Method for producing fluorine-containing elastomer, aqueous dispersion, and solid composition

Abstract

Provided is a method for producing a fluorine-containing elastomer with which it is possible to efficiently produce a fluorine-containing polymer having excellent water dispersion stability without requiring an emulsifier even when an aqueous medium having a small environmental burden is used. A method for producing a fluorine-containing elastomer in which a monomer containing TFE and PAVE is polymerized in an aqueous dispersion that does not substantially contain a water-soluble emulsifier and that contains a first fluorine-containing polymer containing TFE units and PAVE units and an aqueous medium to produce a second fluorine-containing polymer, in which the TFE units and the PAVE units are separated from each other, and in which the TFE units and the PAVE units are separated from each other, the second fluorine-containing polymer is produced by polymerizing a monomer containing TFE and PAVE in an aqueous dispersion that does not substantially contain a water-soluble emulsifier. In the first fluorine-containing polymer, the amount of the PAVE unit is 20-95 mol% relative to the total amount of the TFE unit and the PAVE unit, in the second fluorine-containing polymer, the amount of the PAVE unit is 20-95 mol% relative to the total amount of the TFE unit and the PAVE unit, and the content of the first fluorine-containing polymer is 0.01-4.0 mass% relative to the total mass of the aqueous dispersion before the polymerization of the monomers is started.

Description

Technical Field

[0001] This invention relates to a method for manufacturing fluorinated elastomers, aqueous dispersions, and solid compositions. Background Technology

[0002] Fluorinated elastomers have excellent heat resistance, chemical resistance, flame retardancy, and weather resistance, and are therefore used in various industrial fields.

[0003] As a method for manufacturing fluorinated elastomers, one example is a method of using an emulsifier to carry out emulsion polymerization of fluorinated monomers in an aqueous medium (see Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2022 / 052498 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] In the method for manufacturing fluorinated elastomers in Patent Document 1, the environmental impact is small because an aqueous medium is used. However, if a large amount of emulsifier, which is an essential component, remains in the aqueous dispersion obtained by polymerization, the emulsifier needs to be removed depending on the application.

[0009] In addition, the obtained fluorinated elastomer is required to have excellent water dispersion stability.

[0010] The objective of this invention is to provide a method for manufacturing fluorinated elastomers that does not require emulsifiers even when using aqueous media with low environmental impact, and can efficiently manufacture fluorinated elastomers with excellent water dispersion stability.

[0011] In addition, the subject of this invention is to provide aqueous dispersions and solid compositions.

[0012] Solution for solving the problem

[0013] The inventors conducted in-depth research and found that the above-mentioned problems can be solved by the following configuration. [1]

[0015] A method for manufacturing a fluorinated elastomer, wherein, in an aqueous dispersion substantially free of water-soluble emulsifiers and comprising a first fluorinated polymer and an aqueous medium,

[0016] A second fluoropolymer is produced by polymerizing monomers comprising tetrafluoroethylene and perfluoro(alkyl vinyl ether), wherein the first fluoropolymer comprises tetrafluoroethylene-based units and perfluoro(alkyl vinyl ether)-based units.

[0017] In the first fluoropolymer mentioned above, the content of the perfluoro(alkyl vinyl ether)-based units is 20-95 mol%, relative to the total of the tetrafluoroethylene-based units and the perfluoro(alkyl vinyl ether)-based units.

[0018] In the second fluoropolymer described above, the content of the perfluoro(alkyl vinyl ether)-based units is 20-95 mol%, relative to the total of the tetrafluoroethylene-based units and the perfluoro(alkyl vinyl ether)-based units.

[0019] Before the polymerization of the monomers begins, the content of the first fluoropolymer is 0.01 to 4.0% of the total mass of the aqueous dispersion. [2]

[0021] According to the manufacturing method of the fluorinated elastomer described in [1], the monomer is composed only of tetrafluoroethylene and perfluoro(alkyl vinyl ether), or

[0022] The monomers mentioned above include tetrafluoroethylene and perfluoro(alkyl vinyl ether), and include at least one monomer selected from the group consisting of: monomers having two or more polymerizable unsaturated bonds, monomers having at least one atom selected from the group consisting of chlorine, bromine and iodine atoms, and monomers having a nitrile group. [3]

[0024] According to the manufacturing method of the fluorinated elastomer described in [1] or [2], the amount of the monomer is 1 to 80 parts by mass relative to 100 parts by mass of the aqueous medium. [4]

[0026] According to the manufacturing method of the fluorinated elastomer described in [1] to [3], the monomer is polymerized in the presence of a polymerization initiator. [5]

[0028] An aqueous dispersion comprising an aqueous medium and particles, wherein the particles comprise a fluoropolymer and the average particle size is less than 1 μm.

[0029] The aforementioned particles comprise tetrafluoroethylene-based units and perfluoro(alkyl vinyl ether)-based units.

[0030] The fluoropolymer has at least one of the following at the end and at least one of the side chains: a chlorine atom, a bromine atom, an iodine atom, and a nitrile group.

[0031] The content of the emulsifier is less than 100 ppm by mass relative to the total mass of the above aqueous dispersion. [6]

[0033] According to the aqueous dispersion described in [5], the particles are composed only of tetrafluoroethylene-based units and perfluoro(alkyl vinyl ether)-based units, or

[0034] The aforementioned particles comprise units based on tetrafluoroethylene and units based on perfluorinated (alkyl vinyl ethers), and comprise at least one unit selected from the group consisting of: units based on monomers having two or more polymerizable unsaturated bonds, units based on monomers having at least one atom selected from the group consisting of chlorine, bromine and iodine atoms, and units based on monomers having a nitrile group. [7]

[0036] A solid composition comprising a fluoropolymer,

[0037] The above solid composition comprises tetrafluoroethylene-based units and perfluoro(alkyl vinyl ether)-based units.

[0038] The above solid composition does not substantially contain emulsifiers and has a storage modulus G' of 200~1200 kPa. [8]

[0040] The solid composition according to [7] has at least one of a chlorine atom, a bromine atom, an iodine atom and a nitrile group at at least one of the ends and side chains of the aforementioned fluoropolymer. [9]

[0042] A cross-linked rubber product, which is formed by cross-linking the solid composition described in [8].

[0043] The effects of the invention

[0044] According to the present invention, a method for manufacturing fluorinated elastomers is provided that does not require emulsifiers even when using aqueous media with low environmental impact, and can efficiently manufacture fluorinated elastomers with excellent water dispersion stability.

[0045] In addition, the subject of this invention is to provide aqueous dispersions and solid compositions. Detailed Implementation

[0046] The meanings of the terms used in this invention are as follows.

[0047] The numerical range indicated by "~" refers to the range of values ​​before and after "~" as lower and upper limits. Within the numerical ranges described in this specification, the upper or lower limit value described in a particular numerical range can be replaced by the upper or lower limit value of other numerical ranges described in different stages. Furthermore, within the numerical ranges described in this specification, the upper or lower limit value described in a particular numerical range can be replaced by the value shown in the embodiments. In this specification, each component can be used alone with one equivalent substance, or in combination with two or more substances. Here, regarding each component, when two or more substances are used in combination, unless otherwise specified, the content of that component refers to the total content of the combined substances.

[0048] In this specification, a combination of two or more preferred methods is a more preferred method.

[0049] A "unit" is a general term for atomic groups directly formed by the polymerization of monomers, derived from one molecule of the aforementioned monomer, and for atomic groups obtained by chemically transforming a portion of the aforementioned atomic groups. Hereinafter, "monomer-based units" will also be abbreviated as "units".

[0050] The content (mass % or mole %) of each unit relative to all units contained in the polymer is determined by analyzing the polymer using solid-state nuclear magnetic resonance spectroscopy (NMR). Typically, the content of each unit calculated from the amount of each monomer added is roughly consistent with the actual content of each unit.

[0051] "Fluoropolymers" refer to elastic fluorinated copolymers that do not have a melting point and have a storage modulus G' of 80 or higher at 100°C and 50 cpm as measured by ASTM D6204. They are different from fluoropolymers.

[0052] [Manufacturing method of fluorinated elastomers]

[0053] The method for manufacturing the fluorinated elastomer of the present invention (hereinafter also referred to as "the manufacturing method") involves polymerizing a monomer comprising tetrafluoroethylene and a perfluorinated (alkyl vinyl ether) monomer (hereinafter also referred to as "specific monomer") in an aqueous dispersion comprising a first fluorinated polymer and an aqueous medium (hereinafter also referred to as "the first aqueous dispersion") to produce a second fluorinated polymer, wherein the first fluorinated polymer comprises tetrafluoroethylene-based units and perfluorinated (alkyl vinyl ether)-based units.

[0054] In the first fluoropolymer, the content of perfluoro(alkyl vinyl ether)-based units is 20-95 mol%, relative to the total of tetrafluoroethylene-based units and perfluoro(alkyl vinyl ether)-based units.

[0055] In the second fluoropolymer, the percentage of units based on perfluoro(alkyl vinyl ether) is 20–95 mol%, relative to the total number of tetrafluoroethylene-based units and perfluoro(alkyl vinyl ether)-based units.

[0056] Before the polymerization of the monomers begins, the content of the first fluoropolymer is 0.01 to 4.0% of the total mass of the aqueous dispersion.

[0057] This manufacturing method enables the efficient production of fluorinated elastomers with excellent water dispersion stability even without the need for emulsifiers. The reason for this can be inferred as follows: by using an aqueous dispersion of a first fluorinated polymer in a specified amount containing each unit in a specified ratio, the first fluorinated polymer functions as a good polymerization site for the second fluorinated polymer when the raw material monomers of the second fluorinated polymer are polymerized, thus achieving the desired effect.

[0058] According to this manufacturing method, even without the use of emulsifiers, it is possible to obtain fluorinated emulsifiers with physical properties equal to or greater than those of fluorinated emulsifiers manufactured using emulsifiers.

[0059] <First Aqueous Dispersion>

[0060] In this manufacturing method, a first aqueous dispersion containing a first fluoropolymer and an aqueous medium is used, which is substantially free of water-soluble emulsifiers.

[0061] (Emulsifier)

[0062] The first aqueous dispersion does not actually contain water-soluble emulsifiers.

[0063] Essentially, "free of water-soluble emulsifiers" means that the content of water-soluble emulsifiers in the first aqueous dispersion 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. Furthermore, it is also preferable to be below the quantitation limit of the determination method in the examples. One ppb by mass is an example of a lower limit.

[0064] The content of water-soluble emulsifiers can be determined using liquid chromatography-mass spectrometry. Specifically, the determination methods described in paragraphs 0721 to 0732 of International Publication No. 2018 / 181904, and the determination methods shown in the preferred embodiments, can be cited.

[0065] Water-soluble emulsifiers are those with a solubility of more than 100 mg in 1000 g of water at 25°C.

[0066] Examples of water-soluble emulsifiers include hydrocarbon surfactants, fluorinated emulsifiers, and water-soluble emulsifiers among polymeric emulsifiers.

[0067] Neither the first fluoropolymer described later nor the second fluoropolymer described later are water-soluble emulsifiers.

[0068] Water-soluble emulsifiers can be either ionic or nonionic.

[0069] Hydrocarbon-containing surfactants are surfactants that contain hydrocarbons. More specifically, at least a few of the monovalent substituents on the carbon atom are hydrogen atoms, and halogen atoms such as fluorine and chlorine atoms can also be used for substitution. In hydrocarbon-containing surfactants, it is preferable that at least 75% of the monovalent substituents on the carbon atom are hydrogen atoms, more preferably at least 85% are hydrogen atoms, and even more preferably at least 95% are hydrogen atoms.

