Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F14/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
  • C08F14/18—Monomers containing fluorine
  • C08F14/26—Tetrafluoroethene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F2/00—Processes of polymerisation
  • C08F2/12—Polymerisation in non-solvents
  • C08F2/16—Aqueous medium
  • C08F2/18—Suspension polymerisation
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L27/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers
  • C08L27/02—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L27/12—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
  • C08L27/18—Homopolymers or copolymers or tetrafluoroethene

Definitions

• the present invention relates to a method for producing an aqueous dispersion, a method for producing a second fluorine-containing polymer, an aqueous dispersion, and a solid composition.
• Fluorine-containing polymers are used in various industrial fields because of their excellent heat resistance, chemical resistance, flame retardancy, weather resistance, etc.
• an aqueous dispersion containing fluorine-containing polymer particles may be used.
• Patent Document 1 discloses a method in which a fluorine-containing monomer is polymerized in the presence of a specific compound.
• Patent Document 1 It has been found that the method for producing an aqueous dispersion disclosed in Patent Document 1 produces a small number of fluoropolymer particles, leaving room for improvement. In addition, from the viewpoint of reducing the environmental load, it is desirable to substantially avoid the use of emulsifiers having fluorine atoms. The present inventors have found that the method for producing an aqueous dispersion of Patent Document 1 does not necessarily result in sufficient dispersibility of the fluoropolymer produced, and further found that there is room for improvement in the particle number of the fluoropolymer produced. In addition, from the viewpoint of reducing the environmental load, it is desired to substantially not use an emulsifier having a fluorine atom.
• Another object of the present invention is to realize the same particle number of a fluorine-containing polymer as in the case of using a conventional emulsifier having a fluorine atom, without substantially using an emulsifier having a fluorine atom.
• An object of the present invention is to provide a method for producing an aqueous dispersion, which can produce an aqueous dispersion having a large number of fluorine-containing polymer particles without substantially using an emulsifier having a fluorine atom.
• Another object of the present invention is to provide a process for producing the second fluorine-containing polymer, an aqueous dispersion and a solid composition.
• a method for producing a polymerizable composition comprising the steps of: polymerizing a first monomer containing tetrafluoroethylene in the presence of a compound represented by formula (X) and a polymerization initiator in the presence of an aqueous medium and in the substantial absence of an emulsifier having a fluorine atom;
• a method for producing an aqueous dispersion which comprises producing an aqueous dispersion containing particles of a first fluorine-containing polymer having an average particle size of 500 nm or less and no melting point.
• X 1 , X 2 and X 3 each independently represent a hydrogen atom, a fluorine atom, a perfluoromethyl group or an alkyl group; L is a single bond or a divalent linking group; Z is an anionic group or a salt of an anionic group.
• R M is a hydrogen atom, a metal atom, N(R M1 ) 4 or P(R M2 ) 4 ;
• R M1 and R M2 are each independently a hydrogen atom or a substituent, any two R M1s may be bonded to each other to form a ring, and multiple R M1s may be the same or different from each other, any two R M2s may be bonded to each other to form a ring, and multiple R M2s may be the same or different from each other.
• a solid composition comprising a fluorine-containing polymer having no melting point, The fluorine-containing polymer has units based on tetrafluoroethylene, The content of the emulsifier having a fluorine atom is 1500 ppb by mass or less based on the total mass of the solid composition; The content of the compound represented by formula (S1) is 1500 ppb by mass or less based on the total mass of the solid composition, A solid composition, wherein the content of the compound represented by formula (S3) is 100 ppb by mass or less based on the total mass of the solid composition.
• n1 is an integer from 3 to 13; MS is a hydrogen atom, Na, K or NH4 . H-(CF 2 ) n2 -SO 3 M S (S3) In formula (S3), n2 is an integer from 4 to 10, MS is a hydrogen atom, Na, K or NH4 .
• a method for producing an aqueous dispersion which can produce an aqueous dispersion having a large number of fluorine-containing polymer particles without substantially using an emulsifier having fluorine atoms.
• the present invention can also provide a process for producing a second fluorine-containing polymer, an aqueous dispersion and a solid composition.
• a numerical range expressed using “to” means a range including the numerical values described before and after “to” as the upper and lower limits.
• the upper or lower limit described in a certain numerical range may be replaced with the upper or lower limit of another numerical range described in stages.
• the upper or lower limit described in a certain numerical range may be replaced with a value shown in the examples.
• each component may be used alone or in combination of two or more substances corresponding to each component. When two or more substances are used in combination for each component, the content of the component refers to the total content of the substances used in combination, unless otherwise specified.
• unit refers collectively to an atomic group derived from one molecule of a monomer that is formed directly by polymerization of the monomer, and an atomic group obtained by chemically converting a part of the atomic group.
• a "unit based on a monomer” will also be simply referred to as a "unit”.
• the content (mass % or mol %) of each unit relative to all units contained in the polymer is determined by analyzing the polymer by solid-state nuclear magnetic resonance spectroscopy (NMR), and usually, the content of each unit calculated from the amount of each monomer added substantially coincides with the actual content of each unit.
• NMR nuclear magnetic resonance spectroscopy
• the method for producing an aqueous dispersion of the present invention is a method for producing an aqueous dispersion comprising polymerizing a first monomer containing tetrafluoroethylene in the presence of a compound represented by formula (X) (hereinafter also referred to as “compound X”) and a polymerization initiator under conditions in which an aqueous medium is present and an emulsifier having a fluorine atom is substantially absent, to produce an aqueous dispersion containing particles of a first fluorine-containing polymer having an average particle size of 500 nm or less and having no melting point (hereinafter also referred to as "first aqueous dispersion”).
• the reason why the number of particles of the first fluorine-containing polymer increases by this production method without requiring an emulsifier having fluorine atoms is presumably because the presence of compound X in the reaction system during polymerization of the first monomer improves the dispersibility of the particles of the first fluorine-containing polymer produced in the first aqueous dispersion, and the specific surface area of the particles in the first aqueous dispersion increases.
• one of the factors for improving dispersibility is thought to be the improvement of the zeta potential of the particles of the first fluorine-containing polymer by compound X.
• the present production method is carried out under conditions substantially free of any emulsifier having a fluorine atom.
• substantially free of emulsifiers having fluorine atoms means that in the production of the first aqueous dispersion, the content of emulsifiers having fluorine atoms is 10 mass ppm or less, preferably 150 mass ppb or less, more preferably 50 mass ppb or less, based on the total mass of the aqueous medium. The lower limit is 0 mass ppb.
• the present production method is preferably carried out under conditions substantially free of any emulsifier having a fluorine atom and any emulsifier not having a fluorine atom, in order to prevent a decrease in the molecular weight of the fluoropolymer produced.
• emulsifiers substantially free of emulsifiers having fluorine atoms and emulsifiers not having fluorine atoms (hereinafter collectively referred to as "emulsifiers") means that in the production of the first aqueous dispersion, the content of the emulsifier is 10 ppm by mass or less, preferably 150 ppb by mass or less, more preferably 50 ppb by mass or less, based on the total mass of the aqueous medium. The lower limit is 0 ppb by mass.
• the content of various emulsifiers can be measured using a liquid chromatograph mass spectrometer. Specifically, the measurement method described in paragraphs [0721] to [0732] of WO 2018/181904 can be mentioned.
• the emulsifier having a fluorine atom and the emulsifier not having a fluorine atom are water-soluble.
• the water-soluble emulsifier means an emulsifier having a solubility of 100 mg or more in 1000 g of water at 25° C.
• the non-water-soluble emulsifier means an emulsifier other than the water-soluble emulsifiers.
• the water-soluble emulsifier may be either ionic or non-ionic.
• the emulsifier having a fluorine atom and the emulsifier not having a fluorine atom include those not having a carbon-carbon double bond.
• the first fluorine-containing polymer described below and the second fluorine-containing polymer described below are both water-insoluble. None of the compound X, the polymer of compound X, the first fluorine-containing polymer, and the second fluorine-containing polymer described below are equivalent to an emulsifier.
• the emulsifier having a fluorine atom includes anionic fluorine-containing emulsifiers.
• anionic fluorine-containing emulsifiers include emulsifiers containing fluorine atoms whose total carbon number excluding anionic groups is 20 or less, and emulsifiers containing fluorine atoms whose anionic moiety has a molecular weight of 800 or less.
• anionic moiety means the moiety excluding cations of the fluorine-containing emulsifier.
• An emulsifier that does not have fluorine atoms has no fluorine atoms and has a hydrocarbon group such as an alkyl group as a hydrophobic portion. It is also possible to replace the hydrogen atoms of the hydrocarbon group of an emulsifier that does not have fluorine atoms with halogen atoms other than fluorine atoms.
• Emulsifiers that do not contain fluorine atoms include anionic hydrocarbon emulsifiers and nonionic hydrocarbon emulsifiers.
• Anionic hydrocarbon emulsifier means an emulsifier having a negatively charged hydrophilic portion such as a carboxylate group, a sulfonate group, a sulfate group, a phosphonate group, or a phosphate group, and a hydrophobic portion such as a hydrocarbon group such as an alkyl group.
• anionic hydrocarbon emulsifiers include sodium dodecyl sulfate, highly branched C10 tertiary carboxylic acid supplied as Versatic® 10 by Resolution Performance Products, sodium linear alkyl polyether sulfonate supplied as the Avanel® S series by BASF, and sulfosuccinate emulsifier Lankropol® K8300 available from AkzoNobelSurfaceChemistry LLC.
• a nonionic hydrocarbon emulsifier is an emulsifier that exhibits surface activity in water without dissociating into ions and has a hydrocarbon group such as an alkyl group as a hydrophobic portion.
• the hydrophilic portion of the nonionic hydrocarbon emulsifier includes water-soluble functional groups such as polyethylene oxide chains resulting from the polymerization of ethylene oxide.
• Nonionic hydrocarbon emulsifiers include polyalkylene oxide block copolymers, such as block copolymers having polyethylene oxide and polypropylene oxide.
• nonionic hydrocarbon emulsifiers include those described in paragraphs [0043] to [0052] of JP2016-537499A.
• the emulsifier having a fluorine atom and the emulsifier not having a fluorine atom may contain a silicon atom.
• An example of the emulsifier containing a silicon atom is a siloxane emulsifier.
