorinated alkyl group having 1 to 5 carbon atoms and containing chlorine, n9 is an integer from 0 to 3, n10 is an integer from 0 to 3, and M is a substance as defined above). Examples of compound (XIII) include CF2ClO(CF2CF(CF3)O) n9 (CF2O) n10 CF2COONH4 (a mixture having an average molecular weight of 750, wherein n9 and n10 are the numbers defined above).

[0100] As described above, examples of the anionic fluorinated surfactant include carboxylic acid surfactants and sulfonic acid surfactants.

[0101] The fluorinated surfactant may be a single type of fluorinated surfactant or a mixture of two or more types of fluorinated surfactants.

[0102] The fluorinated surfactant preferably does not have a methylene group (-CH2), more preferably does not have a CH bond. By using a fluorinated surfactant that does not have a methylene group (-CH2) or a CH bond in its molecule, polymerization of the fluorinated monomer in the presence of an aqueous medium can be smoothly performed.

[0103] 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 "part other than the anionic group" in the molecular structure of the fluorinated surfactant. As the hydrophilic group, Y 0 The fluorine-containing surfactant may be a saturated fluorinated surfactant in which all carbon atoms bonded to the hydrophobic group are substituted with fluorine atoms.

[0104] As the fluorinated surfactant, among the above-mentioned 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 ):

[0105] Rf n4 -O-(CY n1 F) p CF2-Y 0 (N 4 )

[0106] (Where Rf n4 is a linear or branched partially or fully fluorinated alkyl group having 1 to 12 carbon atoms which may contain an ether bond (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 ):

[0107] [Chemistry 3]

[0108]

[0109] (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 is H. Rf n5is a linear or branched partially or fully 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).

[0110] As the fluorinated surfactant, among the above-mentioned anionic fluorinated surfactants, more preferably at least one selected from the group consisting of the following substances: 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 perfluoroalkylsulfonic acid (VI) represented by the general formula (VI), an ω-H perfluorosulfonic acid (VII) represented by the general formula (VII), a perfluoroalkyl alkylenesulfonic acid (VIII) represented by the general formula (VIII), and a general formula (X): Rf 7 -O-Rf 8 -O-CF2-COOM

[0111] (Where Rf 7 is a linear or branched partially or fully fluorinated alkyl group having 1 to 6 carbon atoms (excluding an alkyl group having -CH2-), which may contain an ether bond and / or a chlorine atom, 8 is a linear or branched partially or fully fluorinated alkyl group having 1 to 6 carbon atoms (excluding an alkyl group having -CH2-), and M is as defined above. ) represented by a fluorinated carboxylic acid (X), general formula (XI): Rf 9 -O-CY 1 FCF2-SO3M

[0112] (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 an alkyl group having -CH2-), 1 is H or F, and M is as defined above. ) Alkoxy fluorosulfonic acid (XI) represented by general formula (XII):

[0113] [Chemistry 4]

[0114]

[0115] (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. ) represented by compound (XII), and general formula (XIII):

[0116] Rf 11 -O-(CF2CF(CF3)O) n9 (CF2O) n10 CF2COOM

[0117] (Where Rf 11 Compound (XIII) is represented by a fluorinated alkyl group having 1 to 5 carbon atoms (excluding a fluorinated alkyl group having -CH2-) containing chlorine, n9 is an integer from 0 to 3, n10 is an integer from 0 to 3, and M is as defined above. By using these fluorinated surfactants, polymerization of fluorinated monomers in the presence of an aqueous medium can be smoothly carried out.

[0118] Examples of the fluorinated surfactant include compounds represented by the following formula: The fluorinated surfactant may be a mixture of these compounds.

[0119] F(CF2)7COOM,

[0120] F(CF2)5COOM,

[0121] H(CF2)6COOM,

[0122] H(CF2)7COOM,

[0123] CF3O(CF2)3OCHFCF2COOM,

[0124] C3F7OCF(CF3)CF2OCF(CF3)COOM,

[0125] CF3CF2CF2OCF(CF3)COOM,

[0126] CF3CF2OCF2CF2OCF2COOM,

[0127] C2F5OCF(CF3)CF2OCF(CF3)COOM,

[0128] CF3OCF(CF3)CF2OCF(CF3)COOM,

[0129] CF2ClCF2CF2OCF(CF3)CF2OCF2COOM,

[0130] CF2ClCF2CF2OCF2CF(CF3)OCF2COOM,

[0131] CF2ClCF(CF3)OCF(CF3)CF2OCF2COOM,

[0132] CF2ClCF(CF3)OCF2CF(CF3)OCF2COOM,

[0133] [Chemistry 5]

[0134]

[0135] (In each formula, M is H, metal atom, NR 7 4. An imidazolium which may have a substituent group, a pyridinium which may have a substituent group, or a phosphonium which may have a substituent group. 7 is H or an organic group. )

[0136] 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.

[0137] (Polymerization initiator)

[0138] 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. Known oil-soluble and / or water-soluble polymerization initiators can be used. Furthermore, the polymerization can be initiated in a redox manner in combination with a reducing agent. The concentration of the polymerization initiator is appropriately determined based on the type of monomer, the molecular weight of the target fluorinated polymer, and the reaction rate.

[0139] As the polymerization initiator, an oil-soluble radical polymerization initiator or a water-soluble radical polymerization initiator can be used.

[0140] The oil-soluble 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, bis(perfluorononanoyl) peroxide, bis(ω-chloro-hexafluorobutyryl) peroxide, bis(ω-chloro-decafluorohexanoyl) peroxide, bis(ω-chloro-tetrafluorooctanoyl) peroxide, ω-hydro-dodecafluoroheptanoyl-ω-hydrohexafluorononanoyl-peroxide, ω-chloro-hexafluorobutyryl-ω-chloro-decafluorohexanoyl-peroxide, ω-hydro-dodecafluoroheptanoyl-perfluorobutyryl-peroxide, bis(dichloropentafluorobutyryl) peroxide, bis(trichlorooctafluorohexanoyl) peroxide, bis(tetrachloroundecanoyl) peroxide, bis(pentachlorotetrafluorodecanoyl) peroxide, bis(undecachlorotriadecanoyl) peroxide, etc.

[0141] The water-soluble free radical polymerization initiator may be a known water-soluble peroxide, for example, ammonium, potassium, or sodium salts of persulfuric acid, perboric acid, perchloric acid, perphosphoric acid, or percarbonic acid, organic peroxides such as disuccinic acid peroxide and diglutaric acid peroxide, t-butyl peroxymaleate, and t-butyl hydroperoxide. A reducing agent such as a sulfite may also be included, and its amount may be 0.1 to 20 times that of the peroxide.

[0142] For example, when the polymerization is carried out at a low temperature below 30°C, it is preferred to use a redox initiator composed of an oxidizing agent and a reducing agent as the polymerization initiator. Examples of the oxidizing agent include persulfates, organic peroxides, potassium permanganate, manganese triacetate, and ammonium cerium nitrate. Examples of the reducing agent include sulfites, bisulfites, bromates, diimides, and oxalic acid. Examples of the persulfates include ammonium persulfate and potassium persulfate. Examples of the sulfites include sodium sulfite and ammonium sulfite. 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 the redox initiators. Examples of the copper salt include copper (II) sulfate, and examples of the iron salt include iron (II) sulfate.

[0143] Examples of the redox initiator include potassium permanganate / oxalic acid, ammonium persulfate / bisulfite / ferric sulfate, manganese triacetate / oxalic acid, ceric ammonium nitrate / oxalic acid, and bromate / bisulfite, with potassium permanganate / oxalic acid being preferred. When a redox initiator is used, either the oxidizing agent or the reducing agent can be pre-charged into a polymerization vessel, followed by continuous or intermittent addition of the other to initiate polymerization. For example, when potassium permanganate / oxalic acid is used, oxalic acid is preferably added to the polymerization vessel and potassium permanganate is continuously added thereto.

