Method for producing aqueous polytetrafluoroethylene dispersion and aqueous dispersion

Abstract

Provided is a method for producing an aqueous polytetrafluoroethylene dispersion, the method comprising: preparing an aqueous dispersion (A) containing polytetrafluoroethylene by performing emulsion polymerization of at least tetrafluoroethylene in the presence of water with no substantial presence of a surfactant; and preparing an aqueous dispersion (B) by bringing the aqueous dispersion (A) into contact with an adsorbent, wherein the aqueous dispersion (A) contains at least one compound selected from the group consisting of compound (6-16) represented by a general formula disclosed in the specification, compound (6-18) represented by a general formula disclosed in the specification, and compound (6-20) represented by a general formula disclosed in the specification.

Description

Method for producing an aqueous polytetrafluoroethylene dispersion and aqueous dispersion

[0001] This disclosure relates to a method for producing an aqueous polytetrafluoroethylene dispersion and to the aqueous dispersion itself.

[0002] Patent Document 1 describes a method for producing a fluorine-containing polymer, comprising polymerizing a monomer containing tetrafluoroethylene in an aqueous dispersion containing a first fluorine-containing polymer having a glass transition temperature of 10°C or less and an aqueous medium to produce a second fluorine-containing polymer different from the first fluorine-containing polymer, wherein, before starting the polymerization of the monomer, the content of the first fluorine-containing polymer is 0.01 to 4.0% by mass relative to the total mass of the aqueous dispersion, and before starting the polymerization of the monomer, the concentration of the fluorine-based emulsifier is 100 ppm by mass or less relative to the total mass of the first fluorine-containing polymer in the aqueous dispersion.

[0003] International Publication No. 2024 / 214644

[0004] This disclosure aims to provide a method for producing an aqueous polytetrafluoroethylene dispersion in which the content of specific compounds is reduced.

[0005] The present disclosure provides a method for producing an aqueous polytetrafluoroethylene dispersion, comprising preparing an aqueous dispersion (A) containing polytetrafluoroethylene by carrying out emulsion polymerization of at least tetrafluoroethylene in the presence of water and substantially in the absence of a surfactant, and preparing an aqueous dispersion (B) by contacting the aqueous dispersion (A) with an adsorbent, wherein the aqueous dispersion (A) contains at least one compound selected from the group consisting of a compound represented by general formula (6-16) (6-16), a compound represented by general formula (6-18) (6-18), and a compound represented by general formula (6-20) (6-20). General formula (6-16): M ＋ [ － OOC-(CFX) ｎ－２ - COO － ] M ＋ (In the formula, n is 16, M ＋ X is a cation, and X is F, CF, and F are independent in each occurrence.３ , OCF ３ or OC ３ F ７ (each represents a value.) General Formula (6-18): M ＋ － OOC-(CFX) ｎ－２ -COO － M ＋ (wherein n is 18, M ＋ is a cation, and X is independently at each occurrence F, CF ３ , OCF ３ or OC ３ F ７ each represents a value.) General Formula (6-20): M ＋ － OOC-(CFX) ｎ－２ -COO － M ＋ (wherein n is 20, M ＋ is a cation, and X is independently at each occurrence F, CF ３ , OCF ３ or OC ３ F ７ each represents a value.)

[0006] According to the present disclosure, it is possible to provide a method for producing an aqueous polytetrafluoroethylene dispersion in which the content of a specific compound is reduced.

[0007] Before specifically describing the present disclosure, several terms used in the present disclosure are defined or explained.

[0008] In the present disclosure, polytetrafluoroethylene [PTFE] is preferably a fluoropolymer in which the content of tetrafluoroethylene units is 99 mol% or more relative to all polymerized units. The glass transition temperature of PTFE is usually higher than 10°C. The glass transition temperature can be measured by a differential scanning calorimetry (DSC) method.

[0009] 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.

[0010] ​​In this disclosure, the range represented by an endpoint includes all numerical values ​​that fall within that range (for example, 1 to 10 includes 1.4, 1.9, 2.33, 5.75, 9.98, etc.).

[0011] In this disclosure, the phrase "at least one" includes all numbers one or more (for example, at least two, at least four, at least six, at least eight, at least ten, at least 25, at least 50, at least 100, etc.).

[0012] The following describes specific embodiments of this disclosure in detail, but this disclosure is not limited to the embodiments described below.

[0013] 1. Manufacturing Method Patent Document 1 describes that, by the method described above, fluorine-containing polymers can be efficiently produced without the need for emulsifiers, while using an environmentally friendly aqueous medium. For reasons unknown, our inventors' studies have revealed that when an aqueous dispersion is prepared by polymerization in the substantially absence of surfactants, as proposed in Patent Document 1, compounds represented by general formula (6-16) (6-16), general formula (6-18) (6-18), and general formula (6-20) (6-20) are produced. General formula (6-16): M ＋ [ － OOC-(CFX) ｎ－２ - COO － ] M ＋ (In the formula, n is 16, M ＋ X is a cation, and X is F, CF, and F are independent in each occurrence. ３ OCF ３ or OC ３ F ７ (Represents.) General formula (6-18): M ＋ [ － OOC-(CFX) ｎ－２ - COO － ] M ＋ (In the formula, n is 18, M ＋ X is a cation, and X is F, CF, and F are independent in each occurrence. ３ OCF ３ or OC ３ F ７(Represents.) General formula (6-20): M ＋ [ － OOC-(CFX) ｎ－２ - COO － ] M ＋ (In the formula, n is 20, M ＋ X is a cation, and X is F, CF, and F are independent in each occurrence. ３ OCF ３ or OC ３ F ７ (This represents...)

[0014] On the other hand, when an aqueous dispersion was prepared by polymerization in the presence of a fluorine-containing anionic surfactant, the formation of compound (6-16) represented by general formula (6-16), compound (6-18) represented by general formula (6-18), and compound (6-20) represented by general formula (6-20) could not be confirmed.

[0015] In the manufacturing method of this disclosure, an aqueous dispersion (A) containing polytetrafluoroethylene (PTFE) is prepared by carrying out emulsion polymerization of at least tetrafluoroethylene (TFE) in the presence of water and substantially in the absence of a surfactant. Next, aqueous dispersion (B) is prepared by contacting aqueous dispersion (A) with an adsorbent. This makes it possible to remove compounds (6-16), (6-18), and (6-20) contained in aqueous dispersion (A) and prepare aqueous dispersion (B) in which the content of compounds (6-16), (6-18), and (6-20) is reduced.

[0016] Therefore, by using the manufacturing method of this disclosure, an aqueous dispersion containing PTFE can be prepared without using a surfactant, and moreover, an aqueous dispersion with reduced content of compounds (6-16), (6-18), and (6-20) can be prepared. If surfactants, compounds (6-16), (6-18), and (6-20) are present in the aqueous dispersion, the excellent properties of PTFE may be impaired when the aqueous dispersion is used for the desired application, but this problem is brilliantly solved by using the manufacturing method of this disclosure.

[0017] In the manufacturing method of this disclosure, an aqueous dispersion (A) containing PTFE is prepared by carrying out emulsion polymerization of at least TFE in the presence of water and substantially in the absence of a surfactant.

[0018] (Surfactants) In the manufacturing method of the present disclosure, the polymerization of at least TFE is carried out substantially in the absence of surfactants. In the present disclosure, "substantially in the absence of surfactants" means that the amount of surfactant in the aqueous medium is 10 ppm by mass or less. The amount of surfactant in the aqueous medium is preferably 1 ppm by mass or less, more preferably 100 ppb by mass or less, even more preferably 10 ppb by mass or less, and even more preferably 1 ppb by mass or less. "Polymerization carried out in the absence of surfactants" includes polymerization carried out without intentionally adding surfactants.

[0019] Examples of surfactants include anionic surfactants, nonionic surfactants, and cationic surfactants. Other types of surfactants include fluorine-containing surfactants, hydrocarbon-containing surfactants (fluorine-free surfactants), and reactive surfactants.

[0020] Furthermore, known methods may be employed as a method for polymerizing at least TFE in the substantially absence of surfactants. Such methods include International Publication Nos. 2024 / 214644, 2024 / 128263, 2009 / 036131, 2010 / 021962, 2010 / 147815, 2012 / 006487, 2012 / 018603, 2012 / 067936, 2013 / 090251, and 2014 / 071129. International Publication Nos. 2014 / 099311, 2014 / 100593, 2015 / 041948, 2016 / 100420, 2016 / 100421, 2017 / 066266, 2022 / 265048, 1996 / 024622, 1997 / 017381, 2019 / 178430, and Japanese Patent Publication No. 48-01895 Japanese Patent Publication No. 7, Japanese Patent Publication No. S49-025041, Japanese Patent Publication No. S49-087739, Japanese Patent Publication No. S49-087740, Japanese Patent Publication No. S49-087741, Japanese Patent Publication No. S52-062391, Japanese Patent Publication No. S55-116713, International Publication No. 2007 / 123123, International Publication No. 2007 / 129735, Japanese Patent Publication No. S49-082791, Japanese Patent Publication No. S53-149291, International Publication No. 2010 / 033269, International Publication No. Examples of methods include those described in International Publication No. 2009 / 013214, International Publication No. 2014 / 206955, International Publication No. 2017 / 046379, International Publication No. 2019 / 101806, International Publication No. 2022 / 106610, International Publication No. 2022 / 128190, International Publication No. 2022 / 135954, International Publication No. 2024 / 033089, International Publication No. 2024 / 165313, and the specification of Russian Patent Invention No. 2158274.

[0021] (Aqueous medium) In one embodiment, emulsion polymerization is carried out in the presence of water. In one embodiment, emulsion polymerization is carried out in the presence of an aqueous medium containing water.

[0022] The aqueous medium is a reaction medium for polymerization and means a liquid containing water. The aqueous medium is not particularly limited as long as it contains water, and may contain water and, for example, a fluorine-free organic solvent such as ether or ketone, and / or a fluorine-containing organic solvent with a boiling point of 40°C or lower.

[0023] As an aqueous medium, an aqueous medium containing only water, or an aqueous medium containing only water and a fluorine-free organic solvent, is preferred because it allows polymerization to proceed smoothly, and an aqueous medium containing only water is more preferred.

[0024] The water content in the aqueous medium is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 99.0% by mass or more, even more preferably 99.5% by mass or more, particularly preferably 99.9% by mass or more, and may be 100% by mass, in order to facilitate polymerization.

[0025] (Polymerization initiator) In one embodiment, polymerization of at least TFE is carried out in the presence of a polymerization initiator.

[0026] As polymerization initiators, persulfates (e.g., ammonium persulfate) or organic peroxides such as disuccinic acid peroxide and diglutaric acid peroxide can be used alone or in mixtures thereof. They may also be used in combination with reducing agents such as sodium sulfite to form a redox system. Furthermore, during polymerization, radical scavengers such as hydroquinone and catechol, or peroxide decomposition agents such as ammonium sulfite, can be added to adjust the radical concentration in the system.

[0027] 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 oxidizing agents include persulfates, organic peroxides, potassium permanganate, manganese triacetate, and ammonium cerium nitrate. Examples of reducing agents include sulfites, bisulfites, bromates, diimines, and oxalic acid. Examples of persulfates include ammonium persulfate and potassium persulfate. Examples of sulfites include sodium sulfite and ammonium sulfite. To increase the decomposition rate of the initiator, it is also preferable to add copper salts and iron salts to the redox initiator combination. Examples of copper salts include copper(II) sulfate, and examples of iron salts include iron(II) sulfate.

[0028] Examples of the redox initiators mentioned above include potassium permanganate / oxalic acid, potassium permanganate / ammonium oxalate, ammonium persulfate / bisulfite / ferrous sulfate, manganese triacetate / oxalic acid, cerium ammonium nitrate / oxalic acid, bromate / bisulfite, etc., with potassium permanganate / oxalic acid being preferred. When using a redox initiator, either an oxidizing agent or a reducing agent may be charged into the polymerization tank beforehand, 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 then continuously add potassium permanganate thereto.

[0029] The amount of polymerization initiator used is preferably 0.00001 to 10% by mass, more preferably 0.0001% by mass or more, even more preferably 0.001% by mass or more, still more preferably 0.01% by mass or more, preferably 5% by mass or less, and more preferably 2% by mass or less, relative to the aqueous medium. In the manufacturing method of this disclosure, it is preferable to use a relatively large amount of polymerization initiator. By increasing the amount of polymerization initiator used, emulsion polymerization can proceed more smoothly even in the absence of a surfactant.

[0030] (Chain transfer agent) In one embodiment, polymerization of at least TFE can be carried out in the presence of a chain transfer agent.

[0031] Examples of chain transfer agents include esters such as dimethyl malonate, diethyl malonate, methyl acetate, ethyl acetate, butyl acetate, and dimethyl succinate, as well as various halogenated hydrocarbons such as isopentane, methane, ethane, propane, butane, pentane, hexane, heptane, methanol, isopropanol, acetone, various mercaptans, and carbon tetrachloride, and cyclohexane. Among these, at least one selected from the group consisting of hydrocarbon compounds and alcohols is preferred as a chain transfer agent, with isopentane, methane, ethane, propane, butane, pentane, hexane, heptane, methanol, and isopropanol being more preferred.

[0032] The amount of the above-mentioned chain transfer agent used is usually 1 to 50,000 ppm by mass, preferably 1 to 20,000 ppm by mass, relative to the total amount of fluoromonomer supplied.

[0033] (Additives) Additives may be used in the polymerization described above. Examples of such additives include buffers, pH adjusters, stabilizing agents, and dispersion stabilizers.

[0034] Preferred stabilizing agents include paraffin wax, fluorinated oils, fluorinated solvents, and silicone oils. Stabilizing agents may be used individually or in combination of two or more. Paraffin wax is more preferred as a stabilizing agent. Paraffin wax may be liquid, semi-solid, or solid at room temperature, but saturated hydrocarbons with 12 or more carbon atoms are preferred. The melting point of paraffin wax is usually preferably 40 to 65°C, and more preferably 50 to 65°C.

[0035] The amount of stabilizing agent used is preferably 0.1 to 12% by mass, and more preferably 0.1 to 8% by mass, based on the mass of the aqueous medium used. It is desirable that the stabilizing agent is sufficiently hydrophobic and completely separates from the aqueous dispersion after polymerization so as not to become a contaminating component.

[0036] (Monomers) In the manufacturing method of the present disclosure, at least TFE is emulsion polymerized. In emulsion polymerization, only TFE may be polymerized, or TFE and monomers other than TFE (modified monomers) may be polymerized.

[0037] The above-mentioned modified monomers are not particularly limited as long as they can copolymerize with TFE, and include fluoromonomers and non-fluoromonomers. Furthermore, one or more modified monomers may be used.

[0038] The non-fluoro monomer is not particularly limited, and the general formula is CH ２ =CR Ｑ１ -LR Ｑ２ (In the formula, R Ｑ１ represents a hydrogen atom or alkyl group. L represents a single bond, -CO-O-*, -O-CO-*, or -O-. * is R Ｑ２ Represents the connection position with R. Ｑ２ Examples of monomers represented by ) are: (where represents a hydrogen atom, an alkyl group, or a nitrile group.)

[0039] Examples of nonfluoro monomers include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, vinyl methacrylate, vinyl acetate, acrylic acid, methacrylic acid, acrylonitrile, methacrylonitrile, ethyl vinyl ether, and cyclohexyl vinyl ether. Among these, butyl methacrylate, vinyl acetate, and acrylic acid are preferred as nonfluoro monomers.

[0040] Examples of fluoromonomers include perfluoroolefins such as hexafluoropropylene [HFP]; hydrogen-containing fluoroolefins such as trifluoroethylene and vinylidene fluoride [VDF]; perhaloolefins such as chlorotrifluoroethylene; perfluorovinyl ethers; (perfluoroalkyl)ethylenes; and perfluoroallyl ethers.

[0041] From the viewpoint of reactivity with TFE, the above modified monomer preferably includes at least one selected from the group consisting of hexafluoropropylene, perfluoro(alkyl vinyl ether), and (perfluoroalkyl)ethylene. In one embodiment, the above modified monomer includes 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. In one embodiment, the above modified monomer includes at least one selected from the group consisting of hexafluoropropylene, perfluoro(methyl vinyl ether), and perfluoro(propyl vinyl ether).

[0042] The above polymerization can yield an aqueous dispersion (A) containing PTFE. The PTFE is typically present in a concentration of 8 to 50% by mass of the aqueous dispersion (A) obtained by the above polymerization. In the aqueous dispersion (A), the preferred lower limit of the PTFE content is 10% by mass, the more preferred lower limit is 15% by mass, the preferred upper limit is 40% by mass, and the more preferred upper limit is 35% by mass.

[0043] The PTFE content in an aqueous dispersion can be calculated, for example, by taking approximately 1 g (X g) of the sample in a 5 cm diameter aluminum cup, heating it at 110°C for 30 minutes, and then heating it again at 300°C for 30 minutes, based on the residual amount (Z g), using the formula: P = Z / X × 100 (mass%).

[0044] (Polytetrafluoroethylene (PTFE)) In this disclosure, PTFE is a concept that includes not only TFE homopolymers but also copolymers of TFE and monomers other than TFE (modified monomers) (hereinafter referred to as "modified PTFE"). Preferably, the PTFE is a TFE homopolymer or a copolymer of TFE and at least one modified monomer selected from the group consisting of hexafluoropropylene, perfluoro(methyl vinyl ether), and perfluoro(propyl vinyl ether).

[0045] PTFE may have a core-shell structure. Examples of PTFE having a core-shell structure include modified PTFE, which contains a core of high molecular weight PTFE and a shell of lower molecular weight PTFE or modified PTFE within the particle. Examples of such modified PTFE include the PTFE described in Japanese Patent Publication No. 2005-527652.