• the siloxane emulsifier is a hydrocarbon-containing emulsifier having a siloxane skeleton.
• Siloxane emulsifiers include those described in US Pat. Nos. 6,841,616 (Wille et al.) and 7,977,438 (Brothers et al.).
• the emulsifier that does not have fluorine atoms may be a polymer emulsifier.
• polymer emulsifiers include polymers that have hydrophilic groups in their side chains.
• polymer emulsifiers include polymers that contain units based on compounds that have a site capable of reacting by polymerization and a hydrophilic group.
• examples of polymers that do not have hydrophilic groups from the beginning include polymers that have been post-treated, such as by hydrolysis, with polymers that contain units based on compounds that have groups that can become hydrophilic groups.
• the emulsifier having fluorine atoms has a molecular weight of 1,000 g/mol or less, and the emulsifier not having fluorine atoms has a molecular weight of 100,000 g/mol or less.
• ⁇ Aqueous medium> The present production method is carried out in the presence of an aqueous medium.
• the aqueous medium include water and a mixed solvent of water and a water-soluble organic solvent.
• the water-soluble organic solvent include tert-butanol, propylene glycol, dipropylene glycol, dipropylene glycol monomethyl ether, and tripropylene glycol.
• the content of the aqueous medium is preferably from 20 to 80% by volume, more preferably from 40 to 70% by volume, based on the volume of the reactor.
• "before initiating polymerization of the first monomer used in the polymerization of the first fluoropolymer” means immediately before the start of polymerization.
• examples of “the start of polymerization” include the time when the first monomer and the polymerization initiator are made to coexist in the reactor after the reactor is heated to a polymerization temperature or higher, and the time when the reactor is heated to a polymerization temperature or higher after the first monomer and the polymerization initiator are made to coexist in the reactor.
• Compound X is a compound represented by formula (X).
• X 1 , X 2 and X 3 each independently represent a hydrogen atom, a fluorine atom, a perfluoromethyl group or an alkyl group; L is a single bond or a divalent linking group; Z is an anionic group or a salt of an anionic group.
• X 1 , X 2 and X 3 each independently represent a fluorine atom, a perfluoromethyl group, a hydrogen atom or an alkyl group.
• the alkyl group may be linear, branched or cyclic.
• the alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 3 carbon atoms, and even more preferably 1 carbon atom.
• X 1 , X 2 and X 3 are preferably a fluorine atom or a hydrogen atom, and from the viewpoint of excellent polymerization reactivity, a hydrogen atom is preferable.
• L is a single bond or a divalent linking group.
• the divalent linking group include an alkylene group, a carbonyl group, an ether bond, a thioether bond, a sulfonyl group, -NH-, -SiH 2 -, a phenylene group, -CF 2 -, and a group combining two or more of these.
• Examples of the group combining two or more of these include an ester bond, a thioester bond, an amide bond, a sulfonamide bond, a combination of an alkylene group and an ether bond, a combination of an alkylene group and an ester bond, a combination of an alkylene group and an amide bond, etc.
• the alkylene group may be linear, branched, or cyclic, preferably linear or branched, and more preferably branched.
• the number of carbon atoms in the alkylene group is, for example, 1 to 6, and preferably 1 to 4.
• L examples include a single bond, an alkylene group, an ether bond, an ester bond, * C -CO-NH-R-* Z , etc., with a single bond, an alkylene group having 1 to 6 carbon atoms, and * C -CO-NH-R-* Z being preferred, a single bond, an alkylene group having 1 to 2 carbon atoms, and * C -CO-NH-R-* Z being more preferred, with * C -CO-NH-R-* Z being particularly preferred since the number of particles of the resulting fluorine-containing copolymer increases and the content of the compound represented by (S3) in the resulting solid composition containing the fluorine-containing polymer is reduced.
• * C is a bonding site with a carbon atom in formula (X)
• * Z is a bonding site with Z in formula (X)
• R is an alkylene group having 1 to 6 carbon atoms or a fluoroalkylene group having 1 to 6 carbon atoms.
• the alkylene group or the fluoroalkylene group may be linear, branched, or cyclic, and is preferably branched.
• the alkylene group or fluoroalkylene group represented by R has 1 to 6 carbon atoms, preferably 2 to 4 carbon atoms, and more preferably 4 carbon atoms.
• R is preferably a linear or branched alkylene group having 1 to 6 carbon atoms.
• Z is an anionic group or a salt of an anionic group.
• salts of anionic groups include groups in which the hydrogen ion of the above anionic groups is replaced with a cation other than the hydrogen ion.
• the cation include a metal ion, an ammonium ion, an imidazolium cation, a pyrrolidinium cation, a pyridinium cation, a piperidinium cation, and a phosphonium cation.
• Z is --SO 3 M, the latex tends to be more stable and the number of particles of the first fluorine-containing polymer increases.
• M is a hydrogen atom, a metal atom, N(R M1 ) 4 or P(R M2 ) 4 , and R M1 and R M2 are each independently a hydrogen atom or a substituent.
• the metal atom represented by M is preferably a metal atom of Group 1, more preferably Li, Na or K.
• the substituents represented by R M1 and R M2 are preferably a monovalent organic group, more preferably a monovalent hydrocarbon group, and further preferably an alkyl group or an aromatic hydrocarbon group.
• the substituent preferably has 1 to 10 carbon atoms.
• the alkyl group may be linear, branched or cyclic.
• the aromatic hydrocarbon group may be either a monocyclic or polycyclic group, and is preferably a phenyl group.
• the molecular weight of compound X is, for example, 70 to 500, and from the viewpoint of dispersion stability, is preferably 70 to 450, and more preferably 100 to 300.
• Specific examples of compound X include 2-acrylamido-2-methyl-1-propanesulfonic acid, N-tigloylglycine, 6-acrylamidohexanoic acid, 1,1-difluoro-2-methyl-2-[(1-oxo-2-propen-1-yl)amino]-1-propanesulfonic acid, 3-methyl-3-[(2-methyl-1-oxo-2-propen-1-yl)amino]-2-butanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, 2,3-dimethyl-3-[(1-oxo-2-propen-1-yl)amino]-2-butanesulfonic acid, and metal salts thereof.
• the metal salts include metal salts of a metal atom represented by M
• the content of compound X is preferably 1.0 to 1000 ppm by mass relative to the total mass of the aqueous medium, and in terms of better effects of the present invention, is more preferably 1.0 to 500 ppm by mass, even more preferably 3.0 to 100 ppm by mass, and particularly preferably 5.0 to 30.0 ppm by mass.
• the polymerization initiator used in the present production method is preferably a water-soluble polymerization initiator, more preferably a persulfate such as ammonium persulfate, sodium persulfate, or potassium persulfate, or an organic polymerization initiator such as disuccinic acid peroxide or azobisisobutylamidine dihydrochloride, still more preferably a persulfate, and particularly preferably ammonium persulfate.
• a persulfate such as ammonium persulfate, sodium persulfate, or potassium persulfate
• an organic polymerization initiator such as disuccinic acid peroxide or azobisisobutylamidine dihydrochloride
• the amount of the polymerization initiator used is preferably 0.01 to 5 parts by mass, more preferably 0.01 to 3 parts by mass, and even more preferably 0.01 to 2 parts by mass, per 100 parts by mass of the first monomer used.
• the first monomer used in the present production method includes tetrafluoroethylene (hereinafter also referred to as "TFE").
• the first monomer may include a monomer other than TFE.
• the amount of TFE used is preferably 5 to 80 mol %, more preferably 20 to 75 mol %, and even more preferably 50 to 75 mol %, relative to the amount of the first monomer used.
• the first monomer preferably contains perfluoroalkyl vinyl ether (hereinafter, also referred to as "PAVE").
• PAVE perfluoroalkyl vinyl ether
• the PAVE is preferably a monomer represented by formula (1) from the viewpoints of excellent polymerization reactivity in producing the first fluoropolymer and of enabling the second fluoropolymer to be produced more efficiently.
• R f1 is a perfluoroalkyl group having 1 to 10 carbon atoms.
• the number of carbon atoms in R f1 is preferably 1 to 8, more preferably 1 to 6, still more preferably 1 to 5, and particularly preferably 1 to 3, from the viewpoint of superior polymerization reactivity.
• the perfluoroalkyl group may be linear or branched.
• PAVE perfluoro(methyl vinyl ether) (hereinafter also referred to as “PMVE”), perfluoro(ethyl vinyl ether) (hereinafter also referred to as “PEVE”), and perfluoro(propyl vinyl ether) (hereinafter also referred to as “PPVE”).
• PMVE or PPVE are preferred, with PMVE being more preferred, in that the second fluorine-containing polymer can be produced more efficiently.
• the amount of PAVE used is preferably 20 to 95 mol %, more preferably 25 to 80 mol %, and even more preferably 25 to 50 mol %, based on the amount of the first monomer used.
• the amount of the TFE unit and the PAVE unit used 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 %, based on the amount of the first monomer used.
• the first monomer may contain other monomers than TFE and PAVE, but from the viewpoint of enabling the second fluorine-containing polymer to be produced more efficiently, it may be necessary to be substantially free of other monomers.
• substantially free of other monomers means that the amount of other monomers used is 0.01 mol % or less, preferably 0 mol %, based on the amount of the first monomer used.
• the polymerization method for the first fluorine-containing polymer is not particularly limited, so long as it is a method of polymerizing a first monomer containing tetrafluoroethylene using compound X and a polymerization initiator under conditions in the presence of an aqueous medium and in the substantial absence of an emulsifier having a fluorine atom.
• Examples of the above method include a method in which a solution containing an aqueous medium and compound X is prepared, and the first monomer is polymerized using the solution and a polymerization initiator.
• the above method includes a method in which the solution and the first monomer are added to a reactor, the reactor is heated, and a polymerization initiator is added to the reactor to polymerize the first monomer.
• the polymerization of the first fluorine-containing polymer results in the first fluorine-containing polymer dispersed in the aqueous medium in the form of particles.
• the aqueous dispersion thus obtained in which the particles of the first fluorine-containing polymer are dispersed may be used as the first aqueous dispersion as it is, or may be used as the first aqueous dispersion by adding another aqueous medium.
• the particles of the first fluorine-containing polymer may be dispersed in another aqueous medium by solvent replacement, and used as the first aqueous dispersion.