[0070] Examples of hydrocarbon-containing surfactants include hydrocarbon surfactants and siloxane surfactants. Hydrocarbon surfactants are surfactants that do not contain silicon atoms and whose monovalent substituents on carbon atoms are 100% hydrogen atoms, thus lacking halogen atoms such as chlorine and fluorine atoms. Siloxane surfactants are hydrocarbon-containing surfactants having hydrophobic groups comprising a siloxane backbone containing multiple siloxane units.

[0071] Anionic hydrocarbon surfactants can be cited as examples of hydrocarbon surfactants.

[0072] Anionic hydrocarbon surfactants refer to hydrocarbon surfactants that have negatively charged hydrophilic parts such as carboxylic acid groups, sulfonic acid groups, sulfuric acid groups, phosphonic acid groups, and phosphate groups, as well as hydrocarbon parts such as alkyl groups that are hydrophobic.

[0073] As an example of anionic hydrocarbon surfactants, highly branched C10 tertiary carboxylic acids supplied by Resolution Performance Products as Versatic (registered trademark) 10 can be cited. Other examples of anionic hydrocarbon surfactants include linear alkyl polyether sulfonates supplied by BASF as Avanel (registered trademark) S series.

[0074] Sodium dodecyl sulfate can also be cited as an anionic hydrocarbon surfactant.

[0075] Another example of anionic hydrocarbon surfactants is Lankropol (registered trademark) K8300, a sulfosuccinate surfactant available from AkzoNobelSurfaceChemistry LLC.

[0076] Nonionic hydrocarbon surfactants can also be cited as examples of hydrocarbon surfactants.

[0077] Nonionic hydrocarbon surfactants do not possess charged groups, but they do have hydrophobic portions, which are mostly long-chain hydrocarbons. Examples of water-soluble functional groups in nonionic hydrocarbon surfactants include polyoxyethylene chains obtained from the polymerization of ethylene oxide. Examples of nonionic hydrocarbon surfactants include block copolymers containing various polyoxyethylene blocks, such as those containing polyoxyethylene and polypropylene oxide.

[0078] As nonionic hydrocarbon surfactants, the surfactants described in paragraphs

[0043] to

[0052] of Japanese Patent Publication No. 2016-537499 can be cited as examples.

[0079] 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.).

[0080] Anionic fluorinated surfactants can be cited as examples of fluorinated emulsifiers.

[0081] Examples of anionic fluorinated surfactants include surfactants containing fluorine atoms in which the total number of carbon atoms in the portion excluding the anionic group is 20 or less, and surfactants containing fluorine in which the molecular weight of the anionic portion is 800 or less. It should be noted that the "anionic portion" mentioned above refers to the portion of the fluorinated surfactant excluding the cationic portion.

[0082] Examples of polymeric emulsifiers include water-soluble polymers having hydrophilic groups on their side chains. Such polymeric emulsifiers may include, for example, polymers comprising units based on compounds having sites capable of reacting in polymerization and hydrophilic groups. Additionally, examples may include polymers obtained by post-treatment, such as hydrolysis, of polymers comprising units based on compounds that initially do not have hydrophilic groups but have groups that can become hydrophilic.

[0083] The first aqueous dispersion preferably does not contain any of the emulsifiers shown in formulas (S1) to (S4). When an emulsifier is not used when manufacturing the first fluoropolymer contained in the first aqueous dispersion, the amount of compounds shown in formulas (S1) to (S4) generated can be suppressed, and thus the adjustment of the content of these compounds becomes easy.

[0084] H-(CF2) n1 -COOM (S1)

[0085] F-(CF2) n1 -COOM (S2)

[0086] H-(CF2) n2 -SO3M (S3)

[0087] F-(CF2) n2 -SO3M (S4)

[0088] In equations (S1) to (S4),

[0089] n1 is an integer between 3 and 19.

[0090] n² is an integer between 4 and 20.

[0091] M can be a hydrogen atom, Na, K, or NH4.

[0092] (First fluoropolymer)

[0093] The first fluoropolymer comprises units based on tetrafluoroethylene (hereinafter also referred to as "TFE") and units based on perfluoro(alkyl vinyl ether) (hereinafter also referred to as "PAVE").

[0094] It is speculated that the first fluoropolymer adsorbs and absorbs the specific monomer during polymerization using its hydrophobic portion, thereby making the specific monomer soluble even without an emulsifier, facilitating its polymerization. Furthermore, it is speculated that the first fluoropolymer contributes to the dispersion stabilization of particles, etc., described later in the aqueous dispersion.

[0095] From the viewpoint of excellent polymerization reactivity when manufacturing the first fluoropolymer and the viewpoint of being able to manufacture the second fluoropolymer more efficiently, the monomer shown in formula (1) is preferred by PAVE.

[0096] CF2 = CF - OR f1 (1)

[0097] In equation (1), R f1 This refers to perfluoroalkyl groups with 1 to 10 carbon atoms. From the perspective of superior polymerization reactivity, R... 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.

[0098] Perfluoroalkyl groups can be linear or branched.

[0099] 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"). From the perspective of being able to manufacture the second fluoropolymer more efficiently, PMVE and PPVE are preferred, and PMVE is more preferred.

[0100] In the first fluoropolymer, the content of PAVE units is 20 to 95 mol% relative to the total of TFE units and PAVE units, preferably 20 to 60 mol%, more preferably 25 to 60 mol% from the viewpoint of being able to manufacture the second fluoropolymer more efficiently, and even more preferably 25 to 55 mol%.

[0101] In the first fluoropolymer, the total content of TFE unit and PAVE unit relative to all units of the first fluoropolymer 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%.

[0102] The first fluoropolymer may contain units based on monomers other than TFE and PAVE, and from the perspective of being able to manufacture the second fluoropolymer more efficiently, it may substantially not contain units based on other monomers.

[0103] Essentially, "not containing units based on other monomers" means that the content of units based on other monomers is less than 0.01 mol% relative to all units of the first fluoropolymer, preferably 0 mol%.

[0104] Before the polymerization of the monomers used for the polymerization of the second fluoropolymer begins, the content of the first fluoropolymer is 0.01 to 4.0% by mass relative to the total mass of the first aqueous dispersion. From the viewpoint of being able to produce the second fluoropolymer more efficiently, it is preferably 0.01 to 0.6% by mass, and more preferably 0.01 to 0.5% by mass.

[0105] In this specification, "before the polymerization of the monomer used for the polymerization of the second fluoropolymer begins" refers to the moment just before the polymerization begins. Here, "the moment of starting polymerization" can include the moment when the reactor is set above the polymerization temperature and the monomer and polymerization initiator coexist in the reactor, and the moment when the reactor is set above the polymerization temperature after the monomer and polymerization initiator coexist in the reactor.

[0106] It should be noted that the first aqueous dispersion, prior to the start of polymerization of the monomers used for the polymerization of the second fluoropolymer, does not contain the monomers and polymerization initiators used for the polymerization of the second fluoropolymer.

[0107] The content (solid component concentration) of the first fluoropolymer can be determined, for example, by the following methods.

[0108] To determine the content (solid component concentration) of the first fluoropolymer in the first aqueous dispersion, heat 2.0 g of the first aqueous dispersion at 170°C for 20 minutes, weigh the residue, and calculate the solid component concentration using the following formula.

[0109] "Solid component concentration (mass%) = 100 × heating residue of the first aqueous dispersion (g) / mass of the first aqueous dispersion (2.0g)"

[0110] The preferred method for manufacturing the first fluoropolymer is to polymerize a monomer containing TFE and PAVE in an aqueous medium in the presence of a polymerization initiator. This yields the first fluoropolymer dispersed in particulate form in an aqueous medium.

[0111] The aqueous medium containing the particles of the first fluoropolymer obtained therefrom can be used directly as the first aqueous dispersion, or other aqueous media can be added to it for use as the first aqueous dispersion. Alternatively, solvent displacement can be performed to disperse the first fluoropolymer in other aqueous media for use as the first aqueous dispersion.

[0112] As a polymerization initiator for the manufacture of the first fluoropolymer, a water-soluble polymerization initiator is preferred, more preferably a persulfate such as ammonium persulfate, sodium persulfate, or potassium persulfate, an organic polymerization initiator such as disuccinate peroxide or azobisisobutylamidine dihydrochloride, and even more preferably a persulfate, especially ammonium persulfate.

[0113] Water and mixtures of water and water-soluble organic solvents can be listed as aqueous media for the manufacture of the first fluoropolymer. Specific examples of water-soluble organic solvents include tert-butanol, propylene glycol, dipropylene glycol, dipropylene glycol monomethyl ether, and tripropylene glycol.

[0114] When manufacturing the first fluoropolymer, it is preferable to make it substantially free of emulsifiers.

[0115] Emulsifiers (the types of emulsifiers and the definition of "substantially non-existent") are as described above.

[0116] Preferably, it is used in the polymerization process to obtain the second fluoropolymer after a purification treatment is performed to reduce or deactivate the polymerization initiator and its decomposition products from an aqueous dispersion containing particles of the first fluoropolymer.

[0117] In the purification process, by removing the polymerization initiator and its decomposition products that may be contained in the dispersion containing the first fluoropolymer, the second fluoropolymer with the desired physical properties can be easily obtained.

[0118] Purification methods include heat treatment and removal using ion exchange resins (preferably anion exchange resins).

[0119] The purification process can be performed multiple times.

[0120] (Aqueous medium)

[0121] The aqueous dispersion used in this manufacturing method comprises an aqueous medium. As described above, the aqueous medium in the first aqueous dispersion can be a polymerization solvent used in the manufacture of the first fluoropolymer. Specific examples of the aqueous medium in the first aqueous dispersion are the same as those for the aqueous medium used in the manufacture of the first fluoropolymer described above.

[0122] Before the polymerization of the monomers used for the polymerization of the second fluoropolymer begins, the content of the aqueous medium relative to the total mass of the first aqueous dispersion 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.

[0123] (Other ingredients)

[0124] The first aqueous dispersion may contain other components besides the first fluoropolymer and the aqueous medium.

[0125] Specific examples of other components that may be included in the first aqueous dispersion include chain transfer agents, reducing agents, and pH adjusters.

[0126] Specific examples of chain transfer agents include ethyl acetate, methanol, ethanol, tert-butyl methyl ether, diethyl ether, n-pentane, cyclohexane, methane, and propane. Additionally, compounds represented by formula (I) described later can also be cited as chain transfer agents.

[0127] Specific examples of reducing agents include sulfurous acid or its salts, hydrogen sulfite or its salts, thiosulfate or its salts, sulfinic acid or its salts, organic acids, and inorganic salts. Specifically, examples include sodium formaldehyde sulfoxylate dihydrate and disodium 2-hydroxy-2-sulfinate acetic acid.

[0128] 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, and carbonates such as sodium bicarbonate and sodium carbonate. More preferred specific examples of phosphates include disodium hydrogen phosphate dihydrate and disodium hydrogen phosphate dodecahydrate.

[0129] When 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 relative to 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 relative to 100 parts by mass of the specific monomer described later, more preferably 0.1 to 15 parts by mass, and even more preferably 0.1 to 10 parts by mass.

[0130] When the first aqueous dispersion contains a reducing agent, the content of the reducing agent is preferably 0.01 to 3.0 parts by mass relative to 100 parts by mass of the aqueous medium.

[0131] When the first aqueous dispersion contains a pH adjuster, the content of the pH adjuster is preferably 0.01 to 3.0 parts by mass relative to 100 parts by mass of the aqueous medium.

[0132] <Specific Individual>

[0133] The specific monomer is a monomer that contains TFE and PAVE.

[0134] The amounts of TFE and PAVE are preferably 80 to 100 mol%, more preferably 90 to 100 mol%, and even more preferably 95 to 100 mol%, relative to the amount of a specific monomer.

