Method for producing fluorine-containing elastomers, aqueous dispersion, solid composition

Abstract

To provide a method for producing fluorine-containing elastomers that efficiently manufactures fluorine-containing polymers with excellent water dispersion stability without requiring emulsifiers, while using an environmentally friendly aqueous medium. [Solution] A method for producing a fluorine-containing elastomer, comprising polymerizing monomers containing TFE and PAVE in an aqueous dispersion containing a first fluorine-containing polymer containing TFE units and PAVE units, which is substantially free of water-soluble emulsifiers, and an aqueous medium, to produce a second fluorine-containing polymer, wherein the PAVE units in the first fluorine-containing polymer are 20 to 95 mol% of the total TFE units and PAVE units, the PAVE units in the second fluorine-containing polymer are 20 to 95 mol% of the total TFE units and PAVE units, and the content of the first fluorine-containing polymer before starting monomer polymerization is 0.01 to 4.0% by mass of the total mass of the aqueous dispersion.

Description

Technical Field

[0001] The present invention relates to a method for producing a fluorine-containing elastomer, an aqueous dispersion, and a solid composition.

Background Art

[0002] Fluorine-containing elastomers are used in various industrial fields because they are excellent in heat resistance, chemical resistance, flame retardancy, weather resistance, etc. As a method for producing a fluorine-containing elastomer, a method of emulsion polymerization of a fluorine-containing monomer in an aqueous medium using an emulsifier can be mentioned (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the method for producing a fluorine-containing elastomer of Patent Document 1, since an aqueous medium is used, the environmental load is small. However, when a large amount of the essential emulsifier remains in the aqueous dispersion obtained by polymerization, removal of the emulsifier may be required depending on the application. In addition, it is also required that the obtained fluorine-containing elastomer has excellent water dispersion stability.

[0005] An object of the present invention is to provide a method for producing a fluorine-containing elastomer that can efficiently produce a fluorine-containing elastomer having excellent water dispersion stability without using an emulsifier while using an aqueous medium with a small environmental load. Another object of the present invention is to provide an aqueous dispersion and a solid composition.

Means for Solving the Problems

[0006] As a result of diligent research, the inventors have found that the above problem can be solved by the following configuration. [1] In an aqueous dispersion containing a primary fluorine-containing polymer that is substantially free of water-soluble emulsifiers and comprises units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether), and an aqueous medium, A method for producing a fluorine-containing elastomer, comprising polymerizing a monomer containing tetrafluoroethylene and perfluoro(alkyl vinyl ether) to produce a second fluorine-containing polymer, In the above-mentioned first fluorine-containing polymer, the amount of units based on perfluoro(alkyl vinyl ether) is 20 to 95 mol% of the total amount of units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether). In the above-mentioned second fluorine-containing polymer, the amount of units based on perfluoro(alkyl vinyl ether) is 20 to 95 mol% of the total amount of units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether). A method for producing a fluorine-containing elastomer, wherein, before initiating 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. [2] The above monomer consists only of tetrafluoroethylene and perfluoro(alkyl vinyl ether), or A method for producing a fluorine-containing elastomer according to [1], comprising a monomer having two or more polymerizable unsaturated bonds, a monomer having one or more atoms selected from the group consisting of chlorine atoms, bromine atoms and iodine atoms, and a monomer having a nitrile group, selected from the group consisting of tetrafluoroethylene and perfluoro(alkyl vinyl ether), and at least one monomer. [3] A method for producing a fluorine-containing elastomer according to [1] or [2], wherein the amount of the above monomer used is 1 to 80 parts by mass per 100 parts by mass of the above aqueous medium used. [4] A method for producing a fluorine-containing elastomer according to [1] to [3], wherein the monomer is polymerized in the presence of a polymerization initiator. [5] An aqueous dispersion comprising an aqueous medium and particles containing a fluorine-containing polymer, The average particle diameter of the above particles is 1 μm or less. The above particles include units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether), The above fluorine-containing polymer has at least one of a chlorine atom, a bromine atom, an iodine atom, and a nitrile group at the terminal and side chains, An aqueous dispersion in which the emulsifier content is 100 ppm by mass or less relative to the total mass of the aqueous dispersion. [6] The above particles consist only of units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether), or The aqueous dispersion according to [5], comprising units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether), and further comprising units based on monomers having two or more polymerizable unsaturated bonds, units based on monomers having one or more atoms selected from the group consisting of chlorine atoms, bromine atoms and iodine atoms, and units based on monomers having a nitrile group, and at least one unit selected from this group. [7] A solid composition containing a fluorine-containing polymer, The above solid composition comprises a unit based on tetrafluoroethylene and a unit based on perfluoro(alkyl vinyl ether), A solid composition which substantially contains no emulsifier and has a storage modulus G' of 200 to 1200 kPa. [8] The solid composition according to [7], wherein at least one of the terminal and side chains of the fluorine-containing polymer has at least one of a chlorine atom, a bromine atom, an iodine atom, and a nitrile group. [9] A crosslinked rubber article obtained by crosslinking the solid composition described in [8]. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a method for producing fluorine-containing elastomers that have excellent water dispersion stability without requiring emulsifiers, while using an environmentally friendly aqueous medium. Furthermore, the present invention also aims to provide aqueous dispersions and solid compositions. [Modes for carrying out the invention]

[0008] The meanings of the terms used in this invention are as follows: Numerical ranges expressed using "~" mean a range that includes the numbers written before and after "~" as the lower and upper limits. In numerical ranges described stepwise in this specification, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described stepwise. Also, in numerical ranges described in this specification, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples. In this specification, each component may be represented by a single substance or by a combination of two or more substances. Here, when two or more substances are used in combination for each component, the content for that component refers to the total content of the combined substances unless otherwise specified. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment. A "unit" is a general term for an atomic group derived from one monomer molecule, which is directly formed by the polymerization of monomers, and an atomic group obtained by chemically transforming a part of the above atomic group. A "unit based on monomers" will also be simply referred to as a "unit" below. The content (mass %) or mole %) of each unit relative to the total number of units in a polymer is determined by analyzing the polymer using solid-state nuclear magnetic resonance (NMR) spectroscopy. However, the content of each unit calculated from the amount of each monomer used usually closely matches the actual content of each unit. A "fluorine-containing elastomer" is an elastic, non-melting fluorine-containing copolymer that exhibits a storage modulus G' of 80 or higher at 100°C and 50 cpm, as measured according to ASTM D6204, and is distinguished from fluororesins.

[0009] [Method for producing fluorine-containing elastomers] The present invention's method for producing a fluorine-containing elastomer (hereinafter also referred to as "this production method") substantially contains no emulsifier and comprises a first fluorine-containing polymer comprising units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether), and an aqueous dispersion (hereinafter also referred to as "first aqueous dispersion") containing an aqueous medium, A method for producing a fluorine-containing elastomer, comprising polymerizing a monomer containing tetrafluoroethylene and perfluoro(alkyl vinyl ether) (hereinafter also referred to as "specific monomer") to produce a second fluorine-containing polymer, In the first fluorine-containing polymer, the total of the units based on tetrafluoroethylene and the units based on perfluoro(alkyl vinyl ether) is such that the units based on perfluoro(alkyl vinyl ether) are 20 to 95 mol%. In the second fluorine-containing polymer, the total of the units based on tetrafluoroethylene and the units based on perfluoro(alkyl vinyl ether) is such that the units based on perfluoro(alkyl vinyl ether) are 20 to 95 mol%. This is a method for producing a fluorine-containing elastomer, wherein, before the polymerization of the monomer is initiated, 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.

[0010] The reason why this manufacturing method efficiently produced a fluorine-containing elastomer with excellent water dispersion stability without requiring an emulsifier is presumed to be that by using an aqueous dispersion containing a predetermined amount of the first fluorine-containing polymer in a predetermined ratio of each unit, the first fluorine-containing polymer functioned as a good polymerization site for the second fluorine-containing polymer during the polymerization of the raw material monomers for the second fluorine-containing polymer, thus achieving the desired effect. According to this manufacturing method, even without using emulsifiers, a fluorine-containing elastomer with physical properties equivalent to or better than that of a fluorine-containing elastomer manufactured using emulsifiers can be obtained.

[0011] <First aqueous dispersion> This manufacturing method uses a first aqueous dispersion that substantially does not contain a water-soluble emulsifier and contains a first fluorine-containing polymer and an aqueous medium.

[0012] (emulsifier) The first aqueous dispersion is substantially free of water-soluble emulsifiers. "Substantially free of water-soluble emulsifiers" means that in the first aqueous dispersion, the content of water-soluble emulsifiers is 10 ppm by mass or less relative to the total mass of the first aqueous dispersion, preferably 100 ppb by mass or less, and more preferably 50 ppb by mass or less. It is also preferable that it be below the limit of quantification of the measurement method in the examples. A lower limit is given as 1 ppb by mass. The water-soluble emulsifier content can be measured using a liquid chromatograph-mass spectrometer. Specifically, the measurement method described in paragraphs 0721-0732 of International Publication No. 2018 / 181904 is a good example, and the measurement method shown in the examples is preferred.

[0013] A water-soluble emulsifier refers to an emulsifier whose solubility in 1000g of water at 25°C is 100mg or more. Examples of water-soluble emulsifiers include hydrocarbon-containing surfactants, fluorine-containing emulsifiers, and polymer emulsifiers that are water-soluble. Neither the first fluorine-containing polymer nor the second fluorine-containing polymer, described later, are water-soluble emulsifiers. The water-soluble emulsifier may be either ionic or nonionic.

[0014] A hydrocarbon-containing surfactant is a surfactant that contains hydrocarbons. More specifically, at least some of the monovalent substituents on the carbon atoms are hydrogen atoms, and substitution with halogen atoms such as fluorine and chlorine atoms is also possible. In hydrocarbon-containing surfactants, it is preferable that 75% or more of the monovalent substituents substituted on the carbon atoms are hydrogen atoms, more preferably 85% or more are hydrogen atoms, and even more preferably 95% or more are hydrogen atoms.

[0015] Examples of hydrocarbon-containing surfactants include hydrocarbon surfactants and siloxane surfactants. A hydrocarbon surfactant is a surfactant that does not contain silicon atoms, and 100% of the monovalent substituents that substitute for carbon atoms are hydrogen atoms, and therefore does not contain halogen atoms such as chlorine atoms and fluorine atoms. A siloxane surfactant is a hydrocarbon-containing surfactant that has a hydrophobic group containing a siloxane skeleton with numerous siloxane units.

[0016] Examples of hydrocarbon surfactants include anionic hydrocarbon surfactants. Anionic hydrocarbon surfactants refer to hydrocarbon surfactants that have a negatively charged hydrophilic portion such as a carboxylic acid group, sulfonic acid group, sulfate group, phosphonic acid group, and phosphate group, and a hydrocarbon portion such as an alkyl group as a hydrophobic portion. An example of anionic hydrocarbon surfactants is the highly branched C10 tertiary carboxylic acid supplied by ResolutionPerformanceProducts as Versatic® 10. Another example of anionic hydrocarbon surfactants is sodium linear alkyl polyethersulfonate supplied by BASF as the Avane® S series.

[0017] Sodium dodecyl sulfate is another example of anionic hydrocarbon surfactant.

[0018] Another example of anionic hydrocarbon surfactants is the sulfosuccinate surfactant Lankropol® K8300, available from AkzoNobelSurfaceChemistryLLC.