• the first monomer is charged into the reactor by a conventional method.
• the first monomer may be continuously or intermittently charged into the reactor so that the polymerization pressure becomes a predetermined pressure.
• the first monomer may be dissolved in an aqueous medium, and the resulting solution may be continuously or intermittently charged into the reactor.
• the polymerization initiator may be added to the reactor all at once or in portions.
• the polymerization temperature is preferably from 10 to 95°C, more preferably from 15 to 90°C.
• the polymerization pressure is preferably from 0.5 to 4.0 MPaG, more preferably from 0.6 to 3.5 MPaG.
• the polymerization time is preferably from 90 to 1,000 minutes, more preferably from 90 to 700 minutes.
• the first aqueous dispersion preferably does not substantially contain a water-soluble emulsifier.
• the water-soluble emulsifier is as described above. "Substantially free of water-soluble emulsifier” means that the content of the water-soluble emulsifier is 10 mass ppm or less, more preferably 150 mass ppb or less, and even more preferably 50 mass ppb or less, based on the total mass of the first aqueous dispersion. The lower limit is 0 mass ppb.
• the first aqueous dispersion does not substantially contain any of the compounds represented by formulas (S1) to (S4).
• “Substantially free of the compound represented by formula (S1)” means that the content of the compound represented by formula (S1) is 10 mass ppm or less, preferably 5 mass ppm or less, more preferably 150 mass ppb or less, and even more preferably 50 mass ppb or less, based on the total mass of the aqueous dispersion. The lower limit is 0 mass ppb.
• “Substantially free of the compound represented by formula (S2)” means that the content of the compound represented by formula (S2) is 10 mass ppm or less, preferably 5 mass ppm or less, more preferably 150 mass ppb or less, and even more preferably 50 mass ppb or less, based on the total mass of the aqueous dispersion. The lower limit is 0 mass ppb.
• “Substantially free of the compound represented by formula (S3)” means that the content of the compound represented by formula (S3) is 10 mass ppm or less, preferably 5 mass ppm or less, more preferably 150 mass ppb or less, and even more preferably 50 mass ppb or less, based on the total mass of the aqueous dispersion.
• the lower limit is 0 mass ppb.
• “Substantially free of the compound represented by formula (S4)” means that the content of the compound represented by formula (S4) is 10 mass ppm or less, preferably 5 mass ppm or less, more preferably 150 mass ppb or less, and even more preferably 50 mass ppb or less, based on the total mass of the aqueous dispersion.
• the lower limit is 0 mass ppb.
• the methods for measuring each content include the methods described in the Examples.
• the content of the particles of the first fluoropolymer is preferably 0.01 to 5.00% by mass relative to the total mass of the first aqueous dispersion, and more preferably 0.01 to 3.0% by mass from the viewpoint of more efficient production of the second fluoropolymer.
• before initiating polymerization of the second monomer used in the polymerization of the second fluoropolymer means immediately before the start of polymerization.
• the start of polymerization include the time when the second monomer and the polymerization initiator are made to coexist in the reactor after the reactor is heated to a polymerization temperature or higher, and the time when the reactor is heated to a polymerization temperature or higher after the second monomer and the polymerization initiator are made to coexist in the reactor.
• the first aqueous dispersion before the start of polymerization of the second monomer used in the polymerization of the second fluorine-containing polymer does not contain the second monomer and polymerization initiator used in the polymerization of the second fluorine-containing polymer.
• the first aqueous dispersion may contain components other than the various components described above.
• Specific examples of other components that the first aqueous dispersion may contain include a chain transfer agent, a reducing agent, and a pH adjuster.
• Specific examples of the chain transfer agent include ethyl acetate, methanol, ethanol, t-butyl methyl ether, diethyl ether, n-pentane, cyclohexane, methane, and propane.
• examples of the chain transfer agent include the compounds represented by formula (I) described below.
• the pH adjuster include inorganic salts and ammonia.
• the inorganic salts include phosphates such as disodium hydrogen phosphate and sodium dihydrogen phosphate, and carbonates such as sodium hydrogen carbonate and sodium carbonate.
• the phosphates include disodium hydrogen phosphate dihydrate and disodium hydrogen phosphate dodecahydrate.
• the content of the chain transfer agent is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the aqueous medium.
• the content of the pH adjuster is preferably 0.01 to 3.0 parts by mass with respect to 100 parts by mass of the aqueous medium.
• the solid content concentration of the first aqueous dispersion is preferably from 5 to 50% by mass, and more preferably from 10 to 45% by mass.
• the solids concentration of the first aqueous dispersion can be measured, for example, by the following method.
• the first fluoropolymer particles are particles produced by the present production method. It is presumed that the particles of the first fluorine-containing polymer adsorb and incorporate the second monomer at the hydrophobic portion during polymerization of the second monomer described below, thereby solubilizing the second monomer and facilitating polymerization of the second monomer even in the case where the particles do not substantially contain an emulsifier having a fluorine atom.
• the first fluorine-containing polymer may be the same as or different from the second fluorine-containing polymer described below.
• the average particle size of the first fluoropolymer particles is 500 nm or less, and from the viewpoint of dispersion stability of the particles, it is preferably 300 nm or less, more preferably 200 nm or less, and even more preferably 150 nm or less.
• the lower limit is preferably 2 nm or more, more preferably 5 nm or more, and even more preferably 10 nm or more.
• the average particle size of the particles of the first fluoropolymer is a particle size calculated by analyzing an autocorrelation function obtained by dynamic light scattering method using a monodisperse cumulant method.
• the number of particles of the first fluoropolymer is preferably 0.5 x 10 14 particles/mL or more, more preferably 1.0 x 10 14 particles/mL or more, more preferably 2.0 x 10 14 particles/mL or more, even more preferably 3.0 x 10 14 particles/mL or more, and particularly preferably 5.0 x 10 14 particles/mL or more.
• the upper limit is preferably 2.0 x 10 15 particles/mL or less.
• the particle number of the first fluoropolymer is the particle number per 1 mL of the first aqueous dispersion.
• the method for measuring the particle number may be, for example, the measurement method shown in the Examples section.
• the first fluorine-containing polymer has no melting point. "Having no melting point” means that when the melting point of the first fluoropolymer is measured using a differential scanning calorimeter, no melting peak is observed, specifically, no melting peak is observed in a temperature range of 150° C. or higher (preferably a temperature range of 150 to 330° C.) Incidentally, a glass transition peak does not fall under the above-mentioned melting peak.
• a specific method for measuring the melting point may be the method shown in the Examples section.
• the first fluoropolymer has a 1% by mass thermal weight loss temperature of preferably 350° C. or higher, more preferably 375° C. or higher, and even more preferably 400° C. or higher.
• the upper limit is preferably 600° C. or lower.
• the 1% by mass weight loss temperature can be measured, for example, using a thermogravimetric analyzer. A specific method for measuring the 1% by mass weight loss temperature includes the measurement method shown in the Examples section.
• the first fluorine-containing polymer has units based on a first monomer.
• the first fluorine-containing polymer contains units based on tetrafluoroethylene (hereinafter also referred to as "TFE units").
• TFE units tetrafluoroethylene
• the content of the TFE units is preferably from 5 to 80 mol %, more preferably from 20 to 75 mol %, and even more preferably from 50 to 75 mol %, based on the total units of the first fluorine-containing polymer.
• the details of TFE from which the TFE units are derived are the same as those of the TFE in the present production method described above, and the preferred embodiments are also the same.
• all units of the first fluorine-containing polymer means all units contained in that one type of first fluorine-containing polymer.
• all units of the first fluorine-containing polymer means all units contained in the two or more types of first fluorine-containing polymers. The above also applies to other fluorine-containing polymers.
• the first fluorine-containing polymer preferably further contains units based on perfluoroalkyl vinyl ether (hereinafter also referred to as "PAVE units").
• PAVE units perfluoroalkyl vinyl ether
• the content of PAVE units is preferably from 20 to 95 mol %, more preferably from 25 to 80 mol %, and even more preferably from 25 to 50 mol %, based on the total units of the first fluorinated polymer.
• the total content of TFE units and PAVE units is preferably from 99.0 to 100.0 mol %, more preferably from 99.5 to 100.0 mol %, and even more preferably from 99.9 to 100.0 mol %, based on all units of the first fluorine-containing polymer.
• PAVE from which the PAVE unit is derived are the same as those of PAVE in the present production method described above, and the preferred embodiments are also the same.
• the preferred amount is also the same.
• the presence of compound X in the reaction system makes it possible to obtain a first fluorine-containing polymer obtained by polymerizing a first monomer containing TFE units and PAVE units, which is preferably a polymer having a large number of particles.
• a first fluorine-containing polymer obtained by polymerizing a monomer having a TFE unit content of 5 to 80 mol % and a PAVE unit content of 20 to 95 mol % relative to the total units of the first fluorine-containing polymer is preferable because it gives a polymer having a large number of particles and no melting point.
• the first fluoropolymer may contain units other than TFE units and PAVE units, but from the viewpoint of enabling the second fluoropolymer to be produced more efficiently, it may be necessary to be substantially free of other units.
• substantially free of other units means that the content of units based on other monomers is 0.01 mol % or less, preferably 0 mol %, based on the total units of the first fluorine-containing polymer. Details of the other monomers from which the other units are derived include the other monomers in the second fluorine-containing polymer described below.
• the method for producing the second fluoropolymer comprises polymerizing a second monomer in the first aqueous dispersion produced by the above-mentioned present production method to produce the second fluoropolymer.
• the process for producing the second fluoropolymer is preferably a process for producing the second fluoropolymer, which comprises polymerizing a second monomer in the aqueous dispersion produced by the above-mentioned present production process using a polymerization initiator to produce the second fluoropolymer.
• the first aqueous dispersion is an aqueous dispersion produced by the present production method described above.
• the preferred embodiments of the first aqueous dispersion are as described above.
• the purification method includes a heat treatment and a method of removing the ions using an ion exchange resin.
• the ion exchange resin is preferably an anion exchange resin. The purification may be carried out multiple times.
• the second monomer preferably contains at least one selected from the group consisting of TFE, chlorotrifluoroethylene (hereinafter also referred to as "CTFE”), vinylidene fluoride (hereinafter also referred to as "VdF”), PAVE, and hexafluoropropylene, and more preferably contains at least one selected from the group consisting of TFE, CTFE, and VdF.