[0135] A particular monomer may contain monomers other than TFE and PAVE (hereinafter also referred to as "other monomers").

[0136] Specific examples of other 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 also referred to as "R"). CN "), and units based on the compound (6) described later (hereinafter also referred to as "POAVE units").

[0137] DV is a monomer with two or more polymerizable unsaturated bonds.

[0138] Specific examples of polymerizable unsaturated bonds include carbon-carbon double bonds (C=C) and carbon-carbon triple bonds (C≡C).

[0139] The number of polymerizable unsaturated bonds in the DV is preferably 2 to 6, more preferably 2 or 3, and even more preferably 2, from the perspective of better polymerization reactivity.

[0140] From the perspective that cross-linked rubber products have less compression set at high temperatures, DV preferably also contains fluorine atoms.

[0141] From the perspective of superior demolding properties of cross-linked rubber products, DV is preferably the monomer shown in formula (2).

[0142] (CR) 21 R 22 =CR 23 -) a1 R 24 (2)

[0143] In equation (2), R 21 R 22 and R 23 Each of these elements independently represents a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group; a1 represents an integer from 2 to 6; R 24 This refers to a perfluoroalkyl group with 1 to 10 carbon atoms and an a1 valence, or a group having an ether-like oxygen atom at the end of the perfluoroalkyl group or between carbon-carbon bonds. Multiple R 21 Multiple R 22 and multiple R 23 Each can choose to be the same as or different from the others, with a preference for them to be the same.

[0144] a1 is preferably 2 or 3, and particularly preferably 2.

[0145] Based on the superior polymerization reactivity of DV, R is preferred. 21 R 22 R 23 It is a fluorine atom or a hydrogen atom, more preferably R 21 R 22 R 23 R is particularly preferred from the perspective of superior mold release properties of cross-linked rubber products, as it consists entirely of fluorine atoms or entirely of hydrogen atoms. 21 R 22 R 23 It consists entirely of fluorine atoms.

[0146] R 24 It can be selected from any of the following: linear, branched, or cyclic, preferably linear or branched, and particularly preferably linear. 24 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.

[0147] R 24 It may or may not have ether-type oxygen atoms, but in terms of crosslinking reactivity and superior rubber properties, it is preferred to have ether-type oxygen atoms.

[0148] R 24 The number of ether-containing oxygen atoms is preferably 1 to 6, more preferably 1 to 3, and particularly preferably 1 or 2. R 24 The ether oxygen atom in R is preferably present in R 24 The end of.

[0149] Among the monomers shown in Equation (2), specific examples of suitable monomers can be the monomers shown in Equation (3) and Equation (4).

[0150] (CF2=CF-)2R 31 (3)

[0151] In equation (3), R 31It refers to a perfluorocarbon group with 1 to 10 carbon atoms in a divalent state, or a group having an ether-like oxygen atom at the end of the perfluorocarbon group or between carbon-carbon bonds.

[0152] (CH2=CH-)2R 41 (4)

[0153] In equation (4), R 41 It refers to a perfluorocarbon group with 1 to 10 carbon atoms in a divalent state, or a group having an ether-like oxygen atom at the end of the perfluorocarbon group or between carbon-carbon bonds.

[0154] As specific examples of the monomers shown in equation (3), we can list CF2=CFO(CF2)2OCF=CF2, CF2=CFO(CF2)3OCF=CF2, CF2=CFO(CF2)4OCF=CF2, CF2=CFO(CF2)6OCF=CF2, CF2=CFO(CF2)8OCF=CF2, CF2=CFO(CF2)2OCF(CF3)CF2OCF=CF2, CF2=CFO(CF2) 2) 2O (CF (CF3) CF2O) 2CF = CF2, CF2 = CFOCF2O (CF2CF2O) 2CF = CF2, CF2 = CFO (CF2O) 3O (CF (CF3) CF2O) 2C F=CF2, CF2=CFOCF2CF(CF3)O(CF2)2OCF(CF3)CF2OCF=CF2, CF2=CFOCF2CF2O(CF2O)2CF2CF2OCF=CF2.

[0155] As specific examples of more suitable monomers among those shown in equation (3), CF2 = CFO(CF2)3OCF = CF2 (hereinafter also referred to as "C3DVE") and CF2 = CFO(CF2)4OCF = CF2 (hereinafter also referred to as "C4DVE") can be cited.

[0156] As specific examples of the monomers shown in equation (4), CH2=CH(CF2)2CH=CH2, CH2=CH(CF2)4CH=CH2, and CH2=CH(CF2)6CH=CH2 can be given.

[0157] Among the monomers shown in equation (4), CH2=CH(CF2)6CH=CH2 (hereinafter also referred to as "C6DV") is a more suitable example.

[0158] Among them, DV is preferably C3DVE or C4DVE.

[0159] As a monomer having at least one atom selected from the group consisting of chlorine, bromine, and iodine atoms, examples include monomers having chlorine atoms, monomers having bromine atoms, and monomers having iodine atoms.

[0160] Specific examples of monomers containing bromine atoms include CF2=CFOCF2CF2CF2OCF2CF2Br, trifluorobromoethylene, 4-bromo-3,3,4,4-tetrafluorobutene-1 (BTFB), bromoethylene, 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. Additionally, 2-bromo-perfluoroethyl perfluorovinyl ether and CF2Br-R can be listed. f -O-CF=CF2(R f Fluorinated compounds such as perfluoroalkylene (CF2BrCF2O-CF=CF2), ROCF=CFBr, ROCBr=CF2 (where R is a lower alkyl or fluoroalkyl) are fluorinated vinyl ethers. Specifically, CH3OCF=CFBr or CF3CH2OCF=CFBr can be listed.

[0161] As a specific example of a monomer containing an iodine atom, the formula can be given: CHR=CH-Z-CH2CHR-I (where each of the multiple Rs is independently -H or -CH3; Z is a straight-chain or branched C1~C1 chain containing one or more ether oxygen atoms, depending on the case). 18 (Per)fluoroalkylene, or (per)fluoropolyoxyalkylene (as disclosed in U.S. Patent No. 5,674,959) iodinated olefins. Additionally, the formula I(CH2CF2CF2) disclosed in U.S. Patent No. 5,717,036 can be cited as an example. n OCF=CF2 and ICH2CF2O[CF(CF3)CF2O] n Unsaturated ethers such as CF=CF2 (where n=1~3). Examples include iodoethylene, 4-iodine-3,3,4,4-tetrafluorobutene-1 (ITFB), 3-chloro-4-iodine-3,4,4-trifluorobutene, 2-iodine-1,1,2,2-tetrafluoro-1-(vinyloxy)ethane, 2-iodine-1-(perfluoroethyleneoxy)-1,1,2,2-tetrafluoroethylene, 1,1,2,3,3,3-hexafluoro-2-iodine-1-(perfluoroethyleneoxy)propane, 2-iodoethyl vinyl ether, 3,3,4,5,5,5-hexafluoro-4-iodopentene, and iodotrifluoroethylene. Also, allyl iodine and 2-iodine-perfluoroethyl perfluorovinyl ether are also examples.

[0162] As specific examples of monomers containing chlorine atoms, monomers in which the bromine or iodine atoms of any of the above monomers are replaced with chlorine atoms can be cited. Trichlorofluoroethylene (CTFE), vinyl chloride, and vinylidene chloride are additional examples.

[0163] From the perspective of polymerization reactivity, R CN Preferably, it has polymerizable unsaturated bonds, and particularly preferably, 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).

[0164] From the perspective of superior demolding properties and heat resistance, R CN Preferably, the monomer is shown in formula (5).

[0165] CR 51 R 52 =CR 53 -R 54 -CN(5)

[0166] In equation (5), R 51 R 52 and R 53 Each can independently represent a hydrogen atom, a fluorine atom, or a methyl group, R 54 It refers to a perfluorocarbon group with 1 to 10 carbon atoms in a divalent state, or a group having an ether-like oxygen atom at the end of the perfluorocarbon group or between carbon-carbon bonds.

[0167] From R CN Based on the excellent polymerization reactivity of R, R is preferred. 51 R 52 R 53 It is a fluorine atom or a hydrogen atom, more preferably R 51 R 52 R 53 R is particularly preferred due to its superior release properties and heat resistance, consisting entirely of fluorine atoms or entirely of hydrogen atoms, in the context of cross-linked rubber products. 51 R 52 R 53 It consists entirely of fluorine atoms.

[0168] R 54 It can be selected from any one of linear, branched, or cyclic structures, preferably linear or branched. 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.

[0169] R 54 It may or may not have ether-containing oxygen atoms, but in terms of superior rubber properties, it is preferred to have ether-containing oxygen atoms.

[0170] R54 The number of ether oxygen atoms in the sample is preferably 1 to 3, and particularly preferably 1 or 2.

[0171] As specific examples of the monomers shown in formula (5), 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 are given. From the perspective of superior demolding properties and heat resistance, 8CNVE and MV5CN are preferred.

[0172] The POAVE unit is based on compound (6).

[0173] CF2 = CF(OCF2CF2) n -(OCF2) m -OR f2 (6)

[0174] Among them, R f2 It is a perfluoroalkyl group with 1 to 4 carbon atoms, where 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.

[0175] R f2 In this context, perfluoroalkyl groups can be either straight-chain or branched. R f2 The preferred number of carbon atoms is 1 to 3.

[0176] When n is 0, m is preferably 3 or 4. When n is 1, m is preferably an integer from 2 to 4. When n is 2 or 3, m is preferably 0. When n is preferably an integer from 1 to 3.

[0177] R f2 When the carbon number, n, and m are within the above range, the low-temperature properties of fluorinated elastomers when made into cross-linked rubber products are better, and the productivity of fluorinated elastomers is improved.

[0178] As specific examples of compound (6), the following compounds can be listed. It should be noted that the formula in parentheses is the abbreviation of the compound.

[0179] CF2=CF-OCF2CF2-(OCF2)4-OCF3 (C9PEVE),

[0180] CF2=CF-OCF2CF2-(OCF2)2-OCF3 (C7PEVE),

[0181] CF2=CF-(OCF2CF2)2-OCF2CF3 (EEAVE),

[0182] CF2=CF-(OCF2CF2)3-OCF2CF3 (EEEAVE),

[0183] CF2=CF-OCF2-OCF3, CF2=CF-OCF2-OCF2-OCF3

[0184] As compound (6), C9PEVE, C7PEVE, EEAVE, or EEEAVE are preferred from the perspective of having better low-temperature properties when making cross-linked rubber products from fluorinated elastomers and improving the productivity of fluorinated elastomers.

[0185] It should be noted that these compounds can be manufactured using the corresponding alcohols as raw materials, through the method described in International Publication No. 00 / 56694.

[0186] The amount of other monomers used is preferably 0 to 90 mol% relative to the amount of a specific monomer, more preferably 0 to 80 mol%, and even more preferably 0 to 70 mol%.

[0187] The specific monomer is preferably composed of only TFE and PAVE, or contains TFE and PAVE, and includes at least one monomer selected from the group consisting of: monomers having two or more polymerizable unsaturated bonds, monomers having at least one atom selected from the group consisting of chlorine, bromine and iodine atoms, and monomers having a nitrile group.

[0188] Relative to the amount of 100 parts by mass of the aqueous medium contained in the first aqueous dispersion, the amount of the specific monomer 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.

[0189] <Polymerization initiator>

[0190] In this manufacturing method, the specific monomer is preferably polymerized in the presence of a polymerization initiator.

[0191] As polymerization initiators, oil-soluble free radical initiators, water-soluble free radical initiators, or water-soluble redox catalysts are preferred.