[0144] The amount of polymerization initiator added is not particularly limited; it may be added all at once, sequentially, or continuously in the initial stage of polymerization in an amount sufficient to prevent a significant decrease in the polymerization rate (e.g., a concentration of several ppm relative to water). The upper limit is a range within which the heat of polymerization can be removed from the apparatus surface while simultaneously raising the reaction temperature. A more preferred upper limit is a range within which the heat of polymerization can be removed from the apparatus surface.

[0145] As the amount of polymerization initiator added, it is preferably the amount that does not consume the total amount of fluorinated monomer in polymerization and remains in the aqueous dispersion containing fluorinated polymer. As the amount of polymerization initiator added, relative to the mass of the aqueous medium, it is preferably 5 mass ppm or more, more preferably 10 mass ppm or more, further preferably 20 mass ppm or more, and particularly preferably 50 mass ppm or more. The amount of polymerization initiator at the end of polymerization can be calculated based on the polymerization temperature, reaction time and half-life of the initiator. The concentration of the polymerization initiator at the end of polymerization is preferably 5 mass ppm or more, more preferably 10 mass ppm or more, further preferably 20 mass ppm or more, and particularly preferably 50 mass ppm or more relative to the mass of the aqueous medium.

[0146] During the polymerization of fluorinated monomers, the free radical concentration in the polymerization can be adjusted by adding a decomposing agent. Examples of decomposing agents include sulfites, bisulfites, bromates, diimides, oxalic acid, copper salts, iron salts, and the like. Examples of sulfites include sodium sulfite and ammonium sulfite. Examples of copper salts include copper (II) sulfate, and examples of iron salts include iron (II) sulfate. The amount of the decomposing agent added is in the range of 25% to 300% by mass relative to the amount of the oxidizing agent combined with the polymerization initiator (redox initiator). The amount of the decomposing agent added is preferably 25% to 150% by mass, and more preferably 50% to 100% by mass. In addition, the decomposing agent is preferably added after 5% by mass of all fluorinated monomers consumed in the polymerization reaction are polymerized, and more preferably after 10% by mass are polymerized. The amount of the decomposing agent added is preferably an amount equivalent to 0.1% to 20% by mass of the mass of the aqueous medium used, and more preferably an amount equivalent to 3% to 10% by mass.

[0147] (Aqueous medium)

[0148] The aqueous medium used in the polymerization of fluorinated monomers is the reaction medium that allows the polymerization to proceed, and 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 an alcohol, ether, or ketone and / or a fluorinated organic solvent with a boiling point of 40°C or less.

[0149] As the aqueous medium, from the viewpoints 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 surfactant and the fluorinated compound caused by the heat treatment after the preparation of the aqueous dispersion, 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.

[0150] From the viewpoint of enabling smooth polymerization of the fluorinated monomer and suppressing a decrease in the removal efficiency of the fluorinated surfactant and the fluorinated compound caused by heat treatment after preparation of the aqueous dispersion, the water content in the aqueous medium is preferably 90% or more, more preferably 95% or more, further preferably 99.0% or more, even more preferably 99.5% or more, particularly preferably 99.9% or more, and may be 100% based on the mass of the aqueous medium.

[0151] (Fluorinated monomers)

[0152] 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], chlorotrifluoroethylene [CTFE], vinyl fluoride, vinylidene fluoride [VdF], trifluoroethylene, fluoroalkyl vinyl ether, fluoroalkyl ethylene, fluoroalkyl allyl ether, trifluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutylene, hexafluoroisobutylene, general formula (100): CHX 101 =CX 102 Rf 101 (Where, X 101 and X 102 One of them is H and the other is F, Rf 101 It is at least one member selected from the group consisting of a fluorinated monomer represented by a linear or branched fluoroalkyl group having 1 to 12 carbon atoms, a fluorovinyl heterocyclic compound, and a monomer providing a crosslinking site.

[0153] The fluoroalkyl vinyl ether [FAVE] is preferably at least one selected from the group consisting of the following fluorinated monomers:

[0154] General formula (110): CF2=CF-ORf 111

[0155] (Where Rf 111 represents a perfluorinated organic group),

[0156] General formula (120): CF2=CF-OCH2-Rf 121

[0157] (Where Rf 121 is a fluorine-containing monomer represented by a perfluoroalkyl group having 1 to 5 carbon atoms,

[0158] General formula (130): CF2=CFOCF2ORf 131

[0159] (Where Rf 131 a fluorinated 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,

[0160] General formula (140): CF2=CFO(CF2CF(Y 141 )O) m (CF2) n F

[0161] (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

[0162] General formula (150): CF2=CF-O-(CF2CFY 151 -O) n -(CFY 152 ) m -A 151

[0163] (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 from 0 to 3. n Y 151 Can be the same or different. 152 represents a fluorine atom, a chlorine atom or a -SO2F group. m represents an integer from 1 to 5. m Y 152 Can be the same or different. 151 Indicates-SO2X 151 、-COZ 151 or-POZ 152 Z 153 .X 151 Indicates F, Cl, Br, I, -OR 151 or -NR 152 R 153 . Z151 , 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 156 are the same or different and represent H, ammonium, an alkali metal, an alkyl group containing or not containing a fluorine atom, an aryl group, or a sulfonyl group-containing group).

[0164] 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.

[0165] 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.

[0166] Examples of the perfluoroorganic group in the general formula (110) include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, and a perfluorohexyl group.

[0167] As the fluorine-containing monomer represented by the general formula (110), Rf in the general formula (110) can be further exemplified. 111 It is a monomer of a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms, Rf 111 is the following formula:

[0168] [Chemistry 6]

[0169]

[0170] (wherein m represents 0 or an integer of 1 to 4.) a monomer of a group represented by Rf 111 is the following formula:

[0171] CF3CF2CF2-(O-CF(CF3)-CF2) n -

[0172] (wherein n represents an integer of 1 to 4.)

[0173] As the fluorine-containing monomer represented by the general formula (110), preferably

[0174] General formula (160): CF2=CF-ORf 161

[0175] (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.

[0176] 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).

[0177] As the fluorinated monomer represented by the general formula (160), it is preferred to select at least one species from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether) and perfluoro(propyl vinyl ether), and more preferably to select at least one species from the group consisting of perfluoro(methyl vinyl ether) and perfluoro(propyl vinyl ether).

[0178] 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.

[0179] The fluorine-containing 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.

[0180] The fluorine-containing 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.

[0181] As the fluorine-containing monomer represented by the general formula (100), Rf 101 is a fluorinated monomer having a linear fluoroalkyl group, more preferably Rf 101 It is a fluorinated monomer with a straight-chain perfluoroalkyl group. 101The 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-isomer), CHF=CHCF3 (Z-isomer), and the like. Among them, 2,3,3,3-tetrafluoropropylene represented by CH2=CFCF3 is preferred.

[0182] As the fluoroalkylethylene, preferably

[0183] General formula (170): CH2=CH-(CF2) n -X 171

[0184] (Where, X 171 is 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.

[0185] Examples of the fluoroalkyl allyl ether include

[0186] General formula (180): CF2=CF-CF2-ORf 111

[0187] (Where Rf 111 represents a perfluorinated organic group).

[0188] Rf of general formula (180) 111 With 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 even more preferably CF2=CF-CF2-O-CF2CF2CF3.

[0189] Examples of the fluorinated vinyl heterocyclic compound include those represented by the general formula (230):

[0190] [Chemistry 7]

[0191]

[0192] (Where, X 231 and X 232 are independently F, Cl, methoxy or fluoromethoxy, Y 231 Formula Y 232 or Y 233 .

[0193] [Chemistry 8]

[0194] -FC=CF- (Y 232 )

[0195]

[0196] (Where Z 231 and Z 232 and (a) independently represents F or a fluoroalkyl group having 1 to 3 carbon atoms.