• CTFE chlorotrifluoroethylene
• VdF vinylidene fluoride
• PAVE hexafluoropropylene
• the second monomer also preferably contains at least one selected from the group consisting of TFE and PAVE, and more preferably contains both TFE and PAVE.
• the second monomer may include other monomers than the above-mentioned monomers.
• the other monomer include ethylene, propylene, vinyl chloride, vinylidene chloride, a monomer having two or more polymerizable unsaturated bonds (hereinafter also referred to as "BO"), a monomer having one or more atoms of at least one kind selected from the group consisting of a chlorine atom, a bromine atom, and an iodine atom, a monomer having a nitrile group (hereinafter also referred to as "R CN "), and a unit based on compound (6) described below (hereinafter also referred to as "POAVE unit").
• BO is a monomer having two or more polymerizable unsaturated bonds.
• the number of polymerizable unsaturated bonds in BO is preferably 2 to 6, more preferably 2 or 3, and even more preferably 2, in terms of superior polymerization reactivity. It is preferred that BO further contains a fluorine atom since this leads to a smaller compression set of the crosslinked rubber article at high temperatures.
• BO is preferably a monomer represented by formula (2) in that the crosslinked rubber article has better releasability.
• R 21 , R 22 and R 23 each independently represent a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group; a1 is an integer from 2 to 6, R 24 is an a1-valent perfluorohydrocarbon group having 1 to 10 carbon atoms, or a group having an etheric oxygen atom at the end or between the carbon-carbon bonds of the perfluorohydrocarbon group,
• a plurality of R 21 s , a plurality of R 22 s , and a plurality of R 23 s may be the same or different from each other, and are preferably the same from each other.
• a1 is preferably 2 or 3, and more preferably 2.
• R 21 , R 22 and R 23 are fluorine atoms or hydrogen atoms
• R 21 , R 22 and R 23 are fluorine atoms or all of them are hydrogen atoms
• R 24 may be any one of linear, branched, and cyclic, preferably linear or branched, and more preferably linear.
• the number of carbon atoms in R 24 is preferably 2 to 8, more preferably 3 to 7, still more preferably 3 to 6, and particularly preferably 3 to 5.
• R 24 may or may not have an etheric oxygen atom, but preferably has an etheric oxygen atom in terms of better crosslinking reactivity and rubber physical properties.
• the number of ethereal oxygen atoms in R 24 is preferably 1 to 6, more preferably 1 to 3, and even more preferably 1 or 2.
• the ethereal oxygen atom in R 24 is preferably present at the terminal of R 24 .
• Suitable monomers include the monomers represented by formula (3) and the monomers represented by formula (4).
• R 31 is a divalent perfluorohydrocarbon group having 1 to 10 carbon atoms, or a group having an etheric oxygen atom at the end or between the carbon-carbon bonds of the perfluorohydrocarbon group.
• R 41 is a divalent perfluorohydrocarbon group having 1 to 10 carbon atoms, or a group having an etheric oxygen atom at the end or between the carbon-carbon bonds of the perfluorohydrocarbon group.
• CF 2 ⁇ CFO(CF 2 ) 3 OCF ⁇ CF 2 (hereinafter also referred to as "C3DVE") and CF 2 ⁇ CFO(CF 2 ) 4 OCF ⁇ CF 2 (hereinafter also referred to as "C4DVE").
• a more preferred specific example of the monomer is CH 2 ⁇ CH(CF 2 ) 6 CH ⁇ CH 2 (hereinafter, also referred to as "C6DV").
• BO is preferably C3DVE or C4DVE.
• Examples of the monomer having at least one atom of at least one kind selected from the group consisting of a chlorine atom, a bromine atom, and an iodine atom include a monomer having a bromine atom and a monomer having an iodine atom.
• monomers having a bromine atom include CF 2 ⁇ CFOCF 2 CF 2 CF 2 OCF 2 CF 2 Br, bromotrifluoroethylene, 4-bromo-3,3,4,4-tetrafluorobutene-1 (BTFB), vinyl bromide, 1-bromo-2,2-difluoroethylene, perfluoroallyl bromide, 4-bromo-1,1,2-trifluorobutene-1, 4-bromo-1,1,3,3,4,4-hexafluorobutene, 4-bromo-3-chloro-1,1,3,4,4-pentafluorobutene, 6-bromo-5,5,6,6-tetrafluorohexene, and 4-bromoperfluorobutene-1,3,3-difluoroallyl bromide.
• BTFB 4-bromo-3,3,4,4-tetrafluorobutene-1
• R CN has a polymerizable unsaturated bond. From the viewpoint of polymerization reactivity, R CN more preferably has one polymerizable unsaturated bond. Specific examples of the polymerizable unsaturated bond include a carbon atom-carbon atom double bond (C ⁇ C) and a carbon atom-carbon atom triple bond (C ⁇ C).
• R CN is preferably a monomer represented by formula (5) from the viewpoint of better releasability and heat resistance.
• R 51 , R 52 and R 53 each independently represent a hydrogen atom, a fluorine atom or a methyl group;
• R 54 is a divalent perfluorohydrocarbon group having 1 to 10 carbon atoms, or a group having an etheric oxygen atom at the end or between the carbon-carbon bonds of the perfluorohydrocarbon group.
• R51 , R52 and R53 are fluorine atoms or hydrogen atoms, it is more preferable that all of R51 , R52 and R53 are fluorine atoms or all of them are hydrogen atoms, and it is even more preferable that all of R51 , R52 and R53 are fluorine atoms from the viewpoint of excellent mold releasability and heat resistance of the crosslinked rubber article.
• R 54 may be any one of linear, branched, and cyclic, and is preferably linear or branched.
• R 54 preferably has 2 to 8 carbon atoms, more preferably 3 to 7, still more preferably 3 to 6, and particularly preferably 3 to 5.
• R 54 may or may not have an ether type oxygen atom, but preferably has an ether type oxygen atom in terms of better rubber properties.
• the number of etheric oxygen atoms in R 54 is preferably 1 to 3, and more preferably 1 or 2.
• the POAVE unit is a unit based on the compound (6).
• CF 2 CF (OCF 2 CF 2 ) n - (OCF 2 ) m -OR f2 (6)
• R f2 is a perfluoroalkyl group having 1 to 4 carbon atoms
• n is an integer of 0 to 3
• m is an integer of 0 to 4
• n+m is an integer of 1 to 7.
• the perfluoroalkyl group may be linear or branched.
• the number of carbon atoms in R f2 is preferably 1 to 3.
• n is 0, m is preferably 3 or 4.
• n is 1, m is preferably an integer of 2 to 4.
• n is 2 or 3, m is preferably 0.
• n is preferably an integer of 1 to 3.
• the second monomer preferably includes TFE.
• the second monomer preferably includes only TFE and PAVE, or includes TFE and PAVE and further includes other monomers.
• the further monomer preferably includes at least one monomer selected from the group consisting of BO, chlorine atom, bromine atom, and iodine atom, and at least one monomer selected from the group consisting of RCN .
• the amount of TFE used is preferably from 5 to 80 mol %, more preferably from 20 to 75 mol %, and even more preferably from 50 to 75 mol %, based on the total amount of all the second monomers used for producing the second fluorine-containing polymer.
• the amount of PAVE used is preferably from 20 to 95 mol %, more preferably from 25 to 80 mol %, and even more preferably from 25 to 50 mol %, based on the total amount of all the second monomers used to produce the second fluorinated polymer. When TFE and PAVE are used as the second monomer, the suitable amounts of TFE and PAVE are similar.
• the amount of TFE and PAVE used is preferably 95.0 to 100.0 mol %, more preferably 97.0 to 100.0 mol %, and even more preferably 99.0 to 100.0 mol %, based on the total amount of all the second monomers used to produce the second fluorinated polymer.
• the amount of the other monomer used is preferably 0 to 5.0 mol %, more preferably 0 to 3 mol %, and even more preferably 0 to 1 mol %, based on the amount of the second monomer used.
• the amount of the second monomer used is preferably 1 to 80 parts by mass, more preferably 1 to 70 parts by mass, and even more preferably 1 to 65 parts by mass, per 100 parts by mass of the aqueous medium contained in the first aqueous dispersion.
• the second monomer is preferably polymerized using a polymerization initiator.
• the polymerization initiator is preferably an oil-soluble radical initiator, a water-soluble radical initiator, or a water-soluble oxidation-reduction catalyst.
• oil-soluble radical initiators include oil-soluble organic peroxides such as tert-butyl peroxypivalate (hereinafter also referred to as "PBPV”) and diisopropyl peroxydicarbonate (hereinafter also referred to as "IPP").
• water-soluble radical initiator examples include persulfates such as ammonium persulfate and potassium persulfate, disuccinic acid peroxide, bisglutaric acid peroxide, and water-soluble organic peroxides such as tert-butyl hydroperoxide (hereinafter also referred to as "TBHP").
• persulfates such as ammonium persulfate and potassium persulfate
• disuccinic acid peroxide disuccinic acid peroxide
• bisglutaric acid peroxide bisglutaric acid peroxide
• water-soluble organic peroxides such as tert-butyl hydroperoxide (hereinafter also referred to as "TBHP").
• water-soluble redox catalyst a combination of an oxidizing agent such as bromic acid or its salt, chloric acid or its salt, persulfuric acid or its salt, permanganic acid or its salt, or hydrogen peroxide, and a reducing agent such as sulfurous acid or its salt, hydrogen sulfite or its salt, thiosulfuric acid or its salt, organic acid, or inorganic salt, is preferred.
• an oxidizing agent such as bromic acid or its salt, chloric acid or its salt, persulfuric acid or its salt, permanganic acid or its salt, or hydrogen peroxide
• a reducing agent such as sulfurous acid or its salt, hydrogen sulfite or its salt, thiosulfuric acid or its salt, organic acid, or inorganic salt
• a combination of sulfate anion, sulfite anion, or chloride anion and metal ion is preferred.
• the polymerization initiator is preferably an oil-soluble radical initiator or a water-soluble radical initiator, more preferably a water-soluble radical initiator from the viewpoint of more efficient production of the fluorine-containing polymer, and further preferably a persulfate. Two or more types of polymerization initiators may be used in combination.