[0192] Specific examples of oil-soluble free radical initiators include oil-soluble organic peroxides such as tert-butyl peroxypentanoate (hereinafter also referred to as "PBPV") and diisopropyl peroxydicarbonate (hereinafter also referred to as "IPP").

[0193] Specific examples of water-soluble free radical initiators include persulfates such as ammonium persulfate and potassium persulfate, peroxides such as disuccinic acid peroxide, peroxides such as diglutaric acid peroxide, and water-soluble organic peroxides such as tert-butyl hydroperoxide (hereinafter also referred to as "TBHP").

[0194] As a water-soluble redox catalyst, combinations of oxidants such as bromic acid or its salts, chloric acid or its salts, persulfate or its salts, permanganate or its salts, and hydrogen peroxide with reducing agents such as sulfurous acid or its salts, bisulfite or its salts, thiosulfate or its salts, organic acids, and inorganic salts are preferred. Potassium persulfate or ammonium persulfate is preferred as a persulfate. Sodium sulfite is preferred as a sulfite. Combinations of sulfate anions, sulfite anions, or chloride anions with metal ions are possible as inorganic salts. Transition metals are preferred, including manganese, iron, cobalt, nickel, copper, zinc, cerium, and silver ions, with iron ions being preferred. Ferric(II) sulfate is preferred as an inorganic salt.

[0195] The polymerization initiator is preferably an oil-soluble free radical initiator or a water-soluble free radical initiator. From the perspective of being able to manufacture fluoropolymers more efficiently, an oil-soluble free radical initiator is preferred, and an oil-soluble organic peroxide is even more preferred.

[0196] Two or more polymerization initiators can be used in combination.

[0197] The amount of polymerization initiator is preferably 0.01 to 5 parts by mass relative to 100 parts by mass of a specific monomer, more preferably 0.01 to 3 parts by mass, and even more preferably 0.01 to 2 parts by mass.

[0198] <Process>

[0199] In this manufacturing method, the specific monomer is polymerized in the first aqueous dispersion to produce the second fluoropolymer.

[0200] The second fluoropolymer obtained by this manufacturing method comprises units based on the aforementioned specific monomer (hereinafter also referred to as "specific units").

[0201] In the second fluoropolymer, the PAVE unit is 20 to 95 mol% relative to the total of TFE and PAVE units, preferably 20 to 60 mol%, more preferably 25 to 60 mol% from the perspective of being able to manufacture the second fluoropolymer more efficiently, and even more preferably 30 to 55 mol%.

[0202] In the second fluoropolymer, the total content of TFE unit and PAVE unit relative to all units of the second fluoropolymer is preferably 80 to 100 mol%, more preferably 90 to 100 mol%, and even more preferably 95 to 100 mol%.

[0203] Specific monomers are added to the reaction system (i.e., the polymerization reactor) using conventional methods. For example, the specific monomers can be added to the reaction system continuously or intermittently until the polymerization pressure reaches a specified level. Alternatively, the specific monomers can be dissolved in an aqueous medium, and the resulting solution can be added to the reaction system continuously or intermittently.

[0204] When using a polymerization initiator, the initiator can be added to the reaction system all at once or in batches.

[0205] The polymerization temperature is preferably 10~95℃, more preferably 15~90℃.

[0206] The polymerization pressure is preferably 0.5~4.0 MPaG, more preferably 0.6~3.5 MPaG.

[0207] In the case of batch processing, the polymerization time is preferably 90 to 1000 minutes, more preferably 90 to 700 minutes.

[0208] The polymerization of a particular monomer is preferably carried out in the absence of a substantially emulsifier.

[0209] The emulsifiers mentioned above can be cited as examples.

[0210] The condition of the absence of emulsifiers refers to an environment in which the content of emulsifiers is less than 0.03 ppm by mass relative to the total mass of the aqueous medium contained in the above-mentioned aqueous dispersion, preferably less than 0.02 ppm by mass, and more preferably 0 ppm by mass.

[0211] In this manufacturing method, particles containing a second fluoropolymer are generated. Specifically, by this manufacturing method, a second aqueous dispersion in which particles containing the second fluoropolymer are dispersed in the aforementioned aqueous medium is obtained.

[0212] Particles containing the second fluoropolymer may or may not contain the first fluoropolymer.

[0213] [Second Aqueous Dispersion]

[0214] The second aqueous dispersion is an aqueous dispersion obtained by this manufacturing method.

[0215] Specifically, the second aqueous dispersion is an aqueous dispersion comprising an aqueous medium and particles containing a fluoropolymer (hereinafter also referred to as "specific particles").

[0216] The average particle size is less than 1 μm.

[0217] The particles contain tetrafluoroethylene-based units and perfluoro(alkyl vinyl ether)-based units.

[0218] The fluoropolymer has at least one of the following at the end and at least one of the side chains: a chlorine atom, a bromine atom, an iodine atom, and a nitrile group.

[0219] The total content of emulsifier is less than 100 ppm by mass relative to the total mass of the aqueous dispersion.

[0220] <Specific particles>

[0221] The second aqueous dispersion can be readily obtained by the manufacturing method described above. Therefore, the specific particles contained in the second aqueous dispersion are preferably particles containing the second fluoropolymer described above.

[0222] In the case where a particular particle contains a second fluoropolymer, the particular particle may or may not contain a first fluoropolymer.

[0223] In addition to containing specific particles, the second aqueous dispersion may also contain particles of the first fluoropolymer mentioned above.

[0224] The specific particle contains TFE units and PAVE units.

[0225] The details of the TFE unit are the same as those of the TFE unit contained in the first fluoropolymer described above, and the preferred method is also the same.

[0226] The details of the PAVE unit are the same as those of the PAVE unit contained in the first fluoropolymer described above, and the preferred method is also the same.

[0227] Furthermore, the content of TFE units and PAVE units relative to all units of the fluoropolymer is the same as the content of each unit in the second fluoropolymer described above, and the preferred method is also the same.

[0228] In this specification, when a specific particle contains only one type of fluoropolymer, "all units of the fluoropolymer" refers to all units contained in that single fluoropolymer. Conversely, when a specific particle contains two or more types of fluoropolymers, "all units of the fluoropolymer" refers to all units contained in the two or more types of fluoropolymers.

[0229] A particular particle may contain units based on monomers other than a particular unit. For example, other monomers in a second fluoropolymer can be cited.

[0230] The fluoropolymer contained in the specific particles has at least one of a chlorine atom, a bromine atom, an iodine atom, and a nitrile group at at least one of the ends and side chains of the fluoropolymer.

[0231] By using the other monomers mentioned above when manufacturing the fluoropolymer contained in specific particles, chlorine atoms, bromine atoms, iodine atoms, and nitrile groups can be introduced.

[0232] When the fluoropolymer contained in a particular particle has iodine atoms, it is preferable to polymerize the fluoropolymer using a compound represented by formula (I). When using a compound represented by formula (I) (a chain transfer agent having iodine atoms), iodine atoms can be introduced at the ends of the fluoropolymer (polymer chain).

[0233] (R) f )-(X)2(I)

[0234] In formula (I),

[0235] R f It is a fluoroalkylene or aromatic cyclic group having 1 to 16 carbon atoms.

[0236] X is an iodine atom or a bromine atom, with at least one being an iodine atom.

[0237] R f The fluorinated alkyl group can be linear or branched. As R f Perfluoroalkylene groups are preferred.

[0238] Ideally, X should consist entirely of iodine atoms.

[0239] Examples of 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-diiodoperfluorooctane, 1,3-diiodo-2-chloroperfluoropropane, 1,5-diiodo-2,4-dichloroperfluoropentane, 1,12-diiodoperfluorododecane, 1,16-diiodoperfluorohexadecane, and so on. Iodomethane, 1,2-diiodoethane, 1,3-diiodopropane, (2-iodoethyl)-substituted benzene, 1-iodo-4-bromoperfluorobutane, 1-iodo-6-bromoperfluorohexane, 1-iodo-8-bromoperfluorooctane, 1-bromo-2-iodoperfluoroethane, 1-bromo-3-iodoperfluoropropane, 2-bromo-3-iodoperfluorobutane, 3-bromo-4-iodoperfluorobutene-1; 2-bromo-4-iodoperfluorobutene-1, monoiodomonobromo-substituted benzene, and diiodomonobromo-substituted benzene.

[0240] C4DI is preferred as the compound represented by formula (I).

[0241] When the fluoropolymer contained in a particular particle has iodine atoms, the proportion of iodine atoms relative to the total mass of the fluoropolymer 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.

[0242] From the viewpoint of the dispersion stability of specific particles, the content of specific particles relative to the total mass of the aqueous dispersion is preferably 1 to 50% by mass, more preferably 1 to 40% by mass, and even more preferably 1 to 30% by mass.

[0243] The average particle size of the specific particles is less than 1 μm, and from the perspective of the dispersion stability of the specific particles, it is preferably less than 500 nm, more preferably less than 400 nm.

[0244] From the perspective of aggregation, the average particle size of the specific particles is preferably 50 nm or more, more preferably 70 nm or more, and even more preferably 100 nm or more.

[0245] The average particle size of a specific particle is determined by measuring the particle size distribution using laser diffraction / scattering. The total volume of the particle group is set to 100% to obtain a cumulative curve, and the particle size at the point where the cumulative volume becomes 50% on the cumulative curve is obtained.

[0246] <Aqueous Media>

[0247] The specific examples of the aqueous medium contained in this aqueous dispersion are the same as those of the aqueous medium used in the manufacture of the first fluoropolymer described above.

[0248] From the perspective of the dispersion stability of specific particles, the content of the aqueous medium relative to the total mass of the aqueous dispersion is preferably 50 to 99% by mass, more preferably 60 to 99% by mass, and even more preferably 70 to 99% by mass.

[0249] <Emulsifier>

[0250] In the second aqueous dispersion, the emulsifier content relative to the total mass of the second aqueous dispersion 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. Furthermore, it is also preferred to be below the quantitation limit of the determination method in the embodiments. As a lower limit, 1 ppb by mass can be cited as an example.

[0251] The emulsifier content can be determined using the emulsifier content determination method described in the above-mentioned manufacturing method for fluorinated elastomers.

[0252] It should be noted that specific examples of emulsifiers are as described above. Furthermore, the emulsifier in the second aqueous dispersion may or may not be water-soluble.

[0253] <Applications>

[0254] As mentioned above, the second aqueous dispersion does not require an emulsifier, and therefore can be easily prepared into a dispersion of organic solvents such as N-methylpyrrolidone and acetone by solvent substitution.

[0255] For example, by mixing the second aqueous dispersion with an organic solvent and then dehydrating it by evaporation or using anhydrous sodium sulfate, a dispersion of the organic solvent can be prepared.

[0256] The second aqueous dispersion stably disperses fluoropolymers even without emulsifiers. Therefore, it is suitable for coating applications, adhesives, etc.

[0257] Furthermore, specific particles are aggregated by the second aqueous dispersion, thereby obtaining a solid of specific particles. Then, the solid of specific particles obtained through aggregation can be appropriately shaped using known methods. Examples of shaping methods include injection molding, extrusion molding, co-extrusion molding, blow molding, compression molding, blow molding, transfer molding, or calendering.

[0258] Examples of aggregation methods include, but are not limited to, freezing aggregation, acid aggregation, alkali aggregation, mechanical aggregation, and aggregation using flocculants.

[0259] In the case of freezing and gathering, the gathering temperature is preferably -20 to 0°C. The gathering time is preferably 1 hour or more, more preferably 2 hours or more.

[0260] In the case of acid aggregation, it is preferable to add an acid-containing solution to the second aqueous dispersion. Examples of added acids include hydrochloric acid, nitric acid, sulfuric acid, oxalic acid, and hydrofluoric acid, 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.

