Fluoropolymer aqueous dispersion

Abstract

To provide a fluoropolymer aqueous dispersion hardly foaming.SOLUTION: A fluoropolymer aqueous dispersion includes a polymer (I) having a hydrophilic group, a fluoropolymer, a nonionic surface active agent (a) having an HLB of higher than 8, and an aqueous medium, where substantially no fluorine-containing surface active agent is included, the content of the fluoropolymer is 40 mass% or more and 70 mass% or less to the fluoropolymer aqueous dispersion, the content of a nonionic surface active agent (a) is 4.0 mass% or more and 12 mass% or less to the fluoropolymer, and a height of foam of the fluoropolymer aqueous dispersion generated by a foamability test is 140 mm or lower.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to an aqueous dispersion of a fluoropolymer.

Background Art

[0002] Patent Document 1 describes a composition containing polytetrafluoroethylene, a polymer (I) containing a polymerization unit (I) based on a monomer represented by the general formula (I), a nonionic surfactant, and an aqueous medium, wherein the content of the polytetrafluoroethylene in the composition is 10% by mass or more with respect to the composition, and the content of the nonionic surfactant in the composition is 1.0% by mass or more with respect to the polytetrafluoroethylene. CX 1 X 3 =CX 2 R(-CZ 1 Z 2 -A 0 ) m (I) (In the formula, X 1 and X 3 are each independently F, Cl, H, or CF3; X 2 is H, F, an alkyl group, or a fluorine-containing alkyl group; A 0 is an anionic group; R is a linking group; Z 1 and Z 2 are each independently H, F, an alkyl group, or a fluorine-containing alkyl group; and m is an integer of 1 or more.)

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to provide a fluoropolymer aqueous dispersion that is difficult to foam.

Means for Solving the Problems

[0005] According to the present disclosure, there is provided a fluoropolymer aqueous dispersion containing a polymer (I) having a hydrophilic group, a fluoropolymer, a nonionic surfactant (a) having an HLB of more than 8, and an aqueous medium, which substantially does not contain a fluorine-containing surfactant, wherein the content of the fluoropolymer is 40% by mass or more and 70% by mass or less with respect to the fluoropolymer aqueous dispersion, the content of the nonionic surfactant (a) is 4.0% by mass or more and 12% by mass or less with respect to the fluoropolymer, and the height of the foam of the fluoropolymer aqueous dispersion produced by a foaming property test is 140 mm or less.

Advantages of the Invention

[0006] According to the present disclosure, it is possible to provide a fluoropolymer aqueous dispersion that is difficult to foam.

Modes for Carrying Out the Invention

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

[0008] In the present disclosure, a fluororesin is a semi-crystalline fluoropolymer and is a fluoroplastic. The fluororesin has a melting point and has thermoplasticity, and may be melt-processable or non-melt-processable.

[0009] In the present disclosure, melt processability means that it is possible to melt and process a polymer using conventional processing equipment such as an extruder and an injection molding machine. Therefore, a melt-processable fluororesin usually has a melt flow rate measured by the measurement method described below of 0.01 to 500 g / 10 minutes.

[0010] In the present disclosure, fluororubber is an amorphous fluoropolymer. "Amorphous" means that the size of the melting peak (ΔH) appearing in the differential scanning calorimetry [DSC] (heating rate: 10 °C / min) or differential thermal analysis [DTA] (heating rate: 10 °C / min) of the fluoropolymer is 4.5 J / g or less. Fluororubber exhibits elastomeric properties when crosslinked. The elastomeric properties mean that the polymer can be stretched and can retain its original length when the force required to stretch the polymer is no longer applied.

[0011] In the present disclosure, perfluororubber (perfluoroelastomer) is a fluoropolymer having a content of perfluoromonomer units of 90 mol% or more, preferably 91 mol% or more, based on all polymerization units, having a glass transition temperature of 20 °C or lower, and having a melting peak (ΔH) size of 4.5 J / g or less. Further, it is a polymer in which the concentration of fluorine atoms contained in the fluoropolymer is 71 mass% or more, preferably 71.5 mass% or more. In the present disclosure, the concentration of fluorine atoms contained in the fluoropolymer is determined by calculation of the concentration (mass%) of fluorine atoms contained in the fluoropolymer from the types and contents of the respective monomers constituting the fluoropolymer.

[0012] In the present disclosure, a perfluoromonomer is a monomer that does not contain a carbon atom-hydrogen atom bond in its molecule. The above perfluoromonomer may be a monomer in which some of the fluorine atoms bonded to the carbon atom are substituted with chlorine atoms in addition to the carbon atom and fluorine atoms, or may have a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, a boron atom, or a silicon atom in addition to the carbon atom. The above perfluoromonomer is preferably a monomer in which all hydrogen atoms are substituted with fluorine atoms. The above perfluoromonomer does not include a monomer that provides a crosslinking site.

[0013] A monomer that provides a crosslinking site is a monomer (cure site monomer) having a crosslinkable group that provides a crosslinking site for forming a crosslink with a curing agent to the fluoropolymer.

[0014] In the present disclosure, polytetrafluoroethylene [PTFE] is preferably a fluoropolymer in which the content of tetrafluoroethylene units relative to all polymerization units is 99 mol% or more.

[0015] In the present disclosure, fluororesins (excluding polytetrafluoroethylene) and fluororubbers are both preferably fluoropolymers in which the content of tetrafluoroethylene units relative to all polymerization units is less than 99 mol%.

[0016] In the present disclosure, the content of each monomer constituting the fluoropolymer can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and X-ray fluorescence analysis according to the type of monomer.

[0017] In the present disclosure, the "organic group" means a group containing one or more carbon atoms, or a group formed by removing one hydrogen atom from an organic compound. As the above organic group, an alkyl group which may have one or more substituents is preferable.

[0018] In the present disclosure, the range represented by the endpoints includes all numerical values included within that range (for example, 1 to 10 includes 1.4, 1.9, 2.33, 5.75, 9.98, etc.).

[0019] In the present disclosure, the description of "at least 1" includes all numerical values of 1 or more (for example, at least 2, at least 4, at least 6, at least 8, at least 10, at least 25, at least 50, at least 100, etc.).

[0020] Hereinafter, specific embodiments of the present disclosure will be described in detail, but the present disclosure is not limited to the following embodiments.

[0021] An aqueous dispersion of a fluoropolymer containing the fluoropolymer at a high concentration can be used in various applications in the form of the aqueous dispersion. When the aqueous dispersion of a fluoropolymer contains the fluoropolymer at a high concentration, the dispersion stability of the fluoropolymer in the aqueous dispersion of a fluoropolymer is likely to be impaired. Therefore, as described in Patent Document 1, a technique for enhancing the dispersion stability of a fluoropolymer by using a polymer (I) containing a polymerization unit (I) and a nonionic surfactant for the aqueous dispersion of a fluoropolymer is known.

[0022] However, it has now been found that when such an aqueous dispersion of a fluoropolymer is stirred, foaming may occur, and there is a problem of degrading the quality of the final product when applied to various applications. Means for suppressing foaming of an aqueous dispersion of a fluoropolymer containing a fluoropolymer at a high concentration and containing a polymer having a hydrophilic group and a nonionic surfactant have not yet been studied.

[0023] The first aqueous dispersion of a fluoropolymer of the present disclosure is an aqueous dispersion of a fluoropolymer containing a polymer (I) having a hydrophilic group, a fluoropolymer, a nonionic surfactant (a) having an HLB exceeding 8, and an aqueous medium, substantially not containing a fluorine-containing surfactant, wherein the content of the fluoropolymer is 40% by mass or more and 70% by mass or less with respect to the aqueous dispersion of a fluoropolymer, the content of the nonionic surfactant (a) is 4.0% by mass or more and 12% by mass or less with respect to the fluoropolymer, and the height of the foam of the aqueous dispersion of a fluoropolymer generated by a foaming property test is 140 mm or less.

[0024] Since the first aqueous dispersion of a fluoropolymer of the present disclosure has the above-described configuration, despite containing the fluoropolymer at a high concentration, the dispersion stability of the fluoropolymer is high and it is difficult to foam. Therefore, even when the aqueous dispersion of a fluoropolymer is applied to various applications, problems due to foaming of the aqueous dispersion are less likely to occur, and high-quality products can be manufactured.

[0025] Further, the second fluoropolymer aqueous dispersion of the present disclosure is a fluoropolymer aqueous dispersion containing a polymer (I) having a hydrophilic group, a fluoropolymer, a nonionic surfactant (a) with an HLB exceeding 8, a nonionic surfactant (b) with an HLB of 8 or less, and an aqueous medium, which substantially does not contain a fluorine-containing surfactant. The content of the fluoropolymer is 40% by mass or more and 70% by mass or less with respect to the fluoropolymer aqueous dispersion, and the content of the nonionic surfactant (a) is 4.0% by mass or more and 12% by mass or less with respect to the fluoropolymer.

[0026] Since the second fluoropolymer aqueous dispersion of the present disclosure has the above-described configuration, despite containing a high concentration of the fluoropolymer, the dispersion stability of the fluoropolymer is high and it is difficult to foam. Therefore, even when the fluoropolymer aqueous dispersion is applied to various uses, problems caused by foaming of the aqueous dispersion are less likely to occur, and high-quality products can be manufactured.

[0027] Hereinafter, the first and second fluoropolymer aqueous dispersions of the present disclosure (hereinafter, sometimes simply referred to as fluoropolymer aqueous dispersions when both are combined) will be described in detail.

[0028] (Fluoropolymer aqueous dispersion) In one embodiment, the fluoropolymer aqueous dispersion can be characterized in that the height of the foam generated by the foaming property test is 140 mm or less.

[0029] The height of the foam is an index of the foaming power of the fluoropolymer aqueous dispersion. When the height of the foam generated by the foaming property test is 140 mm or less, when the fluoropolymer aqueous dispersion is used for various uses, it is difficult for foam to occur or the generated foam easily disappears, so problems caused by foaming of the aqueous dispersion are less likely to occur, and high-quality products can be manufactured.

[0030] The height of the foam is preferably 120 mm or less, more preferably 100 mm or less, and still more preferably 70 mm or less.

[0031] The height of the foam in the aqueous dispersion can be specified by adjusting the content of the fluoropolymer in the aqueous dispersion to 55% by mass, performing a foaming property test by the Ross-Miles method in accordance with JIS K3362, dropping the fluoropolymer aqueous dispersion with the content of the fluoropolymer adjusted to 55% by mass to generate foam, and measuring the height of the foam immediately after dropping.

[0032] In one embodiment, the content of the fluoropolymer in the fluoropolymer aqueous dispersion is 40% by mass or more and 70% by mass or less, preferably 45% by mass or more, more preferably 55% by mass or more, preferably 67% by mass or less, and more preferably 65% by mass or less, based on the fluoropolymer aqueous dispersion.

[0033] The content (P% by mass) of the fluoropolymer in the fluoropolymer aqueous dispersion is a value calculated according to the formula: P = [Z / X] × 100 (mass%) from the heating residue (Y g) obtained by heating about 1 g (X g) of the sample at 110°C for 30 minutes and the heating residue (Z g) obtained by further heating the obtained heating residue (Y g) at 300°C for 30 minutes.

[0034] In one embodiment, the content of the nonionic surfactant (a) in the fluoropolymer aqueous dispersion is 4.0% by mass or more and 12% by mass or less, preferably 5.0% by mass or more, more preferably 5.5% by mass or more, preferably 10% by mass or less, and more preferably 8.0% by mass or less, based on the fluoropolymer.

[0035] The content (N% by mass) of the nonionic surfactant (a) is a value calculated according to the formula: N = [(Y - Z) / X] × 100 (mass%) from the heating residue (Y g) obtained by heating about 1 g (X g) of the sample at 110°C for 30 minutes and the heating residue (Z g) obtained by further heating the obtained heating residue (Y g) at 300°C for 30 minutes.

[0036] In one embodiment, the content of polymer (I) in the aqueous dispersion of the fluoropolymer is preferably 0.1 ppm by mass or more, more preferably 0.5 ppm by mass or more, still more preferably 10.0 ppm by mass or more, preferably 2000 ppm by mass or less, more preferably 1500 ppm by mass or less, still more preferably less than 1000 ppm by mass, yet still more preferably 500 ppm by mass or less, and particularly preferably 250 ppm by mass or less, based on the aqueous dispersion.

[0037] In one embodiment, the content of polymer (I) in the aqueous dispersion of the fluoropolymer is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, still more preferably 0.01% by mass or more, particularly preferably 0.05% by mass or more, most preferably 0.10% by mass or more, preferably 10% by mass or less, more preferably 5.0% by mass or less, still more preferably 2.0% by mass or less, particularly preferably 1.0% by mass or less, and most preferably 0.50% by mass or less, based on the fluoropolymer.

[0038] The content of polymer (I) in the polymerization dispersion is determined by solid-state NMR measurement or melt NMR measurement. When polymer (I) contains a carbonyl group, it can also be determined by a Fourier transform infrared spectrometer. In addition, the measurement methods of the respective polymers are described in International Publication No. WO2014 / 099453, International Publication No. WO2010 / 075497, International Publication No. WO2010 / 075496, International Publication No. WO2011 / 008381, International Publication No. WO2009 / 055521, International Publication No. WO1987 / 007619, JP-A-61-293476, International Publication No. WO2010 / 075494, International Publication No. WO2010 / 075359, International Publication No. WO2012 / 082454, International Publication No. WO2006 / 119224, International Publication No. WO2013 / 085864, International Publication No. WO2012 / 082707, International Publication No. WO2012 / 082703, International Publication No. WO2012 / 082451, International Publication No. WO2006 / 135825, International Publication No. WO2004 / 067588, International Publication No. WO2009 / 068528, JP-A-2004-075978, JP-A-2001-226436, International Publication No. WO1992 / 017635, International Publication No. WO2014 / 069165, JP-A-11-181009, etc. As the measurement method of the content of polymer (I), the measurement methods of the respective polymers described therein can be used.

[0039] In one embodiment, the fluoropolymer aqueous dispersion substantially does not contain a fluorine-containing surfactant.

[0040] In the present disclosure, "substantially does not contain a fluorine-containing surfactant" means that the content of the fluorine-containing surfactant in the aqueous dispersion is 10 mass ppm or less, preferably 1 mass ppm or less, more preferably 100 mass ppb or less, still more preferably 10 mass ppb or less, even more preferably 1 mass ppb or less, and particularly preferably, the fluorine-containing surfactant is below the detection limit by measurement using liquid chromatography-mass spectrometry (LC / MS).

[0041] The content of the fluorine-containing surfactant can be measured, for example, by adding methanol to the aqueous dispersion, performing extraction, and subjecting the obtained extract to LC / MS analysis. In order to further improve the extraction efficiency, treatment such as Soxhlet extraction or ultrasonic treatment may be performed. Extract the molecular weight information from the obtained LC / MS spectrum and confirm the match with the structural formula of the candidate fluorosurfactant. Subsequently, prepare aqueous solutions of the confirmed fluorosurfactant with a content of 5 levels or more, perform LC / MS analysis on the aqueous solutions of each content, plot the relationship between the content and the area corresponding to that content, and draw a calibration curve. Then, using the calibration curve, the area of the LC / MS chromatogram of the fluorosurfactant in the extract can be converted to the content of the fluorosurfactant.

[0042] (Nonionic surfactant (b)) In one embodiment, the fluoropolymer aqueous dispersion contains a nonionic surfactant (b) with an HLB of 8 or less. The nonionic surfactant (b) with an HLB of 8 or less reduces the foaming power of the fluoropolymer aqueous dispersion and suppresses foaming when the fluoropolymer aqueous dispersion is stirred. When using a nonionic surfactant with a large HLB, it is difficult to suppress foaming when the fluoropolymer aqueous dispersion is stirred.

[0043] The HLB value of the nonionic surfactant (b) is 8 or less, preferably 1 or more.

[0044] In the present disclosure, the HLB of the nonionic surfactant (b) is a value defined by the following calculation formula by the Griffin method. HLB value = 20 × [sum of chemical formula weights of hydrophilic parts] / molecular weight

[0045] As the nonionic surfactant (b), at least one selected from the group consisting of acetylene diol-based surfactants and alkane diol-based surfactants is preferred.

[0046] Acetylenediol-based surfactants are surfactants having a carbon-carbon triple bond in the molecule. Examples of acetylenediol-based surfactants include acetylenediol (having an acetylene bond and two hydroxyl groups in the same molecule) surfactants, and surfactants obtained by adding an alkylene oxide unit to acetylenediol.

[0047] As the acetylenediol-based surfactant, the compound represented by the general formula (11) and the compound represented by the general formula (12) are preferable.

[0048]

Chemical formula

[0049]

Chemical formula

[0050] As the acetylenediol-based surfactant, commercially available products may be used. Examples of commercially available products of acetylenediol-based surfactants include Dynol (registered trademark) 607, Surfynol (registered trademark) 104E, 104H, 420 (manufactured by Nissin Chemical Industry Co., Ltd., etc.).

[0051] Examples of alkanediol-based surfactants include surfactants having one alkylene group and two hydroxyl groups in the same molecule.

[0052] Examples of alkanediol-based surfactants include the compound represented by the general formula (13) and the compound represented by the general formula (14).

[0053] HO-R5 -OH (13) (In the formula, R 5 represents a linear or branched alkylene group having 1 to 200 carbon atoms.)

[0054] HO-R 6 -OH (14) (In the formula, R 6 represents a linear or branched polyoxyalkylene group having 1 to 200 carbon atoms.)

[0055] Commercially available products may be used as the alkanediol-based surfactant. Examples of commercially available products of the alkanediol-based surfactant include Surfynol (registered trademark) AD01 (manufactured by Nissin Chemical Industry Co., Ltd.) and the like.

[0056] In one embodiment, the surface tension of a 0.1% aqueous solution of the nonionic surfactant (b) is 40 mN / m or less.

[0057] In the present disclosure, the surface tension of the nonionic surfactant (b) can be measured by the Wilhelmy method at 25°C.