[0019] Nonionic hydrocarbon surfactants can also be cited as examples of hydrocarbon surfactants. Nonionic hydrocarbon surfactants do not have charged groups but often possess a hydrophobic moiety that is a long-chain hydrocarbon. Examples of hydrophilic moieties in nonionic hydrocarbon surfactants include water-soluble functional groups such as polyethylene oxide chains obtained from the polymerization of ethylene oxide. Examples of nonionic hydrocarbon surfactants include various types of polyalkylene oxide blocks, such as block copolymers containing polyethylene oxide and polypropylene oxide.

[0020] Examples of nonionic hydrocarbon surfactants include those described in paragraphs

[0043] to

[0052] of Japanese Patent Publication No. 2016-537499.

[0021] Examples of siloxane surfactants include those described in U.S. Patent No. 6,841,616 (Wille et al.) and U.S. Patent No. 7,977,438 (Brothers et al.).

[0022] Examples of fluorine-containing emulsifiers include anionic fluorine-containing surfactants. Examples of anionic fluorine-containing surfactants include surfactants containing fluorine atoms with a total carbon number of 20 or less in the portion excluding the anionic group, and surfactants containing fluorine with a molecular weight of 800 or less in the anionic portion. The above-mentioned "anionic portion" refers to the portion of the fluorine-containing surfactant excluding the cation.

[0023] Examples of polymer emulsifiers include polymers that are water-soluble and have hydrophilic groups in their side chains. Such polymer emulsifiers include polymers that contain units based on compounds having both a reactive site for polymerization and a hydrophilic group. Also included are polymers that have undergone post-treatment such as hydrolysis, and which contain units based on compounds that have a group that can become a hydrophilic group, even if they do not initially have a hydrophilic group.

[0024] The first aqueous dispersion preferably contains substantially no emulsifier represented by any of formulas (S1) to (S4). If an emulsifier is not used during the production of the first fluorine-containing polymer contained in the first aqueous dispersion, the amount of compound represented by any of formulas (S1) to (S4) can be suppressed, making it easier to adjust the content of these compounds.

[0025] H-(CF2) n1 -COOM (S1) F-(CF2) n1 -COOM (S2) H-(CF2) n2 -SO3M (S3) F-(CF2) n2 -SO3M (S4) In formulas (S1) to (S4), n1 is an integer between 3 and 19. n² is an integer between 4 and 20. M is independently a hydrogen atom, Na, K, or NH4.

[0026] (First fluoropolymer) The first fluorine-containing polymer includes units based on tetrafluoroethylene (hereinafter also referred to as "TFE") and units based on perfluoro(alkyl vinyl ether) (hereinafter also referred to as "PAVE"). The first fluorine-containing polymer is presumed to facilitate the polymerization of specific monomers by adsorbing and incorporating them at its hydrophobic region during polymerization, thereby solubilizing the specific monomers even without the presence of an emulsifier. Furthermore, the first fluorine-containing polymer is presumed to contribute to the dispersion stabilization of particles, etc., in aqueous dispersions, as described later.

[0027] PAVE is preferred as the monomer represented by formula (1) because of its excellent polymerization reactivity when producing the first fluorine-containing polymer and because it allows for more efficient production of the second fluorine-containing polymer. CF2 = CF - OR f1 (1) In formula (1), R f1 R represents a perfluoroalkyl group having 1 to 10 carbon atoms. f1 The number of carbon atoms is preferably 1 to 8, more preferably 1 to 6, even more preferably 1 to 5, and particularly preferably 1 to 3, from the standpoint of superior polymerization reactivity. Perfluoroalkyl groups may be linear or branched.

[0028] Specific examples of PAVE include perfluoro(methyl vinyl ether) (hereinafter also referred to as "PMVE"), perfluoro(ethyl vinyl ether) (hereinafter also referred to as "PEVE"), and perfluoro(propyl vinyl ether) (hereinafter also referred to as "PPVE"). PMVE and PPVE are preferred, with PMVE being more preferred, because they allow for more efficient production of secondary fluorine-containing polymers.

[0029] In the first fluorine-containing polymer, the PAVE unit content relative to the total of TFE units is 20 to 95 mol%, preferably 20 to 60 mol%, more preferably 25 to 60 mol%, and even more preferably 25 to 55 mol%, from the viewpoint of being able to produce the second fluorine-containing polymer more efficiently. The total content of TFE units and PAVE units in the first fluorine-containing polymer is preferably 99.0 to 100.0 mol%, more preferably 99.5 to 100.0 mol%, and even more preferably 99.9 to 100.0 mol%, relative to the total units of the first fluorine-containing polymer.

[0030] The first fluorine-containing polymer may contain units based on monomers other than TFE and PAVE, and may substantially omit units based on other monomers in order to produce the second fluorine-containing polymer more efficiently. "Substantially free of units based on other monomers" means that the content of units based on other monomers is 0.01 mol% or less relative to the total units of the first fluorine-containing polymer, and 0 mol% is preferred.

[0031] Before initiating the polymerization of the monomer used for the polymerization of the second fluorine-containing polymer, the content of the first fluorine-containing polymer is 0.01 to 4.0% by mass relative to the total mass of the first aqueous dispersion. From the standpoint of producing the second fluorine-containing polymer more efficiently, a content of 0.01 to 0.6% by mass is preferred, and 0.01 to 0.5% by mass is more preferred.

[0032] In this specification, "before starting the polymerization of the monomer used in the polymerization of the second fluorine-containing polymer" means immediately before the start of polymerization. Here, "the start of polymerization" refers to the time when the monomer and polymerization initiator are brought into the reactor after the reactor has been heated to or above the polymerization temperature, and the time when the reactor is heated to or above the polymerization temperature after the monomer and polymerization initiator have been brought into the reactor. Furthermore, the first aqueous dispersion, used before initiating the polymerization of the monomers used in the polymerization of the second fluorine-containing polymer, does not contain the monomers used in the polymerization of the second fluorine-containing polymer or the polymerization initiator.

[0033] The content (solid content concentration) of the first fluorine-containing polymer can be measured, for example, by the following method. The content (solids concentration) of the first fluorine-containing polymer in the first aqueous dispersion is determined by heating 2.0 g of the first aqueous dispersion at 170°C for 20 minutes, weighing the mass of the residue, and calculating the solids concentration using the following formula. "Solid content concentration (mass%) = 100 × Heating residue of the first aqueous dispersion (g) / Mass of the first aqueous dispersion (2.0g)"

[0034] A preferred method for producing the first fluorine-containing polymer is to polymerize monomers containing TFE and PAVE in an aqueous medium in the presence of a polymerization initiator. This yields the first fluorine-containing polymer dispersed in particulate form in an aqueous medium. The aqueous medium in which the particles of the first fluorine-containing polymer obtained in this manner are dispersed may be used as the first aqueous dispersion as is, or another aqueous medium may be added and this may be used as the first aqueous dispersion. Alternatively, the first fluorine-containing polymer may be dispersed in another aqueous medium by solvent substitution and this may be used as the first aqueous dispersion.

[0035] As polymerization initiators used in the production of the first fluorine-containing polymer, water-soluble polymerization initiators are preferred, persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate, disuccinic acid peroxide, or organic polymerization initiators such as azobisisobutylamidine dihydrochloride are more preferred, persulfates are even more preferred, and ammonium persulfate is particularly preferred. Aqueous media used in the production of the first fluorine-containing polymer include water and mixed solvents of water and water-soluble organic solvents. Specific examples of water-soluble organic solvents include tert-butanol, propylene glycol, dipropylene glycol, dipropylene glycol monomethyl ether, and tripropylene glycol.

[0036] In the production of the first fluorine-containing polymer, it is preferable that the product is substantially free of emulsifiers. The emulsifiers (including the type of emulsifier and the definition of "substantially absent") are as described above.

[0037] It is preferable to use an aqueous dispersion containing particles of the first fluorine-containing polymer, after performing a purification treatment to reduce or deactivate the polymerization initiator and its decomposition products, for polymerization to obtain the second fluorine-containing polymer. In the purification process, the polymerization initiator and its decomposition products that may be present in the dispersion containing the first fluorinated polymer can be removed, making it easier to obtain the second fluorinated polymer with the desired physical properties. Purification methods include heat treatment and removal using an ion exchange resin (preferably an anion exchange resin). The purification process may be carried out multiple times.

[0038] (aqueous medium) The aqueous dispersion used in this manufacturing method contains an aqueous medium. The aqueous medium contained in the first aqueous dispersion may be the polymerization solvent used in the production of the first fluorine-containing polymer, as described above. Specific examples of the aqueous medium contained in the first aqueous dispersion are the same as the specific examples of the aqueous medium used in the production of the first fluorine-containing polymer described above. Before initiating the polymerization of the monomer used in the polymerization of the second fluorine-containing polymer, the content of the aqueous medium is preferably 60 to 99.9% by mass, more preferably 96 to 99.9% by mass, and even more preferably 98 to 99.9% by mass, relative to the total mass of the first aqueous dispersion.

[0039] (Other ingredients) The first aqueous dispersion may contain other components besides the first fluorine-containing polymer and the aqueous medium. Specific examples of other components that the first aqueous dispersion may contain include chain transfer agents, reducing agents, and pH adjusters. Specific examples of chain transfer agents include ethyl acetate, methanol, ethanol, t-butyl methyl ether, diethyl ether, n-pentane, cyclohexane, methane, and propane. Compounds represented by formula (I), described later, can also be used as chain transfer agents. Specific examples of reducing agents include sulfurous acid or its salts, bisulfite or its salts, thiosulfate or its salts, sulfinic acid or its salts, organic acids, inorganic salts, etc. Specifically, examples include sodium formaldehyde, sulfoxylate dihydrate, 2-hydroxy-2-sulfinate, acetic acid, and disodium. Specific examples of pH adjusters include inorganic salts and ammonia. Specific examples of inorganic salts include phosphates such as disodium hydrogen phosphate and sodium dihydrogen phosphate, sodium bicarbonate, and carbonates such as sodium carbonate. More preferred examples of phosphates include disodium hydrogen phosphate dihydrate and disodium hydrogen phosphate dodecahydrate. If the first aqueous dispersion contains a chain transfer agent, the content of the chain transfer agent is preferably 0.1 to 5 parts by mass per 100 parts by mass of the aqueous medium. Furthermore, the amount of chain transfer agent used is preferably 0.1 to 20 parts by mass, more preferably 0.1 to 15 parts by mass, and even more preferably 0.1 to 10 parts by mass, per 100 parts by mass of the amount of the specific monomer used, as described later. If the first aqueous dispersion contains a reducing agent, the content of the reducing agent is preferably 0.01 to 3.0 parts by mass per 100 parts by mass of the aqueous medium. If the first aqueous dispersion contains a pH adjusting agent, the content of the pH adjusting agent is preferably 0.01 to 3.0 parts by mass per 100 parts by mass of the aqueous medium.

[0040] <Specific Monomers> The specific monomer is a monomer containing TFE and PAVE. The amount of TFE and PAVE used is preferably 80 to 100 mol%, more preferably 90 to 100 mol%, and even more preferably 95 to 100 mol%, relative to the amount of specific monomers used.

[0041] The specified monomer may also contain monomers other than TFE and PAVE (hereinafter also referred to as "other monomers"). Other specific examples of monomers include monomers having two or more polymerizable unsaturated bonds (hereinafter also referred to as "DV"), monomers having at least one atom selected from the group consisting of chlorine, bromine, and iodine atoms, and monomers having a nitrile group (hereinafter referred to as "R"). CN This also refers to units based on compounds (6) described later (hereinafter also referred to as "POAVE units").