[0261] As a method for alkali aggregation, it is preferable to add a solution containing an alkali to the second aqueous dispersion. Examples of alkalis to be added include sodium hydroxide, potassium hydroxide, and ammonium carbonate, with sodium hydroxide being preferred. The concentration of the alkali in the solution containing the alkali is preferably 0.1 to 50% by mass, more preferably 1 to 30% by mass, and even more preferably 1 to 10% by mass.

[0262] For aggregation utilizing flocculants, known flocculants can be used. Examples of known flocculants include aluminum salts, calcium salts, and magnesium salts. Specifically, examples include aluminum sulfate, alum with the general formula M'Al(SO4)2·12H2O [where M' is a monovalent cation other than lithium], calcium nitrate, and magnesium sulfate, with alum being preferred, and potassium alum, where M is potassium, being more preferred.

[0263] As an aggregation method, alkali aggregation is preferred from the perspective that aggregation is particularly easy to carry out.

[0264] The second aqueous dispersion containing the second fluoropolymer can be used directly, or its concentration can be adjusted appropriately for co-aggregation with aqueous dispersions containing different fluoropolymers. Co-aggregation can be carried out using known methods, such as adding a mixture of the aqueous dispersion dropwise to a flocculant, or adding a flocculant dropwise to a mixture of aqueous dispersions. Specific co-aggregation methods include, but are not limited to, freeze-aggregation, acid-aggregation, alkali-aggregation, mechanical aggregation, and aggregation using flocculants.

[0265] Examples of different fluoropolymers include fluoroelastomers and fluororesins. Examples of fluoroelastomers include HFP / VdF elastomers (polymers using hexafluoropropylene (hereinafter also referred to as "HFP") and vinylidene fluoride (hereinafter also referred to as "VdF"), TFE / HFP / VdF elastomers (polymers using TFE, HFP, and VdF), TFE / propylene elastomers (polymers using TFE and propylene), and TFE / HFP / PAVE elastomers (polymers using TFE, HFP, and PAVE), but are not limited to these. Examples of fluororesins include VdF and polymers containing TFE. Examples of polymers containing TFE include TFE homopolymers and fluoropolymers of TFE with olefins other than TFE. Specifically, examples include TFE / ethylene copolymers, TFE / HFP copolymers, and TFE / PAVE copolymers, but are not limited to these. Emulsifiers may or may not be included in aqueous dispersions of different fluoropolymers.

[0266] The composition obtained by co-aggregation can be used as a base material for molding after cleaning and drying as needed, and can impart excellent heat resistance, mechanical strength, wear resistance, transparency, and molding processability to the molded product.

[0267] [Solid Composition]

[0268] The solid composition of the present invention is a solid composition comprising a fluoropolymer.

[0269] The solid composition comprises tetrafluoroethylene-based units and perfluoro(alkyl vinyl ether)-based units.

[0270] The solid composition is essentially free of emulsifiers.

[0271] The term "solid composition substantially free of emulsifier" means that, in the solid composition of the present invention, the content of water-soluble emulsifier relative to the total mass of the solid composition is 500 ppb or less by mass, preferably 300 ppb or less by mass, and more preferably 250 ppb or less by mass. Furthermore, it is also preferred to be below the quantitative limit of the determination method in the embodiments. As a lower limit, 1 ppb by mass can be cited as an example.

[0272] It should be noted that specific examples of emulsifiers are as described above.

[0273] In this specification, a solid composition refers to a composition in which the solid component accounts for 99% or more by mass.

[0274] Here, the mass of the solid components is calculated based on the mass before and after heating using the following method.

[0275] After heating 2.0g of the solid composition at 170°C for 20 minutes, the mass of the residue was weighed, and the mass of the solid component was calculated using the following formula.

[0276] Mass of solid components (mass%) = 100 × (mass of residue) / (mass of solid composition)

[0277] This solid composition is preferably obtained by using the aggregation method of the second aqueous dispersion described above. The preferred manner in which the fluoropolymer is contained in this solid composition is the same as the preferred manner in which the fluoropolymer is contained in the specific particles of the second aqueous dispersion described above.

[0278] That is, the fluoropolymer contained in this solid composition is preferably the second fluoropolymer described above. The second fluoropolymer may comprise the first fluoropolymer.

[0279] The content of the fluoropolymer relative to the total mass of the solid composition 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.

[0280] The total content of emulsifier in the solid composition is 500 ppb or less relative to the total mass of the fluoropolymer, preferably 300 ppb or less, and more preferably 250 ppb or less. Furthermore, it is also preferred to be below the quantitation limit of the determination method in the examples. Lower limits may include those exceeding 0 ppb.

[0281] The number of emulsifier types contained in a solid composition is the number of emulsifier types whose content exceeds the quantitative limit; emulsifiers whose content is below the quantitative limit are not counted. Specifically, when determining the content of emulsifier X, emulsifier Y, and emulsifier Z in a solid composition, if the content of emulsifier X and emulsifier Y both exceed the quantitative limit, and the content of emulsifier Z is below the quantitative limit, it means that the solid composition contains two emulsifiers, emulsifier X and emulsifier Y.

[0282] To obtain a solid composition that is substantially free of emulsifiers, methods can be cited that do not use hydrocarbon-containing surfactants, fluorinated emulsifiers, and polymeric emulsifiers during the polymerization of fluoropolymers, i.e., during the polymerization of the aforementioned first fluoropolymer and the aforementioned second fluoropolymer.

[0283] The emulsifier content can be determined using the emulsifier content determination method described in the above-mentioned manufacturing method for fluorinated elastomers.

[0284] <Physical properties>

[0285] Excellent processability can be achieved by ensuring that the solid composition is substantially free of emulsifiers and that the storage modulus G' is within a specific range. Processability is evaluated by roll winding properties and roll surface temperature. Better roll winding properties result in greater adhesion between the metal roll surface and the solid composition, making forming easier. Higher roll surface temperatures reduce the need for heating steps required for forming. Emulsifiers hinder adhesion between the roll's metal surface and the solid composition; therefore, lower emulsifier content leads to better roll winding properties. The storage modulus G' affects roll winding properties and roll surface temperature.

[0286] The storage modulus G' of the solid composition is preferably 200~1200 kPa. Below this range, the roller surface temperature decreases; above this range, the roller winding properties decrease and the processability deteriorates.

[0287] From the perspective of excellent processability, the storage modulus G' of the solid composition is preferably 400 kPa or more, preferably 1100 kPa or less, more preferably 500 to 1100 kPa, and particularly preferably 500 to 1100 kPa.

[0288] As an example of a method for manufacturing a solid composition containing a fluoropolymer with a storage modulus G' of 200 to 1200 kPa and which is obtained without the use of an emulsifier, a method can be given in which the order and number of additions of each monomer are adjusted during the manufacture of the fluoropolymer.

[0289] The storage modulus G' of the solid composition in this invention is a value determined according to ASTM D6204, and the detailed measurement conditions are shown in the examples.

[0290] The detailed measurement conditions for the roll winding properties and roll surface temperature of the solid composition of the present invention, as well as the processability evaluation methods, are shown in the examples.

[0291] Example

[0292] The present invention will be described in detail below with examples. Examples 1 to 5 are embodiments, and Examples 6 and 7 are comparative examples. However, the present invention is not limited to these examples.

[0293] [Measurement and Evaluation Methods]

[0294] The various measurement and evaluation methods are described below.

[0295] <Average particle size of particles in the second aqueous dispersion>

[0296] The second aqueous dispersion of each example described below was used as a sample and measured using a laser diffraction / scattering particle size distribution measuring device (Otsuka Electric Co., Ltd., ELSZ).

[0297] It should be noted that if the average particle size of the particles in the first aqueous dispersion is determined by the same method as that used for the second aqueous dispersion, then the average particle size of the particles in the first aqueous dispersion is the same as that of the particles in the second aqueous dispersion.

[0298] <Proportion of units in the polymer>

[0299] The proportions of the units in the polymer are determined by 19 Determined by F-NMR analysis and infrared absorption spectroscopy analysis.

[0300] <Emulsifier content>

[0301] (Sample preparation)

[0302] The solids obtained in the following examples were cryogenically pulverized using a cryogenic pulverizer or cryogenic mill 6775 (manufactured by SPEX) under the following conditions. Before cryogenic pulverization, 10% by mass of butylated hydroxytoluene (BHT) relative to the total mass of the solids was added to obtain the pulverized powder. The cryogenic pulverization conditions were: solids: 3g, BHT: 0.3g, running time: 5 minutes, speed: 15 cps, number of cycles: 3.

[0303] Add 5 mL of methanol to 2.5 g of the obtained pulverized powder, sonicate at 50 °C for 2 hours, centrifuge (5000 rpm, 5 minutes) to allow each fluoropolymer to settle, and use the supernatant as the extract.

[0304] Regarding the content of compounds represented by formula (S1) in each extract, the compounds with n = 3~13, 15, and 17 in formula (S1) are determined by conversion to perfluorocarboxylic acids with the same number of carbon atoms. Furthermore, regarding the content of compounds represented by formula (S3) in the obtained aqueous phase, the compounds with n = 4~10 and 12 in formula (S3) are determined by conversion to perfluorosulfonic acids with the same number of carbon atoms.

[0305] Specifically, firstly, five levels of standard solutions of perfluorocarboxylic acid and perfluorosulfonic acid with known concentrations of 1~180 ng / g and of surfactant A in methanol were prepared. Using an approximation based on the sample concentration and peak integral value, a and a' were calculated using equations (A1), (A1'), and (A'').

[0306] A = a × X (A1)

[0307] A: Peak area of ​​perfluorocarboxylic acid; X: Concentration of perfluorocarboxylic acid (ng / g)

[0308] A' = a' × X' (A1')

[0309] A': Peak area of ​​perfluorosulfonic acid, X': Concentration of perfluorosulfonic acid (ng / g)

[0310] A'' = a'' × X'' (A1'')

[0311] A'': Peak area of ​​surfactant A, X'': Concentration of surfactant A (ng / g)

[0312] The measuring equipment and conditions are shown in Table 1 below.

[0313] [Table 1]

[0314]

[0315] MRM measurement parameters are shown in Tables 2, 3 and 4.

[0316] [Table 2]

[0317]

[0318] [Table 3]

[0319]

[0320] [Table 4]

[0321]

[0322] Specifically, firstly, using the aforementioned liquid chromatography-mass spectrometry (LC-MS) analyzer, the compounds and surfactant A represented by any of formulas (S1) and (S3) contained in each of the above extracts are determined. The peak areas of the compounds and surfactant A represented by formulas (S1) and (S3) with different carbon numbers are determined using the MRM method.

[0323] Next, the contents of the compound shown in formula (S1), the compound shown in formula (S3), and surfactant A are calculated using formulas (A2), (A2'), and (A2''), respectively. It should be noted that 'a' in formula (A2) refers to 'a' obtained from formula (A1) above, 'a' in formula (A2') refers to 'a' obtained from formula (A1') above, and 'a'' in formula (A'') refers to 'a'' obtained from formula (A'') above.

[0324] XCm=ACm / a(A2)

[0325] XCm: The content (ng / g) of the compound represented by formula (S1) with the number of carbons (n+1) in each extract.

[0326] ACm: Peak area of ​​the compound represented by formula (S1) with the number of carbons (n+1) in each extract.

[0327] XCm'=ACm' / a'(A2')

[0328] XCm': The content (ng / g) of the compound with carbon number n represented by formula (S3) in each extract.

[0329] ACm': Peak area of ​​the compound represented by formula (S3) with carbon number n in each extract.

[0330] It should be noted that the quantitative limit in this assay is 1 ng / g.