[0058] In one embodiment, the content of the nonionic surfactant (b) is 0.2% by mass or more and 10% by mass or less, preferably 0.3% by mass or more, more preferably 0.5% by mass or more, preferably 8.0% by mass or less, and more preferably 5.0% by mass or less with respect to the fluoropolymer aqueous dispersion.

[0059] The content of the nonionic surfactant (b) can be calculated from the amount of the nonionic surfactant (b) used in the preparation of the aqueous dispersion and the like.

[0060] (Nonionic surfactant (a)) In one embodiment, the fluoropolymer aqueous dispersion contains a nonionic surfactant (a) having an HLB exceeding 8. By using the nonionic surfactant (a), the dispersion stability of the fluoropolymer aqueous dispersion can be improved. Further, when the nonionic surfactant (a) is used to concentrate the fluoropolymer aqueous dispersion by the phase separation concentration method, the concentration proceeds smoothly. Therefore, the fluoropolymer aqueous dispersion containing the nonionic surfactant (a) is easy to manufacture. Instead of the nonionic surfactant (a), when a nonionic surfactant (b) having an HLB of 8 or less is used to concentrate the fluoropolymer aqueous dispersion by the phase separation concentration method, it is usually difficult to obtain an aqueous dispersion having a fluoropolymer content of 40% by mass or more. Therefore, the fluoropolymer aqueous dispersion containing the nonionic surfactant (a) and the nonionic surfactant (b) is easy to manufacture, has high dispersion stability of the fluoropolymer, and is less likely to foam, even though it contains a high concentration of the fluoropolymer.

[0061] The nonionic surfactant (a) usually does not contain a charged group and has a hydrophobic portion that is a long-chain hydrocarbon. The hydrophilic portion of the nonionic surfactant (a) contains a water-soluble functional group such as a chain of ethylene ether derived from polymerization with ethylene oxide.

[0062] The HLB value of the nonionic surfactant (a) exceeds 8, preferably is 10 or more, and preferably is 18 or less.

[0063] In the present disclosure, the HLB of the nonionic surfactant (a) is a value defined by the following calculation formula by the Griffin method. HLB value = 20 × [sum of chemical formula weights of hydrophilic portions] / molecular weight

[0064] As the nonionic surfactant (a), a nonionic surfactant represented by the general formula (i) is preferable. R 6 -O-A 1 -H (i) (In the formula, R 6is a linear or branched primary or secondary alkyl group having 8 to 18 carbon atoms, and A 1 is a polyoxyalkylene chain.)

[0065] In the general formula (i), R 6 preferably has 10 to 16 carbon atoms, more preferably 12 to 16 carbon atoms. When the number of carbon atoms of R 6 is 18 or less, excellent sedimentation stability of the aqueous dispersion is easily obtained. Also, when the number of carbon atoms of R 6 exceeds 18, it is difficult to handle because the flow temperature is high. When the number of carbon atoms of R 6 is less than 8, the surface tension of the aqueous dispersion becomes high, and the permeability and wettability tend to decrease.

[0066] A 1 The polyoxyalkylene chain of may consist of oxyethylene and oxypropylene. It is a polyoxyalkylene chain consisting of an average repeat number of 5 to 20 of oxyethylene groups and an average repeat number of 0 to 2 of oxypropylene groups, and is a hydrophilic group. The number of oxyethylene units can include either a broad or narrow unimodal distribution that is usually provided, or a broader or bimodal distribution obtained by blending. When the average repeat number of oxypropylene groups exceeds 0, the oxyethylene groups and oxypropylene groups in the polyoxyalkylene chain may be arranged in a block or random manner. From the viewpoints of the viscosity and sedimentation stability of the aqueous dispersion, a polyoxyalkylene chain composed of an average repeat number of 7 to 12 of oxyethylene groups and an average repeat number of 0 to 2 of oxypropylene groups is preferred. In particular, when A 1 has an average of 0.5 to 1.5 oxypropylene groups, it has good low foaming properties and is preferred.

[0067] More preferably, R 6 is (R’)(R’’)HC-, where R’ and R’’ are the same or different linear, branched, or cyclic alkyl groups, and the total amount of carbon atoms is at least 5, preferably 7 to 17. Preferably, at least one of R’ or R’’ is a branched or cyclic hydrocarbon group.

[0068] Specific examples of the above polyoxyethylene alkyl ether include C 13 H 27 -O-(C2H4O) n -H, C 12 H 25 -O-(C2H4O) n -H, C 10 H 21 CH(CH3)CH2-O-(C2H4O) n -H, C 13 H 27 -O-(C2H4O) n -(CH(CH3)CH2O)-H, C 16 H 33 -O-(C2H4O) n -H, HC(C5H 11 )(C7H 15 )-O-(C2H4O) n -H (in each formula, n is an integer of 1 or more), etc. Examples of commercially available products of the above polyoxyethylene alkyl ether include, for example, Genapol X series (manufactured by Clariant) such as Genapol X080 (trade name), Neugen TDS series (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) such as Neugen TDS-80 (trade name), Leocol TD series (manufactured by Lion) such as Leocol TD-90 (trade name), Lionol (registered trademark) TD series (manufactured by Lion), T-Det A series (manufactured by Harcros Chemicals) such as T-Det A138 (trade name), Tergitol (registered trademark) 15-S series (manufactured by The Dow Chemical Company), etc.

[0069] The above nonionic surfactant (a) is preferably an ethoxylate of 2,6,8-trimethyl-4-nonanol having an average of about 4 to about 18 ethylene oxide units, an ethoxylate of 2,6,8-trimethyl-4-nonanol having an average of about 6 to about 12 ethylene oxide units, or a mixture thereof. This type of nonionic surfactant is also commercially available, for example, as TERGITOL TMN-6, TERGITOL TMN-10, and TERGITOL TMN-100X (all trade names, manufactured by The Dow Chemical Company).

[0070] Also, the hydrophobic group of the nonionic surfactant (a) may be any of an alkylphenol group, a linear alkyl group, and a branched alkyl group. For example, as the nonionic surfactant (a), for example, the general formula (ii) R 7 -C6H4-O-A 2 -H (ii) (In the formula, R 7 is a linear or branched alkyl group having 4 to 12 carbon atoms, and A 2 is a polyoxyalkylene chain.) The nonionic surfactant represented by the formula may be mentioned. Specifically, as the nonionic surfactant (a), Triton (registered trademark) X-100 (trade name, manufactured by Dow Chemical Company), etc. may be mentioned.

[0071] A 2 The polyoxyalkylene chain of may be composed of oxyethylene and oxypropylene. It is a polyoxyalkylene chain composed of an average repeating number of 5 to 20 of oxyethylene groups and an average repeating number of 0 to 2 of oxypropylene groups, and is a hydrophilic group. The number of oxyethylene units may include either a broad or narrow unimodal distribution provided usually, or a broader or bimodal distribution obtained by blending. When the average repeating number of oxypropylene groups exceeds 0, the oxyethylene groups and oxypropylene groups in the polyoxyalkylene chain may be arranged in a block form or in a random form. From the viewpoints of the viscosity and sedimentation stability of the aqueous dispersion, a polyoxyalkylene chain composed of an average repeating number of 7 to 12 of oxyethylene groups and an average repeating number of 0 to 2 of oxypropylene groups is preferable. Particularly, when A 2 has an average of 0.5 to 1.5 oxypropylene groups, it has good low foaming properties and is preferable.

[0072] More preferably, R 7is a primary or secondary alkyl group, more preferably (R’)(R’’)HC-, where R’ and R’’ are the same or different linear, branched, or cyclic alkyl groups, and the total amount of carbon atoms is at least 5, preferably 7 to 17. Preferably, at least one of R’ or R’’ is a branched or cyclic hydrocarbon group.

[0073] Examples of other nonionic surfactant (a) include bifunctional block copolymers supplied by BASF as the Pluronic® R series, and tridecyl alcohol alkoxylates supplied by BASF as the Iconol® TDA series.

[0074] As the nonionic surfactant (a) described above, at least one selected from the group consisting of nonionic surfactants represented by the general formula (i) and nonionic surfactants represented by the general formula (ii) is preferred, and nonionic surfactants represented by the general formula (i) are more preferred.

[0075] The nonionic surfactant (a) described above preferably does not contain an aromatic moiety.

[0076] (aqueous medium) In one embodiment, the fluoropolymer aqueous dispersion contains an aqueous medium. The aqueous medium is not particularly limited as long as it contains water, and may contain water and, for example, a fluorine-free organic solvent such as ether or ketone, and / or a fluorine-containing organic solvent having a boiling point of 40 °C or lower. As the aqueous medium, an aqueous medium containing only water or an aqueous medium containing only water and a fluorine-free organic solvent is preferred, and an aqueous medium containing only water is more preferred. That is, the aqueous medium is preferably water.

[0077] (polymer (I) having a hydrophilic group) In one embodiment, the fluoropolymer aqueous dispersion contains a polymer (I) having a hydrophilic group. By using the polymer (I) having a hydrophilic group, the dispersion stability of the fluoropolymer aqueous dispersion can be improved.

[0078] The polymer (I) is a polymer having one or more hydrophilic groups in the molecule. As the hydrophilic group, an ionic group is preferable, and an anionic group is more preferable.

[0079] In the present disclosure, the anionic group includes, in addition to anionic groups such as a sulfate group and a carboxylate group, a functional group that gives an anionic group such as an acid group like -COOH and an acid salt group like -COONH4. As the anionic group, a sulfate group, a carboxylate group, a phosphate group, a phosphonate group, a sulfonate group, or -C(CF3)2OM (wherein M is -H, a metal atom, -NR 7 4, an optionally substituted imidazolium, an optionally substituted pyridinium or an optionally substituted phosphonium, and R 7 is H or an organic group.) is preferable.

[0080] The ion exchange capacity of the polymer (I) is preferably, in descending order, 0.80 meq / g or more, 1.50 meq / g or more, 1.75 meq / g or more, 2.00 meq / g or more, 2.20 meq / g or more, more than 2.20 meq / g, 2.50 meq / g or more, 2.60 meq / g or more, 3.00 meq / g or more, 3.50 meq / g or more. The ion exchange capacity is the content of the ionic group (anionic group) of the polymer (I) and is determined by calculation from the composition of the polymer (I).

[0081] In the polymer (I), the ionic group (anionic group) is typically distributed along the polymer main chain. The polymer (I) includes a polymer main chain together with repeating side chains bonded to this main chain, and it is preferable that these side chains have an ionic group.

[0082] The polymer (I) preferably contains an ionic group having a pKa of less than 10, more preferably less than 7. The ionic group of the polymer (I) is preferably selected from the group consisting of sulfonate, carboxylate, phosphonate, and phosphate.

[0083] The terms "sulfonate, carboxylate, phosphonate, and phosphate" are intended to refer to the respective salts or the respective acids capable of forming salts. When a salt is used, preferably, the salt is an alkali metal salt or an ammonium salt. Preferred ionic groups are carboxylate groups and sulfonate groups.

[0084] The polymer (I) preferably has an ion exchange ratio (IXR) of 53 or less. The above IXR is defined as the number of carbon atoms in the polymer main chain relative to the ionic group. A precursor group that becomes ionic upon hydrolysis (e.g., -SO2F) is not regarded as an ionic group for the purpose of determining the IXR.

[0085] The IXR is preferably 0.5 or more, more preferably 1 or more, still more preferably 3 or more, even more preferably 4 or more, particularly preferably 5 or more, and especially preferably 8 or more. Also, the IXR is more preferably 43 or less, still more preferably 33 or less, and particularly preferably 23 or less.

[0086] The polymer (I) preferably has water solubility. Water solubility means the property of being easily dissolved or dispersed in an aqueous medium. A water-soluble polymer (I) shows, for example, that the particle size cannot be measured by the dynamic light scattering method (DLS) or has a particle size of 10 nm or less.

[0087] The number average molecular weight of the polymer (I) is preferably 0.1×10 4 or more, more preferably 0.2×10 4 or more, still more preferably 0.3×10 4 or more, even more preferably 0.4×10 4 or more, particularly preferably 0.5×10 4 or more, and especially preferably 1.0×104 The above is particularly preferred, 3.0×10 4 The above is even more particularly preferred, 3.1×10 4 The above is most preferred. Also, 75.0×10 4 The following is preferred, 50.0×10 4 The following is more preferred, 40.0×10 4 The following is even more preferred, 30.0×10 4 The following is even more preferred, 20.0×10 4 The following is particularly preferred. The number average molecular weight and the weight average molecular weight are values calculated by gel permeation chromatography (GPC) using monodisperse polystyrene as a standard. Also, when measurement by GPC is not possible, the number average molecular weight of polymer (I) can be determined from the correlation between the number average molecular weight calculated from the number of terminal groups obtained by NMR, FT-IR, etc. and the melt flow rate. The melt flow rate can be measured in accordance with JIS K 7210.

[0088] As the lower limit of the weight average molecular weight of polymer (I), in order of preference, 0.2×10 4 or more, 0.4×10 4 or more, 0.6×10 4 or more, 0.8×10 4 or more, 1.0×10 4 or more, 2.0×10 4 or more, 5.0×10 4 or more, 10.0×10 4 or more, 15.0×10 4 or more, 20.0×10 4 or more, 25.0×10 4 or more. Also, as the upper limit of the weight average molecular weight of polymer (I), in order of preference, 150.0×10 4 or less, 100.0×10 4 or less, 60.0×10 4 or less, 50.0×10 4 or less, 40.0×10 4 or less.

[0089] The viscosity of the aqueous solution of polymer (I) is preferably 5.0 mPa·s or more, more preferably 8.0 mPa·s or more, still more preferably 10.0 mPa·s or more, particularly preferably 12.0 mPa·s or more, most preferably 14.0 mPa·s or more, and preferably 100.0 mPa·s or less, more preferably 50.0 mPa·s or less, still more preferably 25.0 mPa·s or less, and particularly preferably 20.0 mPa·s or less.

[0090] The viscosity of the aqueous solution of polymer (I) can be specified by adjusting the content of polymer (I) in the aqueous solution to 33% by mass based on the aqueous solution and measuring the viscosity of the resulting aqueous solution at 20 °C using a tuning fork vibration viscometer (model number: SV-10) manufactured by A&D Company, Limited.

[0091] The critical micelle concentration (CMC) of polymer (I) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 1% by mass or more, and preferably 20% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less.

[0092] The critical micelle concentration of polymer (I) can be determined by measuring the surface tension. The surface tension can be measured, for example, using a surface tensiometer CBVP-A3 type manufactured by Kyowa Interface Science Co., Ltd.

[0093] The acid value of polymer (I) is preferably 60 or more, more preferably 90 or more, still more preferably 120 or more, particularly preferably 150 or more, most preferably 180 or more, and the upper limit is not particularly limited, but preferably 300 or less.

[0094] The acid value of polymer (I) is such that polymer (I) has an anionic group other than an acid-type functional group, for example, -COOM, -SO3M, -OSO3M or -C(CF3)2OM (M is a metal atom, NR 74. Optionally substituted imidazolium, optionally substituted pyridinium or optionally substituted phosphonium, where R 7 When it has H or an organic group), these groups can be measured by acid-base titration after converting them to acid-type groups.

[0095] As the polymer (I), a polymer containing a polymerization unit (I) based on the monomer (I) represented by the general formula (I) is preferred. CX 1 X 3 =CX 2 R(-CZ 1 Z 2 -A 0 ) m (I) (In the formula, X 1 and X 3 are each independently F, Cl, H or CF3; X 2 is H, F, an alkyl group or a fluorine-containing alkyl group; A 0 is an anionic group; R is a linking group; Z 1 and Z 2 are each independently H, F, an alkyl group or a fluorine-containing alkyl group; m is an integer of 1 or more.)

[0096] R is a linking group. In the present disclosure, the "linking group" is a (m + 1)-valent linking group, and when m is 1, it is a divalent linking group. The linking group may be a single bond, preferably contains at least one carbon atom, and the number of carbon atoms may be 2 or more, 4 or more, 8 or more, 10 or more, or 20 or more. The upper limit is not limited, for example, it may be 100 or less, or 50 or less.

[0097] The linking group may be linear or branched, cyclic or acyclic, saturated or unsaturated, substituted or unsubstituted, and may optionally contain one or more heteroatoms selected from the group consisting of sulfur, oxygen, and nitrogen, and may optionally contain one or more functional groups selected from the group consisting of ester, amide, sulfonamide, carbonyl, carbonate, urethane, urea, and carbamate. The linking group may not contain a carbon atom and may be a chain heteroatom such as oxygen, sulfur, or nitrogen.

[0098] m is an integer of 1 or more, preferably 1 or 2, more preferably 1. When m is an integer of 2 or more, Z 1 , Z 2 and A 0 may be the same or different. Next, a preferred configuration when m is 1 in the general formula (I) will be described.

[0099] R is preferably a chain heteroatom such as oxygen, sulfur, or nitrogen, or a divalent organic group.

[0100] When R is a divalent organic group, the hydrogen atom bonded to the carbon atom may be replaced by a halogen other than fluorine, such as chlorine, and may or may not contain a double bond. Also, R may be either linear or branched, and may be either cyclic or acyclic. Further, R may contain a functional group (for example, ester, ether, ketone (keto group), amine, halide, etc.).

[0101] R may also be a non-fluorinated divalent organic group or a partially fluorinated or perfluorinated divalent organic group.

[0102] Examples of R include a hydrocarbon group in which no fluorine atom is bonded to a carbon atom, a hydrocarbon group in which some of the hydrogen atoms bonded to a carbon atom are substituted with fluorine atoms, or a hydrocarbon group in which all of the hydrogen atoms bonded to a carbon atom are substituted with fluorine atoms. These may contain an oxygen atom, may contain a double bond, or may contain a functional group.

[0103] R is preferably a hydrocarbon group having 1 to 100 carbon atoms which may contain an ether bond or a keto group, and some or all of the hydrogen atoms bonded to the carbon atoms of the hydrocarbon group may be substituted with fluorine.