[0042] DV is a monomer having two or more polymerizable unsaturated bonds. Specific examples of polymerizable unsaturated bonds include carbon-carbon double bonds (C=C) and carbon-carbon triple bonds (C≡C). In DV, the number of polymerizable unsaturated bonds is preferably 2 to 6, more preferably 2 or 3, and even more preferably 2, from the viewpoint of superior polymerization reactivity. DV preferably further has a fluorine atom in that the compression set of the crosslinked rubber article at high temperature becomes smaller.

[0043] DV is preferably a monomer represented by formula (2) in that the mold release property of the crosslinked rubber article is more excellent. (CR 21 R 22 =CR 23 -) a1 R 24 (2) In formula (2), R 21 , R 22 and R 23 each independently represent a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group, a1 represents an integer of 2 to 6, and R 24 represents a perfluorohydrocarbon group having 1 to 10 carbon atoms with a valence of a1, or a group having an etheric oxygen atom at the terminal or between carbon-carbon bonds of the perfluorohydrocarbon group. A plurality of R 21 , a plurality of R 22 and a plurality of R 23 may be the same as or different from each other, and it is particularly preferable that they are the same as each other. a1 is preferably 2 or 3, and particularly preferably 2. From the point that the polymerization reactivity of DV is more excellent, it is preferable that R 21 , R 22 , R 23 are a fluorine atom or a hydrogen atom, and it is more preferable that all of R 21 , R 22 , R 23 are fluorine atoms or all of them are hydrogen atoms. From the point that the mold release property of the crosslinked rubber article is more excellent, it is particularly preferable that all of R 21 , R 22 , R 23 are fluorine atoms. R 24 may be linear, branched or cyclic, preferably linear or branched, and particularly preferably linear. The number of carbon atoms of R 24 is preferably 2 to 8, more preferably 3 to 7, still more preferably 3 to 6, and particularly preferably 3 to 5. R24 The material may or may not have etheric oxygen atoms, but it is preferable to have etheric oxygen atoms because it offers superior crosslinking reactivity and rubber properties. R 24 The number of etheric oxygen atoms in is preferably 1 to 6, more preferably 1 to 3, and particularly preferably 1 or 2. 24 The etheric oxygen atom in R 24 It is preferable that it be located at the terminal end.

[0044] Among the monomers represented by formula (2), suitable specific examples include the monomer represented by formula (3) and the monomer represented by formula (4).

[0045] (CF2=CF-)2R 31 (3) In formula (3), R 31 This refers to a divalent perfluorohydrocarbon group having 1 to 10 carbon atoms, or a group having an etheric oxygen atom at the terminal or between carbon-carbon bonds of the perfluorohydrocarbon group.

[0046] (CH2=CH-)2R 41 (4) In formula (4), R 41 This refers to a divalent perfluorohydrocarbon group having 1 to 10 carbon atoms, or a group having an etheric oxygen atom at the terminal or between carbon-carbon bonds of the perfluorohydrocarbon group.

[0047] Specific examples of monomers represented by equation (3) are CF2=CFO(CF2)2OCF=CF2, CF2=CFO(CF2)3OCF=CF2, CF2=CFO(CF2)4OCF=CF2, and CF2=CFO(CF2)6OCF=CF 2、CF2=CFO(CF2)8OCF=CF2, CF2=CFO(CF2)2OCF(CF3)CF2OCF=CF2, CF2=CFO(CF2)2O(CF(CF3)CF2O)2CF=CF2, CF2=CFOCF2O(CF2CF2O)2CF=CF2, CF Examples include 2=CFO(CF2O)3O(CF(CF3)CF2O)2CF=CF2, CF2=CFOCF2CF(CF3)O(CF2)2OCF(CF3)CF2OCF=CF2, and CF2=CFOCF2CF2O(CF2O)2CF2CF2OCF=CF2. Among the monomers represented by equation (3), more suitable specific examples of monomers include CF2=CFO(CF2)3OCF=CF2 (hereinafter also referred to as "C3DVE") and CF2=CFO(CF2)4OCF=CF2 (hereinafter also referred to as "C4DVE"). Specific examples of monomers represented by equation (4) include CH2=CH(CF2)2CH=CH2, CH2=CH(CF2)4CH=CH2, and CH2=CH(CF2)6CH=CH2. Among the monomers represented by equation (4), a more suitable specific example of a monomer is CH2=CH(CF2)6CH=CH2 (hereinafter also referred to as "C6DV"). In particular, C3DVE or C4DVE is preferred for DV.

[0048] Monomers having at least one atom selected from the group consisting of chlorine atoms, bromine atoms, and iodine atoms include monomers having chlorine atoms, monomers having bromine atoms, and monomers having iodine atoms. Specific examples of monomers containing a bromine atom include CF2=CFOCF2CF2CF2OCF2CF2Br, bromotrifluoroethylene, 4-bromo-3,3,4,4-tetrafluorobutene-1 (BTFB), vinyl bromide, 1-bromo-2,2-difluoroethylene, perfluoroallyl bromide, 4-bromo-1,1,2-trifluorobutene-1, 4-bromo-1,1,3,3,4,4-hexafluorobutene, 4-bromo-3-chloro-1,1,3,4,4-pentafluorobutene, 6-bromo-5,5,6,6-tetrafluorohexene, 4-bromoperfluorobutene-1, and 3,3-difluoroallyl bromide. Also, 2-bromo-perfluoroethyl perfluorovinyl ether and CF2Br-R f -O-CF=CF2(R f Examples of fluorinated compounds (where R is a perfluoroalkylene group) include fluorovinyl ethers such as CF2BrCF2O-CF=CF2, ROCF=CFBr, and ROCBr=CF2 (where R is a lower alkyl group or fluoroalkyl group), specifically CH3OCF=CFBr or CF3CH2OCF=CFBr. A specific example of a monomer containing an iodine atom is given by the formula: CHR=CH-Z-CH2CHR-I (wherein each of the multiple Rs is independently -H or -CH3; Z is a linear or branched C1-C molecule that may contain one or more ether oxygen atoms). 18 Examples include iodized olefins of a (per)fluoroalkylene group, or a (per)fluoropolyoxyalkylene group as disclosed in U.S. Patent No. 5,674,959. Also, as disclosed in U.S. Patent No. 5,717,036, formula: I(CH2CF2CF2) n OCF = CF2 and ICH2CF2O[CF(CF3)CF2O] nExamples include unsaturated ethers such as CF=CF2 (where n=1 to 3 in the formula). Also, as disclosed in U.S. Specification 4694045, examples include iodoethylene, 4-iodo-3,3,4,4-tetrafluorobutene-1 (ITFB), 3-chloro-4-iodo-3,4,4-trifluorobutene, 2-iodo-1,1,2,2-tetrafluoro-1-(vinyloxy)ethane, 2-iodo-1-(perfluorovinyloxy)-1,1,-2,2-tetrafluoroethylene, 1,1,2,3,3,3-hexafluoro-2-iodo-1-(perfluorovinyloxy)propane, 2-iodoethyl vinyl ether, 3,3,4,5,5,5-hexafluoro-4-iodopentene, and iodotrifluoroethylene. Additionally, examples include allyl iodide and 2-iodo-perfluoroethyl perfluorovinyl ether. Specific examples of monomers containing a chlorine atom include those obtained by replacing the bromine or iodine atom of any of the above-mentioned monomers with a chlorine atom. Chlorotrifluoroethylene (CTFE), vinyl chloride, and vinylidene chloride are additional examples.

[0049] R CN From the viewpoint of polymerization reactivity, it is preferable that the material has polymerizable unsaturated bonds, and it is particularly preferable that it has one polymerizable unsaturated bond. Specific examples of polymerizable unsaturated bonds include carbon-carbon double bonds (C=C) and carbon-carbon triple bonds (C≡C).

[0050] R CN It is preferable that the monomer is represented by the following formula (5) because it has superior release properties and heat resistance.

[0051] CR 51 R 52 =CR 53 -R 54 -CN (5) In formula (5), R 51 , R 52 and R 53 Each of these independently represents a hydrogen atom, a fluorine atom, or a methyl group, and R 54This refers to a divalent perfluorohydrocarbon group having 1 to 10 carbon atoms, or a group having an etheric oxygen atom at the terminal or between carbon-carbon bonds of the perfluorohydrocarbon group. R CN Due to its excellent polymerization reactivity, R 51 , R 52 , R 53 It is preferable that R is a fluorine atom or a hydrogen atom. 51 , R 52 , R 53 It is more preferable that all of them are fluorine atoms or all of them are hydrogen atoms, as this provides better release properties and heat resistance for the crosslinked rubber article. 51 , R 52 , R 53 It is particularly preferable that all of them are fluorine atoms. R 54 The chain may be linear, branched, or cyclic, with linear or branched being preferred. 54 The number of carbon atoms is preferably 2 to 8, more preferably 3 to 7, even more preferably 3 to 6, and particularly preferably 3 to 5. R 54 The material may or may not have etheric oxygen atoms, but it is preferable to have etheric oxygen atoms because it provides superior rubber properties. R 54 The number of etheric oxygen atoms in is preferably 1 to 3, and particularly preferably 1 or 2. Specific examples of monomers represented by formula (5) include CF2=CFOCF2CF(CF3)OCF2CF2CN (hereinafter also referred to as "8CNVE"), CF2=CFO(CF2)5CN (hereinafter also referred to as "MV5CN"), CF2=CFOCF2CF2CF2OCF(CF3)CN, and CF2=CFO(CF2)3CN. Of these, 8CNVE and MV5CN are preferred due to their superior release properties and heat resistance.

[0052] The POAVE unit is a unit based on compound (6). CF2 = CF(OCF2CF2) n -(OCF2) m -OR f2 (6) However, R f2 n is a perfluoroalkyl group having 1 to 4 carbon atoms, n is an integer from 0 to 3, m is an integer from 0 to 4, and n+m is an integer from 1 to 7.

[0053] R f2 In this configuration, the perfluoroalkyl group may be linear or branched. f2 The number of carbon atoms is preferably 1 to 3. When n is 0, m is preferably 3 or 4. When n is 1, m is preferably an integer between 2 and 4. When n is 2 or 3, m is preferably 0. n is preferably an integer between 1 and 3. R f2 When the number of carbon atoms, n, and m are within the above range, the low-temperature properties of the fluorine-containing elastomer when used as a crosslinked rubber article are further improved, and the productivity of the fluorine-containing elastomer is enhanced.

[0054] Specific examples of compound (6) are listed below. The abbreviations in parentheses after the formulas indicate the compounds. CF2=CF-OCF2CF2-(OCF2)4-OCF3(C9PEVE), CF2=CF-OCF2CF2-(OCF2)2-OCF3(C7PEVE), CF2=CF-(OCF2CF2)2-OCF2CF3(EEAVE), CF2=CF-(OCF2CF2)3-OCF2CF3(EEEAVE), CF2=CF-OCF2-OCF3, CF2=CF-OCF2-OCF2-OCF3 As for compound (6), C9PEVE, C7PEVE, EEAVE, or EEEAVE are preferred because they provide even better low-temperature properties when the fluorine-containing elastomer is used as a crosslinked rubber article, and also improve the productivity of the fluorine-containing elastomer. These compounds can be produced using the corresponding alcohols as raw materials by the method described in International Publication No. 00 / 56694.

[0055] The amount of other monomers used is preferably 0 to 90 mol%, more preferably 0 to 80 mol%, and even more preferably 0 to 70 mol%, relative to the amount of the specific monomer used.

[0056] The specific monomer preferably consists only of TFE and PAVE, or contains TFE and PAVE and includes at least one monomer selected from the group consisting of a monomer having two or more polymerizable unsaturated bonds, a monomer having at least one atom selected from the group consisting of chlorine atoms, bromine atoms and iodine atoms, and a monomer having a nitrile group.