• the method for producing the second fluoropolymer comprises polymerizing the second monomer in the first aqueous dispersion to produce the second fluoropolymer.
• a method for polymerizing the second monomer the above-mentioned method for polymerizing the first monomer can be mentioned.
• the polymerization of the second monomer is preferably carried out in the substantial absence of an emulsifier having a fluorine atom.
• the polymerization of the second monomer is more preferably carried out in the substantial absence of an emulsifier having a fluorine atom and an emulsifier not having a fluorine atom.
• the emulsifier may be any of the emulsifiers described above.
• the substantial absence of an emulsifier means that, in the process for producing the second fluoropolymer, the content of the emulsifier is 10 ppm by mass or less, preferably 150 ppb by mass or less, more preferably 50 ppb by mass or less, based on the total mass of the first aqueous dispersion. The lower limit is 0 ppb by mass.
• the method for producing the second fluoropolymer particles of the second fluoropolymer are produced. Specifically, the method for producing the second fluoropolymer produces a second aqueous dispersion in which particles of the second fluoropolymer are dispersed in the aqueous medium.
• the second fluorine-containing polymer is a fluorine-containing polymer produced by the above-mentioned method for producing the second fluorine-containing polymer.
• the second fluorine-containing polymer may be in the form of particles.
• the particles of the second fluoropolymer may or may not contain the first fluoropolymer.
• the average particle size of the particles of the second fluorine-containing polymer is preferably 500 nm or less, and from the viewpoint of the dispersion stability of the particles, more preferably 400 nm or less, even more preferably 350 nm or less, particularly preferably 300 nm or less.
• the lower limit is preferably 10 nm or more, more preferably 30 nm or more, and even more preferably 50 nm or more.
• the average particle size of the particles of the second fluoropolymer can be measured in the same manner as for the average particle size of the particles of the first fluoropolymer.
• the number of particles of the second fluoropolymer is preferably 0.5 ⁇ 10 14 particles/mL or more, more preferably 1.0 ⁇ 10 14 particles/mL or more, more preferably 2.0 ⁇ 10 14 particles/mL or more, even more preferably 3.0 ⁇ 10 14 particles/mL or more, and particularly preferably 5.0 ⁇ 10 14 particles/mL or more.
• the upper limit is preferably 10.0 ⁇ 10 15 particles/mL or less.
• the particle number of the second fluoropolymer is the particle number per 1 mL of the second aqueous dispersion.
• the method for measuring the particle number may be, for example, the measurement method shown in the Examples section.
• the second fluorine-containing polymer preferably does not have a melting point. "Having no melting point” means that when the melting point of the second fluoropolymer is measured using a differential scanning calorimeter, no melting peak is observed, specifically, no melting peak is observed in a temperature range of 150° C. or higher (preferably a temperature range of 150 to 330° C.). Note that a glass transition peak does not fall under the above-mentioned melting peak. A specific method for measuring the melting point may be the method shown in the Examples section.
• the 1% by mass thermal weight loss temperature of the second fluoropolymer is preferably 350°C or higher, more preferably 375°C or higher, and even more preferably 380°C or higher.
• the upper limit is preferably 600°C or lower.
• the 1% by mass thermal weight loss temperature can be measured, for example, using a thermogravimetric analyzer. Specific examples of methods for measuring the 1% by mass thermal weight loss temperature include the measurement methods shown in the Examples section.
• the second fluorine-containing polymer has units based on a second monomer.
• the second monomer is as described above, and the preferred embodiments are also the same.
• the TFE units preferably account for from 5 to 80 mol %, more preferably from 20 to 75 mol %, and even more preferably from 50 to 75 mol %, based on the total units of the second fluorine-containing polymer.
• the amount of the PAVE units is preferably from 20 to 95 mol %, more preferably from 25 to 80 mol %, and even more preferably from 25 to 50 mol %, based on the total units of the second fluorine-containing polymer.
• the TFE units and PAVE units preferably account for from 99.0 to 100.0 mol %, more preferably from 99.5 to 100.0 mol %, and even more preferably from 99.9 to 100.0 mol %, based on the total units of the second fluorine-containing polymer.
• the amount of units of the other monomer is preferably from 0 to 90 mol %, more preferably from 0 to 80 mol %, and even more preferably from 0 to 70 mol %, based on the total units of the second fluorine-containing polymer.
• the second aqueous dispersion is an aqueous dispersion obtained by the process for producing the second fluoropolymer.
• the second aqueous dispersion is preferably an aqueous dispersion containing fluoropolymer particles (hereinafter also referred to as "specific particles") and an aqueous medium.
• the second aqueous dispersion is preferably an aqueous dispersion that is substantially free of a water-soluble emulsifier having fluorine atoms and contains specific particles and an aqueous medium, in which the number of the specific particles is 0.5 ⁇ 10 particles/mL or more, the average particle size of the specific particles is 500 nm or less, the fluorine-containing polymer has units based on tetrafluoroethylene and units based on perfluoroalkyl vinyl ether, and the fluorine-containing polymer has no melting point.
• the second aqueous dispersion is preferably an aqueous dispersion that is substantially free of a water-soluble emulsifier having a fluorine atom and a water-soluble emulsifier not having a fluorine atom, and that contains specific particles and an aqueous medium, in which the number of the specific particles is 0.5 ⁇ 10 particles/mL or more, the average particle size of the specific particles is 500 nm or less, the fluorine-containing polymer has units based on tetrafluoroethylene and units based on perfluoroalkyl vinyl ether, and the fluorine-containing polymer has no melting point.
• water-soluble emulsifier having a fluorine atom examples include the water-soluble emulsifier having a fluorine atom in the present production method described above.
• “Substantially free of water-soluble emulsifier having fluorine atoms” means that the content of the water-soluble emulsifier having fluorine atoms is 10 mass ppm or less, preferably 150 mass ppb or less, more preferably 50 mass ppb or less, based on the total mass of the second aqueous dispersion. The lower limit is 0 mass ppb. It is also preferable that the composition is substantially free of a water-soluble emulsifier having no fluorine atoms.
• water-soluble emulsifier having no fluorine atoms examples include the water-soluble emulsifier having no fluorine atoms used in the present production method described above.
• substantially free of water-soluble emulsifier having no fluorine atoms means that the content of the water-soluble emulsifier having no fluorine atoms is 10 mass ppm or less, preferably 150 mass ppb or less, more preferably 50 mass ppb or less, based on the total mass of the second aqueous dispersion. The lower limit is 0 mass ppb.
• the emulsion is substantially free of a water-soluble emulsifier having a fluorine atom and a water-soluble emulsifier not having a fluorine atom.
• the water-soluble emulsifier having a fluorine atom may be the water-soluble emulsifier having a fluorine atom in the above-mentioned production method of the present invention.
• the water-soluble emulsifier not having a fluorine atom may be the water-soluble emulsifier having a fluorine atom in the above-mentioned production method of the present invention.
• Substantially free of water-soluble emulsifiers having fluorine atoms and water-soluble emulsifiers having no fluorine atoms means that the total content of the water-soluble emulsifiers having fluorine atoms and the water-soluble emulsifiers having no fluorine atoms is 10 mass ppm or less, preferably 150 mass ppb or less, more preferably 50 mass ppb or less, relative to the total mass of the second aqueous dispersion. The lower limit is 0 mass ppb.
• the specific particles are preferably particles of the above-mentioned second fluorine-containing polymer.
• the specific particle may or may not contain the first fluoropolymer.
• the second aqueous dispersion may further contain particles of the first fluoropolymer in addition to the specific particles.
• the number of specific particles is 0.5 ⁇ 10 14 particles/mL or more and the average particle size of the particles is 500 nm or less.
• the preferred embodiments of the specific particle number and average particle diameter are the same as the preferred embodiments of the particle number and average particle diameter of the second fluorine-containing polymer.
• the fluoropolymer produced in the first and second aqueous dispersions of the present invention preferably contains TFE units and PAVE units and has no melting point.
• the TFE units and PAVE units and other units contained in the fluoropolymer include each unit which may be contained in the first fluoropolymer and the second fluoropolymer, and the preferred embodiments (type and content thereof) are the same.
• the meaning of "having no melting point" is as described above.
• the content of the specific particles is preferably 1 to 50 mass %, more preferably 1 to 45 mass %, and even more preferably 1 to 40 mass %, relative to the total mass of the second aqueous dispersion, in terms of the dispersion stability of the specific particles.
• aqueous medium contained in the second aqueous dispersion are the same as the specific examples of the aqueous medium in the present production method described above.
• the content of the aqueous medium is preferably 50 to 99 mass %, more preferably 50 to 90 mass %, and even more preferably 50 to 80 mass %, based on the total mass of the second aqueous dispersion, from the viewpoint of dispersion stability of the specific particles.
• a solid composition comprising a fluorine-containing polymer having no melting point, which is produced in the first aqueous dispersion or the second aqueous dispersion of the present invention,
• the solid composition has units based on TFE,
• the content of the emulsifier having a fluorine atom is 1500 ppb by mass or less based on the total mass of the solid composition;
• the content of the compound represented by formula (S1) is 1500 ppb by mass or less based on the total mass of the solid composition,
• the content of the compound represented by formula (S3) is 100 ppb by mass or less based on the total mass of the solid composition.
• H-(CF 2 ) n1 -COOM S (S1)
• n1 is an integer from 3 to 13
• MS is a hydrogen atom, Na, K or NH4
• H-(CF 2 ) n2 -SO 3 M S (S3)
• n2 is an integer from 4 to 10
• MS is a hydrogen atom, Na, K or NH4 .
• the methods for measuring each content include the methods described in the Examples.
• the present solid composition means a composition having a solid content of 99% by mass or more.
• the present solid composition is preferably obtained by coagulating the fluoropolymer produced in the above-mentioned first aqueous dispersion or second aqueous dispersion.
• Preferred embodiments of the fluoropolymer contained in the present solid composition are the same as the preferred embodiments of the fluoropolymer contained in the above-mentioned first aqueous dispersion or second aqueous dispersion. That is, the fluorine-containing polymer contained in the present solid composition is preferably the above-mentioned first fluorine-containing polymer or second fluorine-containing polymer.
• the second fluorine-containing polymer may contain the first fluorine-containing polymer.