[0104] Preferably, R is -(CH2) a -,-(CF2) a -,-(CF2) a -O-,-O-(CF2) a -,-(CF2) a -O-(CF2) b -,-O(CF2) a -O-(CF2) b -,-(CF2) a -[O-(CF2) b c -,-O(CF2) a -[O-(CF2) b c -,-[(CF2) a -O] b -[(CF2) c -O] d -,-O[(CF2) a -O] b -,-O[(CF2) a -O] b -[(CF2) c -O] d -,-O-[CF2CF(CF3)O] a -(CF2) b -,-O-(CF2) a -O-[CF(CF3)CF2O] b -,-O-[CF2CF(CF3)O] a -(CF2) b -O-,-O-[CF2CF(CF3)O] a ​​-(CF2) b -O-[CF(CF3)CF2O] c -,-[CF2CF(CF3)O] a -,-[CF(CF3)CF2O] a -,-(CF2) a -O-[CF(CF3)CF2O] a -,-(CF2) a -O-[CF(CF3)CF2O] a -(CF2) b -,-[CF2CF(CF3)] a -CO-(CF2) b -and at least one selected from combinations thereof. Wherein a, b, c and d are each independently at least 1 or more. a, b, c and d may each independently be 2 or more, 3 or more, 4 or more, 10 or more, 20 or more. The upper limit of a, b, c and d is, for example, 100.

[0105] More preferably as R is at least one selected from -O-CF2-, -O-CF2CF2-, -O-CF2CF2-O-, -O-CF2CF2CF2-, -O-CF2CF2CF2-O-, -O-CF2CF(CF3)-O-, -O-CF2CF2-O-CF(CF3)CF2-O-, -O-CF2CF(CF3)-O-CF2CF2-O-, and -O-CF2CF(CF3)-O-CF2-.

[0106] As R, the general formula (r1): -CF2-O-(CX 6 2) e -{O-CF(CF3)} f -(O) g - (r1) (Wherein X 6 are each independently H, F or CF3, e is an integer from 0 to 3, f is an integer from 0 to 3, and g is 0 or 1) is preferably a divalent group represented by the general formula (r2): -CF2-O-(CX 7 2) e -(O) g- (r2) (wherein X 7 is independently H, F or CF3, e is an integer from 0 to 3, and g is 0 or 1) is more preferred.

[0107] Specific examples suitable as R include -CF2-O-, -CF2-O-CF2-, -CF2-O-CH2-, -CF2-O-CH2CF2-, -O-CF2-, -O-CF2CF2-, -O-CF2CF2CF2-, -O-CF2CF2CF2CF2-, -O-CF2CF(CF3)-O-CF2-, -O-CF2CF(CF3)-O-CF2CF2-, -CF2-O-CF2CF2-, -CF2-O-CF2CH2-, -CF2-O-CF2CF2CH2-, -CF2-O-CF(CF3)-, -CF2-O-CF(CF3)CF2-, -CF2-O-CF(CF3)CF2-O-, -CF2-O-CF(CF3)CF2-O-CF2-, -CF2-O-CF(CF3)CH2-, etc. Among them, R is preferably a perfluoroalkylene group which may contain an oxygen atom. Specifically, -CF2-O-, -CF2-O-CF2-, -O-CF2-, -O-CF2CF2-, -O-CF2CF(CF3)-O-CF2-, -O-CF2CF(CF3)-O-CF2CF2-, -CF2-O-CF2CF2-, -CF2-O-CF(CF3)-, -CF2-O-CF(CF3)CF2-, or -CF2-O-CF(CF3)CF2-O- is preferred.

[0108] -R-CZ in general formula (I) 1 Z 2 - is represented by general formula (s1): -CF2-O-(CX 6 2) e -{O-CF(CF3)} f -(O) g -CZ 1 Z 2 - (s1) (wherein X 6 is independently H, F or CF3, e is an integer from 0 to 3, f is an integer from 0 to 3, g is 0 or 1, Z 1 and Z 2is preferably represented by H, F, an alkyl group or a fluorinated alkyl group respectively and independently. In formula (s1), Z 1 and Z 2 are more preferably F or CF3, and it is even more preferable that one is F and the other is CF3.

[0109] Also, in general formula (I), -R-CZ 1 Z 2 - as general formula (s2): -CF2-O-(CX 7 2) e -(O) g -CZ 1 Z 2 - (s2) (wherein X 7 is respectively and independently H, F or CF3, e is an integer from 0 to 3, g is 0 or 1, and Z 1 and Z 2 are preferably represented by H, F, an alkyl group or a fluorinated alkyl group respectively and independently. In formula (s2), Z 1 and Z 2 are more preferably F or CF3, and it is even more preferable that one is F and the other is CF3.

[0110] -R-CZ in general formula (I) 1 Z 2- include, preferably, -CF2-O-CF2-, -O-CF2CF2-, -O-CF2CF2CF2-, -O-CF2CF2CF2CF2-, -O-CF2CF(CF3)-O-CF2-, -O-CF2CF(CF3)-O-CF2CF2-, -O-CF2CF(CF3)-O-CF2CF2CF2-, -CF2-O-CF(CF3)-, -CF2-O-C(CF3)2-, -CF2-O-CF2-CF2-, -CF2-O-CF2-CF(CF3)-, -CF2-O-CF2-C(CF3)2-, -CF2-O-CF2CF2-CF2-, -CF2-O-CF2CF2-CF(CF3)-, -CF2-O-CF2CF2-C(CF3)2-, -CF2-O-CF(CF3)-CF2-, -CF2-O-CF(CF3)-CF(CF3)-, -CF2-O-CF(CF3)-C(CF3)2-, -CF2-O-CF(CF3)CF2-CF2-, -CF2-O-CF(CF3)CF2-CF(CF3)-, -CF2-O-CF(CF3)CF2-C(CF3)2-, -CF2-O-CF(CF3)CF2-O-CF2-, -CF2-O-CF(CF3)CF2-O-CF(CF3)-, or -CF2-O-CF(CF3)CF2-O-C(CF3)2-; more preferably, -O-CF2CF2-, -O-CF2CF2CF2-, -O-CF2CF2CF2CF2-, -O-CF2CF(CF3)-O-CF2-, -O-CF2CF(CF3)-O-CF2CF2-, -CF2-O-CF(CF3)-, -CF2-O-CF2-CF(CF3)-, -CF2-O-CF2CF2-CF(CF3)-, -CF2-O-CF(CF3)-CF(CF3)-, -CF2-O-CF(CF3)CF2-CF(CF3)-, or -CF2-O-CF(CF3)CF2-O-CF(CF3)-; still more preferably, -O-CF2CF2- or -O-CF2CF(CF3)-O-CF2CF2-

[0111] The polymer (I) is also preferably highly fluorinated. For example, anionic groups (A) such as phosphate group moieties (e.g., CH2OP(O)(OM)2) and sulfate group moieties (e.g., CH2OS(O)2OM) 0Preferably, 80% or more, 90% or more, 95% or more, or 100% of the C-H bonds in the polymer (I) are substituted with C-F bonds, except for .

[0112] The monomer (I) and the polymer (I) preferably have a C-F bond and no C-H bond, except for the anionic group (A 0 ). That is, in the general formula (I), all of X 1 , X 2 , and X 3 are preferably F, and R is preferably a perfluoroalkylene group having 1 or more carbon atoms. The perfluoroalkylene group may be linear or branched, cyclic or acyclic, and may contain at least one catenary heteroatom. The number of carbon atoms of the perfluoroalkylene group may be 2 to 20, or may be 4 to 18.

[0113] The monomer (I) and the polymer (I) may be partially fluorinated. That is, the monomer (I) and the polymer (I) preferably have at least one hydrogen atom bonded to a carbon atom and at least one fluorine atom bonded to a carbon atom, except for the anionic group (A 0 ).

[0114] The anionic group (A 0) may be -SO2M, -SO3M, -OSO3M, -COOM, -SO2NR’CH2COOM, -CH2OP(O)(OM)2, [-CH2O]2P(O)(OM), -CH2CH2OP(O)(OM)2, [-CH2CH2O]2P(O)(OM), -CH2CH2OSO3M, -P(O)(OM)2, -SO2NR’CH2CH2OP(O)(OM)2, [-SO2NR’CH2CH2O]2P(O)(OM), -CH2OSO3M, -SO2NR’CH2CH2OSO3M, or -C(CF3)2OM. Among them, -SO3M, -OSO3M, -COOM, -P(O)(OM)2 or -C(CF3)2OM are preferred, -COOM, -SO3M, -OSO3M, -P(O)(OM)2 or -C(CF3)2OM are more preferred, -SO3M, -COOM or -P(O)(OM)2 are even more preferred, and -SO3M or -COOM are particularly preferred.

[0115] M is H, a metal atom, NR 7 4, an optionally substituted imidazolium, an optionally substituted pyridinium or an optionally substituted phosphonium, and R 7 is H or an organic group.

[0116] Examples of the metal atom include an alkali metal (Group 1), an alkaline earth metal (Group 2), etc., and Na, K or Li is preferred.

[0117] As M, -H, a metal atom or NR 7 4 is preferred, -H, an alkali metal (Group 1), an alkaline earth metal (Group 2) or NR 7 4 is more preferred, -H, -Na, -K, -Li or NH4 is even more preferred, -H, -Na, -K or NH4 is even more preferably, -H, -Na or NH4 is particularly preferred, and -H or -NH4 is most preferred.

[0118] In the polymer (I), each polymer unit (I) may have different anionic groups or the same anionic group.

[0119] The monomer (I) is preferably a monomer (1) represented by the general formula (1). The polymer (I) is preferably a polymer (1) containing a polymerization unit (1) based on the monomer represented by the general formula (1). CX2=CY(-CZ2-O-Rf-A) (1) (In the formula, X is the same or different and is -H or F, Y is -H, -F, an alkyl group or a fluorine-containing alkyl group, and Z is the same or different and is -H, -F, an alkyl group or a fluoroalkyl group. Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having an ether bond with 2 to 100 carbon atoms. A is -COOM, -SO3M, -OSO3M or -C(CF3)2OM (M is -H, a metal atom, -NR 7 4, imidazolium which may have a substituent, pyridinium which may have a substituent or phosphonium which may have a substituent, and R 7 is H or an organic group.) However, at least one of X, Y and Z contains a fluorine atom.)

[0120] The polymer (1) may be a homopolymer of the monomer (1) represented by the general formula (1) or a copolymer with other monomers.

[0121] The fluorine-containing alkylene group having an ether bond with 2 to 100 carbon atoms does not contain a structure in which an oxygen atom is at the terminal and is an alkylene group containing an ether bond between carbon-carbon atoms.

[0122] In the general formula (1), X is -H or F. Both of X may be -F, or at least one of them may be -H. For example, one of them may be -F and the other may be -H, or both may be -H.

[0123] In general formula (1), Y is -H, -F, an alkyl group, or a fluorinated alkyl group. The above alkyl group is an alkyl group that does not contain a fluorine atom, and the number of carbon atoms may be 1 or more. The number of carbon atoms of the above alkyl group is preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less. The above fluorinated alkyl group is an alkyl group that contains at least one fluorine atom, and the number of carbon atoms may be 1 or more. The number of carbon atoms of the above fluorinated alkyl group is preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less. As the above Y, -H, -F, or CF3 is preferable, and -F is more preferable.

[0124] In general formula (1), Z is the same or different and is -H, -F, an alkyl group, or a fluoroalkyl group. The above alkyl group is an alkyl group that does not contain a fluorine atom, and the number of carbon atoms may be 1 or more. The number of carbon atoms of the above alkyl group is preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less. The above fluorinated alkyl group is an alkyl group that contains at least one fluorine atom, and the number of carbon atoms may be 1 or more. The number of carbon atoms of the above fluorinated alkyl group is preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less. As the above Z, -H, -F, or CF3 is preferable, and -F is more preferable.

[0125] In general formula (1), at least one of X, Y, and Z contains a fluorine atom. For example, X may be -H, and Y and Z may be -F.

[0126] In general formula (1), the above Rf is a fluorinated alkylene group having 1 to 40 carbon atoms, or a fluorinated alkylene group having an ether bond and having 2 to 100 carbon atoms.

[0127] The number of carbon atoms of the fluorine-containing alkylene group is preferably 2 or more. Also, the number of carbon atoms of the fluorine-containing alkylene group is preferably 30 or less, more preferably 20 or less, still more preferably 10 or less, particularly preferably 6 or less, and most preferably 3 or less. Examples of the fluorine-containing alkylene group include -CF2-, -CH2CF2-, -CF2CF2-, -CF2CH2-, -CF2CF2CF2-, -CF2CF2CH2-, -CF(CF3)-, -CF(CF3)CF2-, -CF(CF3)CH2-, and the like. The fluorine-containing alkylene group is preferably a perfluoroalkylene group.

[0128] The number of carbon atoms of the fluorine-containing alkylene group having an ether bond is preferably 3 or more. Also, the number of carbon atoms of the fluorine-containing alkylene group having an ether bond is preferably 60 or less, more preferably 30 or less, still more preferably 12 or less, particularly preferably 9 or less, and most preferably 6 or less. The fluorine-containing alkylene group having an ether bond is, for example, represented by the general formula:

Chemical formula

[0129] Specific examples of the fluorine-containing alkylene group having an ether bond include -CF2CF(CF3)OCF2-, -CF(CF3)CF2-O-CF(CF3)-, -(CF(CF3)CF2-O) n -CF(CF3)-(where n is an integer from 1 to 10), -CF(CF3)CF2-O-CF(CF3)CH2-, -(CF(CF3)CF2-O) n-CF(CF3)CH2- (wherein n is an integer from 1 to 10), -CH2CF2CF2O-CH2CF2CH2-, -CF2CF2CF2O-CF2-, -CF2CF2CF2O-CF2CF2-, -CF2CF2CF2O-CF2CF2CF2-, -CF2CF2CF2O-CF2CF2CH2-, -CF2CF2O-CF2-, -CF2CF2O-CF2CH2-, and the like. The fluorine-containing alkylene group having the ether bond is preferably a perfluoroalkylene group.)

[0130] In the general formula (1), A is -COOM, -SO3M, -OSO3M or -C(CF3)2OM (M is H, a metal atom, NR 7 4, an optionally substituted imidazolium, an optionally substituted pyridinium or an optionally substituted phosphonium, and R 7 is H or an organic group).

[0131] R 7 is preferably H or an organic group of C 1-10 more preferably H or an organic group of C 1-4 even more preferably H or an alkyl group of C 1-4 .

[0132] Examples of the metal atom include alkali metals (Group 1), alkaline earth metals (Group 2), etc., and Na, K or Li is preferred.

[0133] M is preferably H, a metal atom or NR 7 4, more preferably H, an alkali metal (Group 1), an alkaline earth metal (Group 2) or NR 7 4, even more preferably H, Na, K, Li or NH4, even more preferably H, Na, K or NH4, particularly preferably H, Na or NH4, and most preferably H or NH4.

[0134] A is preferably -COOM or -SO3M.

[0135] Examples of the monomer represented by the general formula (1) include, for example, the general formula (1a): CX2=CFCF2-O-(CF(CF3)CF2O) n5 -CF(CF3)-A (1a) (In the formula, each X is the same and represents F or H. n5 represents 0 or an integer from 1 to 10, and A is the same as defined above.) Monomers represented thereby are exemplified.

[0136] In the general formula (1a), n5 is preferably 0 or an integer from 1 to 5, more preferably 0, 1, or 2, and even more preferably 0 or 1, in terms of being able to obtain particles with a small primary particle diameter.

[0137] The polymer (1) may be a homopolymer of the monomer represented by the general formula (1a) or a copolymer with other monomers.

[0138] The monomer (1) is preferably a monomer represented by the general formula (1A). The polymerization unit (1) is preferably a polymerization unit (1A) based on the monomer represented by the general formula (1A). CH2=CF(-CF2-O-Rf-A) (1A) (In the formula, Rf and A are the same as above.)

[0139] The polymer (1) may be a homopolymer of the monomer represented by the general formula (1A) or a copolymer with other monomers.

[0140] Specific examples of the monomer represented by the formula (1A) include the general formula

[0141]

Chemical formula

[0142] (In the formula, Z 1 is F or CF3; Z 2 and Z 3 are each H or F; Z 4is H, F or CF3; p1 + q1 + r1 is an integer from 0 to 10; s1 is 0 or 1; t1 is an integer from 0 to 5, provided that Z 3 and Z 4 are both H, p1 + q1 + r1 + s1 is not 0; A is the same as defined above), and monomers represented by the formula are included. More specifically,

[0143] [Chemical formula]

[0144] etc. are preferably mentioned, and among them

[0145] [Chemical formula]

[0146] is preferably the case.

[0147] As the monomer represented by the general formula (1A), it is preferable that A in the formula (1A) is -COOM. In particular, at least one selected from the group consisting of CH2 = CFCF2OCF(CF3)COOM and CH2 = CFCF2OCF(CF3)CF2OCF(CF3)COOM (where M is the same as defined above) is preferable, and CH2 = CFCF2OCF(CF3)COOM is more preferable.

[0148] The monomer (I) is also preferably a monomer (2) represented by the general formula (2). The polymer (I) is also preferably a polymer (2) containing a polymerization unit (2) based on the monomer represented by the general formula (2). CX2 = CY(-O-Rf-A) (2) (In the formula, X is the same or different and is -H or F, Y is -H, -F, an alkyl group or a fluorine-containing alkyl group, Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having an ether bond or a keto group having 2 to 100 carbon atoms. A is the same as above.)

[0149] The monomer (I) is preferably a monomer (3) represented by the general formula (3). The polymer (I) is preferably a polymer (3) containing a polymerization unit (3) based on the monomer represented by the general formula (3). CX2=CY(-Rf-A) (3) (In the formula, X is the same or different and is -H or F, Y is -H, -F, an alkyl group or a fluorine-containing alkyl group, Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having an ether bond with 2 to 100 carbon atoms. A is the same as described above.)