[0197] The monomer providing a crosslinking site is preferably at least one selected from the group consisting of the following monomers:

[0198] General formula (180): CX 181 2=CX 182 -R f 181 CHR 181 X 183

[0199] (Where, X 181 and X 182 are independently hydrogen atoms, fluorine atoms or CH3, R f 181 is a fluoroalkylene, a perfluoroalkylene, a fluoro(poly)oxyalkylene or a perfluoro(poly)oxyalkylene, R 181 is a hydrogen atom or CH3, X 183 is an iodine atom or a bromine atom),

[0200] General formula (190): CX 191 2=CX 192 -R f 191 X 193

[0201] (Where, X 191 and X 192 are independently hydrogen atoms, fluorine atoms or CH3, R f 191 is a fluoroalkylene, a perfluoroalkylene, a fluoropolyoxyalkylene or a perfluoropolyoxyalkylene, X 193is an iodine atom or a bromine atom),

[0202] General formula (200): CF2=CFO(CF2CF(CF3)O) m (CF2) n -X 201

[0203] (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

[0204] General formula (210): CH2=CFCF2O(CF(CF3)CF2O) m (CF(CF3)) n -X 211

[0205] (wherein, m is an integer from 0 to 5, n is an integer from 1 to 3, and X 211 a fluorine-containing monomer represented by a cyano group, a carboxyl group, an alkoxycarbonyl group, an iodine atom, a bromine atom or -CH2OH), and

[0206] General formula (220): CR 221 R 222 =CR 223 -Z 221 -CR 224 =CR 225 R 226

[0207] (Where R 221 、R 222 、R 223 、R 224 、R 225 and R 226 are the same or different and are hydrogen atoms or alkyl groups 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, which may have an oxygen atom or not;

[0208] -(Q) p -CF2O-(CF2CF2O) m (CF2O) n -CF2-(Q) p -

[0209] (wherein Q is an alkylene group or an oxyalkylene group, p is 0 or 1, and m / n is 0.2 to 5) and a monomer represented by a (per)fluoropolyoxyalkylene group having a molecular weight of 500 to 10,000.

[0210] 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.

[0211] 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.

[0212] In the above polymerization, the above fluorine-containing monomer can be polymerized with a non-fluorine-containing monomer. Examples of the above non-fluorine-containing monomer include hydrocarbon monomers reactive with the above fluorine-containing monomer. Examples of the above 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 n-butyrate, vinyl isobutyrate, vinyl valerate, vinyl pivalate, vinyl hexanoate, vinyl octanoate, vinyl decanoate, 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, and ethyl cinnamate. vinyl esters such as vinyl ester, vinyl undecylenate, vinyl glycolate, 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)acrylates 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;

[0213] In addition, the above-mentioned non-fluorine-containing monomer may also be a hydrocarbon monomer containing a functional group (excluding monomers providing a crosslinking site). Examples of the above-mentioned hydrocarbon monomer containing a functional group include hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, hydroxyisobutyl vinyl ether, and hydroxycyclohexyl vinyl ether; non-fluorine-containing monomers having a carboxyl group such as acrylic acid, methacrylic acid, itaconic acid, succinic acid, succinic anhydride, fumaric acid, fumaric anhydride, crotonic acid, maleic acid, maleic anhydride, and perfluorobutenoic acid; non-fluorine-containing monomers having a sulfonic group such as vinyl sulfonic acid; non-fluorine-containing monomers having a glycidyl group such as glycidyl vinyl ether and glycidyl allyl ether; non-fluorine-containing monomers having an amino group such as aminoalkyl vinyl ether and aminoalkyl allyl ether; non-fluorine-containing monomers having an amide group such as (meth)acrylamide and hydroxymethyl acrylamide; non-fluorine-containing monomers having a nitrile group such as acrylonitrile and methacrylonitrile; and the like.

[0214] In the above polymerization, by polymerizing one or two or more of the above fluorinated monomers, desired fluorinated polymer particles can be obtained.

[0215] (Chain transfer agent)

[0216] 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 chain transfer agents, 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, carbon tetrachloride, and cyclohexane can also be mentioned. As chain transfer agents, hydrocarbon chain transfer agents or alcohols are preferred. As hydrocarbon chain transfer agents, there are no particular restrictions as long as they are chain transfer agents containing only carbon atoms and hydrogen atoms. Alkanes with 1 to 5 carbon atoms are preferred, and at least one selected from the group consisting of isopentane, methane, ethane, and propane is more preferred. As alcohols, alcohols with 1 to 3 carbon atoms are preferred, and at least one selected from the group consisting of methanol, ethanol, 1-propanol, and 2-propanol is preferred.

[0217] As a chain transfer agent, a bromine compound or an iodine compound can be used. 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 can be cited (iodine transfer polymerization method). As a representative example of the bromine compound or iodine compound used, for example, the general formula:

[0218] R a I x Br y

[0219] (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, thereby functioning as a crosslinking point.

[0220] Examples of the bromine compound or iodine compound include 1,3-diiodoperfluoropropane, 2-iodoperfluoropropane, 1,3-diiodine-2-chloroperfluoropropane, 1,4-diiodoperfluorobutane, 1,5-diiodine-2,4-dichloroperfluoropentane, 1,6-diiodoperfluorohexane, 1,8-diiodoperfluorooctane, 1,12-diiodoperfluorododecane, 1,16-diiodoperfluorohexadecane, diiodomethane, 1,2-diiodoethane, 1,3-diiodine-n-propane, 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, monoiodinated and monobrominated substitutions of benzene, diiodinated and monobrominated substitutions, and (2-iodinated and (2-bromoethyl) substitutions, etc. These compounds can be used alone or in combination with each other.

[0221] Among these, 1,4-diiodoperfluorobutane, 1,6-diiodoperfluorohexane, and 2-iodoperfluoropropane are preferably used in view of polymerization reactivity, crosslinking reactivity, and availability.

[0222] The amount of chain transfer agent used is generally 1 to 50,000 ppm by mass, preferably 1 to 20,000 ppm by mass, relative to the total amount of fluoromonomer supplied. The amount of chain transfer agent used is preferably such that it is completely consumed during the polymerization of the fluoromonomer and does not remain in the aqueous dispersion containing the fluoropolymer, while minimizing the reduction in the removal efficiency of the fluorosurfactant and fluorochemicals caused by the heat treatment after the preparation of the aqueous dispersion. This is done to minimize the reduction in the removal efficiency of the fluorochemicals having hydrophilic groups. Therefore, the amount of chain transfer agent used is more preferably 10,000 ppm by mass or less, further preferably 5,000 ppm by mass or less, even more 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 fluoromonomer supplied.

[0223] 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.

[0224] (Other additives)

[0225] In the polymerization of fluorinated monomers, additives such as buffers, pH adjusters, stabilizing agents, and dispersion stabilizers may be used. Furthermore, free radical scavengers and decomposers may be added to adjust the polymerization rate and molecular weight. Furthermore, non-fluorinated anionic surfactants, non-fluorinated nonionic surfactants, and non-fluorinated cationic surfactants may also be used in the polymerization of fluorinated monomers.

[0226] Preferred stabilizing agents include paraffin wax, fluorinated oil, fluorinated solvent, and silicone oil. One stabilizing agent may be used alone or in combination of two or more. Paraffin wax is more preferred. Paraffin wax may be liquid, semisolid, or solid at room temperature, but is preferably a saturated hydrocarbon with 12 or more carbon atoms. The melting point of paraffin wax is generally preferably 40°C to 65°C, more preferably 50°C to 65°C.

[0227] 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.

[0228] (Polymerization Conditions)

[0229] The polymerization of the fluorinated monomer can be carried out under conventional pressure and temperature. Typically, the polymerization temperature is 5°C to 120°C, and the polymerization pressure is 0.05 MPaG to 10 MPaG. The polymerization temperature and pressure are appropriately determined based on the type of monomer, the molecular weight of the target fluorinated polymer, the reaction rate, and other factors. The polymerization pressure is preferably greater than 0.05 MPaG, more preferably greater than 0.10 MPaG, and even more preferably greater than 0.20 MPaG.

[0230] (Fluoropolymer)

[0231] Fluorine-containing polymers such as fluororesins and fluororubbers are obtained by polymerizing fluorine-containing monomers.

[0232] Examples of fluororesins include polytetrafluoroethylene [PTFE], TFE / FAVE copolymer [PFA], TFE / fluoroalkyl allyl ether copolymer, TFE / HFP copolymer [FEP], ethylene [Et] / TFE copolymer [ETFE], Et / TFE / HFP copolymer, polychlorotrifluoroethylene [PCTFE], CTFE / TFE copolymer, Et / CTFE copolymer, polyvinyl fluoride [PVF], polyvinylidene fluoride [PVdF], VdF / TFE copolymer, fluorine-containing monomer / vinyl ester copolymer, polymers of fluorine-containing monomers represented by general formula (150), and the like.