• the solid composition contains a first or second fluoropolymer having no melting point and containing units based on TFE.
• the first or second fluoropolymer having no melting point preferably contains units based on TFE and units based on PAVA.
• the content of the fluorine-containing polymer is preferably from 99.0 to 100 mass %, more preferably from 99.5 to 100 mass %, and even more preferably from 99.8 to 100 mass %, based on the total mass of the present solid composition.
• the content of the emulsifier having a fluorine atom is 1500 ppb by mass or less, preferably 1000 ppb by mass or less, more preferably 900 ppb by mass or less, and particularly preferably 850 ppb by mass or less, based on the total mass of the solid composition.
• Specific examples of the emulsifier having a fluorine atom are as described above.
• the emulsifier having no fluorine atom is not substantially contained.
• not substantially containing the emulsifier having no fluorine atom means that the content of the emulsifier having no fluorine atom is 10 mass ppm or less, preferably 5 mass ppm or less, more preferably 150 mass ppb or less, and even more preferably 50 mass ppb or less, based on the total mass of the solid composition.
• the lower limit is 0 mass ppb.
• Specific examples of the emulsifier not having a fluorine atom are as described above.
• the solid composition has a compound represented by formula (S1) content of 1500 ppb by mass or less, preferably 1000 ppb by mass or less, more preferably 900 ppb by mass or less, and particularly preferably 850 ppb by mass or less, based on the total mass of the solid composition.
• the content of the compound represented by formula (S3) is 100 ppb by mass or less, preferably 50 ppb by mass or less, more preferably 25 ppb by mass or less, even more preferably 10 ppb by mass or less, and particularly preferably 0 ppb by mass, relative to the total mass of the solid composition.
• the present solid composition preferably has a metal content of less than 50 ppm by mass, more preferably 10 ppm by mass or less, and particularly preferably 5 ppm by mass or less, based on the total solid content of the solid composition.
• the metal content is less than 50 ppm by mass, the surface smoothness of the obtained solid composition is further improved.
• the second aqueous dispersion does not necessarily require an emulsifier such as an emulsifier having a fluorine atom, and therefore it is easy to make it into a dispersion in an organic solvent such as N-methylpyrrolidone or acetone by solvent substitution.
• the second aqueous dispersion can be mixed with an organic solvent and dehydrated using evaporation or anhydrous sodium sulfate or the like to form a dispersion in the organic solvent.
• the second aqueous dispersion stably disperses the fluoropolymer even without the need for an emulsifier. Therefore, it is suitable for use in coating applications, as a binder, etc.
• a solid of specific particles can be obtained by agglomerating the first fluoropolymer from the first aqueous dispersion, or by agglomerating the specific particles from the second aqueous dispersion. Furthermore, the solid of specific particles obtained by agglomeration can be appropriately molded by a known method. Examples of molding methods include injection molding, extrusion molding, coextrusion molding, blow molding, compression molding, inflation molding, transfer molding, and calendar molding.
• Flocculation methods include, but are not limited to, freeze flocculation, acid flocculation, base flocculation, mechanical flocculation, and flocculation using a coagulant.
• the aggregation temperature is preferably ⁇ 20 to 0° C.
• the aggregation time is preferably 1 hour or more, more preferably 2 hours or more.
• acid coagulation a method of adding an acid-containing solution to the second aqueous dispersion is preferred.
• the acid to be added include hydrochloric acid, nitric acid, sulfuric acid, oxalic acid, and hydrofluoric acid, and nitric acid is 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.
• the base coagulation is preferably carried out by adding a solution containing a base to the second aqueous dispersion.
• the base to be added include sodium hydroxide, potassium hydroxide, and ammonium carbonate, and sodium hydroxide is preferred.
• the concentration of the base in the solution containing the base is preferably 0.1 to 50% by mass, more preferably 1 to 30% by mass, and even more preferably 1 to 10% by mass.
• a known coagulant can be used for the aggregation using a coagulant.
• Known coagulants include aluminum salts, calcium salts, and magnesium salts.
• aluminum sulfate alum represented by the general formula M'Al(SO 4 ) 2 ⁇ 12H 2 O (wherein M' is a monovalent cation other than lithium), calcium nitrate, and magnesium sulfate can be mentioned.
• Alum is preferred, and potassium alum, where M is potassium, is more preferred.
• base aggregation is preferred since aggregation is particularly likely to proceed.
• Example 1 to 5 and Examples 7 to 11 are working examples, and Example 6 is a comparative example. However, the present invention is not limited to these examples.
• ⁇ Average particle size of particles of first fluoropolymer and second fluoropolymer> The first aqueous dispersion of each example described later was degassed for 5 minutes at 25° C., pressurized with nitrogen gas to 0.2 MPaG, purged, and returned to atmospheric pressure to obtain a measurement sample.
• the average particle size of the obtained measurement sample was measured using a dynamic light scattering particle size distribution measurement device (Otsuka Electronics Co., Ltd., ELSZ) with an accumulation number set to 100, and was defined as the average particle size of the particles in each aqueous dispersion.
• ELSZ dynamic light scattering particle size distribution measurement device
• the average particle size of the particles of the first fluoropolymer in raw material liquid B described below was measured in the same manner as for the first aqueous dispersion, the average particle size of the particles of the first fluoropolymer in raw material liquid B was found to be the same as the average particle size of the particles of the first fluoropolymer in the first aqueous dispersion.
• Np Number of particles of the first fluoropolymer in the first aqueous dispersion, or the number of particles of the second fluoropolymer in the second aqueous dispersion, Np (particles/mL), was calculated by the following formula:
• Np (pieces/mL) [(X/100)/(1-X/100)]/[4/3 ⁇ (Dp/2) 3 ⁇ ]
• X solid content concentration (mass%) of the first aqueous dispersion, or solid content concentration (mass%) of the second aqueous dispersion
• ⁇ Circular constant
• Dp average particle size (m) of the particles of the first fluoropolymer in the first aqueous dispersion, or average particle size (m) of the particles of the second fluoropolymer in the second aqueous dispersion
• the first aqueous dispersion or the second aqueous dispersion of each example described later was freeze-aggregated and then filtered to obtain the first fluorine-containing polymer or the second fluorine-containing polymer.
• a 5 mg sample of the first fluorine-containing polymer or the second fluorine-containing polymer obtained was weighed out and placed in an aluminum pan, and heated from 20°C to 360°C at a heating rate of 10°C/min in an air atmosphere using a Hitachi DSC600, and the presence or absence of a melting point peak was confirmed.
• thermogravimetric reduction temperature The first aqueous dispersion or the second aqueous dispersion of each example described later was freeze-aggregated and then filtered to obtain the first fluorine-containing polymer or the second fluorine-containing polymer.
• a 10 mg sample of the first fluorine-containing polymer or the second fluorine-containing polymer obtained was weighed out and placed in an aluminum pan, and heated from 40° C. to 550° C. at a heating rate of 10° C./min in an air atmosphere using a Hitachi STA200, and the 1% thermal weight loss temperature was obtained from the weight loss rate obtained.
• five levels of methanol standard solutions of perfluorocarboxylic acid and perfluorosulfonic acid with known concentrations ranging from 1 to 180 ng/g were first prepared, and a and a' were calculated from the respective sample concentrations and peak integral values using a first-order approximation according to the following formulas (A1) and (A1'):
• A a ⁇ X (A1)
• X concentration of perfluorocarboxylic acid (ng/g)
• A' a' ⁇ X'(A1')
• A' peak area of perfluorosulfonic acid
• X' concentration
• MRM measurement parameters are shown in Tables 2 and 3 below.
• MRM measurement parameters are shown in Tables 4 and 5 below.
• XCm ACm/a (A2)
• XCm content (ng/g) of the compound represented by formula (S1) having the carbon number (n1+1) in the aqueous phase
• ACm peak area of the compound represented by formula (S1) having the carbon number (n1+1) in the aqueous phase
• X'Cm' ACm'/a'(A2')
• XCm' content (ng/g) of the compound represented by formula (S3) having carbon number n in the aqueous phase
• ACm' peak area of the compound represented by formula (S3) having carbon number n in the aqueous phase.
• the quantification limit in this measurement is 1 ng/g.
• A a ⁇ X (A1)
• A peak area of perfluorocarboxylic acid
• X concentration of perfluorocarboxylic acid (ng/g)
• A' a' ⁇ X'(A1')
• A' concentration of perfluorosulfonic acid (ng/g)
• the MRM measurement parameters are as shown in Table 2 above.
• XCm ACm/a (A2)
• XCm Content (ng/g) of the compound represented by formula (S1) having carbon number (n+1) in each extract
• ACm Peak area of the compound represented by formula (S1) having carbon number (n+1) in each extract
• XCm' ACm'/a'(A2')
• XCm' content (ng/g) of the compound represented by formula (S3) having carbon number n in each extract
• ACm' peak area of the compound represented by formula (S3) having carbon number n in each extract.
• the quantification limit in this measurement is 1 ng/g.
• the content (ZCm) of the formula (S1) in the solid matter relative to the total mass of the solid matter was calculated by the following formula (A3).
• ZCm XCm ⁇ 1 ⁇ La/W1 (A3)
• ZCm content of the compound represented by formula (S1) with carbon number (n+1) contained in the solid ⁇ 1: density of the extraction solvent (methanol in each example)
• La volume of the extraction solvent (5 mL in each example)
• W1 sample mass used for extraction (2.5 g solids in each example)
• the content (ZCm') of the compound represented by formula (S3) in the solid matter relative to the total mass of the solid matter was calculated by the following formula (A4).
• ZCm' XCm' ⁇ 1 ⁇ La/W1 (A4)
• La volume of the extraction solvent (5 mL in each example)
• W1 sample mass used for extraction (2.5 g solids in each example)
• the solid composition obtained in each example was freeze-pulverized using a freeze-pulverizer Freezer Mill 6775 (manufactured by SPEX) under the following conditions.
• 10% by mass of dibutylhydroxytoluene (BHT) was added in advance to the total mass of the solid composition to obtain a pulverized powder.
• the freeze-pulverization conditions were: solid composition: 3 g, BHT: 0.3 g, Run time: 5 min, Rate: 15 cps, Cycle: 3. 5 mL of methanol was added to 0.25 g of the obtained pulverized powder, and ultrasonic treatment was performed at 50° C.