[0150] The polymer (I) may be a homopolymer composed only of the polymerization unit (I), or may be a copolymer containing the polymerization unit (I) and a polymerization unit based on another monomer copolymerizable with the monomer represented by the general formula (I). From the viewpoint of solubility in an aqueous medium, a homopolymer composed only of the polymerization unit (I) is preferred. The polymerization unit (I) may be the same or different at each occurrence, and the polymer (I) may contain polymerization units (I) based on two or more different monomers represented by the general formula (I).

[0151] The polymer (I) usually has end groups. The end groups are end groups generated during polymerization, and typical end groups are independently selected from hydrogen, iodine, bromine, linear or branched alkyl groups, and linear or branched fluoroalkyl groups, and may optionally contain at least one catenary heteroatom. The alkyl group or fluoroalkyl group preferably has 1 to 20 carbon atoms. These end groups are generally generated from an initiator or a chain transfer agent used in the formation of the polymer (I), or are generated during a chain transfer reaction.

[0152] In polymer (I), the content of polymerization unit (I) is preferably, in descending order, 1.0 mol% or more, 3.0 mol% or more, 5.0 mol% or more, 10 mol% or more, 20 mol% or more, 30 mol% or more, 40 mol% or more, 50 mol% or more, 60 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, based on all the polymerization units. It is particularly preferable that the content of polymerization unit (I) is substantially 100 mol%, and it is most preferable that polymer (I) consists only of polymerization unit (I).

[0153] In polymer (I), the content of the polymerization unit based on other monomers copolymerizable with the monomer represented by general formula (I) is preferably, in descending order, 99.0 mol% or less, 97.0 mol% or less, 95.0 mol% or less, 90 mol% or less, 80 mol% or less, 70 mol% or less, 60 mol% or less, 50 mol% or less, 40 mol% or less, 30 mol% or less, 20 mol% or less, 10 mol% or less, based on all the polymerization units. It is particularly preferable that the content of the polymerization unit based on other monomers copolymerizable with the monomer represented by general formula (I) is substantially 0 mol%, and it is most preferable that polymer (I) does not contain the polymerization unit based on other monomers.

[0154] Polymer (I) can be obtained by polymerizing monomer (I) using a known method. By polymerizing monomer (I) in an aqueous medium, a crude composition in which polymer (I) is dispersed or dissolved in the aqueous medium can be obtained. The crude composition thus obtained usually contains dimers and trimers of monomer (I) in a total amount exceeding 1.0% by mass based on the mass of polymer (I). The content of dimers and trimers in the crude composition can be specified by performing gel permeation chromatography (GPC) analysis of the crude composition and calculating the ratio (area percentage) of the total peak area of dimers and trimers to the total peak area of each peak in the chromatogram obtained by GPC analysis.

[0155] Next, dimers and trimers of monomer (I) contained in the crude composition obtained by the polymerization of monomer (I) are removed from the crude composition. The means for removing the dimers and trimers is not particularly limited, but at least one means selected from the group consisting of ion exchange treatment, ultrafiltration, microfiltration, dialysis membrane treatment, liquid separation, and reprecipitation is preferred, and at least one means selected from the group consisting of ion exchange treatment, ultrafiltration, microfiltration, and dialysis membrane treatment is more preferred, ion exchange treatment and ultrafiltration are even more preferred, and ultrafiltration is particularly preferred.

[0156] By performing such a removal treatment, not only dimers and trimers of monomer (I) can be removed, but also the initiator added during the polymerization of monomer (I) can be removed. Therefore, when using the obtained polymer (I) for polymerizing the fluoromonomer, since no initiator remains in polymer (I), the influence of the initiator added during the polymerization of monomer (I) can be reduced.

[0157] (fluorosurfactant) In one embodiment, the fluoropolymer aqueous dispersion substantially does not contain a fluorosurfactant. Examples of the above-mentioned fluorosurfactant include anionic fluorosurfactants. The above-mentioned anionic fluorosurfactant may be, for example, a surfactant containing fluorine atoms with a total carbon number of 20 or less in the part excluding the anionic group.

[0158] The above-mentioned fluorosurfactant may also be a surfactant containing fluorine with a molecular weight of the anionic part of 1000 or less. In addition, the above-mentioned "anionic part" means the part excluding the cation of the above-mentioned fluorosurfactant. For example, in the case of F(CF2) n1 COOM represented by formula (I) described later, it is the part of "F(CF2) n1 COO".

[0159] Specific examples of the fluorosurfactant include those described in 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, U.S. Patent No. 3250808, U.S. Patent No. 3271341, Japanese Patent Application Laid-Open No. 2003-119204, International Publication No. 2005 / 042593, International Publication No. 2008 / 060461, International Publication No. 2007 / 046377, Japanese Patent Application Laid-Open 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, International Publication No. 2013 / 189826, and the like.

[0160] Examples of the anionic fluorosurfactant include the following general formula (N 0 ): X n0 -Rf n0 -Y 0 (N 0 ) (In the formula, X n0 is H, Cl, or F. Rf n0 is an alkylene group having 3 to 20 carbon atoms, which is linear, branched, or cyclic, and in which some or all of the H atoms are substituted by F atoms. The alkylene group may contain one or more ether bonds, and some of the H atoms may be substituted by Cl atoms. Y 0 is an anionic group.) Compounds represented by this formula are included. Y 0 The anionic group of Y may be -COOM, -SO2M, or -SO3M, and may be -COOM or -SO3M. 7 M is H, a metal atom, NR 7is H or an organic group. Examples of the metal atom include alkali metals (Group 1) and alkaline earth metals (Group 2), such as Na, K, or Li. R 7 may be H or an organic group of C 1-10 may be H or an organic group of C 1-4 may be H or an organic group of C 1-4 and may be an alkyl group of C. M may be H, a metal atom, or NR 7 4, may be H, an alkali metal (Group 1), an alkaline earth metal (Group 2), or NR 7 4, and may be H, Na, K, Li, or NH4. The above Rf n0 may have 50% or more of H substituted with fluorine.

[0161] Examples of the compound represented by the general formula (N 0 ) include the following general formula (N 1 ): X n0 -(CF2) m1 -Y 0 (N 1 ) (wherein X n0 is H, Cl, or F, m1 is an integer of 3 to 15, and Y 0 is as defined above). A compound represented by the following general formula (N 2 ): Rf n1 -O-(CF(CF3)CF2O) m2 CFX n1 -Y 0 (N 2 ) (wherein Rf n1 is a perfluoroalkyl group having 1 to 5 carbon atoms, m2 is an integer of 0 to 3, X n1 is F or CF3, and Y 0 is as defined above). A compound represented by the following general formula (N 3 ): Rf n2 (CH2) m3 -(Rfn3 ) q -Y 0 (N 3 ) (wherein, Rf n2 is a partially or fully fluorinated alkyl group which may contain an ether bond having 1 to 13 carbon atoms, 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 is as defined above.) A compound represented by the following general formula (N 4 ): Rf n4 -O-(CY n1 Y n2 ) p CF2-Y 0 (N 4 ) (wherein, Rf n4 is a linear or branched partially or fully fluorinated alkyl group which may contain an ether bond and / or a chlorine atom having 1 to 12 carbon atoms, Y n1 and Y n2 are the same or different and are H or F, p is 0 or 1, and Y 0 is as defined above.) A compound represented by the formula, and the general formula (N 5 ): [Chemical formula] (wherein, 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 which may contain an ether bond having 1 to 6 carbon atoms. Rf n5 is a linear or branched partially or fully fluorinated alkylene group which may contain an ether bond having 1 to 3 carbon atoms, L is a linking group, and Y 0 is as defined above. However, the total number of carbon atoms of X n2 , X n3 , X n4 and Rf n5 is 18 or less.) Compounds represented by the formula are included.

[0162] More specifically, as the compound represented by the above general formula (N 0 ), the perfluorocarboxylic acid (I) represented by the following general formula (I), the ω-H perfluorocarboxylic acid (II) represented by the following general formula (II), the perfluoroether carboxylic acid (III) represented by the following general formula (III), the perfluoroalkyl alkylene carboxylic acid (IV) represented by the following general formula (IV), the perfluoroalkoxyfluorocarboxylic acid (V) represented by the following general formula (V), the perfluoroalkylsulfonic acid (VI) represented by the following general formula (VI), the ω-H perfluorosulfonic acid (VII) represented by the following general formula (VII), the perfluoroalkyl alkylene sulfonic acid (VIII) represented by the following general formula (VIII), the alkyl alkylene carboxylic acid (IX) represented by the following general formula (IX), the fluorocarboxylic acid (X) represented by the following general formula (X), the alkoxyfluorosulfonic acid (XI) represented by the following general formula (XI), the compound (XII) represented by the following general formula (XII), the compound (XIII) represented by the following general formula (XIII), etc. may be mentioned.

[0163] The above perfluorocarboxylic acid (I) is represented by the following general formula (I) F(CF2) n1 COOM (I) (In the formula, n1 is an integer of 3 to 14, and M is H, a metal atom, NR 7 4, an imidazolium which may have a substituent, a pyridinium which may have a substituent, or a phosphonium which may have a substituent, and R 7 is H or an organic group.)

[0164] The above ω-H perfluorocarboxylic acid (II) is represented by the following general formula (II) H(CF2) n2 COOM (II) (In the formula, n2 is an integer of 4 to 15, and M is as defined above.)

[0165] The above perfluoroether carboxylic acid (III) is represented by the following general formula (III) Rf 1 -O-(CF(CF3)CF2O) n3 CF(CF3)COOM (III) (In the formula, Rf 1 is a perfluoroalkyl group having 1 to 5 carbon atoms, n3 is an integer of 0 to 3, and M is as defined above.)

[0166] The above perfluoroalkyl alkylene carboxylic acid (IV) is represented by the following general formula (IV) Rf 2 (CH2) n4 Rf 3 COOM (IV) (In the formula, Rf 2 is a perfluoroalkyl group having 1 to 5 carbon atoms, Rf 3 is a linear or branched perfluoroalkylene group having 1 to 3 carbon atoms, n4 is an integer of 1 to 3, and M is as defined above.)

[0167] The above alkoxyfluorocarboxylic acid (V) is represented by the following general formula (V) Rf 4 -O-CY 1 Y 2 CF2-COOM (V) (In the formula, Rf 4 is a linear or branched or completely fluorinated alkyl group which may contain an ether bond and / or a chlorine atom having 1 to 12 carbon atoms, Y 1 and Y 2 are the same or different and are H or F, and M is as defined above.)

[0168] The above perfluoroalkyl sulfonic acid (VI) is represented by the following general formula (VI) F(CF2) n5 SO3M (VI) (In the formula, n5 is an integer of 3 to 14, and M is as defined above.)

[0169] The above ω-H perfluorosulfonic acid (VII) is represented by the following general formula (VII) H(CF2) n6 SO3M (VII) (wherein n6 is an integer from 4 to 14, and M is as defined above).

[0170] The above perfluoroalkylalkylene sulfonic acid (VIII) is represented by the following general formula (VIII) Rf 5 (CH2) n7 SO3M (VIII) (wherein Rf 5 is a perfluoroalkyl group having 1 to 13 carbon atoms, n7 is an integer from 1 to 3, and M is as defined above).

[0171] The above alkylalkylene carboxylic acid (IX) is represented by the following general formula (IX) Rf 6 (CH2) n8 COOM (IX) (wherein Rf 6 is a linear or branched or fully fluorinated alkyl group which may contain an ether bond having 1 to 13 carbon atoms, n8 is an integer from 1 to 3, and M is as defined above).

[0172] The above fluorocarboxylic acid (X) is represented by the following general formula (X) Rf 7 -O-Rf 8 -O-CF2-COOM (X) (wherein Rf 7 is a linear or branched or fully fluorinated alkyl group which may contain an ether bond and / or a chlorine atom having 1 to 6 carbon atoms, Rf 8 is a linear or branched or fully fluorinated alkyl group having 1 to 6 carbon atoms, and M is as defined above).

[0173] The above alkoxyfluorosulfonic acid (XI) is represented by the following general formula (XI) Rf 9 -O-CY 1 Y 2 CF2-SO3M (XI) (In the formula, Rf 9 is a linear or branched alkyl group which may contain an ether bond having 1 to 12 carbon atoms and may contain chlorine, and is a partially or fully fluorinated alkyl group, and Y 1 and Y 2 are the same or different and are H or F, and M is as defined above.)

[0174] The above compound (XII) is represented by the following general formula (XII):

Chemical formula

[0175] The above compound (XIII) is represented by the following general formula (XIII): Rf 11 -O-(CF2CF(CF3)O) n9 (CF2O) n10 CF2COOM (XIII) (In the formula, Rf 11is a fluoroalkyl group having 1 to 5 carbon atoms and containing chlorine, n9 is an integer of 0 to 3, n10 is an integer of 0 to 3, and M is as defined above. It is represented by). As the compound (XIII), CF2ClO(CF2CF(CF3)O) n9 (CF2O) n10 CF2COONH4 (a mixture with an average molecular weight of 750, where n9 and n10 are as defined above).

[0176] As described above, examples of the anionic fluorine-containing surfactant include carboxylic acid surfactants and sulfonic acid surfactants.

[0177] The fluorine-containing surfactant may be a single fluorine-containing surfactant or a mixture containing two or more fluorine-containing surfactants.

[0178] (Anionic hydrocarbon surfactant) In one embodiment, the fluoropolymer aqueous dispersion contains an anionic hydrocarbon surfactant. By using the anionic hydrocarbon surfactant, the dispersion stability of the fluoropolymer aqueous dispersion can be further improved.

[0179] The content of the anionic hydrocarbon surfactant in the fluoropolymer aqueous dispersion is preferably 10 to 5000 ppm by mass, more preferably 50 ppm by mass or more, preferably 3000 ppm by mass or less, and more preferably 2000 ppm by mass or less, based on the fluoropolymer.

[0180] In addition, as the anionic hydrocarbon surfactant, for example, the anionic hydrocarbon surfactants described in International Publication No. 2013 / 146950 and International Publication No. 2013 / 146947 can be used. For example, those having a saturated or unsaturated aliphatic chain with 6 to 40 carbon atoms, preferably 8 to 20 carbon atoms, more preferably 9 to 13 carbon atoms can be mentioned. The above-mentioned saturated or unsaturated aliphatic chain may be either a straight chain or a branched chain, and may have a cyclic structure. The above hydrocarbon may be aromatic or may have an aromatic group. The above hydrocarbon may have a hetero atom such as oxygen, nitrogen, sulfur, etc.

[0181] Examples of the anionic hydrocarbon surfactant include alkyl sulfonate, alkyl sulfate, alkyl aryl sulfate and their salts; aliphatic (carboxylic) acids and their salts; alkyl phosphate esters, alkyl aryl phosphate esters or their salts; etc. Among them, alkyl sulfonate, alkyl sulfate, aliphatic carboxylic acid or their salts are preferred.

[0182] As the alkyl sulfate or its salt, ammonium lauryl sulfate and sodium lauryl sulfate are preferred. As the aliphatic carboxylic acid or its salt, succinic acid, decanoic acid, undecanoic acid, undecenoic acid, lauric acid, hydrododecanoic acid, or their salts are preferred.

[0183] (Other components) In one embodiment, the fluoropolymer aqueous dispersion contains other components. Examples of the other components include preservatives.

[0184] Examples of the preservative include isothiazolone-based, azole-based, pronopol, chlorothalonil, methylsulfonyltetrachloropyridine, carbendazim, fluorophollet, sodium diacetate, diiodomethyl paratolyl sulfone, etc.

[0185] As the content of the preservative in the aqueous dispersion of the fluoropolymer, 0.01 to 0.5% by mass is preferable with respect to the fluoropolymer, and 0.05 to 0.2% by mass is more preferable.

[0186] In addition, examples of other components include water-soluble polymer compounds. Examples of water-soluble polymer compounds include methyl cellulose, alumina sol, polyvinyl alcohol, carboxylated vinyl polymer, polyethylene oxide (dispersion stabilizer), polyethylene glycol (dispersion stabilizer), polyvinyl pyrrolidone (dispersion stabilizer), phenol resin, urea resin, epoxy resin, melamine resin, polyester resin, polyether resin, acrylic silicone resin, silicone resin, silicone polyester resin, polyurethane resin, and the like.

[0187] (Manufacturing method) The aqueous dispersion of the fluoropolymer of the present disclosure is, for example, In the substantial absence of a fluorine-containing surfactant and in the presence of a polymer (I) having a hydrophilic group, a polymerization dispersion liquid containing a fluoropolymer, a polymer (I), and an aqueous medium is prepared by polymerizing a fluoromonomer in an aqueous medium. A pre-concentration composition is prepared by mixing the polymerization dispersion liquid and a nonionic surfactant (a). A post-concentration composition is prepared by concentrating the pre-concentration composition. An aqueous dispersion of a fluoropolymer is prepared by adding a nonionic surfactant (b) to the post-concentration composition. It can be produced by a manufacturing method of an aqueous dispersion of a fluoropolymer.

[0188] (Preparation of polymerization dispersion liquid by polymerization) In one embodiment of the manufacturing method, a polymerization dispersion liquid is prepared by polymerizing a fluoromonomer in an aqueous medium in the substantial absence of a fluorine-containing surfactant and in the presence of a polymer (I) having a hydrophilic group. The resulting polymerization dispersion liquid contains a fluoropolymer, a polymer (I), and an aqueous medium.

[0189] (Fluoromonomer) As the fluoromonomer used in the production method of the present disclosure, those having at least one double bond are preferred. Examples of the above fluoromonomer include tetrafluoroethylene [TFE], hexafluoropropylene [HFP], chlorotrifluoroethylene [CTFE], vinyl fluoride, vinylidene fluoride [VDF], trifluoroethylene, fluoroalkyl vinyl ether, fluoroalkyl ethylene, fluoroalkyl allyl ether, trifluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, hexafluoroisobutene, general formula (100): CHX 101 =CX 102 Rf 101 (wherein X 101 and X 102 are such that one is H and the other is F, and Rf 101 is a linear or branched fluoroalkyl group having 1 to 12 carbon atoms), a fluorinated vinyl heterocyclic compound, and at least one selected from the group consisting of monomers that provide crosslinking sites is preferred.