[0233] Among these, the fluororesin is preferably at least one selected from the group consisting of PTFE, PFA, and FEP, and more preferably at least one selected from the group consisting of PTFE and PFA, in order to significantly exhibit the effects of the production method of the present invention.

[0234] As PTFE, can be homopolymerization PTFE, also can be modified PTFE.Modified PTFE comprises TFE unit and based on can with the modified monomer unit of the modified monomer of TFE copolymerization.In addition, PTFE can be the high molecular weight PTFE with non-melt processability and fibrillation, also can be the low molecular weight PTFE with melt processability, not having fibrillation.

[0235] The modifying monomer is not particularly limited as long as it can copolymerize with TFE. Examples thereof include perfluoroolefins such as hexafluoropropylene [HFP]; chlorofluoroolefins such as CTFE; hydrogen-containing fluoroolefins such as trifluoroethylene and VdF; fluoroalkyl vinyl ethers [FAVE]; fluoroalkyl allyl ethers; perfluoroalkylethylenes; ethylene; and fluorinated vinyl ethers having a nitrile group. The modifying monomers used may be one or two or more.

[0236] The fluororubber may be a partially fluorinated rubber or a perfluororubber.

[0237] Examples of partially fluorinated rubbers include VdF-based fluororubbers, TFE / propylene (Pr)-based fluororubbers, TFE / propylene / VdF-based fluororubbers, ethylene / HFP-based fluororubbers, ethylene / HFP / VdF-based fluororubbers, ethylene / HFP / TFE-based fluororubbers, and ethylene / HFP / FAVE-based rubbers. Among these, at least one selected from the group consisting of VdF-based fluororubbers and TFE / propylene-based fluororubbers is preferred.

[0238] Specific examples of VdF-based fluororubbers include VdF / HFP-based rubbers, VdF / HFP / TFE-based rubbers, VdF / CTFE-based rubbers, VdF / CTFE / TFE-based rubbers, VdF / fluorinated monomer-based rubbers represented by the general formula (100), VdF / fluorinated monomer-based rubbers represented by the general formula (100) / TFE-based rubbers, VdF / perfluoro(methyl vinyl ether) [PMVE]-based rubbers, VdF / PMVE / TFE-based rubbers, and VdF / PMVE / TFE / HFP-based rubbers. Preferred examples of the VdF / fluorinated monomer-based rubber represented by the general formula (100) include VdF / CH2=CFCF3-based rubbers, and preferred examples of the VdF / fluorinated monomer-based rubber represented by the general formula (100) / TFE-based rubber include VdF / TFE / CH2=CFCF3-based rubbers.

[0239] As the perfluororubber, at least one selected from the group consisting of a perfluororubber containing TFE, for example, a copolymer of TFE / a fluorinated monomer represented by the general formula (110), (130) or (140), and a copolymer of TFE / a fluorinated monomer represented by the general formula (110), (130) or (140) / a monomer providing a crosslinking site is preferred.

[0240] In one embodiment of the aqueous dispersion, the fluorinated polymer contains a fluorinated polymer containing a fluoroalkyl vinyl ether unit.

[0241] An aqueous dispersion containing a fluoropolymer containing fluoroalkyl vinyl ether units can be prepared by polymerizing a fluoroalkyl vinyl ether as a fluoromonomer. When a fluoroalkyl vinyl ether is used as a fluoromonomer, a compound represented by general formula (2) (perfluoroalkane acid) may be produced during the polymerization of the fluoromonomer. An aqueous dispersion containing a fluoropolymer containing fluoroalkyl vinyl ether units may also contain a compound represented by general formula (2) as a water-soluble fluorocompound.

[0242] The content of the fluoroalkyl vinyl ether units in the fluoropolymer is preferably from 0.0000001 mol % to 30 mol %, more preferably 0.000001 mol % or more, further preferably 0.00001 mol % or more, preferably 25 mol % or less, further preferably 20 mol % or less, and particularly preferably 8 mol % or less, relative to the total polymerized units constituting the fluoropolymer.

[0243] Examples of the fluorinated polymer containing such polymerized units include:

[0244] Fluororesins such as PTFE and TFE / FAVE copolymers [PFA] modified with fluoroalkyl vinyl ether [FAVE];

[0245] Partially fluorinated rubbers such as ethylene / HFP / FAVE rubber, VdF / PMVE rubber, VdF / PMVE / TFE rubber, and VdF / PMVE / TFE / HFP rubber;

[0246] Perfluororubber; etc.

[0247] In one embodiment of the aqueous dispersion, low-molecular-weight PTFE is contained as the fluorine-containing polymer.

[0248] Low molecular weight PTFE can generally be produced by polymerization using polymerization conditions used to produce low molecular weight PTFE, or by reducing the molecular weight of the high molecular weight PTFE obtained by polymerization using a known method (thermal decomposition, radiation irradiation decomposition, etc.). In the production method of the present invention, an aqueous dispersion containing low molecular weight PTFE can be prepared by polymerization using polymerization conditions used to produce low molecular weight PTFE.

[0249] In the present invention, high molecular weight PTFE refers to PTFE that is not melt-processable and fibrillable. On the other hand, low molecular weight PTFE refers to PTFE that is melt-processable and not fibrillable.

[0250] Non-melt processability refers to the property that the melt flow rate cannot be determined at temperatures above the crystallization melting point according to ASTM D 1238 and D 2116.

[0251] The presence or absence of fibrillation can be determined using "paste extrusion," a typical method for molding a powder made from a TFE polymer, known as "high molecular weight PTFE powder." This is because, generally, high molecular weight PTFE exhibits fibrillation when paste extrusion is possible. If the unfired molded article obtained by paste extrusion lacks substantial strength or elongation, for example, if the elongation is 0% and the article breaks if stretched, it is considered to be non-fibrillating.

[0252] 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.

[0253] The melt viscosity of 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.

[0254] (Aqueous dispersion)

[0255] 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 completed is usually 8% to 50% by mass relative to the aqueous dispersion.

[0256] It has been discovered that aqueous dispersions prepared by polymerizing fluorinated monomers contain polymerization radicals represented by the general formula (1). These polymerization radicals are highly reactive and react with other compounds to produce by-products or to cause undesirable reactions.

[0257] General formula (1): R-(CF2-CF2) n (In the formula, R represents a monovalent group, n represents an integer greater than or equal to 1, and represents an unpaired electron.)

[0258] In particular, when tetrafluoroethylene as a fluorine-containing monomer is polymerized in the presence of a chain transfer agent and a water-soluble radical polymerization initiator, the above-mentioned polymerization radicals tend to be easily generated.

[0259] (Post-processing)

[0260] In the production method of the present invention, after preparing an aqueous dispersion containing a fluoropolymer, a gas containing oxygen is blown into the aqueous dispersion, or the aqueous dispersion is contacted with an oxidizing agent, or the aqueous dispersion is contacted with an alcohol. In the production method of the present invention, both of these methods may be performed.

[0261] By performing at least one of these methods, the oxygen saturation of the aqueous dispersion can be increased. The oxygen saturation of the aqueous dispersion is preferably 53.5% or higher, more preferably 60% or higher, even more preferably 70% or higher, and particularly preferably 80% or higher. The oxygen saturation of the aqueous dispersion can be 99% or lower.

[0262] In the present invention, oxygen saturation refers to the ratio of the actual dissolved oxygen content to the saturated dissolved oxygen content of water at 1 atmosphere. The oxygen saturation can be measured using an optical dissolved oxygen meter.

[0263] Furthermore, by performing at least one of the above methods, the content of polymerization radicals in the aqueous dispersion is reduced.

[0264] (Use of oxygen-containing gas)

[0265] By blowing an oxygen-containing gas into the aqueous dispersion, the oxygen saturation of the aqueous dispersion is increased. In addition, by blowing an oxygen-containing gas into the aqueous dispersion, the polymerization radicals represented by the general formula (1) are converted into oxidation radicals represented by the general formula (2), thereby reducing the content of polymerization radicals in the aqueous dispersion.