[0046] The above core-shell structure can take the following forms: Core: TFE homopolymer Shell: TFE homopolymer Core: Modified PTFE Shell: TFE homopolymer Core: Modified PTFE Shell: Modified PTFE Core: TFE homopolymer Shell: Modified PTFE Core: Low molecular weight PTFE Shell: High molecular weight PTFE Core: High molecular weight PTFE Shell: Low molecular weight PTFE

[0047] In the PTFE having the above-described core-shell structure, the lower limit of the core ratio is preferably 0.5 mass%, more preferably 1.0 mass%, even more preferably 2.0 mass%, even more preferably 3.0 mass%, particularly preferably 5.0 mass%, and most preferably 10.0 mass%. The upper limit of the core ratio is preferably 99.5 mass%, more preferably 99.0 mass%, even more preferably 98.0 mass%, even more preferably 97.0 mass%, particularly preferably 95.0 mass%, and most preferably 90.0 mass%.

[0048] In the PTFE having the above-described core-shell structure, the lower limit of the shell ratio is preferably 0.5 mass%, more preferably 1.0 mass%, even more preferably 2.0 mass%, even more preferably 3.0 mass%, particularly preferably 5.0 mass%, and most preferably 10.0 mass%. The upper limit of the shell ratio is preferably 99.5 mass%, more preferably 99.0 mass%, even more preferably 98.0 mass%, even more preferably 97.0 mass%, particularly preferably 95.0 mass%, and most preferably 90.0 mass%.

[0049] The manufacturing method disclosed herein can also be used to produce low molecular weight PTFE.

[0050] Low molecular weight PTFE with a molecular weight of 600,000 or less is suitable as an additive for purposes such as improving slipperiness and the texture of the coating surface, because it has excellent chemical stability, extremely low surface energy, and is less prone to fibrillation.

[0051] The manufacturing method of this disclosure can also produce high molecular weight PTFE as PTFE. In this disclosure, high molecular weight PTFE means PTFE that is non-melt processable. In one embodiment, high molecular weight PTFE has non-melt processability and fibrillation properties. On the other hand, low molecular weight PTFE means PTFE that is melt processable. In one embodiment, low molecular weight PTFE has melt processability and does not have fibrillation properties.

[0052] The above-mentioned non-melt processability refers to 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.

[0053] The presence or absence of fibrillation properties can be determined by "paste extrusion," a typical method for molding PTFE. Paste extrusion is usually possible because high molecular weight PTFE has fibrillation properties. If an unfired molded product obtained by paste extrusion has no substantial strength or elongation, for example, if it has 0% elongation and breaks when pulled, it can be considered that it does not have fibrillation properties.

[0054] 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 using a sample molded in accordance with ASTM D4895-89 and measured by the water displacement method in accordance with ASTM D 792. In this disclosure, "high molecular weight" means that the above standard specific gravity is within the above range.

[0055] The above low molecular weight PTFE has a melt viscosity of 1 × 10⁻⁶ at 380°C. ２ ~7 x 10 ５The molecular weight is Pa·s. In this disclosure, "low molecular weight" means that the melt viscosity is within the above range. The melt viscosity is measured in accordance with ASTM D 1238, using a flow tester (manufactured by Shimadzu Corporation) and a 2φ-8L die, by preheating a 2g sample at 380°C for 5 minutes and maintaining it at the above temperature under a load of 0.7 MPa.

[0056] The high molecular weight PTFE described above has an extremely high melt viscosity compared to the low molecular weight PTFE described above, making it difficult to accurately measure its melt viscosity. On the other hand, while the melt viscosity of the low molecular weight PTFE can be measured, it is difficult to obtain molded articles from the low molecular weight PTFE that can be used to measure standard specific gravity, making it difficult to accurately measure its standard specific gravity. Therefore, in this disclosure, standard specific gravity is used as an indicator of the molecular weight of the high molecular weight PTFE, and melt viscosity is used as an indicator of the molecular weight of the low molecular weight PTFE. It should be noted that no measurement method is known that can directly determine the molecular weight of either the high molecular weight PTFE or the low molecular weight PTFE.

[0057] The high molecular weight PTFE described above preferably has a peak temperature of 333 to 347°C, and more preferably 335 to 345°C. The low molecular weight PTFE described above preferably has a peak temperature of 322 to 333°C, and more preferably 324 to 332°C. The peak temperature can be determined by using a TG / DTA (differential thermogravimetric analysis device) to heat PTFE that has not been previously heated to a temperature of 300°C or higher at a rate of 10°C / min, and the temperature corresponding to the maximum value of the differential thermal (DTA) curve obtained.

[0058] The peak temperature of PTFE may be between 322 and 347°C. When PTFE is high molecular weight PTFE, the upper limit of the peak temperature of PTFE may be 347°C or less, 346°C or less, 345°C or less, 344°C or less, 343°C or less, 342°C or less, 341°C or less, or 340°C or less. When PTFE is high molecular weight PTFE, the lower limit of the peak temperature of PTFE may be 333°C or higher or 335°C or higher. When PTFE is low molecular weight PTFE, the upper limit of the peak temperature of PTFE may be 333°C or lower or 332°C or lower. When PTFE is low molecular weight PTFE, the lower limit of the peak temperature of PTFE may be 322°C or higher or 324°C or higher.

[0059] The average primary particle diameter of the low molecular weight PTFE primary particles is preferably 10 to 350 nm, more preferably 100 nm or more, even more preferably 150 nm or more, even more preferably 400 nm or less, and even more preferably 350 nm or less.

[0060] The above high molecular weight PTFE is preferably such that, when PTFE that has not been heated to a temperature of 300°C or higher is heated at a rate of 10°C / min using a TG / DTA (differential thermogravimetric analysis device), at least one endothermic peak appears in the range of 333 to 347°C in the differential thermal analysis (DTA) curve, and the heat of fusion at 290 to 350°C calculated from the differential thermal analysis (DTA) curve is 52 mJ / mg or more. The heat of fusion of the PTFE is more preferably 55 mJ / mg or more, and even more preferably 58 mJ / mg or more.

[0061] (Fluorine-containing compounds having hydrophilic groups) The aqueous dispersion (A) is obtained by polymerization substantially in the absence of surfactants. The aqueous dispersion (A) thus obtained may contain fluorine-containing compounds having hydrophilic groups, such as compound (6-16), compound (6-18), and compound (6-20).

[0062] In one embodiment, the aqueous dispersion (A) contains at least one compound selected from the group consisting of the compound (6-16) represented by general formula (6-16), the compound (6-18) represented by general formula (6-18), and the compound (6-20) represented by general formula (6-20). General formula (6-16): M ＋ － OOC-(CFX) ｎ－２ -COO － M ＋ (wherein n is 16, M ＋ is a cation, and X, independently at each occurrence, represents F, CF ３ , OCF ３ or OC ３ F ７ .). General formula (6-18): M ＋ － OOC-(CFX) ｎ－２ -COO － M ＋ (wherein n is 18, M ＋ is a cation, and X, independently at each occurrence, represents F, CF ３ , OCF ３ or OC ３ F ７ .). General formula (6-20): M ＋ － OOC-(CFX) ｎ－２ -COO － M ＋ (wherein n is 20, M ＋ is a cation, and X, independently at each occurrence, represents F, CF ３ , OCF ３ or OC ３ F ７ .)

[0063] In one embodiment, the aqueous dispersion (A) contains at least one compound selected from the group consisting of the compound (6-16) represented by general formula (6-16) and the compound (6-18) represented by general formula (6-18).

[0064] ​​​The total content of compounds (6-16), (6-18), and (6-20) in aqueous dispersion (A) may be more than 1000 ppb by mass, 2000 ppb or more, 3000 ppb or more, 4000 ppb or more, 5000 ppb or more, 6000 ppb or more, 7000 ppb or more, 8000 ppb or more, 9000 ppb or more, or 10000 ppb or more, relative to the mass of PTFE, and may be 5000000 ppb or less or 1000000 ppb or less.

[0065] The total content of compound (6-16) and compound (6-18) in aqueous dispersion (A) may be more than 1000 ppb by mass, 2000 ppb or more, 3000 ppb or more, 4000 ppb or more, 5000 ppb or more, 6000 ppb or more, 7000 ppb or more, 8000 ppb or more, 9000 ppb or more, or 10000 ppb or more, relative to the mass of PTFE, and may be 5000000 ppb or less or 1000000 ppb or less.

[0066] In one embodiment, the aqueous dispersion (A) contains at least one compound selected from the group consisting of the compound represented by general formula (6-16-X) (6-16-X), the compound represented by general formula (6-18-X) (6-18-X), and the compound represented by general formula (6-20-X) (6-20-X). General formula (6-16-X): M ＋ [ － OOC-(CF ２ ) ｃ - (CF (OCF ３ )) ｄ - COO － ] M ＋ (In the formula, c and d are independent integers greater than or equal to 1, the sum of c and d is 14, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of ) is arbitrary in the formula. ) General formula (6-18-X): M ＋ [ － OOC-(CF ２ ) ｃ - (CF (OCF ３ ))ｄ - COO － ] M ＋ (In the formula, c and d are independent integers of 1 or greater, the sum of c and d is 16, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of )- is arbitrary in the formula. ) General formula (6-20-X): M ＋ [ － OOC-(CF ２ ) ｃ - (CF (OCF ３ )) ｄ - COO － ] M ＋ (In the formula, c and d are independent integers greater than or equal to 1, the sum of c and d is 18, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of the elements in the formula is arbitrary.

[0067] In one embodiment, the aqueous dispersion (A) contains at least one compound selected from the group consisting of compounds represented by the general formula (6-16-X) (6-16-X) and compounds represented by the general formula (6-18-X) (6-18-X).

[0068] The total content of compound (6-16-X), compound (6-18-X), and compound (6-20-X) in aqueous dispersion (A) may be more than 1000 ppb by mass, 2000 ppb or more, 3000 ppb or more, 4000 ppb or more, 5000 ppb or more, 6000 ppb or more, 7000 ppb or more, 8000 ppb or more, 9000 ppb or more, or 10000 ppb or more, relative to the mass of PTFE, and may be 5000000 ppb or less or 1000000 ppb or less.

[0069] The total content of compound (6-16-X) and compound (6-18-X) in aqueous dispersion (A) may be more than 1000 ppb by mass, 2000 ppb or more, 3000 ppb or more, 4000 ppb or more, 5000 ppb or more, 6000 ppb or more, 7000 ppb or more, 8000 ppb or more, 9000 ppb or more, or 10000 ppb or more, relative to the mass of PTFE, and may be 5000000 ppb or less or 1000000 ppb or less.

[0070] In one embodiment, the aqueous dispersion (A) contains at least one compound selected from the group consisting of the compound represented by general formula (6-16-1) (6-16-1), the compound represented by general formula (6-16-2) (6-16-2), the compound represented by general formula (6-16-3) (6-16-3), the compound represented by general formula (6-18-1) (6-18-1), the compound represented by general formula (6-18-2) (6-18-2), and the compound represented by general formula (6-20-1) (6-20-1). General formula (6-16-1): M ＋ [ － OOC-(CF ２ ) １４ - COO － ] M ＋ (In the formula, M ＋ represents a cation. ) General formula (6-16-2): M ＋ [ － OOC-(CF ２ ) １２ - (CF (OCF ３ )) ２ - COO － ] M ＋ (In the formula, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of ) is arbitrary in the formula. ) General formula (6-16-3): M ＋ [ － OOC-(CF ２ ) １１ - (CF (OCF ３ )) ３ - COO － ] M ＋ (In the formula, M＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of ) is arbitrary in the formula. ) General formula (6-18-1): M ＋ [ － OOC-(CF ２ ) １６ - COO － ] M ＋ (In the formula, M ＋ (where represents a cation) General formula (6-18-2): M ＋ [ － OOC-(CF ２ ) １５ - (CF (OCF ３ )) １ - COO － ] M ＋ (In the formula, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of ) is arbitrary in the formula. ) General formula (6-20-1): M ＋ [ － OOC-(CF ２ ) １４ - (CF (OCF ３ )) ４ - COO － ] M ＋ (In the formula, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of the elements in the formula is arbitrary.

[0071] In one embodiment, the aqueous dispersion (A) contains at least one compound selected from the group consisting of the compound represented by general formula (6-16-1) (6-16-1), the compound represented by general formula (6-16-2) (6-16-2), the compound represented by general formula (6-16-3) (6-16-3), the compound represented by general formula (6-18-1) (6-18-1), and the compound represented by general formula (6-18-2) (6-18-2).

[0072] The total content of compounds (6-16-1), (6-16-2), (6-16-3), (6-18-1), (6-18-2), and (6-20-1) in aqueous dispersion (A) may be more than 1000 ppb by mass, 2000 ppb or more, 3000 ppb or more, 4000 ppb or more, 5000 ppb or more, 6000 ppb or more, 7000 ppb or more, 8000 ppb or more, 9000 ppb or more, or 10000 ppb or more, relative to the mass of PTFE, and may be 5000000 ppb or less or 1000000 ppb or less.

[0073] The total content of compounds (6-16-1), (6-16-2), (6-16-3), (6-18-1), and (6-18-2) in aqueous dispersion (A) may be more than 1000 ppb by mass, 2000 ppb or more, 3000 ppb or more, 4000 ppb or more, 5000 ppb or more, 6000 ppb or more, 7000 ppb or more, 8000 ppb or more, 9000 ppb or more, or 10000 ppb or more, relative to the mass of PTFE, and may be 5000000 ppb or less or 1000000 ppb or less.

[0074] In one embodiment, the aqueous dispersion (A) contains compound (6) represented by general formula (6). General formula (6): M ＋ [ － OOC-(CFX) ｎ－２ - COO － ] M ＋ (In the formula, n is an integer from 8 to 21, M ＋ X is a cation, and X is F, CF, and F are independent in each occurrence. ３ OCF ３ or OC ３ F ７ (This represents...)

[0075] The content of compound (6) in the aqueous dispersion (A) may be more than 1,000 ppb by mass, 2,000 ppb or more, 3,000 ppb or more, 4,000 ppb or more, 5,000 ppb or more, 6,000 ppb or more, 7,000 ppb or more, 8,000 ppb or more, 9,000 ppb or more, or 10,000 ppb or more, relative to the mass of PTFE, and may be 500,000 ppb or less or 100,000 ppb or less.

[0076] In one embodiment, the aqueous dispersion (A) contains a compound (4-12) represented by the general formula (4-12). General formula (4-12): [H-(CF ２ ) ｍ－１ CO ２ － ] M ＋ (In the formula, m is 12, M ＋ (This represents a cation.)

[0077] The content of compound (4-12) in aqueous dispersion (A) may be more than 100 ppb by mass, 200 ppb or more, 300 ppb or more, 400 ppb or more, 500 ppb or more, 600 ppb or more, 700 ppb or more, 800 ppb or more, 900 ppb or more, 1000 ppb or more, 2000 ppb or more, 3000 ppb or more, 4000 ppb or more, 5000 ppb or more, 6000 ppb or more, 7000 ppb or more, 8000 ppb or more, 9000 ppb or more, or 10000 ppb or more, and may be 100000 ppb or less, relative to the mass of PTFE.

[0078] In one embodiment, the aqueous dispersion (A) contains compound (4) represented by general formula (4). General formula (4): [H-(CF ２ ) ｍ－１ CO ２ － ] M ＋ (In the formula, m is an integer from 4 to 20, M ＋ (where represents a cation.) m may be 8 or more, 10 or more, or 12 or more, and may be 20 or less.

[0079] The content of compound (4) in the aqueous dispersion (A) may be more than 100 ppb by mass, 200 ppb or more, 300 ppb or more, 400 ppb or more, 500 ppb or more, 600 ppb or more, 700 ppb or more, 800 ppb or more, 900 ppb or more, 1000 ppb or more, 2000 ppb or more, 3000 ppb or more, 4000 ppb or more, 5000 ppb or more, 6000 ppb or more, 7000 ppb or more, 8000 ppb or more, 9000 ppb or more, or 10000 ppb or more, and may be 100000 ppb or less, relative to the mass of PTFE.

[0080] Furthermore, examples of fluorine-containing compounds having hydrophilic groups that the aqueous dispersion (A) may contain include the compounds represented by general formulas (1) to (3) and (5), which will be described later. These compounds will be described later.

[0081] (Adsorbent) In the manufacturing method of the present disclosure, an aqueous dispersion (A) is prepared, and then the aqueous dispersion (A) is brought into contact with an adsorbent to prepare an aqueous dispersion (B).

[0082] The adsorbent is preferably at least one selected from the group consisting of ion exchange resins, synthetic adsorbents, silica gel, polymer adsorbents, activated carbon, diatomaceous earth, and zeolite, more preferably ion exchange resins, synthetic adsorbents, and activated carbon, even more preferably ion exchange resins, and even more preferably anion exchange resins.

[0083] An anion exchange resin can be suitably used as the ion exchange resin. The anion exchange resin is the following general formula (A1): -N ＋ R １ R ２ R ３ X － (In the formula, R １ , R ２ and R ３ R is the same or different hydrogen atom or organic group. １ , R ２ and R ３ At least one of them is an organic group with 3 or more carbon atoms. X represents a counterion. An ion exchange group represented by the following general formula (A2): -NR４ R ５ (In the formula, R ４ and R ５ R is the same or different hydrogen atom or organic group. ４ and R ５ A resin having an ion exchange group represented by (at least one of which is an organic group with two or more carbon atoms) is preferred.

[0084] In general formula (A1), R １ , R ２ and R ３ R is either the same or different hydrogen atom or organic group. １ , R ２ and R ３ The group may consist entirely of organic groups, or it may consist of one hydrogen atom and two organic groups. Furthermore, it may consist of two hydrogen atoms and one organic group. The organic group has one or more carbon atoms. Preferably, the organic group has two or more carbon atoms. The above R １ , R ２ and R ３ One preferred form is an organic group having two or more carbon atoms.