[0190] Examples of the above fluoroalkyl vinyl ether include, for example, general formula (110): CF2=CF-ORf 111 (wherein Rf 111 represents a perfluoro organic group.) The fluoromonomer represented by is preferred.

[0191] Among the fluoromonomers represented by the general formula (110), in particular, general formula (160): CF2=CF-ORf 161 (wherein Rf 161 represents a perfluoroalkyl group having 1 to 10 carbon atoms.) The fluoromonomer represented by is preferred. Rf 161 is preferably a perfluoroalkyl group having 1 to 5 carbon atoms.

[0192] As the fluoromonomer represented by the general formula (160), at least one selected from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), and perfluoro(propyl vinyl ether) is preferable, and at least one selected from the group consisting of perfluoro(methyl vinyl ether) and perfluoro(propyl vinyl ether) is more preferable.

[0193] As the fluoromonomer represented by the general formula (100), Rf 101 is preferably a fluoromonomer that is a linear fluoroalkyl group, and Rf 101 is more preferably a fluoromonomer that is a linear perfluoroalkyl group. The number of carbon atoms of Rf 101 is preferably 1 to 6. Examples of the fluoromonomer represented by the general formula (100) include CH2 = CFCF3, CH2 = CFCF2CF3, CH2 = CFCF2CF2CF3, CH2 = CFCF2CF2CF2H, CH2 = CFCF2CF2CF2CF3, CHF = CHCF3 (E isomer), CHF = CHCF3 (Z isomer), etc. Among them, 2,3,3,3 - tetrafluoropropylene represented by CH2 = CFCF3 is preferable.

[0194] As the fluoroalkyl ethylene, the general formula (170): CH2 = CH-(CF2) n -X 171 (wherein X 171 is H or F, and n is an integer from 3 to 10.) The fluoroalkyl ethylene represented by this is preferable, and it is more preferably at least one selected from the group consisting of CH2 = CH-C4F9 and CH2 = CH-C6F 13 .

[0195] Examples of the above fluoroalkyl allyl ether include, for example, the general formula (180): CF2 = CF-CF2-ORf 111 (wherein Rf 111 represents a perfluoro organic group.) The fluoromonomer represented by this is included.

[0196] Rf of the general formula (180) 111 is the same as Rf of the general formula (110). 111 As Rf 111 a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluoroalkoxyalkyl group having 1 to 10 carbon atoms is preferable. As the fluoroalkyl allyl ether represented by the general formula (180), at least one selected from the group consisting of CF2=CF-CF2-O-CF3, CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7, and CF2=CF-CF2-O-C4F9 is preferable, at least one selected from the group consisting of CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7, and CF2=CF-CF2-O-C4F9 is more preferable, and CF2=CF-CF2-O-CF2CF2CF3 is even more preferable.

[0197] As the fluorinated vinyl heterocyclic compound, the general formula (230): [Chemical formula] (In the formula, X 231 and X 232 are independently F, Cl, a methoxy group or a fluorinated methoxy group, and Y 231 is the formula Y 232 or the formula Y 233 .

[0198] [Chemical formula] (In the formula, Z 231 and Z 232 are independently F or a fluorinated alkyl group having 1 to 3 carbon atoms.)) The fluorinated vinyl heterocyclic compound represented by is exemplified.

[0199] The monomers for providing the crosslinked part are preferably at least one selected from the group consisting of CF2=CFOCF2CF(CF3)OCF2CF2CN, CF2=CFOCF2CF(CF3)OCF2CF2COOH, CF2=CFOCF2CF(CF3)OCF2CF2CH2I, CF2=CFOCF2CF2CH2I, CH2=CFCF2OCF(CF3)CF2OCF(CF3)CN, CH2=CFCF2OCF(CF3)CF2OCF(CF3)COOH, CH2=CFCF2OCF(CF3)CF2OCF(CF3)CH2OH, CH2=CHCF2CF2I, CH2=CH(CF2)2CH=CH2, CH2=CH(CF2)6CH=CH2, and CF2=CFO(CF2)5CN, and more preferably at least one selected from the group consisting of CF2=CFOCF2CF(CF3)OCF2CF2CN and CF2=CFOCF2CF2CH2I.

[0200] In the above polymerization, the above fluoromonomer and a fluorine-free monomer may be polymerized. Examples of the fluorine-free monomer include hydrocarbon-based monomers having reactivity with the above fluoromonomer.

[0201] In the above polymerization, particles of a desired fluoropolymer can be obtained by polymerizing one or more of the above fluoromonomers.

[0202] (Polymerization) The polymerization of the fluoromonomer is carried out substantially in the absence of a fluorine-containing surfactant (excluding compounds having a functional group capable of reacting in radical polymerization and a hydrophilic group). Conventionally, fluorine-containing surfactants have been used for the polymerization of fluoromonomers in an aqueous medium, but according to the production method of the present disclosure, a fluoropolymer can be obtained even when no fluorine-containing surfactant is used.

[0203] In the present disclosure, "in the substantial absence of a fluorosurfactant" means that the amount of the fluorosurfactant in the aqueous medium is 10 ppm by mass or less. The amount of the fluorosurfactant in the aqueous medium is preferably 1 ppm by mass or less, more preferably 100 ppb by mass or less, still more preferably 10 ppb by mass or less, and even more preferably 1 ppb by mass or less.

[0204] The polymerization of the fluoromonomer is carried out in the presence of the polymer (I). The addition amount of the polymer (I) in the above polymerization is preferably more than 0.02% by mass and 10% by mass or less, and a more preferable upper limit is 1% by mass or less, based on the aqueous medium. By setting the addition amount of the polymer (I) within the above range, the polymerization of the fluoromonomer in the aqueous medium can proceed smoothly. The addition amount of the polymer (I) is the total addition amount of the polymer (I) added in the above polymerization.

[0205] In the above polymerization, the polymer (I) may be added all at once or continuously. Adding the polymer (I) continuously means, for example, adding the polymer (I) not all at once, but over time, without interruption or in portions. In the above polymerization, an aqueous solution containing the polymer (I) and water may be prepared and the aqueous solution may be added.

[0206] In the above polymerization, it is preferable to start adding the polymer (I) before the solid content of the fluoropolymer formed in the aqueous medium reaches 0.5% by mass, and then continue to add the polymer (I). The start time of adding the polymer (I) is preferably before the solid content of the fluoropolymer reaches 0.3% by mass, more preferably before it reaches 0.2% by mass, still more preferably before it reaches 0.1% by mass, and particularly preferably simultaneously with the start of polymerization. The above solid content is the content of the fluoropolymer relative to the total of the aqueous medium and the fluoropolymer.

[0207] In the above polymerization, if at least one kind of polymer (I) is used, it is possible to efficiently produce a fluoropolymer. Also, two or more kinds of compounds included in the polymer (I) may be used simultaneously, or other compounds having surface activity properties other than the polymer (I) may be used simultaneously as long as they are volatile or may remain in a molded article made of a fluoropolymer or the like.

[0208] In the above polymerization, a nucleating agent may be used. The addition amount of the nucleating agent can be appropriately selected depending on the type of the nucleating agent. The addition amount of the nucleating agent may be 5000 mass ppm or less, preferably 1000 mass ppm or less, more preferably 500 mass ppm or less, still more preferably 100 mass ppm or less, particularly preferably 50 mass ppm or less, and most preferably 10 mass ppm or less with respect to the aqueous medium.

[0209] In the above polymerization, it is preferable to add the nucleating agent to the aqueous medium before the start of polymerization or before the solid content of the fluoropolymer formed in the aqueous medium reaches 5.0 mass%. By adding the nucleating agent in the initial stage of polymerization, an aqueous dispersion having a small average primary particle diameter and excellent stability can be obtained.

[0210] The amount of the nucleating agent added in the initial stage of polymerization is preferably 0.001 mass% or more, more preferably 0.01 mass% or more, still more preferably 0.05 mass% or more, and particularly preferably 0.1 mass% or more with respect to the obtained fluoropolymer. The upper limit of the amount of the nucleating agent added in the initial stage of polymerization is not limited, but for example, it is 2000 mass%.

[0211] By using the nucleating agent, a fluoropolymer having a small primary particle diameter can be obtained as compared with performing polymerization in the absence of the above nucleating agent.

[0212] Examples of the nucleating agent include dicarboxylic acids, perfluoropolyether (PFPE) acids or their salts, and hydrocarbon-containing surfactants. The nucleating agent preferably does not contain an aromatic ring and is preferably an aliphatic compound.

[0213] The nucleating agent is preferably added before the addition of the polymerization initiator or simultaneously with the addition of the polymerization initiator. However, the particle size distribution can also be adjusted by adding it during the polymerization.

[0214] The preferred amount of the dicarboxylic acid is 1000 mass ppm or less, more preferably 500 mass ppm or less, and even more preferably 100 mass ppm or less based on the aqueous medium.

[0215] The perfluoropolyether (PFPE) acid or its salt may have an arbitrary chain structure in which oxygen atoms in the main chain of the molecule are separated by saturated fluorocarbon groups having 1 to 3 carbon atoms. Also, two or more types of fluorocarbon groups may be present in the molecule. Representative structures have repeating units represented by the following formula: (-CFCF3-CF2-O-) n (VII) (-CF2-CF2-CF2-O-) n (VIII) (-CF2-CF2-O-) n -(-CF2-O-) m (IX) (-CF2-CFCF3-O-)n-(-CF2-O-) m (X)

[0216] These structures are described by Kasai in J. Appl. Polymer Sci. 57, 797 (1995). As disclosed in this reference, the above PFPE acid or its salt may have a carboxylic acid group or its salt at one or both ends. The above PFPE acid or its salt may also have a sulfonic acid, phosphonic acid group or their salts at one or both ends. Further, the above PFPE acid or its salt may have different groups at each end. For monofunctional PFPE, the other end of the molecule is usually perfluorinated, but may contain a hydrogen or chlorine atom. The above PFPE acid or its salt has at least two ether oxygens, preferably at least four ether oxygens, and even more preferably at least six ether oxygens. Preferably, at least one of the fluorocarbon groups separating the ether oxygens, more preferably at least two of such fluorocarbon groups, has two or three carbon atoms. Even more preferably, at least 50% of the fluorocarbon groups separating the ether oxygens have two or three carbon atoms. Also preferably, the above PFPE acid or its salt has a total of at least 15 carbon atoms. For example, the preferred minimum value of n or n + m in the above repeating unit structure is at least 5. Two or more of the above PFPE acids or their salts having an acid group at one or both ends can be used in the production method of the present disclosure. The above PFPE acid or its salt preferably has a number average molecular weight of less than 6000 g / mol.

[0217] The addition amount of the hydrocarbon-containing surfactant is preferably 40 mass ppm or less, more preferably 30 mass ppm or less, and still more preferably 20 mass ppm or less, based on the aqueous medium. The ppm amount of the lipophilic nucleation sites present in the aqueous medium is presumed to be less than the addition amount. Therefore, the amount of the lipophilic nucleation sites is smaller than 40 mass ppm, 30 mass ppm, and 20 mass ppm, respectively. Since the lipophilic nucleation sites are considered to exist as molecules, even a very small amount of the hydrocarbon-containing surfactant can generate a large amount of lipophilic nucleation sites. Therefore, even by adding about 1 mass ppm of the hydrocarbon-containing surfactant to the aqueous medium, beneficial effects can be obtained. The preferable lower limit is 0.01 mass ppm.

[0218] The hydrocarbon-containing surfactant includes nonionic surfactants and cationic surfactants including siloxane surfactants such as those disclosed in U.S. Patent No. 7,897,682 (Brothers et al.) and U.S. Patent No. 7,977,438 (Brothers et al.).

[0219] As the hydrocarbon-containing surfactant, a nonionic surfactant (for example, a nonionic hydrocarbon surfactant) is preferable. That is, as the nucleating agent, a nonionic surfactant is preferable. The nonionic surfactant preferably does not contain an aromatic moiety.

[0220] Examples of the nonionic surfactant include nonionic surfactants that can be contained in the fluoropolymer aqueous dispersion.

[0221] In the above polymerization, a compound having a functional group capable of reacting by radical polymerization and a hydrophilic group may be used together with the polymer (I). As the compound having a functional group capable of reacting by radical polymerization and a hydrophilic group, the same compound as the modified monomer (A) described later can be used.

[0222] In the above polymerization, in addition to the polymer (I) and other compounds having surfactant properties used as desired, additives can be used to stabilize each compound. Examples of the above additives include buffers, pH adjusters, stabilization aids, dispersion stabilizers, and the like.

[0223] As the stabilization aid, paraffin wax, fluorinated oil, fluorinated solvent, silicone oil, etc. are preferable. The stabilization aid may be used alone or in combination of two or more. As the stabilization aid, paraffin wax is more preferable. The paraffin wax may be liquid, semi-solid, or solid at room temperature, but saturated hydrocarbons having 12 or more carbon atoms are preferable. The melting point of the paraffin wax is usually preferably 40 to 65°C, more preferably 50 to 65°C.

[0224] The amount of the stabilization aid used is preferably 0.1 to 12% by mass, more preferably 0.1 to 8% by mass based on the mass of the aqueous medium used. It is desirable that the stabilization aid is sufficiently hydrophobic and is completely separated from the aqueous dispersion after polymerization so as not to become a contaminant component.

[0225] The above polymerization is carried out by charging an aqueous medium, the above polymer (I), a monomer, and other additives as necessary into a polymerization reactor, stirring the contents of the reactor, maintaining the reactor at a predetermined polymerization temperature, then adding a predetermined amount of a polymerization initiator, and starting the polymerization reaction. After the start of the polymerization reaction, monomers, polymerization initiators, chain transfer agents, polymers (I), etc. may be additionally added according to the purpose. The polymer (I) may be added after the start of the polymerization reaction.

[0226] Generally, the polymerization temperature is 5 to 120°C, and the polymerization pressure is 0.05 to 10 MPaG. The polymerization temperature and polymerization pressure are appropriately determined according to the type of monomer used, the molecular weight of the target fluoropolymer, and the reaction rate.

[0227] The polymerization initiator is not particularly limited as long as it can generate radicals in the above polymerization temperature range, and known oil-soluble and / or water-soluble polymerization initiators can be used. Furthermore, polymerization can also be initiated as a redox system in combination with a reducing agent or the like. The concentration of the polymerization initiator is appropriately determined according to the type of monomer, the molecular weight of the target fluoropolymer, and the reaction rate.

[0228] As the polymerization initiator, an oil-soluble radical polymerization initiator or a water-soluble radical polymerization initiator can be used.

[0229] The oil-soluble radical polymerization initiator may be a known oil-soluble peroxide, and typical examples include dialkyl peroxydicarbonates such as diisopropyl peroxydicarbonate and di-sec-butyl peroxydicarbonate, peroxy esters such as t-butyl peroxyisobutyrate and t-butyl peroxypivalate, and dialkyl peroxides such as di-t-butyl peroxide.

[0230] The water-soluble radical polymerization initiator may be a known water-soluble peroxide, and examples include ammonium salts, potassium salts, sodium salts of persulfuric acid, perboric acid, perchloric acid, phosphoric acid, carbonic acid, etc., organic peroxides such as disuccinic peroxide and diglutaric peroxide, and t-butyl permaleate, t-butyl hydroperoxide, etc. A reducing agent such as sulfites may also be included, and the amount used may be 0.1 to 20 times that of the peroxide.

[0231] For example, when polymerization is carried out at a low temperature of 30°C or lower, it is preferable to use a redox initiator that combines an oxidizing agent and a reducing agent as the polymerization initiator. Examples of the oxidizing agent include persulfates, organic peroxides, potassium permanganate, manganese triacetate, ammonium cerium nitrate, etc. Examples of the reducing agent include sulfites, bisulfites, bromates, diimines, oxalic acid, etc. Examples of the persulfate include ammonium persulfate and potassium persulfate. Examples of the sulfite include sodium sulfite and ammonium sulfite. In order to increase the decomposition rate of the initiator, it is also preferable to add a copper salt or an iron salt to the combination of the redox initiator. Examples of the copper salt include copper(II) sulfate, and examples of the iron salt include iron(II) sulfate.

[0232] Examples of the above redox initiator include, for example, potassium permanganate / oxalic acid, potassium permanganate / ammonium oxalate, ammonium persulfate / bisulfite / iron sulfate, manganese triacetate / oxalic acid, ammonium cerium nitrate / oxalic acid, bromate / bisulfite, etc., and potassium permanganate / oxalic acid is preferable. When using a redox initiator, either the oxidizing agent or the reducing agent may be charged into the polymerization tank in advance, and then the other may be added continuously or intermittently to initiate polymerization. For example, when using potassium permanganate / oxalic acid, it is preferable to charge oxalic acid into the polymerization tank and continuously add potassium permanganate thereto.

[0233] The addition amount of the polymerization initiator is not particularly limited, but it may be added all at once, sequentially, or continuously at the beginning of polymerization in an amount such that the polymerization rate does not decrease significantly (for example, several ppm with respect to the water concentration) or more. The upper limit is in a range where the reaction temperature may be increased while removing heat by the polymerization reaction heat from the equipment surface, and a more preferable upper limit is in a range where the polymerization reaction heat can be removed from the equipment surface.

[0234] In the above polymerization, further, according to the purpose, a known chain transfer agent, radical scavenger, or decomposer may be added to adjust the polymerization rate and molecular weight.

[0235] Examples of the chain transfer agent include esters such as dimethyl malonate, diethyl malonate, methyl acetate, ethyl acetate, butyl acetate, and dimethyl succinate, as well as isopentane, methane, ethane, propane, methanol, isopropanol, acetone, various mercaptans, various halogenated hydrocarbons such as carbon tetrachloride, and cyclohexane.