[0266] General formula (1): R-(CF2-CF2) n (In the formula, R represents a monovalent group, n represents an integer greater than or equal to 1, and represents an unpaired electron.)

[0267] General formula (2): R-(CF2-CF2) nOO·(wherein, R represents a monovalent group, n represents an integer greater than or equal to 1, and · represents an unpaired electron.)

[0268] In the general formulae (1) and (2), R is a monovalent group. R is preferably COOH, OH, SO3H, CF3, CH3 or R 11 -R 12 -(where R 11 Represents COOH, OH, SO3H, CF3 or CH3, R 12 represents a chain formed by polymerization of tetrafluoroethylene and a modifying monomer).

[0269] As a method for blowing an oxygen-containing gas into the aqueous dispersion, for example, a method in which the oxygen-containing gas is blown into the aqueous dispersion to generate bubbles, thereby contacting the aqueous dispersion with the oxygen-containing gas (bubbling method) can be employed. The flow rate of the oxygen-containing gas when blowing the aqueous dispersion is, for example, 1 L / min to 30 L / min.

[0270] Examples of the oxygen-containing gas include oxygen gas and air. The oxygen content of the oxygen-containing gas may be 20% to 100% by volume.

[0271] The temperature when the aqueous dispersion is brought into contact with the oxygen-containing gas is preferably 5°C to 99°C, more preferably 15°C or higher, and even more preferably lower than 35°C.

[0272] The pressure when the aqueous dispersion is brought into contact with the oxygen-containing gas may be normal pressure.

[0273] The time for contacting the aqueous dispersion with the oxygen-containing gas is preferably 1 minute or longer, more preferably 5 minutes or longer, further preferably 10 minutes or longer, and particularly preferably 30 minutes or longer, and preferably 48 hours or shorter, more preferably 24 hours or shorter, and further preferably 12 hours or shorter.

[0274] (Use of oxidizing agents)

[0275] By contacting the aqueous dispersion with the oxidizing agent, the oxygen saturation of the aqueous dispersion is increased. In addition, by contacting the aqueous dispersion with the oxidizing agent, the polymerization radicals represented by the general formula (1) are converted into oxidized radicals represented by the general formula (2), thereby reducing the content of polymerization radicals in the aqueous dispersion.

[0276] In the method of bringing the aqueous dispersion into contact with the oxidizing agent, for example, a method of adding the oxidizing agent to the aqueous dispersion to bring the aqueous dispersion into contact with the oxidizing agent can be adopted.

[0277] Examples of the oxidizing agent include: gaseous oxidizing agents such as ozone, fluorine, chlorine, bromine, and iodine; inorganic acids and inorganic acid salts such as nitric acid, nitric acid, sulfurous acid, sulfuric acid, persulfuric acid, hydrochloric acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, hydrofluoric acid, bromic acid, iodic acid, phosphoric acid, boric acid, chromic acid, dichromic acid, and permanganic acid; and peroxides such as hydrogen peroxide. Among these, hydrogen peroxide is preferred as the oxidizing agent.

[0278] The amount of the oxidizing agent brought into contact with the aqueous dispersion is preferably 1 to 500 mass ppm, more preferably 3 mass ppm or more, and even more preferably 200 mass ppm or less, relative to the mass of the aqueous dispersion.

[0279] The temperature when the aqueous dispersion is brought into contact with the oxidizing agent is preferably 5°C to 99°C, more preferably 15°C or higher, and even more preferably lower than 35°C.

[0280] The pressure when the aqueous dispersion is brought into contact with the oxidizing agent may be normal pressure.

[0281] The time for contacting the aqueous dispersion with the oxidant is preferably 1 minute or longer, more preferably 5 minutes or longer, further preferably 10 minutes or longer, particularly preferably 30 minutes or longer, and preferably 48 hours or shorter, more preferably 24 hours or shorter, further preferably 12 hours or shorter.

[0282] (Use of alcohol)

[0283] Contacting the aqueous dispersion with alcohol increases the oxygen saturation of the aqueous dispersion. Furthermore, contacting the aqueous dispersion with alcohol causes polymerization radicals contained in the aqueous dispersion to abstract hydrogen atoms from C—H bonds of the alcohol, deactivating the polymerization radicals and reducing the content of polymerization radicals in the aqueous dispersion.

[0284] In the method of bringing the aqueous dispersion into contact with alcohol, for example, a method of adding alcohol to the aqueous dispersion can be adopted.

[0285] The alcohol is preferably an alcohol having 1 to 10 carbon atoms, more preferably at least one selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol, and even more preferably at least one selected from the group consisting of methanol and ethanol.

[0286] The amount of the alcohol brought into contact with the aqueous dispersion is preferably 1 to 500 mass ppm, more preferably 3 mass ppm or more, and even more preferably 200 mass ppm or less, relative to the mass of the aqueous dispersion.

[0287] The temperature when the aqueous dispersion is brought into contact with the alcohol is preferably 5°C to 99°C, more preferably 15°C or higher, and even more preferably lower than 35°C.

[0288] The pressure when the aqueous dispersion is brought into contact with the alcohol may be normal pressure.

[0289] The time for contacting the aqueous dispersion with the alcohol is preferably 1 minute or longer, more preferably 5 minutes or longer, further preferably 10 minutes or longer, particularly preferably 30 minutes or longer, and preferably 48 hours or shorter, more preferably 24 hours or shorter, further preferably 12 hours or shorter.

[0290] By the above-mentioned production method, an aqueous fluorinated polymer dispersion having a reduced content of polymerization radicals can be produced.

[0291] (Fluoropolymer aqueous dispersion)

[0292] The present invention also relates to an aqueous fluoropolymer dispersion having a reduced content of polymerization radicals. Specifically, the aqueous fluoropolymer dispersion of the present invention has an oxygen saturation of 53.5% or greater. The oxygen saturation of the aqueous dispersion is preferably 53.5% or greater, more preferably 60% or greater, even more preferably 70% or greater, and particularly preferably 80% or greater. The oxygen saturation of the aqueous dispersion may be 99% or less.

[0293] The aqueous fluorine-containing polymer dispersion of the present invention preferably contains a fluorine-containing polymer and an aqueous medium, and the content of the polymerization radical represented by the general formula (1) is 0 g -1 Hereinafter, the content of the oxidative radical represented by the general formula (2) is 0.1 g -1 The content of oxidative free radicals can be 4.1g -1 Above, it can be 9.0g -1 Theoretically, the content of polymerization free radicals will not be less than 0g -1 , but sometimes get below 0g -1 The measured value of .

[0294] General formula (1): R-(CF2-CF2) n (In the formula, R represents a monovalent group, n represents an integer greater than or equal to 1, and represents an unpaired electron.)

[0295] General formula (2): R-(CF2-CF2) n OO·(wherein, R represents a monovalent group, n represents an integer greater than or equal to 1, and · represents an unpaired electron.)

[0296] The aqueous fluoropolymer dispersion may further contain the above-mentioned aqueous medium.

[0297] The content of the fluorinated polymer in the aqueous fluorinated polymer dispersion is preferably 8% by mass to 50% by mass, more preferably 15% by mass or more, and more preferably 40% by mass or less.

[0298] The aqueous fluoropolymer dispersion may be diluted or concentrated. Examples of the concentration method include phase separation concentration, electroconcentration, electrophoresis, ion exchange, and membrane concentration. These phase separation concentration, ion exchange, and membrane concentration methods may be carried out under conventionally known treatment conditions, without particular limitation, and may be carried out by methods described in International Publication No. 2004 / 050719, JP-A-2002-532583, and JP-A-55-120630.

[0299] The aqueous fluoropolymer dispersion may further contain the above-mentioned fluorosurfactant. The content of the fluorosurfactant in the aqueous fluoropolymer dispersion may be 200 ppb by mass or more, 300 ppb by mass or more, or 400 ppb by mass or more, and may be 10% by mass or less, 1% by mass or less, or 0.5% by mass or less, relative to the mass of the fluoropolymer.