[0085] In general formula (A1), R １ , R ２ and R ３ At least one of them is an organic group with 3 or more carbon atoms. １ , R ２ and R ３ Of these, one may be an organic group having 3 or more carbon atoms, and the other two may be hydrogen atoms or organic groups having 1 or 2 carbon atoms. Alternatively, two may be organic groups having 3 or more carbon atoms, and one may be a hydrogen atom or an organic group having 1 or 2 carbon atoms. R １ , R ２ and R ３ All of these may be organic groups having three or more carbon atoms.

[0086] R １ , R ２ and R ３ In this, the number of carbon atoms in the organic group is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. The number of carbon atoms in the organic group may also be 5 or less.

[0087] In general formula (A1), R１ , R ２ and R ３ Preferably, at least one of the components is an organic group with four or more carbon atoms. By adopting such a configuration, specific fluorine-containing compounds can be removed more efficiently.

[0088] R １ , R ２ and R ３ The organic group in is preferably an alkyl group, an alkanol group, or an alkenyl group, more preferably an alkyl group or an alkanol group, and even more preferably an alkyl group.

[0089] In this disclosure, "alkyl group" is a general term for the remaining groups obtained by removing one hydrogen atom from an aliphatic saturated hydrocarbon, and includes linear or branched alkyl groups having one or more carbon atoms, or cyclic alkyl groups having three or more carbon atoms.

[0090] Furthermore, in this disclosure, "alkanol group" is a general term for the remaining group after removing one hydrogen atom from an alkanol, and includes linear or branched alkanol groups having one or more carbon atoms, or cyclic alkanol groups having three or more carbon atoms.

[0091] R １ , R ２ and R ３ R is the same or different alkyl group having 2 or more carbon atoms or an alkanol group having 1 or more carbon atoms. １ , R ２ and R ３ Preferably, at least one of them is an alkyl group having 3 or more carbon atoms.

[0092] R １ , R ２ and R ３ R is the same or different alkyl group having 2 or more carbon atoms or an alkanol group having 2 or more carbon atoms, １ , R ２ and R ３ A more preferred configuration is one in which at least one of the elements is an alkyl group having three or more carbon atoms.

[0093] R １ , R ２ and R ３Furthermore, R is either the same or different alkyl group having 2 or more carbon atoms or an alkanol group having 1 or more carbon atoms. １ , R ２ and R ３ A preferred configuration is that at least one of the elements is an alkyl group having four or more carbon atoms.

[0094] Also, R １ , R ２ and R ３ R is the same or different alkyl group having 2 or more carbon atoms or an alkanol group having 2 or more carbon atoms, １ , R ２ and R ３ A preferred configuration is that at least one of the elements is an alkyl group having four or more carbon atoms.

[0095] The alkyl group preferably has 10 or fewer carbon atoms, more preferably 8 or fewer, and even more preferably 6 or fewer. The alkyl group may also have 5 or fewer carbon atoms.

[0096] The number of carbon atoms in the alkanol group is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. The number of carbon atoms in the alkanol group may also be 5 or less.

[0097] In general formula (A1), X is a counterion. X can be Cl, OH, Br, I, or NO. ３ SO ４ Examples include, and it is preferably Cl or OH. ４ In the case of a divalent anion, as shown above, one counterion coordinates to two repeating units of general formula (A1).

[0098] In general formula (A2), R ４ and R ５ R is the same or different hydrogen atom or organic group. ４ and R ５ At least one of them is an organic group with two or more carbon atoms. ４ and R ５ It may be entirely composed of organic groups. Alternatively, one may be a hydrogen atom and one may be an organic group.

[0099] In general formula (A2), R ４ and R５ At least one of them is an organic group with two or more carbon atoms.

[0100] R ４ and R ５ Of these, one may be an organic group having two or more carbon atoms, and the other may be a hydrogen atom or an organic group having one carbon atom. Also, R ４ and R ５ Both may be organic groups having two or more carbon atoms.

[0101] R ４ and R ５ At least one of these may be an organic group having 3 or more carbon atoms, or an organic group having 4 or more carbon atoms.

[0102] Also, R ４ and R ５ It is also preferable that the group is an organic group with two or more carbon atoms.

[0103] R ４ and R ５ In this, the number of carbon atoms in the organic group is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. The number of carbon atoms in the organic group may also be 5 or less.

[0104] The above R ４ and R ５ The organic group in is preferably an alkyl group, an alkanol group, or an alkenyl group, more preferably an alkyl group or an alkanol group, and even more preferably an alkyl group.

[0105] R ４ and R ５ The above R is the same or different alkyl group or alkanol group, ４ and R ５ A more preferred form is that at least one of the members is an alkyl group having 2 or more carbon atoms or an alkanol group having 2 or more carbon atoms.

[0106] The alkyl group preferably has 10 or fewer carbon atoms, more preferably 8 or fewer, and even more preferably 6 or fewer. The alkyl group may also have 5 or fewer carbon atoms.

[0107] The number of carbon atoms in the alkanol group is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. The number of carbon atoms in the above alkanol group may also be 5 or less.

[0108] The anion exchange resin is preferably one in which a group represented by general formula (A1) or a group represented by general formula (A2) is bonded to the resin matrix. An example of an anion exchange resin is one in which a group represented by general formula (A1) or a group represented by general formula (A2) is bonded to a resin matrix made of a styrene-based or acrylic polymer. The styrene-based or acrylic polymer as the resin matrix is ​​not limited, but for example, a resin matrix used in known anion exchange resins can be used. From the viewpoint of the removal efficiency of fluorine-containing compounds having hydrophilic groups, the resin matrix of the anion exchange resin is preferably styrene-based.

[0109] The basicity of anion exchange resins can be set in various ways depending on the type of polymer backbone and / or ion exchange group.

[0110] The anion exchange resin preferably has a pore diameter of 1 to 5000 Å. From the viewpoint of removal efficiency, a pore diameter of 50 Å or more is preferable, 100 Å or more is more preferable, and 150 Å or more is even preferable. It may also be 200 Å or more, or 250 Å or more. Furthermore, the pore diameter may be 1000 Å or less. The pore diameter can be calculated, for example, by measuring the specific surface area and total pore volume using the gas adsorption method.

[0111] From the viewpoint of removal efficiency, the anion exchange resin is preferably given a total exchange capacity of 0.1 eq / L-Resin or more. More preferably, it is 0.3 eq / L-Resin or more, even more preferably, 0.5 eq / L-Resin or more, and particularly preferably, 0.7 eq / L-Resin or more. Furthermore, the upper limit is preferably 5.0 eq / L-Resin or less, more preferably 3.0 eq / L-Resin or less, and particularly preferably 2.0 eq / L-Resin or less.

[0112] The moisture content of the anion exchange resin is preferably 20% by mass or more, more preferably 30 to 70% by mass, and even more preferably 35 to 65% by mass. A moisture content of 30% by mass or more in the anion exchange resin allows for efficient removal of the fluorine-containing compound. Furthermore, the fluorine-containing compound can easily diffuse into the particles of the anion exchange resin. If the moisture content of the anion exchange resin is 70% by mass or less, the decrease in the strength of the anion exchange resin particles due to insufficient crosslinking can be suppressed.

[0113] The moisture content of anion exchange resin can be measured by the following method. First, accurately measure 10 mL of the sample prepared in a reference form using a graduated cylinder. Wrap this resin in cloth and centrifuge to remove any adhering moisture, then quickly measure the mass of the resin. Next, dry the resin in a constant temperature drying oven at 105°C for 4 hours, then allow it to cool in a desiccator for 30 minutes. Measure the mass of the dried resin and calculate the moisture content using the following formula: Moisture content (mass%) = (Mass of resin before drying (g) - Mass of resin after drying (g)) / Mass of resin before drying (g) × 100

[0114] Anion exchange resins are typically spherical. The average particle size of the anion exchange resin is preferably 0.1 to 5 mm, more preferably 0.2 to 2 mm, and particularly preferably 0.3 to 1.5 mm. If the average particle size of the anion exchange resin is within the above range, the packed column of the anion exchange resin is less likely to become clogged. The above average particle size is a value obtained by sieving. Specifically, first, the anion exchange resin is placed in a sieve shaker and the particle size distribution is measured by sieving. Then, the diameter of the sieve corresponding to 50% of the residual classifier is determined and this is taken as the average particle size.

[0115] Commercially available anion exchange resins can be used, such as PFA694E and A592E from Purolite Co., Ltd., AMBERLITE PSR2 PLUS from Organo Corporation, Muromachi Chemical Co., Ltd., and Lewatit TP108 DW and Lewatit MonoPlus TP109 from Lanxess.

[0116] Furthermore, a resin having an ion exchange group (excluding the group represented by the general formula (A1) and the group represented by the general formula (A2) above) can also be used as the anion exchange resin. Examples of such anion exchange resins include a resin having at least one ion exchange group selected from the group consisting of amino groups and quaternary ammonium groups (excluding the group represented by the general formula (A1) and the group represented by the general formula (A2) above). An example of such an anion exchange resin is the following general formula (B1): -N ＋ (CH ３ ) ３ X － A group represented by (wherein X represents the counterion) or the following general formula (B2): -N ＋ (CH ３ ) ２ (C ２ H ４ OH)X － A group represented by (wherein X represents the counterion) is preferred. In general formulas (B1) and (B2), X can be Cl, OH, Br, I, or NO. ３ SO ４ Examples include, and it is preferably Cl or OH. ４ In the case of a divalent anion, as shown above, one counterion coordinates to two repeating units of general formula (A1).

[0117] The anion exchange resin preferably has ion exchange groups (excluding the groups represented by general formula (A1) and general formula (A2)) bonded to a resin matrix, and examples of the resin matrix include styrene-based or acrylic polymers. The styrene-based or acrylic polymer used as the resin matrix is ​​not limited, but for example, resin matrices used in known anion exchange resins can be used. From the viewpoint of the removal efficiency of fluorine-containing compounds having hydrophilic groups, it is preferable that the resin matrix of anion exchange resin B is styrene-based.

[0118] The resin having ion exchange groups (excluding the groups represented by general formula (A1) and general formula (A2) above) may be weakly basic or strongly basic. Preferably, it is a strongly basic anion exchange resin. The basicity of the anion exchange resin can be set in various ways depending on the polymer backbone and / or the type of ion exchange groups.

[0119] Resins having ion exchange groups (excluding the groups represented by the general formula (A1) and the general formula (A2) above) preferably have a pore diameter of 1 to 5000 Å. From the viewpoint of removal efficiency, a pore diameter of 50 Å or more is preferable, 100 Å or more is more preferable, and 150 Å or more is even preferable. It may also be 200 Å or more, or 250 Å or more. Furthermore, the pore diameter may be 1000 Å or less. The pore diameter can be calculated, for example, by measuring the specific surface area and total pore volume using the gas adsorption method.

[0120] Resins having ion exchange groups (excluding the groups represented by general formula (A1) and general formula (A2) above) are preferably such that, from the viewpoint of removal efficiency, the total exchange capacity is 0.1 eq / L-Resin or more. More preferably, it is 0.3 eq / L-Resin or more, even more preferably, 0.5 eq / L-Resin or more, and particularly preferably, 0.7 eq / L-Resin or more. Furthermore, a larger total exchange capacity is preferable, but for example, the upper limit is preferably 5.0 eq / L-Resin, more preferably 3.0 eq / L-Resin or less, and particularly preferably 2.0 eq / L-Resin or less.

[0121] The moisture content of the resin having ion exchange groups (excluding the groups represented by the general formula (A1) and the general formula (A2) above) is preferably 20% by mass or more, more preferably 30 to 70% by mass, and even more preferably 35 to 65% by mass.

[0122] Resins having ion exchange groups (excluding the groups represented by the general formula (A1) and the general formula (A2) above) are usually spherical. The average particle size of the resin having ion exchange groups (excluding the groups represented by the general formula (A1) and the general formula (A2) above) is preferably 0.1 to 5 mm, more preferably 0.2 to 2 mm, and particularly preferably 0.3 to 1.5 mm. If the average particle size is within the above range, the packed column of the anion exchange resin is less likely to become clogged. The above average particle size is a value obtained by the sieving method. Specifically, first, the anion exchange resin is placed in a sieve shaker and the particle size distribution is measured by sieving. Then, the diameter of the sieve corresponding to 50% of the residual classification is determined and this is taken as the average particle size.

[0123] As the resin having ion exchange groups (excluding the groups represented by the general formula (A1) and the general formula (A2) above), commercially available products may be used. For example, the Diaion® SA series from Mitsubishi Chemical Corporation, A400, A300, etc. from Purolite Corporation, and the Amberlite® series, IRA4002OH, etc. from DuPont, etc., can be used.

[0124] As the ion exchange resin, at least one selected from the group consisting of a resin in which a group represented by general formula (B1) is bonded to a styrene-based polymer, and a resin in which a group represented by general formula (B2) is bonded to a styrene-based polymer, is preferred. Among these, OH is preferred as X in general formulas (B1) and (B2).

[0125] Synthetic adsorbents can be used as adsorbents. Synthetic adsorbents are porous resins that do not have ion exchange groups, and known synthetic adsorbents can be used. Examples of ion exchange groups include amino groups, quaternary ammonium groups, carboxylic acid groups, sulfonic acid groups, etc. Specific examples of synthetic adsorbents include styrene resins such as styrene-divinylbenzene copolymers, acrylic resins such as (meth)acrylic acid ester-ethylene glycol dimethacrylate copolymers, methacrylic resins, polyvinyl resins, dextran resins, etc. Commercially available synthetic adsorbents include, specifically, styrene-based resins such as Diaion HP10, Diaion HP20, Diaion HP21, Diaion HP40, Diaion HP50, Sepapies SP207, Sepapies SP70, Sepapies SP825, Sepapies SP850, Sepapies SP207 (all manufactured by Mitsubishi Chemical Corporation), Amberlite XAD1180N, Amberlite XAD2000, Amberlite XAD4, Amberlite FPX66 (all manufactured by Organo Corporation), etc.; and acrylic-based resins such as Diaion HP2MG (manufactured by Mitsubishi Chemical Corporation) and Amberlite HXAD-7HP (manufactured by Organo Corporation), etc.

[0126] The synthetic adsorbent preferably has a pore diameter of 1 to 5000 Å. From the viewpoint of removal efficiency, a pore diameter of 50 Å or more is preferable, 100 Å or more is more preferable, and 150 Å or more is even preferable. It may also be 200 Å or more, or 250 Å or more. Furthermore, the pore diameter may be 1000 Å or less. The pore diameter can be calculated, for example, by measuring the specific surface area and total pore volume using a gas adsorption method.

[0127] Synthetic adsorbents have a specific surface area of ​​300 m². ２ It is preferable that the amount is 1 / g or more. The specific surface area is 400 m². ２ More preferably 500m / g or more. ２ More preferably 600m / g or more. ２ A value of 1 / g or more is particularly preferable. There is no upper limit to the specific surface area, but for example, 2000 m² is preferable. ２ It may be less than or equal to / g, and 1500m ２It may be less than or equal to / g, and 1000m ２ The amount may be less than or equal to / g. Furthermore, the synthetic adsorbent is usually spherical, and the average particle size of the synthetic adsorbent is preferably 0.1 to 2.0 mm, more preferably 0.2 to 1.5 mm, even more preferably 0.2 to 1.3 mm, and particularly preferably 0.3 to 1.0 mm, from the viewpoint of removal efficiency. The average particle size of the synthetic adsorbent refers to the 50% mass value obtained by plotting the integrated mass after classification by sieving on a graph.

[0128] From the viewpoint of improving removal efficiency, synthetic adsorbents preferably contain water. The water content is preferably 20 to 80% by mass, more preferably 40 to 75% by mass, and particularly preferably 50 to 70% by mass.

[0129] Activated carbon can be produced from carbonaceous materials. Examples of carbonaceous materials include any material that produces activated carbon through carbonization or activation, such as wood, sawdust, charcoal, fruit shells like coconut shells and walnut shells, plant-based materials like fruit seeds, coal such as peat, lignite, brown coal, bituminous coal, and anthracite, pitch such as petroleum pitch and coal pitch, tar such as coke, coal tar, and petroleum tar, mineral-based materials such as petroleum distillation residues, natural materials such as cotton and rayon cellulose fibers, and synthetic materials such as phenolic resins, polyvinyl alcohol, and polyacrylonitrile. The material can be in powder, granular, or fibrous form, or molded from these forms.

[0130] Activated carbon has a specific surface area of ​​500 m². ２ It is preferable that the amount is 1 / g or more. The specific surface area is 1000 m². ２ More preferably 1500m / g or more, ２ More preferably 1800m / g or more. ２ A value of 1 / g or more is particularly preferred, and 2000m ２ A value of 1 / g or more is particularly preferred. There is no upper limit to the specific surface area, but for example, 2500 m² is preferable. ２The amount may be / g. The shape of the activated carbon is not particularly limited and may be, for example, pelletized, granular, powdered, or spherical particles. The activated carbon may be a commercially available product. Examples of commercially available activated carbon include Shirasagi (trademark) from Osaka Gas Chemical Co., Ltd., Filtrasorb (trademark) CAL, Diahope (trademark), Diasorb (trademark) from Calgon Carbon Japan Co., Ltd., and the Evadia (trademark) series from Sui-ing Co., Ltd.

[0131] Activated carbon preferably has improved adsorption performance due to steam activation treatment. In the steam activation treatment, it is preferable to expose the activated carbon to steam at a temperature of 120°C or higher, for example 130 to 350°C, particularly 150 to 1000°C, and a pressure of 0.2 MPa or higher, for example 0.5 to 15 MPa, particularly 1 to 15 MPa. The steam activation treatment time is generally 10 seconds to 50 hours, for example 10 minutes to 10 hours. Heating in a furnace may be performed during activation.