[0331] XCm''=ACm'' / a''(A2'')

[0332] XCm'': Content of surfactant A in each extract (ng / g)

[0333] ACm'': Peak area of ​​surfactant A in each extract

[0334] It should be noted that the quantitative limit in this assay is 1 ng / g.

[0335] The content (ZCm) of formula (S1) in a solid relative to the total mass of the solid is obtained by formula (A3).

[0336] ZCm=XCm×ρ1×La / W1(A3)

[0337] ZCm: The content of compounds represented by formula (S1) with the number of carbons (n+1) in a solid.

[0338] ρ1: Density of the extraction solvent (methanol in each example)

[0339] La: Volume of extraction solvent (5 mL in each example)

[0340] W1: Mass of sample used in extraction (2.5g of solids in each example)

[0341] In solids, the content (ZCm') of formula (S3) relative to the total mass of solids is obtained by formula (A4).

[0342] ZCm'=XCm'×ρ1×La / W1(A4)

[0343] ZCm': The content of the compound represented by formula (S3) with the number of carbons n in the solid.

[0344] ρ1: Density of the extraction solvent (methanol in each example)

[0345] La: Volume of extraction solvent (5 mL in each example)

[0346] W1: Mass of sample used in extraction (2.5g of solids in each example)

[0347] The content (ZCm'') of surfactant A relative to the total mass of the solid is determined by the following formula (A5).

[0348] ZCm''=XCm''×ρ1×La / W1 (A5)

[0349] ZCm'': The content of surfactant A in the solid.

[0350] ρ1: Density of the extraction solvent (methanol in each example)

[0351] La: Volume of extraction solvent (5 mL in each example)

[0352] W1: Mass of sample used in extraction (2.5g of solids in each example)

[0353] <Methods for Determination of Iodine Content>

[0354] The solid composition was heated and pressed into sheets with a thickness of 100 μm. The resulting sheet composition was analyzed by fluorescence X-ray diffraction using a ZSX PrimusII (made by RIGAKU), and the iodine content in the solid composition (the total mass of the first and second fluoropolymers) was calculated using the basic parameter method.

[0355] <Method for determining energy storage modulus G'>

[0356] As the measuring apparatus, the rubber processability analysis device "PREMIER RPA (manufactured by Alpha Technologies, mold shape: D0380)" was used.

[0357] Film Production

[0358] The solid compositions obtained in each example were mixed using a two-roller at room temperature for 10 minutes to produce sheets with a thickness of 3 mm. The thickness of the sheets was adjusted by adjusting the gap between the two rolls.

[0359] The obtained sheet was cut into pieces weighing approximately 10g. The pieces were then clamped between two sheets of polyester film (ALFA Technologies PART#F0311-S, 130mm × 130mm × 24μm) to obtain the sample for measurement. The sample was placed on the mold of the aforementioned measuring apparatus. The temperature of the mold was preset to 100°C.

[0360] Next, the sample was held at 100℃, 30 cpm, and 0.2 degrees for 2 minutes. Then, the amplitude angle was set to 0.5 degrees, and the frequency was increased to 10 cpm, 20 cpm, 50 cpm, 100 cpm, 200 cpm, 500 cpm, 1000 cpm, and 2000 cpm, and the storage modulus was measured. The storage modulus at 2000 cpm and 100℃ was taken as the storage modulus G' of the sample (unit: kPa).

[0361] Next, the sample was held at 100℃, 30 cpm, and 0.2 degrees for 2 minutes. Then, the amplitude angle was set to 0.5 degrees, and the frequency was increased to 10 cpm, 20 cpm, 50 cpm, 100 cpm, 200 cpm, 500 cpm, 1000 cpm, and 2000 cpm, and the storage modulus was measured. The storage modulus at 2000 cpm and 100℃ was taken as the storage modulus G' of the sample (unit: kPa).

[0362] <Evaluation Methods for Roller Winding Performance>

[0363] The solid compositions obtained in each example were mixed using a roll mixer (a test roll mixer manufactured by Santeki Co., Ltd.) to produce sheets, thereby confirming the roll winding properties.

[0364] The aforementioned roll mixer has two rolls (8 inches in diameter and 18 inches in length) and two guide members disposed in the gap between the rolls and near both ends of the rolls. The guide members are used to maintain the width of the workpiece, which expands axially along the rolls after passing through the rolls, at a specified width.

[0365] Measure 200g of the solid composition at room temperature (23°C) and add the fluoropolymer between the guide members of the above-mentioned roller mixer under the following conditions. Measure the time from the addition of the solid composition until the fluoropolymer accumulated in the gap between the guide members (bank) disappears and all the fluoropolymer is wound around the roller (also called "winding time").

[0366] Roller temperature: 25℃

[0367] • Roller gap: 2.5mm

[0368] • Front roller speed: 12 rpm

[0369] • Rear roller speed: 10 rpm

[0370] • Width between guide components: 150mm

[0371] The roller temperature is regulated using a water heater (WTC40, manufactured by Nakamura Science & Technology Co., Ltd.).

[0372] The roll-wrapability of the solid composition was evaluated based on the following evaluation criteria, according to the measurement time.

[0373] (Roller winding performance evaluation criteria)

[0374] 〇: The winding time should be within 2 minutes.

[0375] △: The winding time exceeds 2 minutes but is within 3 minutes.

[0376] ×: All fluoropolymers were not wound onto the rollers, or the winding time exceeded 3 minutes.

[0377] <Roller Surface Temperature>

[0378] For the sheet obtained under the above conditions, a contact thermometer (manufactured by HOZAN CO., LTD.; trade name "DT-510") was used to confirm that the sheet surface temperature was 25°C before re-inserting it into a roller with a roller temperature of 25°C. During the test, the temperature adjustment of the water heater was stopped. All other conditions were set to the same conditions as the roller winding test. After 5 minutes of insertion, the wound sheet was immediately removed, and the surface temperature of the roller was measured using the same contact thermometer. This temperature was taken as the roller surface temperature.

[0379] (Roller surface temperature evaluation standard)

[0380] A: Above 45℃

[0381] B: 35~45℃

[0382] C: Below 35℃

[0383] (Processability)

[0384] Evaluation of roll winding performance and roll surface temperature (A): Both 3 points

[0385] Evaluation of roll winding performance and roll surface temperature (B): Both 2 points

[0386] Evaluation of roll winding performance and roll surface temperature (C): Both 1 point

[0387] ◎: Total evaluation score for roll winding performance and roll surface temperature: 6 points

[0388] 〇: Total evaluation value for roll winding performance and roll surface temperature: 5 points

[0389] △: Total evaluation value for roll winding performance and roll surface temperature: 4 points

[0390] ×: Total evaluation values ​​for roll winding performance and roll surface temperature: 2 points, 3 points

[0391] [Preparation of Raw Material Solution A]

[0392] In a 2.2L stainless steel pressure reactor equipped with anchor-shaped blades, 1130g of ultrapure water, 30mg of 30% ammonia solution, 72g of PMVE, and 14g of TFE were added, and the mixture was heated to 90°C while stirring at 600 rpm. Then, 30cc of 5.0% ammonium persulfate solution was added to initiate polymerization. As polymerization began, the pressure inside the reactor decreased, so TFE was added to maintain a constant pressure. The reactor was cooled after adding 4g of TFE to terminate the polymerization reaction. After recovering the residual gas in the reactor, the liquid was extracted. This liquid was used as feedstock A.

[0393] After freezing and agglomerating the raw material liquid A, it was filtered and separated. The obtained fluoropolymer 1A was analyzed by NMR, and the result was that the PMVE unit / TFE unit ratio was 34 / 66 (molar ratio).

[0394] [Preparation of Raw Material Solution B]

[0395] HPR4002Cl (DuPont, anion exchange resin, 200g) was added to the above-mentioned feed solution A. After stirring for 150 minutes, the feed solution and ion exchange resin were separated by filtration. Next, AmberLite (registered trademark) HPR 650H (DuPont, cation exchange resin, 50g) was added to the filtrate. After stirring for 60 minutes, the feed solution and ion exchange resin were separated by filtration to obtain feed solution B. In feed solution B, the fluoropolymer 1A particles were dispersed in an aqueous medium, and the content of fluoropolymer 1A relative to the total mass of feed solution B was 0.6% by mass.

[0396] [Example 1]

[0397] Feed solution B (1000g) and ultrapure water (175g) were added to a 2.2L stainless steel pressure reactor with anchor-shaped blades to obtain aqueous dispersion B (first aqueous dispersion). PMVE (72g) and TFE (14g) were added, and the mixture was heated to 80°C while stirring at 600 rpm. TFE and PMVE were added until the reactor pressure reached 1.2 MPa [gauge pressure], and then ammonium persulfate aqueous solution (2.5% by mass, 7ml) was added to initiate polymerization. As polymerization began, the pressure inside the reactor decreased; therefore, TFE and PMVE were added alternately to maintain a constant pressure. The reactor was cooled when 80g of TFE and 63g of PMVE were added, ending the polymerization reaction. The polymerization time was 138 minutes.

[0398] It should be noted that in aqueous dispersion B, the content of fluoropolymer 1A is 0.5% of the total mass of aqueous dispersion B.

[0399] In addition, when the amount of aqueous medium in the aqueous dispersion B used in the polymerization is set to 100 parts by mass, the amount of monomer used in the polymerization is 12.2 parts by mass.

[0400] Aqueous dispersion B substantially does not contain water-soluble emulsifiers. Specifically, the content of surfactant A (C2F5OCF2CF2OCF2COONH4) and the compounds shown in formulas (S1) to (S4) was determined using the following method. It should be noted that, in the manufacture of aqueous dispersion B, emulsifiers other than surfactant A and the compounds shown in formulas (S1) to (S4) are not generated from the components used in the manufacture of aqueous dispersion B, nor are they used, and therefore are not included in aqueous dispersion B.

[0401] To determine the solid content of aqueous dispersion B, weigh an amount equivalent to 0.05 g of solid content into a 100 mL screw-top bottle. Then, add water and methanol to the weighed aqueous dispersion B to make a water / methanol ratio of 40 g / 50 (volume %). Shake thoroughly until flocculation occurs. Remove the solid content, centrifuge the liquid phase at 4000 rpm for 1 hour, and extract the supernatant. Except for the sample preparation method, the determination was performed using the same method as described above for determining the emulsifier content. The results showed that the content of any of the compounds represented by formulas (S1) to (S4) was below the quantitation limit relative to aqueous dispersion B.

[0402] After recovering the gas remaining in the reactor, the liquid is extracted. This liquid is designated as aqueous dispersion 1 (second aqueous dispersion). Aqueous dispersion 1 is a dispersion containing particles (average particle size 144.1 nm) of fluoropolymer 2A dispersed in an aqueous medium, with a solids concentration of 11.5% by mass.

[0403] The emulsifier content in aqueous dispersion 1 is less than 100 ppm by mass. Specifically, the content of surfactant A and the compounds shown in formulas (S1) to (S4) is determined using the same method as that used in aqueous dispersion B. It should be noted that, in the manufacture of aqueous dispersion 1, the emulsifiers other than surfactant A and the compounds shown in formulas (S1) to (S4) are not generated from the components used in the manufacture of aqueous dispersion 1, nor are they used, and therefore are not included in aqueous dispersion 1.

[0404] An aqueous solution of aluminum sulfate was added to the above aqueous dispersion 1 to induce coagulation. The resulting coagulated material was washed with water and dried to obtain a solid composition 1 containing a rubbery fluorinated copolymer.

[0405] The solid composition 1 was analyzed by NMR, and the result was that the PMVE unit / TFE unit ratio was 66 / 34 (molar ratio).