[0057] The amount of specific monomer used is preferably 1 to 80 parts by mass, more preferably 1 to 70 parts by mass, and even more preferably 1 to 65 parts by mass, based on 100 parts by mass of the aqueous medium used in the first aqueous dispersion.

[0058] <Polymerization initiator> In this manufacturing method, it is preferable that the specific monomer is polymerized in the presence of a polymerization initiator. Preferred polymerization initiators are oil-soluble radical initiators, water-soluble radical initiators, or water-soluble redox catalysts. Specific examples of oil-soluble radical initiators include oil-soluble organic peroxides such as tert-butyl peroxypivalate (hereinafter also referred to as "PBPV") and diisopropyl peroxydicarbonate (hereinafter also referred to as "IPP"). Specific examples of water-soluble radical initiators include persulfates such as ammonium persulfate and potassium persulfate, and water-soluble organic peroxides such as disuccinic acid peroxide, bisglutaric acid peroxide, and tert-butyl hydroperoxide (hereinafter also referred to as "TBHP"). As a water-soluble redox catalyst, a combination of an oxidizing agent such as bromate or its salt, chloric acid or its salt, persulfate or its salt, permanganate or its salt, or hydrogen peroxide, and a reducing agent such as sulfurous acid or its salt, bisulfite or its salt, thiosulfate or its salt, organic acids, or inorganic salts is preferred. As persulfates, potassium persulfate or ammonium persulfate is preferred. As sulfites, sodium sulfite is preferred. As inorganic salts, combinations of sulfate anions, sulfite anions, or chloride anions with metal ions are examples. As metal ions, transition metals are preferred, including manganese, iron, cobalt, nickel, copper, zinc, cerium, and silver ions, with iron ions being preferred. As inorganic salts, iron(II) sulfate is preferred. The polymerization initiator is preferably an oil-soluble radical initiator or a water-soluble radical initiator. Oil-soluble radical initiators are more preferred, and oil-soluble organic peroxides are even more preferred, as they allow for more efficient production of fluorine-containing polymers. Two or more polymerization initiators may be used in combination.

[0059] The amount of polymerization initiator used is preferably 0.01 to 5 parts by mass, more preferably 0.01 to 3 parts by mass, and even more preferably 0.01 to 2 parts by mass, per 100 parts by mass of the specific monomer used.

[0060] <Process> In this manufacturing method, the specific monomer is polymerized in the first aqueous dispersion to produce a second fluorine-containing polymer.

[0061] The second fluorine-containing polymer obtained by this manufacturing method contains units based on the above-mentioned specific monomers (hereinafter also referred to as "specific units").

[0062] In the second fluorine-containing polymer, the PAVE units are 20 to 95 mol% of the total TFE units, preferably 20 to 60 mol%, more preferably 25 to 60 mol%, and even more preferably 30 to 55 mol% from the standpoint of more efficient production of the second fluorine-containing polymer. The total content of TFE units and PAVE units in the second fluorine-containing polymer is preferably 80 to 100 mol%, more preferably 90 to 100 mol%, and even more preferably 95 to 100 mol%, relative to the total units of the second fluorine-containing polymer.

[0063] The specific monomer is introduced into the reaction system (i.e., the polymerization reaction vessel) by conventional methods. For example, the specific monomer may be introduced into the reaction system continuously or intermittently so that the polymerization pressure reaches a predetermined pressure. Alternatively, the specific monomer may be dissolved in an aqueous medium, and the resulting solution may be introduced into the reaction system continuously or intermittently. When a polymerization initiator is used, it may be added to the reaction system all at once or in separate portions.

[0064] The polymerization temperature is preferably 10 to 95°C, and more preferably 15 to 90°C. The polymerization pressure is preferably 0.5 to 4.0 MPaG, and more preferably 0.6 to 3.5 MPaG. For batch processing, the polymerization time is preferably 90 to 1000 minutes, and more preferably 90 to 700 minutes.

[0065] Polymerization of specific monomers is preferably carried out in the substantially absence of emulsifiers. Examples of emulsifiers include those mentioned above. "Substantially free of emulsifiers" means an environment in which the emulsifier content is 0.03 ppm by mass or less relative to the total mass of the aqueous medium contained in the aqueous dispersion, preferably 0.02 ppm by mass or less, and more preferably 0 ppm by mass.

[0066] This manufacturing method produces particles containing a second fluorine-containing polymer. Specifically, this manufacturing method yields a second aqueous dispersion in which particles containing a second fluorine-containing polymer are dispersed in the aqueous medium. Particles containing the second fluorine-containing polymer may contain the first fluorine-containing polymer, or they may not contain the first fluorine-containing polymer.

[0067] [Second aqueous dispersion] The second aqueous dispersion is an aqueous dispersion obtained by this manufacturing method. Specifically, the second aqueous dispersion is an aqueous dispersion comprising an aqueous medium and particles containing a fluorine-containing polymer (hereinafter also referred to as "specific particles"), The average particle diameter is 1 μm or less. The particles contain units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether), The fluorine-containing polymer has at least one of a chlorine atom, a bromine atom, an iodine atom, and a nitrile group at the terminal and side chains, The total amount of emulsifiers is 100 ppm by mass or less relative to the total mass of the aqueous dispersion.

[0068] <Specific particles> The second aqueous dispersion can be easily obtained by the manufacturing method described above. Therefore, it is preferable that the specific particles contained in the second aqueous dispersion are particles containing the second fluorine-containing polymer described above. If a specific particle contains a second fluorine-containing polymer, the specific particle may also contain a first fluorine-containing polymer, or it may not contain a first fluorine-containing polymer. The second aqueous dispersion may further contain particles of the first fluorine-containing polymer described above, in addition to the specific particles.

[0069] The specified particles include TFE units and PAVE units. The details of the TFE units are the same as those of the TFE units contained in the first fluorine-containing polymer described above, and the preferred embodiment is also the same. The details of the PAVE units are the same as those of the PAVE units contained in the first fluorine-containing polymer described above, and the preferred embodiment is also the same. Furthermore, the content of TFE units and PAVE units relative to the total units of the fluorine-containing polymer is the same as the content of each unit in the second fluorine polymer described above, and the preferred embodiment is also the same.

[0070] In this specification, if a specific particle contains only one type of fluorine-containing polymer, "all units of the fluorine-containing polymer" means all units contained in that one type of fluorine-containing polymer. If a specific particle contains two or more types of fluorine-containing polymers, "all units of the fluorine-containing polymer" means all units contained in the two or more types of fluorine-containing polymers.

[0071] The specific particles may include units based on monomers other than the specific unit. For example, other monomers in a deuterated polymer.

[0072] The fluorine-containing polymer contained in the specific particles has at least one chlorine atom, bromine atom, iodine atom, and nitrile group at at least one of its terminal and side chains. By using the other monomers mentioned above during the production of fluorine-containing polymers that specific particles contain, chlorine atoms, bromine atoms, iodine atoms, and nitrile groups can be introduced.

[0073] If the fluorine-containing polymer contained in the specific particles has an iodine atom, it is also preferable that the fluorine-containing polymer be polymerized using a compound represented by formula (I). When a compound represented by formula (I) (a chain transfer agent containing an iodine atom) is used, an iodine atom can be introduced to the ends of the fluorine-containing polymer (polymer chain). (R f )-(X)2(I) In formula (I), R f This is a fluoroalkylene group having 1 to 16 carbon atoms, or an aromatic ring group. X is an iodine atom or a bromine atom, and at least one of them is an iodine atom. R f The fluoroalkylene group may be linear or branched. f A perfluoroalkylene group is preferred as the material. For X, it is preferable that all atoms are iodine.

[0074] Compounds represented by formula (I) include 1,2-diiodoperfluoroethane, 1,3-diiodoperfluoropropane, 1,4-diiodoperfluorobutane (hereinafter also referred to as "C4DI"), 1,5-diiodoperfluoropentane, 1,6-diiodoperfluorohexane, 1,8-diiodoperfluoroctan, 1,3-diiodo-2-chloroperfluoropropane, 1,5-diiodo-2,4-dichloroperfluoropentane, 1,12-diiodoperfluorododecane, 1,16-diiodoperfluorohexadecane, diiodomethane, and 1,2-diiodoperfluoroethane. Examples include doethane, 1,3-diiodo-n-propane, (2-iodoethyl) substituted derivatives of benzene, 1-iodo-4-bromoperfluorobutane, 1-iodo-6-bromoperfluorohexane, 1-iodo-8-bromoperfluoroctan, 1-bromo-2-iodoperfluoroethane, 1-bromo-3-iodoperfluoropropane, 2-bromo-3-iodoperfluorobutane, 3-bromo-4-iodoperfluorobutene-1, 2-bromo-4-iodoperfluorobutene-1, monoiodomonobromo substituted derivatives of benzene, and diiodomonobromo substituted derivatives. C4DI is preferred as the compound represented by formula (I).

[0075] If the fluorine-containing polymer contained in the specific particles has iodine atoms, the proportion of iodine atoms is preferably 0.01 to 5.00% by mass, more preferably 0.01 to 2.00% by mass, and even more preferably 0.01 to 1.00% by mass, relative to the total mass of the fluorine-containing polymer.

[0076] The content of specific particles is preferably 1 to 50% by mass, more preferably 1 to 40% by mass, and even more preferably 1 to 30% by mass, relative to the total mass of the aqueous dispersion, in terms of the dispersion stability of the specific particles.

[0077] The average particle diameter of the specific particles is 1 μm or less, and from the viewpoint of dispersion stability of the specific particles, it is preferably 500 nm or less, and more preferably 400 nm or less. From the viewpoint of aggregation, the average particle diameter of specific particles is preferably 50 nm or more, more preferably 70 nm or more, and even more preferably 100 nm or more. The average particle diameter of a specific particle is determined by measuring the particle size distribution using laser diffraction and scattering, calculating a cumulative curve with the total volume of the particle collection set to 100%, and then determining the particle diameter at the point on the cumulative curve where the cumulative volume reaches 50%.

[0078] <Aqueous medium> Specific examples of the aqueous medium contained in this aqueous dispersion are the same as the specific examples of the aqueous medium used in the production of the first fluorine-containing polymer described above. The content of the aqueous medium is preferably 50 to 99% by mass, more preferably 60 to 99% by mass, and even more preferably 70 to 99% by mass, relative to the total mass of the aqueous dispersion, in terms of the dispersion stability of specific particles.

[0079] <Emulsifier> In the second aqueous dispersion, the emulsifier content is 100 ppm by mass or less, preferably 75 ppm by mass or less, more preferably 50 ppm by mass or less, and even more preferably 1 ppm by mass or less, relative to the total mass of the second aqueous dispersion. It is also preferable that it be below the limit of quantification of the measurement method in the examples. A lower limit of 1 ppb by mass is given. The emulsifier content can be measured using the method for measuring the emulsifier content in the above-described method for producing fluorine-containing elastomers. Specific examples of emulsifiers are as described above. Furthermore, the emulsifier in the second aqueous dispersion may be water-soluble or not.

[0080] <Application> As mentioned above, the second aqueous dispersion does not require an emulsifier, and therefore can be easily converted into a dispersion of an organic solvent such as N-methylpyrrolidone or acetone by solvent substitution. For example, the second aqueous dispersion can be mixed with an organic solvent and dehydrated by evaporation or using anhydrous sodium sulfate or the like to obtain a dispersion of the organic solvent.

[0081] The second aqueous dispersion allows for stable dispersion of fluorine-containing polymers even without the presence of emulsifiers. Therefore, it is suitable for use in coating applications, binders, and the like.