[0132] Cations may be impregnated onto the surface of activated carbon. Examples of cations include metal ions, metal oxide ions, and ammonium ions. Examples of metals include metal atoms from groups 1 to 13 of the periodic table (e.g., alkali metals (e.g., Li, Na, K), alkaline earth metals (e.g., Mg, Ca), Ti, Zr, V, Cr, Fe, Ni, Cu, Zn).

[0133] The contact area (surface area) of the adsorbent is preferably 0.0020 m² relative to the mass of PTFE in the aqueous dispersion. ２ It is 0.0030 m / g or more, and more preferably 0.0030 m ２ It is 1 / g or more, and more preferably 0.0040m ２ The amount is 0.0050 m / g or more, and is particularly preferred. ２ The value is 1 / g or more, and there is no particular upper limit, but for example, 5.0 m ２ It may be less than or equal to / g.

[0134] The exchange capacity of the ion exchange resin is preferably 0.25 meq / g or more, preferably 0.50 meq / g or more, preferably 1.00 meq / g or more, and preferably 1.50 meq / g or more, relative to the mass of PTFE in the aqueous dispersion. There is no particular upper limit, but for example, it may be 2500 meq / g or less.

[0135] The amount of adsorbent to be brought into contact with the aqueous dispersion is preferably 10,000 g or less, preferably 0.1 g or more, more preferably 1 g or more, even more preferably 5 g or more, even more preferably 10 g or more, and particularly preferably 100 g or more, relative to 1,000 g of PTFE in the aqueous dispersion.

[0136] The method of contacting the aqueous dispersion with the adsorbent may be batch-type or fluid-type.

[0137] The number of times the aqueous dispersion and the adsorbent are brought into contact may be once or two or more times. By repeating the contact between the aqueous dispersion and the adsorbent two or more times, the content of compounds (6-16), (6-18), and (6-20) in the aqueous dispersion can be further reduced. The number of times the aqueous dispersion and the adsorbent are brought into contact may be 10 times or less.

[0138] The reason why the content of compounds (6-16), (6-18), and (6-20) can be further reduced by repeating the contact between the aqueous dispersion and the adsorbent two or more times is not clear, but it is presumed to be as follows.

[0139] Firstly, compounds (6-16), (6-18), and (6-20) have a molecular weight distribution. When contact with the adsorbent occurs only once, compounds with relatively low molecular weights are easily removed, while compounds with relatively high molecular weights may remain in the aqueous dispersion without being sufficiently reduced. Therefore, it is presumed that by repeating contact between the aqueous dispersion and the adsorbent two or more times, the content of compounds (6-16), (6-18), and (6-20), including compounds with relatively high molecular weights, can be further reduced.

[0140] Secondly, the aqueous dispersion (A) may contain compounds corresponding to compounds (6-16), compounds (6-18), and compounds (6-20), including compounds with monocarboxylic acid structures, such as compound (4). The compounds corresponding to compounds (6-16), compounds (6-18), and compounds (6-20) (compounds with dicarboxylic acid structures) and compounds with monocarboxylic acid structures may interact with the adsorbent in different ways. For example, it is presumed that compounds with dicarboxylic acid structures interact with the adsorbent at multiple points due to their two carboxyl groups, which may restrict their orientation or cause association (aggregate formation), thereby reducing their apparent adsorption rate or inhibiting adsorption. As a result, it is possible that compounds with monocarboxylic acid structures will be reduced mainly in the first contact, and compounds with dicarboxylic acid structures will be reduced more easily in subsequent contacts.

[0141] Furthermore, in the first contact between the aqueous dispersion and the adsorbent, there is a possibility that compounds with relatively high molecular weights may remain in the aqueous dispersion (A) in amounts of approximately 5000 ppb or more. By repeating the contact between the aqueous dispersion and the adsorbent two or more times, it becomes possible to remove even the relatively high molecular weight components that could not be completely removed in the first contact, and as a result, it is presumed that the content of compounds (6-16), (6-18), and (6-20) can be further reduced.

[0142] Furthermore, when the aqueous dispersion and adsorbent are brought into contact two or more times, the content of compounds (6-16), (6-18), and (6-20) can be further reduced by using different types of ion exchange resins for the first and subsequent contacts. This is presumably because the types of compounds that can be removed in each contact step can be different, resulting in the effective removal of a wider range of compounds.

[0143] Conventional methods can be used to bring the aqueous dispersion and the adsorbent into contact. For example, this can be done by adding the adsorbent to the aqueous dispersion and stirring, or by the column method, in which the aqueous dispersion is flowed through a column packed with the adsorbent. The packed column used in the column method may be a mobile, fixed-bed, or fluidized-bed type.

[0144] After bringing the aqueous dispersion into contact with the adsorbent, the aqueous dispersion and the adsorbent can be separated, and the aqueous dispersion can be recovered.

[0145] When using a method in which an adsorbent is added to an aqueous dispersion and stirred, the adsorbent and aqueous dispersion are separated after contact. The method for separating the adsorbent and aqueous dispersion is not limited and can be, for example, by filtration.

[0146] A nonionic surfactant may be added to the aqueous dispersion (A), and then the aqueous dispersion (A) containing the nonionic surfactant may be brought into contact with an adsorbent. By bringing the aqueous dispersion (A) containing the nonionic surfactant into contact with the adsorbent, the aqueous dispersion (A) and the adsorbent can be brought into contact without impairing the dispersion stability of the primary PTFE particles in the aqueous dispersion (A).

[0147] As the nonionic surfactant to be added to the aqueous dispersion (A), a fluorine-free nonionic surfactant is preferred.

[0148] Examples of fluorine-free nonionic surfactants include nonionic surfactants represented by general formula (i) and nonionic surfactants represented by general formula (ii). ６ -O-A １ -H (i) (wherein, R ６ A is a linear or branched primary or secondary alkyl group having 8 to 18 carbon atoms. １ (This is a polyoxyalkylene chain.) ７ -C ６ H ４ -O-A ２ -H (ii) (wherein, R ７ A is a linear or branched alkyl group having 4 to 12 carbon atoms.２ (This is a polyoxyalkylene chain.)

[0149] As the fluorine-free nonionic surfactant, at least one selected from the group consisting of nonionic surfactants represented by general formula (i) and nonionic surfactants represented by general formula (ii) is preferred, and the nonionic surfactant represented by general formula (i) is more preferred.

[0150] Examples of fluorine-free nonionic surfactants include Dow Chemical Company's Triton® X series (X15, X45, X100, etc.), Tergitol® 15-S series, Tergitol® TMN series (TMN-6, TMN-10, TMN-100, etc.), Tergitol® L series, and BASF's Pluronic® R series (31R1, 17R2, 10R5, 25R4, Examples include m-22, n-23), Iconol® TDA series (TDA-6, TDA-9, TDA-10), Clariant's Genapol series (X080, etc.), Daiichi Kogyo Seiyaku's Neugen TDS series (TDS-80, TDS-100, etc.), Lion Corporation's Leocol TD series (TD-90, etc.), Lion Corporation's Lionol® TD series, Harcross Chemicals' T-Det A series (A-138, A-139, A-1315, etc.), and Nippon Oil & Fats Co., Ltd.'s Dispanol TOC.

[0151] (Concentration) After contacting the aqueous dispersion with the adsorbent, the aqueous dispersion and the adsorbent may be separated, the aqueous dispersion may be recovered, and the recovered aqueous dispersion may be concentrated. Alternatively, after contacting the aqueous dispersion with the adsorbent, the aqueous dispersion and the adsorbent may be separated, the aqueous dispersion may be recovered, a nonionic surfactant may be added to the recovered aqueous dispersion, and then the aqueous dispersion containing the nonionic surfactant may be concentrated. As the nonionic surfactant, the above-mentioned nonionic surfactant can be used as the nonionic surfactant added to the aqueous dispersion (A).

[0152] Concentration methods include phase separation concentration, electrophoresis, ion exchange method, and membrane concentration. Phase separation concentration, ion exchange method, and membrane concentration can be carried out under conventionally known processing conditions and are not particularly limited, but can be carried out by methods described in International Publication No. 2004 / 050719, Japanese Patent Publication No. 2002-532583, and Japanese Patent Publication No. 55-120630.

[0153] As for the concentration method, a method of separating the aqueous dispersion into two or more phases and recovering the concentrated phase is preferred, and concentration by phase separation or electrophoresis is preferred, with phase separation concentration being more preferred. Phase separation concentration can be performed, for example, by heating the aqueous dispersion to separate it into a PTFE-free phase (supernatant phase) and a PTFE-containing phase (concentrated phase), removing the PTFE-free phase, and recovering the PTFE-containing phase (concentrated phase).

[0154] The temperature for phase separation and concentration can be selected based on the cloud point of the nonionic surfactant contained in the aqueous dispersion. Preferably, the temperature for phase separation and concentration is 10°C or more lower than the cloud point of the nonionic surfactant, and preferably 10°C or less higher than the cloud point of the nonionic surfactant.

[0155] The PTFE content in the aqueous dispersion obtained by concentration is preferably more than 50% by mass, more preferably 55% by mass or more, even more preferably 60% by mass or more, preferably 75% by mass or less, more preferably 73% by mass or less, even more preferably 71% by mass or less, and particularly preferably 70% by mass or less, relative to the aqueous dispersion.

[0156] Since aqueous dispersion (B) is obtained by the manufacturing method of the present disclosure, the amount of hydrophilic fluorine-containing compounds such as compound (6-16), compound (6-18), and compound (6-20) is reduced, and it can have the same composition as the aqueous dispersion described below.

[0157] 2. Aqueous dispersions The disclosure also relates to aqueous dispersions containing PTFE and water. The aqueous dispersions of the disclosure can be manufactured, for example, by using the manufacturing method of the disclosure.

[0158] (Fluorine-containing compound having a hydrophilic group) In one embodiment, the aqueous dispersion contains at least one compound selected from the group consisting of compound (6-16) represented by general formula (6-16), compound (6-18) represented by general formula (6-18), and compound (6-20) represented by general formula (6-20). General formula (6-16): M ＋ [ － OOC-(CFX) ｎ－２ - COO － ] M ＋ (In the formula, n is 16, M ＋ X is a cation, and X is F, CF, and F are independent in each occurrence. ３ OCF ３ or OC ３ F ７ (Represents.) General formula (6-18): M ＋ [ － OOC-(CFX) ｎ－２ - COO － ] M ＋ (In the formula, n is 18, M ＋ X is a cation, and X is F, CF, and F are independent in each occurrence. ３ OCF ３ or OC ３ F ７ (Represents.) General formula (6-20): M ＋ [ － OOC-(CFX) ｎ－２ - COO － ] M ＋ (In the formula, n is 20, M ＋ X is a cation, and X is F, CF, and F are independent in each occurrence. ３ OCF ３ or OC ３ F ７ (This represents...)

[0159] In one embodiment, the aqueous dispersion contains at least one compound selected from the group consisting of compounds represented by general formula (6-16) (6-16) and compounds represented by general formula (6-18) (6-18).

[0160] In one embodiment, the total content of compounds (6-16), (6-18), and (6-20) in the aqueous dispersion is less than 5000 ppb by mass, or 1000 ppb by mass or less, relative to the mass of PTFE.

[0161] The total content of compounds (6-16), (6-18), and (6-20) relative to the mass of PTFE may be less than 5000 ppb by mass, 1000 ppb or less, 900 ppb or less, 800 ppb or less, 700 ppb or less, 600 ppb or less, 500 ppb or less, 400 ppb or less, 300 ppb or less, 200 ppb or less, 100 ppb or less, 50 ppb or less, 25 ppb or less, 10 ppb or less, less than 5 ppb or less, or 1 ppb or less. The above content may be below the limit of quantification as measured by liquid chromatography-mass spectrometry (LC / MS). Furthermore, the above content may be greater than 0 ppb by mass, 0.1 ppb or more by mass, 1.0 ppb or more by mass, 5 ppb or more by mass, or 10 ppb or more by mass.

[0162] The total content of compounds (6-16) and (6-18) may be less than 5000 ppb by mass, 1000 ppb or less, 900 ppb or less, 800 ppb or less, 700 ppb or less, 600 ppb or less, 500 ppb or less, 400 ppb or less, 300 ppb or less, 200 ppb or less, 100 ppb or less, 50 ppb or less, 25 ppb or less, 10 ppb or less, less than 5 ppb or less, or 1 ppb or less, relative to the mass of PTFE. The above content may be below the limit of quantification as measured by liquid chromatography-mass spectrometry (LC / MS). Furthermore, the above content may be greater than 0 ppb by mass, 0.1 ppb or more, 1.0 ppb or more, 5 ppb or more, or 10 ppb or more.

[0163] In one embodiment, the aqueous dispersion contains at least one compound selected from the group consisting of compounds represented by general formula (6-16-X) (6-16-X), compounds represented by general formula (6-18-X) (6-18-X), and compounds represented by general formula (6-20-X) (6-20-X). General formula (6-16-X): M ＋ [ － OOC-(CF ２ ) ｃ - (CF (OCF ３ )) ｄ - COO － ] M ＋ (In the formula, c and d are independent integers greater than or equal to 1, the sum of c and d is 14, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of ) is arbitrary in the formula. ) General formula (6-18-X): M ＋ [ － OOC-(CF ２ ) ｃ - (CF (OCF ３ )) ｄ - COO － ] M ＋ (In the formula, c and d are independent integers of 1 or greater, the sum of c and d is 16, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of )- is arbitrary in the formula. ) General formula (6-20-X): M ＋ [ － OOC-(CF ２ ) ｃ - (CF (OCF ３ )) ｄ - COO － ] M ＋ (In the formula, c and d are independent integers greater than or equal to 1, the sum of c and d is 18, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of the elements in the formula is arbitrary.

[0164] In one embodiment, the aqueous dispersion contains at least one compound selected from the group consisting of compounds represented by the general formula (6-16-X) (6-16-X) and compounds represented by the general formula (6-18-X) (6-18-X).

[0165] In one embodiment, the total content of compound (6-16-X), compound (6-18-X), and compound (6-20-X) in the aqueous dispersion is less than 5000 ppb by mass, or 1000 ppb by mass or less, relative to the mass of PTFE.

[0166] The total content of compound (6-16-X), compound (6-18-X), and compound (6-20-X) may be less than 5000 ppb by mass, 1000 ppb or less, 900 ppb or less, 800 ppb or less, 700 ppb or less, 600 ppb or less, 500 ppb or less, 400 ppb or less, 300 ppb or less, 200 ppb or less, 100 ppb or less, 50 ppb or less, 25 ppb or less, 10 ppb or less, less than 5 ppb or less, or 1 ppb or less, relative to the mass of PTFE. The above content may be below the limit of quantification as measured by liquid chromatography-mass spectrometry (LC / MS). Furthermore, the above content may be greater than 0 ppb by mass, 0.1 ppb or more by mass, 1.0 ppb or more by mass, 5 ppb or more by mass, or 10 ppb or more by mass.

[0167] The total content of compound (6-16-X) and compound (6-18-X) may be less than 5000 ppb by mass, 1000 ppb or less, 900 ppb or less, 800 ppb or less, 700 ppb or less, 600 ppb or less, 500 ppb or less, 400 ppb or less, 300 ppb or less, 200 ppb or less, 100 ppb or less, 50 ppb or less, 25 ppb or less, 10 ppb or less, less than 5 ppb or less, or 1 ppb or less, relative to the mass of PTFE. The above content may be below the limit of quantification as measured by liquid chromatography-mass spectrometry (LC / MS). Furthermore, the above content may be greater than 0 ppb by mass, 0.1 ppb or more by mass, 1.0 ppb or more by mass, 5 ppb or more by mass, or 10 ppb or more by mass.

[0168] In one embodiment, the aqueous dispersion contains at least one compound selected from the group consisting of the compound represented by general formula (6-16-1) (6-16-1), the compound represented by general formula (6-16-2) (6-16-2), the compound represented by general formula (6-16-3) (6-16-3), the compound represented by general formula (6-18-1) (6-18-1), the compound represented by general formula (6-18-2) (6-18-2), and the compound represented by general formula (6-20-1) (6-20-1). General formula (6-16-1): M ＋ [ － OOC-(CF ２ ) １４ - COO － ] M ＋ (In the formula, M ＋ represents a cation. ) General formula (6-16-2): M ＋ [ － OOC-(CF ２ ) １２ - (CF (OCF ３ )) ２ - COO － ] M ＋ (In the formula, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of ) is arbitrary in the formula. ) General formula (6-16-3): M ＋ [ － OOC-(CF ２ ) １１ - (CF (OCF ３ )) ３ - COO － ] M ＋ (In the formula, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of ) is arbitrary in the formula. ) General formula (6-18-1): M ＋ [ － OOC-(CF ２ ) １６ - COO － ] M ＋ (In the formula, M ＋(where represents a cation) General formula (6-18-2): M ＋ [ － OOC-(CF ２ ) １５ - (CF (OCF ３ )) １ - COO － ] M ＋ (In the formula, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of ) is arbitrary in the formula. ) General formula (6-20-1): M ＋ [ － OOC-(CF ２ ) １４ - (CF (OCF ３ )) ４ - COO － ] M ＋ (In the formula, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of the elements in the formula is arbitrary.

[0169] In one embodiment, the aqueous dispersion contains at least one compound selected from the group consisting of the compound represented by general formula (6-16-1) (6-16-1), the compound represented by general formula (6-16-2) (6-16-2), the compound represented by general formula (6-16-3) (6-16-3), the compound represented by general formula (6-18-1) (6-18-1), and the compound represented by general formula (6-18-2) (6-18-2).

[0170] The total content of compounds (6-16-1), (6-16-2), (6-16-3), (6-18-1), (6-18-2), and (6-20-1) relative to the mass of PTFE may be less than 5000 ppb by mass, 1000 ppb or less, 900 ppb or less, 800 ppb or less, 700 ppb or less, 600 ppb or less, 500 ppb or less, 400 ppb or less, 300 ppb or less, 200 ppb or less, 100 ppb or less, 50 ppb or less, 25 ppb or less, 10 ppb or less, less than 5 ppb or less, or 1 ppb or less. The above content may be below the limit of quantification as measured by liquid chromatography-mass spectrometry (LC / MS). Furthermore, the above content may be greater than 0 ppb by mass, 0.1 ppb or more by mass, 1.0 ppb or more by mass, 5 ppb or more by mass, or 10 ppb or more by mass.