[0236] A bromine compound or an iodine compound may be used as the chain transfer agent. Examples of the polymerization method using a bromine compound or an iodine compound include, for example, a method of polymerizing a fluoromonomer in an aqueous medium in the presence of a bromine compound or an iodine compound in a substantially oxygen-free state (iodine transfer polymerization method). Representative examples of the bromine compound or iodine compound to be used include, for example, the general formula: R a I x Br y (In the formula, x and y are each an integer from 0 to 2, and satisfy 1 ≤ x + y ≤ 2, and R a is a saturated or unsaturated fluorocarbon group or chlorofluorocarbon group having 1 to 16 carbon atoms, or a hydrocarbon group having 1 to 3 carbon atoms, and may contain an oxygen atom). Compounds represented by this formula are included. By using a bromine compound or an iodine compound, iodine or bromine is introduced into the polymer and functions as a crosslinking point.

[0237] Examples of the bromine compound or iodine compound include 1,3-diiodoperfluoropropane, 2-iodoperfluoropropane, 1,3-diiodo-2-chloroperfluoropropane, 1,4-diiodoperfluorobutane, 1,5-diiodo-2,4-dichloroperfluoropentane, 1,6-diiodoperfluorhexane, 1,8-diiodoperfluorooctane, 1,12-diiodoperfluorododecane, 1,16-diiodoperfluorohexadecane, diiodomethane, 1,2-diiodoethane, 1,3-diiodo-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-iodoperfluorobuten-1, 2-bromo-4-iodoperfluorobuten-1, monoiodomonobromo substitution products of benzene, diiodomonobromo substitution products, and (2-iodoethyl) and (2-bromoethyl) substitution products. These compounds may be used alone or in combination with each other.

[0238] Among these, from the viewpoints of polymerization reactivity, crosslinking reactivity, availability, etc., it is preferable to use 1,4-diiodoperfluorobutane, 1,6-diiodoperfluorohexane, or 2-iodoperfluoropropane.

[0239] The amount of the above chain transfer agent used is usually 1 to 50,000 mass ppm, preferably 1 to 20,000 mass ppm, based on the total amount of the supplied fluoromonomer.

[0240] The above 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 multiple portions during polymerization, or may be continuously added during polymerization.

[0241] As the polymerization initiator, persulfates (e.g., ammonium persulfate) or organic peroxides such as disuccinic peroxide and diglutaric peroxide can be used alone or in the form of a mixture thereof. Further, it may be used in a redox system in combination with a reducing agent such as sodium sulfite. Furthermore, during the polymerization, a radical scavenger such as hydroquinone or catechol may be added, or a peroxide decomposer such as ammonium sulfite may be added to adjust the radical concentration in the system.

[0242] In the above polymerization, in the presence of the polymer (I), a fluoromonomer is polymerized in an aqueous medium to produce an aqueous dispersion of fluoropolymer particles, and in the aqueous dispersion of the above fluoropolymer particles, the fluoromonomer may be seed-polymerized onto the fluoropolymer particles to obtain a fluoropolymer.

[0243] The content (solid content concentration) of the fluoropolymer in the polymerization dispersion is usually 10 to 50% by mass, more preferably 15% by mass or more, preferably 40% by mass or less, and more preferably 35% by mass or less.

[0244] The content of the fluoropolymer in the polymerization dispersion is a value obtained by drying 1 g of the polymerization dispersion in a blow dryer at 150 °C for 60 minutes, measuring the mass of the heat residue, and calculating the mass of the heat residue as a percentage of the mass (1 g) of the polymerization dispersion.

[0245] (Preparation of the pre-concentration composition) In one embodiment of the production method, a pre-concentration composition is prepared by mixing the polymerization dispersion obtained by polymerizing the fluoromonomer and the nonionic surfactant (a). The obtained pre-concentration composition contains a fluoropolymer, a polymer (I), an aqueous medium, and a nonionic surfactant (a).

[0246] The content of the nonionic surfactant (a) in the pre-concentration composition is preferably 1.0% by mass or more, preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less, based on the fluoropolymer. If the content of the nonionic surfactant (a) is too small, concentration may be difficult, and if the content of the nonionic surfactant (a) is too large, economy may be impaired.

[0247] The content (solid content concentration) of the fluoropolymer in the pre-concentration composition is usually 8 to 50% by mass, preferably 10% by mass or more, more preferably 15% by mass or more, preferably 40% by mass or less, and more preferably 35% by mass or less.

[0248] The pH of the pre-concentration composition is preferably 4.0 to 11.5, more preferably 7.0 or more, even more preferably 8.0 or more, and particularly preferably 9.0 or more. By adjusting the pH of the pre-concentration composition within the above range, the concentration rate can be further increased.

[0249] In one embodiment of the pre-concentration composition, it contains a fluorine-containing surfactant. Even when the pre-concentration composition contains a fluorine-containing surfactant, by performing concentration, a fluoropolymer aqueous dispersion in which the fluorine-containing surfactant is removed from the composition and the content of the fluorine-containing surfactant is reduced can be obtained.

[0250] In one embodiment of the pre-concentration composition, it substantially does not contain a fluorine-containing surfactant.

[0251] In the present disclosure, "substantially does not contain a fluorine-containing surfactant" means that the content of the fluorine-containing surfactant in the pre-concentration composition is 10 mass ppm or less, preferably 1 mass ppm or less, more preferably 100 mass ppb or less, still more preferably 10 mass ppb or less, even more preferably 1 mass ppb or less, and particularly preferably, the fluorine-containing surfactant is below the detection limit by measurement using liquid chromatography-mass spectrometry (LC / MS).

[0252] The content of the fluorosurfactant in the pre-concentration composition can be measured by the same method as the content of the fluorosurfactant in the aqueous dispersion.

[0253] (Preparation of the post-concentration composition by concentration) In one embodiment of the production method, a post-concentration composition is prepared by concentrating the pre-concentration composition. The obtained post-concentration composition contains a fluoropolymer, polymer (I), an aqueous medium, and a nonionic surfactant (a).

[0254] Before concentrating the pre-concentration composition, or during the concentration of the pre-concentration composition, an aqueous medium such as water or alcohol may be added to the composition. The aqueous medium may be a single component such as water or alcohol, or a mixture of water and alcohol or the like.

[0255] Examples of the concentration method include phase separation concentration, electrophoresis, ion exchanger method, membrane concentration, etc. Phase separation concentration, ion exchanger method, and membrane concentration can be carried out under conventionally known treatment conditions and are not particularly limited, but can be carried out by the methods described in International Publication No. 2004 / 050719, Japanese Patent Application Laid-Open No. 2002-532583, and Japanese Patent Application Laid-Open No. 55-120630.

[0256] As the concentration method, phase separation concentration is preferable. Phase separation concentration can be carried out, for example, by heating the pre-concentration composition to phase-separate it into a fluoropolymer-free phase (upper clear phase) and a fluoropolymer-containing phase (concentrated phase), removing the fluoropolymer-free phase, and recovering the fluoropolymer-containing phase (concentrated phase).

[0257] The recovered fluoropolymer-containing phase (concentrated phase) contains a fluoropolymer, polymer (I), an aqueous medium, and a nonionic surfactant (a).

[0258] The temperature for phase separation concentration can be selected based on the cloud point of the nonionic surfactant (a) contained in the composition before concentration. The temperature for phase separation concentration is preferably not lower than a temperature 10°C lower than the cloud point of the nonionic surfactant (a), and preferably not higher than a temperature 10°C higher than the cloud point of the nonionic surfactant (a).

[0259] In the production method of the present disclosure, phase separation concentration may be repeated.

[0260] The number of repetitions is not particularly limited, but is preferably 2 or more times, more preferably 3 or more times. The upper limit of the number of times is not limited, and may be, for example, 10 or less.

[0261] When phase separation concentration is performed 2 or more times, it is preferable that the first phase separation concentration is heated at a temperature not lower than a temperature 10°C lower than the cloud point of the nonionic surfactant (a) and then allowed to stand to separate into a supernatant phase and a concentrated phase. Further, it is preferable that the second or subsequent phase separation concentration is heated at a temperature not lower than a temperature 10°C lower than the cloud point of the nonionic surfactant (a) and then allowed to stand to separate into a supernatant phase and a concentrated phase.

[0262] (Addition of nonionic surfactant (b)) In one embodiment of the production method, a fluoropolymer aqueous dispersion is prepared by adding a nonionic surfactant (b) to the composition after concentration. Thereby, the fluoropolymer aqueous dispersion of the present disclosure can be obtained.

[0263] In addition to the nonionic surfactant (b), the above-mentioned nonionic surfactant (a) may be added to the composition after concentration. In addition to the nonionic surfactant (b), the above-mentioned hydrocarbon-based anionic surfactant may be added to the composition after concentration. Further, in addition to the nonionic surfactant (b), other components such as the above-mentioned preservative may be added to the composition after concentration.

[0264] For the purpose of adjusting the pH, a pH adjuster such as aqueous ammonia can also be blended with the composition after concentration.

[0265] The pH of the aqueous dispersion of the fluoropolymer obtained by concentration is preferably 8 to 13, more preferably 9 to 12, and even more preferably 9 to 11.

[0266] The above pH is a value measured at 25 °C in accordance with JIS K6893.

[0267] Next, the fluoropolymer in the aqueous dispersion of the present disclosure and the fluoropolymer in the aqueous dispersion obtained by the production method of the present disclosure will be described in more detail.

[0268] (Fluoropolymer) As the fluoropolymer, a fluoropolymer (excluding polymer (I)) is preferable.

[0269] The above fluoropolymer preferably has an ion exchange rate (IXR) higher than 53. Preferred fluoropolymers have no ionic groups or a limited number of ionic groups that result in an ion exchange rate higher than about 100. The ion exchange rate of a preferred fluoropolymer is preferably 1000 or more, more preferably 2000 or more, and even more preferably 5000 or more.

[0270] Examples of the fluoropolymer include a TFE polymer in which the monomer having the highest molar fraction in the polymer (hereinafter, "most abundant monomer") is TFE, a VDF polymer in which the most abundant monomer is VDF, and a CTFE polymer in which the most abundant monomer is CTFE.

[0271] In the manufacturing method of the present disclosure, for example, (I) as the non-melt processable fluororesin, tetrafluoroethylene polymer [TFE polymer (PTFE)], (II) as the melt processable fluororesin, ethylene / TFE copolymer [ETFE], TFE / HFP copolymer [FEP], TFE / perfluoro(alkyl vinyl ether) copolymer [PFA, MFA, etc.], TFE / perfluoroallyl ether copolymer, TFE / VDF copolymer, electrolyte polymer precursor, (III) as the fluororubber, TFE / propylene copolymer, TFE / propylene / third monomer copolymer (the above third monomer is VDF, HFP, CTFE, fluoroalkyl vinyl ethers, etc.), copolymer composed of TFE and fluoroalkyl vinyl ethers; HFP / ethylene copolymer, HFP / ethylene / TFE copolymer; VDF / HFP copolymer, HFP / ethylene copolymer, VDF / TFE / HFP copolymer; and fluorine-containing segmented polymers described in Japanese Patent Publication No. 61-49327 can be preferably manufactured.

[0272] As the above fluoropolymer, a fluororesin is preferable, and among them, a fluororesin having a fluorine substitution rate calculated by the following formula of 50% or more is more preferable, a fluororesin having a fluorine substitution rate exceeding 50% is further preferable, a fluororesin having a fluorine substitution rate of 55% or more is even more preferable, a fluororesin having a fluorine substitution rate of 60% or more is even more preferable, a fluororesin having a fluorine substitution rate of 75% or more is even more preferable, a fluororesin having a fluorine substitution rate of 80% or more is particularly preferable, and a fluororesin having a fluorine substitution rate of 90 to 100%, that is, a perfluororesin is most preferable. (Formula) Fluorine substitution rate (%) = (number of fluorine atoms bonded to carbon atoms constituting the fluoropolymer) / ((number of hydrogen atoms bonded to carbon atoms constituting the fluoropolymer) + (number of fluorine atoms and chlorine atoms bonded to carbon atoms constituting the fluoropolymer)) × 100

[0273] As the above perfluororesin, a fluororesin having a fluorine substitution rate of 95 to 100% is more preferable, PTFE, FEP or PFA is further preferable, and PTFE is particularly preferable.

[0274] The above fluoropolymer may have a core-shell structure. Examples of the fluoropolymer having a core-shell structure include modified PTFE containing a core of high molecular weight PTFE and a shell of lower molecular weight PTFE or modified PTFE in particles. Examples of such modified PTFE include PTFE described in Japanese Patent Application Laid-Open No. 2005-527652.

[0275] The above-mentioned (I) non-melt processable fluororesin, (II) melt processable fluororesin, and (III) fluororubber preferably produced by the production method of the present disclosure are preferably produced in the following embodiments.

[0276] (I) Non-melt processable fluororesin In the production method of the present disclosure, the polymerization of TFE is usually carried out at a polymerization temperature of 10 to 150°C and a polymerization pressure of 0.05 to 5 MPaG. For example, the polymerization temperature is more preferably 30°C or higher, and even more preferably 50°C or higher. Also, it is more preferably 120°C or lower, and even more preferably 100°C or lower. Further, the polymerization pressure is more preferably 0.3 MPaG or higher, and even more preferably 0.5 MPaG or higher. Also, it is more preferably 5.0 MPaG or lower, and even more preferably 3.0 MPaG or lower. In particular, from the viewpoint of improving the yield of the fluoropolymer, it is preferably 1.0 MPaG or higher, more preferably 1.2 MPaG or higher, even more preferably 1.5 MPaG or higher, and still more preferably 2.0 MPaG or higher.

[0277] In one embodiment, pure water is charged into a pressure-resistant reaction vessel equipped with a stirrer, deoxygenated, then TFE is charged, brought to a predetermined temperature, and a polymerization initiator is added to start the reaction. When the pressure decreases as the reaction proceeds, additional TFE is continuously or intermittently added to maintain the initial pressure. When a predetermined amount of TFE has been supplied, the supply is stopped, the TFE in the reaction vessel is purged, the temperature is returned to room temperature, and the reaction is terminated. Additional TFE may be continuously or intermittently added so that the pressure does not decrease.

[0278] In the production of PTFE, various known modified monomers can also be used in combination. In the present disclosure, PTFE is a concept that includes not only TFE homopolymers but also copolymers of TFE and modified monomers (hereinafter referred to as "modified PTFE").

[0279] The above-mentioned modified monomers are not particularly limited as long as they can copolymerize with TFE, and include fluoromonomers and non-fluoromonomers. Also, one type of modified monomer may be used, or a plurality of types may be used.

[0280] Examples of fluoromonomers include perfluoroolefins such as hexafluoropropylene [HFP]; hydrogen-containing fluoroolefins such as trifluoroethylene and vinylidene fluoride [VDF]; perhaloolefins such as chlorotrifluoroethylene; perfluorovinyl ethers; (perfluoroalkyl)ethylene; perfluoroallyl ethers, and the like.

[0281] The above-mentioned perfluorovinyl ether is not particularly limited. For example, the general formula (A): CF2=CF-ORf (A) (In the formula, Rf represents a perfluoro organic group.) Perfluoro unsaturated compounds represented by the like can be mentioned. In the present disclosure, the above-mentioned "perfluoro organic group" means an organic group in which all hydrogen atoms bonded to carbon atoms are substituted by fluorine atoms. The above-mentioned perfluoro organic group may have ether oxygen.

[0282] Examples of the above-mentioned perfluorovinyl ether include perfluoro(alkyl vinyl ether) [PAVE] in which Rf is a perfluoroalkyl group having 1 to 10 carbon atoms in the general formula (A). The number of carbon atoms of the above-mentioned perfluoroalkyl group is preferably 1 to 5.

[0283] Examples of the perfluoroalkyl group in the above PAVE include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group, and the like.

[0284] Examples of the above perfluorovinyl ether further include those in which, in the general formula (A), Rf is a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms, Rf is a group represented by the following formula:

[0285] [Chemical formula]

[0286] (wherein m represents an integer of 0 or 1 to 4), Rf is a group represented by the following formula:

[0287] CF3CF2CF2-(O-CF(CF3)-CF2) n - (wherein n represents an integer of 1 to 4), and the like.

[0288] Examples of the hydrogen-containing fluoroolefin include CH2=CF2, CFH=CH2, CFH=CF2, CH2=CFCF3, CH2=CHCF3, CHF=CHCF3 (E isomer), CHF=CHCF3 (Z isomer), and the like.

[0289] The (perfluoroalkyl)ethylene (PFAE) is not particularly limited, and examples thereof include (perfluorobutyl)ethylene (PFBE), (perfluorohexyl)ethylene, and the like.

[0290] Examples of the perfluoroallyl ether include, for example, General formula: CF2=CF-CF2-ORf (wherein Rf represents a perfluoro organic group), and the fluoromonomer represented thereby is included.

[0291] Rf in the above general formula is the same as Rf in general formula (A). As Rf, a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluoroalkoxyalkyl group having 1 to 10 carbon atoms is preferable. As the perfluoroallyl ether, at least one selected from the group consisting of CF2=CF-CF2-O-CF3, CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7, and CF2=CF-CF2-O-C4F9 is preferable, at least one selected from the group consisting of CF2=CF-CF2-O-C2F5, CF2=CF-CF2-O-C3F7, and CF2=CF-CF2-O-C4F9 is more preferable, and CF2=CF-CF2-O-CF2CF2CF3 is even more preferable.

[0292] From the viewpoint of reactivity with TFE, the above modified monomer preferably contains at least one selected from the group consisting of hexafluoropropylene, perfluoro(alkyl vinyl ether), and (perfluoroalkyl)ethylene. More preferably, it contains at least one selected from the group consisting of hexafluoropropylene, perfluoro(methyl vinyl ether), perfluoro(propyl vinyl ether), (perfluorobutyl)ethylene, (perfluorohexyl)ethylene, and (perfluorooctyl)ethylene.

[0293] In the production of the above TFE polymer, polymer (I) can be used within the range of use in the production method of the present disclosure described above. The concentration of polymer (I) is not particularly limited as long as it is within the above range. If the addition amount is too large, needle-like particles with a large aspect ratio are generated, and the aqueous dispersion becomes gel-like and its stability is impaired. The lower limit of the usage amount of polymer (I) is preferably 0.0001% by mass, more preferably 0.001% by mass, still more preferably 0.01% by mass, and particularly preferably 0.02% by mass with respect to the aqueous medium. The upper limit of the usage amount of the above polymer (I) is preferably 10% by mass, more preferably 5% by mass with respect to the aqueous medium.