[0406] [Raw Material C]

[0407] Ultrapure water (180g), PMVE (72g), and TFE (14g) were added to a 2.2L stainless steel pressure reactor equipped with anchor-shaped blades. The mixture was heated to 90°C while stirring at 600 rpm. Then, an aqueous solution of ammonium persulfate (5.0% by mass, 30cc) was added to initiate polymerization. As polymerization began, the pressure inside the reactor decreased; therefore, TFE was added to maintain a constant pressure. The reactor was cooled after adding 4g of TFE to terminate the polymerization reaction. After recovering the residual gas in the reactor, the liquid was extracted. This liquid was used as feedstock C.

[0408] After freezing and agglomerating the raw material liquid C, it was filtered and separated. The obtained fluoropolymer 1C was analyzed by NMR, and the result was that PMVE unit / TFE unit = 30 / 70 (molar ratio).

[0409] [Raw Material Solution D]

[0410] Except that raw material solution C is used instead of raw material solution A, raw material solution D is manufactured following the same steps as raw material solution B.

[0411] [Example 2]

[0412] Feed solution D (1000g) and ultrapure water (175g) were added to a 2.2L stainless steel pressure reactor with anchor-shaped blades to obtain aqueous dispersion D (first aqueous dispersion). PMVE (43g) and TFE (32g) were added, and the mixture was heated to 80°C while stirring at 600 rpm. TFE and PMVE were added until the reactor pressure reached 1.2 MPa [gauge]. Ammonium persulfate aqueous solution (2.5% by mass, 7ml) was added to initiate polymerization. As polymerization began, the pressure inside the reactor decreased; therefore, TFE and PMVE were added alternately to maintain a constant pressure. The reactor was cooled when 80g of TFE and 63g of PMVE were added to terminate the polymerization reaction. The polymerization time was 173 minutes.

[0413] It should be noted that in aqueous dispersion D, the content of fluoropolymer 1C is 0.4% of the total mass of aqueous dispersion D.

[0414] In addition, when the amount of aqueous medium in the aqueous dispersion D used in the polymerization is set to 100 parts by mass, the amount of monomer used in the polymerization is 25.1 parts by mass.

[0415] Aqueous dispersion D is substantially free of emulsifiers. Specifically, the content of surfactant A and the compounds shown in formulas (S1) to (S4) is determined using the same method as that used in aqueous dispersion B. It should be noted that, in the manufacture of aqueous dispersion D, emulsifiers other than surfactant A and the compounds shown in formulas (S1) to (S4) are not generated from the components used in the manufacture of aqueous dispersion D, nor are they used, and therefore are not included in aqueous dispersion D.

[0416] After recovering the gas remaining in the reactor, the liquid is extracted. This liquid is used as aqueous dispersion 3 (second aqueous dispersion). Aqueous dispersion 2 is a dispersion containing particles of fluoropolymer 2C (average particle size 174.1 nm) dispersed in an aqueous medium, with a solids concentration of 11.5% by mass.

[0417] The emulsifier content in aqueous dispersion 2 is less than 100 ppm by mass. Specifically, the content of surfactant A and the compounds shown in formulas (S1) to (S4) is determined using the same method as that used in aqueous dispersion B. It should be noted that, in the manufacture of aqueous dispersion 2, the emulsifiers other than surfactant A and the compounds shown in formulas (S1) to (S4) are not generated from the components used in the manufacture of aqueous dispersion 2, nor are they used, and therefore are not included in aqueous dispersion 2.

[0418] An aqueous aluminum sulfate solution was added to the above-mentioned aqueous dispersion 2 to induce coagulation. The resulting coagulated material was washed with water and dried to obtain a solid composition 2 containing a rubber-like fluorinated copolymer.

[0419] The solid composition 2 was analyzed by NMR, and the result was that the PMVE unit / TFE unit ratio was 34 / 66 (molar ratio).

[0420] [Raw Material Solution E]

[0421] By appropriately adjusting the amounts of each component, and otherwise following the same steps as in the preparation of raw material solution A, fluoropolymer 1E was polymerized, and this liquid was used as raw material solution E. After freezing and polymerizing raw material solution E, it was filtered and separated. The obtained fluoropolymer 1E was analyzed by NMR, and the result was PMVE units / TFE units = 32 / 68 (molar ratio).

[0422] [Raw Material Solution F]

[0423] Except that raw material solution E is used instead of raw material solution A, raw material solution F is manufactured following the same steps as raw material solution B.

[0424] [Example 3]

[0425] Feed solution F (1000g) and ultrapure water (182g) were added to a 2.2L stainless steel pressure reactor with anchor-shaped blades to obtain aqueous dispersion F (first aqueous dispersion). PMVE (90g) and TFE (18g) were added, and the mixture was heated to 80°C while stirring at 600 rpm. TFE and PMVE were added until the reactor pressure reached 1.5 MPa [gauge], and then ammonium persulfate aqueous solution (0.5% by mass, 16ml) was added to initiate polymerization. As polymerization began, the pressure inside the reactor decreased; therefore, TFE and PMVE were added alternately to maintain a constant pressure. At the addition of 6.0g of TFE, C4DI (2.0g) and ultrapure water (10cc) were added. The reactor was cooled when 154g of TFE and 133g of PMVE were added, ending the polymerization reaction. The polymerization time was 300 minutes.

[0426] It should be noted that in the aqueous dispersion F, the content of fluoropolymer 1E is 0.4% of the total mass of the aqueous dispersion F.

[0427] In addition, when the amount of aqueous medium in the aqueous dispersion F used in the polymerization is set to 100 parts by mass, the amount of monomer used in the polymerization is 40.6 parts by mass.

[0428] Aqueous dispersion F is substantially free of emulsifiers. Specifically, the content of surfactant A and the compounds shown in formulas (S1) to (S4) is determined using the same method as for aqueous dispersion B. It should be noted that, in the manufacture of aqueous dispersion F, emulsifiers other than surfactant A and the compounds shown in formulas (S1) to (S4) are not generated from the components used in the manufacture of aqueous dispersion F, nor are they used, and therefore are not included in aqueous dispersion F.

[0429] After recovering the gas remaining in the reactor, the liquid is extracted. This liquid is designated as aqueous dispersion 3. Aqueous dispersion 3 is a dispersion containing particles (average particle size 89.9 nm) of fluoropolymer 2E dispersed in an aqueous medium, with a solids concentration of 19.3% by mass.

[0430] The emulsifier content in aqueous dispersion 3 is less than 100 ppm by mass. Specifically, the content of surfactant A and each compound shown in formulas (S1) to (S4) is determined using the same method as that used in aqueous dispersion B. It should be noted that, in the manufacture of aqueous dispersion 3, the emulsifiers other than surfactant A and the compounds shown in formulas (S1) to (S4) are not generated from the components used in the manufacture of aqueous dispersion 3, nor are they used, and therefore are not included in aqueous dispersion 3.

[0431] An aqueous solution of aluminum sulfate 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 3 containing a rubber-like fluorinated copolymer.

[0432] The obtained solid composition 3 was analyzed by NMR, and the result was that the PMVE unit / TFE unit ratio was 35 / 65 (molar ratio). The iodine content was 0.04% by mass relative to the combined mass of fluoropolymer 1E and fluoropolymer 2E.

[0433] [Raw Material G]

[0434] By appropriately adjusting the amounts of each component, and otherwise following the same steps as in the preparation of raw material solution A, fluoropolymer 1G was polymerized, and this liquid was used as raw material solution G. After freeze-polymerization of raw material solution G, it was filtered and separated. The obtained fluoropolymer 1G was analyzed by NMR, and the result was that PMVE units / TFE units = 32 / 68 (molar ratio).

[0435] [Feed solution H]

[0436] Except that raw material solution G is used instead of raw material solution A, raw material solution H is manufactured following the same steps as raw material solution B.

[0437] [Example 4]

[0438] In a 2.2L stainless steel pressure reactor equipped with anchor-shaped blades, feedstock solution H (1000g) and ultrapure water (182g) were added to obtain aqueous dispersion H (first aqueous dispersion). PMVE (90g) and TFE (18g) were added, and the mixture was heated to 75°C while stirring at 600 rpm. TFE and PMVE were added until the reactor pressure reached 1.5 MPa [gauge], and then ammonium persulfate aqueous solution (0.5% by mass, 16ml) was added to initiate polymerization. As polymerization began, the pressure inside the reactor decreased; therefore, TFE and PMVE were added alternately to maintain a constant pressure. At the addition of 6.0g of TFE, C4DI (2.0g) and ultrapure water (10cc) were added. The reactor was cooled when 160g of TFE and 133g of PMVE were added, ending the polymerization reaction. The polymerization time was 440 minutes.

[0439] It should be noted that the content of fluoropolymer 1G is 0.4% of the total mass of the aqueous dispersion H.

[0440] In addition, when the amount of aqueous medium in the aqueous dispersion H used in the polymerization is set to 100 parts by mass, the amount of monomer used in the polymerization is 40.6 parts by mass.

[0441] Aqueous dispersion H is substantially free of emulsifiers. Specifically, the content of surfactant A and the compounds shown in formulas (S1) to (S4) is determined using the same method as that used in aqueous dispersion B. It should be noted that, in the manufacture of aqueous dispersion H, emulsifiers other than surfactant A and the compounds shown in formulas (S1) to (S4) are not generated from the components used in the manufacture of aqueous dispersion H, nor are they used, and therefore are not included in aqueous dispersion H.

[0442] After recovering the gas remaining in the reactor, the liquid is extracted. This liquid is designated as aqueous dispersion 4 (second aqueous dispersion). Aqueous dispersion 4 is a dispersion containing 2G of fluoropolymer particles (average particle size 90.5 nm) dispersed in an aqueous medium, with a solids concentration of 20.1% by mass.

[0443] The emulsifier content in aqueous dispersion 4 is less than 100 ppm by mass. Specifically, the content of surfactant A and each compound shown in formulas (S1) to (S4) is determined using the same method as that used in aqueous dispersion B. It should be noted that, in the manufacture of aqueous dispersion 4, the emulsifiers other than surfactant A and the compounds shown in formulas (S1) to (S4) are not generated from the components used in the manufacture of aqueous dispersion 4, nor are they used, and therefore are not included in aqueous dispersion 4.

[0444] An aqueous solution of aluminum sulfate 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 4 containing a rubber-like fluorinated copolymer.

[0445] The obtained solid composition 4 was analyzed by NMR, and the results showed that the PMVE unit / TFE unit ratio was 34 / 66 (molar ratio). The iodine content was 0.04% by mass relative to the combined mass of the fluoropolymer 1H and the fluoropolymer 2H.

[0446] [Raw Material P]

[0447] By appropriately adjusting the amounts of each component, and following the same steps as in the preparation of raw material solution A, fluoropolymer 1P was polymerized, and this liquid was used as raw material solution P. After freezing and agglomerating raw material solution P, it was filtered and separated. The obtained fluoropolymer 1N was analyzed by NMR, and the result was PMVE unit / TFE unit = 34 / 66 (molar ratio).

[0448] [Raw Material Q]

[0449] Except that feedstock solution P is used instead of feedstock solution A, feedstock solution Q is manufactured using the same steps as feedstock solution B.