[0171] The total content of compounds (6-16-1), (6-16-2), (6-16-3), (6-18-1), and (6-18-2) may be less than 5000 ppb by mass, 1000 ppb or less, 900 ppb or less, 800 ppb or less, 700 ppb or less, 600 ppb or less, 500 ppb or less, 400 ppb or less, 300 ppb or less, 200 ppb or less, 100 ppb or less, 50 ppb or less, 25 ppb or less, 10 ppb or less, less than 5 ppb or less, or 1 ppb or less, relative to the mass of PTFE. The above content may be below the limit of quantification as measured by liquid chromatography-mass spectrometry (LC / MS). Furthermore, the above content may be greater than 0 ppb by mass, 0.1 ppb or more by mass, 1.0 ppb or more by mass, 5 ppb or more by mass, or 10 ppb or more by mass.

[0172] In one embodiment, the aqueous dispersion contains compound (6) represented by general formula (6). General formula (6): M ＋ [ － OOC-(CFX) ｎ－２ - COO － ] M ＋ (In the formula, n is an integer from 8 to 21, M ＋X is a cation, and X is F, CF, and F are independent in each occurrence. ３ OCF ３ or OC ３ F ７ (This represents...)

[0173] In one embodiment, the content of compound (6) in the aqueous dispersion is 10,000 ppb by mass or less relative to the mass of PTFE.

[0174] The content of compound (6) is 10000 mass ppb or less, 9000 mass ppb or less, 8000 mass ppb or less, 7000 mass ppb or less, 6000 mass ppb or less, based on the mass of PTFE. Quantity ppb or less, 5000 mass ppb or less, less than 5000 mass ppb, 4000 mass ppb or less, 3000 mass ppb or less, 2000 mass ppb or less, 1000 mass ppb or less The content may be 900 ppb by mass or less, 800 ppb by mass or less, 700 ppb by mass or less, 600 ppb by mass or less, 500 ppb by mass or less, 400 ppb by mass or less, 300 ppb by mass or less, 200 ppb by mass or less, 100 ppb by mass or less, 50 ppb by mass or less, 25 ppb by mass or less, 10 ppb by mass or less, less than 5 ppb by mass, or 1 ppb by mass or less. The above content may be below the limit of quantification as measured by liquid chromatography-mass spectrometry (LC / MS). In addition, the above content may be greater than 0 ppb by mass, 0.1 ppb by mass or more, 1.0 ppb by mass or more, 5 ppb by mass or more, or 10 ppb by mass or more.

[0175] In one embodiment, the aqueous dispersion contains a compound (4-12) represented by the general formula (4-12). General formula (4-12): [H-(CF ２ ) ｍ－１ CO ２ － ] M ＋ (In the formula, m is 12, M ＋ (This represents a cation.)

[0176] In one embodiment, the content of compound (4-12) in the aqueous dispersion is 100 ppb by mass or less relative to the mass of PTFE.

[0177] The content of compound (4-12) may be 100 ppb by mass or less, 50 ppb by mass or less, 25 ppb by mass or less, 10 ppb by mass or less, less than 5 ppb by mass, or 1 ppb by mass or less, relative to the mass of PTFE. Most preferably, the above content may be below the limit of quantification as measured by liquid chromatography-mass spectrometry (LC / MS). Alternatively, the above content may be greater than 0 ppb by mass, 0.1 ppb by mass or more, 1.0 ppb by mass or more, 5 ppb by mass or more, or 10 ppb by mass or more.

[0178] In one embodiment, the aqueous dispersion contains compound (4) represented by general formula (4). General formula (4): [H-(CF ２ ) ｍ－１ CO ２ － ] M ＋ (In the formula, m is an integer from 4 to 20, M ＋ (This represents a cation.)

[0179] In one embodiment, the content of compound (4) in the aqueous dispersion is 10,000 ppb by mass or less relative to the mass of PTFE.

[0180] The content of compound (4) is 110000 mass ppb or less, 9000 mass ppb or less, 8000 mass ppb or less, 7000 mass ppb or less, 6 000 mass ppb or less, 5000 mass ppb or less, 4000 mass ppb or less, 3000 mass ppb or less, 2000 mass ppb or less, 1000 mass ppb or less, 900 quality amount ppb or less, 800 mass ppb or less, 700 mass ppb or less, 600 mass ppb or less, 500 mass ppb or less, 400 mass ppb or less, 300 mass ppb or less, 20 It may be 0 mass ppb or less, 100 mass ppb or less, 50 mass ppb or less, 25 mass ppb or less, 10 mass ppb or less, less than 5 mass ppb, or 1 mass ppb or less. The above content may be below the limit of quantification as measured by liquid chromatography-mass spectrometry (LC / MS). Furthermore, the above content may be greater than 0 ppb by mass, 0.1 ppb or more by mass, 1.0 ppb or more by mass, 5 ppb or more by mass, or 10 ppb or more by mass.

[0181] In one embodiment, the aqueous dispersion of the present disclosure substantially does not contain a fluorine-containing compound having a hydrophilic group.

[0182] In this disclosure, "substantially free of hydrophilic fluorine-containing compounds" means that the content of hydrophilic fluorine-containing compounds in the aqueous dispersion is 10 ppm by mass or less with respect to the mass of PTFE, preferably 1 ppm by mass or less, more preferably 100 ppb by mass or less, even more preferably 10 ppb by mass or less, even more preferably 1 ppb by mass or less, and particularly preferably below the limit of quantification as measured by liquid chromatography-mass spectrometry (LC / MS).

[0183] Furthermore, the content of the hydrophilic fluorine-containing compound in the aqueous dispersion may be less than 500 ppb by mass and greater than 0 ppb by mass. The content of the hydrophilic fluorine-containing compound in the aqueous dispersion may be 100 ppb by mass or less, 50 ppb by mass or less, 25 ppb by mass or less, 20 ppb by mass or less, 10 ppb by mass or less, less than 5 ppb by mass, 3 ppb by mass or less, or 1 ppb by mass or less, relative to the mass of PTFE. Most preferably, the content of the hydrophilic fluorine-containing compound is below the limit of quantification as measured by liquid chromatography-mass spectrometry (LC / MS).

[0184] The hydrophilic group may be anionic, acidic, or acid-base. Examples of hydrophilic groups include -NH ２ , -PO ３ M, -OPO ３ M, -SO ３ M, -OSO ３ M, -COOM (In each formula, M is H, a metal atom, NR) ７ｙ ４ , optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium, R ７ｙ ) is H or an organic group, and may be the same or different. Any two may bond to each other to form a ring. ) are examples of the above hydrophilic group, among others, -PO ３ M, -OPO ３ M, -SO ３M, -OSO ３ M or -COOM is preferred, and -SO ３ M or -COOM is more preferred, and -COOM is even more preferred. ７ｙ Alkyl alkyl groups are preferred as the organic groups in R. ７ｙ For example, H or C １－１０ The organic group is preferably H or C １－４ The organic group is more preferably H or C １－４ A alkyl group is even more preferred.

[0185] Examples of the above-mentioned metal atoms include monovalent and divalent metal atoms, such as alkali metals (Group 1) and alkaline earth metals (Group 2), with Na, K, or Li being preferred.

[0186] In one embodiment of the aqueous dispersion, the compound represented by the following general formula (1) is substantially not contained as a fluorine-containing compound having a hydrophilic group. General formula (1): [X-Rf-A － ] ｉ M ｉ＋ (wherein X is H, Cl, Br, F or I, Rf is a partially fluorinated or fully fluorinated aliphatic group of a linear or branched chain, or a partially fluorinated or fully fluorinated aliphatic group of a linear or branched chain interrupted by at least one oxygen atom, A － is an acid group, M ｉ＋ (where i is a cation with a valency i, and i is an integer from 1 to 3.)

[0187] In one embodiment of the aqueous dispersion, the fluorine-containing compound having a hydrophilic group is substantially free of the compound represented by the following general formula (2): General formula (2): [C ｎ－１ F ２ｎ－１ COO － ] M ＋ (In the formula, n is an integer from 9 to 14, M ＋ (This represents a cation.)

[0188] Compounds represented by general formula (2) (perfluoroalkanoic acid) are known to be formed during polymerization when perfluoroalkyl vinyl ethers or the like are used as modified monomers (see International Publication No. 2019 / 161153).

[0189] In one embodiment of the aqueous dispersion, the compound represented by the following general formula (3) is substantially not contained as a fluorine-containing compound having a hydrophilic group. General formula (3): [R １ -O-L-CO ２ － ] M ＋ (In the formula, R １ L is a partially fluorinated or fully fluorinated aliphatic group of a linear or branched chain, or a partially fluorinated or fully fluorinated aliphatic group of a linear or branched chain interrupted by at least one oxygen atom, L is a non-fluorinated, partially fluorinated or fully fluorinated alkylene group of a linear or branched chain, M ＋ (This represents a cation.)

[0190] In one embodiment of the aqueous dispersion, the compound represented by general formula (5) is substantially not contained as a fluorine-containing compound having a hydrophilic group. General formula (5): [H-(CF ２ ) ｎ SO ３ － ] M ＋ (In the formula, n is an integer from 4 to 20, M ＋ (This represents a cation.)

[0191] In this disclosure, "substantially free of any of the compounds represented by general formulas (1) to (3) and (5)" means that the content of any of the compounds represented by general formulas (1) to (3) and (5) in the aqueous dispersion is less than 500 ppb by mass relative to the mass of PTFE. The content of any of the compounds represented by general formulas (1) to (3) and (5) in the fluoropolymer may be 100 ppb by mass or less, 50 ppb by mass or less, 25 ppb by mass or less, 10 ppb by mass or less, less than 5 ppb by mass, or 1 ppb by mass or less relative to the fluoropolymer. Most preferably, the above content is below the limit of quantification as measured by liquid chromatography-mass spectrometry (LC / MS).

[0192] As a cation, H ＋ Examples include ammonium ions, alkali metal ions, and alkaline earth metal ions.

[0193] Furthermore, examples of fluorine-containing compounds having hydrophilic groups include fluorine-containing surfactants. Examples of fluorine-containing surfactants include fluorine-containing anionic surfactants. That is, in one embodiment of the aqueous dispersion of this disclosure, fluorine-containing surfactants are substantially not contained. Furthermore, in one embodiment of the aqueous dispersion of this disclosure, fluorine-containing anionic surfactants are substantially not contained.

[0194] Typical compounds used as fluorine-containing anionic surfactants are fluorine-containing anionic surfactants with a molecular weight of 1000 g / mol or less, preferably 800 g / mol or less.

[0195] In this disclosure, "substantially free of fluorine-containing surfactants (fluorine-containing anionic surfactants)" means that the content of fluorine-containing surfactants (fluorine-containing anionic surfactants) in the fluoropolymer or composition is 10 ppm by mass or less, preferably 1 ppm by mass or less, more preferably 100 ppb by mass or less, even more preferably 10 ppb by mass or less, and particularly preferably, the amount of fluorine-containing surfactants (fluorine-containing anionic surfactants) measured by liquid chromatography-mass spectrometry (LC / MS) is below the detection limit.

[0196] Examples of the fluorine-containing surfactant (fluorine-containing anionic surfactant) include the compounds shown in the following formula. The fluorine-containing surfactant may be a mixture of these compounds. F(CF) ２ ) ５ COOM, CF ３ O(CF) ２ ) ３ OCHFCF ２ COOM, C ３ F ７ OCF (CF ３ ) CF ２ OCF (CF ３ ) COOM, CF ３ CF ２ CF ２ OCF (CF ３ ) COOM, CF ３ CF ２ OCF ２ CF２ OCF ２ COOM, C ２ F ５ OCF (CF ３ ) CF ２ OCF (CF ３ ) COOM, CF ３ OCF (CF ３ ) CF ２ OCF (CF ３ ) COOM, CF ２ ClCF ２ CF ２ OCF (CF ３ ) CF ２ OCF ２ COOM, CF ２ ClCF ２ CF ２ OCF ２ CF (CF ３ ) OCF ２ COOM, CF ２ ClCF(CF ３ )OCF(CF ３ ) CF ２ OCF ２ COOM, CF ２ ClCF(CF ３ ) OCF ２ CF (CF ３ ) OCF ２ COOM, and, (In each formula, M is H, metal atom, NR １ ４ , optionally substituted imidazolium, optionally substituted pyridinium, or optionally substituted phosphonium. １ (This is either H or an organic group.)

[0197] The content of surfactants, such as fluorine-containing surfactants, can be quantified by known methods. For example, it can be quantified by LC / MS analysis. First, methanol is added to an aqueous dispersion, extraction is performed, and the obtained extract is analyzed by LC / MS. To further improve the extraction efficiency, treatment by Soxhlet extraction, sonication, etc., may be performed. Molecular weight information is extracted from the obtained LC / MS spectrum and its agreement with the structural formula of the candidate surfactant is confirmed. Then, aqueous solutions with five or more levels of the confirmed surfactant content are prepared, and LC / MS analysis is performed on each aqueous solution with the respective content. The relationship between the content and the area area corresponding to that content is plotted, and a calibration curve is drawn. Then, using the calibration curve, the area area of ​​the LC / MS chromatogram of the surfactant in the extract can be converted to the surfactant content.

[0198] In one embodiment, the aqueous dispersion is an aqueous dispersion obtained by carrying out emulsion polymerization of at least tetrafluoroethylene in the presence of a polymerization initiator and water. The amount of polymerization initiator used is preferably 0.00001 to 10% by mass, more preferably 0.0001% by mass or more, even more preferably 0.001% by mass or more, even more preferably 0.01% by mass or more, preferably 5% by mass or less, and more preferably 2% by mass or less, relative to the aqueous medium. In polymerization to obtain the aqueous dispersion, it is preferable to use a relatively large amount of polymerization initiator. By increasing the amount of polymerization initiator used, emulsion polymerization can proceed more smoothly even in the absence of a surfactant.

[0199] The PTFE content in the aqueous dispersion is preferably 10% by mass or more, more preferably 15% by mass or more, preferably 75% by mass or less, more preferably 73% by mass or less, even more preferably 71% by mass or less, and particularly preferably 70% by mass or less, based on the mass of the aqueous dispersion.

[0200] In one embodiment, the aqueous dispersion contains a nonionic surfactant. As the nonionic surfactant added to the aqueous dispersion (A), the above-mentioned nonionic surfactant can be used.

[0201] The content of the nonionic surfactant in the aqueous dispersion is preferably 4.0 to 12% by mass, more preferably 5.0% by mass or more, and more preferably 10% by mass or less, relative to the PTFE.

[0202] The nonionic surfactant content is calculated using the formula: N = [(Y - Z) / Z] × 100 (mass%), from the heating residue (Yg) obtained by heating approximately 1 g (Xg) of the sample at 110°C for 30 minutes, and the heating residue (Zg) obtained by further heating the obtained heating residue (Yg) at 300°C for 30 minutes.

[0203] The PTFE contained in the aqueous dispersion may have the same composition as the PTFE in the aqueous dispersion obtained by the manufacturing method of this disclosure. Therefore, the PTFE contained in the aqueous dispersion may be high molecular weight PTFE or low molecular weight PTFE. Furthermore, the PTFE contained in the aqueous dispersion may be non-melt-processable PTFE or melt-processable PTFE.

[0204] In one embodiment, the PTFE contained in the aqueous dispersion has a carboxylic acid group.

[0205] The number of carboxylic acid groups (-COOH groups) is 10 carbon atoms. ６ Preferably, there are 5 or more per unit, more preferably 30 or more, even more preferably 40 or more, and still more preferably 50 or more.

[0206] If the PTFE is non-melt-processable PTFE, the number of carboxylic acid groups (-COOH groups) in the PTFE is 10 carbon atoms. ６ Preferably, there are 5 or more per unit, more preferably 30 or more, even more preferably 40 or more, and still more preferably 50 or more.

[0207] If the PTFE is melt-processable PTFE, the number of carboxylic acid groups (-COOH groups) in the PTFE is 10 carbon atoms. ６ Each unit may contain 30 or more, preferably 50 or more, more preferably 100 or more, even more preferably 150 or more, and still more preferably 200 or more.

[0208] The upper limit of the number of carboxylic acid groups (-COOH groups) in PTFE varies depending on the molecular weight of the PTFE, but for example, if there are 10 carbon atoms... ６ Each item may contain 500 or fewer units.

[0209] The number of carboxylic acid groups can be measured in accordance with the method for analyzing end groups described in Japanese Patent Publication No. 4-20507. Specifically, PTFE is pre-formed by hand pressing to produce a film with a thickness of approximately 0.1 mm. The prepared film is subjected to infrared absorption spectroscopy. Infrared absorption spectroscopy is also performed on PTFE with completely fluorinated ends, which is prepared by contacting PTFE with fluorine gas, and the number of carboxylic acid groups is calculated from the difference spectra of the two using the following formula: Number of carboxylic acid groups (10 carbon atoms) ６ Absorbance per unit = (l × K) / t l: absorbance K: correction factor t: film thickness (mm) The absorption frequency of the carboxylic acid group is 3560 cm⁻¹ －１ The correction factor will be 440.

[0210] Carboxylic acid groups can be introduced into PTFE, for example, by using persulfates as polymerization initiators during polymerization.

[0211] The average primary particle size of the PTFE contained in the aqueous dispersion is 500 nm or less, preferably 450 nm or less, more preferably 400 nm or less, even more preferably 350 nm or less, even more preferably 300 nm or less, particularly preferably 250 nm or less, preferably 10 nm or more, more preferably 100 nm or more, and even more preferably 150 nm or more. The average primary particle size of the fluoropolymer can be adjusted to the above range by producing the fluoropolymer using an emulsion polymerization method.