[0300] The fluorinated surfactant in the fluorinated polymer aqueous dispersion can be removed from the aqueous dispersion by known methods such as phase separation concentration, ion exchange, and membrane concentration. In one embodiment of the fluorinated polymer aqueous dispersion, the fluorinated surfactant is substantially not contained.

[0301] In the present invention, "substantially free of fluorinated surfactant" means that the content of fluorinated surfactant in the aqueous fluorinated polymer dispersion is 10 ppm by mass or less, preferably 1 ppm by mass or less, more preferably 100 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 the content of fluorinated surfactant as measured by liquid chromatography-mass spectrometry (LC / MS) is less than the detection limit.

[0302] The content of the fluorinated surfactant in the aqueous fluorinated polymer dispersion can be measured by liquid chromatography-mass spectrometry (LC / MS / MS).

[0303] First, methanol is added to the aqueous fluoropolymer dispersion for extraction, and the resulting extract is analyzed by LC / MS / MS. To further improve the extraction efficiency, Soxhlet extraction or ultrasonic treatment can be used.

[0304] Molecular weight information was extracted from the obtained LC / MS / MS spectrum, and it was confirmed that the molecular weight matched the structural formula of the candidate fluorinated surfactant.

[0305] Then, aqueous solutions of the identified fluorinated surfactant were prepared at five or more levels, and LC / MS / MS analysis was performed on the aqueous solutions at each level. The relationship between the content and the area of ​​the region corresponding to the content was plotted to create a calibration curve.

[0306] Then, using the calibration curve, the area of ​​the LC / MS / MS chromatogram of the fluorinated surfactant in the extract can be converted into the content of the fluorinated surfactant.

[0307] The aqueous fluoropolymer dispersion of the present invention has a reduced content of highly active polymerization radicals and a low content of impurities (by-products), and therefore can be used in various applications.

[0308] Fluoropolymer aqueous dispersions containing PTFE as the fluoropolymer are stabilized and further concentrated by adding a nonionic surfactant. Depending on the intended purpose, these compositions can be used in various applications as compositions with organic or inorganic fillers. By coating these aqueous dispersions onto metal or ceramic substrates, they can be formed into coatings exhibiting non-stick properties, a low coefficient of friction, gloss, smoothness, wear resistance, weather resistance, and heat resistance. These coatings are suitable for coating rollers and cooking equipment, as well as impregnation of glass cloth.

[0309] Also can prepare organosol by containing PTFE as the fluoropolymer aqueous dispersion of fluoropolymer.Above-mentioned organosol can comprise PTFE and organic solvent, as above-mentioned organic solvent, can enumerate ether solvent, ketone solvent, alcohol solvent, amide solvent, ester solvent, aliphatic hydrocarbon solvent, aromatic hydrocarbon solvent, halogenated hydrocarbon solvent, can preferably use N-Methyl-2-Pyrrolidone, dimethylacetamide etc.The preparation of above-mentioned organosol for example can be implemented by the method for putting down in writing in International Publication No. 2012 / 002038.

[0310] Fluoropolymer aqueous dispersions containing PTFE as the fluoropolymer are also preferably used as processing aids. When used as processing aids, by mixing the aqueous dispersion with a host polymer, etc., the melt strength of the host polymer during melt processing can be increased, thereby improving the mechanical strength, electrical properties, flame retardancy, anti-drip properties during combustion, and slip properties of the resulting polymer.

[0311] The aqueous fluoropolymer dispersion containing PTFE as the fluoropolymer is also preferably used as a binder for batteries and for dust prevention purposes.

[0312] Fluoropolymer aqueous dispersions containing PTFE as the fluoropolymer are also preferably used as processing aids after being compounded with resins other than PTFE. Fluoropolymer aqueous dispersions are suitable as raw materials for the PTFEs described in, for example, Japanese Patent Application Laid-Open No. 11-49912, U.S. Patent No. 5,804,654, Japanese Patent Application Laid-Open No. 11-29679, and Japanese Patent Application Laid-Open No. 2003-2980. Processing aids using fluoropolymer aqueous dispersions are comparable to those described in these publications.

[0313] The aqueous fluoropolymer dispersion containing PTFE as the fluoropolymer is preferably mixed with an aqueous dispersion of a melt-processable fluororesin and precipitated to produce a co-precipitated powder. The co-precipitated powder is suitable as a processing aid.

[0314] Examples of the melt-processable fluororesin include FEP, PFA, TFE / fluoroalkyl allyl ether copolymer, ETFE, and ethylene / TFE / HFP copolymer [EFEP]. Among them, PFA, TFE / fluoroalkyl allyl ether copolymer, and FEP are preferred.

[0315] The aqueous dispersion preferably also contains the melt-processable fluororesin. Examples of such melt-processable fluororesins include FEP, PFA, TFE / fluoroalkyl allyl ether copolymers, ETFE, and EFEP. The aqueous dispersion containing such a melt-processable fluororesin can be used as a coating. The melt-processable fluororesin enables the PTFE particles to be fully bonded to each other, thereby improving film-forming properties and imparting a glossy finish to the resulting coating.

[0316] The non-fluorine-containing resin of the coprecipitated powder can be powdered, granular or emulsion. From the aspect of fully mixing each resin, preferably, the addition is carried out while utilizing known methods such as extrusion mixing and roller mixing to impart shearing force.

[0317] Aqueous fluoropolymer dispersions containing PTFE as the fluoropolymer are also preferably used as dust suppressants. These dust suppressants can be used in methods whereby the PTFE is fibrillated by mixing it with a dust-generating substance and applying compression and shear to the mixture at a temperature of 20°C to 200°C, thereby suppressing dust from the dust-generating substance. Examples of these methods include those described in Japanese Patent Nos. 2827152 and 2538783. Aqueous fluoropolymer dispersions can be suitably used in dust suppressant compositions such as those described in International Publication No. 2007 / 004250 and in dust suppression methods such as those described in International Publication No. 2007 / 000812.

[0318] The dust suppression agent is suitable for use in dust suppression in the fields of building materials, soil stabilization materials, solidification materials, fertilizers, landfill treatment of incineration ash and hazardous substances, explosion-proofing, cosmetics, and pet litter such as cat litter.

[0319] Aqueous fluoropolymer dispersions containing PTFE as the fluoropolymer are also preferably used as a raw material for producing PTFE fibers by a dispersion spinning method. The dispersion spinning method involves mixing the aqueous PTFE dispersion with an aqueous dispersion of a matrix polymer, extruding the mixture to form an intermediate fiber structure, and calcining the intermediate fiber structure to decompose the matrix polymer and sinter the PTFE particles, thereby producing PTFE fibers.

[0320] Alternatively, a primer composition can be obtained by appropriately adding a nonionic surfactant to an aqueous fluoropolymer dispersion containing a TFE / FAVE copolymer [PFA] or a TFE / fluoroalkyl allyl ether copolymer as the fluoropolymer, and optionally dissolving or dispersing polyethersulfone, polyamideimide, and / or polyimide, and metal powder in an organic solvent. This primer composition can also be used in a method for coating a metal surface with a fluororesin, the method comprising applying the primer composition to the metal surface, applying a fluoropolymer composition onto the thus formed primer layer, and firing the fluoropolymer composition layer together with the primer layer.

[0321] While the embodiments have been described above, it will be understood that various changes can be made to the aspects and details without departing from the spirit and scope of the claims.

[0322] <1> According to a first aspect of the present invention, there is provided a method for producing an aqueous fluorinated polymer dispersion, comprising:

[0323] 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.

[0324] An aqueous fluoropolymer dispersion is obtained by blowing a gas containing oxygen into the aqueous dispersion, or by bringing the aqueous dispersion into contact with an oxidizing agent, or by bringing the aqueous dispersion into contact with an alcohol.

[0325] <2> According to a second aspect of the present invention, there is provided the production method according to the first aspect, wherein the alcohol is at least one selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol.

[0326] <3> According to a third aspect of the present invention, there is provided the production method according to the first aspect or the second aspect, wherein the oxidizing agent is hydrogen peroxide.