[0294] The polymer (I) may be added all at once into the reaction vessel before the start of polymerization, or all at once after the start of polymerization, or divided and added in multiple portions during polymerization, or continuously added during polymerization.

[0295] In the production of the above TFE polymer, as the polymerization initiator, persulfates (e.g., ammonium persulfate) or organic peroxides such as disuccinic peroxide and diglutaric peroxide can be used alone or in the form of a mixture thereof. Further, it may be used in a redox system in combination with a reducing agent such as sodium sulfite. Furthermore, during polymerization, a radical scavenger such as hydroquinone or catechol can be added, or a peroxide decomposer such as ammonium sulfite can be added to adjust the radical concentration in the system.

[0296] As the above redox polymerization initiator, it is preferable to use a redox initiator that combines an oxidizing agent and a reducing agent. Examples of the oxidizing agent include persulfates, organic peroxides, potassium permanganate, manganese triacetate, ammonium cerium nitrate, etc. Examples of the reducing agent include sulfites, bisulfites, bromates, diimines, oxalic acid, etc. Examples of the persulfate include ammonium persulfate and potassium persulfate. Examples of the sulfite include sodium sulfite and ammonium sulfite. In order to increase the decomposition rate of the initiator, it is also preferable to add a copper salt or an iron salt to the combination of the redox initiator. Examples of the copper salt include copper(II) sulfate, and examples of the iron salt include iron(II) sulfate.

[0297] Examples of the redox initiator include potassium permanganate / oxalic acid, potassium permanganate / ammonium oxalate, ammonium persulfate / bisulfite / iron sulfate, manganese triacetate / oxalic acid, ammonium cerium nitrate / oxalic acid, bromate / bisulfite, etc. Potassium permanganate / oxalic acid is preferred. When using a redox initiator, either an oxidizing agent or a reducing agent may be charged into the polymerization tank in advance, and then the other may be added continuously or intermittently to initiate the polymerization. For example, when using potassium permanganate / oxalic acid, it is preferable to charge oxalic acid into the polymerization tank and continuously add potassium permanganate thereto.

[0298] In the production of the above TFE polymer, known substances can be used as the chain transfer agent. Examples include saturated hydrocarbons such as methane, ethane, propane, and butane, halogenated hydrocarbons such as chloromethane, dichloromethane, and difluoroethane, alcohols such as methanol, ethanol, and isopropanol, and hydrogen. Those in a gaseous state at normal temperature and pressure are preferred.

[0299] The amount of the above chain transfer agent used is usually 1 to 10,000 mass ppm, preferably 1 to 5,000 mass ppm, based on the total amount of TFE supplied.

[0300] In the production of the above TFE polymer, furthermore, a saturated hydrocarbon having 12 or more carbon atoms that is substantially inert to the reaction and is liquid under the above reaction conditions can be used as a dispersion stabilizer for the reaction system in an amount of 2 to 10 parts by mass with respect to 100 parts by mass of the aqueous medium. Also, ammonium carbonate, ammonium phosphate, etc. may be added as a buffer for adjusting the pH during the reaction.

[0301] When the polymerization of TFE is completed, a polymerization dispersion liquid having a solid content concentration of 1.0 to 50% by mass and an average primary particle diameter of 50 to 500 nm can be obtained. The lower limit of the above solid content concentration is preferably 5% by mass, more preferably 8% by mass. The upper limit is not particularly limited and may be 40% by mass or 35% by mass. The lower limit of the average primary particle diameter is preferably 100 nm, more preferably 150 nm. The upper limit is preferably 400 nm, more preferably 350 nm. The average primary particle diameter can be measured by the dynamic light scattering method. An aqueous dispersion adjusted to a solid content concentration of about 1.0 mass% is prepared, and using the dynamic light scattering method, it can be measured at 25°C, with the refractive index of the solvent (water) being 1.3328 and the viscosity of the solvent (water) being 0.8878 mPa·s, with 70 accumulative measurements. As the dynamic light scattering method, for example, ELSZ - 1000S (manufactured by Otsuka Electronics Co., Ltd.) can be used.

[0302] The aqueous dispersion of the TFE polymer can also be stabilized and further concentrated by adding a non - ionic surfactant, and depending on the purpose, it is also preferably used for various applications as a composition added with an organic or inorganic filler. By coating the composition on a substrate made of metal or ceramics, a coating film surface having non - stickiness and a low friction coefficient can be obtained, which is excellent in gloss, smoothness, abrasion resistance, weather resistance, and heat resistance, and is suitable for coating of rolls, cooking utensils, etc., and impregnation processing of glass cloth.

[0303] An organosol of the TFE polymer can also be prepared from the above aqueous dispersion. The organosol can contain the above TFE polymer and an organic solvent. Examples of the organic solvent include ether - based solvents, ketone - based solvents, alcohol - based solvents, amide - based solvents, ester - based solvents, aliphatic hydrocarbon - based solvents, aromatic hydrocarbon - based solvents, and halogenated hydrocarbon - based solvents. N - methyl - 2 - pyrrolidone, dimethylacetamide, etc. can be preferably used. The preparation of the organosol can be carried out, for example, by the method described in International Publication No. 2012 / 002038.

[0304] Examples of the melt - processable fluororesin include FEP, PFA, TFE / perfluoroallyl ether copolymer, ETFE, ethylene / TFE / HFP copolymer [EFEP], etc. Among them, PFA or FEP is preferred.

[0305] It is also preferable that the aqueous dispersion contains the melt-processable fluororesin. Examples of the melt-processable fluororesin include FEP, PFA, TFE / perfluoroallyl ether copolymer, ETFE, EFEP, and the like. The aqueous dispersion containing the melt-processable fluororesin can be used as a paint. Since the melt-processable fluororesin can sufficiently fuse the particles of the TFE polymer together, it can improve the film-forming property and impart gloss to the resulting film.

[0306] It is also preferable that the aqueous dispersion of the TFE polymer be used as a dust suppression treatment agent. The dust suppression treatment agent can be used in methods such as those described in Japanese Patent No. 2827152 and Japanese Patent No. 2538783, which involve mixing the dust-generating substance with the mixture and subjecting the mixture to a compression-shearing action at a temperature of 20 to 200°C to fibrillate the TFE polymer and suppress the dust of the dust-generating substance. The aqueous dispersion of the TFE polymer can be suitably used, for example, in the dust suppression treatment agent composition described in International Publication No. 2007 / 004250 and can also be suitably used in the dust suppression treatment method described in International Publication No. 2007 / 000812.

[0307] The dust suppression treatment agent is suitably used for dust suppression treatment in fields such as building materials, soil stabilizers, solidifying agents, fertilizers, landfilling of incineration ash and harmful substances, explosion protection, cosmetics, and sand for pet excrement represented by cat litter.

[0308] It is also preferable that the aqueous dispersion of the TFE polymer be used as a raw material for obtaining TFE polymer fibers by the dispersion spinning method. The dispersion spinning method is a method in which an aqueous dispersion of the TFE polymer and an aqueous dispersion of a matrix polymer are mixed, the mixture is extruded to form an intermediate fiber structure, and the matrix polymer is decomposed and the TFE polymer particles are sintered by firing the intermediate fiber structure to obtain TFE polymer fibers.

[0309] The fluoropolymer may be low molecular weight PTFE.

[0310] Low molecular weight PTFE with a molecular weight of 600,000 or less (also called PTFE micropowder) has excellent chemical stability, extremely low surface energy, and is less likely to fibrillate. Therefore, as an additive for the purpose of improving slipperiness and the texture of the coating film surface, etc., it is suitable for the production of plastics, inks, cosmetics, paints, greases, office automation equipment parts, toners, etc. (for example, see Japanese Patent Laid-Open No. 10-147617).

[0311] Also, in the presence of a chain transfer agent, a polymerization initiator and a polymer (I) are dispersed in an aqueous medium, and TFE, or a monomer copolymerizable with TFE and TFE are polymerized to obtain low molecular weight PTFE. In this case, as the chain transfer agent, at least one selected from the group consisting of alkanes having 2 to 4 carbon atoms is preferable. Specifically, methane, ethane, propane, butane, and isobutane are more preferable, and ethane and propane are even more preferable. In this case, the amount of the chain transfer agent is preferably 10 mass ppm or more or more than 10 mass ppm with respect to the aqueous medium.

[0312] When using the low molecular weight PTFE obtained by the above polymerization as a powder, the aqueous dispersion can be coagulated to obtain powder particles.

[0313] The fluoropolymer may be high molecular weight PTFE. In the present disclosure, high molecular weight PTFE means PTFE having non-melt processability and fibrillability. On the other hand, low molecular weight PTFE means PTFE having melt processability and no fibrillability.

[0314] The above non-melt processability means the property that the melt flow rate cannot be measured at a temperature higher than the crystallization melting point in accordance with ASTM D 1238 and D 2116.

[0315] The presence or absence of fibrillation properties can be determined by "paste extrusion", which is a typical method for molding "high molecular weight PTFE powder", a powder made from a TFE polymer. Generally, paste extrusion is possible because high molecular weight PTFE has fibrillation properties. When the unfired molded product obtained by paste extrusion has no substantial strength or elongation, for example, when the elongation is 0% and it breaks when pulled, it can be considered that there is no fibrillation property.

[0316] The above high molecular weight PTFE preferably has a standard specific gravity (SSG) of 2.130 to 2.280. The above standard specific gravity is measured by the water displacement method in accordance with ASTM D 792 using a sample molded in accordance with ASTM D4895-89. In the present disclosure, "high molecular weight" means that the above standard specific gravity is within the above range.

[0317] The above low molecular weight PTFE has a melt viscosity at 380°C of 1×10 2 ~7×10 5 Pa·s. In the present disclosure, "low molecular weight" means that the above melt viscosity is within the above range. The melt viscosity is measured in accordance with ASTM D 1238 using a flow tester (manufactured by Shimadzu Corporation) and a 2φ-8L die, and maintaining a 2 g sample preheated at 380°C for 5 minutes at the above temperature under a load of 0.7 MPa.

[0318] The above high molecular weight PTFE has a melt viscosity that is extremely higher than that of the above low molecular weight PTFE, and it is difficult to measure its exact melt viscosity. On the other hand, although the melt viscosity of the above low molecular weight PTFE can be measured, it is difficult to obtain a molded product that can be used for measuring the standard specific gravity from the above low molecular weight PTFE, and it is difficult to measure its exact standard specific gravity. Therefore, in the present disclosure, the standard specific gravity is adopted as an index of the molecular weight of the above high molecular weight PTFE, and the melt viscosity is adopted as an index of the molecular weight of the above low molecular weight PTFE. Note that for both the above high molecular weight PTFE and the above low molecular weight PTFE, there is no known measurement method that can directly specify the molecular weight.

[0319] The above high molecular weight PTFE preferably has a peak temperature of 333 to 347°C, more preferably 335 to 345°C. The above low molecular weight PTFE preferably has a peak temperature of 322 to 333°C, more preferably 324 to 332°C. The peak temperature can be specified as the temperature corresponding to the maximum value appearing in the differential thermal (DTA) curve obtained by heating PTFE without a heating history at 300°C or higher at a rate of 10°C / min using a TG / DTA (simultaneous differential thermal and thermogravimetric analyzer).

[0320] The peak temperature of PTFE may be 322 to 347°C. When PTFE is high molecular weight PTFE, the upper limit of the peak temperature of PTFE may be 347°C or lower, 346°C or lower, 345°C or lower, 344°C or lower, 343°C or lower, 342°C or lower, 341°C or lower, 340°C or lower. When PTFE is high molecular weight PTFE, the lower limit of the peak temperature of PTFE may be 333°C or higher, 335°C or higher. When PTFE is low molecular weight PTFE, the upper limit of the peak temperature of PTFE may be 333°C or lower, 332°C or lower. When PTFE is low molecular weight PTFE, the lower limit of the peak temperature of PTFE may be 322°C or higher, 324°C or higher.

[0321] The average primary particle diameter of the primary particles of the low molecular weight PTFE is preferably 10 to 300 nm, more preferably 50 nm or more, still more preferably 100 nm or more, particularly preferably 150 nm or more, and more preferably 250 nm or less. A relatively small average primary particle diameter of the primary particles can be obtained, for example, by adding a modified monomer to the polymerization system at the initial stage of the polymerization of TFE.

[0322] The average primary particle diameter of the primary particles of low molecular weight PTFE can be measured by the dynamic light scattering method. First, a low molecular weight PTFE aqueous dispersion with a polymer solid content concentration adjusted to about 1.0% by mass is prepared, and using the dynamic light scattering method, the measurement temperature is 25°C, the refractive index of the solvent (water) is 1.3328, the viscosity of the solvent (water) is 0.8878 mPa·s, and the number of integration times is 70 times, and it can be measured. In the dynamic light scattering method, for example, ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.) can be used.

[0323] Regarding the above high molecular weight PTFE, in the melting heat curve when the temperature is raised at a rate of 10°C / min using a differential scanning calorimeter [DSC] for PTFE without a heating history at a temperature of 300°C or higher, at least one endothermic peak appears in the range of 333 to 347°C, and the melting heat amount in the range of 290 to 350°C calculated from the above melting heat curve is preferably 52 mJ / mg or more. The melting heat amount of PTFE is more preferably 55 mJ / mg or more, and even more preferably 58 mJ / mg or more.

[0324] The fluoropolymer may be a TFE / HFP copolymer (FEP). The preferred monomer composition (mass%) of FEP is TFE:HFP = (60 to 95):(5 to 40), more preferably (85 to 92):(8 to 15).

[0325] In addition to TFE and HFP, by polymerizing other monomers copolymerizable with these monomers, a copolymer of TFE, HFP, and other monomers may be obtained as FEP. Examples of other monomers include the above-mentioned fluorine-containing monomers (excluding TFE and HFP) and fluorine-free monomers. One or more kinds can be used as other monomers. As other monomers, perfluoro(alkyl vinyl ether) is preferred. The content of other monomer units in FEP may be 0.1 to 2% by mass based on all monomer units.

[0326] In the polymerization of the above-mentioned FEP, the polymer (I) can be used within the range of use in the production method of the present disclosure, but usually, it is added in an amount of 0.0001 to 10% by mass based on 100% by mass of the aqueous medium.

[0327] The fluoropolymer may be a TFE / perfluoro(alkyl vinyl ether) copolymer (PFA). The preferred monomer composition (mol%) of the TFE / perfluoro(alkyl vinyl ether) copolymer is TFE:perfluoro(alkyl vinyl ether) = (90 to 99.7):(0.3 to 10), more preferably (97 to 99):(1 to 3). As the above-mentioned perfluoro(alkyl vinyl ether), those represented by the formula: CF2=CFORf 4 (wherein, Rf 4 is a perfluoroalkyl group having 1 to 6 carbon atoms) are preferably used.

[0328] In addition to TFE and perfluoro(alkyl vinyl ether), by polymerizing other monomers copolymerizable with these monomers, a copolymer of TFE, perfluoro(alkyl vinyl ether) and other monomers may be obtained as the TFE / perfluoro(alkyl vinyl ether) copolymer. Examples of the other monomers include the above-mentioned fluorine-containing monomers (excluding TFE and perfluoro(alkyl vinyl ether)) and non-fluorine-containing monomers. One or more kinds of other monomers can be used. The content of the other monomer units in the TFE / perfluoro(alkyl vinyl ether) copolymer may be 0.1 to 2% by mass based on all the monomer units.

[0329] In the production method of the present disclosure, when performing condensation, washing, drying, etc. of the fluoropolymer, wastewater and off-gas are generated. From the wastewater generated by the above-mentioned condensation or washing, and / or the off-gas generated by drying, the polymer (I), decomposition products and by-products by-produced from the polymer (I), residual monomers, etc. are recovered and purified, whereby the polymer (I), decomposition products and by-products by-produced from the polymer (I), residual monomers, etc. may be reused. The method for performing the above-mentioned recovery and purification is not particularly limited, but can be performed by a known method. For example, according to the method described in JP-T-2011-520020, the methods described in US Patent Application Publication No. 2007 / 15937, US Patent Application Publication No. 2007 / 25902, and US Patent Application Publication No. 2007 / 27251 can be mentioned, and specifically, the following methods can be mentioned.

[0330] As a method for recovering the polymer (I), decomposition products and by-products of the polymer (I) by-produced from the polymer (I), residual monomers, etc. from the above-mentioned wastewater, adsorption particles such as ion exchange resins, activated carbon, silica gel, clay, zeolite, etc. are brought into contact with the wastewater to adsorb the polymer (I) etc., and then a method of separating the wastewater and the adsorption particles can be mentioned. If the adsorption particles adsorbed with the polymer (I) etc. are incinerated, the release of the polymer (I) etc. into the environment can be prevented.

[0331] Also, the polymer (I) etc. can be recovered by desorbing and eluting the polymer (I) etc. from the ion exchange resin particles adsorbed with the polymer (I) etc. by a known method. For example, when the ion exchange resin particles are anion exchange resin particles, the polymer (I) etc. can be eluted by bringing a mineral acid into contact with the anion exchange resin. Subsequently, when a water-soluble organic solvent is added to the obtained eluate, it usually separates into two phases, so the polymer (I) etc. can be recovered by recovering and neutralizing the lower phase containing the polymer (I) etc. Examples of the water-soluble organic solvent include polar solvents such as alcohol, ketone, and ether.

[0332] As another method for recovering the above polymer (I) etc. from the ion exchange resin particles, there may be mentioned a method using an ammonium salt and a water-soluble organic solvent, and a method using an alcohol and optionally an acid. In the latter method, since an ester derivative of the polymer (I) etc. is formed, it can be easily separated from the alcohol by distillation.