[0212] The average primary particle diameter is the average particle diameter of primary particles dispersed in an aqueous dispersion, and is different from the average particle diameter of secondary particles (powder) formed by the aggregation of primary particles. The average primary particle diameter can be measured by dynamic light scattering. First, an aqueous dispersion is prepared with a polymer solid content concentration of approximately 1.0 mass%, and then measured using dynamic light scattering with a measurement temperature of 25°C, a refractive index of 1.3328 for the solvent (water), a viscosity of 0.8878 mPa·s for the solvent (water), and 70 cumulative measurements. For example, the ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.) can be used for dynamic light scattering.

[0213] Furthermore, the average primary particle diameter can also be measured by the following method: Dilute the dispersion with water until the solid content concentration reaches 0.15% by mass. Measure the transmittance of 550 nm projection light per unit length of the resulting diluted latex, and the average particle diameter determined by measuring the directional diameter using a transmission electron microscope image, to create a calibration curve. Using this calibration curve, the average particle diameter can be determined from the measured transmittance of 550 nm projection light for each sample.

[0214] In one embodiment, the aqueous dispersion contains a viscosity modifier. Suitable viscosity modifiers include alkyl sulfates such as lauryl sulfate, alkylaryl sulfonic acids such as dodecylbenzenesulfonic acid, alkyl sulfosuccinates and their salts, and fluorine-free anionic surfactants. The viscosity modifier content in the aqueous dispersion is preferably 10 to 5000 ppm by mass, more preferably 50 ppm by mass or more, even more preferably 100 ppm by mass or more, even more preferably 4000 ppm by mass or less, and even more preferably 3000 ppm by mass or less, relative to PTFE.

[0215] In one embodiment, the aqueous dispersion contains a preservative. Examples of preservatives include isothiazolone-based, azole-based, pronopol, chlorothalonil, methylsulfonyltetrachlorpyrozine, carbentadium, fluorophorbet, sodium diacetate, and diiodomethylparatolylsulfone. The preservative content in the aqueous dispersion is preferably 0.01 to 0.5% by mass, more preferably 0.05% by mass or more, and more preferably 0.2% by mass or less, relative to PTFE.

[0216] The aqueous dispersion may contain other components. Examples of other components include water-soluble polymer compounds. Examples of water-soluble polymer compounds include methylcellulose, alumina sol, polyvinyl alcohol, carboxylated vinyl polymer, polyethylene oxide (dispersion stabilizer), polyethylene glycol (dispersion stabilizer), polyvinylpyrrolidone (dispersion stabilizer), phenol resin, urea resin, epoxy resin, melamine resin, polyester resin, polyether resin, acrylic silicone resin, silicone resin, silicone polyester resin, and polyurethane resin.

[0217] The aqueous dispersion obtained by the manufacturing method of the present disclosure, and the aqueous dispersion of the present disclosure, can be used, for example, as a paint. Known pigments, thickeners, dispersants, defoamers, antifreeze agents, film-forming aids, and other polymer compounds may be added to the aqueous dispersion. Furthermore, the aqueous dispersion obtained by the manufacturing method of the present disclosure, and the aqueous dispersion of the present disclosure, can be used in known applications, such as processing aids, binders for batteries, dust suppression agents, raw materials for obtaining PTFE fibers, additives, and raw materials for impregnating glass fiber cloth. By impregnating glass fiber cloth with the aqueous dispersion of the present disclosure, an impregnated fiber cloth having a smooth surface can be obtained.

[0218] Although embodiments have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of the claims.

[0219] <1> According to the first aspect of this disclosure, a method for producing an aqueous polytetrafluoroethylene dispersion is provided, comprising: preparing an aqueous dispersion (A) containing polytetrafluoroethylene by carrying out emulsion polymerization of at least tetrafluoroethylene in the presence of water and substantially in the absence of a surfactant; and preparing an aqueous dispersion (B) by contacting the aqueous dispersion (A) with an adsorbent, wherein the aqueous dispersion (A) contains at least one compound selected from the group consisting of compound (6-16) represented by general formula (6-16), compound (6-18) represented by general formula (6-18), and compound (6-20) represented by general formula (6-20). General formula (6-16): M ＋ [ － OOC-(CFX) ｎ－２ - COO － ] M ＋ (In the formula, n is 16, M ＋ X is a cation, and X is F, CF, and F are independent in each occurrence. ３ OCF ３ or OC ３ F ７ (Represents.) General formula (6-18): M ＋ [ － OOC-(CFX) ｎ－２ - COO － ] M ＋ (In the formula, n is 18, M ＋ X is a cation, and X is F, CF, and F are independent in each occurrence. ３ OCF ３ or OC ３ F ７ (Represents.) General formula (6-20): M ＋ [ － OOC-(CFX) ｎ－２ - COO － ] M ＋ (In the formula, n is 20, M ＋ X is a cation, and X is F, CF, and F are independent in each occurrence. ３ OCF ３ or OC ３ F ７) <2> According to a second aspect of this disclosure, a manufacturing method according to a first aspect is provided, wherein the adsorbent is at least one selected from the group consisting of ion exchange resin, synthetic adsorbent, silica gel, polymer adsorbent, activated carbon, diatomaceous earth and zeolite. <3> According to a third aspect of this disclosure, a manufacturing method according to a first or second aspect is provided, wherein the adsorbent is an anion exchange resin. <4> According to a fourth aspect of this disclosure, a manufacturing method according to any one of the first to third aspects is provided, wherein the total content of compound (6-16), compound (6-18) and compound (6-20) in an aqueous dispersion (A) is more than 1000 ppb by mass with respect to the mass of polytetrafluoroethylene. <5> According to the fifth aspect of this disclosure, a manufacturing method according to any of the first to fourth aspects is provided, wherein the total content of compounds (6-16), (6-18), and (6-20) in the aqueous dispersion (A) is 5,000 ppb by mass or more with respect to the mass of the polytetrafluoroethylene. <6> According to the sixth aspect of this disclosure, a manufacturing method according to any of the first to fifth aspects is provided, wherein the aqueous dispersion (A) contains compound (4-12) represented by general formula (4-12), and the content of compound (4-12) in the aqueous dispersion (A) is more than 100 ppb by mass with respect to the mass of the polytetrafluoroethylene. General formula (4-12): [H-(CF ２ ) ｍ－１ CO ２ － ] M ＋ (In the formula, m is 12, M ＋∫ represents a cation.) <7> According to the seventh aspect of this disclosure, a manufacturing method according to any of the first to sixth aspects is provided, wherein a nonionic surfactant is added to an aqueous dispersion (A), and then the aqueous dispersion (A) is brought into contact with the adsorbent. <8> According to the eighth aspect of this disclosure, a manufacturing method according to any of the first to seventh aspects is provided, wherein an aqueous dispersion (A) is brought into contact with the adsorbent, and then a nonionic surfactant is added to prepare an aqueous dispersion (B). <9> According to the ninth aspect of this disclosure, a manufacturing method according to any of the first to eighth aspects is provided, wherein an aqueous dispersion (A) is brought into contact with the adsorbent, a nonionic surfactant is added, and then the aqueous dispersion containing the nonionic surfactant is concentrated to prepare an aqueous dispersion (B). <10> According to the tenth aspect of this disclosure, a manufacturing method according to any of the first to ninth aspects is provided, wherein the total content of compounds (6-16), (6-18), and (6-20) in the aqueous dispersion (B) is less than 5,000 ppb by mass with respect to the mass of the polytetrafluoroethylene. <11> According to the eleventh aspect of this disclosure, a manufacturing method according to any of the first to tenth aspects is provided, wherein the total content of compounds (6-16), (6-18), and (6-20) in the aqueous dispersion (B) is 1,000 ppb by mass or less with respect to the mass of the polytetrafluoroethylene. <12> According to the twelfth aspect of this disclosure, a manufacturing method according to any of the first to eleventh aspects is provided, wherein the content of compound (4-12) in the aqueous dispersion (B) is 100 ppb by mass or less with respect to the mass of the polytetrafluoroethylene. <13> According to the thirteenth aspect of this disclosure, there is an aqueous dispersion containing polytetrafluoroethylene and water, which contains at least one compound selected from the group consisting of a compound represented by general formula (6-16) (6-16), a compound represented by general formula (6-18) (6-18), a compound represented by general formula (6-20) (6-20), and a compound represented by general formula (4-12) (4-12), and which is substantially free of fluorine-containing anionic surfactants. General formula (6-16): M ＋ [ － OOC-(CFX)ｎ－２ - COO － ] M ＋ (In the formula, n is 16, M ＋ X is a cation, and X is F, CF, and F are independent in each occurrence. ３ OCF ３ or OC ３ F ７ (Represents.) General formula (6-18): M ＋ [ － OOC-(CFX) ｎ－２ - COO － ] M ＋ (In the formula, n is 18, M ＋ X is a cation, and X is F, CF, and F are independent in each occurrence. ３ OCF ３ or OC ３ F ７ (Represents.) General formula (6-20): M ＋ [ － OOC-(CFX) ｎ－２ - COO － ] M ＋ (In the formula, n is 20, M ＋ X is a cation, and X is F, CF, and F are independent in each occurrence. ３ OCF ３ or OC ３ F ７ This represents...) General formula (4-12): [H-(CF ２ ) ｍ－１ CO ２ － ] M ＋ (In the formula, m is 12, M ＋∫ represents a cation.) <14> According to the 14th aspect of this disclosure, an aqueous dispersion according to the 13th aspect is provided, wherein the total content of compound (6-16), compound (6-18), and compound (6-20) is less than 5000 ppb by mass with respect to the mass of the polytetrafluoroethylene. <15> According to the 15th aspect of this disclosure, an aqueous dispersion according to the 13th or 14th aspect is provided, wherein the total content of compound (6-16), compound (6-18), and compound (6-20) is 1000 ppb by mass or less with respect to the mass of the polytetrafluoroethylene. <16> According to the 16th aspect of this disclosure, an aqueous dispersion according to the 13th to 15th aspects is provided, wherein the content of compound (4-12) is 100 ppb by mass or less with respect to the mass of the polytetrafluoroethylene. <17> According to the 17th aspect of this disclosure, an aqueous dispersion according to any of the 13th to 16th aspects is provided, wherein the content of the polytetrafluoroethylene is 10% by mass or more relative to the mass of the aqueous dispersion. <18> According to the 18th aspect of this disclosure, an aqueous dispersion according to any of the 13th to 17th aspects is provided, which contains a nonionic surfactant. <19> According to the 19th aspect of this disclosure, an aqueous dispersion according to any of the 13th to 18th aspects is provided, which contains a nonionic surfactant, wherein the content of the nonionic surfactant is 4.0 to 12% by mass relative to the mass of the polytetrafluoroethylene. <20> According to the 20th aspect of this disclosure, an aqueous dispersion according to any of the 13th to 19th aspects is provided, wherein the polytetrafluoroethylene is non-melt processable. <21> According to the 21st aspect of this disclosure, the polytetrafluoroethylene has carboxylic acid groups, and the number of carboxylic acid groups is 10 carbon atoms. ６ Each unit provides an aqueous dispersion according to any of the 13th to 20th viewpoints, with five or more elements present.

[0220] Next, embodiments of the present disclosure will be described with reference to examples, but the present disclosure is not limited to such embodiments.

[0221] Each value in the examples was measured by the following method.

[0222] <Solid content concentration (content) of raw material liquid> One g of the sample was dried in a forced-air dryer at 170°C for 20 minutes, and the value obtained by expressing the ratio of the mass of the heating residue to the mass of the sample (1 g) as a percentage was adopted.

[0223] <Solid content concentration (P) of PTFE aqueous dispersion> The solid content concentration of the PTFE aqueous dispersion was calculated from the amount charged. When the solid content concentration changes due to concentration, the ratio of concentrated phase to unconcentrated phase and the composition of each phase were also taken into consideration in the calculation.

[0224] <Nonionic surfactant content (N)> The nonionic surfactant content was calculated from the amount used. If the content changes due to concentration, the ratio of concentrated phase to unconcentrated phase and the composition of each phase were also taken into consideration in the calculation.

[0225] <Average Primary Particle Size> The aqueous dispersion was diluted with water until the solid content concentration was 0.15% by mass. A calibration curve was created by measuring the transmittance of 550 nm projected light per unit length of the resulting diluted aqueous dispersion and the average primary particle size determined by measuring the directional diameter using transmission electron microscopy. Using this calibration curve, the average primary particle size was determined from the measured transmittance of 550 nm projected light for each sample.

[0226] <Standard Specific Gravity (SSG)> Samples molded in accordance with ASTM D4895-89 were used, and the SSG was measured by the water displacement method in accordance with ASTM D-792.

[0227] <Melting Point (Peak Temperature)> Approximately 10 mg of PTFE that has not been heated to temperatures above 300°C is accurately weighed and placed in a dedicated aluminum pan. The melting point is then measured using a TG / DTA (Differential Thermal Gravimetric Analysis) device. The peak temperature is determined by heating the aluminum pan in an atmospheric environment from 25°C to 600°C at a rate of 10°C / min, and using the temperature corresponding to the maximum value of the differential thermal (DTA) curve.

[0228] <General formula (4): [H-(CF ２ ) ｍ－１ CO ２ － ] M ＋ Measurement of the compound content indicated by > The following measurements were performed using liquid chromatography-mass spectrometry.

[0229] Extraction from aqueous dispersion: 5.0 g of aqueous dispersion was weighed, 10 g of methanol was added, and the mixture was poured into a cylindrical filter paper. Soxhlet extraction was performed until the total amount of methanol used as the extraction solvent reached 150 g. The resulting extract was then diluted with methanol to a volume of 250 ml to obtain an extract containing the compound represented by general formula (4). The obtained extract was further concentrated by nitrogen purging as appropriate to obtain a concentrated extract.

[0230] The content of the compound represented by general formula (4) in the extract was determined by converting it to perfluorooctanoic acid.

[0231] Calibration Curve for Perfluorooctanoic Acid Five levels of methanol standard solutions of perfluorooctanoic acid with known concentrations ranging from 1 ng / mL to 100 ng / mL were prepared and measured using a liquid chromatograph-mass spectrometer (Waters, LC-MS ACQUITY UPLC / TQD). Using a first-order approximation from the concentration of each sample and the integral value of the peak, a and b were determined using the following relationship (1): A = a × X + b (1) A: Peak area of ​​perfluorooctanoic acid X: Concentration of perfluorooctanoic acid (ng / mL)

[0232] Measurement equipment configuration and LC-MS measurement conditions

[0233] MRM measurement parameters (MRM: Multiple Reaction Monitoring)

[0234] The content of the compound represented by general formula (4) with 12 carbon atoms in the extract was measured using a liquid chromatograph-mass spectrometer. The peak area of ​​the compound represented by general formula (4) with 12 carbon atoms was determined from the extracted liquid phase using the MRM method.

[0235] MRM measurement parameters

[0236] The content of the compound represented by general formula (4) for a number of carbon atoms in the extract was calculated using the following formula (3). a and b in formula (3) were obtained from formula (1). XCm = ((ACm - b) / a) × ((50 × (m - 1) + 45) / 413) (3) XCm: Content of the compound represented by general formula (4) for a number of carbon atoms in the extract (ng / mL) ACm: Peak area of ​​the compound represented by general formula (4) for a number of carbon atoms in the extract The limit of quantification in this measurement is 1 ng / mL.

[0237] The content of the compound represented by general formula (4) with several carbon atoms in the aqueous dispersion was determined by the following formula (4): YCm = XCm × 50.0(4) YCm: Content of the compound represented by general formula (4) with several carbon atoms in the aqueous dispersion The limit of quantification is 50 ppb by mass.

[0238] <General formula (6): M ＋ [ － OOC-(CFX) ｎ－２ - COO － ] M ＋ Measurement of the compound content indicated by > The following measurements were performed using liquid chromatography-mass spectrometry.

[0239] Extraction from aqueous dispersion: 5.0 g of aqueous dispersion was weighed, 10 g of methanol was added, and the mixture was poured into a cylindrical filter paper. Soxhlet extraction was performed until the total amount of methanol used as the extraction solvent reached 150 g. The resulting extract was then diluted with methanol to a volume of 250 ml to obtain an extract containing the compound represented by general formula (6). The obtained extract was further concentrated by purging with nitrogen as appropriate to obtain a concentrated extract.

[0240] The content of compounds represented by general formulas (6-16-1) and (6-18-1) in the extract was determined by converting them to dodecafluorosuberic acid.

[0241] Calibration Curve of Dodecafluorosveric Acid Five levels of methanol standard solutions of dodecafluorosveric acid with known concentrations ranging from 20 ng / mL to 500 ng / mL were prepared and measured using a liquid chromatograph-mass spectrometer (Waters, LC-MS ACQUITY UPLC / TQD). Using a first-order approximation from the integral values ​​of the peaks of each sample, a and b were determined using the following relationship (5): A = a × X + b (5) A: Peak area of ​​dodecafluorosveric acid X: Concentration of dodecafluorosveric acid (ng / mL)

[0242] Measurement equipment configuration and LC-MS measurement conditions

[0243] MRM measurement parameters

[0244] The content of compounds represented by general formulas (6-16-1) and (6-18-1) in the extract was measured using a liquid chromatograph-mass spectrometer. The peak areas of the compounds represented by general formulas (6-16-1) and (6-18-1) were determined from the extracted liquid phase using the MRM method.

[0245] Of the compounds represented by general formula (6), the compounds represented by general formula (6-16-1) (6-16-1) and general formula (6-18-1) (6-18-1) were targeted for measurement. General formula (6-16-1): M ＋ [ － OOC-(CF ２ ) １４ - COO － ] M ＋ (In the formula, M ＋ represents a cation. ) General formula (6-18-1): M ＋ [ － OOC-(CF ２ ) １６ - COO － ] M ＋ (In the formula, M ＋ (This represents a cation.)