[0327] <4> According to a fourth aspect of the present invention, there is provided the production method according to any one of the first to third aspects, wherein the polymerization initiator is a water-soluble radical polymerization initiator.

[0328] <5> According to a fifth aspect of the present invention, there is provided a production method based on any one of the first to fourth aspects, wherein the fluorine-containing polymer is selected from polytetrafluoroethylene, tetrafluoroethylene / fluoroalkyl vinyl ether copolymer, tetrafluoroethylene / fluoroalkyl allyl ether copolymer, tetrafluoroethylene / hexafluoropropylene copolymer, ethylene / tetrafluoroethylene copolymer, ethylene / tetrafluoroethylene / hexafluoropropylene copolymer, polychlorotrifluoroethylene, chlorotrifluoroethylene / tetrafluoroethylene copolymer, ethylene / chlorotrifluoroethylene copolymer, polyvinyl fluoride, polyvinylidene fluoride, vinylidene fluoride / tetrafluoroethylene copolymer, fluorine-containing monomer / vinyl ester copolymer, general formula (150): CF2=CF-O-(CF2CFY 151 -O) n -(CFY 152 ) m -A 151 (where Y 151 represents a fluorine atom, a chlorine atom, a -SO2F group or a perfluoroalkyl group. The perfluoroalkyl group may contain ethereal oxygen and a -SO2F group. n represents an integer from 0 to 3. n Y 151 Can be the same or different. 152 represents a fluorine atom, a chlorine atom or a -SO2F group. m represents an integer from 1 to 5. m Y 152 Can be the same or different. 151 Indicates-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 156 The same or different groups represent H, ammonium, an alkali metal, an alkyl group containing or not containing a fluorine atom, an aryl group, or a sulfonyl group-containing group. At least one of the group consisting of a polymer of a fluorinated monomer represented by (a) and a fluororubber.

[0329] <6> According to a sixth aspect of the present invention, there is provided a production method according to any one of the first to fifth aspects, wherein a fluorinated monomer is polymerized in the presence of a chain transfer agent in addition to the fluorinated surfactant, the polymerization initiator, and the aqueous medium.

[0330] The fluorine-containing monomer contains at least tetrafluoroethylene, the polymerization initiator is a persulfate, and the chain transfer agent is at least one selected from the group consisting of alkanes having 1 to 5 carbon atoms and alcohols having 1 to 3 carbon atoms.

[0331] The fluorine-containing polymer is at least one selected from the group consisting of polytetrafluoroethylene and tetrafluoroethylene / fluoroalkyl vinyl ether copolymers.

[0332] After preparing the aqueous dispersion containing the fluorine-containing polymer,

[0333] Blowing a gas containing 20% ​​to 100% by volume of oxygen into the aqueous dispersion at a flow rate of 1 L / min to 30 L / min to generate bubbles, and allowing the aqueous dispersion to contact the oxygen-containing gas at 5° C. to 99° C. for more than 5 minutes; or

[0334] contacting the aqueous dispersion with hydrogen peroxide in an amount corresponding to 1 to 500 ppm by mass relative to the mass of the aqueous dispersion at 5° C. to 99° C. for 1 minute or longer; or

[0335] The aqueous dispersion is brought into contact with an alcohol having 1 to 10 carbon atoms in an amount corresponding to 1 to 500 ppm by mass relative to the mass of the aqueous dispersion at 5° C. to 99° C. for 1 minute or longer.

[0336] In this way, an aqueous dispersion having an oxygen saturation of 80% or more is obtained.

[0337] <7> According to a seventh aspect of the present invention, there is provided an aqueous dispersion comprising a fluoropolymer and an aqueous medium, wherein the dispersion has an oxygen saturation of 53.5% or more.

[0338] <8> According to an eighth aspect of the present invention, there is provided the aqueous dispersion according to the seventh aspect, wherein

[0339] The content of the polymerization radical represented by the general formula (1) is 0g -1 Hereinafter, the content of the oxidative radical represented by the general formula (2) is 0.1 g -1 above.

[0340] General formula (1): R-(CF2-CF2) n (In the formula, R represents a monovalent group, n represents an integer greater than or equal to 1, and represents an unpaired electron.)

[0341] General formula (2): R-(CF2-CF2) n OO·(wherein, R represents a monovalent group, n represents an integer greater than or equal to 1, and · represents an unpaired electron.)

[0342] <9> According to a ninth aspect of the present invention, there is provided the aqueous dispersion according to the seventh or eighth aspect, wherein the fluorinated polymer is at least one selected from the group consisting of polytetrafluoroethylene and tetrafluoroethylene / fluoroalkyl vinyl ether copolymers, and has an oxygen saturation of 80% or higher.

[0343] Example

[0344] Next, embodiments of the present invention will be described with reference to examples, but the present invention is not limited to these examples.

[0345] Each numerical value in the examples was measured by the following method.

[0346] <Amount of Free Radicals in Aqueous Dispersion>

[0347] The contents of polymerization radicals and oxidation radicals in the aqueous dispersion were determined using an electron spin resonance method (ESR method).

[0348] Polymerization radical: HOOC-(CF2-CF2) n (In the formula, n represents an integer greater than or equal to 1, and represents an unpaired electron.)

[0349] Oxidative free radical: HOOC-(CF2-CF2) n OO·(wherein, n represents an integer greater than or equal to 1, and · represents an unpaired electron.)

[0350] The content of polymerization radicals was determined from the intensity of the peak at g = 2.0056, which appeared in the first-order differential spectrum obtained by analyzing the aqueous dispersion using electron spin resonance. The content of oxidation radicals was determined from the intensity of the peak at g = 2.0218, which appeared in the first-order differential spectrum obtained by analyzing the aqueous dispersion using electron spin resonance.

[0351] Analysis conditions

[0352] Device: JEOL Ltd. (JEOL), JES-FR30EX

[0353] Measurement temperature: 23±3℃

[0354] Microwave frequency: 9.42 GHz

[0355] Microwave output power: 0.4mW

[0356] Central magnetic field: 347.548mT

[0357] Scan width: ±25mT

[0358] Scan time: 60s

[0359] Time constant: 0.03s

[0360] Magnetic field modulation width: 0.32mT

[0361] Scan times: 1

[0362] Modulation frequency: 100kHz

[0363] Mark:Mn 2+

[0364] <Oxygen saturation>

[0365] The measurement was performed using an optical dissolved oxygen meter FDO380.

[0366] Comparative Example 1

[0367] A PTFE aqueous dispersion was obtained by conducting a TFE polymerization reaction according to the method of Example 7 of International Publication No. 2009 / 020187.

[0368] Example 1

[0369] A PTFE aqueous dispersion was obtained in the same manner as in Comparative Example 1. 4 kg of the PTFE aqueous dispersion 1 obtained by opening the autoclave was transferred to another container, and air was blown into it at a flow rate of 2 L / min for 6 minutes for bubbling.

[0370] Example 2

[0371] The same procedure as in Example 1 was carried out except that the bubbling time was changed to 10 minutes.

[0372] Example 3

[0373] The same procedure as in Example 1 was carried out except that the bubbling time was changed to 15 minutes.

[0374] Example 4

[0375] The same procedure as in Example 1 was carried out except that the bubbling time was changed to 30 minutes.

[0376] Example 5

[0377] The same procedure as in Example 1 was carried out except that the bubbling time was changed to 60 minutes.

[0378] Comparative Example 2

[0379] The same procedure as in Example 1 was carried out except that the bubbling gas was changed from air to nitrogen, the flow rate was changed to 5 L / min, and the time was changed to 60 minutes.

[0380] Example 6

[0381] The same procedure as in Example 1 was carried out except that the bubbling flow rate was changed to 5 L / min and the bubbling time was changed to 6 minutes.

[0382] Example 7

[0383] The same procedure as in Example 6 was carried out except that the bubbling time was changed to 30 minutes.

[0384] Example 8

[0385] The same procedure as in Example 6 was carried out except that the bubbling time was changed to 60 minutes.

[0386] Example 9

[0387] The same procedure as in Example 6 was carried out except that the bubbling time was changed to 120 minutes.