[0450] [Example 5]

[0451] In a 2.2L stainless steel pressure reactor equipped with anchor-shaped blades, feedstock solution Q (850g), ultrapure water (332g), and disodium hydrogen phosphate dodecahydrate (0.11g) were added to obtain aqueous dispersion Q (first aqueous dispersion). PMVE (90g), TFE (18g), and 8CNVE (1.1g) were then added, and the mixture was heated to 80°C while stirring at 600 rpm. TFE and PMVE were added until the reactor pressure reached 1.5 MPa [gauge]. Ammonium persulfate aqueous solution (3% by mass, 18ml) was added to initiate polymerization. As polymerization began, the pressure inside the reactor decreased; therefore, TFE and PMVE were added alternately to maintain a constant pressure. For every 16g of TFE added, 12g of PMVE and 1.26g of 8CNVE were added. To maintain a constant polymerization rate, an appropriate amount of ammonium persulfate aqueous solution was added. The reactor was cooled when 160g of TFE, 108g of PMVE, and 12.6g of 8CNVE were added, ending the polymerization reaction. The polymerization time was 130 minutes. The total amount of 3% (w / w) ammonium persulfate aqueous solution added was 24 ml.

[0452] It should be noted that the content of fluoropolymer 1P is 0.6% of the total mass of the aqueous dispersion Q.

[0453] In addition, when the amount of aqueous medium in the aqueous dispersion Q used in the polymerization is set to 100 parts by mass, the amount of monomer used in the polymerization is 23 parts by mass.

[0454] Aqueous dispersion Q is substantially free of emulsifiers. Specifically, the content of surfactant A and the compounds shown in formulas (S1) to (S4) is determined using the same method as that used in aqueous dispersion B. It should be noted that, in the manufacture of aqueous dispersion Q, emulsifiers other than surfactant A and the compounds shown in formulas (S1) to (S4) are not generated from the components used in the manufacture of aqueous dispersion Q, nor are they used, and therefore are not included in aqueous dispersion Q.

[0455] After recovering the gas remaining in the reactor, the liquid is extracted. This liquid is designated as aqueous dispersion 5 (second aqueous dispersion). Aqueous dispersion 5 is a dispersion containing particles of fluoropolymer 2P (average particle size 45.5 nm) dispersed in an aqueous medium, with a solids concentration of 19.1% by mass.

[0456] The emulsifier content in aqueous dispersion 5 is less than 100 ppm by mass. Specifically, the content of surfactant A and each compound shown in formulas (S1) to (S4) is determined using the same method as that used in aqueous dispersion B. It should be noted that, in the manufacture of aqueous dispersion 5, the emulsifiers other than surfactant A and the compounds shown in formulas (S1) to (S4) are not generated from the components used in the manufacture of aqueous dispersion 5, nor are they used, and therefore are not included in aqueous dispersion 5.

[0457] A 3% (w / w) aqueous nitric acid 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 5 containing a rubber-like fluorinated copolymer.

[0458] The obtained solid composition 5 was analyzed by NMR, and the results showed that the ratio of PMVE units to TFE units to 8CNVE units was 68.3 / 31.2 / 0.5 (molar ratio).

[0459] [Raw Material Solution K]

[0460] In a 1.0L glass reactor, 593g of ultrapure water and 2.8g of MMA (methyl methacrylate) were added, and the mixture was heated to 60°C while stirring at 500 rpm. Then, 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 extracted and used as feedstock K.

[0461] After heating the raw material liquid K to remove water, the residue is heated and dried to obtain a hydrocarbon polymer (polyMMA).

[0462] [Raw material liquid (L)]

[0463] For the above-mentioned raw material solution K (490g), add Purolite A300 (manufactured by Purolite Corporation), anion exchange resin, 20g. After stirring for 60 minutes, separate the raw material solution and the ion exchange resin by filtration to obtain raw material solution L.

[0464] In feed liquid L, hydrocarbon polymer (poly-MMA) particles (average particle size 116 nm) are dispersed in an aqueous medium. Based on the amount of MMA added, the content of hydrocarbon polymer relative to the total mass of feed liquid L is 0.47 by mass.

[0465] [Example 6]

[0466] In a 2.2L stainless steel pressure reactor equipped with anchor-shaped blades, feed solution L (3.91g) and ultrapure water (1162g) were added to obtain an aqueous dispersion L. While stirring the aqueous dispersion L at 600rpm, the temperature was raised to 80°C, and PMVE (72g) and TFE (14g) were added. Next, an ammonium persulfate aqueous solution (20% by mass, 5mL) was added to initiate polymerization. As polymerization began, the pressure inside the reactor decreased, so TFE and PMVE were further added to maintain a constant pressure of 1.2MPa [gauge]. The reactor was cooled when 160g of TFE and 133g of PMVE were added, ending the polymerization reaction. The polymerization time was 411 minutes.

[0467] After recovering the gas remaining in the reactor, the liquid is extracted. This liquid is designated as aqueous dispersion 6. Aqueous dispersion 6 is a dispersion containing 2L of fluoropolymer particles (average particle size 195.2nm) dispersed in an aqueous medium, with a solid content concentration of 20.7% by mass. An aqueous aluminum sulfate solution is added to the above aqueous dispersion for coagulation. The resulting coagulated material is washed with water and dried to obtain a solid composition 6 containing 2L of rubber-like fluoropolymer.

[0468] [Example 7]

[0469] After degassing a 2.1L stainless steel pressure reactor with anchor blades, the gas phase was purged with nitrogen. While stirring at 600 rpm using the anchor blades, 1004g of ultrapure water, 80.1g of a 30% by mass solution of C2F5OCF2CF2OCF2COONH4 (surfactant A) as an emulsifier, and 10.49g of a 5% by mass aqueous solution of disodium hydrogen phosphate dodecahydrate were added to obtain an aqueous dispersion M. PMVE (72g) and TFE (14g) were then added into the container, and the internal temperature was raised to 80°C. Next, an ammonium persulfate aqueous solution (1.0% by mass, 20mL) was added to begin polymerization. As polymerization began, the pressure inside the reactor decreased; therefore, TFE and PMVE were further added to maintain a constant pressure of 1.2 MPa. The reactor was cooled when 160g of TFE and 133g of PMVE were added, ending the polymerization reaction. The polymerization time was 262 minutes.

[0470] After recovering the gas remaining in the reactor, the liquid is extracted. This liquid is used as aqueous dispersion 7. Aqueous dispersion 7 is a dispersion containing particles (average particle size 80.0 nm) of fluoropolymer 2M dispersed in an aqueous medium, with a solid content concentration of 20.0% by mass. An aqueous solution of aluminum sulfate is added to the above aqueous dispersion for coagulation. The resulting coagulated material is washed with water and dried to obtain a solid composition 7 containing rubbery fluoropolymer 2M.

[0471] [evaluate]

[0472] <2% mass reduction in temperature>

[0473] 10 mg of a solid composition (sample) was weighed in an aluminum pan and heated from 30 °C to 550 °C at a rate of 10 °C / min in air. The sample mass before heating was set as 100%, and the temperature at which 98% of the mass was reached was set as the 2% mass reduction temperature. It can be said that the higher the 2% mass reduction temperature, the better the heat resistance.

[0474] It should be noted that the device uses the Hitachi High Technology Corporation NEXTA STA series STA200.

[0475] <Water Dispersion Stability>

[0476] Using a 60mm diameter disc turbine, the sedimentation rate shown below was measured when 30g of each of the aqueous dispersions 1-7 was stirred at high speed of 2000rpm for 180 minutes to evaluate the water dispersion stability. The lower the sedimentation rate, the better the water dispersion stability.

[0477] Precipitation rate (%) = 100 × precipitated aggregate (g) / (30 (g) × concentration of fluoropolymer (mass%) / 100)

[0478] [Table 5]

[0479]

[0480] In Table 5, the content of formula (S2) refers to the total 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) refers to the total 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) refers to the total 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.

[0481] It should be noted that, during the manufacture of solid compositions 1 to 5, emulsifiers other than the compounds shown in formulas (S1) to (S4) and surfactant A are not generated from the components used in the manufacture of solid compositions 1 to 5, nor are they used, and therefore are not included in solid compositions 1 to 5.

[0482] [Table 6]

[0483]

[0484] <Processability Evaluation Results>

[0485] [Table 7]

[0486]

[0487] According to the method for manufacturing fluorinated elastomers of the present invention, it is shown that even when using an aqueous medium with low environmental impact, no emulsifier is required, and fluorinated elastomers with excellent water dispersion stability can be manufactured efficiently (Examples 1 to 5).

[0488] In contrast, the fluorinated elastomer obtained in Example 6 exhibited poor water dispersion stability. Furthermore, Example 7 is a method for manufacturing a fluorinated elastomer using an emulsifier, confirming that Examples 1 through 5 all possessed the same efficiency and water dispersion stability even without substantially using an emulsifier as when an emulsifier was used.

[0489] It should be noted that the entire contents of the specification, claims and abstract of Japanese Patent Application No. 2023-117444, filed on July 19, 2023, are incorporated herein as a disclosure of the specification of this invention.

Claims

1. A method for manufacturing a fluorinated elastomer, wherein, A second fluoropolymer is manufactured by polymerizing monomers comprising tetrafluoroethylene and perfluorinated (alkyl vinyl ether) in an aqueous dispersion containing a first fluoropolymer and an aqueous medium, which is substantially free of water-soluble emulsifiers. The first fluoropolymer comprises tetrafluoroethylene-based units and perfluorinated (alkyl vinyl ether)-based units. In the first fluoropolymer, the content of the perfluoro(alkyl vinyl ether)-based units is 20-95 mol%, relative to the total of the tetrafluoroethylene-based units and the perfluoro(alkyl vinyl ether)-based units. In the second fluoropolymer, the content of the perfluoro(alkyl vinyl ether)-based units is 20-95 mol%, relative to the total of the tetrafluoroethylene-based units and the perfluoro(alkyl vinyl ether)-based units. Before the polymerization of the monomer begins, the content of the first fluoropolymer is 0.01 to 4.0% by mass relative to the total mass of the aqueous dispersion.

2. The method for manufacturing a fluorinated elastomer according to claim 1, wherein, The monomer consists only of tetrafluoroethylene and perfluoro(alkyl vinyl ether), or The monomer comprises tetrafluoroethylene and perfluoro(alkyl vinyl ether), and contains at least one monomer selected from the group consisting of: Monomers having two or more polymerizable unsaturated bonds, monomers having at least one atom selected from the group consisting of chlorine, bromine and iodine atoms, and monomers having a nitrile group.

3. The method for manufacturing a fluorinated elastomer according to claim 1 or 2, wherein, The amount of monomer used is 1 to 80 parts by mass relative to 100 parts by mass of the aqueous medium.

4. The method for manufacturing a fluorinated 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, said particles comprising a fluoropolymer. The average particle size of the particles is less than 1 μm. The particles comprise tetrafluoroethylene-based units and perfluoro(alkyl vinyl ether)-based units. The fluoropolymer has at least one of a chlorine atom, a bromine atom, an iodine atom, and a nitrile group at at least one of its ends and side chains. The content of the emulsifier is less than 100 ppm by mass relative to the total mass of the aqueous dispersion.

6. The aqueous dispersion according to claim 5, wherein, The particles are composed solely of tetrafluoroethylene-based units and perfluoro(alkyl vinyl ether)-based units, or The particles comprise tetrafluoroethylene-based units and perfluoro(alkyl vinyl ether)-based units, and contain at least one unit selected from the group consisting of: Units based on monomers having two or more polymerizable unsaturated bonds, units based on monomers having at least one atom selected from the group consisting of chlorine, bromine, and iodine atoms, and units based on monomers having a nitrile group.

7. A solid composition comprising a fluoropolymer, The solid composition comprises tetrafluoroethylene-based units and perfluoro(alkyl vinyl ether)-based units. The solid composition is substantially free of emulsifiers and has a storage modulus G' of 200~1200 kPa.

8. The solid composition according to claim 7, wherein, The fluoropolymer has at least one of a chlorine atom, a bromine atom, an iodine atom, and a nitrile group at at least one of its ends and side chains.

9. A crosslinked rubber article formed by crosslinking the solid composition of claim 8.

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