[0246] MRM measurement parameters

[0247] The content of the compound represented by general formula (6) in the extract was calculated using the following formula (6). a and b in formula (6) were obtained from formula (5). XCn = ((ACn - b) / a) × ((50 × c + 116 × d + 89) / 389) (6) XCn: Content of the compound represented by general formula (6) in the extract (ng / mL) ACn: Peak area of ​​the content of the compound represented by general formula (6) in the extract The limit of quantification in this measurement is 20 ng / mL.

[0248] Content of the compound represented by general formula (6) in the aqueous dispersion The content of the compound represented by general formula (6) in the aqueous dispersion was determined by the following formula (7): YCn = XCn × 50 (7) YCn: Content of the compound represented by general formula (6) in the aqueous dispersion (ppb vs. aqueous dispersion) The limit of quantification is 1000 ppb by mass.

[0249] The content of compounds represented by general formulas (6-16-2), (6-16-3), (6-18-2), and (6-20-1) in the extract was determined by converting them to dodecafluorosuberic acid.

[0250] Calibration Curve of Dodecafluorosveric Acid Five levels of methanol standard solutions of dodecafluorosveric acid with known concentrations ranging from 20 ng / mL to 500 ng / mL were prepared and measured using a liquid chromatograph-mass spectrometer (Waters, LC-MS ACQUITY UPLC / TQD). Using a first-order approximation from the integral values ​​of the peaks of each sample, a and b were determined using the following relationship (5): A = a × X + b (5) A: Peak area of ​​dodecafluorosveric acid X: Concentration of dodecafluorosveric acid (ng / mL)

[0251] Measurement equipment configuration and LC-MS measurement conditions

[0252] SIM measurement parameters (SIM: Selected Ion Monitoring)

[0253] The content of compounds represented by general formulas (6-16-2), (6-16-3), (6-18-2), and (6-20-1) in the extract was measured using a liquid chromatograph-mass spectrometer. The peak areas of the compounds represented by general formulas (6-16-2), (6-16-3), (6-18-2), and (6-20-1) were determined from the extracted liquid phase using the SIM method.

[0254] Of the compounds represented by general formula (6), the compounds represented by general formula (6-16-2) (6-16-2), general formula (6-16-3) (6-16-3), general formula (6-18-2) (6-18-2), and general formula (6-20-1) (6-20-1) were targeted for measurement. General formula (6-16-2): M ＋ [ － OOC-(CF ２ ) １２ - (CF (OCF ３ )) ２ - COO － ] M ＋ (In the formula, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of ) is arbitrary in the formula. ) General formula (6-16-3): M ＋ [ － OOC-(CF ２ ) １１ - (CF (OCF ３ )) ３ - COO － ] M ＋ (In the formula, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of ) is arbitrary in the formula. ) General formula (6-18-2): M ＋ [ － OOC-(CF ２ ) １５ - (CF (OCF ３ )) １ - COO－ ] M ＋ (In the formula, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of ) is arbitrary in the formula. ) General formula (6-20-1): M ＋ [ － OOC-(CF ２ ) １４ - (CF (OCF ３ )) ４ - COO － ] M ＋ (In the formula, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of the elements in the formula is arbitrary.

[0255] SIM measurement parameters

[0256] The content of the compound represented by general formula (6) in the extract was calculated using the following formula (6). a and b in formula (6) were obtained from formula (5). XCn = ((ACn - b) / a) × ((50 × c + 116 × d + 89) / 389) (6) XCn: Content of the compound represented by general formula (6) in the extract (ng / mL) ACn: Peak area of ​​the content of the compound represented by general formula (6) in the extract The limit of quantification in this measurement is 20 ng / mL.

[0257] Content of the compound represented by general formula (6) in the aqueous dispersion The content of the compound represented by general formula (6) in the aqueous dispersion was determined by the following formula (7): YCn = XCn × 50 (7) YCn: Content of the compound represented by general formula (6) in the aqueous dispersion (ppb vs. aqueous dispersion) The limit of quantification is 1000 ppb by mass.

[0258] <Surface Smoothness of Impregnated Fiber Cloth> In accordance with the method described in Japanese Patent Publication No. 8-269285, glass fiber cloth (ATE11100, 104.7 g / m2, manufactured by Sakai Sangyo Co., Ltd.) was impregnated with an aqueous PTFE dispersion, dried, and baked at 380°C for 3 minutes. The impregnation, drying, and baking process was repeated to obtain a fabric (impregnated fiber cloth) containing 70-80% by mass of PTFE. The surface of a 10 cm square piece of the fabric was traced with an index finger, and the smoothness was evaluated by touch (feel of unevenness) according to the following criteria. Good: No unevenness felt. Fair: 10 or fewer unevenness felt. Bad: More than 10 unevenness felt.

[0259] Polymerization Example 1 <Preparation of Raw Material Solution A-1> 3309 g of deionized water was placed in a 6.0 L stainless steel pressure-resistant reaction vessel, the reactor was sealed, and while heating to 70°C, suction was applied and the reactor was purged with TFE to remove oxygen from the reactor, and the contents were stirred. Then, 233 g of PMVE and 41 g of TFE were placed in the reactor, and the temperature was raised to 90°C while stirring at 120 rpm. Next, 0.83 g of ammonium persulfate (APS) dissolved in 10 g of deionized water was added as an initiator, and polymerization was started. The pressure at the start of polymerization was 1.3 MPaG. As polymerization started, the pressure in the reactor decreased, so TFE was added to maintain a constant pressure of 1.3 MPaG. After 8 g of TFE was injected under pressure, the supply of TFE was stopped, stirring was stopped, and the reaction was terminated. Then, the reactor was evacuated until the pressure in the reactor reached atmospheric pressure, the contents were removed from the reactor and cooled to obtain Raw Material Solution A-1. The solid content concentration of raw material liquid A-1 was 0.61% by mass.

[0260] <Preparation of Raw Material Solution B-1> 127 g of AmberLite HPR650H (DuPont, cation exchange resin) was added to 3100 g of Raw Material Solution A-1. After 60 minutes of stirring, the raw material solution and ion exchange resin were filtered off. 127 g of Purolite A300 (Purolite, anion exchange resin) was added to the filtered raw material solution. After 60 minutes of stirring, the raw material solution and ion exchange resin were filtered off to obtain Raw Material Solution B-1. The solid content concentration of Raw Material Solution B-1 was 0.56% by mass.

[0261] <Preparation of Aqueous Dispersion (A-1)> 1158 g of deionized water, 2442 g of raw material solution B-1, and 180 g of paraffin wax were charged into a 6.0 L stainless steel reactor. The reactor was sealed and heated to 70°C while being suctioned and simultaneously purged with TFE to remove oxygen from the reactor, and the contents were stirred at 160 rpm. 0.06 g of ammonium persulfate dissolved in 10 g of deionized water was added, and the reactor pressure was increased to 1.4 MPaG using TFE. A decrease in pressure was observed, and thereafter TFE was added to the reactor to maintain the pressure at 1.4 MPaG. When the amount of TFE consumed in the reaction reached 685 g, the supply of TFE was stopped, stirring was stopped, and the reaction was terminated. After that, the reactor was evacuated until the pressure returned to atmospheric pressure, the contents were removed from the reactor and cooled, and the separated paraffin was removed to obtain PTFE aqueous dispersion (A-1).

[0262] The solid content concentration of the obtained PTFE aqueous dispersion (A-1), calculated from the amount charged, was 16.9% by mass, and the average primary particle size was 198 nm.

[0263] The total content of the compounds represented by the following three general formulas in the PTFE aqueous dispersion (A-1) was 27,386 ppb by mass relative to the PTFE. General formula (6-16-1): M ＋ [ － OOC-(CF ２ ) １４ - COO － ] M ＋ (In the formula, M ＋ represents a cation. ) General formula (6-16-2): M ＋ [ － OOC-(CF ２ ) １２ - (CF (OCF ３ )) ２ - COO － ] M ＋ (In the formula, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of ) is arbitrary in the formula. ) General formula (6-16-3): M ＋ [ － OOC-(CF ２ ) １１ - (CF (OCF３ )) ３ - COO － ] M ＋ (In the formula, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of the elements in the formula is arbitrary.

[0264] The total content of the compounds represented by the following three general formulas in the PTFE aqueous dispersion (A-1) was 30,283 ppb by mass relative to the PTFE. General formula (6-18-1): M ＋ [ － OOC-(CF ２ ) １６ - COO － ] M ＋ (In the formula, M ＋ (where represents a cation) General formula (6-18-2): M ＋ [-OOC-(CF ２ ) １５ - (CF (OCF ３ )) １ - COO － ] M ＋ (In the formula, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of ) is arbitrary in the formula. ) General formula (6-20-1): M ＋ [ － OOC-(CF ２ ) １４ - (CF (OCF ３ )) ４ - COO － ] M ＋ (In the formula, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of the elements in the formula is arbitrary.

[0265] PTFE aqueous dispersion (A-1) containing general formula (4-12): [H-(CF ２ ) ｍ－１ CO ２ － ] M ＋ (In the formula, m is 12, M ＋The compound represented by (where represents a cation) was 344 mass ppb relative to PTFE.

[0266] The obtained PTFE aqueous dispersion (A-1) was diluted to a solid content concentration of 15% by mass using deionized water, and coagulated by high-speed stirring to obtain a wet polymer. The obtained wet polymer was dried at 150°C for 18 hours to obtain PTFE powder. The standard specific gravity of the obtained PTFE powder was 2.228, and the peak temperature measured by TG was 335°C.

[0267] Experimental Example 1 2800 g of PTFE aqueous dispersion (A-1) was mixed with 23.7 g of TDS-80 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a nonionic surfactant, and then 567.8 g of A400OH (manufactured by Purolite, anion exchange resin) was added. 60 minutes after stirring began, the aqueous dispersion and ion exchange resin were filtered off. The total content of the compounds represented by general formula (6-18-1), general formula (6-18-2), and general formula (6-20-1) in the PTFE aqueous dispersion obtained after the first ion exchange treatment was 7,412 ppb by mass. This operation was repeated one more time to obtain PTFE aqueous dispersion (B-1).

[0268] To an aqueous PTFE dispersion (B-1), TDS-80 was added as a nonionic surfactant to a concentration of 18% by mass relative to the PTFE. The mixture was kept at 63°C for 3 hours and separated into a supernatant phase and a concentrated phase. Only the concentrated phase was collected to obtain an aqueous PTFE dispersion (C-1).

[0269] The obtained aqueous dispersion (C-1) had a solid content concentration of 64.2% by mass, and the nonionic surfactant content was 3.2% by mass relative to PTFE.

[0270] To the aqueous PTFE dispersion (C-1), TDS-80 was added as a nonionic surfactant at a concentration of 5.5% by mass relative to the PTFE. Ammonium lauryl sulfate was added as a viscosity modifier at 1000 ppm relative to the PTFE, an isothiazolone-based preservative at 1000 ppm relative to the PTFE, and 28% aqueous ammonia was added as a pH adjuster. Furthermore, deionized water was added to bring the solid content to 60% by mass to obtain the aqueous PTFE dispersion (D-1).

[0271] The obtained PTFE aqueous dispersion (D-1) had a solid content concentration of 60.0% by mass, a nonionic surfactant content of 5.5% by mass relative to the PTFE, a pH of 9.5, and a viscosity of 26.2 mPa·s.

[0272] The content of the compound represented by general formula (6-16-1), the compound represented by general formula (6-16-2), and the compound represented by general formula (6-16-3) in the PTFE aqueous dispersion (D-1) was all below the limit of quantification.

[0273] The content of the compound represented by general formula (6-18-1), the compound represented by general formula (6-18-2), and the compound represented by general formula (6-20-1) in the PTFE aqueous dispersion (D-1) was all below the limit of quantification.

[0274] PTFE aqueous dispersion (D-1) containing general formula (4-12): [H-(CF ２ ) ｍ－１ CO ２ － ] M ＋ (In the formula, m is 12, M ＋ The content of the compound indicated by (where represents a cation) was below the limit of quantification.

[0275] The surface smoothness of the impregnated fiber cloth obtained using the PTFE aqueous dispersion (D-1) was good, with no noticeable irregularities.

[0276] Experimental Example 2 This experimental example demonstrates that when an aqueous dispersion is prepared using a conventional technique that involves polymerization in the presence of a fluorinated anionic surfactant such as ammonium perfluoroethercarboxylate, the compounds represented by general formula (6-16), general formula (6-18), and general formula (6-20) are not formed.

[0277] A PTFE aqueous dispersion (1A) was obtained in accordance with Production Example 1 described in International Publication No. 2025 / 037634. ​​The solid content concentration of the obtained PTFE aqueous dispersion (1A), calculated from the amount charged, was 26.5% by mass, the average primary particle size was 295 nm, and the perfluoroether carboxylic acid A content was 12,372 ppm by mass relative to the PTFE.

[0278] The content of the compound represented by general formula (6-16-1), the compound represented by general formula (6-16-2), and the compound represented by general formula (6-16-3) in the PTFE aqueous dispersion (1A) was all below the limit of quantification.

[0279] The content of the compound represented by general formula (6-18-1), the compound represented by general formula (6-18-2), and the compound represented by general formula (6-20-1) in the PTFE aqueous dispersion (1A) was all below the limit of quantification.

[0280] PTFE aqueous dispersion (1A) containing general formula (4-12): [H-(CF ２ ) ｍ－１ CO ２ － ] M ＋ (In the formula, m is 12, M ＋ The content of the compound indicated by (where represents a cation) was below the limit of quantification.

[0281] Polymerization Example 2 <Preparation of Raw Material Solution A-2> 3309 g of deionized water was placed in a 6.0 L stainless steel pressure-resistant reaction vessel, the reactor was sealed, and while heating to 70°C, suction was applied and the reactor was purged with TFE to remove oxygen from the reactor, and the contents were stirred. Then, 138 g of PMVE and 24 g of TFE were placed, and the temperature was raised to 90°C while stirring at 120 rpm. Next, the stirring was reduced to 30 rpm to create a laminar flow region in the reaction vessel, and then 2.49 g of ammonium persulfate (APS) dissolved in 10 g of deionized water was added as an initiator to start polymerization. The pressure at the start of polymerization was 0.8 MPaG. As polymerization started, the pressure in the reactor decreased, so TFE was added to maintain a constant pressure of 0.8 MPaG. When 10 g of TFE was injected under pressure, the supply of TFE was stopped, stirring was stopped, and the reaction was terminated. Subsequently, the reactor was evacuated until the pressure returned to atmospheric pressure, and the contents were removed from the reactor and cooled to obtain raw material liquid A-2. The solid content concentration of raw material liquid A-2 was 0.59% by mass.

[0282] <Preparation of Raw Material Solution B-2> Raw material solution B-2 was obtained in the same manner as the preparation method for raw material solution B-1 in polymerization example 1, except that raw material solution A-2 was used. The solid content concentration of raw material solution B-2 was 0.51% by mass.

[0283] <Preparation of aqueous dispersion (A-2)> Except for using raw material solution B-2, PTFE aqueous dispersion (A-2) was obtained in the same manner as the preparation method for aqueous dispersion (A-1) in polymerization example 1. The solid content concentration calculated from the amount of PTFE aqueous dispersion (A-2) obtained was 16.4% by mass, and the average primary particle size was 195 nm.

[0284] The total content of the compounds represented by the following three general formulas in the PTFE aqueous dispersion (A-2) was 120,456 ppb by mass relative to the PTFE. General formula (6-16-1): M ＋ [ － OOC-(CF ２ ) １４ - COO － ] M ＋ (In the formula, M ＋ represents a cation. ) General formula (6-16-2): M ＋ [ － OOC-(CF ２ ) １２ - (CF (OCF ３ )) ２ - COO － ] M ＋ (In the formula, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of ) is arbitrary in the formula. ) General formula (6-16-3): M ＋ [ － OOC-(CF ２ ) １１ - (CF (OCF ３ )) ３ - COO － ] M ＋ (In the formula, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of the elements in the formula is arbitrary.

[0285] The total content of the compounds represented by the following two general formulas in the PTFE aqueous dispersion (A-2) was 136,679 ppb by mass relative to the PTFE. General formula (6-18-1): M ＋ [ － OOC-(CF ２) １６ - COO － ] M ＋ (In the formula, M+ represents a cation) General formula (6-18-2): M ＋ [-OOC-(CF ２ ) １５ - (CF (OCF ３ )) １ - COO － ] M ＋ (In the formula, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of the elements in the formula is arbitrary.

[0286] PTFE aqueous dispersion (A-2) containing general formula (4-12): [H-(CF ２ ) ｍ－１ CO ２ － ] M ＋ (In the formula, m is 12, M ＋ The compound represented by (where represents a cation) was 989 ppb by mass relative to PTFE.

[0287] Experimental Example 3: PTFE aqueous dispersion (D-2) was obtained in the same manner as in Experimental Example 1, except that PTFE aqueous dispersion (A-2) was used.

[0288] The resulting aqueous PTFE dispersion (D-2) had a solid content of 60.3% by mass, a nonionic surfactant content of 5.5% by mass relative to the PTFE, a pH of 9.6, and a viscosity of 23.8 mPa·s.

[0289] The total content of the compound represented by general formula (6-16-1), the compound represented by general formula (6-16-2), and the compound represented by general formula (6-16-3) in the PTFE aqueous dispersion (D-2) was 337 ppb by mass relative to the PTFE.

[0290] The total content of the compound represented by general formula (6-18-1) and the compound represented by general formula (6-18-2) in the PTFE aqueous dispersion (D-2) was 401 ppb by mass relative to the PTFE.

[0291] PTFE aqueous dispersion (D-2) containing general formula (4-12): [H-(CF ２) ｍ－１ CO ２ － ] M ＋ (In the formula, m is 12, M ＋ The content of the compound indicated by (where represents a cation) was below the limit of quantification.