[0388] Comparative Example 3

[0389] A PFA aqueous dispersion 1 was obtained by conducting a polymerization reaction of PFA according to the method (1) of Example 1 of Japanese Patent Application Laid-Open No. 62-541.

[0390] Reference Example 4

[0391] A PFA aqueous dispersion 2 was obtained by conducting a polymerization reaction of PFA according to the methods (1) and (2) of Example 1 of Japanese Patent Application Laid-Open No. 62-541.

[0392] Reference Example 5

[0393] A PFA aqueous dispersion 3 was obtained by conducting a polymerization reaction of PFA according to the method (1) and (2) and the phase separation and concentration operation of Example 1 of Japanese Patent Application Laid-Open No. 62-541.

[0394] Example 10

[0395] The PFA aqueous dispersion 1 was polymerized in the same manner as in Comparative Example 3. Then, 4 kg of the PTFE aqueous dispersion 1 obtained by opening the autoclave was transferred to another container, and air was blown into it at a flow rate of 5 L / min for 120 minutes for bubbling.

[0396] Example 11

[0397] The PFA aqueous dispersion 2 was polymerized in the same manner as in Reference Example 4. Then, 4 kg of the PTFE aqueous dispersion 1 obtained by opening the autoclave was transferred to another container, and air was blown into it at a flow rate of 5 L / min for 120 minutes for bubbling.

[0398] Example 12

[0399] PFA aqueous dispersion 3 was polymerized in the same manner as in Comparative Example 5. Then, 4 kg of PTFE aqueous dispersion 1 obtained by opening the autoclave was transferred to another container, and air was blown into the container at a flow rate of 5 L / min for 120 minutes for bubbling.

[0400] Example 13

[0401] The PTFE aqueous dispersion was polymerized in the same manner as in Comparative Example 1. Then, 4 kg of the PTFE aqueous dispersion 1 obtained by opening the autoclave was transferred to another container. The temperature in the container was raised under stirring. After the temperature in the container reached 80°C, an aqueous solution of 3.5 g of hydrogen peroxide [H2O2] dissolved in 10 ml of deionized water was added as an oxidizing agent, and the mixture was stirred in an air atmosphere for 10 minutes.

[0402] Example 14

[0403] The same procedure as in Example 13 was carried out except that the amount of H 2 O 2 added was set to 35.4 g.

[0404] Example 15

[0405] The same procedure as in Example 13 was carried out except that the amount of the aqueous hydrogen peroxide solution was changed to 1.7 g of methanol [MeOH].

[0406] Example 16

[0407] The same procedure as in Example 15 was carried out except that the amount of MeOH added was 16.8 g.

[0408] Example 17

[0409] The same procedure as in Example 15 was carried out except that the amount of MeOH added was 168 g.

[0410] Example 18

[0411] The same procedure as in Example 15 was carried out except that the amount of MeOH added was 1680 g.

[0412] The various physical properties of the aqueous PTFE dispersions obtained in Examples and Comparative Examples were evaluated by the above-mentioned methods. The results are shown in Tables 1 to 3.

[0413]

[0414]

[0415]

[0416] Figure 1 The first-order differential spectra of the aqueous dispersions obtained in Examples 6, 8, 13, 14, and Comparative Example 1 (horizontal axis: g value (-), vertical axis: Int.[PTFE] / Int.[Mn 2+ ] / sample weight (g -1 )).according to Figure 1 The results shown show that in the first-order differential spectrum of the aqueous dispersion obtained by the production method of the present invention, only two peaks were observed, not three. This result shows that there are no polymerization radicals in the aqueous dispersion, and only oxidation radicals are present.

Claims

1. A method for producing an aqueous fluoropolymer dispersion, wherein: 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. An aqueous fluoropolymer dispersion is obtained by blowing a gas containing oxygen into the aqueous dispersion, or by bringing the aqueous dispersion into contact with an oxidizing agent, or by bringing the aqueous dispersion into contact with an alcohol.

2. The manufacturing method according to claim 1, wherein The alcohol is at least one selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol.

3. The manufacturing method according to claim 1 or 2, wherein: The oxidant is hydrogen peroxide.

4. The production method according to any one of claims 1 to 3, wherein The polymerization initiator is a water-soluble free radical polymerization initiator.

5. The production method according to any one of claims 1 to 4, wherein The fluorine-containing polymer is selected from polytetrafluoroethylene, tetrafluoroethylene / fluoroalkyl vinyl ether copolymer, tetrafluoroethylene / fluoroalkyl allyl ether copolymer, tetrafluoroethylene / hexafluoropropylene copolymer, ethylene / tetrafluoroethylene copolymer, ethylene / tetrafluoroethylene / hexafluoropropylene copolymer, polychlorotrifluoroethylene, chlorotrifluoroethylene / tetrafluoroethylene copolymer, ethylene / chlorotrifluoroethylene copolymer, polyvinyl fluoride, polyvinylidene fluoride, vinylidene fluoride / tetrafluoroethylene copolymer, fluorine-containing monomer / vinyl ester copolymer, general formula (150): CF2=CF-O-(CF2CFY 151 -O) n -(CFY 152 ) m -A 151 At least one selected from the group consisting of polymers of the fluorinated monomers and fluororubbers, In the general formula (150), Y 151 represents a fluorine atom, a chlorine atom, a -SO2F group or a perfluoroalkyl group; the perfluoroalkyl group may contain ethereal oxygen and a -SO2F group; n represents an integer from 0 to 3; n Y 151 Can be the same or different; Y 152 represents a fluorine atom, a chlorine atom or a -SO2F group; m represents an integer from 1 to 5; m Y 152 Can be the same or different; A 151 Indicates-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 156 The same or different groups represent H, ammonium, an alkali metal, an alkyl group containing or not containing a fluorine atom, an aryl group, or a sulfonyl-containing group.

6. The production method according to any one of claims 1 to 5, wherein In the presence of a chain transfer agent in addition to the fluorine-containing surfactant, the polymerization initiator and the aqueous medium, polymerizing the fluorine-containing monomer, The fluorine-containing monomer contains at least tetrafluoroethylene, the polymerization initiator is a persulfate, and the chain transfer agent is at least one selected from the group consisting of alkanes having 1 to 5 carbon atoms and alcohols having 1 to 3 carbon atoms. The fluorine-containing polymer is at least one selected from the group consisting of polytetrafluoroethylene and tetrafluoroethylene / fluoroalkyl vinyl ether copolymers. After preparing the aqueous dispersion containing the fluorine-containing polymer, Blowing a gas containing 20% ​​to 100% by volume of oxygen into the aqueous dispersion at a flow rate of 1 L / min to 30 L / min to generate bubbles, and allowing the aqueous dispersion to contact the oxygen-containing gas at 5° C. to 99° C. for more than 5 minutes; or contacting the aqueous dispersion with hydrogen peroxide in an amount corresponding to 1 to 500 ppm by mass relative to the mass of the aqueous dispersion at 5° C. to 99° C. for 1 minute or longer; or The aqueous dispersion is brought into contact with an alcohol having 1 to 10 carbon atoms in an amount corresponding to 1 to 500 ppm by mass relative to the mass of the aqueous dispersion at 5° C. to 99° C. for 1 minute or longer. In this way, an aqueous dispersion having an oxygen saturation of 80% or more is obtained.

7. An aqueous dispersion comprising a fluorinated polymer and an aqueous medium, wherein: Oxygen saturation is above 53.5%.

8. The aqueous dispersion according to claim 7, wherein The content of the polymerization radical represented by the general formula (1) is 0g -1 Hereinafter, the content of the oxidative radical represented by the general formula (2) is 0.1 g -1 above, General formula (1): R-(CF2-CF2) n · In the general formula (1), R represents a monovalent group, n represents an integer greater than 1, and · represents an unpaired electron. General formula (2): R-(CF2-CF2) n OO· In the general formula (2), R represents a monovalent group, n represents an integer of 1 or greater, and · represents an unpaired electron.

9. The aqueous dispersion according to claim 7 or 8, wherein The fluorine-containing polymer is at least one selected from the group consisting of polytetrafluoroethylene and tetrafluoroethylene / fluoroalkyl vinyl ether copolymers, and has an oxygen saturation of 80% or more.

Images