[0082] Furthermore, a solid of specific particles can be obtained by agglomerating specific particles from the second aqueous dispersion. The solid of specific particles obtained by agglomeration can then be molded as appropriate by known methods. Examples of molding methods include injection molding, extrusion molding, co-extrusion molding, blow molding, compression molding, inflation molding, transfer molding, or calendering.

[0083] Methods of coagulation include, but are not limited to, freeze coagulation, acid coagulation, base coagulation, mechanical coagulation, and coagulation using coagulants. In the case of freeze-coagulation, the coagulation temperature is preferably -20 to 0°C. The coagulation time is preferably 1 hour or more, and more preferably 2 hours or more. In the case of acid agglutination, it is preferable to add an acid-containing solution to a second aqueous dispersion. Examples of acids to be added include hydrochloric acid, nitric acid, sulfuric acid, oxalic acid, hydrofluoric acid, etc., with nitric acid being preferred. The concentration of the acid in the acid-containing solution is preferably 0.1 to 50% by mass, more preferably 1 to 30% by mass, and even more preferably 1 to 10% by mass. For base aggregation, a method of adding a solution containing a base to a second aqueous dispersion is preferred. Examples of bases to be added include sodium hydroxide, potassium hydroxide, and ammonium carbonate, with sodium hydroxide being preferred. The concentration of the base in the solution containing the base is preferably 0.1 to 50% by mass, more preferably 1 to 30% by mass, and even more preferably 1 to 10% by mass. For aggregation using a coagulant, known coagulants can be used. Known coagulants include aluminum salts, calcium salts, and magnesium salts. Specifically, these include aluminum sulfate, alum represented by the general formula M'Al(SO4)2·12H2O (wherein M' is a monovalent cation other than lithium), calcium nitrate, and magnesium sulfate. Alum is preferred, and potassium alum, where M is potassium, is more preferred. As for the aggregation method, base aggregation is preferred because it is particularly easy to achieve. The second aqueous dispersion containing the second fluorine-containing polymer can be used as is, or with appropriate concentration adjustments, for co-aggregation with aqueous dispersions containing different fluorine-containing polymers. Co-aggregation can be carried out by known methods, such as dropping a mixture of aqueous dispersions into a coagulation solution, or dropping a coagulation solution into a mixture of aqueous dispersions. Specific co-aggregation methods include, but are not limited to, freeze-aggregation, acid-aggregation, base-aggregation, mechanical-aggregation, and coagulation using a coagulant. Examples of different fluorine-containing polymers include fluorine-containing elastomers and fluorine-containing resins. Examples of fluorine-containing elastomers include, but are not limited to, HFP / VdF-based elastomers, which are polymers using hexafluoropropene (hereinafter also referred to as "HFP") and vinylidene fluoride (hereinafter also referred to as "VdF"), TFE / HFP / VdF-based elastomers, which are polymers using TFE, HFP, and VdF, TFE / propylene-based elastomers, which are polymers using TFE and propylene, and TFE / HFP / PAVE-based elastomers, which are polymers using TFE, HFP, and PAVE. Examples of fluorine-containing resins include polymers containing VdF and TFE. Examples of polymers containing TFE include TFE homopolymers and fluorine-containing copolymers of TFE and olefins other than TFE. Specifically, examples include, but are not limited to, TFE / ethylene-based copolymers, TFE / HFP-based copolymers, and TFE / PAVE-based copolymers. The aqueous dispersions of different fluorine-containing polymers may or may not contain emulsifiers. The composition obtained by co-aggregation can be used as a base material for molding by washing and drying as needed, and can provide molded products with excellent heat resistance, mechanical strength, wear resistance, transparency, and moldability.

[0084] [Solid composition] The solid composition of the present invention is a solid composition comprising a fluorine-containing polymer, The solid composition comprises units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether), The solid composition is substantially free of emulsifiers. The statement that a solid composition is substantially free of emulsifiers means that, in the solid composition of the present invention, the content of water-soluble emulsifiers is 500 ppb by mass or less, preferably 300 ppb by mass or less, and more preferably 250 ppb by mass or less, relative to the total mass of the solid composition. It is also preferable that the content be below the limit of quantification of the measurement method in the examples. A lower limit is given as 1 ppb by mass. Specific examples of emulsifiers are as described above.

[0085] In this specification, a solid composition means a composition having a solid content of 99% by mass or more. Here, the solid content mass is calculated based on the mass before and after heating using the following method. After heating 2.0 g of the solid composition at 170°C for 20 minutes, the mass of the residue is weighed, and the mass of solids is calculated using the following formula. Solid content mass (mass%) = 100 × (mass of residue) / (mass of solid composition)

[0086] The solid composition is preferably obtained by an aggregation method using the second aqueous dispersion described above. The preferred embodiment of the fluorine-containing polymer contained in the solid composition is the same as the preferred embodiment of the fluorine-containing polymer in the specific particles contained in the second aqueous dispersion described above. In other words, the fluorine-containing polymer contained in this solid composition is preferably the second fluorine-containing polymer described above. The second fluorine-containing polymer may contain the first fluorine-containing polymer. The content of the fluorine-containing polymer is preferably 99.0 to 100% by mass, more preferably 99.5 to 100% by mass, and even more preferably 99.8 to 100% by mass, based on the total mass of the solid composition.

[0087] The total emulsifier content in the solid composition is 500 ppb by mass or less, preferably 300 ppb by mass or less, and more preferably 250 ppb by mass or less, relative to the total mass of the fluorine-containing polymer. It is also preferable that it be below the limit of quantification of the measurement method in the examples. The lower limit is greater than 0 ppb by mass. The number of emulsifier types contained in a solid composition is the number of emulsifier types whose content exceeds the limit of quantification; emulsifiers below the limit of quantification are not counted. Specifically, when measuring the content of emulsifiers X, Y, and Z in a solid composition, if the content of both emulsifiers X and Y exceeds the limit of quantification, and the content of emulsifier Z is below the limit of quantification, then the solid composition contains two types of emulsifiers, emulsifiers X and Y. To obtain a solid composition substantially free of emulsifiers, one method is to avoid using carbide-based hydrogen-containing surfactants, fluorine-containing emulsifiers, and polymer emulsifiers during the polymerization of the fluorine-containing polymers, that is, during the polymerization of the first fluorine-containing polymer and the second fluorine-containing polymer. The emulsifier content can be measured using the method for measuring the emulsifier content in the above-described method for producing fluorine-containing elastomers.

[0088] <Physical properties> Excellent processability is obtained when the solid composition is substantially free of emulsifiers and its storage modulus G' is within a specific range. Processability is evaluated by roll wrapability and roll surface temperature. Better roll wrapability increases the adhesion between the metal roll surface and the solid composition, making molding easier. Higher roll surface temperature eliminates the need for heating steps required for molding. Since emulsifiers inhibit adhesion between the metal surface of the roll and the solid composition, the less emulsifier contained, the better the roll wrapability. The storage modulus G' affects roll wrapability and roll surface temperature. The storage modulus G' of the solid composition is preferably between 200 and 1200 kPa. If it is lower than this range, the roll surface temperature decreases, and if it is higher than this range, the roll wrapping properties decrease, resulting in poor processability. The storage modulus G' of the solid composition is preferably 400 kPa or higher, preferably 1100 kPa or lower, more preferably 500 to 1100 kPa, and particularly preferably 500 to 1100 kPa, from the viewpoint of excellent processability. An example of a method for producing a solid composition containing a fluorine-containing polymer having a storage modulus G' of 200 to 1200 kPa and obtained without the use of emulsifiers is a method in which the order and number of additions of each monomer are adjusted during the production of the fluorine-containing copolymer. The storage modulus G' of the solid composition in this invention is a value measured in accordance with ASTM D6204, and the detailed measurement conditions are as shown in the examples. The detailed measurement conditions for the roll wrapability and roll surface temperature of the solid composition in the present invention, as well as the processability evaluation method, are as shown in the examples. [Examples]

[0089] The present invention will be described in detail below with reference to examples. Examples 1 to 5 are examples, and Examples 6 and 7 are comparative examples. However, the present invention is not limited to these examples.

[0090] [Measurement and evaluation methods] The various measurement and evaluation methods are as follows.

[0091] <Average particle size of particles in the second aqueous dispersion> The second aqueous dispersion of each example described below was used as a sample, and the particle size distribution was measured using a laser diffraction / scattering particle size analyzer (Otsuka Electronics Co., Ltd., ELSZ). Furthermore, when the average particle size of the particles in the first aqueous dispersion was measured using the same method as for the second aqueous dispersion, the average particle size of the particles in the first aqueous dispersion was found to be the same as the average particle size of the particles in the second aqueous dispersion.

[0092] <Percentage of each unit in polymerization> The proportion of each unit in a polymer is, 19 The results were obtained from F-NMR analysis and infrared absorption spectroscopy.

[0093] <Emulsifier content> (Preparation of measurement samples) The solids obtained in each of the examples described below were freeze-milled using a freeze mill 6775 (manufactured by SPEX) under the following conditions. Before freeze-milling, 10% by mass of dibutylhydroxytoluene (BHT) was added to the total mass of the solid to obtain a pulverized powder. The freeze-milling conditions were: solid: 3g, BHT: 0.3g, Run time: 5 mins, Rate: 15cps, Cycle: 3. 2.5 g of the obtained pulverized powder was mixed with 5 mL of methanol and subjected to sonication at 50°C for 2 hours. Centrifugation (5000 rpm, 5 minutes) was then performed to settle each fluorine-containing polymer, and the supernatant was used as the extract. The content of the compound represented by formula (S1) in each extract was determined by converting each compound with n=3 to 13, 15, and 17 in formula (S1) to a perfluorocarboxylic acid with the same number of carbon atoms. Furthermore, the content of the compound represented by formula (S3) in the resulting aqueous phase was determined by converting each compound with n=4 to 10 and 12 in formula (S3) to a perfluorosulfonic acid with the same number of carbon atoms. Specifically, five levels of methanol standard solutions were prepared for perfluorocarboxylic acid and perfluorosulfonic acid with known concentrations of 1 to 180 ng / g, and for surfactant A. Using a first-order approximation based on the sample concentrations and peak integral values, a and a' were determined using equations (A1), (A1'), and (A''). A = a × X (A1) A: Peak area of ​​perfluorocarboxylic acid, X: Concentration of perfluorocarboxylic acid (ng / g) A' = a' × X' (A1') A': Peak area of ​​perfluorosulfonic acid, X': Concentration of perfluorosulfonic acid (ng / g) A'' = a'' × X'' (A1'') A'': Peak area of ​​surfactant A, X'': Concentration of surfactant A (ng / g) The measuring equipment and conditions are shown in Table 1 below.

[0094] [Table 1] The MRM measurement parameters are shown in Tables 2, 3, and 4.

[0095] [Table 2]

[0096] [Table 3]

[0097] [Table 4]

[0098] Specifically, first, the compounds represented by either formula (S1) or formula (S3) and surfactant A contained in each of the extracts were measured using the liquid chromatograph-mass spectrometer described above. The peak areas of the compounds represented by formula (S1) and formula (S3) and surfactant A for each carbon number were determined using the MRM method.