[0292] The surface smoothness of the impregnated fiber cloth obtained using the PTFE aqueous dispersion (D-2) was such that no more than 10 irregularities were felt (Fair).

[0293] Experimental Example 4: A PTFE aqueous dispersion (D-3) was obtained in the same manner as in Experimental Example 3, except that PFA694E (Purolite, an anion exchange resin) was used as the ion exchange resin for the second repeat.

[0294] The aqueous PTFE dispersion (D-3) obtained by a total of two ion exchange treatments had a solid content concentration of 60.2% by mass, a nonionic surfactant content of 6.0% by mass relative to the PTFE, a pH of 9.8, and a viscosity of 26.7 mPa·s.

[0295] The content of the compound represented by general formula (6-16-1), the compound represented by general formula (6-16-2), and the compound represented by general formula (6-16-3) in the PTFE aqueous dispersion (D-3) was all below the limit of quantification.

[0296] The content of the compound represented by general formula (6-18-1) and the compound represented by general formula (6-18-2) in the PTFE aqueous dispersion (D-3) was both below the limit of quantification.

[0297] PTFE aqueous dispersion (D-3) containing general formula (4-12): [H-(CF ２ ) ｍ－１ CO ２ － ] M ＋ (In the formula, m is 12, M ＋ The content of the compound indicated by (where represents a cation) was below the limit of quantification.

[0298] The surface smoothness of the impregnated fiber cloth obtained using the PTFE aqueous dispersion (D-3) was good, with no noticeable irregularities.

[0299] Polymerization Example 3 <Preparation of Raw Material Solution A-3> Raw material solution A-3 was obtained in the same manner as the preparation of raw material solution A-1 in Polymerization Example 1, except that the amount of ammonium persulfate (APS) was changed to 3.14 g. The solid content concentration of raw material solution A-3 was 0.63% by mass.

[0300] <Preparation of Raw Material Solution B-3> Raw material solution B-3 was obtained in the same manner as the preparation method for raw material solution B-1 in polymerization example 1, except that raw material solution A-3 was used. The solid content concentration of raw material solution B-3 was 0.58% by mass.

[0301] <Preparation of aqueous dispersion (A-3)> Except for using raw material solution B-3, PTFE aqueous dispersion (A-3) was obtained in the same manner as the preparation method for aqueous dispersion (A-1) in polymerization example 1. The solid content concentration calculated from the amount of PTFE aqueous dispersion (A-3) obtained was 16.5% by mass, and the average primary particle size was 199 nm.

[0302] The total content of the compounds represented by the following three general formulas in the PTFE aqueous dispersion (A-3) was 48,721 ppb by mass relative to the PTFE. General formula (6-16-1): M ＋ [ － OOC-(CF ２ ) １４ - COO － ] M ＋ (In the formula, M ＋ represents a cation. ) General formula (6-16-2): M ＋ [ － OOC-(CF ２ ) １２ - (CF (OCF ３ )) ２ - COO － ] M ＋ (In the formula, M ＋ represents a cation. -CF ２ - and -CF (OCF ３ The order of existence of ) is arbitrary in the formula. ) General formula (6-16-3): M ＋ [ － OOC-(CF ２ ) １１ - (CF (OCF ３ )) ３ - COO － ] M ＋(wherein, M ＋ represents a cation. The order of presence of -CF ２ - and -CF(OCF ３ )- is arbitrary in the formula.)

[0303] The total content of the compounds represented by the following two general formulas in the PTFE aqueous dispersion (A-3) was 49,301 mass ppb relative to PTFE. General Formula (6-18-1): M ＋ － OOC-(CF ２ ) １６ -COO － M ＋ (wherein, M+ represents a cation) General Formula (6-18-2): M ＋ [-OOC-(CF ２ ) １５ -(CF(OCF ３ )) １ -COO － M ＋ (wherein, M ＋ represents a cation. The order of presence of -CF ２ - and -CF(OCF ３ )- is arbitrary in the formula.)

[0304] The content of the compound represented by General Formula (4-12): [H-(CF ２ ) ｍ－１ CO ２ － M ＋ (wherein, m is 12, M ＋ represents a cation.) in the PTFE aqueous dispersion (A-3) was 627 mass ppb relative to PTFE.

[0305] ​Experimental Example 5: 2800 g of PTFE aqueous dispersion (A-3) was mixed with 23.7 g of TDS-80 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a nonionic surfactant, and then ammonia water was added to bring the pH to 10.0 to prepare a PTFE aqueous dispersion. Subsequently, 567.8 g of A400OH (manufactured by Purolite, anion exchange resin) was added. 60 minutes after starting stirring, the aqueous dispersion and ion exchange resin were filtered off. Then, 567.8 g of PSR2 PLUS (manufactured by Organo, anion exchange resin) was added, and 60 minutes after starting stirring, the aqueous dispersion and ion exchange resin were filtered off to obtain PTFE aqueous dispersion (B-3).

[0306] Using the PTFE aqueous dispersion (B-3), the same procedure as in Experimental Example 1 was performed to obtain the PTFE aqueous dispersion (D-4).

[0307] The obtained PTFE aqueous dispersion (D-4) had a solid content concentration of 60.0% by mass, a nonionic surfactant content of 5.5% by mass relative to the PTFE, a pH of 9.4, and a viscosity of 23.3 mPa·s.

[0308] The content of the compound represented by general formula (6-16-1), the compound represented by general formula (6-16-2), and the compound represented by general formula (6-16-3) in the PTFE aqueous dispersion (D-4) was all below the limit of quantification.

[0309] The content of the compound represented by general formula (6-18-1) and the compound represented by general formula (6-18-2) in the PTFE aqueous dispersion (D-4) was both below the limit of quantification.

[0310] PTFE aqueous dispersion (D-4) containing general formula (4-12): [H-(CF ２ ) ｍ－１ CO ２ － ] M ＋ (In the formula, m is 12, M ＋ The content of the compound indicated by (where represents a cation) was below the limit of quantification.

[0311] The surface smoothness of the impregnated fiber cloth obtained using the PTFE aqueous dispersion (D-4) was good, with no noticeable irregularities.

[0312] Polymerization Example 4 <Preparation of Raw Material Solution A-4> 3309 g of deionized water was placed in a 6.0 L stainless steel pressure-resistant reaction vessel, the reactor was sealed, and while heating to 70°C, suction was applied and the reactor was purged with TFE to remove oxygen from the reactor, and the contents were stirred. Then, 233 g of PMVE and 41 g of TFE were placed in the reactor, and the temperature was raised to 90°C while stirring at 120 rpm. Next, the stirring speed was reduced to 30 rpm, and 0.83 g of ammonium persulfate (APS) dissolved in 10 g of deionized water was added as an initiator to start polymerization. The pressure at the start of polymerization was 1.3 MPaG. As polymerization began, the pressure in the reactor decreased, so TFE was added to maintain a constant pressure of 1.3 MPaG. When 10 g of TFE was injected under pressure, the supply of TFE was stopped, stirring was stopped, and the reaction was terminated. Subsequently, the reactor was evacuated until the pressure returned to atmospheric pressure, and the contents were removed from the reactor and cooled to obtain raw material liquid A-4. The solid content concentration of raw material liquid A-4 was 0.60% by mass.

[0313] <Preparation of Raw Material Solution B-4> Raw material solution B-4 was obtained in the same manner as the preparation method for raw material solution B-1 in polymerization example 1, except that raw material solution A-4 was used. The solid content concentration of raw material solution B-4 was 0.56% by mass.

[0314] <Preparation of aqueous dispersion (A-4)> Except for using raw material solution B-4, PTFE aqueous dispersion (A-4) was obtained in the same manner as the preparation method for aqueous dispersion (A-1) in polymerization example 1. The solid content concentration calculated from the amount of PTFE aqueous dispersion (A-4) obtained was 16.0% by mass, and the average primary particle size was 200 nm.

[0315] The total content of the compounds represented by the following three general formulas in the PTFE aqueous dispersion (A-4) was 37,351 ppb by mass relative to the PTFE. General formula (6-16-1): M ＋ [ － OOC-(CF ２ ) １４ - COO － ] M ＋ (In the formula, M ＋ represents a cation. ) General formula (6-16-2): M ＋ [ － OOC-(CF ２ )１２ -(CF(OCF ３ )) ２ -COO － M ＋ (wherein, M ＋ represents a cation. The order of presence of -CF ２ - and -CF(OCF ３ )- is arbitrary in the formula.) General Formula (6-16-3): M ＋ － OOC-(CF ２ ) １１ -(CF(OCF ３ )) ３ -COO － M ＋ (wherein, M ＋ represents a cation. The order of presence of -CF ２ - and -CF(OCF ３ )- is arbitrary in the formula.)

[0316] The total content of the compounds represented by the following three general formulas in the PTFE aqueous dispersion (A-4) was 40,922 mass ppb relative to PTFE. General Formula (6-18-1): M ＋ － OOC-(CF ２ ) １６ -COO － M ＋ (wherein, M ＋ represents a cation) General Formula (6-18-2): M ＋ [-OOC-(CF ２ ) １５ -(CF(OCF ３ )) １ -COO － M ＋ (wherein, M ＋ represents a cation. The order of presence of -CF ２ - and -CF(OCF ３ )- is arbitrary in the formula.)

[0317] In the PTFE aqueous dispersion (A-4), General Formula (4-12): [H-(CF ２ ) ｍ－１ CO ２ － M ＋ (wherein, m is 12, M​​＋ The compound represented by (where represents a cation) was 564 ppb by mass relative to PTFE.

[0318] Experimental Example 6: 2800 g of PTFE aqueous dispersion (A-4) was mixed with 23.7 g of TDS-80 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a nonionic surfactant and heated to 40°C. Then, 567.8 g of A400OH (manufactured by Purolite, anion exchange resin) was added. 60 minutes after stirring began, the aqueous dispersion and ion exchange resin were filtered off. Then, 567.8 g of PFA694E (manufactured by Purolite, anion exchange resin) was added, and 60 minutes after stirring began, the aqueous dispersion and ion exchange resin were filtered off to obtain PTFE aqueous dispersion (B-4).

[0319] Using the PTFE aqueous dispersion (B-4), the same procedure as in Experimental Example 1 was performed to obtain the PTFE aqueous dispersion (D-5).

[0320] The resulting aqueous PTFE dispersion (D-5) had a solid content concentration of 59.8% by mass, a nonionic surfactant content of 5.6% by mass relative to the PTFE, a pH of 9.3, and a viscosity of 25.2 mPa·s.

[0321] The content of the compound represented by general formula (6-16-1), the compound represented by general formula (6-16-2), and the compound represented by general formula (6-16-3) in the PTFE aqueous dispersion (D-5) was all below the limit of quantification.

[0322] The content of the compound represented by general formula (6-18-1) and the compound represented by general formula (6-18-2) in the PTFE aqueous dispersion (D-5) was both below the limit of quantification.

[0323] PTFE aqueous dispersion (D-5) containing general formula (4-12): [H-(CF ２ ) ｍ－１ CO ２ － ] M ＋ (In the formula, m is 12, M ＋ The content of the compound indicated by (where represents a cation) was below the limit of quantification.

[0324] The surface smoothness of the impregnated fiber cloth obtained using the PTFE aqueous dispersion (D-5) was good, with no noticeable irregularities.

Claims

1. A method for producing an aqueous polytetrafluoroethylene dispersion, comprising: performing emulsion polymerization of at least tetrafluoroethylene substantially in the absence of a surfactant and in the presence of water to prepare an aqueous dispersion (A) containing polytetrafluoroethylene, and bringing the aqueous dispersion (A) into contact with an adsorbent to prepare an aqueous dispersion (B), wherein the aqueous dispersion (A) contains at least one compound selected from the group consisting of a compound (6-16) represented by general formula (6-16), a compound (6-18) represented by general formula (6-18), and a compound (6-20) represented by general formula (6-20). General formula (6-16): M ＋ － OOC-(CFX) ｎ－２ -COO － M ＋ (wherein n is 16, M ＋ represents a cation, and X is, independently at each occurrence, F, CF ３ , OCF ３ or OC ３ F ７ .) General formula (6-18): M ＋ － OOC-(CFX) ｎ－２ -COO － M ＋ (wherein n is 18, M ＋ represents a cation, and X is, independently at each occurrence, F, CF ３ , OCF ３ or OC ３ F ７ .) General formula (6-20): M ＋ － OOC-(CFX) ｎ－２ -COO － M ＋ (wherein n is 20, M ＋ represents a cation, and X is, independently at each occurrence, F, CF ３ , OCF ３ or OC ３ F ７ .)​​​ 2. The manufacturing method according to claim 1, wherein the adsorbent is at least one selected from the group consisting of ion exchange resin, synthetic adsorbent, silica gel, polymer adsorbent, activated carbon, diatomaceous earth, and zeolite.

3. The manufacturing method according to claim 1 or 2, wherein the adsorbent is an anion exchange resin.

4. The manufacturing method according to any one of claims 1 to 3, wherein the total content of compound (6-16), compound (6-18), and compound (6-20) in the aqueous dispersion (A) is more than 1,000 ppb by mass relative to the mass of the polytetrafluoroethylene.

5. The manufacturing method according to any one of claims 1 to 4, wherein the total content of compound (6-16), compound (6-18), and compound (6-20) in the aqueous dispersion (A) is 5,000 ppb by mass or more relative to the mass of the polytetrafluoroethylene.

6. A method for producing a product according to any one of claims 1 to 5, wherein the aqueous dispersion (A) contains a compound (4-12) represented by general formula (4-12), and the content of compound (4-12) in the aqueous dispersion (A) is greater than 100 ppb by mass relative to the mass of the polytetrafluoroethylene. General formula (4-12): [H-(CF ２ ) ｍ－１ CO ２ － ] M ＋ (In the formula, m is 12, M ＋ (This represents a cation.) 7. A manufacturing method according to any one of claims 1 to 6, wherein a nonionic surfactant is added to the aqueous dispersion (A), and then the aqueous dispersion (A) is brought into contact with the adsorbent.

8. The manufacturing method according to any one of claims 1 to 7, wherein an aqueous dispersion (A) is brought into contact with the adsorbent, and then a nonionic surfactant is added to prepare an aqueous dispersion (B).

9. The manufacturing method according to any one of claims 1 to 8, wherein an aqueous dispersion (A) is brought into contact with the adsorbent, a nonionic surfactant is added, and then the aqueous dispersion containing the nonionic surfactant is concentrated to prepare an aqueous dispersion (B).

10. The manufacturing method according to any one of claims 1 to 9, wherein the total content of compound (6-16), compound (6-18), and compound (6-20) in the aqueous dispersion (B) is less than 5,000 ppb by mass relative to the mass of the polytetrafluoroethylene.

11. The manufacturing method according to any one of claims 1 to 10, wherein the total content of compound (6-16), compound (6-18), and compound (6-20) in the aqueous dispersion (B) is 1000 ppb by mass or less with respect to the mass of the polytetrafluoroethylene.

12. The manufacturing method according to any one of claims 1 to 11, wherein the content of compound (4-12) in the aqueous dispersion (B) is 100 ppb by mass or less with respect to the mass of the polytetrafluoroethylene.

13. An aqueous dispersion containing polytetrafluoroethylene and water, comprising at least one compound selected from the group consisting of the compound represented by general formula (6-16) (6-16), the compound represented by general formula (6-18) (6-18), the compound represented by general formula (6-20) (6-20), and the compound represented by general formula (4-12) (4-12), and substantially free of fluorine-containing anionic surfactants. General formula (6-16): M ＋ [ － OOC-(CFX) ｎ－２ - COO － ] M ＋ (In the formula, n is 16, M ＋ X is a cation, and X is F, CF, and F are independent in each occurrence. ３ OCF ３ or OC ３ F ７ (Represents.) General formula (6-18): M ＋ [ － OOC-(CFX) ｎ－２ - COO － ] M ＋ (In the formula, n is 18, M ＋ X is a cation, and X is F, CF, and F are independent in each occurrence. ３ OCF ３ or OC ３ F ７ (Represents.) General formula (6-20): M ＋ [ － OOC-(CFX) ｎ－２ - COO － ] M ＋ (In the formula, n is 20, M ＋ X is a cation, and X is F, CF, and F are independent in each occurrence. ３ OCF ３ or OC ３ F ７ This represents...) General formula (4-12): [H-(CF ２ ) ｍ－１ CO ２ － ] M ＋ (In the formula, m is 12, M ＋ (This represents a cation.) 14. The aqueous dispersion according to claim 13, wherein the total content of compound (6-16), compound (6-18), and compound (6-20) is less than 5,000 ppb by mass relative to the mass of the polytetrafluoroethylene.

15. The aqueous dispersion according to claim 13 or 14, wherein the total content of compound (6-16), compound (6-18), and compound (6-20) is 1,000 ppb by mass or less with respect to the mass of the polytetrafluoroethylene.

16. The aqueous dispersion according to any one of claims 13 to 15, wherein the content of compound (4-12) is 100 ppb by mass or less relative to the mass of the polytetrafluoroethylene.

17. The aqueous dispersion according to any one of claims 13 to 16, wherein the content of polytetrafluoroethylene is 10% by mass or more relative to the mass of the aqueous dispersion.

18. An aqueous dispersion according to any one of claims 13 to 17, containing a nonionic surfactant.

19. An aqueous dispersion according to any one of claims 13 to 18, wherein the content of the nonionic surfactant is 4.0 to 12% by mass relative to the mass of the polytetrafluoroethylene.

20. The aqueous dispersion according to any one of claims 13 to 19, wherein the polytetrafluoroethylene is non-melt processable.

21. The polytetrafluoroethylene has carboxylic acid groups, and the number of carboxylic acid groups is 10 carbon atoms. ６ An aqueous dispersion according to any one of claims 13 to 20, wherein each unit contains five or more particles.

Images