• the obtained extract was measured by LC/MS/MS.
• the emulsifier having fluorine atoms in the extract was measured using a liquid chromatograph mass spectrometer. The measurement equipment configuration and LC-MS measurement conditions are shown in Table 1. Using an aqueous solution of an emulsifier having fluorine atoms with a known concentration, methanol solutions with five or more levels of content were prepared, and LC/MS analysis was performed on the methanol solutions with each content. The relationship between the content and the area area relative to the content was plotted, and a calibration curve was drawn. Using the above calibration curve, the area area of the LC/MS chromatogram of the emulsifier having fluorine atoms in the extract was converted to the content of the emulsifier having fluorine atoms.
• the MRM measurement parameters are appropriately selected according to the structure of the emulsifier containing fluorine atoms to be measured.
• the MRM parameters can be those from literature, or can be calculated using the LC-MS device.
• the specific procedure for determining the MRM parameters using an LC-MS device is as follows. Using an LC/MS device (Shimadzu Corporation, LCMS-8060NX), select product ion search, input the molecular weight of the emulsifier containing fluorine atoms to be measured, and perform precursor ion, precursor adjustment, voltage optimization, and product m/z optimization. The calculated MRM measurement parameters are used.
• the content (ZCm'') of the emulsifier in the solid composition relative to the total mass of the solid composition was calculated by the following formula (A3'').
• ZCm'' XCm'' ⁇ 1 ⁇ La/W1
• ZCm′′ content of emulsifier contained in the solid composition
• La volume of extraction solvent (5 mL in each example)
• W1 sample mass used for extraction (2.5 g of solid composition in each example)
• (1+1) sulfuric acid Koreano Chemical Co., Ltd., Ultrapur sulfuric acid, 1 mL
• the metal elements in the resulting sample solution were measured by ICP-MS and quantified by the absolute calibration curve method.
• the metal element types measured were 29 types of metal elements (Li, Be, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Zr, Mo, Ag, Cd, In, Sn, Cs, Ba, Pb, and Bi).
• Example 1 Ultrapure water (1774 g), 50% by mass aqueous solution of sodium 2-acrylamido-2-methyl-1-propanesulfonate (NaAAMPS, corresponding to compound X) (15 ⁇ L, 7.5 mg of NaAAMPS), PMVE (105 g), and TFE (22 g) were added to a 3.2 L stainless steel pressure-resistant reactor, and the temperature was raised to 80 ° C. while stirring at 385 rpm. The pressure inside the reactor at 80 ° C. was 1.4 MPaG. Next, an aqueous solution of ammonium persulfate (2.5% by mass, 10 g) was added to initiate polymerization.
• NaAAMPS sodium 2-acrylamido-2-methyl-1-propanesulfonate
• PMVE 105 g
• TFE 22 g
• the total amount of monomers added before the start of polymerization was 22g of TFE and 105g of PMVE.
• the total amount of monomers added after the start of polymerization was 133g of TFE and 80g of PMVE.
• the total amount of TFE added was 155g, and the total amount of PMVE added was 185g.
• the average particle size of the particles of the first fluoropolymer A1 in the first aqueous dispersion A1 was 79.6 nm, the number of particles of the first fluoropolymer A1 was 2.6 ⁇ 10 particles/mL, and the solids concentration of the first aqueous dispersion A1 was 12.4 mass%.
• the first aqueous dispersion A1 was freeze-aggregated, filtered, and the first fluoropolymer A1 obtained was washed with ultrapure water.Then, it was vacuum-dried at 100°C.
• the first fluoropolymer A1 obtained was analyzed by NMR, and the ratio of PMVE/TFE was 33/67 (molar ratio).
• the 1% by mass thermal weight loss temperature of the first fluoropolymer A1 was 412°C.
• the first fluorine-containing polymer A1 did not have a melting point.
• Example 2 A first aqueous dispersion A2 was obtained in the same manner as in Example 1, except that the amount of the 50% by mass aqueous solution of NaAAMPS added was changed to 30 ⁇ L (NaAAMPS: 15 mg).
• the average particle size of the particles of the first fluoropolymer A2 in the first aqueous dispersion A2 was 64.3 nm, the number of particles of the first fluoropolymer A2 was 5.0 ⁇ 10 particles/mL, and the solids concentration of the first aqueous dispersion A2 was 12.4 mass%.
• the first aqueous dispersion A2 was freeze-aggregated, filtered, and the first fluoropolymer A2 obtained was washed with ultrapure water.Then, it was vacuum-dried at 100°C.
• the first fluoropolymer A2 obtained was analyzed by NMR, and the ratio of PMVE/TFE was 33/67 (molar ratio).
• the 1% by mass thermal weight loss temperature of the first fluoropolymer A2 was 412°C.
• the first fluoropolymer A2 had no melting point.
• Example 3 Polymerization was started in the same manner as in Example 1, except that the amount of the 50% by mass aqueous solution of NaAAMPS was changed to 45 ⁇ L (NaAAMPS was 22.5 mg). Since the pressure in the reactor decreased with the start of polymerization, TFE was added to keep the pressure constant. This was repeated, and when the amount of TFE added after the start of polymerization reached 37 g, 10 g of PMVE was injected. Thereafter, 10 g of PMVE was injected every time 12 g of TFE was injected.
• the average particle size of the particles of the first fluoropolymer A3 in the first aqueous dispersion A3 was 68.2 nm, the number of particles of the first fluoropolymer A3 was 9.8 ⁇ 10 particles/mL, and the solids concentration of the first aqueous dispersion A3 was 24.9 mass %.
• the first aqueous dispersion A3 was freeze-aggregated, filtered, and the first fluorine-containing polymer A3 obtained was washed with ultrapure water.Then, it was vacuum-dried at 100°C.
• the first fluorine-containing polymer A3 obtained was analyzed by NMR, and the ratio of PMVE/TFE was 33/67 (molar ratio).
• the 1% by mass thermal weight loss temperature of the first fluorine-containing polymer A3 was 412°C.
• the first fluorine-containing polymer A3 had no melting point.
• Example 4 Polymerization was started in the same manner as in Example 1, except that the 50% by mass aqueous solution of NaAAMPS was replaced with a 25% by mass aqueous solution of sodium vinyl sulfonate (VSA) (17 ⁇ L). Since the pressure in the reactor decreased with the start of polymerization, TFE was added to keep the pressure constant. This was repeated, and when the amount of TFE added after the start of polymerization reached 37 g, 10 g of PMVE was injected. Thereafter, 10 g of PMVE was injected every time 12 g of TFE was injected.
• VSA sodium vinyl sulfonate
• the average particle size of the fluoropolymer C1 particles in the aqueous dispersion C1 was 86.9 nm, the number of the fluoropolymer C1 particles was 0.9 ⁇ 10 14 particles/mL, and the solids concentration of the aqueous dispersion C1 was 6.4 mass %.
• the aqueous dispersion C1 was freeze-aggregated, filtered, and the obtained fluoropolymer C1 was washed with ultrapure water. It was then vacuum-dried at 100°C.
• the obtained fluoropolymer C1 was analyzed by NMR, and found to have a PMVE/TFE molar ratio of 31.8/68.2.
• the 1% by mass thermal weight loss temperature of the fluoropolymer C1 was 415°C.
• the first fluorine-containing polymer C1 did not have a melting point.
• Example 5 Polymerization was started in the same manner as in Example 1, except that the 50% by mass aqueous solution of NaAAMPS was replaced with sodium styrene vinyl sulfonate (NaSS, 7 mg). Since the pressure in the reactor decreased with the start of polymerization, TFE was added to keep the pressure constant. When the amount of TFE added after the start of polymerization reached 37 g, the temperature inside the reactor was cooled to 10 ° C. to stop the polymerization reaction, and the gas remaining in the reactor was recovered, and then the liquid was extracted to obtain an aqueous dispersion C2. The total amount of monomers added before the start of polymerization was 22 g of TFE and 105 g of PMVE.
• the total amount of monomers added after the start of polymerization was 37 g of TFE and 0 g of PMVE.
• the total amount of TFE added was 59 g, and the total amount of PMVE added was 105 g.
• the average particle size of the fluoropolymer C2 particles in the aqueous dispersion C2 was 78.1 nm, the number of the fluoropolymer C2 particles was 0.6 ⁇ 10 14 particles/mL, and the solids concentration of the aqueous dispersion C2 was 3.0 mass %.
• the aqueous dispersion C2 was freeze-aggregated, filtered, and the obtained fluoropolymer C2 was washed with ultrapure water. It was then vacuum-dried at 100°C.
• the obtained fluoropolymer C2 was analyzed by NMR, and found to have a PMVE/TFE molar ratio of 31.8/68.2.
• the 1% by mass thermal weight loss temperature of the fluoropolymer C2 was 363°C.
• the first fluorine-containing polymer C2 had no melting point.
• the total amount of monomers added after the start of polymerization was 160 g of TFE and 133 g of PMVE.
• the total amount of TFE added was 174 g, and the total amount of PMVE added was 205 g.
• the average particle size of the fluoropolymer C3 particles in aqueous dispersion C3 was 84.2 nm, the number of fluoropolymer C3 particles was 3.1 ⁇ 10 14 particles/mL, and the solids concentration of aqueous dispersion C3 was 21.1 mass %.
• the aqueous dispersion C3 was freeze-aggregated, filtered, and the obtained fluoropolymer C3 was washed with ultrapure water. It was then vacuum-dried at 100°C.
• the obtained fluoropolymer C3 was analyzed by NMR, and found to have a PMVE/TFE ratio of 34.2/65.8 (molar ratio).
• the 1% by mass thermal weight loss temperature of the fluoropolymer C3 was 406°C.
• the first fluoropolymer C3 had no melting point.
• the average particle size of the particles of the first fluoropolymer A4 in the raw material liquid A was 43.5 nm, the number of particles of the first fluoropolymer A4 was 3.9 ⁇ 10 14 particles/mL, and the solids concentration of the raw material liquid A was 3.3 mass %.
• After freeze-flocculation of the raw material liquid A it was filtered, and the first fluoropolymer A4 obtained was washed with ultrapure water. Then, it was vacuum-dried at 100°C.
• the first fluoropolymer A4 obtained was analyzed by NMR, and the ratio of PMVE/TFE was 33/67 (molar ratio).