[0099] Next, the content of the compound represented by formula (S1), the compound represented by formula (S3), and surfactant A was calculated using formulas (A2), (A2'), and (A2''), respectively. In formula (A2), a means the a obtained by formula (A1), a' means the a' obtained by formula (A1'), and a'' means the a'' obtained by formula (A''). XCm ​​= ACm / a (A2) XCm: Content (ng / g) of the compound represented by formula (S1) for the number of carbon atoms (n+1) in each extract. ACm: Peak area of ​​the compound represented by formula (S1) for each extract with (n+1) carbon atoms. XCm'=ACm' / a' (A2') XCm': Content (ng / g) of the compound represented by formula (S3) for n carbon atoms in each extract. ACm': Peak area of ​​the compound represented by formula (S3) for n carbon atoms in each extract. The limit of quantification in this measurement is 1 ng / g. XCm''=ACm'' / a'' (A2'') XCm'': Content of surfactant A in each extract (ng / g) ACm.'' Peak area of ​​surfactant A in each extract The limit of quantification in this measurement is 1 ng / g.

[0100] The content (ZCm) of formula (S1) relative to the total mass of the solid was determined by the following formula (A3). ZCm = XCm × ρ1 × La / W1 (A3) ZCm: Content of the compound represented by formula (S1) with (n+1) carbon atoms in the solid. ρ1: Density of the extraction solvent (methanol in each example). La: Volume of extraction solvent (5 mL in each example) W1: Sample mass used for extraction (2.5g of solid material in each example)

[0101] The content (ZCm') of formula (S3) relative to the total mass of the solid was determined by the following formula (A4). ZCm' = XCm' × ρ1 × La / W1 (A4) ZCm': Content of the compound represented by formula (S3) with n carbon atoms in the solid. ρ1: Density of the extraction solvent (methanol in each example) La: Volume of extraction solvent (5 mL in each example) W1: Sample mass used for extraction (2.5g of solid material in each example) The content of surfactant A relative to the total mass of the solid (ZCm'') was determined by the following formula (A5). ZCm''=XCm''×ρ1×La / W1 (A5) ZCm'': Content of surfactant A contained in the solid matter ρ1: Density of the extraction solvent (methanol in each example) La: Volume of extraction solvent (5 mL in each example) W1: Sample mass used for extraction (2.5g of solid material in each example)

[0102] <Method for measuring iodine content> The solid composition was heated and pressed to form a 100 μm thick sheet. The resulting sheet composition was subjected to X-ray fluorescence analysis using ZSX Primus II (manufactured by RIGAKU), and the iodine content in the solid composition (total mass of the first and second fluorine-containing polymers) was calculated using the fundamental parameter method.

[0103] <Method for measuring the storage modulus G'> The rubber processability analysis device "PREMIER RPA (manufactured by Alpha Technologies, die shape: D0380)" was used as the measurement device.

[0104] <Sheet creation> The solid compositions obtained in each example were kneaded using a two-roller system at room temperature for 10 minutes to produce a 3 mm thick sheet. The sheet thickness was adjusted by adjusting the gap between the two roller systems. The obtained sheet was cut to a weight of approximately 10g to obtain cut sheets. The cut sheets were sandwiched between two polyester films (ALFA Technologies PART#F0311-S, 130mm x 130mm x 24μm) to obtain a sample for measurement. The sample was placed on the die of the above measuring apparatus. The die temperature was pre-set to 100°C. Next, the sample was held for 2 minutes under conditions of 100°C, frequency of 30 cpm, and amplitude angle of 0.2 degrees. Then, the amplitude angle was changed to 0.5 degrees, and the storage modulus was measured by increasing the frequency to 10 cpm, 20 cpm, 50 cpm, 100 cpm, 200 cpm, 500 cpm, 1000 cpm, and 2000 cpm. The storage modulus at a frequency of 2000 cpm and 100°C was defined as the storage modulus G' (unit: kPa) of the sample. Next, the sample was held for 2 minutes under conditions of 100°C, frequency of 30 cpm, and amplitude angle of 0.2 degrees. Then, the amplitude angle was changed to 0.5 degrees, and the storage modulus was measured by increasing the frequency to 10 cpm, 20 cpm, 50 cpm, 100 cpm, 200 cpm, 500 cpm, 1000 cpm, and 2000 cpm. The storage modulus at a frequency of 2000 cpm and 100°C was defined as the storage modulus G' (unit: kPa) of the sample.

[0105] <Method for evaluating roll-wrapping properties> The roll-wrap properties were confirmed by mixing the solid compositions obtained in each example using a roll kneader (test roll machine manufactured by Yamate Co., Ltd.) to produce sheets. The roll kneader described above consisted of two rolls (roll diameter 8 inches, roll length 18 inches) and two guide members positioned on the gap between the rolls and near both ends of the rolls. The guide members maintained the width of the workpiece, which expanded in the direction of the roll axis after passing through the rolls, at a predetermined width. 200g of a solid composition at room temperature (23°C) was weighed out and the fluorine-containing polymer was placed between the guide members of the roll kneader set to the following conditions. The time (also called "wrapping time") was measured from the time the solid composition was placed until the fluorine-containing polymer (bank) that had accumulated on the roll gap between the guide members was gone and all of the fluorine-containing polymer was wrapped around the rolls. • Roll temperature: 25℃ • Roll gap: 2.5mm • Front roll rotation speed: 12 rpm Rear roll rotation speed: 10 rpm • Width between guide members: 150 mm The roll temperature was adjusted using a water heater (WTC40, manufactured by Nakamura Kagaku Kogyo Co., Ltd.). Based on the measurement time, the roll-wrap properties of the solid composition were evaluated according to the following evaluation criteria. (Evaluation criteria for roll winding properties) ○: The wrapping time was less than 2 minutes. △: The wrapping time was between 2 minutes and 3 minutes. ×: Either none of the fluorine-containing polymers wrapped around the roll, or the wrapping time exceeded 3 minutes.

[0106] <Roll surface temperature> The sheet obtained under the above conditions was checked for a surface temperature of 25°C using a contact thermometer (Hozan Corporation; product name "DT-510"), and then placed back into a roll with a roll temperature of 25°C. During the test, the water heater's temperature control was turned off. All other conditions were the same as those for the roll wrapping test. After 5 minutes, the wrapped sheet was immediately removed, and the surface temperature of the roll was measured with the same contact thermometer. This temperature was defined as the roll surface temperature. (Roll surface temperature evaluation criteria) A: Over 45℃ B: 35~45℃ C: Below 35℃ (processability) Evaluation of roll wrapability and roll surface temperature: A: 3 points for both. Evaluation of roll wrapability and roll surface temperature B: 2 points for both. Evaluation of roll wrapability and roll surface temperature: C: 1 point each ◎: Total evaluation score for roll wrapability and roll surface temperature: 6 points ○: Total evaluation score for roll wrapability and roll surface temperature: 5 points △: Total evaluation score for roll wrapability and roll surface temperature: 4 points ×: Total evaluation scores for roll wrapability and roll surface temperature: 2 points, 3 points

[0107] [Manufacturing of raw material liquid A] In a 2.2 L stainless steel pressure reactor equipped with anchor blades, ultrapure water (1130 g), 30% ammonia aqueous solution (30 mg), PMVE (72 g), and TFE (14 g) were charged, and the temperature was raised to 90°C while stirring at 600 rpm. Next, ammonium persulfate aqueous solution (5.0% by mass, 30 cc) was added, and polymerization was started. As polymerization began, the pressure inside the reactor decreased, so TFE was added to maintain a constant pressure. After 4 g of TFE was added under pressure, the reactor was cooled, and the polymerization reaction was terminated. After recovering the remaining gas in the reactor, the liquid was drained. This liquid was designated as raw material solution A. After freezing and condensing the raw material liquid A, it was filtered off, and the resulting fluorine-containing polymer 1A was analyzed by NMR. The result showed that the PMVE units / TFE units = 34 / 66 (molar ratio).

[0108] [Manufacturing of raw material liquid B] HPR4002Cl (DuPont, anion exchange resin, 200g) was added to the above raw material solution A. After 150 minutes of stirring, the raw material solution and ion exchange resin were filtered off. Next, AmberLite® HPR650H (DuPont, cation exchange resin, 50g) was added to the filtrate. After 60 minutes of stirring, the raw material solution and ion exchange resin were filtered off to obtain raw material solution B. Raw material solution B contained particles of fluorine-containing polymer 1A dispersed in an aqueous medium, and the content of fluorine-containing polymer 1A was 0.6% by mass of the total mass of raw material solution B.

[0109] [Example 1] A stainless steel pressure reactor with an internal volume of 2.2 L and equipped with anchor blades was charged with raw material liquid B (1000 g) and ultrapure water (175 g) to obtain aqueous dispersion B (first aqueous dispersion). PMVE (72 g) and TFE (14 g) were added to this, and the mixture was heated to 80°C while stirring at 600 rpm. TFE and PMVE were injected under pressure until the reactor pressure reached 1.2 MPa [gauge], and an aqueous solution of ammonium persulfate (2.5 mass%, 7 ml) was added to start polymerization. As polymerization began, the pressure inside the reactor decreased, so TFE and PMVE were added alternately to maintain a constant pressure. After 80 g of TFE and 63 g of PMVE were injected under pressure, the reactor was cooled and the polymerization reaction was terminated. The polymerization time was 138 minutes.

[0110] Furthermore, the content of fluorine-containing polymer 1A in aqueous dispersion B was 0.5% by mass relative to the total mass of aqueous dispersion B. Furthermore, when the amount of aqueous medium used in aqueous dispersion B used for polymerization was 100 parts by mass, the amount of monomer used for polymerization was 12.2 parts by mass. Aqueous dispersion B contained virtually no water-soluble emulsifiers. Specifically, the content of surfactant A (C2F5OCF2CF2OCF2COONH4) and each compound represented by formulas (S1) to (S4) was measured by the following method. In the production of aqueous dispersion B, emulsifiers other than surfactant A and the compounds represented by formulas (S1) to (S4) were neither generated from the components used in the production of aqueous dispersion B nor used, and therefore are not contained in aqueous dispersion B. The solid content of aqueous dispersion B was measured, and an amount of aqueous dispersion B equivalent to 0.05 g of solid content was weighed into a 100 mL screw tube. Then, water and methanol were added to the weighed aqueous dispersion B so that 40 g of water / methanol = 50 / 50 volume%. The mixture was then shaken well until coagulation occurred. The solid content was removed, and the liquid phase was centrifuged at 4000 rpm for 1 hour, and the supernatant was extracted. Except for the sample preparation method, the measurement method was the same as the emulsifier content measurement method described above, and the content of the compound represented by any of formulas (S1) to (S4) was also below the limit of quantification in aqueous dispersion B.

[0111] After recovering the gas remaining in the reactor, the liquid was withdrawn. This liquid was designated as aqueous dispersion 1 (second aqueous dispersion). Aqueous dispersion 1 was a dispersion in which particles containing fluorine-containing polymer 2A (average particle size 144.1 nm) were dispersed in an aqueous medium, and the solid content concentration was 11.5% by mass. The emulsifier content in aqueous dispersion 1 was 100 ppm by mass or less. Specifically, the content of surfactant A and each compound represented by formulas (S1) to (S4) was measured in the same manner as in aqueous dispersion B. In the production of aqueous dispersion 1, emulsifiers other than surfactant A and the compounds represented by formulas (S1) to (S4) were neither generated from the components used in the production of aqueous dispersion 1 nor used, and therefore are not contained in aqueous dispersion 1.

[0112] An aqueous aluminum sulfate solution was added to the above aqueous dispersion 1 and solidification was carried out. The resulting solid was washed with water and dried to obtain a solid composition 1 containing a rubbery fluorine-containing copolymer. Analysis of the obtained solid composition 1 by NMR revealed that the PMVE unit / TFE unit ratio was 66 / 34 (molar ratio).