[0333] When the above-mentioned waste water contains fluoropolymer particles or other solid components, it is preferable to remove them before bringing the waste water into contact with the adsorption particles. As a method for removing the fluoropolymer particles or other solid components, there may be mentioned a method in which these are precipitated by adding an aluminum salt etc. and then the waste water and the precipitate are separated, an electrocoagulation method, etc. Further, they may be removed by a mechanical method, for example, a crossflow filtration method, a deep bed filtration method, a precoat filtration method. From the viewpoint of productivity, the concentration of the unaggregated above-mentioned fluoropolymer in the above-mentioned waste water is preferably low, more preferably less than 0.4% by mass, and particularly preferably less than 0.3% by mass.

[0334] As a method for recovering the polymer (I) etc. from the above off-gas, there may be mentioned a method in which a scrubber is used to bring it into contact with deionized water, an aqueous alkali solution, an organic solvent such as a glycol ether solvent, etc. to obtain a scrubber solution containing the polymer (I) etc. When a high-concentration aqueous alkali solution is used as the aqueous alkali solution, the scrubber solution can be recovered with the polymer (I) etc. in a phase-separated state, so that the recovery and reuse of the polymer (I) etc. are easy. Examples of the alkali compound include alkali metal hydroxides, quaternary ammonium salts, etc.

[0335] The scrubber solution containing the polymer (I) etc. may be concentrated using a reverse osmosis membrane etc. The concentrated scrubber solution usually contains fluoride ions, but by further adding alumina after concentration to remove the fluoride ions, the reuse of the polymer (I) etc. can also be facilitated. Further, the polymer (I) etc. may be adsorbed by bringing adsorption particles into contact with the scrubber solution, and the polymer (I) etc. may be recovered by the method described above.

[0336] The polymer (I) etc. recovered by any of the above methods can be reused in the production of fluoropolymers.

[0337] Although the embodiments have been described above, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the claims.

[0338] <1> According to the first aspect of the present disclosure, a polymer (I) having a hydrophilic group, a fluoropolymer, a nonionic surfactant (a) having an HLB exceeding 8, and an aqueous medium A fluoropolymer aqueous dispersion containing substantially free of a fluorine-containing surfactant, wherein the content of the fluoropolymer is 40% by mass or more and 70% by mass or less with respect to the fluoropolymer aqueous dispersion, the content of the nonionic surfactant (a) is 4.0% by mass or more and 12% by mass or less with respect to the fluoropolymer, the height of the foam of the fluoropolymer aqueous dispersion produced by the foaming property test is 140 mm or less A fluoropolymer aqueous dispersion is provided. <2> According to the second aspect of the present disclosure, A fluoropolymer aqueous dispersion according to the first aspect further containing a nonionic surfactant (b) having an HLB of 8 or less is provided. <3> According to the third aspect of the present disclosure, a polymer (I) having a hydrophilic group, a fluoropolymer, a nonionic surfactant (a) having an HLB exceeding 8, a nonionic surfactant (b) having an HLB of 8 or less, and an aqueous medium A fluoropolymer aqueous dispersion containing substantially free of a fluorine-containing surfactant, The content of the fluoropolymer is 40% by mass or more and 70% by mass or less with respect to the aqueous dispersion of the fluoropolymer, There is provided an aqueous dispersion of a fluoropolymer in which the content of the nonionic surfactant (a) is 4.0% by mass or more and 12% by mass or less with respect to the fluoropolymer. <4> According to a fourth aspect of the present disclosure, There is provided an aqueous dispersion of a fluoropolymer according to the second or third aspect, in which the content of the nonionic surfactant (b) is 0.2% by mass or more and 10% by mass or less with respect to the aqueous dispersion of the fluoropolymer. <5> According to a fifth aspect of the present disclosure, There is provided an aqueous dispersion of a fluoropolymer according to any one of the second to fourth aspects, in which the nonionic surfactant (b) is at least one selected from the group consisting of an acetylene diol-based surfactant and an alkane diol-based surfactant. <6> According to a sixth aspect of the present disclosure, There is provided an aqueous dispersion of a fluoropolymer according to any one of the second to fifth aspects, in which the surface tension of a 0.1% aqueous solution of the nonionic surfactant (b) is 40 mN / m or less. <7> According to a seventh aspect of the present disclosure, There is provided an aqueous dispersion of a fluoropolymer according to any one of the first to sixth aspects, in which the nonionic surfactant (a) is at least one selected from the group consisting of a nonionic surfactant represented by the general formula (i) and a nonionic surfactant represented by the general formula (ii). R 6 -O-A 1 -H (i) (In the formula, R 6 is a linear or branched primary or secondary alkyl group having 8 to 18 carbon atoms, and A 1 is a polyoxyalkylene chain.) R 7 -C6H4-O-A 2 -H (ii) (In the formula, R 7 is a linear or branched alkyl group having 4 to 12 carbon atoms, and A 2is a polyoxyalkylene chain.) <8> According to the eighth aspect of the present disclosure, there is provided an aqueous dispersion of a fluoropolymer according to any one of the first to seventh aspects, wherein the hydrophilic group of the polymer (I) is an ionic group and the ion exchange capacity of the polymer (I) is 0.80 meq / g or more. <9> According to the ninth aspect of the present disclosure, there is provided an aqueous dispersion of a fluoropolymer according to any one of the first to eighth aspects, wherein the ion exchange rate of the polymer (I) is 53 or less. <10> According to the tenth aspect of the present disclosure, there is provided an aqueous dispersion of a fluoropolymer according to any one of the first to ninth aspects, wherein the polymer (I) has water solubility. <11> According to the eleventh aspect of the present disclosure, there is provided an aqueous dispersion of a fluoropolymer according to any one of the first to tenth aspects, wherein the number average molecular weight of the polymer (I) is 0.1×10 4 or more. <12> According to the twelfth aspect of the present disclosure, there is provided an aqueous dispersion of a fluoropolymer according to any one of the first to eleventh aspects, wherein the polymer (I) contains a polymerization unit (I) based on a monomer (I) represented by the general formula (I). CX 1 X 3 =CX 2 R(-CZ 1 Z 2 -A 0 ) m (I) (In the formula, X 1 and X 3 are each independently F, Cl, H or CF3; X 2 is H, F, an alkyl group or a fluorinated alkyl group; A 0 is an anionic group; R is a linking group; Z 1 and Z 2 are each independently H, F, an alkyl group or a fluorinated alkyl group; and m is an integer of 1 or more.) <13> According to the thirteenth aspect of the present disclosure, The fluoropolymer aqueous dispersion according to any one of the first to twelfth aspects, wherein the fluoropolymer is a perfluororesin, is provided. <14> According to a fourteenth aspect of the present disclosure, The fluoropolymer aqueous dispersion according to any one of the first to thirteenth aspects, wherein the fluoropolymer is polytetrafluoroethylene, is provided. <15> According to a fifteenth aspect of the present disclosure, The fluoropolymer aqueous dispersion according to any one of the first to fourteenth aspects, wherein the fluoropolymer is non-melt-processable polytetrafluoroethylene, is provided. <16> According to a sixteenth aspect of the present disclosure, The polymer (I) is a polymer containing a polymerization unit (1) based on a monomer represented by the general formula (1) or a polymer containing a polymerization unit (2) based on a monomer represented by the general formula (2), wherein the content of the polymerization unit (1) is 90 mol% or more based on all the polymerization units, the content of the polymerization unit (2) is 90 mol% or more based on all the polymerization units, the content of the polymer (I) is 10.0 to 1000 ppm by mass with respect to the fluoropolymer aqueous dispersion, the HLB of the nonionic surfactant (a) is 10 or more, and the content of the nonionic surfactant (a) is 4.0% by mass or more and 8.0% by mass or less with respect to the fluoropolymer, the content of the nonionic surfactant (b) is 0.5% by mass or more and 5.0% by mass or less with respect to the fluoropolymer aqueous dispersion The fluoropolymer aqueous dispersion according to any one of the first to fifteenth aspects is provided. CX2=CY(-CZ2-O-Rf-A) (1) (In the formula, X is the same or different and is -H or F; Y is -H, -F, an alkyl group or a fluorine-containing alkyl group; Z is the same or different and is -H, -F, an alkyl group or a fluoroalkyl group. Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having an ether bond or a keto group and having 2 to 100 carbon atoms. A is -COOM or -SO3M (M is H or NH4). However, at least one of X, Y and Z contains a fluorine atom.) CX2=CY(-O-Rf-A) (2) (In the formula, X is the same or different and is -H or F; Y is -H, -F, an alkyl group or a fluorine-containing alkyl group; Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having an ether bond or a keto group and having 2 to 100 carbon atoms. A is -COOM or -SO3M (M is H or NH4).)

Example

[0339] Next, embodiments of the present disclosure will be described with examples, but the present disclosure is not limited only to such examples.

[0340] Each numerical value in the examples was measured by the following method.

[0341] <PTFE solid content concentration (content) in the aqueous dispersion)> The PTFE solid content concentration (P mass %) in the aqueous dispersion was calculated from the formula: P = [Z / X] × 100 (mass %), where about 1 g (X g) of the sample was placed in an aluminum cup with a diameter of 5 cm and heated at 110 °C for 30 minutes to obtain a heating residue (Y g), and further, the obtained heating residue (Y g) was heated at 300 °C for 30 minutes to obtain a heating residue (Z g).

[0342] <Content of nonionic surfactant> The content of the nonionic surfactant (a) in the aqueous dispersion obtained in Production Example 1 with respect to PTFE (N mass%) was calculated from the formula: N = [(Y - Z) / Z] × 100 (mass%), where about 1 g (X g) of the sample was placed in an aluminum cup with a diameter of 5 cm and heated at 110°C for 30 minutes to obtain a heating residue (Y g), and further, the obtained heating residue (Y g) was heated at 300°C for 30 minutes to obtain a heating residue (Z g). The content of the nonionic surfactant (b) was calculated from the amount used of the nonionic surfactant (b) used in the preparation of the aqueous dispersion, etc.

[0343] <Surface tension> A 0.1% aqueous solution at 25°C was prepared, and the surface tension of the obtained aqueous solution was measured by the Wilhelmy method.

[0344] <Foam height> The content of PTFE in the aqueous dispersion was adjusted to 55 mass%, and a foaming property test was carried out by the Ross-Miles method in accordance with JIS K3362, and the foam height immediately after dropping the PTFE aqueous dispersion was measured.

[0345] The nonionic surfactants used in the examples are as follows.

[0346] Nonionic surfactant (a) with an HLB exceeding 8 Nonionic surfactant (a1): Neugen TDS-80 (HLB: 13) manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. Nonionic surfactant (a2): TERGITOL TMN6 (HLB: 13) manufactured by DOW Chemical Company

[0347] Nonionic surfactant (b) with an HLB of 8 or less Nonionic surfactant (b1): Dynol 607 (surface tension of 0.1% aqueous solution: 27 mN / m, HLB: 8) manufactured by Evonik Industries AG Nonionic surfactant (b2): Surfynol 104E (surface tension of 0.1% aqueous solution: 33 mN / m, HLB: 4) manufactured by Evonik Industries AG Nonionic surfactant (b3): Surfynol AD01 manufactured by Evonik (surface tension of 0.1% aqueous solution: 36 mN / m, HLB: 3)

[0348] Production Example 1 According to the method described in Example 4 of International Publication No. 2021 / 045227, an aqueous PTFE dispersion 1 was obtained. The obtained aqueous PTFE dispersion 1 had a solid content concentration of 60.3% by mass and a content of nonionic surfactant (a1) of 5.5% by mass based on PTFE. Other components such as the content of polymer (I) having a hydrophilic group (concentration of polymer D) and the content of fluorine-containing surfactant also had the same composition as the aqueous PTFE dispersion 4-1 described in Example 4 of International Publication No. 2021 / 045227.

[0349] Examples 1 to 4 Deionized water and the nonionic surfactants described in Table 1 were added to the aqueous PTFE dispersion 1, and a foaming property test was carried out. The results are shown in Table 1. The content of the nonionic surfactants described in Table 1 is the content of the nonionic surfactants added to the aqueous PTFE dispersion 1 and does not include the content of nonionic surfactant (a1).

[0350] Comparative Example 1 Deionized water was added to the aqueous PTFE dispersion 1, and a foaming property test was carried out. The results are shown in Table 1.

[0351] Comparative Example 2 Deionized water and nonionic surfactant (a2) were added to the aqueous PTFE dispersion 1, and a foaming property test was carried out. The results are shown in Table 1.

[0352]

Table 1

Claims

1. A polymer (I) having a hydrophilic group, Fluoropolymers, (a) a nonionic surfactant having an HLB greater than 8; and aqueous medium An aqueous fluoropolymer dispersion comprising: Substantially free of fluorine-containing surfactants, The content of the fluoropolymer is 40% by mass or more and 70% by mass or less based on the fluoropolymer aqueous dispersion, The content of the nonionic surfactant (a) is 4.0% by mass or more and 12% by mass or less based on the fluoropolymer, The foam height of the aqueous fluoropolymer dispersion produced by a foaming test is 140 mm or less. Aqueous fluoropolymer dispersions.

2. The aqueous fluoropolymer dispersion according to claim 1, further comprising a nonionic surfactant (b) having an HLB of 8 or less.

3. A polymer (I) having a hydrophilic group, Fluoropolymers, (a) a nonionic surfactant having an HLB greater than 8; (b) a nonionic surfactant having an HLB of 8 or less; and aqueous medium An aqueous fluoropolymer dispersion comprising: Substantially free of fluorine-containing surfactants, The content of the fluoropolymer is 40% by mass or more and 70% by mass or less based on the fluoropolymer aqueous dispersion, The aqueous fluoropolymer dispersion has a nonionic surfactant (a) content of 4.0% by mass or more and 12% by mass or less, based on the fluoropolymer.

4. 4. The aqueous fluoropolymer dispersion according to claim 2, wherein the content of the nonionic surfactant (b) is 0.2% by mass or more and 10% by mass or less based on the aqueous fluoropolymer dispersion.

5. 4. The aqueous fluoropolymer dispersion according to claim 2, wherein the nonionic surfactant (b) is at least one selected from the group consisting of acetylene diol surfactants and alkane diol surfactants.

6. 4. The aqueous fluoropolymer dispersion according to claim 2, wherein the surface tension of a 0.1% aqueous solution of the nonionic surfactant (b) is 40 mN / m or less.

7. The fluoropolymer aqueous dispersion according to claim 1 or 3, wherein the nonionic surfactant (a) is at least one selected from the group consisting of nonionic surfactants represented by general formula (i) and nonionic surfactants represented by general formula (ii). R ６ -O-A １ -H (i) (In the formula, R ６ is a linear or branched primary or secondary alkyl group having 8 to 18 carbon atoms; A １ is a polyoxyalkylene chain. ( ７  ６ H ４ - ２  ( ) ) (In the formula, R ７ is a linear or branched alkyl group having 4 to 12 carbon atoms; A ２ is a polyoxyalkylene chain.

8. 4. The aqueous fluoropolymer dispersion according to claim 1, wherein the hydrophilic group of the polymer (I) is an ionic group, and the ion exchange capacity of the polymer (I) is 0.80 meq / g or more.

9. 4. The aqueous fluoropolymer dispersion according to claim 1, wherein the ion exchange rate of the polymer (I) is 53 or less.

10. 4. The aqueous fluoropolymer dispersion according to claim 1, wherein the polymer (I) is water-soluble.

11. The number average molecular weight of the polymer (I) is 0.1×10 ４ The aqueous fluoropolymer dispersion according to claim 1 or 3.

12. 4. The aqueous fluoropolymer dispersion according to claim 1, wherein the polymer (I) contains polymerized units (I) based on a monomer (I) represented by general formula (I). CX １ X ３ =CX ２ R(-CZ １ Z ２ -A ０ ) ｍ (I) (In the formula, X １ and X ３ are each independently F, Cl, H or CF ３ and X ２ is H, F, an alkyl group or a fluorine-containing alkyl group; A ０ is an anionic group; R is a linking group; Z １ and Z ２ are each independently H, F, an alkyl group or a fluorine-containing alkyl group; and m is an integer of 1 or more.

13. 4. The aqueous fluoropolymer dispersion according to claim 1, wherein the fluoropolymer is a perfluororesin.

14. 4. The aqueous fluoropolymer dispersion according to claim 1, wherein the fluoropolymer is polytetrafluoroethylene.

15. 4. The aqueous fluoropolymer dispersion according to claim 1, wherein the fluoropolymer is a non-melt processable polytetrafluoroethylene.

16. The polymer (I) is a polymer containing polymerization units (1) based on a monomer represented by general formula (1), or a polymer containing polymerization units (2) based on a monomer represented by general formula (2), in which the content of the polymerization units (1) is 90 mol% or more based on the total polymerization units, the content of the polymerization units (2) is 90 mol% or more based on the total polymerization units, and the content of the polymer (I) is 10.0 to 1000 ppm by mass based on the aqueous fluoropolymer dispersion, The HLB of the nonionic surfactant (a) is 10 or more, and the content of the nonionic surfactant (a) is 4.0 mass% or more and 8.0 mass% or less based on the fluoropolymer; The content of the nonionic surfactant (b) is 0.5% by mass or more and 5.0% by mass or less with respect to the fluoropolymer aqueous dispersion.

4. The aqueous fluoropolymer dispersion according to claim 1 or 3. CX ２ =CY(-CZ ２ -O-Rf-A) (1) (In the formula, X may be the same or different and is -H or F; Y is -H, -F, an alkyl group or a fluorine-containing alkyl group; Z may be the same or different and is -H, -F, an alkyl group or a fluoroalkyl group; Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having 2 to 100 carbon atoms and an ether bond; A is -COOM or -SO ３ M (M is H or NH ４ ) where at least one of X, Y and Z contains a fluorine atom. CX ２ =CY(-O-Rf-A) (2) (In the formula, X may be the same or different and is -H or F; Y is -H, -F, an alkyl group or a fluorine-containing alkyl group; Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having 2 to 100 carbon atoms and an ether bond or a keto group; A is -COOM or -SO ３ M (M is H or NH ４ )

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