• the 1% by mass thermal weight loss temperature of the first fluoropolymer A4 was 350°C.
• the first fluorine-containing polymer A4 had no melting point.
• the total amount of TFE added was 273 g, and the total amount of PMVE added was 284 g.
• the average particle size of the fluoropolymer B1 particles in the second aqueous dispersion B1 was 67.6 nm, the number of the fluoropolymer B1 particles was 3.6 ⁇ 1014 particles/mL, and the solids concentration of the second aqueous dispersion B1 was 10.5 mass%.
• the second aqueous dispersion B1 was freeze-aggregated, filtered, and the obtained fluoropolymer B1 was washed with ultrapure water. Then, it was vacuum-dried at 100°C.
• the obtained fluoropolymer B1 was analyzed by NMR, and the ratio of PMVE/TFE was 33/67 (molar ratio).
• the 1% by mass thermal weight loss temperature of the fluoropolymer B1 was 411°C.
• the fluoropolymer B1 did not have a melting point.
• Example 8 Polymerization was started in the same manner as in Example 1, except that the amount of the 50% by mass aqueous solution of NaAAMPS was changed to 45 ⁇ L (NaAAMPS was 22.5 mg) and the amount of the ammonium persulfate aqueous solution (2.5% by mass) was changed to 7 g. Since the pressure in the reactor decreased with the start of polymerization, TFE was added to keep the pressure constant. This was repeated, and when the amount of TFE added after the start of polymerization reached 37 g, octafluoro-1,4-diiodobutane (C4DI, 1.25 g) and 10 g of PMVE were injected.
• C4DI octafluoro-1,4-diiodobutane
• the rotation speed was reduced to 325 rpm, and 10 g of PMVE was injected every time 12 g of TFE was injected.
• the amount of TFE added after the start of polymerization reached 325g
• the addition of TFE and PMVE to be injected after the start of polymerization was stopped, the temperature inside the reactor was cooled to 10°C, the polymerization reaction was stopped, and the gas remaining in the reactor was recovered, and then the liquid was extracted to obtain a first aqueous dispersion A5.
• the total amount of monomers added before the start of polymerization was 22g of TFE and 105g of PMVE.
• the total amount of monomers added after the start of polymerization was 325g of TFE and 240g of PMVE.
• the total amount of TFE added was 347g, and the total amount of PMVE added was 345g.
• the average particle size of the particles of the first fluoropolymer A5 in the first aqueous dispersion A5 was 77.1 nm, the number of particles of the first fluoropolymer A5 was 6.1 x 10 particles/mL, and the solids concentration of the first aqueous dispersion A5 was 23.0 mass%.
• the first aqueous dispersion A5 was freeze-aggregated, filtered, and the first fluoropolymer A5 obtained was washed with ultrapure water. It was then vacuum-dried at 100°C.
• the first fluoropolymer A5 obtained was analyzed by NMR, and found to have a PMVE/TFE molar ratio of 33/67.
• the iodine content was 0.1% by mass relative to the fluoropolymer A5.
• the 1% by mass thermal weight loss temperature of the first fluoropolymer A5 was 405°C.
• the first fluorine-containing polymer A5 had no melting point.
• Example 9 Ultrapure water (1206 g), a 50% by mass aqueous solution of NaAAMPS (30 ⁇ L, 15 mg of NaAAMPS), PMVE (81 g), and TFE (17 g) were added to a 2.2 L stainless steel pressure-resistant reactor, and the temperature was raised to 80 ° C. while stirring at 600 rpm. The pressure inside the reactor at 80 ° C. was 1.4 MPaG. Next, an aqueous solution of ammonium persulfate (2.5% by mass, 7 g) was added to start polymerization. Since the pressure inside the reactor decreased with the start of polymerization, TFE was added to keep the pressure constant.
• the total amount of TFE added was 202 g, the total amount of PMVE added was 189 g, and the amount of 8CNVE added was 13.7 g.
• the polymerization time was 400 minutes, and the amount of the added aqueous ammonium persulfate solution was 14 cc.
• the average particle size of the particles of the first fluoropolymer A6 in the first aqueous dispersion A6 was 76.6 nm, the number of particles of the first fluoropolymer A6 was 5.2 ⁇ 10 particles/mL, and the solids concentration of the first aqueous dispersion A6 was 20.04 mass%.
• the first aqueous dispersion A6 was freeze-aggregated, filtered, and the first fluorine-containing polymer A6 obtained was washed with ultrapure water.Then, it was vacuum-dried at 100°C.
• the 1% by mass thermal weight loss temperature of the first fluorine-containing polymer A6 was 392°C.
• the first fluorine-containing polymer A6 had no melting point.
• Example 10 Polymerization was started in the same manner as in Example 8, except that CF 2 ⁇ CFO(CF 2 ) 3 OCF ⁇ CF 2 (3.69 g) was added before the polymerization was started. Since the pressure in the reactor decreased with the start of polymerization, TFE was added to keep the pressure constant. This was repeated, and when the amount of TFE added after the start of polymerization reached 37 g, octafluoro-1,4-diiodobutane (C4DI, 1.25 g) and PMVE were injected 10 g. The rotation speed was reduced to 325 rpm, and 10 g of PMVE was injected every time 12 g of TFE was injected.
• C4DI octafluoro-1,4-diiodobutane
• the average particle size of the particles of the first fluoropolymer A7 in the first aqueous dispersion A7 was 94.8 nm, the number of particles of the first fluoropolymer A7 was 4.2 ⁇ 10 particles/mL, and the solids concentration of the first aqueous dispersion A5 was 27.9 mass%.
• the first aqueous dispersion A5 was freeze-aggregated, filtered, and the first fluoropolymer A5 obtained was washed with ultrapure water.Then, it was vacuum-dried at 100°C.
• the first fluoropolymer A5 obtained was analyzed by NMR, and the ratio of PMVE/TFE was 34/66 (molar ratio).
• the iodine content was 0.1% by mass relative to the fluoropolymer A5.
• the 1% by mass thermal weight loss temperature of the first fluoropolymer A7 was 403°C.
• the first fluoropolymer A7 had no melting point.
• Example 11 Polymerization was started in the same manner as in Example 8, except that the amount of 50% by mass aqueous solution of NaAAMPS was changed from 45 ⁇ L (22.5 mg of NaAAMPS) to 45 ⁇ L (22.5 mg of NaMAMPS) of 50% by mass aqueous solution of sodium 2-methacrylamide-2-methylpropanesulfonate. Since the pressure in the reactor decreased with the start of polymerization, TFE was added to keep the pressure constant. This was repeated, and when the amount of TFE added after the start of polymerization reached 37 g, octafluoro-1,4-diiodobutane (C4DI, 1.25 g) and 10 g of PMVE were injected.
• C4DI octafluoro-1,4-diiodobutane
• the rotation speed was reduced to 325 rpm, and 10 g of PMVE was injected every time 12 g of TFE was injected.
• the amount of TFE added after the start of polymerization reached 325g
• the addition of TFE and PMVE to be injected after the start of polymerization was stopped, the temperature inside the reactor was cooled to 10°C, the polymerization reaction was stopped, and the gas remaining in the reactor was recovered, and then the liquid was extracted to obtain a first aqueous dispersion A5.
• the total amount of monomers added before the start of polymerization was 22g of TFE and 105g of PMVE.
• the total amount of monomers added after the start of polymerization was 325g of TFE and 240g of PMVE.
• the total amount of TFE added was 347g, and the total amount of PMVE added was 345g.
• the average particle size of the particles of the first fluoropolymer A8 in the first aqueous dispersion A8 was 103.1 nm, the number of particles of the first fluoropolymer A8 was 3.46 ⁇ 10 particles/mL, and the solids concentration of the first aqueous dispersion A8 was 28.8 mass%.
• the first aqueous dispersion A5 was freeze-aggregated, filtered, and the first fluoropolymer A5 obtained was washed with ultrapure water. It was then vacuum-dried at 100°C.
• the first fluoropolymer A5 obtained was analyzed by NMR, and found to have a PMVE/TFE molar ratio of 35/65.
• the iodine content was 0.1% by mass relative to the fluoropolymer A5.
• the 1% by mass thermal weight loss temperature of the first fluoropolymer A8 was 400°C.
• the first fluorine-containing polymer A8 had no melting point.
• Example 1 to 5 and 7 to 11 the polymerization of the first fluorine-containing polymer was carried out under conditions in which an emulsifier having a fluorine atom and an emulsifier not having a fluorine atom were substantially absent.
• the aqueous dispersions obtained in Examples 1 to 5 and 7 to 11 did not substantially contain an emulsifier having a fluorine atom and an emulsifier not having a fluorine atom.
• the content of the compound represented by formula (S1) relative to the total mass of the aqueous dispersion and the content of the compound represented by formula (S3) relative to the total mass of the aqueous dispersion were both 5 ppm by mass or less (50 ppb by mass or less).
• the aqueous dispersion of Example 6 contained an emulsifier.
• the concentration in the aqueous dispersion relative to the aqueous medium in Table 6 represents the content of compound X.
• the table below specifically shows the contents of the compound represented by formula (S1) and the compound represented by formula (S3) in raw material liquid A and raw material liquid B in Example 7.
• the content of formula (S1) means the total content of each compound in formula (S1) where n1 is an integer from 3 to 13 relative to the total mass of each raw material liquid
• the content of formula (S3) means the total content of each compound in formula (S3) where n2 is an integer from 4 to 10 relative to the total mass of each raw material liquid.
• Tables 8 and 9 below show the specific contents of the compound represented by (S1) and the compound represented by (S3) contained in the solid compositions in Examples 1 to 6 and 8 to 11.
• N.D. indicates that the amount is below the limit of quantification in this measurement.
• Table 10 below shows the specific contents of emulsifiers having fluorine atoms contained in the solid compositions in Examples 1 to 6 and 8 to 11.
• N.D. indicates that the amount is below the limit of quantification in this measurement.
• Table 11 shows the specific contents (ppm) of metal elements contained in the solid compositions in Examples 1 to 3, 6, and 8 to 11.
• Example 6 is a production method of an aqueous dispersion using an emulsifier. It was shown that the effect of the present invention was more excellent when the content of compound X was 5.0 to 30.0 ppm by mass based on the total mass of the aqueous medium (Examples 2 and 3).

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