[0113] [Raw material liquid C] Ultrapure water (180g), PMVE (72g), and TFE (14g) were charged into a 2.2L stainless steel pressure reactor equipped with anchor blades, and the temperature was raised to 90°C while stirring at 600 rpm. Next, an aqueous solution of ammonium persulfate (5.0% by mass, 30cc) was added to start polymerization. As polymerization began, the pressure inside the reactor decreased, so TFE was added to maintain a constant pressure. After adding 4g of TFE under pressure, the reactor was cooled and the polymerization reaction was terminated. After recovering the remaining gas in the reactor, the liquid was drained. This liquid was designated as raw material liquid C. After freezing and condensing the raw material liquid C, it was filtered off, and the resulting fluorine-containing polymer 1C was analyzed by NMR. The result showed that the PMVE units / TFE units = 30 / 70 (molar ratio).

[0114] [Raw material liquid D] Raw material liquid D was manufactured using the same procedure as raw material liquid B, except that raw material liquid C was used instead of raw material liquid A.

[0115] [Example 2] A stainless steel pressure reactor with an internal volume of 2.2 L and equipped with anchor blades was charged with raw material liquid D (1000 g) and ultrapure water (175 g) to obtain aqueous dispersion D (first aqueous dispersion). PMVE (43 g) and TFE (32 g) were added to this, and the mixture was heated to 80°C while stirring at 600 rpm. TFE and PMVE were injected under pressure until the reactor pressure reached 1.2 MPa [gauge], and an aqueous solution of ammonium persulfate (2.5 mass%, 7 ml) was added to start polymerization. As polymerization began, the pressure inside the reactor decreased, so TFE and PMVE were added alternately to maintain a constant pressure. After 80 g of TFE and 63 g of PMVE were injected under pressure, the reactor was cooled and the polymerization reaction was terminated. The polymerization time was 173 minutes.

[0116] Furthermore, the content of fluorine-containing polymer 1C in aqueous dispersion D was 0.4% by mass relative to the total mass of aqueous dispersion D. Furthermore, when the amount of aqueous medium used in aqueous dispersion D used for polymerization was 100 parts by mass, the amount of monomer used for polymerization was 25.1 parts by mass. Aqueous dispersion D contained virtually no emulsifiers. Specifically, the content of surfactant A and each compound represented by formulas (S1) to (S4) was measured using the same method as for aqueous dispersion B. In the production of aqueous dispersion D, emulsifiers other than surfactant A and each compound represented by formulas (S1) to (S4) were neither generated from the components used in the production of aqueous dispersion D nor used, and therefore are not contained in aqueous dispersion D.

[0117] After recovering the gas remaining in the reactor, the liquid was withdrawn. This liquid was designated as aqueous dispersion 3 (second aqueous dispersion). Aqueous dispersion 2 was a dispersion in which particles containing fluorine-containing polymer 2C (average particle size 174.1 nm) were dispersed in an aqueous medium, and the solid content concentration was 11.5% by mass. The emulsifier content in aqueous dispersion 2 was 100 ppm by mass or less. Specifically, the content of surfactant A and each compound represented by formulas (S1) to (S4) was measured using the same method as for aqueous dispersion B. In the production of aqueous dispersion 2, emulsifiers other than surfactant A and the compounds represented by formulas (S1) to (S4) were neither generated from the components used in the production of aqueous dispersion 2 nor used, and therefore are not contained in aqueous dispersion 2.

[0118] An aqueous aluminum sulfate solution was added to the above aqueous dispersion 2 and solidification was carried out. The resulting solid was washed with water and dried to obtain a solid composition 2 containing a rubbery fluorine-containing copolymer. Analysis of the obtained solid composition 2 by NMR revealed that the PMVE unit / TFE unit ratio was 34 / 66 (molar ratio).

[0119] [Raw material liquid E] Except for appropriately changing the amounts of each component used, fluorine-containing polymer 1E was polymerized using the same procedure as in the production of raw material liquid A, and this liquid was used as raw material liquid E. After freezing and condensing raw material liquid E, it was filtered off, and the obtained fluorine-containing polymer 1E was analyzed by NMR, and the result was PMVE units / TFE units = 32 / 68 (molar ratio).

[0120] [Raw material liquid F] Raw material liquid F was manufactured using the same procedure as for raw material liquid B, except that raw material liquid E was used instead of raw material liquid A.

[0121] [Example 3] A stainless steel pressure reactor with an internal volume of 2.2 L and equipped with anchor blades was charged with raw material liquid F (1000 g) and ultrapure water (182 g) to obtain an aqueous dispersion F (first aqueous dispersion). PMVE (90 g) and TFE (18 g) were then charged, and the mixture was heated to 80°C while stirring at 600 rpm. TFE and PMVE were injected under pressure until the reactor pressure reached 1.5 MPa [gauge], and an aqueous solution of ammonium persulfate (0.5 mass%, 16 ml) was added to start polymerization. As polymerization began, the pressure inside the reactor decreased, so TFE and PMVE were added alternately to maintain a constant pressure. When 6.0 g of TFE had been added, C4DI (2.0 g) and ultrapure water (10 cc) were injected under pressure. After 154 g of TFE and 133 g of PMVE had been injected under pressure, the reactor was cooled and the polymerization reaction was terminated. The polymerization time was 300 minutes.

[0122] Furthermore, the content of fluorine-containing polymer 1E in aqueous dispersion F was 0.4% by mass relative to the total mass of aqueous dispersion F. Furthermore, when the amount of aqueous medium used in the aqueous dispersion F used for polymerization was 100 parts by mass, the amount of monomer used for polymerization was 40.6 parts by mass. Aqueous dispersion F contained virtually no emulsifiers. Specifically, the content of surfactant A and each compound represented by formulas (S1) to (S4) was measured using the same method as for aqueous dispersion B. In the production of aqueous dispersion F, emulsifiers other than surfactant A and each compound represented by formulas (S1) to (S4) were neither generated from the components used in the production of aqueous dispersion F nor used, and therefore are not contained in aqueous dispersion F.

[0123] After recovering the gas remaining in the reactor, the liquid was withdrawn. This liquid was designated as aqueous dispersion 3. Aqueous dispersion 3 was a dispersion in which particles containing fluorine-containing polymer 2E (average particle size 89.9 nm) were dispersed in an aqueous medium, and the solid content concentration was 19.3% by mass. The emulsifier content in aqueous dispersion 3 was 100 ppm by mass or less. Specifically, the content of surfactant A and each compound represented by formulas (S1) to (S4) was measured using the same method as for aqueous dispersion B. In the production of aqueous dispersion 3, emulsifiers other than surfactant A and the compounds represented by formulas (S1) to (S4) were neither generated from the components used in the production of aqueous dispersion 3 nor used, and therefore are not contained in aqueous dispersion 3.

[0124] An aqueous solution of aluminum sulfate was added to the above aqueous dispersion to induce solidification. The resulting solid was washed with water and dried to obtain a solid composition 3 containing a rubbery fluorine-containing copolymer. Analysis of the obtained solid composition 3 by NMR revealed a PMVE / TFE ratio of 35 / 65 (molar ratio). The iodine content relative to the total mass of fluorine-containing polymer 1E and fluorine-containing polymer 2E was 0.04% by mass.

[0125] [Raw material liquid G] Except for appropriately changing the amounts of each component used, fluorine-containing polymer 1G was polymerized using the same procedure as in the production of raw material liquid A, and this liquid was used as raw material liquid G. After freezing and condensing raw material liquid G, it was filtered off, and the obtained fluorine polymer 1G was analyzed by NMR, and the result was PMVE units / TFE units = 32 / 68 (molar ratio).

[0126] [Raw material liquid H] Raw material solution H was manufactured using the same procedure as for raw material solution B, except that raw material solution G was used instead of raw material solution A.

[0127] [Example 4] A stainless steel pressure reactor with an internal volume of 2.2 L and equipped with anchor blades was charged with raw material liquid H (1000 g) and ultrapure water (182 g) to obtain aqueous dispersion H (first aqueous dispersion). PMVE (90 g) and TFE (18 g) were then charged, and the mixture was heated to 75°C while stirring at 600 rpm. TFE and PMVE were injected under pressure until the reactor pressure reached 1.5 MPa [gauge], and an aqueous solution of ammonium persulfate (0.5 mass%, 16 ml) was added to start polymerization. As polymerization began, the pressure inside the reactor decreased, so TFE and PMVE were added alternately to maintain a constant pressure. When 6.0 g of TFE had been added, C4DI (2.0 g) and ultrapure water (10 cc) were injected under pressure. After 160 g of TFE and 133 g of PMVE had been injected under pressure, the reactor was cooled and the polymerization reaction was terminated. The polymerization time was 440 minutes.

[0128] The content of 1G of fluorine-containing polymer was 0.4% by mass relative to the total mass of aqueous dispersion H. Furthermore, when the amount of aqueous medium used in the aqueous dispersion H used for polymerization was 100 parts by mass, the amount of monomer used for polymerization was 40.6 parts by mass. Aqueous dispersion H contained virtually no emulsifiers. Specifically, the content of surfactant A and each compound represented by formulas (S1) to (S4) was measured using the same method as for aqueous dispersion B. In the production of aqueous dispersion H, emulsifiers other than surfactant A and each compound represented by formulas (S1) to (S4) were neither generated from the components used in the production of aqueous dispersion H nor used, and therefore are not contained in aqueous dispersion H.

[0129] After recovering the gas remaining in the reactor, the liquid was withdrawn. This liquid was designated as aqueous dispersion 4 (second aqueous dispersion). Aqueous dispersion 4 was a dispersion in which particles containing fluorine-containing polymer 2G (average particle size 90.5 nm) were dispersed in an aqueous medium, and the solid content concentration was 20.1% by mass. The emulsifier content in aqueous dispersion 4 was 100 ppm by mass or less. Specifically, the content of surfactant A and each compound represented by formulas (S1) to (S4) was measured using the same method as for aqueous dispersion B. In the production of aqueous dispersion 4, emulsifiers other than surfactant A and the compounds represented by formulas (S1) to (S4) were neither generated from the components used in the production of aqueous dispersion 4 nor used, and therefore are not contained in aqueous dispersion 4.

[0130] An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce solidification. The resulting solid was washed with water and dried to obtain a solid composition 4 containing a rubbery fluorine-containing copolymer. NMR analysis of the obtained solid composition 4 revealed a PMVE / TFE ratio of 34 / 66 (molar ratio). The iodine content relative to the total mass of fluorine-containing polymer 1H and fluorine-containing polymer 2H was 0.04% by mass.

[0131] [Raw material liquid P] Except for appropriately changing the amounts of each component used, the fluorine-containing polymer 1P was polymerized using the same procedure as in the production of raw material liquid A, and this liquid was used as raw material liquid P. After freezing and condensing raw material liquid P, it was filtered off, and the resulting fluorine polymer 1N was analyzed by NMR, and the result was PMVE units / TFE units = 34 / 66 (molar ratio).

[0132] [Raw material liquid Q] Raw material liquid Q was manufactured using the same procedure as for raw material liquid B, except that raw material liquid P was used instead of raw material liquid A.

[0133] [Example 5] In a 2.2 L stainless steel pressure reactor equipped with anchor blades, 850 g of raw material solution Q, 332 g of ultrapure water, and 0.11 g of disodium hydrogen phosphate dodecahydrate were charged to obtain aqueous dispersion Q (first aqueous dispersion). 90 g of PMVE, 18 g of TFE, and 1.1 g of 8CNVE were then added, and the mixture was heated to 80°C while stirring at 600 rpm. TFE and PMVE were injected under pressure until the reactor pressure reached 1.5 MPa [gauge], and an aqueous solution of ammonium persulfate (3% by mass, 18 ml) was added to initiate polymerization. As polymerization began, the pressure in the reactor decreased, so TFE and PMVE were added alternately to maintain a constant pressure. For every 16 g of TFE added, 12 g of PMVE and 1.26 g of 8CNVE were added. To maintain a constant polymerization rate, aqueous solution of ammonium persulfate was added as needed. The polymerization reaction was terminated by cooling the reactor after adding 160g of TFE, 108g of PMVE, and 12.6g of 8CNVE under pressure. The polymerization time was 130 minutes. The total amount of 3% by mass ammonium persulfate aqueous solution added was 24 ml. The content of fluorine-containing polymer 1P was 0.6% by mass relative to the total mass of the aqueous dispersion Q. Furthermore, when the amount of aqueous medium used in the aqueous dispersion Q used for polymerization was 100 parts by mass, the amount of monomer used for polymerization was 23 parts by mass. Aqueous dispersion Q contained virtually no emulsifiers. Specifically, the content of surfactant A and each compound represented by formulas (S1) to (S4) was measured using the same method as for aqueous dispersion B. In the production of aqueous dispersion Q, emulsifiers other than surfactant A and each compound represented by formulas (S1) to (S4) were neither generated from the components used in the production of aqueous dispersion Q nor were used, and therefore are not contained in aqueous dispersion Q.

[0134] After recovering the gas remaining in the reactor, the liquid was withdrawn. This liquid was designated as aqueous dispersion 5 (second aqueous dispersion). Aqueous dispersion 5 was a dispersion in which particles containing fluorine-containing polymer 2P (average particle size 45.5 nm) were dispersed in an aqueous medium, and the solid content concentration was 19.1% by mass. The emulsifier content in aqueous dispersion 5 was 100 ppm by mass or less. Specifically, the content of surfactant A and each compound represented by formulas (S1) to (S4) was measured in the same manner as in aqueous dispersion B. In the production of aqueous dispersion 5, emulsifiers other than surfactant A and the compounds represented by formulas (S1) to (S4) were neither generated from the components used in the production of aqueous dispersion 5 nor used, and therefore are not contained in aqueous dispersion 5. A 3% by mass aqueous solution of nitric acid was added to the above aqueous dispersion to induce coagulation. The resulting coagulated material was washed with water and dried to obtain a solid composition 5 containing a rubbery fluorine-containing copolymer. Analysis of the obtained solid composition 5 by NMR revealed that the PMVE units / TFE units / 8CNVE units were 68.3 / 31.2 / 0.5 (molar ratio).

[0135] [Raw material liquid K] Ultrapure water (593g) and MMA (methyl methacrylate, 2.8g) were charged into a 1.0L glass reactor, and the temperature was raised to 60°C while stirring at 500 rpm. Next, an aqueous solution of ammonium persulfate (10% by mass, 6.0cc) was added, and polymerization was carried out for 60 minutes. After the polymerization reaction was complete, the liquid was removed and this liquid was used as the starting material solution K. The raw material liquid K was heated to remove water, and the residue was then heated and dried to obtain a hydrocarbon polymer (poly-MMA).

[0136] [Raw material liquid L] To the above raw material solution K (490g), Purolite A300 (Purolite, anion exchange resin, 20g) was added. 60 minutes after stirring began, the raw material solution and the ion exchange resin were filtered apart to obtain raw material solution L. The raw material liquid L contained hydrocarbon polymer (polyMMA) particles (average particle size 116 nm) dispersed in an aqueous medium. Based on the amount of MMA used, the hydrocarbon polymer content was 0.47% by mass relative to the total mass of the raw material liquid L.

[0137] [Example 6] A stainless steel pressure reactor with an internal volume of 2.2 L, equipped with anchor blades, was charged with a raw material solution L (3.91 g) and ultrapure water (1162 g) to obtain an aqueous dispersion L. The aqueous dispersion L was heated to 80°C while being stirred at 600 rpm, and PMVE (72 g) and TFE (14 g) were added. Next, an aqueous solution of ammonium persulfate (20% by mass, 5 mL) was added to start polymerization. As the pressure inside the reactor decreased as polymerization began, more TFE and PMVE were added to maintain a constant pressure of 1.2 MPa [gauge]. After 160 g of TFE and 133 g of PMVE were injected under pressure, the reactor was cooled and the polymerization reaction was terminated. The polymerization time was 411 minutes. After recovering the gas remaining in the reactor, the liquid was withdrawn. This liquid was designated as aqueous dispersion 6. Aqueous dispersion 6 was a dispersion in which particles (average particle size 195.2 nm) containing 2 L of fluorine-containing polymer were dispersed in an aqueous medium, and the solid content concentration was 20.7% by mass. An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce coagulation. The resulting coagulated material was washed with water and dried to obtain a solid composition 6 containing 2 L of rubbery fluorine-containing polymer.

[0138] [Example 7] After degassing a 2.1 L stainless steel pressure reactor equipped with anchor blades, the gas phase was replaced with nitrogen, and while stirring at a speed of 600 rpm using the anchor blades, ultrapure water (1004 g), a 30% by mass solution of C2F5OCF2CF2OCF2COONH4 (surfactant A) as an emulsifier (80.1 g), and a 5% by mass aqueous solution of disodium hydrogen phosphate dodecahydrate (10.49 g) were charged to obtain aqueous dispersion M. Then, PMVE (72 g) and TFE (14 g) were injected under pressure into the container, and the internal temperature was raised to 80°C. Next, an aqueous solution of ammonium persulfate (1.0% by mass, 20 mL) was added, and polymerization was started. As the pressure inside the reactor decreased with the start of polymerization, TFE and PMVE were further added to maintain a constant pressure of 1.2 MPa [gauge]. The polymerization reaction was terminated by cooling the reactor after injecting 160g of TFE and 133g of PMVE. The polymerization time was 262 minutes. After recovering the gas remaining in the reactor, the liquid was removed. This liquid was designated as aqueous dispersion 7. Aqueous dispersion 7 was a dispersion in which particles (average particle size 80.0 nm) containing fluorine-containing polymer 2M were dispersed in an aqueous medium, and the solid content concentration was 20.0% by mass. An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce coagulation. The resulting coagulated material was washed with water and dried to obtain a rubbery solid composition 7 containing fluorine-containing polymer 2M.

[0139] [evaluation] <2 mass% reduction temperature> A 10 mg solid composition (sample) was weighed into an aluminum pan and heated in an air atmosphere at a rate of 10°C / min from 30°C to 550°C. The temperature at which the mass of the sample became 98% of its original mass (with the sample mass before heating being considered 100%) was defined as the 2% mass reduction temperature. A higher 2% mass reduction temperature indicates superior heat resistance. The equipment used was the Hitachi High-Tech NEXTA STA series STA200.

[0140] <Water dispersion stability> The water dispersion stability was evaluated by measuring the precipitation rates shown below when 30g of each aqueous dispersion (1-7) was stirred at high speed of 2000 rpm x 180 min using a 60mm diameter disk turbine. A lower precipitation rate indicates superior water dispersion stability. Sedimentation rate (%) = 100 × Precipitated aggregates (g) / (30 (g) × Concentration of fluorine-containing polymer (mass%) / 100)

[0141] [Table 5]

[0142] In Table 5, the content of formula (S2) means the sum of the content of each compound in formula (S2) where n1 is an integer from 3 to 19, relative to the total mass of the solid composition; the content of formula (S3) means the sum of the content of each compound in formula (S3) where n2 is an integer from 4 to 20, relative to the total mass of the solid composition; and the content of formula (S4) means the sum of the content of each compound in formula (S4) where n2 is an integer from 4 to 20, relative to the total mass of the solid composition. Furthermore, in the production of solid compositions 1 to 5, compounds represented by formulas (S1) to (S4) and emulsifiers other than surfactant A were neither generated from the components used in the production of solid compositions 1 to 5 nor were used, and therefore are not included in solid compositions 1 to 5.

[0143] [Table 6] <Processability Evaluation Results>

[0144] [Table 7]

[0145] The present invention demonstrates that the method for producing fluorine-containing elastomers can efficiently produce fluorine-containing elastomers with excellent water dispersion stability without requiring emulsifiers, while using an environmentally friendly aqueous medium (Examples 1 to 5). In contrast, Example 6 showed poor water dispersion stability of the resulting fluorine-containing elastomer. Furthermore, Example 7 is a method for producing a fluorine-containing elastomer using an emulsifier, and it was confirmed that Examples 1 to 5 all exhibited the same efficiency and water dispersion stability as when an emulsifier was used, even when an emulsifier was substantially not used.

[0146] Furthermore, the entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2023-117444, filed on July 19, 2023, are incorporated herein by reference as disclosure of the present invention.

Claims

1. In an aqueous dispersion containing a primary fluorine-containing polymer that is substantially free of water-soluble emulsifiers and comprises units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether), and an aqueous medium, A method for producing a fluorine-containing elastomer, comprising polymerizing a monomer containing tetrafluoroethylene and perfluoro(alkyl vinyl ether) to produce a secondary fluorine-containing polymer, In the first fluorine-containing polymer, the content of the units based on perfluoro(alkyl vinyl ether) is 20 to 95 mol% relative to the total of the units based on tetrafluoroethylene and the units based on perfluoro(alkyl vinyl ether). In the second fluorine-containing polymer, the content of the units based on perfluoro(alkyl vinyl ether) is 20 to 95 mol% relative to the total of the units based on tetrafluoroethylene and the units based on perfluoro(alkyl vinyl ether). A method for producing a fluorine-containing elastomer, wherein, before the polymerization of the monomer is started, 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.

2. The monomer consists only of tetrafluoroethylene and perfluoro(alkyl vinyl ether), or A method for producing a fluorine-containing elastomer according to claim 1, comprising tetrafluoroethylene and perfluoro(alkyl vinyl ether), and further comprising a monomer having two or more polymerizable unsaturated bonds, a monomer having one or more atoms selected from the group consisting of chlorine atoms, bromine atoms and iodine atoms, and a monomer having a nitrile group, selected from the group consisting of these elements.

3. The method for producing a fluorine-containing elastomer according to claim 1 or 2, wherein the amount of monomer used is 1 to 80 parts by mass per 100 parts by mass of the aqueous medium used.

4. A method for producing a fluorine-containing elastomer according to claim 1 or 2, wherein the monomer is polymerized in the presence of a polymerization initiator.

5. An aqueous dispersion comprising an aqueous medium and particles containing a fluorine-containing polymer, The average particle diameter of the aforementioned particles is 1 μm or less. The particles include units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether), The fluorine-containing polymer has at least one of a chlorine atom, a bromine atom, an iodine atom, and a nitrile group at the end and side chains, An aqueous dispersion in which the emulsifier content is 100 ppm by mass or less relative to the total mass of the aqueous dispersion.

6. The particles consist solely of units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether), or The aqueous dispersion according to claim 5, comprising units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether), and further comprising units based on monomers having two or more polymerizable unsaturated bonds, units based on monomers having one or more atoms selected from the group consisting of chlorine atoms, bromine atoms and iodine atoms, and units based on monomers having a nitrile group, and at least one unit selected from this group.

7. A solid composition containing a fluorine-containing polymer, The solid composition comprises a unit based on tetrafluoroethylene and a unit based on perfluoro(alkyl vinyl ether), A solid composition which is substantially free of emulsifiers and has a storage modulus G' of 200 to 1200 kPa.

8. The solid composition according to claim 7, wherein at least one of the terminal and side chains of the fluorine-containing polymer has at least one of a chlorine atom, a bromine atom, an iodine atom, and a nitrile group.

9. A crosslinked rubber article obtained by crosslinking the solid composition described in claim 8.

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